Riccardo Maccioni

Sphingosine-1-phosphate (S1P) is a lipid mediator signaling through broadly expressed G protein-coupled receptors. We found that S1P is regulated by alcohol and that S1P receptor agonists reduce alcohol drinking in rodent models. Specifically, we observed that two S1P receptor agonists FDA-approved for multiple sclerosis, fingolimod and ozanimod, and the more brain penetrant S1P ₁ receptor agonist CYM5442, reduced binge alcohol drinking in the drinking in the dark (DID) paradigm in mice. CYM5442 also reduced drinking in dependent mice in the chronic intermittent ethanol vapor paradigm of dependence-induced increased drinking paired with 2 bottle-choice (CIE-2BC) as well as in non-dependent mice. CYM5442 also reduced operant oral alcohol self-administration in both non-dependent and dependent rats made dependent by vapor exposure, and reduced motivation for alcohol in dependent rats tested in a progressive ratio schedule of reinforcement. CYM5442 significantly prevented cue-induced reinstatement of alcohol seeking behavior in alcohol-dependent rats, a model of relapse to alcohol use. CYM5442 also reduced intake of non-drug reinforcers, including sucrose, food, water and, to a lesser extent, saccharine. Notably, CYM5442 was less aversive than naltrexone, an FDA-approved medication for the treatment of alcohol use disorder that shares a similar broad reducing action on alcohol intake and non-drug reinforcers. CYM5442 had no effect on loss of righting reflex, alcohol metabolism, motor coordination or spontaneous locomotor activity in rodents. Lastly, gene expression analysis by RNA-Seq revealed that S1P regulates a complex set of genes in the transition to alcohol dependence. Overall, our results establish S1P signaling as a novel therapeutic target for alcohol use disorder.

Alcohol is a molecule whose multiple effects in living organisms exemplify how profound biological complexity can arise from an exceptionally simple chemical structure interacting with the cellular biochemical machinery. This review was conceived to provide an up-to-date synthesis of the current knowledge on the multifaceted consequences of alcohol oxidative metabolism and alcohol-derived oxidative stress, ranging from disruption of subcellular and cellular homeostasis to impairment of organ function. This study primarily focuses on the consequences of alcohol metabolism and on the mechanisms by which the rise of its main metabolite, acetaldehyde, and of reactive oxygen species (ROS), generates oxidative stress by-products and molecular adducts responsible for compromising cellular energy balance and antioxidant defense mechanisms. In particular, this review aims to provide an exhaustive representation of the mechanisms, causes, and consequences of alcohol oxidative metabolism: this is accomplished by taking into account alcohol-induced modifications of gene expression of cellular antioxidant determinants, the role of epigenetic mechanisms, and that of gene polymorphisms linked to alcohol-dependent oxidative stress and responsible for serious diseases such as, among others, alcoholic hepatitis, cirrhosis, and hepatocellular carcinoma. In addition, this review highlights the role of alcohol oxidative metabolism in the brain, which, in the acute setting, activates the dopaminergic system mainly involved in alcohol reinforcing properties and, upon chronic exposure, contributes to neurodegenerative disorders. Finally, a dedicated paragraph explores autophagy as an integrative mechanism underlying the effects of alcohol-related oxidative stress across multiple organs, including the liver, heart, and brain.

The consumption of alcohol and caffeine affects the lives of billions of individuals worldwide. Although recent evidence indicates that caffeine impairs the reinforcing properties of alcohol, a characterization of its effects on alcohol-stimulated mesolimbic dopamine (DA) function was lacking. Acting as the pro-drug of salsolinol, alcohol excites DA neurons in the posterior ventral tegmental area (pVTA) and increases DA release in the nucleus accumbens shell (AcbSh). Here we show that caffeine, via antagonistic activity on A_2A adenosine receptors (A_2AR), prevents alcohol-dependent activation of mesolimbic DA function as assessed, in-vivo, by brain microdialysis of AcbSh DA and, in-vitro, by electrophysiological recordings of pVTA DA neuronal firing. Accordingly, while the A₁R antagonist DPCPX fails to prevent the effects of alcohol on DA function, both caffeine and the A_2AR antagonist SCH 58261 prevent alcohol-dependent pVTA generation of salsolinol and increase in AcbSh DA in-vivo, as well as alcohol-dependent excitation of pVTA DA neurons in-vitro. However, caffeine also prevents direct salsolinol- and morphine-stimulated DA function, suggesting that it can exert these inhibitory effects also independently from affecting alcohol-induced salsolinol formation or bioavailability. Finally, untargeted metabolomics of the pVTA showcases that caffeine antagonizes alcohol-mediated effects on molecules (e.g. phosphatidylcholines, fatty amides, carnitines) involved in lipid signaling and energy metabolism, which could represent an additional salsolinol-independent mechanism of caffeine in impairing alcohol-mediated stimulation of mesolimbic DA transmission. In conclusion, the outcomes of this study strengthen the potential of caffeine, as well as of A_2AR antagonists, for future development of preventive/therapeutic strategies for alcohol use disorder.

The consumption of alcohol and caffeine affects the lives of billions of individuals worldwide. Although recent evidence indicates that caffeine impairs the reinforcing properties of alcohol, a characterization of its effects on alcohol-stimulated mesolimbic dopamine (DA) function was lacking. Acting as the pro-drug of salsolinol, alcohol excites DA neurons in the posterior ventral tegmental area (pVTA) and increases DA release in the nucleus accumbens shell (AcbSh). Here we show that caffeine, via antagonistic activity on A2A adenosine receptors (A2AR), prevents alcohol-dependent activation of mesolimbic DA function as assessed, in-vivo, by brain microdialysis of AcbSh DA and, in-vitro, by electrophysiological recordings of pVTA DA neuronal firing. Accordingly, while the A1R antagonist DPCPX fails to prevent the effects of alcohol on DA function, both caffeine and the A2AR antagonist SCH 58261 prevent alcohol-dependent pVTA generation of salsolinol and increase in AcbSh DA in-vivo, as well as alcohol-dependent excitation of pVTA DA neurons in-vitro. However, caffeine also prevents direct salsolinol- and morphine-stimulated DA function, suggesting that it can exert these inhibitory effects also independently from affecting alcohol-induced salsolinol formation or bioavailability. Finally, untargeted metabolomics of the pVTA showcases that caffeine antagonizes alcohol-mediated effects on molecules (e.g. phosphatidylcholines, fatty amides, carnitines) involved in lipid signaling and energy metabolism, which could represent an additional salsolinol-independent mechanism of caffeine in impairing alcohol-mediated stimulation of mesolimbic DA transmission. In conclusion, the outcomes of this study strengthen the potential of caffeine, as well as of A2AR antagonists, for future development of preventive/therapeutic strategies for alcohol use disorder.