Cataract and posterior capsule opacification (PCO) are major drains on health budgets throughout the world and it is a long-term objective of this project to develop strategies to prevent both of these conditions. Calcium is known to play a critical role in cortical cataract, and activation of the protease calpain is implicated. More recently it has been revealed that calcium also has an important role in normal human lens cell signaling through calcium mobilization from endoplasmic reticulum stores, via G-protein coupled receptors. Agonists for these receptors include ATP and acetylcholine and the latter has been implicated in cataract formation.
The specific aims are firstly to elucidate the sites of agonist-induced calcium release from intracellular stores in the intact human lens. Secondly to localize the store-operated calcium entry pathways and study their activation and inactivation characteristics. Thirdly to localize where a calcium increase leads to calpain activation and loss of transparency, and to test calpain antagonists.
The final aim will be to develop and test hydrophobic intraocular lens coatings to prevent PCO, based on knowledge of calcium cell signaling antagonists such as thapsigargin (Tg). Since there are considerable interspecies differences in lens behaviour a significant aspect of project design has been the development of techniques, including long-term culture, employing only human lens and capsular bag preparations. Techniques include confocal fluorescent (Fluo-3) imaging for cell calcium dynamics and electrophysiological and radiotracer methods to characterize the calcium entry pathways. Calpain activation will be measured with a fluorescent probe, lens opacification localized and quantified by digital imaging, and proteolysis studied by immunocytochemistry and gel electrophoresis. Calpain antagonists will be tested to determine those which best preserve lens transparency. The capsular bag culture system will be invaluable for testing the growth-inhibiting (and hence PCO inhibiting) properties of intraocular lenses (IOLs) coated with thapsigargin. 3H-labeled Tg will be used to optimize the coating technology. The ability of Tg-coated IOLs to abolish agonist-induced calcium signaling in capsular bag preparations will serve as an accurate assessment of coating efficacy. This investigation aims therefore not only to elucidate the role of calcium in the normal human lens, but also to identify strategies for preventing both cortical cataract and PCO based on that knowledge.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY010558-04A2
Application #
2690742
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1994-06-01
Project End
2001-09-29
Budget Start
1998-09-30
Budget End
1999-09-29
Support Year
4
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of East Anglia
Department
Type
DUNS #
City
Norfolk
State
Country
United Kingdom
Zip Code
Hu, Rebecca G; Suzuki-Kerr, Haruna; Webb, Kevin F et al. (2008) Molecular and functional mapping of regional differences in P2Y receptor expression in the rat lens. Exp Eye Res 87:137-46
Marcantonio, J M; Reddan, J R (2004) TGFbeta2 influences alpha5-beta1 integrin distribution in human lens cells. Exp Eye Res 79:437-42
Marcantonio, J M; Syam, P P; Liu, C S C et al. (2003) Epithelial transdifferentiation and cataract in the human lens. Exp Eye Res 77:339-46
Williams, M R; Riach, R A; Collison, D J et al. (2001) Role of the endoplasmic reticulum in shaping calcium dynamics in human lens cells. Invest Ophthalmol Vis Sci 42:1009-17
Collison, D J; Duncan, G (2001) Regional differences in functional receptor distribution and calcium mobilization in the intact human lens. Invest Ophthalmol Vis Sci 42:2355-63
Wormstone, I M; Del Rio-Tsonis, K; McMahon, G et al. (2001) FGF: an autocrine regulator of human lens cell growth independent of added stimuli. Invest Ophthalmol Vis Sci 42:1305-11
Marcantonio, J M; Rakic, J M; Vrensen, G F et al. (2000) Lens cell populations studied in human donor capsular bags with implanted intraocular lenses. Invest Ophthalmol Vis Sci 41:1130-41
Sanderson, J; Marcantonio, J M; Duncan, G (2000) A human lens model of cortical cataract: Ca2+-induced protein loss, vimentin cleavage and opacification. Invest Ophthalmol Vis Sci 41:2255-61
Wormstone, I M; Tamiya, S; Marcantonio, J M et al. (2000) Hepatocyte growth factor function and c-Met expression in human lens epithelial cells. Invest Ophthalmol Vis Sci 41:4216-22
Wormstone, I M; Liu, C S; Rakic, J M et al. (1997) Human lens epithelial cell proliferation in a protein-free medium. Invest Ophthalmol Vis Sci 38:396-404

Showing the most recent 10 out of 14 publications