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ABSTRACT: The ability of light to enact damage on the neurosensory retina and underlying structures has been well understood for hundreds of years. While the eye has adapted several mechanisms to protect itself from such damage, certain exposures to light can still result in temporal or permanent damage. Both clinical observations and laboratory studies have enabled us to understand the various ways by which the eye can protect itself from such damage. Light or electromagnetic radiation can result in damage through photothermal, photomechanical, and photochemical mechanisms. The following review seeks to describe these various processes of injury and many of the variables, which can mitigate these modes of injury.
Eye (London, England) 01/2011; 25(1):1-14. · 1.97 Impact Factor
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ABSTRACT: We determined the effects of a low dose of the actin-disrupting agent latrunculin (LAT)-A on dexamethasone (DEX)-induced changes in actin organization, focal adhesions, and production of extracellular matrix proteins in cultured human trabecular meshwork (HTM) cells. HTM cells were cultured to a highly confluent stage with stable endothelium-like morphology and incubated with 0.1 or 0.2 microM DEX and/or 0.1 microM LAT-A. Changes in the actin cytoskeleton and vinculin-containing focal contacts were evaluated by immunofluorescence microscopy. Expression of thrombospondin-1 (TSP1) and fibronectin (FN) in HTM cells was evaluated by Western blot analysis. The results showed that DEX induced morphological changes and actin reorganization in HTM cells. The cells partly recovered after DEX withdrawal, but the addition of low dose LAT-A hastened the recovery. In addition, DEX failed to induce changes when co-incubated with LAT-A for at least 4 weeks, and for at least 2 weeks when cells were pre-treated with LAT-A for 2 weeks. HTM cells treated with 0.1 microM LAT-A only for 5 days showed mild disorganization of the actin cytoskeleton and focal adhesions, which persisted during the 4 weeks of treatment. DEX stimulated production of FN in HTM cells independent of LAT-A treatment. LAT-A and, to a lesser extent, DEX inhibited production of TSP1 by HTM cells. Although LAT-A is not a DEX receptor antagonist, it is able to prevent the effects of DEX on the actin cytoskeleton in cultured HTM cells at a dose subthreshold for increasing outflow facility in monkeys. This suggests that LAT-A at low doses may be useful in treating steroid and other glaucomas. TSP1 may be an important target of LAT-A in HTM cells and modulation of TSP may influence the actin cytoskeleton of the trabecular meshwork (TM), and consequently, intraocular pressure.
Experimental Eye Research 09/2003; 77(2):181-8. · 3.26 Impact Factor
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ABSTRACT: We have investigated the role of transforming growth factor-beta 1 (TGF-beta 1) in suspension-induced programmed cell death of cultured human keratinocytes. Suspension of keratinocytes in semisolid medium induces TGF-beta 1 mRNA levels and synthesis of bioactive TGF-beta 1 protein. Concomitant with the suspension-induced increase in secreted TGF-beta 1 levels, steady state mRNA levels for c-myc are decreased. Both exogenously added and endogenously produced TGF-beta 1 attenuate suspension-induced nucleosomal fragmentation in keratinocytes. We propose that TGF-beta 1 may function to protect keratinocytes from DNA fragmentation following loss of cell-substratum and/or cell-cell contact. Taken together, our findings suggest that loss of cell-substratum and/or cell-cell adhesion is an important component of an apoptotic signal transduction cascade regulated by TGF-beta 1 in normal human stratified squamous epithelia.
Journal of Biological Chemistry 02/1996; 271(1):5-8. · 4.77 Impact Factor
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ABSTRACT: We found that keratinocytes immortalized with human papillomavirus (HPV) type 16 DNA and malignantly converted by H-ras transfection (HPK-1A/ras) exhibit an enhanced ability to synthesize a fibronectin-containing extracellular matrix. Gene expression of fibronectin and thrombospondin was increased in tumorigenic keratinocytes compared to control and immortalized keratinocytes, 6- and 9-fold, respectively. Increased production of soluble and cell surface-associated fibronectin was not specific for HPV 16 transformed keratinocytes. Ad12-SV40-immortalized keratinocytes malignantly converted by H-ras transfection (RHEK-1/ras) also exhibited enhanced expression of fibronectin and thrombospondin, as well as pro-alpha 1 type I collagen. Steady state mRNA levels for autocrine growth-regulatory factors, transforming growth factors alpha and beta 1, were increased in Ad12-SV40 but not HPV 16-transformed human keratinocytes. We then determined whether increased production of fibronectin was associated with aberrant differentiation of transformed keratinocytes. Less than 10% of the HPV 16-transformed cells produced cornified envelopes after suspension-induced differentiation compared to 70% of normal keratinocytes. However, immortalization by HPV 16 DNA was sufficient to confer a differentiation-defective phenotype. Both involucrin mRNA and protein levels were decreased 8-fold in HPV 16-immortalized keratinocytes compared to normal cells and malignant conversion further attenuated involucrin levels. These studies demonstrate that aberrant differentiation is an early event in the transformation of the human keratinocytes and is not the result of enhanced expression of the extracellular matrix proteins. Unlike transformed fibroblastic cell types, up-regulation of fibronectin gene expression and matrix formation is a consistent characteristic of malignantly converted human keratinocytes.
Cancer Research 12/1991; 51(21):5967-75. · 7.86 Impact Factor
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ABSTRACT: We determined the effects of a low dose of the actin-disrupting agent latrunculin (LAT)-A on dexamethasone (DEX)-induced changes in actin organization, focal adhesions, and production of extracellular matrix proteins in cultured human trabecular meshwork (HTM) cells. HTM cells were cultured to a highly confluent stage with stable endothelium-like morphology and incubated with 0·1 or 0·2 μm DEX and/or 0·1 μm LAT-A. Changes in the actin cytoskeleton and vinculin-containing focal contacts were evaluated by immunofluorescence microscopy. Expression of thrombospondin-1 (TSP1) and fibronectin (FN) in HTM cells was evaluated by Western blot analysis. The results showed that DEX induced morphological changes and actin reorganization in HTM cells. The cells partly recovered after DEX withdrawal, but the addition of low dose LAT-A hastened the recovery. In addition, DEX failed to induce changes when co-incubated with LAT-A for at least 4 weeks, and for at least 2 weeks when cells were pre-treated with LAT-A for 2 weeks. HTM cells treated with 0·1 μm LAT-A only for 5 days showed mild disorganization of the actin cytoskeleton and focal adhesions, which persisted during the 4 weeks of treatment. DEX stimulated production of FN in HTM cells independent of LAT-A treatment. LAT-A and, to a lesser extent, DEX inhibited production of TSP1 by HTM cells. Although LAT-A is not a DEX receptor antagonist, it is able to prevent the effects of DEX on the actin cytoskeleton in cultured HTM cells at a dose subthreshold for increasing outflow facility in monkeys. This suggests that LAT-A at low doses may be useful in treating steroid and other glaucomas. TSP1 may be an important target of LAT-A in HTM cells and modulation of TSP may influence the actin cytoskeleton of the trabecular meshwork (TM), and consequently, intraocular pressure.
Experimental Eye Research.
