Involvement of metabotropic glutamate receptor 5, AKT/PI3K signaling and NF-κB pathway in methamphetamine-mediated increase in IL-6 and IL-8 expression in astrocytes

Therapeutic targeting of neuroinflammation in methamphetamine use disorder

Methamphetamine (METH) is a highly addictive illicit psychostimulant with a significant annual fatality rate. Emerging studies highlight its role in neuroinflammation and a range of neurological disorders. This review examines the current landscape of potential drug targets for managing neuroinflammation in METH use disorders (MUDs), with a particular focus on the rationale behind targeting Toll-like receptor 4 (TLR4), the NLR family pyrin domain containing 3 (NLRP3) inflammasome, and other promising targets. Given the multifactorial neurological effects of METH, including cognitive impairment and neurodegeneration, addressing METH-induced neuroinflammation has shown considerable promise in partially mitigating the damaging effects on the central nervous system and improving behavioral outcomes. This article provides an overview of the existing understanding while charting a promising path forward for developing innovative MUD treatments, focusing on neuroinflammation as a therapeutic target. Targeting neuroinflammation in METH-induced neurological disorders shows significant promise in mitigating cognitive impairment and neurodegeneration, offering a potential therapeutic strategy for improving outcomes in MUD. While challenges remain in optimizing treatments, ongoing research into combination therapies, novel drug delivery systems, and neuroprotective agents suggests a positive outlook for more effective interventions.

Elucidating the molecular symphony: unweaving the transcriptional & epigenetic pathways underlying neuroplasticity in opioid dependence and withdrawal

The persistent use of opioids leads to profound changes in neuroplasticity of the brain, contributing to the emergence and persistence of addiction. However, chronic opioid use disrupts the delicate balance of the reward system in the brain, leading to neuroadaptations that underlie addiction. Chronic cocaine usage leads to synchronized alterations in gene expression, causing modifications in the Nucleus Accumbens (NAc), a vital part of the reward system of the brain. These modifications assist in the development of maladaptive behaviors that resemble addiction. Neuroplasticity in the context of addiction involves changes in synaptic connectivity, neuronal morphology, and molecular signaling pathways. Drug-evoked neuroplasticity in opioid addiction and withdrawal represents a complicated interaction between environmental, genetic, and epigenetic factors. Identifying specific transcriptional and epigenetic targets that can be modulated to restore normal neuroplasticity without disrupting essential physiological processes is a critical consideration. The discussion in this article focuses on the transcriptional aspects of drug-evoked neuroplasticity, emphasizing the role of key transcription factors, including cAMP response element-binding protein (CREB), ΔFosB, NF-kB, Myocyte-enhancing factor 2 (MEF2), Methyl-CpG binding protein 2 (MeCP2), E2F3a, and FOXO3a. These factors regulate gene expression and lead to the neuroadaptive changes observed in addiction and withdrawal. Epigenetic regulation, which involves modifying gene accessibility by controlling these structures, has been identified as a critical component of addiction development. By unraveling these complex molecular processes, this study provides valuable insights that may pave the way for future therapeutic interventions targeting the mechanisms underlying addiction and withdrawal.

Combined Diagnostic Value of Hsa-miR-592 and Hsa-miR-9-3p in Plasma for Methamphetamine Addicts

A number of studies have reported that drug addiction is associated with microRNAs (miRNAs). However, the roles of plasma miRNAs in methamphetamine (METH) addicts have not been clearly explained. This study aimed to profile a panel of miRNAs as non-invasive predictive biomarkers and therapeutic targets for METH addiction. Differentially expressed miRNAs were derived from next-generation sequencing technology (NGS) and were validated by quantitative real-time PCR (RT-qPCR). The diagnostic value of specific altered miRNAs was evaluated by receiver operating characteristic (ROC) analysis and area under the curve (AUC). NGS results revealed that 63 miRNAs were significantly altered in the METH-exposed paradigm. The levels of hsa-miR-592, hsa-miR-9-3p, hsa-miR-206 and hsa-let-7b-3p were significantly elevated in the plasma of METH addicts. Hsa-miR-9-3p was a useful biomarker discriminating METH addicts from normal (AUC was 0.756). Importantly, combining detection of hsa-miR-592 and hsa-miR-9-3p achieved the highest AUC of 0.87, with a sensitivity and specificity of 82.7% and 78.9%, respectively. Target gene BDNF decreased significantly in METH addicts. Although METH addicts showed significant depressive symptoms, there was no correlation between the expression level of miR-592 and miR-9-3p and the degree of depression. Our findings suggested that hsa-miR-592, hsa-miR-9-3p, hsa-miR-206, and hsa-let-7b-3p may play a potential role in the pathology of METH addiction, and a combination of hsa-miR-592 and hsa-miR-9-3p could serve as potential peripheral biomarker and therapeutic target for METH addiction.

Evaluation of Complete Blood Cell Count Parameters and Their Role in Inflammation in Patients with Methamphetamine and Synthetic Cannabis Use Disorder

Background

The aim of this study was to compare the complete blood cell count parameters of patients with methamphetamine and synthetic cannabis use disorder (MCUD), a condition that has recently exhibited a gradual increase in prevalence, with those of healthy subjects.

Methods

In total, 76 patients diagnosed with MCUD and 78 healthy controls were included in the study. Venous blood samples were collected from all participants at presentation for laboratory examination.

Results

The rate of mono- and poly-substance users in the patient group was 14.5% and 85.5%, respectively. The average duration of methamphetamine (METH) use in the patient group is 3.0 ± 1.9 years. White blood cell (P < .001), PLT (P = .005), monocyte count (P < .001), basophil count (P < .001), neutrophil count (P < .001), lymphocyte count (P < .001) basophil/lymphocyte ratio (BLR) (P = .04), SII (P = .006), and SIRI (P = .001) values were significantly higher. In contrast Hgb (P = .043), Hct (P = .002), monocyte percentage (P = .004), and RBC (P = .021) values were significantly lower in the MCUD group compared to the control group. There was a significant positive correlation between neutrophil/lymphocyte ratio and platelet/lymphocyte ratio (r = .552 P < .001) and between systemic immune inflammatory index (SII) and systemic inflammation response index (SIRI) (r = 0.580 P < .001).

Conclusion

Methamphetamine and cannabis may affect the levels of inflammatory markers and SII and SIRI values through various mechanisms. To the best of our knowledge, this is the first study in the relevant literature, which investigated SII and SIRI values in patients with MCUD, therefore, the results can contribute to the future development of immune system-related markers in this field.

HIV-1 and methamphetamine co-treatment in primary human astrocytes: TAARgeting ER/UPR dysfunction

Objectives

Human immunodeficiency virus 1 (HIV-1) can invade the central nervous system (CNS) early during infection and persist in the CNS for life despite effective antiretroviral treatment. Infection and activation of residential glial cells lead to low viral replication and chronic inflammation, which damage neurons contributing to a spectrum of HIV-associated neurocognitive disorders (HAND). Substance use, including methamphetamine (METH), can increase one's risk and severity of HAND. Here, we investigate HIV-1/METH co-treatment in a key neurosupportive glial cell, astrocytes. Specifically, mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) signaling pathways, such as calcium and the unfolded protein response (UPR), are key mechanisms underlying HAND pathology and arise as potential targets to combat astrocyte dysfunction.

Methods

Primary human astrocytes were transduced with a pseudotyped HIV-1 model and exposed to low-dose METH for seven days. We assessed changes in astrocyte HIV-1 infection, inflammation, mitochondrial antioxidant and dynamic protein expression, respiratory acitivity, mitochondrial calcium flux, and UPR/MAM mediator expression. We then tested a selective antagonist for METH-binding receptor, trace amine-associated receptor 1 (TAAR1) as a potetnial upstream regulator of METH-induced calcium flux and UPR/MAM mediator expression.

Results

Chronic METH exposure increased astrocyte HIV-1 infection. Moreover, HIV-1/METH co-treatment suppressed astrocyte antioxidant and metabolic capacity while increasing mitochondrial calcium load and protein expression of UPR messengers and MAM mediators. Notably, HIV-1 increases astrocyte TAAR1 expression, thus, could be a critical regulator of HIV-1/METH co-treatment in astrocytes. Indeed, selective antagonism of TAAR1 significantly inhibited cytosolic calcium flux and induction of UPR/MAM protein expression.

Conclusion

Altogether, our findings demonstrate HIV-1/METH-induced ER-mitochondrial dysfunction in astrocytes, whereas TAAR1 may be an upstream regulator for HIV-1/METH-mediated astrocyte dysfunction.

Microglia in neuroimmunopharmacology and drug addiction

Drug addiction is a chronic and debilitating disease that is considered a global health problem. Various cell types in the brain are involved in the progression of drug addiction. Recently, the xenobiotic hypothesis has been proposed, which frames substances of abuse as exogenous molecules that are responded to by the immune system as foreign "invaders", thus triggering protective inflammatory responses. An emerging body of literature reveals that microglia, the primary resident immune cells in the brain, play an important role in the progression of addiction. Repeated cycles of drug administration cause a progressive, persistent induction of neuroinflammation by releasing microglial proinflammatory cytokines and their metabolic products. This contributes to drug addiction via modulation of neuronal function. In this review, we focus on the role of microglia in the etiology of drug addiction. Then, we discuss the dynamic states of microglia and the correlative and causal evidence linking microglia to drug addiction. Finally, possible mechanisms of how microglia sense drug-related stimuli and modulate the addiction state and how microglia-targeted anti-inflammation therapies affect addiction are reviewed. Understanding the role of microglia in drug addiction may help develop new treatment strategies to fight this devastating societal challenge.

Metabotropic glutamate receptor 5 promotes blood-brain barrier recovery after traumatic brain injury

Blood-brain barrier (BBB) impairment and glutamate release are two pathophysiological features of traumatic brain injury (TBI), contributing to secondary brain damage and neuroinflammation. However, our knowledge of BBB integrity damage and dysfunction are still limited due to the diverse and fluctuating expression of glutamate receptors after trauma. Here, we confirmed the downregulation of metabotropic glutamate receptor 5 (mGluR5) on microvascular endothelial cell within the acute phase of TBI, and the recovered mGluR5 levels on BBB was positively associated with blood perfusion and neurological recovery. In whole body mGluR5-knockout mice, BBB dysfunction and neurological deficiency were exacerbated after TBI compared with wild type mice. In terms of mechanism, the amino acid sequence 201-259 of cytoskeletal protein Alpha-actinin-1 (ACTN1) interacted with mGluR5, facilitating mGluR5 translocation from cytoplasmic compartment to plasma membrane in endothelial cells. Activation of plasma membrane mGluR5 triggers the PLC/PKCμ/c-Jun signaling pathway, leading to increased expression of the tight junction-actin cytoskeleton connecting protein zonula occludens-1 (ZO-1). Our findings uncover a novel mechanism mediated by membrane and cytoplasmic mGluR5 in endothelial cell integrity maintenance and repair, providing the potential therapeutic target for TBI treatment targeting at mGluR5 and mGluR5/ACTN1 complex in BBB.

Blockade of mGluR5 in astrocytes derived from human iPSCs modulates astrocytic function and increases phagocytosis

TNF-α is essential for induction and maintenance of inflammatory responses and its dysregulation is associated with susceptibility to various pathogens that infect the central nervous system. Activation of both microglia and astrocytes leads to TNF-α production, which in turn triggers further activation of these cells. Astrocytes have been implicated in the pathophysiology of a wide range of neurodegenerative diseases with either harmful or protective roles, as these cells are capable of secreting several inflammatory factors and also promote synapse elimination and remodeling. These responses are possible because they sense their surroundings via several receptors, including the metabotropic glutamate receptor 5 (mGluR5). Under neuroinflammatory conditions, mGluR5 activation in astrocytes can be neuroprotective or have the opposite effect. In the current study, we investigated the role of mGluR5 in hiPSC-derived astrocytes subjected to pro-inflammatory stimulation by recombinant TNF-α (rTNF-α). Our results show that mGluR5 blockade by CTEP decreases the secreted levels of pro-inflammatory cytokines (IL-6 and IL-8) following short rTNF-α stimulation, although this effect subsides with time. Additionally, CTEP enhances synaptoneurosome phagocytosis by astrocytes in both non-stimulated and rTNF-α-stimulated conditions, indicating that mGluR5 blockade alone is enough to drive synaptic material engulfment. Finally, mGluR5 antagonism as well as rTNF-α stimulation augment the expression of the reactivity marker SERPINA3 and reduces the expression of synaptogenic molecules. Altogether, these data suggest a complex role for mGluR5 in human astrocytes, since its blockade may have beneficial and detrimental effects under inflammatory conditions.

Peripheral inflammation and neurocognitive impairment: correlations, underlying mechanisms, and therapeutic implications

Cognitive impairments, such as learning and memory deficits, may occur in susceptible populations including the elderly and patients who are chronically ill or have experienced stressful events, including surgery, infection, and trauma. Accumulating lines of evidence suggested that peripheral inflammation featured by the recruitment of peripheral immune cells and the release of pro-inflammatory cytokines may be activated during aging and these conditions, participating in peripheral immune system-brain communication. Lots of progress has been achieved in deciphering the core bridging mechanism connecting peripheral inflammation and cognitive impairments, which may be helpful in developing early diagnosis, prognosis evaluation, and prevention methods based on peripheral blood circulation system sampling and intervention. In this review, we summarized the evolving evidence on the prevalence of peripheral inflammation-associated neurocognitive impairments and discussed the research advances in the underlying mechanisms. We also highlighted the prevention and treatment strategies against peripheral inflammation-associated cognitive dysfunction.

Genetic Downregulation of the Metabotropic Glutamate Receptor Type 5 Dampens the Reactive and Neurotoxic Phenotype of Adult ALS Astrocytes

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive degeneration of motor neurons (MNs). Astrocytes display a toxic phenotype in ALS, which results in MN damage. Glutamate (Glu)-mediated excitotoxicity and group I metabotropic glutamate receptors (mGluRs) play a pathological role in the disease progression. We previously demonstrated that in vivo genetic ablation or pharmacological modulation of mGluR5 reduced astrocyte activation and MN death, prolonged survival and ameliorated the clinical progression in the SOD1G93A mouse model of ALS. This study aimed to investigate in vitro the effects of mGluR5 downregulation on the reactive spinal cord astrocytes cultured from adult late symptomatic SOD1G93A mice. We observed that mGluR5 downregulation in SOD1G93A astrocytes diminished the cytosolic Ca2+ overload under resting conditions and after mGluR5 simulation and reduced the expression of the reactive glial markers GFAP, S100β and vimentin. In vitro exposure to an anti-mGluR5 antisense oligonucleotide or to the negative allosteric modulator CTEP also ameliorated the altered reactive astrocyte phenotype. Downregulating mGluR5 in SOD1G93A mice reduced the synthesis and release of the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and ameliorated the cellular bioenergetic profile by improving the diminished oxygen consumption and ATP synthesis and by lowering the excessive lactate dehydrogenase activity. Most relevantly, mGluR5 downregulation hampered the neurotoxicity of SOD1G93A astrocytes co-cultured with spinal cord MNs. We conclude that selective reduction in mGluR5 expression in SOD1G93A astrocytes positively modulates the astrocyte reactive phenotype and neurotoxicity towards MNs, further supporting mGluR5 as a promising therapeutic target in ALS.

MPEP Attenuates Intrahepatic Fat Accumulation in Obese Mice

The blockade of metabotropic glutamate receptor type 5 (mGluR5) was previously found to reduce fat accumulation in HEPG2 cells. Here, we evaluated the effects of mGluR5 blockade in a mouse model of steatosis. Male ob/ob mice fed a high-fat diet were treated with MPEP or vehicle. After 7 weeks, liver biopsies were collected, and nuclei were isolated from fresh tissue. Lipid droplet area and collagen deposition were evaluated on tissue slices; total lipids, lipid peroxidation, and ROS were evaluated on tissue homogenates; PPARα, SREBP-1, mTOR, and NF-κB were assayed on isolated nuclei by Western Blot. Target genes of the above-mentioned factors were assayed by RT-PCR. Reduced steatosis and hepatocyte ballooning were observed in the MPEP group with respect to the vehicle group. Concomitantly, increased nuclear PPARα and reduced nuclear SREBP-1 levels were observed in the MPEP group. Similar trends were obtained in target genes of PPARα and SREBP-1, Acox1 and Acc1, respectively. MPEP administration also reduced oxidative stress and NF-κB activation, probably via NF-κB inhibition. Levels of common markers of inflammation (Il-6, Il1β and Tnf-α) and oxidative stress (Nrf2) were significantly reduced. mTOR, as well as collagen deposition, were unchanged. Concluding, MPEP, a selective mGluR5 negative allosteric modulator, reduces both fat accumulation and oxidative stress in a 7-week murine model of steatosis. Although underlying mechanisms need to be further investigated, this is the first in vivo study showing the beneficial effects of MPEP in a murine model of steatosis.

Randomized placebo-controlled crossover trial of memantine in children with epileptic encephalopathy

Memantine is an N-methyl-D-aspartate receptor antagonist, approved for dementia treatment. There is limited evidence of memantine showing benefit for paediatric neurodevelopmental phenotypes, but no randomized placebo-controlled trials in children with developmental and epileptic encephalopathy. In this randomized double-blind placebo-controlled crossover trial (Trial registration: https://clinicaltrials.gov/ct2/show/NCT03779672), patients with developmental and epileptic encephalopathy received memantine and placebo, each for a 6-week period separated by a 2-week washout phase. Electroencephalography, seizure diary, patient caregivers' global impression, serum inflammatory markers and neuropsychological evaluation were performed at baseline and after each treatment phase. The primary outcome measure was classification as a 'responder', defined as ≥2 of: >50% seizure frequency reduction, electroencephalography improvement, caregiver clinical impression improvement or clear neuropsychological testing improvement. Thirty-one patients (13 females) enrolled. Two patients withdrew prior to initiating medication and two (twins) had to be removed from analysis. Of the remaining 27 patients, nine (33%) were classified as responders to memantine versus two (7%) in the placebo group (P < 0.02). Electroencephalography improvement was seen in eight patients on memantine compared to two on placebo (P < 0.04). Seizure improvement was observed in eight patients on memantine and two on placebo (P < 0.04). Caregivers reported overall clinical improvement in 10 patients on memantine compared to seven on placebo (not significant). Statistical analysis of neuropsychological evaluation suggested improvements in symptoms of attention-deficit hyperactivity disorder and autism. Memantine is a safe and effective treatment for children with developmental and epileptic encephalopathy, having the potential to improve both seizure control and cognitive function.

Cognitive impairment and changes of red blood cell components and serum levels of IL-6, IL-18, and L-tryptophan in methamphetamine abusers

The deficit in cognitive function is more concerning in methamphetamine (MA) users. The cognitive deficit was suspected to be the consequence of neuroinflammation-induced neurological dysregulation. In addition, activating the key enzyme in the tryptophan metabolic pathway by pro-inflammatory cytokines results in metabolite toxicity, further generating cognitive impairments. However, the evidence for the role of neuroinflammation and tryptophan metabolites involved in MA-induced cognitive deficit needs more conclusive study.

OBJECTIVES

This retrospective study aimed to determine blood-inflammatory markers, tryptophan metabolite-related molecules, and cognitive function in MA abusers compared to healthy control (HC) participants.

METHODS

The cognitive functions were evaluated using Stroop, Go/No-Go, One Back Task (OBT), and Wisconsin Card Sorting Test-64 (WCST-64). Blood samples were analyzed for complete blood count (CBC) analysis, serum inflammatory cytokines interleukin (IL)-6 and IL-18 and tryptophan metabolites.

RESULTS

MA group exhibited poor cognitive performance in selective attention, inhibition, working memory, cognitive flexibility, concept formation and processing speed compared to HC. Reduction in red blood cell (RBC) components but induction in white blood cells (WBCs) and IL-6 were observed in MA abusers, which might indicate anemia of (systemic chronic low-grade) inflammation. In addition, the depletion of precursor in the tryptophan metabolic pathway, L-tryptophan was also observed in MA users, which might represent induction in tryptophan metabolites.

CONCLUSION

These findings emphasize that blood biomarkers might be a surrogate marker to predict the role of neuroinflammation and abnormal tryptophan metabolite in MA-induced cognitive impairments.

Inhibition of mGluR5/PI3K-AKT Pathway Alleviates Alzheimer's Disease-Like Pathology Through the Activation of Autophagy in 5XFAD Mice

BACKGROUND

The metabotropic glutamate receptor 5 (mGluR5) is widely expressed in postsynaptic neurons and plays a vital role in the synaptic plasticity of the central nervous system. mGluR5 is a coreceptor for amyloid-β (Aβ) oligomer, and downregulation or pharmacological blockade of mGluR5 presents the therapeutic potential of Alzheimer's disease (AD). However, the abnormality of mGluR5 in the pathogenesis of AD and its mechanism of pathology is not clear.

OBJECTIVE

In this study, we would like to investigate the expression of mGluR5 in the process of AD and explore the effects and the underlying mechanisms of antagonizing mGluR5 on cognitive function, synaptic structure, and inflammation in 5xFAD mice.

METHODS

mGluR5 expression and interactions with PrPc in 5XFAD mice were detected using western blot and co-immunoprecipitation. The selective mGluR5 antagonist MPEP was infused into 4-month-old 5XFAD mice for 60 consecutive days. Then, cognitive function, AD-like pathology and synaptic structure were measured. Further observations were made in mGluR5 knockdown 5XFAD mice.

RESULTS

mGluR5 expression was increased with Aβ levels at 6 months in 5XFAD mice. mGluR5 antagonist rescued cognitive disorders, promoted synaptic recovery, and alleviated both the Aβ plaque load and abnormal hyperphosphorylation in 6-month-old 5XFAD mice. Meanwhile, the results were validated in mGluR5 knockdown mice. Blockade of mGluR5 efficiently alleviates AD-like pathologies by inhibiting the PI3K/AKT/mTOR pathway and activates autophagy in 5XFAD mice. Furthermore, antagonism of mGluR5 attenuated neuroinflammation by inactivating the IKK/NF-κB pathway.

CONCLUSION

These findings suggest that mGluR5 may be an effective drug target for AD treatment, and inhibition of the mGluR5/PI3K-AKT pathway alleviates AD-like pathology by activating autophagy and anti-neuroinflammation in 5XFAD mice.

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.

Leukocyte telomere length is not shortened in methamphetamine dependence or methamphetamine-induced psychosis but is increased following traumatic events

OBJECTIVE

This study aims to examine the effects of methamphetamine (MA) use and dependence and MA withdrawal symptoms on the telomere length and whether shortening of the latter is associated with MA-induced psychosis (MIP).

METHODS

This study included 185 MA-abuse, 118 MA-dependent, and 67 MIP patients, diagnosed using DSM-IV criteria. The Semi-structured Assessment for Drug Dependence and Alcoholism (SSADDA) questionnaire was employed to collect MA-related data. MIP was confirmed using the Methamphetamine Experience Questionnaire (MEQ). The leukocyte telomere length was measured using real-time polymerase chain reaction measuring the Telomere/Single gene ratio (T/S ratio). Data were analysed using multivariate statistical analyses.

RESULTS

There were no significant associations between the T/S ratio and severity of MA-use, MIP, and MA withdrawal symptoms. MIP was significantly predicted by alcohol dependence, antisocial personality disorder, and MA-use severity. There were significantly positive associations between the T/S ratio and previous traumatic and life-threatening events. The T/S ratio was not affected by alcohol and nicotine dependence. Alcohol and nicotine dependence, antisocial personality disorder, and severity of MA use increased risk of MA withdrawal symptoms.

CONCLUSION

MIP and MA-use severity are not associated with leukocyte telomere length, but previous traumatic and life-threatening events are associated with increased telomere length.

Drugs and Bugs: The Gut-Brain Axis and Substance Use Disorders

Substance use disorders (SUDs) represent a significant public health crisis. Worldwide, 5.4% of the global disease burden is attributed to SUDs and alcohol use, and many more use psychoactive substances recreationally. Often associated with comorbidities, SUDs result in changes to both brain function and physiological responses. Mounting evidence calls for a precision approach for the treatment and diagnosis of SUDs, and the gut microbiome is emerging as a contributor to such disorders. Over the last few centuries, modern lifestyles, diets, and medical care have altered the health of the microbes that live in and on our bodies; as we develop, our diets and lifestyle dictate which microbes flourish and which microbes vanish. An increase in antibiotic treatments, with many antibiotic interventions occurring early in life during the microbiome's normal development, transforms developing microbial communities. Links have been made between the microbiome and SUDs, and the microbiome and conditions that are often comorbid with SUDs such as anxiety, depression, pain, and stress. A better understanding of the mechanisms influencing behavioral changes and drug use is critical in developing novel treatments for SUDSs. Targeting the microbiome as a therapeutic and diagnostic tool is a promising avenue of exploration. This review will provide an overview of the role of the gut-brain axis in a wide range of SUDs, discuss host and microbe pathways that mediate changes in the brain's response to drugs, and the microbes and related metabolites that impact behavior and health within the gut-brain axis.

Dynamics and correlations in multiplex immune profiling reveal persistent immune inflammation in male drug users after withdrawal

Drug withdrawal elicits immune responses that contribute to the development of withdrawal symptoms and relapse. The understanding of the immunologic dynamics after drug withdrawal is limited, precluding the finding of promising immune intervention measures. Here, we performed cytokine and multiplex immune profiling in heroin, methamphetamine (METH) and ephedrine users after withdrawal and identified the correlation between cytokines and other immune parameters. We showed that broad and strong inflammatory responses occurred at the early stage after drug withdrawal, and the inflammatory responses showed a downtrend with the extension of withdrawal time. Notably, immune dysregulation remained through and may last longer than 12 months after withdrawal in heroin and METH users. Our findings suggest that cytokines, immune cells, complement and immunoglobulin form a complex immune network that regulates immune responses after withdrawal. These data provide a reference for future scientific research and drug research and development.

Methamphetamine: burden, mechanism and impact on pregnancy, the fetus, and newborn

While the opioid epidemic has garnered worldwide attention, increasing methamphetamine use has drawn less scrutiny. Methamphetamine is a highly addictive psychostimulant affecting people from all backgrounds and regions. It is a potent vasoconstrictor, is associated with arrhythmias and dilated cardiomyopathy. Cardiovascular disease-related mortality is a leading cause of death in methamphetamine users. Women of childbearing age increasingly use methamphetamine and continue during pregnancy. In the short term, prenatal methamphetamine use is associated with fetal growth restriction and low birth weight in the newborn. Animal studies show reduction in uterine and umbilical blood flow following maternal methamphetamine administration. Based on currently available evidence, prenatal methamphetamine exposure has transient effects on gross motor development, no effect on language and cognition, and modest effects on behavior and executive functioning with poor inhibitory control, which may be attributable to early adversity. Further research is needed to evaluate long-term effects of prenatal methamphetamine exposure.

Prevention of L-Dopa-Induced Dyskinesias by MPEP Blockade of Metabotropic Glutamate Receptor 5 Is Associated with Reduced Inflammation in the Brain of Parkinsonian Monkeys

Proinflammatory markers were found in brains of Parkinson’s disease (PD) patients. After years of L-Dopa symptomatic treatment, most PD patients develop dyskinesias. The relationship between inflammation and L-Dopa-induced dyskinesias (LID) is still unclear. We previously reported that MPEP (a metabotropic glutamate receptor 5 antagonist) reduced the development of LID in de novo MPTP-lesioned monkeys. We thus investigated if MPEP reduced the brain inflammatory response in these MPTP-lesioned monkeys and the relationship to LID. The panmacrophage/microglia marker Iba1, the phagocytosis-related receptor CD68, and the astroglial protein GFAP were measured by Western blots. The L-Dopa-treated dyskinetic MPTP monkeys had increased Iba1 content in the putamen, substantia nigra, and globus pallidus, which was prevented by MPEP cotreatment; similar findings were observed for CD68 contents in the putamen and globus pallidus. There was a strong positive correlation between dyskinesia scores and microglial markers in these regions. GFAP contents were elevated in MPTP + L-Dopa-treated monkeys among these brain regions and prevented by MPEP in the putamen and subthalamic nucleus. In conclusion, these results showed increased inflammatory markers in the basal ganglia associated with LID and revealed that MPEP inhibition of glutamate activity reduced LID and levels of inflammatory markers.

Natural Products in Modulating Methamphetamine-Induced Neuronal Apoptosis

Methamphetamine (METH), an amphetamine-type psychostimulant, is highly abused worldwide. Chronic abuse of METH causes neurodegenerative changes in central dopaminergic neurons with numerous neuropsychiatric consequences. Neuronal apoptosis plays a critical role in METH-induced neurotoxicity and may provide promising pharmacological targets for preventing and treating METH addiction. In recent years, accumulating evidence has revealed that natural products may possess significant potentials to inhibit METH-evoked neuronal apoptosis. In this review, we summarized and analyzed the improvement effect of natural products on METH-induced neuronal apoptosis and their potential molecular mechanisms on modulating dopamine release, oxidative stress, mitochondrial-dependent apoptotic pathway, endoplasmic reticulum stress-mediated apoptotic pathway, and neuroinflammation. Hopefully, this review may highlight the potential value of natural products in modulating METH-caused neuronal apoptosis and provide useful information for future research and developments of novel and efficacious pharmacotherapies in this field.

The Crosstalk Between Neurons and Glia in Methamphetamine-Induced Neuroinflammation

Methamphetamine (METH), an illicit psycho-stimulant, is widely known as an addictive drug that may cause neurotoxic effects. Previous researches on METH abuse have mainly focused on neurotransmitters, such as dopamine and glutamate. However, there is growing evidence that neuroinflammation also plays an important role in the etiology and pathophysiology of brain dysfunction induced by METH abuse. This has cast a spotlight on the research of microglia and astrocyte, which are critical mediators of neuroimmune pathology in recent years. In the central nervous system (CNS) immunity, abnormalities of the microglia and astrocytes have been observed in METH abusers from both postmortem and preclinical studies. The bidirectional communication between neurons and glia is essential for the homeostasis and biological function of the CNS while activation of glia induces the release of cytokines and chemokines during pathological conditions, which will affect the neuron-glia interactions and lead to adverse behavioral consequences. However, the underlying mechanisms of interaction between neurons and glia in METH-induced neuroinflammation remain elusive. Notably, discovering and further understanding glial activity and functions, as well as the crosstalk between neurons and glia may help to explain the pathogenesis of METH abuse and behavioral changes in abusers. In this review, we will discuss the current understanding of the crosstalk between neurons and glia in METH-induced neuroinflammation. We also review the existing microglia-astrocyte interaction under METH exposure. We hope the present review will lead the way for more studies on the development of new therapeutic strategies for METH abuse in the near future.

Pharmacological characterization and biological function of the interleukin-8 receptor, CXCR2, in largemouth bass (Micropterus salmoides)

Interleukin-8 (IL-8 or C-X-C motif chemokine ligand 8, CXCL8) is a cytokine secreted by numerous cell types and is best known for its functional roles in inflammatory response by binding to specific receptors (the interleukin-8 receptors, IL-8Rs). From the transcriptomic data of largemouth bass (Micropterus salmoides), we identified an IL-8R that is highly homologous to the functionally validated teleost IL-8Rs. The M. salmoides IL-8 receptor (MsCXCR2) was further compared with the C-X-C motif chemokine receptor 2 subfamily by phylogenetic analysis. Briefly, the full-length CDS sequence of MsCXCR2 was cloned into the pEGFP-N1 plasmid, and the membrane localization of fusion expressing MsCXCR2-EGFP was revealed in HEK293 cells. To determine the functional interaction between IL-8 and MsCXCR2, secretory expressed Larimichthys crocea IL-8 (LcIL-8) was used to stimulate MsCXCR2 expressing cells. MsCXCR2 was demonstrated to be activated by LcIL-8, leading to receptor internalization, which was further revealed by the detection of extracellular regulated protein kinase (ERK) phosphorylation. Quantitative real-time PCR was used to evaluate the expressional distribution and variation of MsCXCR2 in healthy and Nocardia seriolae infected fish. Based on our findings, MsCXCR2 was constitutively expressed in all examined tissues, despite at different levels. Furthermore, gene expression was found to be significantly upregulated in the liver and head kidney of diseased fish. Collectively, our findings reveal the molecular activity of MsCXCR2 and indicate the functional involvement of this IL-8R in the immune response induced by N. seriolae in M. salmoides.

A comprehensive study to delineate the role of an extracellular vesicle-associated microRNA-29a in chronic methamphetamine use disorder

Extracellular vesicles (EVs), which express a repertoire of cargo molecules (cf. proteins, microRNA, lipids, etc.), have been garnering a prominent role in the modulation of several cellular processes. Here, using both non-human primate and rodent model systems, we provide evidence that brain-derived EV (BDE) miRNA, miR-29a-3p (mir-29a), is significantly increased during chronic methamphetamine (MA) exposure. Further, miR-29a levels show significant increase both with drug-seeking and reinstatement in a rat MA self-administration model. We also show that EV-associated miR-29a is enriched in EV pool comprising of small EVs and exomeres and further plays a critical role in MA-induced inflammation and synaptodendritic damage. Furthermore, treatment with the anti-inflammatory drug ibudilast (AV411), which is known to reduce MA relapse, decreased the expression of miR-29a and subsequently attenuated inflammation and rescued synaptodendritic injury. Finally, using plasma from MUD subjects, we provide translational evidence that EV-miR29a could potentially serve as a biomarker to detect neuronal damage in humans diagnosed with MA use disorder (MUD). In summary, our work suggests that EV-associated miR-29a-3p plays a crucial role in MUD and might be used as a potential blood-based biomarker for detecting chronic inflammation and synaptic damage.

Methamphetamine Dysregulation of the Central Nervous System and Peripheral Immunity

Methamphetamine (METH) is a potent psychostimulant that increases extracellular monoamines, such as dopamine and norepinephrine, and affects multiple tissue and cell types in the central nervous system (CNS) and peripheral immune cells. The reinforcing properties of METH underlie its significant abuse potential and dysregulation of peripheral immunity and central nervous system functions. Together, the constellation of METH's effects on cellular targets and regulatory processes has led to immune suppression and neurodegeneration in METH addicts and animal models of METH exposure. Here we extensively review many of the cell types and mechanisms of METH-induced dysregulation of the central nervous and peripheral immune systems. SIGNIFICANCE STATEMENT: Emerging research has begun to show that methamphetamine regulates dopaminergic neuronal activity. In addition, METH affects non-neuronal brain cells, such as microglia and astrocytes, and immunological cells of the periphery. Concurrent disruption of bidirectional communication between dopaminergic neurons and glia in the CNS and peripheral immune cell dysregulation gives rise to a constellation of dysfunctional neuronal, cell, and tissue types. Therefore, understanding the pathophysiology of METH requires consideration of the multiple targets at the interface between basic and clinical neuroscience.

Glia: A major player in glutamate-GABA dysregulation-mediated neurodegeneration

The imbalance between glutamate and γ-aminobutyric acid (GABA) results in the loss of synaptic strength leading to neurodegeneration. The dogma on the field considered neurons as the main players in this excitation-inhibition (E/I) balance. However, current strategies focusing only on neurons have failed to completely understand this condition, bringing up the importance of glia as an alternative modulator for neuroinflammation as glia alter the activity of neurons and is a source of both neurotrophic and neurotoxic factors. This review's primary goal is to illustrate the role of glia over E/I balance in the central nervous system and its interaction with neurons. Rather than focusing only on the neuronal targets, we take a deeper look at glial receptors and proteins that could also be explored as drug targets, as they are early responders to neurotoxic insults. This review summarizes the neuron-glia interaction concerning GABA and glutamate, possible targets, and its involvement in the E/I imbalance in neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis.

The Chronic Oral Administration of Clobenzorex or Amphetamine Decreases Motor Behavior and Induces Glial Activation in the Striatum Without Dopaminergic Degeneration

Described as amphetamine-like due to their structural and stimulant similarities, clobenzorex is one of the five most-commonly used drugs in Mexico for the treatment of obesity. Various studies have shown that amphetamines induce dopaminergic neurotoxicity and neuroinflammation in the striatum, symptoms which are associated with motor damage. For this reason, the present study aimed to evaluate the effect of chronic clobenzorex administration on motor behaviors, TH immunoreactivity, gliosis, and the neurodegenerative process in the striatum and substantia nigra pars compacta (SNpc). The present research was conducted on three experimental groups of male Wistar rats: the vehicle group, the amphetamine group (2 mg/kg), and the clobenzorex group (30 mg/kg). All groups were subject to oral administration every 24 h for 31 days. Motor activity and motor coordination were evaluated in the open field test and the beam walking test, respectively. The animals were euthanized after the last day of treatment to enable the extraction of their brains for the evaluation of tyrosine hydroxylase (TH) levels, the immunoreactivity of the glial cells, and the neurodegeneration of both the striatum and SNpc via amino-cupric-silver stain. The results obtained show that amphetamine and clobenzorex administration decrease motor activity and motor coordination in the beam walking test and cause increased gliosis in the striatum, while no significant changes were observed in terms of immunoreactivity to TH and neurodegeneration in both the striatum and SNpc. These results suggest that the chronic administration of clobenzorex may decrease motor function in a manner similar to amphetamine, via the neuroadaptive and non-neurotoxic changes caused to the striatum under this administration scheme.

Blocking glutamate mGlu5 receptors with the negative allosteric modulator CTEP improves disease course in SOD1G93A mouse model of amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

The pathogenesis of amyotrophic lateral sclerosis (ALS) is not fully clarified, although excessive glutamate (Glu) transmission and the downstream cytotoxic cascades are major mechanisms for motor neuron death. Two metabotropic glutamate receptors (mGlu₁ and mGlu₅ ) are overexpressed in ALS and regulate cellular disease processes. Expression and function of mGlu₅ receptors are altered at early symptomatic stages in the SOD1^G93A mouse model of ALS and knockdown of mGlu5 receptors in SOD1^G93A mice improved disease progression.

EXPERIMENTAL APPROACH

We treated male and female SOD1^G93A mice with 2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine (CTEP), an orally available mGlu₅ receptor negative allosteric modulator (NAM), using doses of 2 mg·kg^-1 per 48 h or 4 mg·kg^-1 per 24 h from Day 90, an early symptomatic disease stage. Disease progression was studied by behavioural and histological approaches.

KEY RESULTS

CTEP dose-dependently ameliorated clinical features in SOD1^G93A mice. The lower dose increased survival and improved motor skills in female mice, with barely positive effects in male mice. Higher doses significantly ameliorated disease symptoms and survival in both males and females, females being more responsive. CTEP also reduced motor neuron death, astrocyte and microglia activation, and abnormal glutamate release in the spinal cord, with equal effects in male and female mice. No differences were also observed in CTEP access to the brain.

CONCLUSION AND IMPLICATIONS

Our results suggest that mGlu₅ receptors are promising targets for the treatment of ALS and highlight mGlu5 receptor NAMs as effective pharmacological tools with translational potential.

Autophagy as a gateway for the effects of methamphetamine: From neurotransmitter release and synaptic plasticity to psychiatric and neurodegenerative disorders

As a major eukaryotic cell clearing machinery, autophagy grants cell proteostasis, which is key for neurotransmitter release, synaptic plasticity, and neuronal survival. In line with this, besides neuropathological events, autophagy dysfunctions are bound to synaptic alterations that occur in mental disorders, and early on, in neurodegenerative diseases. This is also the case of methamphetamine (METH) abuse, which leads to psychiatric disturbances and neurotoxicity. While consistently altering the autophagy machinery, METH produces behavioral and neurotoxic effects through molecular and biochemical events that can be recapitulated by autophagy blockade. These consist of altered physiological dopamine (DA) release, abnormal stimulation of DA and glutamate receptors, as well as oxidative, excitotoxic, and neuroinflammatory events. Recent molecular insights suggest that METH early impairs the autophagy machinery, though its functional significance remains to be investigated. Here we discuss evidence suggesting that alterations of DA transmission and autophagy are intermingled within a chain of events underlying behavioral alterations and neurodegenerative phenomena produced by METH. Understanding how METH alters the autophagy machinery is expected to provide novel insights into the neurobiology of METH addiction sharing some features with psychiatric disorders and parkinsonism.

Alpha and beta adrenoceptors activate interleukin-6 transcription through different pathways in cultured astrocytes from rat spinal cord

In brain astrocytes, noradrenaline (NA) has been shown to up-regulate IL-6 production via β-adrenoceptors (ARs). However, the underlying intracellular mechanisms for this regulation are not clear, and it remains unknown whether α-ARs are involved. In this study, we investigated the AR-mediated regulation of IL-6 mRNA levels in the cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol increased IL-6 mRNA levels. The phenylephrine-induced IL-6 increase was accompanied by an increase in ERK phosphorylation, and these effects were blocked by inhibitors of PKC and ERK. The isoproterenol-induced IL-6 increase was accompanied by an increase in CREB phosphorylation, and these effects were blocked by a PKA inhibitor. Our results indicate that IL-6 increases by α1- and β-ARs are mediated via the PKC/ERK and cAMP/PKA/CREB pathways, respectively. Moreover, conditioned medium collected from astrocytes treated with the α2-AR agonist dexmedetomidine, increased IL-6 mRNA in other astrocytes. In this study, we elucidate that α1- and α2-ARs, in addition to β-ARs, promote IL-6 transcription through different pathways in spinal cord astrocytes.

Targeting mGlu5 for Methamphetamine Use Disorder

Methamphetamine abuse leads to devastating consequences, including addiction, crime, and death. Despite decades of research, no medication has been approved by the U.S. Food and Drug Administration for the treatment of Methamphetamine Use Disorder. Thus, there is a need for new therapeutic approaches. Animal studies demonstrate that methamphetamine exposure dysregulates forebrain function involving the Group-I metabotropic glutamate receptor subtype 5 (mGlu₅), which is predominantly localized to postsynaptic sites. Allosteric modulators of mGlu₅ offer a unique opportunity to modulate glutamatergic neurotransmission selectively, thereby potentially ameliorating methamphetamine-induced disruptions. Negative allosteric modulators of mGlu₅ attenuate the effects of methamphetamine, including rewarding/reinforcing properties of the drug across animal models, and have shown promising effects in clinical trials for Anxiety Disorder and Major Depressive Disorder. Preclinical studies have also sparked great interest in mGlu₅ positive allosteric modulators, which exhibit antipsychotic and anxiolytic properties, and facilitate extinction learning when access to methamphetamine is removed, possibly via the amelioration of methamphetamine-induced cognitive deficits. Clinical research is now needed to elucidate the mechanisms underlying the mGlu₅ receptor-related effects of methamphetamine and the contributions of these effects to addictive behaviors. The growing array of mGlu₅ allosteric modulators provides excellent tools for this purpose and may offer the prospect of developing tailored and effective medications for Methamphetamine Use Disorder.

Glial cell diversity and methamphetamine-induced neuroinflammation in human cerebral organoids

Methamphetamine (METH) is a potent stimulant that induces a euphoric state but also causes cognitive impairment, neurotoxicity and neurodevelopmental deficits. Yet, the molecular mechanisms by which METH causes neurodevelopmental defects have remained elusive. Here we utilized human cerebral organoids and single-cell RNA sequencing (scRNA-seq) to study the effects of prenatal METH exposure on fetal brain development. We analyzed 20,758 cells from eight untreated and six METH-treated cerebral organoids and found that the organoids developed from embryonic stem cells contained a diverse array of glial and neuronal cell types. We further identified transcriptionally distinct populations of astrocytes and oligodendrocytes within cerebral organoids. Treatment of organoids with METH-induced marked changes in transcription in multiple cell types, including astrocytes and neural progenitor cells. METH also elicited novel astrocyte-specific gene expression networks regulating responses to cytokines, and inflammasome. Moreover, upregulation of immediate early genes, complement factors, apoptosis, and immune response genes suggests a neuroinflammatory program induced by METH regulating neural stem cell proliferation, differentiation, and cell death. Finally, we observed marked METH-induced changes in neuroinflammatory and cytokine gene expression at the RNA and protein levels. Our data suggest that human cerebral organoids represent a model system to study drug-induced neuroinflammation at single-cell resolution.

Inflammatory factors and amyloid β-induced microglial polarization promote inflammatory crosstalk with astrocytes

The immunological responses are a key pathological factor in Alzheimer's disease (AD). We hypothesized that microglial polarization alters microglia-astrocyte immune interactions in AD. M1 and M2 microglia were isolated from primary rat microglia and were confirmed to secrete pro-inflammatory and anti-inflammatory factors, respectively. Primary rat astrocytes were co-cultured with M1 or M2 microglial medium. M1 microglial medium increased astrocyte production of pro-inflammatory factors (interleukin [IL]-1β, tumor necrosis factor α and IL-6), while M2 microglial medium enhanced astrocyte production of anti-inflammatory factors (IL-4 and IL-10). To analyze the crosstalk between microglia and astrocytes after microglial polarization specifically in AD, we co-cultured astrocytes with medium from microglia treated with amyloid-β (Aβ) alone or in combination with other inflammatory substances. Aβ alone and Aβ combined with lipopolysaccharide/interferon-γ induced pro-inflammatory activity in M1 microglia and astrocytes, whereas IL-4/IL-13 inhibited Aβ-induced pro-inflammatory activity. Nuclear factor κB p65 was upregulated in M1 microglia and pro-inflammatory astrocytes, while Stat6 was upregulated in M2 microglia and anti-inflammatory astrocytes. These results provide direct evidence that microglial polarization governs communication between microglia and astrocytes, and that AD debris alters this crosstalk.

Complex Interaction between Resident Microbiota and Misfolded Proteins: Role in Neuroinflammation and Neurodegeneration

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and Creutzfeldt-Jakob disease (CJD) are brain conditions affecting millions of people worldwide. These diseases are associated with the presence of amyloid-β (Aβ), alpha synuclein (α-Syn) and prion protein (PrP) depositions in the brain, respectively, which lead to synaptic disconnection and subsequent progressive neuronal death. Although considerable progress has been made in elucidating the pathogenesis of these diseases, the specific mechanisms of their origins remain largely unknown. A body of research suggests a potential association between host microbiota, neuroinflammation and dementia, either directly due to bacterial brain invasion because of barrier leakage and production of toxins and inflammation, or indirectly by modulating the immune response. In the present review, we focus on the emerging topics of neuroinflammation and the association between components of the human microbiota and the deposition of Aβ, α-Syn and PrP in the brain. Special focus is given to gut and oral bacteria and biofilms and to the potential mechanisms associating microbiome dysbiosis and toxin production with neurodegeneration. The roles of neuroinflammation, protein misfolding and cellular mediators in membrane damage and increased permeability are also discussed.

Repurposing Fragile X Drugs to Inhibit SARS-CoV-2 Viral Reproduction

The COVID-19 pandemic is a global health crisis that requires the application of interdisciplinary research to address numerous knowledge gaps including molecular strategies to prevent viral reproduction in affected individuals. In response to the Frontiers Research Topic, "Coronavirus disease (COVID-19): Pathophysiology, Epidemiology, Clinical Management, and Public Health Response," this Hypothesis article proposes a novel therapeutic strategy to repurpose metabotropic glutamate 5 receptor (mGluR₅) inhibitors to interfere with viral hijacking of the host protein synthesis machinery. We review pertinent background on SARS-CoV-2, fragile X syndrome (FXS) and metabotropic glutamate receptor 5 (mGluR₅) and provide a mechanistic-based hypothesis and preliminary data to support testing mGluR₅ inhibitors in COVID-19 research.

Hypoxic colorectal cancer cells promote metastasis of normoxic cancer cells depending on IL-8/p65 signaling pathway

Tumor heterogeneity is an important feature of malignant tumors, and cell subpopulations may positively interact to facilitate tumor progression. Studies have shown that hypoxic cancer cells possess enhanced metastatic capacity. However, it is still unclear whether hypoxic cancer cells may promote the metastasis of normoxic cells, which have greater access to the blood circulation. When cocultured with hypoxic CRC cells or treated with hypoxic CRC cell-derived CM, normoxic CRC cells possessed increased metastatic capacity. Furthermore, hypoxic CRC cell-derived CM was enriched in interleukin 8. Hypoxic CRC cell-derived CM and recombinant human IL-8 both enhanced the metastatic capacity of normoxic cells by increasing the phosphorylation of p65 and then by inducing epithelial-mesenchymal transition. Knockdown of IL-8 in hypoxic CRC cells or the use of an anti-IL-8 antibody attenuated the CM- or rhIL-8-induced prometastatic capacity of normoxic CRC cells. Inhibition or knockdown of p65 abrogated IL-8-induced prometastatic effects. Most importantly, hypoxia-treated xenograft tumors enhanced the metastasis of normoxic CRC cells. Hypoxic CRC cell-derived IL-8 promotes the metastatic capacity of normoxic cells, and novel therapies targeting the positive interactions between hypoxic and normoxic cells should be developed.

The association between interleukin-8 levels and the development of withdrawal symptoms during methamphetamine abstinence

OBJECTIVE

Withdrawal symptoms are common during methamphetamine (METH) abstinence. This study aimed to explore the association between serum interleukins and withdrawal symptoms during METH abstinence.

METHODS

This study recruited 120 METH users, and 94 of them completed the 2-week follow-up. Serum interleukin-1β, 6,8,10 were tested at admission. Withdrawal symptoms were assessed by the Methamphetamine Withdrawal Questionnaire (MAWQ).

RESULTS

Serum IL-8 levels were positively correlated with MAWQ scores at the 2-week endpoint (r = .257, p = .013). The variation of the MAWQ scores during the 2-week follow-up was negatively correlated with serum IL-8 levels at admission (r = -.249, p = .026). Serum IL-8 levels remained associated with the severity of METH withdrawal symptoms (β = .363, p = .023), after adjusting for potential confounders.

LIMITATIONS

This study did not include normal controls. Most patients were male and cigarette smokers. Patients were only followed up for 2 weeks, and their toxicology data were not collected. Interleukins were only measured at admission, and were tested in serum, not in the cerebrospinal fluid.

CONCLUSIONS

Our study demonstrated that higher serum IL-8 levels may predict more severe withdrawal symptoms at 2 weeks after METH abstinence.

Effects of Drugs of Abuse on the Blood-Brain Barrier: A Brief Overview

The use of psychostimulants and alcohol disrupts blood-brain barrier (BBB) integrity, resulting in alterations to cellular function, and contributes to neurotoxicity. The BBB is the critical boundary of the central nervous system (CNS) where it maintains intracellular homeostasis and facilitates communication with the peripheral circulation. The BBB is regulated by tight junction (TJ) proteins that closely interact with endothelial cells (EC). The complex TJ protein network consists of transmembrane proteins, including claudins, occludins, and junction adhesion molecules (JAM), as well as cytoskeleton connected scaffolding proteins, zonula occludentes (ZO-1, 2, and 3). The use of psychostimulants and alcohol is known to affect the CNS and is implicated in various neurological disorders through neurotoxicity that partly results from increased BBB permeability. The present mini review primarily focuses on BBB structure and permeability. Moreover, we assess TJ protein and cytoskeletal changes induced by cocaine, methamphetamine, morphine, heroin, nicotine, and alcohol. These changes promote glial activation, enzyme potentiation, and BBB remodeling, which affect neuroinflammatory pathways. Although the effect of drugs of abuse on BBB integrity and the underlying mechanisms are well studied, the present review enhances the understanding of the underlying mechanisms through which substance abuse disorders cause BBB dysfunction.

Enhanced Akt/GSK-3β/CREB signaling mediates the anti-inflammatory actions of mGluR5 positive allosteric modulators in microglia and following traumatic brain injury in male mice

We have previously shown that treatment with a mGluR5 positive allosteric modulator (PAM) is neuroprotective after experimental traumatic brain injury (TBI), limiting post-traumatic neuroinflammation by reducing pro-inflammatory microglial activation and promoting anti-inflammatory and neuroprotective responses. However, the specific molecular mechanisms governing this anti-inflammatory shift in microglia remain unknown. Here we show that the mGluR5 PAM, VU0360172 (VuPAM), regulates microglial inflammatory responses through activation of Akt, resulting in the inhibition of GSK-3β. GSK-3β regulates the phosphorylation of CREB, thereby controlling the expression of inflammation-related genes and microglial plasticity. The anti-inflammatory action of VuPAM in microglia is reversed by inhibiting Akt/GSK-3β/CREB signaling. Using a well-characterized TBI model and CX3CR1^gfp/+ mice to visualize microglia in vivo, we demonstrate that VuPAM enhances Akt/GSK-3β/CREB signaling in the injured cortex, as well as anti-inflammatory microglial markers. Furthermore, in situ analysis revealed that GFP + microglia in the cortex of VuPAM-treated TBI mice co-express pCREB and the anti-inflammatory microglial phenotype marker YM1. Taken together, our data show that VuPAM decreases pro-inflammatory microglial activation by modulating Akt/GSK-3β/CREB signaling. These findings serve to clarify the potential neuroprotective mechanisms of mGluR5 PAM treatment after TBI, and suggest novel therapeutic targets for post-traumatic neuroinflammation. Cover Image for this issue: https://doi.org/10.1111/jnc.15048.

The Relationship Between Serum Cytokine Levels and the Degree of Psychosis and Cognitive Impairment in Patients With Methamphetamine-Associated Psychosis in Chinese Patients

Background: Cytokine levels can be changed in methamphetamine (METH) use disorders (MUDs) and primary psychosis. The present study assessed serum levels of some kinds of interleukins (ILs) in METH-associated psychosis (MAP) and their relationships with psychotic symptoms and cognitive dysfunction. Methods: Serum IL-2R, IL-6, IL-8, and IL-10 levels were examined by chemiluminescence assays in MAP patients (n = 119) and healthy controls (n = 108). The Positive and Negative Syndrome Scale (PANSS) and Montreal Cognitive Assessment (MOCA) were administered. Results: Serum levels of IL-6 and IL-8 were significantly increased in MAP patients (all p < 0.05). There was a negative relationship between IL-2R levels and PANSS positive (P) subscale scores (r = -0.193, p = 0.035). IL-6, IL-8 and IL-10 levels were all negatively correlated with the naming, delayed recall and orientation subscores on the MOCA (r = -0.209, p = 0.022; r = -0.245, p = 0.007; r = -0.505, p < 0.001, respectively). Conclusions: Our results indicate that immune disturbances are related to MAP and that IL-2R, IL-6, IL-8, and IL-10 are associated with the severity of psychotic symptoms and cognitive function impairment.

Angiotensin II modulates amphetamine-induced glial and brain vascular responses, and attention deficit via angiotensin type 1 receptor: Evidence from brain regional sensitivity to amphetamine

Amphetamine-induced neuroadaptations involve vascular damage, neuroinflammation, a hypo-functioning prefrontal cortex (PFC), and cognitive alterations. Brain angiotensin II, through angiotensin type 1 receptor (AT₁ -R), mediates oxidative/inflammatory responses, promoting endothelial dysfunction, neuronal oxidative damage and glial reactivity. The present work aims to unmask the role of AT₁ -R in the development of amphetamine-induced changes over glial and vascular components within PFC and hippocampus. Attention deficit was evaluated as a behavioral neuroadaptation induced by amphetamine. Brain microvessels were isolated to further evaluate vascular alterations after amphetamine exposure. Male Wistar rats were administered with AT₁ -R antagonist, candesartan, followed by repeated amphetamine. After one week drug-off period, animals received a saline or amphetamine challenge and were evaluated in behavioral tests. Afterward, their brains were processed for cresyl violet staining, CD11b (microglia marker), GFAP (astrocyte marker) or von Willebrand factor (vascular marker) immunohistochemistry, and oxidative/cellular stress determinations in brain microvessels. Statistical analysis was performed by using factorial ANOVA followed by Bonferroni or Tukey tests. Repeated amphetamine administration increased astroglial and microglial markers immunoreactivity, increased apoptotic cells, and promoted vascular network rearrangement at the PFC concomitantly with an attention deficit. Although the amphetamine challenge improved the attentional performance, it triggers detrimental effects probably because of the exacerbated malondialdehyde levels and increased heat shock protein 70 expression in microvessels. All observed amphetamine-induced alterations were prevented by the AT₁ -R blockade. Our results support the AT₁ -R involvement in the development of oxidative/inflammatory conditions triggered by amphetamine exposure, affecting cortical areas and increasing vascular susceptibility to future challenges.

Family C G-Protein-Coupled Receptors in Alzheimer's Disease and Therapeutic Implications

Alzheimer’s disease (AD), particularly its sporadic or late-onset form (SAD/LOAD), is the most prevalent (96–98% of cases) neurodegenerative dementia in aged people. AD’s neuropathology hallmarks are intrabrain accumulation of amyloid-β peptides (Aβs) and of hyperphosphorylated Tau (p-Tau) proteins, diffuse neuroinflammation, and progressive death of neurons and oligodendrocytes. Mounting evidences suggest that family C G-protein-coupled receptors (GPCRs), which include γ-aminobutyric acid B receptors (GABA_BRs), metabotropic glutamate receptors (mGluR1-8), and the calcium-sensing receptor (CaSR), are involved in many neurotransmitter systems that dysfunction in AD. This review updates the available knowledge about the roles of GPCRs, particularly but not exclusively those expressed by brain astrocytes, in SAD/LOAD onset and progression, taking stock of their respective mechanisms of action and of their potential as anti-AD therapeutic targets. In particular, GABA_BRs prevent Aβs synthesis and neuronal hyperexcitability and group I mGluRs play important pathogenetic roles in transgenic AD-model animals. Moreover, the specific binding of Aβs to the CaSRs of human cortical astrocytes and neurons cultured in vitro engenders a pathological signaling that crucially promotes the surplus synthesis and release of Aβs and hyperphosphorylated Tau proteins, and also of nitric oxide, vascular endothelial growth factor-A, and proinflammatory agents. Concurrently, Aβs•CaSR signaling hinders the release of soluble (s)APP-α peptide, a neurotrophic agent and GABA_BR1a agonist. Altogether these effects progressively kill human cortical neurons in vitro and likely also in vivo. Several CaSR’s negative allosteric modulators suppress all the noxious effects elicited by Aβs•CaSR signaling in human cortical astrocytes and neurons thus safeguarding neurons’ viability in vitro and raising hopes about their potential therapeutic benefits in AD patients. Further basic and clinical investigations on these hot topics are needed taking always heed that activation of the several brain family C GPCRs may elicit divergent upshots according to the models studied.

Combination of acute intravenous methamphetamine injection and LPS challenge facilitate leukocyte infiltration into the central nervous system of C57BL/6 mice

Methamphetamine (METH) is a stimulant of the central nervous system (CNS) that causes behavioral changes in users. METH is slowly cleared from brain tissue and its chronic use is neurotoxic. METH also alters the cellular and chemical components of inflammation. However, little is known about the effect of a single intravenous dose of METH followed by bacterial lipopolysaccharide (LPS) injection on cellular infiltration and cytokine release in brain tissue. Using a murine model of acute METH administration and flow cytometry, we found that combination of METH and LPS stimulate the infiltration of macrophages (F4/80⁺cells) and neutrophils (Ly-6G⁺cells) into the CNS. Histological sections of the brainstem of METH-treated and LPS-challenged C57BL/6 mice demonstrated considerable leukocyte infiltration relative to untreated, LPS, and METH groups. Moreover, rodents treated with LPS alone or combined with METH showed elevated levels of pro-inflammatory cytokines mRNA in brain tissue. Our observations are important because recognizing neuroinflammatory changes after acute METH administration might help us to understand METH-induced neurotoxicity in users.

Neuroinflammation in addiction: A review of neuroimaging studies and potential immunotherapies

Addiction is a worldwide public health problem and this article reviews scientific advances in identifying the role of neuroinflammation in the genesis, maintenance, and treatment of substance use disorders. With an emphasis on neuroimaging techniques, this review examines human studies of addiction using positron emission tomography to identify binding of translocator protein (TSPO), which is upregulated in reactive glial cells and activated microglia during pathological states. High TSPO levels have been shown in methamphetamine use but exhibits variable patterns in cocaine use. Alcohol and nicotine use, however, are associated with lower TSPO levels. We discuss how mechanistic differences at the neurotransmitter and circuit level in the neural effects of these agents and subsequent immune response may explain these observations. Finally, we review the potential of anti-inflammatory drugs, including ibudilast, minocycline, and pioglitazone, to ameliorate the behavioral and cognitive consequences of addiction.

A novel neurotherapeutic for multiple sclerosis, ischemic injury, methamphetamine addiction, and traumatic brain injury

Neurovascular, autoimmune, and traumatic injuries of the central nervous system (CNS) all have in common an initial acute inflammatory response mediated by influx across the blood-brain barrier of activated mononuclear cells followed by chronic and often progressive disability. Although some anti-inflammatory therapies can reduce cellular infiltration into the initial lesions, there are essentially no effective treatments for the progressive phase. We here review the successful treatment of animal models for four separate neuroinflammatory and neurodegenerative CNS conditions using a single partial MHC class II construct called DRa1-hMOG-35-55 or its newest iteration, DRa1(L50Q)-hMOG-35-55 (DRhQ) that can be administered without a need for class II tissue type matching due to the conserved DRα1 moiety of the drug. These constructs antagonize the cognate TCR and bind with high affinity to their cell-bound CD74 receptor on macrophages and dendritic cells, thereby competitively inhibiting downstream signaling and pro-inflammatory effects of macrophage migration inhibitory factor (MIF) and its homolog, d-dopachrome tautomerase (D-DT=MIF-2) that bind to identical residues of CD74 leading to progressive disease. These effects suggest the existence of a common pathogenic mechanism involving a chemokine-driven influx of activated monocytes into the CNS tissue that can be reversed by parenteral injection of the DRa1-MOG-35-55 constructs that also induce anti-inflammatory macrophages and microglia within the CNS. Due to their ability to block this common pathway, these novel drugs appear to be prime candidates for therapy of a wide range of neuroinflammatory and neurodegenerative CNS conditions.

Metabotropic Glutamate Receptors in Glial Cells: A New Potential Target for Neuroprotection?

Neurodegenerative disorders are characterized by excitotoxicity and neuroinflammation that finally lead to slow neuronal degeneration and death. Although neurons are the principal target, glial cells are important players as they contribute by either exacerbating or dampening the events that lead to neuroinflammation and neuronal damage. A dysfunction of the glutamatergic system is a common event in the pathophysiology of these diseases. Metabotropic glutamate (mGlu) receptors belong to a large family of G protein-coupled receptors largely expressed in neurons as well as in glial cells. They often appear overexpressed in areas involved in neurodegeneration, where they can modulate glutamatergic transmission. Of note, mGlu receptor upregulation may involve microglia or, even more frequently, astrocytes, where their activation causes release of factors potentially able to influence neuronal death. The expression of mGlu receptors has been also reported on oligodendrocytes, a glial cell type specifically involved in the development of multiple sclerosis. Here we will provide a general overview on the possible involvement of mGlu receptors expressed on glial cells in the pathogenesis of different neurodegenerative disorders and the potential use of subtype-selective mGlu receptor ligands as candidate drugs for the treatment of neurodegenerative disorders. Negative allosteric modulators (NAM) of mGlu5 receptors might represent a relevant pharmacological tool to develop new neuroprotective strategies in these diseases. Recent evidence suggests that targeting astrocytes and microglia with positive allosteric modulators (PAM) of mGlu3 receptor or oligodendrocytes with mGlu4 PAMS might represent novel pharmacological approaches for the treatment of neurodegenerative disorders.

Differential effect of the DRD3 genotype on inflammatory cytokine responses during abstinence in amphetamine-dependent women

Amphetamine exposure impacts on innate and adaptive immunity and DRD3 may modulate the effect of amphetamine on the immune response. We assessed the immune-cytokine markers in 72 female patients with amphetamine dependence (AD) at baseline and after 4-week drug abstinence and in 51 healthy women. Multiplex magnetic bead assay was used to measure the plasma cytokine expression level simultaneously in all participants and DRD3 rs6280 polymorphism was genotyped in patients. We demonstrated an increase of the T helper 1 (Th1) cytokines (IL-2), Th2 cytokines (IL-4, IL-5, IL-6 and IL-10) and other cytokines (IL-1β) in the entire AD cohort. A similar cytokine pattern, along with a significantly decreased IL-8 and IL-10 levels was observed after 4-week abstinence. Among AD patients with DRD3 rs6280 TT genotype, the cytokine expression profile was consistent with total AD cohort at baseline and revealed a significant down-regulated plasma level of the Th1, Th2, and other cytokines except for IL-6 after 4-week abstinence. In AD group with DRD3 rs6280 C allele carrier, we found IL-2 level was significantly higher than healthy controls at baseline and remained higher, accompanied with a borderline increase in IL-4, IL-6 and IL-1β levels after 4-week abstinence. Our results suggest that chronic use of amphetamine increased both pro- and anti-inflammatory cytokines in AD patients, indicating the immune imbalance that may persist for 4 weeks or more. Besides, DRD3 rs6280 TT genotype may be associated with favorable recovery in general inflammatory cytokines during period of abstinence.