Leptin induces IL-6 and IL-8 expression through leptin receptor Ob-Rb in human dental pulp fibroblasts

Abstract

Objective: Leptin, through binding to its special receptor (Ob-Rb), has potent effects on immunity and inflammation. This study aimed to investigate the expression of leptin receptor Ob-Rb in human dental pulp fibroblasts (HDPFs) and the effects of leptin on the production of proinflammatory cytokines of IL-6 and IL-8 by HDPFs.

Methods: Ob-Rb expression was determined by quantitative real-time PCR (real-time PCR), Western blot and immunofluorescence analyses in cultured HDPFs. Small interfering RNA (siRNA) was transfected into HDPFs to down-regulate the expression of Ob-Rb. Real-time PCR and enzyme-linked immunosorbent assay (ELISA) were used to determine the proinflammatory cytokines of IL-6 and IL-8 levels in leptin-stimulated HDPFs. The involved signalling pathways that mediate the leptin-stimulated production of proinflammatory cytokines were investigated using Western blot and specific signalling inhibitor analyses.

Results: The expression levels of Ob-Rb mRNA and protein were detected in HDPFs. Leptin could stimulate mRNA and protein expression of IL-6 and IL-8 in HDPFs in a concentration-dependent and time-dependent manner. Transfection with siRNA targeting Ob-Rb resulted in remarkable reduction of IL-6 and IL-8 expressions by HDPFs. In accordance with the enhanced expression of proinflammatory cytokines, leptin stimulation resulted in rapid phosphorylation of STAT3, p38 MAPK, ERK and Akt in HDPFs. Inhibiting JAK2/STAT3, p38 MAPK or PI3K/Akt substantially decreased leptin-induced IL-6 production, whereas blocking ERK and p38 MAPK substantially suppressed IL-8 production from leptin-stimulated HDPFs.

Conclusions: Leptin may up-regulate IL-6 and IL-8 production through binding with Ob-Rb in HDPFs via the activation of different intracellular signalling pathways.

Keywords:

• Leptin
• IL-6
• IL-8
• human dental pulp fibroblasts

Disclosure statement

The authors deny any conflicts of interest related to this study.

Additional information

Funding

This work was supported by grants from National Natural Science Foundation of China (no. 81100744 and 81500878).