Zn2+ stimulates salivary secretions via metabotropic zinc receptor ZnR/GPR39 in human salivary gland cells

AbstractZn2+ is a divalent cation that is essential for many biological activities, as it influences many ion channels and enzymatic activities. Zn2+ can evoke G-protein-coupled receptor signaling via activation of the metabotropic zinc receptor ZnR/GPR39. In spite of evidence suggesting the presence of ZnR/GPR39 in salivary gland cells, there has been no evidence of ZnR/GPR39-mediated modulation of salivary gland function. Here we characterized the role of ZnR/GPR39 in human submandibular gland cells. A 0.25% ZnCl2 solution evoked secretion of unstimulated and stimulated whole saliva in humans. We found that ZnR/GPR39 is expressed in human submandibular glands and HSG cells. Zn2+ increased cytosolic Ca2+ concentration ([Ca2+]i) in a concentration-dependent manner. Muscarinic antagonist had no effect on Zn2+-induced [Ca2+]i increase, which was completely blocked by the phospholipase C-β inhibitor. As with muscarinic agonist, Zn2+ also induced the translocation of aquaporin-5 (AQP-5) to the plasma membrane, which was drastically decreased in ZnR/GPR39-knockdown cells. These data suggest that the metabotropic Zn2+ receptor ZnR/GPR39 can modulate salivary secretion in human submandibular gland cells independent of muscarinic or histamine receptor signaling.

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Constitutive Expression of a Bacterial Pattern Recognition Receptor, CD14, in Human Salivary Glands and Secretion as a Soluble Form in Saliva

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.10.2.286-292.2003 ◽

2003 ◽

Vol 10 (2) ◽

pp. 286-292 ◽

Cited By ~ 28

Author(s):

Akiko Uehara ◽

Shunji Sugawara ◽

Kouichi Watanabe ◽

Seishi Echigo ◽

Mitsunobu Sato ◽

...

Keyword(s):

Pattern Recognition ◽

Salivary Gland ◽

Pattern Recognition Receptor ◽

Soluble Form ◽

Dependent Manner ◽

Parotid Saliva ◽

Gland Cells ◽

Salivary Gland Cells ◽

Whole Saliva ◽

Recognition Receptor

ABSTRACT Saliva contains a number of proteins and glycoproteins that protect oral tissues, but little is known about the role of human saliva in innate immunity. Here we showed that human major salivary gland cells constitutively expressed a bacterial pattern recognition receptor, CD14, by immunohistochemistry. Human salivary gland cells in culture express CD14 mRNA and a 55-kDa CD14 protein in, but not on the cells, and secrete a soluble form with the same molecular mass. Human whole saliva contains a 55-kDa CD14, and the concentration of parotid saliva was 10-fold higher than whole saliva, which is comparable to that of serum CD14. Levels of CD14 in unstimulated whole and parotid saliva were unchanged before and after a meal and between unstimulated and stimulated saliva, indicating that saliva CD14 is constitutively secreted into the oral cavity. In contrast, lipopolysaccharide (LPS)-binding protein was below the detectable level. The saliva CD14 is functionally active in that it mediated the activation of CD14-lacking intestinal epithelial cells by LPS in a Toll-like receptor 4-dependent manner. These results suggested that saliva CD14 is important for the maintenance of oral health and possibly intestinal homeostasis.

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Salivary Growth Factors in Health and Disease

Advances in Dental Research ◽

10.1177/08959374000140011601 ◽

2000 ◽

Vol 14 (1) ◽

pp. 99-102 ◽

Cited By ~ 24

Author(s):

H. Kagami ◽

Y. Hiramatsu ◽

S. Hishida ◽

Y. Okazaki ◽

K. Horie ◽

...

Keyword(s):

Cell Proliferation ◽

Salivary Gland ◽

Growth Factors ◽

Growth Factor ◽

Submandibular Gland ◽

Cultured Cells ◽

Healing Process ◽

Physiological Role ◽

Gland Cells ◽

Salivary Gland Cells

The salivary gland is considered to be a reservoir of many growth factors in rodents. In humans, the epidermal growth factor, basic fibroblast growth factor, and insulin and insulin-like growth factor family have also been detected in this gland, but their physiological role remains unclear. In this study, we focused on bFGF, which is a well-known mitogen for various types of cells, and is present in the salivary gland as well as in saliva. The roles of bFGF in the salivary gland were investigated by three different procedures. First, the effects of bFGF on the salivary gland cells were investigated with a monolayer culture of normal submandibular gland cells. The effects of different concentrations of bFGF on the second passage of these cultured cells were examined. In both human and rat cultured submandibular gland cells, bFGF accelerated the cell proliferation at a concentraion of 100 ng/mL or higher. Next, an atrophic model of the rat submandibular gland was used to examine the ability of bFGF to accelerate tissue repair. Two weeks after ductal ligation, the ligature was removed, and various amounts of bFGF, isoproterenol, or saline were administered via a retrograde duct instillation. Both isoproterenol and bFGF increased acinar and ductal cell proliferation significantly. To determine the role of bFGF in saliva, we investigated its effect on the healing process of oral mucosal defects. Four-millimeter mucosal defects were made to the depth of the periosteum in the rat palate under anesthesia. bFGF or vehicle alone was applied once only at the time of surgery as a suspension. At days 3, 5, and 7 in the bFGF group, significant increases in the degree of re-epithelialization were found in treated groups. These results indicate that its action as a mitogen stimulus is the major effect of bFGF on salivary gland cells and mucosal epithelium.

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Novel phosphorylation of aquaporin-5 at its threonine 259 through cAMP signaling in salivary gland cells

AJP Cell Physiology ◽

10.1152/ajpcell.00058.2011 ◽

2011 ◽

Vol 301 (3) ◽

pp. C667-C678 ◽

Cited By ~ 15

Author(s):

Takahiro Hasegawa ◽

Ahmad Azlina ◽

Purevjav Javkhlan ◽

Chenjuan Yao ◽

Tetsuya Akamatsu ◽

...

Keyword(s):

Salivary Gland ◽

Water Channel ◽

Calcium Ionophore ◽

Wild Type Mouse ◽

Protein Band ◽

Parotid Glands ◽

Aquaporin 5 ◽

Short Term Treatment ◽

Gland Cells ◽

Salivary Gland Cells

Aquaporin-5 (AQP5), a water channel, plays key roles in salivary secretion. The novel phosphorylation of AQP5 was investigated by using human salivary gland (HSG) cells and mouse salivary glands. In the HSG cells stably transfected with a wild-type mouse AQP5 construct, a protein band immunoreactive with antibody against phosphorylated PKA substrate was detected in the AQP5 immunoprecipitated sample, and its intensity was enhanced by short-term treatment of the cells with 8-bromo-cAMP, forskolin, or phorbol 12-myristate 13-acetate, but not by that with A23187 calcium ionophore. Such enhancement was inhibited in the presence of H-89, a PKA inhibitor. An AQP5 mutant (AQP5-T259A) expressed by transfection of HSG cells was not recognized by anti-phosphorylated PKA substrate antibody, even when the cells were stimulated with the protein kinase activators. Immunoblotting and immunofluorescence studies using a specific antibody detecting AQP5 phosphorylated at its Thr259 demonstrated that AQP5 was rapidly and transiently phosphorylated at the apical membrane of acinar cells in the submandibular and parotid glands after administration of isoproterenol, but not pilocarpine. Furthermore, both AQP5 and AQP5-T259A were constitutively localized at the plasma membrane in HSG cells under the resting and forskolin-stimulated conditions. These results suggest that AQP5 is phosphorylated at its Thr259 by PKA through cAMP, but not Ca2+, signaling pathways, and that this phosphorylation does not contribute to AQP5 trafficking in the salivary gland cells.

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Activation of transient receptor potential vanilloid subtype 1 increases secretion of the hypofunctional, transplanted submandibular gland

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00528.2009 ◽

2010 ◽

Vol 299 (1) ◽

pp. G54-G62 ◽

Cited By ~ 19

Author(s):

Y. Zhang ◽

X. Cong ◽

L. Shi ◽

B. Xiang ◽

Y. M. Li ◽

...

Keyword(s):

Mrna Expression ◽

Submandibular Gland ◽

Transient Receptor Potential ◽

Keratoconjunctivitis Sicca ◽

Receptor Potential ◽

Transient Receptor Potential Vanilloid ◽

Dependent Manner ◽

Aquaporin 5 ◽

Gland Cells ◽

Transient Receptor

Hyposecretion occurs in most patients early after submandibular gland autotransplantation for severe keratoconjunctivitis sicca. Endogenous transient receptor potential vanilloid subtype 1 (TRPV1) has been recently demonstrated in rabbit submandibular glands, and activation of TRPV1 by capsaicin increases secretion in isolated glands, but the TRPV1-mediated secretory mechanism remains to be elucidated. The purpose of this study was to verify whether activation of TRPV1 by capsaicin could improve the secretion of transplanted gland and its underlying mechanism. The salivary flow of the transplanted glands was significantly decreased, and the mRNA and protein levels of TRPV1 and aquaporin 5 (AQP5) were downregulated in the transplanted glands. Topical capsaicin cream increased secretion and upregulated levels of TRPV1 and AQP5 in transplanted glands. Moreover, in cultured submandibular gland cells, capsaicin increased the mRNA expression of AQP5 and led to redistribution of AQP5 from the cytoplasm to the plasma membrane via TRPV1 activation. Capsaicin enhanced the phosphorylation of extracellular signal-regulated kinase (ERK). Preincubation of cells with PD98059, an inhibitor of ERK kinase, suppressed the capsaicin-induced mRNA expression of AQP5. In summary, the capsaicin-induced secretory mechanism involved activation of TRPV1 and upregulation of AQP5 in an ERK-dependent manner and promoted the redistribution of AQP5 in submandibular gland cells. Activation of TRPV1 may provide a new therapeutic strategy to improve submandibular gland hypofunction.

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