Lipopolysaccharide Inhibits the Channel Activity of the P2X7 Receptor
LPS does not affect ATP-induced ERK activation in P2X7R-HEK293 cells. (a) Representative gel showing ERK phosphorylation (P-ERK, middle panel) induced by 1 mM ATP applied at different times. The upper panel shows P2X7R immunoreactivity of stable transfected cells; the lower panel shows total ERK. (b) Quantification of the effects on ERK activation obtained by the application of 1 mM ATP (open circles) or 1 μg/mL LPS (closed squares). Data were normalized against the phosphorylation induced by 2 min of ATP application, . (c) Representative gel showing control cells or pretreated with 1 μg/mL LPS for 30 min. ATP was applied for 5 min, and ERK activation was evaluated. Upper panels show the detection of P-ERK; lower panels show total ERK. (d) Quantification of ERK activation in control (open circles) and LPS-treated (closed squares) cells at different ATP concentrations applied for 5 (upper graph) and 15 min (lower graph). Experiments were normalized against ERK phosphorylation induced by 600 μM ATP for 15 min in LPS-treated cells.