Effects And Mechanisms Of Glycine Protecting Cardiomyocyte From Endotoxin Injury

Septic shock is a dangerous disease frequently in clinic with a heavy mortality.Gram-negative bacterium will release more endotoxin into the blood and lead toendotoxemia and endotoxic shock at the same time of gram-negative bacterium killedby the antibiotic which can control gram-negative bacteremia. Endotoxic shockusually result in cadiocyte damage and cardia insufficiency. Then it is important toprevent and cure heart function disturbance induced by endotoxemia.It is to observe antagonistic effect of glycine in cultured cardiomyocyte damageinduced by lipopolysaccharide (LPS) that provide proofs of glycine preventing andcuring endotoxic myocardial damage. All experiments were divided into three parts:Part 1. To observe the effects of glycine on cultured cardiomyocytes damage inducedby LPS in MTT viability assay. The results showed that the protection ofglycine attenuated dose-dependent with LPS rising in culture medium after 48hours. The glycine control group (1.720±0.105) have no difference wirth thecontrol group((1.791±0.124, P＞0.05). It suggested that glycine antagonisedendotoxin and increased the cardiomyocytes viability at dose-dependent insome degree.Part 2. To observe the effects of glycine on cultured cardiomyocytes apoptosis rateinduced by LPS in Annexin V/PI flowcytometry. The results showed that thecardiomyocyte apoptosis rate of Gly+LPS groups are higher than that ofcontrol group (P＜0.01). The apoptosis rate of 4mmol/L Gly group and8mmol/L Gly group were lower than that of LPS group (P＜0.01). Theapoptosis of 8mmol/LGly group have no difference with the controlgroup(P＞0.05). It suggested that glycine inhibited cardiomyocyte apoptosisinduced by endotoxin at dose-dependent. Part 3. The mechanism study of glycine antagonise cardiomyocytes apoptosis inducedby endotoxin:(1) To observe the effects of glycine on cultured cardiomyocytes damage induced byLPS in DIOC₆(3) staining flowcytometry. The results showed that mitochondriamembrane potential of glycine+LPS group, control group and glycine group werehigher than that of LPS group (P＜0.05). The mitochondria membrane potential ofGly group is higher than that of control group (P＜0.05). It suggested that glycinestabilized mitochondria membrane potential against damage from endotoxin toprotect cardiomyocyte.(2) To observe the changes of caspase-3 activity in cardiomyocyte induced by LPSand glycine. The results showed the caspase-3 activity in Gly+LPS group and Glygroup are lower than that in LPS group. There were no difference between Glygroup and control group (P＞0.05). It suggested that glycine inhibited caspase-3activity and cardiomyocyte apoptosis induced by endotoxin to protectcardiomyocyte.(3) To observe Bcl-2 protein expression of glycine antagonise cardiomyocyte damageinduce by LPS in Western blot. The results showed that the protein expression ofBcl-2 in Gly+LPS group and Gly group are higher than that in LPS group (P＜0.05).There were no significant difference between Gly group and control group(P＞0.05). It suggested that glycine enhanced the protein expression ofanti-apoptosis gene Bcl-2 to inhibit cardiomyocyte apoptosis by endotoxin andprotected cardiomyocyte.In brief, these findings demonstrated that glycine improved the cardiomyocytesviability and inhibited cardiomyocyte apoptosis induced by LPS at dose-dependent, itsmechanism was related that glycine stabilized mitochondria membrane potential,inhibited caspase-3 activity, enhanced the protein expression of anti-apoptosis geneBcl-2 and reduced cardiomyocyte apoptosis.