Expression of nitric oxide synthase and 27-kD heat shock protein in motor neurons of ventral root-avulsed rats.
Root avulsion of adult spinal nerves causes the subacute cell loss of motor neurons. To explore the mechanisms of the elimination of motor neurons, we investigated the expression of two molecules--neuronal nitric oxide synthase (nNOS) as a cytotoxity marker and a 27-kD heat shock protein (HSP27) as a cytoprotection marker--in rat spinal motor neurons after ventral root avulsion, using immunofluorescent labeling technique for confocal laser microscopy. A drastic cell loss of motor neurons occurred during the first week following the avulsion, and the surviving motor neurons fell to approximately 60% of the control value at one week. Subsequent cell loss proceeded slowly, as the surviving motor neurons decreased to 35% at nine weeks. HSP27 immunohistochemistry showed that normal spinal motor neurons consisted of two types of motor neurons: HSP27-negative small motor neurons (< 500 micrometer2 ) (about 30%), and HSP27-positive large motor neurons (> 500 micrometer2) (about 70%). At one week, all of the HSP27-negative small motor neurons had died and only HSP27-positive large motor neurons survived. This event was followed by the induction of nNOS in the surviving large motor neurons, which showed a significant upregulation of HSP27. HSP27-negative small motor neurons were thus found to be more vulnerable to avulsion than HSP27-positive large motor neurons, suggesting that HSP27 may have protected the avulsed motor neurons from cell death. In addition, NO was involved in the gradual cell death of large motor neurons. The persistent upregulation of HSP27 and its colocalization with nNOS in surviving motor neurons may imply a keen competition in motor neuron survival between cytotoxic and cytoprotective systems.
He
Jian-Wen
JW
Department of Anatomy and Cell Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Hirata
Kazuho
K
Wang
Songyan
S
Kawabuchi
Masaru
M
D000818:Animals; D015415:Biomarkers; D002452:Cell Count; D005260:Female; D019922:GAP-43 Protein / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008297:Male; D009046:Motor Neurons / Q000201:enzymology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D011843:Radiculopathy / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013126:Spinal Nerve Roots / Q000166:cytology* / Q000201:enzymology; D015854:Up-Regulation
D015415:Biomarkers; D019922:GAP-43 Protein; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C486114:Hspb1 protein, rat; D009363:Neoplasm Proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat