STAT5 activation by human GH protects insulin-producing cells against interleukin-1β, interferon-γ and tumour necrosis factor-α-induced apoptosis independent of nitric oxide production
STAT5 activation by human GH protects insulin-producing cells against interleukin-1β, interferon-γ and tumour necrosis factor-α-induced apoptosis independent of nitric oxide production
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DOI：
10.1677/joe.1.06086
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发表时间：
2005-10-01
影响因子：
4
通讯作者：
Nielsen, JH
中科院分区：
文献类型：
--
作者：
Jensen, J;Galsgaard, ED;Nielsen, JH
促炎症细胞因子IL-1β、干扰素-γ和肿瘤坏死因子-α对胰腺P细胞有毒性作用，参与了1型糖尿病的发病机制。我们先前发现生长激素和催乳素(PRL)能刺激胰腺P细胞和大鼠胰岛素分泌细胞INS-1的增殖和胰岛素产生。在此，我们报道了人(H)GH可以阻止IL-1β、干扰素-γ和肿瘤坏死因子-α对INS-1和INS-1E细胞的凋亡作用。利用腺病毒介导的基因转移，我们发现hGH的抗凋亡作用被INS-1E细胞中一个显性负信号转导和转录激活因子(STAT5)突变体的表达所抵消。HGH和毒性细胞因子在暴露4h后可增加细胞因子信号转导-3mRNA的表达抑制因子。为了确定STAT5介导的INS-1E细胞保护的可能靶点，我们研究了hGH对转录因子STAT1和核因子-kappaB(NF-kappa B)分别由干扰素-γ和IL-1β+TNF-α激活的影响。凝胶滞留实验表明，hGH既不影响干扰素-γ+肿瘤坏死因子-α诱导的STAT1 DNA结合，也不影响IL-1β和干扰素-γ+肿瘤坏死因子-α诱导的核因子-kappaB DNA结合。HGH对细胞因子诱导的STAT1和NF-kappaB的激活没有影响，这与hGH对细胞因子诱导的诱导型一氧化氮合酶(INOS)基因表达的影响很小，而实际上是增强了IL-1β刺激的一氧化氮产生的结果一致。由于抗凋亡基因Bclx(L)已被证明含有STAT5结合元件，我们检测了Bclx(L)和促凋亡基因bax的表达。我们发现，无论是否存在细胞毒性细胞因子，hGH都能增加Bclx(L)/bax的比值。综上所述，这些结果提示生长激素和催乳素可能通过诱导型一氧化氮合酶激活远端的STAT5依赖机制保护胰岛细胞免受细胞毒性细胞因子的伤害，可能是在Bclx水平(L)。
The proinflainniatory cytokines interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma) and turnour necrosis factor-a (TNF-alpha) are toxic to pancreatic P-cells and are implicated in the pathogenesis of type 1 diabetes. We have previously found that GH and prolactin (PRL) stimulate both proliferation and insulin production in pancreatic P-cells and rat insulin-producing INS-1 cells. Here we report that human (h) GH can prevent the apoptotic effects of IL-1 beta IFN-gamma and TNF-alpha in INS-1 and INS-1E cells. Using adenovirus-inediated gene transfer, we found that the anti-apoptotic effect of hGH is abrogated by expression of a dominant negatne signal transducer and activator of transcription (STAT5) mutant in INS-1E cells. hGH and the cvtotoxic cytokines was found to additively increase suppressor of cytokine signalling-3 mRNA expression after 4 h of exposure. In order to identify possible targets for the STAT5-mediated protection of INS-1E cells, we studied the effect of hGH on activation of the transcription factors STAT1 and nuclear factor-kappa B (NF-kappa B) by IFN-gamma and IL-1 beta+TNF-alpha respectively. Gel retardation experimerits showed that hGH affects neither IFN-gamma+ TNF-alpha-induced STAT1 DNA binding nor IL-1 beta and IFN-gamma+TNF-alpha-induced NF kappa B DNA binding. The lack of influence of hGH on cytokine-inediated activation of STAT1 and NF kappa B is in accordance with the finding that hGH had only a minor effect on cytokine-induced inducible nitric oxide synthase (iNOS) gene expression and in fact augmented the IL-1 beta-stimulated nitric oxide production. As the anti-apoptotic Bcl-x(L) gene has been shown to harbour a STAT5-binding element we measured the expression of Bcl-x(L) as well as the pro-apoptotic Bax. We found that hGH increased the Bcl-x(L)/Bax ratio both in the absence and in the presence of cytotoxic cytokines. In conclusion, these results suggested that GH and PRL protect beta-cells against cytotoxic cytokines via STAT5- dependent mechanisms distal to iNOS activation possibly at the level of Bcl-x(L).