Involvement of ceramide in inhibitory effect of IL-1 beta on L-type Ca2+ current in adult rat ventricular myocytes.

Interleukin (IL)-1 beta has previously been shown to decrease the L-type Ca2+ channel current (ICa,L). Because ceramide has been suggested to mediate many biological effects of IL-1 beta, we examined whether ceramide was involved in the IL-1 beta-induced suppression of ICa,L in adult rat ventricular myocytes. Exposure of myocytes to 5 ng/ml IL-1 beta elicited a 140% increase in ceramide production within 2 min, as measured with 32P phosphorylation. Whole cell patch-clamp techniques were used to measure ICa,L in myocytes internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions. C2 ceramide (1 nM-1 microM), a membrane-permeable analog of ceramide, caused a concentration-dependent inhibition of ICa,L and increased the rate of ICa,L inactivation without altering its gating properties. An inactive ceramide analog failed to inhibit ICa,L. At submaximal concentrations, effects of C2 ceramide and IL-1 beta on ICa,L were additive and saturable. In the presence of a maximally effective concentration of IL-1 beta, C2 ceramide had no further effect on ICa,L. These results suggest that ceramide mediates IL-1 beta-induced suppression of cardiac ICa,L.