Project description:Steatotic livers are vulnerable to the deleterious effects of ischaemia-reperfusion injury (IRI) that occur after hepatic surgery. Ischaemic preconditioning (IPC) has been shown to abrogate the effects of IRI in patients undergoing hepatic surgery. Experimental studies have suggested that IPC may be beneficial in steatotic livers subjected to IRI.The aim of this systematic review was to evaluate the effects of IPC on steatotic livers following hepatic IRI in experimental models.An electronic search of the OVID Medline and EMBASE databases was performed to identify studies that reported clinically relevant outcomes in animal models of hepatic steatosis subjected to IPC and IRI.A total of 1093 articles were identified, of which 18 met the inclusion criteria. There was considerable heterogeneity in the type of animal model, and duration and type of IRI. Increased macrovesicular steatosis (>?30%) was associated with a poor outcome following IRI. Ischaemic preconditioning was found to be beneficial in >?30% steatotic livers and provided for decreased histological damage, improved liver function findings and increased survival.Experimental evidence supports the use of IPC in steatotic livers undergoing IRI. These findings may be applicable to patients undergoing liver surgery. However, clinical studies are required to validate the efficacy of IPC in this setting.
Project description:Remote ischaemic preconditioning (RIPC) is well known to protect the myocardium against ischaemia/reperfusion injury (IRI). Exosomes are small extracellular vesicles that have become the key mediators of intercellular communication. Various studies have confirmed that circulating exosomes mediate RIPC. However, the underlying mechanisms for RIPC-induced exosome-mediated cardioprotection remain elusive. In our study, we found that the expression level of miR-24 was higher in exosomes derived from the plasma of rats subjected to RIPC than in exosomes derived from the plasma of control rats in vivo. The rat plasma exosomes could be taken up by H9c2 cells. In addition, miR-24 was present in RIPC-induced exosomes and played a role in reducing oxidative stress-mediated injury and decreasing apoptosis by downregulating Bim expression in H2O2-treated H9c2 cells in vitro. In vivo, miR-24 in RIPC-induced exosomes reduced cardiomyocyte apoptosis, attenuated the infarct size and improved heart function. Furthermore, the apoptosis-reducing effect of miR-24 was counteracted by miR-24 antagomirs or inhibitors both in vitro and in vivo. Therefore, we provided evidence that RIPC-induced exosomes could reduce apoptosis by transferring miR-24 in a paracrine manner and that miR-24 in the exosomes plays a central role in mediating the protective effects of RIPC.
Project description:Small intestinal strangulation associated with ischaemia-reperfusion injury (IRI) is common in horses. In laboratory animals IRI can be ameliorated by ischaemic preconditioning (IPC) and pharmacological preconditioning (PPC) with dexmedetomidine. The aim of this study was to determine the effect of PPC with dexmedetomidine or IPC in an equine model of small intestinal ischaemia-reperfusion (IR). In a randomized controlled experimental trial, 15 horses were assigned to three groups: control (C), IPC, and PPC with dexmedetomidine (DEX). All horses were placed under general anaesthesia and 90% jejunal ischaemia was induced for 90 minutes, followed 30 minutes of reperfusion. In group IPC, three short bouts of ischaemia and reperfusion were implemented, and group DEX received a continuous rate infusion of dexmedetomidine prior to the main ischaemia. Jejunal biopsies were collected before ischaemia (P), and at the end of ischaemia (I) and reperfusion (R). Mucosal injury was assessed by the Chiu-Score, inflammatory cells were stained by cytosolic calprotectin. The degree of apoptosis and cell necrosis was assessed by cleaved-caspase-3 and TUNEL. Parametric data were analyzed by two-way ANOVA for repeated measurements followed by Dunnetts t-test. Non parametric data were compared between groups at the different time points by a Kruskal-Wallis-Test and a Wilcoxon-2-Sample-test. The mucosal injury score increased during I in all groups. After reperfusion, IRI further progressed in group C, but not in IPC and DEX. In all groups the number of cleaved caspase-3 and TUNEL positive cells increased from P to I. The number of TUNEL positive cells were lower in group DEX compared to group C after I and R. Infiltration with calprotectin positive cells was less pronounced in group DEX compared to group C, whereas in group IPC more calprotectin positive cells were seen. In conclusion, IPC and DEX exert protective effects in experimental small intestinal ischaemia in horses.
Project description:Liver Ischaemia Reperfusion (IR) injury is a major cause of post-operative liver dysfunction, morbidity and mortality following liver resection surgery and transplantation. There are no proven therapies for IR injury in clinical practice and new approaches are required. Ischaemic Preconditioning (IPC) can be applied in both a direct and remote fashion and has been shown to ameliorate IR injury in small animal models. Its translation into clinical practice has been difficult, primarily by a lack of knowledge regarding the dominant protective mechanisms that it employs. A review of all current studies would suggest that IPC/RIPC relies on creating a small tissue injury resulting in the release of adenosine and l-arginine which act through the Adenosine receptors and the haem-oxygenase and endothelial nitric oxide synthase systems to reduce hepatocyte necrosis and improve the hepatic microcirculation post reperfusion. The next key step is to determine how long the stimulus requires to precondition humans to allow sufficient injury to occur to release the potential mediators. This would open the door to a new therapeutic chapter in this field.
Project description:Ischaemia-reperfusion (I/R) is a pivotal mechanism of organ injury during stroke, myocardial infarction, organ transplantation and vascular surgeries. Ischaemic preconditioning (IPC) is a potent endogenous form of tissue protection against I/R injury. On the one hand, endocannabinoids have been implicated in the protective effects of IPC through cannabinoid CB1/CB2 receptor-dependent and -independent mechanisms. However, there is evidence suggesting that endocannabinoids are overproduced during various forms of I/R, such as myocardial infarction or whole body I/R associated with circulatory shock, and may contribute to the cardiovascular depressive state associated with these pathologies. Previous studies using synthetic CB1 receptor agonists or knockout mice demonstrated CB1 receptor-dependent protection against cerebral I/R injury in various animal models. In contrast, several follow-up reports have shown protection afforded by CB1 receptor antagonists, but not agonists. Excitedly, emerging studies using potent CB2 receptor agonists and/or knockout mice have provided compelling evidence that CB2 receptor activation is protective against myocardial, cerebral and hepatic I/R injuries by decreasing the endothelial cell activation/inflammatory response (for example, expression of adhesion molecules, secretion of chemokines, and so on), and by attenuating the leukocyte chemotaxis, rolling, adhesion to endothelium, activation and transendothelial migration, and interrelated oxidative/nitrosative damage. This review is aimed to discuss the role of endocannabinoids and CB receptors in various forms of I/R injury (myocardial, cerebral, hepatic and circulatory shock) and preconditioning, and to delineate the evidence supporting the therapeutic utility of selective CB2 receptor agonists, which are devoid of psychoactive effects, as a promising new approach to limit I/R-induced tissue damage.
Project description:AimThe aim of this article is to test the hypothesis that remote ischaemic preconditioning (RIPC) increases circulating endogenous local and systemic plasma (nitrite) during RIPC and ischaemia-reperfusion (IR) as a potential protective mechanism against ischaemia-reperfusion injury (IRI).MethodsSix healthy male volunteers (mean age 29.5 ± 7.6 years) were randomized in a crossover study to initially receive either RIPC (4 × 5 min cycles) to the left arm, or no RIPC (control), both followed by an ischaemia-reperfusion (IR) sequence (20 min cuff inflation to 200 mmHg, 20 min reperfusion) to the right arm. The volunteers returned at least 7 days later for the alternate intervention. The primary outcome was the effect of RIPC vs. control on local and systemic plasma (nitrite).ResultsRIPC did not significantly change plasma (nitrite) in either the left or the right arm during the RIPC sequence. However, compared to control, RIPC decreased plasma (nitrite) during the subsequent IR sequence by ~26% (from 118 ± 9 to 87 ± 5 nmol l-1 ) locally in the left arm (P = 0.008) overall, with an independent effect of -58.70 nmol l-1 (95% confidence intervals -116.1 to -1.33) at 15 min reperfusion, and by ~24% (from 109 ± 9 to 83 ± 7 nmol l-1 ) systemically in the right arm (P = 0.03).ConclusionsRIPC had no effect on plasma (nitrite) during the RIPC sequence, but instead decreased plasma (nitrite) by ~25% during IR. This would likely counteract the protective mechanisms of RIPC, and contribute to RIPC's lack of efficacy, as observed in recent clinical trials. A combined approach of RIPC with nitrite administration may be required.
Project description:BACKGROUND: Ischaemic preconditioning (IPC) has emerged as a method of reducing ischaemia-reperfusion injury. However, the complex mechanism through which IPC elicits this protection is not fully understood. The aim of this study was to investigate the genomic response induced by IPC in muscle biopsies taken from the operative leg of total knee arthroplasty patients in order to gain insight into the IPC mechanism. METHODS: Twenty patients, undergoing primary total knee arthroplasty, were randomly assigned to IPC (n = 10) and control (n = 10) groups. Patients in the IPC group received ischaemic preconditioning immediately prior to surgery. IPC was induced by three five-minute cycles of tourniquet insufflation interrupted by five-minute cycles of reperfusion. A muscle biopsy was taken from the operative knee of control and IPC-treated patients at the onset of surgery and, again, at one hour into surgery. The gene expression profile of muscle biopsies was determined using the Affymetrix Human U113 2.0 microarray system and validated using real-time polymerase chain reaction (RT-PCR). Measurements of C-reactive protein (CRP), erythrocyte sedimentation (ESR), white cell count (WCC), cytokines and haemoglobin were also made pre- and post-operatively. RESULTS: Microarray analysis revealed a significant increase in the expression of important oxidative stress defence genes, immediate early response genes and mitochondrial genes. Upregulation of pro-survival genes was also observed and correlated with a downregulation of pro-apoptotic gene expression. CRP, ESR, WCC, cytokine and haemoglobin levels were not significantly different between control and IPC patients. CONCLUSIONS: The findings of this study suggest that IPC of the lower limb in total knee arthroplasty patients induces a protective genomic response, which results in increased expression of immediate early response genes, oxidative stress defence genes and pro-survival genes. These findings indicate that ischaemic preconditioning may be of potential benefit in knee arthroplasty and other musculoskeletal conditions.
Project description:Brief episodes of ischaemia and reperfusion render the heart resistant to subsequent prolonged ischaemic insult, termed ischaemic preconditioning. Here, we hypothesized that transient non-ischaemic stress by hypertrophic stimulation would induce endogenous cardioprotective signalling and enhance cardiac resistance to subsequent ischaemic damage. Transient transverse aortic constriction (TAC) or Ang-Ⅱ treatment was performed for 3-7 days in male mice and then withdrawn for several days by either aortic debanding or discontinuing Ang-Ⅱ treatment, followed by subsequent exposure to regional myocardial ischaemia by in situ coronary artery ligation. Following ischaemia/reperfusion (I/R) injury, myocardial infarct size and apoptosis were markedly reduced and contractile function was significantly improved in the TAC preconditioning group compared with that in the control group. Similar results were observed in mice receiving Ang-Ⅱ infusion. Mechanistically, TAC preconditioning enhanced ALDH2 activity, promoted AMPK activation and improved mitochondrial energy metabolism by increasing myocardial OXPHOS complex expression, elevating the mitochondrial ATP content and improving viable myocardium glucose uptake. Moreover, TAC preconditioning significantly mitigated I/R-induced myocardial iNOS/gp91phox activation, inhibited endoplasmic reticulum stress and ameliorated mitochondrial impairment. Using a pharmacological approach to inhibit AMPK signalling in the presence or absence of preconditioning, we demonstrated AMPK-dependent protective mechanisms of TAC preconditioning against I/R injury. Furthermore, treatment with adenovirus-encoded ALDH2 partially emulated the actions of hypertrophic preconditioning, as evidenced by improved mitochondrial metabolism, inhibited oxidative stress-induced mitochondrial damage and attenuated cell death through an AMPK-dependent mechanism, whereas genetic ablation of ALDH2 abrogated the aforementioned actions of TAC preconditioning. The present study demonstrates that preconditioning with hypertrophic stress protects the heart from I/R injury via mechanisms that improve mitochondrial metabolism, reduce oxidative/nitrative stress and inhibit apoptosis. ALDH2 is obligatorily required for the development of cardiac hypertrophic preconditioning and acts as the mediator of this process.
Project description:Aims:Myocardial ischaemia followed by reperfusion (IR) causes an oxidative burst resulting in cellular dysfunction. Little is known about the impact of oxidative stress on cardiomyocyte lipids and their role in cardiac cell death. Our goal was to identify oxidized phosphatidylcholine-containing phospholipids (OxPL) generated during IR, and to determine their impact on cell viability and myocardial infarct size. Methods and results:OxPL were quantitated in isolated rat cardiomyocytes using mass spectrophotometry following 24 h of IR. Cardiomyocyte cell death was quantitated following exogenously added OxPL and in the absence or presence of E06, a 'natural' murine monoclonal antibody that binds to the PC headgroup of OxPL. The impact of OxPL on mitochondria in cardiomyocytes was also determined using cell fractionation and Bnip expression. Transgenic Ldlr-/- mice, overexpressing a single-chain variable fragment of E06 (Ldlr-/--E06-scFv-Tg) were used to assess the effect of inactivating endogenously generated OxPL in vivo on myocardial infarct size. Following IR in vitro, isolated rat cardiomyocytes showed a significant increase in the specific OxPLs PONPC, POVPC, PAzPC, and PGPC (P < 0.05 to P < 0.001 for all). Exogenously added OxPLs resulted in significant death of rat cardiomyocytes, an effect inhibited by E06 (percent cell death with added POVPC was 22.6 ± 4.14% and with PONPC was 25.3 ± 3.4% compared to 8.0 ± 1.6% and 6.4 ± 1.0%, respectively, with the addition of E06, P < 0.05 for both). IR increased mitochondrial content of OxPL in rat cardiomyocytes and also increased expression of Bcl-2 death protein 3 (Bnip3), which was inhibited in presence of E06. Notably cardiomyocytes with Bnip3 knock-down were protected against cytotoxic effects of OxPL. In mice exposed to myocardial IR in vivo, compared to Ldlr-/- mice, Ldlr-/--E06-scFv-Tg mice had significantly smaller myocardial infarct size normalized to area at risk (72.4 ± 21.9% vs. 47.7 ± 17.6%, P = 0.023). Conclusions:OxPL are generated within cardiomyocytes during IR and have detrimental effects on cardiomyocyte viability. Inactivation of OxPL in vivo results in a reduction of infarct size.
Project description:BackgroundIschaemic preconditioning elicited by brief periods of coronary occlusion and reperfusion protects the heart from a subsequent prolonged ischaemic insult. Here, we test the hypothesis that short-term non-ischaemic stimulation of hypertrophy renders the heart resistant to subsequent ischaemic injury.Methods and resultsTransient transverse aortic constriction (TAC) was performed for 3 days in mice and then withdrawn for 4 days by aortic debanding, followed by subsequent exposure to myocardial ischaemia-reperfusion (I/R) injury. Following I/R injury, myocardial infarct size and apoptosis were significantly decreased, and cardiac dysfunction was markedly improved in the TAC preconditioning group compared with the control group. Mechanistically, TAC preconditioning markedly suppressed I/R-induced autophagy and preserved autophagic flux by deacetylating SOD2 via a SIRT3-dependent mechanism. Moreover, treatment with an adenovirus encoding SIRT3 partially mimicked the effects of hypertrophic preconditioning, whereas genetic ablation of SIRT3 in mice blocked the cardioprotective effects of hypertrophic preconditioning. Furthermore, in vivo lentiviral-mediated knockdown of Beclin 1 in the myocardium ameliorated the I/R-induced impairment of autophagic flux and was associated with a reduction in cell death, whereas treatment with a lentivirus encoding Beclin 1 abolished the cardioprotective effect of TAC preconditioning.ConclusionsThe present study identifies TAC preconditioning as a novel strategy for induction of an endogenous self-defensive and cardioprotective mechanism against cardiac injury. Specifically, TAC preconditioning reduced myocardial autophagic cell death in a SIRT3/SOD2 pathway-dependent manner.