Paper Title
Anti-Apoptotic Effect Of Epigallocatechin-3-Gallate In Alleviating The Cathepsin D Mediated Lysosomal Membrane Permeabilization In High Cholesterol Diet Stressed Aged Rat Liver

Abstract
Aging characterized by progressive accumulation of deleterious changes in various cell and tissues results in increased oxidative stress leading to increased production of reactive oxygen species (ROS) and eventually leads to cell death. Lysosomal pathway is the major degradation pathway of biological organisms popularly referred to as �suicidal bag� of the cell. In senescent lysosomes there will be loss in function of lysosomal enzymes and decreased lysosomal degradation capacity. Accumulation of lipids inside the lysosomal compartment is found to destabilize the lysosomal membrane causing lysosomal membrane permeabilization (LMP) and cell death. Release of lysosomal cathepsin D (CatD) from lysosomal lumen to cytosol promotes mitochondrial mediated cell death. The present study was carried out to substantiate the effect of cholesterol loaded lysosomes in mediating mitochondrial apoptotic pathway. Aged rats (24 months old) were fed with high cholesterol diet (HCD) and treated with green tea catechin (EGCG). Morphological, biochemical and molecular expression studies were carried out to corroborate with the present study. Histological and transmission electron microscopy (TEM) studies confirmed the deleterious changes of hepatic cells and various intracellular organelles in animals fed with HCD. Biochemical investigations like antioxidant status, liver marker enzymes, lipid profile and enzymes of lysosomal membrane integrity were carried out. We observed an altered antioxidant status, decreased membrane integrity of liver and lysosomes, and increased low density lipoprotein levels (LDL) with concomitant decrease in HDL levels. Cytosolic localization of CatD mediated intrinsic cell death pathway was confirmed by molecular expression studies in aged HCD fed animals. Treatment with EGCG culminated the cholesterol mediated apoptotic pathway in aged HCD fed animals. EGCG alone treated animals showed protective effect against cholesterol mediated cell death. The results of the present study showed protective effect of EGCG in improving the regeneration capacity of liver from the deleterious effects of cholesterol in HCD fed aged rats. EGCG also showed to exert its protective effect as an antioxidant, antihypercholesterolemic and anti-apoptotic agent in lysosomes mediated mitochondrial apoptotic pathway. Keywords - Aging, Lysosomes, Lysosomal cell death, Cathepsin D, EGCG, High cholesterol diet, Oxidative stress