P-449: EXP-2528, a novel angiotensin II type 1 receptor antagonist, protects angiotensin II-stimulated intercellular adhesion molecule-1 via nuclear factor-[kappa]B activation in brain microvascular endothelial cells

• Published in: American journal of hypertension 2005-05, Vol.18 (S4), p.168A
• Main Authors: Liu, Huiqing, Zhang, Xiumei, Wei, Xinbing, Lou, Haiyan, Sun, Ru, Cai, Yawei
• Format: Article
• Language: English
• ISSN: 0895-7061; 1941-7225
• DOI: 10.1016/j.amjhyper.2005.03.466

Purpose: There is increasing data showing that angiotensin (Ang) II may be involve in the initiation and regulation of processes occurring in brain ischemia. Microvascular changes in the brain are notably the cause of cerebral edema and ischemia injury. we have recently shown Ang II injuries brain microvascular endothelial cells (BMECs) partly via regulation of intercellular adhesion molecule-1 (ICAM-1) expression. However, the signaling cascade leading to Ang II-induced ICAM-1 expression in BMECs had not been well elucidated. The transcription factor, nuclear factor-κB (NF-κB) is involved in the expression of several proinflammatory genes including cell adhesion molecules. The aim of the present study was to investigate the possible mechanism of Ang II regulating the expression of ICAM-1 in BMECs and evaluated the effect of a novel selective AT 1 receptor antagonist EXP-2528.Methods: Cultured BCMECs were incubated with Ang II (10-7 mol/L) with or without the specific AT1 receptor inhibitor losartan (10-6 mol/L) and EXP-2528 (10-6 mol/L) and the specific AT2 receptor inhibitor PD 123,319 (10-6 mol/L) for indicated times. Total RNA, cytoplasmic and nuclear protein were extracted from different groups of cultured BMECs. RT-PCR was used to assess ICAM-1 mRNA expression, western blot analysis was used to assess ICAM-1 and IκBα protein expression. Nuclear extracts were used for western blot analysis of p65 protein expression and for electrophoretic mobility shift assay of NF-κB activity.Results: Ang II directly stimulates ICAM-1 mRNA and protein expression in BMECs. Ang II treatment also resulted in the degradation of IκBα, an evident increasing of p65 subunit expression in the nucleus as well as the nuclear translocation of NF-κB. These effects were abolished by preincubation with the AT 1 -specific antagonist losartan or EXP-2528 or losartan plus the AT2 receptor antagonist PD123319 but not by PD123319 alone. Moreover, there were no significant difference between losartan group and losartan + PD 123,319 group.Conclusions: The present study demonstrates that Ang II upregulated ICAM-1 expression via NF-κB activation in BMECs by activating AT 1 receptor, AT1 receptor antagonists, both EXP-2528 and losartan inhibit such effect of Ang II.