On interaction of activated protein C with human aortic smooth muscle cells attenuating the secretory group IIA phospholipase A2 expression.

INTRODUCTION: Pharmacological restriction of secretory group IIA phospholipase A(2) (sPLA(2)-IIA) expression is thought to be beneficial in the treatment of inflammatory diseases such as sepsis and septic shock. In this study we investigated the effects of activated protein C (APC) on sPLA(2)-IIA expression, phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, and on DNA-binding activities of nuclear factor-kappaB (NF-kappaB) and CCAAT box enhancer binding protein-beta (C/EBP-beta) in human aortic smooth muscle cells (HASMC).
MATERIALS AND METHODS: To achieve elevated sPLA(2)-IIA production as occurring during inflammation, HASMC were stimulated with interferon-gamma (IFN-gamma) alone and in combination with other inductors, thus modeling the strong sPLA(2)-IIA elevation by inflammation. RESULTS AND
CONCLUSIONS: APC inhibited the stimulated expression of sPLA(2)-IIA in HASMC dose-dependently (1-300 nM). At the same time, APC increased the phosphorylation of ERK 1/2 and decreased NF-kappaB and C/EBP-beta DNA-binding activities in these cells, as compared with respective stimulated controls. Reverse transcriptase-polymerase chain reaction and cell-based ELISA reveal an endothelial protein C receptor (EPCR) expression in HASMC. Application of antibodies against EPCR and protease-activated receptor-1 (PAR-1) reduced the APC-induced ERK 1/2 activation and the treatment of cells with a PAR-1 antagonist diminished the sPLA(2)-IIA inhibition. The obtained results show that APC effectively suppresses the up-regulated sPLA(2)-IIA expression, which might contribute to the reported beneficial effects of APC in the treatment of severe inflammatory disorders.