Anti-oxidation Of Docosahexaenoic Acid (DHA) And Its Regulatory Roles In The Mitochondria

Reactive oxygen species(ROS)are oxidation-reduction products bearing single electron.They are mainly produced in the mitochondria,and excessive accumulation of ROS can lead to aberrant structure and functions of mitochondria.As a polyunsaturated fatty acid,docosahexaenoic acid(DHA)is an important component of brain phospholipid,and is essential for human body.It has many physiological functions,including antioxidant activity.There have been extensive studies on the antioxidant effect of DHA,however,little was known about its regulatory roles in the mitochondria,especially mitochondrial epigenetics.In this study,upon examing the antioxidant activity of DHA in HepG2 cells,DHA’s regulatory roles in mitochondrial function and biosynthesis were investigated.Furthermore,the effect of DHA on mitochondrial microRNA(miRNA)expression was tested.The main findings are as follows:(1)DHA increased ROS levels in HepG2 cells.In addition,the total antioxidant capacity was significantly increased upon DHA treatment,as well as the activities and expression levels of major antioxidases(including superoxide dismutase(SOD),catalase(CAT)and glutathion peroxidase(GPx)).(2)DHA can prevent H2O2-induced antioxidant capacity reduction.(3)DHA affected mitochondrial oxidative phosphorylation by up-regulating ADP/ATP ratio and reducing ATP content.It also increased mitochondrial membrane potential.Moreover,DHA promoted mitochondrial biosynthesis and modulated mitochondrial miRNA expression.These results suggest that DHA may activate the endogenous antioxidant defense system of HepG2 cells by increasing ROS levels,and improve the antioxidant capacity and protect cells against oxidative stress.In addition,the antioxidant effect of DHA may be related to regulation of mitochondrial function and biosynthesis,as well as mitochondrial miRNA.This study may provide a new theoretical fundament for the application of DHA in improving body resistance.