Brilliant Blue G selectively blocks ATP-gated rat P2X7 receptors

There are few antagonists selective for subtypes of the several P2X receptors, but these are needed to identify the receptors expressed on native cells and tissues. In particular, P2X(4) and P2X(7) receptor subunits are colocalized on immune, epithelial, and exocrine gland cells, but both are relatively insensitive to suramin and pyridoxal-5-phosphate-6-azo-2',4'-disulfonic acid derivative. In this article, we show that Coomassie Brilliant Blue G selectively inhibits P2X(7) receptors with nanomolar affinity. We measured currents in response to P2X receptor activation in HEK293 cells heterologously expressing human or rat P2X(1), P2X(2), P2X(3), P2X(2/3), P2X(4), P2X(1/5), and P2X(7) receptors. Brilliant Blue G produced a noncompetitive inhibition of rat and human P2X(7) receptors with IC50 values of 10 and 200 nM, respectively. IC50 values for inhibition of the other receptors ranged from 2 to >30 mu M; the rat and human P2X(4) receptors showed IC50 values of >10 and 3.2 mu M. Coomassie Blue G also blocked YO-PRO1 uptake and membrane blebbing, which are uniquely associated with activation of P2X(7) receptors. Thus, Brilliant Blue G is at least 1000-fold more potent at rat P2X(7) receptors than at rat P2X(4) receptors.