Novel insight into the mechanisms involved in the regulation of the m1 muscarinic receptor, iNOS and nNOS mRNA levels.
In this paper we have determined the different signaling pathways involved in M(1) muscarinic acetylcholine receptor (mAChR)-dependent stimulation of m1 mAChRs, neural and inducible isoforms of nitric oxide synthase (nNOS and iNOS)-mRNA gene expression of rat frontal cortex. Carbachol-stimulation of M(1) mAChRs exerts an increase in m1 mAChR-mRNA, activation of phosphoinositide (PI) turnover, translocation of protein kinase C (PKC) and stimulation of NOS activity. Inhibitors of phospholipase C (PLC), calcium/calmodulin and NOS, but not guanylate cyclase, prevent the carbachol-dependent increase of m1 mAChR-mRNA levels. These inhibitors also attenuate the muscarinic receptor-dependent increase in nNOS and iNOS mRNA levels. These results suggest that carbachol-activation of M(1) mAChRs increases m1 mAChR, nNOS and iNOS mRNA levels associated with increased production of nitric oxide (NO). The mechanism appears to occur secondarily to stimulation of PI turnover via PLC activation. This in turn, triggers a cascade reaction involving calcium/calmodulin and PKC, leading to activation of NOS. On the basis of our results, the activation of M(1) mAChRs appears to induce nNOS and iNOS expression and, reciprocally, the activator of NOS up-regulates m1 mAChR gene expression. These results may contribute to a better understanding of the effects and side effects of cholinomimetic treatment in patients with neurodegenerative diseases.
Sterin-Borda
Leonor
L
Pharmacology and Pathology Department, School of Medicine and Pharmacology Unit, School of Dentistry, University of Buenos Aires, Buenos Aires, Argentina. leo@farmaco.odon.uba.ar
Ganzinelli
Sabrina
S
Berra
Alejandro
A
Borda
Enri
E
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic / Q000378:metabolism*
D012333:RNA, Messenger; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat