Division of Pharmacology and Pathophysiology, Kinki University School of Pharmacy, Higashi-Osaka 577-8502, Japan.
Department of Life Science, Kinki University School of Science and Engineering, Higashi-Osaka 577-8502, Japan.
Biochem Biophys Res Commun. 2014 Feb 28;445(1):225-9. doi: 10.1016/j.bbrc.2014.01.185. Epub 2014 Feb 6.
Hydrogen sulfide (H2S), a gasotransmitter, is formed from l-cysteine by multiple enzymes including cystathionine-γ-lyase (CSE). We have shown that an H2S donor, NaHS, causes hyperalgesia in rodents, an effect inhibited by knockdown of Cav3.2 T-type Ca(2+) channels (T-channels), and that NaHS facilitates T-channel-dependent currents (T-currents) in NG108-15 cells that naturally express Cav3.2. In the present study, we asked if endogenous and exogenous H2S participates in regulation of the channel functions in Cav3.2-transfected HEK293 (Cav3.2-HEK293) cells. dl-Propargylglycine (PPG), a CSE inhibitor, significantly decreased T-currents in Cav3.2-HEK293 cells, but not in NG108-15 cells. NaHS at 1.5mM did not affect T-currents in Cav3.2-HEK293 cells, but enhanced T-currents in NG108-15 cells. In the presence of PPG, NaHS at 1.5mM, but not 0.1-0.3mM, increased T-currents in Cav3.2-HEK293 cells. Similarly, Na2S, another H2S donor, at 0.1-0.3mM significantly increased T-currents in the presence, but not absence, of PPG in Cav3.2-HEK293 cells. Expression of CSE was detected at protein and mRNA levels in HEK293 cells. Intraplantar administration of Na2S, like NaHS, caused mechanical hyperalgesia, an effect blocked by NNC 55-0396, a T-channel inhibitor. The in vivo potency of Na2S was higher than NaHS. These results suggest that the function of Cav3.2 T-channels is tonically enhanced by endogenous H2S synthesized by CSE in Cav3.2-HEK293 cells, and that exogenous H2S is capable of enhancing Cav3.2 function when endogenous H2S production by CSE is inhibited. In addition, Na2S is considered a more potent H2S donor than NaHS in vitro as well as in vivo.
硫化氢（H2S）是一种气体递质，由胱硫醚-γ-裂解酶（CSE）等多种酶从 L-半胱氨酸形成。我们已经证明，H2S 供体 NaHS 可引起啮齿动物痛觉过敏，该作用可被 Cav3.2 T 型钙（Ca2+）通道（T 通道）敲低所抑制，并且 NaHS 促进在天然表达 Cav3.2 的 NG108-15 细胞中介导 T 通道的电流（T 电流）。在本研究中，我们询问内源性和外源性 H2S 是否参与调节 Cav3.2 转染的 HEK293（Cav3.2-HEK293）细胞中的通道功能。dl-炔丙基甘氨酸（PPG），一种 CSE 抑制剂，显著降低 Cav3.2-HEK293 细胞中的 T 电流，但不降低 NG108-15 细胞中的 T 电流。1.5mM 的 NaHS 对 Cav3.2-HEK293 细胞中的 T 电流没有影响，但增强了 NG108-15 细胞中的 T 电流。在 PPG 存在的情况下，1.5mM 的 NaHS，但不是 0.1-0.3mM 的 NaHS，增加了 Cav3.2-HEK293 细胞中的 T 电流。同样，另一种 H2S 供体 Na2S 在 0.1-0.3mM 时，在存在 PPG 的情况下，可显著增加 Cav3.2-HEK293 细胞中的 T 电流，但在不存在 PPG 的情况下则不会。在 HEK293 细胞中，CSE 在蛋白质和 mRNA 水平上均有表达。Na2S 的皮内给药，与 NaHS 一样，引起机械性痛觉过敏，该作用可被 T 通道抑制剂 NNC 55-0396 阻断。Na2S 的体内效力高于 NaHS。这些结果表明，Cav3.2 T 通道的功能在 Cav3.2-HEK293 细胞中被 CSE 合成的内源性 H2S 持续增强，并且当 CSE 产生的内源性 H2S 被抑制时，外源性 H2S 能够增强 Cav3.2 功能。此外，Na2S 被认为是一种比 NaHS 更有效的体内外 H2S 供体。
