Androgen regulation of SMR2 gene expression in rat submandibular gland: evidence for a graded but not a binary response

Cimetidine-induced androgenic failure causes cell death and changes in actin, EGF and V-ATPase immunoexpression in rat submandibular glands

Submandibular gland (SMG) is responsive to androgens via androgen receptor (AR). We verified whether cimetidine induces androgenic dysfunction in SMG, and evaluated the structural integrity, cell death and immunoexpression of actin, EGF and V-ATPase in androgen-deficient SMG. Male rats received cimetidine (CMTG) and control animals (CG) received saline. Granular convoluted tubules (GCTs) diameter and number of acinar cell nuclei were evaluated. TUNEL and immunofluorescence reactions for detection of AR, testosterone, actin, EGF and V-ATPase were quantitatively analysed. In CG, testosterone immunolabelling was detected in acinar and ductal cells cytoplasm. AR-immunolabelled nuclei were observed in acinar cells whereas ductal cells showed AR-immunostained cytoplasm, indicating a non-genomic AR action. In CMTG, the weak testosterone and AR immunoexpression confirmed cimetidine-induced androgenic failure. A high cell death index was correlated with decreased number of acinar cells, GCTs diameter and EGF immunoexpression under androgenic dysfunction. Actin immunofluorescence decreased in the SMG cells, but an increased and diffuse cytoplasmic V-ATPase immunolabelling was observed in striated ducts, suggesting a disruption in the actin-dependent V-ATPase recycling due to androgenic failure. Our findings reinforce the androgenic role in the maintenance of SMG histophysiology, and point to a potential clinical use of cimetidine against androgen-dependent glandular tumour cells.

Generation and initial characterization of the prolactin-inducible protein (PIP) null mouse: accompanying global changes in gene expression in the submandibular gland

The human prolactin-inducible protein/gross cystic disease fluid protein-15 (hPIP/GCDFP-15) is a secretory glycoprotein found primarily in apocrine tissues including the breast and salivary glands. With largely unknown functions, PIP has been implicated in breast cancer and metastasis, host defense processes and T lymphocyte apoptosis. To begin to address PIP function in vivo, we generated the PIP null mouse (Pip-/-). Additionally, to determine the effect of the loss of PIP on gene expression and to gain insight into some of the molecular mechanisms underlying PIP function, microarray analysis of the submandibular gland was also undertaken. Pip-/- mice developed normally with no overt differences in behaviour or gross morphology and were fertile. However, histological examination of 3-month-old Pip-/- mice sometimes showed enlarged submandibular lymph nodes, lymphocytic aggregations within the prostate lobes, and enlarged medulla in the thymus. Functional analysis of gene expression revealed sets of multiple differentially expressed genes associated with cell death and survival, lipid metabolism, inflammation, immune disease, and cancer, as a consequence of mPIP abrogation. Taken together, these studies lend support to an immunomodulatory role for PIP in vivo and provide further insights into potentially novel signaling pathways and regulatory networks for PIP.

Parasympathectomy induces morphological changes and alters gene-expression profiles in the rat submandibular gland

OBJECTIVE

The chorda-lingual (CL) nerve carries parasympathetic fibers to the hilum of the sublingual and submandibular glands (SMGs) and evokes the secretion of saliva. The effect of cutting the CL nerve on the biological processes in SMGs was investigated by examining the gene-expression profiles in the SMGs after a surgical parasympathectomy.

METHODS

At day 3 after the CL nerve cut, the changes in the SMGs at both the experimental cut and contralateral control sides were analysed by microarray and light microscopy. The expression levels of 6 selected genes were confirmed by real-time PCR, Western blot and immunofluorescence staining.

RESULTS

The wet weight of the parasympathectomised SMGs decreased significantly compared to that of the contralateral side (p<0.05). Histological analyses after the parasympathectomy showed a widened interacinar space as well as some atropic changes to the acini of the SMGs in the cut side. Microarray analysis revealed that twofold differential expression in mRNA expression in the parasympathectomized SMGs were detected in 88 genes (0.004%): 41 genes were overexpressed, 11 were underexpressed and 36 were unknown. Changes of the expression of 6 selected genes detected by Western blot and/or real-time PCR were consistent with the microarray data.

CONCLUSION

The important genes involved in biological processes for salivation were identified through a large-scale gene expression analysis.

A novel mouse protein differentially regulated by androgens in the submandibular and lacrimal glands

We characterized a cDNA clone derived from the female mouse submandibular gland (SMG). The transcript of this cDNA was approximately 1.2kb in size and predicted to code a 165-amino acid protein with a putative signal peptide for a secretory pathway. This protein, named submandibular androgen-repressed protein (SMARP), had homology in the N-terminal region with members of the glutamine/glutamic acid-rich protein (GRP) family from rats. Northern blot analysis revealed that SMARP mRNA is expressed, out of the major mouse organs, only in the SMG and exorbital lacrimal gland (LG), with much more abundance in the former. For the SMG, the level of SMARP mRNA was 36 times higher in females than males, whereas for the LG it was 28 times higher in males than females. Furthermore, the level of SMARP mRNA was increased in the SMG but reduced in the LG with castration in males, whereas it was reduced in SMG but increased in LG after administration of testosterone in females or castrated males. In situ hybridization detected the signal for SMARP mRNA in the female SMG, and immunohistochemistry detected the signal for SMARP protein in the female SMG and male LG. In the female SMG, SMARP mRNA, and protein were localized intensively in a subpopulation of acinar cells, whereas in the male LG, SMARP protein was distributed diffusely in all acinar cells. These results suggested that SMARP is a secretory protein whose expression is regulated by androgens negatively in the SMG and positively in the LG.