title: Signaling pathways regulating dose-dependent dual effects of TNF-α on primary cultured Schwann cells.
abstract: After peripheral nerve injury, Schwann cells are rapidly activated to participate in the regenerative process and modulate local immune reactions. Tumor necrosis factor-α (TNF-α), one of the major initiators of the inflammatory cascade, has been known to exert pleiotropic functions during peripheral nerve injury and regeneration. In this study, we aimed to investigate the in vitro effects of TNF-α on peripheral neural cells. First, gene-microarray analysis was applied to the RNA samples extracted from injured peripheral nerves, providing the information of gene interactions post nerve injury. Then, after primary cultured Schwann cells were treated with increasing dosages (0-40 ng/ml) of TNF-α, cell proliferation and migration were examined by EdU incorporation and a transwell-based assay, and cell apoptosis was observed and quantified by electron microscopy and Annexin V-FITC assay, respectively. The results showed that lower dosages of TNF-α increased cell proliferation and migration, whereas higher dosages of TNF-α decreased cell proliferation and migration and enhanced cell apoptosis. The tests using a chemical inhibitor of TNF-α further confirmed the above effects of TNF-α. To understand how TNF-α produced the dose-dependent dual effects on primary cultured Schwann cells, we performed co-immunoprecipitation, Western blot analysis, and immunocytochemistry to decipher the complex network of biochemical pathways involving many signaling molecules, i.e., TNF receptor-associated death domain, Fas-associated death domain, receptor interacting protein, JNK, NF-κB p65, and caspases, thus assuming the mechanisms by which TNF-α activated the death and survival pathways and achieved a balance between the two opposite actions in primary cultured Schwann cells.
authors.affiliation: School of Biology and Basic Medical Sciences, Soochow University, Suzhou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Tang
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Wang
authors.forename: Songlin
authors.initials: S
authors.lastname: Zhou
authors.forename: Tianmei
authors.initials: T
authors.lastname: Qian
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Gu
mesh_terms: D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D048430:Cell Shape; D002470:Cell Survival; D002478:Cells, Cultured; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D061251:Primary Cell Culture; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism; D012583:Schwann Cells / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D015398:Signal Transduction; D059467:Transcriptome; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: D053200:Fas-Associated Death Domain Protein; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases