SELECTIVE PROTEIN KINASE C INHIBITION ATTENUATES PULMONARY ARTERY CYTOKINE EXPRESSION WITHOUT AFFECTING HYPOXIC PULMONARY VASOCONSTRICTION

Abstract

Hypoxic pulmonary vasoconstriction may be an adaptive response to shunt blood to well-oxygenated areas of the lung, but hypoxia-induced inflammatory cytokine production leads to acute lung injury. We have previously shown that protein kinase C (PKC) mediates both hypoxic pulmonary vasoconstriction and inflammatory cytokine expression from the pulmonary artery; however, the effect of specific PKC isoform inhibition is currently unknown. We hypothesized that inhibition of classical PKC (cPKC) isoforms would attenuate hypoxic pulmonary vasoconstriction and downregulate hypoxia-induced pulmonary artery cytokine expression. To study this, isometric force displacement was measured in isolated rat pulmonary artery rings (n = 6 per group) during hypoxia (95% N2/5% CO2) in the presence of the nonspecific PKC inhibitor bisindolylmaleimide (1 micromol/L), the cPKC inhibitor Gö 6976 (1 - 10 micromol/L), or vehicle (dimethyl sulfoxide, 0.001%). After 60 min of hypoxia, pulmonary artery rings were analyzed for tumor necrosis factor (TNF) alpha and interleukin (IL) 1beta messenger RNA via reverse transcriptase-polymerase chain reaction. Nonspecific PKC inhibition (bisindolylmaleimide) significantly attenuated hypoxic pulmonary vasoconstriction (44.59 +/- 10.52% vs. 87.06 +/- 10.91% vehicle; P < 0.001) and downregulated hypoxia-induced expression of pulmonary artery TNF-alpha. Specific cPKC inhibition (Gö 6976) attenuated pulmonary artery TNF-alpha expression but had no effect on hypoxic pulmonary vasoconstriction. These data are indicative of the following: (1) nonspecific PKC inhibition attenuates both hypoxic pulmonary vasoconstriction and pulmonary artery TNF-alpha expression, (2) cPKC inhibition downregulates hypoxia-induced pulmonary artery TNF-alpha expression but has no effect on hypoxic pulmonary vasoconstriction, and (3) hypoxic pulmonary vasoconstriction and hypoxia-induced pulmonary artery cytokine expression are independent processes.