apelin-13-peptide and Brain-Ischemia

The precise mechanisms whereby apelin-13 acts against ischemic stroke have remained in the dark. Hence, this study aims to examine the effects of apelin-13 on hypothalamic-pituitary-adrenal (HPA) axis over activation, Jak2-STAT3 signaling pathway, and inflammation following ischemic stroke.. Middle cerebral artery occlusion (MCAO) was used to induce the cerebral ischemic/reperfusion injury (I/RI). Thirty-five male Wistar rats (250-300 g, 8 weeks old) were randomly divided into sham, MCAO, and intravenous (IV) apelin-13 treated groups which received 10, 20, and 40 µg/kg 5 min before reperfusion (n = 7). Neurological status (modified Longa scoring scale), infarct volume, serum levels of malondialdehyde (MDA), total antioxidant capacity (TAC), interleukin 6 (IL-6), corticosterone, and the expressions of the Jak2/STAT3 were assessed.. Our results confirm that IV administration of all three doses of apelin-13 significantly improved neurological defects and reduced infarct volume following cerebral I/RI. Furthermore, we observed that acute stroke caused a rise in the expression of the Jak2/STAT3, IL-6, corticosterone, and MDA content, while apelin-13 could reduce the expression of the Jak2/STAT3 and the serum indices in a dose-dependent manner. The 40 µg/kg dose of apelin-13 was also more effective in reducing the infarct volume and improving TAC.. Our findings suggest that apelin-13 has protective effects against cerebral I/RI-related inflammation and also could attenuate the HPA axis over activation.

Topics: Animals; Brain Ischemia; Corticosterone; Hypothalamo-Hypophyseal System; Infarction, Middle Cerebral Artery; Inflammation; Interleukin-6; Ischemic Stroke; Janus Kinase 2; Male; Pituitary-Adrenal System; Rats; Rats, Wistar; Reperfusion Injury; Signal Transduction

Previous studies had showed that Apelin 13 could protect against apoptosis induced by ischemic/reperfusion (I/R). However, the mechanisms whereby Apelin 13 protected brain I/R remained to be elucidated. The present study was designed to determine whether Apelin 13 provided protection through AMPK/GSK-3β/Nrf2 pathway.. In vivo, the I/R model was induced and Apelin 13 was given intracerebroventricularly 15 min before reperfusion. The neurobehavioral scores, infarction volumes, and some cytokines in the brain were measured. For in vitro study, PC12 cells were used. To clarify the mechanisms, proteases inhibitors or siRNA were used. Protein levels were investigated by western blotting.. The results showed that Apelin 13 treatment significantly reduced infarct size, improved neurological outcomes, decreased brain edema, and inhibited cell apoptosis, oxidative stress, and neuroinflammation after I/R. Apelin 13 significantly increased the expression of Nrf2 and the phosphorylation levels of AMPK and GSK-3β. Furthermore, in cultured PC12 cells, the same protective effects were also observed. Silencing Nrf2 gene with its siRNA abolished the Apelin 13's prevention of I/R-induced PC12 cell injury, oxidative stress, and inflammation. Inhibition of AMPK by its siRNA decreased the level of Apelin 13-induced Nrf2 expression and diminished the protective effects of Apelin 13. The interplay relationship between GSK-3β and Nrf2 was also verified with relative overexpression. Using selective inhibitors, we further identified the upstream of AMPK/GSK-3β/Nrf2 is AR/Gα/PLC/IP3/CaMKK.. In conclusion, the previous results showed that Apelin 13 protected against I/R-induced ROS-mediated inflammation and oxidative stress through activating the AMPK/GSK-3β pathway by AR/Gα/PLC/IP3/CaMKK signaling, and further upregulated the expression of Nrf2-regulated antioxidant enzymes.

Topics: Animals; Brain Ischemia; Glycogen Synthase Kinase 3 beta; Infarction, Middle Cerebral Artery; Injections, Intraventricular; Intercellular Signaling Peptides and Proteins; Male; Mitogen-Activated Protein Kinases; Neuroprotective Agents; NF-E2-Related Factor 2; Oxidative Stress; PC12 Cells; Rats; Rats, Sprague-Dawley; RNA, Small Interfering; Signal Transduction; Stroke

Apelin-13 has protective effects on many neurological diseases, including cerebral ischemia. Here, we aimed to test Apelin-13's effects on ischemic neurovascular unit (NVU) injuries and investigate whether the effects were dependent on vascular endothelial growth factor (VEGF). We detected the expression of VEGF and its receptors (VEGFRs) induced by Apelin-13 injection at 1d, 3d, 7d and 14d after middle cerebral artery occlusion (MCAO). Meanwhile, we examined the effects of Apelin-13 on NVU in both in vivo and in vitro experiments as well as whether the effects were VEGF dependent by using VEGF antibody. We also assessed the related signal transduction pathways via multiple inhibitors. We demonstrated Apelin-13 highly increased VEGF and VEGFR-2 expression, not VEGFR-1. Importantly, Apelin-13 led to neurological functions improvement by associating with promotion of angiogenesis as well as reduction of neuronal death and astrocyte activation, which was markedly blocked by VEGF antibody. In cell cultures, Apelin-13 protected neurons, astrocytes and endothelial cells against oxygen-glucose deprivation (OGD) injuries. Moreover, the effect of Apelin-13 to up-regulate VEGF was suppressed by extracellular signal-regulated kinase (ERK) inhibitor U0126 and phosphatidylinositol 3'-kinase (PI3K) inhibitor LY294002. Our data suggest protective effects of Apelin-13 on ischemic NVU injuries are highly associated with the increase of VEGF binding to VEGFR-2, possibly acting through activation of ERK and PI3K/Akt pathways.

Topics: Animals; Astrocytes; Brain Ischemia; Cell Survival; Infarction, Middle Cerebral Artery; Intercellular Signaling Peptides and Proteins; Male; Neurons; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Signal Transduction; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

To investigate the protective effect of Apelin-13 on focal cerebral ischemia-reperfusion injury in rats.. Focal transient cerebral ischemia-reperfusion injury was induced in male SD rats using modified suture occlusion technique. The rats were randomly divided into 5 groups: Sham group, Model group, Apelin-low dose (A) group, Apelin-middle dose (B) group and Apelin-high dose (C) group. Apelin-13 was injected into lateral cerebral ventricle, and the neurological function score, brain edema, infarct volume, apoptosis, malondialdehyde (MDA), superoxide dismutase (SOD) and extracellular regulated kinase1/2 (ERK1/2) protein were measured.. Neurological function scores, percentage of brain water content, infarct volumes and TUNEL-positive cells in B and C groups were lower than those in Model group (P<0.05). The level of MDA in the tissue bomogenate of brain tissue in the surrounding area of ischemia of B and C groups was lower than that of Model group, while the activity of SOD was higher (P<0.05). There was no significant difference in ERK1/2 protein expression among the groups (P>0.05). P-ERK1/2 increased in Model group and A, B, and C groups compared with Sham group (P<0.05), and that of A, B, and C group was higher than that of Model group (P<0.05).. Apelin-13 may play an important role by inhibiting oxidative stress to protect against focal cerebral ischemia-reperfusion injury; ERK1/2 signaling pathway may be involved in the protective mechanism of Apelin-13.

Topics: Animals; Apoptosis; Brain Edema; Brain Ischemia; Intercellular Signaling Peptides and Proteins; Male; Malondialdehyde; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Signal Transduction; Superoxide Dismutase

Apelin has been proved to protect the heart against ischemia/reperfusion (I/R) injury via the activation of phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) signaling pathways. Whether this protective effect applies to brain I/R injury needed to be explored. We therefore investigated the potential neuroprotective role of Apelin-13 and the underlying mechanisms. Focal transient cerebral I/R model in male ICR mice was induced by 60min of ischemia followed by reperfusion. Apelin-13 intracerebroventricular injection was performed 15 min before reperfusion. Neurological function, infarct volume, brain edema and apoptosis were measured at 24h after stroke. To further test the mechanism of Apelin-13, PI3K inhibitor LY294002 and ERK1/2 inhibitor PD98059 were injected into the lateral cerebral ventricle 15min before ischemia. Compared with the Vehicle group, Apelin-13 significantly ameliorated neurological deficit, infarct volume, brain edema and reduced TUNEL-positive cells. Bax, caspase-3 and cleaved caspase-3 were down-regulated and Bcl-2 up-regulated. While, the effect of Apelin-13 on Bax, Bcl-2, caspase-3 and cleaved caspase-3 was attenuated by LY294002 and PD98059. Apelin protected the brain against I/R insult injury, and this effect may be through activation of PI3K/Akt and ERK1/2 signaling pathways.

Topics: Animals; Apoptosis; Brain; Brain Edema; Brain Infarction; Brain Ischemia; Caspase 3; Chromones; Enzyme Activation; Flavonoids; Gene Expression Regulation; Intercellular Signaling Peptides and Proteins; Male; Mice, Inbred ICR; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Morpholines; Neuroprotective Agents; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Reperfusion Injury; Signal Transduction

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