An autophagy-related protein Becn2 regulates cocaine reward behaviors in the dopaminergic system

The role of macroautophagy in substance use disorders

Macroautophagy, a universal cellular process, sends cellular material to lysosomes for breakdown and is often activated by stressors like hypoxia or drug exposure. It is vital for protein balance, neurotransmitter release, synaptic function, and neuron survival. The role of macroautophagy in substance use disorders is dual. On one hand, substances like cocaine, methamphetamine, opiates, and alcohol can activate macroautophagy pathways to degrade various neuroinflammatory factors in neuronal cells, providing a protective function. On the other hand, long-term and excessive use of addictive substances can inhibit macroautophagy pathways, obstructing the fusion of autophagosomes with lysosomes and losing the original protective function. This review first summarizes the key proteins and signaling pathways involved in macroautophagy, including mTORC1, AMPK, and endoplasmic reticulum stress, and suggests that the regulation of macroautophagy plays a central role in drug-rewarding behavior and addiction. Second, we focus on the interactions between macroautophagy and neuroinflammation induced by drugs, evaluating the potential of macroautophagy modulators as therapeutic strategies for substance use disorder (SUD), and identifying autophagy-related biomarkers that can be used for early diagnosis and monitoring of treatment response. Our review summarizes the important scientific basis involved in macroautophagy pathways for the development of new therapies for SUD.

CB2 agonist mitigates cocaine-induced reinstatement of place preference and modulates the inflammatory response in mice

Chronic exposure to cocaine is known to have profound effects on the brain, leading to the dysregulation of inflammatory signalling pathways, the activation of microglia, and the manifestation of cognitive and motivational behavioural impairments. The endocannabinoid system has emerged as a potential mediator of cocaine's deleterious effects. In this study, we sought to investigate the therapeutic potential of the cannabinoid CB2 receptor agonist, JWH-133, in mitigating cocaine-induced inflammation and associated motivational behavioural alterations in an in vivo model. Our research uncovered compelling evidence that JWH-133, a selective CB2 receptor agonist, exerts a significant dampening effect on the reinstatement of cocaine-induced conditioned place preference. This effect was accompanied by notable changes in the neurobiological landscape. Specifically, JWH-133 administration was found to upregulate Δ-FOSB expression in the nucleus accumbens (Nac), elevate CX3CL1 levels in both the ventral tegmental area and prefrontal cortex (PFC), and concurrently reduce IL-1β expression in the PFC and NAc among cocaine-treated animals. These findings highlight the modulatory role of CB2 cannabinoid receptor activation in altering the reward-seeking behaviour induced by cocaine. Moreover, they shed light on the intricate interplay between the endocannabinoid system and cocaine-induced neurobiological changes, paving the way for potential therapeutic interventions targeting CB2 receptors in the context of cocaine addiction and associated behavioural deficits.

Sesamin-mediated high expression of BECN2 ameliorates cartilage endplate degeneration by reducing autophagy and inflammation

Lumbar disc degeneration (LDD) is a prevalent clinical spinal disease characterized by the calcification and degeneration of the cartilage endplate (CEP), which significantly reduces nutrient supply to the intervertebral disc. Traditional Chinese medicine offers a conservative and effective approach for treating LDD. We aimed to investigate the molecular mechanisms underlying the therapeutic effects of Sesamin in LDD treatment. Transcriptome sequencing was used to analyze the effect of Sesamin on LPS-induced ATDC5. We explored the role of BECN2, a target gene of Sesamin, in attenuating LPS-induced degeneration of ATDC5 cells. Our results revealed the identification of 117 differentially expressed genes (DEGs), with 54 up-regulated and 63 down-regulated genes. Notably, Sesamin significantly increased the expression of BECN2 in LPS-induced ATDC5 cell degeneration. Overexpressed BECN2 enhanced cell viability and inhibited cell apoptosis in LPS-induced ATDC5 cells, while BECN2 knockdown reduced cell viability and increased apoptosis. Furthermore, BECN2 played a crucial role in attenuating chondrocyte degeneration by modulating autophagy and inflammation. Specifically, BECN2 suppressed autophagy by reducing the expression of ATG14, VPS34, and GASP1, and alleviated the inflammatory response by decreasing the expression of inflammasome proteins NLRP3, NLRC4, NLRP1, and AIM2. In vivo experiments further supported the beneficial effects of Sesamin in mitigating LDD. This study provides novel insights into the potential molecular mechanism of Sesamin in treating LDD, highlighting its ability to mediate autophagy and inflammation inhibition via targeting the BECN2. This study provides a new therapeutic strategy for the treatment of LDD, as well as a potential molecular target for LDD.

The potent BECN2-ATG14 coiled-coil interaction is selectively critical for endolysosomal degradation of GPRASP1/GASP1-associated GPCRs

ABBREVIATIONS

AMBRA1 autophagy and beclin 1 regulator 1; ATG14 autophagy related 14; ATG5 autophagy related 5; ATG7 autophagy related 7; BECN1 beclin 1; BECN2 beclin 2; CC coiled-coil; CQ chloroquine CNR1/CB1R cannabinoid receptor 1 DAPI 4',6-diamidino-2-phenylindole; dCCD delete CCD; DRD2/D2R dopamine receptor D2 GPRASP1/GASP1 G protein-coupled receptor associated sorting protein 1 GPCR G-protein coupled receptor; ITC isothermal titration calorimetry; IP immunoprecipitation; KD knockdown; KO knockout; MAP1LC3/LC3 microtubule associated protein 1 light chain 3; NRBF2 nuclear receptor binding factor 2; OPRD1/DOR opioid receptor delta 1 PIK3C3/VPS34 phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4/VPS15 phosphoinositide-3-kinase regulatory subunit 4; PtdIns3K class III phosphatidylinositol 3-kinase; PtdIns3P phosphatidylinositol-3-phosphate; RUBCN rubicon autophagy regulator; SQSTM1/p62 sequestosome 1; UVRAG UV radiation resistance associated; VPS vacuolar protein sorting; WT wild type.

Cell type-specific NRBF2 orchestrates autophagic flux and adult hippocampal neurogenesis in chronic stress-induced depression

Dysfunctional autophagy and impairment of adult hippocampal neurogenesis (AHN) each contribute to the pathogenesis of major depressive disorder (MDD). However, whether dysfunctional autophagy is linked to aberrant AHN underlying MDD remains unclear. Here we demonstrate that the expression of nuclear receptor binding factor 2 (NRBF2), a component of autophagy-associated PIK3C3/VPS34-containing phosphatidylinositol 3-kinase complex, is attenuated in the dentate gyrus (DG) under chronic stress. NRBF2 deficiency inhibits the activity of the VPS34 complex and impairs autophagic flux in adult neural stem cells (aNSCs). Moreover, loss of NRBF2 disrupts the neurogenesis-related protein network and causes exhaustion of aNSC pool, leading to the depression-like phenotype. Strikingly, overexpressing NRBF2 in aNSCs of the DG is sufficient to rescue impaired AHN and depression-like phenotype of mice. Our findings reveal a significant role of NRBF2-dependent autophagy in preventing chronic stress-induced AHN impairment and suggest the therapeutic potential of targeting NRBF2 in MDD treatment.

Different Roles of Beclin1 in the Interaction Between Glia and Neurons after Exposure to Morphine and the HIV- Trans-Activator of Transcription (Tat) Protein

Previously we showed that Beclin1 has a regulatory role in the secretion of inflammatory molecules in glia after exposure to morphine and Tat (an HIV protein). Here we show increased secretion of neuronal growth factors and increased neuronal survival in Beclin1-deficient glia. However, without glia co-culture, neurons deficient in Beclin1 showed greater death and enhanced dendritic beading when compared to wild-type neurons, suggesting that glial-secreted growth factors compensate for the damage reduced autophagy causes neurons. To assess if our ex vivo results correlated with in vivo studies, we used a wild-type (Becn1+/+) and Beclin1-deficient (Becn1+/+) mouse model and intracranially infused the mice with Tat and subcutaneously administered morphine pellets. After morphine implantation, significantly impaired locomotor activities were detected in both Becn1+/+ and Becn1+/- mice, irrespective of Tat infusion. After induction of pain, morphine-induced antinociception was detected. Interestingly, co-exposure to morphine and Tat increased sensitivity to pain in Becn1+/+ mice, but not in similarly treated Becn1+/- mice. Brain homogenates from Becn1+/+ mice exposed to Tat, alone and in combination with morphine, showed increased secretion of pro-inflammatory cytokines and reduced expression of growth factors when compared to similarly treated Becn1+/- mice. Likewise, increased neuronal loss was detected when both Tat and morphine were administered to Becn1+/+ mice, but not in similarly treated Becn1+/- mice. Overall, our findings show that there is a Beclin1-driven interaction between Tat and morphine in glia and neurons. Moreover, reduced glial-Beclin1 may provide a layer of protection to neurons under stressful conditions, such as when exposed to morphine and Tat.

Balancing nutrient and energy demand and supply via autophagy

Maintaining nutrient and energy homeostasis is crucial for the survival and function of cells and organisms in response to environmental stress. Cells have evolved a stress-induced catabolic pathway, termed autophagy, to adapt to stress conditions such as starvation. During autophagy, damaged or non-essential cellular structures are broken down in lysosomes, and the resulting metabolites are reused for core biosynthetic processes or energy production. Recent studies have revealed that autophagy can target and degrade different types of nutrient stores and produce a variety of metabolites and fuels, including amino acids, nucleotides, lipids and carbohydrates. Here, we will focus on how autophagy functions to balance cellular nutrient and energy demand and supply - specifically, how energy deprivation switches on autophagic catabolism, how autophagy halts anabolism by degrading the protein synthesis machinery, and how bulk and selective autophagy-derived metabolites recycle and feed into a variety of bioenergetic and anabolic pathways during stress conditions. Recent new insights and progress in these areas provide a better understanding of how resource mobilization and reallocation sustain essential metabolic and anabolic activities under unfavorable conditions.

Degradative and Non-Degradative Roles of Autophagy Proteins in Metabolism and Metabolic Diseases

Autophagy is a stress-induced lysosomal degradation pathway regulated by evolutionarily conserved autophagy-related (ATG) genes. Recent research has revealed that autophagy plays an important role in the regulation of energy metabolism, development of metabolic tissues, and pathogenesis of metabolic disorders. Bulk and selective degradation by autophagy helps maintain protein homeostasis and physiological function of cells. Aside from classical degradative roles, ATG proteins also carry out non-classical secretory functions of metabolic tissues. In this review, we summarize recent progresses and unanswered questions on the mechanisms of autophagy and ATG proteins in metabolic regulation, with a focus on organelle and nutrient storage degradation, as well as vesicular and hormonal secretion. Such knowledge broadens our understanding on the cause, pathophysiology, and prevention of metabolic diseases including obesity and diabetes.

Dopamine D1 receptors mediate methamphetamine-induced dopaminergic damage: involvement of autophagy regulation via the AMPK/FOXO3A pathway

RATIONALE

Clinical studies have revealed that methamphetamine abuse increases risk for developing Parkinson's diseases. It is thus important to elucidate the mechanisms by which methamphetamine damages dopaminergic neurons.

OBJECTIVES

The present study was designed to elucidate the role of the dopamine D1 receptor in methamphetamine-mediated dopaminergic neuronal damage and its underlying mechanisms.

METHODS

Mice were treated for 4 days with vehicle, methamphetamine, or the D1 agonist SKF38393 and then assessed for locomotion and performance in the pole and rotarod tests. Cellular indices of autophagy, LC3, P62, and Beclin-1, tyrosine hydroxylase, and the AMPK/FOXO3A pathway were analyzed in striatal tissue from treated mice, in PC12 cells, and in D1 receptor mutant mice.

RESULTS

Repeated treatment with a relatively high dose of methamphetamine for 4 days induced both loss of dopaminergic neurons and activation of autophagy in the striatum as evidenced by increased expression of LC3 and P62. However, such treatment did not induce either loss of dopaminergic neurons or activation of autophagy in D1 receptor knockout mice. D1 receptor-mediated activation of autophagy was also confirmed in vitro using dopaminergic neuronal PC12 cells. Further studies demonstrated that the AMPK/FOXO3A signaling pathway is responsible for D1 receptor-mediated activation of autophagy.

CONCLUSIONS

The present data indicate a novel mechanism for methamphetamine-induced dopaminergic neuronal damage and reveal an important role for D1 receptors in the neurotoxicity of this drug.

Ketamine enhances dopamine D1 receptor expression by modulating microRNAs in a ketamine-induced schizophrenia-like mouse model

The abnormal expression of the dopamine D1 receptor (DRD1) may be associated with schizophrenia. MicroRNAs (miRNAs) can post-transcriptionally regulate DRD1 expression. Here, we established a ketamine-induced schizophrenia-like behavior mouse model and investigated the changes in miR-15a-3p, miR-15b-3p, miR-16-1-3p, and DRD1 in response to ketamine. Administration of high-dose ketamine for seven consecutive days to mice simulated the main symptoms of schizophrenia. The mice exhibited increasing excitability and autonomous activity and reduced learning and memory, including spatial memory. Moreover, ketamine decreased miR-15a-3p, miR-15b-3p, and miR-16-1-3p expression levels in the prefrontal cortex (PFC) and miR-16-1-3p expression in the hippocampus, whereas DRD1 expression increased in these brain regions. In HT22 mouse hippocampal neuronal cells, ketamine induced a dose-dependent increase of endogenous DRD1, which was partially attenuated by a combination of miR-15b-3p and miR-16-1-3p mimics. Indeed, the miR-15b-3p and miR-16-1-3p mimics could significantly inhibit endogenous DRD1expression. We identified +72 to +78 bp (TGCTGCT) of the DRD1 3'UTR as the core regulatory region recognized by the target miRNAs. In summary, we developed a ketamine-induced schizophrenia-like behavior mouse model and found that ketamine inhibited the levels of miR-15a-3p, miR-15b-3p, miR-16-1-3p and increased DRD1 expression in mice.