In Vitro Activation of Murine Peritoneal Macrophages by Monocyte Chemoattractant Protein-1: Upregulation of CD11b,Production of Proinflammatory Cytokines,and the Signal Transduction Pathway

Abstract

The CC chemokine monocyte chemotactic protein-1 (MCP-1) is a major mediator of monocyte/macrophage infiltration at the inflammatory sides under both physiologic and pathologic conditions. We report the ability of MCP-1 to activate murine peritoneal macrophages in vitro for enhanced expression of CD11b, macrophage-mediated cytotoxicity, and production of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). The macrophages treated with MCP-1 in vitro displayed significant cytolytic activity toward TNF-α-sensitive L929 cells in a dose-dependent manner. The macrophage-mediated L929 cytotoxicity was blocked in the presence of anti-TNF-α antibodies, suggesting the involvement of TNF-α. Production of TNF-α and IL-1 macrophages on MCP-1 treatment was maximum at 24 h of incubation with 100 ng/ml MCP-1. Enhanced TNF-α and IL-1β mRNA expression was also demonstrated by RT-PCR, which revealed transcription of interferon γ(IFN-γ), IL-12, and related T cell-specific chemokine genes, KC and IP-10, in the MCP-1-treated macrophages. The pharmacologic inhibitors pertussis toxin (100 ng/ml), wortmannin (200 ng/ml), H-7 (10 μM), PD98059 (25 μM), and genistein (10 μg/ml) significantly inhibited TNF-α and IL-1 production in the MCP1-treated macrophages, suggesting the involvement of G-proteins, phosphoinositol-3-kinase (PI3K), protein kinase C, p42/44 MAPK, and tyrosine kinases in this process.