Hormonal Support of Lacrimal Function, Primary Lacrimal Deficiency, Autoimmunity, and Peripheral Tolerance in the Lacrimal Gland

Evaluation of dry eye

Dry eye is a common yet complex condition. Intrinsic and extrinsic factors can cause dysfunction of the lids, lacrimal glands, meibomian glands, ocular surface cells, or neural network. These problems would ultimately be expressed at the tear film-ocular surface interface. The manifestations of these problems are experienced as symptoms such as grittiness, discomfort, burning sensation, hyperemia, and secondary epiphora in some cases. Accurate investigation of dry eye is crucial to correct management of the condition. Techniques can be classed according to their investigation of tear production, tear stability, and surface damage (including histological tests). The application, validity, reliability, compatibility, protocols, and indications for these are important. The use of a diagnostic algorithm may lead to more accurate diagnosis and management. The lack of correlation between signs and symptoms seems to favor tear film osmolarity, an objective biomarker, as the best current clue to correct diagnosis.

A review on recent advances in dry eye: Pathogenesis and management

Keratoconjunctivitis sicca, more commonly known as dry eye, is an extremely common and often unrecognized disease. It is the condition in ophthalmology that in its mild grade of severity will affect most of the population at one time or other. Due to a wide variety of presentations and symptoms, it often frustrates the ophthalmologists as well as patients. Due to multifactorial and elusive etiology, it is often challenging to treat dry eye. Ocular surface disorders are also clinically important to treat especially in terms of visual acuity. Xero-dacryology is therefore becoming a very important branch of ophthalmology. Recent studies have given insight into the inflammatory etiology of dry eye. The conventional and main approach to the treatment of dry eye is providing lubricating eye drops or tear substitutes. However, the newer treatment approach is to target the underlying cause of dry eye instead of conventional symptomatic relief. In light of the above knowledge, the present article focuses on newer theories on pathogenesis of dry eye and their impact on dry eye management. METHOD OF LITERATURE SEARCH: A systematic literature review was performed using PubMed databases in two steps. The first step was oriented to articles published for dry eye. The second step was focused on the role of inflammation and anti-inflammatory therapy for dry eye. The search strategy was not limited by year of publication. A manual literature search was also undertaken from authentic reference books on ocular surface disease.

Immunohistochemical detection of estrogen and progesterone receptors in the human lacrimal gland

The nature and extent of estrogen and progesterone action on the lacrimal gland is not known, and neither are the targets for their action. Immunohistochemical detection of estrogen and progesterone receptors in the human lacrimal glands in both sexes in different age groups was performed in this study. Twenty human lacrimal glands from autopsies were analyzed by the immunohistochemical method of cell counting and the ?? test. Estrogen and progesterone receptors were detected in the lacrimal glands of both sexes with significantly higher total and average cell counts in females (p<0,001). Estrogen and progesterone receptors are present in human lacrimal glands with age and gender dependent expression.

Adeno-associated virus-mediated IL-10 gene transfer suppresses lacrimal gland immunopathology in a rabbit model of autoimmune dacryoadenitis

PURPOSE

To evaluate the effect of adeno-associated virus (AAV) vector-mediated viral (v)IL-10 gene expression on lacrimal gland (LG) immunopathology and ocular surface disease in a rabbit model of induced autoimmune dacryoadenitis (ID).

METHODS

Autologous peripheral blood lymphocytes, activated in a mixed-cell reaction when cocultured with purified rabbit lacrimal epithelial cells, induce a Sjögren's-like autoimmune dacryoadenitis when injected directly back into the donor animal's inferior LG. Four weeks after disease induction, AAV vector expressing the vIL-10 gene under control of a tetracycline-inducible promoter was injected into the inferior LG of the treatment group (ID/Rx), and doxycycline was fed orally to induce transgene expression. The ID group serving as control also received doxycycline. All LGs were removed 16 weeks after disease induction.

RESULTS

Clinical symptoms showed overall improvement in the ID/Rx group compared with the ID group. Histopathologic examination of the ID group's LG revealed scattered large lymphocytic foci and areas of altered or distorted acini, whereas the ID/Rx group had scattered small lymphocytic foci. The number of CD18(+) cells was almost fivefold lower in the ID/Rx group than in the ID group. Although the total number of RTLA(+) cells did not differ between the groups, the CD4/CD8 ratio was 16-fold smaller in the ID/Rx group.

CONCLUSIONS

Animals with experimentally induced autoimmune dacryoadenitis appeared to benefit from AAV-mediated vIL-10 gene transfer therapy. Quantitative immunohistochemical analysis suggested that the therapy might not have been simply immunosuppressive but rather supported the induction of CD8(+) regulatory cells.

Autoimmune dacryoadenitis and keratoconjunctivitis induced in rabbits by subcutaneous injection of autologous lymphocytes activated ex vivo against lacrimal antigens

Autologous peripheral blood lymphocytes (PBL), activated in a mixed cell reaction when co-cultured with purified rabbit lacrimal epithelial cells, are known to induce a Sjögren's-like autoimmune dacryoadenitis and keratoconjunctivitis when injected directly back into the donor animal's inferior lacrimal gland (LG). This study shows that autoreactive lymphocytes injected subcutaneously in a site away from the LG is capable of inducing an autoimmune disease in a rabbit. Induced disease (ID) develops more slowly, taking 4weeks as compared to 2weeks in the direct injection model. Initially, both clinical symptoms and histopathology are less pronounced than in the direct injection ID model, but later the immunocytochemistry shows the same CD4+/CD8+ ratio of 4:1 for both injection methods. The finding that lymphocytes activated against lacrimal antigens can travel or home from the injection site back to the inferior and superior LG, as well as the conjunctiva, suggests that these anatomical sites may have common epitopes that induce pathogenic CD4+ T cells that produce a Sjögren's-like syndrome.

Traffic of endogenous, transduced, and endocytosed prolactin in rabbit lacrimal acinar cells

The rabbit lacrimal gland undergoes an immunophysiological transformation during pregnancy, reminiscent of that of the mammary gland as it prepares to deliver secretory IgA into the nascent fluid product. The contents of TGF-beta and prolactin (PRL) within ductal epithelial cells increase, and their primary localizations shift from the apical to the basal cytoplasm, suggesting a transformation from exocrine to paracrine secretion. Studies with ex vivo acinar cell models demonstrated that elevated PRL suppresses traffic of secretory proteins into the regulated exocrine apparatus and directs them into a novel, induced, regulated paracrine apparatus [Wang, Y., Chiu, C.T., Nakamura, T., Walker, A.M., Petridou, B., Trousdale M.D., Hamm-Alvarez S.F., Schechter J.E., Mircheff A.K., 2007. Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells. Am. J. Physiol. Endocrinol. Metab. 292, E1122-E1134]. However, it was not clear whether PRL itself entered the induced paracrine apparatus. In the present study, confocal immunofluorescence microscopy revealed that natively expressed PRL and over-expressed PRL co-localized with PRL receptors (PRLR); rab11, a marker for the recycling endosome; gamma-adaptin, a marker for the Golgi complex and trans-Golgi network; and rab7, a marker for the autophagic lysosomal apparatus. Natively expressed, over-expressed, and endocytosed PRL also co-localized with rab4 and rab5A, markers for the early endosome, and with rab3D, a marker for regulated exocrine secretory vesicles. Endocytosed PRL was stored in intact form and released in response to stimulation with carbachol. Subcellular fractionation analysis detected relative excesses of PRL over PRLR in fractions that contained fragments of the recycling endosome and fractions that contained both secretory vesicle fragments and prelysosomal and autolysosomal fragments. EM-gold microscopy demonstrated PRL within small vesicles, consistent with endosomes or secondary lysosomes, and in large vesicles, consistent with regulated secretory vesicles. The secretory vesicles were preponderantly localized in the apical cytoplasm of control cells, and in the basal cytoplasm of PRL over-expressing cells. These results indicate that when lacrimal epithelial cells synthesize PRL, and when they endocytose it from their ambient medium, they traffic it both into the endosomes that constitute the constitutive transcytotic paracrine apparatus and also into regulated secretory vesicles, which are associated with the exocrine apparatus at low PRL levels and with the induced paracrine apparatus at high PRL levels.

Corneal topographic changes in premenopausal and postmenopausal women

BACKGROUND

To asses the effect of menopause on the corneal curvature changes using corneal computerized videokeratography (CVK) in premenopausal and postmenopausal healthy women.

METHODS

Thirty-six postmenopausal women with mean ages of 49.2 (range 39 to 57) were enrolled in this randomized, prospective study, comparing with 26 healthy controls with mean ages of 38.5 +/- 4.9 (range 32 to 49). Subjects were determined to be postmenopausal, by the Gynecology and Obstetrics Department, based on blood Follicular Stimulating Hormone (FSH), Luteinizing Hormone (LH), Estradiol, Progesterone levels and clinical complaints. Complete ophthalmic examination and CVK using Haag-Streit System was performed in both premenopausal and postmenopausal women.

RESULTS

Mean horizontal curvature and vertical curvature of central corneal power in premenopausal women were 43.5 +/- 1.25 Diopter (D), and 44.1 +/- 1.53 D. Mean horizontal curvature and vertical curvature of central corneal power in postmenopausal women were 43.9 +/- 1.4 D, and 44.6 +/- 1.3 D. The mean keratometric astigmatisms of premenopausal and postmenopausal women were 0.81 +/- 0.57 D (4-179 degrees), 0.74 degrees +/- 0.5 D (1-180 degrees) respectively. No significant corneal curvature changes were detected between premenopausal and postmenopausal groups (P > 0.05). On the other hand, we only found negative but significant correlation between horizontal corneal curvature and estrogen level of postmenopausal women (r = -0.346, p = 0.038).

CONCLUSION

Menopause is physiologic process and may also affect corneal topographic changes. In postmenopausal women, corneal steeping was observed minimally compared to premenopausal women. The results suggest that changes in estrogen level of women with menopause are associated with slightly alteration of horizontal curvature of cornea.

Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells

During pregnancy, lymphocytes infiltrating the rabbit lacrimal gland disperse to the interacinar space from their normal focal concentrations, basal fluid secretion decreases, pilocarpine-induced fluid secretion increases, and stimulated fluid protein concentration decreases. Ductal epithelial cell prolactin (PRL) content increases and redistributes from the apical to the basal-lateral cytoplasm. A replication-incompetent adenovirus vector for rabbit PRL (AdPRL) was used to test the hypothesis that increased intracrine/autocrine PRL signaling alters secretory protein traffic in an ex vivo lacrimal acinar cell model. AdPRL had no discernable influence on microtubules or actin microfilaments or their responses to carbachol (CCh). Endogenous and transduced PRLs exhibited similar, nonpolarized, punctate distributions. Cells secreted PRL consititutively and at increased rates in response to CCh. In contrast, constitutive secretion of beta-hexosaminidase was negligible, suggesting that the constitutive pathway for PRL is relatively inaccessible to typical secretory proteins. AdPRL had no significant effect on total secretion of beta-hexosaminidase or syncollin-green fluorescent protein (GFP), a chimeric secretory protein construct. However, it reversed the polarized distributions of vesicles containing rab3D and syncollin-GFP. Live-cell imaging indicated that AdPRL redirected CCh-dependent syncollin-GFP exocytosis from the apical plasma membrane to the basal-lateral membrane. Elevated concentrations of exogenous rabbit PRL in the ambient medium elicited similar changes. These observations suggest that elevated PRL, as occurs in the physiological hyperprolactinemia of pregnancy, induces lacrimal epithelial cells to express a mixed exocrine/endocrine phenotype that secretes fluid to the acinus-duct lumen but secretes proteins to the underlying tissue space. This phenotype may contribute to the pregnancy-associated immunoarchitecture.

Mucosal Immunity and Self-Tolerance in the Ocular Surface System

This paper articulates a new working hypothesis that explains many of the pathophysiological conditions described under the common rubric "dry eye" as altered states of mucosal immune regulation. A central principle of mucosal immune physiology is that the parenchymal tissues at the effector sites, i.e., the sites at which secretory antibodies are produced, maintain local signaling milieus that support differentiation of IgA+ plasmablasts and survival of IgA+ plasmacytes. These local signaling milieus also support robust regulatory networks that maintain tolerance to commensual microbes, benign antigens, and parenchymal autoantigens. The regulatory networks are mediated by cycles of interactions between successive generations of dendritic cells, which normally mature with tolerogenic functions, and regulatory T cells, which normally reinforce the system's ability to generate new tolerogenic dendritic cells. The systemic endocrine environment controls expression of the local signaling milieu in the mammary gland and in the prostate and male urethral glands. Emerging evidence indicates that the local signaling milieu in the lacrimal gland also is determined, in part, by the systemic endocrine environment. This working hypothesis suggests explanations for the excess incidence of Sjogren syndrome among women and for the mechanisms of several different immunophysiological states in addition to Sjogren syndrome that, like Sjogren syndrome, are associated with the classical symptoms and signs of dry eye. It also comprises a promising rationale for specific new approaches to therapy.

Combined esterified estrogen and methyltestosterone treatment for dry eye syndrome in postmenopausal women

PURPOSE

To determine whether systemic replacement with combined esterified estrogen (EE) and methyltestosterone (MT) (EE + MT) would reduce symptoms and promote clinical improvement in postmenopausal women with dry eye syndrome (DES).

DESIGN

Retrospective, noncomparative, interventional case series.

METHODS

Investigators reviewed the charts of 11 postmenopausal women treated within the last 3 years with EE + MT.

RESULTS

The mean patient age was 65.2 years (standard deviation [SD] 11.4, range 48-84 years). The mean treatment duration was 12.2 months (SD 6.2 months, range 4-24 months). Ten (91%) of 11 patients reported improvement in dry eye symptoms while receiving treatment. For these 10, relief occurred after an average of 4.1 months of treatment (SD 3.2, range, 1-9 months).

CONCLUSIONS

Treatment with EE + MT may be efficacious for DES of various etiologies. A randomized placebo-controlled trial is planned to further evaluate these encouraging findings.

Accumulation of catalytically active proteases in lacrimal gland acinar cell endosomes during chronic ex vivo muscarinic receptor stimulation

Chronic muscarinic stimulation induces functional quiescence (Scand J Immunol 2003;58:550-65) and alters the traffic of immature cathepsin B (Exp Eye Res 2004;79:665-75) in lacrimal acinar cells. To test whether active proteases aberrantly accumulate in the endosomes, cell samples were cultured 20 h with and without 10-microm carbachol (CCh), incubated with [125I]-bovine serum albumin and then lysed and analysed by subcellular fractionation. CCh decreased total cysteine protease and cathepsin S activities in the isolated lysosome, redistributing them to early endocytic and biosynthetic compartments. CCh decreased [125I] accumulation in all compartments of cells loaded in the absence of protease inhibitors; the cysteine protease inhibitor, leupeptin, prevented the endosomal decrease but not the lysosomal decrease. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography demonstrated [125I]-labelled proteolytic products in endomembrane compartments of both control and CCh-stimulated cells, even in the presence of leupeptin, but analysis indicated that CCh increased the amount in endosomes. Two-dimensional fractionation analyses suggest that the CCh-induced redistributions result from blocks in traffic to the late endosome from both the early endosome and the trans-Golgi network. Therefore, we conjecture that chronic muscarinic acetylcholine receptor stimulation leads to aberrant proteolytic processing of autoantigens in endosomes, from whence previously cryptic epitopes may be secreted to the underlying interstitial space.

Influence des hormones sur le film lacrymal

Tear film quality depends on fine regulatory mechanisms affected by neuronal and hormonal influences. Indeed, receptors for androgens, estrogens, progesterone and prolactin have been identified in several ocular tissues in the rat, rabbit and in humans. The eye is thus a target organ for sex hormones, particularly the androgens. These hormones regulate the immune system, the morphology and secretory functions of lacrimal glands and the functioning of Meibomian glands. The influence of hormone replacement therapy in menopausal women remains unclear, as some authors support the idea that they improve the quality and the volume of tear film, whereas others have shown that they increase the risk of dry eye. Finally, knowledge of the interactions between the hormones that influence the lacrimal glands is essential for the understanding of the regulation of lacrimal gland function. However, the data presently available strongly suggest that optimal bioavailable androgen levels are essential for normal lacrimal gland function and that prolactin and estrogens also play important roles in providing a hormonal milieu that contributes to normal lacrimal gland function.

Role of the microtubule cytoskeleton in traffic of EGF through the lacrimal acinar cell endomembrane network

We have previously documented a novel biphasic traffic pattern for epidermal growth factor (EGF) in the acinar epithelial cell of the lacrimal gland. Different from the typical paradigm observed in many other cell types, EGF initially accumulates in the acinar basal-lateral recycling endosome, then is re-directed to the prelysosomes and lysosomes and degraded. While the cellular content of intact EGF decreases by 40% between 20 and 120 m of continuous incubation at 37 degrees C, the EGF receptor (EGFR) content decreases only modestly [J. Cell Physiol. 199 (2004) 108]. The purpose of the present study was to investigate the role of the microtubule cytoskeleton in this traffic. Primary cultured rabbit lacrimocytes were incubated with [(125)I]-EGF, lysed, and analyzed by subcellular fractionation on sorbitol density gradients. Nocodazole treatment appeared to slightly decrease the initial uptake rate but to have no significant effect on the total amount of [(125)I] accumulation. However, it enhanced accumulation of [(125)I]-EGF and EGFR in the basal-lateral recycling endosome, and it enhanced accumulation of prepro- and pro- cathepsin B in fractions containing late endosomes and prelysosomes. Nocodazole permitted the time-dependent release of [(125)I]-EGF from the recycling endosome, but it partially inhibited [(125)I]-EGF degradation and decreased accumulation of [(125)I]-labeled degradation products in the lysosome. The microtubule-based molecular motors, cytoplasmic dynein and kinesin, were localized in compartments containing the late endosomes, prelysosomes, and lysosomes, consistent with the suggestion that microtubule-based molecular motors play important roles in traffic within the lysosomal pathway. Confocal fluorescence microscopy imaging of FITC-EGF substantiated the effects observed in biochemical studies by demonstrating that nocodazole increased accumulation in a peripheral compartment and decreased traffic to a perinuclear compartment. These data suggest that initial accumulation in the basal-lateral recycling endosome and subsequent release from the recycling endosome to the late endosomes and prelysosome are not microtubule-dependent. On the other hand, microtubule-based motors are more critical for traffic from the prelysosome to the lysosome.

Microarray analysis of the rat lacrimal gland following the loss of parasympathetic control of secretion

Previous studies showed that loss of muscarinic parasympathetic input to the lacrimal gland (LG) leads to a dramatic reduction in tear secretion and profound changes to LG structure. In this study, we used DNA microarrays to examine the regulation of the gene expression of the genes for secretory function and organization of the LG. Long-Evans rats anesthetized with a mixture of ketamine/xylazine (80:10 mg/kg) underwent unilateral sectioning of the greater superficial petrosal nerve, the input to the pterygopalatine ganglion. After 7 days, tear secretion was measured, the animals were killed, and structural changes in the LG were examined by light microscopy. Total RNA from control and experimental LGs (n = 5) was used for DNA microarray analysis employing the U34A GeneChip. Three statistical algorithms (detection, change call, and signal log ratio) were used to determine differential gene expression using the Microarray Suite (5.0) and Data Mining Tools (3.0). Tear secretion was significantly reduced and corneal ulcers developed in all experimental eyes. Light microscopy showed breakdown of the acinar structure of the LG. DNA microarray analysis showed downregulation of genes associated with the endoplasmic reticulum and Golgi, including genes involved in protein folding and processing. Conversely, transcripts for cytoskeleton and extracellular matrix components, inflammation, and apoptosis were upregulated. The number of significantly upregulated genes (116) was substantially greater than the number of downregulated genes (49). Removal of the main secretory input to the rat LG resulted in clinical symptoms associated with severe dry eye. Components of the secretory pathway were negatively affected, and the increase in cell proliferation and inflammation may lead to loss of organization in the parasympathectomized lacrimal gland.

Klassifikation der Erkrankungen der Augenoberfl�che

The ocular surface consists of the lid margin, conjunctiva and cornea which together with the tear system represent a functional entity. The diagnosis of ocular surface disease can be very difficult due to the similarity of various disease entities. The classification should be made on the pathological and pathophysiological characteristics of ocular surface disease. The first part of the classification comprises diseases of the lid margin, the tear system as well as diseases of the conjunctiva. Both the clinical presentation as well as the underlying pathophysiological and pathological characteristics of the most important ocular surface diseases are reviewed.

Tumor necrosis factor inhibitor gene expression suppresses lacrimal gland immunopathology in a rabbit model of autoimmune dacryoadenitis

PURPOSE

To evaluate the effect of tumor necrosis factor (TNF) inhibitor protein on lacrimal gland immunopathology and ocular surface disease resulting from induced dacryoadenitis.

METHODS

Autoimmune dacryoadenitis was induced in rabbits by injecting the lacrimal glands with peripheral blood lymphocytes (PBLs) activated by 5 days of coculture with autologous acinar cells in a mixed cell reaction. In the treated group, an adenoviral vector carrying the TNF inhibitor gene (AdTNFRp55-Ig) was concurrently injected with AMCR-PBL. Tear production was monitored by Schirmer test, and tears were collected for detection of TNF-inhibitor protein. Frozen sections of the glands were immunostained for expression of CD4, CD8, rabbit thymic lymphocyte antigen (RTLA), and CD18. Histological sections of lacrimal glands were examined using the TUNEL technique to monitor apoptosis.

RESULTS

Soluble TNF-inhibitor protein was detected by ELISA in tears, with titers at a maximum on day 3, declining by day 7, and undetectable by day 14. Tear production declined in the induced dacryoadenitis group but did not change when glands had been treated with AdTNFRp55-Ig simultaneously with disease induction. Tear break-up time and rose bengal staining properties were not altered by treatment. Fourteen days after the glands were injected with activated PBLs, focal mononuclear cell infiltrates were observed around ducts and venules, some of which assumed the high endothelial phenotype, and between acini. Immune cells in the infiltrates stained positive for CD4, RTLA, and CD18. Glands that received AdTNFRp55-Ig concurrently with activated PBLs had decreased numbers of CD4 cells, CD18 cells, RTLA, and apoptotic cells.

CONCLUSIONS

In vivo transduction of the lacrimal gland with AdTNFRIp55-Ig resulted in transient expression in the gland and the appearance of TNF-inhibitor protein in tears. The presence of soluble TNF-inhibitor protein partially suppressed the appearance of Sjögren's syndrome-like features of reduced tear production and the immunohistopathology associated with induced autoimmune dacryoadenitis but not tear break-up time and ocular surface disease. This may reflect immunoregulation in the lacrimal gland but not in the conjunctiva.

Diverse perturbations may alter the lacrimal acinar cell autoantigenic spectra

Lacrimal gland acinar cell autoantigens in Sjögren's syndrome include both intracellular proteins and plasma membrane proteins, to which the immune system normally must be tolerant. Attention has largely focused on the roles apoptotic cell death may play in exposing sequestered autoantigens and novel surface epitopes. We hypothesize that perturbations of ongoing membrane traffic in intact, functioning cells may also increase autoantigen exposure. We review the vesicular traffic between acinar cell basal-lateral plasma membranes (blm) and endomembrane compartments, then describe experiments in which isolated acinar cells were stimulated with epidermal growth factor (EGF), lysed, and analyzed by sorbitol gradient centrifugation. Whereas the cholinergic agonist, carbachol, impairs traffic from the trans-Golgi network to prelysosomes, causing Golgi, secretory, and lysosomal proteins to reflux into domains of the trans-Golgi network that communicate with the blm and to accumulate in the blm, EGF specifically causes a 2.6-fold (P < 0.05) increase in the beta-hexosaminidase content of the blm fraction, apparently by impairing traffic from early endosomes to prelysosome. We, therefore, suggest that a variety of physiologic stimuli may alter the spectra of autoantigens acinar cells secrete to the interstitium, express in their blm, and present via MHC Class II molecules after proteolytic processing.

Growth of purified lacrimal acinar cells in Matrigel raft cultures

The objective of this study was to develop a tissue culture system which closely mimics the in situ lacrimal gland for improved study of lacrimal acinar cell physiology. Highly purified preparations of lacrimal acinar cells from adult female New Zealand White rabbits were isolated and grown in suspension culture in the form of Matrigel 'rafts', i.e., aggregates of acinar cells enclosed within a Matrigel coating. The rafts were seeded onto Matrigel-coated culture plates and their growth was followed for up to 28 days. Immunohistochemistry was used to demonstrate the cellular sites of prolactin (PRL), epidermal growth factor (EGF), basic fibroblast growth factor (FGF-2), secretory component (SC) and major histocompatibility complex class-II molecules (MHC-II) within the acinar cells. By 3 days the cultures contained numerous, well-formed acini enclosed within the Matrigel. The acinar epithelial cells demonstrated histotypic polarity, with large, pale-staining, secretory granules aggregated adjacent to the lumen, and exocytotic release of secretory material into the lumen. From 5-10 days the pale-staining secretory granules decreased in number, while the lumenal contents of the acini increased in staining density. Throughout the culturing period as the pale-staining, secretory granules decreased in number, smaller more densely stained, secretory granules increased in number. The number of cells and size of acinar clusters increased steadily throughout the culturing period, and acini frequently achieved dimensions in excess of 0.5 mm. Increases in the size of acinar clusters were often accompanied by an increase in the size of the lumen. Frequently the lumen and its contents bulged asymmetrically towards one edge of the acinus. Immunhistochemistry demonstrated PRL and EGF within the lumens and within the apical cytoplasm of the acinar cells. Acini were strongly immunopositive for SC throughout the 28 day culture period, whereas immunopositivity for MHC-II molecules was strong initially, but diminished dramatically by 21 days. Immunostaining for FGF-2 was most intense on days 1 and 3, with staining throughout the cytoplasm, but became progressively more localized to the periphery of the acini as the culture period lengthened. In cultures of 1-28 days duration, Western blots of cell lysates demonstrated a major band (approximately 40 kDa) for PRL in 3-28 day preparations; a major band (approximately 80 kDa) for SC in 3 day and 7 day preparations that decreased in intensity in 14-28 day preparations; and a major band (approximately 23 kDa) for MHC-II protein in 1-21 day preparations that decreased in intensity in 28 day preparations. Lysosomes increased in number with time in culture, becoming a dominant cytoplasmic feature in 21 and 28 day cultures. Carbachol stimulation of 4 day rafts resulted in increased release of beta-hexosaminidase and SC from the rafts. The authors conclude that Matrigel rafts containing purified lacrimal gland acinar cells offer a highly advantageous system for study of lacrimal acinar cell function and one that correlates well with the in situ gland.

Heterotrimeric GTP-binding proteins in the lacrimal acinar cell endomembrane system

Secretagogues accelerate traffic in the lysosomal and basal-lateral pathways, as well as in the regulated apical secretory pathway, of lacrimal acinar cells. It has been proposed that alterations of protein segregation in compartments where these traffic pathways intersect may influence autoimmune responses. Heterotrimeric GTP-binding proteins couple secretagogue receptor ligand binding to activation of intracellular signaling cascades, but they are also suggested to participate in endomembrane traffic phenomena. Distributions of G(o), G(i3), G(q), G(11), and two G(s)isoforms were mapped in reconstituted lacrimal acini by confocal immunofluorescence microscopy and in lysates of the reconstituted acini by analytical subcellular fractionation. All G proteins examined were detected at low levels in isolated compartments (blm(i,j)) believed to represent the basal-lateral plasma membrane. G(i3), G(11), and the G(s)isoforms were concentrated in a series of isolated compartments believed to be related to domains of a basal-lateral endosome with sorting and recycling functions (ble-s/r(i,j,k)), a distinct endosomal compartment with basal-lateral membrane-like composition (e-blml), and domains of the trans-Golgi network believed to be involved in traffic to and from the basal-lateral membrane (tgn-blmr). G(o)and G(q)were concentrated in compartments believed to represent a mixture of immature and mature secretory vesicle membranes (isvm and svm) and domains of the trans-Golgi network compartment believed to mediate traffic to secretory vesicles (tgn-svr) and to pre-lysosomes (tgn-lr). Confocal fluorescence microscopy confirmed the presence of both basal-lateral membrane and intracellular pools of the G proteins. Stimulation with 10 microM carbachol for 20min caused a component of the G(o)to redistribute away from the isvm+svm; components of the G(i3), G(q), and G(s)to redistribute away from the tgn-svr+tgn-lr; and a component of the G(i3)to redistribute away from the ble-blml+tgn-blmr. Thus, these proteins may participate in endomembrane traffic steps activated by cholinergic stimulation in addition to playing their classical roles in plasma membrane signal transduction.

Distribution of growth factors and immune cells are altered in the lacrimal gland during pregnancy and lactation

We have undertaken a series of studies to elucidate the roles of growth factors (FGF-2, EGF, TGF-beta1) and prolactin (PRL) in lacrimal gland function during pregnancy and lactation, and to better understand the status of the immune system within the lacrimal gland during those physiological states. In this initial study, lacrimal glands of pregnant (d15, d29), lactating (9d, 22d), and adult female control rabbits, were evaluated by immunohistochemistry, Western blotting and image analysis. In control rabbits EGF, TGF-beta1, and PRL, were immunolocalized primarily in the apical cytoplasm of intralobular ductal epithelial cells, and acini demonstrated a basement membrane-associated immunopositivity for TGF-beta1. FGF-2 immunolocalized in myoepithelial cells in the basal ductal epithelium and complexed to the basement membrane enclosing ducts and acini. Cells immunopositive for immune cell markers (RTLA and CD18) were apparent primarily around interlobular ducts. In d29 pregnant rabbits immunopositivity for EGF and TGF-beta1 was increased within intralobular ducts, both apically and basally, and within some interlobular ductal epithelial cells. Immunopositivity for PRL was strongest in d29 pregnant rabbits within the apical and basal cytoplasm of intralobular ductal epithelial cells. Immunopositivity for FGF-2 in myoepithelial cells was strong in d15 and d29 pregnant rabbits, although basement membrane-associated immunopositivity around acini was often decreased. Immunostaining for EGF and TGF-beta1 in lactating rabbits was similar to that in d29 pregnant rabbits, although basement membrane-associated immunopositivity around acini was more comparable to controls. By 22d lactation immunopositivity for FGF-2 closely resembled that in controls. Image analysis of pregnant and lactating rabbits demonstrated that cells immunopositive for RTLA and CD18 were less abundant around ducts and more abundant between acini, although in 22d lactating rabbits the size of periductal foci was increased to nearly that of controls. Western blots correlated well with the immunohistochemistry. Our findings demonstrate that pregnancy and lactation are accompanied by a shift in the distributions of growth factors and PRL, suggestive of increased release both apically into the lacrimal fluid and basally into the interstitium. Additional shifts in the distributions of cells of the immune system from periductal foci to interacinar sites suggest that there is a recruitment of immune cells away from ducts and toward the connective tissue interstitium surrounding the acini, possibly as part of a heightened state of immune readiness during pregnancy and lactation.

Lacrimal gland epithelial cells stimulate proliferation in autologous lymphocyte preparations

Autoimmune dacryoadenitis is a frequent cause of lacrimal insufficiency. In order to test hypotheses regarding mechanisms that can trigger this syndrome, we developed a method to obtain a preparation of rabbit lacrimal gland epithelial cells essentially free of immune-system cells. The method relies on controlled digestion to disperse lacrimal acini, and recovers acini by filtration through various sizes of nylon mesh. Purity and integrity of the preparation were established qualitatively using light and electron microscopy. Contamination by immune-system cells was quantitated by immunohistochemistry using anti-CD18, and -RTLA (rabbit thymic lymphocyte antigen) antibodies. The novel method produced preparations of highly-purified lacrimal gland epithelial cells (pLGEC) with expected morphological characteristics with less than 1.5% of the cells staining for CD18 or RTLA. The method also yielded preparations of lacrimal gland interstitial cells (LGIC) enriched for lymphocytes; in these preparations either CD18 or RTLA were detected on nearly 10% of the cells. pLGEC promoted proliferation in preparations of autologous splenic lymphocytes (SPL) that was blocked by anti-MHC class II but not anti-MHC class I antibodies. This observation, combined with the apparent requirement that pLGEC must contact the autologous lymphocyte preparation to promote proliferation, supports the hypothesis the proliferation arises from antigen-presentation via MHC class II by pLGEC.

Proliferation of lacrimal gland acinar cells in primary culture. Stimulation by extracellular matrix, EGF, and DHT

The study of lacrimal dysfunction and insufficiency, a major cause of dry eye, has been hampered by the inability to induce the proliferation of primary lacrimal acinar cells in vitro. Particularly in light of observations that androgens are able to support the overall size and functional status of the lacrimal glands as well as certain specific lacrimal functions, an in vitro culture system that is permissive for cell proliferation would be most beneficial to study the molecular basis for these processes. Here, we report on the successful establishment of such a system. Using a culture system containing Hepato Stim Medium and Matrigel, we were able to induce the efficient proliferation of primary rabbit lacrimal gland acinar cells with epidermal growth factor (EGF) and dihydrotestosterone (DHT). The generation of this in vitro cell culture system should greatly facilitate study of the regulation of acinar cell function at the molecular and cellular levels.

Stimulation with carbachol alters endomembrane distribution and plasma membrane expression of intracellular proteins in lacrimal acinar cells

The events that lead to Sjögren's autoimmune processes in the lacrimal gland remain poorly understood. The acinar cell's responses to acute cholinergic stimulation include release of secretory products across the apical plasma membrane (apm) and a number of processes related to traffic between endomembrane compartments and the basal-lateral plasma membranes (blm), such as recruitment of Na, K-ATPase, accelerated recycling, and accelerated transcytosis of secretory IgA. We tested the hypothesis that stimulation-induced acceleration of endomembrane traffic is accompanied by changes in compartmentation and increased blm expression of proteins that are normally sequestered in endomembrane compartments. Isolated rabbit lacrimal gland acinar cells were cultured in serum-free media for 2 days. After harvesting, cells were incubated with or without 10 microm carbachol at 37 degrees C for 20 min. Cells were lysed, and lysates were analysed by isopycnic centrifugation on sorbitol gradients. Galactosyltransferase catalytic activity was determined biochemically. Different forms of cathepsin B were detected by Western blotting. Carbachol stimulation decreased the contents of beta-hexosaminidase, alpha-glucosidase, and protein in secretory vesicles and increased them in specific compartments of the trans-Golgi network (ld-tgns). Stimulation also caused levels of galactosyltransferase, preprocathepsin B, and procathepsin B to increase two- to three-fold in the blm as well as increasing in the ld-tgns. Other changes caused by sustained stimulation included: (a) increased levels of protein and procathepsin B in compartments of the lysosomal pathway; (b) changes in the distributions of Rab5 within the endomembrane system; (c) changes in the distribution of Rab6 within the Golgi complex and tgn; (d) decreased expression of acid phosphatase and MHC class II molecules in the blm; and (e) decreased total content of Na,K-ATPase, which appeared to have been selectively depleted from the tgn and blmre. We propose that the normal compartmentation of certain proteins may allow them to remain cryptic, such that they are not subject to central tolerance. Stimulation-induced increases in the levels expressed at the blm or secreted to the interstitium may, therefore, contribute to initiation of local autoimmune responses.

MHC class II molecules, cathepsins, and La/SSB proteins in lacrimal acinar cell endomembranes

Sjögren's syndrome is a chronic autoimmune disease affecting the lacrimal glands and other epithelia. It has been suggested that acinar cells of the lacrimal glands provoke local autoimmune responses, leading to Sjögren's syndrome when they begin expressing major histocompatibility complex (MHC) class II molecules. We used isopycnic centrifugation and phase partitioning to resolve compartments that participate in traffic between the basolateral membranes and the endomembrane system to test the hypothesis that MHC class II molecules enter compartments that contain potential autoantigens, i.e., La/SSB, and enzymes capable of proteolytically processing autoantigen, i.e., cathepsins B and D. A series of compartments identified as secretory vesicle membranes, prelysosomes, and microdomains of the trans-Golgi network involved in traffic to the basolateral membrane, to the secretory vesicles, and to the prelysosomes were all prominent loci of MHC class II molecules, La/SSB, and cathepsins B and D. These observations support the thesis that lacrimal gland acinar cells that have been induced to express MHC class II molecules function as autoantigen processing and presenting cells.

Prolactin and prolactin receptors in the lacrimal gland

Light and electron microscopic immunocytochemistry, in situ hybridization and Dot Blot analysis revealed intracellular localization of prolactin-like molecules and prolactin mRNA in epithelial cells of the lacrimal glands of rabbits. There was also positive immunostaining for prolactin receptors on acinar cells and some interstitial cells. On Western blots of homogenates of whole lacrimal gland, isolated lacrimal acinar cells, isolated lacrimal interstitial cells and peripheral blood lymphocytes, prolactin antibody consistently labeled protein bands migrating at approximately 36 and 50 kD. These data confirm that lacrimal gland acinar cells produce endogenous prolactin-like molecules, but also express prolactin receptors. Since prolactin immunoreactivity has been detected in tear fluid and we found no accumulations of immunogold label in endocytic or transport vesicles, we hypothesize that the prolactin-like molecules in tear fluid originate primarily from synthesis within the acinar cells. We hypothesize further that prolactin from pituitary and other non-acinar cell origin has a modulating influence on acinar cell activity as well as immune function in the lacrimal gland, and that some of the prolactin-like molecules produced by the acinar cells contribute to these functions by autocrine/paracrine mechanisms.

Role of laminin-1, collagen IV, and an autocrine factor(s) in regulated secretion by lacrimal acinar cells

Adhesion to novel basement membrane component BM180 in the presence of laminin-1 promotes stimulus-secretion coupling in lacrimal acinar cells [G. W. Laurie, J. D. Glass, R. A. Ogle, C. M. Stone, J. R. Sluss, and L. Chen. Am. J. Physiol. 270 (Cell Physiol. 39): C1743-C1750, 1996]. The identity of the active laminin-1 site and the possibility that other promoters of coupling are present in the acinar cell microenvironment were probed by use of different substrates, media, neutralizing antibodies and cell numbers. Regulated peroxidase secretion was unaffected by basement membrane coat concentration and was detectable at reduced levels in serum-free medium. Anti-laminin-1 antibodies, particularly against sites in the beta1 and gamma1 chains, but not alpha1 chains, partially suppressed regulated secretion, as did an anti-collagen IV antibody. Without effect were RGD peptide and antibodies against entactin, the beta1-integrin subunit, and several growth factors. Increasing cell number in serum-free medium revealed an unknown, serum-maskable, secretion-enhancing activity with a remarkable specificity for regulated secretion. Stimulus-secretion coupling, therefore, appears to be modulated by several extracellular factors whose relative contributions remain to be determined.

A unified theory of the role of the ocular surface in dry eye

It is our belief that the pathology of dry eye occurs when systemic androgen levels fall below the threshold necessary for support of secretory function and generation of an anti-inflammatory environment (Fig. 3). When this occurs, both the lacrimal gland and the ocular surface become irritated and inflamed, and they secrete cytokines that interfere with the normal neural connections that drive the tearing reflex. This leaves the lacrimal gland in an isolated condition, perhaps exacerbating atrophic alterations of the glandular tissue. These changes allow for antigen presentation at the surface of the lacrimal acinar cells and increase lymphocytic infiltration of the gland. A similar series of events may be occurring on the ocular surface. From this hypothesis we conclude: 1. The ocular surface, lacrimal gland, and interconnecting innervation act as an integrated servo-mechanism. 2. Once the lacrimal gland loses its androgen support, it is subject to immune/neurally mediated dysfunction. 3. The ocular surface is an appropriate target for dry eye therapeutics.

The meibomian glands and tear film lipids. Structure, function, and control

Meibomian gland disease--and, in particular, obstructive meibomian gland disease--makes an important contribution to ocular surface disease, in the form of meibomian keratoconjunctivitis. With improved methods for the study of meibomian oil composition and function, we are moving closer to the possibility of distinguishing the contribution of meibomian deficiency, as opposed to inflammatory events, to this disorder. More importantly, where aqueous tear deficiency and meibomian gland disease coincide in patients with dry eye, we are closer to the possibility of distinguishing their relative contributions to the dry eye state. This has implications for future therapies.