Arnold Robyn E, Weigent Douglas A
Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Ala. 35294-0005, USA.
Neuroimmunomodulation. 2004;11(3):149-59. doi: 10.1159/000076764.
The antiapoptotic action of exogenous growth hormone (GH) has been reported for several lymphoid cell lines; however, the potential role of endogenous GH in apoptosis has not been thoroughly investigated. This study was designed to investigate the effects of endogenous GH on apoptosis induced by methyl methanesulfonate (MMS) in a T cell lymphoma overexpressing GH (GHo). The results of these experiments have shown that in EL4 lymphoma cells, overexpression of GH sustained viability after exposure to MMS compared to control cells. The extent of DNA fragmentation measured by ladder formation on agarose gels was reduced in GHo cells following treatment with MMS, when compared to control cells. Adding exogenous GH to control cells and treatment of GHo cells with antibodies to GH had no effect on MMS-induced DNA ladder formation. In further studies, DNA microarray analysis suggested a marked decrease in the constitutive expression of bax, BAD, and caspases 3, 8, and 9 in GHo cells compared to controls. In addition, after treatment with MMS, the activities of caspases 2, 3, 6, 8, and 9 were all lower than control in GHo cells. Western blot analysis detected an increase in Bcl-2 while the levels of nuclear factor kappa B (NFkappaB) remained unchanged in GHo cells. Treatment of EL4 cells with antisense deoxyoligonucleotides to GH and specific inhibitors of NFkappaB (SN-50) increased DNA fragmentation. GHo cells show increased levels of phosphorylated Akt and GSK-3, suggesting inactivation of this proapoptotic protein. The results, taken together with our previous data which showed increased nitric oxide formation in GHo cells, suggest a possible mechanism for the antiapoptotic effects of endogenous GH through the production of nitric oxide and support the idea that endogenous GH may play an important role in the survival of lymphocytes exposed to stressful stimuli.
已有报道称外源性生长激素（GH）对多种淋巴细胞系具有抗凋亡作用；然而，内源性GH在细胞凋亡中的潜在作用尚未得到充分研究。本研究旨在探讨内源性GH对过表达GH（GHo）的T细胞淋巴瘤中甲基磺酸甲酯（MMS）诱导的细胞凋亡的影响。这些实验结果表明，在EL4淋巴瘤细胞中，与对照细胞相比，GH过表达使细胞在暴露于MMS后仍能维持活力。与对照细胞相比，用MMS处理后的GHo细胞中，通过琼脂糖凝胶上的梯状条带形成检测到的DNA片段化程度降低。向对照细胞中添加外源性GH以及用抗GH抗体处理GHo细胞，对MMS诱导的DNA梯状条带形成均无影响。在进一步的研究中，DNA微阵列分析表明，与对照相比，GHo细胞中bax、BAD以及半胱天冬酶3、8和9的组成型表达明显降低。此外，用MMS处理后，GHo细胞中半胱天冬酶2、3、6、8和9的活性均低于对照。蛋白质印迹分析检测到GHo细胞中Bcl-2增加，而核因子κB（NFκB）水平保持不变。用针对GH的反义脱氧寡核苷酸和NFκB特异性抑制剂（SN-50）处理EL4细胞会增加DNA片段化。GHo细胞中磷酸化Akt和GSK-3水平升高，表明这种促凋亡蛋白失活。这些结果与我们之前的数据（显示GHo细胞中一氧化氮生成增加）相结合，提示内源性GH通过一氧化氮产生发挥抗凋亡作用的可能机制，并支持内源性GH可能在暴露于应激刺激的淋巴细胞存活中起重要作用这一观点。
