title: Elevated protein carbonylation, and misfolding in sciatic nerve from db/db and Sod1(-/-) mice: plausible link between oxidative stress and demyelination.
abstract: Diabetic peripheral polyneuropathy is associated with decrements in motor/sensory neuron myelination, nerve conduction and muscle function; however, the mechanisms of reduced myelination in diabetes are poorly understood. Chronic elevation of oxidative stress may be one of the potential determinants for demyelination as lipids and proteins are important structural constituents of myelin and highly susceptible to oxidation. The goal of the current study was to determine whether there is a link between protein oxidation/misfolding and demyelination. We chose two distinct models to test our hypothesis: 1) the leptin receptor deficient mouse (dbdb) model of diabetic polyneuropathy and 2) superoxide dismutase 1 knockout (Sod1(-/-) ) mouse model of in vivo oxidative stress. Both experimental models displayed a significant decrement in nerve conduction, increase in tail distal motor latency as well as reduced myelin thickness and fiber/axon diameter. Further biochemical studies demonstrated that oxidative stress is likely to be a potential key player in the demyelination process as both models exhibited significant elevation in protein carbonylation and alterations in protein conformation. Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice. Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice. Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice. Collectively, these data strongly suggest for the first time that oxidation-mediated protein misfolding and aggregation of key myelin proteins may be linked to demyelination and reduced nerve conduction in peripheral neuropathies.
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Hamilton
authors.forename: Arunabh
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Michael E
authors.initials: ME
authors.lastname: Walsh
authors.forename: Yun
authors.initials: Y
authors.lastname: Shi
authors.forename: Rochelle
authors.initials: R
authors.lastname: Wei
authors.forename: Yiqiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Karl A
authors.initials: KA
authors.lastname: Rodriguez
authors.forename: Rochelle
authors.initials: R
authors.lastname: Buffenstein
authors.forename: Asish R
authors.initials: AR
authors.lastname: Chaudhuri
authors.forename: Holly
authors.initials: H
authors.lastname: Van Remmen
mesh_terms: D000818:Animals; D051379:Mice; D009185:Myelin Proteins / Q000737:chemistry / Q000378:metabolism; D009186:Myelin Sheath / Q000187:drug effects / Q000502:physiology*; D009431:Neural Conduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D050050:Protein Carbonylation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D020836:Protein Structure, Quaternary; D012584:Sciatic Nerve / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013482:Superoxide Dismutase / Q000172:deficiency*; D000072105:Superoxide Dismutase-1; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D009185:Myelin Proteins; C489545:Pmp22 protein, mouse; D020122:tert-Butylhydroperoxide; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1