Valente Raphael C, Capella Luiz S, Monteiro Robson Q, Rumjanek Vivian M, Lopes Aníbal G, Capella Márcia A M
Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro (UFRJ), Brazil.
FASEB J. 2003 Sep;17(12):1700-2. doi: 10.1096/fj.02-0937fje. Epub 2003 Jul 18.
The suggested involvement of ouabain in hypertension raised the need for a better understanding of its cellular action, but the mechanisms of ouabain toxicity are only now being uncovered. In the present study, we show that reduced glutathione (GSH) protected ouabain-sensitive (OS) cells from ouabain-induced toxicity and that the inhibition of GSH synthesis by D, L-buthionine-(S,R)-sulfoximine (BSO) sensitized ouabain-resistant (OR) cells. We could not observe formation of OH or H2O2, but there was an increase in O2-only in OS cells. Unexpectedly, an increased number of OR cells depolarized after treatment with ouabain, and BSO blocked this depolarization. Moreover, GSH increased ouabain-induced depolarization in OS cells. A sustained increase in tyrosine phosphorylation (P-Tyr) and Ras expression was observed after treatment of OS cells, and GSH prevented it. Conversely, BSO induced P-Tyr and Ras expression in ouabain-treated OR cells. The results obtained have three major implications: There is no direct correlation between membrane depolarization and ouabain-induced cell death; ouabain toxicity is not directly related to its classical action as a Na+, K+-ATPase inhibitor but seems to be associated to signal transduction, and GSH plays a major role in preventing ouabain-induced cell death.
哇巴因与高血压之间可能存在的关联引发了人们对其细胞作用进行更深入了解的需求，但哇巴因毒性的机制直到现在才被揭示出来。在本研究中，我们发现还原型谷胱甘肽（GSH）可保护哇巴因敏感（OS）细胞免受哇巴因诱导的毒性作用，而D，L-丁硫氨酸-（S，R）-亚砜亚胺（BSO）对GSH合成的抑制作用则使哇巴因耐药（OR）细胞变得敏感。我们未观察到OH或H2O2的形成，但仅在OS细胞中观察到超氧阴离子（O2）增加。出乎意料的是，用哇巴因处理后，去极化的OR细胞数量增加，而BSO可阻止这种去极化。此外，GSH可增强哇巴因诱导的OS细胞去极化。在处理OS细胞后，观察到酪氨酸磷酸化（P-Tyr）和Ras表达持续增加，而GSH可阻止这种增加。相反，BSO可诱导经哇巴因处理的OR细胞中的P-Tyr和Ras表达。所得结果有三个主要意义：膜去极化与哇巴因诱导的细胞死亡之间没有直接关联；哇巴因毒性与其作为Na +，K + -ATP酶抑制剂的经典作用没有直接关系，而似乎与信号转导有关，并且GSH在预防哇巴因诱导的细胞死亡中起主要作用。
