神经递质和神经肽类物质调控阴道上皮离子转运的机制研究

The ion transport of epithelium plays a critical role in the formation of microenvironment in female reproductive tract. Unlike endometrial or oviduct epithelia, there are few studies on the ion transport of vaginal epithelium and the mechanisms underlying it. Vaginal fluid is derived from several sources including vaginal epithelium transudate and cervical secretion. In the unstimulated state, vaginal fluid has a lower Na+ and Cl- concentration compared to plasma and the amount of that makes the vaginal surfaces "just moist", which may result from the amiloride-sensitive and electrogenic Na+ ion transport vectorially from lumen to serosa. When female sexually aroused, vasocongestion in the vaginas and enhanced capillary pressure force more plasma transudate passing between and through the vaginal epithelium, and the final arousal lubrication fluid has a much higher Na+ and Cl- concentration than the basal fluid. However, the relationships underlying the changes of ion concentration, vaginal lubrication and sexual arousal are still not extensively investigated. In order to investigate whether vaginal epithelial ion transport is regulated by neurotransmitters or neuropeptides and the process has a facilitory role in vaginal lubrication during sexual arousal, the program is ready to be conducted by our group. Understanding the mechanisms involved in the vaginal epithelial ion transport and the regulation of it by neurotransmitters or neuropeptides is potential for discovering new drugs in treating sexual arousal disorders, including vaginal dyness or inadequate vaginal lubrication.

女性生殖道上皮离子转运对其管腔液体微环境的形成具有重要的作用。不同于子宫上皮及输卵管上皮，阴道上皮的离子转运及其调控机制目前仍然不是非常清楚。阴道上皮分泌液是构成女性阴道液来源的一个重要部分，在静息状态下阴道上皮具有钠离子吸收特点使得阴道上皮表面仅覆盖较薄的液体层，以及管腔液中钠离子和氯离子浓度低于血浆的特点。但当女性性唤起时，阴道的湿润程度显著增加，并且液体中钠离子和氯离子的浓度上升至血浆中的浓度。但是，离子浓度改变、性唤起以及阴道湿润之间的相互影响迄今为止仍然不清楚。为了探究性唤起过程中是否会有神经递质或神经肽等物质参与调节阴道上皮组织的离子转运而导致阴道湿润，我们拟开展本项目的研究，希望通过明了阴道上皮离子的转运及调节机制来揭示性唤起障碍疾病如阴道湿润不足或阴道干燥症的机理。

本研究运用了细胞培养、RT-PCR、Western Blot、电生理、免疫组化和酶联免疫等技术和方法，在细胞水平和组织水平上对神经递质类物质和神经肽类物质调控阴道上皮细胞离子分泌的机制进行了系统的研究，阐述了其在阴道上皮细胞离子分泌的生理意义。我们发现，β-肾上腺素能受体（β-AR）在大鼠阴道上皮组织和人阴道上皮细胞株VK2/E6E7中均有表达。当肾上腺素（Adr）作用于大鼠阴道上皮组织后，可结合于阴道上皮细胞β-AR，进而激活Gs蛋白。Gs蛋白激活腺苷酸环化酶，进而升高胞内cAMP浓度，激活CFTR并诱导Cl分泌。最终，Adr诱导的Cl分泌连同渗出液带来的高浓度Na+以及水共同引起阴道湿润。这一机制的发现突出了神经递质类物质和神经肽类物质对阴道上皮细胞离子分泌的调节作用，以及阴道上皮细胞离子分泌对阴道管腔微环境及性唤起时阴道湿润的调节作用。此外，我们还发现阴道上皮细胞胞内CSE酶催化L-Cys生成的硫化氢（H2S），可作为一种气体信号分子，直接作用于顶膜面的KATP通道介导K+分泌。另外，H2S可能通过作用于AC或PDEs而升高胞内cAMP浓度，进而通过cAMP/PKA途径激活顶膜面的CFTR，介导Cl分泌。并且H2S诱导的跨阴道上皮离子分泌引起阴道液K+及Cl浓度升高,升高的阴道液离子浓度可通过渗透压差驱使水的流动，引起阴道管腔湿润。因此，H2S有望开发成为一种潜在的治疗阴道干燥或阴道湿润不足的药物。