Methods: We cultured the HSG cells, A253 cells and dissociated human submandibular cells human submandibular acinar cells. We monitored the intracellular Ca2+ level using fura2-AM. RT-PCR analysis was used for the identification of mRNA expression.
Results: S1P induced intracellular Ca2+ increase in a concentration-dependent manner. S1P increased levels of intracellular [Ca2+], which was inhibited by pretreatment with U73122 (an inhibitor for phosdfdpholipase C beta) or 2-aminoethoxydiphenyl borate (an inhibitor for InsP3 receptor). Pretreated S1P did not inhibit subsequent carbachol-induced [Ca2+]i increase, which suggests that S1P and muscarinic signaling are independent from each other without heterologous desensitization. S1P1, S1P2, S1P3, S1P4 receptors, SphK1 and SphK2 were expressed in human salivary gland cells. S1P, but not carbachol, induces the expression of interleukin-6 and Fas.
Conclusion: Our results suggest that S1P triggers Ca2+ signaling and the apoptotic pathway in normal human submandibular gland cells, which suggests in turn that S1P affects the progression of Sjögren syndrome.
Acknowledgements: This work was supported by the Korea Science & Engineering Foundation grant [R13-2008-008-01001-0] through the Oromaxillofacial Dysfunction Research Center for the Elderly at Seoul National University.