A novel mechanism of action and potential use for lobeline as a treatment for psychostimulant abuse

Lobeline, an alkaloidal constituent of Lobelia inflata LINN., has a long history of therapeutic usage ranging from emetic and respiratory stimulant to tobacco smoking cessation agent. Although classified as both an agonist and an antagonist at nicotinic receptors, lobeline has no structural resemblance to nicotine, and structure--function relationships do not suggest a common pharmacophore. Lobeline inhibits nicotine-evoked dopamine release and [3H]nicotine binding, thus acting as a potent antagonist at both alpha3beta2(*) and alpha4beta2(*) neuronal nicotinic receptor subtypes. However, lobeline does not release dopamine from its presynaptic terminal, but appears to induce the metabolism of dopamine intraneuronally. Reevaluation of the mechanism by which lobeline alters dopamine function reveals that its primary mechanism is inhibition of dopamine uptake and promotion of dopamine release from the storage vesicles within the presynaptic terminal, via an interaction with the tetrabenazine-binding site on the vesicular monoamine transporter (VMAT2). Thus, lobeline appears to perturb the fundamental mechanisms of dopamine storage and release. Based on its neurochemical mechanism, the ability of lobeline to functionally antagonize the neurochemical and behavioral effects of the psychostimulants amphetamine and methamphetamine was examined. Lobeline was found to inhibit the amphetamine-induced release of dopamine in vitro, and amphetamine-induced hyperactivity, drug discrimination, and self-administration. However, lobeline does not support self-administration in rats, suggesting a lack of addiction liability. Thus, lobeline may reduce the abuse liability of these psychostimulants. The development of lobeline and lobeline analogs with targeted selectivity at VMAT2 represents a novel class of therapeutic agents having good potential as efficacious treatments for methamphetamine abuse.

Pharmacotherapy of methamphetamine addiction: an update

Methamphetamine dependence is a serious public health problem worldwide for which there are no approved pharmacological treatments. Psychotherapy is still the mainstay of treatment; however, relapse rates are high. The search for effective pharmacological treatment has intensified in the last decade. This review will highlight progress in pharmacological interventions to treat methamphetamine dependence as well as explore new pharmacological targets. Published data from clinical trials for stimulant addiction were searched using PubMed and summarized, as well as highlights from a recent symposium on methamphetamine pharmacotherapy presented at the ISAM 2006 meeting, including interim analysis data from an ongoing D-amphetamine study in Australia. Early pilot data are encouraging for administering D-amphetamine and methylphenidate as treatment for heavy amphetamine users. Abilify at 15 mg/day dose increased amphetamine use in an outpatient pilot study. Sertraline, ondansetron, baclofen, tyrosine, and imipramine were ineffective in proof-of-concept studies. Development of pharmacotherapy for methamphetamine dependence is still in an early stage. Data suggesting D-amphetamine and methylphenidate as effective pharmacotherapy for methamphetamine addiction will need to be confirmed by larger trials. Preclinical data suggest that use of GVG, CB1 antagonist, and lobeline are also promising therapeutic strategies.

Pharmacological chaperones increase residual β-galactocerebrosidase activity in fibroblasts from Krabbe patients

Krabbe disease or globoid cell leukodystrophy is a degenerative, lysosomal storage disease resulting from the deficiency of β-galactocerebrosidase activity. This enzyme catalyzes the lysosomal hydrolysis of galactocerebroside and psychosine. Krabbe disease is inherited as an autosomal recessive trait, and many of the 70 disease-causing mutations identified in the GALC gene are associated with protein misfolding. Recent studies have shown that enzyme inhibitors can sometimes translocate misfolded polypeptides to their appropriate target organelle bypassing the normal cellular quality control machinery and resulting in enhanced activity. In search for pharmacological chaperones that could rescue the β-galactocerebrosidase activity, we investigated the effect of α-Lobeline or 3',4',7-trihydroxyisoflavone on several patient-derived fibroblast cell lines carrying missense mutations, rather than on transduced cell lines. Incubation of these cell lines with α-lobeline or 3',4',7-trihydroxyisoflavone leads to an increase of β-galacocerebrosidase activity in p.G553R + p.G553R, in p.E130K + p.N295T and in p.G57S + p.G57S mutant forms over the critical threshold. The low but sustained expression of β-galactocerebrosidase induced by these compounds is a promising result; in fact, it is known that residual enzyme activity of only 15-20% is sufficient for clinical efficacy. The molecular interaction of the two chaperones with β-galactocerebrosidase is also supported by in silico analysis. Collectively, our combined in silico-in vitro approach indicate α-lobeline and 3',4',7-trihydroxyisoflavone as two potential pharmacological chaperones for the treatment or improvement of quality of life in selected Krabbe disease patients.

Lobelane inhibits methamphetamine-evoked dopamine release via inhibition of the vesicular monoamine transporter-2

Lobeline is currently being evaluated in clinical trials as a methamphetamine abuse treatment. Lobeline interacts with nicotinic receptor subtypes, dopamine transporters (DATs), and vesicular monoamine transporters (VMAT2s). Methamphetamine inhibits VMAT2 and promotes dopamine (DA) release from synaptic vesicles, resulting ultimately in increased extracellular DA. The present study generated structure-activity relationships by defunctionalizing the lobeline molecule and determining effects on [(3)H]dihydrotetrabenazine binding, inhibition of [(3)H]DA uptake into striatal synaptic vesicles and synaptosomes, the mechanism of VMAT2 inhibition, and inhibition of methamphetamine-evoked DA release. Compared with lobeline, the analogs exhibited greater potency inhibiting DA transporter (DAT) function. Saturated analogs, lobelane and nor-lobelane, exhibited high potency (K(i) = 45 nM) inhibiting vesicular [(3)H]DA uptake, and lobelane competitively inhibited VMAT2 function. Lobeline and lobelane exhibited 67- and 35-fold greater potency, respectively, in inhibiting VMAT2 function compared to DAT function. Lobelane potently decreased (IC(50) = 0.65 microM; I(max) = 73%) methamphetamine-evoked DA overflow, and with a greater maximal effect compared with lobeline (IC(50) = 0.42 microM, I(max) = 56.1%). These results provide support for VMAT2 as a target for inhibition of methamphetamine effects. Both trans-isomers and demethylated analogs of lobelane had reduced or unaltered potency inhibiting VMAT2 function and lower maximal inhibition of methamphetamine-evoked DA release compared with lobelane. Thus, defunctionalization, cis-stereochemistry of the side chains, and presence of the piperidino N-methyl are structural features that afford greatest inhibition of methamphetamine-evoked DA release and enhancement of selectivity for VMAT2. The current results reveal that lobelane, a selective VMAT2 inhibitor, inhibits methamphetamine-evoked DA release and is a promising lead for the development of a pharmacotherapeutic for methamphetamine abuse.

Lobeline and reduction of cigarette smoking

An empirical and logical analysis of research employing lobeline sulfate in reducing cigarette smoking raises serious doubts as to the utility of this chemical “nicotine substitute.” An experiment is also described in which predominantly college-aged volunteers desiring to stop smoking were given either specially prepared troches containing 0.5 mg. lobeline or placebos in a double-blind design. Neither during treatment nor during an immediately following post-treatment period did the drug achieve greater gains than the placebo. Correlational and other analyses of psychological data suggest that the local throat irritation commonly regarded as a side-effect of lobeline lozenges actually plays a central role in discouraging smoking in those persons motivated to continue sucking the lozenges. Suggestions are also offered as to procedures that might prove useful in maintaining treatment gains, whether drug-produced or part of the familiar placebo effect.

Lobeline for smoking cessation

BACKGROUND

Lobeline is a partial nicotine agonist, which has been used in a variety of commercially available preparations to help stop smoking.

OBJECTIVES

The objective of this review was to assess the effects of lobeline on long term smoking cessation.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group trials register (most recent search December 2011).

SELECTION CRITERIA

Randomized trials comparing lobeline to placebo or an alternative therapeutic control, which reported smoking cessation with at least six months follow-up.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of subjects, the dose and form of lobeline, the outcome measures, method of randomisation, and completeness of follow-up.

MAIN RESULTS

We identified no trials meeting the full inclusion criteria including long term follow-up. One large trial failed to detect any effect on short-term abstinence.

AUTHORS' CONCLUSIONS

There is no evidence available from long term trials that lobeline can aid smoking cessation, and the short-term evidence suggests there is no benefit.

Lobeline for smoking cessation

BACKGROUND

Lobeline is a partial nicotine agonist, which has been used in a variety of commercially available preparations to help stop smoking.

OBJECTIVES

The objective of this review was to assess the effects of lobeline on long term smoking cessation.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group trials register.

SELECTION CRITERIA

Randomized trials comparing lobeline to placebo or an alternative therapeutic control, which reported smoking cessation with at least six months follow-up.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of subjects, the dose and form of lobeline, the outcome measures, method of randomisation, and completeness of follow-up.

MAIN RESULTS

We identified no trials meeting the full inclusion criteria including long term follow-up.

REVIEWER'S CONCLUSIONS

There is no evidence available from long term trials that lobeline can aid smoking cessation.

Lobeline: A multifunctional alkaloid modulates cholinergic and glutamatergic activities

Developing drugs for Alzheimer's disease (AD) is an extremely challenging task due to its devastating pathology. Previous studies have indicated that natural compounds play a crucial role as lead molecules in the development of drugs. Even though, there are remarkable technological advancements in the isolation and synthesis of natural compounds, the targets for many of them are still unknown. In the present study, lobeline, a piperidine alkaloid has been identified as a cholinesterase inhibitor through chemical similarity assisted target fishing method. The structural similarities between lobeline and donepezil, a known acetylcholinesterase (AChE) inhibitor encouraged us to hypothesize that lobeline may also exhibit AChE inhibitory properties. It was further confirmed by in silico, in vitro and biophysical studies that lobeline could inhibit cholinesterase. The binding profiles indicated that lobeline has a higher affinity for AChE than BChE. Since excitotoxicity is one of the major pathological events associated with AD progression, we also investigated the neuroprotective potential of lobeline against glutamate mediated excitotoxicity in rat primary cortical neurons. The cell based NMDA receptor (NMDAR) assay with lobeline suggested that neuroprotective potential of lobeline is mediated through the blockade of NMDAR activity.

[Effect of various analeptics on the outcome of acute microwave lesion in mice]

The survival of albino mice irradiated by microwaves till the terminal state (wave length of 12.5 cm, intensity-62 +/- 5 microvat, for 14-16 minutes), given directly after irradiation diethylamide of nicotinic acid (cordiamine) in a dose of 50 mg/kg intraperitoneally and strychnine nitrate in a dose of 1 mg/kg, subcutaneously, i. e. nearly 1.5 times as much as received by controls, was studied. The application of caffeine sodium benzoate, camphor, metrasol, lobeline hydrochloride and cytisine, employed in different doses, proved to be little effective.