Study of corneal hydration and corneal uptake of 35S and 45Ca in rats after administration of a single dose of estrogens during the first days of postnatal life

Tearful relationships? Sex, hormones, the lacrimal gland, and aqueous-deficient dry eye

Sex and the endocrine system exert a significant influence on the physiology and pathophysiology of the lacrimal gland. The purpose of this article is to briefly review the nature and magnitude of these interactions between sex, hormones and lacrimal tissue, and to address how they may relate to the pathogenesis of aqueous-deficient dry eye. Towards this end, this article has a 3-fold approach: first, to summarize the influence of androgens, estrogens, glucocorticoids, mineralocorticoids, retinoic acid, prolactin, alpha-melanocyte stimulating hormone, adrenocorticotropic hormone, luteinizing hormone, follicle-stimulating hormone, growth hormone, thyroid-stimulating hormone, arginine vasopressin, oxytocin, thyroxine, parathyroid hormone, insulin, glucagon, melatonin, human chorionic gonadotropin and cholecystokinin on the structure and function of the lacrimal gland; second, to discuss the mechanism of action of each hormone on lacrimal tissue; and third, to discuss the clinical relevance of the endocrine-lacrimal gland interrelationship, with a particular focus on each hormone's role (i.e. if relevant) in the development of aqueous-tear deficiency.

Estrogen Stimulation of Proinflammatory Cytokine and Matrix Metalloproteinase Gene Expression in Human Corneal Epithelial Cells

PURPOSE

Researchers have proposed that the secretion of proinflammatory cytokines and matrix metalloproteinases (MMPs) by corneal epithelial cells contributes to the development of ocular surface inflammation in dry eye syndromes. We hypothesize that this cytokine and MMP production is promoted by estrogens, given that dry eye syndromes occur predominantly in women and estrogen therapy is associated with an increase in dry eye signs and symptoms. Moreover, corneal epithelial cells contain estrogen receptors and estrogens are known to influence other aspects of corneal immunity. The purpose of this study was to test our hypothesis.

METHODS

Immortalized human corneal epithelial cells were exposed to vehicle, lipopolysaccharide (LPS), or varying concentrations of 17beta-estradiol. After 6 or 24 hours of hormone treatment, cells were harvested and processed for total RNA isolation, cDNA synthesis, and the analysis of cytokine and MMP mRNA levels by multiplex and real-time PCR methods.

RESULTS

Our results demonstrate that 17beta-estradiol upregulates the expression of proinflammatory cytokine and MMP genes in human corneal epithelial cells. Estrogen administration significantly increased the levels of IL-1beta, IL-6, IL-8, and GM-CSF mRNAs, as well as MMP 2, 7, and 9 mRNAs, compared with those of placebo-treated controls. This estrogen effect was found after 6 and/or 24 hours of hormone treatment. An analogous stimulation of gene expression was observed following cellular exposure to LPS.

CONCLUSIONS

Our findings show that 17beta-estradiol increases the expression of inflammatory genes in human corneal epithelial cells. This hormone action may play an etiologic role in the ocular surface inflammation of dry eye.

Indentification and radioimmunologic estimation of sexual steroid hormones in aqueous humor and vitreous of rabbit eye

The occurrence of testosterone, estrone, and estradiol-17 alpha in aqueous humor and vitreous body of the rabbit eye was demonstrated. The identity of the steroid hormones was confirmed by their chromatographic properties, microreactions, and radiochemically by crystallization to constant specific activity of their labeled acetates. The levels of testosterone and estrogens in rabbit male and female plasma, aqueous, and vitreous were determined by radioimmunologic assay. The concentrations of the steroid hormones in plasma are higher than in aqueous and vitreous. However, testosterone in aqueous circulates in free form and lacks the binding to sexual hormone-binding globulin as in plasma.

In vitro estrone-estradiol-17beta interconversion in the cornea, lens, iris and retina of the rabbit eye

Estrone and estradiol-17beta were incubated with various eye tissues of female rabbits. The interconversion of both estrogenes by the action of 17beta-hydroxysteroid dehydrogenase decreased in the sequence cornea, iris, retina, and lens. In a smaller yield estradiol-17alpha was also formed from estrone. The cornea seems to be an active estrogen-metabolizing tissue. The role of estrogens and progestogens in the tissues of the anterior eye segment is briefly discussed.