Proinflammatory effects of tumour necrosis factor‐like weak inducer of apoptosis (TWEAK) on human gingival fibroblasts

Summary Tumour necrosis factor (TNF)‐like weak inducer of apoptosis (TWEAK), a member of the TNF family, is a multi‐functional cytokine that regulates cellular proliferation, angiogenesis, inflammation and apoptosis. In this study, we investigated TWEAK expression in periodontally diseased tissues and the effect of TWEAK on human gingival fibroblasts (HGF). Reverse transcription–polymerase chain reaction (RT–PCR) analysis and immunohistochemistry revealed that TWEAK and the TWEAK receptor, fibroblast growth factor‐inducible 14 (Fn14), mRNA and protein were expressed in periodontally diseased tissues. HGF expressed Fn14 and produced interleukin (IL)‐8 and vascular endothelial growth factor (VEGF) production upon TWEAK stimulation in a dose‐dependent manner. The IL‐8 and VEGF production induced by TWEAK was augmented synergistically by simultaneous stimulation with transforming growth factor (TGF)‐β1 or IL‐1β. IL‐1β and TGF‐β1 enhanced Fn14 expression in a dose‐dependent manner. Moreover, TWEAK induced intercellular adhesion molecule‐1 (ICAM‐1) and vascular cell adhesion molecule‐1 (VCAM‐1) expression on HGF in a dose‐dependent manner. The ICAM‐1 expression induced by TWEAK was augmented by TGF‐β1. On the other hand, the TWEAK‐induced VCAM‐1 expression was inhibited by TGF‐β1. Phosphatidylinositol 3‐kinase (PI3K) and nuclear factor‐kappaB (NF‐κB) inhibitor inhibit both ICAM‐1 and VCAM‐1 expression induced by TWEAK. However, mitogen‐activated protein kinase (MEK) and c‐Jun NH2‐terminal kinase (JNK) inhibitor enhanced only VCAM‐1 expression on HGF. These results suggest that TWEAK may be involved in the pathophysiology of periodontal disease. Moreover, in combination with IL‐1β or TGF‐β1, TWEAK may be related to the exacerbation of periodontal disease to induce proinflammatory cytokines and adherent molecules by HGF.