Macrophages play a central role in immunity, where a switch from initiation to resolution of inflammation is crucial for a robust and beneficial immune response. However, an imbalance in this switch culminates in prolonged inflammation that is seen in many disease states. Imbalances in the redox status of these cells could be one of the underlying crucial determinants of delayed and/or unsuccessful resolution. Selenoproteins, which contain selenium (Se), are a member of the cellular antioxidant machinery that effectively regulate the redox changes, and thus, brings in a nutritional component to immune function. Selenium-deficiency is characteristic of cigarette smokers and individuals with AIDS and breast cancer, where macrophage activation is accompanied by increased pro-inflammatory cytokines and prostaglandin (PG) E2, an oxidized arachidonic acid product of the cyclooxygenase (COX)-2 pathway. The pro- inflammatory gene expression is effected by differential modulation of the redox- sensitive transcription factor, NF-:B, and peroxisome proliferator activated receptor (PPAR)-3. Interestingly, Se-supplementation of macrophages leads to the preferential production of 15d-PGJ2 that covalently modifies the two transcription factors. The specific hypothesis to be tested is that Se-supplementation selectively modulates several enzymes associated with the arachidonic acid metabolism via the COX pathway, thereby influencing the preferential formation of anti-inflammatory 15d- PGJ2, which attenuates the expression of pro-inflammatory genes through the modulation of the NF-:B and PPAR-3. Synthesis of 15d-PGJ2, which occurs at the intracellular membrane-cytoplasmic interface, is susceptible to inactivation that potentially blunts its biologic activity. An additional complementary hypothesis to be tested is that the expression of a microsomal glutathione S-transferase (MGSTA1) is up- regulated during Se-deficiency, which is partially responsible for the metabolic inactivation of 15d-PGJ2. The hypotheses will be tested in C57BL/6 mice maintained on Se-deficient (0.01 ppm), Se-adequate (0.08 ppm), and Se-supplemented (0.4 ppm) diets as well as in the macrophages isolated from these mice in the following Specific Aims: 1) to examine the effect of cellular Se status on the regulation of PG production via the COX-1 and COX-2- dependent pathways, 2) to examine the role and regulation of microsomal PGE2 synthase and hematopoietic PGD2 synthase involved in inflammatory pathways during Se-deficiency, and 3) to elucidate the role of MGSTA1 in 15d-PGJ2 metabolism during Se deficiency. Our studies provide insight into a previously unappreciated link between cellular Se status and anti-inflammatory axis, producing increased 15d-PGJ2, by suppressing pro-inflammatory PGE2. The proposed studies will open new avenues of research where dietary interventions to counteracting NF-:B-dependent pro- inflammatory gene expression may be applied for long-term benefits and well-being of individuals suffering from HIV-AIDS, cancer, and atherosclerosis. Project Narrative: Professional phagocytes, such as macrophages, are good sources of cytokines, chemokines, enzymes, and lipid mediators and, thus, play a pivotal role not only in the onset of inflammation, but also in the resolution process. However, it is unclear as to what reprograms the macrophage to switch from pro-inflammatory gene expression networks to anti-inflammatory programs. Based on the preliminary data, we believe that cellular antioxidant status may play an important role in such reprogramming events. The primary objective of this project is to investigate the underlying molecular mechanism of the anti-inflammatory effects of selenium, a micronutrient and antioxidant, in primary macrophages. The proposed studies will delineate a selenium-dependent switch in arachidonic acid metabolism from pro-inflammatory prostaglandin (PG) E2 to an anti-inflammatory 15-deoxy-12,14-PGJ2 (15d-PGJ2) that effects the resolution process of inflammation. Studies proposed here will also unravel the anti-inflammatory mechanism of action of selenium, particularly on the suppression of IKK2/NF-:B- dependent inactivation of pro-inflammatory gene expression via a unique mechanism involving 15d-PGJ2.
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