SIRT1/PGC-1a Signaling Protects Hepatocytes Against Mitochondrial Oxidative Stress Induced By Bile Acids

BACKGROUND:Cholestasis liver disease is liver lesions caused by bile formation,secretion or(and)bile excretion disorder.GCDCA is one of the main representative bile salts of cholestasis toxic ingredients.it's been researched from cholestasis damage mechanism that GCDCA can damageand stimulate peroxidation,and even induce mitochondrial dysfunction.It's recognized as the international complex and difficult problem.Cholestasis liver cell damage caused by heat pathological mechanism is involved in the liver ischemia and ischemia-reperfusion and is closely related to oxidative stress.In terms of its main mechanism,the liver mitochondrial respiratory complex electronic chain transmission could be damaged by bile acid,thus stimulating mitochondrial ROS(reactive oxygen species(ROS)production increase and excessive ROS will impair liver cell.The study found that in case of excessive ROS formed in the mitochondria,mitochondria itself will be the first ROS attack target,it further activates mitochondrial apoptosis pathway and arise cell apoptosis.It is concluded that the oxidative stress to mitochondrial damage plays an important role in in cholestasis pathology.Silent information adjustment factor 2 related enzymes 1(SIRT1)is a protein acetylation enzymes dependent by nicotinamide adenine dinucleotide,which plays a significant part in regulating fat,sugar metabolism and anti oxidative stress ect.SIRT1 and PGC-1a are closed interrelated.Both of them are the main 'participants'of antagonism oxidative stress pathological reaction.SIRT1 can form the complex with PGC-la and directly remove acetylation PGC-1a,which generates mitochondrial biosynthesis and maintain mitochondrial function.Studies have also shown that in the case of oxidative stress,SIRT1/PGC-la signaling pathway can mediate a variety of antioxidant program representation,and thus play the part in the antioxidant.At present,the study of SIRT1/PGC-la signaling pathway in cholestasis in the liver disease mechanism still has not been reported at home and abroad.In conclusion,through the study of the clinical data of patients with extrahepatic cholestasis,pathologic specimens and GCDCA intervention in vitro culture of human normal liver cell line L02,it will be mainly studied in terms of three aspects in the thesis:(1)the analysis of cholestasis jaundice patients clinical data;the observation of mitochondrial function and generation change among patients' liver pathological specimens;the observation of SIRT1 expression and activity change among patients'liver pathological specimens.This experiment study is that extrahepatic cholestasis will have definite toxicity effect on liver cells;(2)as the research object of in vitro liver L02 cells,extrahepatic cholestasis liver model at different concentrations of GCDCA toxic effects on the liver L02 cells and mitochondria damage;Cell viability assessment bile acid damage of liver cells;intracellular ROS level and the change of mitochondrial membrane potential and ATP levels inferred cholestasis effect on mitochondrial function state;from mitochondrial DNA copy number,the change of the quality and level of 8-OHdG evaluation bile acid effect on mitochondrial generation.This experiment study is that GCDCA exposure,which brings the damage to mitochondria generation level in the liver cells and mitochondrial dysfunction,may be of the important reason of liver toxicity effect;(3)To assess the influence of GCDCA SIRT1 of L02 cell and PGC-la expression and activity,and preliminary discuss SIRT1/PGC-la signal path protection mechanism;based on the established GCDCA model in the previous step experiments,through adjusting the SIRT1 expression on SIRT1 molecules in cells function,We further proved that GCDCA exposure to damage of mitochondria generation and dysfunction restrains SIRT1 protein expression in the cell and its active state,increases the expression of acetylated PGC-1a alpha level without changing the effect of total protein in the pgc-1 alpha alpha,disorders and abates interrelations with SIRT1&PGC-1a.More importantly,SIRT1/PGC-1? signaling pathways exposure in the bile acid can promote mitochondria generation and mitochondrial function,so as to achieve the liver cell protective effect,which may be involved in the molecular mechanisms of bile acid exposure to the liver toxicity effect.