Characterization of protoberberine analogs employed as novel human P2X 7 receptor antagonists

Abstract

The P2X 7 receptor (P2X 7R), a member of the ATP-gated ion channel family, is regarded as a promising target for therapy of immune-related diseases including rheumatoid arthritis and chronic pain. A group of novel protoberberine analogs (compounds 3–5), discovered by screening of chemical libraries, was here investigated with respect to their function as P2X 7R antagonists. Compounds 3–5 non-competitively inhibited BzATP-induced ethidium ion influx into hP2X 7 -expressing HEK293 cells, with IC 50 values of 100–300 nM. This antagonistic action on the channel further confirmed that both BzATP-induced inward currents and Ca 2+ influx were strongly inhibited by compounds 3–5 in patch-clamp and Ca 2+ influx assays. The antagonists also effectively suppressed downstream signaling of P2X 7 receptors including IL-1β release and phosphorylation of ERK1/2 and p38 proteins in hP2X 7 -expressing HEK293 cells or in differentiated human monocytes (THP-1 cells). Moreover, IL-2 secretion from CD3/CD28-stimulated Jurkat T cell was also dramatically inhibited by the antagonist. These results imply that novel protoberberine analogs may modulate P2X 7 receptor-mediated immune responses by allosteric inhibition of the receptor.