Department of Obstetrics and Gynecology, Meharry Medical College, Nashville, TN 37208, USA.
Endocrinology. 2010 Jul;151(7):3407-19. doi: 10.1210/en.2009-1321. Epub 2010 May 5.
TNFalpha is an inflammatory-related cytokine that has inhibitory effects on gonadotropin- and cAMP-stimulated steroidogenesis and folliculogenesis. Because ovulation is an inflammatory reaction and TNF specifically induces serum amyloid A3 (SAA3) in mouse granulosa cells, the effect of cAMP on TNF-induced SAA3 promoter activity, mRNA and protein was investigated. Granulosa cells from immature mice were cultured with TNF and/or cAMP. TNF increased SAA3 promoter activity, mRNA, and protein, which were further increased by cAMP. cAMP alone increased SAA3 promoter activity, but SAA3 mRNA and protein remained undetectable. Thus, there appeared to be different mechanisms by which TNF and cAMP regulated SAA3 expression. SAA3 promoters lacking a nuclear factor (NF)-kappaB-like site or containing its mutant were not responsive to TNF but were responsive to cAMP. Among four CCAAT-enhancing binding protein (C/EBP) sites in the SAA3 promoter, the C/EBP site nearest the NF-kappaB-like site was required for TNF-induced SAA3. The C/EBP site at -75/-67 was necessary for responsiveness to cAMP. Dominant-negative C/EBP and cAMP response element-binding protein or short interfering RNA of C/EBPbeta blocked TNF- or cAMP-induced SAA3 promoter activity. The combination of TNF and cAMP increased C/EBPbeta protein above that induced by TNF or cAMP alone. Thus, cAMP in combination with TNF specifically induced C/EBPbeta protein, leading to enhanced SAA3 expression but requiring NF-kappaB in mouse granulose cells. In addition, like TNF, SAA inhibited cAMP-induced estradiol accumulation and CYP19 levels. These data indicate SAA may play a role in events occurring during the ovulation process.
肿瘤坏死因子-α（TNFalpha）是一种与炎症相关的细胞因子，它对促性腺激素和 cAMP 刺激的类固醇生成和卵泡发生具有抑制作用。由于排卵是一种炎症反应，而 TNF 特异性地诱导小鼠颗粒细胞中的血清淀粉样蛋白 A3（SAA3），因此研究了 cAMP 对 TNF 诱导的 SAA3 启动子活性、mRNA 和蛋白的影响。用 TNF 和/或 cAMP 培养来自未成熟小鼠的颗粒细胞。TNF 增加了 SAA3 启动子活性、mRNA 和蛋白，而 cAMP 进一步增加了它们。cAMP 单独增加了 SAA3 启动子活性，但 SAA3 mRNA 和蛋白仍无法检测到。因此，TNF 和 cAMP 调节 SAA3 表达的机制似乎不同。缺乏核因子（NF）-kappaB 样位点或含有其突变的 SAA3 启动子对 TNF 无反应，但对 cAMP 有反应。在 SAA3 启动子中的四个 CCAAT 增强结合蛋白（C/EBP）位点中，靠近 NF-kappaB 样位点的 C/EBP 位点是 TNF 诱导 SAA3 所必需的。-75/-67 处的 C/EBP 位点对于对 cAMP 的反应是必需的。显性失活的 C/EBP 和 cAMP 反应元件结合蛋白或 C/EBPbeta 的短发夹 RNA 阻断了 TNF 或 cAMP 诱导的 SAA3 启动子活性。TNF 和 cAMP 的组合使 C/EBPbeta 蛋白增加超过 TNF 或 cAMP 单独诱导的水平。因此，cAMP 与 TNF 一起特异性地诱导 C/EBPbeta 蛋白，导致 SAA3 表达增强，但在小鼠颗粒细胞中需要 NF-kappaB。此外，与 TNF 一样，SAA 抑制 cAMP 诱导的雌二醇积累和 CYP19 水平。这些数据表明，SAA 可能在排卵过程中发生的事件中发挥作用。
