Nitric oxide triggers classic ischemic preconditioning

Gasotransmitters and noble gases in cardioprotection: unraveling molecular pathways for future therapeutic strategies

Despite recent progress, ischemic heart disease poses a persistent global challenge, driving significant morbidity and mortality. The pursuit of therapeutic solutions has led to the emergence of strategies such as ischemic preconditioning, postconditioning, and remote conditioning to shield the heart from myocardial ischemia/reperfusion injury (MIRI). These ischemic conditioning approaches, applied before, after, or at a distance from the affected organ, inspire future therapeutic strategies, including pharmacological conditioning. Gasotransmitters, comprising nitric oxide, hydrogen sulfide, sulfur dioxide, and carbon monoxide, play pivotal roles in physiological and pathological processes, exhibiting shared features such as smooth muscle relaxation, antiapoptotic effects, and anti-inflammatory properties. Despite potential risks at high concentrations, physiological levels of gasotransmitters induce vasorelaxation and promote cardioprotective effects. Noble gases, notably argon, helium, and xenon, exhibit organ-protective properties by reducing cell death, minimizing infarct size, and enhancing functional recovery in post-ischemic organs. The protective role of noble gases appears to hinge on their modulation of molecular pathways governing cell survival, leading to both pro- and antiapoptotic effects. Among noble gases, helium and xenon emerge as particularly promising in the field of cardioprotection. This overview synthesizes our current understanding of the roles played by gasotransmitters and noble gases in the context of MIRI and cardioprotection. In addition, we underscore potential future developments involving the utilization of noble gases and gasotransmitter donor molecules in advancing cardioprotective strategies.

Ischemic Preconditioning Improves Handgrip Strength and Functional Capacity in Active Elderly Women

Background: Aging decreases some capacities in older adults, sarcopenia being one of the common processes that occur and that interfered with strength capacity. The present study aimed to verify the acute effect of IPC on isometric handgrip strength and functional capacity in active elderly women. Methods: In a single-blind, placebo-controlled design, 16 active elderly women (68.1 ± 7.6 years) were randomly performed on three separate occasions a series of tests: (1) alone (control, CON); (2) after IPC (3 cycles of 5-min compression/5-min reperfusion at 15 mmHg above systolic blood pressure, IPC); and (3) after placebo compressions (SHAM). Testing included a handgrip isometric strength test (HIST) and three functional tests (FT): 30 s sit and stand up from a chair (30STS), get up and go time (TUG), and 6 min walk distance test (6MWT). Results: HIST significantly increased in IPC (29.3 ± 6.9 kgf) compared to CON (27.3 ± 7.1 kgf; 7.1% difference; p = 0.01), but not in SHAM (27.7 ± 7.9; 5.5%; p = 0.16). The 30STS increased in IPC (20.1 ± 4.1 repetitions) compared to SHAM (18.5 ± 3.5 repetitions; 8.7%; p = 0.01) and CON (18.5 ± 3.9 repetitions; 8.6%; p = 0.01). TUG was significantly lower in IPC (5.70 ± 1.35 s) compared to SHAM (6.14 ± 1.37 s; −7.2%; p = 0.01), but not CON (5.91 ± 1.45 s; −3.7%; p = 0.24). The 6MWT significantly increased in IPC (611.5 ± 93.8 m) compared to CON (546.1 ± 80.5 m; 12%; p = 0.02), but not in SHAM (598.7 ± 67.6 m; 2.1%; p = 0.85). Conclusions: These data suggest that IPC can promote acute improvements in handgrip strength and functional capacity in active elderly women.

S-nitroso-glutathione limits apoptosis and reduces pulmonary vascular dysfunction after bypass

BACKGROUND

During hypoxia or acidosis, S-nitrosoglutathione (GSNO) has been shown to protect the cardiomyocyte from IR injury. In a randomised double blinded control study of a porcine model of paediatric CPB, we aimed to evaluate the effects of two different doses (low and high) of GSNO.

METHODS

Pigs weighing 15-20 kg were exposed to CPB with one hour of aortic cross-clamp. Prior to and during CPB, animals were randomised to receive low dose (up to 20 nmol/kg/min) GSNO (n=8), high dose (up to 60 nmol/kg/min) GSNO (n=6) or normal saline (n=7). Standard cardiac intensive care management was continued for 4 hours post-bypass.

RESULTS

There was a reduction in myocyte apoptosis after administration of GSNO (p=0.04) with no difference between low and high dose GSNO. The low dose GSNO group had lower pulmonary vascular resistance post-CPB (p=0.007). Mitochondrial Complex I activity normalised to citrate synthase activity was higher after GSNO compared to control (p=0.02), with no difference between low and high dose GSNO.

CONCLUSIONS

In a porcine model of CPB intravenous administration of GSNO limits myocardial apoptosis through preservation of mitochondrial complex I activity, and improves pulmonary vascular resistance. There appears to be a dose dependent effect to this protection.

Implications of Oxidative and Nitrosative Post-Translational Modifications in Therapeutic Strategies against Reperfusion Damage

Post-translational modifications based on redox reactions "switch on-off" the biological activity of different downstream targets, modifying a myriad of processes and providing an efficient mechanism for signaling regulation in physiological and pathological conditions. Such modifications depend on the generation of redox components, such as reactive oxygen species and nitric oxide. Therefore, as the oxidative or nitrosative milieu prevailing in the reperfused heart is determinant for protective signaling, in this review we defined the impact of redox-based post-translational modifications resulting from either oxidative/nitrosative signaling or oxidative/nitrosative stress that occurs during reperfusion damage. The role that cardioprotective conditioning strategies have had to establish that such changes occur at different subcellular levels, particularly in mitochondria, is also presented. Another section is devoted to the possible mechanism of signal delivering of modified proteins. Finally, we discuss the possible efficacy of redox-based therapeutic strategies against reperfusion damage.

Role of Remote Ischemic Preconditioning in Hepatic Ischemic Reperfusion Injury

The effect of remote ischemic preconditioning (RIPC) has been proposed that mediates the protective response in ischemia reperfusion injury (IRI) of various organs. In this study, we investigated the effect of RIPC in hepatic IRI, by assessing biomarker of oxidative stress and inflammatory cytokines. Moreover, we intended to demonstrate any such protective effect through nitric oxide (NO). Twenty-five rats were divided into the 5 groups: (1) Sham; (2) RIPC; (3) hepatic IRI; (4) RIPC + hepatic IRI; (5) C-PTIO, 2-(4-carboxyphenyl)-4,5dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3oxide, + RIPC + hepatic IRI. RIPC downregulated the level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), histologic damage, and activity of Malondialdehyde (MDA). However, there was no significant reduction in the level of tumor necrosis factor-alpha (TNF-α) and nuclear factor kappa B (NF-κB). AST and ALT levels, and hepatic tissue morphology in the C-PTIO group showed a significant improvement compared to those of the RIPC + hepatic IRI group. The application of RIPC before hepatic ischemia downregulated the oxidative stress, not the inflammatory cytokines. Moreover, these protective effect of RIPC would be mediated through the activation of NO as well as anti-oxidant effect.

Investigating the possible mechanisms involved in adenosine preconditioning-induced cardioprotection in rats

BACKGROUND

Adenosine is a breakdown product of adenosine triphosphate and plays an important role in pharmacological preconditioning. The cardioprotective effects of adenosine preconditioning are well established. However, the possible mechanisms need to be explored.

AIM

This study was aimed to investigate the possible mechanisms involved in adenosine preconditioning-induced cardioprotection in rats.

METHODS

Rat heart was isolated and perfused on Langendorff apparatus. Global ischemia for 30 minutes followed by reperfusion for 120 minutes was employed to produce myocardial injury. Myocardial injury was assessed by measuring myocardial infarct size, release of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and hemodynamic parameters including left ventricular developed pressure (LVDP), dp/dt_max, and dp/dt_min . Serum nitrite levels were measured as an index of nitric oxide release in blood.

RESULTS

Adenosine (4 mg/kg) preconditioning significantly decreased ischemia-reperfusion-induced increase in LDH, CK release, infarct size, improved LVDP, dp/dt_max and dp/dt_min, and increased serum nitrite levels. Pretreatment with L-NAME, a specific NOS inhibitor, (5 mg/kg) and montelukast, leukotriene receptor antagonist, (10 mg/kg) significantly abrogated the cardioprotective effect of adenosine preconditioning. However, seratrodast, thromboxane A₂ antagonist, (15 mg/kg) had no effect on adenosine-induced cardioprotection. Sodium nitroprusside (SNP) preconditioning also produced cardioprotective effects. However, caffeine (20 mg/kg) (adenosine receptor blocker) and seratrodast (15 mg/kg) had no effect on SNP-induced cardioprotection. Administration of montelukast abrogated the cardioprotective effects of SNP preconditioning-induced cardioprotection.

CONCLUSION

Adenosine preconditioning may increase the release of nitric oxide, which in turn may increase the release of cysteinyl leukotrienes to confer cardioprotection.

Interaction between connexin 43 and nitric oxide synthase in mice heart mitochondria

Connexin 43 (Cx43), which is highly expressed in the heart and especially in cardiomyocytes, interferes with the expression of nitric oxide synthase (NOS) isoforms. Conversely, Cx43 gene expression is down-regulated by nitric oxide derived from the inducible NOS. Thus, a complex interplay between Cx43 and NOS expression appears to exist. As cardiac mitochondria are supposed to contain a NOS, we now investigated the expression of NOS isoforms and the nitric oxide production rate in isolated mitochondria of wild-type and Cx43-deficient (Cx43(Cre-ER(T)/fl) ) mice hearts. Mitochondria were isolated from hearts using differential centrifugation and purified via Percoll gradient ultracentrifugation. Isolated mitochondria were stained with an antibody against the mitochondrial marker protein adenine-nucleotide-translocator (ANT) in combination with either a neuronal NOS (nNOS) or an inducible NOS (iNOS) antibody and analysed using confocal laser scanning microscopy. The nitric oxide formation was quantified in purified mitochondria using the oxyhaemoglobin assay. Co-localization of predominantly nNOS (nNOS: 93 ± 4.1%; iNOS: 24.6 ± 7.5%) with ANT was detected in isolated mitochondria of wild-type mice. In contrast, iNOS expression was increased in Cx43(Cre-ER(T)/fl) mitochondria (iNOS: 90.7 ± 3.2%; nNOS: 53.8 ± 17.5%). The mitochondrial nitric oxide formation was reduced in Cx43(Cre-ER(T)/fl) mitochondria (0.14 ± 0.02 nmol/min./mg protein) in comparison to wild-type mitochondria (0.24 ± 0.02 nmol/min./mg). These are the first data demonstrating, that a reduced mitochondrial Cx43 content is associated with a switch of the mitochondrial NOS isoform and the respective mitochondrial rate of nitric oxide formation.

Postconditioning leads to an increase in protein S-nitrosylation

Previous studies have shown a role for nitric oxide and S-nitrosylation (SNO) in postconditioning (PostC), but specific SNO proteins and sites have not been identified in the myocardium after PostC. In this study, we examined SNO signaling in PostC using a Langendorff-perfused mouse heart model. After 20 min of equilibrium perfusion and 25 min of global ischemia, PostC was applied at the beginning of reperfusion with six cycles of 10 s of reperfusion and 10 s of ischemia. The total period of reperfusion was 90 min. Compared with the ischemia-reperfusion (I/R) control, PostC significantly reduced postischemic contractile dysfunction and infarct size. PostC-induced protection was blocked by treatment with N(G)-nitro-l-arginine methyl ester (l-NAME) (10 μmol/l; a constitutive NO synthase inhibitor), but not by either ODQ (10 μmol/l, a highly selective soluble guanylyl cyclase inhibitor) or KT5823 (1 μmol/l, a specific protein kinase G inhibitor). Two biotin switch based methods, two dimensional CyDye-maleimide difference gel electrophoresis (2D CyDye-maleimide DIGE) and SNO-resin-assisted capture (SNO-RAC), were utilized to identify SNO-modified proteins and sites. Using 2D CyDye-maleimide DIGE analysis, PostC was found to cause a 25% or greater increase in SNO of a number of proteins, which was blocked by treatment with l-NAME in parallel with the loss of protection. Using SNO-RAC, we identified 77 unique proteins with SNO sites after PostC. These results suggest that NO-mediated SNO signaling is involved in PostC-induced cardioprotection and these data provide the first set of candidate SNO proteins in PostC hearts.

Essential role of nitric oxide in acute ischemic preconditioning: S-nitros(yl)ation versus sGC/cGMP/PKG signaling?

Nitric oxide (NO) plays an important role in acute ischemic preconditioning (IPC). In addition to activating soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) signaling pathways, NO-mediated protein S-nitros(yl)ation (SNO) has been recently shown to play an essential role in cardioprotection against ischemia-reperfusion (I/R) injury. In our previous studies, we have shown that IPC-induced cardioprotection could be blocked by treatment with either N-nitro-L-arginine methyl ester (L-NAME, a constitutive NO synthase inhibitor) or ascorbate (a reducing agent to decompose SNO). To clarify NO-mediated sGC/cGMP/PKG-dependent or -independent (i.e., SNO) signaling involved in IPC-induced cardioprotection, mouse hearts were Langendorff-perfused in the dark to prevent SNO decomposition by light exposure. Treatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, a highly selective inhibitor of sGC) or KT5823 (a potent and selective inhibitor of PKG) did not abolish IPC-induced acute protection, suggesting that the sGC/cGMP/PKG signaling pathway does not play an important role in NO-mediated cardioprotective signaling during acute IPC. In addition, treatment with ODQ in IPC hearts provided an additional protective effect on functional recovery, in parallel with a higher SNO level in these ODQ+IPC hearts. In conclusion, these results suggest that the protective effect of NO is not related primarily to activation of the sGC/cGMP/PKG signaling pathway, but rather through SNO signaling in IPC-induced acute cardioprotection.

Time course analysis of cardiac pacing-induced gene expression changes in the canine heart

Rapid right ventricular pacing in anesthetized dogs results in marked protection against ischemia and reperfusion-induced ventricular arrhythmias, 24 h later. We have previous evidence that this protection associates with altered expression of genes, encoding proteins involved in the delayed cardioprotection. However, the sequence of transcriptional changes occurring between the pacing stimulus and the test ischemia has not yet been elucidated. Thus, we designed studies in which the expression of 29 genes was examined by real-time PCR at various time intervals, i.e., immediately (0 h), 6, 12, and 24 h after short periods (4 times 5 min) of rapid (240 beats min(-1)) right ventricular pacing in the canine. Sham-operated dogs (the pacing electrode was introduced but the dogs were not paced) served as controls. Compared with these dogs, pacing induced an early up-regulation of genes which encode, for example, HSP90, MnSOD, ERK1, PKCε, Bcl2, and sGC; all these somehow relate to the early phase of the protection. These genes remained either up-regulated or, after a transient lower expression (around 6 h), were up-regulated again, suggesting their involvement in the delayed protection. There were also some genes which down-regulated soon after the pacing stimulus (e.g., Bax, Casp3, Casp9, MMP9, GSK3β), and showed also low expression 24 h later. Genes encoding eNOS and iNOS, as well as Cx43 were only up-regulated 12 h after pacing. We conclude that cardiac pacing induces time-dependent changes in gene expression, and the sequence of these changes is important in the development of the delayed protection.

Role of Mitogen-Activated Protein Kinases in Myocardial Ischemia-Reperfusion Injury during Heart Transplantation

In solid organ transplantation, ischemia/reperfusion (IR) injury during organ procurement, storage and reperfusion is an unavoidable detrimental event for the graft, as it amplifies graft inflammation and rejection. Intracellular mitogen-activated protein kinase (MAPK) signaling pathways regulate inflammation and cell survival during IR injury. The four best-characterized MAPK subfamilies are the c-Jun NH2-terminal kinase (JNK), extracellular signal- regulated kinase-1/2 (ERK1/2), p38 MAPK, and big MAPK-1 (BMK1/ERK5). Here, we review the role of MAPK activation during myocardial IR injury as it occurs during heart transplantation. Most of our current knowledge regarding MAPK activation and cardioprotection comes from studies of preconditioning and postconditioning in nontransplanted hearts. JNK and p38 MAPK activation contributes to myocardial IR injury after prolonged hypothermic storage. p38 MAPK inhibition improves cardiac function after cold storage, rewarming and reperfusion. Small-molecule p38 MAPK inhibitors have been tested clinically in patients with chronic inflammatory diseases, but not in transplanted patients, so far. Organ transplantation offers the opportunity of starting a preconditioning treatment before organ procurement or during cold storage, thus modulating early events in IR injury. Future studies will need to evaluate combined strategies including p38 MAPK and/or JNK inhibition, ERK1/2 activation, pre- or postconditioning protocols, new storage solutions, and gentle reperfusion.

AMP-activated protein kinase as a target for preconditioning in transplantation medicine

Graft quality before transplantation is a major factor influencing chronic rejection. Organ preservation and ischemia/reperfusion play an important role in the induction of organ injury. Although both suppression of metabolism by hypothermic preservation and preconditioning before ischemia limit injury, understanding the biochemical signaling pathways will allow us to optimize graft preservation further. Adenosine monophosphate-activated protein kinase (AMPK) is an important enzyme sensing cellular energy balance and regulating downstream signaling pathways, signaling toward an energy-conserving state. In this review, we summarize available literature regarding the protective signaling pathways activated by (hypothermic) ischemia and preconditioning and how they can be activated pharmacologically. Optimizing the graft quality before transplantation improves long-term graft survival. The major factor influencing organ quality is organ preservation, cold storage, currently, being a common practice. Loss of cellular homeostasis, inflammation, and endothelial dysfunction are the major factors inducing injury after cold storage. Adenosine triphosphate depletion and anaerobic metabolism during the cold ischemic period lead to mitochondrial dysfunction, disturbed osmoregulation, and cell death inducing inflammation. Ischemic preconditioning consists of brief periods of ischemia preceding preservation and protects organs against injury because of subsequent ischemia/reperfusion, in which endothelial nitric oxide synthase, nuclear factor-kB, and adenosine play a major role. After conversion of adenosine to AMP, AMPK can be activated, a central kinase involved in sensing cellular [AMP]:[adenosine triphosphate] levels and signaling toward an energy-conserving state. Pharmacologic activation of AMPK demonstrated its ability to activate endothelial nitric oxide synthase and inhibit nuclear factor-kB, thereby limiting endothelial dysfunction and inflammation. Further, studies in knock-out mice lacking ENTDP1 and NT5E (enzymes catalyzing formation and degradation of AMP, respectively) demonstrated a clear protective role for AMP in ischemia/reperfusion. AMPK activation before or during organ preservation might be a promising pharmacologic approach to limit organ injury and maintain graft quality before transplantation.

Protein S-nitrosylation and cardioprotection

Nitric oxide (NO) plays an important role in the regulation of cardiovascular function. In addition to the classic NO activation of the cGMP-dependent pathway, NO can also regulate cell function through protein S-nitrosylation, a redox dependent, thiol-based, reversible posttranslational protein modification that involves attachment of an NO moiety to a nucleophilic protein sulfhydryl group. There are emerging data suggesting that S-nitrosylation of proteins plays an important role in cardioprotection. Protein S-nitrosylation not only leads to changes in protein structure and function but also prevents these thiol(s) from further irreversible oxidative/nitrosative modification. A better understanding of the mechanism regulating protein S-nitrosylation and its role in cardioprotection will provide us new therapeutic opportunities and targets for interventions in cardiovascular diseases.

Role of ischemic preconditioning in liver surgery and hepatic transplantation

INTRODUCTION

The purpose of this review is to summarize intraoperative surgical strategies available to decrease ischemia-reperfusion injury associated with liver resection and liver transplantation.

MATERIAL AND METHOD

We conducted a critical review of the literature evaluating the potential applications of hepatic ischemic preconditioning (IPC) for hepatic resection surgery and liver transplantation. In addition, we provide a basic bench-to-bedside summary of the liver physiology and cell signaling mechanisms that account for the protective effects seen with hepatic IPC.

Bosentan affects 15-F2t-isoprostane adverse effects on postischemic rat hearts

BACKGROUND

15-F(2t)-isoprostane (IsoP), a marker of reactive oxygen species-induced oxidative stress, is increased after myocardial ischemia and reperfusion. It exerts deleterious effects on postischemic myocardium accompanied with increased release of endothelin-1 (ET-1), a potent vasoconstrictor. We hypothesized that IsoP exacerbates myocardial ischemia-reperfusion injury by stimulating ET-1 production, and that ET-1 blockade can attenuate or prevent these deleterious effects of IsoP.

METHODS

Adult rat hearts were perfused by the Langendorff technique with Krebs-Henseleit solution (KH) at a constant flow rate of 10 mL/min. Global myocardial ischemia was induced by stopping KH perfusion for 40 min followed by 60 min of reperfusion. Hearts were randomized to one of the five groups (n = 8 each): untreated control, treated with IsoP (100 nM), or the ET-1 receptor A/B antagonist bosentan (1 μM) alone or in combination 10 min prior to, during 40 min global ischemia and 15 min of reperfusion, or treated with IsoP as above plus delayed administration of bosentan after 15 min of reperfusion.

RESULTS

Coronary effluent ET-1 concentrations in the IsoP group were higher than those in the control group during ischemia and reperfusion (P < 0.05), which was associated with increased release of cardiac-specific creatine kinase, reduced cardiac contractility during reperfusion, and increased myocardial infarct size (all P < 0.05 versus control). Bosentan administration during early reperfusion exacerbated the IsoP deleterious effects, while delayed administration attenuated it.

CONCLUSION

15-F(2t)-isoprostane-induced ET-1 production during later reperfusion is detrimental to functional recovery of damaged myocardium, while ET-1 increase during early reperfusion seems to improve it.

Actions and interactions of nitric oxide, carbon monoxide and hydrogen sulphide in the cardiovascular system and in inflammation--a tale of three gases!

Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulphide (H(2)S) together make up a family of biologically active gases (the so-called 'gaseous triumvirate') with an increasingly well defined range of physiological effects plus roles to play in a number of disease states. Over the years, most researchers have concentrated their attention on understanding the part played by a single gas in one or more body systems. It is becoming more clear that all three gases are synthesised naturally in the body, often by the same cells within the same organs, and that all three gases exert essentially similar biological effects albeit via different mechanisms. Within the cardiovascular system, for example, all are vasodilators, promote angiogenesis and vascular remodelling and are protective towards tissue damage in for example, ischaemia-reperfusion injury in the heart. Similarly, all exhibit complex effects in inflammation with both pro- and anti-inflammatory effects recognised. It seems likely that cell function is controlled not by the activity of single gases working in isolation but by the concerted activity of all three of these gases working together.

Late protective effect of pharmacological preconditioning with total flavones of rhododendra against myocardial ischemia–reperfusion injury

The aim of the present study was to investigate the protective effect of total flavones of rhododendra (TFR) pharmacological preconditioning against myocardial ischemia–reperfusion (I/R) injury and its probable mechanisms in rats. Rat myocardial I/R injury was induced by ligating and untying the left anterior descending coronary artery. Male Sprague–Dawley rats were anesthetized and the chests were opened. All animals were subjected to 30 min of occlusion and 1 h of reperfusion. Twenty-four hours before the 30-minute occlusion, rats received 3 cycles of 5 min intravenous perfusion of TFR (10, 20, 40 mg/kg) or morphine hydrochloride (0.3 mg/kg) or normal saline interspersed with drug-free periods. Changes in the ST segment of ECG, the content of cardiac troponin I (cTnI), malondialdehyde (MDA), and nitric oxide (NO), and the activity of superoxide dismutase (SOD), lactate dehydrogenase (LDH), creatine phosphokinase (CK), and nitric oxide synthase (NOS) in serum were measured. Infarct size (IS), as a percentage of the area at risk (AAR), was determined by TTC staining. The expression of inducible nitric oxide synthase (iNOS) mRNA in rat myocardium was detected by RT-PCR and the expression of iNOS protein was detected by Western blot. Pretreatment with TFR (10, 20, 40 mg/kg) markedly inhibited I/R-induced ST segment elevation of ECG. TFR (20, 40 mg/kg) pretreatment decreased I/R-induced IS/AAR, markedly inhibited the increase of MDA content and the activity of CK and LDH, and also significantly inhibited the decline of NO content and the activity of NOS and SOD in serum. TFR (40 mg/kg) preconditioning significantly inhibited the increase of serum cTnI induced by I/R injury and increased the expression of iNOS both at mRNA and protein levels in rat myocardium. Our findings indicate that TFR preconditioning has a protective effect against myocardial I/R injury in rats. The cardioprotection involves the stimulation of NO release and the inhibition of lipid peroxidation.

Remote ischemic preconditioning: a novel protective method from ischemia reperfusion injury--a review

BACKGROUND

Restoration of blood supply to an organ after a critical period of ischemia results in parenchymal injury and dysfunction of the organ referred to as reperfusion injury. Ischemia reperfusion injury is often seen in organ transplants, major organ resections and in shock. Ischemic preconditioning (IPC) is an adaptational response of briefly ischemic tissues which serves to protect against subsequent prolonged ischemic insults and reperfusion injury. Ischemic preconditioning can be mechanical or pharmacological. Direct mechanical preconditioning in which the target organ is exposed to brief ischemia prior to prolonged ischemia has the benefit of reducing ischemia-reperfusion injury (IRI) but its main disadvantage is trauma to major vessels and stress to the target organ. Remote (inter organ) preconditioning is a recent observation in which brief ischemia of one organ has been shown to confer protection on distant organs without direct stress to the organ.

AIM

To discuss the evidence for remote IPC (RIPC), underlying mechanisms and possible clinical applications of RIPC. METHODS OF SEARCH: A Pubmed search with the keywords "ischemic preconditioning," "remote preconditioning," "remote ischemic preconditioning," and "ischemia reperfusion" was done. All articles on remote preconditioning up to September 2006 have been reviewed. Relevant reference articles from within these have been selected for further discussion.

RESULTS

Experimental studies have demonstrated that the heart, liver, lung, intestine, brain, kidney and limbs are capable of producing remote preconditioning when subjected to brief IR. Remote intra-organ preconditioning was first described in the heart where brief ischemia in one territory led to protection in other areas. Translation of RIPC to clinical application has been demonstrated by the use of brief forearm ischemia in preconditioning the heart prior to coronary bypass and in reducing endothelial dysfunction of the contra lateral limb. Recently protection of the heart has been demonstrated by remote hind limb preconditioning in children who underwent surgery on cardiopulmonary bypass for congenital heart disease. The RIPC stimulus presumably induces release of biochemical messengers which act either by the bloodstream or by the neurogenic pathway resulting in reduced oxidative stress and preservation of mitochondrial function. Studies have demonstrated endothelial NO, Free radicals, Kinases, Opioids, Catecholamines and K(ATP) channels as the candidate mechanism in remote preconditioning. Experiments have shown suppression of proinflammatory genes, expression of antioxidant genes and modulation of gene expression by RIPC as a novel method of IRI injury prevention.

CONCLUSION

There is strong evidence to support RIPC. The underlying mechanisms and pathways need further clarification. The effective use of RIPC needs to be investigated in clinical settings.

CoCl2 induces protective events via the p38-MAPK signalling pathway and ANP in the perfused amphibian heart

Mitogen-activated protein kinases (MAPKs) constitute one of the most important intracellular signalling pathways. In particular, the p38-MAPK subfamily is known to be activated under various stressful conditions, such as mechanical or oxidative stress. Furthermore, cobalt chloride (CoCl2) has been shown to mimic hypoxic responses in various cell lines and cause overproduction of reactive oxygen species (ROS). In the current study, we investigated the effect of CoCl2 on p38-MAPK signalling pathway in the perfused Rana ridibunda heart. Immunoblot analysis of the phosphorylated, and thus activated, form of p38-MAPK revealed that maximum phosphorylation was attained at 500 micromol l(-1) CoCl2. A similar profile was observed for MAPKAPK2 and Hsp27 phosphorylation (direct and indirect p38-MAPK substrates, respectively). Time course analysis of p38-MAPK phosphorylation pattern showed that the kinase reached its peak within 15 min of treatment with 500 micromol l(-1) CoCl2. Similar results were obtained for Hsp27 phosphorylation. In the presence of the antioxidants Trolox or Lipoic acid, p38-MAPK CoCl2-induced phosphorylation was attenuated. Analogous results were obtained for Hsp27 and MAPKAPK2. In parallel, mRNA levels of the ANP gene, a hormone whose transcriptional regulation has previously been shown to be regulated by p38-MAPK, were examined (semi-quantitative ratiometric RT-PCR). CoCl2 treatment significantly increased ANP mRNA levels, whereas, in the presence of antioxidants, the transcript levels returned to basal values. All the above data indicate that CoCl2 stimulates compensatory mechanisms involving the p38-MAPK signalling cascade along with ANP.

Pentaerythrityl Tetranitrate and Nitroglycerin, but not Isosorbide Mononitrate, Prevent Endothelial Dysfunction Induced by Ischemia and Reperfusion

BACKGROUND

Short term exposure to nitroglycerin (GTN) has protective properties that are similar to ischemic preconditioning. Whether other organic nitrates such as pentaerithrityl tetranitrate (PETN) and isosorbide mononitrate (ISMN) have similar protective effects has not been explored.

METHODS AND RESULTS

In a randomized, parallel, double blind, controlled trial, 37 healthy young volunteers received no therapy (n=10), transdermal GTN 1.2 mg for 2 hours (n=9), PETN 80 mg (n=9), or ISMN 40 mg (n=9). Twenty-four hours later, endothelium-dependent flow-mediated vasodilation (FMD) was measured before and after local exposure to ischemia and reperfusion (IR). In the no therapy group, IR blunted FMD (FMD after IR: 1.9+/-0.6%, P<0.05), an effect that was prevented by GTN (FMD after IR: 5.3+/-1.4%, P<0.05 compared with no therapy). PETN had the same protective effect (FMD after IR: 8.1+/-1.3%, P<0.05 compared with no therapy), whereas ISMN had no significant pharmacological preconditioning effect (FMD after-IR: 3.6+/-0.8%, P=ns compared with no therapy). While it blocked the effect of GTN, Vitamin C (n=8) did not modify PETN preconditioning (FMD after IR: 6.3+/-0.9%, P=ns compared with before IR), showing that this phenomenon is not mediated by oxygen free radical production. In an effort to identify the mechanism of PETN preconditioning, isolated human endothelial cells were incubated with PETN, GTN, or ISMN. Only PETN induced expression of the genes encoding for heme oxygenase and ferritin, which have been involved in ischemic and pharmacological preconditioning.

CONCLUSIONS

We show important differences among organic nitrates in their capacity to prevent IR-induced endothelial dysfunction. GTN and PETN, but not ISMN, have this preconditioning effect. The potential clinical implications of these data warrant further investigation.

Cyclic GMP and protein kinase-G in myocardial ischaemia-reperfusion: opportunities and obstacles for survival signaling

It is clear that multiple signalling pathways regulate the critical balance between cell death and survival in myocardial ischaemia-reperfusion. Recent attention has focused on the activation of survival or salvage kinases, particularly during reperfusion, as a common mechanism of many cardioprotective interventions. The phosphatidyl inositol 3'-hydroxy kinase/Akt complex (PI3K/Akt) and p42/p44 mitogen-activated protein kinase cascades have been widely promoted in this respect but the cyclic guanosine 3',5'-monophosphate/cGMP-dependent protein kinase (cGMP/PKG) signal transduction cassette has been less systematically investigated as a survival cascade. We propose that activation of the cGMP/PKG signalling pathway, following activation of soluble or particulate guanylate cyclases, may play a pivotal role in survival signalling in ischaemia-reperfusion, especially in the classical preconditioning, delayed preconditioning and postconditioning paradigms. The resurgence of interest in reperfusion injury, largely as a result of postconditioning-related research, has confirmed that the cGMP/PKG pathway is a pivotal salvage mechanism in reperfusion. Numerous studies suggest that the infarct-limiting effects of preconditioning and postconditioning, exogenously donated nitric oxide (NO), natriuretic peptides, phosphodiesterase inhibitors, and other diverse drugs and mediators such as HMG co-A reductase inhibitors (statins), Rho-kinase inhibitors and adrenomedullin, whether given before and during ischaemia, or specifically at the onset of reperfusion, may be mediated by activation or enhancement of the cGMP pathway, either directly or indirectly via endogenous NO generation downstream of PI3K/Akt. Putative mechanisms of protection include PKG regulation of Ca(2+) homeostasis through the modification of sarcoplasmic reticulum Ca(2+) uptake mechanisms, and PKG-induced opening of ATP-sensitive K(+) channels during ischaemia and/or reperfusion. At present, significant technical obstacles in defining the precise roles played by cGMP/PKG signalling include the heavy reliance on pharmacological PKG inhibitors of uncertain selectivity, difficulties in determining PKG activity in intact tissue, and the growing recognition that intracellular compartmentalisation of the cGMP pool may contribute markedly to the nucleotide's biological actions and biochemical determination. Overall, the body of experimental evidence suggests that cGMP/PKG survival signalling ameliorates irreversible injury associated with ischaemia-reperfusion and may be a tractable therapeutic target.

Early Microcirculatory Changes after Ischemic Preconditioning and Small Bowel Autotransplantation

BACKGROUND/AIMS

Ischemia-reperfusion injury contributes to the high complication rate of small bowel transplantation (SBTX). Ischemic preconditioning (IPC) protects against reperfusion injury in several organs, but the IPC-induced microcirculatory reaction in the intestine is unknown.

METHODS

We examined the effects of IPC on the macrohemodynamics and graft microcirculation in a canine model of SBTX during a 4-hour reperfusion period. In group 1 SBTX was performed, in group 2 IPC was induced before graft harvesting (ischemia 3 times for 5 min, followed by 10 min of reperfusion). Cardiac index and mesenteric blood flow were measured, and the mucosal microcirculation, villus epithelial thickness and functional capillary density were monitored by orthogonal polarization spectral imaging. Leukocyte-endothelial cell interactions were monitored in the postcapillary venules, with intravital fluorescence microscopy.

RESULTS

Reperfusion decreased cardiac index and mesenteric blood flow during reperfusion; IPC significantly improved these changes. Reperfusion was accompanied by decreased functional capillary density and epithelial thickness of the villi and increased leukocyte-endothelial cell interactions. IPC increased functional capillary density, prevented epithelial narrowing and reduced leukocyte rolling and adherence.

CONCLUSION

IPC improves the macrohemodynamics and the intestinal microcirculation and reduces leukocyte-mediated tissue injury during reperfusion. IPC can be an effective tool to limit reperfusion injury during SBTX.

The Role of Nitric Oxide in the Neuroprotection of Limb Ischemic Preconditioning in Rats

Brief limb ischemia was reported to protect neurons against injury induced by subsequent cerebral ischemia-reperfusion, and this phenomenon is known as limb ischemic preconditioning (LIP). To explore the role of nitric oxide (NO) in neuroprotection of LIP in rats, we observed changes in the content of nitric oxide (NO) and activity of NO synthase (NOS) in the serum and CA1 hippocampus of rats after transient limb ischemic preconditioning (LIP), and the influence of N(G)-nitro-L-arginine methylester (L-NAME), a NOS inhibitor, on the neuroprotection of LIP against cerebral ischemia-reperfusion injury. Results showed that NO content and NOS activity in serum increased significantly after LIP compared with the sham group. The increase showed a double peak pattern, in which the first one appeared at time 0 (immediate time point) and the second one appeared at 48 h after the LIP (P < 0.01). The NO content and NOS activity in the CA1 hippocampus in LIP group showed similar change pattern with the changes in the serum, except for the first peak of up-regulation of NO content and NOS activity appeared at 6 h after LIP. Pretreatment with L-NAME before LIP blocked the neuroprotection of LIP against subsequent cerebral ischemic insult. The blocking effect of L-NAME was abolished with pretreatment of L-Arg. These findings indicated that NO may be associated with the tolerance of pyramidal cells in the CA1 hippocampus to ischemia induced by LIP in rats.

Myocardial protection evoked by hyperoxic exposure involves signaling through nitric oxide and mitogen activated protein kinases

BACKGROUND

Hyperoxic exposure in vivo (> 95% oxygen) attenuates ischemia-reperfusion injury, but the signaling mechanisms of this cardioprotection are not fully determined. We studied a possible role of nitric oxide (NO) and mitogen activated protein kinases (MAPK) in hyperoxic protection.

METHODS

Mice (n = 7-9 in each group) were kept in normoxic or hyperoxic environments for 15 min prior to harvesting the heart and Langendorff perfusion with global ischemia (45 min) and reperfusion (60 min). Endpoints were cardiac function and infarct size. Additional hearts were collected to evaluate MAPK phosphorylation (immunoblot). The nitric oxide synthase inhibitor L-NAME, the ERK1/2 inhibitor PD98059 and the p38 MAPK inhibitor FR167653 were injected intraperitoneally before hyperoxia or normoxia.

RESULTS

Hyperoxia improved postischemic functional recovery and reduced infarct size (p < 0.05). Hyperoxic exposure caused cardiac phosphorylation of the MAPK family members p38 and ERK1/2, but not JNK. L-NAME, PD98059 and FR167653 all reduced the protection afforded by hyperoxic exposure, but did not influence performance or infarction in hearts of normoxic mice. The hyperoxia-induced phosphorylation of ERK1/2 and p38 was reduced by L-NAME and both MAPK inhibitors.

CONCLUSION

Nitric oxide triggers hyperoxic protection, and ERK1/2 and p38 MAPK are involved in signaling of protection against ischemia-reperfusion injury.

Efficacy of ischaemic preconditioning in the eNOS overexpressed working mouse heart model

We recently demonstrated that exogenous nitric oxide (NO) acts as a trigger for preconditioning in the isolated rat heart model. There is however little data concerning the effects of elevated cardiac endothelial nitric oxide synthase (eNOS) expression on myocardial tolerance to ischaemia. Similarly, the effects of gender and eNOS overexpression on ischaemic preconditioning is unknown. We hypothesized that: 1) eNOS overexpression increases myocardial tolerance to ischaemia, and, 2) eNOS overexpressed hearts cannot be preconditioned, since the hearts are already maximally protected. Male and female wild-type and transgenic mice that overexpress eNOS exclusively in cardiac myocytes were perfused in the working heart mode with a modified Krebs-Henseleit buffer at a pre-load of 12.5 mm Hg and afterload of 50 mm Hg. Cardiac output, coronary flow, peak aortic systolic pressure and total work were determined before hearts were preconditioned by 4x5 min cycles of ischaemia/reperfusion, and then subjected to 20 min total global ischaemia, followed by reperfusion. Reperfusion function and myocardial infarct size were used as endpoints. Pre-ischaemic mechanical function (rate pressure product and cardiac output) was similar for wild-type and transgenic mice of both sexes. The eNOS overexpressed hearts had smaller infarcts than the hearts from their wild-type littermates (26.9+/-1.4% vs. 37.0+/-2.1% for controls, P<0.05). Preconditioning the eNOS overexpressed hearts resulted in infarct sizes comparable with control non-preconditioned hearts (27.5+/-2.0% vs. 26.9+/-1.4% for controls). Myocardial cGMP levels were elevated during sustained ischaemia in the transgenic hearts when compared with wild-type hearts (22.43+/-1.63 pmol/g ww vs 16.54+/-1.48 pmol/g ww, P<0.05). Preconditioning also elevated myocardial cGMP levels during sustained ischaemia in the wild-type hearts (26.77+/-2.81 pmol/g ww, P<0.05). We conclude that: 1) basal mechanical function is similar for both wild-type and transgenic mice of both sexes, 2) reperfusion function and infarct size was also similar for both sexes under both control conditions and after preconditioning, 3) the transgenic mice are more tolerant of ischaemia as reflected by their smaller myocardial infarcts, and, 4) the eNOS overexpressed mouse heart cannot be preconditioned regardless of whether mechanical function or infarct size is used as an end-point. These hearts may be maximally protected against ischaemia/reperfusion injury by their elevated endogenous NO levels.

Nitric oxide stimulates cyclooxygenase-2 in cultured cTAL cells through a p38-dependent pathway

To examine the interaction of nitric oxide (NO) and cyclooxygenase (COX-2) and the signaling pathway involved, primary cultured rabbit cortical thick ascending limb (cTAL) were used. In these cells, immunoreactive COX-2 and vasodilatory prostaglandins were increased by a NO donor, S-nitros- N-acetylpenicillamine (SNAP; 2.5 ± 0.3-fold control, n = 6, P < 0.01). SNAP increased expression of phosphorylated p38 (pp38; 2.4 ± 0.3-fold control; n = 5; P < 0.01), which was inhibited by the p38 inhibitor SB-203580 (1.3 ± 0.1-fold control, n = 5, P < 0.01). SB-203580 inhibited SNAP-induced COX-2 expression [1.4 ± 0.2-fold control, n = 6, not significant (NS) vs. control] and levels of PGE2significantly. In cTAL cells transfected with a luciferase reporter driven by the wild-type mouse COX-2 promoter, SNAP stimulated luciferase activity, which was reversed by SB-203580 (control vs. SNAP vs. SNAP + SB-203580: 1.4 ± 0.2-, 8.3 ± 1.4-, and 0.4 ± 0.1-fold control, respectively, n = 4, P < 0.01). Electrophoretic mobility shift assay indicated that SNAP stimulated nuclear factor (NF)-κB binding activity in cTAL that was also inhibited by the p38 inhibitor. SNAP was not able to stimulate a mutant COX-2 promoter construct that is not activated by NF-κB (0.9 ± 0.1, 1.2 ± 0.1, and 1.0 ± 0.2 respectively, n = 4, NS). Low chloride increased COX-2 expression (2.7 ± 0.4-fold control, n = 6, P < 0.01) and pp38 expression (2.8 ± 0.3-fold; n = 5, P < 0.01), which were reversed by the specific NO synthase (NOS) inhibitor 7-nitroindazole. Administration of a low-salt diet increased immunoreactive COX-2 and neuronal NOS (nNOS) in the macula densa and surrounding cTAL of kidneys of wild-type mice but did not significantly elevate COX-2 expression in nNOS−/−mice. In summary, these studies indicate that, in cTAL, NO can increase COX-2 expression in cTAL and macula densa through p38-dependent signaling pathways via activation of NF-κB.

Delayed energy protection of ischemic preconditioning on hepatic ischemia/reperfusion injury in rats

BACKGROUND

Hepatic ischemia/reperfusion (IR) injuries associated with hepatic resections are unresolved problems in the clinical practice. The aim of this study is to elucidate the effect of ischemic preconditioning (IPC) on the energy charge (EC) and related mechanisms at the late phase of hepatic IR injury.

METHODS

30 Wistar rats were randomly divided into sham, IR and IPC groups. The model of partial hepatic IR was used. The rats were subjected to 60 min hepatic ischemia, pretreated by IPC (10/15 min) or not. After 24 h of reperfusion, serum alanine aminotransferase (ALT), nitrite/nitrate (NOx), malondialdehyde (MDA), hepatic tissue arginase activity, adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and EC of the liver were measured.

RESULTS

Liver injury reduced by IPC is measured by liver tissue arginase activity and serum ALT. Tissue NOx levels in rats pretreated with IPC were significantly higher than levels in the IR group (p < 0.001). Tissue levels of MDA in the liver of the IPC group were found to be significantly lower than the levels in the IR group (p < 0.001). ATP and EC levels 24 h after hepatic ischemia in rats pretreated with IPC were higher than the levels in the IR (p < 0.05). All groups had similar ADP and AMP levels in the liver tissues. The IPC procedure significantly reduced the hepatic necrosis (p < 0.001).

CONCLUSION

The results of this study demonstrated that pretreatment with IPC improved tissue ATP, EC, and hepatic necrosis at late stages of ischemia reperfusion injury of the liver. Increased nitric oxide, reduced MDA and arginase activity seemed to play a regulatory role in this delayed protective effect of IPC.

Proteasomal proteolysis in anoxia-reoxygenation, preconditioning and postconditioning of isolated cardiomyocytes

The role of proteasomal proteolysis in the pathogenesis of ischemia-reperfusion is being actively studied. To evaluate the participation of the proteasome in the preconditioning and postconditioning phenomena we used primary culture of neonatal cardiomyocytes. This culture was undergone 30min of anoxia followed by 60min of reoxygenation. Preconditioning was modeled by three cycles of 3min anoxia followed by 3min reoxygenation. Postconditioning was modeled by three cycles of 1min reoxygenation followed by 1min anoxia, respectively. Clasto-lactacystin beta-lactone, a specific proteasome inhibitor, was added to the culture medium right before the cycles of preconditioning or postconditioning in the dose that does not cause cell death (2.5muM). Percentages of living, necrotic, and apoptotic cells were determined by staining with bisbenzimide and propidium iodide. Autophagy was demonstrated by staining vacuolar structures with monodansyl cadaverine. Proteasomal activity was determined by cleavage intensity of specific fluorogenic substrates. Trypsin-like, chymotrypsin-like and peptidyl-glutamyl peptide-hydrolyzing (PGPH) activities were decreased after anoxia. Reoxygenation has led to the increase in trypsin-like and chymotrypsin-like activities comparing to anoxia, but these parameters have never reached the control levels. PGPH activity has been restored up to the initial level. Preconditioning and postconditioning increased numbers of living cells and decreased that of necrotic, apoptotic and autophagic cells. Paradoxically, it was established that proteasome inhibitors prevented the necrotic and apoptotic cell death of cardiomyocytes in anoxia-reoxygenation, but in the same concentration abolished the effects of preconditioning and postconditioning. Low doses of proteasome inhibitors, particularly the ones used in our experiments, resulted in the abolishing of preconditioning and postconditioning phenomena, but at the same time led to the increase of the population of living cells in anoxia-reoxygenation, and can be considered as potential pharmacological agents of preconditioning and postconditioning.

Signaling Pathways Involved in the Cardioprotective Effects of Cannabinoids

The aim of the present article is to review the cardioprotective properties of cannabinoids, with an emphasis on the signaling pathways involved. Cannabinoids have been reported to protect against ischemia in rat isolated hearts, as well as in rats and mice in vivo. Although these effects have been observed mostly with a pre-treatment of a cannabinoid, we report that the selective CB(2)-receptor agonist JWH133 is able to reduce infarct size when administered either before ischemia, during the entire ischemic period, or just upon reperfusion. Little is known about the signaling pathways involved in these cardioprotective effects. Likely candidates include protein kinase C (PKC) and mitogen-activated protein kinases (MAPK) since they are activated during ischemia-reperfusion and contribute to the protective effect ischemic preconditioning. The use of pharmacological inhibitors suggests that PKC, p38 MAPK, and p42/p44 MAPK (ERK1/2) contribute to the protective effect of cannabinoids. In addition, perfusion with JWH133 in healthy hearts caused an increase in both p38 MAPK phosphorylation level and activity, whereas the CB(1)-receptor agonist ACEA was associated with an increase in the phosphorylation status of both ERK1 and ERK2 without any change in activity. During ischemia, both agonists doubled p38 MAPK activity, whereas ERK1/2 phosphorylation level and activity during reperfusion were enhanced only by the CB(1)-receptor agonist. Finally, although nitric oxide (NO) was shown to exert both pro and anti-apoptotic effects on cardiomyocytes, with an apparently controversial effect on myocardial survival, our data suggest that NO may contribute to the cardioprotective effect of some cannabinoids.

Ischaemic preconditioning in transplantation and major resection of the liver

BACKGROUND

Ischaemia-reperfusion injury (IRI) contributes significantly to the morbidity and mortality of transplantation and major resection of the liver. Its severity is reduced by ischaemic preconditioning (IP), the precise mechanisms of which are not completely understood. This review discusses the pathophysiology and role of IP in this clinical setting.

METHODS

A Medline search was performed using the keywords 'ischaemic preconditioning', 'ischaemia-reperfusion injury', 'transplantation' and 'hepatic resection'. Additional articles were obtained from references within the papers identified by the Medline search.

RESULTS AND CONCLUSION

The mechanisms underlying hepatic IRI are complex, but IP reduces the severity of such injury in several animal models and in recent human trials. Increased understanding of the cellular processes involved in IP is of importance in the development of treatment strategies aimed at improving outcome after liver transplantation and major hepatic resection.

Préconditionnement myocardique induit par les agents anesthésiques halogénés : bases fondamentales et implications cliniques

OBJECTIVE

Volatile halogenated anaesthetics offer a myocardial protection when they are administrated before a myocardial ischaemia. Cellular mechanisms involved in anaesthetic preconditioning are now better understood. The objectives of this review are to understand the anaesthetic-induced preconditioning underlying mechanisms and to know the clinical implications.

DATA SOURCES

References were obtained from PubMed data bank (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) using the following keywords: volatile anaesthetic, isoflurane, halothane, sevoflurane, desflurane, preconditioning, protection, myocardium.

DATA SYNTHESIS

Ischaemic preconditioning (PC) is a myocardial endogenous protection against ischaemia. It has been described as one or several short ischaemia before a sustained ischemia. These short ischaemia trigger a protective signal against this longer ischaemia. An ischemic organ is able to precondition a remote organ. It is possible to replace the short ischaemia by a preadministration of halogenated volatile anaesthetic with the same protective effect, this is called anaesthetic PC (APC). APC and ischaemic PC share similar underlying biochemical mechanisms including protein kinase C, tyrosine kinase activation and mitochondrial and sarcolemnal K(ATP) channels opening. All halogenated anaesthetics can produce an anaesthetic PC effect. Myocardial protection during reperfusion, after the long ischaemia, has been shown by successive short ischaemia or volatile anaesthetic administration, this is called postconditioning. Ischaemic PC has been described in humans in 1993. Clinical studies in human cardiac surgery have shown the possibility of anaesthetic PC with volatile anaesthetics. These studies have shown a decrease of postoperative troponin in patient receiving halogenated anaesthetics.

Ischemic preconditioning of remote organs attenuates gastric ischemia-reperfusion injury through involvement of prostaglandins and sensory nerves

Limitation of the stomach damage by its earlier brief ischemia and reperfusion before prolonged ischemia is defined as gastric ischemic preconditioning but whether such brief ischemia of remote organs like heart or liver can also attenuate the gastric damage caused by longer and severe ischemia-reperfusion remains unknown. The cardiac, hepatic and gastric preconditioning were induced by brief ischemia (occlusion of coronary, hepatic and celiac arteries twice for 5 min) applied 30 min before 3 h of ischemia/reperfusion. Standard 3 h ischemia-reperfusion of the stomach produced numerous gastric lesions, decreased gastric blood flow and mucosal prostaglandin E2 generation and increased expression and plasma release of interleukin-1beta and tumor necrosis factor-alpha (TNF-alpha). These effects were significantly attenuated by brief cardiac, hepatic and gastric preconditioning which upregulated cyclooxygenase-2 mRNA but not cyclooxygenase-1 mRNA. The protective effects of brief gastric, cardiac and hepatic preconditioning were attenuated by selective cyclooxygenase-1 and cyclooxygenase-2 inhibitors and capsaicin denervation. We conclude that brief ischemia of remote preconditioning such as heart or liver protects gastric mucosa against severe ischemia-reperfusion-induced gastric lesions as effectively as local preconditioning of the stomach itself via the mechanism involving prostaglandin derived from cyclooxygenase-1 and cyclooxygenase-2 and the activation of sensory nerves releasing calcitonin gene-related peptide (CGRP) combined with the suppression of interleukin-1beta and TNF-alpha expression and release.

Regulation of inducible nitric oxide synthase in ischemic preconditioning of muscle flap in a rat model

PURPOSE

Ischemic preconditioning has been shown to influence flap tolerance to prolonged ischemia. Nitric oxide (NO) synthesis is one of the proposed mechanisms involved in ischemic preconditioning. In this study, the molecular marker of NO is examined in correlation with ischemic preconditioning on improving muscle flap survival.

METHODS

Fifty male Sprague-Dawley rats were randomized into experimental and control groups. The gracilis muscle flap with femoral vascular pedicle was used as a flap model. Ischemic preconditioning consisted of 3 sequences of clamping the pedicle for 10 minutes followed by 10 minutes of reperfusion for a total of 1 hour. In part I, the experimental group (n = 10) underwent ischemic preconditioning for 1 hour. In the control group (n = 10), the flaps were dissected without clamping of the pedicle. Both groups were then subjected to 4 hours of global ischemia by continuous pedicle clamping, after which the flaps were sutured to their beds. On postoperative day 3, flap survival was determined by gross and histologic examinations. The evaluators were blinded to the treatment. In part II, the experimental group (n = 12) underwent ischemic preconditioning, while the control group (n = 12) did not. The flaps from each group were harvested for inducible nitric oxide synthase (iNOS) gene expression using reverse transcriptase-polymerase chain reaction at the end of 1 hour after reperfusion and at 4 hours of global ischemia.

RESULTS

The results indicated a significantly higher survival rate in the experimental group than in the control group (90 versus 50%, P < 0.05). iNOS gene expression was significantly higher in the experimental group than in the control group at 1 hour after ischemic preconditioning (0.73+/-0.18 versus 0.26+/-0.11, P < 0.01). However, after 4 hours of global ischemia, iNOS expression in the control group was statistically higher than in the experimental group (0.83+/-0.16 versus 0.26+/-0.07, P < 0.01).

CONCLUSIONS

We conclude that ischemic preconditioning can enhance flap tolerance to ischemia-reperfusion injury and improve flap viability rate. This study provides evidence that the regulation of NOS may play a role in ischemic preconditioning phenomenon and warrants further investigation.