Brodie C, Tordai A, Saloga J, Domenico J, Gelfand E W
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
J Cell Physiol. 1995 Nov;165(2):246-53. doi: 10.1002/jcp.1041650205.
Ouabain, a specific inhibitor of the Na-K ATPase, has been shown to exert immunosuppressive effects. The goals of this study were to define the stage of the proliferative response which is sensitive to ouabain and to correlate the inhibitory action of ouabain on cell proliferation with its effect on Na-K ATPase activity. We found that ouabain inhibited T-cell proliferation in a dose-dependent manner and this inhibition was similar in CD4+ and CD8+ T cells. To define the role of the Na-K ATPase in early activation of T lymphocytes, we examined the effects of ouabain on the induction of competence (acquisition of responsiveness to interleukin (IL)-2 or IL-4) by phytohemagglutinin (PHA) or the combination of phorbol dibutyrate/ionomycin. Ouabain, at concentrations that completely inhibited the enzyme activity, did not interfere with the induction of competence, suggesting that although activated cells express increased activity of Na-K ATPase, this enzyme activity does not play a role in early activation pathways. In contrast, ouabain inhibited the progression phase to DNA synthesis in a dose-dependent manner even at concentrations that had little or no effect on Na-K ATPase activity. This inhibition was not due to a decrease in the production of IL-2 but rather to an inhibition of the expression of the p55 and p75 subunits of the IL-2 receptor (IL-2R). The inhibition of p55 appeared to occur at the mRNA level. These results indicate that the activity of the Na-K ATPase is not essential for the induction of competence or early activation. On the other hand, inhibition of cell proliferation and transcription of IL-2R subunits by low concentrations of ouabain may be related to changes in intracellular K+ concentrations or to inhibition of membranal phospholipid metabolism secondary to alteration in Na-K ATPase activity.
哇巴因是钠钾ATP酶的一种特异性抑制剂，已被证明具有免疫抑制作用。本研究的目的是确定对哇巴因敏感的增殖反应阶段，并将哇巴因对细胞增殖的抑制作用与其对钠钾ATP酶活性的影响相关联。我们发现哇巴因以剂量依赖的方式抑制T细胞增殖，并且这种抑制在CD4+和CD8+ T细胞中相似。为了确定钠钾ATP酶在T淋巴细胞早期激活中的作用，我们研究了哇巴因对植物血凝素（PHA）或佛波酯/离子霉素组合诱导的反应能力（获得对白介素（IL）-2或IL-4的反应性）的影响。在完全抑制酶活性的浓度下，哇巴因并不干扰反应能力的诱导，这表明尽管活化细胞表达增加的钠钾ATP酶活性，但这种酶活性在早期激活途径中不起作用。相反，即使在对钠钾ATP酶活性几乎没有影响的浓度下，哇巴因也以剂量依赖的方式抑制向DNA合成的进展阶段。这种抑制不是由于IL-2产生的减少，而是由于对IL-2受体（IL-2R）的p55和p75亚基表达的抑制。对p55的抑制似乎发生在mRNA水平。这些结果表明钠钾ATP酶的活性对于反应能力的诱导或早期激活不是必需的。另一方面，低浓度的哇巴因对细胞增殖和IL-2R亚基转录的抑制可能与细胞内钾离子浓度的变化或继发于钠钾ATP酶活性改变的膜磷脂代谢抑制有关。
