Melanocyte-Keratinocyte Cross-Talk In Relation To Barrier Function

描述(申请人提供)：我们已经证明，与种族或民族无关的黑色色素沉着，赋予表皮增强的屏障功能和抗菌防御。因此，浅色皮肤天生更容易患炎症性皮肤疾病，如特应性皮炎和成人湿疹，以及所有类型的皮肤感染。但色素沉着和表皮功能之间的联系的基础仍然不清楚。使用器官型人类角质形成细胞培养，与黑素细胞一起生长，以及选定的小鼠模型，我们将首先评估黑素细胞密度和黑素细胞色素沉着在调节表皮功能中的作用。功能终点将包括通透性屏障动态平衡、角质层(SC)完整性/凝聚力的变化，以及有助于皮肤抗菌防御的某些关键抗菌肽的表达。由于我们最近的研究表明，深色黑素细胞通过酸化外层表皮来影响表皮功能，接下来我们将评估黑素细胞对表皮酸化的细胞学基础；然后在突变小鼠模型中，黑素小体形成、酸化或分泌调节这一过程。如果酸化本身不能解释黑素细胞对表皮功能的影响，我们计划寻找其他黑素细胞启动的调节信号，以旁分泌的方式影响表皮功能。在目标3中，我们将研究相反的问题；即，表皮屏障要求的改变、表面pH的升高或环境湿度(UV-B)的降低如何调节毛囊(表皮)间的色素沉积，从而以前馈方式改善屏障功能。我们先前的研究已经表明，屏障破坏会增加IL-1a和NGF的产生，而破坏屏障的UV-B剂量会上调P53的表达。已知这些信号通过增加表皮POMC的表达和对aMSH的蛋白分解处理来增加表皮色素沉着，和/或黑素细胞功能的MC1R信号。我们已经发现另外两个角质形成细胞调节信号也可以将表皮屏障功能的变化与色素沉着联系起来，即i)表皮干细胞因子，它诱导黑素细胞从毛囊迁移到毛囊间表皮；以及ii)转录因子FOXN1，它将黑素细胞靶向基底层。我们将评估屏障要求的改变是否调节这5个信号机制中的一个或多个，从而导致黑色素产生的关键下游酶--即酪氨酸酶、酪氨酸酶羟化酶和/或黑素体酸化的表达或活性增加。最后，我们将评估TRPV4，表皮感应器或外部湿度是否调节色素对环境湿度下降的反应。总之，这些研究将为色素沉着在调节表皮功能中的作用提供新的见解，潜在地解释不同色素组的疾病易感性差异，并可能导致浅色表皮的疾病预防。相反，他们应该准确地定位表皮来源的信号，这些信号调节毛囊间色素沉着的发展，以应对外部压力。 公共卫生相关性：色素沉着的减少降低了退伍军人患炎症性皮肤疾病和感染的门槛；相反，更多的色素沉着提供了保护。这些研究将揭示黑素细胞调节表皮功能的机制，反之亦然；即，表皮功能需求如何反过来调节色素沉着。我们的研究可以指出直接的方法，可以改善因色素沉着而处于危险之中的个人的健康状况，包括患有特应性皮炎和牛皮癣的退伍军人。

DESCRIPTION (provided by applicant): We have shown that dark pigmentation independent of race or ethnicity, endows the epidermis with enhanced barrier function and antimicrobial defense. As a result, lightly-pigmented skin should be inherently more at risk for development of inflammatory skin disorders, such as atopic dermatitis and adult eczemas, well as all types of skin infections. But the basis for the link between pigmentation and epidermal function remains unknown. Using organotypic human keratinocyte cultures, grown with melanocytes, as well as selected mouse models, we will assess first, the role of melanocyte density and the extent of melanocyte pigmentation in regulating epidermal function. The functional end-points will comprise changes in permeability barrier homeostasis, stratum corneum (SC) integrity/cohesion, and expression of certain key antimicrobial peptides that contribute to cutaneous antimicrobial defense. Since our recent studies suggest that darkly-pigmented melanocytes influence epidermal function by acidifying the outer epidermis, we next will assess the cellular basis for epidermal acidification by melanocytes; and then in mutant mouse models, which step in melanosome formation, acidification, or secretion regulates this process. If acidification alone fails to account for the impact of melanocytes on epidermal function, we plan to search for other melanocyte-initiated regulatory signals that influence epidermal function in a paracrine fashion. In Aim 3 we will examine the converse issue; i.e., how alterations in epidermal barrier requirements, elevations in surface pH, or a reduced environmental humidity ( UV-B) could regulate interfollicular (epidermal ) pigmentation, which then would improve barrier function in a feed forward fashion. Our prior studies have already shown that barrier disruption increases both IL-1a and NGF production, and that dose of UV-B that damage the barrier upregulate p53 expression. These signals are known to either increase epidermal pigmentation by increasing epidermal POMC expression and proteolytic processing to aMSH, and/or MC1R signalling of melanocyte function. We have identified two other keratinocyte regulatory signals could also link changes in epidermal barrier function to pigmentation; i.e., i) epidermal stem cell factor, which induces melanocytes to migrate from follicles to interfollicular epidermis; and ii) the transcription factor, foxn1, which targets melanocytes to the basal layer. We will assess whether altered barrier requirements regulate one or more of these 5 signaling mechanisms, leading to increased expression or activity of the key downstream enzymes of melanin production; i.e., tyrosinase, tyrosinase hydroxylase, and/or melanosome acidification. Finally, we will assess whether TRPV4, the epidermal sensor or external humidity, regulates pigmentary responses to decreased environmental humidity. Together, these studies will provide new insights into the role of pigmentation in regulating epidermal function, potentially explaining differences in disease susceptibility in different pigment groups, and perhaps leading to disease prevention in lightly-pigmented epidermis. Conversely, they should pinpoint epidermal-derived signals that regulate the development of interfollicular pigmentation in response to exogenous stress. PUBLIC HEALTH RELEVANCE: Decreased pigmentation reduces veterans' threshold for the development of inflammatory skin conditions and infections; while conversely, more pigmentation provides protection. These studies will reveal mechanisms whereby melanocytes regulate epidermal function, and vice-versa; i.e., how epidermal functional requirements in turn regulate pigmentation. Our research could point to straight-forward methods that could improve the health status of individuals at risk due to fair pigmentation, including veterans with atopic dermatitis and psoriasis.