Developmental pattern of androgen receptor immunoreactivity in the mouse submandibular gland

Runx1 mediates the development of the granular convoluted tubules in the submandibular glands

The mouse granular convoluted tubules (GCTs), which are only located in the submandibular gland (SMG) are known to develop and maintain their structure in an androgen-dependent manner. We previously demonstrated that the GCTs are involuted by the epithelial deletion of core binding factor β (CBFβ), a transcription factor that physically interacts with any of the Runt-related transcription factor (RUNX) proteins (RUNX1, 2 and 3). This result clearly demonstrates that the Runx /Cbfb signaling pathway is indispensable in the development of the GCTs. However, it is not clear which of the RUNX proteins plays useful role in the development of the GCTs by activating the Runx /Cbfb signaling pathway. Past studies have revealed that the Runx /Cbfb signaling pathway plays important roles in various aspects of development and homeostatic events. Moreover, the Runx genes have different temporospatial requirements depending on the biological situation. In the present study, the GCTs of the SMG showed a remarkable phenotype of, which phenocopied the epithelial deletion of Cbfb, in epithelial-specific Runx1 conditional knock-out (cKO) mice. The results indicate that Runx1 works as a partner of Cbfb during the development of the GCTs. We also discovered that the depletion of Runx1 resulted in the reduced secretion of saliva in male mice. Consistent with this finding, one of the water channels, Aquaporin-5 (AQP5) was mislocalized in the cytoplasm of the Runx1 mutants, suggesting a novel role of Runx1 in the membrane trafficking of AQP5. In summary, the present findings demonstrated that RUNX1 is essential for the development of the GCTs. Furthermore, RUNX1 could also be involved in the membrane trafficking of the AQP5 protein of the acinar cells in the SMG in order to allow for the proper secretion of saliva.

Extra-prostatic transgene-associated neoplastic lesions in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice

Male transgenic adenocarcinoma of the mouse prostate (TRAMP) mice are frequently used in prostate cancer research because their prostates consistently develop a series of preneoplastic and neoplastic lesions. Disease progression in TRAMP mouse prostates culminates in metastatic, poorly differentiated carcinomas with neuroendocrine features. The androgen dependence of the rat probasin promoter largely limits transgene expression to the prostatic epithelium. However, extra-prostatic transgene-positive lesions have been described in TRAMP mice, including renal tubuloacinar carcinomas, neuroendocrine carcinomas of the urethra, and phyllodes-like tumors of the seminal vesicle. Here, we describe the histologic and immunohistochemical features of 2 novel extra-prostatic lesions in TRAMP mice: primary anaplastic tumors of uncertain cell origin in the midbrain and poorly differentiated adenocarcinomas of the submandibular salivary gland. These newly characterized tumors apparently result from transgene expression in extra-prostatic locations rather than representing metastatic prostate neoplasms because lesions were identified in both male and female mice and in male TRAMP mice without histologically apparent prostate tumors. In this article, we also calculate the incidences of the urethral carcinomas and renal tubuloacinar carcinomas, further elucidate the biological behavior of the urethral carcinomas, and demonstrate the critical importance of complete necropsies even when evaluating presumably well characterized phenotypes in genetically engineered mice.

Exosomal secretion of death bullets: a new way of apoptotic escape?

Ovariectomy/estrogen deficiency causes selective apoptosis of the serous epithelial cells of the submandibular glands (SMG) in female mice. Because such apoptosis does not occur in healthy, estrogen-deficient male mice, it was hypothesized that dihydrotestosterone (DHT) protects epithelial SMG cells against apoptosis. The antiapoptotic effect of DHT on human epithelial HSG cells exposed to tumor necrosis factor-α and cycloheximide was studied. Correspondingly, the proapoptotic effect of androgen deficiency was studied in orchiectomized (ORX) androgen-knockout (ARKO) and wild-type (WT) mice. The health state of the SMG cells was studied with Alcian blue-periodic acid Schiff (AB-PAS) and amylase staining and transmission electron microscopy (TEM). The eventual protective antiapoptotic effect of dehydroepiandrosterone (DHEA) treatment was tested in this model. Apoptosis was assessed using immunohistochemisty of cleaved effector caspase-3 and its activator caspase-8 and the TUNEL assay. To test for the bioavailability, intracrine metabolism and sex steroid effects of DHEA, cystein-rich secretory protein-3 (CRISP-3), and leucine-isoleucine-valine transport system 1 (LIV-1) were used as androgen- and estrogen-regulated biomarkers, respectively. DHT protected HSG cells against induced apoptosis. In mice, androgen deficiency resulted in extensive activation of apoptotic caspase-8/3 cascade in serous epithelial cells. However, in salivary glands, active caspases were not translocated to nuclei but secreted to salivary ducts in exosome-like particles, which are associated with weak AB-PAS and amylase staining of the androgen-deprived cells and reduced number of intracellular secretory granules. DHEA treatment suppressed induction of proapoptotic caspases and almost normalized mucins and amylase and ultramophology of the serous epithelial cells in WT ORX but not ARKO ORX mice. According to the CRISP-3 and LIV-1 markers, DHEA probably exerted its effects via intracrine conversion to DHT.

Hypophysectomy and hormonal therapy modulate mK1-immunoreactive duct cells in the mice sublingual glands

The immunocytochemical localization of a true tissue kallikrein, mK1, in mouse sublingual glands (SLGs) was examined following hypophysectomy and hormonal replacement therapy. In the glands of intact mice (14 weeks of age), mK1 was detected in the striated ducts (SDs). Full-fledged granular cells were scattered in the SDs of male mice (but not in those of female mice), showing a cellular mosaic distribution of mK1 with some being positive and others being negative. mK1 was also detected in transitional-type granular cells, though the secretory granules were too small and scarce to be visible by a light microscopy. Hypophysectomy in male mice resulted in the atrophy and loss of secretory granules in many SD cells. Granulation recovered after the repeated injection of 5alpha-dihydrotestosterone (DHT), 3,5,3'-triiodo-L: thyronine (T3), and dexamethasone (Dex), given either alone or in combination to the hypophysectomized mice. The concomitant injection of DHT and T3, with or without Dex, resulted in the reappearance of the full-fledged granular cells, only some of which were mK1-positive. Electron microscopy revealed mK1 to be present exclusively in the secretory granules of these mK1-positive cells, and no ultrastructural differences were observed between mK1-positive and mK1-negative full-fledged granular cells. These results show that the differentiation of the granular cell phenotype in the mouse SLG duct system requires the concomitant action of androgen and thyroid hormone and retards mK1 synthesis.

Repeated androgen and thyroid hormone injection modulates the morphology of hormone-responsive duct cells in the mouse parotid gland

When the parotid glands of normal male and female ICR mice (12 weeks of age) were examined under a light microscope, no granular cells were seen in the duct system. However, transmission electron microscopy revealed that, in both sexes, many striated duct cells contained a few electron-dense secretory granules in their subluminal cytoplasm and had formed so-called granular striated tubules (GSTs) in some of the striated duct segments. These secretory granules were not large enough to be visible with a light microscope. Fully fledged granular cells, containing large secretory granules visible with a light microscope, could be induced in the GST segments of the glands of males by injection with 5alpha-dihydrotestosterone (DHT), triiodothyronine (T(3)), and dexamethasone (Dex), given alone or in combination every other day for 2 weeks. Dex alone showed no effect on the GSTs in this study. Both DHT and T(3), either individually or with Dex, were moderately effective, inducing a few scattered fully fledged granular cells. A stronger effect was detected after concomitant injection of DHT and T(3), with or without Dex, with more abundant fully developed granular cells appearing in the GST segments. Electron microscopy revealed that these granular cells had abundant large secretory granules in their apical two-thirds, a basal nucleus, and modest basal infoldings. By contrast, the effect of the same hormones was very weak in the glands of females, and even the concomitant injection of DHT and T(3), with or without Dex, rarely induced fully fledged granular cells. These results indicate a close similarity between the ductal systems of the major salivary glands of the mouse, in terms of some of the striated duct segments containing secretory granules, being under the same multihormonal regulation, and being sexually dimorphic.

Localization and potential function of androgen receptor in rat salivary gland

AIM

To investigate the localization and quantity of androgen receptor (AR) in the salivary glands of rats with further analysis on the effect of castration.

METHODS

Sixty male Wistar rats, aged 30-60 days, were randomly divided into three groups (castrated, sham-operated and normal controls) with 20 rats in each group. The rats in the castrated group were castrated and the submaxillary glands were removed after 1 week. The salivary glands of the rats in the sham-operated and the normal control groups were also removed. Parts of the salivary glands were fixed for immunohistochemistry and in situ hybridization assays. Other parts were used for Western blot.

RESULTS

AR immunoreactivity in the three groups was localized in the glandular epithelial cells of the serous acinus and the glandular duct of the salivary gland, mainly in the nuclei. AR mRNA hybridization signals in the salivary glands of the castrated group were mainly distributed in the epithelial cells of the convoluted and secretary ducts; AR mRNA in the sham-operated and the normal control groups were found in the epithelial cells of the convoluted, the secretary and the excretory ducts. The quantity of AR in the salivary glands was decreased significantly in the castrated rats compared with the sham-operated and the normal controls. Moreover, epidermal growth factor (EGF) secreted by the salivary glands was also decreased in the castrated rats.

CONCLUSION

Castration appears to affect the production of AR in the salivary gland and the distribution of the AR mRNA and could further affect the function of the salivary gland. The changes of AR and the distribution of AR mRNA may play an important role in the interactions between the testes and the salivary gland.

Additive and/or synergistic action (downregulation) of androgens and thyroid hormones on the cellular distribution and localization of a true tissue kallikrein, mK1, in the mouse submandibular gland

We investigated the effects of 5alpha-dihydrotestosterone (DHT), 3,5,3'-triiodo-l-thyronine (T(3)), and dexamethasone (Dex) on the expression of mK1 in the granular convoluted tubule (GCT) cells of the submandibular gland (SMG) of hypophysectomized (Hypox) male mice by indirect enzyme-labeled antibody and immunogold antibody methods for light and electron microscopy. Hypox resulted in considerable atrophy of the GCT cells, which were always immunoreactive for mK1, and the cells were characterized by apical small dense secretory granules labeled with gold particles suggesting the presence of mK1, small Golgi apparatus, sparse rough endoplasmic reticulum (RER), and developed basal infoldings. Each of the hormones, DHT, T(3), and Dex, enhanced the GCT phenotype to various degrees in Hypox male mice. Both DHT alone and T(3) alone moderately inhibited mK1 synthesis by increasing the number of mK1-immunonegative GCT cells in Hypox males, but Dex alone had no inhibitory effect on mK1 synthesis. A significant trophic effect on GCT cells was induced by combined injection of DHT and T(3) or of all three hormones, and was reflected in the appearance of abundant large secretory granules, well-developed Golgi apparatus and RER, and reduced basal infoldings. Only a few such GCT cells were immunopositive for mK1, and the pattern of immunopositive and immunonegative cells very closely resembled the mosaic pattern seen in normal male GCTs. These findings suggested that the sexual dimorphism of mK1 expression and the morphological appearance of GCT cells can be induced by treatment with two hormones, DHT and T(3), but not by either of them alone. T(3) appears to have a permissive effect on committed GCT cells that results in downregulation of mK1 expression in these cells.

Sexual dimorphism and seasonal variation in submandibular gland histology of Bolomys lasiurus (Rodentia, Muridae)

Wild rodents (Bolomys lasiurus) of both sexes were caught in a cerrado grassland area during the dry (July-September) and rainy (January-March) seasons of Brazil. Fasted animals were perfused with Karnovsky fixative through the left ventricle, under ether anesthesia, and the submandibular gland was processed for embedding in historesin. Histological and histometric data show sexual dimorphism at both seasons. In the volume percentage of the granular convoluted tubules (GCT) and their secretory granules, the males exhibited higher values. The absolute volume occupied by these structures, however, was dimorphic only in the rainy season. The diameter of the GCT, the height of its epithelium, and its total length were also greater in males during the rainy season. The absolute volumes of the acini and of the ductal tree were identical in both sexes in the dry and rainy seasons but the acinar diameter increased in the males and females during the rainy season. The sexual dimorphism and the seasonal variations now described in the B. lasiurus submandibular glands could be explained by the augmented reproductive activity of the males in the rainy period.

Developmental and androgenic regulation of the immunocytochemical distribution of mK1, a true tissue kallikrein, in the granular convoluted tubule of the mouse submandibular gland

The action of androgens on the immunocytochemical distribution of mK1, a true tissue kallikrein, was examined in the submandibular gland (SMG) of developing and adult mice by indirect enzyme-labeled and immunogold-labeled antibody methods for light and electron microscopy, respectively. In both sexes at 3 weeks of age, essentially all of the immature granular convoluted tubule (GCT) cells were uniformly immunostained. At 4 weeks of age (the onset of puberty), morphological differences between the two sexes appeared in the GCTs, in which some cells became immunonegative. Thereafter, the immunonegative GCT cells became more abundant in the SMG of males than of females and considerable intercellular variation in staining intensity for mK1 was seen, especially in males. A few slender GCT cells with strong immunoreactivity appeared in GCT segments only in males. Castration of males resulted in an increase in the number of immunopositive GCT cells, whereas administration of dihydrotestosterone (DHT) decreased the number of immunopositive GCT cells in the SMGs of both sexes. Slender GCT cells immunoreactive for mK1 were seen in females treated with DHT for 6 days. However, there were no immunostained slender GCT cells in female SMGs after injection of DHT for 2 weeks. Immunoelectron microscopy disclosed this type of cell in male SMGs, which closely resembles immature GCT cells of prepubertal mice, with a few small secretory granules uniformly labeled with gold particles, a sparse Golgi apparatus and RER, and basal infoldings. In mature male SMGs and in SMGs of DHT-treated females and castrated males, typical GCT cells had a well-developed Golgi apparatus and a net-like RER but few to no basal infoldings, whereas in the female gland equivalent cells had moderately developed RER and some basal infoldings. These results suggest that mK1 is one of the enzymes characteristically present in immature GCT cells and that its synthesis is inhibited in part by androgens, resulting in decreased numbers of immunopositive cells.

Photoperiod-dependent capability of androgen aromatization and the role of estrogens in the bank vole testis visualized by means of immunohistochemistry

Detection of steroid hormone receptors within a target tissue is important for an understanding of their crucial role in regulating of steroids' action. In the light of recent knowledge on the role of estrogens in male gonads the efforts were undertaken to clarify and discuss a role of androgen receptors, aromatase and estrogen receptors (ER) in mediating testosterone and/or estradiol action in testicular cells of bank voles that were kept under short or long light cycles. Immunohistochemistry was performed on paraplast embedded sections of the bank vole testes. First, androgen receptors were immunolocalized in testicular somatic cells while germ cell did not express any immunoreaction. Moreover, the ability to convert androgens to estrogens by various testicular cells was documented; aromatase immunoexpression was found in testis sections, not only in Leydig cells and Sertoli cells but also in germ cells. Finally, the expression of estrogen receptor-alpha (ERalpha) was observed in Leydig cells whereas the presence of estrogen receptor-beta (ERbeta) was detected in Sertoli and germ cells, namely spermatocytes and spermatids. The cellular distribution of androgen receptors appeared to be light -and age-dependent in adults; immunoexpression of aromatase and ERbeta was found to be both age -and photoperiod-dependent in germ cells.

Rodent submandibular gland peptide hormones and other biologically active peptides

The cervical sympathetic trunk-submandibular gland neuroendocrine axis plays an integral role in physiological adaptations and contributes to the maintenance of systemic homeostasis, particularly under the 'stress conditions' seen with tissue damage, inflammation, and aggressive behavior. The variety of polypeptides, whose release from acinar and ductal cells is under sympathetic nervous system control, offers coordinated and progressive levels of endocrine communication. Proteolytic enzymes (e.g. the kallikreins and furin maturases) are involved in the conversion of inactive precursors (e. g. Pro-EGF and SMR1) into biologically active molecules (e.g. EGF, SMR1-pentapeptide), which act on local or distant targets and thereby modulate the homeostatic process.

Immunolocalization of androgen receptors in testicular cells during postnatal development of the bank vole (Clethrionomys glareolus, S.)

Determination of the cellular distribution of the androgen receptors within the testis is of great importance for an understanding of their essential role in mediating of androgen action in the male gonad. In bank voles, which are seasonally breeding rodents, photoperiod is one of the most important factors inducing profound changes in the morphology and hormonal activity of the testes. Immunolocalization of androgen receptors was found in all somatic cells such as Sertoli cells, Leydig cells, and peritubular-myoid cells, however, distribution of the androgen receptors in various cell types depended on age of animals. Intensity of immunoreactivity was noticed as age and photoperiod-dependent. Males reared under different light regimes showed a significant correlation between the length of light and sexual maturation. Therefore, morphology of the testis from young and adult bank voles was also presented.

Differential androgen regulation of the murine genes for cysteine-rich secretory proteins (CRISP)

The androgen dependency of the genes coding for the cysteine-rich secretory proteins (CRISP) was analysed in their main sites of expression. Male mice were treated with the gonadotropin-releasing hormone antagonist Ac-DNapAla-DClPhAla-DPyrAla-Ser-Tyr-DCtl-Leu-Lys (Mor)-Pro-DAla-NH2 [DNapAla, D-2-naphthyl-Ala; DClPhAla, D-4-chlorphenyl-Ala; DPyrAla, D-pyridyn-3-yl-Ala; DCtl, D-citrulline; Lys(Mor), L-2-amino-6-(morpholin-4-yl)-hexanoic acid], and CRISP RNA levels were assessed by northern blot and competitive reverse transcriptase-mediated (RT)-PCR. In the salivary gland, CRISP-1 and to a lesser extent CRISP-3 expression was markedly reduced, in spite of an up-regulation of androgen receptor transcript levels. A down-regulation of CRISP-1 expression was also observed in the epididymis. Conversely, the levels of the testicular CRISP-2 transcripts were hardly affected at all. Female mice were ovariectomised and treated with testosterone propionate, and their salivary gland RNAs analysed. CRISP-1 and CRISP-3 RNA levels were significantly increased, and these effects were prevented by a concomitant treatment with the antiandrogen flutamide. Androgen receptor transcript levels were not affected by androgen administration but increased following antiandrogen treatment. CRISP expression during postnatal development was monitored by northern blot analysis. CRISP-1 and CRISP-2 transcripts were detected as early as 22 days after birth in the epididymis and testis, respectively, whereas CRISP-3 mRNA was visible only from day 30 in the salivary gland. A sharp increase of all CRISP levels was noted on day 40, coincident with the onset of sexual maturity. Altogether these results indicate that despite their high similarity, the CRISP genes are differentially regulated by androgens.

Immunocytochemical demonstration of androgen receptors in Leydig cells of the bank vole (Clethrionomys glareolus, Schreber): an in vitro study

Androgen receptors of the bank vole Leydig cells in vitro were immunostained using a polyclonal antibody against androgen receptors followed by streptavidine-peroxidase complex or rhodamine-labelled goat anti-rabbit IgG visualization. The immunocytochemical studies revealed localization of androgen receptors in the whole cytoplasm or in the perinuclear area of the cells. Addition of dehydroepiandrosterone into the culture medium resulted in nuclear localization of the androgen receptors. Long (18L : 6D) and short (6L : 18D) photoperiods as well as the age of animals were taken into account. The concentration of androgen receptors was changed dependent on age and status of reproduction.