DeVito W J, Stone S
Division of Endocrinology, University of Massachusetts Medical Center, Worcester 01655, USA.
J Cell Biochem. 1999 Aug 1;74(2):278-91.
Alcohol consumption has multiple effects in the central nervous system (CNS). Whereas, alcohol is an immunosuppressive drug the effect of alcohol on the neuroimmune system, remains unclear. In cultured astrocytes, prolactin (PRL) induces mitogenesis and the expression of inflammatory cytokines, including tumor necrosis factor-alpha (TNF alpha). We have recently shown that whereas ethanol does not inhibit PRL receptor binding, it markedly inhibits PRL-induced mitogenesis and TNF alpha secretion in cultured astrocytes. It is clear that PRL activates the tyrosine phosphorylation of several proteins, including members of a novel family of protein tyrosine kinases, the Janus Kinases (JAKs). The aims of this study were to characterize PRL-induced activation of the JAK/STAT (signal transducers and activators of transcription) pathway, and to determine if ethanol affects JAK/STAT activation in cultured astrocytes. We found that PRL specifically increases the tyrosine phosphorylation of JAK2, but not JAK1, JAK3, or Tyk2, and the subsequent phosphorylation of STAT1 alpha, STAT5a, and STAT5b. Preincubation of astrocytes with ethanol markedly inhibited phosphorylation of JAK2, STAT1 alpha, STAT5a, and STAT5b. In PRL-stimulated astrocytes, ethanol inhibited binding of nuclear proteins to oligonucleotides corresponding to the gamma-interferon activated sequence (GAS). Further, ethanol blocked PRL-induced increases in interferon regulatory factor-1 (IRF-1) mRNA, a PRL/cytokine inducible transcription factor involved in the regulation of a number of cytokine inducible genes. The inhibition of tyrosine phosphorylation by ethanol was not a general effect, however, as we found that ethanol increased basal and NGF-induced tyrosine phosphorylation of extracellular signal-activated protein kinase-1 (ERK-1). These data indicate that ethanol inhibits PRL-induced tyrosine phosphorylation of the JAK/STAT pathway resulting in decreased nuclear GAS DNA binding and inhibition of the PRL inducible gene, IRF-1. Thus, suggesting that ethanol-induced inhibition of JAK2 phosphorylation may be one mechanism though which ethanol could after the brain's response to injury or infection.
酒精摄入对中枢神经系统（CNS）有多种影响。然而，酒精是一种免疫抑制药物，其对神经免疫系统的影响仍不清楚。在培养的星形胶质细胞中，催乳素（PRL）可诱导有丝分裂以及包括肿瘤坏死因子-α（TNFα）在内的炎性细胞因子的表达。我们最近发现，虽然乙醇不抑制PRL受体结合，但它能显著抑制培养的星形胶质细胞中PRL诱导的有丝分裂和TNFα分泌。很明显，PRL可激活多种蛋白质的酪氨酸磷酸化，包括一个新的蛋白质酪氨酸激酶家族——Janus激酶（JAKs）的成员。本研究的目的是表征PRL诱导的JAK/STAT（信号转导子和转录激活子）途径的激活，并确定乙醇是否影响培养的星形胶质细胞中JAK/STAT的激活。我们发现PRL特异性增加JAK2的酪氨酸磷酸化，但不增加JAK1、JAK3或Tyk2的酪氨酸磷酸化，以及随后STAT1α、STAT5a和STAT5b的磷酸化。用乙醇对星形胶质细胞进行预孵育可显著抑制JAK2、STAT1α、STAT5a和STAT5b的磷酸化。在PRL刺激的星形胶质细胞中，乙醇抑制核蛋白与对应于γ-干扰素激活序列（GAS）的寡核苷酸的结合。此外，乙醇阻断了PRL诱导的干扰素调节因子-1（IRF-1）mRNA的增加，IRF-1是一种PRL/细胞因子诱导的转录因子，参与多种细胞因子诱导基因的调控。然而，乙醇对酪氨酸磷酸化的抑制并非普遍效应，因为我们发现乙醇增加了细胞外信号激活蛋白激酶-1（ERK-1）的基础酪氨酸磷酸化以及NGF诱导的酪氨酸磷酸化。这些数据表明，乙醇抑制PRL诱导的JAK/STAT途径的酪氨酸磷酸化，导致核GAS DNA结合减少以及PRL诱导基因IRF-1的抑制。因此，提示乙醇诱导的JAK2磷酸化抑制可能是乙醇影响大脑对损伤或感染反应的一种机制。
