Figure 1.

Ivermectin augments sustained ATP-induced currents in hMDM. Human monocytes were obtained from healthy volunteers, and allowed to spontaneously differentiate into hMDM. Whole cell recordings were performed in the voltage-clamp mode at a holding potential of −60 mV and with a bath solution containing low concentrations of divalent cations (low DIC; 0.1 mM CaCl₂ and no MgCl₂). ATP (1 mM) was applied seven times for 6 s and at 2 min intervals. Shown are superimposed responses to the first, sixth and seventh challenge (left panels in A–D). Note that the first ATP application occasionally elicits a rapidly inactivating current component (transient current, I_t), whereas the following applications cause sustained inward currents (I_s). In panel A–D, dashed lines indicate the levels I_s reached after the run-up of ATP-induced currents (I_ATP) was allowed to saturate (usually after five to six ATP pulses). After that, ATP was applied, to the same set of cells, for the eighth time and for 14 s. Solvent (DMSO 0.1 %) or ivermectin (3 µM) was added acutely to ATP for 6 s as indicated by the bars below the current traces in the right panels of A–D. The dotted lines indicate, in this and subsequent electrophysiological figures, the zero current level. The inset in panel A shows a phase contrast microphotograph from the recorded hMDM between the outlet of the perfusion system (left) and the attached patch pipette. Low DIC bath solution (saline; A, B), the P2X4 receptor blocker 5-BDBD (5 µM; C), the P2X7 receptor -specific blocker A 438079 (10 µM; D) or a combination of both (E) were superfused for 4 min before and during the eighth ATP application. (E) Statistical analysis of ATP-induced current densities in n= 7–11 experiments performed as illustrated in panels A–D. Columns represent the ratio of I₁ (I_ATP just before the application of ivermectin, see panel A) with respect to I_s, expressed as percentage of I_s. *P < 0.05, significantly different from the control condition. (F) Statistical analysis of DMSO or ivermectin-induced current potentiation (I₂; peak current in the presence of DMSO or ivermectin, see panel A) without or with pre-incubation of 5-BDBD, A 438079 or 5-BDBD plus A 438079. Columns represent the ratio of I₂ with respect to I₁, expressed as percentage of I₁. *P < 0.05, significantly different from the effects of DMSO; n.s., not significant.