Protective Role of Lactobacillus rhamnosus Probiotic in Reversing Cocaine-Induced Oxidative Stress, Glial Activation and Locomotion in Mice

Gut microbiome depletion modulates cocaine-induced behavioral and transcriptional responses in female mice

Cocaine use disorder is a chronic relapsing condition with no FDA-approved biological treatments. The gut microbiome has emerged as a key modulator of neurobehavioral responses to drugs of abuse, yet its role in female animals has been under studied. Here, we investigated the effects of gut microbiome depletion on cocaine-induced behavioral and transcriptional responses in female mice. Adult female C57BL/6 J mice were treated with a non-absorbable oral antibiotic (Abx) cocktail for two weeks to deplete the gut microbiome, followed by behavioral assays assessing locomotor sensitization and conditioned place preference (CPP) to cocaine. Abx-treated females displayed reduced locomotor sensitization and a shifted CPP dose-response curve, characterized by attenuated preference at higher cocaine doses. Transcriptional analysis of the nucleus accumbens (NAc) revealed that microbiome depletion suppressed cocaine-induced expression of immediate early genes (c-Fos, FosB, Nr4a1, Egr4) and altered dopamine-related (Drd1) and microglial (Cx3cr1) markers. These findings contrast with prior studies in males, where microbiome depletion enhanced cocaine-induced behavioral plasticity. The observed effects suggest distinct gut-brain signaling as an important contributor to cocaine reinforcement and neuroadaptations in females. This study provides novel insights into microbiome regulation of addiction-relevant behaviors and highlights the necessity of sex-specific investigations in neuropsychiatric disorders. Further research is needed to elucidate the molecular pathways linking gut dysbiosis to substance use vulnerability in females.

The superoxide dismutase mimetic TEMPOL modulates nicotine-induced hyperlocomotor activity and nicotine-taking behavior in male rats

Reactive oxygen species (ROS) have been implicated in behaviors induced by acute or repeated cocaine or methamphetamine administration in rodents. In the present study, we investigated the involvement of ROS in behavioral changes induced by nicotine administration and dopamine (DA) transmission changes in the nucleus accumbens (NAc) of rats. Rats were given repeated saline or nicotine (0.4 mg/kg) administration once daily for seven days, and the induction of hyperlocomotor activity, and oxidative stress marker expression induced by the increase in ROS production in the NAc were measured on day 7. We also tested the effect of ROS scavengers on repeated nicotine-induced hyperlocomotor activity and nicotine self-administration, and DA levels in the NAc. Repeated nicotine administration induced hyperlocomotor activity and decreased the expression of oxidative stress markers, such as superoxide dismutase-1 and glutathione peroxidase 1/2, by elevating ROS production in the NAc. Pretreatment with the nonspecific ROS scavenger PBN and the superoxide-selective scavenger TEMPOL significantly attenuated nicotine-induced hyperlocomotor activity without impairing motor function in nicotine-naïve rats on day 7. In addition, in intravenous nicotine self-administration study, TEMPOL significantly reduced nicotine-taking behavior without affecting food intake in nicotine-naïve rats. Furthermore, TEMPOL pretreatment prevented nicotine effects on stimulated DA release in the NAc, which was associated with nicotine-induced behavioral changes. Taken together, these findings suggest that increased ROS production in the NAc contributes to the neuropharmacological properties of nicotine.

Neuroglia in substance use disorders

Substance use disorders (SUD) remain a major public health concern in which individuals are unable to control their use of substances despite significant harm and negative consequences. Drugs of abuse dysregulate major brain and behavioral functions. Glial cells, primarily microglia and astrocytes, play a crucial role in these drug-induced molecular and behavioral changes. This review explores preclinical and clinical studies of how neuroglia and their associated neuroinflammatory responses contribute to SUD and reward-related properties. We evaluate preclinical and clinical evidence for targeting neuroglia as therapeutic interventions. In addition, we evaluate the literature on the gut microbiome and its role in SUD. Clinical treatments are most effective for reducing drug cravings, and some have yielded promising results in other measures of drug use. N-Acetylcysteine, through modulation of cysteine-glutamate antiporter of glial cells, shows encouraging results across a variety of drug classes. Neuroglia and gut microbiome interactions are important factors to consider with regard to SUD and could lead to novel therapeutic avenues. Age- and sex-dependent properties of neuroglia, gut microbiome, and drug use behaviors are important areas in need of further investigation.

Gut-brain communication mediates the impact of dietary lipids on cognitive capacity

Cognitive impairment, as a prevalent symptom of nervous system disorders, poses one of the most challenging aspects in the management of brain diseases. Lipids present in the cell membranes of all neurons within the brain and dietary lipids can regulate the cognition and memory function. In recent years, the advancements in gut microbiome research have enabled the exploration of dietary lipids targeting the gut-brain axis as a strategy for regulating cognition. This present review provides an in-depth overview of how lipids modulate cognition via the gut-brain axis depending on metabolic, immune, neural and endocrine pathways. It also comprehensively analyzes the effects of diverse lipids on the gut microbiota and intestinal barrier function, thereby affecting the central nervous system and cognitive capacity. Moreover, comparative analysis of the positive and negative effects is presented between beneficial and detrimental lipids. The former encompass monounsaturated fatty acids, short-chain fatty acids, omega-3 polyunsaturated fatty acids, phospholipids, phytosterols, fungal sterols and bioactive lipid-soluble vitamins, as well as lipid-derived gut metabolites, whereas the latter (detrimental lipids) include medium- or long-chain fatty acids, excessive proportions of n-6 polyunsaturated fatty acids, industrial trans fatty acids, and zoosterols. To sum up, the focus of this review is on how gut-brain communication mediates the impact of dietary lipids on cognitive capacity, providing a novel theoretical foundation for promoting brain cognitive health and scientific lipid consumption patterns.

Connecting the Dots: The Cerebral Lymphatic System as a Bridge Between the Central Nervous System and Peripheral System in Health and Disease

As a recently discovered waste removal system in the brain, cerebral lymphatic system is thought to play an important role in regulating the homeostasis of the central nervous system. Currently, more and more attention is being focused on the cerebral lymphatic system. Further understanding of the structural and functional characteristics of cerebral lymphatic system is essential to better understand the pathogenesis of diseases and to explore therapeutic approaches. In this review, we summarize the structural components and functional characteristics of cerebral lymphatic system. More importantly, it is closely associated with peripheral system diseases in the gastrointestinal tract, liver, and kidney. However, there is still a gap in the study of the cerebral lymphatic system. However, we believe that it is a critical mediator of the interactions between the central nervous system and the peripheral system.

Effect of germ-free status on transcriptional profiles in the nucleus accumbens and transcriptomic response to chronic morphine

Opioid use disorder is a public health crisis that causes tremendous suffering for patients as well as substantial social and economic costs for society. There are currently available treatments for patients with opioid use disorder, but they remain intolerable or ineffective for many. Thus the need to develop new avenues for therapeutics development in this space is great. Substantial work in models of substance use disorders, including opioid use disorder, demonstrates that prolonged exposure to drugs of abuse leads to marked transcriptional and epigenetic dysregulation in limbic substructures. It is widely believed that these changes in gene regulation in response to drugs are a key driving factor in the perpetuation of drug taking and seeking behaviors. Thus, development of interventions that could shape transcriptional regulation in response to drugs of abuse would be of high value. Over the past decade there has been a surge in research demonstrating that the resident bacteria of the gastrointestinal tract, collectively the gut microbiome, can have tremendous influence on neurobiological and behavioral plasticity. Previous work from our group and others has demonstrated that alterations in the gut microbiome can alter behavioral responses to opioids in multiple paradigms. Additionally, we have previously reported that depletion of the gut microbiome with antibiotics markedly shifts the transcriptome of the nucleus accumbens following prolonged morphine exposure. In this manuscript we present a comprehensive analysis of the effects of the gut microbiome on transcriptional regulation of the nucleus accumbens following morphine by utilizing germ-free, antibiotic treated, and control mice. This allows for detailed understanding of the role of the microbiome in regulating baseline transcriptomic control, as well as response to morphine. We find that germ-free status leads to a marked gene dysregulation in a manner distinct to adult mice treated with antibiotics, and that altered gene pathways are highly related to cellular metabolic processes. These data provide additional insight into the role of the gut microbiome in modulating brain function and lay a foundation for further study in this area.

Role of Dysregulated Autophagy in HIV Tat, Cocaine, and cART Mediated NLRP3 Activation in Microglia

Despite the ability of combination antiretroviral therapy (cART) to suppress viremia, there is persistence low levels of HIV proteins such as Transactivator of transcription (Tat) in the central nervous system (CNS), contributing to glial activation and neuroinflammation. Accumulating evidence also implicates the role of drugs of abuse in exacerbating neurological complications associated with HIV-1. The combined effects of HIV Tat, drugs of abuse, and cART can thus create a toxic milieu in the CNS. The present study investigated the combinatorial effects of HIV-Tat, cocaine, and cART on autophagy and NLRP3 inflammasome activation. We selected a combination of three commonly used cART regimens: tenofovir, emtricitabine, and dolutegravir. Our results demonstrated that exposure of mouse primary microglia (MPMs) to these agents-HIV Tat (25 ng/ml), cocaine (1 μM), and cART (1 μM each) resulted in upregulation of autophagy markers: Beclin1, LC3B-II, and SQSTM1 with impaired lysosomal functioning involving increased lysosomal pH, decreased LAMP2 and cathepsin D, ultimately leading to dysregulated autophagy. Our findings also demonstrated activation of the NLRP3 signaling in microglia exposed to these agents. We further demonstrated that gene silencing of key autophagy protein BECN1 significantly blocked NLRP3-mediated activation of microglia. Silencing of NLRP3, however, failed to block HIV Tat, cocaine, and cART-mediated dysregulation of the autophagy-lysosomal axis; these in vitro phenomena were also validated in vivo using iTat mice administered cocaine and cART. This study thus underscores the cooperative effects of HIV Tat, cocaine, and cART in exacerbating microglial activation involving dysregulated autophagy and activation of the NLRP3 inflammasome signaling.

Ketogenic diet: a potential adjunctive treatment for substance use disorders

Substance use disorders (SUD) can lead to serious health problems, and there is a great interest in developing new treatment methods to alleviate the impact of substance abuse. In recent years, the ketogenic diet (KD) has shown therapeutic benefits as a dietary therapy in a variety of neurological disorders. Recent studies suggest that KD can compensate for the glucose metabolism disorders caused by alcohol use disorder by increasing ketone metabolism, thereby reducing withdrawal symptoms and indicating the therapeutic potential of KD in SUD. Additionally, SUD often accompanies increased sugar intake, involving neural circuits and altered neuroplasticity similar to substance addiction, which may induce cross-sensitization and increased use of other abused substances. Reducing carbohydrate intake through KD may have a positive effect on this. Finally, SUD is often associated with mitochondrial damage, oxidative stress, inflammation, glia dysfunction, and gut microbial disorders, while KD may potentially reverse these abnormalities and serve a therapeutic role. Although there is much indirect evidence that KD has a positive effect on SUD, the small number of relevant studies and the fact that KD leads to side effects such as metabolic abnormalities, increased risk of malnutrition and gastrointestinal symptoms have led to the limitation of KD in the treatment of SUD. Here, we described the organismal disorders caused by SUD and the possible positive effects of KD, aiming to provide potential therapeutic directions for SUD.

Role of Microglia in Psychostimulant Addiction

The use of psychostimulant drugs can modify brain function by inducing changes in the reward system, mainly due to alterations in dopaminergic and glutamatergic transmissions in the mesocorticolimbic pathway. However, the etiopathogenesis of addiction is a much more complex process. Previous data have suggested that microglia and other immune cells are involved in events associated with neuroplasticity and memory, which are phenomena that also occur in addiction. Nevertheless, how dependent is the development of addiction on the activity of these cells? Although the mechanisms are not known, some pathways may be involved. Recent data have shown psychoactive substances may act directly on immune cells, alter their functions and induce various inflammatory mediators that modulate synaptic activity. These could, in turn, be involved in the pathological alterations that occur in substance use disorder. Here, we extensively review the studies demonstrating how cocaine and amphetamines modulate microglial number, morphology, and function. We also describe the effect of these substances in the production of inflammatory mediators and a possible involvement of some molecular signaling pathways, such as the toll-like receptor 4. Although the literature in this field is scarce, this review compiles the knowledge on the neuroimmune axis that is involved in the pathogenesis of addiction, and suggests some pharmacological targets for the development of pharmacotherapy.

Mapping trends and hotspot regarding gastrointestinal microbiome and neuroscience: A bibliometric analysis of global research (2002-2022)

BACKGROUND

Scholars have long understood that gastrointestinal microorganisms are intimately related to human disorders. The literature on research involving the gut microbiome and neuroscience is emerging. This study exposed the connections between gut microbiota and neuroscience methodically and intuitively using bibliometrics and visualization. This study's objectives were to summarize the knowledge structure and identify emerging trends and potential hotspots in this field.

MATERIALS AND METHODS

On October 18, 2022, a literature search was conducted utilizing the Web of Science Core Collection (WoSCC) database for studies on gut microbiota and neuroscience studies from 2002 to 2022 (August 20, 2022). VOSviewer and CiteSpace V software was used to conduct the bibliometrics and visualization analysis.

RESULTS

From 2002 to 2022 (August 20, 2022), 2,275 publications in the WoSCC database satisfied the criteria. The annual volume of publications has rapidly emerged in recent years (2016-2022). The most productive nation (n = 732, 32.18%) and the hub of inter-country cooperation (links: 38) were the United States. University College Cork had the most research papers published in this area, followed by McMaster University and Harvard Medical School. Cryan JF, Dinan TG, and Clarke G were key researchers with considerable academic influence. The journals with the most publications are "Neurogastroenterology and Motility" and "Brain Behavior and Immunity." The most cited article and co-cited reference was Cryan JF's 2012 article on the impact of gut microbiota on the brain and behavior. The current research hotspot includes gastrointestinal microbiome, inflammation, gut-brain axis, Parkinson's disease (PD), and Alzheimer's disease (AD). The research focus would be on the "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases." Burst detection analysis showed that schizophrenia, pathology, and psychiatric disorder may continue to be the research frontiers.

CONCLUSION

Research on "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases" will continue to be the hotspot. Schizophrenia and psychiatric disorder will be the key research diseases in the field of gut microbiota and neuroscience, and pathology is the key research content, which is worthy of scholars' attention.

Substance use, microbiome and psychiatric disorders

Accumulating evidence from several studies has shown association between substance use, dysregulation of the microbiome and psychiatric disorders such as depression, anxiety, and psychosis. Many of the abused substances such as cocaine and alcohol have been shown to alter immune signaling pathways and cause inflammation in both the periphery and the central nervous system (CNS). In addition, these substances of abuse also alter the composition and function of the gut microbiome which is known to play important roles such as the synthesis of neurotransmitters and metabolites, that affect the CNS homeostasis and consequent behavioral outcomes. The emerging interactions between substance use, microbiome and CNS neurochemical alterations could contribute to the development of psychiatric disorders. This review provides an overview of the associative effects of substance use such as alcohol, cocaine, methamphetamine, nicotine and opioids on the gut microbiome and psychiatric disorders involving anxiety, depression and psychosis. Understanding the relationship between substance use, microbiome and psychiatric disorders will provide insights for potential therapeutic targets, aimed at mitigating these adverse outcomes.