Elevated potassium ion in lacrimal fluid and the health of the ocular surface

描述（由申请人提供）：泪液与大多数细胞外液不同，泪液的K+浓度约为20 mEq/l。据认为泪腺导管分泌K+;然而，这种分泌的机制尚未完全阐明，泪液中高[K+]与眼表细胞的关系的目的尚不清楚。要解决的关键假设是基于这些观察结果：1）泪腺导管表达K+转运蛋白和与导管分泌K+一致的通道，2）UV辐射导致K+通道开放和角膜上皮细胞K+损失，这种K+损失激活凋亡途径。3)升高细胞外K+（[K+]o）阻止淋巴细胞中凋亡途径的激活。我们提出，泪腺导管细胞分泌的液体高K+，这提供了一个细胞外离子环境，保护这些细胞免受紫外线（UV）辐射的环境水平的有害影响的眼表面。当眼表细胞暴露于UV辐射时，泪液中相对高水平的K+防止细胞内K+的损失和凋亡机制的激活。拟议研究的具体目的是，1）使用膜片钳记录，确定先前通过微阵列和共聚焦显微镜在泪管细胞中鉴定的K+和Cl-通道是否在这些细胞中活跃。2)为了确定泪液中升高的[K+]的作用，将角膜上皮细胞在不同的[K+]o存在下暴露于UV辐射，随后测量细胞活力、凋亡途径的活化和离子通道的活性。3）为了确定培养基中升高的[K+]是否会促进培养物中角膜上皮细胞的增殖和活力。这项研究的作用，高钾的眼泪将阐明眼泪的关系，眼睛的健康，在正常人和干眼症患者。每个人都暴露在环境紫外线辐射下，拟议中的研究将有助于解释角膜如何保护透镜和视网膜免受紫外线辐射，同时受到最小的伤害。在干眼症中，泪膜不足可能会使角膜更容易受到紫外线辐射的损害，从而促进疾病的进程。如果泪液中的高钾对眼表健康很重要，那么这一信息将有助于开发干眼病的改进治疗方法。

DESCRIPTION (provided by applicant): The tears differ from most extracellular fluids in that the K+ concentration of tears is about 20 mEq/l. It is thought that the ducts of the lacrimal gland secrete K+; however, the mechanism of this secretion has not been fully elucidated, and the purpose of the high [K+] in tears with respect to its relationship to the cells of the ocular surface is unknown. The key hypotheses to be addressed are based on these observations: 1) Lacrimal gland ducts express K+ transporters and channels consistent with secretion of K+ by the ducts, 2) UV radiation causes opening of K+ channels and loss of K+ from corneal epithelial cells and this loss of K+ activates apoptotic pathways. 3) Elevating extracellular K+ ([K+]o) prevents activation of apoptotic pathways in lymphocytes. We propose that the lacrimal gland duct cells secrete fluid high in K+, which provides the ocular surface with an extracellular ionic environment that protects these cells from the deleterious effects of ambient levels of ultraviolet (UV) radiation. The relatively high level of K+ in tears prevents the loss of intracellular K+ and the activation of apoptotic mechanisms when ocular surface cells are exposed to UV radiation. The specific aims of the proposed research are, 1) to determine, using patch clamp recording, whether K+ and Cl- channels, previously identified in lacrimal duct cells by microarrays and confocal microscopy are active in these cells. 2) To determine the role of elevated [K+] in tears, corneal epithelial cells will be exposed to UV radiation in the presence of varying [K+]o followed by measurement of cell viability, activation of apoptotic pathways and activity of ion channels, 3) To determine whether elevating [K+] in culture medium will promote the proliferation and viability corneal epithelial cells in culture. This study of the role of high potassium in tears will elucidate the relationship of the tears to the health of the eye in normal individuals and dry-eye patients. Everyone is exposed to ambient UV radiation and the proposed research will help to explain how the cornea protects the lens and retina from UV radiation while suffering minimal damage. In dry eye disease an inadequate tear film may make the cornea more susceptible to damage by UV radiation, thereby contributing to the disease process. If the high potassium in tears is important for the health of the ocular surface, this information will be useful in the development of improved treatments for dry eye disease.