title: Diabetes impairs an interleukin-1β-dependent pathway that enhances neurite outgrowth through JAK/STAT3 modulation of mitochondrial bioenergetics in adult sensory neurons.
abstract: BACKGROUND
  A luminex-based screen of cytokine expression in dorsal root ganglia (DRG) and nerve of type 1 diabetic rodents revealed interleukin-1 (IL-1α) and IL-1β to be significantly depressed. We, therefore, tested the hypothesis that impaired IL-1α and IL-1β expression in DRG may contribute to aberrant axon regeneration and plasticity seen in diabetic sensory neuropathy. In addition, we determined if these cytokines could optimize mitochondrial bioenergetics since mitochondrial dysfunction is a key etiological factor in diabetic neuropathy.
  
  
  RESULTS
  Cytokines IL-1α and IL-1β were reduced 2-fold (p<0.05) in DRG and/or nerve of 2 and 5 month streptozotocin (STZ)-diabetic rats. IL-2 and IL-10 were unchanged. IL-1α and IL-1β induced similar 2 to 3-fold increases in neurite outgrowth in cultures derived from control or diabetic rats (p<0.05). STAT3 phosphorylation on Tyr705 or Ser727 was depressed in DRG from STZ-diabetic mice and treatment of cultures derived from STZ-diabetic rats with IL-1β for 30 min raised phosphorylation of STAT3 on Tyr705 and Ser727 by 1.5 to 2-fold (p<0.05). shRNA-based or AG490 inhibition of STAT3 activity or shRNA blockade of endogenous IL-1β expression completely blocked neurite outgrowth. Cultured neurons derived from STZ-diabetic mice were treated for 24 hr with IL-1β and maximal oxygen consumption rate and spare respiratory capacity, both key measures of bioenergetic fidelity that were depressed in diabetic compared with control neurons, were enhanced 2-fold. This effect was blocked by AG490.
  
  
  CONCLUSIONS
  Endogenous synthesis of IL-1β is diminished in nerve tissue in type 1 diabetes and we propose this defect triggers reduced STAT3 signaling and mitochondrial function leading to sup-optimal axonal regeneration and plasticity.
authors.affiliation: Division of Neurodegenerative Disorders, St, Boniface Hospital Research Centre, R4048 - 351 Tache Ave, Winnipeg, MB R2H 2A6, Canada. asaleh@sbrc.ca.
authors.forename: Ali
authors.initials: A
authors.lastname: Saleh
authors.forename: Subir K Roy
authors.initials: SK
authors.lastname: Chowdhury
authors.forename: Darrell R
authors.initials: DR
authors.lastname: Smith
authors.forename: Savitha
authors.initials: S
authors.lastname: Balakrishnan
authors.forename: Lori
authors.initials: L
authors.lastname: Tessler
authors.forename: Emily
authors.initials: E
authors.lastname: Schartner
authors.forename: Andre
authors.initials: A
authors.lastname: Bilodeau
authors.forename: Randy
authors.initials: R
authors.lastname: Van Der Ploeg
authors.forename: Paul
authors.initials: P
authors.lastname: Fernyhough
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D004734:Energy Metabolism / Q000187:drug effects; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D053582:Interleukin-1alpha / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism*; D053612:Janus Kinases / Q000378:metabolism*; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D016501:Neurites / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D012584:Sciatic Nerve / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013311:Streptozocin; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D053582:Interleukin-1alpha; D053583:Interleukin-1beta; D050796:STAT3 Transcription Factor; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D019000:Phosphotyrosine; D013311:Streptozocin; D053612:Janus Kinases