title: Tumor necrosis factor-α elevates neurite outgrowth through an NF-κB-dependent pathway in cultured adult sensory neurons: Diminished expression in diabetes may contribute to sensory neuropathy.
abstract: The presence of a proinflammatory environment in the sensory neuron axis in diabetes was tested by measuring levels of proinflammatory cytokines in lumbar dorsal root ganglia (DRG) and peripheral nerve from age matched control and streptozotocin (STZ)-induced diabetic rats. The levels of tumor necrosis factor-α (TNFα) and other cytokines were diminished in lumbar DRG from diabetic animals. Consequently, we tested the hypothesis that TNFα modulated axonal plasticity in adult sensory neurons and posited that impairments in this signal transduction pathway may underlie degeneration in diabetic sensory neuropathy. Cultured adult rat sensory neurons were grown under defined conditions and TNFα caused a dose-dependent 2-fold (P<0.05) elevation in neurite outgrowth. Neurons derived from 3 to 5month STZ-induced diabetic rats exhibited significantly reduced levels of neurite outgrowth in response to TNFα. TNFα enhanced NF-κB activity as assessed using Western blotting and plasmid reporter technology. Blockade of TNFα-induction of NF-κB activation caused inhibition of neurite outgrowth in cultured neurons. Immunofluorescent staining for NF-κB subunit p50 within neuronal nuclei revealed that medium to large diameter neurons were most susceptible to NF-κB inhibition and was associated with decreased neurite outgrowth. The results demonstrating reduced cytokine expression in DRG confirm that diabetic sensory neuropathy does not involve a neuroinflammatory component at this stage of the disease in experimental animal models. In addition, it is hypothesized that reduced TNFα expression in the DRG and possibly associated deficits in anterograde transport may contribute to impaired collatoral sprouting and regeneration in target tissue in type 1 diabetes.
authors: Division of Neurodegenerative Disorders, St Boniface Hospital Research Centre, Winnipeg, MB, Canada.
authors: Ali
authors: A
authors: Saleh
authors: Darrell R
authors: DR
authors: Smith
authors: Savitha
authors: S
authors: Balakrishnan
authors: Lori
authors: L
authors: Dunn
authors: Corina
authors: C
authors: Martens
authors: Christopher W
authors: CW
authors: Tweed
authors: Paul
authors: P
authors: Fernyhough
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000473:pathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000473:pathology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008297:Male; D016328:NF-kappa B / Q000378:metabolism*; D016501:Neurites / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014404:Tubulin / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D014404:Tubulin; D014409:Tumor Necrosis Factor-alpha