EFFECTS OF [symbol removed]3-POLYUNSATURATED FATTY ACIDS ON TIlE FORMATION OF sn-1,2-DIRADYLGLYCEROL, CYTOKINE SECRETION AND THE REGULATION OF PROTEIN KINASE C ACTIVITY

Abstract

<p>The focus of my thesis was to investigate changes in the formation of<br />second messenger sn-1,2-diradylglycerol (DG) and phospholipids (PL) in murine<br />peritoneal macrophages in vitro and in vivo in response to varying concentrations<br />of the 3-olyunsaturated fatty acids ([symbol removed]3PUFA), eicosapentaenoic (EPA, 20:5[symbol removed]3) and docosahexaenoic (DHA, 22:6[symbol removed]3) acids. My findings establish for the first time that the incorporation of EPA and DHA into DG and membrane PL occurs<br />independently and dose-dependently, with EPA being incorporated to a greater<br />extent than DHA.</p> <p>It was of interest to investigate the functional correlations of the substitution<br />of [symbol removed]3PUFA into DG and PL molecular species. DG is classically known as the physiological activator of protein kinase C (PKC). I investigated the effects on<br />PKC activation by pure species of diacylglycerol (DAG) with oleoyl, arachidonoyl,<br />eicosapentaenoyl or docosahexaenoyl at the sn-2 position. These results showed<br />that DG species with DHA or EPA incorporated at the sn-2 position activate PKC.<br />However, while DG with DHA at the sn-2 position activated PKC to a similar<br />extent as did DG with AA at the sn-2 position (representative of physiological DG),<br />DG with EPA at the sn-2 position activated PKC to a significantly lesser degree.<br />To the best of my knowledge, this is the first demonstration in the literature that the activation of PKC in vitro differs significantly among these molecular species<br />of DAG.</p> <p>The immunoregulatory cytokine, interleukin-6 (IL-6), is produced in<br />response to tissue injury and inflammation and in vitro by LPS-stimulated<br />macrophages. I investigated the correlation of [symbol removed]3PUFA substitution into DC and<br />secretion of IL-6 by LPS-stimulated murine peritoneal macrophages. These results<br />show for the first time that IL-6 secretion is attenuated by [symbol removed]3PUFA, and to a<br />greater extent by DHA than by EPA.</p> <p>I have obtained several novel findings that contribute to improved<br />understanding of the underlying mechanisms by which [symbol removed]3PUFA function at the<br />level of signal transduction. The ability to modify the fatty acid composition of the<br />signalling molecule, DG, with [symbol removed]3PUFA can now be used for future research to<br />further elucidate the functional ramifications of [symbol removed]3PUFA in cell signal<br />transduction.</p>