Expression and Regulation of AT1 Receptor in Rat Lung Microvascular Endothelial Cell 1

BackgroundThe renin-angiotensin system is thought to be involved in the development and progression of vascular endothelium inflammation, thereby contributing to vascular endothelium injury. To clarify the role of angiotensin II (Ang II) in rat pulmonary microvascular endothelial cells (RPMVECs), we examined the expression and functional significance of angiotensin II (AngII) receptors in normal and lipopolysacchride (LPS) treated RPMVECs.MethodsThe expressions of Ang II type1(AT1) and Ang II type 2 (AT2) receptors in cultured RPMVECs were identified by the reverse transcription-polymerase chain reaction (RT-PCR) technique, Western blot and 125I-labeled [Sar1,Ile8] Ang II binding assays. The RPMVECs were treated with LPS (0.1–100 μg/ml) and Ang II (10−8–10−5 M) for 24 h, respectively. Next, RPMVECs were treated with 10 μg/ml LPS or 10−7 M AngII for various times (3, 6, 12, and 24 h). The mRNA and protein levels of, AT1 and AT2 receptors, were evaluated at 3, 6, 12, and 24 h, respectively.ResultsThe presence of specific Ang II binding sites in RPMVECs was found by Ang II saturated assays. RT-PCR revealed that only the AT1 receptor mRNA is presented in RPMVECs. Western blot analysis of the RPMVECs protein extracts showed only one prominent band of the protein at approximately 41 KDa when probed with anti-AT1 antibody and anti-AT2 antibody. No AT2 receptor mRNA and protein was detected. LPS treated cells resulted in an increase in the mRNA and protein levels of AT1 receptor, whereas, AngII treated cells showed a decrease in the mRNA and protein levels of AT1 receptor.ConclusionsWe found that primary cultured RPMVECs expressed only AT1 receptor, but not AT2 receptor. LPS up-regulated the transcriptional and post-transcriptional expression of AT1 receptor in RPMVECS; in contrast, Ang II treatment caused a reduction in the mRNA and protein of AT1 receptor in a time-dependant manner.