Microvascular degeneration is an important event in oxygen-induced retinopathy (OIR), a model of retinopathy of prematurity. Because oxidant stress abundantly generates thromboxane A2(TxA2), we tested whether TxA2plays a role in retinal vasoobliteration of OIR and contributes to such vascular degeneration by direct endothelial cytotoxicity. Hyperoxia-induced retinal vasoobliteration in rat pups (80% O2exposure from postnatal days 5–14) was associated with increased TxB2generation and was significantly prevented by TxA2synthase inhibitor CGS-12970 (10 mg · kg−1· day−1) or TxA2-receptor antagonist CGS-22652 (10 mg · kg−1· day−1). TxA2mimetics U-46619 (EC5050 nM) and I-BOP (EC505 nM) caused a time- and concentration-dependent cell death of neuroretinovascular endothelial cells from rats as well as newborn pigs but not of smooth muscle and astroglial cells; other prostanoids did not cause cell death. The peroxidation product 8-iso-PGF2, which is generated in OIR, stimulated TxA2formation by endothelial cells and triggered cell death; these effects were markedly diminished by CGS-12970. TxA2-dependent neuroretinovascular endothelial cell death was mostly by necrosis and to a lesser extent by apoptosis. The data identify an important role for TxA2in vasoobliteration of OIR and unveil a so far unknown function for TxA2in directly triggering neuroretinal microvascular endothelial cell death. These effects of TxA2might participate in other ischemic neurovascular injuries.
Apoptosis and necrosis: two different outcomes of cigarette smoke condensate-induced endothelial cell death