Possible effects of melatonin on reperfusion injury following coronary artery bypass graft surgery

BACKGROUND

Although coronary artery bypass graft (CABG) surgery has been reported to be one of the most effective internentions in terms of myocardial salvage, reperfusion itself can cause additional damage to the myocardium. Since there is strong evidence that free radicals are the principal offender in ischemia-reperfusion (I/R) injury, it has been suggested that treatment with antioxidant agents can be protective. Investigations have shown that melatonin secretion is partially disturbed in CABG patients. The aim of this study was to evaluate the protective effect of melatonin as an antioxidant agent on I/R injury.

METHODS

164 elective CABG candidates participated in this randomized clinical trial during the preoperative period. The candidates were randomized to receive 3 mg of melatonin tablets (physiologic dose) from 3 days before surgery until the day of discharge. Cardiac biomarkers [troponin and creatine kinase myocardial band (CKMB)] were assessed once before surgery (24 hours before surgery), and 8 and 24 hours after surgery.

RESULTS

Finally, 130 patients, 65 (50%) patients in the melatonin group and 65 (50%) in the control arm finished our study. Mean age of melatonin and control groups was 59.90 ± 9.59 and 60.80 ± 8.00 years, respectively; moreover, 47 (72.30%) in melatonin and 45 (69.23%) in control group were men. No significant difference was seen in baseline cardiac biomarkers between two groups (P > 0.05). In both groups, cardiac biomarkers (CKMB and troponin) elevated after surgery in comparison to their preoperative values. There was no statistically significant difference between the control and melatonin groups regarding the 8-hour and 24-hour troponin and CKMB when adjusted for interacting factors (P > 0.05).

CONCLUSION

Although physiological concentration of melatonin is protective against I/R injury, substitution of endogenous melatonin with the oral supplement which creates physiologic concentration may not prevent I/R injury. In order to have antioxidant effect, pharmacologic doses of melatonin should be employed.

Targeting the mitochondrial permeability transition pore for drug discovery: Challenges and opportunities

Several drug targets have been amenable to drug discovery pursuit not until the characterization of the mitochondrial permeability transition pore (MPTP), a pore with an undefined molecular identity that forms on the inner mitochondrial membrane upon mitochondrial permeability transition (MPT) under the influence of calcium overload and oxidative stress. The opening of the pore which is presumed to cause cell death in certain human diseases also has implications under physiological parlance. Different models for this pore have been postulated following its first identification in the last six decades. The mitochondrial community has witnessed many protein candidates such as; voltage-dependent anion channel (VDAC), adenine nucleotide translocase (ANT), Mitochondrial phosphate carrier (PiC), Spastic Paralegin (SPG7), disordered proteins, and F1Fo ATPase. However, genetic studies have cast out most of these candidates with only F1Fo ATPase currently under intense argument. Cyclophilin D (CyPD) remains the widely accepted positive regulator of the MPTP known to date, but no drug candidate has emerged as its inhibitor, raising concern issues for therapeutics. Thus, in this review, we discuss various models of MPTP reported with the hope of stimulating further research in this field. We went beyond the classical description of the MPTP to ascribe a 'two-edged sword property' to the pore for therapeutic function in human disease because its inhibition and activation have pharmacological relevance. We suggested putative proteins upstream to CyPD that can regulate its activity and prevent cell deaths in neurodegenerative disease and ischemia-reperfusion injury.

Role of Complement Activation in Allograft Inflammation

PURPOSE

Novel paradigms have broadened our understanding of mechanisms through which complement mediates allograft inflammation/injury. Herein we review advances in the field and highlight therapeutic implications.

RECENT FINDINGS

Pre-clinical and translational human trials have elucidated complement-dependent mechanisms of post-transplant ischemia-reperfusion (I/R) injury. Immune cell-derived, and intracellular, complement activation are newly linked to proinflammatory T cell immunity relevant to allograft rejection. Complement-induced immune regulation, including C5a ligation of C5a receptor 2 on T cells, C5a/C5a receptor 1 interactions on regulatory myeloid cells, and C1q binding to CD8+ T cells can inhibit proinflammatory T cells and/or prolong murine allograft survival. Pilot trials of complement inhibition to treat/prevent human I/R- or antibody-initiated allograft injury show promise.

SUMMARY

The complement system participates in allograft injury through multiple context- dependent mechanisms involving various components and receptors. These new insights along with development and implementation of individualized complement inhibitory strategies have potential to improve transplant outcomes.

Therapeutic Strategies of Kidney Transplant Ischemia Reperfusion Injury: Insight From Mouse Models

Ischemia/reperfusion injury (IRI) is inherent to all transplanted organs and is adversely associated with early renal graft function and graft longevity. Despite the progress in immunosuppressive regimens and perioperative care, no FDA-approved treatment for kidney transplant IRI is available to date. In recent years, by utilizing the modified and clinically-relevant mouse models of kidney transplantation (KT_x) in which extended IRI is induced by the prolonged warm or cold ischemic time, studies have identified several potential therapeutic approaches for KT_x IRI, including the hormone supplement, promoting tubular repair and regeneration, and targeting complement system, inflammation, and necroptosis. This review describes some of the lessons learned from mouse models of KT_x with regard to factors that influence the severity of transplant IRI and the potential therapeutic targets.

Comparison of the Protective Effects of Erythropoietin and Melatonin on Renal Ischemia-Reperfusion Injury

Background

Renal ischemia-reperfusion (IR) contributes to the development of acute renal failure (ARF). Oxygen free radicals are considered to be the principal components involved in the pathophysiological tissue alterations observed during renal IR.

Objectives

In this study, we compared the effects of melatonin (MEL) and erythropoietin (EPO), both known antioxidant and anti-inflammatory agents, on IR-induced renal injury in rats.

Materials and Methods

Wistar albino rats were unilaterally nephrectomized and then subjected to 45 minutes of renal pedicle occlusion followed by 24 hours of reperfusion. MEL (10 mg/kg, i.p) and EPO (5000 U/kg, i.p) were administered prior to the onset of ischemia. After 24 hours of reperfusion and following decapitation, blood samples were collected for the determination of the hemoglobin (Hb) and hematocrit (Hct) levels. Additionally, renal samples were taken for histological evaluation.

Results

Ischemia-reperfusion significantly decreased the observed Hb and Hct values. The histopathological findings in the IR group confirmed that there was an increase in the hyaline cast and thickening of the Bowman capsule basement membrane. Treatment with EPO or MEL significantly increased the Hb and Hct values. In the MEL + IR group, the histopathological changes were lower than those found in the EPO + IR group.

Conclusions

Treatment with EPO and MEL had a beneficial effect on renal IR injury. The results may also indicate that MEL protects against morphological damage better than EPO in renal IR injury.

Correlation of Histopathologic Findings of Non-Graft Threatening Preservation/Reperfusion Injury in Time-Zero Liver Needle Biopsies With Short-Term Post-transplantation Laboratory Alterations

BACKGROUND

Early post-transplantation alterations in liver tests are caused by a variety of etiologies including rejection, biliary or vascular complications, and preservation/reperfusion injury (PRI).

OBJECTIVES

The aim of this study was to show the correlation between histopathologic changes of PRI and the alterations in liver tests in the early post-transplantation period.

MATERIALS AND METHODS

Between April 2013 and August 2014, histopathologic findings of protocol, time-zero, Tru-Cut, liver needle biopsies were evaluated in 94 cases of cadaveric liver transplantation. The histopathologic changes included ballooning degeneration, micro- and macro-vesicular steatosis, bilirubinostasis, apoptotic cells, bile plugs and neutrophilic infiltration. These histopathologic changes were compared with the early (15 days) post-transplantation liver laboratory findings.

RESULTS

Clinico-pathologic evaluation of all 94 cases was done by assessment of PRI findings in time-zero biopsies and possible causes of allograft injury were appraised. In 21 patients, a specific cause for allograft injury was found including rejection and/or surgical complications. In the remaining 73 cases, there was no specific cause for allograft injury and histopathologic findings of time-zero liver needle biopsies supported PRI. We classified liver laboratory tests alterations as: hepatocellular damage (elevation of transaminases and lactate dehydrogenase), cholestatic damage (elevation of alkaline phosphatase and total bilirubin) and mixed. Hepatocellular and cholestatic alterations in liver function tests were associated with the presence of marked apoptotic bodies and neutrophilic aggregates in time zero biopsies, respectively. On the other hand, macrovesicular steatosis was dominantly associated with mixed (hepatocellular and cholestatic) laboratory alterations of liver tests.

CONCLUSIONS

Any discrepancy between histopathologic changes in time-zero biopsies and pattern of early liver laboratory alterations may be considered as a warning for causes other than PRI.

Combination antioxidant effect of erythropoietin and melatonin on renal ischemia-reperfusion injury in rats

OBJECTIVE(S)

Renal ischemia reperfusion (IR) contributes to the development of acute renal failure (ARF). Oxygen free radicals are considered to be principal components involved in the pathophysiological tissue alterations observed during renal IR. The purpose of this study was to investigate the effect of co-administration of melatonin (MEL) and erythropoietin (EPO), potent antioxidant and anti-inflammatory agents, on IR-induced renal injury in rats.

MATERIALS AND METHODS

Wistar albino rats were unilaterally nephrectomized and subjected to 45 min of renal pedicle occlusion followed by 24 hr reperfusion. MEL (10 mg/kg, IP) and EPO (5000 U/kg, IP) were administered prior to ischemia. After 24 hr reperfusion, following decapitation, renal samples were taken for the determination of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) levels and histological evaluation. The level of urea was measured in serum samples.

RESULTS

Ischemia reperfusion significantly increased urea, and MDA levels, and decreased CAT and SOD activities. Histopathological findings of the IR group confirmed that there was renal impairment in the tubular epithelium. Treatment with EPO and MEL markedly decreased urea level and increased SOD and GPx activities.

CONCLUSION

Treatment with EPO and MEL had a beneficial effect on renal IR injury. These results may show that the co-administration of MEL and EPO cannot exert more beneficial effects than either agent alone.

Amiodarone versus lidocaine for the prevention of reperfusion ventricular fibrillation: A randomized clinical trial

BACKGROUND

Reperfusion ventricular fibrillation after aortic cross clamp is one of the important complications of open cardiac surgery and its prevention could reduce myocardial injuries. This study aimed to evaluate the efficacy of single dose of amiodarone or lidocaine by the way of pump circuit three minutes before aortic cross clamp release and compare the results with normal saline as placebo in a randomized double blinded controlled trial.

METHODS

One hundred fifty patients scheduled for first time elective coronary artery bypass graft surgery were randomly assigned to receive either single dose of amiodarone (150 mg), lidocaine (100 mg), or normal saline (5 ml) three minutes before aortic cross clamp release. The incidence of ventricular fibrillation and the need for reuse of drug were compared between these groups by chi-square, Student's t-test, Mann-Whitney test, and One-way ANOVA. SPSS software was used for statistical analysis.

RESULTS

The incidence of ventricular fibrillation is higher in the placebo group (15.9%) compare to lidocaine (11.8%) and amiodarone (8.9%) groups; however, there was no statistical difference among the three groups (P = 0.41). Moreover, the reuse of amiodarone (22.7%) was statistically higher (P < 0.05) than lidocaine (5.9%).

CONCLUSION

This study showed no difference among lidocaine, amiodarone, and placebo in preventing ventricular fibrillation after aortic cross clamp release.