Molecular hydrogen attenuates methamphetamine-induced behavioral sensitization and activation of ERK-ΔFosB signaling in the mouse nucleus accumbens

Exploring the potential link between ΔFosB and N-acetylcysteine in craving/relapse dynamics: can N-acetylcysteine stand out as a possible treatment candidate?

From a neuroscientific point of view, one of the unique archetypes of substance use disorders is its road to relapse, in which the reward system plays a crucial role. Studies on the neurobiology of substance use disorders have highlighted the central role of a protein belonging to the Fos family of transcription factors, ΔFosB. Relying on the roles ΔFosB plays in the pathophysiology of substance use disorders, we endeavour to present some evidence demonstrating that N-acetylcysteine, a low-cost and well-tolerated over-the-counter medicine, may influence the downstream pathway of ΔFosB, thereby serving as a treatment strategy to mitigate the risk of relapse in cases of substance use.

A novel intervention of molecular hydrogen on the unbalance of the gut microbiome in opioid addiction: Experimental and human studies

The gut-brain axis mediates the interaction pathway between microbiota and opioid addiction. In recent years, many studies have shown that molecular hydrogen has therapeutic and preventive effects on various diseases. This study aimed to investigate whether molecular hydrogen could serve as pharmacological intervention agent to reduce risks of reinstatement of opioid seeking and explore the mechanism of gut microbiota base on animal experiments and human studies. Morphine-induced conditioned place preference (CPP) was constructed to establish acquisition, extinction, and reinstatement stage, and the potential impact of H2 on the behaviors related to morphine-induced drug extinction was determined using both free accessible and confined CPP extinction paradigms. The effects of morphine on microbial diversity and composition of microbiota, as well as the subsequent changes after H2 intervention, were assessed using 16 S rRNA gene sequencing. Short-Chain Fatty Acids (SCFAs) in mice serum were detected by gas chromatography-mass spectrometry (GC-MS). Meanwhile, we also conducted molecular hydrogen intervention and gut microbiota testing in opioid-addicted individuals. Our results revealed that molecular hydrogen could enhance the extinction of morphine-related behavior, reducing morphine reinstatement. Gut microbes may be a potential mechanism behind the therapeutic effects of molecular hydrogen on morphine addiction. Additionally, molecular hydrogen improved symptoms of depression and anxiety, as well as gut microbial features, in individuals with opioid addiction. This study supports molecular hydrogen as a novel and effective intervention for morphine-induced addiction and reveals the mechanism of gut microbiota.

Cellular and molecular basis of drug addiction: The role of neuronal ensembles in addiction

Addiction has been conceptualized as a disease of learning and memory. Learned associations between environmental cues and unconditioned rewards induced by drug administration, which play a critical role in addiction, have been shown to be encoded in sparsely distributed populations of neurons called neuronal ensembles. This review aims to highlight how synaptic remodeling and alterations in signaling pathways that occur specifically in neuronal ensembles contribute to the pathogenesis of addiction. Furthermore, a causal link between transcriptional and epigenetic modifications in neuronal ensembles and the development of the addictive state is proposed. Translational studies of molecular and cellular changes in neuronal ensembles that contribute to drug-seeking behavior, will allow the identification of molecular and circuit targets and interventions for substance use disorders.

Effects of molecular hydrogen intervention on the gut microbiome in methamphetamine abusers with mental disorder

Methamphetamine (METH) is a potent and highly addictive psychostimulant and one of the most widely used illicit drugs, the abuse of which has become a severe public health problem worldwide. A growing amount of evidence has indicated potential connections between gut microbiota and mental disorders induced by METH and associations with neural and metabolic pathways. The present study aimed to explore the relationship between fecal microbial alterations and neuropsychiatric diseases in METH addictions. Thus, mental disorders and gut microbial alterations were analyzed by self-rating depression (SDS) and anxiety (SAS) scales and 16 S rRNA gene sequencing, respectively. Our results showed that increased SDS and SAS indices and decreased alpha diversity indicated more serious mental disorders and lower bacterial diversity in METH users than in the age-matched healthy control group. The gut microbial composition in female METH users was also significantly altered, with reductions in hydrogen-producing bacteria, including Bacteroides and Roseburia. Molecular hydrogen (H₂) is spontaneously produced by intestinal bacteria in the process of anaerobic metabolism, which is the main pathway for H₂ production in vivo. Numerous studies have shown that hydrogen intervention can significantly improve neuropsychiatric diseases, including Alzheimer's disease and Parkinson's disease. Our results showed that hydrogen intervention, including drinking and inhaling, significantly alleviated mental disorders induced by METH abuse, and the inhalation of hydrogen also altered gut microbiota profiles in the METH abusers. These results suggest that hydrogen intervention has potential therapeutic applicability in the treatment of mental disorders in METH abusers.

The Role of Hyperthermia in Methamphetamine-Induced Depression-Like Behaviors: Protective Effects of Coral Calcium Hydride

Methamphetamine (METH) abuse causes irreversible damage to the central nervous system and leads to psychiatric symptoms including depression. Notably, METH-induced hyperthermia is a crucial factor in the development of these symptoms, as it aggravates METH-induced neurotoxicity. However, the role of hyperthermia in METH-induced depression-like behaviors needs to be clarified. In the present study, we treated mice with different doses of METH under normal (NAT) or high ambient temperatures (HAT). We found that HAT promoted hyperthermia after METH treatment and played a key role in METH-induced depression-like behaviors in mice. Intriguingly, chronic METH exposure (10 mg/kg, 7 or 14 days) or administration of an escalating-dose (2 ∼ 15 mg/kg, 3 days) of METH under NAT failed to induce depression-like behaviors. However, HAT aggravated METH-induced damage of hippocampal synaptic plasticity, reaction to oxidative stress, and neuroinflammation. Molecular hydrogen acts as an antioxidant and anti-inflammatory agent and has been shown to have preventive and therapeutic applicability in a wide range of diseases. Coral calcium hydride (CCH) is a newly identified hydrogen-rich powder which produces hydrogen gas gradually when exposed to water. Herein, we found that CCH pretreatment significantly attenuated METH-induced hyperthermia, and administration of CCH after METH exposure also inhibited METH-induced depression-like behaviors and reduced the hippocampal synaptic plasticity damage. Moreover, CCH effectively reduced the activity of lactate dehydrogenase and decreased malondialdehyde, TNF-α and IL-6 generation in hippocampus. These results suggest that CCH is an efficient hydrogen-rich agent, which has a potential therapeutic applicability in the treatment of METH abusers.

The Adverse Effects of Prenatal METH Exposure on the Offspring: A Review

Abuse of methamphetamine (METH), an illicit psychostimulant, is a growing public health issue. METH abuse during pregnancy is on the rise due to its stimulant, anorectic, and hallucinogenic properties. METH can lead to multiple organ toxicity in adults, including neurotoxicity, cardiovascular toxicity, and hepatotoxicity. It can also cross the placental barrier and have long-lasting effects on the fetus. This review summarizes neurotoxicity, cardiovascular toxicity, hepatotoxicity, toxicity in other organs, and biomonitoring of prenatal METH exposure, as well as the possible emergence of sensitization associated with METH. We proposed the importance of gut microbiota in studying prenatal METH exposure. There is rising evidence of the adverse effects of METH exposure during pregnancy, which are of significant concern.

Behavioural and biochemical responses to methamphetamine are differentially regulated by mGlu2 and mGlu3 metabotropic glutamate receptors in male mice

Group II metabotropic glutamate receptors (mGlu2 and mGlu3 receptors) shape mechanisms of methamphetamine addiction, but the individual role played by the two subtypes is unclear. We measured methamphetamine-induced conditioned place preference (CPP) and motor responses to single or repeated injections of methamphetamine in wild-type, mGlu2^-/-, and mGlu3^-/-mice. Only mGlu3^-/-mice showed methamphetamine preference in the CPP test. Motor response to the first methamphetamine injection was dramatically reduced in mGlu2^-/-mice, unless these mice were treated with the mGlu5 receptor antagonist, MTEP. In contrast, methamphetamine-induced sensitization was increased in mGlu3^-/-mice compared to wild-type mice. Only mGlu3^-/-mice sensitized to methamphetamine showed increases in phospho-ERK1/2 levels in the nucleus accumbens (NAc) and free radical formation in the NAc and medial prefrontal cortex. These changes were not detected in mGlu2^-/-mice. We also measured a series of biochemical parameters related to the mechanism of action of methamphetamine in naïve mice to disclose the nature of the differential behavioural responses of the three genotypes. We found a reduced expression and activity of dopamine transporter (DAT) and vesicular monoamine transporter-2 in the NAc and striatum of mGlu2^-/-and mGlu3^-/-mice, whereas expression of the DAT adaptor, syntaxin 1A, was selectively increased in the striatum of mGlu3^-/-mice. Methamphetamine-stimulated dopamine release in striatal slices was largely reduced in mGlu2^-/-, but not in mGlu3^-/-, mice. These findings suggest that drugs that selectively enhance mGlu3 receptor activity or negatively modulate mGlu2 receptors might be beneficial in the treatment of methamphetamine addiction and associated brain damage.

The Role of CaMKII and ERK Signaling in Addiction

Nicotine is the predominant addictive compound of tobacco and causes the acquisition of dependence through its interactions with nicotinic acetylcholine receptors and various neurotransmitter releases in the central nervous system. The Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinase (ERK) play a pivotal role in synaptic plasticity in the hippocampus. CaMKII is involved in long-term potentiation induction, which underlies the consolidation of learning and memory; however, the roles of CaMKII in nicotine and other psychostimulant-induced addiction still require further investigation. This article reviews the molecular mechanisms and crucial roles of CaMKII and ERK in nicotine and other stimulant drug-induced addiction. We also discuss dopamine (DA) receptor signaling involved in nicotine-induced addiction in the brain reward circuitry. In the last section, we introduce the association of polyunsaturated fatty acids and cellular chaperones of fatty acid-binding protein 3 in the context of nicotine-induced addiction in the mouse nucleus accumbens and provide a novel target for the treatment of drug abuse affecting dopaminergic systems.

ERK-Directed Phosphorylation of mGlu5 Gates Methamphetamine Reward and Reinforcement in Mouse

Methamphetamine (MA) is a highly addictive psychomotor stimulant drug. In recent years, MA use has increased exponentially on a global scale, with the number of MA-involved deaths reaching epidemic proportions. There is no approved pharmacotherapy for treating MA use disorder, and we know relatively little regarding the neurobiological determinants of vulnerability to this disease. Extracellular signal-regulated kinase (ERK) is an important signaling molecule implicated in the long-lasting neuroadaptations purported to underlie the development of substance use disorders, but the role for this kinase in the propensity to develop addiction, particularly MA use disorder, is uncharacterized. In a previous MA-induced place-conditioning study of C57BL/6J mice, we characterized mice as MA-preferring, -neutral, or -avoiding and collected tissue from the medial prefrontal cortex (mPFC). Using immunoblotting, we determined that elevated phosphorylated ERK expression within the medial prefrontal cortex (mPFC) is a biochemical correlate of the affective valence of MA in a population of C57BL/6J mice. We confirmed the functional relevance for mPFC ERK activation for MA-induced place-preference via site-directed infusion of the MEK inhibitor U0126. By contrast, ERK inhibition did not have any effect upon MA-induced locomotion or its sensitization upon repeated MA treatment. Through studies of transgenic mice with alanine point mutations on T1123/S1126 of mGlu5 that disrupt ERK-dependent phosphorylation of the receptor, we discovered that ERK-dependent mGlu5 phosphorylation normally suppresses MA-induced conditioned place-preference (MA-CPP), but is necessary for this drug’s reinforcing properties. If relevant to humans, the present results implicate individual differences in the capacity of MA-associated cues/contexts to hyper-activate ERK signaling within mPFC in MA Use Disorder vulnerability and pose mGlu5 as one ERK-directed target contributing to the propensity to seek out and take MA.