Fatty acid epoxides produced by cytochrome P450s mediate the deleterious effects of dietary DGLA in the C. elegans germ line
MetadataShow full item record
Polyunsaturated fatty acids (PUFAs) are precursors to bioactive molecules which play essential roles in development, immune response, and reproduction. This process is moderated by three pathways which act on PUFAs to form prostaglandins, leukotrienes, and monooxygenated fatty acids. The formation and mechanisms of prostaglandins and leukotrienes formed from arachidonic acid (AA, 20:4n-6) have been well defined. However the monooxygenated fatty acids formed through cytochrome P450 (CYP) activity have just recently begun to be defined, and the metabolism and mechanisms of other PUFAs, especially dihomo gamma linolenic acid (DGLA, 20:3n-6) have largely been ignored. Therefore, understanding the PUFA metabolism pathways, as well as the activities of the resulting metabolites is crucial to human health. Our lab previously identified a striking phenotype when supplementing the diet of the roundworm C. elegans DGLA. This supplementation resulted in the destruction of proliferating germ cells and ultimately led to sterility. Dietary fatty acid induced sterility was found to be highly specific to the feeding of DGLA to C. elegans. Thus, we hypothesized that a dietary metabolite of DGLA is causing cytotoxic effects on C. elegans germ cells. We predicted that C. elegans with RNAi knocked-down expression of PUFA metabolizing genes would resist sterility when supplemented with DGLA. C. elegans knock-down of the CYP encoding gene cyp-33E2 was found to be resistant to DGLA-induced sterility. We then used a biochemical approach to identify that the CYP encoded by cyp-33E2 has activity on DGLA substrates producing epoxide and hyrdroxide metabolites. Further we show that C. elegans microsomes are similarly able to produce these metabolites and that these metabolites are produced endogenously by C. elegans from DGLA supplementation. These metabolites were tested individually by injection into the gonad syncytium of C. elegans for their ability to produce cytotoxic germ cell defects. Injection of two of the discovered epoxides, 8,9-epoxyeicosadienoic acid (EED) and 14,15-EED, resulted in the formation of multinuclear germ cells. Our results suggest a role for CYP directed PUFA metabolism in the regulation of C. elegans reproduction. These findings highlight the importance and potency of PUFA metabolites in health and development.