Interleukin-4 rapidly inhibits calcium transients in response to carbachol in bovine airway smooth muscle cells.

To assess interleukin (IL)-4 effects on calcium signaling, bovine airway smooth-muscle (ASM) cells were loaded with fura-2 and cytosolic calcium ([Ca2 +]i) was measured in single cells by digital microscopy. Human recombinant IL-4 (50 ng/ml) caused small increases in [Ca2 +]i. For single cells, carbachol-stimulated calcium transients were compared before (S1) and after (S2) exposure to IL-4 or IL-13. When cells were treated with IL-4 (50 ng/ml) for 20 min, the S2/S1 ratio was 0.17 ± 0.04 (n = 7) even though IL-4 had been washed from the chamber for 10 min before the S2 response. In contrast, controls not treated with IL-4 had S2/S1 of 0.70 ± 0.04 (n = 13, P < 0.01). Lower concentrations of IL-4 variably decreased transients and IL-13 had no effect. In other experiments, 5 min of IL-4 did not immediately decrease transients but did after a 25-min delay. Goat antihuman IL-4 antibody abolished the effect of IL-4. IL-4 (50 ng/ml) also inhibited responses to caffeine (S2/S1: 0.30 ± 0.04 and 0.54 ± 0.06 for IL-...