Abstract P99: Oxidative Mitochondrial DNA Damage is Associated With Injury of Respiratory Chains, Especially Complex2 During Sepsis-induced Myocardial Dysfunction
Introduction: Excessive reactive oxygen species(ROS) is considered to play a role in development of sepsis-induced myocardial dysfunction(SIMD) through direct cardiac mitochondrial(mt) nucleic acid injury, which can result in defects of mtDNA replication. However, the mechanisms have not yet been well isolated clearly. CoenzymeQ1 (CoQ1) and CytochromeC play a key physiological role in oxidative phosphorylation as electron carrier in respiratorychains (complex1–2–3:CoenzymeQ1,complex3– 4:CytochromeC). CytochromeC also forms apoptotic protease activating factor-1 which leads to activate caspase-3 pathway followed by exposure to H2O2 or O2− radical. On the other hand,8-oxo-dGTP during oxidative nucleic acid injury can lead to misincorporation into mtDNA, which is prevented by 8-oxo-dGTPase, such as OGG1.
Materials and Methods: Sepsis were induced by Ceacal Ligation and Puncture (CLP). Adult male Sprague-Dawley rat (n=30) were administrated intraperitoneally with or without both H2O2 and O2− radical scavenger (PolyethyleneGlycole-Catalase: PEG-CAT) 4 hours after CLP. We isolated mitochondria from cardiomyocyte 20 hours after CLP and measured its OGG1, caspase-3 by RT-PCR, NAD+/NADH ratio(as a complex1 activity), CoQ1/CoQ1H2 ratio(as a complex2–3 activity), CytochromeC(as a complex3– 4 activity), ATP production(as a complex4 activity), and 8-oxo-dG by HPLC with or without inhibition of ROS by PEG-CAT. Apoptotic cell death was determined using Trypan blue staining and TUNNEL assay.
Results: Survival rate, mean aortic pressure, ATP production and mRNA of caspase-3, OGG1 densitometry level of PEG-CAT(+) groups were significantly higher compared with PEG-CAT(−) groups(p<0.05). 8-oxo-dG, CoQ1/CoQ1H2, CytochromeC level in PEG-CAT(−) groups were significantly higher compare with PEG-CAT(+) groups(p<0.05). There was no difference in NAD+/NADH ratio among both groups.
Conclusion: Cardiac mitochondrial dysfunction of may be caused by injury of respiratory chains, especially complex2, followed by oxidative mtDNA damage.