Hyaluronan fragments induce the synthesis of MCP-1 and IL-8 in cultured human peritoneal mesothelial cells

Human peritoneal mesothelial cells (HMC) play an important role in inflamma tory processes by their ability to produce various cytokines and chemokines , such as monocyte chemoattractant protein 1 (MCP-1) and interleukin 8 (IL- 8). In this study we investigated the effect of experimentally generated hy aluronan (HA) fragments, degradation products of the extracellular matrix c omponent hyaluronan, which accumulate at inflammatory sites, on the express ion of MCP-1 and IL-8 in cultured HMC. MCP-1 and IL-8 mRNA expression was d etermined by RNase protection assays, and protein levels in the supernatant s were measured by enzyme-linked immunosorbent assays. HA fragments with a molecular mass of approximately 1-7x10(5) daltons upregulate MCP-1 and IL-8 synthesis in HMC dose and time dependently. The effect of HA fragments cou ld be blocked by Ro31-8220, a specific protein kinase C inhibitor, and by P D98059, an inhibitor of the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. Upregulation of chemokine synthesis was pr eceded by an increase in NF-kappaB and AP-1 DNA-binding activity, suggestin g that these transcription factors are activated to increase MCP-1 and IL-8 expression by HA fragments. These data demonstrate that HA fragments marke dly enhance the mRNA expression and protein synthesis of MCP-1 and IL-8 in HMC. In concert with previous findings, our observations indicate that enha nced levels of HA, which are present in the peritoneal cavity of peritoneal dialysis patients, may account for a locally increased chemokine productio n.