Exogenous and endogenous ceramides elicit volume-sensitive chloride current in ventricular myocytes.
OBJECTIVE
Because ceramide accumulates in several forms of cardiovascular disease and ceramide-induced apoptosis may involve the volume-sensitive Cl(-) current, I(Cl,swell), we assessed whether ceramide activates I(Cl,swell).


RESULTS
I(Cl,swell) was measured in rabbit ventricular myocytes by whole-cell patch clamp after isolating anion currents. Exogenous C(2)-ceramide (C(2)-Cer), a membrane-permeant short-chain ceramide, elicited an outwardly rectifying Cl(-) current in both physiological and symmetrical Cl(-) solutions that was fully inhibited by DCPIB, a specific I(Cl,swell) blocker. In contrast, the metabolically inactive C(2)-Cer analogue C(2)-dihydroceramide (C(2)-H(2)Cer) failed to activate Cl(-) current. Bacterial sphingomyelinase (SMase), which generates endogenous long-chain ceramides as was confirmed by tandem mass spectrometry, also elicited an outwardly rectifying Cl(-) current that was inhibited by DCPIB and tamoxifen, another I(Cl,swell) blocker. Bacterial SMase-induced current was partially reversed by osmotic shrinkage and fully suppressed by ebselen, a scavenger of reactive oxygen species. Outward rectification with physiological and symmetrical Cl(-) gradients, block by DCPIB and tamoxifen, and volume sensitivity are characteristics that identify I(Cl,swell). Insensitivity to C(2)-H(2)Cer and block by ebselen suggest involvement of ceramide signalling rather than direct lipid-channel interaction.


CONCLUSIONS
Exogenous and endogenous ceramide elicited I(Cl,swell) in ventricular myocytes. This may contribute to persistent activation of I(Cl,swell) and aspects of altered myocyte function in cardiovascular diseases associated with by ceramide accumulation.
Raucci
Frank J
FJ
Department of Physiology and Biophysics, Medical College of Virginia, Virginia Commonwealth University, 1101 East Marshall Street, PO Box 980551, Richmond, VA 23298-0551, USA.
Wijesinghe
Dayanjan S
DS
Chalfant
Charles E
CE
Baumgarten
Clive M
CM
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001393:Azoles / Q000494:pharmacology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D003517:Cyclopentanes / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology; D007189:Indans / Q000494:pharmacology; D054833:Isoindoles; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D016566:Organoselenium Compounds / Q000494:pharmacology; D009997:Osmotic Pressure / Q000502:physiology; D018408:Patch-Clamp Techniques; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D013629:Tamoxifen / Q000494:pharmacology
C443139:4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-one-5-yl)oxybutyric acid; D000975:Antioxidants; D001393:Azoles; D018118:Chloride Channels; D002712:Chlorides; D003517:Cyclopentanes; D004965:Estrogen Antagonists; D007189:Indans; D054833:Isoindoles; C064769:N-acetylsphingosine; D016566:Organoselenium Compounds; D017382:Reactive Oxygen Species; D013629:Tamoxifen; C042986:ebselen; D013108:Sphingomyelin Phosphodiesterase; D013110:Sphingosine