apelin-13-peptide and Disease-Models--Animal

Chronic stress induces neuronal death and impairs hippocampal neurogenesis, thus leading to cognitive deficits and depressive-like behaviors. Our previous studies found that apelin-13, a novel neuropeptide, and its receptors can improve cognitive impairment and depressive-like behaviors in rats, but its mechanism remains unknown. The study aims to evaluate the underlying mechanism of apelin-13 on cognitive impairment and depressive-like behaviors. A 4-week chronic unpredictable mild stress (CUMS) is used to establish a rat model of depression. Apelin-13(2 ug/day) is administered daily to the rats during the last 1 week. Depressive-like behaviors, including tail suspension test (TST) and sucrose preference test (SPT), are performed. The cognitive functions are established by identify index of novel objects recognition test (NORT) and the number of crossing hidden platform in morris water maze (MWM). The neuronal death is measured by popidium iodide (PI) and flow cytometry. The activity of superoxide dismutase (SOD) and glutathione-peroxidase (GSH-PX) in the hippocampus are determined. The protein expressions of p-AMPK, AMPK, BDNF, FNDC5 and PGC-1α are examined. Golgi staining observed the spine dendritic arborization of the hippocampal cornu ammonis 1 (CA1) subregion. Results showed that apelin-13 improves cognitive impairment and ameliorates depressive-like behaviors. Moreover, apelin-13 significantly inhibits neuronal death via AMPK/PGC-1α/FNDC5/BDNF pathway. Taken together, apelin-13 could exert antidepressant effects via protecting neuron functions, which might be related to the activation of AMPK/PGC-1α/FNDC5/BDNF pathway.

Topics: AMP-Activated Protein Kinases; Animals; Antidepressive Agents; Apelin; Brain-Derived Neurotrophic Factor; Depression; Disease Models, Animal; Fibronectins; Glutathione; Hippocampus; Intercellular Signaling Peptides and Proteins; Iodides; Peroxidases; Rats; Stress, Psychological; Sucrose; Superoxide Dismutase

Cardiotoxicity can be induced by the commonly used amide local anesthetic, bupivacaine. Bupivacaine can inhibit protein kinase B (AKT) phosphorylation and activated adenosine monophosphate-activated protein kinase alpha (AMPKα). It can decouple mitochondrial oxidative phosphorylation and enhance reactive oxygen species (ROS) production. Apelin enhances the phosphatidylinositol 3-kinase (PI3K)/AKT and AMPK/acetyl-CoA carboxylase (ACC) pathways, promotes the complete fatty acid oxidation in the heart, and reduces the release of ROS. In this study, we examined whether exogenous (Pyr1) apelin-13 could reverse bupivacaine-induced cardiotoxicity.. We used the bupivacaine-induced inhibition model in adult male Sprague Dawley (SD) rats (n = 48) and H9c2 cardiomyocyte cell cultures to explore the role of apelin-13 in the reversal of bupivacaine cardiotoxicity, and its possible mechanism of action. AMPKα, ACC, carnitine palmitoyl transferase (CPT), PI3K, AKT, superoxide dismutase 1 (SOD1), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (p47-phox) were quantified. Changes in mitochondrial ultrastructure were examined, and mitochondrial DNA, cell viability, ROS release, oxygen consumption rate (OCR) were determined.. Apelin-13 reduced bupivacaine-induced mitochondrial DNA lesions in SD rats (P < .001), while increasing the expression of AMPKα (P = .007) and PI3K (P = .002). Furthermore, apelin-13 blocked bupivacaine-induced depolarization of the mitochondrial membrane potential (P = .019) and the bupivacaine-induced increases in ROS (P = .001). Also, the AMPK pathway was activated by bupivacaine as well as apelin-13 (P = .002) in H9c2 cardiomyocytes. Additionally, the reduction in the PI3K expression by bupivacaine was mitigated by apelin-13 in H9c2 cardiomyocytes (P = .001). While the aforementioned changes induced by bupivacaine were not abated by apelin-13 after pretreatment with AMPK inhibitor compound C; the bupivacaine-induced changes were still mitigated by apelin-13, even when pretreated with PI3K inhibitor-LY294002.. Apelin-13 treatment reduced bupivacaine-induced oxidative stress, attenuated mitochondrial morphological changes and mitochondrial DNA damage, enhanced mitochondrial energy metabolism, and ultimately reversed bupivacaine-induced cardiotoxicity. Our results suggest a role for the AMPK in apelin-13 reversal of bupivacaine-induced cardiotoxicity.

Topics: AMP-Activated Protein Kinases; Animals; Bupivacaine; Cardiotoxicity; Cell Line; Disease Models, Animal; DNA Damage; Heart Diseases; Intercellular Signaling Peptides and Proteins; Male; Mitochondria, Heart; Myocytes, Cardiac; Oxidative Stress; Phosphatidylinositol 3-Kinase; Rats, Sprague-Dawley; Signal Transduction

It has been reported that apelin-13 possesses neuroprotective effects against cerebral ischemia/reperfusion injury (IRI). Disabilities in sense, movement and balance are the major stroke complications which, result in a high rate of mortality. Here, effects of intravenous (IV) injection of apelin-13 on the severity of neural death, infarct volume, neurological defects and its association with nitric oxide (NO) were investigated. A rat model of cerebral IRI was created by middle cerebral artery occlusion (MCAO) for 60 min and restoration of blood flow for 23 h. Animals were randomly assigned into six groups: sham, ischemia (MCAO), vehicle (MCAO + PBS) and three treatment groups (MCAO + apelin-13 in 10, 20, 40 μg/kg doses, IV). All injections were carried out via tail vein injection 5 min before reperfusion. Neural loss and infarct volume were evaluated by Nissl and 2,3,5-triphenyltetrazolium chloride (TTC) staining, respectively. Neurological defects were scored by standard modified criteria. Serum NO was measured by colorimetric method. Apelin-13 in doses of 20 and 40 μg/kg significantly reduced neural death, infarct volume and disturbance of sensory-motor balance compared to control and vehicle groups (p < 0.05). Serum NO levels reduced in MCAO groups compared to sham. Apelin-13 restored serum NO levels at 20 μg/kg dose (p < 0.05). Our data showed beneficial effect of IV injection of apelin-13 on sensory-motor balance defects by reducing neural death and restoration of serum NO levels. The present study shows the validity of apelin-13 in treatment of ischemic stroke in different administration methods.

Topics: Animals; Disease Models, Animal; Infarction, Middle Cerebral Artery; Injections, Intravenous; Intercellular Signaling Peptides and Proteins; Male; Motor Skills; Neuroprotective Agents; Nitric Oxide; Rats; Rats, Wistar; Reperfusion Injury

Apelin receptor (APJ) activation by apelin-13 (APLN-13) engages both Gαi proteins and β-arrestins, stimulating distinct intracellular pathways and triggering physiological responses like enhanced cardiac contractility. Substituting the C-terminal phenylalanine of APLN-13 with α-methyl-l-phenylalanine [(l-α-Me)Phe] or p-benzoyl-l-phenylalanine (Bpa) generates biased analogs inducing APJ functional selectivity toward Gαi proteins. Using these original analogs, we proposed to investigate how the canonical Gαi signaling of APJ regulates the cardiac function and to assess their therapeutic impact in a rat model of isoproterenol-induced myocardial dysfunction. In vivo and ex vivo infusions of either Bpa or (l-α-Me)Phe analogs failed to enhance rats' left ventricular (LV) contractility compared with APLN-13. Inhibition of Gαi with pertussis toxin injection optimized the cardiotropic effect of APLN-13 and revealed the inotropic impact of Bpa. Moreover, both APLN-13 and Bpa efficiently limited the forskolin-induced and PKA-dependent phosphorylation of phospholamban at the Ser16 in neonatal rat ventricular myocytes. However, only Bpa significantly reduced the inotropic effect of forskolin infusion in isolated-perfused heart, highlighting its efficient bias toward Gαi. Compared with APLN-13, Bpa also markedly improved isoproterenol-induced myocardial systolic and diastolic dysfunctions. Bpa prevented cardiac weight increase, normalized both ANP and BNP mRNA expressions, and decreased LV fibrosis in isoproterenol-treated rats. Our results show that APJ-driven Gαi/adenylyl cyclase signaling is functional in cardiomyocytes and acts as negative feedback of the APLN-APJ-dependent inotropic response. Biased APJ signaling toward Gαi over the β-arrestin pathway offers a promising strategy in the treatment of cardiovascular diseases related to myocardial hypertrophy and high catecholamine levels.

Topics: Adenylyl Cyclases; Animals; Apelin; Apelin Receptors; Calcium-Binding Proteins; Cells, Cultured; Cyclic AMP-Dependent Protein Kinases; Disease Models, Animal; GTP-Binding Protein alpha Subunits; Intercellular Signaling Peptides and Proteins; Isolated Heart Preparation; Isoproterenol; Ligands; Male; Myocytes, Cardiac; Phosphorylation; Rats, Sprague-Dawley; Signal Transduction; Ventricular Dysfunction, Left; Ventricular Function, Left

The present study aimed to determine whether apelin-13 could attenuate cardiac fibrosis via inhibiting the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway to inhibit reactive oxygen species in heart failure (HF) rats. HF models were established by inducing ischemia myocardial infarction (MI) through ligation of the left anterior descending artery in Sprague-Dawley (SD) rats. MI-induced changes in hemodynamics and cardiac function were reversed by apelin-13 administration. The increases in the levels of collagen I, collagen III, α-smooth muscle actin (SMA), and transforming growth factor-β (TGF-β) in the heart of MI rats and cardiac fibroblasts (CFs) treated with angiotensin (Ang) II were inhibited by apelin-13. The levels of PI3K and p-Akt increased in Ang II-treated CFs, and these increases were blocked by apelin-13. The PI3K overexpression reversed the effects of apelin-13 on Ang II-induced increases in collagen I, collagen III, α-SMA, and TGF-β, NADPH oxidase activity and superoxide anions in CFs. Apelin-13 reduced the increases in the levels of NADPH oxidase activity and superoxide anions in the heart of MI rats and CFs with Ang II treatment. The results demonstrated that apelin-13 improved cardiac dysfunction, impaired cardiac hemodynamics, and attenuated fibrosis of CFs induced by Ang II via inhibiting the PI3K/Akt signaling pathway to inhibit oxidative stress.

Topics: Angiotensin II; Animals; Disease Models, Animal; Echocardiography; Fibroblasts; Fibrosis; Heart; Heart Failure; Humans; Injections, Intraperitoneal; Intercellular Signaling Peptides and Proteins; Male; Myocardial Infarction; Myocardium; Oxidative Stress; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Signal Transduction

This study aimed to explore the effect of Apelin-13 in protecting rats against spinal cord ischemia reperfusion injury (SCIR), as well as the related molecular mechanisms.. One week prior to the experiment, experimental Sprague-Dawley rats were injected with Apelin-13 and the autophagy activator rapamycin through the tail vein once a day for 7 consecutive days. The SCIR rat model was prepared through the abdominal aorta clamping method. At 72 h after injury, the spinal cord tissue water content, infarct volume, and normal neuron count were determined to evaluate the degree of spinal cord tissue injury in the rats. The Basso-Beattie-Bresnahan scoring standard was adopted for functional scoring of the rat hind leg, to reflect the post-injury motor function. At 72 h after injury, changes in mitochondrial membrane potential, reactive oxygen species content, and mitochondrial ATP were detected. ELISA was carried out to detect the malonaldehyde content, as well as catalase, superoxide dismutase, and glutathione catalase activities in spinal cord tissues at 72 h after injury. Quantitative chemistry was conducted to examine the contents of nitric oxide (NO) and endothelial nitric oxide synthase (eNOS) in spinal cord tissues. Finally, the expression of autophagy-related proteins, Beclin1, ATG5, and LC3, in spinal cord tissues was detected through the Western blotting assay.. Apelin-13 pretreatment alleviated SCIR, promoted motor function recovery, suppressed mitochondrial dysfunction, resisted oxidative stress, and inhibited autophagy in spinal cord tissues following ischemia reperfusion injury.. Apelin-3 exerts protection against SCIR by suppressing autophagy.

Topics: Animals; Autophagy; Disease Models, Animal; Dose-Response Relationship, Drug; Injections, Intravenous; Intercellular Signaling Peptides and Proteins; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Spinal Cord Ischemia; Structure-Activity Relationship

Aberrant proliferation of vascular smooth muscle cells (VSMC) is a critical contributor to the pathogenesis of atherosclerosis (AS). Our previous studies have demonstrated that apelin-13/APJ confers a proliferative response in VSMC, however, its underlying mechanism remains elusive. In this study, we aimed to investigate the role of mitophagy in apelin-13-induced VSMC proliferation and atherosclerotic lesions in apolipoprotein E knockout (ApoE-/-) mice. Apelin-13 enhances human aortic VSMC proliferation and proliferative regulator proliferating cell nuclear antigen expression in dose and time-dependent manner, while is abolished by APJ antagonist F13A. We observe the engulfment of damage mitochondria by autophagosomes (mitophagy) of human aortic VSMC in apelin-13 stimulation. Mechanistically, apelin-13 increases p-AMPKα and promotes mitophagic activity such as the LC3I to LC3II ratio, the increase of Beclin-1 level and the decrease of p62 level. Importantly, the expressions of PINK1, Parkin, VDAC1, and Tom20 are induced by apelin-13. Conversely, blockade of APJ by F13A abolishes these stimulatory effects. Human aortic VSMC transfected with AMPKα, PINK1, or Parkin and subjected to apelin-13 impairs mitophagy and prevents proliferation. Additional, apelin-13 not only increases the expression of Drp1 but also reduces the expressions of Mfn1, Mfn2, and OPA1. Remarkably, the mitochondrial division inhibitor-1(Mdivi-1), the pharmacological inhibition of Drp1, attenuates human aortic VSMC proliferation. Treatment of ApoE-/- mice with apelin-13 accelerates atherosclerotic lesions, increases p-AMPKα and mitophagy in aortic wall in vivo. Finally, PINK1-/- mutant mice with apelin-13 attenuates atherosclerotic lesions along with defective in mitophagy. PINK1/Parkin-mediated mitophagy promotes apelin-13-evoked human aortic VSMC proliferation by activating p-AMPKα and exacerbates the progression of atherosclerotic lesions.

Topics: AMP-Activated Protein Kinases; Animals; Aortic Diseases; Atherosclerosis; Case-Control Studies; Cell Proliferation; Cells, Cultured; Disease Models, Animal; Humans; Intercellular Signaling Peptides and Proteins; Male; Mice, Inbred C57BL; Mice, Knockout, ApoE; Mitochondria, Muscle; Mitophagy; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphorylation; Plaque, Atherosclerotic; Protein Kinases; Signal Transduction; Ubiquitin-Protein Ligases

The dopaminergic neurodegeneration in the substantia nigrapars compacta (SNpc) and striatum of the midbrain is the important pathological feature of Parkinson's disease (PD). It has been shown that autophagy and endoplasmic reticulum stress (ERS) are involved in the occurrence and development of PD. The neuropeptide Apelin-13 is neuroprotective in the neurological diseases such as PD, Alzheimer's disease and cerebral ischemic stroke. In the present work, we investigated the neuroprotective effects of Apelin-13 on ERS and autophagy in the dopaminergic neurodegeneration of SNpc of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridin (MPTP)-treated mice. The intranigral injection of Apelin-13 alleviated the behavioral dysfunction and dopaminergic neurodegeneration induced by MPTP. After the exposure to MPTP, the expression of tyrosine hydroxylase (TH) was significantly decreased as well as the increased α-synuclein expression, which was significantly reversed by the intranigral injection of Apelin-13. Also, Apelin-13 significantly reversed the decreasing autophagy induced by MPTP which was indicated by the up-regulation of LC3B-II and Beclin1 and down-regulation of p62. And MPTP-induced ERS such as IRE1α, XBP1s, CHOP and GRP78 was significantly inhibited by Apelin-13. Taken together, Apelin-13 protects dopaminergic neurons in MPTP-induced PD model mice in vivo through inhibiting ERS and promoting autophagy, which contributes to the therapy for PD in the future.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; alpha-Synuclein; Animals; Apelin; Autophagy; Beclin-1; Brain; Corpus Striatum; Disease Models, Animal; Dopamine; Dopaminergic Neurons; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Intercellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Parkinson Disease; Substantia Nigra; Tyrosine 3-Monooxygenase

Critical lower-limb ischemia (CLLI) is characterized by high morbidity and mortality. The aim of this study was to explore the effectiveness of the combination of cell therapy with apelin-13 and hyperbaric oxygen in CLLI animal model.. The experimental ischemic rats were divided into five groups, including negative control, bone marrow derived mononuclear cells (BM-MNCs), apelin-13, hyperbaric oxygen treatment (HBOT) and apelin-13 with HBOT group. Each group was composed of 10 rats. Endothelial progenitor cells (EPCs) derived from bone marrow were transplanted into the ischemia rat model. After 3 weeks of transplantation, the formation of new vessels was evaluated by examining cluster of differentiation (CD)31, CD34 and vascular endothelial growth factor receptor 2 (VEGFR-2) expressions as well as a direct vision of vessels by hematoxylin and eosin (HE) staining and immunohistochemistry.. Compared with the negative control group, both angiogenic factors expressions and the number of new vessels increased notably by the transplantation of BM-MNCs in the ischemic models. Apelin-13 or HBOT alone improved the efficacy within limit while the combination of the three elements remarkably promoted the neovascularization in ischemic limbs.. BM-MNC induced angiogenesis in the ischemic limbs and was considered an effective resource for cell therapy. The preliminary data of this study showed that the combination of cell therapy with apelin-13 and HBOT improved the efficacy of angiogenesis.

Topics: Animals; Antigens, CD34; Combined Modality Therapy; Disease Models, Animal; Endothelial Progenitor Cells; Gene Expression Regulation; Hindlimb; Hyperbaric Oxygenation; Intercellular Signaling Peptides and Proteins; Ischemia; Male; Neovascularization, Physiologic; Platelet Endothelial Cell Adhesion Molecule-1; Rats; Vascular Endothelial Growth Factor Receptor-2

The peptide apelin and its receptor APJ are found to express in multiple brain regions, especially in the regions such as the hippocampus and hypothalamus that play important roles in stress and depression. The distribution of apelin and APJ suggests that the apelinergic signaling may be a key mediator in the development of stress-related depressive behavior. We recently demonstrated that intracerebroventricular (i.c.v) injection of apelin-13 exerts an antidepressant-like activity in the rat forced swimming test (FST). However, the possible brain region mediating apelin-13's antidepressant-like activity remains unclear. In the present study, we determined whether the hippocampus and hypothalamus are the possible regions mediating antidepressant-like activity of apelin-13. We found that forced swimming exposure upregulated apelin and APJ protein expression levels in the hippocampus but not hypothalamus in rats. Further, intrahippocampal injection of apelin-13 exerted an antidepressant-like activity (as indicated by a decreased immobility behavior), and intrahippocampal infusion of APJ receptor antagonist F13A blocked the antidepressant-like activity produced by i.c.v injection of apelin-13 in the FST. Moreover, intrahypothalamic injection of apelin-13 did not affect the immobility behavior in the FST. These findings suggest that the hippocampus, but not hypothalamus, is a critical site mediating antidepressant-like activity of apelin-13 in rats.

Topics: Animals; Antidepressive Agents; Apelin Receptors; Depressive Disorder; Disease Models, Animal; Hippocampus; Hypothalamus; Intercellular Signaling Peptides and Proteins; Male; Motor Activity; Rats, Sprague-Dawley; Stress, Psychological

Neuronal apoptosis plays important roles in the early brain injury after subarachnoid hemorrhage (SAH). This study first showed that inhibition of activating transcription factor 6 (ATF6) by apelin-13 could reduce endoplasmic reticulum (ER)-stress-mediated apoptosis and blood-brain-barrier (BBB) disruption after SAH. We chose apelin-13, ATF6 and CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) siRNAs to verify the hypothesis. Brain water content, neurological behavior and Evans Blue (EB) were assessed at 24 h after SAH. Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) were applied to evaluate the expression of targets in both protein and mRNA levels. Neuronal apoptosis was assessed with Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) and caspase-3 staining. The results showed that the levels of ATF6, and its downstream protein, CHOP were upregulated and reached the peak at 24 h after SAH. ATF6 was highly expressed in neurons. The administration of apelin-13 could significantly reduce the mRNA and protein levels of ATF6, and its downstream targets, CHOP and caspase-3, but increase the Bcl-2/Bax ratio, Claudin-5, Occludin and ZO-1. What's more, the administration of apelin-13 could reduce brain edema, ameliorate BBB disruption and improve neurological functions. However, the CHOP siRNA could significantly reverse the pro-apoptotic effect induced by the increased ATF6 level after SAH. Apelin-13 could exert its neuroprotective effects via suppression of ATF6/CHOP arm of ER-stress-response pathway in the early brain injury after SAH.

Topics: Activating Transcription Factor 6; Animals; Apoptosis; Blood-Brain Barrier; Brain Edema; Brain Injuries; Disease Models, Animal; Intercellular Signaling Peptides and Proteins; Male; Neurons; Neuroprotective Agents; Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction; Subarachnoid Hemorrhage; Time Factors; Transcription Factor CHOP

Apelin has been reported to be associated with multiple physiological processes in the cardiovascular system. The aim of the present study was to investigate the effects of Apelin‑13 administration on cardiac function, hyperglycemia, insulin resistance (IR), dyslipidemia, endothelial function, inflammation and glucose metabolism in type 2 diabetic Goto‑Kakizaki (GK) rats, and compare the protective effects of Apelin‑13 with metformin or atorvastatin. In the present study, type 2 diabetes was induced in male Goto‑Kakizaki (GK) rats fed with high‑fat diet (HFD). Simultaneously, the rats were treated with metformin (350 mg/kg/d, by gavage), atorvastatin (50 mg/kg/d, by gavage) or Apelin‑13 (200 µg/kg/d, intraperitoneal injection) once daily for 4 consecutive weeks. Hemodynamic parameters were examined by RM6240BD multi‑channel physiological signal monitoring. Fasting plasma glucose (FPG), fasting insulin (FINS), homeostasis model assessment for insulin resistance (HOMA‑IR), total cholesterol (TC), triglyceride (TG), high density lipoprotein‑cholesterol (HDL‑C), low density lipoprotein‑cholesterol (LDL‑C), endothelin‑1 (ET‑1), nitric oxide (NO), constitutive nitric oxide synthase (cNOS) activity, tumor necrosis factor‑α (TNF‑α), leptin and Apelin‑12 levels were measured. Western blotting was performed to determine the levels of Apelin‑12, glucose transporter 4 (GLUT4) and phosphorylated (p)‑5'adenosine monophosphate‑activated protein kinase (AMPK) α2. It was demonstrated that Apelin‑13 decreased heart rate, left ventricular end‑diastolic pressure, FPG, FINS, HOMA‑IR, TC, TG, LDL‑C, ET‑1, TNF‑α and leptin, whereas it increased the rise and fall of maximum rate of left ventricular pressure, HDL‑C, NO, cNOS activity and Apelin‑12 compared with the GK‑HFD group. In addition, GLUT4 and p‑AMPKα2 levels in myocardial tissues were elevated by administration of Apelin‑13. This protective effect of Apelin‑13 was comparable to that of metformin or atorvastatin. Overall, the present study demonstrated that administration ofApelin‑13 may be a promising therapeutic agent for the treatment of type 2 diabetes and metabolic syndrome.

Topics: Animals; Atorvastatin; Biomarkers; Blood Glucose; Cardiovascular Diseases; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diet, High-Fat; Disease Models, Animal; Energy Metabolism; Heart Function Tests; Hemodynamics; Intercellular Signaling Peptides and Proteins; Lipid Metabolism; Male; Metformin; Oxidation-Reduction; Protective Agents; Rats

Apelin-13 has been found to have protective effects on many neurological diseases, including cerebral ischemia. However, whether Apelin-13 acts on blood-brain barrier (BBB) disruption following cerebral ischemia is largely unknown. Aquaporin-4 (AQP4) has a close link with BBB due to the high concentration in astrocyte foot processes and regulation of astrocytes function. Here, we aimed to test Apelin-13's effects on ischemic BBB injury and examine whether the effects were dependent on AQP4.. We detected the expression of AQP4 induced by Apelin-13 injection at 1, 3, and 7 days after middle cerebral artery occlusion. Meanwhile, we examined the effects of Apelin-13 on neurological function, infarct volume, and BBB disruption owing to cerebral ischemia in wild type mice, and tested whether such effects were AQP4 dependent by using AQP4 knock-out mice. Furthermore, we assessed the possible signal transduction pathways activated by Apelin-13 to regulate AQP4 expression via astrocyte cultures.. It was found that Apelin-13 highly increased AQP4 expression as well as reduced neurological scores and infarct volume. Importantly, Apelin-13 played a role of BBB protection in both types of mice by reducing BBB permeability, increased vascular endothelial growth factor, upregulated endothelial nitric oxide synthase, and downregulated inducible NOS. In morphology, we demonstrated Apelin-13 suppressed tight junction opening and endothelial cell swelling via electron microscopy detection. Meanwhile, Apelin-13 also alleviated apoptosis of astrocytes and promoted angiogenesis. Interestingly, effects of AQP4 on neurological function and infarct volume varied with time course, while AQP4 elicited protective effects on BBB at all time points. Statistical analysis of 2-way analysis of variance with replication indicated that AQP4 was required for these effects. In addition, Apelin-13 upregulated phosphorylation of extracellular signal-regulated kinase (ERK) and Akt as well as AQP4 protein in cultured astrocytes. The latter was inhibited by ERK and phosphatidylinositol 3'-kinase (PI3K) inhibitors.. Our data suggest that Apelin-13 protects BBB from disruption after cerebral ischemia both morphologically and functionally, which is highly associated with the increased levels of AQP4, possibly through the activation of ERK and PI3K/Akt pathways. This study provides double targets to protection of ischemic BBB damage, which can present new insights to drugs development.

Topics: Animals; Apoptosis; Aquaporin 4; Astrocytes; Blood-Brain Barrier; Capillary Permeability; Cells, Cultured; Disease Models, Animal; Endothelial Cells; Extracellular Signal-Regulated MAP Kinases; Infarction, Middle Cerebral Artery; Intercellular Signaling Peptides and Proteins; Male; Mice, Knockout; Neovascularization, Physiologic; Neuroprotective Agents; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinase; Phosphorylation; Proto-Oncogene Proteins c-akt; Signal Transduction; Tight Junctions; Time Factors; Vascular Endothelial Growth Factor A

Apelin, an endogenous ligand for apelin receptor (APJ), is reported to be involved in cardiomyocyte hypertrophy. In this study, we explored the mechanism of cardiomyocyte hypertrophy induced by apelin-13/APJ system. Left ventricular hypertrophy (LVH) rat model was established by constricting the abdominal aorta. Western blots were used for protein expression in LVH rats and cultured H9c2 cardiomyocytes. Transmission electron microscopy (TEM) was used to monitor morphological features of cells. In addition, the diameter and volume of H9c2 cells were detected by Scepter™ Handheld Automated Cell Counter. We found that the APJ was increased, but caveolin-1 was decreased in heart of LVH rats. In addition, caveolin-1 was suppressed by apelin-13, and this effect was reversed by APJ antagonist F13A in cultured H9c2 cardiomyocytes. Apelin-13 not only stimulated the formation of autophagolysosomes, autophagosome, and lysosomes but also increased the expression of autophagic markers Beclin-1 and LC3II/I. Besides, the increase of Beclin-1 and LC3 II/I was reversed by F13A or caveolin-1 overexpression and further enhanced by caveolin inhibitor. Furthermore, the cardiomyocyte hypertrophy index brain natriuretic peptide (BNP) induced by apelin-13 was blunt by F13A or autophagy inhibitor 3-methyladenine and further promoted by caveolin inhibitor. And caveolin-1 overexpression reduced the diameter and volume of H9c2 cells induced by apelin-13. Our study indicates that caveolin-1-autophagy pathway mediated cardiomyocyte hypertrophy induced by apelin-13/APJ system, which might provide a novel therapeutic target for cardiac hypertrophy disease.

Topics: Adenine; Animals; Aorta, Abdominal; Apelin Receptors; Autophagosomes; Autophagy; Beclin-1; Caveolin 1; Cell Line; Disease Models, Animal; Hypertrophy, Left Ventricular; Intercellular Signaling Peptides and Proteins; Microtubule-Associated Proteins; Myocytes, Cardiac; Natriuretic Peptide, Brain; Phosphatidylinositol 3-Kinases; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled

Apelin-13 was recently proposed as an alternative to the recommended β-adrenergic drugs for supporting endotoxin-induced myocardial dysfunction. Since Apelin-13 signals through its receptor (Apelin peptide jejunum) to exert singular inotropic/vasotropic actions and to optimize body fluid balance, this candidate pathway might benefit septic shock management. Whether the newly discovered ELABELA (ELA), a second endogenous ligand of the Apelin peptide jejunum receptor highly expressed in the kidney, further improves cardio-renal impairment remains unknown.. Interventional study in a rat model of septic shock (128 adult males) to assess the effects of ELA and Apelin-13 on vascular and cardio-renal function. Experiments were performed in a tertiary care University-based research institute.. Polymicrobial sepsis-induced cardiac dysfunction was produced by cecal ligation puncture to assess hemodynamic efficacy, cardioprotection, and biomechanics under acute or continuous infusions of the apelinergic agonists ELA or Apelin-13 (39 and 15 µg/kg/hr, respectively) versus normal saline.. Apelinergic agonists improved 72-hour survival after sepsis induction, with ELA providing the best clinical outcome after 24 hours. Apelinergic agonist infusion counteracted cecal ligation puncture-induced myocardial dysfunction by improving left ventricular pressure-volume relationship. ELA-treated cecal ligation puncture rats were the only group to 1) display a significant improvement in left ventricular filling as shown by increased E-wave velocity and left ventricular end-diastolic volume, 2) exhibit a higher plasma volume, and 3) limit kidney injury and free-water clearance. These beneficial renal effects were superior to Apelin-13, likely because full-length ELA enabled a distinctive regulation of pituitary vasopressin release.. Activation of the apelinergic system by exogenous ELA or Apelin-13 infusion improves cardiovascular function and survival after cecal ligation puncture-induced sepsis. However, ELA proved better than Apelin-13 by improving fluid homeostasis, cardiovascular hemodynamics recovery, and limiting kidney dysfunction in a vasopressinergic-dependent manner.

Topics: Animals; Biomarkers; Cytokines; Disease Models, Animal; Echocardiography; Hemodynamics; Intercellular Signaling Peptides and Proteins; Male; Peptide Hormones; Rats; Real-Time Polymerase Chain Reaction; Shock, Septic

Dobutamine is the currently recommended β-adrenergic inotropic drug for supporting sepsis-induced myocardial dysfunction when cardiac output index remains low after preload correction. Better and safer therapies are nonetheless mandatory because responsiveness to dobutamine is limited with numerous side effects. Apelin-13 is a powerful inotropic candidate that could be considered as an alternative noncatecholaminergic support in the setting of inflammatory cardiovascular dysfunction.. Interventional controlled experimental animal study.. Tertiary care university-based research institute.. One hundred ninety-eight adult male rats.. Using a rat model of "systemic inflammation-induced cardiac dysfunction" induced by intraperitoneal lipopolysaccharide injection (10 mg/kg), hemodynamic efficacy, cardioprotection, and biomechanics were assessed under IV osmotic pump infusions of apelin-13 (0.25 μg/kg/min) or dobutamine (7.5 μg/kg/min).. In this model and in both in vivo and ex vivo studies, apelin-13 compared with dobutamine provoked distinctive effects on cardiac function: 1) optimized cardiac energy-dependent workload with improved cardiac index and lower vascular resistance, 2) upgraded hearts' apelinergic responsiveness, and 3) consecutive downstream advantages, including increased urine output, enhanced plasma volume, reduced weight loss, and substantially improved overall outcomes. In vitro studies confirmed that these apelin-13-driven processes encompassed a significant and rapid reduction in systemic cytokine release with dampening of myocardial inflammation, injury, and apoptosis and resolution of associated molecular pathways.. In this inflammatory cardiovascular dysfunction, apelin-13 infusion delivers distinct and optimized hemodynamic support (including positive fluid balance), along with cardioprotective effects, modulation of circulatory inflammation and extended survival.

Topics: Animals; Body Weight; Cardiac Output; Cardiomyopathies; Cardiotonic Agents; Cytokines; Disease Models, Animal; Dobutamine; Intercellular Signaling Peptides and Proteins; Lipopolysaccharides; Male; Mitogen-Activated Protein Kinases; Myocardium; Nitric Oxide Synthase Type II; Peroxidase; Phosphorylation; Plasma Volume; Rats; Survival Rate; Vascular Resistance; Water-Electrolyte Balance

Apelin is an endogenous ligand for apelin receptor (APJ) with analgesic effect on visceral, analgesic and proanalgesic influences on acute pains in animal models. The purpose of this study was to determine the possible analgesic effects of [Pyr

Topics: Analgesics; Animals; Apoptosis; Caspase 3; Disease Models, Animal; Hyperalgesia; Intercellular Signaling Peptides and Proteins; Male; Motor Activity; Neuralgia; Pain Threshold; Physical Stimulation; Rats; Rats, Wistar; Spinal Cord; Spinal Cord Compression

Elabela/toddler (ELA) is a critical cardiac developmental peptide that acts through the G-protein-coupled apelin receptor, despite lack of sequence similarity to the established ligand apelin. Our aim was to investigate the receptor pharmacology, expression pattern, and in vivo function of ELA peptides in the adult cardiovascular system, to seek evidence for alteration in pulmonary arterial hypertension (PAH) in which apelin signaling is downregulated, and to demonstrate attenuation of PAH severity with exogenous administration of ELA in a rat model.. ELA competed for binding of apelin in human heart with overlap for the 2 peptides indicated by. These results show that ELA is an endogenous agonist of the human apelin receptor, exhibits a cardiovascular profile comparable to apelin, and is downregulated in human disease and rodent PAH models, and exogenous peptide can reduce the severity of cardiopulmonary remodeling and function in PAH in rats. This study provides additional proof of principle that an apelin receptor agonist may be of therapeutic use in PAH in humans.

Topics: Amino Acid Sequence; Animals; Apelin; Binding Sites; Catheterization; Disease Models, Animal; Down-Regulation; Endothelium, Vascular; Heart Ventricles; Humans; Hypertension, Pulmonary; Intercellular Signaling Peptides and Proteins; Male; Molecular Dynamics Simulation; Peptide Hormones; Protein Structure, Tertiary; Rats; Rats, Sprague-Dawley

Apelin-13 is an endogenous peptide with potential analgesic action, although the sites of its analgesic effects remain uncertain and the results are even controversial with regard to its pain modulating action. This study evaluated the possible pain-modulating action of peripherally administered apelin-13 using heat-induced, withdrawal latency to the thermal stimuli, acute pain model in mice. Involvement of peripheral mechanisms was tested, by using the intracellular calcium concentrations as a key signal for nociceptive transmission, in cultured rat dorsal root ganglion (DRG) neurons.. DRG neurons were cultured on glass coverslips following enzymatic digestion and mechanical agitation, and loaded with the calcium-sensitive dye Fura-2 acetoxymethyl ester (1 µM). Intracellular calcium responses in individual DRG neurons were quantified by ratiometric calcium imaging technique.. Peripheral injection of a single dose of apelin-13 (100 mg/kg and 300 mg/kg) significantly decreases the latency to painful stimuli in a dose and time-dependent manner (p < 0.01, p < 0.05, respectively, n = 8 each). Apelin-13 (0.1 µM and 1 µM) did not produce a significant effect on cytoplasmic Ca(2+) ([Ca(2+)](i)) responses, evoked by membrane depolarization, in cultured rat DRG neurons.. Together these results indicate that apelin-13 can cause increased pain sensitivity after peripheral administration, but this effect does not involve calcium mediated signaling in primary sensory neurons.

Topics: Animals; Calcium Signaling; Disease Models, Animal; Fluorescence; Ganglia, Spinal; Hot Temperature; Injections, Intraperitoneal; Intercellular Signaling Peptides and Proteins; Male; Mice, Inbred BALB C; Nociception; Pain; Pain Threshold; Potassium Chloride; Rats, Wistar; Sensory Receptor Cells; Signal Transduction

Hypoxic pretreatment of peripheral blood mononuclear cells (PBMNCs) enhances therapeutic angiogenesis in ischemic tissues after cell transplantation. However, newly formed vessels generated using this approach are immature and insufficient for promoting functional recovery from severe ischemia. In this study, we examined whether apelin-13, a regulator of vessel maturation, could be an effective promoter of therapeutic angiogenesis, following severe limb ischemia. Combinatorial treatment of hypoxic preconditioned PBMNCs with apelin-13 resulted in increased blood perfusion and vascular reactivity in ischemic mouse hindlimbs compared with a monotherapy comprising each factor. Apelin-13 upregulated expression of PDGF-BB and TGF-β1 in hypoxic PBMNCs, as well as that of PDGFR-β in vascular smooth muscle cells (VSMCs). Proliferation and migration of VSMCs treated with apelin-13 was accelerated in the presence of PDGF-BB. Interestingly, expression of an apelin receptor, APJ, in PBMNC was increased under hypoxia but not under normoxia. In addition, an in vitro angiogenesis assay using a co-culture model comprising mouse thoracic aorta, hypoxic PBMNCs, and apelin-13 demonstrated that combinatorial treatment recruited mural cells to sprouted vessel outgrowths from the aortic ring, thereby promoting neovessel maturation. Thus, combinatorial injection of hypoxic PBMNCs and apelin-13 could be an effective therapeutic strategy for patients with severe ischemic diseases.

Topics: Animals; Apelin Receptors; Cell Movement; Cell Proliferation; Cell Transplantation; Cell- and Tissue-Based Therapy; Combined Modality Therapy; Disease Models, Animal; Gene Expression; Hindlimb; Hypoxia; Intercellular Signaling Peptides and Proteins; Ischemia; Ischemic Preconditioning; Leukocytes, Mononuclear; Male; Mice; Neovascularization, Physiologic; Receptors, G-Protein-Coupled

Apelin is a peptide hormone defined as a ligand for G-protein clamped receptor (APJ) receptor. It is indicated in the literature both apelin and APJ are synthesized on the peripheral tissues including the renal tissues. Which roles does the apelin play on the renal tissue has not been completely illuminated yet. This study is designed to determine the possible protective effect of apelin-13 on the kidney I/R injury. Adult male Sprague-Dawley rats were used in this study. In the sham group, right kidneys of the animals were dissected. In the I/R group, right kidney was dissected and ischemia of 45 min was performed, and then reperfusion was applied for 3 h. In the treatment groups, three different doses of apelin were injected at the beginning of the ischemia unlike the I/R group. BUN, Cre, Na, K, Cl, total protein and albumin from serum samples were determined and TNF-α, IL-1β, IL-6, TAS and TOS parameters were read with ELISA reader. MDA, SOD, CAT and GSH-Px enzyme activations from renal tissues were measured. In comparison with the sham and I/R groups, while the serum BUN, CRE, CI and TNF-α levels showed an increase in the groups on which the apelin-13 was applied, Na, total protein, albumin, TAS levels decreased. Serum TOS level of other groups showed an increase by comparison with the sham group. Our results showed that apelin-13 applied after I/R increased the antioxidant enzyme activity in a dose dependent manner, prevented the lipid oxidation and improved the renal functions.

Topics: Acute Kidney Injury; Animals; Antioxidants; Apelin Receptors; Disease Models, Animal; Humans; Intercellular Signaling Peptides and Proteins; Kidney; Kidney Function Tests; Male; Oxidative Stress; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Reperfusion Injury

Adipocytokine apelin-13 is a peptide which could reportedly protect the brain against ischemic reperfusion injury and traumatic brain injury (TBI). Whether apelin-13 has any roles to play in intracerebral hemorrhage (ICH) has not been clarified. We aimed to investigate the roles of apelin-13 in ICH and effects on ICH-induced apoptosis. Firstly, CD-1 mice were subjected to infusion of Type IV collagenase (to induce ICH) or saline (for shams) into the left striatum. ICH animals received intracerebroventricular administration of vehicle, apelin-13 (50μg dissolved in 5μl saline) immediately after ICH. The motor function and the cerebral water content (CWC) as well as blood brain barrier (BBB) disruption were measured, coupled with determination of ICH-induced neural cell death by Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL). The apoptosis-associated proteins caspase-3 and Bcl-2 as well as the brain edema-associated proteins aquaporin-4 (AQP4) and MMP-9 were all assessed with western blotting. The results showed that apelin-13 decreased CWC and reduced Evans blue leakage into injured hemispheres, with the motor function significantly improved. Additionally, apelin-13 also acutely decreased the number of ICH-induced TUNEL-positive (TUNEL(+)) cells at 48h after ICH. The expressions of AQP4, MMP-9, caspse-3 and Bcl-2 were all downregulated by apelin-13 at 24h and 48h after ICH. All these results revealed that apelin-13 attenuated brain edema and reduced cellular death by suppressing apoptosis after ICH in mice.

Topics: Animals; Apoptosis; Blood-Brain Barrier; Brain Edema; Cerebral Hemorrhage; Disease Models, Animal; Intercellular Signaling Peptides and Proteins; Male; Mice; Motor Activity; Neuroprotective Agents

Epilepsy is a common neurological disorder with no effective treatment or cure. Neuropeptide apelin is an endogenous ligand of angiotensin receptor-like 1 (APJ). It has been shown that apelin has protective and anti-neurodegenerative properties. This study was designed to evaluate the effect of apelin-13 on pentylenetetrazole (PTZ)-induced rat model of seizure. Adult male Wistar rats were divided into the experimental groups as follows: control group receiving PTZ; apelin-treated group which received apelin-13 before PTZ; apelin+F13A-treated group which received apelin-13 plus the apelin receptor antagonist (F13A) before PTZ; apelin+naloxone group which received apelin-13+naloxone before PTZ. Behavioral scoring was used to access seizure. The expression level of APJ was measured by western blotting. Neuronal degeneration, apoptosis and astrocyte activation were evaluated by vanadium acid fuchsin (VAF) staining and immunohistochemistry. Our data demonstrated that apelin-13 pretreatment significantly inhibited seizure threshold (p<0.001) and tonic-clonic latency (p<0.001) compared with the control group. In addition, PTZ-induced up-regulation of APJ was attenuated by apelin-13 treatment. Histological and immunohistochemical findings also showed that apelin-13 could protect cortical neurons against PTZ-induced neuroinflammation and apoptosis. In conclusion, apelin-13 has anticonvulsive and neuroprotective properties against PTZ-induced seizure in rats and provided a new pharmacological aspect of the neuropeptide apelin.

Topics: Animals; Anticonvulsants; Apelin Receptors; Apoptosis; Astrocytes; Brain; Disease Models, Animal; Glial Fibrillary Acidic Protein; Intercellular Signaling Peptides and Proteins; Male; Nerve Degeneration; Neurons; Neuroprotective Agents; Pentylenetetrazole; Rats, Wistar; Receptors, G-Protein-Coupled; Seizures

Angiogenesis plays an important role in myocardial infarction. Apelin and its natural receptor (angiotensin II receptor-like 1, AGTRL-1 or APLNR) induce sprouting of endothelial cells in an autocrine or paracrine manner. The aim of this study is to investigate whether apelin can improve the cardiac function after myocardial infarction by increasing angiogenesis in infarcted myocardium. Left ventricular end-diastolic pressure (LVEDP), left ventricular end systolic pressure (LVESP), left ventricular developed pressure (LVDP), maximal left ventricular pressure development (±LVdp/dtmax), infarct size, and angiogenesis were evaluated to analyze the cardioprotective effects of apelin on ischemic myocardium. Assays of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, 5-bromo-2'-deoxyuridine incorporation, wound healing, transwells, and tube formation were used to detect the effects of apelin on proliferation, migration, and chemotaxis of cardiac microvascular endothelial cells. Fluorescein isothiocyanate-labeled bovine serum albumin penetrating through monolayered cardiac microvascular endothelial cells was measured to evaluate the effects of apelin on permeability of microvascular endothelial cells. In vivo results showed that apelin increased ±LV dp/dtmax and LVESP values, decreased LVEDP values (all p < 0.05), and promoted angiogenesis in rat heart after ligation of the left anterior descending coronary artery. In vitro results showed that apelin dose-dependently enhanced proliferation, migration, chemotaxis, and tube formation, but not permeability of cardiac microvascular endothelial cells. Apelin also increased the expression of vascular endothelial growth factor receptors-2 (VEGFR2) and the endothelium-specific receptor tyrosine kinase (Tie-2) in cardiac microvascular endothelial cells. These results indicated that apelin played a protective role in myocardial infarction through promoting angiogenesis and decreasing permeability of microvascular endothelial cells via upregulating the expression of VEGFR2 and Tie-2 in cardiac microvascular endothelial cells.

Topics: Angiogenesis Inducing Agents; Animals; Capillary Permeability; Cardiotonic Agents; Cell Proliferation; Cells, Cultured; Chemotaxis; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelial Cells; Intercellular Signaling Peptides and Proteins; Male; Myocardial Infarction; Myocardium; Neovascularization, Physiologic; Rats, Wistar; Receptor, TIE-2; Recovery of Function; Time Factors; Vascular Endothelial Growth Factor Receptor-2; Ventricular Function, Left; Ventricular Pressure

Apelin is a newly discovered peptide that has been recently shown to have cardioprotective effects in the animal model of myocardial infarction (MI) and ischemia/reperfusion (I/R) injuries. The aim of the present study was to investigate the long term cardioprotective effect of [Pyr1]-apelin-13 in the rat model of MI. Male Wistar rats (n=22) were randomly divided into three groups: (1) sham operated group (2) control MI group and (3) MI treated with apelin (MI-AP group). MI animals were subjected to 30 min of left anterior descending coronary artery (LAD) ligation and 14 days of reperfusion. 24h after LAD ligation, apelin (10 mol/kg/day) was administered i.p. for 5 days. Blood sampling was performed at days 1, 3, 5 and 7 after MI for determination of serum changes of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), malondialdehyde (MDA) and nitric oxide (NO). Myocardial infarct size (IS) and hemodynamic function were also measured at the end of the study at day 14. We found out that post infarct treatment with apelin decreases infarct size, serum levels of LDH, CK-MB and MDA and increases heart rate and serum level of NO in the consecutive days, but there were no significant differences in blood pressure in the MI-AP group in comparison with MI. In conclusion, apelin has long term cardioprotective effects against myocardial infarction through attenuation of cardiac tissue injury and lipid peroxidation and enhancement of NO production.

Topics: Animals; Blood Pressure; Cardiotonic Agents; Coronary Vessels; Creatine Kinase, MB Form; Disease Models, Animal; Heart Rate; Hemodynamics; Intercellular Signaling Peptides and Proteins; L-Lactate Dehydrogenase; Male; Malondialdehyde; Myocardial Infarction; Myocardial Reperfusion Injury; Nitric Oxide; Oxidative Stress; Rats; Rats, Wistar; Reactive Oxygen Species

Asymmetric dimethylarginine (ADMA) is a risk factor for endothelial dysfunction. The polypeptide apelin has biphasic effects on blood vessels in vivo and in vitro. We investigated the effect of apelin-13 on ADMA-damaged vessels. Rats were divided among ADMA-treated and control groups, which were treated with ADMA (10 mg·(kg body mass)(-1)·day(-1)) or saline, respectively, for 4 weeks. Systolic blood pressure (SBP) was measured before and after the injection of apelin-13. The ultrastructure of endothelial cells in caudal arteries was examined using transmission electron microscopy. The reactivities of isolated caudal artery rings were observed after exposure to apelin-13, and myosin light chain (MLC) phosphorylation was assessed by immunohistochemistry in rings treated with or without apelin-13. ADMA induced hypertension and endothelial dysfunction. After injection of apelin-13, SBP declined in the control group but was elevated in the ADMA-treated group. In vitro, apelin-13 caused relaxation in rings in the control group, but it contracted rings in the ADMA-treated group. Apelin-13 promoted MLC phosphorylation in vascular smooth muscle cells (VSMCs) in the ADMA group. These results indicate that apelin-13 might pass through ADMA-damaged endothelium and act on VSMCs to increase MLC phosphorylation, thus contributing to vasoconstriction and exacerbating hypertension.

Topics: Animals; Arginine; Blood Pressure; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Hypertension; Injections, Intravenous; Intercellular Signaling Peptides and Proteins; Male; Myosin Light Chains; Nitric Oxide; Phosphorylation; Rats; Rats, Sprague-Dawley; Time Factors; Vasoconstriction; Vasodilation; von Willebrand Factor

Glucose is absorbed into intestine cells via the sodium glucose transporter 1 (SGLT-1) and glucose transporter 2 (GLUT2); various peptides and hormones control this process. Apelin is a peptide that regulates glucose homeostasis and is produced by proximal digestive cells; we studied whether glucose modulates apelin secretion by enterocytes and the effects of apelin on intestinal glucose absorption.. We characterized glucose-related luminal apelin secretion in vivo and ex vivo by mass spectroscopy and immunologic techniques. The effects of apelin on (14)C-labeled glucose transport were determined in jejunal loops and in mice following apelin gavage. We determined levels of GLUT2 and SGLT-1 proteins and phosphorylation of AMPKα2 by immunoblotting. The net effect of apelin on intestinal glucose transepithelial transport was determined in mice.. Glucose stimulated luminal secretion of the pyroglutaminated apelin-13 isoform ([Pyr-1]-apelin-13) in the small intestine of mice. Apelin increased specific glucose flux through the gastric epithelial barrier in jejunal loops and in vivo following oral glucose administration. Conversely, pharmacologic apelin blockade in the intestine reduced the increased glycemia that occurs following oral glucose administration. Apelin activity was associated with phosphorylation of AMPKα2 and a rapid increase of the GLUT2/SGLT-1 protein ratio in the brush border membrane.. Glucose amplifies its own transport from the intestinal lumen to the bloodstream by increasing luminal apelin secretion. In the lumen, active apelin regulates carbohydrate flux through enterocytes by promoting AMPKα2 phosphorylation and modifying the ratio of SGLT-1:GLUT2. The glucose-apelin cycle might be pharmacologically handled to regulate glucose absorption and assess better control of glucose homeostasis.

Topics: Analysis of Variance; Animals; Biological Transport; Blotting, Western; Carbohydrates; Chromatography, Liquid; Disease Models, Animal; Glucose; Glucose Transporter Type 2; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Intestinal Absorption; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Random Allocation; Reference Values; Sodium-Glucose Transporter 1

Apelin and its cognate G protein-coupled receptor, APJ, constitute a signaling pathway with a positive inotropic effect on cardiac function. Recently, we and other investigators demonstrated that a reduction in myocardial apelin/APJ expression might play a critical role in experimental models of end-stage heart failure (HF). Therefore, we evaluated whether exogenous apelin infusion restores apelin/APJ expression and improves cardiac function in the failing heart of Dahl salt-sensitive hypertensive (DS) rats.. High salt-loaded DS rats were treated with vehicle and pyroglutamylated apelin-13 (Pyr-AP13; 200µg·kg(-1)·day(-1), IP) from the age of 11 to 18 weeks. Decreased end-systolic elastance and percent fractional shortening in failing rats was significantly ameliorated by Pyr-AP13. Pyr-AP13 effectively inhibited vascular lesion formation and suppressed expression of inflammation factors such as tumor necrosis factor-α and interleukin-1β protein. Downregulation of apelin and APJ expression, and phosphorylation of endothelial nitric oxide synthase at Ser(1177) and Akt at Ser(473) in failing rats was significantly increased by Pyr-AP13. Upregulation of NAD(P)H oxidase p22(phox), p47(phox), and gp91(phox) in DS rats was significantly suppressed by Pyr-AP13.. Exogenous apelin-13 may ameliorate cardiac dysfunction and remodeling and restore apelin/APJ expression in DS rats with end-stage HF. Thus, apelin-13 may have significant therapeutic potential for end-stage HF.

Topics: Animals; Apelin Receptors; Blood Pressure; Cardiotonic Agents; Disease Models, Animal; Heart; Heart Failure; Intercellular Signaling Peptides and Proteins; Male; Nitric Oxide Synthase Type III; Phosphorylation; Rats; Rats, Inbred Dahl; Receptors, G-Protein-Coupled; Signal Transduction; Systole; Ventricular Remodeling

The adipocytokine apelin is a peptide that was isolated from a bovine stomach for the first time. This peptide and its receptor are abundantly expressed in the nervous and cardiovascular systems. According to previous studies, apelin-13 protects cardiomyocytes from ischemic injury as well as apoptosis. In addition, this peptide has a neuroprotective effect on hippocampal and cultured mouse cortical neurons against NMDA receptor-mediated excitotoxicity. The present study was conducted to determine whether apelin-13 provides protection in transient focal cerebral ischemia. Focal ischemia was induced by 60-min middle cerebral artery occlusion (MCAO), followed by 23-h reperfusion. Saline as a vehicle and apelin-13 at doses of 25, 50, and 100 μg were injected intracerebroventriculary (ICV) at the beginning of ischemia. Infarct volume ,brain edema, motor dysfunction, and apoptosis were assessed 24 h after MCAO. Treatment with apelin-13 at doses of 50 and 100 μg ICV markedly reduced total infarct volumes by 45 and 55 %, respectively (P < 0.001), but injection of apelin at lower dose (25 μg) did not change infarct volume significantly (P > 0.05). In addition, apelin-13 at doses of 50 and 100 μg reduced brain edema (P < 0.001) and inhibited apoptosis by decreasing caspase-3 activation (P < 0.001). Apelin-13 did not significantly change neurological dysfunction (P > 0.05).

Topics: Animals; Apoptosis; Brain Edema; Brain Ischemia; Caspase 3; Cattle; Disease Models, Animal; Dose-Response Relationship, Drug; Infarction, Middle Cerebral Artery; Injections, Intraventricular; Intercellular Signaling Peptides and Proteins; Male; Neuroprotective Agents; Rats; Rats, Wistar; Severity of Illness Index

Apelin is an endogenous ligand for the angiotensin-like 1 receptor (APJ) and has beneficial effects against myocardial ischemia-reperfusion injury. Little is known about the role of apelin in the homing of vascular progenitor cells (PCs) and cardiac functional recovery postmyocardial infarction (post-MI). The present study investigated whether apelin affects PC homing to the infarcted myocardium, thereby mediating repair and functional recovery post-MI. Mice were infarcted by coronary artery ligation, and apelin-13 (1 mg·kg(-1)·day(-1)) was injected for 3 days before MI and for 14 days post-MI. Homing of vascular PCs [CD133(+)/c-Kit(+)/Sca1(+), CD133(+)/stromal cell-derived factor (SDF)-1α(+), and CD133(+)/CXC chemokine receptor (CXCR)-4(+)] into the ischemic area was examined. Myocardial Akt, endothelial nitric oxide synthase (eNOS), VEGF, jagged1, notch3, SDF-1α, and CXCR-4 expression were assessed at 24 h and 14 days post-MI. Functional analyses were performed on day 14 post-MI. Mice that received apelin-13 treatment demonstrated upregulation of SDF-1α/CXCR-4 expression and dramatically increased the number of CD133(+)/c-Kit(+)/Sca1(+), CD133(+)/SDF-1α(+), and c-Kit(+)/CXCR-4(+) cells in infarcted hearts. Apelin-13 also significantly increased Akt and eNOS phosphorylation and upregulated VEGF, jagged1, and notch3 expression in ischemic hearts. This was accompanied by a significant reduction of myocardial apoptosis. Furthermore, treatment with apelin-13 promoted myocardial angiogenesis and attenuated cardiac fibrosis and hypertrophy together with a significant improvement of cardiac function at 14 days post-MI. Apelin-13 increases angiogenesis and improves cardiac repair post-MI by a mechanism involving the upregulation of SDF-1α/CXCR-4 and homing of vascular PCs.

Topics: AC133 Antigen; Adipokines; Animals; Antigens, CD; Antigens, Ly; Apelin; Apoptosis; Biomarkers; Calcium-Binding Proteins; Cardiomegaly; Cardiotonic Agents; Cell Movement; Cells, Cultured; Chemokine CXCL12; Disease Models, Animal; Fibrosis; Glycoproteins; Intercellular Signaling Peptides and Proteins; Jagged-1 Protein; Membrane Proteins; Mice; Mice, Inbred C57BL; Myocardial Infarction; Myocytes, Cardiac; Neovascularization, Physiologic; Nitric Oxide Synthase Type III; Peptides; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-kit; Receptor, Notch3; Receptors, CXCR4; Receptors, Notch; Recovery of Function; Regeneration; Serrate-Jagged Proteins; Stem Cells; Time Factors; Vascular Endothelial Growth Factor A; Ventricular Function, Left

Apelin is a potent inodilator with recently described antiatherogenic properties. We hypothesized that apelin might also attenuate abdominal aortic aneurysm (AAA) formation by limiting disease-related vascular wall inflammation. C57BL/6 mice implanted with osmotic pumps filled with apelin or saline were treated with pancreatic elastase to create infrarenal AAAs. Mice were euthanized for aortic PCR analysis or followed ultrasonographically and then euthanized for histological analysis. The cellular expression of inflammatory cytokines and chemokines in response to apelin was also assessed in cultured macrophages, smooth muscle cells, and fibroblasts. Apelin treatment resulted in diminished AAA formation, with a 47% reduction in maximal cross-sectional area (0.74 vs. 1.39 mm(2), P < 0.03) and a 57% reduction in macrophage infiltrate (113 vs. 261.3 cells/high-power field, P < 0.0001) relative to the saline-treated group. Apelin infusion was also associated with significantly reduced aortic macrophage colony-stimulating factor expression and decreased monocyte chemattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha mean mRNA levels. Apelin stimulation of cultured macrophages significantly reduced MCP-1 and TNF-alpha mRNA levels relative to baseline (2.03- and 1.89-fold reduction, P < 0.03, respectively) but did not affect intimal adhesion molecule expression or medial or adventitial cell cytokine production. Apelin significantly reduces aneurysm formation in the elastase model of human AAA disease. The mechanism appears to be decreased macrophage burden, perhaps related to an apelin-mediated decrease in proinflammatory cytokine and chemokine activation.

Topics: Animals; Anti-Inflammatory Agents; Aorta, Abdominal; Aortic Aneurysm, Abdominal; Aortitis; Chemokines; Cytokines; Disease Models, Animal; Down-Regulation; Immunohistochemistry; Inflammation Mediators; Infusion Pumps, Implantable; Intercellular Signaling Peptides and Proteins; Macrophages; Male; Mice; Mice, Inbred C57BL; NIH 3T3 Cells; Pancreatic Elastase; Rats; Reverse Transcriptase Polymerase Chain Reaction; Ultrasonography

Apelin is a peptide that plays an important role in heart physiology and pathophysiology, inflammation, and angiogenesis. We evaluated whether the endogenous apelin system is involved in the pathogenesis of the hepatic remodeling and cardiovascular and renal complications occurring in advanced liver disease. The circulating levels of apelin, the messenger RNA (mRNA) and protein expression of apelin and apelin receptor, the immunohistological detection of apelin and apelin receptor, and the effects induced by the chronic administration of an apelin receptor antagonist on fibrosis and vessel density were evaluated in rats with cirrhosis and ascites and in control rats. The serum levels of apelin in patients with cirrhosis were also measured. Apelin levels were higher in rats with cirrhosis than in controls. Apelin mRNA showed a four-fold rise only in hepatic tissue, but not in the lung, heart, or kidney of rats with cirrhosis. These animals also showed hepatic apelin receptor mRNA levels 300 times higher than controls. Apelin was highly expressed by stellate cells, whereas apelin receptor was overexpressed in the hepatic parenchyma of animals with cirrhosis. Rats with cirrhosis treated with the apelin receptor antagonist showed diminished hepatic fibrosis and vessel density, improved cardiovascular performance, and renal function and lost ascites. Human patients also showed a marked increase in apelin levels.. The selective hepatic activation of the apelin system, together with the drop in fibrosis and neoangiogenesis and the improvement in cardiovascular and excretory function resulting from apelin receptor blockade, points to the hepatic apelin system as a novel therapeutic target in liver disease.

Topics: Adult; Animals; Apelin; Blood Pressure; Carbon Tetrachloride; Carrier Proteins; Case-Control Studies; Disease Models, Animal; Female; Humans; Intercellular Signaling Peptides and Proteins; Liver; Liver Cirrhosis; Male; Middle Aged; Rats; Rats, Wistar; Renin-Angiotensin System; RNA, Messenger; Sympathetic Nervous System; Vascular Resistance

Protection against myocardial ischemia-reperfusion (I/R) injury involves activation of phosphatidylinositol-3-OH kinase (PI3K)- Akt/protein kinase B and p44/42 mitogen-activated protein kinase (MAPK), components of the reperfusion injury salvage kinase (RISK) pathway. The adipocytokine, apelin, activates PI3K-Akt and p44/42 in various tissues and we, therefore, hypothesised that it might demonstrate cardioprotective activity. Employing both in vivo (open-chest) and in vitro (Langendorff and cardiomyocytes) rodent (mouse and rat) models ofmyocardial I/R injury we investigated if apelin administered at reperfusion at concentrations akin to pharmacological doses possesses cardioprotective activity. Apelin-13 and the physiologically less potent peptide, apelin-36, decreased infarct size in vitro by 39.6% (p<0.01) and 26.1% (p<0.05) respectively. In vivo apelin-13 and apelin-36 reduced infarct size by 43.1% (p<0.01) and 32.7% (p<0.05). LY294002 and UO126, inhibitors of PI3K-Akt and p44/42 phosphorylation respectively, abolished the protective effects of apelin-13 in vitro.Western blot analysis provided further evidence for the involvement of PI3K-Akt and p44/42 in the cardioprotective actions of apelin. In addition,mitochondrial permeability transition pore (MPTP) opening was delayed by both apelin- 13 (127%, p<0.01) and apelin-36 (93%, p<0.01) which, in the case of apelin-13, was inhibited by LY294002 and mitogen-activated protein kinase kinase (MEK) inhibitor 1. This is the first study to yield evidence that the adipocytokine, apelin, produces direct cardioprotective actions involving the RISK pathway and the MPTP.

Topics: Adipokines; AMP-Activated Protein Kinase Kinases; Animals; Apelin; Cardiotonic Agents; Carrier Proteins; Disease Models, Animal; Dose-Response Relationship, Drug; Intercellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Mitogen-Activated Protein Kinase Kinases; Myocardial Infarction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinases; Protein Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Signal Transduction