Identification of androgen receptor protein and 5alpha-reductase mRNA in human ocular tissues.
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BACKGROUND/AIMS: Androgens have been reported to influence the structural organisation, functional activity, and/or pathological features of many ocular tissues. In addition, these hormones have been proposed as a topical therapy for such conditions as dry eye syndromes, corneal wound healing, and high intraocular pressure. To advance our understanding of androgen action in the eye, the purpose of the present study was twofold: firstly, to determine whether tissues of the anterior and posterior segments contain androgen receptor protein, which might make them susceptible to hormone effects following topical application; and, secondly, to examine whether these tissues contain the mRNA for types 1 and/or 2 5alpha-reductase, an enzyme that converts testosterone to the very potent metabolite, dihydrotestosterone. METHODS: Human ocular tissues and cells were obtained and processed for histochemical and molecular biological procedures. Androgen receptor protein was identified by utilising specific immunoperoxidase techniques. The analysis of type 1 and type 2 5alpha-reductase mRNAs was performed by the use of RT-PCR, agarose gel electrophoresis, and DNA sequence analysis. All immunohistochemical evaluations and PCR amplifications included positive and negative controls. RESULTS: These findings show that androgen receptor protein exists in the human lacrimal gland, meibomian gland, cornea, bulbar and forniceal conjunctivae, lens epithelial cells, and retinal pigment epithelial cells. In addition, our results demonstrate that the mRNAs for types 1 and 2 5alpha-reductase occur in the human lacrimal gland, meibomian gland, bulbar conjunctiva, cornea, and RPE cells. CONCLUSION: These combined results indicate that multiple ocular tissues may be target sites for androgen action. (+info)
Regulation of MMP-9 activity in human tear fluid and corneal epithelial culture supernatant.
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PURPOSE: To evaluate human corneal epithelial culture supernatant and tear fluid for the presence of activators and inhibitors of matrix metalloproteinase (MMP)-9, MMP-3, and tissue inhibitor of metalloproteinase (TIMP)-1, respectively, and to evaluate the effect of MMP-3 on the activation of MMP-9 in these specimens. METHODS: Unstimulated tear fluid was collected from patients with ocular rosacea and normal control subjects. Levels of MMP-9, MMP-3, and TIMP-1 were determined by enzyme-linked immunosorbent assay (ELISA) and/or immunoblot analysis. Supernatants from primary human corneal epithelial cultures and human tear fluid were incubated with MMP-3. Cultured epithelial cells and their supernatants were also treated with doxycycline before MMP-3 was added. Gelatin zymography was used to identify activated 82-kDa MMP-9. MMP-9 activity was assessed with a commercial MMP-9 activity assay system. RESULTS: MMP-9 and TIMP-1 were detected at significantly higher concentrations in rosacea-affected than in normal tear fluids. MMP-3 was detected exclusively in the tear fluid of patients with ocular rosacea who had corneal epithelial disease. Treatment of the supernatant and tear fluid with MMP-3 resulted in two bands with molecular weights of 92 kDa and 82 kDa, representing pro-MMP-9 and activated MMP-9, respectively. Doxycycline added to the conditioned media did not affect activation of MMP-9 by MMP-3. However, 24-hour treatment of corneal epithelial cultures with doxycycline resulted in a lower concentration and activity of MMP-9 in their supernatants. CONCLUSIONS: MMP-9 and TIMP-1 are produced by the human corneal epithelium and are present in tear fluid. MMP-3 alone is sufficient to activate MMP-9 on the ocular surface. Doxycycline does not directly inhibit this activation by MMP-3, but it decreases MMP-9 activity when added to corneal epithelial cultures. (+info)
The instilled fluid dynamics and surface chemistry of polymers in the preocular tear film.
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Using slit lamp fluorophotometry it was demonstrated that the rate of drainage of a vehicle placed in the eye increased with increasing volume and that polymer solutions increased the thickness of the precorneal tear film (PTF). By increasing the viscosity of the delivery vehicle, (e.g., a hydroxypropylmethylcellulose polymer solutions), the PTF retention of fluorescein could be increased. The increased retention was shown to be due to an increase in the tear reservoir volume provided by the more viscous solutions. The PTF retention of fluorescein in a polyvinyl alcohol (PVA) vehicle was not as viscosity dependent, although PVA did seem to produce greater initial PTF fluorescence. This suggested that PVA initially produced a thicker PTF. The PTF retention of fluorescein by five commercial solutions did not have any relation to their wetting properties. The only good correlation with fluorescein retention in the PTF measured, seemed to be the ability of different polymer solutions to stabilize a thick layer of water as measured by the spontaneous spreading of polymer molecules at the air/liquid interface on wet glass surfaces. This model was designed to simulate tear film spreading in vivo. The results suggest that different polymer solutions may produce thicker PTF's than normal by virtue of their ability to drag water with them as they spread over the ocular surface with each blink. Mechanisms by which polymer solutions may increase the thickness of the PTF are discussed. (+info)
Androgen influence on the meibomian gland.
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PURPOSE: The hypothesis in the study was that androgens control meibomian gland function, regulate the quality and/or quantity of lipids produced by this tissue, and promote the formation of the tear film's lipid layer. To test this hypothesis, a study was conducted to determine whether androgen receptor protein exists in the epithelial cell nuclei of rat meibomian glands and, in addition, whether androgen deficiency and/or treatment influences the gross morphology, neutral lipid content, and fatty acid profile of the rabbit meibomian gland, as well as the appearance of the tear film lipid layer. METHODS: Rat lids were obtained and processed for immunohistochemistry. Meibomian glands from intact, androgen- and/or placebo-treated rabbits were analyzed by histology, and glandular lipids were evaluated by gas chromatography, high-performance liquid chromatography (HPLC), and mass spectrometry. The rabbit tear film lipid layer was assessed by interferometry. RESULTS: In the current study androgen receptor protein existed within acinar epithelial cell nuclei of rat meibomian glands; androgen deficiency was associated with alterations in the lipid content of the rabbit meibomian gland; 19-nortestosterone treatment modulated the fatty acid profile in the total and neutral lipid fractions of the rabbit meibomian gland; and androgens did not appear to influence the gross morphology of meibomian tissue or to exert a demonstrable effect on the rabbit tear film lipid layer. CONCLUSIONS: The findings show that the meibomian gland is an androgen target organ and that androgens influence the lipid profile within this tissue. However, the extent to which androgens regulate the production of these lipids and whether this action may impact tear film stability remain to be determined. (+info)
The SAFE strategy for the elimination of trachoma by 2020: will it work?
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WHO has recently launched a programme (GET 2020) for the elimination of trachoma, the leading cause of preventable blindness. GET 2020 has adopted the SAFE strategy, a comprehensive set of control measures (Surgery for entropion/trichiasis; Antibiotics for infectious trachoma; Facial cleanliness to reduce transmission; Environmental improvements such as control of disease-spreading flies and access to clean water). The present article reviews the strengths and weaknesses of each component of the strategy. Although significant hurdles remain to be overcome there is every reason to hope that GET 2020 will be successful. (+info)
Polychlorinated biphenyls poisoning in monkey eye.
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Poisoning by polychlorinated biphenyl(s) (PCB) in humans leads to cutaneous and ocular findings. A white, cheeselike secretion issuing from the orifice of the Meibomian gland duct when the eyelid is squeezed is one sign of this intoxiation. In the rhesus monkey, abnormal hyperkeratosis of the ductal epithelium was observed histopathologically. (+info)
15-Lipoxygenase-2 expression in benign and neoplastic sebaceous glands and other cutaneous adnexa.
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15-Lipoxygenase-2 has a limited tissue distribution in epithelial tissues, with mRNA detected in skin, cornea, lung, and prostate. It was originally cloned from human hair rootlets. In this study the distribution of 15-lipoxygenase-2 was characterized in human skin using immunohistochemistry and in situ hybridization. Strong uniform 15-lipoxygenase-2 in situ hybridization (n = 6) and immunostaining (n = 16) were observed in benign cutaneous sebaceous glands, with expression in differentiated secretory cells. Strong 15-lipoxygenase-2 immunostaining was also observed in secretory cells of apocrine and eccrine glands. Variable reduced immunostaining was observed in skin-derived sebaceous neoplasms (n = 8). In the eyelid, Meibomian glands were uniformly negative for 15-lipoxygenase-2 in all cases examined (n = 9), and sebaceous carcinomas apparently derived from Meibomian glands were also negative (n = 12). The mechanisms responsible for differential expression in cutaneous sebaceous vs eyelid Meibomian glands remain to be established. In epidermis, positive immunostaining was observed in the basal cell layer in normal skin, whereas five examined basal cell carcinomas were negative. Thus, the strongest 15-lipoxygenase-2 expression is in the androgen regulated secretory cells of sebaceous, apocrine, and eccrine glands. This compares with the prostate, in which 15-lipoxygenase-2 is expressed in differentiated prostate secretory cells (and reduced in the majority of prostate adenocarcinomas). The product of 15-lipoxygenase-2, 15-hydroxyeicosatetraenoic acid, may be a ligand for the nuclear receptor peroxisome proliferator activated receptor-gamma, which is expressed in sebocytes, and contribute to secretory differentiation in androgen regulated tissues such as prostate and sebaceous glands. (+info)
Targeted disruption of stearoyl-CoA desaturase1 gene in mice causes atrophy of sebaceous and meibomian glands and depletion of wax esters in the eyelid.
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Stearoyl-CoA desaturase (SCD) is a microsomal rate-limiting enzyme in the cellular synthesis of monounsaturated fatty acids (MUFA), mainly oleate (18:1) and palmitoleate (16:1), which are the major MUFA of membrane phospholipids, cholesterol esters and triglycerides. Three well-characterized isoforms of SCD, SCD1, SCD2 and SCD3, exist in mice. To investigate the physiologic functions of SCD1, we generated SCD1 null (SCD1-/-) mice. The skin and eyelid of SCD1-/- mice are deficient in triglycerides and cholesterol esters, and the eyelid also is deficient in wax esters. Furthermore, the eyelid and skin of SCD1-/- mice have higher levels of free cholesterol. SCD1-/- mice develop cutaneous abnormalities and narrow eye fissure with atrophic sebaceous and meibomian glands. Consumption of diets containing high levels of oleate, failed to restore the levels of triglycerides, cholesterol esters and wax esters in SCD1-/- mice to the levels found in the eyelid of wild-type mice. These results reveal a physiologic role of SCD in cholesterol homeostasis as well as in the de novo biosynthesis of cholesterol esters, triglycerides and wax esters required for normal skin and eyelid function. (+info)