Free radical theory of aging suggests that aging increases the generation of reactive oxygen species (ROS) and alter redox status. Recently, cellular redox status have been proposed to regulate signal transduction. Therefore, we established a long-term objective to test the hypothesis that alteration of signal transduction patterns associated with aging process is due, in part, to changes in redox status and subsequent modulation of redox regulation of signal transduction. In this proposal, we will specifically test the hypothesis that oxidation is a determinant of diverse actions of Ca2+ to elicit cell signaling, and therefore 1) oxidant-responsive signal transduction components such as MAP kinase and NF-kappaB are differentially activated by Ca2+ depending on the route of entry into the cytosol; and 2) aging modulates differential signaling patterns elicited by Ca2+ in freshly isolated cardiac myocytes. Myocytes will be isolated from 6-month old Wistar rats. Ca2+ signals will be elicited by treating myocytes with: thapsigargin to activate non-specific Ca2+ flux from the sarcoplasmic reticulum (SR); caffeine to activate Ca2+ flux from the SR through the ryanodine receptor; A23187 to activate non- specific Ca2+ influx through the sarcolemma; KC1 to cause depolarization to activate Ca2+ influx through the L-type Ca2+ channel; and low Na+ solution to activate influx through the Na+-Ca2+ exchanger. Ca2+ signals elicited by various pathways will be examined in terms of kinetics of p44/p42 MAP kinase phosphorylation, NF-kappaB activation and changes in GSSG/GSH ratio as well as inhibitable effects of a Ras inhibitor and antioxidants because Ras-generated ROS may occur in response to Ca2+. Furthermore, the effect of aging on the differential patterns of Ca2+- signals will be assessed by studying cardiac myocytes from 24-months old rats. Information obtained-from this proposal will be used ultimately to determine the ability of dietary antioxidants to modulate redox status and signal transduction, and to impact age-related physiological processes including the pathogenesis of cardiovascular disease.
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