Corso María Clara, Cortasa Santiago Andrés, Schmidt Alejandro Raúl, Proietto Sofía, Inserra Pablo Ignacio Felipe, Fernández Marina Olga, Di Giorgio Noelia, Lux-Lantos Victoria, Vitullo Alfredo Daniel, Dorfman Verónica Berta, Halperin Julia
Centro de Estudios Biomédicos Básicos, Aplicados y Desarrollo (CEBBAD), Universidad Maimónides, Ciudad Autónoma de Buenos Aires, Argentina(2); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IByME)-CONICET, Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
Gen Comp Endocrinol. 2020 Sep 15;296:113518. doi: 10.1016/j.ygcen.2020.113518. Epub 2020 May 29.
In addition to key mammotrophic hormones such as the pituitary prolactin (PRL) and the ovarian steroids progesterone and estradiol, there are local factors that modulate the tissue dynamics of the mammary glands during pregnancy and lactation. By immunohistochemistry and RT-PCR, we found local transcription and translation of gonadotropin-releasing hormone (GNRH), GNRH receptor (GNRHR), PRL and PRL receptor (PRLR) in mammary glands of adult vizcachas during pregnancy and lactation. Both GNRH and GNRHR showed a lag between protein expression and gene transcription throughout the gestational period: while the highest transcription levels of these genes were recorded at early-pregnancy, the epithelial immunoexpressions of both showed their maximum during lactation. RIA results corroborated the presence of GNRH in mammary glands at all the analyzed stages and confirmed the maximum amount of this peptide in the lactating group. Significant amounts of GNRH were detected in milk samples as well. Conversely, PRL and PRLR shared similar protein and gene expression profiles, all exhibiting maximum values during lactation. GNRH peptide content in mammary glands of females with sulpiride-induced hyperprolactinemia (HP) was significantly lower than that of control females (CT). Although PRL mRNA levels remained unchanged, there was a marked increase in theα-lactalbumin (LALBA) transcription in mammary glands of HP- vs CT-females. These results suggest that after targeting mammary glands, PRL stimulates the expression of milk protein genes, but also, tempers the local expression of GNRH. Mammary gland-explantssupplemented with a GNRH analogue (GN-explants) had no differences in terms of PRLR orLALBA transcription levels compared to CT-explants, so the mammary PRLR signaling would not appear to be modulated by GNRH. Yet, mRNA expression levels of both GNRH and the GNRHR-downstream factor, EGR1, were significantly higher in GN-explants compared to that of CT which would point to a GNRH-positive feedback mechanism. In summary, the local coupled expression of GNRH, GNRHR and EGR1 in the mammary gland throughout pregnancy of vizcachas, the PRL-dependent mammary GNRH secretion as well as the GNRH positive feedback on its own transcription suggest an autocrine-paracrine regulatory mechanism and propose an active role for GNRH in mammary gland tissue remodeling.
除了关键的促乳腺激素，如垂体催乳素（PRL）、卵巢类固醇孕酮和雌二醇外，还有一些局部因子在妊娠和哺乳期调节乳腺的组织动态。通过免疫组织化学和逆转录-聚合酶链反应（RT-PCR），我们发现成年草原犬鼠在妊娠和哺乳期乳腺中存在促性腺激素释放激素（GNRH）、GNRH受体（GNRHR）、PRL和PRL受体（PRLR）的局部转录和翻译。在整个妊娠期，GNRH和GNRHR的蛋白表达和基因转录之间均存在滞后现象：虽然这些基因的最高转录水平出现在妊娠早期，但二者的上皮免疫表达在哺乳期达到最大值。放射免疫分析（RIA）结果证实了在所有分析阶段乳腺中均存在GNRH，并确认哺乳期组中该肽的含量最高。在乳汁样本中也检测到了大量的GNRH。相反，PRL和PRLR具有相似的蛋白和基因表达谱，在哺乳期均呈现最大值。舒必利诱导的高催乳素血症（HP）雌性大鼠乳腺中的GNRH肽含量显著低于对照雌性大鼠（CT）。虽然PRL mRNA水平保持不变，但HP雌性大鼠乳腺中α-乳白蛋白（LALBA）的转录显著增加。这些结果表明，PRL作用于乳腺后，不仅刺激乳蛋白基因的表达，还调节GNRH的局部表达。与CT外植体相比，补充GNRH类似物的乳腺外植体（GN外植体）在PRLR或LALBA转录水平上没有差异，因此乳腺PRLR信号似乎不受GNRH的调节。然而，与CT外植体相比，GN外植体中GNRH及其下游因子早期生长反应蛋白1（EGR1）的mRNA表达水平均显著升高，这表明存在GNRH阳性反馈机制。总之，在草原犬鼠整个妊娠期乳腺中GNRH、GNRHR和EGR1的局部偶联表达、PRL依赖的乳腺GNRH分泌以及GNRH对其自身转录的阳性反馈，提示了一种自分泌-旁分泌调节机制，并表明GNRH在乳腺组织重塑中发挥积极作用。
