Potential Ago2/miR-3068-5p Cascades in the Nucleus Accumbens Contribute to Methamphetamine-Induced Locomotor Sensitization of Mice

Transcriptomic Profile of the Male Rat Hypothalamus and Nucleus Accumbens After Paroxetine Treatment and Withdrawal: Possible Causes of Sexual Dysfunction

Paroxetine, a selective serotonin reuptake inhibitor (SSRI), may induce sexual dysfunction during treatment and upon discontinuation. The mechanisms involved have been poorly explored so far. We have analyzed, by RNA sequencing, the whole transcriptomic profile in the hypothalamus and nucleus accumbens (NAc) (two brain regions involved in sexual behavior) of male rats daily treated for 2 weeks with paroxetine (T0) and at 1 month of withdrawal (T1). Data here reported show seven differentially expressed genes (DEGs) at T0 and 1 at T1 in the hypothalamus and 245 at T0 and 6 at T1 in the NAc. In addition, Gene-Set Enrichment, Gene Ontology, and Reactome analyses confirm that inflammatory signature and immune system activation were present at T0 in both brain areas. Considering that inflammation is generally associated with depression and that no paradigms inducing the pathology were here applied, these SSRI pro-depressive effects should be considered in patients without a clear indication of depression. Moreover, DEGs related to neurotransmitters with a role in sexual behavior and the reward system, such as dopamine (e.g., sialyltransferase 8B-ST8SIA3), glutamate (e.g., glutamate receptor ionotropic delta-2-GRID2) and GABA (e.g., glutamate decarboxylase type 2-GAD2) or associated with neurexin and neuroligin pathways and brain-derived neurotrophic factor (BDNF) signaling, were reported to be dysregulated in the NAc, further confirming dysfunction in this brain area. Interestingly, the analysis of DEGs altered at T1 in the NAc confirms the persistence of some of these side effects providing further information for post-SSRI sexual dysfunction (PSSD) etiopathogenesis.

Brain microRNA profiles after exposure to heroin in rats

Heroin addiction is one of the neuropsychiatric burdens that affects many genetic and epigenetic systems. While it is known that heroin may change the expressions of some genes in the brain during dependence, there is no detailed study related to which gene are mostly affected. Therefore, in the current study, we aimed to determine alterations in the miRNA profiles of rats' brains for providing a detailed analysis of molecular mechanisms in heroin addiction-related toxicology. Next generation global miRNA sequencing was used to predict potential miRNAs in prefrontal cortex (PC), hippocampus, ventral tegmental area (VTA), striatum, and Nucleus accumbens (NA) of rats that exposed to heroin by intravenous injections. The total daily dose was started with 2 mg/kg and ended with 10 mg/kg on the 10th day. In the striatum, miR-18a, miR-17-5p, miR-20a-5p, miR-106a, miR-301a-3p, miR872-5p, miR-15a-5p, miR-500-3p, and miR-339-5p expressions were upregulated by nearly 2-to-4 times with heroin. The expressions of hippocampal miR-153-3p, miR-130a-3p, miR-204-5p, miR-15b-5p, and miR-137-3p and the expressions of miR-872, miR-183-5p, miR-20a-5p, miR-325-5p, miR-379-5p, and miR-340-5p in the VTA were 2-times higher in the heroin-addicted rats. While there was nearly 2-times increase in the miR-129-1-3p and miR-3068-3p expressions in the NA, no change was noted in the PC due to heroin. The only heroin-dependent downregulation was observed in the expressions of striatal miR-450b-3p and miR-103-1-5p of VTA. These results suggested that heroin addiction might give harm to brain by altering cytokine balance and increasing neuroinflammation and apoptosis. In addition, neurons also try to compensate these abnormalities by enhancing neurogenesis and angiogenesis through several miRNAs in the different brain regions. In conclusion, the present study may provide a more integrated view of the molecular mechanism and a potential biomarker that will aid in clinical diagnosis and treatment of heroin-dependence.

An update: epigenetic mechanisms underlying methamphetamine addiction

Methamphetamine (METH) is one of the most widely abused illicit drugs globally. Despite its widespread abuse, the effects of methamphetamine on the brain and the precise mechanisms underlying addiction remain poorly understood. Elucidating these biological mechanisms and developing effective treatments is of utmost importance. Researchers have adopted a multi-faceted approach, combining studies at the genetic, molecular, organ, and individual levels, to explore the epigenetic changes that methamphetamine use brings to an organism from both micro and macro perspectives. They utilize a comparative analysis of experimental animal data and clinical cases to ascertain differences and identify potential targets for translating METH addiction research from the experimental to the clinical setting. Recent studies have demonstrated that epigenetic regulation plays a pivotal role in neural mechanisms, encompassing DNA methylation, histone modifications (such as acetylation and methylation), ubiquitination, phosphorylation, and the regulation of non-coding RNA. These epigenetic factors influence an individual's susceptibility and response to methamphetamine addiction by regulating the expression of specific genes. Specifically, methamphetamine use has been observed to cause alterations in DNA methylation status, which in turn affects the expression of genes associated with neuroreward pathways, leading to alterations in brain function and structure. Furthermore, histone modifications have significant implications for the neurotoxicity associated with methamphetamine addiction. For instance, the methylation and acetylation of histone H3 modify chromatin structure, consequently influencing the transcriptional activity of genes. Non-coding RNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), also play a pivotal role in methamphetamine addiction by interacting with messenger RNAs (mRNAs) and regulating gene expression. To further advance our understanding, researchers employ advanced technologies such as high-throughput sequencing, chromatin immunoprecipitation sequencing (ChIP-seq), and RNA sequencing (RNA-seq) to comprehensively analyze epigenetic changes in both animal models and human subjects. These technologies enable researchers to identify specific epigenetic markers associated with methamphetamine addiction and to explore their functional consequences. This article reviews the role of these epigenetic mechanisms in methamphetamine addiction and discusses their potential implications for future clinical treatment strategies, particularly in the development of drugs targeting methamphetamine addiction. By deepening our comprehension of these epigenetic regulatory mechanisms, it is anticipated that targeted therapeutic strategies may be devised to reverse the gene expression alterations associated with methamphetamine addiction, thus enhancing the efficacy of addiction treatment and paving the way for future research in this domain.

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.

The Role of Non-coding RNAs in Methamphetamine-Induced Neurotoxicity

Methamphetamine (METH) is an amphetamine-type stimulant that is highly toxic to the central nervous system (CNS). Repeated intake of METH can lead to addiction, which has become a globalized problem, resulting in multiple public health and safety problems. Recently, the non-coding RNA (ncRNA) has been certified to play an essential role in METH addiction through various mechanisms. Herein, we mainly focused on three kinds of ncRNAs including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), which are involved in neurotoxicity effects such as cognitive impairment, behavioral abnormalities, and psychiatric disorders due to METH abuse. In addition, differential expression (DE) ncRNAs also suggest that specific responses and sensitivity to METH neurotoxicity exist in different brain regions and cells. We summarized the relationships between the ncRNAs and METH-induced neurotoxicity and psychiatric disturbances, respectively, hoping to provide new perspectives and strategies for the prevention and treatment of METH abuse. Schematic diagram of the non-coding RNAs (ncRNAs) was involved in methamphetamine (METH)-induced neurotoxicity. The ncRNAs were involved in METH-induced blood-brain barrier disruption, neuronal, astrocyte, and microglial damage, and synaptic neurotransmission impairment. The study of ncRNAs is a hot spot in the future to further understand the neurotoxicity of METH and provide more favorable scientific support for clinical diagnosis and innovation of related treatments.

Epigenetic mechanisms involved in methamphetamine addiction

Methamphetamine (METH) is an illicit psychostimulant that is widely abused. The molecular mechanism of METH addiction is complicated and still unknown. METH causes the release of the neurotransmitters including dopamine, glutamate, norepinephrine and serotonin, which activate various brain areas in the central nervous system. METH also induces synaptic plasticity and pathological memory enhancement. Epigenetics plays the important roles in regulating METH addiction. This review will briefly summarize the studies on epigenetics involved in METH addiction.

Methamphetamine Exposure in Adolescent Impairs Memory of Mice in Adulthood Accompanied by Changes in Neuroplasticity in the Dorsal Hippocampus

Methamphetamine (METH) has been shown to alter learning and memory by affecting the neuroplasticity of the dorsal hippocampus, a key structure that undergoes extensive remodeling during adolescence. In this study, we investigated whether mid-to-late adolescent exposure to METH leads to long-lasting memory impairment. To do this, adolescents (35–48 postnatal days) were exposed to different doses of METH for 14 days and then evaluated by the Morris water maze (MWM), new object recognition test (NORT), and the Y-maze, to investigate the learning and memory abilities of mice in their adolescence and adulthood, respectively. We also detected the mRNA levels of genes associated with neuroplasticity in the dorsal hippocampus. The synaptic ultrastructure and the number of neurons and astrocytes in the dorsal hippocampus were also determined by transmission electron microscopy (TEM) and immunofluorescence (IF). Exposure to METH in mid-to-late adolescence impaired spatial memory retrieval ability and the long-term recognition memory of mice in their adulthood, but not in their adolescence. Of note, the impairment of memory capacity in adulthood was accompanied by molecular and structural changes in synapses in the dorsal hippocampus. Our results indicate that mice exposed to METH in mid-to-late adolescence have impaired memory ability in their adulthood; this may be the result of abnormal changes in the structural plasticity of the dorsal hippocampus; the causal relationship between changes in synaptic structural plasticity and memory impairment needs to be further confirmed. In summary, our study provides evidence for the detrimental consequences of adolescent addiction and the prevention of adolescent drug abuse.

MicroRNAs in Methamphetamine-Induced Neurotoxicity and Addiction

Methamphetamine (METH) abuse remains a significant public health concern globally owing to its strong addictive properties. Prolonged abuse of the drug causes irreversible damage to the central nervous system. To date, no efficient pharmacological interventions are available, primarily due to the unclear mechanisms underlying METH action in the brain. Recently, microRNAs (miRNAs) have been identified to play critical roles in various cellular processes. The expression levels of some miRNAs are altered after METH administration, which may influence the transcription of target genes to regulate METH toxicity or addiction. This review summarizes the miRNAs in the context of METH use, discussing their role in the reward effect and neurotoxic sequelae. Better understanding of the molecular mechanisms involved in METH would be helpful for the development of new therapeutic strategies in reducing the harm of the drug.

Medial prefrontal cortex Notch1 signalling mediates methamphetamine-induced psychosis via Hes1-dependent suppression of GABAB1 receptor expression

Methamphetamine (METH), a widely abused stimulant drug, induces psychosis in approximately half of abusers; this effect is becoming a major concern for society. Although the Notch1 signalling pathway has been shown to play a part in the pathogenesis of some psychiatric disorders, its role in METH-induced psychosis (MIP) is still unknown. Here, the METH-induced locomotor sensitization model in rodents is considered to represent the underlying neurochemical changes driving psychoses. We found that the Notch1 signalling was downregulated in the medial prefrontal cortex (mPFC) in sensitized mice. Direct genetic and pharmacological manipulations of Notch1 signalling bidirectionally altered METH-induced locomotor sensitization and other MIP-related behaviours through governing neuronal activity in the mPFC. Moreover, Notch1 signalling negatively regulated GABA_B1 receptor expression in the mPFC of METH-sensitized mice through Hes1, a transcriptional repressor in Notch1 signalling. Further, we show that Hes1 can directly bind to the GABA_B1 receptor promoter. Notably, pharmacological regulation of the GABA_B receptor in the mPFC reversed the changes in METH-induced locomotor sensitization caused by the dysfunction of Notch1 signalling. Together, our findings uncover a previously unrecognised Notch1-Hes1-GABA_B1 receptor-dependent mechanism involved in regulating mPFC neuronal activity and behavioural phenotypes in MIP. Our work provides mechanistic insight into the aetiology and pathophysiology of MIP.

Epigenetic Regulatory Dynamics in Models of Methamphetamine-Use Disorder

Methamphetamine (METH)-use disorder (MUD) is a very serious, potentially lethal, biopsychosocial disease. Exposure to METH causes long-term changes to brain regions involved in reward processing and motivation, leading vulnerable individuals to engage in pathological drug-seeking and drug-taking behavior that can remain a lifelong struggle. It is crucial to elucidate underlying mechanisms by which exposure to METH leads to molecular neuroadaptive changes at transcriptional and translational levels. Changes in gene expression are controlled by post-translational modifications via chromatin remodeling. This review article focuses on the brain-region specific combinatorial or distinct epigenetic modifications that lead to METH-induced changes in gene expression.