Sex-dependent role of 20-HETE synthesis in outcome from ischemic stroke in rats

The lipid mediator 20-HETE is produced by ω-hydroxylation of arachidonic acid mediated by cytochrome P450 (CYP) enzymes including CYP4A, which has four distinct isoforms in rodents. Several laboratories demonstrated that 20-HETE synthesis inhibition reduces infarct volume following middle cerebral artery occlusion (MCAO) in male animals. Here, we investigated whether neuroprotection with the 20-HETE synthesis inhibitor HET0016 administered after transient MCAO in rats differs by sex and whether ischemia differentially induces Cyp4a genes in a sex-dependent manner. HET0016 significantly improved sensorimotor performance and reduced infarct volume compared to vehicle treatment in males. However, these improvements were less consistent in females. Cyp4a2 and Cyp4a3 genes were detected at similar levels in brain tissue from male and female rats undergoing sham surgery or MCAO/reperfusion. Interestingly, the Cyp4a8 gene was detectable in intact and castrated males and increased 3-4-fold after MCAO. In contrast, Cyp4a8 was undetectable in brains of intact or ovariectomized female rats. Oxygen-glucose deprivation in cultured murine neurons revealed male-selective induction of the homolog gene Cyp4a12a, the knockdown of which blocked the increase in 20-HETE. These results indicate that innate male-selective Cyp4a gene induction and 20-HETE signaling are significant factors that can contribute to sex differences in the outcomes from ischemic stroke.