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

Abstract

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.

Positive inotropic effect of ceramide in adult ventricular myocytes: mechanisms dissociated from its reduction in Ca2+influx

“…In patch-clamped myocytes, n-ceramide, a naturally occurring ceramide, produced an inhibitory effect on I Ca,L , similar to C 2 -ceramide, as described previously (31). This effect, however, was accompanied by increases in systolic amplitude and the duration of contraction.…”

“…C 2 -ceramide has also been shown to reduce I Ca,L in these preparations (29,31). The present study demonstrated that despite its reduction in I Ca,L , ceramide induced a positive inotropic effect and an increase in systolic free Ca i 2ϩ , a positive lusitropic effect, and an increase in the Ca 2ϩ sensitivity of contractile proteins.…”

“…Our previous study (31) has shown that IL-1␤ increases intracellular ceramide production in 5 min and that C 2 -ceramide mediates the IL-1␤-induced decrease in L-type Ca 2ϩ channel current (I Ca,L ) in adult rat ventricular myocytes. Other studies in rat ventricular myocytes have also shown that C 2 -ceramide reduces I Ca,L (29), whereas sphingosine, an interconvertible metabolite of ceramide, completely abolishes Ca 2ϩ transients (29) and inhibits I Ca,L (29,38).…”

“…Ceramides have been shown to stimulate the production of other cytokines (e.g., IL-2 and IL-6) (28) and prostaglandin E 2 (2,3), induce transcription factors (e.g., NF-B) (3,11,32,37), suppress cell growth (19), and induce apoptosis (15,16,21,23). Moreover, studies in cardiac myocytes have shown that intracellular ceramide levels are increased in response to IL-1␤ stimulation (31), during ischemia-reperfusion (8), after treatment with doxorubicin (1), and during hypoxia/reoxygenation (18). It has also been suggested that ceramide is associated with the TNF-␣-induced and ischemia-reperfusion-and doxorubicin-associated apoptosis (1,8,24).…”

Alterations in Ceramide Concentration and pH Determine the Release of Reactive Oxygen Species by Cftr-Deficient Macrophages on Infection

“…This characteristic is important because some diets have been shown to alter membrane lipid composition (5,(16)(17)(18). Changes in lipid composition, in particular an alteration in cholesterol and sphingolipids concentrations, may regulate the activity of ion channels and pumps (19)(20)(21). Littermates of the C57BL/6 mice were used as control animals.…”