Role of sirtuins in ischemia-reperfusion injury

Ischemia-reperfusion injury(IRI)remains an unresolved and complicated situation in clinical practice,especially in the case of organ transplantation.Several factors contribute to its complexity;the depletion of energy during ischemia and the induction of oxidative stress during reperfusion initiate a cascade of pathways that lead to cell death and finally to severe organ injury.Recently,the sirtuin family of nicotinamide adenine dinucleotide-dependent deacetylases has gained increasing attention from researchers,due to their involvement in the modulation of a wide variety of cellular functions.There are seven mammalian sirtuins and,among them,the nuclear/cytoplasmic sirtuin 1(SIRT1)and the mitochondrial sirtuin 3(SIRT3)are ubiquitously expressed in many tissue types.Sirtuins are known to play major roles in protecting against cellular stress and in controlling metabolic pathways,which are key processes during IRI.In this review,we mainly focus on SIRT1 and SIRT3 and examine their role in modulating pathways against energy depletion during ischemia and their involvement in oxidative stress,apoptosis,microcirculatory stress and inflammation during reperfusion.We present evidence of the beneficial effects of sirtuins against IRI and emphasize the importance of developing new strategies by enhancing their action.

Role of aldehyde dehydrogenase 2 in ischemia reperfusion injury:An update

Aldehyde dehydrogenase 2(ALDH2) is best known for its critical detoxifying role in liver alcohol metabolism. However, ALDH2 dysfunction is also involved in a wide range of human pathophysiological situations and is associated with complications such as cardiovascular diseases, diabetes mellitus, neurodegenerative diseases and aging. A growing body of research has shown that ALDH2 provides important protection against oxidative stress and the subsequent loading of toxic aldehydes such as 4-hydroxy-2-nonenal and adducts that occur in human diseases, including ischemia reperfusion injury(IRI). There is increasing evidence of its role in IRI pathophysiology in organs such as heart, brain, small intestine and kidney; however, surprisingly few studies have been carried out in the liver, where ALDH2 is found in abundance. This study reviews the role of ALDH2 in modulating the pathways involved in the pathophysiology of IRI associated with oxidative stress, autophagy and apoptosis. Special emphasis is placed on the role of ALDH2 in different organs, on therapeutic "preconditioning" strategies, and on the use of ALDH2 agonists such as Alda-1, which may become a useful therapeutic tool for preventing the deleterious effects of IRI in organ transplantation.

Peroxisome proliferator-activated receptor γ agonist reduces the severity of post-ERCP pancreatitis in rats

AIM: To determine the effects of prophylactic peroxi-some proliferator-activated receptor (PPARγ) agonist administration in an experimental model of post-endoscopic retrograde cholangiopancreatography (post-ERCP) acute pancreatitis.METHODS: Post-ERCP pancreatitis was induced in male Wistar rats by infusion of contrast medium into the pancreatic duct. In additional group, rosiglitazone, a PPARγ agonist, was administered 1 h before infusion of contrast medium. Plasma and pancreas samples were obtained 6 h after the infusion.RESULTS: Infusion of contrast medium into the pan-creatic duct resulted in an inflammatory process characterized by increased lipase levels in plasma, and edema and myeloperoxidase activity (MPO) in pancreas. This result correlated with the activation of nuclear factor κB (NFκB) and the inducible NO synthase (iNOS) expression in pancreatic cells. Rosiglitazone reduced the increase in lipase and the level of edema and the increase in myeloperoxidase as well as the activation of NFκB and iNOS expression.CONCLUSION: A single oral dose of rosiglitazone, given 1 h before post-ERCP pancreatitis induction is effective in reducing the severity of the subsequent inflammatory process. The protective effect of rosiglitazone was associated with NFκB inhibition and the blockage of leukocyte infiltration in pancreas.

Emerging concepts in liver graft preservation

The urgent need to expand the donor pool in order to attend to the growing demand for liver transplantation has obliged physicians to consider the use of suboptimal liver grafts and also to redefine the preservation strategies. This review examines the different methods of liver graft preservation, focusing on the latest advances in both static cold storage and machine perfusion(MP). The new strategies for static cold storage are mainly designed to increase the fatty liver graft preservation via the supplementation of commercial organ preservation solutions with additives. In this paper we stress the importance of carrying out effective graft washout after static cold preservation, and present a detailed discussion of the future perspectives for dynamic graft preservation using MP at different temperatures(hypothermia at 4 ℃, normothermia a t 3 7 ℃ and subnormothermia at 20 ℃- 2 5 ℃). Finally, we highlight some emerging applications of regenerative medicine in liver graft preservation. In conclusion, this review discusses the "state of the art" and future perspectives in static and dynamic liver graft preservation in order to improve graft viability.

Polyethylene glycol rinse solution:An effective way to prevent ischemia-reperfusion injury

AIM:To test whether a new rinse solution containing polyethylene glycol 35(PEG-35)could prevent ischemia-reperfusion injury(IRI)in liver grafts.METHODS:Sprague-Dawley rat livers were stored in University of Wisconsin preservation solution and then washed with different rinse solutions(Ringer’s lactate solution and a new rinse solution enriched with PEG-35 at either 1 or 5 g/L)before ex vivo perfusion with Krebs-Heinseleit buffer solution.We assessed the following:liver injury(transaminase levels),mitochondrial damage(glutamate dehydrogenase activity),liver function(bile output and vascular resistance),oxidative stress(malondialdehyde),nitric oxide,liver autophagy(Beclin-1 and LCB3)and cytoskeleton integrity(filament and globular actin fraction);as well as levels of metalloproteinases(MMP2 and MMP9),adenosine monophosphate-activated protein kinase(AMPK),heat shock protein 70(HSP70)and heme oxygenase 1(HO-1).RESULTS:When we used the PEG-35 rinse solution,reduced hepatic injury and improved liver function were noted after reperfusion.The PEG-35 rinse solution prevented oxidative stress,mitochondrial damage,and liver autophagy.Further,it increased the expression of cytoprotective heat shock proteins such as HO-1 and HSP70,activated AMPK,and contributed to the restoration of cytoskeleton integrity after IRI.CONCLUSION:Using the rinse solution containing PEG-35 was effective for decreasing liver graft vulnerability to IRI.

Sirtuin 1 in rat orthotopic liver transplantation:An I GL-1 preservation solution approach

AIM:To investigate the possible involvement of Sirtuin1(SIRT1)in rat orthotopic liver transplantation(OLT),when Institute Georges Lopez 1(IGL-1)preservation solution is enriched with trimetazidine(TMZ).METHODS:Male Sprague-Dawley rats were used as donors and recipients.Livers were stored in IGL-1 preservation solution for 8h at 4℃,and then underwent OLT according to Kamada’s cuff technique without arterialization.In another group,livers were stored in IGL-1 preservation solution supplemented with TMZ,at10-6 mol/L,for 8 h at 4℃and then underwent OLT.Rats were sacrificed 24 h after reperfusion,and liver and plasma samples were collected.Liver injury(transaminase levels),mitochondrial damage(glutamate dehydrogenase activity)oxidative stress(malondialdehyde levels),and nicotinamide adenine dinucleotide(NAD+),the cofactor necessary for SIRT1 activity,were determined by biochemical methods.SIRT1 and its substrates(acFox O1,ac-p53),the precursor of NAD+,nicotinamide phosphoribosyltransferase(NAMPT),as well as the phosphorylation of adenosine monophosphate activated protein kinase(AMPK),p-m TOR,p-p70S6K(direct substrate of m TOR),autophagy parameters(beclin-1,LC3B)and MAP kinases(p-p38 and p-ERK)were determined by Western blot.RESULTS:Liver grafts preserved in IGL-1 solution enriched with TMZ presented reduced liver injury and mitochondrial damage compared with those preservedin IGL-1 solution alone.In addition,livers preserved in IGL-1+TMZ presented reduced levels of oxidative stress.This was consistent with enhanced SIRT1 protein expression and elevated SIRT1 activity,as indicated by decreased acetylation of p53 and Fox O1.The elevated SIRT1 activity in presence of TMZ can be attributed to the enhanced NAMPT protein and NAD+/NADH levels.Up-regulation of SIRT1 was consistent with activation of AMPK and inhibition of phosphorylation of m TOR and its direct substrate(p-p70S6K).As a consequence,autophagy mediators(beclin-1 and LC3B)were overexpressed.Furthermore,MAP kinases were regulated in livers preserved with IGL-1+TMZ,as they were characterized by enhanced p-ERK and decreased p-p38protein expression.CONCLUSION:Our study shows that IGL-1 preservation solution enriched with TMZ protects liver grafts from the IRI associated with OLT,through SIRT1 up-regulation.

Polyethylene glycols: An effective strategy for limiting liver ischemia reperfusion injury

Liver ischemia-reperfusion injury(IRI) is an inherent feature of liver surgery and liver transplantation in which damage to a hypoxic organ(ischemia) is exacerbated following the return of oxygen delivery(reperfusion). IRI is a major cause of primary nonfunction after transplantation and may lead to graft rejection, regardless of immunological considerations. The immediate response involves the disruption of cellular mitochondrial oxidative phosphorylation and the accumulation of metabolic intermediates during the ischemic period, and oxidative stress during blood flow restoration. Moreover, a complex cascade of inflammatory mediators is generated during reperfusion, contributing to the extension of the damage and finally to organ failure. A variety of pharmacological interventions(antioxidants, anticytokines, etc.) have been proposed to alleviate graft injury but their usefulness is limited by the local and specific action of the drugs and by their potential undesirable toxic effects. Polyethylene glycols(PEGs), which are non-toxic water-soluble compounds approved by the FDA, have been widely used as a vehicle or a base in food, cosmetics and pharmaceuticals, and also as adjuvants for ameliorating drug pharmacokinetics. Some PEGs are also currently used as additives in organ preservation solutions prior to transplantation in order to limit the damage associated with cold ischemia reperfusion. More recently, the administration of PEGs of different molecular weights by intravenous injection has emerged as a new therapeutic tool to protect liver grafts from IRI. In this review, we summarize the current knowledge concerning the use of PEGs as a useful target for limiting liver IRI.

Relevance of proteolysis and proteasome activation in fatty liver graft preservation: An Institut Georges Lopez-1 vs University of Wisconsin appraisal

AIM To compare liver proteolysis and proteasome activation in steatotic liver grafts conserved in University of Wisconsin(UW) and Institut Georges Lopez-1(IGL-1)solutions.METHODS Fatty liver grafts from male obese Zücker rats were conserved in UW and IGL-1 solutions for 24 h at 4 ℃and subjected to "ex vivo " normo-thermic perfusion(2 h; 37 ℃). Liver proteolysis in tissue specimens and perfusate was measured by reverse-phase high performance liquid chromatography. Total free amino acid release was correlated with the activation of the ubiquitin proteasome system(UPS: measured as chymotryptic-like activity and 20 S and 19 S proteasome), the prevention of liver injury(transaminases), mitochondrial injury(confocal microscopy) and inflammation markers(TNF 1 alpha, high mobility group box-1(HGMB-1) and PPAR gamma), and liver apoptosis(TUNEL assay, cytochrome c and caspase 3).RESULTS Profiles of free AA(alanine, proline, leucine, isoleucine, methionine, lysine, ornithine, and threonine, among others) were similar for tissue and reperfusion effluent. In all cases, the IGL-1 solution showed a significantly higher prevention of proteolysis than UW(P < 0.05) after cold ischemia reperfusion. Livers conserved in IGL-1 presented more effective prevention of ATP-breakdown and more inhibition of UPS activity(measured as chymotryptic-like activity). In addition, the prevention of liver proteolysis and UPS activation correlated with the prevention of liver injury(AST/ALT) and mitochondrial damage(revealed by confocal microscopy findings) as well as with the prevention of inflammatory markers(TNF1alpha and HMGB) after reperfusion. In addition, the liver grafts preserved in IGL-1 showed a significant decrease in liver apoptosis, as shown by TUNEL assay and the reduction of cytochrome c, caspase 3 and P62 levels. CONCLUSION Our comparison of these two preservation solutions suggests that IGL-1 helps to prevent ATP breakdown more effectively than UW and subsequently achieves a higher UPS inhibition and reduced liver proteolysis.

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-kDa 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(50μg/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.AR42J pancreatic acinar cells were treated with increasing concentrations of PEG35 prior to exposure with tumor necrosis factorα(TNFα),staurosporine or cerulein.The severity of AP was determined 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 AR42J-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 mRNA 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 AR42J-treated cells through the attenuation of the inflammatory response and associated cell death.PEG35 may be a valuable option in the management of AP.

Losartan activates sirtuin 1 in rat reduced-size orthotopic liver transplantation

AIM: To investigate a possible association between losartan and sirtuin 1(SIRT1) in reduced-size orthotopic liver transplantation(ROLT) in rats.METHODS: Livers of male Sprague-Dawley rats(200-250 g) were preserved in University of Wisconsin preservation solution for 1 h at 4 ℃ prior to ROLT.In an additional group,an antagonist of angiotensin Ⅱ type 1 receptor(AT1R),losartan,was orally administered(5 mg/kg) 24 h and 1 h before the surgical procedure to both the donors and the recipients.Transaminase(as an indicator of liver injury),SIRT1 activity,and nicotinamide adenine dinucleotide(NAD+,a co-factor necessary for SIRT1 activity) levels were determined by biochemical methods.Protein expression of SIRT1,acetylated Fox O1(ac-Fox O1),NAMPT(the precursor of NAD+),heat shock proteins(HSP70,HO-1) expression,endoplasmic reticulum stress(GRP78,IRE1 a,p-e IF2) and apoptosis(caspase 12 and caspase 3) parameters were determined by Western blot.Possible alterations in protein expression of mitogen activated protein kinases(MAPK),such as p-p38 and p-ERK,were also evaluated.Furthermore,the SIRT3 protein expression and m RNA levels were examined.RESULTS: The present study demonstrated that losartan administration led to diminished liver injury when compared to ROLT group,as evidenced by the significant decreases in alanine aminotransferase(358.3 ± 133.44 vs 206 ± 33.61,P < 0.05) and aspartate aminotransferase levels(893.57 ± 397.69 vs 500.85 ± 118.07,P < 0.05).The lessened hepatic injury in case of losartan was associated with enhanced SIRT1 protein expression and activity(5.27 ± 0.32 vs 6.08 ± 0.30,P < 0.05).This was concomitant with increased levels of NAD+(0.87 ± 0.22 vs 1.195 ± 0.144,P < 0.05) the co-factor necessary for SIRT1 activity,as well as with decreases in ac-Fox O1 expression.Losartan treatment also provoked significant attenuation of endoplasmic reticulum stress parameters(GRP78,IRE1 a,p-e IF2) which was consistent with reduced levels of both caspase 12 and caspase 3.Furthermore,losartan administration stimulated HSP70 protein expression and attenuated HO-1 expression.However,no changes were observed in protein or m RNA expression of SIRT3.Finally,the protein expression pattern of p-ERK and p-p38 were not altered upon losartan administration.CONCLUSION: The present study reports that losartan induces SIRT1 expression and activity,and that it reduces hepatic injury in a ROLT model.