The Protective Effects Of Methylsulfonylmethane Preconditioning On Myocardial Ischemia Reperfusion Injury In Rats

Ischemia reperfusion injury is a clinical patho-process that tissue injury augments under sustained ischemic condition followed by restoring perfusion. IRI is characterized by low function of left ventricle (myocardial stunning), reperfusion arrhythmia and conspicuous injury in reperfusion myocardium. It has been widely accepted that injuries caused by the reactive oxygen species (ROS), abnormal energy metabolism and high levels of calcium ions could be the underlying mechanisms for IRI. In recent years, studies on heart protections have mostly focused on investigating the endogenous protective mechanisms, such as improving the tolerance of heart to ischemia and ischemic preconditioning (IPC) is used to describe the protective effects of short periods of ischemia to an organ or tissue against longer periods of ischemia. It is known that IPC is so far the most effective endogenous protection for myocardium. The protective effects of preconditioning include minimizing infarct size, reducing the happening of ventricular arrhythmia and improving postischemic cardiac function. The trauma and latent risk of IPC makes it difficult to introduce and spread. Pharmacological preconditioning protection against heart injury is trigged by medicines which can mimic beneficial effects of cardiac ischemic preconditioning. The method of pharmacological preconditioning is simple and the dose of the drug is convenience to control. It has become a research trend. The study of pharmacological preconditioning would help us to elucidate the mechanism of ischemic preconditioning and develop novel access to treat cardiovascular diseases. ROS is an important factor which contributes ischemia reperfusion injury. Oxidative stress is usually associated with increased formation of ROS, which could decrease the activities of Ca²⁺-pump ATPase, Na⁺-K⁺-ATPase in the sarcolem. As the result, Ca²⁺-efflux decreased and Ca²⁺-influx increased. ROS can also depress the sarcoplasmic reticulum Ca²⁺-pump ATPase and thus inhibit Ca²⁺ ingestion from the cytoplasm in cardiomyocytes. The depression in Ca²⁺ -regulatory mechanism by ROS ultimately results in intracellar Ca²⁺ overload. All endogenous antioxidants may act in inhibiting or delaying the oxidative damage to subcellular proteins, carbohydrates, lipids and DNA. During the past few years, there has been great development in Western medicine to protect myocardium against ischemia reperfusion injury. Fructose-1, 6-diphosphate (FDP), an effective medicine has been being used in clinic to treat myocardial ischemic disease. The methylsulfonylmethane (MSM) has been reported it can increase antioxidants, cleanse ROS from the body, however, in myocardial protection has not been reported. In this study, the FDP as a positive control drug, myocardial ischemia-reperfusion as a model, we investigateed the effects of MSM on myocardial ischemia-reperfusion model in rats.Methods96 Wistar rats (half in male and female) were randomly divided into 6 groups, named: sham operation (Sham) group, myocardial ischemia/reperfusion model (I/R) group, positive control drug (FDP) group, and three different doses of MSM: 8.0g/kg, 4.0g/kg, 2.0g/kg groups. The rats in FDP and three different doses of MSM groups were infused intragastricly with the FDP solution of 0.6 g/ml and the MSM solution of 0.8 g/ml 0.4 g/ml 0.2 g/ml respectively 10ml/kg·d for 7 days, while deionized water infused intragastricly in Sham and I/R groups with the dose of 10ml/kg·d for 7 days. After 1 hour of the last intragastric infusion, all rats were subjected to openning chest then the left anterior desending coronary arteries (LAD) were ligated for 30min and undamped for 90min. Rats in sham group were subjected to the same surgical procedures without LAD ligation. Hemodynamics and scores of ventricular arrhythmia were measured.At the end of 60 min reperfusion, the LAD of half rats in every group was religated and 1% (w/v) of Evans blue was injected through the femoral vein to distinguish the area at risk from the area of myocardium that was perfused by the nonoccluded coronary arteries. After that, hearts were excised, washed with ice-cooled Saline and the atria and right ventricle were removed. The heart was cut into 4 slices vertical to the apex/base axis and incubated with 1 % triphenyltetrazolium chloride (TTC) at 37℃for 20 min to stain the non-infarcted region in area at risk and the non-infarcted area in the area at risk was stained red by TTC (indicating the presence of a formazin precipitate, which results from the reduction of TTC by dehydrogenase enzymes present in viable tissue), whereas the infracted tissue remains unstained. After storage in 10 % formaldehyde, infarcted and non-infarcted tissues within the area at risk were carefully separated and weighed. Infarct size and ischemic zone size were expressed as the percentage of the aera at risk and and as the percentage of the entire left ventricle respectively.Other half hearts were made into tissue homogenate, then Na⁺-K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and creatine kinase (CK) were measured.Resultsâ‘ Hemodynamics There were no significant differences in Myocardial functional parameters, such as left ventricular systolic pressure (LVSP), maximum positive and negative change in pressure (±dp/dt) and left ventricular end-diastolic pressure (LVEDP) among the six groups before the ligation of LAD (P > 0.05). In the ischemic/reperfused especially reperfused period, LVSP and±dp/dt were significantly lower in the I/R group as compared with the Sham group (P < 0.01), which were higher in the FDP and MSM 8.0g/kg groups than those of I/R group (P < 0.05, P < 0.01). In the reperfused period,LVEDP was obviously lower in the FDP and MSM 8.0g/kg groups than that of I/R group (P < 0.05). All those parameters were similar between FDP and MSM 8.0g/kg groups (P>0.05).â‘¡Scores of arrhythmia During reperfused period the scores of FDP and MSM 8.0g/kg groups were obviously lower compared with I/R groups (P<0.05).â‘¢Ischemic zone size and infarct size IZS was not different among the groups except Sham group[(33.30±0.89)%, (32.86±0.91)%, (34.02±1.20)%, (32.96±1.26)%, (33.56±0.93)%]. IS was significantly lower in FDP, MSM 8.0g/kg and 4.0g/kg groups vs I/R group[(11.29±1.17)%, (12.40±0.98)%, (19.70±1.63)% vs (21.74±1.20)%, P < 0.05] but there was no difference between FDP and MSM 8.0g/kg groups.â‘£SOD, CAT, GSH-Px, MDA and CK Compared with Sham group, the level of myocardial SOD, CAT and GSH-Px were significantly lower (493.27±51.70 vs 662.05±43.65, 26.96±9.42 vs 45.61±3.94, 16.82±4.55 vs 22.58±3.12, P < 0.01) but MDA and CK were higher markedly in the I/R group (4.50±0.57 vs 2.42±0.55, 8.02±1.09 vs 4.56±0.78, P < 0.01). The level of SOD, CAT and GSH-Px in FDP, MSM 8.0g/kg and 4.0g/kg groups were significantly higher but the level of MDA and CK were lower than the I/R group (P < 0.01).⑤Na⁺-K⁺-ATPase, Ca²⁺-ATPase and Mg²⁺-ATPase The level of Na⁺-K⁺-ATPase, Ca²⁺-ATPase and Mg²⁺-ATPase in the I/R group were lower than Sham group (1.79±0.41 vs 3.78±0.53, 2.40±0.36 vs 5.31±0.74, 2.04±0.40 vs 4.96±0.59, P < 0.01), but in FDP (3.64±0.90, 5.16±0.86, 4.79±0.89) and MSM 8.0g/kg (3.76±0.97, 4.93±0.70, 4.81±0.84) increased markedly vs the I/R group (P < 0.01) and there were no difference between FDP and MSM 8.0g/kg groups (P > 0.05).Conclusions1 Our data indicated that pretreatment of rats with MSM had cardial protective effects. It can improve cardiac function, minimize infarct size and reduce the happing of ventricular arrhythmia.2 The protective effects of MSM on ischemia-reperfusion myocardium may be relevant to increasing antioxidants, inhibiting lipid from being peroxidized in rat hearts when they were subjected to ischemia/reperfusion injury and increasing the level of myocardic Na⁺-K⁺-ATPase, Ca²⁺ATPase and Mg²⁺-ATPase in rats.