The Study Of Mechanisms About Cardiomyocyte Apoptosis And Action Potential Changes Induced By Sleep Deprivation

Objective In this study, tissue structural changes of rats’myocardium, cardiomyocytes apoptosis and expression of apoptosis related factors such as P53, Bcl-2, Bax, Caspase-3 and Caspase-9 were oboserved, the changes of ultral structure and function of mitochondria, electrophysiological changes on action potential of cardiomyocytes were also evaluated after sleep deprication. Then possible mechanisms involved in myocardial injury and cardiac arrhythmias caused by sleep deprivation were analyzed.Method 50 male adult Sprague-Dawley rats were divided into 5 groups, big platform control group (ctrl group), sleep deprivation 1 day group(SD1d group), sleep deprivation 3 day group(SD3d group), sleep deprivation 5 day group(SD5d group), sleep deprivation 7 day group(SD7d group),10 for each group. A modified multi-platform sleep deprivation model were adopt in this study.1. After sleep deprivation, the tissue structural changes of rats myocardium were observed with HE stain; cardiomyocytes apoptosis evaluated with TUNEL; Caspase-3 expression were analyzed by Immunohistochemical stain; the protein and mRNA levels were measured with Western Blot and RT-PCR.2. Spectrophotometry was adopt to detect swollen and ATP concentration changes of cardiomyocyte mitochondria; cytochrome C (cyt C) was analyzed by immunohistochemical stain; the changes of protein and mRNA levels cardiomyocyte mitochondrial protein VDAC1 were measured with Western Blot and RT-PCR after sleep deprivation.3. A whole cell patch clamp was used to detect action potential duration (APD) changes of cardiomyocytes in deferent sleep deprivation groups.Results1. The structural impairments and increasing apoptosis cells were found after sleep deprivation with apoptosis related proteins P53, Bax, Caspase-9, Caspase-3 over expression, Bcl-2 expression reduced and Bax/Bcl-2 ratio raised dramatically.2. Significant swollen with decreased ATP concentration of cardiomyocyte mitochondria were found after sleep deprivation. Cyt C and mitochondrial protein VDAC1 levels were elevated dramatically in cardiomyocyte of sleep deprived rats.3. Compared with control group, the phases of APD of ventricular myocytes in sleep deprivation 3,5,7 days SD groups were prolongated and APD at 20% and 50% level of repolarization (APD20 and APD50) significantly elongated (P<0.01, n=18).Conclusions1. Sleep deprivation resulted in myocardial tissue structure impairment with inflammatory responses.2. Sleep deprivation led to over expression of pro-apoptosis factors and down regulation of anti apoptosis factors. Theses initiated apoptosis of cardiomyocyte after sleep deprivation.3. Sleep deprivation may cause metabolic and energy dysfunction, mitochondria swollen, Cyt C leakage and finally cell apoptosis.4. Sleep deprivation induced APD elongation of cardiomyocyte, especially significant in APD20. This suggests sleep deprivation mainly affect early repolarization of cardiomyocyte, which might be a mechanism of sleep deprivation induced arrhythmias.