Monoamine oxidase inhibition for tobacco pharmacotherapyTP George, AH Weinberger - Clinical Pharmacology & Therapeutics, 2008 - nature.com
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There has been a considerable amount of work dealing with the genetics of MAO-A and MAO-B [...] and two known genetic polymorphisms in MAO-A and MAO-B genes may influence smoking behavior: a variable number of tandem repeat polymorphism in the promoter region of MAO-A, and a single nucleotide polymorphism in the MAO-B gene’s coding region comprised of an A→G transition, leading to lowerenzyme activity and increased levels of synaptic monoamine concentrations. However, only the MAO-A variable number1 [...] of tandem repeat polymorphism appears to have functional con-sequences for smoking behavior."
[...]
"Several clinical and neuroimaging reports suggest that
cigarette smoke contains components that inhibit both MAO iso-forms. Humanex vivostudies have suggested that
smokers have reduced levels of platelet MAO-A and MAO-B activity whencompared with non-smokers.15–17 Consistent with these results, positron emission tomography studies using labeled clorgylineand selegiline have shown that binding of these ligands to brain and peripheral organs is reduced in smokers when comparedwith non-smokers.18,19 Both clinical studies, assaying platelet MAO inhibition and positron emission tomography imaging, suggest that this inhibition persists for >30 days, consistentwith the irreversible inhibition produced by these agents.15,20
This inhibition of MAO by smoking is not related to the direct effects of nicotine. Interestingly,in vitrostudies have identifiedseveral components, namely the
alkaloids harman (a specificcompetitive MAO-A inhibitor; IC50= 0.34μM) and
norhar-man (nonspecific competitive inhibitor of MAO-A and MAO-B,with IC50s of 6.5 and 4.7μM, respectively) as contributing to the inhibitory effects of tobacco smoke on MAO isoforms.21 Besides harman alkaloids, other components of tobacco smoke may also inhibit MAO-A and MAO-B.22,23 In the light of the observation that: (i) MAO inhibition leads to increases in synaptic monoamines which are also increasedby nicotinic acetylcholine receptor activation; and (ii) cigarette smoke possesses components that inhibit MAO isoforms, we(and others) have reasoned that MAOIs may be promising candidates for developing medications to aid smokers to stop tobacco use."
[...]
"Inhibition of monoamine metabolism by MAO inhibitors leads to increased synaptic levels of dopamine, serotonin, and norepinephrine. There is also a compensatory decrease in the respective monoamine metabolites (homovanillic acid, 5-hydroxyindoleacetic acid, and 3-methoxy-4-hydroxymandelic acid), which are produced by the sequential actions of MAO and catechol-O-methyl transferase. Overall, the increase in monoaminelevels is hypothesized to lead to a decrease in the craving for nicotine in tobacco, and thereby in a reduction in the urge to smoke. This process facilitates smoking cessation."
[...]
"MAO subtype-selective inhibitors may represent a novel class of medications that can be developed as adjuncts tobehavioral therapies aimed at quitting cigarette smoking. Initial proof-of-concept studies in human subjects support the case for further development of these agents.
Given the evidence that both MAO-A and MAO-B genes show genetic variationsthat may alter the functioning of the corresponding enzymes, there will be considerable interest in the application of pharma-cogenetic methods to tailor antismoking therapy using agentsthat target these MAO isoforms."
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The journal quoted above also has a great diagram showing the mechanism of how MAOIs can treat tabacco addiction, I would encourage anyone interested in these pathways to get the
full text version of this article!It seems that rasagiline hasn't yet been tested extensively in this regard (unless anyone knows otherwise), but selegiline has been tested with some good results, although I have also found some mixed studies.
H Ito, N Hamajima, K Matsuo, K Okuma… - Pharmacogenetics …, 2003 - journals.lww.com
R Biberman, R Neumann, I Katzir, Y Gerber - Addiction, 2003 - Wiley Online Library
I think the major thing that could set rasagiline apart from selegiline is the fact that it's MAO A gene expression mechanism leads to increased GDNF. Perhaps it would make sense to cycle the two for alternating GDNF and BDNF.
Edited by Phoenicis, 23 March 2014 - 08:26 PM.