Semaphorin3A Inhibits Pro-inflammatory Cytokine Production in Human Dental Pulp Cells

Objectives: Semaphorin3A (Sema3A) which is a member of the secretory semaphorin family is an axon guidance molecule in the nervous system. Recently, Sema3A has been reported to be an osteoprotective factor and be related with immune response. Moreover, Sema3A is produced by human dental pulp cells (HDPCs). However, the role of Sema3A on dental pulp inflammation remains unknown. The aim of this study is to reveal the effect of Sema3A on pro-inflammatory cytokine production, such as IL-6 and CXCL10, in cultures of HDPCs stimulated with TNF-α, and the role of Sema3A released from HPDCs.
Methods: HDPCs were obtained from non-carious teeth extracted for orthodontic reasons under informed consent at Hiroshima University Hospital (Ethical approval number: E-133). TNF-α-stimulated HDPCs were cultured in the presence or absence of recombinant Sema3A, an anti-Sema3A antibody, a control IgG antibody, or specific signal transduction inhibitors (p38-MAPK, ERK, JNK, and NF-kB) for the designated periods. After the incubation, IL-6, CXCL10 and Sema3A productions in culture supernatant were determined by enzyme-linked immunosorbent assay (ELISA).
Results: TNF-α induced productions of Sema3A, IL-6 and CXCL10 in HDPCs. The P38 MAPK inhibitor and the ERK inhibitor inhibited Sema3A production in TNF-α-stimulated HDPCs. Recombinant Sema3A inhibited IL-6 and CXCL10 production in TNF-α-stimulated HDPCs in a dose-dependent manner. The anti-Sema3A antibody increased IL-6 and CXCL10 productions in TNF-α-stimulated HDPCs compared with the control IgG antibody.
Conclusions: Sema3A released from HDPCs has been found to be involved in suppression of IL-6 and CXCL10 productions in TNF-α-stimulated HDPCs. Furthermore, TNF-α induced Sema3A production in HDPCs through p38 MAPK and ERK pathways. Therefore, these results suggested that Sema3A is possible to act on HDPCs in an autocrine fashion and to suppress excess immune response at pulpal inflammatory site. This work was supported by Grant-in-Aid for Research Activity start-up (17H0689600) from Japan Society for the Promotion of Science.