Arai Koji Y, Roby Katherine F, Terranova Paul F
Department of Molecular and Integrative Physiology, Center for Reproductive Sciences, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Endocrine. 2005 Jun;27(1):17-24. doi: 10.1385/ENDO:27:1:017.
TNF is known to suppress gonadotropin-induced steroid secretion by Leydig cells. However, the mechanisms by which this occurs are largely unknown. Because expression of many steroidogenic proteins is regulated by the PKA pathway, effects of TNF on CRE activity were examined using MA-10 mouse Leydig tumor cells. The cells were transfected with a CRE-luciferase construct, and stimulated with either LH or 8Br-cAMP in the presence or absence of TNF. TNF suppressed, LH-stimulated and 8Br-cAMP stimulated CRE activity. TNF also suppressed CRE activity stimulated with a PKA expression vector. Further experiments suggested that the effect of TNF on CRE activity was not mediated by the NF-kappaB pathway. TNF did not affect levels of either CREB or phospho-CREB in whole cell lysates; however, TNF decreased both CREB and phospho-CREB in nuclear extracts in a time-dependent manner. The decrease in nuclear CREB is likely to be a major mechanism of the suppressive effects of TNF on steroidogenesis in MA-10 Leydig cells.
已知肿瘤坏死因子（TNF）可抑制促性腺激素诱导的睾丸间质细胞分泌类固醇。然而，其发生机制在很大程度上尚不清楚。由于许多类固醇生成蛋白的表达受蛋白激酶A（PKA）途径调控，因此利用MA-10小鼠睾丸间质细胞瘤细胞研究了TNF对环磷腺苷反应元件（CRE）活性的影响。用CRE-荧光素酶构建体转染细胞，并在存在或不存在TNF的情况下用促黄体生成素（LH）或8-溴环磷腺苷（8Br-cAMP）刺激。TNF抑制LH刺激和8Br-cAMP刺激的CRE活性。TNF还抑制用PKA表达载体刺激的CRE活性。进一步的实验表明，TNF对CRE活性的影响不是由核因子κB（NF-κB）途径介导的。TNF不影响全细胞裂解物中CREB或磷酸化CREB的水平；然而，TNF以时间依赖性方式降低核提取物中的CREB和磷酸化CREB。核CREB的减少可能是TNF对MA-10睾丸间质细胞类固醇生成抑制作用的主要机制。
