PLC-dependent intracellular Ca2+ release was associated with C6-ceramide-induced inhibition of Na+ current in rat granule cells.
In this report, the effects of C(6)-ceramide on the voltage-gated inward Na(+) currents (I(Na)), two types of main K(+) current [outward rectifier delayed K(+) current (I(K)) and outward transient K(+) current (I(A))], and cell death in cultured rat cerebellar granule cells were investigated. At concentrations of 0.01-100 microM, ceramide produced a dose-dependent and reversible inhibition of I(Na) without alteration of the steady-state activation and inactivation properties. Treatment with C(2)-ceramide caused a similar inhibitory effect on I(Na). However, dihydro-C(6)-ceramide failed to modulate I(Na). The effect of C(6)-ceramide on I(Na) was abolished by intracellular infusion of the Ca(2+)-chelating agent, 1,2-bis (2-aminophenoxy) ethane-N, N, N9, N9-tetraacetic acid, but was mimicked by application of caffeine. Blocking the release of Ca(2+) from the sarcoplasmic reticulum with ryanodine receptor blocker induced a gradual increase in I(Na) amplitude and eliminated the effect of ceramide on I(Na). In contrast, the blocker of the inositol 1,4,5-trisphosphate-sensitive Ca(2+) receptor did not affect the action of C(6)-ceramide. Intracellular application of GTPgammaS also induced a gradual decrease in I(Na) amplitude, while GDPbetaS eliminated the effect of C(6)-ceramide on I(Na). Furthermore, the C(6)-ceramide effect on I(Na) was abolished after application of the phospholipase C (PLC) blockers and was greatly reduced by the calmodulin inhibitors. Fluorescence staining showed that C(6)-ceramide decreased cell viability and blocking I(Na) by tetrodotoxin did not mimic the effect of C(6)-ceramide, and inhibiting intracellular Ca(2+) release by dantrolene could not decrease the C(6)-ceramide-induced cell death. We therefore suggest that increased PLC-dependent Ca(2+) release through the ryanodine-sensitive Ca(2+) receptor may be responsible for the C(6)-ceramide-induced inhibition of I(Na), which does not seem to be associated with C(6)-ceramide-induced granule neuron death.
Liu
Zheng
Z
Institute of Brain Science, School of Life Sciences, Fudan University, Shanghai, PR China.
Fei
Xiao-Wei
XW
Fang
Yan-Jia
YJ
Shi
Wen-Jie
WJ
Zhang
Yu-Qiu
YQ
Mei
Yan-Ai
YA
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000494:pharmacology*; D002525:Cerebellar Cortex / Q000166:cytology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
D002518:Ceramides; D015221:Potassium Channels; D019837:Ryanodine Receptor Calcium Release Channel; D015222:Sodium Channels; D010738:Type C Phospholipases; C504327:N-(alpha-hydroxyoctadecanoyl)phytosphingosine; D002118:Calcium