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Adasme-Reyes S, Fuentes J, Gutiérrez-Vega I, Isla E, Pérez V, Ponce C, Quilaqueo ME, Herrera-Marschitz M, Quintanilla ME, Vásquez D, Rivera-Meza M. Pharmacological activators of ALDH2: A new strategy for the treatment of alcohol use disorders. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2024; 178:153-177. [PMID: 39523053 DOI: 10.1016/bs.irn.2024.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2024]
Abstract
In mammals, ethanol is metabolized to acetaldehyde mainly by the liver alcohol dehydrogenase (ADH), and acetaldehyde is subsequently oxidized to acetate by mitochondrial aldehyde dehydrogenase (ALDH2). The presence of an inactive variant of ALDH2 or the use of inhibitors of this enzyme leads to an accumulation of acetaldehyde after ethanol consumption, generating an aversive reaction that inhibits subsequent alcohol intake. However, experimental evidence shows that acetaldehyde has potent rewarding effects at the central level, suggesting that acetaldehyde would be responsible for the addictive effect of alcohol. Alda-1 is an organic molecule that acts as a pharmacological activator of ALDH2. Studies in animal models of alcohol use disorders (AUD; i.e. alcoholism) have shown that Alda-1 can inhibit the acquisition, the chronic intake, and the relapse of alcohol consumption. These effects are reversible without any effects on water consumption or other natural reinforcer such as saccharin. It has also been reported that Alda-1 can act as a protective agent from the toxic effects on various tissues and organs mediated by ethanol-derived acetaldehyde, including liver damage, cancer, and central nervous system (CNS) alterations. Using in silico tools such as molecular docking the identification of important molecular interactions between Alda-1 and ALDH2 has been demonstrated, identifying new molecules with higher pharmacological features. Thus, there is now preclinical evidence supporting the use of activators of ALDH2 as a pharmacological strategy for the treatment of AUD.
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Affiliation(s)
- Sofía Adasme-Reyes
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Juan Fuentes
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Ignacio Gutiérrez-Vega
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Eduardo Isla
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Vicente Pérez
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Carolina Ponce
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - María Elena Quilaqueo
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Mario Herrera-Marschitz
- Program of Molecular and Clinical Pharmacology, Faculty of Medicine, University of Chile, Santiago, Chile
| | - María Elena Quintanilla
- Program of Molecular and Clinical Pharmacology, Faculty of Medicine, University of Chile, Santiago, Chile
| | - David Vásquez
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Mario Rivera-Meza
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile.
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Ibáñez C, Acuña T, Quintanilla ME, Pérez-Reytor D, Morales P, Karahanian E. Fenofibrate Decreases Ethanol-Induced Neuroinflammation and Oxidative Stress and Reduces Alcohol Relapse in Rats by a PPAR-α-Dependent Mechanism. Antioxidants (Basel) 2023; 12:1758. [PMID: 37760061 PMCID: PMC10525752 DOI: 10.3390/antiox12091758] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 09/06/2023] [Accepted: 09/08/2023] [Indexed: 09/29/2023] Open
Abstract
High ethanol consumption triggers neuroinflammation, implicated in sustaining chronic alcohol use. This inflammation boosts glutamate, prompting dopamine release in reward centers, driving prolonged drinking and relapse. Fibrate drugs, activating peroxisome proliferator-activated receptor alpha (PPAR-α), counteract neuroinflammation in other contexts, prompting investigation into their impact on ethanol-induced inflammation. Here, we studied, in UChB drinker rats, whether the administration of fenofibrate in the withdrawal stage after chronic ethanol consumption reduces voluntary intake when alcohol is offered again to the animals (relapse-type drinking). Furthermore, we determined if fenofibrate was able to decrease ethanol-induced neuroinflammation and oxidative stress in the brain. Animals treated with fenofibrate decreased alcohol consumption by 80% during post-abstinence relapse. Furthermore, fenofibrate decreased the expression of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukins IL-1β and IL-6, and of an oxidative stress-induced gene (heme oxygenase-1), in the hippocampus, nucleus accumbens, and prefrontal cortex. Animals treated with fenofibrate showed an increase M2-type microglia (with anti-inflammatory proprieties) and a decrease in phagocytic microglia in the hippocampus. A PPAR-α antagonist (GW6471) abrogated the effects of fenofibrate, indicating that they are dependent on PPAR-α activation. These findings highlight the potential of fenofibrate, an FDA-approved dyslipidemia medication, as a supplementary approach to alleviating relapse severity in individuals with alcohol use disorder (AUD) during withdrawal.
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Affiliation(s)
- Cristina Ibáñez
- Institute of Biomedical Sciences, Faculty of Health Sciences, Universidad Autónoma de Chile, Santiago 8910060, Chile; (C.I.); (D.P.-R.)
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago 8910060, Chile;
| | - Tirso Acuña
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago 8380453, Chile;
| | - María Elena Quintanilla
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago 8910060, Chile;
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago 8380453, Chile;
| | - Diliana Pérez-Reytor
- Institute of Biomedical Sciences, Faculty of Health Sciences, Universidad Autónoma de Chile, Santiago 8910060, Chile; (C.I.); (D.P.-R.)
| | - Paola Morales
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago 8910060, Chile;
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago 8380453, Chile;
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago 8380453, Chile
| | - Eduardo Karahanian
- Institute of Biomedical Sciences, Faculty of Health Sciences, Universidad Autónoma de Chile, Santiago 8910060, Chile; (C.I.); (D.P.-R.)
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago 8910060, Chile;
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Quintanilla ME, Israel Y. Role of Metabolism on Alcohol Preference, Addiction, and Treatment. Curr Top Behav Neurosci 2023. [PMID: 37221350 DOI: 10.1007/7854_2023_422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Studies presented in this chapter show that: (1) in the brain, ethanol is metabolized by catalase to acetaldehyde, which condenses with dopamine forming salsolinol; (2) acetaldehyde-derived salsolinol increases the release of dopamine mediating, via opioid receptors, the reinforcing effects of ethanol during the acquisition of ethanol consumption, while (3) brain acetaldehyde does not influence the maintenance of chronic ethanol intake, it is suggested that a learned cue-induced hyperglutamatergic system takes precedence over the dopaminergic system. However, (4) following a prolonged ethanol deprivation, the generation of acetaldehyde in the brain again plays a role, contributing to the increase in ethanol intake observed during ethanol re-access, called the alcohol deprivation effect (ADE), a model of relapse behavior; (5) naltrexone inhibits the high ethanol intake seen in the ADE condition, suggesting that acetaldehyde-derived salsolinol via opioid receptors also contributes to the relapse-like drinking behavior. The reader is referred to glutamate-mediated mechanisms that trigger the cue-associated alcohol-seeking and that also contribute to triggering relapse.
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Affiliation(s)
- María Elena Quintanilla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile.
| | - Yedy Israel
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
- Centro de Medicina Regenerativa, ICM Clinica Alemana-Universidad de Desarrollo, Santiago, Chile
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Can gene therapy be used to prevent cancer? Gene therapy for aldehyde dehydrogenase 2 deficiency. Cancer Gene Ther 2022; 29:889-896. [PMID: 34799722 PMCID: PMC9117562 DOI: 10.1038/s41417-021-00399-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 09/24/2021] [Accepted: 10/08/2021] [Indexed: 11/08/2022]
Abstract
Approximately 8% of the world population and 35-45% of East Asians are carriers of the hereditary disorder aldehyde dehydrogenase 2 (ALDH2) deficiency. ALDH2 plays a central role in the liver to metabolize ethanol. With the common E487K variant, there is a deficiency of ALDH2 function; when ethanol is consumed, there is a systemic accumulation of acetaldehyde, an intermediate product in ethanol metabolism. In ALDH2-deficient individuals, ethanol consumption acutely causes the "Alcohol Flushing Syndrome" with facial flushing, tachycardia, nausea, and headaches. With chronic alcohol consumption, ALDH2 deficiency is associated with a variety of disorders, including a remarkably high risk for aerodigestive tract cancers. Acetaldehyde is a known carcinogen. The epidemiologic data relating to the association of ALDH2 deficiency and cancer risk are striking: ALDH2 homozygotes who are moderate-to-heavy consumers of ethanol have a 7-12-fold increased risk for esophageal cancer, making ALDH2 deficiency the most common hereditary disorder associated with an increased cancer risk. In this review, we summarize the genetics and biochemistry of ALDH2, the epidemiology of cancer risk associated with ALDH2 deficiency, the metabolic consequences of ethanol consumption associated with ALDH2 deficiency, and gene therapy strategies to correct ALDH2 deficiency and its associated cancer risk. With the goal of reducing the risk of aerodigestive tract cancers, in the context that ALDH2 is a hereditary disorder and ALDH2 functions primarily in the liver, ALDH2 deficiency is an ideal target for the application of adeno-associated virus-mediated liver-directed gene therapy to prevent cancer.
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Ezquer F, Quintanilla ME, Morales P, Santapau D, Munita JM, Moya-Flores F, Ezquer M, Herrera-Marschitz M, Israel Y. A dual treatment blocks alcohol binge-drinking relapse: Microbiota as a new player. Drug Alcohol Depend 2022; 236:109466. [PMID: 35489181 DOI: 10.1016/j.drugalcdep.2022.109466] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 04/05/2022] [Accepted: 04/13/2022] [Indexed: 11/17/2022]
Abstract
RATIONALE Gut microbiota communicates information to the brain. Some animals are born with a gut microbiota that predisposes to high alcohol consumption, and transplantation of fecal material from alcoholics to mice increases animal preference for ethanol. Alcohol-use-disorders are chronic conditions where relapse is the hallmark. A predictive animal model of relapse is the "alcohol deprivation effect" where ethanol re-access is allowed following chronic alcohol intake and a long alcohol deprivation. The present study evaluates the effect of gut microbiota modification on relapse, as an adjunct to N-acetylcysteine + Acetylsalicylic acid administration, which inhibits the alcohol-induced hyper-glutamatergic condition. METHODS Rats bred as heavy alcohol consumers (UChB) were allowed ethanol intake for one month, were deprived of alcohol for two-weeks and subsequently offered re-access to ethanol. Prior to ethanol re-access animals received orally either (i) vehicle-control, (ii) Lactobacillus-rhamnosus-GG after antibiotic treatment (LGG); (iii) N-acetylcysteine+Acetylsalicylic acid (NAC/ASA) or (iv) both treatments: LGG+ (NAC/ASA). RESULTS Marked binge drinking (1.75 g ethanol/kg in 60 min) and blood alcohol levels exceeding 80 mg/dl were observed in the control group upon ethanol-re-access. Lactobacillus-GG or (NAC+ASA) treatments inhibited alcohol intake by 66-80%. The combination of both treatments virtually suppressed (inhibition of 90%) the re-access binge-like drinking, showing additive effects. Treatment with NAC+ASA increased the levels of glutamate transporters xCT and GLT-1 in nucleus accumbens, while Lactobacillus-GG administration increased those of the dopamine transporter (DAT). CONCLUSIONS The administration of a well-accepted probiotic may be of value as an adjunct in the treatment of alcohol-use-disorders.
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Affiliation(s)
- Fernando Ezquer
- Center for Regenerative Medicine, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile; Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago, Chile.
| | - María Elena Quintanilla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Science, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Paola Morales
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Science, Faculty of Medicine, Universidad de Chile, Santiago, Chile; Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Daniela Santapau
- Center for Regenerative Medicine, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - José Manuel Munita
- Genomics and Resistant Microbes Group, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Francisco Moya-Flores
- Genomics and Resistant Microbes Group, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Marcelo Ezquer
- Center for Regenerative Medicine, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Mario Herrera-Marschitz
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Science, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Yedy Israel
- Center for Regenerative Medicine, Faculty of Medicine Clínica Alemana-Universidad del Desarrollo, Santiago, Chile; Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago, Chile; Molecular and Clinical Pharmacology Program, Institute of Biomedical Science, Faculty of Medicine, Universidad de Chile, Santiago, Chile.
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Salinas-Luypaert C, Sáez-Cortez F, Quintanilla ME, Herrera-Marschitz M, Rivera-Meza M. Gene knockdown of HCN2 ion channels in the ventral tegmental area reduces ethanol consumption in alcohol preferring rats. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 2022; 48:165-175. [PMID: 35377277 DOI: 10.1080/00952990.2022.2033759] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 01/04/2022] [Accepted: 01/15/2022] [Indexed: 06/14/2023]
Abstract
Background: Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) ionic channels are known to play a key role in the control of neuron excitability and have been proposed as a molecular target of ethanol. Previous studies in rats have shown that gene-induced overexpression of the HCN2 channel in the ventral tegmental area (VTA) increases the rewarding effects of ethanol and its intake by the animals.Objective: The aim of this work was to study the effects of VTA HCN2 gene knockdown in the voluntary ethanol consumption of alcohol-preferring UChB rats.Methods: Two lentiviral vectors were generated; LV-siRNA-HCN2, coding for a siRNA that elicited >95% reduction of HCN2 protein levels in vitro, and a control vector coding for a scrambled siRNA sequence. Female UChB naïve rats (n = 14) were microinjected into the VTA with LV-siRNA-HCN2 or the scrambled control vector (n = 11). Four days after, animals were given a daily free access to 10% ethanol and water for 10 days.Results: Rats treated with the LV-siRNA-HCN2 vector showed a ~ 70% reduction (p < .001) in their ethanol preference and ethanol intake compared to control animals. No changes were observed in the total fluid intake of both groups. HCN2 levels in the VTA were measured by Western blot showing a reduction of 40% (p < .05) in the rats injected with LV-siRNA-HCN2, compared to control animals.Conclusion: These results show that knockdown of HCN2 ionic channels in the VTA of UChB rats markedly reduces their voluntary ethanol intake, supporting the idea that HCN2 channels may constitute a therapeutic target for alcohol use disorders.
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Affiliation(s)
- Catalina Salinas-Luypaert
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical and Pharmaceutical Sciences Santiago, Chile
| | - Felipe Sáez-Cortez
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - María Elena Quintanilla
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Mario Herrera-Marschitz
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Mario Rivera-Meza
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical and Pharmaceutical Sciences Santiago, Chile
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders, Santiago, Chile
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Quintanilla ME, Ezquer F, Morales P, Santapau D, Ezquer M, Herrera‐Marschitz M, Israel Y. A dual mechanism fully blocks ethanol relapse: Role of vagal innervation. Addict Biol 2022; 27:e13140. [PMID: 35229957 DOI: 10.1111/adb.13140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 12/20/2021] [Accepted: 01/03/2022] [Indexed: 11/01/2022]
Abstract
Previous studies showed that vagotomy markedly inhibits alcohol self-administration. Present studies hypothesised that vagotomy significantly adds to the inhibition of alcohol relapse induced by drugs that reduce the alcohol-induced hyperglutamatergic state (e.g., N-acetylcysteine + acetylsalicylic acid). The alcohol relapse paradigm tested gauges the elevated alcohol intake observed in animals that had consumed ethanol chronically, were subjected to a prolonged alcohol deprivation and are subsequently allowed ethanol re-access. Ethanol-drinker rats (UChB) were exposed to 10% and 20% ethanol and water concurrently for 4 months, were alcohol deprived for 14 days and were thereafter allowed re-access to the ethanol solutions. An initial binge-like drinking episode is observed upon ethanol re-access, followed by a protracted elevated ethanol intake that exceeds the predeprivation intake baseline. Prior to ethanol re-access, animals were (i) administered N-acetylcysteine (40 mg/kg/day) + acetylsalicylic acid (15 mg/kg/day), (ii) were bilaterally vagotomised, (iii) were exposed to both treatments or (iv) received no treatments. The initial binge-like relapse intake and a protracted elevated ethanol intake observed after repeated ethanol deprivations/re-access cycles were inhibited by 50%-70% by the administration of N-acetylcysteine + acetylsalicylic acid and by 40%-70% by vagotomy, while the combined vagotomy plus N-acetylcysteine + acetylsalicylic acid treatment inhibited both the initial binge-like intake and the protracted ethanol intake by >95% (p < 0.001), disclosing a dual mechanism of ethanol relapse and subsequent inhibition beyond that induced by either treatment alone. Future exploration into the mechanism by which vagal activity contributes to ethanol relapse may have translational promise.
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Affiliation(s)
- María Elena Quintanilla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine University of Chile Santiago Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa Facultad de Medicina Clínica Alemana‐Universidad del Desarrollo Santiago Chile
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders Santiago Chile
| | - Paola Morales
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine University of Chile Santiago Chile
- Department of Neuroscience, Faculty of Medicine University of Chile Santiago Chile
| | - Daniela Santapau
- Centro de Medicina Regenerativa Facultad de Medicina Clínica Alemana‐Universidad del Desarrollo Santiago Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa Facultad de Medicina Clínica Alemana‐Universidad del Desarrollo Santiago Chile
| | - Mario Herrera‐Marschitz
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine University of Chile Santiago Chile
| | - Yedy Israel
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine University of Chile Santiago Chile
- Centro de Medicina Regenerativa Facultad de Medicina Clínica Alemana‐Universidad del Desarrollo Santiago Chile
- Research Center for the Development of Novel Therapeutic Alternatives for Alcohol Use Disorders Santiago Chile
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8
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Holbrook OT, Molligoda B, Bushell KN, Gobrogge KL. Behavioral consequences of the downstream products of ethanol metabolism involved in alcohol use disorder. Neurosci Biobehav Rev 2021; 133:104501. [PMID: 34942269 DOI: 10.1016/j.neubiorev.2021.12.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 12/08/2021] [Accepted: 12/12/2021] [Indexed: 01/04/2023]
Abstract
Research concerning Alcohol Use Disorder (AUD) has previously focused primarily on either the behavioral or chemical consequences experienced following ethanol intake, but these areas of research have rarely been considered in tandem. Compared with other drugs of abuse, ethanol has been shown to have a unique metabolic pathway once it enters the body, which leads to the formation of downstream metabolites which can go on to form biologically active products. These metabolites can mediate a variety of behavioral responses that are commonly observed with AUD, such as ethanol intake, reinforcement, and vulnerability to relapse. The following review considers the preclinical and chemical research implicating these downstream products in AUD and proposes a chemobehavioral model of AUD.
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Affiliation(s)
- Otto T Holbrook
- Program in Neuroscience, Boston University, Boston, MA, 02215-2425, USA.
| | - Brandon Molligoda
- Program in Neuroscience, Boston University, Boston, MA, 02215-2425, USA.
| | - Kristen N Bushell
- Program in Neuroscience, Boston University, Boston, MA, 02215-2425, USA
| | - Kyle L Gobrogge
- Program in Neuroscience, Boston University, Boston, MA, 02215-2425, USA
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de Melo-Martin I, Crystal RG. Primum Non Nocere: Should Gene Therapy Be Used to Prevent Potentially Fatal Disease but Enable Potentially Destructive Behavior? Hum Gene Ther 2021; 32:529-534. [PMID: 33752441 DOI: 10.1089/hum.2021.039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Aldehyde dehydrogenase 2 (ALDH2) deficiency constitutes one of the most common hereditary enzyme deficiencies, affecting 35% to 40% of East Asians and 8% of the world population. It causes the well-known Asian Alcohol Flush Syndrome, characterized by facial flushing, palpitation, tachycardia, nausea, and other unpleasant feelings when alcohol is consumed. It is also associated with a marked increase in the risk of a variety of serious disorders, including esophageal cancer and osteoporosis. Our recent studies with murine models have demonstrated that a one-time administration of an adeno-associated virus (AAV) gene transfer vector expressing the human ALDH2 coding sequence (AAVrh.10hALDH2) will correct the deficiency state and prevent alcohol-induced abnormalities of the esophagus and bone. If successful in humans, such strategy would reduce the increased risk-associated disorders such as esophageal cancer and osteoporosis, but also prevent the Asian Alcohol Flush Syndrome. This treatment thus raises ethical concerns: although it would potentially prevent fatal disease, it could also allow affected individuals to drink alcohol without suffering the Asian Alcohol Flush Syndrome and, hence, potentially enable personal destructive behavior. Here we explore the ethical arguments against the development of a gene therapy for ALDH2 deficiency and we find them wanting. We contend that development of such treatments is ethically appropriate and should be part and parcel of the solutions offered against the condition.
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Affiliation(s)
| | - Ronald G Crystal
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York, USA
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Quintanilla ME, Ezquer F, Morales P, Ezquer M, Olivares B, Santapau D, Herrera-Marschitz M, Israel Y. N-Acetylcysteine and Acetylsalicylic Acid Inhibit Alcohol Consumption by Different Mechanisms: Combined Protection. Front Behav Neurosci 2020; 14:122. [PMID: 32848653 PMCID: PMC7412547 DOI: 10.3389/fnbeh.2020.00122] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 06/23/2020] [Indexed: 12/20/2022] Open
Abstract
Chronic ethanol intake results in brain oxidative stress and neuroinflammation, which have been postulated to perpetuate alcohol intake and to induce alcohol relapse. The present study assessed the mechanisms involved in the inhibition of: (i) oxidative stress; (ii) neuroinflammation; and (iii) ethanol intake that follow the administration of the antioxidant N-acetylcysteine (NAC) and the anti-inflammatory acetylsalicylic acid (ASA) to animals that had consumed ethanol chronically. At doses used clinically, NAC [40 mg/kg per day orally (p.o.)] and ASA (15 mg/kg per day p.o.) significantly inhibited chronic alcohol intake and relapse intake in alcohol-preferring rats. The coadministration of both drugs reduced ethanol intake by 65% to 70%. N-acetylcysteine administration: (a) induced the Nrf2-ARE system, lowering the hippocampal oxidative stress assessed as the ratio of oxidized glutathione (GSSG)/reduced glutathione (GSH); (b) reduced the neuroinflammation assessed by astrocyte and microglial activation by immunofluorescence; and (c) inhibited chronic and relapse ethanol intake. These effects were blocked by sulfasalazine, an inhibitor of the xCT transporter, which incorporates cystine (precursor of GSH) and extrudes extracellular glutamate, an agonist of the inhibitory mGlu2/3 receptor, which lowers the synaptic glutamatergic tone. The inhibitor of mGlu2/3 receptor (LY341495) blocked the NAC-induced inhibition of both relapse ethanol intake and neuroinflammation without affecting the GSSG/GSH ratio. Unlike N-acetylcysteine, ASA inhibited chronic alcohol intake and relapse via lipoxin A4, a strong anti-inflammatory metabolite of arachidonic acid generated following the ASA acetylation of cyclooxygenases. Accordingly, the lipoxin A4 receptor inhibitor, WRW4, blocked the ASA-induced reduction of ethanol intake. Overall, via different mechanisms, NAC and ASA administered in clinically relevant doses combine their effects inhibiting ethanol intake.
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Affiliation(s)
- María Elena Quintanilla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Paola Morales
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile.,Department of Neuroscience, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Belen Olivares
- Centro de Química Médica, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Daniela Santapau
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Mario Herrera-Marschitz
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Yedy Israel
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
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Wilson DF, Matschinsky FM. Ethanol metabolism: The good, the bad, and the ugly. Med Hypotheses 2020; 140:109638. [PMID: 32113062 DOI: 10.1016/j.mehy.2020.109638] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 12/20/2022]
Abstract
Throughout the world, ethanol is both an important commercial commodity and a source of major medical and social problems. Ethanol readily passes through biological membranes and distributes throughout the body. It is oxidized, first to acetaldehyde and then to acetate, and finally by the citric acid cycle in virtually all tissues. The oxidation of ethanol is irreversible and unregulated, making the rate dependent only on local concentration and enzyme activity. This unregulated input of reducing equivalents increases reduction of both cytoplasmic and intramitochondrial NAD and, through the latter, cellular energy state {[ATP]/([ADP][Pi])}. In brain, this increase in energy state stimulates dopaminergic neural activity signalling reward and a sense of well being, while suppressing glutamatergic neural activity signalling anxiety and unease. These positive responses to ethanol ingestion are important to social alcohol consumption. Importantly, decreased free [AMP] decreases AMP-dependent protein kinase (AMPK) activity, an important regulator of cellular energy metabolism. Oxidation of substrates used for energy metabolism in the absence of ethanol is down regulated to accommodate the input from ethanol. In liver, chronic ethanol metabolism results in fatty liver and general metabolic dysfunction. In brain, transport of other oxidizable metabolites through the blood-brain barrier and the enzymes for their oxidation are both down regulated. For exposures of short duration, ethanol induced regulatory changes are rapid and reversible, recovering completely when the concentrations of ethanol and acetate fall again. Longer periods of ethanol exposure and associated chronic suppression of AMPK activity activates regulatory mechanisms, including gene expression, that operate over longer time scales, both in onset and reversal. If chronic alcohol consumption is abruptly ended, metabolism is no longer able to respond rapidly enough to compensate. Glutamatergic neural activity adapts to chronic dysregulation of glutamate metabolism and suppression of glutamatergic neural activity by increasing excitatory and decreasing inhibitory amino acid receptors. A point is reached (ethanol dependence) where withdrawal of ethanol results in significant metabolic energy depletion in neurons and other brain cells as well as hyperexcitation of the glutamatergic system. The extent and regional specificity of energy depletion in the brain, combined with hyperactivity of the glutamatergic neuronal system, largely determines the severity of withdrawal symptoms.
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Affiliation(s)
- David F Wilson
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - Franz M Matschinsky
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
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Matsumura Y, Li N, Alwaseem H, Pagovich OE, Crystal RG, Greenblatt MB, Stiles KM. Systemic Adeno-Associated Virus-Mediated Gene Therapy Prevents the Multiorgan Disorders Associated with Aldehyde Dehydrogenase 2 Deficiency and Chronic Ethanol Ingestion. Hum Gene Ther 2020; 31:163-182. [PMID: 31801381 DOI: 10.1089/hum.2019.268] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Aldehyde dehydrogenase type 2 (ALDH2), a key enzyme in ethanol metabolism, processes toxic acetaldehyde to nontoxic acetate. ALDH2 deficiency affects 8% of the world population and 35-45% of East Asians. The ALDH2*2 allele common genetic variant has a glutamic acid-to-lysine substitution at position 487 (E487K) that reduces the oxidizing ability of the enzyme resulting in systemic accumulation of acetaldehyde with ethanol ingestion. With chronic ethanol ingestion, mutations in ALDH2 are associated with a variety of hematological, neurological, and dermatological abnormalities, and an increased risk for esophageal cancer and osteoporosis. Based on our prior studies demonstrating that a one-time administration of an adeno-associated virus (AAV) serotype rh.10 gene transfer vector expressing the human ALDH2 cDNA (AAVrh.10hALDH2) prevents the acute effects of ethanol administration (the "Asian flush syndrome"), we hypothesized that AAVrh.10hALDH2 would also prevent the chronic disorders associated with ALDH2 deficiency and chronic ethanol ingestion. To assess this hypothesis, AAVrh.10hALDH2 (1011 genome copies) was administered intravenously to two models of ALDH2 deficiency, Aldh2 knockout homozygous (Aldh2-/-) and knockin homozygous (Aldh2E487K+/+) mice (n = 10 per group). Four weeks after vector administration, mice were given drinking water with 10-15% ethanol for 12 weeks. Strikingly, compared with nonethanol drinking littermates, AAVrh.10hALDH2 administration prevented chronic ethanol-induced serum acetaldehyde accumulation and elevated liver malondialdehyde levels, loss of body weight, reduced hemoglobin levels, reduced performance in locomotor activity tests, accumulation of esophageal DNA damage and DNA adducts, and development of osteopenia. AAVrh.10hALDH2 should be considered as a preventative therapy for the increased risk of chronic disorders associated with ALDH2 deficiency and chronic alcohol exposure.
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Affiliation(s)
- Yuki Matsumura
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York
| | - Na Li
- Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York
| | - Hanan Alwaseem
- Proteomics Resource Center, The Rockefeller University, New York, New York
| | - Odelya E Pagovich
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York
| | - Ronald G Crystal
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York
| | - Matthew B Greenblatt
- Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York
- Research Division, Hospital for Special Surgery, New York, New York
| | - Katie M Stiles
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York
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13
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Gene and cell therapy on the acquisition and relapse-like binge drinking in a model of alcoholism: translational options. Gene Ther 2019; 26:407-417. [DOI: 10.1038/s41434-019-0064-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 02/06/2019] [Accepted: 02/11/2019] [Indexed: 12/11/2022]
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14
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Mattalloni MS, Albrecht PA, Salinas-Luypaert C, Deza-Ponzio R, Quintanilla ME, Herrera-Marschitz M, Cancela LM, Rivera-Meza M, Virgolini MB. Silencing brain catalase expression reduces ethanol intake in developmentally-lead-exposed rats. Neurotoxicology 2019; 70:180-186. [DOI: 10.1016/j.neuro.2018.10.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/11/2018] [Accepted: 10/27/2018] [Indexed: 11/30/2022]
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15
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Rivera-Meza M, Vásquez D, Quintanilla ME, Lagos D, Rojas B, Herrera-Marschitz M, Israel Y. Activation of mitochondrial aldehyde dehydrogenase (ALDH2) by ALDA-1 reduces both the acquisition and maintenance of ethanol intake in rats: A dual mechanism? Neuropharmacology 2018; 146:175-183. [PMID: 30521820 DOI: 10.1016/j.neuropharm.2018.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 11/28/2018] [Accepted: 12/02/2018] [Indexed: 12/31/2022]
Abstract
A number of pre-clinical studies have shown that brain-generated acetaldehyde, the first metabolite of ethanol, exerts reinforcing effects that promote the acquisition of ethanol intake, while chronic intake maintenance appears to be mediated by alcohol-induced brain neuroinflammation/oxidative stress. Recently, it was described that N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (ALDA-1) activates aldehyde dehydrogenase-2 (ALDH2), enzyme that catalyzes the oxidation of ethanol-derived acetaldehyde to acetate. The aim of this study was to determine the effects of ALDA-1 on both the acquisition and the maintenance of alcohol intake in alcohol-preferring UChB rats. For ethanol acquisition studies, naïve UChB rats were treated with five daily doses of ALDA-1 (12.5, 25 or 50 mg/kg, i.p.) from one day before the start of ethanol exposure. For chronic intake studies, UChB rats exposed for 98 days to a free access to 10% ethanol and water were treated daily with ALDA-1 (12.5, 25 or 50 mg/kg, i.p.) for five days. The administration of ALDA-1 reduced by 72-90% (p < 0.001) the acquisition of ethanol consumption in naïve rats. At chronic ethanol consumption, ALDA-1 reduced ethanol intake by 61-82% (p < 0.001). ALDA-1 administration increased by 3- and 2.3-fold the activity of ALDH2 in brain and liver, respectively. ALDA-1 did not affect saccharin consumption, nor it modified the rate of ethanol elimination. The study shows that the activation of ALDH2 by ALDA-1 is effective for inhibiting both the acquisition and the maintenance of chronic ethanol intake by alcohol-preferring rats. Thus, the activation of brain ALDH2 may constitute a novel approach in the treatment of alcohol use disorders.
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Affiliation(s)
- Mario Rivera-Meza
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile.
| | - David Vásquez
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - María Elena Quintanilla
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Diego Lagos
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Braulio Rojas
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical Sciences and Pharmacy, University of Chile, Santiago, Chile
| | - Mario Herrera-Marschitz
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Yedy Israel
- Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
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16
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Peana AT, Pintus FA, Bennardini F, Rocchitta G, Bazzu G, Serra PA, Porru S, Rosas M, Acquas E. Is catalase involved in the effects of systemic and pVTA administration of 4-methylpyrazole on ethanol self-administration? Alcohol 2017; 63:61-73. [PMID: 28847383 DOI: 10.1016/j.alcohol.2017.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 01/31/2017] [Accepted: 04/03/2017] [Indexed: 12/31/2022]
Abstract
The oxidative metabolism of ethanol into acetaldehyde involves several enzymes, including alcohol dehydrogenase (ADH) and catalase-hydrogen peroxide (H2O2). In this regard, while it is well known that 4-methylpyrazole (4-MP) acts by inhibiting ADH in the liver, little attention has been placed on its ability to interfere with fatty acid oxidation-mediated generation of H2O2, a mechanism that may indirectly affect catalase whose enzymatic activity requires H2O2. The aim of our investigation was twofold: 1) to evaluate the effect of systemic (i.p. [intraperitoneal]) and local (into the posterior ventral tegmental area, pVTA) administration of 4-MP on oral ethanol self-administration, and 2) to assess ex vivo whether or not systemic 4-MP affects liver and brain H2O2 availability. The results show that systemic 4-MP reduced ethanol but not acetaldehyde or saccharin self-administration, and decreased the ethanol deprivation effect. Moreover, local intra-pVTA administration of 4-MP reduced ethanol but not saccharin self-administration. In addition, although unable to affect basal catalase activity, systemic administration of 4-MP decreased H2O2 availability both in liver and in brain. Overall, these results indicate that 4-MP interferes with ethanol self-administration and suggest that its behavioral effects could be due to a decline in catalase-H2O2 system activity as a result of a reduction of H2O2 availability, thus highlighting the role of central catalase-mediated metabolism of ethanol and further supporting the key role of acetaldehyde in the reinforcing properties of ethanol.
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17
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Peana AT, Sánchez-Catalán MJ, Hipólito L, Rosas M, Porru S, Bennardini F, Romualdi P, Caputi FF, Candeletti S, Polache A, Granero L, Acquas E. Mystic Acetaldehyde: The Never-Ending Story on Alcoholism. Front Behav Neurosci 2017; 11:81. [PMID: 28553209 PMCID: PMC5425597 DOI: 10.3389/fnbeh.2017.00081] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/18/2017] [Indexed: 12/12/2022] Open
Abstract
After decades of uncertainties and drawbacks, the study on the role and significance of acetaldehyde in the effects of ethanol seemed to have found its main paths. Accordingly, the effects of acetaldehyde, after its systemic or central administration and as obtained following ethanol metabolism, looked as they were extensively characterized. However, almost 5 years after this research appeared at its highest momentum, the investigations on this topic have been revitalized on at least three main directions: (1) the role and the behavioral significance of acetaldehyde in different phases of ethanol self-administration and in voluntary ethanol consumption; (2) the distinction, in the central effects of ethanol, between those arising from its non-metabolized fraction and those attributable to ethanol-derived acetaldehyde; and (3) the role of the acetaldehyde-dopamine condensation product, salsolinol. The present review article aims at presenting and discussing prospectively the most recent data accumulated following these three research pathways on this never-ending story in order to offer the most up-to-date synoptic critical view on such still unresolved and exciting topic.
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Affiliation(s)
| | - María J. Sánchez-Catalán
- Department of Pharmacy, Pharmaceutical Technology and Parasitology, University of ValenciaValència, Spain
| | - Lucia Hipólito
- Department of Pharmacy, Pharmaceutical Technology and Parasitology, University of ValenciaValència, Spain
| | - Michela Rosas
- Department of Life and Environmental Sciences, University of CagliariCagliari, Italy
| | - Simona Porru
- Department of Life and Environmental Sciences, University of CagliariCagliari, Italy
| | | | - Patrizia Romualdi
- Department of Pharmacy and Biotechnology, University of BolognaBologna, Italy
| | - Francesca F. Caputi
- Department of Pharmacy and Biotechnology, University of BolognaBologna, Italy
| | - Sanzio Candeletti
- Department of Pharmacy and Biotechnology, University of BolognaBologna, Italy
| | - Ana Polache
- Department of Pharmacy, Pharmaceutical Technology and Parasitology, University of ValenciaValència, Spain
| | - Luis Granero
- Department of Pharmacy, Pharmaceutical Technology and Parasitology, University of ValenciaValència, Spain
| | - Elio Acquas
- Department of Life and Environmental Sciences, University of CagliariCagliari, Italy
- Centre of Excellence on Neurobiology of Addiction, University of CagliariCagliari, Italy
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18
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Israel Y, Karahanian E, Ezquer F, Morales P, Ezquer M, Rivera-Meza M, Herrera-Marschitz M, Quintanilla ME. Acquisition, Maintenance and Relapse-Like Alcohol Drinking: Lessons from the UChB Rat Line. Front Behav Neurosci 2017; 11:57. [PMID: 28420969 PMCID: PMC5378819 DOI: 10.3389/fnbeh.2017.00057] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 03/20/2017] [Indexed: 12/31/2022] Open
Abstract
This review article addresses the biological factors that influence: (i) the acquisition of alcohol intake; (ii) the maintenance of chronic alcohol intake; and (iii) alcohol relapse-like drinking behavior in animals bred for their high-ethanol intake. Data from several rat strains/lines strongly suggest that catalase-mediated brain oxidation of ethanol into acetaldehyde is an absolute requirement (up 80%–95%) for rats to display ethanol’s reinforcing effects and to initiate chronic ethanol intake. Acetaldehyde binds non-enzymatically to dopamine forming salsolinol, a compound that is self-administered. In UChB rats, salsolinol: (a) generates marked sensitization to the motivational effects of ethanol; and (b) strongly promotes binge-like drinking. The specificity of salsolinol actions is shown by the finding that only the R-salsolinol enantiomer but not S-salsolinol accounted for the latter effects. Inhibition of brain acetaldehyde synthesis does not influence the maintenance of chronic ethanol intake. However, a prolonged ethanol withdrawal partly returns the requirement for acetaldehyde synthesis/levels both on chronic ethanol intake and on alcohol relapse-like drinking. Chronic ethanol intake, involving the action of lipopolysaccharide diffusing from the gut, and likely oxygen radical generated upon catechol/salsolinol oxidation, leads to oxidative stress and neuro-inflammation, known to potentiate each other. Data show that the administration of N-acetyl cysteine (NAC) a strong antioxidant inhibits chronic ethanol maintenance by 60%–70%, without inhibiting its initial intake. Intra-cerebroventricular administration of mesenchymal stem cells (MSCs), known to release anti-inflammatory cytokines, to elevate superoxide dismutase levels and to reverse ethanol-induced hippocampal injury and cognitive deficits, also inhibited chronic ethanol maintenance; further, relapse-like ethanol drinking was inhibited up to 85% for 40 days following intracerebral stem cell administration. Thus: (i) ethanol must be metabolized intracerebrally into acetaldehyde, and further into salsolinol, which appear responsible for promoting the acquisition of the early reinforcing effects of ethanol; (ii) acetaldehyde is not responsible for the maintenance of chronic ethanol intake, while other mechanisms are indicated; (iii) the systemic administration of NAC, a strong antioxidant markedly inhibits the maintenance of chronic ethanol intake; and (iv) the intra-cerebroventricular administration of anti-inflammatory and antioxidant MSCs inhibit both the maintenance of chronic ethanol intake and relapse-like drinking.
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Affiliation(s)
- Yedy Israel
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, University of ChileSantiago, Chile
| | - Eduardo Karahanian
- Center for Biomedical Research, Universidad Autónoma de ChileSantiago, Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana-Universidad del DesarrolloSantiago, Chile
| | - Paola Morales
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, University of ChileSantiago, Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana-Universidad del DesarrolloSantiago, Chile
| | - Mario Rivera-Meza
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of ChileSantiago, Chile
| | - Mario Herrera-Marschitz
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, University of ChileSantiago, Chile
| | - María E Quintanilla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, University of ChileSantiago, Chile
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Orrico A, Martí-Prats L, Cano-Cebrián MJ, Granero L, Polache A, Zornoza T. Pre-Clinical Studies with D-Penicillamine as a Novel Pharmacological Strategy to Treat Alcoholism: Updated Evidences. Front Behav Neurosci 2017; 11:37. [PMID: 28326026 PMCID: PMC5339308 DOI: 10.3389/fnbeh.2017.00037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 02/21/2017] [Indexed: 11/29/2022] Open
Abstract
Ethanol, as other drugs of abuse, is able to activate the ventral tegmental area dopamine (VTA-DA) neurons leading to positively motivational alcohol-seeking behavior and use, and, ultimately to ethanol addiction. In the last decades, the involvement of brain-derived acetaldehyde (ACD) in the ethanol actions in the mesolimbic pathway has been widely demonstrated. Consistent published results have provided a mechanistic support to the use of ACD inactivating agents to block the motivational and reinforcing properties of ethanol. Hence, in the last years, several pre-clinical studies have been performed in order to analyze the effects of the sequestering ACD agents in the prevention of ethanol relapse-like drinking behavior as well as in chronic alcohol consumption. In this sense, one of the most explored interventions has been the administration of D-Penicillamine (DP). These pre-clinical studies, that we critically summarize in this article, are considered a critical step for the potential development of a novel pharmacotherapeutic strategy for alcohol addiction treatment that could improve the outcomes of current ones. Thus, on one hand, several experimental findings provide the rationale for using DP as a novel therapeutic intervention alone and/or in combination to prevent relapse into alcohol seeking and consumption. On the other hand, its effectiveness in reducing voluntary ethanol consumption in long-term experienced animals still remains unclear. Finally, this drug offers the additional advantage that has already been approved for use in humans, hence it could be easily implemented as a new therapeutic intervention for relapse prevention in alcoholism.
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Affiliation(s)
- Alejandro Orrico
- Área de Investigación en Vacunas, Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO) Valencia, Spain
| | | | - María J Cano-Cebrián
- Department of Pharmacy and Pharmacy Technology and Parasitology, University of Valencia Valencia, Spain
| | - Luis Granero
- Department of Pharmacy and Pharmacy Technology and Parasitology, University of Valencia Valencia, Spain
| | - Ana Polache
- Department of Pharmacy and Pharmacy Technology and Parasitology, University of Valencia Valencia, Spain
| | - Teodoro Zornoza
- Department of Pharmacy and Pharmacy Technology and Parasitology, University of Valencia Valencia, Spain
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Berríos-Cárcamo P, Quintanilla ME, Herrera-Marschitz M, Vasiliou V, Zapata-Torres G, Rivera-Meza M. Racemic Salsolinol and its Enantiomers Act as Agonists of the μ-Opioid Receptor by Activating the Gi Protein-Adenylate Cyclase Pathway. Front Behav Neurosci 2017; 10:253. [PMID: 28167903 PMCID: PMC5253357 DOI: 10.3389/fnbeh.2016.00253] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/28/2016] [Indexed: 01/07/2023] Open
Abstract
Background: Several studies have shown that the ethanol-derived metabolite salsolinol (SAL) can activate the mesolimbic system, suggesting that SAL is the active molecule mediating the rewarding effects of ethanol. In vitro and in vivo studies suggest that SAL exerts its action on neuron excitability through a mechanism involving opioid neurotransmission. However, there is no direct pharmacologic evidence showing that SAL activates opioid receptors. Methods: The ability of racemic (R/S)-SAL, and its stereoisomers (R)-SAL and (S)-SAL, to activate the μ-opioid receptor was tested in cell-based (light-emitting) receptor assays. To further characterizing the interaction of SAL stereoisomers with the μ-opioid receptor, a molecular docking study was performed using the crystal structure of the μ-opioid receptor. Results: This study shows that SAL activates the μ-opioid receptor by the classical G protein-adenylate cyclase pathway with an half-maximal effective concentration (EC50) of 2 × 10−5 M. The agonist action of SAL was fully blocked by the μ-opioid antagonist naltrexone. The EC50 for the purified stereoisomers (R)-SAL and (S)-SAL were 6 × 10−4 M and 9 × 10−6 M respectively. It was found that the action of racemic SAL on the μ-opioid receptor did not promote the recruitment of β-arrestin. Molecular docking studies showed that the interaction of (R)- and (S)-SAL with the μ-opioid receptor is similar to that predicted for the agonist morphine. Conclusions: It is shown that (R)-SAL and (S)-SAL are agonists of the μ-opioid receptor. (S)-SAL is a more potent agonist than the (R)-SAL stereoisomer. In silico analysis predicts a morphine-like interaction between (R)- and (S)-SAL with the μ-opioid receptor. These results suggest that an opioid action of SAL or its enantiomers is involved in the rewarding effects of ethanol.
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Affiliation(s)
- Pablo Berríos-Cárcamo
- Program of Molecular and Clinical Pharmacology, Faculty of Medicine, Institute of Biomedical Sciences, University of ChileSantiago, Chile; Department of Environmental Health Sciences, Yale School of Public HealthNew Haven, CT, USA
| | - María E Quintanilla
- Program of Molecular and Clinical Pharmacology, Faculty of Medicine, Institute of Biomedical Sciences, University of Chile Santiago, Chile
| | - Mario Herrera-Marschitz
- Program of Molecular and Clinical Pharmacology, Faculty of Medicine, Institute of Biomedical Sciences, University of Chile Santiago, Chile
| | - Vasilis Vasiliou
- Department of Environmental Health Sciences, Yale School of Public Health New Haven, CT, USA
| | - Gerald Zapata-Torres
- Department of Analytical and Inorganic Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile Santiago, Chile
| | - Mario Rivera-Meza
- Department of Pharmacological and Toxicological Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile Santiago, Chile
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21
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Peana AT, Rosas M, Porru S, Acquas E. From Ethanol to Salsolinol: Role of Ethanol Metabolites in the Effects of Ethanol. J Exp Neurosci 2016; 10:137-146. [PMID: 27891052 PMCID: PMC5117487 DOI: 10.4137/jen.s25099] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 10/13/2016] [Accepted: 11/03/2016] [Indexed: 12/29/2022] Open
Abstract
In spite of the global reputation of ethanol as the psychopharmacologically active ingredient of alcoholic drinks, the neurobiological basis of the central effects of ethanol still presents some dark sides due to a number of unanswered questions related to both its precise mechanism of action and its metabolism. Accordingly, ethanol represents the interesting example of a compound whose actions cannot be explained as simply due to the involvement of a single receptor/neurotransmitter, a scenario further complicated by the robust evidence that two main metabolites, acetaldehyde and salsolinol, exert many effects similar to those of their parent compound. The present review recapitulates, in a perspective manner, the major and most recent advances that in the last decades boosted a significant growth in the understanding on the role of ethanol metabolism, in particular, in the neurobiological basis of its central effects.
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Affiliation(s)
- Alessandra T Peana
- Department of Chemistry and Pharmacy, University of Sassari, Sassari, Italy
| | - Michela Rosas
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Simona Porru
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Elio Acquas
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.; Centre of Excellence on Neurobiology of Addiction, University of Cagliari, Cagliari, Italy
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22
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Quintanilla ME, Rivera-Meza M, Berríos-Cárcamo P, Cassels BK, Herrera-Marschitz M, Israel Y. (R)-Salsolinol, a product of ethanol metabolism, stereospecifically induces behavioral sensitization and leads to excessive alcohol intake. Addict Biol 2016; 21:1063-1071. [PMID: 26032572 DOI: 10.1111/adb.12268] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ethanol is oxidized in the brain to acetaldehyde, which can condense with dopamine to generate (R/S)-salsolinol [(RS)-SAL]. Racemic salsolinol [(RS)-SAL] is self-infused by rats into the posterior ventral tegmental area (VTA) at significantly lower concentrations than those of acetaldehyde, suggesting that (RS)-SAL is a most active product of ethanol metabolism. Early studies showed that repeated intraperitoneal or intra-VTA administration of (RS)-SAL (10 mg/kg) induced conditioned place preference, led to locomotor sensitization and increased voluntary ethanol consumption. In the present study, we separated the (R)- and (S)-enantiomers from a commercial (RS)-SAL using a high-performance liquid chromatography with electrochemical detection system fitted with a β-cyclodextrin-modified column. We injected (R)-SAL or (S)-SAL (30 pmol/1.0 μl) into the VTA of naïve UChB rats bred as alcohol drinkers to study whether one or both SAL enantiomers are responsible for the motivated behavioral effects, sensitization and increase in voluntary ethanol intake. The present results show that repeated administration of (R)-SAL leads to (1) conditioned place preference; (2) locomotor sensitization; and (3) marked increases in binge-like ethanol intake. Conversely, (S)-SAL did not influence any of these parameters. Overall, data indicate that (R)-SAL stereospecifically induces motivational effects, behavioral sensitization and increases ethanol intake.
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Affiliation(s)
- María Elena Quintanilla
- Molecular and Clinical Pharmacology Program; Institute of Biomedical Sciences; University of Chile; Chile
| | - Mario Rivera-Meza
- Molecular and Clinical Pharmacology Program; Institute of Biomedical Sciences; University of Chile; Chile
- Millennium Institute BNI; Faculty of Medicine; University of Chile; Chile
| | - Pablo Berríos-Cárcamo
- Molecular and Clinical Pharmacology Program; Institute of Biomedical Sciences; University of Chile; Chile
| | - Bruce K. Cassels
- Department of Chemistry; Faculty of Sciences; University of Chile; Chile
| | - Mario Herrera-Marschitz
- Molecular and Clinical Pharmacology Program; Institute of Biomedical Sciences; University of Chile; Chile
- Millennium Institute BNI; Faculty of Medicine; University of Chile; Chile
| | - Yedy Israel
- Molecular and Clinical Pharmacology Program; Institute of Biomedical Sciences; University of Chile; Chile
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Quintanilla ME, Rivera-Meza M, Berríos-Cárcamo P, Salinas-Luypaert C, Herrera-Marschitz M, Israel Y. Beyond the “First Hit”: Marked Inhibition byN-Acetyl Cysteine of Chronic Ethanol Intake But Not of Early Ethanol Intake. Parallel Effects on Ethanol-Induced Saccharin Motivation. Alcohol Clin Exp Res 2016; 40:1044-51. [DOI: 10.1111/acer.13031] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 01/28/2016] [Indexed: 02/06/2023]
Affiliation(s)
- María Elena Quintanilla
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
| | - Mario Rivera-Meza
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
- Department of Pharmacological and Toxicological Chemistry; Faculty of Chemical and Pharmaceutical Sciences; University of Chile; Santiago Chile
| | - Pablo Berríos-Cárcamo
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
| | - Catalina Salinas-Luypaert
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
| | - Mario Herrera-Marschitz
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
| | - Yedy Israel
- Molecular and Clinical Pharmacology Program; Faculty of Medicine; Institute of Biomedical Sciences; University of Chile; Santiago Chile
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Trantham-Davidson H, Chandler LJ. Alcohol-induced alterations in dopamine modulation of prefrontal activity. Alcohol 2015; 49:773-9. [PMID: 26558348 DOI: 10.1016/j.alcohol.2015.09.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 09/01/2015] [Accepted: 09/01/2015] [Indexed: 02/06/2023]
Abstract
Long-term alcohol use leads to persistent cognitive deficits that may be associated with maladaptive changes in the neurocircuitry that mediates executive functions. Impairments caused by these changes can persist well into abstinence and have a negative impact on quality of life and job performance, and can increase the probability of relapse. Many of the changes that affect cognitive function appear to involve dysregulation of the mesocortical dopamine system. This includes changes in dopamine release and alterations in dopamine receptor expression and function in the medial prefrontal cortex (PFC). This review summarizes the cellular effects of acute and chronic ethanol exposure on dopamine release and dopamine receptor function in the PFC with the goal of providing greater understanding of the effects of alcohol-use disorders on the dopamine system and how this relates to deficits in the executive function of the PFC.
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Affiliation(s)
| | - L Judson Chandler
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425, USA
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Role of ethanol-derived acetaldehyde in operant oral self-administration of ethanol in rats. Psychopharmacology (Berl) 2015; 232:4269-76. [PMID: 26292801 DOI: 10.1007/s00213-015-4049-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/10/2015] [Indexed: 01/12/2023]
Abstract
RATIONALE The role of ethanol-derived acetaldehyde has not been examined yet on performance in a model of operant oral self-administration. However, previous studies reported that an acetaldehyde-sequestering agent, D-penicillamine (DP) and an inhibitor of catalase-mediated acetaldehyde production, 3-amino-1,2,4-triazole (3-AT) reduce voluntary ethanol consumption. OBJECTIVES The aim of our investigation was to evaluate the effects of DP and 3-AT on acquisition and maintenance of oral operant ethanol self-administration. METHODS Using operant chambers, rats learned to nose poke in order to receive ethanol solution (5-10 % v/v) under an FR1 schedule of reinforcement in which discrete light and tone cues were presented during ethanol delivery. RESULTS DP and 3-AT impair the acquisition of ethanol self-administration, whereas its maintenance is not affected neither by drug given alone for both 10 or 5 % ethanol nor by drugs association for 5 % ethanol. Moreover, when the concentration of ethanol was diminished from 10 to 5 %, rats increased the rate of self-administration behaviour. CONCLUSIONS These findings suggest that brain acetaldehyde plays a critical role during acquisition of operant self-administration in ethanol-naïve rats. In contrast, during the maintenance phase, acetaldehyde could contribute to ethanol self-administration by a combined mechanism: On one hand, its lack (by DP or 3-AT) might result in further ethanol-seeking and taking and, on the other, inhibition of ethanol metabolism (by 3-AT) might release an action of the un-metabolised fraction of ethanol that does not overall result in compromising maintenance of ethanol self-administration.
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Song BJ, Akbar M, Jo I, Hardwick JP, Abdelmegeed MA. Translational Implications of the Alcohol-Metabolizing Enzymes, Including Cytochrome P450-2E1, in Alcoholic and Nonalcoholic Liver Disease. ADVANCES IN PHARMACOLOGY 2015; 74:303-72. [PMID: 26233911 DOI: 10.1016/bs.apha.2015.04.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fat accumulation (hepatic steatosis) in alcoholic and nonalcoholic fatty liver disease is a potentially pathologic condition which can progress to steatohepatitis (inflammation), fibrosis, cirrhosis, and carcinogenesis. Many clinically used drugs or some alternative medicine compounds are also known to cause drug-induced liver injury, which can further lead to fulminant liver failure and acute deaths in extreme cases. During liver disease process, certain cytochromes P450 such as the ethanol-inducible cytochrome P450-2E1 (CYP2E1) and CYP4A isozymes can be induced and/or activated by alcohol and/or high-fat diets and pathophysiological conditions such as fasting, obesity, and diabetes. Activation of these P450 isozymes, involved in the metabolism of ethanol, fatty acids, and various drugs, can produce reactive oxygen/nitrogen species directly and/or indirectly, contributing to oxidative modifications of DNA/RNA, proteins and lipids. In addition, aldehyde dehydrogenases including the mitochondrial low Km aldehyde dehydrogenase-2 (ALDH2), responsible for the metabolism of acetaldehyde and lipid aldehydes, can be inactivated by various hepatotoxic agents. These highly reactive acetaldehyde and lipid peroxides, accumulated due to ALDH2 suppression, can interact with cellular macromolecules DNA/RNA, lipids, and proteins, leading to suppression of their normal function, contributing to DNA mutations, endoplasmic reticulum stress, mitochondrial dysfunction, steatosis, and cell death. In this chapter, we specifically review the roles of the alcohol-metabolizing enzymes including the alcohol dehydrogenase, ALDH2, CYP2E1, and other enzymes in promoting liver disease. We also discuss translational research opportunities with natural and/or synthetic antioxidants, which can prevent or delay the onset of inflammation and liver disease.
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Affiliation(s)
- Byoung-Joon Song
- Section of Molecular Pharmacology and Toxicology, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland, USA.
| | - Mohammed Akbar
- Section of Molecular Pharmacology and Toxicology, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland, USA
| | - Inho Jo
- Department of Molecular Medicine, Ewha Womans University School of Medicine, Seoul, South Korea
| | - James P Hardwick
- Biochemistry and Molecular Pathology in Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, Ohio, USA
| | - Mohamed A Abdelmegeed
- Section of Molecular Pharmacology and Toxicology, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland, USA
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Israel Y, Quintanilla ME, Karahanian E, Rivera-Meza M, Herrera-Marschitz M. The "first hit" toward alcohol reinforcement: role of ethanol metabolites. Alcohol Clin Exp Res 2015; 39:776-86. [PMID: 25828063 DOI: 10.1111/acer.12709] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 02/22/2015] [Indexed: 12/20/2022]
Abstract
This review analyzes literature that describes the behavioral effects of 2 metabolites of ethanol (EtOH): acetaldehyde and salsolinol (a condensation product of acetaldehyde and dopamine) generated in the brain. These metabolites are self-administered into specific brain areas by animals, showing strong reinforcing effects. A wealth of evidence shows that EtOH, a drug consumed to attain millimolar concentrations, generates brain metabolites that are reinforcing at micromolar and nanomolar concentrations. Salsolinol administration leads to marked increases in voluntary EtOH intake, an effect inhibited by mu-opioid receptor blockers. In animals that have ingested EtOH chronically, the maintenance of alcohol intake is no longer influenced by EtOH metabolites, as intake is taken over by other brain systems. However, after EtOH withdrawal brain acetaldehyde has a major role in promoting binge-like drinking in the condition known as the "alcohol deprivation effect"; a condition seen in animals that have ingested alcohol chronically, are deprived of EtOH for extended periods, and are allowed EtOH re-access. The review also analyzes the behavioral effects of acetate, a metabolite that enters the brain and is responsible for motor incoordination at low doses of EtOH. Also discussed are the paradoxical effects of systemic acetaldehyde. Overall, evidence strongly suggests that brain-generated EtOH metabolites play a major role in the early ("first-hit") development of alcohol reinforcement and in the generation of relapse-like drinking.
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Affiliation(s)
- Yedy Israel
- Program of Molecular and Clinical Pharmacology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
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Involvement of dopamine D2 receptors in addictive-like behaviour for acetaldehyde. PLoS One 2014; 9:e99454. [PMID: 24926837 PMCID: PMC4057173 DOI: 10.1371/journal.pone.0099454] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/14/2014] [Indexed: 12/29/2022] Open
Abstract
Acetaldehyde, the first metabolite of ethanol, is active in the central nervous system, where it exerts motivational properties. Acetaldehyde is able to induce drinking behaviour in operant-conflict paradigms that resemble the core features of the addictive phenotype: drug-intake acquisition and maintenance, drug-seeking, relapse and drug use despite negative consequences. Since acetaldehyde directly stimulates dopamine neuronal firing in the mesolimbic system, the aim of this study was the investigation of dopamine D2-receptors' role in the onset of the operant drinking behaviour for acetaldehyde in different functional stages, by the administration of two different D2-receptor agonists, quinpirole and ropinirole. Our results show that acetaldehyde was able to induce and maintain a drug-taking behaviour, displaying an escalation during training, and a reinstatement behaviour after 1-week forced abstinence. Acetaldehyde operant drinking behaviour involved D2-receptor signalling: in particular, quinpirole administration at 0.03 mg/kg, induced a significant decrease in the number of lever presses both in extinction and in relapse. Ropinirole, administered at 0.03 mg/kg during extinction, did not produce any modification but, when administered during abstinence, induced a strong decrease in acetaldehyde intake in the following relapse session. Taken together, our data suggest that acetaldehyde exerts its own motivational properties, involving the dopaminergic transmission: indeed, activation of pre-synaptic D2-receptors by quinpirole, during extinction and relapse, negatively affects operant behaviour for acetaldehyde, likely decreasing acetaldehyde-induced dopamine release. The activation of post-synaptic D2-receptors by ropinirole, during abstinence, decreases the motivation to the consecutive reinstatement of acetaldehyde drinking behaviour, likely counteracting the reduction in the dopaminergic tone typical of withdrawal. These data further strengthen the evidence that acetaldehyde may play a crucial role as mediator of ethanol's central effects.
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