Abstinence from Escalation of Cocaine Intake Changes the microRNA Landscape in the Cortico-Accumbal Pathway

Epigenetic Insights into Substance Use Disorder and Associated Psychiatric Conditions

Background

Substance use disorder (SUD) is closely associated with epigenetic modifications that significantly impact mental health outcomes. Alcohol and drug misuse induce widespread changes in the epigenome and transcriptome of the central nervous system, disrupting critical processes such as reward signaling and emotional regulation. These alterations in epigenetic regulation and gene expression often persist even after substance cessation, potentially contributing to the onset or worsening of psychiatric conditions, including schizophrenia, depression, stress, and anxiety.

Summary

This review delves into key epigenetic mechanisms underlying SUD and its comorbid psychiatric disorders, with a focus on DNA methylation, histone modifications, and noncoding RNA regulation. Additionally, it examines the influence of environmental and biological factors on the epigenome and evaluates emerging epigenetic-based therapeutic strategies aimed at treating SUD and related psychiatric conditions.

Key Messages

Gaining a deeper understanding of the epigenetic mechanisms driving SUD and its associated psychiatric disorders is crucial for the development of effective therapeutic interventions. This review highlights the potential of epigenetic-based pharmacological strategies to mitigate the societal and personal burdens linked to SUD and its mental health complications.

Hypocretin Receptor 1 Blockade Early in Abstinence Prevents Incubation of Cocaine Seeking and Normalizes Dopamine Transmission

Abstinence from cocaine use has been shown to elicit a progressive intensification or incubation of cocaine craving/seeking that is posited to contribute to propensity for relapse. While the mechanisms underlying incubation of cocaine seeking remain elusive, considerable evidence suggests that abstinence from cocaine promotes mesolimbic dopamine adaptations that contribute to exaggerated cocaine seeking. Consequently, preventing these dopamine adaptations may reduce incubation of cocaine seeking and thereby reduce the likelihood of relapse. In the present studies, we first examined if incubation of cocaine seeking was associated with aberrant dopamine transmission in the nucleus accumbens after seven days of abstinence from intermittent access to cocaine. Given the extensive evidence that hypocretins/orexins regulate motivation for cocaine, we then examined to what extent hypocretin receptor 1 antagonism on the first day of abstinence prevented incubation of cocaine seeking and dopamine adaptations later in abstinence. Results indicated that abstinence from intermittent access to cocaine engendered robust incubation of cocaine seeking in both female and male rats. We also observed aberrant dopamine transmission, but only in rats that displayed incubation of cocaine seeking. Further, we showed that a single injection of the hypocretin receptor 1 antagonist, RTIOX-276, on the first day of abstinence prevented incubation of cocaine seeking and aberrant dopamine transmission. These findings suggest that hypocretin receptor 1 antagonism may serve as a viable therapeutic for reducing cocaine craving/seeking, thus reducing the likelihood of relapse.

miRNAs and Substances Abuse: Clinical and Forensic Pathological Implications: A Systematic Review

Substance addiction is a chronic and relapsing brain disorder characterized by compulsive seeking and continued substance use, despite adverse consequences. The high prevalence and social burden of addiction are indisputable; however, the available intervention is insufficient. The modulation of gene expression and aberrant adaptation of neural networks are attributed to the changes in brain functions under repeated exposure to addictive substances. Considerable studies have demonstrated that miRNAs are strong modulators of post-transcriptional gene expression in substance addiction. The emerging role of microRNA (miRNA) provides new insights into many biological and pathological processes in the central nervous system: their variable expression in different regions of the brain and tissues may play a key role in regulating the pathophysiological events of addiction. This work provides an overview of the current literature on miRNAs involved in addiction, evaluating their impaired expression and regulatory role in neuroadaptation and synaptic plasticity. Clinical implications of such modulatory capacities will be estimated. Specifically, it will evaluate the potential diagnostic role of miRNAs in the various stages of drug and substance addiction. Future perspectives about miRNAs as potential novel therapeutic targets for substance addiction and abuse will also be provided.