dihydropyridines and Reperfusion-Injury

Stroke is a leading cause of death and disability worldwide with limited therapeutic interventions. The current study explored proton nuclear magnetic resonance spectroscopy (. In the present investigation, male Wistar rats were subjected to middle cerebral artery occlusion (MCAo) for 2 h followed by reperfusion using intraluminal filament method. Rats were randomly divided into three groups as vehicle-treated sham control, vehicle-treated MCAo control and lercanidipine-treated MCAo. Vehicle or lercanidipine (0.5 mg/kg, i.p.) was administered 120 min post-reperfusion. The rat brain cortex tissues were isolated 24 h post-MCAo and were investigated by. A total of 23 metabolites were altered significantly after cerebral ischaemic-reperfusion injury in MCAo control as compared to sham control rats. Lercanidipine significantly reduced the levels of valine, alanine, lactate, acetate and tyrosine, while N-acetylaspartate, glutamate, glutamine, aspartate, creatine/phosphocreatine, choline, glycerophosphorylcholine, taurine, myo-inositol and adenosine di-phosphate were elevated as compared to MCAo control.. Present study illustrates effect of lercanidipine on neurometabolic alterations which might be mediated through its antioxidant, anti-inflammatory, vasodilatory and anti-apoptotic property in MCAo model of stroke.

Topics: Animals; Dihydropyridines; Infarction, Middle Cerebral Artery; Ischemic Stroke; Magnetic Resonance Spectroscopy; Male; Rats; Rats, Wistar; Reperfusion Injury

Nifedipine is a calcium channel blocker dihydropyridine that has been used in the treatment of hypertension. The production of reactive species and calcium overload are the main contributors to myocardial ischemia-reperfusion (I / R) injury. We investigated the ability of novel dihydropyridines (DHPs) to improve the effect of protecting against the injury induced by ischemia and reperfusion in cardioblasts when compared to nifedipine. Forty three DHPs were created varying the fatty chains derived from palmitic acid, stearic acid and oleic acids and aromatic moiety in addition to the addition of chemical elements such as chlorine, nitrogen dioxide, furfural, hydroxyl and methoxy. Cytotoxicity and inhibition of linoleic oxidation were evaluated for all new DHPs and also for nifedipine. The alpha-tocopherol and butylated hydroxytoluene (BHT) were used as antioxidants controls. The compounds with the best antioxidant potential were used in the ischemia and reperfusion (I / R) induction test in cardioblasts (H9c2). Cardioblasts were treated 24 h after assembly of plates and submitted to the ischemia simulation (30 min), after which, normoxia and cellular nutrition conditions were reestablished, simulating reperfusion (additional 30 min). Right after, cell viability, apoptosis, necrosis, and the generation of reactive oxygen species (ROS) were evaluated. Cell viability during I / R was not altered in cells treated with nifedipine, BHT and the new DHP composed of palmitic acid with hydroxyl group in the aromatic substituent. The other new DHPs increased cell viability during I / R simulation and reduced levels of reactive species compared to the I / R group, demonstrating the antioxidant capacity of the new DHPs. Therefore, DHPS with palmitic and oleic acids in the C3 and C5 position with NO2 or Cl in aromatic moiety, presented the highest antioxidant potential (linoleic oxidant test). The new DHPs increased cell viability during I / R simulation and reduced levels of reactive species compared to the ischemia and reperfusion group, demonstrating the antioxidant capacity of the new DHPs. Taken together, these results indicate that those new DHPs have a greater cardioprotective antioxidant capacity to face the damages of ischemia and reperfusion.

Topics: Animals; Antioxidants; Cardiotonic Agents; Cell Line; Cell Survival; Dihydropyridines; Myoblasts; Myocardial Reperfusion Injury; Necrosis; Rats; Rats, Wistar; Reactive Oxygen Species; Reperfusion Injury

Benidipine has been reported to prevent the ischemia/reperfusion (I/R) damage in heart tissue and to suppress oxidant and proinflammatory cytokine production, increased by I/R. However, There was no information about the effects of benidipine on I/R injury in the ovary and the damage of I/R-induced infertility.. The aim of the study was to investigate the effects of benidipine on bilateral ovarian I/R injury and whether or not effective in the treatment of I/R-induced infertility in rats.. Forty-eight females, albino Wistar rats were randomly divided into 4 groups: IRC group (ovarian I/R group, n=12), IRB-2 group (ovarian I/R+2mg/kg benidipine group, n=12), IRB-4 group (ovarian I/R+4mg/kg benidipine group, n=12) and HG group (healthy group with sham operation, n=12). In IRB-2 and IRB-4 groups, two hours ischemia and two hours reperfusion was performed following orally benidipine administration. After this I/R procedure, 6 rats from each group performed bilateral overectomy. Ovarian levels of malondialdehyde (MDA) and total glutathione (tGSH), ovarian gene expressions of interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) and also apoptosis were evaluated. The other 6 rats from each group were put in together with six male rats in separated cages for 2 months in order to reproduce. During this period, rats which did not become pregnant were accepted as infertile.. MDA levels, expressions of TNF-α and IL-1β in IRC group were significantly higher than in the SGA group and tGSH was decreased. In total, 4mg/kg benidipine has better prevented ovaries from the increase of oxidants and proinflammatory cytokines, the decrease of antioxidants than 2mg/kg benedipine. In the histopathological examination hemorrhage, congestion, follicle degeneration, neutrophil infiltration and necrosis were seen in ovarian tissue of IRC group. Only dilated and congested blood vessels were found in the IRB-2 group. No histopathological finding was encountered in the IRB-4 group. I/R caused infertility in rats. In total, 4mg/kg benidipine prevented from infertility better than the dose of 2mg/kg benedipine.. In total, 4mg/kg benidipine reduced I/R injury and I/R-related infertility more significantly compared to 2mg/kg benedipine in rat ovaries.

Topics: Animals; Apoptosis; Dihydropyridines; Female; Gene Expression; Glutathione; Infertility, Female; Interleukin-1beta; Malondialdehyde; Models, Animal; Ovary; Rats, Wistar; Reperfusion Injury; Tumor Necrosis Factor-alpha; Vasodilator Agents

AKI is associated with high mortality rates and the development of CKD. Ischemia/reperfusion (IR) is an important cause of AKI. Unfortunately, there is no available pharmacologic approach to prevent or limit renal IR injury in common clinical practice. Renal IR is characterized by diminished nitric oxide bioavailability and reduced renal blood flow; however, the mechanisms leading to these alterations are poorly understood. In a rat model of renal IR, we investigated whether the administration of the novel nonsteroidal mineralocorticoid receptor (MR) antagonist BR-4628 can prevent or treat the renal dysfunction and tubular injury induced by IR. Renal injury induced by ischemia was associated with increased oxidant damage, which led to a cysteine sulfenic acid modification in endothelin B receptor and consequently decreased endothelial nitric oxide synthase activation. These modifications were efficiently prevented by nonsteroidal MR antagonism. Furthermore, we demonstrated that the protective effect of BR-4628 against IR was lost when a selective endothelin B receptor antagonist was coadministered. These data describe a new mechanism for reduced endothelial nitric oxide synthase activation during renal IR that can be blocked by MR antagonism with BR-4628.

Topics: Animals; Chromones; Dihydropyridines; Kidney; Male; Mineralocorticoid Receptor Antagonists; Rats; Rats, Wistar; Receptor, Endothelin B; Reperfusion Injury; Sulfenic Acids

C5-unsubstituted-C6-aryl-1,4-dihydropyridines were prepared by a CAN-catalyzed multicomponent reaction from chalcones, β-dicarbonyl compounds, and ammonium acetate. These compounds were able to block Ca(2+) entry after a depolarizing stimulus and showed an improved Cav1.3/Cav1.2 selectivity in comparison with nifedipine. Furthermore, they were able to protect neuroblastoma cells against Ca(2+) overload and oxidative stress models. Their selectivity ratio makes them highly interesting for the treatment of neurological disorders where Ca(2+) dyshomeostasis and high levels of oxidative stress have been demonstrated. Furthermore, their low potency toward the cardiovascular channel subtype makes them safer by reducing their probable side effects, in comparison to classical 1,4-dihydropyridines. Some compounds afforded good protective profile in a postincubation model that simulates the real clinical situation of ictus patients, offering a therapeutic window of opportunity of great interest for patient recovery after a brain ischemic episode. Good activities were also found in acute ischemia/reperfusion models of oxygen and glucose deprivation.

Topics: Animals; Brain Ischemia; Calcium; Calcium Channels, L-Type; Calcium Signaling; Cell Line, Tumor; Dihydropyridines; Hippocampus; Humans; Models, Molecular; Molecular Docking Simulation; Neuroprotective Agents; Oxidative Stress; Rats; Rats, Inbred WKY; Reperfusion Injury

Effects of azelnidipine were examined and compared with those of amlodipine on stunned myocardium in dogs. The left anterior descending (LAD) coronary artery was ligated for 20 min and subsequently released for 60 min. A vehicle, azelnidipine (0.3 mg/kg), or amlodipine (0.3 or 1 mg/kg) was injected intravenously 20 min before LAD ligation. The heart rate increased after a depressor response in the presence of amlodipine, while it decreased despite a decrease in arterial pressures in the presence of azelnidipine. After reperfusion, the coronary flow (CF) significantly increased in the presence of azelnidipine, but did not change with amlodipine after reperfusion. A positive inotropic effect was observed after treatment with both calcium antagonists. Ischemia significantly decreased the percentage of segment shortening (%SS) in all groups. Treatment with both calcium antagonists significantly increased %SS after reperfusion, although high-energy phosphate levels did not improve in the presence of calcium antagonists 60 min after reperfusion. Mortality with azelnidipine was significantly lower than that with 0.3 mg/kg amlodipine immediately after reperfusion. In conclusion, improvement in myocardial stunning after pretreatment with azelnidipine is associated with an increase in CF after reperfusion. The negative chronotropic action may have contributed to decreased mortality due to reperfusion arrhythmias. Azelnidipine is more beneficial than amlodipine and may provide an additional advantage to patients with angina and hypertension.

Topics: Amlodipine; Animals; Azetidinecarboxylic Acid; Calcium Channel Blockers; Dihydropyridines; Dog Diseases; Dogs; Energy Metabolism; Female; Male; Myocardium; Reperfusion Injury

Nitric oxide (NO) and the partial pressure of oxygen (pO(2)) in the liver were simultaneously quantified in rats with partial hepatic ischemia/reperfusion injury (PHIRI). Real-time NO/pO(2) monitoring and immunohistochemical analysis for superoxide dismutase and inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) were performed to evaluate the protective effects of a dihydropyridine-type calcium-channel blocker--CV159--on PHIRI. Serum high-mobility-group box-1 (HMGB-1) was measured to assess cellular necrosis. Moreover, we used in vitro/ex vivo electron paramagnetic resonance spin trapping to assess the hydroxyl radical (*OH)-scavenging activity (OHSA) of CV159 and the liver tissue. The NO levels were significantly higher in CV159-treated rats than in control rats throughout the ischemic phase. Immediately after reperfusion, the levels temporarily increased in waves and then gradually decreased in the treated rats but remained constant in the control rats. pO(2) was continually higher in the treated rats. In these rats, hepatic eNOS expression increased, whereas iNOS expression decreased. The treated rats exhibited significantly higher cytosolic and mitochondrial concentrations NOx (NO(2)+NO(3)). The serum HMGB-1 levels significantly decreased in the treated rats. Moreover, CV159 directly scavenged *OH and both mitochondrial and cytosolic OHSA were preserved in the treated rats. Thus, CV159-mediated inhibition of intracellular Ca(2+) overloading may effectively minimize organ damage and also have *OH-scavenging activity and the cytoprotective effects of eNOS-derived NO.

Topics: Animals; Calcium Channel Blockers; Cytosol; Dihydropyridines; Electrodes; Electron Spin Resonance Spectroscopy; Endothelium; Free Radical Scavengers; HMGB1 Protein; Hydroxyl Radical; Liver; Male; Mitochondria; Necrosis; Nitric Oxide; Nitric Oxide Synthase; Nitrogen Oxides; Oxygen; Rats; Rats, Sprague-Dawley; Reperfusion Injury

Although a blockade or lack of N-type Ca(2+) channels has been reported to suppress neuronal injury induced by ischemia-reperfusion in several animal models, information is still limited regarding the neuroprotective effects of a dual L/N-type Ca(2+) channel blocker, cilnidipine. We histologically examined the effects of cilnidipine on neuronal injury induced by ischemia-reperfusion, intravitreous N-methyl-D-aspartate (NMDA) (200nmol/eye) and intravitreous NOC12 (400nmol/eye), an nitric oxide donor, in the rat retina, and compared its effects with those of omega-conotoxin MV IIA, an N-type Ca(2+) channel blocker and amlodipine, an L-type Ca(2+) channel blocker. Morphometric evaluation at 7 days after ischemia-reperfusion showed that treatment with cilnidipine (100microg/kg, i.v. or 0.5pmol/eye, intravitreous injection) prior to ischemia dramatically reduced the retinal damage. Treatment with omega-conotoxin MV IIA before ischemia (0.1pmol/eye, intravitreous injection) significantly reduced the retinal damage. However, amlodipine (30-100microg/kg, i.v. or 0.1-1pmol/eye, intravitreous injection) did not show any protective effects. Treatment with cilnidipine (100microg/kg, i.v.) reduced the retinal damage induced by intravitreous NMDA, but not NOC12. These results suggest that cilnidipine reduces Ca(2+) influx via N-type Ca(2+) channels after NMDA receptors activation and then protects neurons against ischemia-reperfusion injury in the rat retina in vivo. Cilnidipine may be useful as a therapeutic drug against retinal diseases which cause neuronal cell death, such as glaucoma and central retinal vessel occlusion.

Topics: Amlodipine; Animals; Calcium Channel Blockers; Calcium Channels, L-Type; Calcium Channels, N-Type; Dihydropyridines; Drug Evaluation, Preclinical; In Situ Nick-End Labeling; Injections; Injections, Intravenous; Male; N-Methylaspartate; Neuroprotective Agents; Nitroso Compounds; omega-Conotoxins; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Retinal Degeneration; Retinal Diseases; Vitreous Body

We investigated the organ-reducing ability of 1,2-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine-dicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy) hexyl ester (CV159) that exhibits selective blocking of Ca(2+)/calmodulin and inhibition of Ca(2+) overloading in living organisms (Sprague Dawley rats) using an in vivo and an ex vivo electron paramagnetic imaging technique. Decay rates in CV159-treated rats were significantly higher than those in untreated rats and were almost equal to those in the sham group. Both cytosol and mitochondrial superoxide scavenging activity in CV159-treated rats were significantly higher than those in untreated rats, and cytosol superoxide scavenging activity only was slightly higher than that in the sham group. Faint staining for anti-superoxide dismutase antibody was markedly observed in necrotic lesions in the liver of control group. Alanine aminotransferase level in CV-treated rats were significantly decreased as compared with the levels in untreated rats. Electron microscopy showed a decreased number of damaged mitochondria, whereas mitochondrial damage was significantly reduced in CV-treated animals. We conclude that CV159 retains the organ-reducing activity against radicals in hepatic I/R injury that is mediated by the inhibition of Ca(2+) overloading.

Topics: Alanine Transaminase; Animals; Calcium; Calmodulin; Dihydropyridines; Disease Models, Animal; Electron Spin Resonance Spectroscopy; Liver; Male; Mitochondria; Myosin-Light-Chain Kinase; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Reperfusion Injury; Survival Rate

1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy)hexyl ester (CV159) exhibits selective blocking of Ca(2+)/calmodulin and inhibits Ca(2+) overloading in living organisms. The effects of this antagonist in mice with hepatic ischemia-reperfusion injury were investigated using electron paramagnetic resonance imaging (EPRI) and ex vivo EPR (x-band EPR) techniques. The EPRI determined that the 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl half-life in CV159-treated mice was significantly shorter than that in untreated mice and was almost equal to that in the sham group. Both the cytosolic and the mitochondrial superoxide scavenging activities in CV-treated mice were significantly higher than that in untreated mice. Faint staining of the anti-superoxide dismutase antibody and strong staining of anti-inducible nitric oxide synthase antibody were observed in the liver of control group. In contrast to these findings, immunostaining of these antibodies in the liver of CV159-treated mice were reversed compared to control group. Western blotting showed that CV159 contributed to the high superoxide dismutase expression and low expression of inducible nitric oxide synthase. The alanine aminotransferase level in CV159-treated mice significantly decreased in comparison to that observed in the untreated mice. We conclude that CV159 retains its organ-reducing activity against radicals in hepatic reperfusion injury, which is mediated by the inhibition of Ca(2+) overloading.

Topics: Alanine Transaminase; Animals; Calcium; Calmodulin; Dihydropyridines; Electron Spin Resonance Spectroscopy; Immunohistochemistry; Liver; Mice; Mice, Inbred BALB C; Nitric Oxide Synthase Type II; Oxidation-Reduction; Reperfusion Injury; Superoxide Dismutase; Superoxide Dismutase-1

This study investigated whether oral simvastatin and manidipine interact in protecting the perfused rat heart from ischemia-reperfusion damage. Simvastatin (0.3 to 3 mg/kg) and manidipine (1 to 10 mg/kg) were given orally singly or together to normocholesterolemic rats once a day for seven consecutive days. At the end of treatment, systolic blood pressure and heart rate were measured in conscious rats, and the lipid profile and other biochemical markers, such as thromboxane B(2), nitrite/nitrates and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)) were determined in the plasma. Hearts were then isolated, perfused with Krebs-Henseleit, and subjected to low flow ischemia-reperfusion injury. Post-ischemic recovery of left ventricular function was measured as left ventricular developed pressure and left ventricular end-diastolic pressure. Creatine kinase, lactate dehydrogenase, tumor necrosis factor-alpha and 6-keto-PGF(1alpha) were measured in the heart effluents. In conscious animals, simvastatin alone increased plasma 6-keto-PGF(1alpha) release while manidipine alone reduced systolic blood pressure with a slight sympathetic reflex increase in heart rate, and increased plasma nitrite/nitrates. The combined treatment produced the same effects, but significantly more marked, and accompanied by a significant reduction of thromboxane B(2). Combined treatment was also significantly more effective than the single drugs in protecting the hearts from ischemia-reperfusion injury, with inhibition of creatine kinase, lactate dehydrogenase and tumor necrosis factor-alpha, and enhancement of 6-keto-PGF(1alpha) during reperfusion. These data show that simvastatin and manidipine interact positively in protecting the rat heart from ischemia-reperfusion injury, possibly through increased prostaglandin and nitric oxide formation by the vascular endothelial cells.

Topics: Animals; Blood Glucose; Blood Pressure; Calcium Channel Blockers; Cholesterol; Creatine Kinase; Dihydropyridines; Epoprostenol; Heart Rate; Hydroxymethylglutaryl-CoA Reductase Inhibitors; In Vitro Techniques; Kinetics; L-Lactate Dehydrogenase; Lipids; Male; Nitrobenzenes; Piperazines; Rats; Reperfusion Injury; Simvastatin; Thromboxane B2; Triglycerides; Tumor Necrosis Factor-alpha

Cerebral ischemia is a major leading cause of death and at the first place cause of disability all over the world. There are a lot of drugs that are in experimental stage for treatment of stroke. Among them are calcium channel blockers (CCBs) that have, in animal models, different effectiveness in healing of ischemic damage in brain. Mechanism of CCBs' action in cerebral ischemia is still unclear, but antioxidative property is supposed to be implicated. In the present study, we investigated antioxidative and neuroprotective properties of two CCBs, azelnidipine and amlodipine.. Male Wistar Kyoto rats were subjected to 90 min of transient middle cerebral artery occlusion (MCAO) by a nylon thread. Animals were divided into 3 groups, vehicle, azelnidipine and amlodipine group. In the azelnidipine and amlodipine groups, rats were treated with azelnidipine (1 mg/kg) and amlodipine (1 mg/kg) by gastric gavage for 2 weeks before MCAO. Vehicle group was treated by solution of methyl cellulose for 2 weeks. Rats were killed 24 h after MCAO. Physiological parameters (mean arterial pressure, heart rate, body weight), infarct volume, brain edema index, cerebral blood flow (CBF), oxidative stress markers which are HEL, 4-HNE, AGE and 8-OHdG, and evidence of apoptosis by TUNEL, were investigated.. There were no significant differences among groups in mean arterial pressure, heart rate and body weight. Treatment with azelnidipine and amlodipine reduced infarct volume and brain edema. Azelnidipine treated group showed more marked reduction of infarct volume and cerebral edema than amlodipine group. There was no attenuation of CBF in CCBs groups. The number of HEL, 4-HNE, AGE and 8-OHdG positive cells were significantly decreased in the CCBs treated groups. These molecules were again fewer in the azelnidipine group than in the amlodipine group. In TUNEL staining, the numbers of positive cells was smaller in the CCBs treated groups, especially in the azelnidipine group.. Pretreatment of azelnidipine and amlodipine had a neuroprotective effect in ischemic brain. Antioxidative property is one of the important profiles of CCBs that is implicated in brain protection.

Topics: Amlodipine; Animals; Antioxidants; Apoptosis; Azetidinecarboxylic Acid; Brain; Brain Edema; Brain Infarction; Calcium Channel Blockers; Dihydropyridines; Immunohistochemistry; In Situ Nick-End Labeling; Infarction, Middle Cerebral Artery; Male; Nerve Degeneration; Neuroprotective Agents; Oxidative Stress; Rats; Rats, Inbred WKY; Reperfusion Injury; Treatment Outcome

Although adenosine exerts cardio-and vasculoprotective effects, the roles and signaling mechanisms of different adenosine receptors in mediating skeletal muscle protection are not well understood. We used a mouse hindlimb ischemia-reperfusion model to delineate the function of three adenosine receptor subtypes. Adenosine A(3) receptor-selective agonist 2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (Cl-IBMECA; 0.07 mg/kg ip) reduced skeletal muscle injury with a significant decrease in both Evans blue dye staining (5.4 +/- 2.6%, n = 8 mice vs. vehicle-treated 28 +/- 6%, n = 7 mice, P < 0.05) and serum creatine kinase level (1,840 +/- 910 U/l, n = 13 vs. vehicle-treated 12,600 +/- 3,300 U/l, n = 14, P < 0.05), an effect that was selectively blocked by an A(3) receptor antagonist 3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenylethynyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191; 0.05 mg/kg). The adenosine A(1) receptor agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA; 0.05 mg/kg) also exerted a cytoprotective effect, which was selectively blocked by the A(1) antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.2 mg/kg). The adenosine A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680; 0.07 mg/kg)-induced decrease in skeletal muscle injury was selectively blocked by the A(2A) antagonist 2-(2-furanyl)-7-[3-(4-methoxyphenyl)propyl]-7H-pyrazolo[4,3-e] [1,2,4]triazolo[1,5-C]pyrimidin-5-amine (SCH-442416; 0.017 mg/kg). The protection induced by the A(3) receptor was abrogated in phospholipase C-beta2/beta3 null mice, but the protection mediated by the A(1) or A(2A) receptor remained unaffected in these animals. The adenosine A(3) receptor is a novel cytoprotective receptor that signals selectively via phospholipase C-beta and represents a new target for ameliorating skeletal muscle injury.

Topics: Adenosine; Animals; Dihydropyridines; Disease Models, Animal; Hindlimb; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Skeletal; Phenethylamines; Phospholipase C beta; Pyrazoles; Pyrimidines; Receptor, Adenosine A1; Receptor, Adenosine A2A; Receptor, Adenosine A3; Reperfusion Injury; Signal Transduction; Xanthines

Ischemic preconditioning (IPC) elicits two distinct windows of cardioprotection, an early phase that lasts for 1-2 h and a delayed phase that lasts for 24-72 h. However, there is conflicting data as to how long the heart is resistant to IPC-induced cardioprotection after the initial protection wanes, leading to the demonstration of IPC-resistance. This resistance to IPC appears to be dependent on the timing of the next IPC stimulus, the species of animals used and the model studied. Furthermore, the mechanisms responsible IPC-resistance are unknown. It is also important to demonstrate therapeutic interventions that will produce cardioprotection during this period of IPC-resistance.. To examine potential mechanisms responsible for acute IPC-induced resistance, the NHE-1 inhibitor EMD 85131 (2-methyl-5-methylsulfonyl-1-(1-pyrrollyl)-benzoylguanidine), which exerts its effects via mechanisms distinct from IPC, and the K(ATP) channel opener bimakalim, which bypasses the signaling mechanisms of IPC to directly open K(ATP) channels, were examined in a canine model of IPC-resistance. One 10 min. IPC stimulus followed by 10 min. of reperfusion produced a significant reduction in IS/AAR compared to Control (7.1 +/- 2.6% versus 26.0 +/- 6.2%; P < 0.05). However, IPC did not significantly protect the myocardium if a 2 h reperfusion period occurred between the initial IPC stimulus and the subsequent prolonged (60 min) ischemic challenge (IS/AAR: 22.5 +/- 4.8%: P > 0.05). Furthermore, hearts treated with IPC followed by 2 h of reperfusion were resistant to an additional IPC stimulus administered just prior to the subsequent 60 min. occlusion period (IS/AAR: 22.9 +/- 3.2%: P > 0.05). In contrast, administration of the NHE-1 inhibitor EMD 85131 (IS/AAR: 7.4 +/- 2.5%: P < 0.05) or the K(ATP) channel opener bimakalim (IS/AAR: 11.8 +/- 2.4%: P < 0.05) both afforded significant cardioprotection when administered at 2 h of reperfusion in previously preconditioned canine hearts resistant to IPC.. IPC resistance occurs in this canine model of ischemia-reperfusion injury. However, in spite of IPC resistance, hearts can still be pharmacologically protected by direct application of the K(ATP) channel opener bimakalim or the NHE inhibitor EMD 85131.

Topics: Animals; Benzamides; Benzopyrans; Cardiotonic Agents; Dihydropyridines; Disease Models, Animal; Dogs; Heart; Ischemic Preconditioning, Myocardial; Myocardial Infarction; Potassium Channels; Pyrroles; Reperfusion Injury; Sodium-Hydrogen Exchangers; Time Factors

A3 adenosine receptor (AR) activation worsens or protects against renal and cardiac ischemia-reperfusion (IR) injury, respectively. The aims of the current study were to examine in an in vivo model the effect of A3AR activation on IR lung injury and investigate the mechanism by which it exerts its effect.. The arterial branch of the left lower lung lobe in intact-chest, spontaneously breathing cats was occluded for 2 h and reperfused for 3 h (IR group). Animals were treated with the selective A3 receptor agonist IB-MECA (300 microg/kg intravenously) given 15 min before ischemia or with IB-MECA as described, with pretreatment 15 min earlier with the selective A3AR antagonist MRS-1191, the nonsulfonylurea adenosine triphosphate-sensitive potassium channel-blocking agent U-37883A, or the nitric oxide synthase inhibitor N-nitro-l-arginine benzyl ester.. IB-MECA markedly (P < 0.01) reduced the percentage of injured alveoli (IR, 48 +/- 4%; IB-MECA, 18 +/- 2%), wet:dry weight ratio (IR, 8.2 +/- 0.4; IB-MECA, 4 +/- 2), and myeloperoxidase activity (IR, 0.52 +/- 0.06 U/g; IB-MECA, 0.17 +/- 0.04 U/g). This protective effect was completely blocked by pretreatment with the selective A3AR antagonist MRS-1191 and the adenosine triphosphate-sensitive potassium channel blocking agent U-37883A but not the nitric oxide synthase inhibitor N-nitro-l-arginine benzyl ester.. In the feline lung, the A3AR agonist IB-MECA confers a powerful protection against IR lung injury. This effect is mediated by a nitric oxide synthase-independent pathway and involves opening of adenosine triphosphate-sensitive potassium channels. Therefore, selective activation of A3AR may be an effective means of protecting the reperfused lung.

Topics: Adamantane; Adenosine; Adenosine A3 Receptor Agonists; Adenosine A3 Receptor Antagonists; Animals; ATP-Binding Cassette Transporters; Cats; Dihydropyridines; Enzyme Inhibitors; Hemodynamics; Histamine; In Vitro Techniques; KATP Channels; Lung; Morpholines; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Inwardly Rectifying; Pulmonary Artery; Reperfusion Injury

1 The reperfusion of ischemic tissues may be associated with local and systemic inflammation that prevents the full benefit of blood flow restoration. The present study aimed to confirm a role for platelet-activating factor receptor(s) (PAFR) during ischemia and reperfusion injury by using genetically modified mice deficient in the PAFR (PAFR(-/-) mice) and to evaluate comparatively the effectiveness of pharmacological treatment using the PAFR antagonist UK-74,505 (modipafant). 2 The reperfusion of the ischemic superior mesenteric artery (SMA) induced marked local (intestine) and remote (lungs) tissue injury, as assessed by the increase in vascular permeability, neutrophil influx and intestinal hemorrhage and in the production of TNF-alpha. There was also a systemic inflammatory response, as shown by the increase in serum TNF-alpha concentrations and marked reperfusion-associated lethality. 3 After reperfusion of the ischemic SMA, PAFR(-/-) mice had little tissue or systemic inflammation and lethality was delayed, but not prevented, in these mice. Interestingly, the reperfusion-associated increases in tissue concentrations of IL-10 were significantly greater in PAFR(-/-) than wild-type mice. 4 Pretreatment with PAFR antagonist UK-74,505 (1 mg kg(-1)) markedly prevented tissue injury, as assessed by the increase in vascular permeability, neutrophil accumulation, hemorrhage and TNF-alpha concentrations in the intestine and lungs. In contrast, UK-74,505 failed to affect reperfusion-associated lethality and increases in serum TNF-alpha when used at 1 mg kg(-1). 5 Reperfusion-associated lethality and increase in serum TNF-alpha were only affected when a supra-maximal dose of the antagonist was used (10 mg kg(-1)). At this dose, UK-74,505 also induced a marked enhancement of reperfusion-associated increases in tissue concentrations of IL-10. However, at the same dose, UK-74,505 failed to prevent reperfusion-associated lethality in PAFR(-/-) mice any further. 6 The present studies using genetically modified animals and a receptor antagonist firmly establish a role of PAFR activation for the local, remote and systemic inflammatory injury and lethality which follows reperfusion of the ischemic SMA in mice. Moreover, it is suggested that high doses of PAFR antagonists need to be used if the real efficacy of these compounds is to be tested clinically.

Topics: Animals; Dihydropyridines; Disease Models, Animal; Imidazoles; Intestinal Diseases; Intestines; Lung Diseases; Male; Mesenteric Artery, Superior; Mice; Mice, Inbred C57BL; Platelet Activating Factor; Platelet Membrane Glycoproteins; Receptors, G-Protein-Coupled; Reperfusion Injury

We investigated the effects of administration of non-hypotensive doses of ATP-sensitive K+ channel (KATP) openers (nicorandil and bimakalim), and a specific mitochondrial KATP channel blocker (5-hydroxydecanoate) prior to and during coronary occlusion as well as prior to and during post-ischemic reperfusion on survival rate, ischemia-induced and reperfusion-induced arrhythmias and myocardial infarct size in anesthetized albino rabbits. The thorax was opened in the left fourth intercostal space and after pericardiotomy the heart was exposed. In Part I, occlusion of the left main coronary artery and hence, myocardial ischemia-induced arrhythmias were achieved by tightening a previously placed loose silk ligature for 30 min. In Part II, arrhythmias were induced by reperfusion following a 20-min ligation of the left main coronary artery. In Part I, early intravenous infusion of nicorandil (100 microg/kg bolus + 10 microg/kg per min) or bimakalim (3 microg/kg bolus + 0.1 microg/kg per min) just prior to and during ischemia increased survival rate (75% and 67% vs. 60% in the control group), significantly decreased the incidence and severity of life-threatening arrhythmias and significantly decreased myocardial infarct size. In Part II also, early intervention by intravenous infusion of nicorandil (100 microg/kg bolus + 10 microg/kg per min) or bimakalim (3 microg/kg bolus + 0.1 microg/kg per min) just before and during ischemia increased survival rate (86% and 75% vs. 55% in the control group), significantly decreased the incidence and severity of life-threatening arrhythmias and significantly decreased myocardial infarct size. However, late intravenous administration of nicorandil or bimakalim at the onset and during reperfusion did not increase survival rate nor confer any antiarrhythmic or cardioprotective effects. The antiarrhythmic and cardioprotective effects of both nicorandil and bimakalim were abolished by pretreating the rabbits with 5-hydroxydecanoate (5 mg/kg, i.v. bolus), a selective mitochondrial KATP channel blocker. In conclusion, intervention by intravenous administration of nicorandil and bimakalim (through the activation of mitochondrial KATP channels), increased survival rate and exhibited antiarrhythmic and cardioprotective effects during coronary occlusion and reperfusion in anesthetized rabbits when administered prior to and during coronary occlusion.

Topics: Animals; Antihypertensive Agents; Arrhythmias, Cardiac; Benzopyrans; Blood Gas Analysis; Coronary Disease; Decanoic Acids; Dihydropyridines; Drug Combinations; Hemodynamics; Hydroxy Acids; Male; Myocardial Ischemia; Nicorandil; Potassium Channels; Rabbits; Reperfusion Injury; Survival Rate

Ischemic acute renal failure is associated with vascular endothelial dysfunction. We examined whether vasodilatory antihypertensive agents would improve endothelial function in rats with ischemia/reperfusion renal injury. Rat kidneys were isolated and perfused after clipping of the bilateral renal arteries for 45 min and reperfusion for 24 h, and renal perfusion pressure and nitric oxide concentration in the venous effluent (chemiluminescence assay) were monitored. Preischemic administration of celiprolol (a beta-blocker; 100 mg/kg p.o.), benidipine (a calcium channel blocker; 1 mg/kg p.o.), or imidapril (an angiotensin converting-enzyme inhibitor; 3 mg/kg p.o.) restored endothelial function in rats subjected to acute renal ischemia (deltarenal perfusion pressure [10(-8) M acetylcholine]: sham -42+/-3%, ischemia -31+/-1%, ischemia +celiprolol -39+/-1%*, ischemia+benidipine -38+/-2%*, ischemia+imidapril -42+/-2%*; *p<0.05 vs. ischemia). Serum urea nitrogen and creatinine levels were also lower in the treated groups. Furthermore, ischemia-induced decreases in the response to acetylcholine and renal excretory function were smaller in SHR than in deoxycorticosterone-salt hypertensive rats, in which endothelial damage was marked. These results suggest that preischemic endothelial function may influence the degree of ischemic renal injury. Calcium channel blockers, converting-enzyme inhibitors, and endothelial NO synthase-activating beta-blockers had beneficial effects on renovascular endothelial dysfunction due to ischemia.

Topics: Acetylcholine; Acute Kidney Injury; Angiotensin-Converting Enzyme Inhibitors; Animals; Antihypertensive Agents; Blood Pressure; Blood Urea Nitrogen; Body Weight; Calcium Channel Blockers; Celiprolol; Creatinine; Desoxycorticosterone; Dihydropyridines; Endothelium, Vascular; Imidazoles; Imidazolidines; Male; Nitric Oxide; Rats; Rats, Inbred SHR; Rats, Wistar; Reperfusion Injury; Vasodilator Agents

The effects of the long lasting and potent PAF receptor antagonist UK74505 were assessed on the local and remote injuries following ischaemia and reperfusion (I/R) of the superior mesenteric artery (SMA) in rats. In a severe model of ischaemia (120 min) and reperfusion (120) injury, in addition to the local and remote increases in vascular permeability and neutrophil accumulation, there was significant tissue haemorrhage, blood neutropenia, systemic hypotension and elevated local and systemic TNF-alpha levels. Post-ischaemic treatment with the selectin blocker fucoidin (10 mg kg(-1)) prevented neutrophil accumulation in tissue and, in consequence, all the local and systemic injuries following severe I/R. Treatment with an optimal dose of UK74505 (1 mg kg(-1)) also reversed local and remote neutrophil accumulation, increases in vascular permeability and intestinal haemorrhage. UK74505 partially inhibited blood neutropenia and reperfusion-induced hypotension. Interestingly, both fucoidin and UK74505 prevented the local, but not systemic, increases of TNF-alpha levels following severe I/R injury, demonstrating an important role of migrating cells for the local production of TNF-alpha. However, the results do not support a role for PAF as an intermediate molecule in the production of systemic TNF-alpha. The beneficial effects of UK74505 and other PAF receptor antagonists in models of I/R injury in animals and the safety of UK74505 use in man warrant further investigations of the use of this drug as preventive measure for I/R injury in humans.

Topics: Animals; Azepines; Capillary Permeability; Dihydropyridines; Disease Models, Animal; Dose-Response Relationship, Drug; Imidazoles; Intestine, Small; Male; Mesenteric Artery, Superior; Neutrophils; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Polysaccharides; Rats; Rats, Wistar; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Reperfusion Injury; Triazoles; Tumor Necrosis Factor-alpha