Although the immune cells experience mechanical forces and pressures throughout their life cycle, little is known about how such mechanical processes regulate the immune cell function. We previously reported that cyclical stretch (CS) stimulation of murine macrophage RAW264.7 (RAW) cells evoked release of nucleotides including ATP and also triggered elevation of mRNAs for various pro-inflammatory factors. In this study, we investigated the role of extracellular nucleotides on RAW cells activation induced by CS stimulation.
In RAW cells, CS stimulation evoked a marked release of ATP and also elevated mRNA and protein levels for monocyte chemoattractant protein-1 (MCP-1). Direct stimulation of RAW cells with extracellular nucleotides also triggered MCP-1 mRNA expression with a rank order efficacy: UTP, UDP >> ATP. RAW cells expressed functional P2 receptors including P2Y₆ receptor for uridine nucleotide. In the presence of P2Y₆ receptor antagonists, CS-induced MCP-1 expression was suppressed. In addition, P2Y₆ receptor gene knock-down with siRNA reduced CS-induced MCP-1 mRNA elevation without affecting ATP release.
These results suggest that P2Y₆ receptor activation via autocrine stimulation by released extracellular nucleotides may be involved in CS-induced MCP-1 expression in macrophages.