Nornicotine

Nornicotine and Nicotine Induced Neovascularization via Increased VEGF/PEDF Ratio.[Pubmed:26536586]

Ophthalmic Res. 2015;55(1):1-9.

PURPOSE: The purpose of the current study was to evaluate the influences of Nornicotine and nicotine (NT) in cigarette smoke on the expression of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in retinal pigment epithelium cells and human umbilical vein endothelial cells (HUVECs). Furthermore, the angiogenic behaviors of endothelial cells under Nornicotine and NT treatment were assessed by using in vitro methods. METHODS: ARPE-19 cells and HUVECs were treated with different concentrations of either Nornicotine or NT for different periods of time. The cell proliferative effect was investigated by using the method of MTT analysis. HUVEC migration and tube formation were assessed by using the scratch assay and Matrigel models. The expressions of VEGF and PEDF gene and protein in both types of cells were examined by real-time RT-PCR and Western blot. RESULTS: There was no proliferation of ARPE-19 cells following treatment with various concentrations of Nornicotine or NT. In contrast, Nornicotine or NT significantly stimulated HUVEC proliferation, migration and tube formation. Nornicotine and NT upregulated the expression of VEGF but suppressed the expression of PEDF at both mRNA and protein levels in a dose- and time-dependent manner in ARPE-19 cells and HUVECs. CONCLUSIONS: Our results demonstrate that Nornicotine and NT promoted endothelial cellular proliferation, migration and tube formation of HUVECs in vitro. These effects might be partly due to simultaneous modulation of VEGF/PEDF signaling in ARPE-19 cells and HUVECs.

Nornicotine pretreatment decreases intravenous nicotine self-administration in rats.[Pubmed:11105939]

Psychopharmacology (Berl). 2000 Oct;152(3):289-94.

RATIONALE: Nicotine has been shown to be effective as a treatment for reducing tobacco dependence. However, few studies have examined the effect of other nicotinic agonists to determine if they can also decrease nicotine self-administration. OBJECTIVE: The present study determined if Nornicotine, a tobacco alkaloid and major nicotine metabolite in brain, could reduce nicotine self-administration in rats. METHODS: Each rat was prepared with an indwelling jugular catheter and trained to self-administer intravenous nicotine (0.03 mg/kg per infusion). After nicotine self-administration stabilized, rats were pretreated with either (-)-nicotine (0, 0.1, 0.3, and 1.0 mg/kg free base) or (+/-)-Nornicotine (0, 1, 3, 5.6, and 10.0 mg/kg free base) and assessed for nicotine self-administration. A separate group of rats was maintained on sucrose reinforced responding and pretreated with Nornicotine to determine the specificity of the pretreatment effect. In another group of rats, the time course of the pretreatment effect of either (-)-nicotine (0.56 and 1.0 mg/kg) or (+/-)-Nornicotine (5.6 and 10.0 mg/kg) was examined. RESULTS: Nicotine and Nornicotine each produced a dose-dependent decrease in nicotine self-administration. Furthermore, the decrease in nicotine self-administration in response to the 5.6 mg/kg Nornicotine pretreatment was specific to nicotine self-administration, as this dose did not decrease sucrose reinforced responding in tolerant animals. In addition, within the dose range tested, the suppressant effect of Nornicotine had a two-fold longer duration than that of nicotine (120 versus 60 min). CONCLUSION: These results suggest that Nornicotine may be an effective treatment for tobacco dependence.

Nornicotine inhibition of dopamine transporter function in striatum via nicotinic receptor activation.[Pubmed:17146768]

Synapse. 2007 Mar;61(3):157-65.

Nornicotine, a tobacco alkaloid and N-demethylated nicotine metabolite, releases DA from superfused rat striatal slices in a mecamylamine-sensitive manner, indicating nicotinic receptor (nAChR) modulation of this response. The current study determined the effect of Nornicotine on rat striatal dopamine transporter (DAT) function using in vivo voltammetry. In a dose-related and mecamylamine-sensitive manner, Nornicotine (0.35-12.0 mg/kg, s.c.) decreased DA clearance, suggesting that Nornicotine inhibits striatal DAT function via a nAChR-mediated mechanism. Furthermore, the nAChRs mediating the Nornicotine-induced inhibition of DAT function appear to be different from those activated by nicotine which increases DA clearance. Understanding the actions of Nornicotine in brain may have significance for emerging therapeutics and for the management of nicotine dependence.

Three nicotine demethylase genes mediate nornicotine biosynthesis in Nicotiana tabacum L.: functional characterization of the CYP82E10 gene.[Pubmed:20977974]

Phytochemistry. 2010 Dec;71(17-18):1988-98.

In most tobacco (Nicotiana tabacum L.) plants, Nornicotine is a relatively minor alkaloid, comprising about 2-5% of the total pyridine alkaloid pool in the mature leaf. Changes in gene expression at an unstable locus, however, can give rise to plants that produce high levels of Nornicotine, specifically during leaf senescence and curing. Minimizing the Nornicotine content in tobacco is highly desirable, because this compound serves as the direct precursor in the synthesis of N'-nitrosoNornicotine, a potent carcinogen in laboratory animals. Nornicotine is likely produced almost entirely via the N-demethylation of nicotine, in a process called nicotine conversion that is catalyzed by the enzyme nicotine N-demethylase (NND). Previous studies have identified CYP82E4 as the specific NND gene responsible for the unstable conversion phenomenon, and CYP82E5v2 as a putative minor NND gene. Here, by discovery and characterization of CYP82E10, a tobacco NND gene, is reported. PCR amplification studies showed that CYP82E10 originated from the N. sylvestris ancestral parent of modern tobacco. Using a chemical mutagenesis strategy, knockout mutations were induced and identified in all three tobacco NND genes. By generating a series of mutant NND genotypes, the relative contribution of each NND gene toward the Nornicotine content of the plant was assessed. Plants possessing knockout mutations in all three genes displayed Nornicotine phenotypes that were much lower ( approximately 0.5% of total alkaloid content) than that found in conventional tobacco cultivars. The introduction of these mutations into commercial breeding lines promises to be a viable strategy for reducing the levels of one of the best characterized animal carcinogens found in tobacco products.

The analgesic and toxic effects of nornicotine enantiomers alone and in interaction with morphine in rodent models of acute and persistent pain.[Pubmed:19800911]

Pharmacol Biochem Behav. 2010 Jan;94(3):352-62.

Neuronal nicotinic acetylcholinic receptors (nAChR) are promising targets for the development of novel analgesics. Nicotine and other nAChR-agonists produce profound analgesia in rodent models of acute and persistent pain. However, significant side-effects are of concern. Nornicotine (N-desmethyl-nicotine) appears to activate different nAChR subtypes, has a better pharmacokinetic profile, and produces less toxicity than nicotine. Little is known about its analgesic properties. In the present study, the S(-)- and R(+)-enantiomers of Nornicotine were characterized with regard to analgesia and side-effects profile. Efficacy was demonstrated in rat models of pain where central sensitization is involved: i.e. the chronic constriction nerve injury model of peripheral neuropathy and the formalin model of tonic inflammatory pain. The desirable (analgesic) properties resided predominantly in the S(-)- rather than the R(+)-enantiomer. In contrast, undesirable effects (motor in-coordination, reduced locomotor activity, ataxia) were more pronounced with the R(+)-enantiomer. This is an interesting finding, which may suggest separation of toxicity from analgesia by utilization of S(-)-enantiomer of Nornicotine. Maximum analgesic effectiveness without significant side-effects was achieved when S(-)-Nornicotine (sub-analgesic dose) was combined with a low-dose of the micro-opioid, morphine. These preclinical data suggest that S(-)-Nornicotine may be of value, either alone or in combination with an opioid, for treatment of a broad-spectrum of pain (i.e. nociceptive, neuropathic, and mixed pain).