Effects of trimetazidine on the Akt/eNOS signaling pathway and oxidative stress in an in vivo rat model of renal ischemia-reperfusion

Renal ischemia reperfusion (I/R) injury, which occurs during renal surgery or transplantation, is the major cause of acute renal failure. Trimetazidine (TMZ), an anti-ischemic drug, protects kidney against the deleterious effects of I/R. However its protective mechanism remains unclear. The aim of this study is to examine the relevance of Akt, endothelial nitric oxide synthase (eNOS), and hypoxia inducible factor-1α (HIF-1α) on TMZ induced protection of kidneys against I/R injury. Wistar rats were subjected to 60?min of warm renal ischemia followed by 120?min of reperfusion, or to intraperitoneal injection of TMZ (3?mg/kg) 30?min before ischemia. In sham operated group renal pedicles were only dissected. Compared to I/R, TMZ treatment decreased lactate dehydrogenase (845?±?13 vs. 1028?±?30?U/L). In addition, creatinine clearance and sodium reabsorption rates reached 105?±?12 versus 31?±?11?μL/min/g kidney weight and 95?±?1 versus 68?±?5%, respectively. Besides, we noted a decrease in malondialdehyde concentration (0.33?±?0.01 vs. 0.59?±?0.03?nmol/mg of protein) and an increase in glutathione concentration (2.6?±?0.2 vs. 0.93?±?0.16?µg GSH/mg of protein), glutathione peroxidase (95?±?4 vs. 61?±?3?µg GSH/min/mg of protein), and superoxide dismutase (25?±?3 vs. 11?±?2?U/mg of protein) and catalase (91?±?12 vs. 38?±?9?μmol/min/mg of protein) activities. Parallely, we noted a significant increase in p-Akt, eNOS, nitrite and nitrate (18?±?2 vs. 8?±?0.1?pomL/mg of protein), HIF-1α (333?±?48 vs. 177?±?14?µg/mg of protein) and heme oxygenase-1 (HO-1) levels regarding I/R. TMZ treatment improves renal tolerance to warm I/R. Such protection implicates an activation of Akt/eNOS signaling pathway, HIF-1α stabilization and HO-1 activation.     

Polyethylene glycol 35 ameliorates pancreatic inflammatory response in cerulein-induced acute pancreatitis in rats

BACKGROUND Acute pancreatitis(AP) is a sudden inflammatory process of the pancreas that may also involve surrounding tissues and/or remote organs. Inflammation and parenchymal cell death are common pathological features of this condition and determinants of disease severity. Polyethylene glycols(PEGs) are nonimmunogenic, non-toxic water-soluble polymers widely used in biological, chemical, clinical and pharmaceutical settings.AIM To evaluate the protective effect of a 35-k Da molecular weight PEG(PEG35) on the pancreatic damage associated to cerulein-induced acute pancreatitis in vivo and in vitro.METHODS Wistar rats were assigned at random to a control group, a cerulein–induced AP group and a PEG35 treatment group. AP was induced by five hourly intraperitoneal injections of cerulein(50 μg/kg/bw), while the control animals received saline solution. PEG35 was administered intraperitoneally 10 minutes before each cerulein injection in a dose of 10 mg/kg. After AP induction, samples of pancreatic tissue and blood were collected for analysis. AR42 J pancreatic acinar cells were treated with increasing concentrations of PEG35 prior to exposure with tumor necrosis factor α(TNFα), staurosporine or cerulein. The severity of AP wasdetermined on the basis of plasma levels of lipase, lactate dehydrogenase activity, pancreatic edema and histological changes. To evaluate the extent of the inflammatory response, the gene expression of inflammation-associated markers was determined in the pancreas and in AR42 J-treated cells. Inflammation-induced cell death was also measured in models of in vivo and in vitro pancreatic damage.RESULTS Administration of PEG35 significantly improved pancreatic damage through reduction on lipase levels and tissue edema in cerulein-induced AP rats. The increased associated inflammatory response caused by cerulein administration was attenuated by a decrease in the gene expression of inflammation-related cytokines and inducible nitric oxide synthase enzyme in the pancreas. In contrast, pancreatic tissue m RNA expression of interleukin 10 was markedly increased. PEG35 treatment also protected against inflammation-induced cell death by attenuating lactate dehydrogenase activity and modulating the pancreatic levels of apoptosis regulator protein BCL-2 in cerulein hyperstimulated rats. Furthermore, the activation of pro-inflammatory markers and inflammationinduced cell death in pancreatic acinar cells treated with TNFα, cerulein or staurosporine was significantly reduced by PEG35 treatment, in a dose-dependent manner.CONCLUSION PEG35 ameliorates pancreatic damage in cerulein-induced AP and AR42 J-treated cells through the attenuation of the inflammatory response and associated cell death. PEG35 may be a valuable option in the management of AP.     

Effects of Institut Georges Lopez-1 and Celsior preservation solutions on liver graft injury

AIM: To compare Institut Georges Lopez(IGL-1) and Celsior preservation solutions for hepatic endothelium relaxation and liver cold ischemia reperfusion injury(IRI).METHODS: Two experimental models were used.In the first one, acetylcholine-induced endotheliumdependent relaxation(EDR) was measured in isolated ring preparations of rat hepatic arteries preserved or not in IGL-1 or Celsior solutions(24 h at 4 ℃).To determine nitric oxide(NO) and cyclooxygenase EDR, hepatic arteries were incubated with L-NG-nitroarginine methyl ester(L-NAME), an inhibitor of endothelium nitric oxide synthase(e NOS), or with L-NAME plus indomethacin, an inhibitor of cyclooxygenase.In the second experiment, rat livers were cold-stored in IGL-1 or Celsior solutions for 24 h at 4 ℃ and then perfused "ex vivo " for 2 h at 37 ℃.Liver injury was assessed by transaminase measurements, liver function by bile production and bromosulfophthalein clearance, oxidative stress by malondialdehyde levels and catalase activity and alterations in cell signaling pathways by pA kt, pA MPK, eN OS and MAPKs proteins level.RESULTS: After cold storage for 24 h with either Celsior or IGL-1, EDR was only slightly altered.Infreshly isolated arteries, EDR was exclusively mediated by NO.However, cold-stored arteries showed NOand COX-dependent relaxation.The decrease in NO-dependent relaxation after cold storage was significantly more marked with Celsior.The second study indicated that IGL-1 solution obtained better liver preservation and protection against IRI than Celsior.Liver injury was reduced, function was improved and there was less oxidative stress.IGL-1 solution activated Akt and AMPK, which was concomitant with increased eN OS expression and nitrite/nitrate levels.Furthermore, MAPKs kinases were regulated in livers preserved with IGL-1 solution since reductions in p-p38, p-ERK and p-JNK protein levels were observed.CONCLUSION: IGL-1 solution preserved NO-dependent relaxation better than Celsior storage solution and enhanced liver graft preservation.     

Preconditioning protects against systemic disorders associated with hepatic ischemia-reperfusion through blockade of tumor necrosis factor-induced P-selectin up-regulation in the rat

Previous studies indicate that ischemic preconditioning protects against lung injury resulting from hepatic ischemia-reperfusion (I/R) through inhibition of tumor necrosis factor (TNF) release from Kupffer cells. The present study investigated whether this effect is limited to the lung or is a generalized systemic response and explores the molecular mechanisms involved. Hepatic I/R led to an increase in neutrophil accumulation in liver, lung, and splanchnic organs. Although preconditioning did not modify neutrophil infiltration in liver during reperfusion, it conferred protection against hepatic injury associated with I/R. In remote organs, preconditioning abrogated the increase in P-selectin up-regulation, preventing neutrophil infiltration and thus reducing the oxidative stress and microvascular disorders following hepatic I/R in these organs. Administration of Abs against P-selectin or TNF previous to ischemia had the same effects as preconditioning. The effects of preconditioning on the blockade of P-selectin up-regulation probably results from inhibition of systemic TNF release from Kupffer cells. Supplementation of TNF abolished the benefits of preconditioning, whereas the injurious effects of TNF were prevented by previous blockade of P-selectin. The results of the present study suggest that ischemic preconditioning protects the liver against I/R injury by a mechanism independent of adhesion molecule expression and neutrophil accumulation. In remote organs, however, hepatic preconditioning prevents inflammatory damage by reducing the systemic TNF release from the liver and thus preventing P-selectin up-regulation.     

Insulin like growth factor-1 increases fatty liver preservation in IGL-1 solution

AIM: To investigate the benefits of insulin like growth factor-1 (IGF-1) supplementation to serum-free institut georges lopez-1 (IGL-1) solution to protect fatty liver against cold ischemia reperfusion injury. METHODS: Steatotic livers were preserved for 24 h in IGL-1  solution supplemented with or without IGF-1 and then perfused "ex vivo " for 2 h at 37℃. We examined the effects of IGF-1 on hepatic damage and function (transaminases, percentage of sulfobromophthalein clearance in bile and vascular resistance). We also studied other factors associated with the poor tolerance of fatty livers to cold ischemia reperfusion injury such as mitochondrial damage, oxidative stress, nitric oxide, tumor necrosis factor-α (TNF-α) and mitogen-activated protein kinases.RESULTS: Steatotic livers preserved in IGL-1 solutionsupplemented with IGF-1 showed lower transaminase levels, increased bile clearance and a reduction in vascular resistance when compared to those preserved in IGL-1solution alone. These benefits are mediated by activation of AKT and constitutive endothelial nitric oxide synthase (eNOS), as well as the inhibition of inflammatory cytokines such as TNF-α. Mitochondrial damage and oxidative stress were also prevented.CONCLUSION: IGL-1  enrichment with IGF-1 increasedfatty liver graft preservation through AKT and eNOS activation, and prevented TNF-α release during normothermic reperfusion.     

Therapeutic Targets in Liver Transplantation: Angiotensin II in Nonsteatotic Grafts and Angiotensin-(1–7) in Steatotic Grafts

Numerous steatotic livers are discarded as unsuitable for transplantation because of their poor tolerance of ischemia-reperfusion(I/R). The injurious effects of angiotensin (Ang)-II and the benefits of Ang-(1–7) in various pathologies are well documented. We examined the generation of Ang II and Ang-(1–7) in steatotic and nonsteatotic liver grafts from Zucker rats following transplantation. We also studied in both liver grafts the effects of Ang-II receptors antagonists and Ang-(1–7) receptor antagonists on hepatic I/R damage associated with transplantation. Nonsteatotic grafts showed higher Ang II levels than steatotic grafts, whereas steatotic grafts showed higher Ang-(1–7) levels than nonsteatotic grafts. Ang II receptor antagonists protected only nonsteatotic grafts against damage, whereas Ang-(1–7) receptor antagonists were effective only in steatotic grafts. The protection conferred by Ang II receptor antagonists in nonsteatotic grafts was associated with ERK 1/2 overexpression, whereas the beneficial effects of Ang-(1–7) receptor antagonists in steatotic grafts may be mediated by NO inhibition. Our results show that Ang II receptor antagonists are effective only in nonsteatotic liver transplantation and point to a novel therapeutic target in liver transplantation based on Ang-(1–7), which is specific for steatotic liver grafts.     

New Insights Into Fatty Liver Preservation Using Institute Georges Lopez Preservation Solution

Institute Georges Lopez preservation solution (IGL-1) has been demonstrated to be useful for fatty liver preservation. The mechanisms responsible for this effective graft protection against ischemia-reperfusion injury are pivotal actions on generation of nitric oxide a diffusible molecule with vasodilator properties, that facilitates the up-regulation of other well-known cytoprotective genes, such as hypoxia-inducible factor-1 alpha (HIF-1α) and heme-oxygenase 1 (HO-1). During normoxic reperfusion, the presence of nitric oxide permits HIF-1α accumulation to inhibit prolyl-hydoxylases, thus promoting an additional overexpression of the HO-1 in steatotic and nonsteatotic graft livers preserved in IGL-1.     

Adenosine monophosphate-activated protein kinase mediates the protective effects of ischemic preconditioning on hepatic ischemia-reperfusion injury in the rat.

Hepatic ischemia-reperfusion (I/R) injury associated with liver transplantation and hepatic resections are an unresolved problem in the clinical practice. Preconditioning is known to preserve energy metabolism in liver during sustained ischemia, but the molecular mechanisms underlying this effect are still unclear. Different metabolic signals, including adenosine monophosphate (AMP) and nitric oxide (NO), have been implicated in preconditioning. AMP-activated protein kinase (AMPK) protects cells by acting as a low-fuel warning system, becoming switched on by adenosine triphosphate (ATP) depletion. NO synthesis is induced by AMPK in the heart during ischemia. The aim of this study was to investigate: 1) whether preconditioning induces AMPK activation; and 2) if AMPK activation leads to ATP preservation and reduced lactate accumulation during prolonged ischemia and its relationship with NO. Preconditioning activated AMPK and concomitantly reduced ATP degradation, lactate accumulation, and hepatic injury. The administration of an AMPK activator, AICAR, before ischemia simulated the benefits of preconditioning on energy metabolism and hepatic injury. The inhibition of AMPK abolished the protective effects of preconditioning. The effect of AMPK on energy metabolism was independent of NO because the inhibition of NO synthesis in the preconditioned group and the administration of the NO donor before ischemia, or to the preconditioned group with previous inhibition of AMPK, had no effect on energy metabolism. Both preconditioning and AICAR pretreatment, through AMPK activation, may be useful surgical and pharmacologic strategies aimed at reducing hepatic I/R injury.     

Ischemic preconditioning increases the tolerance of Fatty liver to hepatic ischemia-reperfusion injury in the rat

Hepatic steatosis is a major risk factor in ischemia-reperfusion. The present study evaluates whether preconditioning, demonstrated to be effective in normal livers, could also confer protection in the presence of steatosis and investigates the potential underlying protective mechanisms. Fatty rats had increased hepatic injury and decreased survival after 60 minutes of ischemia compared with lean rats. Fatty livers showed a degree of neutrophil accumulation and microcirculatory alterations similar to that of normal livers. However, in presence of steatosis, an increased lipid peroxidation that could be reduced with glutathione-ester pretreatment was observed after hepatic reperfusion. Ischemic preconditioning reduced hepatic injury and increased animal survival. Both in normal and fatty livers, this endogenous protective mechanism was found to control lipid peroxidation, hepatic microcirculation failure, and neutrophil accumulation, reducing the subsequent hepatic injury. These beneficial effects could be mediated by nitric oxide, because the inhibition of nitric oxide synthesis and nitric oxide donor pretreatment abolished and simulated, respectively, the benefits of preconditioning. Thus, ischemic preconditioning could be an effective surgical strategy to reduce the hepatic ischemia-reperfusion injury in normal and fatty livers under normothermic conditions, including hepatic resections, and liver transplantation.