Department of Physiology and Biophysics, Medical College of Virginia, Virginia Commonwealth University, 1101 East Marshall Street, PO Box 980551, Richmond, VA 23298-0551, USA.
Cardiovasc Res. 2010 Apr 1;86(1):55-62. doi: 10.1093/cvr/cvp399. Epub 2009 Dec 14.
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).
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.
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.
由于神经酰胺在几种心血管疾病中积累，并且神经酰胺诱导的细胞凋亡可能涉及体积敏感性氯离子电流 I(Cl,swell)，我们评估了神经酰胺是否激活 I(Cl,swell)。
在通过全细胞膜片钳技术分离阴离子电流后，用兔心室肌细胞测量 I(Cl,swell)。外源性 C(2)-神经酰胺（C(2)-Cer），一种膜通透性的短链神经酰胺，在生理和对称氯离子溶液中引发外向整流氯离子电流，该电流被特异性 I(Cl,swell)阻断剂 DCPIB 完全抑制。相比之下，代谢不活跃的 C(2)-神经酰胺类似物 C(2)-二氢神经酰胺（C(2)-H(2)Cer）未能激活氯离子电流。细菌鞘氨醇酶（SMase），其通过串联质谱证实生成内源性长链神经酰胺，也引发外向整流氯离子电流，该电流被 DCPIB 和他莫昔芬（另一种 I(Cl,swell)阻断剂）抑制。细菌 SMase 诱导的电流部分被渗透压收缩逆转，完全被活性氧清除剂 ebselen 抑制。具有生理和对称氯离子梯度的外向整流、DCPIB 和他莫昔芬的阻断以及体积敏感性是鉴定 I(Cl,swell)的特征。对 C(2)-H(2)Cer 的不敏感性和 ebselen 的阻断表明涉及神经酰胺信号转导而不是直接的脂质通道相互作用。
外源性和内源性神经酰胺在心室肌细胞中引发 I(Cl,swell)。这可能导致与神经酰胺积累相关的心血管疾病中持续激活 I(Cl,swell)和改变心肌细胞功能的某些方面。
