Androgen influence on lacrimal gland apoptosis, necrosis, and lymphocytic infiltration.
PURPOSE: Previous studies have shown that ovariectomy and hypophysectomy cause regression of the lacrimal gland and have implicated androgens as trophic hormones that support the gland. The purposes of this study were to test the hypothesis that glandular regression after ovariectomy is due to apoptosis, to identify the cell type or types that undergo apoptosis, to survey the time course of the apoptosis, and to determine whether ovariectomy-induced apoptosis could be prevented by dihydrotestosterone (DHT) treatment. METHODS: Groups of sexually mature female New Zealand White rabbits were ovariectomized and killed at various time periods up to 9 days. Additional groups of ovariectomized rabbits were treated with 4 mg/kg DHT per day. At each time period, sham-operated rabbits were used as controls. Lacrimal glands were removed and processed for analysis of apoptosis as assessed by DNA fragmentation and for morphologic examination. DNA fragmentation was determined using the TdT-dUTP terminal nick-end labeling assay and by agarose gel electrophoresis. Labeled nuclei were quantified by automated densitometry. Sections were also stained for RTLA (rabbit thymic lymphocyte antigen), rabbit CD18, and La antigen. Morphology was evaluated by both light and electron microscopy. RESULTS: The time course of apoptosis exhibited two phases, a rapid and transient phase and a second prolonged phase. A transient phase peaked at approximately 4 to 6 hours after ovariectomy. The values for degraded DNA as a percentage of total nuclear area were 4.29%+/-0.79% and 4.26%+/-0.54%, respectively. The values for sham-operated controls examined at the same time periods were 1.77%+/-0.08% and 0.82%+/-0.21%, respectively. The percentage of degraded DNA at 24 hours after ovariectomy was not different from controls examined at the same interval after sham operation. The percentage of degraded DNA 6 days after ovariectomy was significantly increased (8.5%+/-2.4%), compared with sham-operated animals at the same time period (0.68%+/-0.03%). DNA laddering was more pronounced after ovariectomy. Dihydrotestosterone treatment in ovariectomized rabbits suppressed the increase in DNA degradation. Morphologic examination of lacrimal gland sections indicated that ovariectomy caused apoptosis of interstitial cells rather than acinar or ductal epithelial cells. Tissue taken 4 hours and 6 days after ovariectomy showed nuclear chromatin condensation principally in plasma cells. Increased numbers of macrophages were also evident. Significant levels of cell degeneration and cell debris, characteristic of necrosis, were observed in acinar regions 6 days after ovariectomy. Dihydrotestosterone prevented this necrosis. Increased numbers of RTLA+, CD18+, and La+ interstitial cells were also evident 6 days after ovariectomy. In addition, ovariectomy increased La expression in ductal cells. Dihydrotestosterone treatment prevented the increase in numbers of lymphoid cells and La expression. Dihydrotestosterone also promoted the appearance of mitotic figures in acinar cells and increased the sizes of acini by 43% (P < 0.05). CONCLUSIONS: Glandular atrophy observed after ovariectomy is likely to proceed by necrosis of acinar cells rather than apoptosis. This process begins with an apparent time lag after a rapid phase of interstitial cell apoptosis. These processes are accompanied by increased lymphocytic infiltration. These results suggest that a critical level of androgen is necessary to maintain lacrimal gland structure and function and that a decrease in available androgen below this level could trigger lacrimal gland apoptosis and necrosis, and an autoimmune response. Because apoptotic and necrotic cell fragments may be sources of autoantigens that can be processed and presented to initiate an autoimmune reaction, we surmise that cell death triggered by androgen withdrawal may trigger an autoimmune response such as that encountered in Sjogren's syndrome. (ABSTRACT TRUNCATED) (+info)
Retarded growth and deficits in the enteric and parasympathetic nervous system in mice lacking GFR alpha2, a functional neurturin receptor.
Glial cell line-derived neurotrophic factor (GDNF) and a related protein, neurturin (NTN), require a GPI-linked coreceptor, either GFR alpha1 or GFR alpha2, for signaling via the transmembrane Ret tyrosine kinase. We show that mice lacking functional GFR alpha2 coreceptor (Gfra2-/-) are viable and fertile but have dry eyes and grow poorly after weaning, presumably due to malnutrition. While the sympathetic innervation appeared normal, the parasympathetic cholinergic innervation was almost absent in the lacrimal and salivary glands and severely reduced in the small bowel. Neurite outgrowth and trophic effects of NTN at low concentrations were lacking in Gfra2-/- trigeminal neurons in vitro, whereas responses to GDNF were similar between the genotypes. Thus, GFR alpha2 is a physiological NTN receptor, essential for the development of specific postganglionic parasympathetic neurons. (+info)
Gene targeting reveals a critical role for neurturin in the development and maintenance of enteric, sensory, and parasympathetic neurons.
Neurturin (NTN) is a neuronal survival factor that activates the Ret tyrosine kinase in the presence of a GPI-linked coreceptor (either GFR alpha1 or GFR alpha2). Neurturin-deficient (NTN-/-) mice generated by homologous recombination are viable and fertile but have defects in the enteric nervous system, including reduced myenteric plexus innervation density and reduced gastrointestinal motility. Parasympathetic innervation of the lacrimal and submandibular salivary gland is dramatically reduced in NTN-/- mice, indicating that Neurturin is a neurotrophic factor for parasympathetic neurons. GFR alpha2-expressing cells in the trigeminal and dorsal root ganglia are also depleted in NTN-/- mice. The loss of GFR alpha2-expressing neurons, in conjunction with earlier studies, provides strong support for GFR alpha2/Ret receptor complexes as the critical mediators of NTN function in vivo. (+info)
EGF precursor mRNA and membrane-associated EGF precursor protein in rat exorbital lacrimal gland.
This study was designed to demonstrate the presence of epidermal growth factor (EGF) in the rat exorbital lacrimal gland. EGF precursor gene transcription was demonstrated first by RT-PCR analysis of lacrimal gland RNA using a set of specific primers and second by Northern blot analysis of rat lacrimal gland mRNA. A rabbit polyclonal antibody (rEGF2) directed against rat submaxillary gland EGF was used to detect EGF-containing proteins by RIA. Results indicate that the rat lacrimal gland does not contain detectable soluble and mature EGF but that the EGF immunoreactivity is associated with the membrane-enriched fraction. Analysis of the detergent-solubilized membrane proteins by gel filtration shows that membrane-associated EGF immunoreactivity was present as a high-molecular-mass protein. Moreover, as shown by Western blot analysis, a specific anti-rat EGF precursor antibody (ppEGF1) can immunoprecipitate a 152-kDa EGF-containing protein. Taken together, these results demonstrate for the first time both EGF precursor gene transcription and EGF precursor protein expression in a lacrimal tissue, i.e., the rat exorbital lacrimal gland. The demonstration that EGF appears to be stored only as its full-length membrane precursor may provide important information to study the regulation of its secretory process. (+info)
Dacryolith formation around an eyelash retained in the lacrimal sac.
A dacryolith was discovered in the lacrimal sac during a dacryocystorhinostomy for chronic dacryocystitis in which there was mucocele formation. Morphological examination confirmed the presence of an eyelash at the centre of the stone and electron microscopy demonstrated the presence of fungi (Candida sp.) in a matrix which was of markedly vairable morphology. The mechanism by which a hair enters the punctum and passes along the canaliculus may be attributed to the step-like pattern of ridges on the surface of a hair. The directional nature of these ridges dictates preferential movement towards the root end of the hair and prevents movements in the opposite direction. (+info)
Targeted disruption of the murine Nhe1 locus induces ataxia, growth retardation, and seizures.
In most cells, the ubiquitously expressed Na+/H+ exchanger isoform 1 (NHE1) is thought to be a primary regulator of pH homeostasis, cell volume regulation, and the proliferative response to growth factor stimulation. To study the function of NHE1 during embryogenesis when these cellular processes are very active, we targeted the Nhe1 gene by replacing the sequence encoding transmembrane domains 6 and 7 with the neomycin resistance gene. NHE activity assays on isolated acinar cells indicated that the targeted allele is functionally null. Although the absence of NHE1 is compatible with embryogenesis, Nhe1 homozygous mutants (-/-) exhibit a decreased rate of postnatal growth that is first evident at 2 wk of age. At this time, Nhe1 -/- animals also begin to exhibit ataxia and epileptic-like seizures. Approximately 67% of the -/- mutants die before weaning. Postmortem examinations frequently revealed an accumulation of a waxy particulate material inside the ears, around the eyes and chin, and on the ventral surface of the paws. Histological analysis of adult tissues revealed a thickening of the lamina propria and a slightly atrophic glandular mucosa in the stomach. (+info)
Pancreatic lipase-related protein 1 mRNA in female mouse lacrimal gland.
PURPOSE: Differential display analysis was used to look for gender differences in lacrimal gland gene expression. The expression of a female-specific mouse lacrimal gland mRNA that encoded pancreatic lipase-related protein 1 (PLRP1) was identified and characterized. METHODS: Differential display analysis of the exorbital lacrimal glands of male and female Swiss Webster mice detected a potential female-specific cDNA, designated Y2. Using the technique of rapid amplification of cDNA ends, a full-length cDNA of Y2 was obtained and the nucleotide sequence determined. To assess tissue-specific expression, a labeled Y2 cDNA probe was hybridized to RNA blots of male and female mouse lacrimal, harderian, parotid, mandibular, sublingual, and pancreas glands and liver. Y2 cDNA was also hybridized to RNA blots of male and female rat lacrimal gland and male rat pancreas. To determine subcellular localization, Y2 sense and antisense RNA probes were hybridized to female mouse lacrimal gland frozen sections. RESULTS: GenBank database sequence comparisons indicated that Y2 encoded mouse PLRP1. RNA blots documented that PLRP1 was expressed in female, but not in male, mouse lacrimal gland. PLRP1 mRNA was also expressed in male and female mouse sublingual gland and pancreas. Expression of PLRP1 was not detected in male or female rat lacrimal gland. In situ hybridization showed that PLRP1 was expressed in the acinar cells of the female mouse lacrimal gland. CONCLUSIONS: Lacrimal gland expression of PLRP1 mRNA was gender and species specific. Female, but not male, mouse lacrimal gland expressed PLRPI mRNA. Neither female nor male rat lacrimal gland expressed PLRP1 mRNA. PLRP1 protein may be secreted in mouse tears, where it may function as a lipolytic enzyme, modifying tear film lipids. (+info)
Does androgen insufficiency cause lacrimal gland inflammation and aqueous tear deficiency?
PURPOSE: The current investigators have shown that androgen treatment suppresses inflammation and stimulates the function of lacrimal glands in mouse models of Sjogren's syndrome. Recently, others have hypothesized that androgen insufficiency induces an autoimmune process in lacrimal tissue, leading to inflammation, a Sjogren's syndrome-like pathology, and aqueous tear deficiency. The purpose of the present study was to test this hypothesis. METHODS: Lacrimal glands were obtained from adult testicular feminized (Tfm) and control mice; castrated rats, guinea pigs, and rabbits; and castrated rats without anterior or whole pituitary glands and were processed for histology and image analysis. Tear volumes were measured in mice, in patients taking antiandrogen medications, and in age-matched human control subjects. RESULTS: Tfm mice, which are completely resistant to classical androgen action, did not have increased lymphocyte infiltration in their lacrimal glands or decreased tear volumes. No inflammation was evident in lacrimal tissues of male or female rats, guinea pigs, or rabbits 12 to 31 days after castration, no inflammation existed in rat lacrimal glands 15 to 31 days after orchiectomy and pituitary removal, and no aqueous tear deficiency was apparent in patients receiving antiandrogen therapy. CONCLUSIONS: Androgen deficiency may promote the progression of Sjogren's syndrome and its associated lacrimal gland inflammation, meibomian gland dysfunction, and severe dry eye. However, androgen insufficiency alone does not cause lacrimal gland inflammation, a Sjogren's syndrome-like pathology in lacrimal tissue, or aqueous tear deficiency in nonautoimmune animals and humans. (+info)