Expression and induction by beta-adrenergic agonists of the cystatin S gene in submandibular glands of developing rats.

Repeated administration of the beta-adrenergic agonist isoprenaline (isoproterenol, IPR), which produces hypertrophic/hyperplastic enlargements of rat submandibular and parotid glands, induces synthesis of a secretory protein shown to be a cysteine proteinase inhibitor, rat cystatin S. In the current study, Northern blot and hybridizations in situ were carried out to establish the developmental and beta-adrenergic regulation of the expression of the cystatin S gene. Cystatin S mRNA was not detected in submandibular glands of 20-day-old fetuses, nor in the glands of newborn or 10-day-old rats. However, steady-state levels of cystatin S mRNA increased between 21 and 28 days, reaching a conspicuously high concentration at 28 days; cystatin S mRNA then declined rapidly to a barely detectable level in glands of 32-day-old rats. IPR administration for 4 days induced high levels of cystatin S mRNA in submandibular glands of developing and adult rats. In both prepubertal and mature animals, induction of cystatin S mRNA in submandibular glands was more pronounced in female than in male animals. Hybridizations in situ revealed cystatin S mRNA only in acinar but not in duct cells of the submandibular gland. Developmentally, expression of the cystatin S gene coincided with acinar cell differentiation. These data suggest a complex neural, hormonal and developmental regulation of salivary cystatin genes.     

Immunocytochemical localization of a developmentally regulated, isoproterenol-inducible protein (LM protein) in rat submandibular gland

Administration of the beta-adrenergic drug isoproterenol (IPR) produces hyperplastic and hypertrophic enlargements of the submandibular gland of the rat and induces the synthesis of specific proteins in this organ. One of these proteins, the LM (large mobile) protein, was demonstrated immunocytochemically in the submandibular glands of developing untreated and IPR-treated rats. Immunoreactive LM protein was absent in the glands of 20-day-old fetuses and 1- and 2-day-old rats. It was localized in the proacinar and immature acinar cells in the glands of 6- to 21-day-old animals, but it was undetectable at 28 days of age. In the glands of adult rats, secretory granules of the granular convoluted tubule cells showed immunostaining for the LM protein which was also present in trace amounts in the acinar cells. Daily administration of IPR for 5 days to newborn or 8- or 15-day-old rats caused an apparent acceleration of proacinar/acinar cell differentiation, and consequently it increased the frequency of cells immunostained for the LM protein as well as the amount of immunoreactive material in these cells. Thus, the expression of LM protein in the submandibular gland is developmentally regulated, and it is restricted to the stage of differentiation of proacinar cells from terminal tubule cells. IPR is capable of inducing this protein in fully differentiated acinar cells in 3-week-old or older animals.     

Regulation of proto-oncogenes in rat parotid acinar cells in vitro after stimulation of beta-adrenergic receptors

Stimulation of beta-adrenoreceptors in rat parotid acinar cells in vitro by the beta-adrenergic agonist isoproterenol induces steady-state levels of c-fos mRNA and c-fos protein in these cells. A dramatic increase in the steady-state levels of c-fos mRNA was observed at 60 min, followed by a decrease at 2 h with a second peak at 4 h. c-fos induction in rat parotid acinar cells in vitro seems to be mediated by cAMP. Increased levels of p53 and c-myc mRNA were detected only at 60 min. c-abl and c-sis were also induced by isoproterenol but in a pattern different from that seen with c-fos. c-abl was the only oncogene in rat parotid gland which showed increased expression after chronic isoproterenol treatment of rats. In rat parotid acinar cells we observed no correlation between DNA synthesis and c-fos induction.     

Androgen regulation of secretory component synthesis by lacrimal gland acinar cells in vitro

This study sought to determine whether androgens directly stimulate the production of secretory component (SC) by acinar cells from the rat lacrimal gland. Homogeneous populations of acrinar cells were isolated from lacrimal tissues by serial enzymatic digestion and Ficoll gradient centrifugation and then cultured on reconstituted basement membranes in supplemented, serum-free medium. Acinar cell exposure in vitro to dihydrotestosterone (DHT) resulted in a significant increase in cellular SC output. This hormone action was dose dependent and androgen specific. Testosterone, but not 17 beta-estradiol, progesterone, dexamethasone, or aldosterone, also induced a considerable elevation in acinar cell SC production. The effect of testosterone may not require intracellular enzymatic conversion to DHT. The impact of androgens on SC output was associated with enhanced cellular synthesis and secretion and did not involve variations in acinar cell viability or density. Moreover, the SC response to DHT occurred irrespective of whether lacrimal gland acinar cells were obtained from young adult male or female rats. In contrast, the androgen-related rise in SC production was significantly reduced in acinar cells isolated from tissue of orchiectomized and hypophysectomized rats. In summary, these findings demonstrate that androgens directly increase the synthesis of SC by lacrimal gland acinar cells in vitro. This effect, however, may be significantly altered by prior changes in the endocrine environment of acinar cells in vivo.     

Morphological changes and EGF expression in the granular convoluted tubule cells of submandibular glands of Trypanosoma cruzi infected rats

We have previously demonstrated in rats that Chagas' disease affects the salivary glands, by promoting an enlargement of the submandibular gland. In order to further investigate possible functional alterations on infected submandibular glands, the objective of the present study was to analyze epidermal growth factor (EGF) expression on rat submandibular glands during Trypanosoma cruzi infection. Results demonstrated that infected rats presented lower levels of testosterone, and morphological changes in the granular convoluted tubule (GCT) cells of the submandibular glands, along with acinar enlargement and delayed ductal maturation at the developing granular ducts. Immunohistochemistry analysis additionally showed that only few cells immunolabelled with anti-EGF on infected rats during the acute phase of Chagas' disease, while after 64 and 90 days (chronic phase) of infection, EGF expression was similar to non-infected rats. The present findings suggest that at the acute phase of Chagas' disease, lower levels of testosterone may lead to a delayed maturation of GCT, which positively correlates with decreased EGF production by submandibular glands cells.     

Regeneration of acinar cells following ligation of rat submandibular gland retraces the embryonic-perinatal pathway of cytodifferentiation

Rat submandibular gland can regenerate following ligation-induced atrophy, eventually recovering its normal morphology and function. Previous studies have suggested that the regeneration process implies both self-proliferation of existing acini and formation of new acinar cells. One hypothesis is that new acinar cells may differentiate from the ductal cells in a similar fashion to the process of cytodifferentiation occurring during submandibular glandular development. In this study atrophy was induced, under recovery anaesthesia, by applying a metal clip on the main duct of the submandibular gland without including the chorda lingual nerve. After 2 weeks the duct was deligated for 3, 5 or 7 days or 8 weeks and the glands collected. Tissue was prepared for immunohistochemstry, biochemical analysis and RNA extraction. The histology of the regenerated glands shows several normal-looking acini, which have regained their glycoprotein content (AB/PAS positive), data also confirmed by biochemical analysis (SDS-PAGE/PAS). Regenerating tissue was characterized by the presence of embryonic-like branched structures ending with AB/PAS positive acinar cells. The proteins SMG-B and PSP are normally expressed in acinar cell precursors during development but only by intercalated ductal cells in the adult stage. In the adult regenerating gland mRNA levels of both SMG-B and PSP were found to be up-regulated compared to ligated glands and SMG-B expression localized to acinar cells whilst the ductal cells were negative. This study of rat submandibular gland regeneration suggests new acinar cells have differentiated from ducts and express markers of acinar cell precursors in a similar manner to the cytodifferentiation process occurring during glandular development.     

Occurrence and Nuclear Localization of cAMP Response Element- Binding Protein in the Post-natal Development of the Rat Submandibular Gland

Cyclic AMP response element-binding protein (CREB) is a 43-kDa polypeptide that binds a cAMP response element located at the 5 promoter region of cAMP regulatory genes. The spatial and temporal distribution of CREB in the post-natal development of the rat submandibular gland was investigated using immunohistochemistry with a specific antibody. At birth, cells of the terminal tubules and ducts in the submandibular gland showed a nuclear CREB immunoreactivity of moderate intensity. At 1–2 weeks after birth, an intense CREB immunoreactivity was localized primarily to acinar cells. When the r352;-adrenergic agonist isoproterenol was administered to 2-week-old rats, a twofold transient increase in the number of immunoreactive acinar cells was induced. Beginning 3 weeks after birth, CREB immunoreactivity shifted from acini to the duct system and showed a clear localization in the cells of the intercalated ducts and distal portions of striated ducts, where the granular convoluted tubule develops after 4 weeks. Immunopositive materials were localized exclusively in the nuclei of both acinar and ductal immunoreactive cells. After the development of the granular convoluted tubules, CREB immunoreactivity was absent in the tubule cells and was gradually reduced in intensity over the entire gland. In order to examine a hypothesis that CREB is involved in the initial differentiation of the granular convoluted tubular cells, testosterone was administered to hypophysectomized adult rats. Whereas the tubular cells of hypophysectomized rats showed a complete regression, and no CREB immunoreactivity was found in any acinar or duct cells, administration of testosterone for a few days induced an intense CREB immunoreactivity in the nuclei of duct cells, followed by their differentiation into the granular convoluted tubular cells. These results suggested that CREB is involved not only in the growth and differentiation of acinar ce lls that are regulated by r352;-adrenergic nerves but also in those of the duct system, and especially in the androgen-regulated differentiation of the granular convoluted tubular cells, during the post-natal development of the rat submandibular gland.     

Quantitative immunocytochemistry of rat submandibular secretory proteins during chronic isoproterenol administration and recovery

We utilized quantitative electron microscopic immunogold labeling procedures to follow changes in the intragranular content of five secretory proteins of the rat submandibular gland (SMG) during and after chronic treatment with the beta-adrenergic agonist isoproterenol (IPR). Labeling intensities (gold particles/microns2) of acinar cell secretory granules for mucin and glutamine/glutamic acid-rich proteins, major secretory proteins of the normal SMG, showed opposite responses to IPR. Labeling intensities increased for mucin and decreased for glutamine/glutamic acid-rich proteins immediately after IPR injections began, then rapidly returned to control levels after cessation of IPR treatment. SMG Protein C immunoreactivity, found in both acinar and intercalated duct granules, was less affected by IPR. However, opposite changes in labeling intensity were observed between acinar and intercalated duct granules. Labeling intensities for proline-rich proteins, IPR-inducible secretory proteins, increased only after 10 days of stimulation and maintained a high level even after cessation of drug treatment. Type 2 cystatin, another IPR-inducible protein, increased gradually with chronic IPR treatment and decreased slowly during the recovery phase. These results suggest that chronic beta-adrenergic stimulation affects the expression of genes for several rat SMG secretory proteins in a different manner.     

Secretory proteins as markers for cellular phenotypes in rat salivary glands

The neonatal submandibular glands (SMG) of the rat contain two types of cells: Type III cells secrete a group of proteins in response to beta-adrenergic stimulation, and Type I cells secrete a different protein, called Protein C (89 kDa), in response to cholinergic stimuli (Ball and Redman, 1984). Polyclonal antibodies raised to Protein B1 (26 kDa) showed that the several proteins in the B1-Immunoreactive Protein (B1-IP) group are localized exclusively to Type III cells. Although we expected that antibodies to Protein B1 would label only the submandibular gland, we found instead that the serous demilunes of the sublingual gland (SLG) and the acinar cells and intercalated ducts of the parotid gland (PRG) were strongly reactive in both the neonate and the adult. Immunoelectrophoretic analysis of gland extracts showed the major reactive species in the sublingual gland to have different mobilities than the B1-IP. On the other hand, reactive species in the parotid gland had mobilities identical to those of two SMG proteins. In the adult SMG, the neonatal Type I and Type III cells are not present, and the acinar cells are devoid of B1-IP reactivity; however, the cells of the intercalated ducts have components reactive with anti-B1 antibodies, and these do not appear to be identical to any neonatal bands. In contrast to the submandibular gland, the adult parotid and sublingual glands retain the localization of B1-IP reactivity in PRG acinar and intercalated duct cells and in SLG demilunes, and they show the neonatal immunoelectrophoretic pattern. This raises the possibility that the major B1-IP species in the adult PRG may be identical to transient proteins of the neonatal SMG.     

Monoclonal antibodies against rat saliva and salivary gland antigens

Hybridomas were produced by the fusion of NS1 myeloma cells with spleen cells of a BALB/c mouse immunized with rat submandibular saliva. Growth of hybridomas was evident in 60/96 wells, and colonies secreting antibodies against saliva components were identified in 20 wells by using a solid phase enzyme-linked immunoassay. Cloning of cells from 12 wells yielded originally 43 hybridoma cell lines secreting anti-saliva antibodies. After recloning, one hybridoma (4Cl3) was selected for further studies. The hybridoma (4Cl3) cells were grown as ascites tumors, and the antibodies were purified from the ascitic fluid by diethylaminoethyl Affi-gel Blue chromatography. The purified antibody (MA4), immunoglobulin G1, immunoprecipitated a 39K dalton protein from submandibular saliva, and also reacted with a protein of the same electrophoretic mobility on immunoblots. From extracts of submandibular gland slices, incubated with [3H]leucine, the antibody again immunoprecipitated a 39K protein, indicating that this protein is synthesized in the gland. MA4 was used for immunocytochemical stainings of submandibular glands of rats of different ages. In general, immunostaining was seen only in acinar cells. Thus, there was no staining in the glands of 1-day-old rats that lack differentiated acinar cells. In the glands of 1- to 4-week-old rats the number of immunoreactive cells and the extent of immunostaining paralleled the differentiation of the acinar cells. In the glands of adult rats a uniform staining of the secretory granules of the acinar cells was observed. The immunoreactive 39K protein seemed to be restricted to the acinar cells in the submandibular gland; there was no immunostaining in the parotid, sublingual, or lingual salivary glands, or in the pancreas, colon, and duodenum. Stimulation of saliva secretion by isoproterenol resulted in a virtual depletion of the antigen from the acinar cells. These results indicate the feasibility of producing mouse hybridomas that secrete antibodies against rat saliva components. The monoclonal antibody at hand will be useful in analyzing the differentiation of the acinar cells, and the factors that influence this differentiation process.     

The influence of fixation on the carbohydrate cytochemistry of rat salivary gland secretory granules

Synopsis A series of studies was performed to assess the optimum fixation conditions for staining of carbohydrate-containing constituents of rat salivary gland secretory granules. In the parotid and submandibular salivary glands of the rat, the reactivity of secretory granules, at both the light and electron microscopic level, with routine stains and with cytochemical reagents was highly dependent upon the nature of the fixative employed. At the light microscopic level, secretory granules in rat parotid gland were periodic acid-Schiff (PAS) positive if fixed with buffered formalin fixatives. However, if the gland was fixed with lipid-solvent-containing fixatives, or with formalin at a very acid pH (as in Bouin's fixative), the PAS reactivity of the granules was lost. In the submandibular gland of rats, the acinar cells and granular tubules behaved similarly after such fixation in terms of their PAS reactivity, particularly in males; acinar cells of the female submandibular gland stained only lightly with PAS. At the fine structural level, the morphology of secretory granule constituents depended on the buffer used (cacodylate, phosphate or collidine) and on whether or not tissue was post-osmicated. Post-osmication considerably reduced the reaction of secretory granule components with stains for carbohydrates.The experimental evidence indicated that the carbohydrate-containing components of both parotid and submandibular gland secretory granules were not typical long-chain neutral or acidic mucins, but were rather glycolipids or lipophilic glycoproteins that were solubilized by lipid solvents or at acidic pH and were lost or destroyed in the presence of strong oxidants.     

Potential therapeutic effects of induced pluripotent stem cells on induced salivary gland cancer in experimental rats

Salivary gland neoplasms exhibit complex histopathology in a variety of tumor types and treatment options depend largely on the stage of the cancer. Induced pluripotent stem cells (iPS) have been investigated for treating induced salivary gland cancer and for restoring salivary gland function. We investigated iPS treatment for salivary gland cancer both in vitro and in vivo. For our study in vitro, we re-programmed human skin fibroblasts to form iPS cells using a plasmid containing Oct4, Sox2, L-MYC and LIN28. For our study in vivo, we used 30 white male albino rats divided into the following groups of 10: group 1 (control): rats were injected with phosphate-buffered saline (PBS), group 2 induced squamous cell carcinoma (SCC): rat submandibular glands were injected with squamous carcinoma cells (SCC), group 3 (induced SCC/iPS): SCC treated rats treated with 5 × 106 iPS cells. Submandibular glands from rats of all groups were examined histologically and real time PCR was performed for amylase, and COX I and COX II gene expression. We confirmed that submandibular gland specimens included tumor tissue before starting treatment with iPS. iPS treated cases exhibited regeneration of salivary glands, although minor degenerative and vascularization changes remained. The acinar cells regained their proper organization, but continued to exhibit abnormal activity including hyperchromatism. iPS cells may be useful for treating salivary gland carcinomas.     

A Comparison of the Effects of Estrogen and Cimicifuga racemosa on the Lacrimal Gland and Submandibular Gland in Ovariectomized Rats

This study aims to observe the effects of estradiol and Cimicifuga racemosa on the lacrimal gland and submandibular gland of ovariectomized rats. We randomly divided 20 adult female SD rats into four groups—a sham-operated group (SHAM), ovariectomized (OVX) group, ovariectomized group treated with estradiol (OVX+ E), and ovariectomized group treated with the isopropanolic extract of Cimicifuga racemosa (OVX+ iCR). The SHAM group and OVX group used distilled water to instead the drugs. Two weeks after ovariectomy, the estradiol and iCR were administered for 4 weeks. Next, we used H&E staining and electron microscopy to observe any histological changes in the lacrimal and submandibular glands and immunohistochemical staining to observe the expressions of cleaved caspase-3 (Casp-3) and Cu-Zn SOD (superoxide dismutase). The H&E staining find that both drugs can prevent the cells of area from shrinkage in the two kinds of gland. But under the electron microscopy, estradiol and iCR have different efficacy. Estradiol is more effective at protecting mitochondria in lacrimal gland acinar cells than iCR, and iCR is more effective at suppressing endoplasmic reticulum expansion than estradiol. Both estradiol and iCR have a similar protective function on mitochondria in the submandibular gland. The protective function of the two glands may inhibit apoptosis by suppressing the expression of Casp-3. In addition, iCR increases the expression of Cu-Zn SOD in duct system of submandibular gland. The results suggest that both estradiol and iCR confer a protective effect on the lacrimal and submandibular glands of ovariectomized rats via different mechanisms.     

Localization of a mouse submandibular sialomucin by indirect immunofluorescence

Summary A sialomucin from the mouse submandibular gland was localized in the gland by indirect immunofluorescence. Fluorescence was localized over the acinar cells and, to a lesser extent, in the lumen of the ducts. The mucin antiserum did not show cross-reactivity with cells from the sublingual gland or with other mucous-producing cells from the respiratory and gastrointestinal tracts of the mouse, or with salivary gland tissue of the rat. The sialomucin lacks both sulphate andl-fucose. Localization of a mucin with such a composition, within acinar cells of the mouse submandibular gland, is consistent with previous observations from histochemistry and autoradiography.     

Rate of protein synthesis in rat salivary gland cells after pilocarpine or feeding

The effect of pilocarpine and food uptake on the rate of incorporation of [3H]-leucine in vivo was measured by means of quantitative radioautography in three exocrine cells of the rat: the acinar and the granular duct cells of the submandibular and the acinar cells of the parotid gland. The three cell types react differently. The submandibular acinar cells showed a decrease in incorporation rate after pilocarpine administration but not after feeding. The incorporation rate of the granular duct cells of the submandibular gland remains constant after both stimulations. The acinar cells of the parotid gland show an increase in incorporation rate of [3H]-leucine in response to both. The contrast between the submandibular and the parotid gland could also be demonstrated radiobiochemically, the results reflecting the incorporation rates of the acinar cells of both glands, giving no information on the contribution of other cell types. The decrease in incorporation rate of the submandibular gland acinar cells is accompained by a shift of polyribosomes towards monomers.     

Immunohistochemistry of carbonic anhydrase isozymes VI and II during development of the rat salivary glands

 Secreted carbonic anhydrase (isozyme VI; CA VI) was localized by immunohistochemistry in the developing postnatal rat submandibular and parotid glands using a specific monoclonal antibody to the rat enzyme. CA VI immunostaining was not detectable in the glands before birth. In the submandibular gland, granular immunostaining for CA VI was detectable in several terminal tubule cells of 1-day-old rats. At 1 week, the CA VI-positive cells were located at the periphery of the terminal tubules and appeared to be budding off the tubules. These cellular buds gradually increased, and, by 4 weeks, formed acini. CA VI was also detected in the duct lumen from day 1. The immunostaining in the parotid gland was detected sporadically in the acinar cells at 2 or 3 weeks. By 4 weeks, when the gland was almost indistinguishable from the adult one, the number of positive acinar cells had increased. Their number, however, was far smaller than in the adult gland, and the enzyme could not be detected in the duct lumen. CA II was also localized using specific antibodies to the rat isozyme. CA II was detectable in the inter- and intralobular striated ducts at 2 weeks after birth in the submandibular gland and at 3 weeks in the parotid gland. These results suggset that CA VI is secreted into saliva from soon after birth and that CA II appears in parallel with the functional maturation of the ducts. In addition, CA II was transiently expressed by the cellular buds of the submandibular gland at 2 and 3 weeks. Accepted: 7 January 1998     

Immunohistochemical localization of dipeptidyl aminopeptidase (DAP) IV in the rat submandibular gland during postnatal development

Summary The localization of dipeptidyl aminopeptidase (DAP) IV in the rat submandibular gland during postnatal development was studied immunohistochemically using the unlabeled antibody enzyme method. Cryostat sections of rat submandibular glands were examined in animals 1 to 50 days old. In the first postnatal week, faint immunoreaction was detected in the apical region of the cytoplasm of terminal tubules. During the second postnatal week the reaction was gradually restricted to the luminal region of terminal tubules or developing acinar cells, and its intensity increased. The most striking change of the enzyme localization was observed in 15-day-old rats. At this time, DAP IV was confined to the luminal and lateral membranes of differentiated acinar cells and to the luminal membranes of intercalated and striated duct cells. This localization pattern was similar to that of the adult animal. DAP IV activity in the gland was also measured biochemically during the postnatal development. The results were in agreement with those of the immunohistochemical study. These results suggest that the localization of DAP IV is closely related to the postnatal differentiation and proliferation of acinar cells.     

Activin A induces expression of rat Sel-1l mRNA, a negative regulator of notch signaling, in rat salivary gland-derived epithelial cells

We previously established a rat submandibular gland (SMG)-derived epithelial cell line (RSMG-1) to study the mechanism of morphogenesis in salivary gland development and regeneration. We found that activin A regulated the branching morphogenesis of RSMG-1 cells, suggesting that it is involved in SMG morphogenesis. We used a subtraction cloning procedure with activin-A-treated and untreated RSMG-1 cells to identify activin-A-induced genes. One of the genes detected encoded a rat homologue of Sel-1l (rSel-1l). rSel-1l is a mammalian homologue of C. elegans sel-1, which is a negative regulator of Notch signaling. In this study, we confirmed that activin A induces rSel-1l mRNA expression in RSMG-1 cells, and that rSel-1l is expressed in SMG acinar cells. These results suggest that activin A regulates the differentiation of RSMG-1 cells to acinar cells.