Nitric oxide via macrophage iNOS induces apoptosis following traumatic spinal cord injury.
To investigate the pathophysiological mechanisms involved in post-traumatic impairment of the spinal cord, we analyzed expression patterns of the inducible nitric oxide synthase (iNOS) gene following acute injury of rat spinal cord using a weight drop technique. PCR analysis revealed that iNOS mRNA appeared at 3-12 h after injury and declined thereafter. Immunohistochemical analysis showed that iNOS-positive cells invaded the lesioned area through the perivascular space at 6 h after injury. The population of these cells peaked at 24 h and then declined to disappear 3 days after injury. The iNOS-positive cells were also stained with ED-2 but not with ED-1 or OX-42, indicating that these cells were macrophages and/or perivascular cells. In parallel with the appearance of iNOS-positive cells, other cells emerged that were positively stained by the terminal deoxynucleotidyl-transferase-mediated dUDP-biotin nick end-labeling (TUNEL) assay. TUNEL-positive cells were scattered in the lesioned area 1 day after injury, but some in the surrounding area close to iNOS-positive cells. Administration of L-Ng-nitro-arginine methylester, a competitive inhibitor of NOS, resulted in a reduction of TUNEL-positive cells in the lesioned area. These results suggest that nitric oxide generated by iNOS of macrophages and/or perivascular cells plays a significant role in eliminating damaged cells from the lesioned area by apoptosis.
Satake
K
K
Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya 466-8550, Japan.
Matsuyama
Y
Y
Kamiya
M
M
Kawakami
H
H
Iwata
H
H
Adachi
K
K
Kiuchi
K
K
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D020287:In Situ Nick-End Labeling; D008264:Macrophages / Q000201:enzymology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013119:Spinal Cord Injuries / Q000378:metabolism* / Q000473:pathology*
D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D019331:NG-Nitroarginine Methyl Ester