Human salivary gland cells express bradykinin receptors that modulate the expression of proinflammatory cytokines

Abstract

Bradykinin is an important peptide modulator that affects the function of neurons and immune cells. However, there is no evidence of the bradykinin receptors and their functions in human salivary glands. Here we have identified and characterized bradykinin receptors on human submandibular gland cells. Both bradykinin B1 and B2 receptors are expressed on human submandibular gland cells, A253 cells, and HSG cells. Bradykinin increased the intracellular Ca concentration ([Ca ] ) in a concentration-dependent manner. Interestingly, a specific agonist of the B1 receptor did not have any effect on [Ca ] in HSG cells, whereas specific agonists of the B2 receptor had a Ca mobilizing effect. Furthermore, application of the B1 receptor antagonist, R715, did not alter the bradykinin-mediated increase in cytosolic Ca , whereas the B2 receptor antagonist, HOE140, showed a strong inhibitory effect, which implies that bradykinin B2 receptors are functional in modulating the concentration of cytosolic Ca . Bradykinin did not affect a carbachol-induced rise of [Ca ] and did not modulate translocation of aquaporin-5. However, bradykinin did promote the expression of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), implying the role of bradykinin in salivary gland inflammation. These data suggest that bradykinin receptors are involved in Ca signaling in human submandibular gland cells and serve a unique role, which is separate from that of other salivary gland G protein-coupled receptors.

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

“…We have studied salivary GPCRs for the past decade. We found that histamine H1 receptor 27 as well as muscarinic receptors causes aquaporin-5 translocation, but that the stimulation of sphingosine-1-phosphate receptor 28 and bradykinin B2 receptor 29 does not affect AQP-5 translocation. Therefore, our current study of salivary secretion by ZnR/GPR39 in human subjects is of significance in salivary translational research.…”

“…The fluorescent Ca 2+ indicator Fura-2 was used to determine [Ca 2+ ] i level, as previously reported 27,29 . Briefly, cell suspensions were incubated in Locke’s solution (154 mM NaCl, 5.6 mM KCl, 5.6 mM glucose, 2 mM CaCl 2 , 2 mM MgCl 2 , and 5 mM HEPES buffer adjusted to pH 7.4) supplemented with 3 μM Fura-2/AM for 50 min at 37 °C with continuous stirring.…”

Muscarinic Receptors and BK Channels Are Affected by Lipid Raft Disruption of Salivary Gland Cells

“…SOCE is mediated by a series of factors, including TRPC1, Orai1, and STIM1 [ 41 ]. We have previously observed that thapsigargin-induced SOCE in PC12 cells is different from those in HL-60 cells and Jurkat T cells [ 42 ]. Therefore, we concluded that lipid rafts do not affect SOCE in salivary gland cells.…”

Xerostomia and Its Cellular Targets

“…In addition to mAChRs, a series of GPCRs, including GPR39, histamine H 1 receptor, sphingosine–1–phosphate (S1P) receptor, bradykinin receptor, and P2Y 2 receptor (P2Y 2 R), has been investigated to identify salivary gland-related functions [ 52 , 58 , 59 , 60 , 61 ]. GPR39 is a type of GPCR with zinc as a ligand and is expressed in human SM gland tissues [ 52 ].…”