Search

Alcohol use disorder (AUD) is characterized by loss of control over intake and drinking despite harmful consequences. At a molecular level, AUD is associated with long-term neuroadaptations in key brain regions that are involved in reward processing and decision-making. Over the last decades, a great effort has been made to understand the neurobiological basis underlying AUD. Epigenetic mechanisms have emerged as an important mechanism in the regulation of long-term alcohol-induced gene expression changes. Here, we review the literature supporting a role for epigenetic processes in AUD. We particularly focused on the three most studied epigenetic mechanisms: DNA methylation, Histone modification and non-coding RNAs. Clinical studies indicate an association between AUD and DNA methylation both at the gene and global levels. Using behavioral paradigms that mimic some of the characteristics of AUD, preclinical studies demonstrate that changes in epigenetic mechanisms can functionally impact alcohol-associated behaviors. While many studies support a therapeutic potential for targeting epigenetic enzymes, more research is needed to fully understand their role in AUD. Identification of brain circuits underlying alcohol-associated behaviors has made major advances in recent years. However, there are very few studies that investigate how epigenetic mechanisms can affect these circuits or impact the neuronal ensembles that promote alcohol-associated behaviors. Studies that focus on the role of circuit-specific and cell-specific epigenetic changes for clinically relevant alcohol behaviors may provide new insights on the functional role of epigenetic processes in AUD.

Alcohol use is a leading cause of death and disease worldwide. A large part of this disease burden is associated with alcohol use disorder (AUD), a diagnostic category characterized by excessive use in spite of negative consequences ("compulsive use"), a loss of control over intake, and choice of alcohol over natural rewards. These behavioral symptoms are believed to reflect the emergence of persistent neuroadaptations in key brain regions that exert control over motivated behavior. A major challenge to addressing the treatment needs of patients with AUD is the high prevalence of co-occurring psychiatric disorders, of which anxiety disorders are the most common. Both AUD and anxiety disorders are characterized by broad changes in gene expression within brain regions that include the prelimbic cortex (PL) and the amygdala complex. Although the risk for AUD has a substantial genetic component, heavy alcohol use and stress also contribute to disease risk. Our lab previously identified DNA hypermethylation as a mechanism behind alcohol-induced downregulation of prelimbic Syt1 and Prdm2. In a subsequent study, our lab demonstrated a functional role of Prdm2 in alcohol-associated behaviors. In the work that constitutes this thesis, we have further investigated the behavioral consequences of Syt1 and Prdm2 downregulation. We found that Syt1 knock-down in the PL of non-dependent rats is sufficient to promote several behaviors that model critical aspects of AUD. We further identified the PL-basolateral amygdala (BLA) projection as a key brain circuit within which Syt1 knock-down promotes compulsive-like alcohol intake. In another study, we showed that Prdm2 knock-down in the PL increases the expression of fear memory, a central feature of anxiety disorders. Knock-down after memory formation (consolidation) did not increase the fear expression, indicating that Prdm2 regulates fear memory consolidation. We further showed that knock-down of Prdm2 in the PL-BLA projection was s, Alkoholbruk är en av huvudorsakerna till den globala sjukdomsbördan, och står för ungefär 5 % av alla dödsfall i världen. Sjukdomsbördan från alkohol orsakas till stor del av alkoholberoende, en komplex psykiatrisk sjukdom som kännetecknas av kontrollförlust, val av alkohol framför naturliga belöningar, och fortsatt bruk trots negativa konsekvenser (så kallat "kompulsivt bruk"). Dessa beteenden tros avspegla långvariga förändringar i funktionen hos hjärnstrukturer som styr motiverade beteenden. Av alla individer som brukar alkohol är det endast en minoritet, ca 15 %, som utvecklar alkoholberoende. Kända riskfaktorer inkluderar ärftlighet, mängd alkohol som konsumeras och stress. Behandlingar som finns tillgängliga för patienter med alkoholberoende har i dagsläget en otillräcklig effekt. För att utveckla nya läkemedel är det viktigt att förstå mekanismer som ligger bakom utveckling och vidmakthållande av beroende. Övergången från rekreationsbruk till beroende sker genom flera mekanismer. Likt andra droger kan alkohol aktivera hjärnans belöningssystem, och man tror att konsumtionen i tidigare stadier drivs av dessa "positivt förstärkande", eller belönande effekter. Utvecklingen av beroende avspeglar en förskjutning till ett tillstånd där bruket i allt högre grad sker för att dämpa negativa känslor (s.k. "negativ förstärkning"). Denna utveckling avspeglar att system i hjärnan som styr reaktioner på stress och upplevelser av oro och ångest blir aktiverade. En yttring av detta är att patienter med alkoholberoende ofta uppvisar en samsjuklighet med ångestsjukdomar. Patienter med samsjukligt alkoholberoende och ångest uppvisar ofta svårare symtom, och är mer svårbehandlade. Det finns idag ingen evidensbaserad behandling för dessa patienter. Stress är en viktig riskfaktor för både alkoholberoende och ångest, men det finns en betydande individuell variation i sårbarheten för stress. Vi har tidigare visat att utveckling av alkoholberoende i en råttmodell leder till beteendef

Comorbidity between alcohol use and anxiety disorders is associated with more severe symptoms and poorer treatment outcomes than either of the conditions alone. There is a well-known link between stress and the development of these disorders, with post-traumatic stress disorder as a prototypic example. Post-traumatic stress disorder can arise as a consequence of experiencing traumatic events firsthand and also after witnessing them. Here, we used a model of social defeat and witness stress in rats, to study shared mechanisms of stress-induced anxiety-like behavior and escalated alcohol self-administration. Similar to what is observed clinically, we found considerable individual differences in susceptibility and resilience to the stress. Both among defeated and witness rats, we found a subpopulation in which exposure was followed by emergence of increased anxiety-like behavior and escalation of alcohol self-administration. We then profiled gene expression in tissue from the amygdala, a key brain region in the regulation of stress, alcohol use, and anxiety disorders. When comparing "comorbid" and resilient socially defeated rats, we identified a strong upregulation of vasopressin and oxytocin, and this correlated positively with the magnitude of the alcohol self-administration and anxiety-like behavior. A similar trend was observed in comorbid witness rats. Together, our findings provide novel insights into molecular mechanisms underpinning the comorbidity of escalated alcohol self-administration and anxiety-like behavior., Funding Agencies|Wallenberg FoundationEuropean Commission [KAW 2018.0322]; Region Ostergotland; Stiftelsen psykiatriska forskningsfonden; Swedish Research CouncilSwedish Research CouncilEuropean Commission [2013-07434]

BACKGROUND: Alcohol addiction is characterized by persistent neuroadaptations in brain structures involved in motivation, emotion, and decision making, including the medial prefrontal cortex, the nucleus accumbens, and the amygdala. We previously reported that induction of alcohol dependence was associated with long-term changes in the expression of genes involved in neurotransmitter release. Specifically, Syt1, which plays a key role in neurotransmitter release and neuronal functions, was downregulated. Here, we therefore examined the role of Syt1 in alcohol-associated behaviors in rats. METHODS: We evaluated the effect of Syt1 downregulation using an adeno-associated virus (AAV) containing a short hairpin RNA against Syt1. Cre-dependent Syt1 was also used in combination with an rAAV2 retro-Cre virus to assess circuit-specific effects of Syt1 knockdown (KD). RESULTS: Alcohol-induced downregulation of Syt1 is specific to the prelimbic cortex (PL), and KD of Syt1 in the PL resulted in escalated alcohol consumption, increased motivation to consume alcohol, and increased alcohol drinking despite negative consequences ("compulsivity"). Syt1 KD in the PL altered the excitation/inhibition balance in the basolateral amygdala, while the nucleus accumbens core was unaffected. Accordingly, a projection-specific Syt1 KD in the PL-basolateral amygdala projection was sufficient to increase compulsive alcohol drinking, while a KD of Syt1 restricted to PL-nucleus accumbens core projecting neurons had no effect on tested alcohol-related behaviors. CONCLUSIONS: Together, these data suggest that dysregulation of Syt1 is an important mechanism in long-term neuroadaptations observed after a history of alcohol dependence, and that Syt1 regulates alcohol-related behaviors in part by affecting a PL-basolateral amygdala brain circuit., Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [201307434, 2018-028149]; Region Ostergotland; Stiftelsen Psykiatriska Forskningsfonden; Wallenberg FoundationEuropean Commission

Prior work suggests a role of kappa-opioid signaling in the control of alcohol drinking, in particular when drinking is escalated due to alcohol-induced long-term neuroadaptations. Here, we examined the small molecule selective kappa antagonist CERC-501 in rat models of alcohol-related behaviors, with the objective to evaluate its potential as a candidate therapeutic for alcohol use disorders. We first tested the effect of CERC-501 on acute alcohol withdrawal-induced anxiety-like behavior. CERC-501 was then tested on basal as well as escalated alcohol self-administration induced by 20% alcohol intermittent access. Finally, we determined the effects of CERC-501 on relapse to alcohol seeking triggered by both stress and alcohol-associated cues. Control experiments were performed to confirm the specificity of CERC-501 effects on alcohol-related behaviors. CERC-501 reversed anxiety-like behavior induced by alcohol withdrawal. It did not affect basal alcohol self-administration but did dose-dependently suppress self-administration that had escalated following long-term intermittent access to alcohol. CERC-501 blocked relapse to alcohol seeking induced by stress, but not when relapse-like behavior was triggered by alcohol-associated cues. The effects of CERC-501 were observed in the absence of sedative side effects and were not due to effects on alcohol metabolism. Thus, in a broad battery of preclinical alcohol models, CERC-501 has an activity profile characteristic of anti-stress compounds. Combined with its demonstrated preclinical and clinical safety profile, these data support clinical development of CERC-501 for alcohol use disorders, in particular for patients with negatively reinforced, stress-driven alcohol seeking and use., Funding Agencies|Swedish Research Council; Cerecor Inc.

Background: Reward and energy homeostasis are both regulated by a network of hypothalamic neuropeptide systems. The melanin-concentrating hormone (MCH) and its MCH-1 receptor (MCH1-R) modulate alcohol intake, but it remains unknown to what extent this reflects actions on energy balance or reward. Here, we evaluated the MCH1-R in regulation of caloric intake and motivation to consume alcohol in states of escalated consumption. Methods: Rats had intermittent access (IA) to alcohol and were divided into high- and low-drinking groups. Food and alcohol consumption was assessed after administration of an MCH1-R antagonist, GW803430. Next, GW803430 was evaluated on alcohol self-administration in protracted abstinence induced by IA in high-drinking rats. Finally, the effect of GW803430 was assessed on alcohol self-administration in acute withdrawal in rats exposed to alcohol vapor. Gene expression of MCH and MCH1-R was measured in the hypothalamus and nucleus accumbens (NAc) in both acute and protracted abstinence. Results: High-drinking IA rats consumed more calories from alcohol than chow and GW803430 decreased both chow and alcohol intake. In low-drinking rats, only food intake was affected. In protracted abstinence from IA, alcohol self-administration was significantly reduced by pretreatment with GW803430 and gene expression of both MCH and the MCH1-R were dysregulated in hypothalamus and NAc. In contrast, during acute withdrawal from vapor exposure, treatment with GW803430 did not affect alcohol self-administration, and no changes in MCH or MCH1-R gene expression were observed. Conclusions: Our data suggest a dual role of MCH and the MCH1-R in regulation of alcohol intake, possibly through mechanisms involving caloric intake and reward motivation. A selective suppression of alcohol self-administration during protracted abstinence by GW803430 was observed and accompanied by adaptations in gene expression of MCH and MCH1-R. Selective suppression of escalated consumption