Effect of desflurane-induced preconditioning following ischemia-reperfusion on nitric oxide release in rabbits

Azelnidipine protects HL-1 cardiomyocytes from hypoxia/reoxygenation injury by enhancement of NO production independently of effects on gene expression

It remains to be elucidated whether Ca2+ antagonists induce pharmacological preconditioning to protect the heart against ischemia/reperfusion injury. The aim of this study was to determine whether and how pretreatment with a Ca2+ antagonist, azelnidipine, could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury in vitro. Using HL-1 cardiomyocytes, we studied effects of azelnidipine on NO synthase (NOS) expression, NO production, cell death and apoptosis during H/R. Action potential durations (APDs) were determined by the whole-cell patch-clamp technique. Azelnidipine enhanced endothelial NOS phosphorylation and NO production in HL-1 cells under normoxia, which was abolished by a heat shock protein 90 inhibitor, geldanamycin, and an antioxidant, N-acetylcysteine. Pretreatment with azelnidipine reduced cell death and shortened APDs during H/R. These effects of azelnidipine were diminished by a NOS inhibitor, L-NAME, but were influenced by neither a T-type Ca2+ channel inhibitor, NiCl2, nor a N-type Ca2+ channel inhibitor, ω-conotoxin. The azelnidipine-induced reduction in cell death was not significantly enhanced by either additional azelnidipine treatment during H/R or increasing extracellular Ca2+ concentrations. RNA sequence (RNA-seq) data indicated that azelnidipine-induced attenuation of cell death, which depended on enhanced NO production, did not involve any significant modifications of gene expression responsible for the NO/cGMP/PKG pathway. We conclude that pretreatment with azelnidipine protects HL-1 cardiomyocytes against H/R injury via NO-dependent APD shortening and L-type Ca2+ channel blockade independently of effects on gene expression.

Phellinus linteus Mycelium Alleviates Myocardial Ischemia-Reperfusion Injury through Autophagic Regulation

The incidence of myocardial ischemia-reperfusion (IR) injury is rapidly increasing around the world and this disease is a major contributor to global morbidity and mortality. It is known that regulation of programmed cell death including apoptosis and autophagy reduces the impact of myocardial IR injury. In this study, the cardioprotective effects and underlying mechanisms of Phellinus linteus (Berk. and Curt.) Teng, Hymenochaetaceae (PL), a type of medicinal mushroom, were examined in rats subjected to myocardial IR injury. The left main coronary artery of rats was ligated for 1 h and reperfused for 3 h. The arrhythmia levels were monitored during the entire process and the infarct size was evaluated after myocardial IR injury. Furthermore, the expression levels of proteins in apoptotic and autophagic pathways were observed. Pretreatment with PL mycelium (PLM) significantly reduced ventricular arrhythmia and mortality due to myocardial IR injury. PLM also significantly decreased myocardial infarct size and plasma lactate dehydrogenase level after myocardial IR injury. Moreover, PLM administration resulted in decreased caspase 3 and caspase 9 activation and increased Bcl-2/Bax ratio. Phosphorylation level of AMPK was elevated while mTOR level was reduced. Becline-1 and p62 levels decreased. These findings suggest that PLM is effective in protecting the myocardium against IR injury. The mechanism involves mediation through suppressed pro-apoptotic signaling and regulation of autophagic signaling, including stimulation of AMPK-dependent pathway and inhibition of beclin-1-dependent pathway, resulting in enhancement of protective autophagy and inhibition of excessive autophagy.

Peri-operative anaesthetic myocardial preconditioning and protection - cellular mechanisms and clinical relevance in cardiac anaesthesia

Preconditioning has been shown to reduce myocardial damage caused by ischaemia–reperfusion injury peri-operatively. Volatile anaesthetic agents have the potential to provide myocardial protection by anaesthetic preconditioning and, in addition, they also mediate renal and cerebral protection. A number of proof-of-concept trials have confirmed that the experimental evidence can be translated into clinical practice with regard to postoperative markers of myocardial injury; however, this effect has not been ubiquitous. The clinical trials published to date have also been too small to investigate clinical outcome and mortality. Data from recent meta-analyses in cardiac anaesthesia are also not conclusive regarding intra-operative volatile anaesthesia. These inconclusive clinical results have led to great variability currently in the type of anaesthetic agent used during cardiac surgery. This review summarises experimentally proposed mechanisms of anaesthetic preconditioning, and assesses randomised controlled clinical trials in cardiac anaesthesia that have been aimed at translating experimental results into the clinical setting.

Cellular signaling pathways and molecular mechanisms involving inhalational anesthetics-induced organoprotection

Inhalational anesthetics-induced organoprotection has received much research interest and has been consistently demonstrated in different models of organ damage, in particular, ischemia-reperfusion injury, which features prominently in the perioperative period and in cardiovascular events. The cellular mechanisms accountable for effective organoprotection over heart, brain, kidneys, and other vital organs have been elucidated in turn in the past two decades, including receptor stimulations, second-messenger signal relay and amplification, end-effector activation, and transcriptional modification. This review summarizes the signaling pathways and the molecular participants in inhalational anesthetics-mediated organ protection published in the current literature, comparing and contrasting the 'preconditioning' and 'postconditioning' phenomena, and the similarities and differences in mechanisms between organs. The salubrious effects of inhalational anesthetics on vital organs, if reproducible in human subjects in clinical settings, would be of exceptional clinical importance, but clinical studies with better design and execution are prerequisites for valid conclusions to be made. Xenon as the emerging inhalational anesthetic, and its organoprotective efficacy, mechanism, and relative advantages over other anesthetics, are also discussed.

The role of Volatile Anesthetics in Cardioprotection: a systematic review

This review evaluates the mechanism of volatile anesthetics as cardioprotective agents in both clinical and laboratory research and furthermore assesses possible cardiac side effects upon usage. Cardiac as well as non-cardiac surgery may evoke perioperative adverse events including: ischemia, diverse arrhythmias and reperfusion injury. As volatile anesthetics have cardiovascular effects that can lead to hypotension, clinicians may choose to administer alternative anesthetics to patients with coronary artery disease, particularly if the patient has severe preoperative ischemia or cardiovascular instability. Increasing preclinical evidence demonstrated that administration of inhaled anesthetics - before and during surgery - reduces the degree of ischemia and reperfusion injury to the heart. Recently, this preclinical data has been implemented clinically, and beneficial effects have been found in some studies of patients undergoing coronary artery bypass graft surgery. Administration of volatile anesthetic gases was protective for patients undergoing cardiac surgery through manipulation of the potassium ATP (K_ATP) channel, mitochondrial permeability transition pore (mPTP), reactive oxygen species (ROS) production, as well as through cytoprotective Akt and extracellular-signal kinases (ERK) pathways. However, as not all studies have demonstrated improved outcomes, the risks for undesirable hemodynamic effects must be weighed against the possible benefits of using volatile anesthetics as a means to provide cardiac protection in patients with coronary artery disease who are undergoing surgery.

Aromatase inhibition attenuates desflurane-induced preconditioning against acute myocardial infarction in male mouse heart in vivo

The volatile anesthetic desflurane (DES) effectively reduces cardiac infarct size following experimental ischemia/reperfusion injury in the mouse heart. We hypothesized that endogenous estrogens play a role as mediators of desflurane-induced preconditioning against myocardial infarction. In this study, we tested the hypothesis that desflurane effects local estrogen synthesis by modulating enzyme aromatase expression and activity in the mouse heart. Aromatase metabolizes testosterone to 17β- estradiol (E2) and thereby significantly contributes to local estrogen synthesis. We tested aromatase effects in acute myocardial infarction model in male mice. The animals were randomized and subjected to four groups which were pre-treated with the selective aromatase inhibitor anastrozole (A group) and DES alone (DES group) or in combination (A+DES group) for 15 minutes prior to surgical intervention whereas the control group received 0.9% NaCl (CON group). All animals were subjected to 45 minutes ischemia following 180 minutes reperfusion. Anastrozole blocked DES induced preconditioning and increased infarct size compared to DES alone (37.94±15.5% vs. 17.1±3.62%) without affecting area at risk and systemic hemodynamic parameters following ischemia/reperfusion. Protein localization studies revealed that aromatase was abundant in the murine cardiovascular system with the highest expression levels in endothelial and smooth muscle cells. Desflurane application at pharmacological concentrations efficiently upregulated aromatase expression in vivo and in vitro. We conclude that desflurane efficiently regulates aromatase expression and activity which might lead to increased local estrogen synthesis and thus preserve cellular integrity and reduce cardiac damage in an acute myocardial infarction model.

Emulsified isoflurane produces cardiac protection after ischemia-reperfusion injury in rabbits

BACKGROUND

In this study, we examined the cardioprotective effects of parental emulsified isoflurane compared with inhaled isoflurane.

METHODS

Thirty-two rabbits were subjected to 30 min of myocardial ischemia induced by temporary ligation of the left anterior descending coronary artery followed by 3 h of reperfusion. Before left anterior descending coronary artery occlusion, the rabbits were randomly allocated into one of four groups (eight for each group): group C, no ischemia preconditioning treatment; group IS, inhaled isoflurane 1.1% end-tidal; group EI, a continuous infusion of 8% emulsified isoflurane to an end-tidal concentration of 0.64%; and group IN, a continuous infusion of 30% Intralipid started 30 min. Treatments were started 30 min before ischemia followed by a 15 min washout period for isoflurane groups. Myocardial infarct volume, lactate dehydrogenase, and creatine kinase levels were measured and changes in mitochondrial ultrastructure assessed after 3 h myocardial reperfusion.

RESULTS

Myocardial infarct size 3 h after reperfusion was lower in groups IS and EI compared with groups C and IN (20% +/- 8%, 18% +/- 8%, 39% +/- 6%, and 34% +/- 9%, respectively, P < 0.01). There were no differences in myocardial infarct size between groups IS and EI or between groups C and IN. Plasma lactate dehydrogenase and creatine kinase levels were lower in group IS (456 +/- 58 U/L and 1725 +/- 230 U/L) and group EI (451 +/- 54 U/L and 1686 +/- 444 U/L) 3 h after myocardial reperfusion compared with groups C (676 +/- 82 U/L and 2373 +/- 529 U/L; P < 0.01). Mitochondrial ultrastructure changes were less pronounced in groups IS and EI compared with group C.

CONCLUSIONS

Our results indicate that, in rabbits, i.v. emulsified isoflurane provides similar myocardial protection against ischemia-reperfusion injury as inhaled isoflurane.

Inflammatory response and cardioprotection during open-heart surgery: the importance of anaesthetics

Open-heart surgery triggers an inflammatory response that is largely the result of surgical trauma, cardiopulmonary bypass, and organ reperfusion injury (e.g. heart). The heart sustains injury triggered by ischaemia and reperfusion and also as a result of the effects of systemic inflammatory mediators. In addition, the heart itself is a source of inflammatory mediators and reactive oxygen species that are likely to contribute to the impairment of cardiac pump function. Formulating strategies to protect the heart during open heart surgery by attenuating reperfusion injury and systemic inflammatory response is essential to reduce morbidity. Although many anaesthetic drugs have cardioprotective actions, the diversity of the proposed mechanisms for protection (e.g. attenuating Ca(2+) overload, anti-inflammatory and antioxidant effects, pre- and post-conditioning-like protection) may have contributed to the slow adoption of anaesthetics as cardioprotective agents during open heart surgery. Clinical trials have suggested at least some cardioprotective effects of volatile anaesthetics. Whether these benefits are relevant in terms of morbidity and mortality is unclear and needs further investigation. This review describes the main mediators of myocardial injury during open heart surgery, explores available evidence of anaesthetics induced cardioprotection and addresses the efforts made to translate bench work into clinical practice.

Protective effect of EDTA preadministration on renal ischemia

BACKGROUND

Chelation therapy with sodium edetate (EDTA) improved renal function and slowed the progression of renal insufficiency in patients subjected to lead intoxication. This study was performed to identify the underlying mechanism of the ability of EDTA treatment to protect kidneys from damage.

METHODS

The effects of EDTA administration were studied in a rat model of acute renal failure induced by 60 minutes ischemia followed or not by 60 minutes reperfusion. Renal ischemic damage was evaluated by histological studies and by functional studies, namely serum creatinine and blood urea nitrogen levels. Treatment with EDTA was performed 30 minutes before the induction of ischemia. Polymorphonuclear cell (PMN) adhesion capability, plasmatic nitric oxide (NO) levels and endothelial NO synthase (eNOS) renal expression were studied as well as the EDTA protection from the TNFalpha-induced vascular leakage in the kidneys. Data was compared by two-way analysis of variance followed by a post hoc test.

RESULTS

EDTA administration resulted in the preservation of both functional and histological parameters of rat kidneys. PMN obtained from peripheral blood of EDTA-treated ischemized rats, displayed a significant reduction in the expression of the adhesion molecule Mac-1 with respect to controls. NO was significantly increased by EDTA administration and eNOS expression was higher and more diffuse in kidneys of rats treated with EDTA than in the controls. Finally, EDTA administration was able to prevent in vivo the TNFalpha-induced vascular leakage in the kidneys.

CONCLUSION

This data provides evidence that EDTA treatment is able to protect rat kidneys from ischemic damage possibly through the stimulation of NO production.