Age-related changes of the redox state of glutathione in plasma

Glutathione (GSH) is the principal non-protein thiol responsible for maintaining intracellular redox status and protecting cells against oxidative/nitrosative stresses. In the biological system, some GSH is bound to proteins, and others exist freely, including the reduced glutathione and oxidized glutathione (GSSG). Generally it is in a steady redox state for GSH/GSSG couple to participate in a variety of physiological functions. Earlier studies showed that chemically induced oxidative stress in vivo in rats resulted in increased GSSG and decreased GSH/GSSG ratio.1 The impairment of the glutathione homeostasis represents an indicator of tissue oxidative stresss status in human subjects. The “free radical theory of aging” considers that aging resulted from the accumulation of oxidative lesions mediated by free radicals. In the present study, we therefore investigated the effect of aging on the redox state of GSH/GSSG redox couple, which integrates the GSH concentration and the redox potential for GSSG/GSH couple.