TITLE:
Administration of grape seed extract alleviates age-associated decline in ubiquitin-proteasome system and cardiomyocyte apoptosis in rats
AUTHORS:
Arun Kumar Vijayakumar, Vasanthan Kuppuswamy, Panneerselvam Chinnakkannu
KEYWORDS:
Aging; Proteasome Dysfunction; Cardiac Muscle Cell Death
JOURNAL NAME:
Advances in Biological Chemistry,
Vol.3 No.2,
April
30,
2013
ABSTRACT: Effective
clearance of oxidized, damaged, and/or misfolded proteins in the cell by the ubiquitin-proteasome system (UPS) is critical for cell homeostasis, survival and function. We hypothesized
that in the aging heart, generation of free radicals could impair UPS where the
associated build-up of polyubiquitinated proteins could trigger programmed cell
death. To test this, we used young (4 months old) and aged (24 months old) rats
to analyze polyubiquitinated proteins, proteasome activity and programmed cell death
in the ventricular tissue samples. Our studies reveal excessive deposition of polyubiquitinated
proteins in the ventricular tissue extracts of old rats when compared to younger
rats. The increased ubiquitination was accompanied by a significant decrease in
20S proteasome activity. Since the loss of proteasome-mediated clearance of ubiquitinated
proteins is linked to programmed cell death, we measured TUNEL activity in aged
rat heart and compared with younger animals. Aged animal hearts showed a substantial
increase in programmed cell death as evidenced by TUNEL positive nuclei and DNA
fragmentation. Analyses of cell death/survival pathways support our findings in
terms of age-associated increase in the nuclear localization of p53, Bax/Bcl2
ratio and cleaved (active) caspase-3 and decreased expression of cellular inhibitor
of apoptosis (cIAP1). Administration of grape seed extract (GSE) as a source of
antioxidants significantly reduced these age-associated deleterious changes suggesting
that free radicals primarily contribute to impaired UPS function and increased
programmed cell death and that administration of antioxidants during aging could
protect cardiac muscle cells and preserve ventricular
function.