Lipopolysaccharide decreases bradykinin receptor-induced acidification responses in cultured bovine aortic endothelial cells

Abstract

The effects of bacterial lipopolysaccharide ( Escherichia coli 0127-B8) on bradykinin receptor function in bovine aortic endothelial cells were investigated using a microphysiometer. Bradykinin and Lys 0–desArg 10-bradykinin produced concentration-dependent acidification responses with pEC 50 values of 8.87±0.20 and 9.78±0.08, respectively. These responses were competitively and selectively antagonised by the bradykinin B 2 receptor antagonist, icatibant and the bradykinin B 1 receptor antagonist, desArg 9–Leu 8-bradykinin, respectively. The non-peptide bradykinin B 2 receptor antagonist, FR173657 (0.3 and 3 nM), selectively antagonised bradykinin-induced acidification responses, causing rightward shifts of the concentration–response curves to bradykinin, but at the same time, significantly decreasing the maximum response. A preincubation with lipopolysaccharide (0.01 and 0.1 μg/ml) for 24 h caused a significant concentration-dependent decrease in maximal response to bradykinin (27.2±1.9 and 9.7±0.4% of control) and the bradykinin B 1 receptor agonist, Lys 0–desArg 10-bradykinin (59.0±7.14 and 25.3±7.8% of control), without affecting the EC 50. These results suggest that bradykinin B 1 receptors are constitutively expressed in cultured bovine aortic endothelial cells and that the microphysiometer provides a rapid, sensitive technique to characterise bradykinin receptors and investigate their regulation by cytokines. Interactions between bradykinin receptors and lipopolysaccharide may play a part in the cascade of deleterious effects that occur during septic shock.