L. Alexandra Wickham

Androgens and Dry Eye in Sjögren's Syndromea

ABSTRACT: Sjögrens syndrome is an extremely complex and currently incurable autoimmune disorder, which occurs primarily in females, and is associated with lacrimal gland inflammation, meibomian gland dysfunction, and severe dry eye. We hypothesize that androgen deficiency, which reportedly occurs in primary and secondary Sjögrens syndrome (e.g., systemic lupus erythematosus, rheumatoid arthritis), is a critical etiologic factor in the pathogenesis of dry eye syndromes. We further hypothesize that androgen treatment to the ocular surface will promote both lacrimal and meibomian gland function and alleviate both “aqueous‐deficient” and “evaporative” dry eye. Our results demonstrate that androgens regulate both lacrimal and meibomian gland function, and suggest that topical androgen administration may serve as a safe and effective therapy for the treatment of dry eye in Sjögrens syndrome.

Influence of Gender, Sex Steroid Hormones, and the Hypothalamic-Pituitary Axis on the Structure and Function of the Lacrimal Gland

Throughout the twentieth century it has become increasingly apparent that males and females are different, and not just in terms of physical characteristics. Scientists have discovered that fundamental, gender-related differences exist in almost every cell, tissue and organ of the body, including those associated with respiration, digestion, metabolism, circulation, renal function, and neural and endocrine activity. Indeed, during a recent five year period, at least 8,159 scientific reports were published that addressed the basic and/or clinical influence of gender on health and disease (Table 1).

Influence of gender and the endocrine environment on the distribution of androgen receptors in the lacrimal gland

Androgens are known to regulate both the structure and function of lacrimal tissue in a variety of species. To explore the endocrine basis for this hormone action, the following study was designed to: (1) determine the cellular distribution of androgen receptors in the lacrimal gland; and (2) examine the influence of gender and the endocrine environment on the glandular content of these binding sites. Lacrimal glands were obtained from intact, castrated, hypophysectomized, diabetic or sham-operated male or female adult rats, mice or hamsters, as well as from orchiectomized rats exposed to placebo compounds or physiological levels of testosterone. The cellular location of androgen receptors was evaluated by utilizing an immunoperoxidase protocol, in which a purified rabbit polyclonal antibody to the rat androgen receptor was used as the first antibody. Our findings with lacrimal glands showed that: (1) androgen receptors are located almost exclusively in nuclei of epithelial cells; (2) the cellular distribution or intranuclear density of these binding sites is far more extensive in glands of males, as compared to females; (3) orchiectomy or hypophysectomy, but not sham-surgery or diabetes, lead to a dramatic reduction in the immunocytochemical expression of androgen receptors; and (4) testosterone administration to orchiectomized rats induces a marked increase in androgen receptor content, relative to that in placebo-exposed glands. Our results also reveal that a 10 kb androgen receptor mRNA exists in the rat lacrimal gland. Overall, these findings demonstrate that gender and the endocrine system may significantly influence the distribution of androgen binding sites in rat lacrimal tissue. Moreover, our results show that androgens up-regulate their own lacrimal gland receptors.

Androgen Regulation of the Meibomian Gland

Androgens are known to control the development, differentiation and lipid production of sebaceous glands throughout the body.1 Given that the meibomian gland is a large sebaceous gland,1,2 we hypothesize that androgens may regulate meibomian gland function, enhance the quality and quantity of lipids produced by this tissue and stimulate the formation of the tear film’s lipid layer. In addition, we hypothesize that androgen deficiency (e.g. due to menopause, aging, Sjogren’s syndrome, anti-androgen medications, inherent insensitivity) may lead to meibomian gland dysfunction and consequent ‘evaporative’ dry eye.

Presence and Testosterone Influence on the Levels of Anti- and Pro-Inflammatory Cytokines in Lacrimal Tissues of a Mouse Model of Sjögren’s Syndrome

During the past several years our laboratory has shown that testosterone treatment suppresses the inflammation in, and enhances the functional activity of, lacrimal glands in female mouse models (MRL/Mp-1pr/lpr [MRL/lpr] and NZB/NZW Fl [F1]) of Sjogren’;s syndrome.1–5 This hormone action seems to be a unique, tissue-specific effect, that may be reproduced by therapy with a variety of androgen analogues, but not by the administration of danazol, estradiol, dexamethasone, cyclosporine A, or an experimental, non-androgenic steroid.3,4The precise mechanism(s) underlying this androgen influence is unclear, but we hypothesize that this hormone effect is mediated through an interaction with receptors in epithelial cell nuclei, which then cause an altered expression of proto-oncogenes, apoptotic factors and cytokines in lacrimal tissue, thereby leading to the contraction of immunopathological lesions and an improvement in glandular function.6 In support of this hypothesis, we have found that epithelial cells are the target cells for androgen activity,7 and that androgen exposure elicits significant changes in the levels of apoptotic factor mRNAs in the lacrimal glands of autoimmune mice.8,9

Identification and Hormonal Control of Sex Steroid Receptors in the Eye

During the past several decades, it has become quite evident that androgens, estrogens and progestins may exert a significant influence on the structure and/or function of a variety of ocular tissues, including the lacrimal gland, meibomian gland, conjunctiva, goblet cells, cornea, anterior chamber, lens and/or retina.1,2 The nature of these sex steroid effects appears to involve modulation of such ocular parameters as tissue morphology, gene expression, protein synthesis, lipid production, mucous secretion, aqueous tear output, tear film stability, immunological activity, corneal curvature, aqueous humor outflow and visual acuity.1,2 In addition, these hormones have been proposed as topical therapies for such conditions as dry eye syndromes (both aqueous-deficient and evaporative), corneal wound healing and high intraocular pressure.1,3,4 However, despite these findings, very little information exists concerning the precise target cells for sex steroid action, the specific ocular processes controlled by these hormones, or the mechanisms (e.g. classical vs. non-classical) underlying potential sex steroid-eye interactions.

Effect of sialodacryoadenitis virus exposure on acinar epithelial cells from the rat lacrimal gland

Sialodacryoadenitis virus (SDAV), a RNA coronavirus, induces degenerative, necrotic and atrophic alterations in acinar epithelial cells of the rat lacrimal gland. To begin to explore the underlying mechanism(s) of this viral effect, we sought in the present study to: (1) determine whether SDAV invades and replicates in lacrimal gland acinar cells in vitro and (2) assess whether short-term SDAV challenge interferes with the viability or function of acinar cells in vitro. For comparison we also evaluated the relative infectivity of SDAV in acinar epithelial cells from lacrimal, submandibular and parotid glands, given that salivary tissues are known to be highly susceptible to SDAV infection in vivo. Acinar epithelial cells from lacrimal, submandibular or parotid glands were isolated from male rats, exposed briefly to SDAV or control cell antigen and then cultured for four, eight or twelve days. At experimental termination, SDAV titers in both media and sonicated cell extracts were evaluated by plaque assay titration on mouse L2 cell monolayers. To evaluate functional aspects of lacrimal gland acinar cells, SDAV-infected cells were incubated in the presence or absence of dihydrotestosterone and culture media were analyzed by RIA to measure the extent of the androgen-induced increase in secretory component (SC) production. Our results showed that: (1) SDAV invades and replicates in lacrimal gland acinar cells, Viral challenge resulted in a significant, time-dependent increase in SDAV titers, that were primarily cell-associated and greatly exceeded amounts contained in the original inoculum; (2) SDAV infection did not compromise lacrimal acinar cell viability or prevent the cellular SC response to androgens. Viral presence, though, did often attenuate the magnitude of this hormone action; and (3) SDAV infects salivary acinar cells, but the kinetics and magnitude or viral replication in lacrimal, submandibular and parotid cells showed considerable variations. These findings demonstrate that SDAV invades and replicates in acinar epithelial cells from lacrimal and salivary glands. The resulting release of infectious progeny may play a role in the SDAV-induced pathology of exocrine tissues in vivo.

Gender- and Androgen-Related Impact on the Expression of Proto-Oncogenes and Apoptotic Factors in Lacrimal and Salivary Glands of Mouse Models of Sjögren’s Syndrome

Sjogren’s syndrome, a complex autoimmune disorder that occurs almost exclusively in females, is one of the leading causes of aqueous tear deficiency throughout the world.1 This disease is associated with an extensive lymphocyte accumulation in the lacrimal gland, a destruction and/or dysfunction of epithelial cells, a significant decline in tear secretion and consequent dry eye.2,3 The precise etiology of Sjogren’s syndrome is unknown, but the progression of this disease has been linked to the action of sex steroids,3–5 as well as to the inappropriate expression of cytokines, proto-oncogenes and other apoptotic factors related to programmed cell death.3,6–13

Neural-Endocrine Control of Secretory Component Synthesis by Lacrimal Gland Acinar Cells: Specificity, Temporal Characteristics and Molecular Basis

The ocular surface appears to be protected from bacterial and viral pathogens by polymeric IgA antibodies.1 These antibodies, which are produced by plasma cells in the lacrimal gland, bind to secretory component (SC) in the basolateral membrane of acinar epithelial cells, and are then transported to the apical membrane and secreted into tears.2 Of interest, the lacrimal secretion of sIgA, as well as free SC, appears to be significantly influenced by gender and hormones from the hypothalamic-pituitary-gonadal axis.2 Thus, almost 10 years ago, it was found that the concentrations of free SC and IgA in the tears of male rats were 2 to 5-fold higher than those in tears of female rats. These gender-associated differences in tear SC and IgA were shown to be caused by androgens.2 For example, castration led to a significant reduction in SC levels in tears of males, while having no impact on SC content in tears of females. In addition, administration of testosterone for 4 days to castrated male or female rats significantly increased tear SC levels. These studies showed that exposure of castrated rats to androgens resulted in alterations of lacrimal SC production.2 Moreover, later experiments demonstrated that this androgen control of SC, as well as IgA, is modulated by factors from the hypothalamus and pituitary.2 However, this research did not address whether androgens act directly on lacrimal tissue to change SC or IgA, or indirectly via an androgen-sensitive site, which in tum acts to modulate lacrimal SC and IgA.

Sialodacryoadenitis virus infection of rat lacrimal gland acinar cells.

The secretory immune system of the eye is designed to protect the ocular surface against microbial challenge and infectious disease.1 This immunological role is mediated primarily through secretory IgA (sIgA) antibodies, which are produced by plasma cells in interstitial areas of the lacrimal gland and are selectively transported to tears by secretory component (SC), the polymeric TgA receptor.1 After delivery to the eye’s anterior surface, sIgA antibodies may act to prevent viral internalization, inhibit bacterial colonization, curtail parasitic infestation and attenuate toxin-related damage.2