Analysis of B7-H4 Expression Across Salivary Gland Carcinomas Reveals Adenoid Cystic Carcinoma-Specific Prognostic Relevance.

B7-H4 (VTCN1), a member of the B7 family, is overexpressed in several types of cancer. Here we investigated the pattern of expression of B7-H4 in salivary gland carcinomas (SGC) and assessed its potential as a prognostic marker and therapeutic target. Immunohistochemistry (IHC) analyses were performed in a cohort of 340 patient tumors, composed of 124 adenoid cystic carcinomas (ACC), 107 salivary duct carcinomas (SDC), 64 acinic cell carcinomas, 36 mucoepidermoid carcinomas (MEC), 9 secretory carcinomas (SC), as well as 20 normal salivary glands (controls). B7-H4 expression was scored and categorized into negative (<5% expression of any intensity), low (5%-70% expression of any intensity or >70% with weak intensity), or high (>70% moderate or strong diffuse intensity). The associations between B7-H4 expression and clinicopathologic characteristics, as well as overall survival, were assessed. Among all tumors, B7-H4 expression was more prevalent in ACC (94%) compared with those of SC (67%), MEC (44%), SDC (32%), and acinic cell carcinomas (0%). Normal salivary gland tissue did not express B7-H4. High expression of B7-H4 was found exclusively in ACC (27%), SDC (11%), and MEC (8%). In SDC, B7-H4 expression was associated with female gender (P = .002) and lack of androgen receptor expression (P = .012). In ACC, B7-H4 expression was significantly associated with solid histology (P < .0001) and minor salivary gland primary (P = .02). High B7-H4 expression was associated with a poorer prognosis in ACC, regardless of clinical stage and histologic subtype. B7-H4 expression was not prognostic in the non-ACC SGC evaluated. Our comparative study revealed distinct patterns of B7-H4 expression according to SGC histology, which has potential therapeutic implications. B7-H4 expression was particularly high in solid ACC and was an independent prognostic marker in this disease but not in the other SGC assessed.

Immunoassay Detects Salivary Anti-SSA/Ro-52 Autoantibodies in Seronegative Patients with Primary Sjögren's Syndrome.

The diagnostic work-up for Sjögren's syndrome is challenging and complex, including testing for serum autoantibodies to SSA/Ro and a labial salivary gland biopsy. Furthermore, the diagnosis is often delayed. In this study, we tested the hypothesis that anti-SSA/Ro autoantibodies are detectable in the saliva of patients with primary Sjögren's syndrome (pSS) because the disease affects the salivary glands, and these autoantibodies display greater discriminatory performance in saliva than in serum. SSA/Ro-52 Ags were used to develop what is, to our knowledge, a novel quantitative electrochemical-based immunoassay: the electric field-induced release and measurement (EFIRM) platform. The clinical utility was determined by measuring salivary anti-SSA/Ro-52 autoantibodies in patients with pSS and sicca (n = 34), patients without pSS with sicca (n = 35), and healthy subjects (n = 41). The statistical analysis of discrimination included the area under the receiver operating characteristic curve. Salivary anti-SSA/Ro-52 autoantibodies were measured in 94% (32 of 34) of patients with pSS with 85% (29 of 34) seropositivity. Four of the five seronegative patients with pSS had EFIRM-measurable anti-SSA/Ro-52 autoantibodies in saliva. Additionally, 60% (21 of 35) of the seronegative patients without pSS who had sicca had EFIRM-detectable SSA/Ro-52 autoantibodies in saliva, indicating the onset of autoimmune disease. Two of the 41 healthy control subjects had EFIRM-detectable SSA/Ro-52 autoantibodies in their saliva. Salivary SSA/Ro-52 autoantibodies significantly discriminated patients with pSS or patients with the initial stage of autoimmune disease from healthy subjects with an area under the receiver operating characteristic curve of 0.91. Our findings suggest that the proposed saliva SSA/Ro-52 immunoassay improves early and accurate diagnosis of seronegative patients with pSS and patients with early-onset autoimmune disease.

Performing Immunohistochemistry in Mosquito Salivary Glands.

Studying protein localization in mosquito salivary glands provides novel insights on the function and physiological relevance of salivary proteins and also provides an avenue to study interactions between mosquitoes and pathogens. Salivary proteins display compartmentalization. For example, proteins involved in blood feeding are stored in the medial and distal lateral lobes, whereas proteins related to sugar metabolism localize to the proximal portion of the lateral lobes. Immunohistochemistry assays use antibodies raised against recombinant salivary proteins to reveal the protein localization and interactions within the tissue. In this assay, permeabilization of the salivary glands allows the antibodies to enter the cells and bind their target proteins. The primary antibody-antigen complexes are later marked with fluorescently labeled secondary antibodies. Antibodies that recognize pathogen-specific proteins can also be incorporated in these assays, providing information about pathogen localization within the salivary glands or pathogen interactions with mosquito salivary proteins. Here, we introduce immunohistochemistry assays for use in mosquito salivary glands.

A Simple Method for Immunohistochemistry and Imaging of Mosquito Salivary Glands.

Immunohistochemistry is a valuable technique that provides information on protein localization and interactions in tissues. Mosquito salivary gland immunohistochemistry requires the meticulous dissection of a delicate tissue. The integrity of the salivary glands must be closely monitored throughout the entire process to prevent structural damage and loss of saliva. This protocol describes a series of simple steps to perform salivary gland immunohistochemistry including tissue dissection, permeabilization, immunostaining, mounting, and imaging by confocal microscopy.

Evaluation of HER2/neu expression in different types of salivary gland tumors: a systematic review and meta-analysis.

This study is a systematic review and meta-analysis to assess the overexpression rate of HER2 in patients with salivary gland tumors. We included peer-reviewed publications from 1995 to 2020, indexed in medical databases, using search terms such as "human epidermal growth factor receptor 2 (HER2)" and "salivary gland tumors", and extracted relevant data. The extracted data were analyzed with RevMan 5.3 software. Intra-and intergroup post hoc analyses of outcome variables were performed using t-tests, and the rates of HER2 positivity among studies were evaluated. 80 studies were included in the analysis. The positive rates of HER2 ranged from 3.3% to 84.0% and 1% to 9% in malignant and benign subtypes, respectively. The highest HER2 overexpression rate among malignant tumors was in salivary ductal carcinomas (SDC), with a 45% positive rate (CI 95%: 21.9-70.3%). Mucoepidermoid carcinoma (MEC) had the highest positive rate of 84% (CI 95%: 74.1-90.0%). Among benign salivary gland tumors, the highest rate was found in myoepithelioma, with a positive rate of 9% (CI 95%: 1.7-33.6%). The highest rate of HER2 overexpression is present in malignant subtypes of salivary gland tumors, more specifically in salivary ductal carcinoma, mucoepidermoid carcinomas, salivary duct carcinoma in situ, and carcinoma ex pleomorphic adenoma.

Characterization of a single-domain von Willebrand factor type C protein (HaSVC) from the salivary gland of the tick Hyalomma asiaticum.

As a widely distributed arthropod and vector for various pathogens, Hyalomma asiaticum presents great risk and potential losses in animal husbandry. Effective measures, including the use of vaccines, are necessary for controlling ticks and tick-borne diseases. A concise understanding of the tick-host interaction associated molecules and pathways is required for vaccine development. In the present study, a protein containing a single-domain von Willebrand factor type C (HaSVC) was isolated from H. asiaticum and was subjected to functional identification. As a result, the full-length sequence of the HaSVC (506 bp) gene was obtained, which putatively encodes 100 amino acids with a predicted molecular mass of 11 kDa, excluding the 23-amino acid signal peptide. HaSVC contains 8 cysteines to form 4 disulfide bonds. The native HaSVC protein was detected in multiple tick organs. HaSVC neither attenuated the anti-coagulation process nor directly affected the blood feeding of adult ticks. However, the purified recombinant protein HaSVC (rHaSVC/GST) significantly increased the proliferation of mice spleen cells. This might suggest a regulatory function for HaSVC on inflammation, thus providing new information that may explain the "crosstalk" between ticks and hosts.

The toxin mimic FS48 from the salivary gland of Xenopsylla cheopis functions as a Kv1.3 channel-blocking immunomodulator of T cell activation.

The Kv1.3 channel has been widely demonstrated to play crucial roles in the activation and proliferation of T cells, which suggests that selective blockers could serve as potential therapeutics for autoimmune diseases mediated by T cells. We previously described that the toxin mimic FS48 from salivary gland of Xenopsylla cheopis downregulates the secretion of proinflammatory factors by Raw 264.7 cells by blocking the Kv1.3 channel and the subsequent inactivation of the proinflammatory MAPK/NF-κB pathways. However, the effects of FS48 on human T cells and autoimmune diseases are unclear. Here, we described its immunomodulatory effects on human T cells derived from suppression of Kv1.3 channel. Kv1.3 currents in Jurkat T cells were recorded by whole-cell patch-clamp, and Ca2+ influx, cell proliferation, and TNF-α and IL-2 secretion were measured using Fluo-4, CCK-8, and ELISA assays, respectively. The in vivo immunosuppressive activity of FS48 was evaluated with a rat DTH model. We found that FS48 reduced Kv1.3 currents in Jurkat T cells in a concentration-dependent manner with an IC50 value of about 1.42 µM. FS48 also significantly suppressed Kv1.3 protein expression, Ca2+ influx, MAPK/NF-κB/NFATc1 pathway activation, and TNF-α and IL-2 production in activated Jurkat T cells. Finally, we show that FS48 relieved the DTH response in rats. We therefore conclude that FS48 can block the Kv1.3 channel and inhibit human T cell activation, which most likely contributes to its immunomodulatory actions and highlights the great potential of this evolutionary-guided peptide as a drug template in future studies.

Identification of a substrate-like cleavage-resistant thrombin inhibitor from the saliva of the flea Xenopsylla cheopis.

The salivary glands of the flea Xenopsylla cheopis, a vector of the plague bacterium, Yersinia pestis, express proteins and peptides thought to target the hemostatic and inflammatory systems of its mammalian hosts. Past transcriptomic analyses of salivary gland tissue revealed the presence of two similar peptides (XC-42 and XC-43) having no extensive similarities to any other deposited sequences. Here we show that these peptides specifically inhibit coagulation of plasma and the amidolytic activity of α-thrombin. XC-43, the smaller of the two peptides, is a fast, tight-binding inhibitor of thrombin with a dissociation constant of less than 10 pM. XC-42 exhibits similar selectivity as well as kinetic and binding properties. The crystal structure of XC-43 in complex with thrombin shows that despite its substrate-like binding mode, XC-43 is not detectably cleaved by thrombin and that it interacts with the thrombin surface from the enzyme catalytic site through the fibrinogen-binding exosite I. The low rate of hydrolysis was verified in solution experiments with XC-43, which show the substrate to be largely intact after 2 h of incubation with thrombin at 37 °C. The low rate of XC-43 cleavage by thrombin may be attributable to specific changes in the catalytic triad observable in the crystal structure of the complex or to extensive interactions in the prime sites that may stabilize the binding of cleavage products. Based on the increased arterial occlusion time, tail bleeding time, and blood coagulation parameters in rat models of thrombosis XC-43 could be valuable as an anticoagulant.

Localization and Bioreactivity of Cysteine-Rich Secretions in the Marine Gastropod Nucella lapillus.

Marine biodiversity has been yielding promising novel bioproducts from venomous animals. Despite the auspices of conotoxins, which originated the paradigmatic painkiller Prialt, the biotechnological potential of gastropod venoms remains to be explored. Marine bioprospecting is expanding towards temperate species like the dogwhelk Nucella lapillus, which is suspected to secrete immobilizing agents through its salivary glands with a relaxing effect on the musculature of its preferential prey, Mytilus sp. This work focused on detecting, localizing, and testing the bioreactivity of cysteine-rich proteins and peptides, whose presence is a signature of animal venoms and poisons. The highest content of thiols was found in crude protein extracts from the digestive gland, which is associated with digestion, followed by the peribuccal mass, where the salivary glands are located. Conversely, the foot and siphon (which the gastropod uses for feeding) are not the main organs involved in toxin secretion. Ex vivo bioassays with Mytilus gill tissue disclosed the differential bioreactivity of crude protein extracts. Secretions from the digestive gland and peribuccal mass caused the most significant molecular damage, with evidence for the induction of apoptosis. These early findings indicate that salivary glands are a promising target for the extraction and characterization of bioactive cysteine-rich proteinaceous toxins from the species.

Stingless Bee-Collected Pollen (Bee Bread): Chemical and Microbiology Properties and Health Benefits.

Stingless bee-collected pollen (bee bread) is a mixture of bee pollen, bee salivary enzymes, and regurgitated honey, fermented by indigenous microbes during storage in the cerumen pot. Current literature data for bee bread is overshadowed by bee pollen, particularly of honeybee Apis. In regions such as South America, Australia, and Southeast Asia, information on stingless bee bee bread is mainly sought to promote the meliponiculture industry for socioeconomic development. This review aims to highlight the physicochemical properties and health benefits of bee bread from the stingless bee. In addition, it describes the current progress on identification of beneficial microbes associated with bee bread and its relation to the bee gut. This review provides the basis for promoting research on stingless bee bee bread, its nutrients, and microbes for application in the food and pharmaceutical industries.

The leishmanicidal effect of Lucilia sericata larval saliva and hemolymph on in vitro Leishmania tropica.

BACKGROUND: Leishmaniasis is a major parasitic disease worldwide, except in Australia and Antarctica, and it poses a significant public health problem. Due to the absence of safe and effective vaccines and drugs, researchers have begun an extensive search for new drugs. The aim of the current study was to investigate the in vitro leishmanicidal activity of larval saliva and hemolymph of Lucilia sericata on Leishmania tropica. METHODS: The effects of different concentrations of larval products on promastigotes and intracellular amastigotes of L. tropica were investigated using the mouse cell line J774A.1 and peritoneal macrophages as host cells. The 3-(4.5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and direct observation and counting method were used to assess the inhibitory effects and cell cytotoxicity of the larval products. The effects of larval products on the amastigote form of L. tropica were quantitatively estimated by calculating the rate of macrophage infection, number of amastigotes per infected macrophage cell, parasite load and survival index. RESULTS: The 50% cytotoxicity concentration (CC50) value of both larval saliva and hemolymph was 750 µg/ml, and the 50% inhibitory concentration (IC50) values were 134 µg/ml and 60 µg/ml for larval saliva and larval hemolymph, respectively. The IC50 for Glucantime, used a positive control, was (11.65 µg/ml). Statistically significant differences in viability percentages of promastigotes were observed for different doses of both larval saliva and hemolymph when compared with the negative control (p ≤ 0.0001). Microscopic evaluation of the amastigote forms revealed that treatment with 150 µg/ml larval hemolymph and 450 µg/ml larval saliva significantly decreased the rate of macrophage infection and the number of amastigotes per infected macrophage cell. CONCLUSION: Larval saliva and hemolymph of L. sericata have acceptable leishmanicidal properties against L. tropica.

The sialotranscriptome of the gopher-tortoise tick, Amblyomma tuberculatum.

The gopher tortoise tick, Amblyomma tuberculatum, is known to parasitize keystone ectotherm reptile species. The biological success of ticks requires precise mechanisms to evade host hemostatic and immune responses. Acquisition of a full blood meal requires attachment, establishment of the blood pool, and engorgement of the tick. Tick saliva contains molecules which counter the host responses to allow uninterrupted feeding on the host. RNASeq of the salivary glands of Amblyomma tuberculatum ticks were sequenced resulting in 138,030 pyrosequencing reads which were assembled into 29,991 contigs. A total of 1875 coding sequences were deduced from the transcriptome assembly, including 602 putative secretory and 982 putative housekeeping proteins. The annotated data sets are available as a hyperlinked spreadsheet. The sialotranscriptome assembled for this tick species made available a valuable resource for mining novel pharmacological activities and comparative analysis.

Human immunoglobulin G responses to Cimex lectularius L. saliva.

AIMS: To investigate the immunoglobulin (Ig) G response after being fed upon by Cimex lectularius L. METHODS AND RESULTS: Participants were fed upon by three male C lectularius insects weekly for a month. Blood was obtained before the feeding and at the last feeding, which was used for immunoblots against bed bug salivary gland extract, with antihuman Immunoglobulin G (IgG) secondary antibodies. No consistent IgG changes developed in 11 humans serially fed upon by C lectularius. Two participants had new IgG responses to proteins at molecular weights of approximately 12-13 kDa, and one had an IgG response to a protein at approximately 40 kDa. At the last study visit, more intense IgG bands to proteins at molecular weights of 12-13 kDa had developed in 55% of participants (6/11) and at molecular weights of ≈30, ≈40 and ≈70 kDa in 45% (5/11) compared with the first study visit. Nitrophorin and apyrase were the most common C lectularius proteins identified with liquid chromatography-tandem mass spectrometry in both crushed bed bug salivary gland extract and post-bed bug feeding extract. CONCLUSIONS: Human participants did not have consistent IgG responses to crushed C lectularius salivary gland extract.

Salivary gland transcriptome of the Asiatic Triatoma rubrofasciata.

Salivary gland transcriptome analysis of the Asiatic Triatoma rubrofasciata was performed by high-throughput RNA sequencing. This analysis showed that the majority of reads accounting for 85.38% FPKM (fragments per kilobase of exon per million mapped fragments) were mapped with a secreted class. Of these, the most abundant subclass accounting for 89.27% FPKM was the lipocalin family. In the lipocalin family, the most dominant molecules making up 70.49% FPKM were homologues of procalin, a major allergen identified from T. protracta saliva, suggesting an important role in blood-sucking of T. rubrofasciata. Other lipocalins showed similarities to pallidipin and triplatin, inhibitors of collagen-induced platelet aggregation identified from T. pallidipennis and T. infestans, respectively, Td38 from T. dimidiata with unknown function, triatin-like lipocalin with unknown function, and triafestin, an inhibitor of the activation of the kallikrein-kinin system, identified from T. infestans saliva. Other than lipocalin family proteins, homologues of antigen-5 (3.38% FPKM), Kazal-type serine protease inhibitor (1.36% FPKM), inositol polyphosphate 5-phosphatase (1.32% FPKM), and apyrase/5'-nucleotidase (0.64% FPKM) were identified as abundant molecules in T. rubrofasciata saliva. Through this study, de novo assembly of 42,580,822 trimmed reads generated 35,781 trinity transcripts, and a total of 1,272 coding sequences for the secreted class were deposited in GenBank. The results provide further insights into the evolution of salivary components in blood-sucking arthropods.

Changes in human health parameters associated with an immersive exhibit experience at a zoological institution.

Zoological institutions often use immersive, naturalistic exhibits to create an inclusive atmosphere that is inviting for visitors while providing for the welfare of animals in their collections. In this study, we investigated physiological changes in salivary cortisol and blood pressure, as well as psychological changes among visitors before and after a walk through the River's Edge, an immersive, naturalistic exhibit at the Saint Louis Zoo. Study participants had a significant reduction in salivary cortisol and blood pressure after walking through the exhibit. Psychological assessments of mood found that most visitors felt happier, more energized, and less tense after the visit. Additionally, participants who spent more time in River's Edge, had visited River's Edge prior to the study, and had seen more exhibits at the Zoo prior to entering River's Edge experienced greater psychological and/or physiological benefits. We conclude that immersive, naturalistic exhibits in zoos can elicit positive changes in physiological and psychological measures of health and well-being and argue for a greater scientific focus on the role of zoos and other green spaces in human health.

The Pharmacopea within Triatomine Salivary Glands.

Triatomines are blood-feeding insects that prey on vertebrate hosts. Their saliva is largely responsible for their feeding success. The triatomine salivary content has been studied over the past decades, revealing multifunctional bioactive proteins targeting the host´s hemostasis and immune system. Recently, sequencing of salivary-gland mRNA libraries revealed increasingly complex and complete transcript databases that have been used to validate the expression of deduced proteins through proteomics. This review provides an insight into the journey of discovery and characterization of novel molecules in triatomine saliva.

Comparison of Prostate-Specific Membrane Antigen Expression Levels in Human Salivary Glands to Non-Human Primates and Rodents.

Background: Prostate-specific membrane antigen (PSMA) has emerged as a promising target for developing radionuclide therapy (RNT) in prostate cancer; however, accumulation of PSMA-RNT in salivary glands can result in irreversible xerostomia. Methods to prevent PSMA-RNT-related xerostomia could be clinically useful; however, little is known about PSMA expression in salivary glands of preclinical animal models. Using [18F]DCFPyL autoradiography/biodistribution, PSMA expression levels were determined in salivary glands of various preclinical monkey and rodent species and compared with humans. Methods: Binding affinities (Kd) and PSMA levels (Bmax) were determined by in vitro [18F]DCFPyL autoradiography studies. In vivo rodent tissue uptakes (%ID/g) were determined from [18F]DCFPyL biodistributions. Results: [18F]DCFPyL exhibited low nanomolar Kd for submandibular gland (SMG) PSMA across all the species. PSMA levels in human SMG (Bmax = 60.91 nM) were approximately two-fold lower compared with baboon SMG but were two- to three-fold higher than SMG PSMA levels of cynomolgus and rhesus. Rodents had the lowest SMG PSMA levels, with the mouse being 10-fold higher than the rat. In vivo rodent biodistribution studies confirmed these results. Conclusions: SMG of monkeys exhibited comparable PSMA expression to human SMG whereas rodents were lower. However, the results suggest that mice are relatively a better small animal preclinical model than rats for PSMA salivary gland studies.

Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania.

BACKGROUND: Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. METHODS: The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.-8 a.m.), evenings (6 p.m.-8 p.m.) and at night (11 p.m.-12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets). RESULTS: Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus; 60-66% of An. arabiensis). CONCLUSION: While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

Study of the pharmacokinetics of eriodictyol-6-C-ß-d-glucoside, a flavonoid of rooibos (Aspalathus linearis) extract, after its oral administration in mice.

Systemic dry syndrome affects quality of life, and various effective methods are being developed for its treatment. We recently found that rooibos (Aspalathus linearis) extract activates muscarinic M3 receptor and improves dryness in mice and humans. We identified eriodictyol-6-C-ß-D-glucoside (E6CG) as the active component affecting the secretory functions of exocrine glands; however, the pharmacokinetics and distribution of E6CG in exocrine glands have not been elucidated in mice receiving rooibos extract. We have developed a quantification method using LC-MS/MS to detect E6CG without an internal standard. Experiments on C57BL/6 mice administered rooibos extract showed that E6CG was transferred into blood plasma, with its concentration levels peaking 19.3 min after treatment. Substantial levels of E6CG were detected in the submandibular, sublingual, parotid, and lacrimal glands and in the sweat glands in palm skin. This study reports that rooibos extracts containing E6CG can be used as functional foods for improving systemic dryness.

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

Zn2+ 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-ß 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.