title: Ceramide inhibits L-type calcium channel currents in rat pinealocytes.
abstract: In rat pinealocytes, ceramide can inhibit the KCl- and BayK 8644-mediated potentiation of cAMP and cGMP accumulation, suggesting that the L-type Ca2+ channel is a target of ceramide action. This was examined in the present study using intracellular Ca2+ measurement and patch-clamp studies. In fura-2-loaded pinealocytes, C2- and C6-ceramide inhibited the Ca2+ increase caused by BayK 8644 and KCl, but not that caused by norepinephrine, suggesting an inhibitory effect of ceramide on the L-type Ca2+ channels. Patch-clamp analysis confirmed that C2- and C6-ceramide, but not C2-dihydroceramide (the inactive analog) inhibited the L-type Ca2+ channel current. Furthermore, treatments known to increase cellular ceramide levels, including a glucosylceramide synthase inhibitor and sphingomyelinase, also inhibited this current. The inhibitory effect of ceramide on the current was attenuated by lavendustin A, a tyrosine kinase inhibitor, but not by H7, a serine/threonine kinase inhibitor. The effect of ceramide was mimicked by interleukin-1beta, a cytokine highly expressed in the pineal that is known to activate the sphingomyelin pathway. These results indicate that the sphingomyelin pathway is another important signaling mechanism that regulates the L-type Ca2+ channel, and tyrosine kinase appears to be involved in the effect of ceramide.
authors.affiliation: Department of Physiology and Medicine, Faculty of Medicine, University of Alberta, Edmonton, Canada. cchik@ualberta.ca
authors.forename: C L
authors.initials: CL
authors.lastname: Chik
authors.forename: B
authors.initials: B
authors.lastname: Li
authors.forename: T
authors.initials: T
authors.lastname: Negishi
authors.forename: E
authors.initials: E
authors.lastname: Karpinski
authors.forename: A K
authors.initials: AK
authors.lastname: Ho
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology*; D002518:Ceramides / Q000494:pharmacology*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors; D007375:Interleukin-1 / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D009712:Nucleotides, Cyclic / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010636:Phenols / Q000494:pharmacology; D010870:Pineal Gland / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002518:Ceramides; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D009712:Nucleotides, Cyclic; D010636:Phenols; D047428:Protein Kinase Inhibitors; C062898:lavendustin A; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D013108:Sphingomyelin Phosphodiesterase; D007545:Isoproterenol; D002118:Calcium; D009638:Norepinephrine