Development of selective axonopathy in adult sensory neurons isolated from diabetic rats: role of glucose-induced oxidative stress.
OBJECTIVE
Reactive oxygen species (ROS) are pro-oxidant factors in distal neurodegeneration in diabetes. We tested the hypothesis that sensory neurons exposed to type 1 diabetes would exhibit enhanced ROS and oxidative stress and determined whether this stress was associated with abnormal axon outgrowth.


METHODS
Lumbar dorsal root ganglia sensory neurons from normal or 3- to 5-month streptozotocin (STZ)-diabetic rats were cultured with 10 or 25-50 mmol/l glucose. Cell survival and axon outgrowth were assessed. ROS were analyzed using confocal microscopy. Immunofluorescent staining detected expression of manganese superoxide dismutase (MnSOD) and adducts of 4-hydroxy-2-nonenal (4-HNE), and MitoFluor Green dye detected mitochondria.


RESULTS
Dorsal root ganglion neurons from normal rats exposed to 25-50 mmol/l glucose did not exhibit oxidative stress or cell death. Cultures from diabetic rats exhibited a twofold (P < 0.001) elevation of ROS in axons after 24 h in 25 mmol/l glucose compared with 10 mmol/l glucose or mannitol. Perikarya exhibited no change in ROS levels. Axonal outgrowth was reduced by approximately twofold (P < 0.001) in diabetic cultures compared with control, as was expression of MnSOD. The antioxidant N-acetyl-cysteine (1 mmol/l) lowered axonal ROS levels, normalized aberrant axonal structure, and prevented deficits in axonal outgrowth in diabetic neurons (P < 0.05).


CONCLUSIONS
Dorsal root ganglia neurons with a history of diabetes expressed low MnSOD and high ROS in axons. Oxidative stress was initiated by high glucose concentration in neurons with an STZ-induced diabetic phenotype. Induction of ROS was associated with impaired axonal outgrowth and aberrant dystrophic structures that may precede or predispose the axon to degeneration and dissolution in human diabetic neuropathy.
Zherebitskaya
Elena
E
Division of Neurodegenerative Disorders, St Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada.
Akude
Eli
E
Smith
Darrell R
DR
Fernyhough
Paul
P
D000375:Aging / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000378:metabolism / Q000473:pathology*; D020169:Caspases / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology*; D005947:Glucose / Q000494:pharmacology*; D008297:Male; D016900:Neurofilament Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000378:metabolism / Q000473:pathology*; D013482:Superoxide Dismutase / Q000378:metabolism
D016900:Neurofilament Proteins; C051774:neurofilament protein H; D013482:Superoxide Dismutase; D020169:Caspases; D005947:Glucose