Effect of bradykinin, TGF-β1, IL-1β, and hypoxia on COX-2 expression in pulmonary artery smooth muscle cells

Abstract

Prostanoids are major regulators of smooth muscle function that are generated by cyclooxygenase (COX). Here we hypothesized that cytokines and mediators that regulate the pulmonary circulation would alter COX expression and prostanoid generation in pulmonary artery smooth muscle cells. Bradykinin, transforming growth factor-β1 (TGF-β1), and interleukin-1β (IL-1β) increased inducible COX-2 expression and prostaglandin E2 (PGE2) release. Transfection studies using a COX-2 promoter construct demonstrated that all three agents acted transcriptionally. Constitutive COX-1 protein expression was unchanged. The COX inhibitor indomethacin, the COX-2 inhibitor NS-398, the protein synthesis inhibitor cycloheximide, and the glucocorticoid dexamethasone abrogated the increased PGE2levels. Dexamethasone and cycloheximide prevented COX-2 induction. Hypoxia (3% O2-5% CO2-92% N2) for 24 h selectively augmented TGF-β1-stimulated PGE2 production and COX-2 induction but had no effect alone. Prolonged hypoxic culture alone for 48 and 72 h enhanced COX-2 induction and increased PGE2. These studies show that a number of stimuli are capable of inducing COX-2 in pulmonary artery smooth muscle cells. The interaction between hypoxia and TGF-β1 may be particularly relevant to pulmonary hypertension.