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

描述(申请人提供)：泪液与大多数细胞外液的不同之处在于，泪液中的K+浓度约为20mEq/L。人们认为泪腺的导管分泌K+；然而，这种分泌的机制尚未完全阐明，眼泪中高[K+]的目的与其与眼表细胞的关系尚不清楚。需要解决的关键假设是：1)泪腺导管表达与K+分泌一致的K+转运体和通道；2)紫外线辐射导致K+通道开放和角膜上皮细胞K+丢失，这种K+丢失激活了细胞凋亡途径。3)升高细胞外K+([K+]o)可阻止淋巴细胞凋亡通路的激活。我们认为泪腺导管细胞分泌高K+的液体，这为眼表面提供了一个细胞外离子环境，保护这些细胞免受环境水平紫外线(UV)辐射的有害影响。当眼表细胞暴露在紫外线辐射下时，泪液中相对较高的K+水平可以防止细胞内K+的损失和凋亡机制的激活。这项研究的具体目的是：1)利用膜片钳记录，确定先前通过微阵列和共聚焦显微镜在泪道细胞中发现的K+和Cl-通道是否在这些细胞中活动。2)为了确定[K+]升高在泪液中的作用，将角膜上皮细胞暴露在不同[K+]O存在下的紫外线照射下，然后测定细胞活力、凋亡通路的激活和离子通道的活性；3)测定培养液中升高的[K+]是否会促进培养的角膜上皮细胞的增殖和活性。这项关于高钾在泪水中的作用的研究将阐明泪水与正常人和干眼症患者眼睛健康的关系。每个人都暴露在周围的紫外线辐射下，这项拟议的研究将有助于解释角膜如何在遭受最小损害的情况下保护晶状体和视网膜免受紫外线辐射的伤害。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，从而促进疾病的发展。如果眼泪中的高钾对眼表的健康很重要，那么这一信息将有助于改进干眼病的治疗方法。

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.