Dual modulation of cyclooxygenase and CYP epoxygenase metabolism and acute vascular inflammation in mice

Abstract

Cyclooxygenase (COX)-derived prostaglandins and cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids are important regulators of inflammation; however, functional interactions between these pathways in the regulation of vascular inflammation in vivo have not been studied. We investigated the relative and additive effects of endothelial CYP2J2 overexpression (Tie2-CYP2J2-Tr), global sEH disruption (Ephx2(-/-)), and pharmacologic COX inhibition with indomethacin on the acute vascular inflammatory response to endotoxin in mice. Compared to vehicle-treated wild-type C57BL/6 controls, induction of myeloperoxidase (MPO) activity in lung and liver was similarly attenuated in Tie2-CYP2J2-Tr mice, Ephx2(-/-) mice and wild-type mice treated with moderate dose indomethacin. Dual modulation of both pathways, however, did not produce an additive anti-inflammatory effect. These findings demonstrate that both COX and CYP epoxygenase-mediated eicosanoid metabolism are important regulators of the acute vascular inflammatory response in vivo, and suggest that the anti-inflammatory effects of modulating each pathway may be mediated, at least in part, by overlapping mechanisms.

Figure 1. Relative effect of endothelial CYP2J2 overexpression and high-dose indomethacin on acute vascular inflammation

LPS-induced lung MPO activity in indomethacin- (10 mg/kg) and vehicle-treated wild-type (WT) mice and Tie2-CYP2J2-Tr mice. Data are expressed relative to saline (PBS)-treated WT controls. N=6–8 per group. *P<0.05 versus LPS WT-vehicle. ^#P<0.05, indomethacin versus CYP2J2-Tr.

Figure 2. Dose-dependent inhibition of acute vascular inflammation by indomethacin

LPS-induced (A) plasma PGEM levels, (B) lung MPO activity, (C) and liver MPO activity following administration of vehicle (Veh) or incremental doses of indomethacin (1, 2.5, 5 or 10 mg/kg) to wild-type C57BL/6 mice. Data are expressed relative to saline (PBS) and Veh-treated controls. The mean PGEM levels in the PBS control group and LPS-treated vehicle group were 6.6 and 658 pg/mL, respectively. N=4–9 per group. *P<0.05 versus LPS-vehicle.

Figure 3. Relative effect of endothelial CYP2J2 overexpression, global sEH disruption, and moderate-dose indomethacin on acute vascular inflammation

LPS-induced (A) lung MPO activity and (B) liver MPO activity following administration of vehicle or indomethacin (2.5 mg/kg) to wild-type (WT), Tie2-CYP2J2-Tr, and Ephx2^−/− mice. Data are expressed relative to saline (PBS)-treated WT controls. PBS: N=6 per group, LPS: N=9–18 per group. *P<0.05 versus LPS WT-vehicle. NS=not significant.

Figure 4. Relative effect of endothelial CYP2J2 overexpression, global sEH disruption, and moderate-dose indomethacin on eicosanoid metabolite levels

LPS-induced plasma (A) PGEM, (B) TxB2, and (C) 6-keto-PGF1α levels, (D) the total sum of EET+DHETs, and (E) the 14,15-EET:DHET ratio following administration of vehicle or indomethacin (2.5 mg/kg) to wild-type (WT), Tie2-CYP2J2-Tr, and Ephx2^−/− mice. The mean eicosanoid levels for the PBS control group are as follows: (A) PGEM, below the limit of detection (the mean level in the LPS-treated WT group is 379 pg/mL); (B) TxB2, 214 pg/mL; (C) 6-keto-PGF1α, 49.5 pg/mL; (D) sum of EET+DHETs, 13.7 ng/mL; (E) 14,15-EET:DHET, 0.035 (ratio). PBS: N=5 per group, LPS: N=9–16 per group. *P<0.05 versus LPS WT-vehicle. ^#P<0.05, indomethacin versus vehicle within the Tie2-CYP2J2-Tr and Ephx2^−/− genotype groups. ND=below the limit of detection. NS=not significant.