Activation of constitutive nitric oxide synthase(s) and absence of inducible isoform in aged rat brain.
In this study, the effect of aging on nitric oxide synthases (NOS) was investigated in homogenates and cytosolic fractions from hippocampus, brain cortex and cerebellum of adult, old adult and old Wistar rats (3-4, 14, and 24 months old, respectively). Our results indicate the enhancement of Ca(2+) and calmoduline-dependent NOS activity in all investigated aged brain parts. Significantly higher NOS activity was found in the cerebellum. In the absence of Ca(2+) or in the presence of N-nitro-L-arginine (NNLA) the activity of NOS was absent. Inhibitor of constitutive NOS isoforms which preferentially inhibits neuronal NOS (nNOS), 7-nitroindazole, decreased NOS activity by 60 and 75% in adult and aged brain, respectively. However, using RT-PCR a significantly lower amount of mRNA for nNOS was detected in hippocampus. The ratio of NOS activity to nNOS mRNA was significantly higher in hippocampus and cerebellum of aged brain. No expression of the gene for inducible NOS was observed in adult and aged brain. These results indicate that probably nNOS is responsible for higher NOS activity in aged brain. Our data suggest that alteration of nNOS phosphorylation state may be responsible for the activation of NOS in aged brain. The down-regulation of nNOS mRNA expression may be an adaptive mechanism that protects the brain against excessive NO release.
Jesko
Henryk
H
Department of Cellular Signalling, Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego St. PL-02106 Warsaw, Poland.
Chalimoniuk
Malgorzata
M
Strosznajder
Joanna B
JB
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000254:growth & development; D002118:Calcium / Q000502:physiology; D002147:Calmodulin / Q000502:physiology; D002531:Cerebellum / Q000201:enzymology / Q000254:growth & development; D002540:Cerebral Cortex / Q000201:enzymology / Q000254:growth & development; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000201:enzymology / Q000254:growth & development; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology
D002147:Calmodulin; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; D010744:Phosphoric Monoester Hydrolases; D002118:Calcium