Abstract P358: Cardiac Innervation Remodeling And Impaired Brain Derived Neurotrophic Factor (bdnf) Levels In Physiological Aging Vivo Model

Abstract

Aging is a multifactorial process associated with gradual loss of function and decay involving several neurohormonal systems, such as the autonomic nervous system (ANS). Progressive remodeling of ANS, induces a circulating catecholamines spillover and cardiac autonomic fibers depletion with raising both morbidities and mortality risk. Neurotrophic factors (NF) play a pivotal role in modulating neuronal function and are impaired in cardiovascular disorders. Whether and how physiological aging impacts these neurobiomarkers and cardiac innervation remains still unclear. Therefore, we investigated the impact of aging on neurotrophins (such as BDNF and NGF) production and secretion and its consequences, on cardiac nervous system homeostasis. In vivo, we used young (age: 3 months; n=10) and old (age: 24 months; n=11) male Fisher rats. In vitro, human neuroblastoma cells (SH-SY5Y) were stimulated with serum withdrawn from both experimental groups. Old rats showed a significant reduction in overall ANS fiber density, sympathetic (marked by dopamine β-hydroxylase, dβh) and cholinergic compartment (evidenced by vesicular acetylcholine transporter, VaChT) compared to the young group, assessed by immunohistochemical staining. In addition, we observed a marked downregulation of GAP-43 and BDNF protein levels in left ventricle total lysates via immunoblot analysis, in aged hearts as opposed to young ones. Conversely, no changes were observed in NGF protein expression. To further investigate the autocrine effect of aging on autonomic nerve fibers, we treated SH-SY5Y cells in vitro, with blood serum obtained by young or old rats. Both stimuli induced a remarkable increase in neuronal sprouting, as evidenced via crystal violet assay. Nevertheless, we found a bulky drop in the neuronal function of cells stimulated with old rat serum. Interestingly, this effect was accompanied by a sizeable blunt in GAP-43 and BDNF protein levels, compared to cells treated with young rat serum. Taken together, our data suggest that neuronal function impairment aging-induced associated with significant BDNF impoverishment, might favor maladaptive remodeling of cardiac ANS.