Studies On The Influence Of Antioxidants On Platelets Under Oxidative Stress Situations

Abstract

Thrombocytes (or platelets) are anucleate particles circulating in blood (Quinn and Fitzgerald, 2005). They were first discovered microscopically by Donne in 1842. Platelets maintain the integrity of the vascular endothelium. They are activated during endothelial damage or coagulation cascade (Quinn and Fitzgerald, 2005). Their size is 2-4 and#956;m, with average volume of 6-8 fl. Platelet concentration varies from 2.5-4.5 lakhs/mm3 of blood in humans (Stiff, 1990; Johns, 2004; Harrison, 2005) and 7-9 lakhs/mm3 of blood in rats (young adults) (Hjort and Papuchis, 1960). Platelets are derived from megakaryocytes, with a life span of ~ 10 days in peripheral circulation, after which they are cleared by the reticulo-endothelial system (Johns, 2004; Harrison, 2005; Eppley et al., 2006).Platelets play a major role in atherosclerosis, by releasing micro-particles (MPs) in activated state. Adhesion molecules and chemokines that are carried by platelet MPs (PMPs) can lead to confinement of monocytes on vessel wall, giving rise to atherosclerosis and its progression (Mause et al., 2005). PMPs also promote angiogenesis during tumour growth (Brill et al., 2005). Secretion of matrix metalloproteinase (MMP-2) is triggered by PMPs in prostate cancer, which promotes tumour invasiveness through ECM collagen (Dashevsky et al., 2009). It is necessary to assess PMP count during chemotherapy, since increased PMPs can be lethal over a period. They aid in tumour growth by interacting with the tumour cells and the environment (Aharon and Brenner, 2009). Our study investigates the effects of exogenous antioxidants on platelet efficacy under two different oxidative stress situations, viz. newline1. Platelet storage (in vitro) newline2. Thrombocytopenia (in vivo) newline