Expression of proteinase-activated receptors in mouse microglial cells.

Microglia are the resident immune cells of the CNS: they are activated rapidly by CNS damage and perform the function of tissue macrophages. The first steps during microglial activation are currently under intense study, and it is widely believed that substances released from damaged brain tissue can trigger this process. We recently reported that the blood coagulation factor thrombin, which enters the CNS during breakdown of the blood-brain barrier, activates microglial cells. The cellular effects of thrombin and trypsin-like proteases are mediated by proteinase-activated receptors (PARs). Based on our prior data we hypothesized that microglial cells express these receptors. Using RT-PCR and flow cytometry, we report that primary mouse microglial cells, as well as the murine microglial cell lines BV-2 and N9, indeed express PARs, albeit at different levels. Demonstrating multiple PARs on microglia may enhance the attractiveness of PARs as therapeutic targets in neuroinflammatory disorders.