Silencing synaptic MicroRNA-411 reduces voluntary alcohol consumption in mice.

Chronic alcohol consumption alters the levels of microRNAs and mRNAs in the brain, but the specific microRNAs and processes that target mRNAs to affect cellular function and behavior are not known. We examined the in vivo manipulation of previously identified alcohol-responsive microRNAs as potential targets to reduce alcohol consumption. Silencing of miR-411 by infusing antagomiR-411 into the prefrontal cortex of female C57BL/6J mice reduced alcohol consumption and preference, without altering total fluid consumption, saccharin consumption, or anxiety-related behaviors. AntagomiR-411 reduced alcohol consumption when given to mice exposed to a chronic alcohol drinking paradigm but did not affect the acquisition of consumption in mice without a history of alcohol exposure, suggesting that antagomiR-411 has a neuroadaptive, alcohol-dependent effect. AntagomiR-411 decreased the levels of miR-411, as well as the association of immunoprecipitated miR-411 with Argonaute2; and, it increased levels of Faah and Ppard mRNAs. Moreover, antagomiR-411 increased the neuronal expression of glutamate receptor AMPA-2 protein, a known alcohol target and a predicted target of miR-411. These results suggest that alcohol and miR-411 function in a homeostatic manner to regulate synaptic mRNA and protein, thus reversing alcohol-related neuroadaptations and reducing chronic alcohol consumption.

Synaptic microRNAs Coordinately Regulate Synaptic mRNAs: Perturbation by Chronic Alcohol Consumption.

Local translation of mRNAs in the synapse has a major role in synaptic structure and function. Chronic alcohol use causes persistent changes in synaptic mRNA expression, possibly mediated by microRNAs localized in the synapse. We profiled the transcriptome of synaptoneurosomes (SN) obtained from the amygdala of mice that consumed 20% ethanol (alcohol) in a 30-day continuous two-bottle choice test to identify the microRNAs that target alcohol-induced mRNAs. SN are membrane vesicles containing pre- and post-synaptic compartments of neurons and astroglia and are a unique model for studying the synaptic transcriptome. We previously showed that chronic alcohol regulates mRNA expression in a coordinated manner. Here, we examine microRNAs and mRNAs from the same samples to define alcohol-responsive synaptic microRNAs and their predicted interactions with targeted mRNAs. The aim of the study was to identify the microRNA-mRNA synaptic interactions that are altered by alcohol. This was accomplished by comparing the effect of alcohol in SN and total homogenate preparations from the same samples. We used a combination of unbiased bioinformatic methods (differential expression, correlation, co-expression, microRNA-mRNA target prediction, co-targeting, and cell type-specific analyses) to identify key alcohol-sensitive microRNAs. Prediction analysis showed that a subset of alcohol-responsive microRNAs was predicted to target many alcohol-responsive mRNAs, providing a bidirectional analysis for identifying microRNA-mRNA interactions. We found microRNAs and mRNAs with overlapping patterns of expression that correlated with alcohol consumption. Cell type-specific analysis revealed that a significant number of alcohol-responsive mRNAs and microRNAs were unique to glutamate neurons and were predicted to target each other. Chronic alcohol consumption appears to perturb the coordinated microRNA regulation of mRNAs in SN, a mechanism that may explain the aberrations in synaptic plasticity affecting the alcoholic brain.

Molecular basis of alcoholism.

Acute alcohol intoxication causes cellular changes in the brain that last for hours, while chronic alcohol use induces widespread neuroadaptations in the nervous system that can last a lifetime. Chronic alcohol use and the progression into dependence involve the remodeling of synapses caused by changes in gene expression produced by alcohol. The progression of alcohol use, abuse, and dependence can be divided into stages, which include intoxication, withdrawal, and craving. Each stage is associated with specific changes in gene expression, cellular function, brain circuits, and ultimately behavior. What are the molecular mechanisms underlying the transition from recreational use (acute) to dependence (chronic)? What cellular adaptations result in drug memory retention, leading to the persistence of addictive behaviors, even after prolonged drug abstinence? Research into the neurobiology of alcoholism aims to answer these questions. This chapter will describe the molecular adaptations caused by alcohol use and dependence, and will outline key neurochemical participants in alcoholism at the molecular level, which are also potential targets for therapy.

Synaptic adaptations by alcohol and drugs of abuse: changes in microRNA expression and mRNA regulation.

Local translation of mRNAs is a mechanism by which cells can rapidly remodel synaptic structure and function. There is ample evidence for a role of synaptic translation in the neuroadaptations resulting from chronic drug use and abuse. Persistent and coordinated changes of many mRNAs, globally and locally, may have a causal role in complex disorders such as addiction. In this review we examine the evidence that translational regulation by microRNAs drives synaptic remodeling and mRNA expression, which may regulate the transition from recreational to compulsive drug use. microRNAs are small, non-coding RNAs that control the translation of mRNAs in the cell and within spatially restricted sites such as the synapse. microRNAs typically repress the translation of mRNAs into protein by binding to the 3'UTR of their targets. As 'master regulators' of many mRNAs, changes in microRNAs could account for the systemic alterations in mRNA and protein expression observed with drug abuse and dependence. Recent studies indicate that manipulation of microRNAs affects addiction-related behaviors such as the rewarding properties of cocaine, cocaine-seeking behavior, and self-administration rates of alcohol. There is limited evidence, however, regarding how synaptic microRNAs control local mRNA translation during chronic drug exposure and how this contributes to the development of dependence. Here, we discuss research supporting microRNA regulation of local mRNA translation and how drugs of abuse may target this process. The ability of synaptic microRNAs to rapidly regulate mRNAs provides a discrete, localized system that could potentially be used as diagnostic and treatment tools for alcohol and other addiction disorders.

PPAR agonists regulate brain gene expression: relationship to their effects on ethanol consumption.

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that act as ligand-activated transcription factors. Although prescribed for dyslipidemia and type-II diabetes, PPAR agonists also possess anti-addictive characteristics. PPAR agonists decrease ethanol consumption and reduce withdrawal severity and susceptibility to stress-induced relapse in rodents. However, the cellular and molecular mechanisms facilitating these properties have yet to be investigated. We tested three PPAR agonists in a continuous access two-bottle choice (2BC) drinking paradigm and found that tesaglitazar (PPARα/γ; 1.5 mg/kg) and fenofibrate (PPARα; 150 mg/kg) decreased ethanol consumption in male C57BL/6J mice while bezafibrate (PPARα/γ/ß; 75 mg/kg) did not. We hypothesized that changes in brain gene expression following fenofibrate and tesaglitazar treatment lead to reduced ethanol drinking. We studied unbiased genomic profiles in areas of the brain known to be important for ethanol dependence, the prefrontal cortex (PFC) and amygdala, and also profiled gene expression in liver. Genomic profiles from the non-effective bezafibrate treatment were used to filter out genes not associated with ethanol consumption. Because PPAR agonists are anti-inflammatory, they would be expected to target microglia and astrocytes. Surprisingly, PPAR agonists produced a strong neuronal signature in mouse brain, and fenofibrate and tesaglitazar (but not bezafibrate) targeted a subset of GABAergic interneurons in the amygdala. Weighted gene co-expression network analysis (WGCNA) revealed co-expression of treatment-significant genes. Functional annotation of these gene networks suggested that PPAR agonists might act via neuropeptide and dopaminergic signaling pathways in the amygdala. Our results reveal gene targets through which PPAR agonists can affect alcohol consumption behavior.

Neuroimmune pathways in alcohol consumption: evidence from behavioral and genetic studies in rodents and humans.

Immune or brain proinflammatory signaling has been linked to some of the behavioral effects of alcohol. Immune signaling appears to regulate voluntary ethanol intake in rodent models, and ethanol intake activates the immune system in multiple models. This bidirectional link raises the possibility that consumption increases immune signaling, which in turn further increases consumption in a feed-forward cycle. Data from animal and human studies provide overlapping support for the involvement of immune-related genes and proteins in alcohol action, and combining animal and human data is a promising approach to systematically evaluate and nominate relevant pathways. Based on rodent models, neuroimmune pathways may represent unexplored, nontraditional targets for medication development to reduce alcohol consumption and prevent relapse. Peroxisome proliferator-activated receptor agonists are one class of anti-inflammatory medications that demonstrate antiaddictive properties for alcohol and other drugs of abuse. Expression of immune-related genes is altered in animals and humans following chronic alcohol exposure, and the regulatory influences of specific mRNAs, microRNAs, and activated cell types are areas of intense study. Ultimately, the use of multiple datasets combined with behavioral validation will be needed to link specific neuroimmune pathways to addiction vulnerability.

Differential effects of deep TMS of the prefrontal cortex on apathy and depression.

BACKGROUND: Apathy is one hallmark of major depression (MDD). It is distinguished by lack of emotion, whereas other aspects of depression involve considerable emotional distress. Investigating both apathy and depression may increase the degree of treatment efficacy for both ailments together and apart. OBJECTIVE: Evaluate the differential effects of deep transcranial magnetic stimulation (DTMS) over the prefrontal cortex (PFC) on apathy and other aspects of depression in patients suffering from a depressive episode. METHODS: Fifty-four treatment-resistant MDD patients were evaluated with the Hamilton Rating Scale for Depression (HRSD), and then treated with DTMS. Apathy-related items from HRSD (ApHRSD) were compared with the remaining items from HRSD (DepHRSD). Antidepressant medications were withdrawn and active DTMS treatment was administered at 20 Hz, 5 days a week for 4 weeks. Changes in HRSD were recorded. Primary efficacy time point was 1 week after the end of active treatment. RESULTS: At screening, ApHRSD distribution was unimodal (moderate apathy), with low correlation (r = 0.17) between ApHRSD and DepHRSD. After treatment, a third had remitted apathy, and the correlation between ApHRSD and DepHRSD had dramatically increased (r = 0.83). Severe ApHRSD (≥ 7) at screening correlated with nonremission for both ApHRSD (R(2) = 0.1993, P = .0012) and DepHRSD (R(2) = 0.0860, P = .0334). CONCLUSIONS: DTMS over the PFC improved both apathy and depression similarly. However, DTMS did not lead to MDD remission if ApHRSD at screening was ≥ 7 of 12. Further investigation using a larger sample will determine whether screening apathy at baseline could be used to predict efficacy of DTMS in MDD patients.

Deep transcranial magnetic stimulation over the prefrontal cortex: evaluation of antidepressant and cognitive effects in depressive patients.

BACKGROUND: Electroconvulsive therapy (ECT) is an effective alternative for pharmacotherapy in treatment-resistant depressive patients, but the side effects limit its use. Transcranial magnetic stimulation (TMS) has been proposed as a refined alternative, but most studies do not indicate that TMS is as effective as ECT for severe depression. OBJECTIVE: We propose that the limited effectiveness of standard TMS resides in its superficial effect on the cortex, although much of the pathophysiology of depression is associated with deeper and larger brain regions implicated in the reward system. Herein, we tested the effectiveness and safety of a novel TMS coil, the "H-coil," which enables direct stimulation of deeper brain regions, at the expense of focality. METHODS: We have studied the antidepressant and cognitive effects induced by 4 weeks of high-frequency (20 Hz) repeated deep TMS (DTMS) over the prefrontal cortex (PFC) of 65 medication-free depressive patients, who have failed to benefit from prior medications. Patients were randomly assigned to various treatment configurations, differing in stimulation intensity and laterality. Effects were assessed by the 24-item Hamilton depression rating scale (HDRS-24) and several secondary outcome measures. RESULTS: A significant improvement in HDRS scores was found when high, but not low, stimulation intensity was used. Several cognitive improvements were evident, and no treatment-related serious adverse events were observed. CONCLUSIONS: DTMS over the PFC was found safe and effective in alleviating depression. The results accentuate the significance of deep, high-intensity stimulation over low, and serve as the first study to indicate the potential of DTMS in psychiatric and neurologic disorders.