Monocyte Chemotactic Protein 1 Upregulates IL-1β Expression in Human Monocytes

Monocyte chemotactic protein-1 (MCP-1) chemoattracts and activates monocytes. The nature of the genes that are transcriptionally activated in the monocytes by MCP-1 is not well understood. To identify such genes, human blood monocytes were incubated with or without MCP-1 for periods of 1, 4, and 12 h and the RNA extracted from these monocytes was subjected to differential display. The differentially expressed transcripts were cloned and sequenced. Differential display showed that interleukin-1β (IL-1β) gene expression was upregulated by MCP-1 treatment of monocytes for 4 to 12 h. Quantitative PCR and ELISA assays showed that MCP-1 treatment caused elevation in the levels of IL-1β transcripts and protein, respectively. Immunoblot analysis showed that most of the protein was pro-IL-1β. Since IL-1β is known to induce MCP-1 synthesis, the present demonstration that MCP-1 induces IL-1β synthesis suggests that the induction of each other would amplify the biological effects of these cytokines during inflammation.