Effect of dexamethasone on nitric oxide synthase and Caspase-3 gene expressions in endotoxemia in neonate rat brain.
OBJECTIVE
To investigate the gene and protein expressions of three isoforms of nitric oxide synthase (NOS) and gene expression of Caspase-3, and effect of dexamethasone on them in neonatal rats with lipopolysaccharide (LPS)-induced endotoxemic brain damage.


METHODS
Expressions of the three isoforms of NOS and caspase-3 mRNA in the brain were investigated by RT-PCR in postnatal 7-day Wistar rats with acute endotoxemia by intraperitoneal administration of LPS. Regional distributions of NOSs were examined by immunohistochemical technique.


RESULTS
nNOS and Caspase-3 mRNA were obviously detected. eNOS mRNA was faintly expressed, but iNOS mRNA was undetectable in the control rat brain. The expressions of NOS mRNA of three isoforms were weak 2 h after LPS (5 mg/mg) delivery, peaked at 6 h, and thereafter, reduced gradually up to 24 h. The expression intensity was in the order of nNOS> iNOS> eNOS. Widespread nNOS, scattered eNOS distribution and negative iNOS were identified in the control rat brain and all isoforms of NOS could be induced by LPS which reached the apex at 24 h in the order of nNOS> iNOS> eNOS as detected by immunostaining. Although Caspase-3 mRNA could be found in all groups, DNA fragmentation was only seen at 6 h and 24 h. The expressions of NOS and Caspase-3 mRNA were inhibited in the rat brain when dexamethasone was administrated.


CONCLUSIONS
LPS-induced NO production induces apoptosis of neurons through mechanism involving the Caspase-3 activation, which may play an important role in the pathogenesis of brain damage during endotoxemia, and neuro-protective effects of dexamethasone may be partially realized by inhibiting the expression of NOS mRNA.
Wang
Hua
H
Department of Pediatrics, Second Clinical College, China Medical University, Shenyang 110004, Liaoning, China. wanghua62@hotmail.com
Wu
Yu-Bin
YB
Du
Xiu-Hua
XH
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000139:chemically induced / Q000201:enzymology*; D005260:Female; D008070:Lipopolysaccharides; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D008070:Lipopolysaccharides; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D003907:Dexamethasone; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases