Characterization of protoberberine analogs employed as novel human P2X7 receptor antagonists

The P2X7 receptor (P2X7R), 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 P2X7R antagonists. Compounds 3-5 non-competitively inhibited BzATP-induced ethidium ion influx into hP2X7-expressing HEK293 cells, with IC50 values of 100-300 nM. This antagonistic action on the channel further confirmed that both BzATP-induced inward currents and Ca2+ influx were strongly inhibited by compounds 3-5 in patch-clamp and Ca2+ influx assays. The antagonists also effectively suppressed downstream signaling of P2X7 receptors including IL-1β release and phosphorylation of ERK1/2 and p38 proteins in hP2X7-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 P2X7 receptor-mediated immune responses by allosteric inhibition of the receptor. - Graphical abstract: Display Omitted