Modulation of cocaine-induced activity by intracerebral administration of CXCL12

Cyanidin prevents MDPV withdrawal-induced anxiety-like effects and dysregulation of cytokine systems in rats

Psychostimulant exposure and withdrawal cause neuroimmune dysregulation and anxiety that contributes to dependence and relapse. Here, we tested the hypothesis that withdrawal from the synthetic cathinone MDPV (methylenedioxypyrovalerone) produces anxiety-like effects and enhanced levels of mesocorticolimbic cytokines that are inhibited by cyanidin, an anti-inflammatory flavonoid and nonselective blocker of IL-17A signaling. For comparison, we tested effects on glutamate transporter systems that are also dysregulated during psychostimulant free period. Rats injected for 9 d with MDPV (1 mg/kg, IP) or saline were pretreated daily with cyanidin (0.5 mg/kg, IP) or saline, followed by behavioral testing on the elevated zero maze (EZM) 72 h after the last MDPV injection. MDPV withdrawal caused a reduction in time spent on the open arm of the EZM that was prevented by cyanidin. Cyanidin itself did not affect locomotor activity or time spent on the open arm, or cause aversive or rewarding effects in place preference experiments. MDPV withdrawal caused enhancement of cytokine levels (IL-17A, IL-1β, IL-6, TNF=α, IL-10, and CCL2) in the ventral tegmental area, but not amygdala, nucleus accumbens, or prefrontal cortex, that was prevented by cyanidin. During MDPV withdrawal, mRNA levels of glutamate aspartate transporter (GLAST) and glutamate transporter subtype 1 (GLT-1) in the amygdala were also elevated but normalized by cyanidin treatment. These results show that MDPV withdrawal induced anxiety, and brain-region specific dysregulation of cytokine and glutamate systems, that are both prevented by cyanidin, thus identifying cyanidin for further investigation in the context of psychostimulant dependence and relapse.

The Inflammatory Signals Associated with Psychosis: Impact of Comorbid Drug Abuse

Psychosis and substance use disorders are two diagnostic categories whose association has been studied for decades. In addition, both psychosis spectrum disorders and drug abuse have recently been linked to multiple pro-inflammatory changes in the central nervous system. We have carried out a narrative review of the literature through a holistic approach. We used PubMed as our search engine. We included in the review all relevant studies looking at pro-inflammatory changes in psychotic disorders and substance use disorders. We found that there are multiple studies that relate various pro-inflammatory lipids and proteins with psychosis and substance use disorders, with an overlap between the two. The main findings involve inflammatory mediators such as cytokines, chemokines, endocannabinoids, eicosanoids, lysophospholipds and/or bacterial products. Many of these findings are present in different phases of psychosis and in substance use disorders such as cannabis, cocaine, methamphetamines, alcohol and nicotine. Psychosis and substance use disorders may have a common origin in an abnormal neurodevelopment caused, among other factors, by a neuroinflammatory process. A possible convergent pathway is that which interrelates the transcriptional factors NFκB and PPARγ. This may have future clinical implications.

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.

Vascular Endothelial Growth Factor as a Potential Biomarker of Neuroinflammation and Frontal Cognitive Impairment in Patients with Alcohol Use Disorder

(1) Background: Alcohol Use Disorder (AUD) is associated with functional disruption of several brain structures that may trigger cognitive dysfunction. One of the mechanisms of alcohol-associated cognitive impairment has been proposed to arise from its direct impact on the immune system, which culminates in the release of cytokines and chemokines which can eventually reach the brain. Alcohol can also disrupt the blood–brain barrier, facilitating the penetration of pro-inflammatory molecules throughout vascular endothelial growth factor A (VEGFA). Thus, alcohol-induced alterations in chemokines and VEGFA might contribute to the neuroinflammation and cognitive impairment associated with AUD. (2) Methods: The present cross-sectional study investigates whether patients with AUD (n = 86) present cognitive disability associated to alterations in plasma concentration of SDF-1, fractalkine, eotaxin, MCP-1, MIP-1α and VEGFA when compared to control subjects (n = 51). (3) Results: The analysis indicated that SDF-1 and MCP-1 concentrations were higher in AUD patients than in controls. Concentrations of VEGFA were higher in AUD patients with severe frontal deficits, and the score of frontal lobe functions was negatively correlated with VEGFA and fractalkine. Acute alcohol effects on VEGFA plasma levels in healthy volunteers demonstrated the induction of VEGFA release by heavy alcohol drinking. VEGFA was positively correlated with pro-inflammatory chemokines in AUD patients with frontal cognitive impairment. (4) Conclusions: we propose VEGFA/chemokine monitoring as biomarkers of potential cognitive impairment in AUD patients.

Paradoxical anxiolytic effect of the 'bath salt' synthetic cathinone MDPV during early abstinence is inhibited by a chemokine CXCR4 or CCR5 receptor antagonist

Chemokine CXCR4 and CCR5 receptors are best known as HIV co-entry receptors, but evidence that CXCR4 or CCR5 blockade reduces rewarding and locomotor-stimulant effects of psychostimulants in rats suggests a role in psychostimulant use disorders. We investigated the impact of CXCR4 or CCR5 receptor antagonism on anxiety-related effects of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV) in the elevated zero-maze (EZM) assay. Rats exposed to a 4-day MDPV binge dosing paradigm and tested 24 or 72 h post-treatment spent more time in the open compartment at the 24-h time point but less time at the 72-h post-binge time point. Daily administration of AMD 3100, a CXCR4 antagonist (10 mg/kg), or maraviroc, a CCR5 antagonist (2.5 mg/kg), during MDPV treatment inhibited the MDPV-induced increase in time spent in the open compartment. Neither antagonist affected the MDPV-induced reduction in time spent in the open compartment at the 72-h post-binge time point. Cocaine, administered in the same paradigm as MDPV, did not increase time spent in the open compartment 24-h post-binge, suggesting specificity to MDPV. The present results identify a surprising anxiolytic-like effect of MDPV 24 h after cessation of repeated exposure that is sensitive to chemokine CXCR4 and CCR5 receptor activity.

Trefoil Factor Family Member 2: From a High-Fat-Induced Gene to a Potential Obesity Therapy Target

Obesity has its epidemiological patterns continuously increasing. With controlling both diet and exercise being the main approaches to manage the energy metabolism balance, a high-fat (HF) diet is of particular importance. Indeed, lipids have a low satiety potential but a high caloric density. Thus, focusing on pharmacologically targetable pathways remains an approach with promising therapeutic potential. Within this context, trefoil factor family member 2 (Tff2) has been characterized as specifically induced by HF diet rather than low-fat diet. TFF2 has also been linked to diverse neurological mechanisms and metabolic patterns suggesting its role in energy balance. The hypothesis is that TFF2 would be a HF diet-induced signal that regulates metabolism with a focus on lipids. Within this review, we put the spotlight on key findings highlighting this line of thought. Importantly, the hypothetical mechanisms pointed highlight TFF2 as an important contributor to obesity development via increasing lipids intestinal absorption and anabolism. Therefore, an outlook for future experimental activities and evaluation of the therapeutic potential of TFF2 inhibition is given. Indeed, its knockdown or downregulation would contribute to an antiobesity phenotype. We believe this work represents an addition to our understanding of the lipidic molecular implications in obesity, which will contribute to develop therapies aiming to manage the lipidic metabolic pathways including the absorption, storage and metabolism via targeting TFF2-related pathways. We briefly discuss important relevant concepts for both basic and clinical researchers.

Chemokines, cytokines and substance use disorders

Efficacious pharmacotherapies for the treatment of substance use disorders need to be expanded and improved. Non-neuronal cells, particularly astrocytes and microglia, have emerged as therapeutic targets for the development of pharmacotherapies to treat dependence and relapse that accompanies chronic drug use. Cytokines and chemokines are neuroimmune factors expressed in neurons, astrocytes, and microglia that demonstrate promising clinical utility as therapeutic targets for substance use disorders. In this review, we describe a role for cytokines and chemokines in the rewarding and reinforcing effects of alcohol, opioids, and psychostimulants. We also discuss emerging cytokine- and chemokine-based therapeutic strategies that differ from conventional strategies directed toward transporters and receptors within the dopamine, glutamate, GABA, serotonin, and GABA systems.

CXCR4 inhibition with AMD3100 attenuates amphetamine induced locomotor activity in adolescent Long Evans male rats

Adolescent psychostimulant abuse has been on the rise over the past decade. This trend has demonstrable ramifications on adolescent behavior and brain morphology, increasing risk for development of addiction during adolescence and in later adulthood. Neuroimmune substrates are implicated in the etiology of substance use disorders. To add to this body of work, the current study was developed to explore the role of a chemokine receptor, CXC Chemokine Receptor 4 (CXCR4), in the development of amphetamine (AMPH) sensitization. We targeted CXCR4 as it is implicated in developmental processes, dopaminergic transmission, neuroimmune responses, and the potentiation of psychostimulant abuse pathology. To evaluate the role of CXCR4 activity on the development of AMPH sensitization, a CXCR4 antagonist (Plerixafor; AMD3100) was administered to rats as a pretreatment variable. Specifically, adolescent Long Evans male rats (N = 37) were divided into four groups: (1) AMD3100 (IP, 4.0 mg/kg) + AMPH (IP, 4.0 mg/kg), (2) saline (SAL; 0.9% NaCl) + AMPH, (3) AMD3100 + SAL, and (4) SAL + SAL. Animals were first habituated to locomotor activity (LMA) chambers, then injected with a pretreatment drug (AMD3100 or SAL) followed by AMPH or SAL every other for four days. After a one-week withdrawal period, all animals were administered a low challenge dose of AMPH (IP, 1.0 mg/kg). AMPH-injected rats displayed significantly more locomotor activity compared to controls across all testing days. CXCR4 antagonism significantly attenuated AMPH-induced locomotor activity. On challenge day, AMD3100 pre-treated animals exhibited diminutive AMPH-induced locomotor activity compared to SAL pre-treated animals. Postmortem analyses of brain tissue revealed elevated CXCR4 protein levels in the striatum of all experimental groups. Our results implicate CXCR4 signaling in the development of AMPH sensitization and may represent an important therapeutic target for future research in psychostimulant abuse.

Interactions of neuroimmune signaling and glutamate plasticity in addiction

Chronic use of drugs of abuse affects neuroimmune signaling; however, there are still many open questions regarding the interactions between neuroimmune mechanisms and substance use disorders (SUDs). Further, chronic use of drugs of abuse can induce glutamatergic changes in the brain, but the relationship between the glutamate system and neuroimmune signaling in addiction is not well understood. Therefore, the purpose of this review is to bring into focus the role of neuroimmune signaling and its interactions with the glutamate system following chronic drug use, and how this may guide pharmacotherapeutic treatment strategies for SUDs. In this review, we first describe neuroimmune mechanisms that may be linked to aberrant glutamate signaling in addiction. We focus specifically on the nuclear factor-kappa B (NF-κB) pathway, a potentially important neuroimmune mechanism that may be a key player in driving drug-seeking behavior. We highlight the importance of astroglial-microglial crosstalk, and how this interacts with known glutamatergic dysregulations in addiction. Then, we describe the importance of studying non-neuronal cells with unprecedented precision because understanding structure-function relationships in these cells is critical in understanding their role in addiction neurobiology. Here we propose a working model of neuroimmune-glutamate interactions that underlie drug use motivation, which we argue may aid strategies for small molecule drug development to treat substance use disorders. Together, the synthesis of this review shows that interactions between glutamate and neuroimmune signaling may play an important and understudied role in addiction processes and may be critical in developing more efficacious pharmacotherapies to treat SUDs.

Chemokine CCR5 and cocaine interactions in the brain: Cocaine enhances mesolimbic CCR5 mRNA levels and produces place preference and locomotor activation that are reduced by a CCR5 antagonist

C-C chemokine receptor type 5, also known as CCR5 or CD195, is best known as a viral co-receptor that facilitates entry of HIV into cells. Evidence that CCR5 knockout mice display fewer dopamine neurons, lower striatal dopamine levels, and reduced locomotor activation compared to wild types also suggest a link between CCR5 receptors and cocaine dependence. Here, we tested the hypothesis using male Sprague-Dawley rats that cocaine-induced locomotor activation and conditioned place preference (CPP) are inhibited by a FDA-approved CCR5 antagonist (maraviroc), and that CCR5 gene expression in mesolimbic substrates is enhanced by repeated cocaine exposure. Pretreatment with maraviroc (1, 2.5, 5 mg/kg, IP) reduced hyperlocomotion induced by acute cocaine (10 mg/kg) without affecting spontaneous locomotor activity. For CPP experiments, rats conditioned with cocaine (10 mg/kg × 4 days, IP) were injected with maraviroc (1, 2.5, 5 mg/kg, IP) before each injection of cocaine. Maraviroc dose-dependently inhibited development of cocaine CPP, with a dose of 5 mg/kg producing a significant reduction. In rats treated repeatedly with cocaine (10 mg/kg × 4 days, IP), CCR5 gene expression was upregulated in the nucleus accumbens and ventral tegmental area but mRNA levels of CCR5 ligands (i.e., CCL3, CCL4 and CCL5) were not affected. Our results suggest that mesolimbic CCR5 receptors are dysregulated by cocaine exposure and, similar to CXCR4 and CCR2 receptors, influence behavioral effects related to the abuse liability of cocaine.

Neuroimmune mechanisms of psychostimulant and opioid use disorders

Substance use disorders are global health problems with few effective treatment options. Unfortunately, most potential pharmacological treatments are hindered by abuse potential of their own, limited efficacy, or adverse side effects. As a consequence, there is a pressing need for the development of addiction treatments with limited abuse potential and fewer off target effects. Given the difficulties in developing new pharmacotherapies for substance use disorders, there has been growing interest in medications that act on non-traditional targets. Recent evidence suggests a role for dysregulated immune signaling in the pathophysiology of multiple psychiatric diseases. While there is evidence that immune responses in the periphery and the central nervous system are altered by exposure to drugs of abuse, the contributions of neuroimmune interactions to addictive behaviors are just beginning to be appreciated. In this review, we discuss the data on immunological changes seen in clinical populations with substance use disorders, as well as in translational animal models of addiction. Importantly, we highlight those mechanistic findings showing causal roles for central or peripheral immune mediators in substance use disorder and appropriate animal models. Based on the literature reviewed here, it is clear that brain-immune system interactions in substance use disorders are much more complex and important than previously understood. While much work remains to be done, there are tremendous potential therapeutic implications for immunomodulatory treatments in substance use disorders.

Inflammatory mediators and dual depression: Potential biomarkers in plasma of primary and substance-induced major depression in cocaine and alcohol use disorders

Major depressive disorder (MDD) is the most prevalent comorbid mental disorder among people with substance use disorders. The MDD can be both primary and substance-induced and its accurate diagnosis represents a challenge for clinical practice and treatment response. Recent studies reported alterations in the circulating expression of inflammatory mediators in patients with psychiatric disorders, including those related to substance use. The aim of the study was to explore TNF-α, IL-1β, CXCL12, CCL2, CCL11 (eotaxin-1) and CX3CL1 (fractalkine) as potential biomarkers to identify comorbid MDD and to distinguish primary MDD from substance-induced MDD in patients with substance disorders. Patients diagnosed with cocaine (CUD, n = 64) or alcohol (AUD, n = 65) use disorders with/without MDD were recruited from outpatient treatment programs [CUD/non-MDD (n = 31); CUD/primary MDD (n = 18); CUD/cocaine-induced MDD (N = 15); AUD/non-MDD (n = 27); AUD/primary MDD (n = 16) and AUD/alcohol-induced MDD (n = 22)]. Sixty-two healthy subjects were also recruited as control group. Substance and mental disorders were assessed according to "Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision" (DSM-IV-TR) and a blood sample was collected for determinations in the plasma. The cocaine group showed lower TNF-α (p<0.05) and CCL11 (p<0.05), and higher IL-1β (p<0.01) concentrations than the control group. In contrast, the alcohol group showed higher IL-1β (p<0.01) and lower CXCL12 (p<0.01) concentrations than the control group. Regarding MDD, we only observed alterations in the cocaine group. Thus, CUD/MDD patients showed lower IL-1β (p<0.05), CXCL12 (p<0.05) and CCL11 (p<0.05), and higher CXC3CL1 (p<0.05) concentrations than CUD/non-MDD patients. Moreover, while CUD/primary MDD patients showed higher CCL11 (p<0.01) concentrations than both CUD/non-MDD and CUD/cocaine-induced MDD patients, CUD/cocaine-induced MDD patients showed lower CXCL12 (p<0.05) concentrations than CUD/non-MDD patients. Finally, a logistic regression model in the cocaine group identified CXCL12, CCL11 and sex to distinguish primary MDD from cocaine-induced MDD providing a high discriminatory power. The present data suggest an association between changes in inflammatory mediators and the diagnosis of primary and substance-induced MDD, namely in CUD patients.

Bath salts and polyconsumption: in search of drug-drug interactions

BACKGROUND AND RATIONALE

Polydrug use is a widespread phenomenon, especially among adolescents and young adults. Synthetic cathinones are frequently consumed in combination with other drugs of abuse. However, there is very little information regarding the consequences of this specific consumption pattern.

OBJECTIVES

The aim of this review is to introduce this topic and highlight the gaps in the existing literature. In three different sections, we focus on specific interactions of synthetic cathinones with alcohol, cannabinoids, and the stimulants nicotine and cocaine. We then dedicate a section to the existence of sex and gender differences in the effects of synthetic cathinones and the long-term psychophysiological consequences of adolescent and prenatal exposure to these drugs.

MAJOR FINDINGS

Epidemiological studies, case reports, and results obtained in animal models point to the existence of pharmacological and pharmacokinetic interactions between synthetic cathinones and other drugs of abuse. This pattern of polyconsumption can cause the potentiation of negative effects, and the dissociation between objective and subjective effects can increase the combined use of the drugs and the risk of toxicity leading to serious health problems. Certain animal studies indicate a higher vulnerability and effect of cathinones in females. In humans, most of the users are men and case reports show long-term psychotic symptoms after repeated use.

CONCLUSIONS

The co-use of synthetic cathinones and the other drugs of abuse analyzed indicates potentiation of diverse effects including dependence and addiction, neurotoxicity, and impaired cognition and emotional responses. The motivations for and effects of synthetic cathinone use appear to be influenced by sex/gender. The long-term consequences of their use by adolescents and pregnant women deserve further investigation.

Chemokines and 'bath salts': CXCR4 receptor antagonist reduces rewarding and locomotor-stimulant effects of the designer cathinone MDPV in rats

BACKGROUND AND PURPOSE

Little is known about how chemokine systems influence the behavioral effects of designer cathinones and psychostimulants. The chemokine CXCL12 and its principal receptor target, CXCR4, are of particular interest because CXCR4 activation enhances mesolimbic dopamine output that facilitates psychostimulant reward, reinforcement, and locomotor activation. Repeated cocaine enhances CXCL12 gene expression in the midbrain and produces conditioned place preference (CPP) that is inhibited by a CXCR4 antagonist. Yet, interactions between chemokines and synthetic cathinones remain elusive.

METHODS

We tested the hypothesis that an FDA-approved CXCR4 antagonist (AMD3100) inhibits MDPV-induced reward, locomotor activation and positive affective state in rats using a triad of behavioral assays (CPP, open field, and 50-kHz ultrasonic vocalizations [USVs]).

KEY RESULTS

AMD3100 (1, 2.5, 5, 10 mg/kg, ip) significantly reduced MDPV (2 mg/kg, ip)-evoked hyper-locomotion in a dose-related manner. AMD3100 (1, 5, 10 mg/kg) administered during CPP conditioning caused a significant, dose-dependent reduction of MDPV (2 mg/kg x 4 days) place preference. MDPV injection elicited significantly greater 50 kHz USVs in vehicle-pretreated rats but not in AMD3100-pretreated rats.

CONCLUSION AND IMPLICATION

A CXCR4 antagonist reduced the rewarding and locomotor-activating effects of MDPV. Our results identify the existence of chemokine/cathinone interactions and suggest the rewarding and stimulant effects of MDPV, similar to cocaine, require an active CXCL12/CXCR4 system.

SDF1-CXCR4 Signaling Maintains Central Post-Stroke Pain through Mediation of Glial-Neuronal Interactions

Central post-stroke pain (CPSP) is an intractable central neuropathic pain that has been poorly studied mechanistically. Here we showed that stromal cell-derived factor 1 (SDF1 or CXCL12), a member of the CXC chemokine family, and its receptor CXCR4 played a key role in the development and maintenance of thalamic hemorrhagic CPSP through hypoxia inducible factor 1α (HIF-1α) mediated microglial-astrocytic-neuronal interactions. First, both intra-thalamic collagenase (ITC) and SDF1 injections could induce CPSP that was blockable and reversible by intra-thalamic administration of both AMD3100 (a selective CXCR4 antagonist) and inhibitors of microglial or astrocytic activation. Second, long-term increased-expression of SDF1 and CXCR4 that was accompanied by activations of both microglia and astrocytes following ITC could be blocked by both AMD-3100 and YC-1, a selective inhibitor of HIF-1α. AMD-3100 could also inhibit release of proinflammatory mediators (TNFα, IL1β and IL-6). Increased-expression of HIF-1α, SDF1, CXCR4, Iba1 and GFAP proteins could be induced by both ITC and intra-thalamic CoCl₂, an inducer of HIF-1α that was blockable by both HIF-1α inhibition and CXCR4 antagonism. Finally, inhibition of HIF-1α was only effective in prevention, but not in treatment of ITC-induced CPSP. Taken together, the present study demonstrated that in the initial process of thalamic hemorrhagic state HIF-1α up-regulated SDF1-CXCR4 signaling, while in the late process SDF1-CXCR4 signaling-mediated positive feedback plays more important role in glial-glial and glial-neuronal interactions and might be a novel promising molecular target for treatment of CPSP in clinic.

Chemokines and cocaine: CXCR4 receptor antagonist AMD3100 attenuates cocaine place preference and locomotor stimulation in rats

Plasma levels of the chemokine CXCL12 are elevated in mice following acute cocaine exposure and decreased in human cocaine abusers during withdrawal. CXCL12 is also one of the few chemokines located in the brain and can modulate dopamine transmission through activation of its receptor CXCR4. To assess a role for the CXCL12/CXCR4 system in behavioral effects of cocaine, we tested the hypothesis that AMD 3100 (Plerixafor), a CXCR4 antagonist, would inhibit conditioned place preference (CPP) and locomotor activation produced by cocaine. Rats injected with cocaine (10mg/kg) displayed CPP relative to saline-injected controls following 4 conditioning sessions. AMD 3100 (1, 2.5, 5mg/kg) administered prior to cocaine conditioning reduced development of cocaine CPP. AMD 3100 (5mg/kg) also inhibited expression of cocaine-induced CPP in a paradigm in which it was injected once (following cocaine conditioning and just prior to CPP testing). In addition, AMD 3100 (5, 10mg/kg) pretreatment reduced locomotor activation produced by an acute cocaine injection (15mg/kg) but did not affect basal locomotor activity relative to saline-injected controls. Repeated cocaine exposure produced a significant increase (1.49-fold) in CXCL12 mRNA expression in the ventral tegmental area (VTA). Our results suggest that the CXCL12/CXCR4 system in the brain reward circuit is impacted by cocaine exposure and influences behavioral effects related to the abuse liability of cocaine.

Relationship of the Chemokine, CXCL12, to Effects of Dietary Fat on Feeding-Related Behaviors and Hypothalamic Neuropeptide Systems

The intake of a high fat diet (HFD), in addition to stimulating orexigenic neuropeptides in the hypothalamus while promoting overeating and reducing locomotor behavior, is known to increase inflammatory mediators that modulate neuronal systems in the brain. To understand the involvement of chemokines in the effects of a HFD, we examined in rats whether HFD intake affects a specific chemokine, CXCL12, and its receptors, CXCR4 and CXCR7, in the hypothalamus together with the neuropeptides and whether CXCL12 itself acts similarly to a HFD in stimulating the neuropeptides and altering ingestion and locomotor behavior. Compared to low-fat chow, a HFD for 5 days significantly increased the expression of CXCL12 and its receptors, in both the paraventricular nucleus (PVN) where the neuropeptides enkephalin (ENK) and galanin were also stimulated and the perifornical lateral hypothalamus (PFLH) where orexin (OX) and melanin-concentrating hormone (MCH) were increased. In contrast, the HFD had no impact on expression of CXCL12 or its receptors in the arcuate nucleus (ARC) where the carbohydrate-related peptide, neuropeptide Y (NPY), was suppressed. Analysis of protein levels revealed a similar stimulatory effect of a HFD on CXCL12 levels in the PVN and PFLH, as well as in blood, and an increase in the number of CXCR4-positive cells in the PVN. In the ARC, in contrast, levels of CXCL12 and number of CXCR4-positive cells were too low to measure. When centrally administered, CXCL12 was found to have similar effects to a HFD. Injection of CXCL12 into the third cerebral ventricle immediately anterior to the hypothalamus significantly stimulated the ingestion of a HFD, reduced novelty-induced locomotor activity, and increased expression of ENK in the PVN where the CXCR4 receptors were dense. It had no impact, however, on NPY in the ARC or on OX and MCH in the PFLH where the CXCR4 receptors were not detected. These results, showing CXCL12 in the hypothalamus to be stimulated by a HFD and to mimic the effects of the HFD where its receptors are located, suggest that this chemokine system may have a role in mediating both the neuronal and behavioral effects induced by a fat-rich diet.

Plasma Chemokines in Patients with Alcohol Use Disorders: Association of CCL11 (Eotaxin-1) with Psychiatric Comorbidity

Recent studies have linked changes in peripheral chemokine concentrations to the presence of both addictive behaviors and psychiatric disorders. The present study further explore this link by analyzing the potential association of psychiatry comorbidity with alterations in the concentrations of circulating plasma chemokine in patients of both sexes diagnosed with alcohol use disorders (AUD). To this end, 85 abstinent subjects with AUD from an outpatient setting and 55 healthy subjects were evaluated for substance and mental disorders. Plasma samples were obtained to quantify chemokine concentrations [C-C motif (CC), C-X-C motif (CXC), and C-X₃-C motif (CX₃C) chemokines]. Abstinent AUD patients displayed a high prevalence of comorbid mental disorders (72%) and other substance use disorders (45%). Plasma concentrations of chemokines CXCL12/stromal cell-derived factor-1 (p < 0.001) and CX₃CL1/fractalkine (p < 0.05) were lower in AUD patients compared to controls, whereas CCL11/eotaxin-1 concentrations were strongly decreased in female AUD patients (p < 0.001). In the alcohol group, CXCL8 concentrations were increased in patients with liver and pancreas diseases and there was a significant correlation to aspartate transaminase (r = +0.456, p < 0.001) and gamma-glutamyltransferase (r = +0.647, p < 0.001). Focusing on comorbid psychiatric disorders, we distinguish between patients with additional mental disorders (N = 61) and other substance use disorders (N = 38). Only CCL11 concentrations were found to be altered in AUD patients diagnosed with mental disorders (p < 0.01) with a strong main effect of sex. Thus, patients with mood disorders (N = 42) and/or anxiety (N = 16) had lower CCL11 concentrations than non-comorbid patients being more evident in women. The alcohol-induced alterations in circulating chemokines were also explored in preclinical models of alcohol use with male Wistar rats. Rats exposed to repeated ethanol (3 g/kg, gavage) had lower CXCL12 (p < 0.01) concentrations and higher CCL11 concentrations (p < 0.001) relative to vehicle-treated rats. Additionally, the increased CCL11 concentrations in rats exposed to ethanol were enhanced by the prior exposure to restraint stress (p < 0.01). Concordantly, acute ethanol exposure induced changes in CXCL12, CX₃CL1, and CCL11 in the same direction to repeated exposure. These results clearly indicate a contribution of specific chemokines to the phenotype of AUD and a strong effect of sex, revealing a link of CCL11 to alcohol and anxiety/stress.

Plasma profile of pro-inflammatory cytokines and chemokines in cocaine users under outpatient treatment: influence of cocaine symptom severity and psychiatric co-morbidity

The treatment for cocaine use constitutes a clinical challenge because of the lack of appropriate therapies and the high rate of relapse. Recent evidence indicates that the immune system might be involved in the pathogenesis of cocaine addiction and its co-morbid psychiatric disorders. This work examined the plasma pro-inflammatory cytokine and chemokine profile in abstinent cocaine users (n = 82) who sought outpatient cocaine treatment and age/sex/body mass-matched controls (n = 65). Participants were assessed with the diagnostic interview Psychiatric Research Interview for Substance and Mental Diseases according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR). Tumor necrosis factor-alpha, chemokine (C-C motif) ligand 2/monocyte chemotactic protein-1 and chemokine (C-X-C motif) ligand 12 (CXCL12)/stromal cell-derived factor-1 (SDF-1) were decreased in cocaine users, although all cytokines were identified as predictors of a lifetime pathological use of cocaine. Interleukin-1 beta (IL-1β), chemokine (C-X3-C motif) ligand 1 (CX3CL1)/fractalkine and CXCL12/SDF-1 positively correlated with the cocaine symptom severity when using the DSM-IV-TR criteria for cocaine abuse/dependence. These cytokines allowed the categorization of the outpatients into subgroups according to severity, identifying a subgroup of severe cocaine users (9-11 criteria) with increased prevalence of co-morbid psychiatric disorders [mood (54%), anxiety (32%), psychotic (30%) and personality (60%) disorders]. IL-1β was observed to be increased in users with such psychiatric disorders relative to those users with no diagnosis. In addition to these clinical data, studies in mice demonstrated that plasma IL-1β, CX3CL1 and CXCL12 were also affected after acute and chronic cocaine administration, providing a preclinical model for further research. In conclusion, cocaine exposure modifies the circulating levels of pro-inflammatory mediators. Plasma cytokine/chemokine monitoring could improve the stratification of cocaine consumers seeking treatment and thus facilitate the application of appropriate interventions, including management of heightened risk of psychiatric co-morbidity. Further research is necessary to elucidate the role of the immune system in the etiology of cocaine addiction.

Sex differences in psychiatric comorbidity and plasma biomarkers for cocaine addiction in abstinent cocaine-addicted subjects in outpatient settings

There are sex differences in the progression of drug addiction, relapse, and response to therapies. Because biological factors participate in these differences, they should be considered when using biomarkers for addiction. In the current study, we evaluated the sex differences in psychiatric comorbidity and the concentrations of plasma mediators that have been reported to be affected by cocaine. Fifty-five abstinent cocaine-addicted subjects diagnosed with lifetime cocaine use disorders (40 men and 15 women) and 73 healthy controls (48 men and 25 women) were clinically assessed with the diagnostic interview "Psychiatric Research Interview for Substance and Mental Disorders." Plasma concentrations of chemokines, cytokines, N-acyl-ethanolamines, and 2-acyl-glycerols were analyzed according to history of cocaine addiction and sex, controlling for covariates age and body mass index (BMI). Relationships between these concentrations and variables related to cocaine addiction were also analyzed in addicted subjects. The results showed that the concentrations of chemokine (C-C motif) ligand 2/monocyte chemotactic protein-1 (CCL2/MCP-1) and chemokine (C-X-C motif) ligand 12/stromal cell-derived factor-1 (CXCL12/SDF-1) were only affected by history of cocaine addiction. The plasma concentrations of interleukin 1-beta (IL-1β), IL-6, IL-10, and tumor necrosis factor-alpha (TNFα) were affected by history of cocaine addiction and sex. In fact, whereas cytokine concentrations were higher in control women relative to men, these concentrations were reduced in cocaine-addicted women without changes in addicted men. Regarding fatty acid derivatives, history of cocaine addiction had a main effect on the concentration of each acyl derivative, whereas N-acyl-ethanolamines were increased overall in the cocaine group, 2-acyl-glycerols were decreased. Interestingly, N-palmitoleoyl-ethanolamine (POEA) was only increased in cocaine-addicted women. The covariate BMI had a significant effect on POEA and N-arachidonoyl-ethanolamine concentrations. Regarding psychiatric comorbidity in the cocaine group, women had lower incidence rates of comorbid substance use disorders than did men. For example, alcohol use disorders were found in 80% of men and 40% of women. In contrast, the addicted women had increased prevalences of comorbid psychiatric disorders (i.e., mood, anxiety, and psychosis disorders). Additionally, cocaine-addicted subjects showed a relationship between the concentrations of N-stearoyl-ethanolamine and 2-linoleoyl-glycerol and diagnosis of psychiatric comorbidity. These results demonstrate the existence of a sex influence on plasma biomarkers for cocaine addiction and on the presence of comorbid psychopathologies for clinical purposes.

Neuroimmune mechanisms of alcohol and drug addiction

Alcohol and other drugs of abuse have significant impacts on the neuroimmune system. Studies have demonstrated that drugs of abuse interact with the neuroimmune system and alter neuroimmune gene expression and signaling, which in turn contribute to various aspects of addiction. As the key component of the CNS immune system, neuroimmune factors mediate neuroinflammation and modulate a wide range of brain function including neuronal activity, endocrine function, and CNS development. These neuromodulatory properties of immune factors, together with their essential role in neuroinflammation, provide a new framework to understand neuroimmune mechanisms mediating brain functional and behavioral changes contributing to addiction. This chapter highlights recent advances in understanding neuroimmune changes associated with exposure to alcohol and other drugs of abuse, including opiates, marijuana, methamphetamine, and cocaine. It provides a brief overview on what we know about neuroimmune signaling and its role in drug action and addiction.

Iron deficiency alters expression of dopamine-related genes in the ventral midbrain in mice

A clear link exists between iron deficiency (ID) and nigrostriatal dopamine malfunction. This link appears to play an important role in at least restless legs syndrome (RLS) if not several other neurological diseases. Yet, the underlying mechanisms remain unclear. The effects of ID on gene expression in the brain have not been studied extensively. Here, to better understand how exactly ID alters dopamine functioning, we investigated the effects of ID on gene expression in the brain, seeking to identify any potential transcription-based mechanisms. We used six strains of recombinant inbred mice (BXD type) known to differ in susceptibility to ID in the brain. Upon weaning, we subjected mice from each strain to either an iron-deficient or iron-adequate diet. After 100 days of dietary treatment, we measured the effects of ID on gene expression in the ventral midbrain, a region containing the substantia nigra. The substantia nigra is the base of the nigrostriatal dopamine pathway and a region particularly affected by iron loss in RLS. We screened for ID-induced changes in expression, including changes in that of both iron-regulating and dopamine-related genes. Results revealed a number of expression changes occurring in ID, with large strain-dependent differences in the genes involved and number of expression changes occurring. In terms of dopamine-related genes, results revealed ID-induced expression changes in three genes with direct ties to nigrostriatal dopamine functioning, two of which have never before been implicated in an iron-dopamine pathway. These were stromal cell-derived factor 1 (Cxcl12, or SDF-1), a ferritin regulator and potent dopamine neuromodulator, and hemoglobin, beta adult chain 1 (Hbb-b1), a gene recently shown to play a functional role in dopaminergic neurons. The extent of up-regulation of these genes varied by strain. This work not only demonstrates a wide genetic variation in the transcriptional response to ID in the brain, but also reveals two novel biochemical pathways by which iron may potentially alter dopamine function.

Implications of central immune signaling caused by drugs of abuse: mechanisms, mediators and new therapeutic approaches for prediction and treatment of drug dependence

In the past two decades a trickle of manuscripts examining the non-neuronal central nervous system immune consequences of the drugs of abuse has now swollen to a significant body of work. Initially, these studies reported associative evidence of central nervous system proinflammation resulting from exposure to the drugs of abuse demonstrating key implications for neurotoxicity and disease progression associated with, for example, HIV infection. However, more recently this drug-induced activation of central immune signaling is now understood to contribute substantially to the pharmacodynamic actions of the drugs of abuse, by enhancing the engagement of classical mesolimbic dopamine reward pathways and withdrawal centers. This review will highlight the key in vivo animal, human, biological and molecular evidence of these central immune signaling actions of opioids, alcohol, cocaine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA). Excitingly, this new appreciation of central immune signaling activity of drugs of abuse provides novel therapeutic interventions and opportunities to identify 'at risk' individuals through the use of immunogenetics. Discussion will also cover the evidence of modulation of this signaling by existing clinical and pre-clinical drug candidates, and novel pharmacological targets. Finally, following examination of the breadth of central immune signaling actions of the drugs of abuse highlighted here, the current known common immune signaling components will be outlined and their impact on established addiction neurocircuitry discussed, thereby synthesizing a common neuroimmune hypothesis of addiction.

The Transcription Factor NURR1 Exerts Concentration-Dependent Effects on Target Genes Mediating Distinct Biological Processes

The transcription factor NURR1 plays a pivotal role in the development and maintenance of neurotransmitter phenotype in midbrain dopamine neurons. Conversely, decreased NURR1 expression is associated with a number of dopamine-related CNS disorders, including Parkinson's disease and drug addiction. In order to better understand the nature of NURR1-responsive genes and their potential roles in dopamine neuron differentiation and survival, we used a human neural cellular background (SK-N-AS cells) in which to generate a number of stable clonal lines with graded NURR1 gene expression that approximated that seen in DA cell-rich human substantia nigra. Gene expression profiling data from these NURR1-expressing clonal lines were validated by quantitative RT-PCR and subjected to bioinformatic analyses. The present study identified a large number of NURR1-responsive genes and demonstrated the potential importance of concentration-dependent NURR1 effects in the differential regulation of distinct NURR1 target genes and biological pathways. These data support the promise of NURR1-based CNS therapeutics for the neuroprotection and/or functional restoration of DA neurons.

Locomotion and self-administration induced by cocaine in 129/OlaHsd mice lacking galanin

Previous studies have demonstrated that the galanin system modulates responses to drugs of abuse such as morphine. The current study examined whether genetic deletion of galanin could affect the locomotor and reinforcing effects of cocaine in mice. We analyzed spontaneous motor activity and cocaine-induced hyperactivity in wild-type (GAL-WT) and knockout mice lacking galanin (GAL-KO) maintained on the 129/OlaHsd background. Our results indicate that cocaine enhanced locomotion (defined as moving more than 5 cm) dose-dependently in GAL-WT and GAL-KO mice. However, general activity (total beam breaks) was increased by cocaine only in GAL-WT mice. An additional experiment indicated that galnon, a nonselective galanin receptor agonist, did not affect cocaine-induced hyperactivity. In a second set of experiments, mice of both genotypes were trained to self-administer cocaine under a fixed ratio schedule, tested with various doses of cocaine and under different schedules of reinforcement. This set of experiments showed that cocaine self-administration did not differ markedly between genotypes. However, while GAL-WT mice acquired cocaine self-administration, a median split analysis showed that mice could be divided into large and small drug takers, whereas all GAL-KO mice behaved as small drug takers. Our results indicate that wild-type and galanin knockout mice on a congenic 129/OlaHsd background are responsive to the locomotor effects of cocaine and can acquire intravenous cocaine self-administration. However, the phenotype observed in GAL-KO mice does not support a major role for galanin in cocaine-induced hyperlocomotion and self-administration.

Localization of CXCR4 in the forebrain of the adult rat

Chemokines are small secreted proteins that act as chemoattractants, and their role as neuromodulators in the brain has recently been appreciated. CXCL12 is one of the few chemokines found in neurons and expressed constitutively in the central nervous system. Previous data from our laboratory demonstrate the ability of CXCL12 to modulate the behavioral effects of cocaine, and this modulation is dependent on the central site of administration of CXCL12. The present study used single-staining immunohistochemical and dual-staining immunofluorescent methods to determine the localization of the CXCL12 receptor, CXCR4, in the caudate putamen and nucleus accumbens of the adult rat brain. Results demonstrated that individual neurons in both the caudate putamen and lateral shell of the nucleus accumbens express both CXCR4 and D1 dopamine receptors. Immunofluorescent studies showed that CXCR4 was co-expressed with ChAT, a marker for cholinergic neurons, and with GAD C38, a marker for GABAergic neurons, in the caudate putamen and lateral shell of the accumbens. No evidence of CXCR4 was found in the medial shell or core regions of the nucleus accumbens. These data demonstrate that CXCR4 is expressed by subpopulations of cholinergic and GABAergic neurons in the striatum and suggest that CXCR4 is well-positioned to modulate striatal function.