Thrombin upregulates interleukin-8 in lung fibroblasts via cleavage of proteolytically activated receptor-I and protein kinase C-gamma activation

Acute and chronic interstitial lung diseases are accompanied by evidence of inflammation and vascular injury. Thrombin activity in bronchoalveolar lav age fluid from such conditions is often increased, as well as interleukin ( IL)-8, We observed that conditioned medium from lung fibroblasts exposed to thrombin has chemotactic activity for polymorphonuclear cells, and that th is activity can be abolished by antibody to IL-8, We report that thrombin s timulates expression of IL-8 in human lung fibroblasts on both the messenge r RNA and protein levels in a time- and dose-dependent manner. Stimulation of IL-8 expression by thrombin is inhibited by specific thrombin inhibitors . Synthetic thrombin receptor agonist peptide-14 mimics thrombin's stimulat ion of IL-8 expression in a dose-dependent manner consistent with the idea that upregulation of IL-8 by thrombin in human lung fibroblasts requires cl eavage of proteolytically activated receptor-I. We demonstrate further that thrombin-induced IL-8 synthesis is regulated by protein kinase (PK) C. PKC -gamma may be involved in the upregulation of lung fibroblast IL-8 by throm bin because stimulation of lung fibroblasts with thrombin caused significan t upregulation of PKC-gamma and because PKC-gamma antisense oligonucleotide s inhibited the accumulation of PKC-gamma protein and IL-8 protein, Our dat a suggest that the PKC-gamma isoform increase observed after thrombin stimu lation is required for thrombin-induced IL-8 formation by human lung fibrob lasts.