Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
Int J Mol Sci. 2021 Oct 17;22(20):11186. doi: 10.3390/ijms222011186.
Roles of Clock genes and the bone morphogenetic protein (BMP) system in the regulation of gonadotropin secretion by gonadotropin-releasing hormone (GnRH) were investigated using mouse gonadotropin LβT2 cells. It was found that luteinizing hormone (LH)β mRNA expression level in LβT2 cells changed gradually over time, with LHβ expression being suppressed in the early phase up to 12 h and then elevated in the late phase 24 h after GnRH stimulation. In addition, the mRNA expression levels of Clock genes, including Bmal1, Clock, Per2, and Cry1, also showed temporal changes mimicking the pattern of LHβ expression in the presence and absence of GnRH. Notably, the expression levels of Bmal1 and Clock showed strong positive correlations with LHβ mRNA expression levels. Moreover, a functional link of the ERK signaling of mitogen-activated protein kinases (MAPKs) in the suppression of LHβ mRNA expression, as well as Bmal1 and Clock mRNA expression by GnRH at the early phase, was revealed. Inhibition of Bmal1 and Clock expression using siRNA was involved in the reduction in LHβ mRNA levels in the late phase 24 h after GnRH stimulation. Furthermore, in the presence of BMP-6 and -7, late-phase Bmal1 and LHβ mRNA expression after GnRH stimulation was significantly attenuated. Collectively, the results indicated that LH expression in gonadotrope cells exhibits Bmal1/Clock-dependent fluctuations under the influence of GnRH and that the fluctuations are regulated by ERK and BMPs in the early and late stages, respectively, in a phase-dependent manner after GnRH stimulation.
研究了时钟基因和骨形态发生蛋白（BMP）系统在调节促性腺激素释放激素（GnRH）对促性腺激素分泌的作用，使用的是小鼠促性腺激素 LβT2 细胞。结果发现，LβT2 细胞中 LHβmRNA 的表达水平随时间逐渐变化，GnRH 刺激后 12 h 早期 LHβ表达受到抑制，24 h 晚期升高。此外，Clock 基因（包括 Bmal1、Clock、Per2 和 Cry1）的 mRNA 表达水平也随时间发生变化，模式与 LHβ表达相似，无论是否存在 GnRH。值得注意的是，Bmal1 和 Clock 的表达水平与 LHβmRNA 表达水平呈强正相关。此外，还揭示了 GnRH 在早期通过丝裂原活化蛋白激酶（MAPKs）ERK 信号抑制 LHβmRNA 表达以及 Bmal1 和 Clock mRNA 表达的功能联系。使用 siRNA 抑制 Bmal1 和 Clock 的表达会导致 GnRH 刺激后 24 h 晚期 LHβmRNA 水平降低。此外，在 BMP-6 和 BMP-7 的存在下，GnRH 刺激后晚期的 Bmal1 和 LHβmRNA 表达明显减弱。综上所述，结果表明，在 GnRH 的影响下，促性腺激素细胞中的 LH 表达表现出 Bmal1/Clock 依赖性波动，并且这些波动分别受 ERK 和 BMP 在 GnRH 刺激后的早期和晚期以时相依赖的方式调节。
