Pharmacologic prophylactic treatment for perioperative protection of skeletal muscle from ischemia-reperfusion injury in reconstructive surgery

Combined Systemic Intake of K-ATP Opener (Nicorandil) and Mesenchymal Stem Cells Preconditioned With Nicorandil Alleviates Pancreatic Insufficiency in a Model of Bilateral Renal Ischemia/Reperfusion Injury

We used nicorandil, a K-ATP channel opener, to study the role of these channels in the amelioration of renal ischemia/reperfusion (I/R)-induced pancreatic injury, and the possible involvement of PI3K/Akt/mTOR signaling pathway. Forty-two male Wistar rats were included in this study, six were sacrificed for extraction of bone marrow mesenchymal stem cells (BM-MSCs) and conducting the in-vitro work, the others were included in vivo study and equally divided into six groups. Group 1 (sham control), but groups 2–6 were subjected to bilateral renal I/R: Group 2 (I/R); Group 3 (I/R-NC), treated with nicorandil; Group 4 (I/R-MSCs), treated with BM-MSCs; Group 5 (I/R-MSCC), treated with nicorandil-preconditioned BM-MSCs; Group 6 (I/R-NC-MSCC), treated with both systemic nicorandil and preconditioned BM-MSCC. Renal injury and subsequent pancreatic damage were detected in the I/R group by a significant increase in serum urea, creatinine, fasting glucose, and pancreatic enzymes. The pancreatic tissues showed a reduction in cellularity and a significant decrease in the expression of the cell survival pathway, PI3K/Akt/mTOR, in the I/R group compared to the control. Preconditioning MSCs with nicorandil significantly enhanced the proliferation assay and decreased their apoptotic markers. Indeed, combined systemic nicorandil and nicorandil-preconditioning maintained survival of MSC in the pancreatic tissue and amelioration of apoptotic markers and pancreatic TNF-α production. Histologically, all treated groups revealed better pancreatic architecture, and increased area % of anti-insulin antibody and CD31, which were all best observed in the NC-MSCC group. Thus, using K-ATP channel opener was efficient to enhance PI3K/Akt/mTOR expression levels (in vivo and in vitro).

Nicorandil decreases oxidative stress in slow- and fast-twitch muscle fibers of diabetic rats by improving the glutathione system functioning

AIMS/INTRODUCTION

Myopathy is a common complication of any diabetes type, consisting in failure to preserve mass and muscular function. Oxidative stress has been considered one of the main causes for this condition. This study aimed to search if Nicorandil, a KATP channel opener, could protect slow- and fast-twitch diabetic rat muscles from oxidative stress, and to unveil its possible mechanisms.

MATERIALS AND METHODS

Diabetes was induced in male Wistar rats by applying intraperitoneally streptozotocin (STZ) at 100 mg/kg doses. Nicorandil (3 mg/kg/day) was administered along 4 weeks. An insulin tolerance test and assessment of fasting blood glucose (FBG), TBARS, reduced (GSH), and disulfide (GSSG) glutathione levels, GSH/GSSG ratio, and mRNA expression of glutathione metabolism-related genes were performed at end of treatment in soleus and gastrocnemius muscles.

RESULTS

Nicorandil significantly reduced FBG levels and enhanced insulin tolerance in diabetic rats. In gastrocnemius and soleus muscles, Nicorandil attenuated the oxidative stress by decreasing lipid peroxidation (TBARS), increasing total glutathione and modulating GPX1-mRNA expression in both muscle's types. Nicorandil also increased GSH and GSH/GSSG ratio and downregulated the GCLC- and GSR-mRNA in gastrocnemius, without significative effect on those enzymes' mRNA expression in diabetic soleus muscle.

CONCLUSIONS

In diabetic rats, Nicorandil attenuates oxidative stress in slow- and fast-twitch skeletal muscles by improving the glutathione system functioning. The underlying mechanisms for the modulation of glutathione redox state and the transcriptional expression of glutathione metabolism-related genes seem to be fiber type-dependent.

Diazoxide and Exercise Enhance Muscle Contraction during Obesity by Decreasing ROS Levels, Lipid Peroxidation, and Improving Glutathione Redox Status

Obesity causes insulin resistance and hyperinsulinemia which causes skeletal muscle dysfunction resulting in a decrease in contraction force and a reduced capacity to avoid fatigue, which overall, causes an increase in oxidative stress. K_ATP channel openers such as diazoxide and the implementation of exercise protocols have been reported to be actively involved in protecting skeletal muscle against metabolic stress; however, the effects of diazoxide and exercise on muscle contraction and oxidative stress during obesity have not been explored. This study aimed to determine the effect of diazoxide in the contraction of skeletal muscle of obese male Wistar rats (35 mg/kg), and with an exercise protocol (five weeks) and the combination from both. Results showed that the treatment with diazoxide and exercise improved muscular contraction, showing an increase in maximum tension and total tension due to decreased ROS and lipid peroxidation levels and improved glutathione redox state. Therefore, these results suggest that diazoxide and exercise improve muscle function during obesity, possibly through its effects as K_ATP channel openers.

Nicorandil Affects Mitochondrial Respiratory Chain Function by Increasing Complex III Activity and ROS Production in Skeletal Muscle Mitochondria

Adenosine triphosphate (ATP)-dependent potassium channels openers (K_ATP) protect skeletal muscle against function impairment through the activation of the mitochondrial K_ATP channels (mitoK_ATP). Previous reports suggest that modulators of the mitochondrial K_ATP channels have additional effects on isolated mitochondria. To determine whether the K_ATP channel opener nicorandil has non-specific effects that explain its protective effect through the mitochondrial function, chicken muscle mitochondria were isolated, and respiration rate was determined pollarographically. The activity of the electron transport chain (ETC) complexes (I-IV) was measured using a spectrophotometric method. Reactive oxygen species (ROS) levels and lipid peroxidation were assessed using flow cytometry and thiobarbituric acid assay, respectively. Both K_ATP channel opener nicorandil and K_ATP channel blocker 5-hydroxydecanoate (5-HD) decreased mitochondrial respiration; nicorandil increased complex III activity and decreased complex IV activity. The effects of nicorandil on complex III were antagonized by 5-HD. Nicorandil increased ROS levels, effect reverted by either 5-HD or the antioxidant N-2-mercaptopropionyl glycine (MPG). None of these drugs affected lipid peroxidation levels. These findings suggest that K_ATP channel opener nicorandil increases mitochondrial ROS production from complex III. This results by partially blocking electron flow in the complex IV, setting electron carriers in a more reduced state, which is favored by the increase in complex III activity by nicorandil. Overall, our study showed that nicorandil like other mitochondrial K_ATP channel openers might not act through mitoK_ATP channel activation.

Protective effects of epigallocatechin gallate against ischemia reperfusion injury in rat skeletal muscle via activating Nrf2/HO-1 signaling pathway

AIMS

Previous studies have demonstrated that epigallocatechin gallate (EGCG) had certain protective effects on myocardial and renal ischemia reperfusion (I/R) injury. We aimed to research the special effects and underling mechanisms of EGCG on skeletal muscle I/R injury.

MAIN METHOD

We established an experimental rat model of I/R skeletal muscle injury and treated with different doses of EGCG. Hematoxylin eosin staining, TUNEL assay, ELISA, qRT-PCR and Western blotting were used to evaluate the effects of EGCG.

KEY FINDINDS

EGCG significantly improved skeletal muscle function of I/R injury rats. Moreover, EGCG had positive effects on decreasing apoptosis of skeletal muscle tissues, alleviating oxidative stress damage and suppressing the production of inflammatory cytokines. Further, EGCG had positive effects on activating Nrf2/HO-1 signaling pathway.

SIGNIFICANCE

EGCG might be a powerful candidate compound for alleviating I/R injury in rat skeletal muscle.

Single Muscle Fibre Contractility Testing in Rats to Quantify Ischaemic Muscle Damage During Reperfusion Injury

OBJECTIVES

In this study, the aim was to investigate the potential for single muscle fibre contractility (SMFC) testing to detect the extent of reperfusion injury following various reperfusion periods. The hypothesis was that force generated by muscle fibres will correlate inversely with the extent of reperfusion injury.

METHODS

Twenty-four Lewis rats were distributed among five groups. Group 1 served as normal muscle control. In all other groups, femoral artery flow was occluded for four hours. Muscle biopsies were obtained at 0 hour, six hours, day two, and day seven after reperfusion in Groups 2, 3, 4, and 5, respectively. Samples then underwent ultrastructural analysis (H&E stain) and SMFC testing.

RESULTS

The maximum isometric force (mN) generated on Days two and seven after reperfusion decreased from baseline by 21% (p < 0.05), and 53% (p < .001), respectively. The specific force (kPa) followed a similar pattern with a 13% decrease at Day two (p > 0.05) and 31% decrease at Day 7 (p < .001). These results correlated inversely with the extent of quantitative injury on histology.

CONCLUSIONS

The study demonstrated an inverse relationship between single muscle fibre contractility testing and neutrophil infiltration during the reperfusion phase. Further clinical studies are needed to evaluate its potential in providing prognostic information for patient outcomes.

Extrapolating novel techniques utilised in solid organ transplantation to the microsurgical and vascularised composite allograft arena

Ischemia reperfusion injury (IRI) is characterised initially by restriction of oxygenated blood flow to an organ bed, resulting in tissue hypoxia and ischaemic injury, followed by further 'reperfusion' injury upon restoration of perfusion, with an influx of oxygen, inflammatory cells and generation of free radicals. The culmination is a complex interplay between cellular and biochemical processes involved in inflammation and coagulation, exhibited as the 'no re-flow' phenomenon. Under ideal circumstances, autologous free tissue transfer is performed with short ischemic times. However, there are certain clinical scenarios where the ischaemic period can be prolonged due to technical and non-technical factors. IRI is inevitable and can be possibly more pronounced in such cases. In these cases, there may be a role for plastic surgeons to adopt some of the anti-ischaemia reperfusion injury (IRI) practices used in solid organ transplantation (SOT). Knowledge of the current trends in SOT IRI reduction should be discussed by plastic surgeons to assess whether certain facets can be extrapolated into the plastic and reconstructive armamentarium. These can be applicable to more challenging microsurgical cases, including composite free tissue transfer. Three important aspects are discussed further in this editorial: (1) cold flushing, (2) machine perfusion and pharmacological manipulation. Ongoing research will need to study the impact these potential interventions will have on the acute complications but also in which subset of patients they would be most beneficial. This area is novel and exciting but cautious implementation is advised with careful scrutiny of future data.

Effect of C1-INH on ischemia/reperfusion injury in a porcine limb ex vivo perfusion model

Revascularization of an amputated limb within 4-6h is essential to avoid extensive ischemia/reperfusion (I/R) injury leading to vascular leakage, edema and tissue necrosis. I/R injury is a pathological inflammatory condition that occurs during reperfusion of an organ or tissue after prolonged ischemia. It is characterized by a complex crosstalk between endothelial cell activation and the activation of plasma cascades. Vasculoprotective pharmacological intervention to prevent I/R injury might be an option to prolong the time window between limb amputation and successful replantation. We used C1-easterase inhibitor (C1-INH) in this study because of its known inhibitory effects on the activation of the complement, coagulation and kinin cascades. Forelimbs of 8 large white pigs were amputated, subjected to ischemia, and then reperfused with autologous whole blood. All limbs were exposed to 9h of cold ischemia at 4°C. After 2h of cold ischemia the limbs were either perfused with of C1-INH (1U/ml in hydroxyethyl starch, n=8) or hydroxyethyl starch alone (n=7). After completion of the 9-h ischemia period, all limbs were ex vivo perfused with heparinized autologous whole blood for 12h using a pediatric heart lung machine to simulate in vivo revascularization. Our results show that I/R injury in the control group led to a significant elevation of tissue deposition of IgG and IgM, complement C3b/c, C5b-9 and MBL. Also, activation of the kinin system was significantly increased, namely bradykinin in plasma, and expression of bradykinin receptors 1 and 2 in tissue. In addition, markers for endothelial integrity like expression of CD31, VE-cadherin and heparan sulfate proteoglycans were decreased in reperfused tissue. Limb I/R injury also led to activation of the coagulation cascade with a significant elevation of fibrin and thrombin deposition and increased fibrinogen-like protein-2 expression. C1-INH treated limbs showed much less activation of plasma cascades and better protection of endothelial integrity compared to the reperfused control limbs. In conclusion, the use of the cytoprotective drug C1-INH significantly reduced I/R injury by protecting the vascular endothelium as well as the muscle tissue from deposition of immunoglobulins, complement and fibrin.

Etanercept protects myocutaneous flaps from ischaemia reperfusion injury: An experimental study in a rat tram flap model

Background Being an inevitable component of free tissue transfer, ischemia-reperfusion injury tends to contribute to flap failure. TNF-α is an important proinflammatory cytokine and a prominent mediator of the ischemia-reperfusion injury. Etanercept, a soluble TNF-α binding protein, has shown anti-inflammatory and anti-apoptotic effects in animal models of renal and myocardial ischemia-reperfusion injury. We have designed an experimental study to investigate the effect of etanercept on myocutaneous ischemia-reperfusion injury on transverse rectus abdominis myocutaneous flap model in rats. Methods Twenty-four male Sprague-Dawley rats were divided into 3 groups: In group 1 (sham), the TRAM flap was raised and sutured back without further intervention. In group 2 (control), the flap was raised and the ischemia-reperfusion protocol was followed. In group 3, etanercept (10 mg/kg, i.v.) was administered 10 minutes before reperfusion. At the end of the reperfusion period, biochemical and histolopathological evaluations were performed on serum and tissue samples. Results In the etanercept group the IMA and 8-OHdG levels (p = 0.005 and p = 0.004, respectively) were found significantly lower, and the GSH and SOD levels (p = 0.01 and p < 0.001, respectively) significantly higher in comparison to the control group. The histopathological analysis has revealed a lower degree of hyalinization, degenerated muscle fibers and nuclear change in the etanercept group compared to the control group. Conclusion The results of our experimental study indicate that etanercept offers protection against ischemia-reperfusion injury in skeletal muscle tissue, enhancing the TRAM flap viability. The ability of etanercept to induce ischemic tolerance suggests that it may be applicable in free-flap surgery.

Muscle fiber viability, a novel method for the fast detection of ischemic muscle injury in rats

Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic muscle injury.