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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: A major variant of myocilin (MYOC) [TIGR/MYOC mt.1 (-1000 C/G)], present in the gene's promoter, is found to be associated with more rapid progression of the glaucoma disease state. Time-to-event analyses using the Cox proportional hazards model produced substantial statistical evidence that this TIGR/MYOC mt.1(+) variant accelerates worsening for both optic disc and visual field measures of disease progression. These analyses were based on evaluations of 147 patients with primary open-angle glaucoma (POAG) over 35 years of age with an average follow-up of approximately 15 years. Our analyses showed that there are independent effects of the variant on disease progression, taking into account other relevant disease-related baseline risk factors, including age, family history, initial drug treatment, initial surgical treatment, diabetes, gender, myopia, and initial disease severity. The finding that a TIGR/MYOC mt.1(+) determination provided a strong marker for glaucoma progression, above and beyond the other baseline risk factors, suggests a clinical utility in testing for this promoter genotype.
Clinical Genetics 08/2003; 64(1):18-27. · 3.13 Impact Factor
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Journal of Glaucoma 11/2001; 10(5 Suppl 1):S9-12. · 1.78 Impact Factor
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ABSTRACT: Mutations in the trabecular meshwork inducible glucocorticoid response (TIGR) gene, also known as myocilin, have recently been linked to some forms of glaucoma. Recent studies have shown that TIGR protein also is expressed in the ciliary muscle. Because uveoscleral outflow, which traverses the ciliary muscle, is increased by prostaglandins (PGs), the present study assessed whether topical PGs alter the amount of TIGR protein within the ciliary muscle.
Vehicle was topically applied to one eye, and 2 microg PGF(2alpha)-isopropyl ester (PGF(2alpha)-IE) was applied to the other eye of cynomolgus monkeys twice daily for 5 days. Pressure reductions of 5 mm Hg in the PGF(2alpha)-IE-treated eyes were confirmed. The eyes were then fixed and paraffin sections were cut from each eye. The distribution of TIGR protein in the ciliary muscle was determined by confocal scanning laser microscopy. Additional sections were immunostained with a polyclonal antibody to recombinant TIGR protein or with a polyclonal antibody to a synthetic peptide corresponding to the leucine zipper region within the TIGR protein. Staining intensity in the ciliary muscle was assessed by measuring optical density (OD) along two line segments overlying the ciliary muscle, by using a high-resolution imaging densitometer.
TIGR protein immunoreactivity was observed in ciliary muscle fibers throughout the ciliary muscle. Extracellular TIGR immunoreactivity colocalized with collagen type IV immunoreactivity. Intracellular staining also was present. Immunoreactivity was less intense in the sections from the PGF(2alpha)-IE-treated eyes compared with the vehicle-treated eyes. This was reflected in the reduction of mean OD scores in each monkey. Overall, the reduction of mean OD scores in the treated eyes was 42.1% +/- 9.9% (P < 0.005) with the anti-recombinant TIGR antibody and 27.3% +/- 10.4% with the anti-TIGR peptide antibody (P < 0.005).
TIGR protein immunoreactivity was present both intracellularly and extracellularly in the ciliary muscle of the cynomolgus monkey. This suggests that extracellular TIGR protein is in contact with aqueous humor in the uveoscleral outflow pathway. Moreover, IOP-lowering topical PGF(2alpha)-IE treatment decreases the amount of TIGR protein in the ciliary muscle.
Investigative Ophthalmology & Visual Science 07/2001; 42(8):1781-6. · 3.60 Impact Factor
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ABSTRACT: To determine the effect of the serine-threonine kinase inhibitor H-7, which blocks actomyosin contractility and increases outflow facility in live monkeys, on morphology, cytoskeleton, and cellular adhesions of human trabecular meshwork (HTM) cells in culture.
Cultured HTM cells were videographically recorded and evaluated before and after exposure to H-7 at different concentrations. The subcellular distribution of the actin-based cytoskeleton and associated anchor proteins including vinculin, paxillin, and beta-catenin, as well as phosphotyrosine-containing proteins were evaluated by fluorescence immunocytochemistry and digital fluorescence microscopy.
H-7 induced pronounced but reversible HTM cell thickening toward the cell center and deterioration of the actin cytoskeletal network. Cell-extracellular matrix (ECM) and cell-cell adhesions were also affected, but the beta-catenin-rich, vinculin-containing adherens junctions were clearly more resistant than focal contacts. Phosphotyrosine labeling in focal contacts was highly sensitive to H-7.
H-7 induces alterations in cell shape, actin cytoskeleton, and associated focal adhesions in cultured HTM cells, which may be responsible for the effects of H-7 on outflow facility in live monkey eyes.
Molecular vision 07/2001; 7:145-53. · 2.20 Impact Factor
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ABSTRACT: Particle Irradiation Induces FGF2 Expression in Normal Human Lens Cells. Particle radiations, including both proton and helium-ion beams, have been used to successfully treat choroidal melanoma, but with the complication of radiation-induced cataract. We have investigated a role for radiation-induced changes in the expression of basic fibroblast growth factor (FGF2) gene expression as part of the mechanism(s) underlying lens cell injury associated with cataract. Normal human lens epithelial (HLE) cells were cultured in vitro on extracellular matrix (ECM) originated from bovine corneal endothelial cells. This study reports evidence for rapid but transient induction of FGF2 transcripts, an increase of between 5- and 8-fold, within 0.5 h after exposure to particle radiation, followed by another wave of increased transcription at 2-3 h postirradiation. Immunofluorescence results confirm the enhanced levels of FGF2 protein rapidly after exposure to protons or helium ions, followed by another wave of increased activity unique to helium at 6 h postirradiation. This second wave of increased immunoreactivity was not observed in the proton-irradiated samples. Total FGF2 protein analysis after helium-ion exposures shows induced expression of three FGF2 isoforms, with an increase of up to 2-fold in the 18-kDa low-molecular-weight species. Studies of the effects of protons on individual FGF2 protein isoforms are in progress. Several mechanisms involving a role for FGF2 in radiation-induced cataract are discussed.
Radiation Research 12/2000; 154(5):477-84. · 2.68 Impact Factor
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ABSTRACT: To characterize the growth and maturation of nonimmortalized human lens epithelial (HLE) cells grown in vitro.
HLE cells, established from 18-week prenatal lenses, were maintained on bovine corneal endothelial (BCE) extracellular matrix (ECM) in medium supplemented with basic fibroblast growth factor (FGF-2). The identity, growth, and differentiation of the cultures were characterized by karyotyping, cell morphology, and growth kinetics studies, reverse transcription-polymerase chain reaction (RT-PCR), immunofluorescence, and Western blot analysis.
HLE cells had a male, human diploid (2N = 46) karyotype. The population-doubling time of exponentially growing cells was 24 hours. After 15 days in culture, cell morphology changed, and lentoid formation was evident. Reverse transcription-polymerase chain reaction (RT-PCR) indicated expression of alphaA- and betaB2-crystallin, fibroblast growth factor receptor 1 (FGFR1), and major intrinsic protein (MIP26) in exponential growth. Western analyses of protein extracts show positive expression of three immunologically distinct classes of crystallin proteins (alphaA-, alphaB-, and betaB2-crystallin) with time in culture. By Western blot analysis, expression of p57(KIP2), a known marker of terminally differentiated fiber cells, was detectable in exponential cultures, and levels increased after confluence. MIP26 and gamma-crystallin protein expression was detected in confluent cultures, by using immunofluorescence, but not in exponentially growing cells.
HLE cells can be maintained for up to 4 months on ECM derived from BCE cells in medium containing FGF-2. With time in culture, the cells demonstrate morphologic characteristics of, and express protein markers for, lens fiber cell differentiation. This in vitro model will be useful for investigations of radiation-induced cataractogenesis and other studies of lens toxicity.
Investigative Ophthalmology & Visual Science 12/2000; 41(12):3898-907. · 3.60 Impact Factor
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ABSTRACT: Determine the effects of the actin cytoskeleton disrupting compound latrunculin-A (LAT-A) on morphology, cytoskeleton, and cellular adhesions of cultured human trabecular meshwork (HTM) cells.
HTM cells were cultured to high confluence with endothelial-like morphology and treated with LAT-A at different doses and duration. Topography of living cells was evaluated by videomicroscopy. Distribution and organization of the actin-based cytoskeleton, vinculin- and paxillin-containing focal contacts, and beta-catenin-rich intercellular adhesions were determined by immunofluorescence and digital microscopy.
LAT-A induced pronounced but highly reversible rounding of HTM cells, intercellular separation, and disruption of actin filaments. beta-catenin-rich intercellular adherens junctions were particularly sensitive to LAT-A. Vinculin- and paxillin-containing focal contacts were only partially affected and appeared to be more resistant to the drug than the intercellular interactions.
The increase in outflow facility in the living primate eye induced by LAT-A may be due to the disorganization and disruption of the actin cytoskeleton and its associated cellular adhesions in the trabecular meshwork.
Molecular vision 08/2000; 6:132-43. · 2.20 Impact Factor
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ABSTRACT: Glucocorticoid (GC) treatment of human trabecular meshwork (HTM) cells produces delayed, progressive cellular and extracellular protein/glycoprotein inductions with characteristics matching those for intraocular pressure elevation with corticosteroid eyedrops. The cloning of the Trabecular Meshwork Inducible Glucocorticoid Response (TIGR) gene from this system has suggested possible environmental and genetic influences in relation to glaucoma mechanisms. As reported here, the major GC-induced increase of TIGR expression in HTM cells is reduced approximately 4-fold by basic fibroblast growth factor (bFGF, 100-1000 pM), with a somewhat smaller inhibition noted with the thyroid hormone triiodothyronine (T3, 100 nM). Such endogenous 'protective' factors could help balance stimulatory effects on TIGR gene expression from 'stress' and/or mechanical perturbations in the trabecular meshwork. TIGR coding region mutations affecting the gene's olfactomedin (OLF) homology domain may also perturb biosynthetic pathways and cellular homeostatic functions. Our recent studies have shown the OLF domain corresponds to a major translocational 'pause', an area where critical processes for normal TIGR biogenesis are expected to take place. Observations that Glu323Lys (and other mutations early in the OLF domain) altered the pattern of paused protein intermediates provide possible clues to previously unexplained pathogenetic mechanisms. HTM cell transfection studies using TIGR-green fluorescent protein (GFP) fusions showed increased and altered distribution of the expressed protein with constructs missing the OLF domain, an effect also found with the Pro370 Leu mutation for early-onset glaucoma. The data suggest an activation of stress/apoptotic pathways in HTM cells as a potential mechanism for environmental/genetic interactions in glaucoma pathogenesis.
Eye 07/2000; 14 ( Pt 3B):503-14. · 1.85 Impact Factor
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ABSTRACT: Decreased flow of aqueous humor through the trabecular meshwork (TM) and into Schlemm's canal (SC) is believed to be a predominant factor in the development of the elevated intraocular pressure found in primary open-angle and steroid glaucoma. Recent biochemical and genetic evidence has suggested that alterations in the expression of the TM glucocorticoid response (TIGR) protein within the chamber angle may play a role in the development of these glaucomas. To understand the process of TIGR induction in outflow pathway cells we developed an assay for TIGR expression that could distinguish both individual cell responses and also provide a semi-quantitative comparison between cell cultures. The present study demonstrates this approach, using digital image capture of immunofluorescently stained human TM and SC cells after treatment with dexamethasone (Dex).
Confluent cultures of human TM and SC cells were treated with 1 M Dex or vehicle control for 10 days. The cells were then fixed, permeabilized, and stained using polyclonal antibodies produced against recombinant TIGR. Digital images of fluorescently stained cells, using the same exposure time within an experiment, were evaluated by tabulating the staining intensity of all cells on each image. Between 10 and 40 cells were evaluated per image, 8-10 frames/ sample, 2-3 samples per treatment. Each cell was ranked as either 0 (background), 1+ (minor), 2+ (moderate) or 3+ (very bright staining).
TM cells showed a significant basal level of TIGR staining. About 20% of control cells showed appreciable levels of TIGR staining, with intensity levels evenly distributed between 1, 2 and 3+. Dex treatment increased the number of TM cells expressing TIGR to 60-80%, with the majority of cells showing 2+ to 3+ staining throughout the cytoplasm. SC cells showed no basal TIGR staining, but Dex-treated cells exhibited TIGR staining in 6-15% of cells. SC cell TIGR staining varied between 1+ to 2+ in intensity, and showed a distribution different from TM cells. Staining in SC cells was localized to a ribbon-like compartment adjacent to the nucleus. Such perinuclear localization was rarely seen in TM cells.
The low standard errors of the mean TIGR responses within each experiment, and the reproducibility between experiments for each cell type, suggests good reliability for this method. At the same time, the consistent, marked contrast between TM and SC cells in their response to glucocorticoids demonstrates that the assay can distinguish significant differences between cell types. The data support the view that Dex has a cell type specific effect on TIGR induction. The different extent, pattern and localization of TIGR staining between cell types suggests that TIGR expression in SC cells could play a functional role in the outflow pathway, but one that may be distinct from that played in TM cells.
Current Eye Research 01/2000; 19(6):517-24. · 1.28 Impact Factor
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ABSTRACT: To examine possible effects of the E323K mutation in the trabecular meshwork glucocorticoid response (TIGR) gene (also known as myocilin [MYOC]), using assays of translocational processing through the endoplasmic reticulum (ER). The E323K mutation was of particular interest, since the mutation shows a strong association with early onset open-angle glaucoma, but has a minimal predicted effect on protein structure.
Normal and mutant TIGR cDNA constructs were used to generate protein products in the presence of endoplasmic reticulum (ER) membranes, using an assay previously developed to detect alterations in the ER translocation function. "Paused" regions for potential protein modifications were defined by proteinase K (PK) sensitivity in the presence of ER membranes, with the ability to restart translocation when treated with EDTA. The effects of the E323K mutation were evaluated, as well as mutations located on either side of E323K (G246R, G364V, P370L) as the other mutations had substantial predicted structural changes in addition to clear disease associations.
The native TIGR molecule was observed to have a paused region that corresponds to the region of highest olfactomedin (OLF) homology. The E323K mutation, located near the beginning of this region, dramatically altered the normal pattern of nascent proteins observed in the translocational pausing assay. A prominent band appeared with the E323K mutation, which could represent a new product or a marked enhancement of a faint band normally seen, approximately 3 kDa higher than the major paused band. The other TIGR mutants examined did not show this effect.
The major translocational pause that starts near the beginning of the region of high OLF homology may help to explain the high frequency of glaucoma-associated mutations in this area. The observed effect of the E323K mutation on the products of translocational processing suggests a delay in the normal pausing process of TIGR biogenesis. This delay points to a potentially distinct pathogenic mechanism for E323K as compared with the other TIGR mutations so far evaluated.
Molecular vision 09/1999; 5:19. · 2.20 Impact Factor
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ABSTRACT: Cyclic AMP production in the presence or absence of various adrenergic agonists and antagonists was determined in cultured human trabecular cells using a gammaflow automated radioimmunoassay that allowed multiple simultaneous experiments and reproducible results. Adrenergic agonists and antagonists showed activation and inhibition constants consistent with the presence of beta2-receptors: Ka of isoproterenol < epinephrine < norepinephrine < phenylephrine; Ki of timolol < betaxolol < celiprolol < atenolol. Selective ICI antagonists showed beta2-specificity.
Ophthalmic Research 02/1999; 31(1):53-8. · 1.56 Impact Factor
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ABSTRACT: Important advances have been made within the past year in the area of glaucoma genetics, including the identification of the TIGR gene for adult as well as juvenile GLC1A glaucoma, a P450 gene for GLC3A congenital glaucoma, and a bicoidhomeobox transcription factor gene RIEG for developmental glaucoma. The cloning of TIGR as a candidate gene for glaucoma is based on its distinctive induction in human trabecular meshwork cells and tissues, its induction profile, and the expressed molecule's putative biologic properties. Results from several laboratories showing defects in the olfactomedin homology domain of the TIGR gene have generated particular interest concerning potential pathogenic mechanisms. Recent progress in glaucoma genetics has also included the identification of new loci in familial adult open-angle glaucoma, the identification of a locus associated with pigment dispersion syndrome, and the collection of new families for linkage analyses and clinical assessments. Taken together, these findings offer future prospects for improving diagnostic criteria, for understanding disease etiologies, and for developing improved therapeutic strategies.
Current Opinion in Ophthalmology 05/1998; 9(2):15-23. · 2.65 Impact Factor
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ABSTRACT: Expression of the trabecular meshwork inducible glucocorticoid response (TIGR) gene progressively increases from barely detectable levels to greater than 2% of total cellular mRNA over 10 days exposure of trabecular meshwork (TM) cells to dexamethasone. Cycloheximide blocked most of the TIGR mRNA induction, suggesting a requirement for ongoing protein synthesis. The genomic structure of TIGR (approximately 20 kilobases) consists of 3 exons, and a 5-kilobase promoter region that contains 13 predicted hormone response elements, including several glucocorticoid regulatory elements, and other potentially important regulatory motifs. TIGR cDNA encodes an olfactomedin-related glycoprotein of 504 amino acids with motifs for N- and O-linked glycosylation, glycosaminoglycan initiation, hyaluronic acid binding, and leucine zippers. Recombinant TIGR (rTIGR) showed oligomerization and specific binding to TM cells. Anti-rTIGR antibody detected multiple translational/post-translational forms of TIGR produced by the cells (including secreted 66 kDa/55 kDa glycoproteins/proteins in the media and 55 kDa cellular proteins), whereas Northern blot showed a single mRNA species. The findings suggest potential mechanisms by which TIGR could obstruct the aqueous humor fluid flow and participate in the pathogenesis of glaucoma.
Journal of Biological Chemistry 04/1998; 273(11):6341-50. · 4.77 Impact Factor
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ABSTRACT: To examine the differential staining of two potential stress-response markers, alpha B-crystallin and the trabecular meshwork inducible glucocorticoid response protein (TIGR), in meshwork from normal and glaucomatous human eyes.
Trabecular meshwork from 35 eyes from 23 donors with either primary open-angle glaucoma, pseudoexfoliative glaucoma, or low-tension glaucoma, and from age-matched normal eyes, was examined. Sagittal and tangential frozen sections were stained with polyclonal antibodies to alpha B-crystallin or TIGR and then by a fluorescent secondary antibody.
In normal eyes, labeling for alpha B-crystallin occurred in the subendothelial region of Schlemm's canal and outer corneoscleral regions, whereas TIGR labeling was found in the inner uveal meshwork region and the anterior portion of the meshwork. In contrast, in many glaucomatous eyes, labeling for alpha B-crystallin and TIGR occurred in more regions of the meshwork and appeared more intense than in normal eyes, regardless of the type or clinical severity of glaucoma.
The differences in localization of alpha B-crystallin and TIGR may relate to functional specialization within meshwork tissues. The increase in the staining for these proteins in glaucomatous eyes could involve environmental and genetic factors in the disease processes.
Investigative Ophthalmology & Visual Science 03/1998; 39(3):517-25. · 3.60 Impact Factor
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ABSTRACT: Hyaluronan (HA) is a high-molecular weight glycosaminoglycan that can affect water and solute fluxes in the extracellular matrix. The distribution of HA in the human trabecular meshwork of nonglaucomatous eyes was examined to help understand the potential role of HA in the regulation of aqueous outflow resistance.
Histolocalization of HA was established in situ in the trabecular meshwork of human eyes with no known diseases of the anterior segment. A specific biotinylated HA-binding peptide was used as a probe for this study, with enhanced sensitivity of HA detection achieved by modifications of the fixation and staining procedures.
Evaluation of HA staining in the aqueous outflow pathway in comparison to that in other ocular structures (e.g., the vitreous) showed pronounced staining in the trabecular meshwork. The staining intensity was similar between various layers of the meshwork. Both the filtering and the anterior nonfiltering portions of the trabecular meshwork showed pronounced HA staining. The staining was localized primarily to the trabecular meshwork endothelial cells.
Pronounced HA staining observed in the various layers of the trabecular meshwork suggests that substantial amount of HA is present in the nonglaucomatous outflow pathway. The staining pattern suggests that HA is associated with the endothelial cells lining the trabecular beams. This finding supports potential roles for this glycosaminoglycan in the regulation of the physiological aqueous outflow resistance or in the maintenance of the outflow channels or both. Histochemical localization of HA in the various layers of the non-glaucomatous meshwork provides a useful basis for future comparative studies of HA distribution and relative amounts in the trabecular meshworks of eyes affected by various types of glaucoma.
Investigative Ophthalmology & Visual Science 06/1997; 38(6):1222-8. · 3.60 Impact Factor
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ABSTRACT: Studies of the effects of glucocorticoid (GC) and oxidative stress stimuli in differentiated cultures of human trabecular meshwork (HTM) cells have provided the rationale for our studies of a major new gene termed TIGR (trabecular meshwork inducible GC response). The TIGR clone was isolated by differential library screening using selection criteria based on the induction pattern of a new protein/glycoprotein found in HTM cultures after prolonged but not brief exposure to GCs. This GC induction pattern matched the time course and dose response required for intraocular pressure elevation in patients receiving corticosteroids. The very large, progressive induction of TIGR combined with specific structural features of its cDNA suggested that TIGR should be considered a candidate gene for outflow obstruction in glaucoma. Among the properties of TIGR cDNA were a signal sequence for secretion, several structural features for interactions with glycosaminoglycans and other glycoproteins and putative sites for cell surface interactions. In addition, the leucine zippers in the structure were related to TIGR-TIGR oligomerization that was shown to occur with native and recombinant TIGR protein. The verification that TIGR was a major stress response protein in HTM cells following hydrogen peroxide (or phorbol esters) exposure provided a potential link between GC and oxidative mechanisms thought to be involved in glaucoma pathogenesis. Pharmacological evaluation showed that basic fibroblast growth factory and transforming growth factor beta decreased the GC induction of TIGR, and certain nonsteroidal anti-inflammatory drugs protected against both GC- and oxidation-induced stress responses in HTM cells. Our recent studies of TIGR's genomic structure have shown motifs in the promoter region that suggest a basis by which multiple hormonal/environmental stimuli can regulate TIGR production and by which putative genetic alterations could lead to an overexpression of the protein. Further application of cell biology/biochemistry, molecular biology, genetic and histological approaches will be helpful in understanding the role of TIGR in different glaucoma syndromes.
Ophthalmologica 02/1997; 211(3):126-39. · 1.42 Impact Factor
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ABSTRACT: The effects of natriuretic peptides on cGMP formation and [125I]ANP binding in human trabecular meshwork cells were investigated. CNP at 1 microM stimulated cGMP formation approximately 18-25 fold, with a half maximal effective concentration approximately 20-30nM. BNP at 1 microM stimulated approximately 7 fold, while ANP stimulated cGMP formation 2-fold at 1 microM but had little or no effect at concentrations below 1 microM. Displacement binding of [125I]ANP to intact TM cells in the presence of unlabeled ANP indicated a single binding site with a dissociation constant approximately 0.15nM.c-ANP, which binds specifically to natriuretic peptide C receptors, displaced > 95% [125I]ANP binding to surface receptor sites with a half-maximal effective concentration comparable to that of ANP or BNP. c-ANP had no inhibitory effect on CNP stimulation of cGMP formation. The data suggest that human TM cells possess natriuretic peptide B receptors as the primary guanylyl cyclase-containing subtype and C receptors as the numerically predominant subtype of natriuretic peptide receptors.
Current Eye Research 02/1996; 15(2):137-43. · 1.28 Impact Factor
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ABSTRACT: The radiation from quartz halogen light bulbs has been reported to cause erythema in humans and skin tumors in experimental animals.
The objective of this study was to determine the relative risk of injury to humans due to the radiation from these lamps.
We studied a 12-volt 50-watt quartz halogen lamp. We measured its ultraviolet output spectrum and the biological toxicity of its radiation by means of its pyrimidine dimer-inducing capability.
At a 1-cm distance, the 254-nm light output of the lamp is 3 x 10(-7) W/cm2/nm. Solar radiation at this wavelength is undetectable on the earth's surface, i.e., less than 10(-12) W/cm2/nm. At 290 nm, the lamp output is approximately 3 x 10(-6) W/cm2/nm, 5,000 times greater than the summertime sun at 1 p.m. at sea level in Kuwait. The UVB and UVA output of the lamp is roughly similar to the solar output under these conditions. We also measured the pyrimidine dimer-forming potential of the lamps relative to the sun for the purpose of estimating the DNA toxicity of the lamps. At a 7-cm distance the lamp induces approximately 3.9 pyrimidine dimers/100,000 bp/min. This is approximately 4 times more rapid than that of the noontime summer sun in Michigan.
We conclude that direct radiation from these lamps can cause damage to human skin, due to their UVC and UVB output. We estimate that the relative risk to keratinocyte DNA in human skin, in vivo, from exposure to the 50-watt halogen lamp at a distance of 7 cm is between 27 and 400% of the noontime summer sun in Michigan.
Dermatology 02/1996; 193(3):207-11. · 2.05 Impact Factor
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ABSTRACT: To determine the stoichiometry of Na+,K+,Cl- cotransport in fetal human nonpigmented ciliary epithelial cells and the effect of forskolin, an adenylyl cyclase activator, on Na+,K+,Cl- cotransport.
86Rb+ as a marker for K+ was used to study ouabain-insensitive, bumetanide-sensitive 86Rb+ uptake in cultured human nonpigmented epithelial (NPE) monolayers.
The dependence of ouabain-insensitive, bumetanide-sensitive 86Rb+ uptake upon Na+, K+, and Cl- concentrations was determined. Maximal uptake was observed at about 12 mM, 20 mM, and 120 mM of these ions, respectively. Analysis by Hill plot suggested that the stoichiometry of Na+,K+,Cl- cotransport is 1:1:2, making this an electroneutral process. Na+,K+,Cl- cotransport was found to be stimulated approximately 1.5- to 2-fold after incubation of cells for 15 minutes with 1 microM forskolin. neither ouabain-sensitive 86Rb+ uptake nor bumetanide-insensitive, ouabain-insensitive uptake was affected. 8-Bromoadenosine cAMP and 8-chlorophenylthio cAMP at 1 mM stimulated Na+,K+,Cl- cotransport approximately 30% to 40%, whereas 1,9 dideoxyforskolin, a non-adenylyl cyclase-activating analogue of forskolin, had little effect. Stimulation of Na+,K+,Cl- cotransport by forskolin was blocked by prior exposure of cells to 10 microM H-89, a protein kinase A inhibitor. Stimulation by forskolin was also observed in the presence of either 1 mM DIDS, 30 microM NPPB, 3 mM DPC, or 5 mM BaCl2, although all four channel blockers inhibited Na+,K+,Cl- cotransport to various degrees.
The data suggest that the human NPE Na+,K+,Cl- cotransporter transports Na+, K+, and Cl- in the ratio of 1:1:2. Activation of adenylyl cyclase stimulates Na+,K+,Cl(-)-cotransport via a mechanism involving protein kinase A. Reduction of Na+,K+,Cl- cotransport by chloride channel blockers raises the possibility that activities of some ion channels can influence the rate of ion influx via Na+,K+,Cl- cotransport.
Investigative Ophthalmology & Visual Science 09/1994; 35(9):3374-83. · 3.60 Impact Factor
