Mitochondrial Function In Cholestasis And Clinical Analysis Of Hepatic MtDNA Damage In Obstructive Jaundice

Mitochondrion is the"powerhouse of the cell"as it generates most of the cell's supply of adenosine triphosphate (ATP) through the process of cellular respiration and its function plays an important role in maintaining balance of liver function . Mitochondrial DNA (mtDNA) is self-replication and controls the most basic properties of mitochondria. Its damage can cause a series of cell dysfunction and are closely related to the disease progression. Obstructive jaundice (OJ) caused mostly by the stones and tumors and reduction of mtDNA copies will cause liver cell necrosis. . Mitochondria is considered as the first damaged organelle of liver cells in OJ and mtDNA is the most fundamental factor that affects the mitochondrial function.. Therefore, analysis mtDNA damage and mitochondrial functional could improve the mechanisms of cholestatic liver injury that would open a new path for early treatment and prognosis in the patients with obstructive cholestasis.Objective:(1) Analyse muted hepatocyte mtDNA in patients with obstructive jaundice and combine those results with previous studies. (2) Detection of the indexes for liver mitochondrial function at different time points in OJ.Methods:(1) 30 patients were randomly selected from OJ group (case group) and 10 patients were used as control. To preliminary estimate the localization of hepatic mtDNA damage in patients with OJ, PCR will be used to detect human mitochondrial genome with 17 mismatch-specific overlapping fragments and combine with the gene sequencing. (2) OJ rat model will be divided into control, Sham and BDL groups, detect the changes of mitochondrial ATPase activities and lipid peroxidation product (MDA) by using ELISA assay.Results:(1) PCR results have shown that mtDNA deletion occurs in some hepatocytes in case group that respective is 8429~9591 of about 1.1kb, 16024~60 of about 0.6kb,1889~3031 of about 1.1kb and 4977bp's common deletion and the high mutation rate of some bases in D-loop region. (2) With prolonged obstruction, compared with the control group, the MDA of BDL group gradually accumulates in the liver mitochondria (p <0.05), and proceed to irreversible changes at d14 (p <0.05); ATPase activity in BDL group reduced significantly (p <0.05), and reached the lowest point at d14. However, the reduction of ATPase activity is not obviously shown in the early stage of OJ (1-3d)(p> 0.05).Conclusion:A large number of oxygen free radicals more act on the lipid, mitochondrial protein, and mtDNA by lipid peroxidation in cholestasis. These results have shown that in the mitochondria, MDA accumulated, ATPase activity decreases, leading to the damage of mitochondrion. Some mitochondrial genome was changed (mtDNA deletions and mutations) within liver cells due to lacking of effective histone protection and the capacity of scavenging oxygen free radicals. Those results were similar to the previous studies of National Natural Science Foundation. We believe that retention of MDA plays a positive role in mtDNA damage in cholestasis that might be an important factor dealing with the damage of mitochondrial and liver functions. Therefore, it will be the future focus study how to remove MDA actively and protect effectively the integrity and functionality of mtDNA, that will open a new path for early treatment and prognosis in obstructive cholestasis.