The cytokine IL-1β transiently enhances P2X7 receptor expression and function in human astrocytes

Extracellular nucleotide di- and triphosphates such as ATP and ADP mediate their effects through purinergic P2 receptors belonging to either the metabotropic P2Y or the ionotropic P2X receptor family. The P2X(7)R is a unique member of the P2X family, which forms a pore in response to ligand stimulation. regulating cell permeability, cytokine release, and/or apoptosis. This receptor is also unique in that its affinity for the ligand benzoyl-benzoyl ATP (BzATP) is at least 10-fold greater than that of ATP. Primary human fetal astrocytes in culture express low-level-s of P2X(7)R mRNA and protein, and BzATP induces only a slight influx in intracellular calcium [Ca-2divided by](i) , with little demonstrable effect on gene expression or pore formation in these cells. We now show that, following treatment with the proinflaininatory cytokine IL-1beta, BzATP induces a robust rise in [Ca-2divided by](i) with agonist and antagonist profileS indicative of the P2X(7)R. IL-1beta also induced the formation of membrane pores as evidenced by the uptake of YO-PRO-1 (375 Da). Quantitative real-time PGR demonstrated transient upregulation of P2X(7)R mRNA in IL-lbeta-treated cells, While FACS analysis indicated a similar upregulation of P2X7R protein at the cell membrane. In multiple sclerosis lesions, immunoreactivity for the P2X(7)R was demonstrated on reactive astrocytes in autopsy brain tissues. In turn, P2X(7)R stimulation increased the production of IL-1-induced nitric oxide synthase activity by astrocytes in culture. These studies suggest that signaling via the P2X(7)R may modulate the astrocytic response to inflammation in the human central nervous system. (C) 2004 Wiley-Liss. Inc.