Inhibitory effects of tumor necrosis factor-alpha on migration of human periodontal ligament cells

Background: Tumor necrosis factor-alpha (TNF-alpha) is associated with chronic gingival inflammation and is suspected to influence periodontal destruction. However, the exact roles of TNF-alpha in wound healing and periodontal tissue regeneration are largely unknown. In the present study, we examined the effects of TNF-alpha on migration and proliferation of human periodontal ligament (PDL) cells. Methods: PDL cells were cultured in the presence of TNF-alpha to determine its effects on cellular migration and proliferation. The protein expression profiles of alpha 5 and beta 1 integrin subunits and their related molecules, paxillin and focal adhesion kinases (FAK), were investigated. Gene expression of fibronectin also was assayed. Further, the activation of Rho-family small guanosine triphosphate (GTP)-binding protein (RhoA) was evaluated using a GTP-loading pull-down assay, and focal adhesion formation by PDL cells after transfection with the expression vector of paxillin-fused green fluorescent protein (GFP) also was observed with confocal microscopy. Results: Cellular migration was impaired by TNF-a and recovered following the addition of anti-TNF-alpha antibodies. In contrast, PDL cell proliferation was not affected by TNF-alpha. TNF-alpha upregulated the expression of the alpha 5 and beta 1 integrin subunits, whereas fibronectin was not overexpressed. Phosphorylation of paxillin and FAK by PDL cells was induced, and RhoA activation also was induced. Confocal microscopic analysis revealed that TNF-alpha induced focal adhesion and stress fiber formation in all parts of the cells. Conclusion: Our results suggested that TNF-alpha impairs cellular migration by enhancing cellular adhesive ability following significant focal adhesion and stress fiber formation.