Brain-specific inhibition of mTORC1 eliminates side effects resulting from mTORC1 blockade in the periphery and reduces alcohol intake in mice

Acute rapamycin treatment reveals novel mechanisms of behavioral, physiological, and functional dysfunction in a maternal inflammation mouse model of autism and sensory over-responsivity

Maternal inflammatory response (MIR) during early gestation in mice induces a cascade of physiological and behavioral changes that have been associated with autism spectrum disorder (ASD). In a prior study and the current one, we find that mild MIR results in chronic systemic and neuro-inflammation, mTOR pathway activation, mild brain overgrowth followed by regionally specific volumetric changes, sensory processing dysregulation, and social and repetitive behavior abnormalities. Prior studies of rapamycin treatment in autism models have focused on chronic treatments that might be expected to alter or prevent physical brain changes. Here, we have focused on the acute effects of rapamycin to uncover novel mechanisms of dysfunction and related to mTOR pathway signaling. We find that within 2 hours, rapamycin treatment could rapidly rescue neuronal hyper-excitability, seizure susceptibility, functional network connectivity and brain community structure, and repetitive behaviors and sensory over-responsivity in adult offspring with persistent brain overgrowth. These CNS-mediated effects are also associated with alteration of the expression of several ASD-,ion channel-, and epilepsy-associated genes, in the same time frame. Our findings suggest that mTOR dysregulation in MIR offspring is a key contributor to various levels of brain dysfunction, including neuronal excitability, altered gene expression in multiple cell types, sensory functional network connectivity, and modulation of information flow. However, we demonstrate that the adult MIR brain is also amenable to rapid normalization of these functional changes which results in the rescue of both core and comorbid ASD behaviors in adult animals without requiring long-term physical alterations to the brain. Thus, restoring excitatory/inhibitory imbalance and sensory functional network modularity may be important targets for therapeutically addressing both primary sensory and social behavior phenotypes, and compensatory repetitive behavior phenotypes.

Sex Differences In The Interaction Between Alcohol And mTORC1

The kinase mechanistic target of rapamycin complex 1 (mTORC1) plays an essential role in learning and memory by promoting mRNA to protein translation of a subset of synaptic proteins at dendrites. We generated a large body of data in male rodents indicating that mTORC1 is critically involved in mechanisms that promote numerous adverse behaviors associated with alcohol use disorder (AUD) including heavy alcohol use. For example, we found that mTORC1 is activated in the nucleus accumbens (NAc) and orbitofrontal cortex (OFC) of male mice and rats that were subjected to 7 weeks of intermittent access to 20% alcohol two-bottle choice (IA20%2BC). We further showed that systemic or intra-NAc administration of the selective mTORC1 inhibitor, rapamycin, decreases alcohol seeking and drinking, whereas intra-OFC administration of rapamycin reduces alcohol seeking and habit in male rats. This study aimed to assess mTORC1 activation in these corticostriatal regions of female mice and to determine whether the selective mTORC1 inhibitor, rapamycin, can be used to reduce heavy alcohol use in female mice. We found that mTORC1 is not activated by 7 weeks of intermittent 20% alcohol binge drinking and withdrawal in the NAc and OFC. Like in males, mTORC1 signaling was not activated by chronic alcohol intake and withdrawal in the medial prefrontal cortex (mPFC) of female mice. Interestingly, Pearson correlation comparisons revealed that the basal level of mTORC1 activation between the two prefrontal regions, OFC and mPFC were correlated and that the drinking profile predicts the level of mTORC1 activation in the mPFC after 4-hour binge drinking. Finally, we report that administration of rapamycin does not attenuate heavy alcohol drinking in female animals. Together, our results suggest a sex-dependent contribution of mTORC1 to the neuroadaptation that drives alcohol use and abuse.

Potential role of the lncRNA "HOTAIR"/miRNA "206"/BDNF network in the alteration in expression of synaptic plasticity gene arc and BDNF level in sera of patients with heroin use disorder through the PI3K/AKT/mTOR pathway compared to the controls

INTRODUCTION

Heroin use disorder (HUD) is a seriously increasing health issue, accounting for most deaths among drug abusers. Studying non-coding ribonucleic acid gene expression among drug abusers is a promising approach, as it may be used in diagnosis and therapeutics.

PARTICIPANTS AND METHODS

A total of 49 male heroin-dependent patients and 49 male control participants were recruited from Kasr Al Ainy Psychiatry and Addiction outpatient clinics, Faculty of Medicine, Cairo University. Sera were gathered. qRT-PCR was utilized for the detection of gene expression of non-coding RNAs such as "HOX transcript antisense RNA" (HOTAIR), micro-RNA (miRNA-206), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), mechanistic target of rapamycin (mTOR), and Activity Regulated Cytoskeleton Associated Protein (Arc). Sera Brain-Derived Neurotrophic Factor (BDNF) levels were assessed using ELISA. Using a western blot made it possible to determine the protein expression of PI3K, AKT, and mTOR.

RESULTS

The study demonstrated that gene expressions of HOTAIR, AKT, PI3K, and Arc were considerably lowered between cases and controls, while gene expressions of miR-206 and mTOR1 were significantly raised. PI3K and AKT protein expressions were downregulated, while mTOR expressions were upregulated. BDNF levels were significantly decreased in some cases.

CONCLUSION

The results of this study suggest that decreased HOTAIR in HUD relieves miR-206 inhibition, which thus increases and affects downstream PI3K/AKT/mTOR, ARC, and BDNF expression. This may be shared in addictive and relapsing behaviors.

Paradoxical mTORC1-Dependent microRNA-mediated Translation Repression in the Nucleus Accumbens of Mice Consuming Alcohol Attenuates Glycolysis

mTORC1 promotes protein translation, learning and memory, and neuroadaptations that underlie alcohol use and abuse. We report that activation of mTORC1 in the nucleus accumbens (NAc) of mice consuming alcohol promotes the translation of microRNA (miR) machinery components and the upregulation of microRNAs (miRs) expression including miR34a-5p. In parallel, we detected a paradoxical mTORC1-dependent repression of translation of transcripts including Aldolase A, an essential glycolytic enzyme. We found that miR34a-5p in the NAc targets Aldolase A for translation repression and promotes alcohol intake. Our data further suggest that glycolysis is inhibited in the NAc manifesting in an mTORC1-dependent attenuation of L-lactate, the end product of glycolysis. Finally, we show that systemic administration of L-lactate attenuates mouse excessive alcohol intake. Our data suggest that alcohol promotes paradoxical actions of mTORC1 on translation and glycolysis which in turn drive excessive alcohol use.

Abstract Figure

Alcohol Dependence Modulates Amygdalar mTORC2 and PKCε Expression in a Rodent Model

Multiple alcohol use disorder (AUD)-related behavioral alterations are governed by protein kinase C epsilon (PKCε), particularly in the amygdala. Protein kinase C (PKC) is readily phosphorylated at Ser729 before activation by the mTORC2 protein complex. In keeping with this, the current study was conducted to assess the variations in mTORC2 and PKCε during different ethanol exposure stages. The following groups of rats were employed: control, acute, chronic, ethanol withdrawal (EW), and EW + ethanol (EtOH). Ethanol-containing and non-ethanol-containing modified liquid diets (MLDs) were administered for 27 days. On day 28, either saline or ethanol (2.5 g/kg, 20% v/v) was intraperitoneally administered, followed by bilateral amygdala extraction. PKCε mRNA levels were noticeably increased in the amygdala of the EW + EtOH and EW groups. Following chronic ethanol consumption, the stress-activated map kinase-interacting protein 1 (Sin1) gene expression was markedly decreased. In the EW, EW + EtOH, and chronic ethanol groups, there was a profound increase in the protein expression of mTOR, Sin1, PKCε, and phosphorylated PKCε (Ser729). The PKCε gene and protein expressions showed a statistically significant moderate association, according to a correlation analysis. Our results suggest that an elevated PKCε protein expression in the amygdala during EW and EW + EtOH occurred at the transcriptional level. However, an elevation in the PKCε protein expression, but not its mRNA, after chronic ethanol intake warrants further investigation to fully understand the signaling pathways during different episodes of AUD.

Brain-restricted mTOR inhibition with binary pharmacology

On-target-off-tissue drug engagement is an important source of adverse effects that constrains the therapeutic window of drug candidates1,2. In diseases of the central nervous system, drugs with brain-restricted pharmacology are highly desirable. Here we report a strategy to achieve inhibition of mammalian target of rapamycin (mTOR) while sparing mTOR activity elsewhere through the use of the brain-permeable mTOR inhibitor RapaLink-1 and the brain-impermeable FKBP12 ligand RapaBlock. We show that this drug combination mitigates the systemic effects of mTOR inhibitors but retains the efficacy of RapaLink-1 in glioblastoma xenografts. We further present a general method to design cell-permeable, FKBP12-dependent kinase inhibitors from known drug scaffolds. These inhibitors are sensitive to deactivation by RapaBlock, enabling the brain-restricted inhibition of their respective kinase targets.

Alcohol and the brain: from genes to circuits

Alcohol use produces wide-ranging and diverse effects on the central nervous system. It influences intracellular signaling mechanisms, leading to changes in gene expression, chromatin remodeling, and translation. As a result of these molecular alterations, alcohol affects the activity of neuronal circuits. Together, these mechanisms produce long-lasting cellular adaptations in the brain that in turn can drive the development and maintenance of alcohol use disorder (AUD). We provide an update on alcohol research, focusing on multiple levels of alcohol-induced adaptations, from intracellular changes to changes in neural circuits. A better understanding of how alcohol affects these diverse and interlinked mechanisms may lead to the identification of novel therapeutic targets and to the development of much-needed novel and efficacious treatment options.