Selective neuromicrovascular endothelial cell death by 8-Iso-prostaglandin F2alpha: possible role in ischemic brain injury.

Abstract

Free radical-induced peroxidation is an important factor in the genesis of hypoxic-ischemic encephalopathy, including that of the preterm infant. Isoprostanes are major peroxidation products. Since microvascular dysfunction seems to contribute to ischemic encephalopathies, we studied the cytotoxicity of 8-iso-prostaglandin F2alpha (PGF2alpha) on cerebral microvascular cells. Microvascular endothelial, astroglial, and smooth muscle cells from newborn brain were cultured. The cytotoxicity of 8-iso-PGF2alpha on these cells was determined by MTT assays and lactate dehydrogenase (LDH) release, propidium iodide incorporation, and DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling [TUNEL]). In addition, effects of intraventricular injections of 8-iso-PGF2alpha and possible involvement of thromboxane in 8-iso-PGF2alpha-induced cytotoxicity were determined. 8-Iso-PGF2alpha induced time- and concentration-dependent endothelial cell death (EC50=0.1 nmol/L) but exerted little effect on smooth muscle and astroglial cells; endothelial cell death seemed mostly of oncotic nature (propidium iodide incorporation and LDH release). Cell death was associated with increased endothelial thromboxane A2 (TXA2) formation and was prevented by TXA2 synthase inhibitors (CGS12970 and U63557A); TXA2 mimetics U46619 and I-BOP also caused endothelial cell death. Intraventricular injection of 8-iso-PGF2alpha induced periventricular damage, which was attenuated by CGS12970 pretreatment. These data disclose a novel action of 8-iso-PGF2alpha involving TXA2 in oxidant stress-induced cerebral microvascular injury and brain damage.