Is Cholesterol Crystalline Domain a Barrier to Oxygen Transport in the Eye Lens?

胆固醇晶域是眼晶状体中氧气传输的障碍吗？

• 批准号: 7558402
• 负责人: WITOLD K SUBCZYNSKI
• 金额: $ 3.9万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-02-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7558402
• 关键词: Affect; Age; Aging; Amino Acids; Attention; Blindness; Cataract; Cell Nucleus; Cell membrane; Cell surface; Cholesterol; Collaborations; Complement; Computer Simulation; Computers; Crystalline Lens; Data; Developed Countries; Developing Countries; Development; Diffuse; Diffusion; Discrimination; Disease; Electron Spin Resonance Spectroscopy; Equilibrium; Evaluation; Evolution; Goals; Grant; Human; Hydrocarbons; Lead; Lens Fiber; Lipid Bilayers; Lipids; Liquid substance; Lymphocyte-Specific p56LCK Tyrosine Protein Kinase; Mammalian Cell; Measurement; Measures; Membrane; Membrane Microdomains; Methods; Modeling; Mole the mammal; Molecular; N-terminal; NR4A1 gene; Nuclear; Oxygen; Paper; Peptides; Permeability; Phase; Phospholipids; Physiologic pulse; Play; Poland; Positioning Attribute; Prevention; Process; Research; Research Personnel; Resistance; Role; Side; Simulate; Spin Labels; Staging; Sterols; Structure; Surface; System; Temperature; Testing; Time; United States National Institutes of Health; Universities; age related; aged; base; crosslink; design; fiber cell; insight; lens; lens cortex; membrane model; molecular dynamics; oxygen transport; parent grant; physical property; prevent; public health relevance; research study; simulation; theories

DESCRIPTION (provided by applicant): This research will be done primarily in Krakow, Poland, at the Jagiellonian University in collaboration with Dr. Marta Pasenkiewicz-Gierula as an extension of NIH Grant No. R01-EY015526. Cholesterol, the most prominent sterol of mammalian cells, is located predominantly in the plasma membrane, where it comprises 40-45 mol% of the total lipids. However, in membranes of fiber cells, the cholesterol level is extremely high, showing cholesterol-to-phospholipids mole ratios from 1 to 2 in the cortex of the lens to as high as 3 to 4 in the lens nucleus, which leads to the formation of immiscible cholesterol crystalline domains within this membrane. The long-term objective of this proposal is to achieve a greater understanding of the function of cholesterol in membranes of the eye lens, including the effect on the transport of metabolites, particularly oxygen, within the lens. It is proposed to (1) build computer models of selected domains of the fiber cell membrane, with special attention paid to its cholesterol crystalline domain, which can occupy as much as 50% of the cell surface in the lens nucleus, and (2) calculate the oxygen permeability coefficient across membrane domains arising from an oxygen concentration gradient across the membrane. This will allow testing of the hypothesis that the rigid cholesterol crystalline domain can be a barrier to oxygen transport, which, if true, should help to maintain low oxygen concentration in the eye-lens interior. Finally, it is proposed to (3) calculate profiles of both oxygen concentration and the oxygen translational diffusion coefficient across membrane domains and, based on these profiles, determine their oxygen permeability coefficients. Two methods of evaluation of the oxygen permeability coefficient will be compared, namely one that is based on oxygen flux in an oxygen concentration gradient, and one that depends on the details of oxygen self-diffusion in a membrane at equilibrium. Computer experiments will be performed using molecular dynamics (MD) membrane simulations to provide information that is not available from experimental studies about oxygen permeability, structure, and the dynamics of the cholesterol crystalline domain. When possible, the results of MD simulations will be compared with experimental data acquired by the PI under support of the Parent Grant. PUBLIC HEALTH RELEVANCE: Age-related cataracts are a major cause of blindness in developing countries. The reason for the onset of cataracts is unknown, but a great deal of evidence suggests that an increase in oxygen concentration in the lens interior can lead to the development of cataracts. The proposed studies will generate important fundamental information about the contribution of cholesterol to the process of oxygen transport within the eye lens, which should increase our understanding of the role cholesterol plays and, in turn, help contribute to the prevention of age-related nuclear cataracts.

描述（由申请人提供）：这项研究将主要在波兰克拉科夫的雅盖隆大学与 Marta Pasenkiewicz-Gierula 博士合作完成，作为 NIH 拨款号 R01-EY015526 的延伸。胆固醇是哺乳动物细胞中最重要的甾醇，主要位于质膜中，占总脂质的 40-45 mol%。然而，在纤维细胞膜中，胆固醇水平极高，晶状体皮质中胆固醇与磷脂的摩尔比为1至2，晶状体核中高达3至4，从而导致形成该膜内不混溶的胆固醇结晶域。该提案的长期目标是更好地了解胆固醇在晶状体膜中的功能，包括对晶状体内代谢物（特别是氧气）运输的影响。建议 (1) 建立纤维细胞膜选定域的计算机模型，特别关注其胆固醇结晶域，它可以占据晶状体核中细胞表面的 50% 之多，以及 (2)计算由跨膜的氧浓度梯度引起的跨膜域的透氧系数。这将允许测试刚性胆固醇结晶结构域可能成为氧运输障碍的假设，如果这是真的，则应有助于维持眼晶状体内部的低氧浓度。最后，建议（3）计算氧浓度和跨膜域的氧平移扩散系数的分布，并根据这些分布确定它们的氧渗透系数。将比较两种评估透氧系数的方法，即一种基于氧浓度梯度中的氧通量，另一种取决于平衡时膜中氧自扩散的细节。将使用分子动力学（MD）膜模拟进行计算机实验，以提供有关胆固醇结晶结构域的氧渗透性、结构和动力学的实验研究中无法获得的信息。如果可能，MD 模拟的结果将与 PI 在家长资助的支持下获得的实验数据进行比较。公共卫生相关性：与年龄相关的白内障是发展中国家失明的主要原因。白内障发病的原因尚不清楚，但大量证据表明晶状体内部氧气浓度的增加可导致白内障的发生。拟议的研究将产生有关胆固醇对眼晶状体内氧气运输过程的贡献的重要基本信息，这将增加我们对胆固醇所发挥作用的理解，进而有助于预防与年龄相关的核性白内障。