The beta-lactam antibiotic, ceftriaxone, attenuates morphine-evoked hyperthermia in rats

Effects of Beta Lactams on Behavioral Outcomes of Substance Use Disorders: A Meta-Analysis of Preclinical Studies

INTRODUCTION

Preclinical studies demonstrated that beta-lactams have neuroprotective effects in conditions involving glutamate neuroexcitotoxicity, including substance use disorders (SUDs). This meta-analysis aims to analyze the existing evidences on the effects of beta-lactams as glutamate transporter 1 (GLT-1) upregulators in animal models of SUDs, identification of gaps in the literature, and setting the stage for potential translation into clinical phases.

METHODS

Meta-analysis was conducted on preclinical studies retrieved systematically from MEDLINE and ScienceDirect databases. Abused substances were identified by refereeing to the National Institute on Drug Abuse (NIDA). The results were quantitatively described with a focus on the behavioral outcomes. Treatment effect sizes were described using standardized mean difference, and they were pooled using random effect model. I2-statistic was used to assess heterogeneity, and Funnel plot and Egger's test were used for assessment of publication bias.

RESULTS

Literature search yielded a total of 71 studies that were eligible to be included in the analysis. Through these studies, the effects of beta-lactams were evaluated in animal models of nicotine, cannabis, amphetamines, synthetic cathinone, opioids, ethanol, and cocaine use disorders as well as steroids-related aggressive behaviors. Meta-analysis showed that treatments with beta-lactams consistently reduced the pooled undesired effects of the abused substances in several paradigms, including drug-self administration, conditioned place preference, drug seeking behaviors, hyperlocomotion, withdrawal syndromes, tolerance to analgesic effects, hyperalgesia, and hyperthermia.

CONCLUSION

This meta-analysis revealed that enhancing GLT-1 expression in the brain through beta-lactams seemed to be a promising treatment approach in the context of substance use disorders, as indicated by results in animal models.

β_lactam antibiotics against drug addiction: A novel therapeutic option

Drug addiction as a problem for the health of the individual and the society is the result of a complex process in which there is an interaction between brain nuclei and neurotransmitters (such as glutamate). β-lactam antibiotics, due to their enhancing properties on the glutamate transporter glutamate transporter-1, can affect and counteract the addictive mechanisms of drugs through the regulation of extracellular glutamate. Since glutamate is a key neurotransmitter in the development of drug addiction, it seems that β-lactams can be considered as a promising treatment for addiction. However, more research in this field is necessary to identify other mechanisms involved in their effectiveness. This article is a review of the studies conducted on the effect of β-lactam administration in preventing the development of drug addiction, as well as their possible cellular and molecular mechanisms. This review suggests the clinical use of β-lactam antibiotics that have weak antimicrobial properties (such as clavulanic acid) in the treatment of drug dependence.

Ceftriaxone as a Novel Therapeutic Agent for Hyperglutamatergic States: Bridging the Gap Between Preclinical Results and Clinical Translation

Dysregulation of glutamate homeostasis is a well-established core feature of neuropsychiatric disorders. Extracellular glutamate concentration is regulated by glutamate transporter 1 (GLT-1). The discovery of a beta-lactam antibiotic, ceftriaxone (CEF), as a safe compound with unique ability to upregulate GLT-1 sparked the interest in testing its efficacy as a novel therapeutic agent in animal models of neuropsychiatric disorders with hyperglutamatergic states. Indeed, more than 100 preclinical studies have shown the efficacy of CEF in attenuating the behavioral manifestations of various hyperglutamatergic brain disorders such as ischemic stroke, amyotrophic lateral sclerosis (ALS), seizure, Huntington’s disease, and various aspects of drug use disorders. However, despite rich and promising preclinical data, only one large-scale clinical trial testing the efficacy of CEF in patients with ALS is reported. Unfortunately, in that study, there was no significant difference in survival between placebo- and CEF-treated patients. In this review, we discussed the translational potential of preclinical efficacy of CEF based on four different parameters: (1) initiation of CEF treatment in relation to induction of the hyperglutamatergic state, (2) onset of response in preclinical models in relation to onset of GLT-1 upregulation, (3) mechanisms of action of CEF on GLT-1 expression and function, and (4) non-GLT-1-mediated mechanisms for CEF. Our detailed review of the literature brings new insights into underlying molecular mechanisms correlating the preclinical efficacy of CEF. We concluded here that CEF may be clinically effective in selected cases in acute and transient hyperglutamatergic states such as early drug withdrawal conditions.

Selective toxicity of antibacterial agents-still a valid concept or do we miss chances and ignore risks?

BACKGROUND

Selective toxicity antibacteribiotics is considered to be due to interactions with targets either being unique to bacteria or being characterized by a dichotomy between pro- and eukaryotic pathways with high affinities of agents to bacterial- rather than eukaryotic targets. However, the theory of selective toxicity oversimplifies the complex modes of action of antibiotics in pro- and eukaryotes.

METHODS AND OBJECTIVE

This review summarizes data describing multiple modes of action of antibiotics in eukaryotes.

RESULTS

Aminoglycosides, macrolides, oxazolidinones, chloramphenicol, clindamycin, tetracyclines, glycylcyclines, fluoroquinolones, rifampicin, bedaquillin, ß-lactams inhibited mitochondrial translation either due to binding to mitosomes, inhibition of mitochondrial RNA-polymerase-, topoisomerase 2ß-, ATP-synthesis, transporter activities. Oxazolidinones, tetracyclines, vancomycin, ß-lactams, bacitracin, isoniazid, nitroxoline inhibited matrix-metalloproteinases (MMP) due to chelation with zinc and calcium, whereas fluoroquinols fluoroquinolones and chloramphenicol chelated with these cations, too, but increased MMP activities. MMP-inhibition supported clinical efficacies of ß-lactams and daptomycin in skin-infections, and of macrolides, tetracyclines in respiratory-diseases. Chelation may have contributed to neuroprotection by ß-lactams and fluoroquinolones. Aminoglycosides, macrolides, chloramphenicol, oxazolidins oxazolidinones, tetracyclines caused read-through of premature stop codons. Several additional targets for antibiotics in human cells have been identified like interaction of fluoroquinolones with DNA damage repair in eukaryotes, or inhibition of mucin overproduction by oxazolidinones.

CONCLUSION

The effects of antibiotics on eukaryotes are due to identical mechanisms as their antibacterial activities because of structural and functional homologies of pro- and eukaryotic targets, so that the effects of antibiotics on mammals are integral parts of their overall mechanisms of action.

The influence of the host microbiome on 3,4-methylenedioxymethamphetamine (MDMA)-induced hyperthermia and vice versa

Hyperthermia induced by 3,4-methylenedioxymethamphetamine (MDMA) can be life-threatening. Here, we investigate the role of the gut microbiome and TGR5 bile acid receptors in MDMA-mediated hyperthermia. Fourteen days prior to treatment with MDMA, male Sprague-Dawley rats were provided water or water treated with antibiotics. Animals that had received antibiotics displayed a reduction in gut bacteria and an attenuated hyperthermic response to MDMA. MDMA treated animals showed increased uncoupling protein 1 (UCP1) and TGR5 expression levels in brown adipose tissue and skeletal muscle while increased expression of UCP3 was observed only in skeletal muscle. Antibiotics prior to MDMA administration significantly blunted these increases in gene expression. Furthermore, inhibition of the TGR5 receptor with triamterene or of deiodinase II downstream of the TGR5 receptor with iopanoic acid also resulted in the attenuation of MDMA-induced hyperthermia. MDMA-treatment enriched the relative proportion of a Proteus mirabilis strain in the ceca of animals not pre-treated with antibiotics. These findings suggest a contributing role for the gut microbiota in MDMA-mediated hyperthermia and that MDMA treatment can trigger a rapid remodeling of the composition of the gut microbiome.

Glial mechanisms underlying substance use disorders

Addiction is a devastating disorder that produces persistent maladaptive changes to the central nervous system, including glial cells. Although there is an extensive body of literature examining the neuronal mechanisms of substance use disorders, effective therapies remain elusive. Glia, particularly microglia and astrocytes, have an emerging and meaningful role in a variety of processes beyond inflammation and immune surveillance, and may represent a promising therapeutic target. Indeed, glia actively modulate neurotransmission, synaptic connectivity and neural circuit function, and are critically poised to contribute to addictive-like brain states and behaviors. In this review, we argue that glia influence the cellular, molecular, and synaptic changes that occur in neurons following drug exposure, and that this cellular relationship is critically modified following drug exposure. We discuss direct actions of abused drugs on glial function through immune receptors, such as Toll-like receptor 4, as well as other mechanisms. We highlight how drugs of abuse affect glia-neural communication, and the profound effects that glial-derived factors have on neuronal excitability, structure, and function. Recent research demonstrates that glia have brain region-specific functions, and glia in different brain regions have distinct contributions to drug-associated behaviors. We will also evaluate the evidence demonstrating that glial activation is essential for drug reward and drug-induced dopamine release, and highlight clinical evidence showing that glial mechanisms contribute to drug abuse liability. In this review, we synthesize the extensive evidence that glia have a unique, pivotal, and underappreciated role in the development and maintenance of addiction.

Effects of ceftriaxone on conditioned nicotine reward in rats

Nicotine is the addictive compound in tobacco products which exerts psychosomatic effects that contribute to abuse and to low rates of abstinence in treatment-seeking smokers. At present, the most successful smoking cessation aide helps one in four individuals quit smoking at 1 year postcessation. New adjunctive therapies are needed to improve status of smoking-related public health crises, and β-lactam antibiotics are one class of potential therapies as they favorably augment extrasynaptic glutamate clearance. Our study used two-chamber place conditioning to assess effects of ceftriaxone (CTX) on persistence of conditioned nicotine reward. Rats were conditioned to associate nicotine (0.4 mg/kg, subcutaneous) with one context and vehicle with an alternative context. After initial post-test, rats received either daily ceftriaxone (200 mg/kg, intraperitoneal) or saline. All rats showed nicotine place preference during post-test 1. CTX-treated rats meeting extinction criterion by post-test 7 showed significantly reduced preference for the nicotine-paired context during post-test 2 compared with vehicle-treated rats. We interpret these data to support the further study of CTX as a smoking cessation aide. Our results suggest that CTX reduces persistence of conditioned nicotine reward and may be helpful for improving abstinence rates in a subset of treatment-seeking smokers.

Glial and neuroinflammatory targets for treating substance use disorders

BACKGROUND

The plenary session at the 2016 Behavior, Biology and Chemistry: Translational Research in Addiction Conference focused on glia as potential players in the development, persistence and treatment of substance use disorders. Glia partake in various functions that are important for healthy brain activity. Drugs of abuse alter glial cell activity producing several perturbations in brain function that are thought to contribute to behavioral changes associated with substance use disorders. Consequently, drug-induced changes in glia-driven processes in the brain represent potential targets for pharmacotherapeutics treating substance use disorders.

METHODS

Four speakers presented preclinical and clinical research illustrating the effects that glial modulators have on abuse-related behavioral effects of psychostimulants and opioids. This review highlights some of these findings and expands its focus to include other research focused on drug-induced glia abnormalities and glia-focused treatment approaches in substance use disorders.

RESULTS

Preclinical findings show that drugs of abuse induce neuroinflammatory signals and disrupt glutamate homeostasis through their interaction with microglia and astrocytes. Preclinical and clinical studies testing the effects of glial modulators show general effectiveness in reducing behaviors associated with substance use disorders.

CONCLUSIONS

The contribution of drug-induced glial activity continues to emerge as an intriguing target for substance use disorder treatments. Clinical investigations of glial modulators have yielded promising results on substance use measures and indicate that they are generally safe and well-tolerated. However, results have not been entirely positive and more questions remain for continued exploration in the development and testing of glial-directed treatments for substance use disorders.

Effects of Ceftriaxone on Glial Glutamate Transporters in Wistar Rats Administered Sequential Ethanol and Methamphetamine

Methamphetamine (METH) is one of the psychostimulants that is co-abused with ethanol. Repeated exposure to high dose of METH has been shown to cause increases in extracellular glutamate concentration. We have recently reported that ethanol exposure can also increase the extracellular glutamate concentration and downregulate the expression of glutamate transporter subtype 1 (GLT-1). GLT-1 is a glial transporter that regulates the majority of extracellular glutamate. A Wistar rat model of METH and ethanol co-abuse was used to examine the expression of GLT-1 as well as other glutamate transporters such as cystine/glutamate exchanger (xCT) and glutamate aspartate transporter (GLAST). We also examined the body temperature in rats administered METH, ethanol or both drugs. We further investigated the effects of ceftriaxone (CEF), a β-lactam antibiotic known to upregulate GLT-1, in this METH/ethanol co-abuse rat model. After 7 days of either ethanol (6 g/kg) or water oral gavage, Wistar rats received either saline or METH (10 mg/kg i.p. every 2 h × 4), followed by either saline or CEF (200 mg/kg) posttreatment. METH administered alone decreased GLT-1 expression in the nucleus accumbens (NAc) and prefrontal cortex (PFC) and increased body temperature, but did not reduce either xCT or GLAST expression in ethanol and water-pretreated rats. Interestingly, ethanol and METH were found to have an additive effect on the downregulation of GLT-1 expression in the NAc but not in the PFC. Moreover, ethanol alone caused GLT-1 downregulation in the NAc and elevated body temperature compared to control. Finally, CEF posttreatment significantly reversed METH-induced hyperthermia, restored GLT-1 expression, and increased xCT expression. These findings suggest the potential therapeutic role of CEF against METH- or ethanol/METH-induced hyperglutamatergic state and hyperthermia.

Excess cerebral TNF causing glutamate excitotoxicity rationalizes treatment of neurodegenerative diseases and neurogenic pain by anti-TNF agents

The basic mechanism of the major neurodegenerative diseases, including neurogenic pain, needs to be agreed upon before rational treatments can be determined, but this knowledge is still in a state of flux. Most have agreed for decades that these disease states, both infectious and non-infectious, share arguments incriminating excitotoxicity induced by excessive extracellular cerebral glutamate. Excess cerebral levels of tumor necrosis factor (TNF) are also documented in the same group of disease states. However, no agreement exists on overarching mechanism for the harmful effects of excess TNF, nor, indeed how extracellular cerebral glutamate reaches toxic levels in these conditions. Here, we link the two, collecting and arguing the evidence that, across the range of neurodegenerative diseases, excessive TNF harms the central nervous system largely through causing extracellular glutamate to accumulate to levels high enough to inhibit synaptic activity or kill neurons and therefore their associated synapses as well. TNF can be predicted from the broader literature to cause this glutamate accumulation not only by increasing glutamate production by enhancing glutaminase, but in addition simultaneously reducing glutamate clearance by inhibiting re-uptake proteins. We also discuss the effects of a TNF receptor biological fusion protein (etanercept) and the indirect anti-TNF agents dithio-thalidomides, nilotinab, and cannabinoids on these neurological conditions. The therapeutic effects of 6-diazo-5-oxo-norleucine, ceptriaxone, and riluzole, agents unrelated to TNF but which either inhibit glutaminase or enhance re-uptake proteins, but do not do both, as would anti-TNF agents, are also discussed in this context. By pointing to excess extracellular glutamate as the target, these arguments greatly strengthen the case, put now for many years, to test appropriately delivered ant-TNF agents to treat neurodegenerative diseases in randomly controlled trials.

Glutamate Transporter GLT-1 as a Therapeutic Target for Substance Use Disorders

The development of new treatments for substance use disorders requires identification of targetable molecular mechanisms. Pathology in glutamatergic neurotransmission system in brain reward circuitry has been implicated in relapse to multiple classes of drugs. Glutamate transporter 1 (GLT-1) crucially regulates glutamatergic signaling by removing excess glutamate from the extrasynaptic space. The purpose of this review is to highlight the effects of addictive drug use on GLT-1 and glutamate uptake, and using GLT-1 as a target in addiction pharmacotherapy. Cocaine, opioids, ethanol, nicotine, amphetamines, and cannabinoids each affect GLT-1 expression and glutamate uptake, and restoring GLT-1 expression with N-acetylcysteine or ceftriaxone shows promise in correcting pre-clinical and clinical manifestations of drug addiction.

Effects of Low-Dose Escherichia coli Lipopolysaccharide-Induced Endotoxemia on Morphine Pharmacokinetics in an Animal Model

OBJECTIVE

Systemic inflammation may change the bioavailability and pharmacokinetics of opioids. However, there are insufficient data on morphine pharmacokinetics in mild inflammatory conditions. This study aimed to determine the pharmacokinetics of morphine during low-dose endotoxemia in rabbits.

DESIGN

In two experiments (separated by a 14-day washout period), 10 rabbits received intravenous morphine at a dose of 3 mg/kg. In the second set of experiments, morphine infusion was preceded by low-dose endotoxemia induced with lipopolysaccharide (Escherichia coli 0111: B4) at a dose of 5 µg/kg. The kinetics of systemic morphine concentrations and chosen physiological parameters were measured at specific time intervals up to 6 hours after morphine administration.

RESULTS

In endotoxemia, decreased elimination half-life (P = 0.017), mean residence time (P = 0.022), and volume of distribution (P = 0.037) as well as an increased elimination rate constant (P = 0.013) and total body clearance (P = 0.023) were noted. The inverse linear correlation between morphine clearance versus the percentage (%) change in body temperature and pulse rate observed under control conditions was abolished under endotoxemia.

CONCLUSIONS

Low-dose endotoxemia is correlated with significant alterations in morphine pharmacokinetics in rabbits, leading to the faster elimination of the drug.

CLINICAL IMPLICATIONS

These findings may have important implications in patients with low-grade inflammation and imply the need to modify morphine dosing regimens to ensure optimal analgesia. The issue warrants further experimental and clinical investigation.

Effect of ceftriaxone and topiramate treatments on naltrexone-precipitated morphine withdrawal and glutamate receptor desensitization in the rat locus coeruleus

RATIONALE

Morphine withdrawal is associated with a hyperactivity of locus coeruleus (LC) neurons by an elevated glutamate neurotransmission in this nucleus. We postulate that reductions in the amount of glutamate in the LC by enhancing its reuptake or inhibiting its release could attenuate the behavioral and cellular consequences of morphine withdrawal.

OBJECTIVES

We investigated the effect of chronic treatment with ceftriaxone (CFT), an excitatory amino acid transporter (EAAT2) enhancer, and acute administration of topiramate (TPM), a glutamate release inhibitor, on morphine withdrawal syndrome and withdrawal-induced glutamate receptor (GluR) desensitization in LC neurons from morphine-dependent rats.

METHODS

Morphine withdrawal behavior was measured after naltrexone administration in rats implanted with a morphine (200 mg kg(-1)) emulsion for 3 days. GluR desensitization in the LC was assessed by performing concentration-effect curves for glutamate by extracellular electrophysiological recordings in vitro.

RESULTS

Treatments with CFT or TPM reduced, in a dose-related manner, the total behavioral score of naltrexone-precipitated morphine withdrawal. CFT and TPM, at doses that were effective in behavioral tests, also reduced the induction of GluR desensitization normally occurring in LC neurons from morphine-dependent rats. Acute treatment with the specific EAAT2 inhibitor dihydrokainic acid (DHK) prevented the effect of CFT on withdrawal syndrome and GluR desensitization. Perfusion with TPM inhibited KCl-evoked but not glutamate-induced activation of LC neurons in vitro.

CONCLUSIONS

Our results suggest that a reduction of synaptic concentrations of glutamate by enhancing EAAT2-mediated uptake or inhibiting glutamate release alleviates the behavioral response and the cellular changes in the LC during opiate withdrawal.

Ceftriaxone attenuates ethanol drinking and restores extracellular glutamate concentration through normalization of GLT-1 in nucleus accumbens of male alcohol-preferring rats

Alteration of glutamatergic-neurotransmission is a hallmark of alcohol dependence. We have previously reported that chronic ethanol-drinking downregulated glutamate transporter 1 (GLT-1) in nucleus accumbens (NAc) in male P rats in a manner that was reversed by ceftriaxone treatment. However, the effect of ceftriaxone on extracellular glutamate concentrations in NAc after chronic ethanol-drinking has not yet been studied. In the present study, male P rats were treated with ceftriaxone (100 mg/kg/day, i.p.) for five consecutive days following five-weeks of free choice ethanol (15% and 30%) drinking. In vivo microdialysis was performed to measure the extracellular glutamate concentrations in NAc and the effect of blockade of GLT-1 with dihydrokainic acid (DHK) on extracellular glutamate in NAc of ceftriaxone-treated rats was determined. Ceftriaxone treatment attenuated ethanol intake as well as ethanol preference. Extracellular glutamate was significantly higher in NAc after five-weeks of ethanol drinking in saline-treated compared to water control rats. Ceftriaxone treatment blocked the increase extracellular glutamate produced by ethanol intake. Blockade of GLT-1 by DHK reversed the effects of ceftriaxone on glutamate and implicated the role of GLT-1 in the normalization of extracellular glutamate by ceftriaxone. In addition, GLT-1 protein was decreased in ethanol exposed animals and ceftriaxone treatment reversed this deficit. Ceftriaxone treatment also increased glutamine synthetase activity in NAc but not in PFC as compared to ethanol drinking saline-treated rats. Our present study demonstrates that ceftriaxone treatment prevents ethanol drinking in part through normalization of extracellular glutamate concentrations in NAc of male P rats via GLT-1.

Attenuation of morphine-induced dependence and tolerance by ceftriaxone and amitriptyline in mice

INTRODUCTION

Tolerance to and dependence on the analgesic effect of opioids is a pharmacological phenomenon that occurs after their prolonged administration.

OBJECTIVE

The aim of this study was to evaluate the protective effects of ceftriaxone and amitriptyline on the development of morphine-induced tolerance and dependence.

METHODS

In this study, 18 groups (9 groups each for tolerance and dependency tests) of mice (n = 8) received saline [10 mL/kg, intraperitoneally (i.p.)], morphine (50 mg/kg, i.p.), ceftriaxone (50 mg/kg, i.p., 100 mg/kg, i.p., and 200 mg/kg, i.p.), amitriptyline (5 mg/kg, i.p., 10 mg/kg, i.p., and 15 mg/kg, i.p.), or a combination of ceftriaxone (50 mg/kg, i.p.) and amitriptyline (5 mg/kg, i.p.) once per day for 4 days for investigation and comparison of the effects of ceftriaxone and amitriptyline on the prevention of dependency and tolerance to morphine. Tolerance was assessed with administration of morphine (9 mg/kg, i.p.) and using the hot plate test on the 5(th) day. In dependency tests, withdrawal symptoms were assessed on the 4(th) day for each animal 30 minutes after the administration of naloxone (4 mg/kg, i.p.; 2 hours after the last dose of morphine).

RESULTS

It was found that treatment with ceftriaxone or amitriptyline attenuated the development of tolerance to the antinociceptive effect of morphine and also reduced naloxone-precipitated withdrawal jumping and standing on feet. Furthermore, coadministration of ceftriaxone and amitriptyline at low doses (50 mg/kg, i.p. and 5 mg/kg, i.p., respectively) prior to morphine injection also decreased both morphine-induced tolerance and dependence.

CONCLUSION

Results indicate that the treatment with ceftriaxone and amitriptyline, alone or in combination, could attenuate the development of morphine-induced tolerance and dependence.

Clavulanic acid reduces rewarding, hyperthermic and locomotor-sensitizing effects of morphine in rats: a new indication for an old drug?

BACKGROUND

Despite the efficacy of ceftriaxone (CTX) in animal models of CNS diseases, including drug addiction, its utility as a CNS-active therapeutic may be limited by poor brain penetrability and cumbersome parenteral administration. An alternative is the β-lactamase inhibitor clavulanic acid (CA), a constituent of Augmentin that prevents antibiotic degradation. CA possesses the β-lactam core necessary for CNS activity but, relative to CTX, possesses: (1) oral activity; (2) 2.5-fold greater brain penetrability; and (3) negligible antibiotic activity.

METHODS

To compare the effectiveness of CA (10mg/kg) and CTX (200mg/kg) against centrally-mediated endpoints, we investigated their effects against morphine's rewarding, hyperthermic, and locomotor-sensitizing actions. Endpoints were based on prior evidence that CTX attenuates morphine-induced physical dependence, tolerance, and hyperthermia.

RESULTS

As expected, rats treated with morphine (4 mg/kg) displayed hyperthermia and conditioned place preference (CPP). Co-treatment with CTX or CA inhibited development of morphine-induced CPP by approximately 70%. Morphine's hyperthermic effect was also suppressed, with CTX and CA producing 57% and 47% inhibition, respectively. Locomotor sensitization induced by repeated morphine exposures was inhibited by CA but not CTX.

CONCLUSIONS

The present findings are the first to suggest that CA disrupts the in vivo actions of morphine and point toward further studying CA as a potential therapy for drug addiction. Further, its ability to disrupt morphine's rewarding effects at 20-fold lower doses than CTX identifies CA as an existing, orally-active alternative to direct CTX therapy for CNS diseases.

Effects of the beta-lactam antibiotic ceftriaxone on nicotine withdrawal and nicotine-induced reinstatement of preference in mice

RATIONALE

Several studies suggest that repeated nicotine administration causes alterations in glutaminergic transmission that may play an important role in developing and maintaining nicotine addiction. Chronic nicotine administration in rats decreases the expression of the glutamate transporter-1 (GLT-1) and cysteine-glutamate exchanger (system xC-) in the nucleus accumbens. We hypothesized that ceftriaxone, a GLT-1 and system xC- activator, would decrease murine behavioral aspects of nicotine dependence.

OBJECTIVE

This study aimed to investigate the effect of repeated ceftriaxone administration on the behavioral effects of nicotine using mouse models of conditioned reward and withdrawal.

METHOD

Using male ICR mice, the ability of repeated ceftriaxone injections to modulate the development and reinstatement of a nicotine-conditioned place preference (CPP) was evaluated. Additionally, nicotine withdrawal-associated signs were assessed. These included both physical (somatic signs and hyperalgesia) and affective (anxiety-related behaviors) withdrawal signs in mice. Finally, the effects of ceftriaxone on nicotine-induced antinociception and hypothermia after acute nicotine injection were measured.

RESULT

Ceftriaxone had no effect on the development of nicotine preference but significantly attenuated nicotine-induced reinstatement of CPP. Furthermore, ceftriaxone reversed all nicotine withdrawal signs measured in mice.

CONCLUSION

Altogether, these findings show that a β-lactam antibiotic reduces nicotine withdrawal and nicotine-seeking behavior. Our results suggest that the documented efficacy of ceftriaxone against cocaine and morphine dependence-related behaviors effects extends to nicotine.

Role of the major glutamate transporter GLT1 in nucleus accumbens core versus shell in cue-induced cocaine-seeking behavior

Relapse to cocaine-seeking behavior requires an increase in nucleus accumbens (NAc) core glutamate transmission. Decreased expression of glutamate type I transporter (GLT1), which is responsible for >90% of glutamate clearance, occurs in the core of rats withdrawn from cocaine self-administration, while treatment with ceftriaxone, a β-lactam antibiotic previously shown to increase GLT1 expression and function in rodents, upregulates GLT1 and attenuates cue-induced cocaine reinstatement. Here, we tested the effects of increasing GLT1 expression on cue-induced cocaine seeking in rats exposed to either limited (2 h/d) or extended (6 h/d) cocaine access followed by short (2 d) or long (45 d) withdrawal periods. Treatment with ceftriaxone (200 mg/kg, i.p.) upregulated core GLT1 expression and attenuated cue-induced cocaine-seeking behavior only in rats exposed to long withdrawal periods, with a greater effect in the extended-access condition. Pearson's correlation revealed GLT1 expression in core to be inversely correlated with cue-induced cocaine-seeking behavior. To localize the effects of GLT1 upregulation within NAc, we tested the hypothesis that blockade of GLT1 in NAc core, but not shell, would reverse the ceftriaxone-mediated effect. Rats withdrawn from cocaine self-administration were treated with the same dose of ceftriaxone followed by intracore or intrashell infusions of one of two GLT1 blockers, dihydrokainic acid (500 μM) or DL-threo-β-benzyloxyaspartate (250 μM), or saline. Our results reveal that the ceftriaxone-mediated attenuation of cue-induced cocaine reinstatement is reversed by GLT1 blockade in core, but not shell, and further implicate core GLT1 as a potential therapeutic target for cocaine relapse.

Glutamate transporter 1: target for the treatment of alcohol dependence

Emerging evidence indicates that many aspects of alcohol and drug dependence involve changes in glutamate transmission. A number of studies have reported that drugs of abuse, including alcohol and cocaine, alter glutamate transport. Extracellular glutamate is regulated by a number of glutamate transporters in various brain regions. Of these transporters, glutamate transporter (GLT1) is a key player in the removal of most of the extracellular glutamate. Similar to neurodegenerative disease models, in which there is dysfunction of the glutamatergic excitatory system, the role of GLT1 has been tested in drug dependence models that show dysfunction of glutamate transmission. We and others have recently found that ceftriaxone, an FDA-approved drug known to elevate GLT1 expression, attenuates cue-induced cocaine relapse. Moreover, we recently found that alcohol-preferring rats treated with ceftriaxone showed a significant dosedependent reduction in alcohol consumption. We also demonstrated that ceftriaxone-induced upregulation of GLT1 expression was associated with increases in glutamate uptake in Huntington's disease mouse model. Importantly, ceftriaxone is currently in clinical trials for the treatment of amyotrophic lateral sclerosis. This review provides information about the potential therapeutic role of GLT1 for the treatment of alcohol abuse and dependence.

Glutamate transporter activation enhances nicotine antinociception and attenuates nicotine analgesic tolerance

Analgesic tolerance is partially mediated by enhanced glutamatergic transmission in the CNS. β-lactam antibiotics, through glutamate transporter subtype 1 (GLT-1) activation, reduce extracellular glutamate levels and attenuate tolerance to morphine analgesia in rats. Similar to opioids, nicotine has potent analgesic properties that are subject to tolerance. The purpose of this study was to evaluate the effects of ceftriaxone, a β-lactam antibiotic and GLT-1 activator on nicotine antinociception and its tolerance. Rats were pretreated for 5 days with ceftriaxone (200 mg/kg, intraperitoneally) before evaluating their analgesic response to nicotine (1.0 or 2.5 mg/kg, subcutaneously) for seven consecutive days using the tail-flick assay. Ceftriaxone-treated rats displayed an enhanced antinociceptive response to nicotine and unlike saline-injected controls, did not develop tolerance to nicotine's analgesic effects. These results suggest that GLT-1 transporter activation enhances and preserves nicotine antinociception and identify β-lactam antibiotics as potential complementary therapeutic agents for the treatment of chronic pain.

Nuclear factor-κB contributes to neuron-dependent induction of glutamate transporter-1 expression in astrocytes

The glutamate transporter-1 [GLT-1 (excitatory amino acid transporter 2)] subtype of glutamate transporter ensures crisp excitatory signaling and limits excitotoxicity in the CNS. Astrocytic expression of GLT-1 is regulated during development, by neuronal activity, and in neurodegenerative diseases. Although neurons activate astrocytic expression of GLT-1, the mechanisms involved have not been identified. In the present study, astrocytes from transgenic mice that express enhanced green fluorescent protein (eGFP) under the control of a bacterial artificial chromosome (BAC) containing a very large region of DNA surrounding the GLT-1 gene (BAC GLT-1 eGFP mice) were used to assess the role of nuclear factor-κB (NF-κB) in neuron-dependent activation of the GLT-1 promoter. We provide evidence that neurons activate NF-κB signaling in astrocytes. Transduction of astrocytes from the BAC GLT-1 eGFP mice with dominant-negative inhibitors of NF-κB signaling completely blocked neuron-dependent activation of a NF-κB reporter construct and attenuated induction of eGFP. Exogenous expression of p65 and/or p50 NF-κB subunits induced expression of eGFP or GLT-1 and increased GLT-1-mediated transport activity. Using wild-type and mutant GLT-1 promoter reporter constructs, we found that NF-κB sites at -583 or -251 relative to the transcription start site were required for neuron-dependent reporter activation. Electrophoretic mobility shift and supershift assays reveal that p65 and p50 interact with these same sites ex vivo. Finally, chromatin immunoprecipitation showed that p65 and p50 interact with these sites in adult cortex, but not in kidney (a tissue that expresses no detectable GLT-1). Together, these studies strongly suggest that NF-κB contributes to neuron-dependent regulation of astrocytic GLT-1 transcription.

Effects of opioids, cannabinoids, and vanilloids on body temperature

Cannabinoid and opioid drugs produce marked changes in body temperature. Recent findings have extended our knowledge about the thermoregulatory effects of cannabinoids and opioids, particularly as related to delta opioid receptors, endogenous systems, and transient receptor potential (TRP) channels. Although delta opioid receptors were originally thought to play only a minor role in thermoregulation compared to mu and kappa opioid receptors, their activation has been shown to produce hypothermia in multiple species. Endogenous opioids and cannabinoids also regulate body temperature. Mu and kappa opioid receptors are thought to be in tonic balance, with mu and kappa receptor activation producing hyperthermia and hypothermia, respectively. A particularly intense research focus is TRP channels, where TRPV1 channel activation produces hypothermia whereas TRPA1 and TRPM8 channel activation causes hyperthermia. The marked hyperthermia produced by TRPV1 channel antagonists suggests these warm channels tonically control body temperature. A better understanding of the roles of cannabinoid, opioid, and TRP systems in thermoregulation may have broad clinical implications and provide insights into interactions among neurotransmitter systems involved in thermoregulation.

Effects of opioids, cannabinoids, and vanilloids on body temperature

Cannabinoid and opioid drugs produce marked changes in body temperature. Recent findings have extended our knowledge about the thermoregulatory effects of cannabinoids and opioids, particularly as related to delta opioid receptors, endogenous systems, and transient receptor potential (TRP) channels. Although delta opioid receptors were originally thought to play only a minor role in thermoregulation compared to mu and kappa opioid receptors, their activation has been shown to produce hypothermia in multiple species. Endogenous opioids and cannabinoids also regulate body temperature. Mu and kappa opioid receptors are thought to be in tonic balance, with mu and kappa receptor activation producing hyperthermia and hypothermia, respectively. A particularly intense research focus is TRP channels, where TRPV1 channel activation produces hypothermia whereas TRPA1 and TRPM8 channel activation causes hyperthermia. The marked hyperthermia produced by TRPV1 channel antagonists suggests these warm channels tonically control body temperature. A better understanding of the roles of cannabinoid, opioid, and TRP systems in thermoregulation may have broad clinical implications and provide insights into interactions among neurotransmitter systems involved in thermoregulation.

beta-Lactam antibiotic inhibits development of morphine physical dependence in rats

beta-Lactam antibiotics enhance cellular glutamate uptake. As increased glutamatergic transmission is a primary mediator of opiate dependence, we tested the hypothesis that a beta-lactam antibiotic (ceftriaxone) prevents development of morphine physical dependence in rats. Morphine (20 mg/kg) was injected twice daily for 10 days to induce physical dependence. Naloxone (10 mg/kg) administration 1, 48, and 96 h after the last morphine injection induced a withdrawal syndrome characterized by the appearance of wet-dog shakes, teeth chattering, eye blinking, jumping, and paw tremor. Ceftriaxone (150, 200 mg/kg) injected once daily during chronic morphine exposure inhibited each naloxone-precipitated withdrawal sign. Ceftriaxone efficacy persisted even after the 96 h-naloxone (10 mg/kg) injection. These results suggest that beta-lactam antibiotics inhibit processes leading to development of morphine physical dependence.

Beta-lactam antibiotic reduces morphine analgesic tolerance in rats through GLT-1 transporter activation

Glutamate transporter subtype 1 (GLT-1) activation is a promising - and understudied - approach for managing aspects of morphine tolerance caused by increased glutamatergic transmission. Identification of beta-lactam antibiotics as pharmaceuticals which activate GLT-1 transporters prompted us to hypothesize that repeated beta-lactam antibiotic (ceftriaxone) administration blocks development of tolerance to morphine antinociception through GLT-1 activation. Here, we injected rats with morphine (10mg/kg, s.c.) twice daily for 7 days to induce tolerance and used the hot-plate assay to determine antinociception on days 1, 4 and 7 of repeated morphine administration. Ceftriaxone and a selective GLT-1 transporter inhibitor dihydrokainate (DHK) were co-administered with morphine to determine if GLT-1 activation mediated the ceftriaxone effect. Tolerance was present on days 4 and 7 of repeated morphine administration. Ceftriaxone (50, 100 or 200mg/kg, i.p.) administration dose-dependently blocked development of morphine tolerance. DHK (10mg/kg, s.c.), administered 15 min before each morphine injection, prevented inhibition of morphine tolerance by ceftriaxone (200mg/kg, i.p.). These results identify an interaction between ceftriaxone and morphine in opioid-tolerant rats and suggest beta-lactam antibiotics preserve analgesic efficacy during chronic morphine exposure.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Beta-lactam antibiotic prevents tolerance to the hypothermic effect of a kappa opioid receptor agonist

Beta-lactam antibiotics are the only clinically approved drugs which directly increase glutamate uptake. They activate the glutamate transporter subtype 1 (GLT-1), the protein responsible for 90% of glutamate uptake in the mammalian brain. The capacity of GLT-1 to clear extracellular glutamate suggests that glutamate transporter activators be explored for therapeutic approaches to clinical conditions caused by increased glutamatergic transmission. One of the most common drug effects mediated by increased glutamatergic signaling is opioid tolerance. Therefore, we tested the hypothesis that a beta-lactam antibiotic (ceftriaxone), by increasing glutamate uptake, prevents tolerance to hypothermia induced by a kappa opioid receptor agonist (U-50,488H). A single injection of U-50,488H (20mg/kg, s.c.) caused significant hypothermia in rats. Tolerance to the hypothermic effect of U50,488H was induced by injecting U50,488H (20mg/kg) twice daily for 7days. Pretreatment with ceftriaxone (200mg/kg, i.p.) for 7days did not alter the acute hypothermic response to U50,488H (20mg/kg) but did prevent tolerance to U50,488H-induced hypothermia. Central administration of dl-threo-beta-benzyloxyaspartic acid (TBOA) (0.2micromol, i.c.v.), a glutamate transporter inhibitor, abolished the effect of ceftriaxone. These results identify a functional interaction between ceftriaxone and U50,488H in vivo and provide pharmacological evidence that a beta-lactam antibiotic abolishes tolerance to hypothermia induced by a kappa opioid receptor agonist.

Mechanism of ceftriaxone induction of excitatory amino acid transporter-2 expression and glutamate uptake in primary human astrocytes

Glutamate is an essential neurotransmitter regulating brain functions. Excitatory amino acid transporter (EAAT)-2 is one of the major glutamate transporters primarily expressed in astroglial cells. Dysfunction of EAAT2 is implicated in acute and chronic neurological disorders, including stroke/ischemia, temporal lobe epilepsy, amyotrophic lateral sclerosis, Alzheimer disease, human immunodeficiency virus 1-associated dementia, and growth of malignant gliomas. Ceftriaxone, one of the beta-lactam antibiotics, is a stimulator of EAAT2 expression with neuroprotective effects in both in vitro and in vivo models based in part on its ability to inhibit neuronal cell death by glutamate excitotoxicity. Based on this consideration and its lack of toxicity, ceftriaxone has potential to manipulate glutamate transmission and ameliorate neurotoxicity. We investigated the mechanism by which ceftriaxone enhances EAAT2 expression in primary human fetal astrocytes (PHFA). Ceftriaxone elevated EAAT2 transcription in PHFA through the nuclear factor-kappaB (NF-kappaB) signaling pathway. The antibiotic promoted nuclear translocation of p65 and activation of NF-kappaB. The specific NF-kappaB binding site at the -272 position of the EAAT2 promoter was responsible for ceftriaxone-mediated EAAT2 induction. In addition, ceftriaxone increased glutamate uptake, a primary function of EAAT2, and EAAT2 small interference RNA completely inhibited ceftriaxone-induced glutamate uptake activity in PHFA. Taken together, our data indicate that ceftriaxone is a potent modulator of glutamate transport in PHFA through NF-kappaB-mediated EAAT2 promoter activation. These findings suggest a mechanism for ceftriaxone modulation of glutamate transport and for its potential effects on ameliorating specific neurodegenerative diseases through modulation of extracellular glutamate.

The beta-lactam antibiotic ceftriaxone inhibits physical dependence and abstinence-induced withdrawal from cocaine, amphetamine, methamphetamine, and clorazepate in planarians

Ceftriaxone (a beta-lactam antibiotic) has recently been identified as having the rare ability to increase the expression and functional activity of the glutamate transporter subtype 1 (GLT-1) in rat spinal cord cultures. GLT-1 has been implicated in diverse neurological disorders and in opioid dependence and withdrawal. It has been speculated that it might also be involved in the physical dependence and withdrawal of other abused drugs, but demonstration of this property can be difficult in mammalian models. Here, we demonstrate for the first time using a planarian model that ceftriaxone attenuates both the development of physical dependence and abstinence-induced withdrawal from cocaine, amphetamine, methamphetamine, and a benzodiazepine (clorazepate) in a concentration-related manner. These results suggest that physical dependence and withdrawal from several drugs involve a common - beta-lactam-sensitive - mechanism in planarians. If these findings can be shown to extend to mammals, beta-lactam antibiotics might represent a novel pharmacotherapy or adjunct approach for treating drug abuse or serve as a template for drug discovery efforts aimed at treating drug abuse, recovery from drug abuse, or ameliorating the withdrawal from chronic use of therapeutic medications.

Up-regulation of GLT1 expression increases glutamate uptake and attenuates the Huntington's disease phenotype in the R6/2 mouse

The striatum, which processes cortical information for behavioral output, is a key target of Huntington's disease (HD), an autosomal dominant condition characterized by cognitive decline and progressive loss of motor control. Increasing evidence implicates deficient glutamate uptake caused by a down-regulation of GLT1, the primary astroglial glutamate transporter. To test this hypothesis, we administered ceftriaxone, a beta-lactam antibiotic known to elevate GLT1 expression (200 mg/kg, i.p., for 5 days), to symptomatic R6/2 mice, a widely studied transgenic model of HD. Relative to vehicle, ceftriaxone attenuated several HD behavioral signs: paw clasping and twitching were reduced, while motor flexibility, as measured in a plus maze, and open-field climbing were increased. Assessment of GLT1 expression in striatum confirmed a ceftriaxone-induced increase relative to vehicle. To determine if the change in behavior and GLT1 expression represented a change in striatal glutamate handling, separate groups of behaving mice were evaluated with no-net-flux microdialysis. Vehicle treatment revealed a glutamate uptake deficit in R6/2 mice relative to wild-type controls that was reversed by ceftriaxone. Vehicle-treated animals, however, did not differ in GLT1 expression, suggesting that the glutamate uptake deficit in R6/2 mice reflects dysfunctional rather than missing GLT1. Our results indicate that impaired glutamate uptake is a major factor underlying HD pathophysiology and symptomology. The glutamate uptake deficit, moreover, is present in symptomatic HD mice and reversal of this deficit by up-regulating the functional expression of GLT1 with ceftriaxone attenuates the HD phenotype.

Icilin induces a hyperthermia in rats that is dependent on nitric oxide production and NMDA receptor activation

Icilin (AG-3-5) is a cold-inducing agent that activates the transient receptor potential channels TRPM8 and TRPA1. Both channels are members of the transient receptor potential (TRP) superfamily of ion channels and are activated by cold. Despite the key role of cold-activated TRPM8 and TRPA1 channels in temperature sensation and other physiological processes, the significance of these channels in thermoregulation in conscious animals is poorly understood. Therefore, in the present study we investigated the effects of icilin on body temperature in rats and tested the hypothesis that cold-activated TRP channel activation by icilin causes a hyperthermia which requires nitric oxide (NO) production and NMDA receptor stimulation. Our experiments revealed that icilin (2.5, 5, 7.5 and 10 mg/kg, i.m.) elicits a dose-related hyperthermia that is rapid in onset and of long duration. Pretreating rats with N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME) (10, 25 and 50 mg/kg, i.p.), a non-selective NO synthase inhibitor, attenuated the hyperthermia associated with icilin (7.5 mg/kg, i.m.). Pretreatment with (-)-6-[phosphonomethyl-1,2,3,4,4a,5,6,7,8,8a-decahydro-isoquinoline-2-carboxylate] (LY 235959) (0.25, 0.5 and 1 mg/kg, i.p.), a selective NMDA receptor antagonist, also attenuated the icilin-evoked hyperthermia. The administration of icilin (5 and 100 microg) into the lateral cerebroventricle of rats did not affect body temperature, thus indicating a peripheral site of action. These results indicate that icilin, a TRPM8/TRPA1 agonist, produces a dose-related hyperthermia in rats which requires both NO production and NMDA receptor activation.