Novel medication targets for the treatment of alcoholism: preclinical studies.

Alcoholism is a complex heterogeneous disease and a number of neurotransmitter and neuromodulator systems have been implicated in its manifestation. Consequently, it is unlikely that existing medications such as disulfiram (Antabuse®), naltrexone (ReVia®), acamprosate (Campral®)) can be efficacious in every individual. Thus, the development of novel therapeutic agents with greater selectivity and less unwanted effects for the treatment of this disease is one of the major objectives of alcohol research. This review summarizes the findings of five novel compounds with different neuronal targets for treating alcoholism. These compounds include sazetidine-A, which selectively desensitizes α4ß2 nicotinic receptors; carisbamate, a novel anti-epileptic agent; JNJ5234801, a novel anxiolytic agent; GS-455534, a highly selective inhibitor of mitochondrial aldehyde dehydrogenase; and JNJ-39220675, a selective histamine H3 antagonist. Inbred alcohol-preferring rats (iP), Fawn-Hooded (FH) rats, and P rats were used to evaluate the compounds. Naltrexone was used as a positive control in some experiments. All five compounds reduced alcohol consumption and preference. The mechanisms thought to underlie these effects suggest that, in addition to dopaminergic and opioidergic systems, other neuronal systems such as sodium channels (carisbamate), mitochondrial aldehyde dehydrogenase (GS-455534), 5-HT2 receptors (JNJ-5234801), histamine H3 receptors (JNJ-39220675), and α4ß2 nicotinic receptors (sazetidine-A) can be involved in alcohol drinking. Further work is necessary to confirm the exact mechanisms of action of each drug and to determine any viable targets for putative treatment of alcohol-use disorders. The article presents some promising patents on novel medication targets for the treatment of alcoholism.

Inhibition of aldehyde dehydrogenase-2 suppresses cocaine seeking by generating THP, a cocaine use-dependent inhibitor of dopamine synthesis.

There is no effective treatment for cocaine addiction despite extensive knowledge of the neurobiology of drug addiction. Here we show that a selective aldehyde dehydrogenase-2 (ALDH-2) inhibitor, ALDH2i, suppresses cocaine self-administration in rats and prevents cocaine- or cue-induced reinstatement in a rat model of cocaine relapse-like behavior. We also identify a molecular mechanism by which ALDH-2 inhibition reduces cocaine-seeking behavior: increases in tetrahydropapaveroline (THP) formation due to inhibition of ALDH-2 decrease cocaine-stimulated dopamine production and release in vitro and in vivo. Cocaine increases extracellular dopamine concentration, which activates dopamine D2 autoreceptors to stimulate cAMP-dependent protein kinase A (PKA) and protein kinase C (PKC) in primary ventral tegmental area (VTA) neurons. PKA and PKC phosphorylate and activate tyrosine hydroxylase, further increasing dopamine synthesis in a positive-feedback loop. Monoamine oxidase converts dopamine to 3,4-dihydroxyphenylacetaldehyde (DOPAL), a substrate for ALDH-2. Inhibition of ALDH-2 enables DOPAL to condense with dopamine to form THP in VTA neurons. THP selectively inhibits phosphorylated (activated) tyrosine hydroxylase to reduce dopamine production via negative-feedback signaling. Reducing cocaine- and craving-associated increases in dopamine release seems to account for the effectiveness of ALDH2i in suppressing cocaine-seeking behavior. Selective inhibition of ALDH-2 may have therapeutic potential for treating human cocaine addiction and preventing relapse.

Suppression of heavy drinking and alcohol seeking by a selective ALDH-2 inhibitor.

BACKGROUND: Inherited human aldehyde dehydrogenase 2 (ALDH-2) deficiency reduces the risk for alcoholism. Kudzu plants and extracts have been used for 1,000 years in traditional Chinese medicine to treat alcoholism. Kudzu contains daidzin, which inhibits ALDH-2 and suppresses heavy drinking in rodents. Decreased drinking due to ALDH-2 inhibition is attributed to aversive properties of acetaldehyde accumulated during alcohol consumption. However, daidzin can reduce drinking in some rodents without necessarily increasing acetaldehyde. Therefore, a selective ALDH-2 inhibitor might affect other metabolic factors involved in regulating drinking. METHODS: Aldehyde dehydrogenase 2 inhibitors were synthesized based on the co-crystal structure of ALDH-2 and daidzin. We tested the efficacy of a highly selective reversible ALDH-2 inhibitor, CVT-10216, in models of moderate and high alcohol drinking rats. We studied 2-bottle choice and deprivation-induced drinking paradigms in Fawn Hooded (FH) rats, operant self-administration in Long Evans (LE), FH, and inbred P (iP) rats and in cue-induced reinstatement in iP rats. We also assayed blood acetaldehyde levels as well as dopamine (DA) release in the nucleus accumbens (NAc) and tested possible rewarding/aversive effects of the inhibitor in a conditioned place preference (CPP) paradigm. RESULTS: CVT-10216 increases acetaldehyde after alcohol gavage and inhibits 2-bottle choice alcohol intake in heavy drinking rodents, including deprivation-induced drinking. Moreover, CVT-10216 also prevents operant self-administration and eliminates cue-induced reinstatement of alcohol seeking even when alcohol is not available (i.e., no acetaldehyde). Alcohol stimulates DA release in the NAc, which is thought to contribute to increased drinking and relapse in alcoholism. CVT-10216 prevents alcohol-induced increases in NAc DA without changing basal levels. CVT-10216 does not show rewarding or aversive properties in the CPP paradigm at therapeutic doses. CONCLUSION: Our findings suggest that selective reversible ALDH-2 inhibitors may have therapeutic potential to reduce excessive drinking and to suppress relapse in abstinent alcoholics.