The primary objective of the proposed research is to continue our current investigations into the elucidation of the molecular basis for the regulation of prostaglandin (PG) and leukotriene (LT) biosynthesis by vitamin E and selenium (Se). Our working hypotheses are the vitamin E and/or Se deficiency can influence the expression of key enzymes associated with PG and LT biosynthesis as well as their product profiles in the lung, and this altered eicosanoid synthesis is, in part, responsible for the impairment of a number of critical physiological functions, including those of the immune system. this hypothesis is based on the premise that fatty acid hydroperoxides (FAHPs) and free radicals are integral parts of PG and LT biosynthesis. Therefore, by maintaining the critical concentrations of FAHPs and essential free radicals, Se-GSH-Px and vitamin E have the potential to modulate the arachidonic acid cascade.
The specific aims of the proposed research are to determine the expression of (1) cyclooxygenase and 5-lipoxygenase, which catalyze the first committed step in PG and LT biosynthesis; (2) LTC4 synthase, a key enzyme involved in the biosynthesis of sulfido LTs; and (3) microsomal glutathione S-transferase, an important protein responsible for GSH/GSSG-dependent antioxidant protection against membrane peroxidative damage in the lung during vitamin E and/or Se deficiency. Additional specific aims are (4) to examine in detail, the role of dietary vitamin E and Se status on the production of cytokines in the lung by macrophages and neutrophils, and (5) to examine the potential relationships of vitamin E and Se deficiency, cytokine production, and arachidonic acid metabolism to alterations in lymphocyte function. We propose to employ ozone exposure as an additional oxidant stress model to delineate further the regulatory mechanisms underlying the antioxidant defense functions of vitamin E and Se in PG and LT biosynthesis. Such molecular probes as polyclonal antibodies, monoclonal antibodies and cDNAs, will be employed to determine whether the effects of altered vitamin E and Se nutrition on the expression of key enzymes associated with the arachidonic acid cascade are at the translational level or the transcriptional level. We also plan to assess the effects at the enzyme activity level by determining the product profiles. The experiments will also include the examination of direct effects of vitamin E and/or Se deficiency on cytokine production by leukocytes -- as well as indirect effects mediated by eicosanoids known to be affected by altered vitamin E and Se nutrition. Finally, additional experiments will examine the mechanisms that may explain the decreased proliferative and cytotoxic capabilities of lymphocytes by vitamin E and/or Se deficiency. Our long range objective is to establish the precise role of PGs and LTs in the pathophysiology of oxidant-induced respiratory diseases under such compromised antioxidant defense functions as those seen in vitamin E- and/or Se-deficient states.
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