The Effects of in Vitro Fish Oil and Dietary Fish Meal Supplementation on Microdomains Within Bovine Luteal Cells

摘要

Lipid microdomains are regions of plasma membrane rich in cholesterol and sphingolipids, ranging in size from 10--200 nm in diameter. These structures serve as platforms to facilitate co-localization of intracellular signaling proteins during agonist-induced signal transduction. The omega-3 polyunsaturated fatty acids are a distinct class of fatty acids that have been shown to incorporate into lipid microdomains, disrupting the structural integrity of domains, and possibly attenuation of cell signaling. Fish byproducts, such as fish oil or meal, are a rich source of omega-3 polyunsaturated fatty acids that can be supplemented into cell cultures and diets of breeding females as a means for incorporating fatty acids into reproductive tissues. In chapter 2, we report that 0.03% (v/v) fish oils disrupt the spatial distribution of lipid microdomain and increases the lateral mobility of the prostaglandin (PG) F2alpha (FP) receptor, which was unaffected by PGF 2alpha treatment. In charter 3, we report that fish oil inhibited PGF2alpha-induced mitogen-activated protein kinase (MAPK) signaling and disrupt PGF2alpha-induced receptor internalization and endosomal trafficking of the FP receptor in bovine luteal cells. In chapter 4, we examined the effect of individual omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on disruption of lipid microdomains and lateral mobility of the FP receptor. We found that 10 and 100 microM EPA and DHA equally disrupts lipid microdomains and increase the lateral mobility of the FP receptor. Additionally, this disruption was equivalent to media supplementation of fish oil. Taken together, we found that supplementing cultured bovine luteal cells with fish oil leads to disruption of lipid microdomains, localization, and increases lateral mobility of the FP receptor, while attenuating PGF2alpha-induced MAPK signaling and receptor internalization. The effect of dietary fish meal supplementation on structural integrity of lipid microdomains, lateral mobility of the FP receptor, and luteal sensitivity to intrauterine infusions of PGF2alpha are reported in Chapters 5 through 7. In Chapter 5, We report that fish oil and meal disrupted both lipid-lipid and lipid-protein interactions within lipid microdomains, translocating ganglioside, GM1, and critical structural proteins (flotillin and caveolin) from lipid microdomain regions of plasma membrane into bulk lipid fractions. Additionally, we show that omega-3 polyunsaturated fatty acids, EPA and DHA, incorporated into bulk lipid fractions forming EPA- and DHA-rich domains. These EPA- and DHA-rich domains have a poor affinity for cholesterol, which resulted in translocation of cholesterol from bulk lipid into lipid microdomains. Next, we examined the effect of dietary supplementation on spatial distribution of lipid microdomains and the lateral mobility of the FP receptor. In Chapter 6, it was demonstrated that dietary supplementation of fish meal effected the fatty acid composition in luteal cells which lead to disruption in spatial distribution of lipid microdomains, and increased the lateral mobility of the FP receptor. Lastly, the final experiment investigated the effects of supplementation of fish meal on the structural and functional regression of the corpus luteum following intrauterine infusion of low doses of PGF2?. In chapter 7, we report that dietary supplementation of fish meal decreases luteal.