Fenofibrate (a PPAR-α Agonist) Administered During Ethanol Withdrawal Reverts Ethanol-Induced Astrogliosis and Restores the Levels of Glutamate Transporter in Ethanol-Administered Adolescent Rats.

High-ethanol intake induces a neuroinflammatory response, which has been proposed as responsible for the maintenance of chronic ethanol consumption. Neuroinflammation decreases glutamate transporter (GLT-1) expression, increasing levels of glutamate that trigger dopamine release at the corticolimbic reward areas, driving long-term drinking behavior. The activation of peroxisome proliferator-activated receptor alpha (PPARα) by fibrates inhibits neuroinflammation, in models other than ethanol consumption. However, the effect of fibrates on ethanol-induced neuroinflammation has not yet been studied. We previously reported that the administration of fenofibrate to ethanol-drinking rats decreased ethanol consumption. Here, we studied whether fenofibrate effects are related to a decrease in ethanol-induced neuroinflammation and to the normalization of the levels of GLT-1. Rats were administered ethanol on alternate days for 4 weeks (2 g/kg/day). After ethanol withdrawal, fenofibrate was administered for 14 days (50 mg/kg/day) and the levels of glial fibrillary acidic protein (GFAP), phosphorylated NF-κB-inhibitory protein (pIκBα) and GLT-1, were quantified in the prefrontal cortex, hippocampus, and hypothalamus. Ethanol treatment increased the levels of GFAP in the hippocampus and hypothalamus, indicating a clear astrocytic activation. Similarly, ethanol increased the levels of pIκBα in the three areas. The administration of fenofibrate decreased the expression of GFAP and pIκBα in the three areas. These results indicate that fenofibrate reverts both astrogliosis and NF-κB activation. Finally, ethanol decreased GLT-1 expression in the prefrontal cortex and hippocampus. Fenofibrate normalized the levels of GLT-1 in both areas, suggesting that its effect in reducing ethanol consumption could be due to the normalization of glutamatergic tone.

Activation of Melanocortin-4 Receptor Inhibits Both Neuroinflammation Induced by Early Exposure to Ethanol and Subsequent Voluntary Alcohol Intake in Adulthood in Animal Models: Is BDNF the Key Mediator?

The concept that neuroinflammation induced by excessive alcohol intake in adolescence triggers brain mechanisms that perpetuate consumption has strengthened in recent years. The melanocortin system, composed of the melanocortin 4 receptor (MC4R) and its ligand α-melanocyte-stimulating hormone (α-MSH), has been implicated both in modulation of alcohol consumption and in ethanol-induced neuroinflammation decrease. Chronic alcohol consumption in adolescent rats causes a decrease in an α-MSH release by the hypothalamus, while the administration of synthetic agonists of MC4R causes a decrease in neuroinflammation and a decrease in voluntary alcohol consumption. However, the mechanism that connects the activation of MC4R with the decrease of both neuroinflammation and voluntary alcohol consumption has not been elucidated. Brain-derived neurotrophic factor (BDNF) has been implicated in alcohol drinking motivation, dependence and withdrawal, and its levels are reduced in alcoholics. Deficiencies in BDNF levels increased ethanol self-administration in rats. Further, BDNF triggers important anti-inflammatory effects in the brain, and this could be one of the mechanisms by which BDNF reduces chronic alcohol intake. Interestingly, MC4R signaling induces BDNF expression through the activation of the cAMP-responsive element-binding protein (CREB). We hypothesize that ethanol exposure during adolescence decreases the expression of α-MSH and hence MC4R signaling in the hippocampus, leading to a lower BDNF activity that causes dramatic changes in the brain (e.g., neuroinflammation and decreased neurogenesis) that predispose to maintain alcohol abuse until adulthood. The activation of MC4R either by α-MSH or by synthetic agonist peptides can induce the expression of BDNF, which would trigger several processes that lead to lower alcohol consumption.

Fenofibrate -a PPARα agonist- increases alcohol dehydrogenase levels in the liver: implications for its possible use as an ethanol-aversive drug. / Fenofibrato -un agonista de PPARα- incrementa los niveles de la alcohol deshidrogenasa hepática: implicaciones para su posible uso como una droga de aversión al etanol.

After ethanol consumption, disulfiram increases blood-acetaldehyde levels, generating an aversive reaction that deters alcohol drinking. Given the major secondary effects of disulfiram, finding other effective drugs to reduce alcohol consumption in individuals with alcohol-use-disorder is highly desirable. It has been reported that administering fenofibrate to high-drinking rats increases hepatic catalase levels and blood acetaldehyde after administering ethanol and a 60-70% inhibition of voluntary alcohol intake. This work evaluated whether fenofibrate has an additional effect on the activity of other ethanol-metabolizing enzymes, which could contribute to the high acetaldehyde levels generated upon administering ethanol. Male high-drinker rats were allowed to voluntary drink 10% ethanol or water for 2 months. Subsequently, fenofibrate (100 mg/kg/day) or vehicle was administered orally for 14 days. Then, alcohol dehydrogenase (ADH1) and aldehyde dehydrogenase (ALDH2) protein levels and enzymatic activities in the livers were quantified. Fenofibrate treatment produced a marked increase in ADH1 protein levels (396% ± 18%, p < 0.001) and enzymatic activity (425% ± 25%, p < 0.001). Fenofibrate did not result in differences in ALDH2 activity or in ALDH2 protein levels. The studies show that treatment with fenofibrate not only increased the activity of catalase in the liver of alcohol-drinking rats, as reported earlier, but also increased the levels and enzymatic activity of ADH1, while ALDH2 remained unchanged. The increases in ADH1 contribute to explaining the remarkable effect of fenofibrate in raising blood levels of acetaldehyde in ethanol-consuming animals, in which a marked reduction of alcohol intake is recorded.

Tras consumir etanol, el disulfiram incrementa los niveles de acetaldehído en sangre y genera una reacción aversiva que desalienta el consumo de alcohol. Dados los importantes efectos secundarios del disulfiram, es altamente deseable hallar otros fármacos efectivos para tratar el trastorno por uso de alcohol. Se ha reportado que administrar fenofibrato a ratas altamente bebedoras de alcohol aumenta los niveles de catalasa hepática y acetaldehído en sangre después de la administración de etanol, y disminuye el consumo voluntario de alcohol (60-70%). Este trabajo evalúa si el fenofibrato tiene un efecto adicional sobre la actividad de otras enzimas en el metabolismo del etanol que podría contribuir a generar altos niveles de acetaldehído. Se permitió a ratas macho altamente bebedoras beber voluntariamente etanol 10% durante 2 meses. Después, se les administró oralmente fenofibrato (100 mg/kg/día) o solo vehículo durante 14 días. Tras eso, se midieron los niveles hepáticos y actividades enzimáticas de alcohol deshidrogenasa (ADH1) y de aldehído deshidrogenasa (ALDH2). El fenofibrato produjo un marcado aumento en los niveles proteicos de ADH1 (396% ± 18%, p < 0,001) y de actividad enzimática (425% ± 25%, p < 0,001) sin alterar los niveles protéicos ni la actividad de ALDH2. Los resultados muestran que el tratamiento con fenofibrato no solo aumenta la actividad de catalasa en el hígado de ratas bebedoras de alcohol, sino que también incrementa los niveles y la actividad de ADH1, sin alterar ALDH2. Esto contribuye a explicar el notable efecto del fenofibrato en aumentar los niveles de acetaldehído en sangre en animales bebedores de alcohol, en los que se registra una marcada reducción en la ingesta de etanol.

Fenofibrato -un agonista de PPARalpha- incrementa los niveles de la alcohol deshidrogenasa hepática: implicaciones para su posible uso como una droga de aversión al etanol / Fenofibrate -a PPARalfa agonist- increases alcohol dehydrogenase levels in the liver: implications for its possible use as an ethanol-aversive drug

Tras consumir etanol, el disulfiram incrementa los niveles de acetaldehído en sangre y genera una reacción aversiva que desalienta el consumo de alcohol. Dados los importantes efectos secundarios del disulfiram, es altamente deseable hallar otros fármacos efectivos para tratar el trastorno por uso de alcohol. Se ha reportado que administrar fenofibrato a ratas altamente bebedoras de alcohol aumenta los niveles de catalasa hepática y acetaldehído en sangre después de la administración de etanol, y disminuye el consumo voluntario de alcohol (60-70%). Este trabajo evalúa si el fenofibrato tiene un efecto adicional sobre la actividad de otras enzimas en el metabolismo del etanol que podría contribuir a generar altos niveles de acetaldehído. Se permitió a ratas macho altamente bebedoras beber voluntariamente etanol 10% durante 2 meses. Después, se les administró oralmente fenofibrato (100 mg/kg/día) o solo vehículo durante 14 días. Tras eso, se midieron los niveles hepáticos y actividades enzimáticas de alcohol deshidrogenasa (ADH1) y de aldehído deshidrogenasa (ALDH2). El fenofibrato produjo un marcado aumento en los niveles proteicos de ADH1 (396% ± 18%, p < ,001) y de actividad enzimática (425% ± 25%, p < ,001) sin alterar los niveles protéicos ni la actividad de ALDH2. Los resultados muestran que el tratamiento con fenofibrato no solo aumenta la actividad de catalasa en el hígado de ratas bebedoras de alcohol, sino que también incrementa los niveles y la actividad de ADH1, sin alterar ALDH2. Esto contribuye a explicar el notable efecto del fenofibrato en aumentar los niveles de acetaldehído en sangre en animales bebedores de alcohol, en los que se registra una marcada reducción en la ingesta de etanol

After ethanol consumption, disulfiram increases blood-acetaldehyde levels, generating an aversive reaction that deters alcohol drinking. Given the major secondary effects of disulfiram, finding other effective drugs to reduce alcohol consumption in individuals with alcohol-use-disorder is highly desirable. It has been reported that administering fenofibrate to high-drinking rats increases hepatic catalase levels and blood acetaldehyde after administering ethanol and a 60-70% inhibition of voluntary alcohol intake. This work evaluated whether fenofibrate has an additional effect on the activity of other ethanol-metabolizing enzymes, which could contribute to the high acetaldehyde levels generated upon administering ethanol. Male high-drinker rats were allowed to voluntary drink 10% ethanol or water for 2 months. Subsequently, fenofibrate (100 mg/kg/day) or vehicle was administered orally for 14 days. Then, alcohol dehydrogenase (ADH1) and aldehyde dehydrogenase (ALDH2) protein levels and enzymatic activities in the livers were quantified. Fenofibrate treatment produced a marked increase in ADH1 protein levels (396% ± 18%, p < 0.001) and enzymatic activity (425% ± 25%, p < 0.001). Fenofibrate did not result in differences in ALDH2 activity or in ALDH2 protein levels. The studies show that treatment with fenofibrate not only increased the activity of catalase in the liver of alcohol-drinking rats, as reported earlier, but also increased the levels and enzymatic activity of ADH1, while ALDH2 remained unchanged. The increases in ADH1 contribute to explaining the remarkable effect of fenofibrate in raising blood levels of acetaldehyde in ethanol-consuming animals, in which a marked reduction of alcohol intake is recorded

Activation of Melanocortin-4 Receptor by a Synthetic Agonist Inhibits Ethanolinduced Neuroinflammation in Rats.

BACKGROUND: High ethanol intake induces a neuroinflammatory response resulting in the subsequent maintenance of chronic alcohol consumption. The melanocortin system plays a pivotal role in the modulation of alcohol consumption. Interestingly, it has been shown that the activation of melanocortin-4 receptor (MC4R) in the brain decreases the neuroinflammatory response in models of brain damage other than alcohol consumption, such as LPS-induced neuroinflammation, cerebral ischemia, glutamate excitotoxicity, and spinal cord injury. OBJECTIVES: In this work, we aimed to study whether MC4R activation by a synthetic MC4R-agonist peptide prevents ethanol-induced neuroinflammation, and if alcohol consumption produces changes in MC4R expression in the hippocampus and hypothalamus. METHODS: Ethanol-preferring Sprague Dawley rats were selected offering access to 20% ethanol on alternate days for 4 weeks (intermittent access protocol). After this time, animals were i.p. administered an MC4R agonist peptide in the last 2 days of the protocol. Then, the expression of the proinflammatory cytokines interleukin 6 (IL-6), interleukin 1-beta (IL-1ß), and tumor necrosis factor-alpha (TNF-α) were measured in the hippocampus, hypothalamus and prefrontal cortex. It was also evaluated if ethanol intake produces alterations in the expression of MC4R in the hippocampus and the hypothalamus. RESULTS: Alcohol consumption increased the expression of MC4R in the hippocampus and the hypothalamus. The administration of the MC4R agonist reduced IL-6, IL-1ß and TNF-α levels in hippocampus, hypothalamus and prefrontal cortex, to those observed in control rats that did not drink alcohol. CONCLUSION: High ethanol consumption produces an increase in the expression of MC4R in the hippocampus and hypothalamus. The administration of a synthetic MC4R-agonist peptide prevents neuroinflammation induced by alcohol consumption in the hippocampus, hypothalamus, and prefrontal cortex. These results could explain the effect of α-MSH and other synthetic MC4R agonists in decreasing alcohol intake through the reduction of the ethanol-induced inflammatory response in the brain.

Neuroinflammation produced by heavy alcohol intake is due to loops of interactions between Toll-like 4 and TNF receptors, peroxisome proliferator-activated receptors and the central melanocortin system: A novel hypothesis and new therapeutic avenues.

Excessive alcohol intake induces an inflammatory response in the brain, via TNFα, TLR4 and NF-κB signaling pathways. It has been proposed that neuroinflammation would play a very important role in the development of alcohol addiction. In addition to stimulating the synthesis of inflammatory mediators such as IL-6, IL-1ß and TNFα, NF-κB is capable of reducing the anti-inflammatory activity of PPARα and PPARγ. Reciprocally, PPARα, PPARγ and melanocortin 4 receptor (MC4R) can decrease the proinflammatory activity of NF-κB, establishing an interplay of inactivations between such nuclear factors and receptors. In this review, we hypothesize that one of the mechanisms by which alcohol produces neuroinflammation is through NF-κB-mediated decrease in PPARα and PPARγ anti-inflammatory activities; in addition, ethanol negatively affects MC4R activity, decreasing the ability of this receptor to activate PPARγ. PPARα, PPARγ and MC4R can be pharmacologically activated by synthetic ligands (fibrates, thiazolidinediones and synthetic peptides, respectively); in this context, we propose that the administration of such ligands would decrease neuroinflammation produced by alcohol intake. The advantage of this approach is that fibrates and thiazolidinediones are FDA-approved drugs that have been used for years in other clinical conditions, and now may offer a new perspective for the treatment of alcoholism.