Dupuis Lisa, Schuermann Yasmin, Cohen Tamara, Siddappa Dayananda, Kalaiselvanraja Anitha, Pansera Melissa, Bordignon Vilceu, Duggavathi Raj
Department of Animal Science, McGill University, Sainte Anne de Bellevue, Quebec, Canada H9X 3V9.
Reproduction. 2013 Dec 19;147(2):221-9. doi: 10.1530/REP-13-0356. Print 2014 Feb.
Leptin is an important hormone influencing reproductive function. However, the mechanisms underpinning the role of leptin in the regulation of reproduction remain to be completely deciphered. In this study, our objective is to understand the mechanisms regulating the expression of leptin receptor (Lepr) and its role in ovarian granulosa cells during ovulation. First, granulosa cells were collected from superovulated mice to profile mRNA expression of Lepr isoforms (LeprA and LeprB) throughout follicular development. Expression of LeprA and LeprB was dramatically induced in the granulosa cells of ovulating follicles at 4 h after human chorionic gonadotropin (hCG) treatment. Relative abundance of both mRNA and protein of CCAAT/enhancer-binding protein β (Cebpβ) increased in granulosa cells from 1 to 7 h post-hCG. Furthermore, chromatin immunoprecipitation assay confirmed the recruitment of Cebpβ to Lepr promoter. Thus, hCG-induced transcription of Lepr appears to be regulated by Cebpβ, which led us to hypothesise that Lepr may play a role during ovulation. To test this hypothesis, we used a recently developed pegylated superactive mouse leptin antagonist (PEG-SMLA) to inhibit Lepr signalling during ovulation. I.p. administration of PEG-SMLA (10 μg/g) to superovulated mice reduced ovulation rate by 65% compared with control treatment. Although the maturation stage of the ovulated oocytes remained unaltered, ovulation genes Ptgs2 and Has2 were downregulated in PEG-SMLA-treated mice compared with control mice. These results demonstrate that Lepr is dramatically induced in the granulosa cells of ovulating follicles and this induction of Lepr expression requires the transcription factor Cebpβ. Lepr plays a critical role in the process of ovulation by regulating, at least in part, the expression of the important genes involved in the preovulatory maturation of follicles.
瘦素是一种影响生殖功能的重要激素。然而，瘦素在生殖调节中发挥作用的机制仍有待完全阐明。在本研究中，我们的目的是了解调节瘦素受体（Lepr）表达的机制及其在排卵过程中卵巢颗粒细胞中的作用。首先，从超排卵小鼠中收集颗粒细胞，以分析整个卵泡发育过程中Lepr亚型（LeprA和LeprB）的mRNA表达。人绒毛膜促性腺激素（hCG）处理后4小时，排卵卵泡的颗粒细胞中LeprA和LeprB的表达显著诱导。hCG处理后1至7小时，颗粒细胞中CCAAT/增强子结合蛋白β（Cebpβ）的mRNA和蛋白质相对丰度增加。此外，染色质免疫沉淀试验证实Cebpβ被募集到Lepr启动子。因此，hCG诱导的Lepr转录似乎受Cebpβ调节，这使我们推测Lepr可能在排卵过程中发挥作用。为了验证这一假设，我们使用了最近开发的聚乙二醇化超活性小鼠瘦素拮抗剂（PEG-SMLA）来抑制排卵过程中的Lepr信号传导。与对照处理相比，给超排卵小鼠腹腔注射PEG-SMLA（10μg/g）可使排卵率降低65%。虽然排卵卵母细胞的成熟阶段保持不变，但与对照小鼠相比，PEG-SMLA处理的小鼠中排卵相关基因Ptgs2和Has2的表达下调。这些结果表明，Lepr在排卵卵泡的颗粒细胞中显著诱导，并且这种Lepr表达的诱导需要转录因子Cebpβ。Lepr在排卵过程中发挥关键作用，至少部分通过调节卵泡排卵前成熟所涉及的重要基因的表达来实现。
