Abstract 2514: Role of NADPH oxidase 4 in Brain Endothelial Cells after Ischemic Stroke
NADPH oxidase (Nox) family proteins are membrane-bound enzymes, which are a major source of reactive oxygen species (ROS) and play various important roles in immune systems, arteriosclerosis, angiogenesis and aging. Nox4, a member of the Nox family, is abundantly expressed in the cardiovascular system. We have previously reported that it is a major ROS producing enzyme in endothelial cells; however, its roles in endothelial cells are not fully understood. In the present study, we investigated roles of Nox4 in acute brain ischemia using mice with endothelial cell-specific Nox4 overexpression (Tg-EC-Nox4) and cultured human brain microvascular endothelial cells (HBMEC). Nox4 was abundantly expressed in HBMEC and was significantly upregulated in response to hypoxia at O2 1% (2.0-fold increase, p < 0.001). In order to investigate the effects of upregulated Nox4 on endothelial functions during ischemia, we overexpressed Nox4 by adenovirus in HBMEC. Immunoblot analyses showed that phosphorylation of Akt at Ser-473 (47 %, p < 0.001) and endothelial nitric oxide synthase (eNOS) at Ser-1177 (43 %, p < 0.01) was significantly attenuated by Nox4. We next subjected Tg-EC-Nox4 to a permanent middle cerebral artery occlusion (MCAO) stroke model. Triphenyltetrazolium chloride (TTC) staining at 1 day after MCAO demonstrated that infarct volume was significantly greater in Tg-EC-Nox4 than wild-type mice (120 % vs wild-type, p < 0.05). Since it has been established that infarct volume is increased in eNOS-deficient mice, the enlargement of infarct volume in Tg-EC-Nox4 may be attributable in part to suppression of eNOS by Nox4. In conclusion, Nox4 may be an important regulator of endothelial functions. In ischemic stroke, Nox4 may increase infarct volume by suppressing eNOS activity.
- © 2012 by American Heart Association, Inc.