Effect of lipopolysaccharide on angiotensin II type 1 receptor expression and function in human pulmonary microvascular endothelial cells.

Abstract

Lipopolysaccharides (LPSs) are an important initiation factor in acute respiratory distress syndrome. The aim of the present study was to investigate the effect of LPSs on the regulation of angiotensinII (AngII) receptors in human pulmonary microvascular endothelial cells (HPMECs). HPMECs were treated with 0, 50, 100 or 200ng/ml LPS and incubated for 4, 8, 12 or 16h. The expression of AngII type1 receptor (AT1R) and AngII type2 receptor (AT2R) was determined using reverse transcription‑polymerase chain reaction and western blot analysis. The affinity to AngII was measured using a radioligand binding assay. No AT2R expression was detected with or without LPS administration in HPMECs, and LPS treatment increased the expression level of AT1R. A time‑dependent increase of AT1R transcription was observed in the 50ng/ml group, while in the 100 and 200ng/ml groups, the AT1R mRNA levels reached peak values at 4h and remained unchanged. The protein level of AT1R increased significantly in a dose‑dependent manner for each incubation time period. A time‑dependent increase in the protein level was observed in the 50 and 100ng/ml groups. As for the 200ng/ml group, the level of AT1R reached a peak value at 8h. Maximal binding (Bmax) significantly increased following LPS treatment and Bmax of the 50ng/ml group exhibited a time‑dependent increase. The Bmax of the100 and 200ng/ml groups reached peak values at 12 and 8h, respectively, and decreased thereafter. The dissociation constant remained unchanged following LPS treatment. Thus, treatment with LPS increased AT1R expression and its Bmax to AngII in HPMECs, however, did not alter the affinity of AT1R to AngII.