Fawaz Alasmari

Effects of ampicillin on cystine/glutamate antiporter and glutamate transporter 1 isoforms as well as ethanol drinking in male P rats

Evidence demonstrated that glial cells, mainly astrocytes, regulate glutamate uptake through several glutamate transporters. Among these glutamate transporters, glutamate transporter 1 (GLT-1; its human homolog is excitatory amino acid transporter-2) is responsible for the majority of glutamate uptake. Cystine-glutamate antiporter (xCT) is another glial protein critical in regulating glutamate transmission. Several studies from our laboratory demonstrated that attenuation of ethanol intkae was associated in part with upregulation of xCT and GLT-1 expression suggesting the important role of these transporters in the treatment of ethanol dependence. We found recently that β-lactam antibiotic, ampicillin, upregulated GLT-1 expression in the prefrontal cortex (PFC) and nucleus accumbens (NAc) and consequently reduced ethanol intake in alcohol-preferring (P) rats. In this study, we investigated the effects of ampicillin on the expression of xCT and GLT-1 isoforms (GLT-1a and GLT-1b) as well as on GLAST expression. We found that ampicillin reduced ethanol intake as compared to the saline (control)-treated group. In addition, we found that ampicillin induced upregulation of xCT, GLT-1a, and GLT-1b expression in both the PFC and NAc, but had no effect on GLAST expression. Our findings provide significant role of ampicillin on upregulating xCT and GLT-1 isoforms expression, might be suggested as possible targets for the attenuation of ethanol consumption.

Metabotropic and ionotropic glutamate receptors as potential targets for the treatment of alcohol use disorder

Emerging evidence indicates that dysfunctional glutamate neurotransmission is critical in the initiation and development of alcohol and drug dependence. Alcohol consumption induced downregulation of glutamate transporter 1 (GLT-1) as reported in previous studies from our laboratory. Glutamate is the major excitatory neurotransmitter in the brain, which acts via interactions with several glutamate receptors. Alcohol consumption interferes with the glutamatergic signal transmission by altering the functions of these receptors. Among the glutamate receptors involved in alcohol-drinking behavior are the metabotropic receptors such as mGluR1/5, mGluR2/3, and mGluR7, as well as the ionotropic receptors, NMDA and AMPA. Preclinical studies using agonists and antagonists implicate these glutamatergic receptors in the development of alcohol use disorder (AUD). Therefore, the purpose of this review is to discuss the neurocircuitry involving glutamate transmission in animals exposed to alcohol and further outline the role of metabotropic and ionotropic receptors in the regulation of alcohol-drinking behavior. This review provides ample information about the potential therapeutic role of glutamatergic receptors for the treatment of AUD.

Effects of cefazolin and cefoperazone on glutamate transporter 1 isoforms and cystine/glutamate exchanger as well as alcohol drinking behavior in male alcohol-preferring rats.

Previously, we have reported that cefazolin and cefoperazone treatments attenuated ethanol consumption, at least in part, through upregulation of GLT-1 expression in male alcohol-preferring (P) rats. In this study, we determined the effects of these compounds on the expression of GLT-1 isoforms (GLT-1a and GLT-1b), cysteine/glutamate exchanger (xCT), which is another glial glutamate transporter co-localized with GLT-1, and glutamate/aspartate transporter (GLAST). We found that cefazolin and cefoperazone treatments decreased ethanol intake and upregulated both GLT-1 isoforms, GLT-1a and GLT-1b, in nucleus accumbens (NAc) and prefrontal cortex (PFC) compared to saline treated group. In addition, cefazolin increased the expression of xCT in NAc and PFC, while cefoperazone upregulated xCT expression only in NAc. However, we did not find any significant differences in GLAST expression between the treated and control groups. Overall, our findings suggest that cefazolin and cefoperazone may be considered as potential compounds for the treatment of ethanol dependence.

Effects of chronic inhalation of electronic cigarettes containing nicotine on glial glutamate transporters and α-7 nicotinic acetylcholine receptor in female CD-1 mice

ABSTRACT Alteration in glutamate neurotransmission has been found to mediate the development of drug dependence, including nicotine. We and others, through using western blotting, have reported that exposure to drugs of abuse reduced the expression of glutamate transporter‐1 (GLT‐1) as well as cystine/glutamate antiporter (xCT), which consequently increased extracellular glutamate concentrations in the mesocorticolimbic area. However, our previous studies did not reveal any changes in glutamate/aspartate transporter (GLAST) following exposure to drugs of abuse. In the present study, for the first time, we investigated the effect of chronic exposure to electronic (e)‐cigarette vapor containing nicotine, for one hour daily for six months, on GLT‐1, xCT, and GLAST expression in frontal cortex (FC), striatum (STR), and hippocampus (HIP) in outbred female CD1 mice. In this study, we also investigated the expression of alpha‐7 nicotinic acetylcholine receptor (&agr;‐7 nAChR), a major pre‐synaptic nicotinic receptor in the glutamatergic neurons, which regulates glutamate release. We found that inhalation of e‐cigarette vapor for six months increased &agr;‐7 nAChR expression in both FC and STR, but not in the HIP. In addition, chronic e‐cigarette exposure reduced GLT‐1 expression only in STR. Moreover, e‐cigarette vapor inhalation induced downregulation of xCT in both the STR and HIP. We did not find any significant changes in GLAST expression in any brain region. Finally, using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) techniques, we detected high concentrations of nicotine and cotinine, a major metabolite of nicotine, in the FC tissues of e‐cigarette exposed mice. These data provide novel evidence about the effects of chronic nicotine inhalation on the expression of key glial glutamate transporters as well as &agr;‐7 nAChR. Our work may suggest that nicotine exposure via chronic inhalation of e‐cigarette vapor may be mediated in part by alterations in the glutamatergic system. HIGHLIGHTSInhalation of e‐Cig vapor containing nicotine upregulates &agr;‐7 nAChR in FC and STR.Inhalation of e‐Cig vapor containing nicotine downregulates GLT‐1 in STR.Inhalation of e‐Cig vapor containing nicotine downregulates xCT in STR and HIP.GLAST is not changed following chronic exposure to e‐Cig vapor containing nicotine.

Modulatory effects of Ampicillin/Sulbactam on glial glutamate transporters and metabotropic glutamate receptor 1 as well as reinstatement to cocaine-seeking behavior

&NA; Glutamatergic system has an important role in cocaine‐seeking behavior. Studies have reported that chronic exposure to cocaine induces downregulation of glutamate transporter‐1 (GLT‐1) and cystine/glutamate exchanger (xCT) in the central reward brain regions. Ceftriaxone, a &bgr;‐lactam antibiotic, restored GLT‐1 expression and consequently reduced cue‐induced reinstatement of cocaine‐seeking behavior. In this study, we investigated the reinstatement to cocaine (20 mg/kg, i.p.) seeking behavior using a conditioned place preference (CPP) paradigm in male alcohol‐preferring (P) rats. In addition, we investigated the effects of Ampicillin/Sulbactam (AMP/SUL) (200 mg/kg, i.p.), a &bgr;‐lactam antibiotic, on cocaine‐induced reinstatement. We also investigated the effects of AMP/SUL on the expression of glial glutamate transporters and metabotropic glutamate receptor 1 (mGluR1) in the nucleus accumbens (NAc) core and shell and the dorsomedial prefrontal cortex (dmPFC). We found that AMP/SUL treatment reduced cocaine‐triggered reinstatement. This effect was associated with a decrease in locomotor activity. Moreover, GLT‐1 and xCT were downregulated in the NAc core and shell, but not in the dmPFC, following cocaine‐primed reinstatement. However, cocaine exposure increased the expression of mGluR1 in the NAc core, but not in the NAc shell or dmPFC. Importantly, AMP/SUL treatment normalized GLT‐1 and xCT expression in the NAc core and shell; however, the drug normalized mGluR1 expression in the NAc core only. Additionally, AMP/SUL increased the expression of GLT‐1 and xCT in the dmPFC as compared to the water naïve group. These findings demonstrated that glial glutamate transporters and mGluR1 in the mesocorticolimbic area could be potential therapeutic targets for the attenuation of reinstatement to cocaine‐seeking behavior. HighlightsCocaine downregulated GLT‐1 and xCT in the NAc core and shell but not dmPFC.Cocaine upregulated mGluR1 in the NAc core but not shell or dmPFC.AMP/SUL attenuated reinstatement to cocaine seeking behavior.AMP/SUL normalized GLT‐1, xCT and mGluR 1 in the mesocorticolimbic regions.AMP/SUL attenuated cocaine‐increased locomotion activity.

Targeting glutamate homeostasis for potential treatment of nicotine dependence

Several studies demonstrated that impairment in glutamatergic neurotransmission is linked to drug dependence and drug-seeking behavior. Increased extracellular glutamate concentration in mesocorticolimbic regions has been observed in animals developing nicotine dependence. Changes in glutamate release might be associated with stimulatory effect of nicotinic acetylcholine receptors (nAChRs) via nicotine exposure. We and others have shown increased extracellular glutamate concentration, which was associated with down regulation of the major glutamate transporter, glutamate transporter 1 (GLT-1), in brain reward regions of animals exposed to drug abuse, including nicotine and ethanol. Importantly, studies from our laboratory and others showed that upregulation of GLT-1 expression in the mesocorticolimbic brain regions may have potential therapeutic effects in drug dependence. In this review article, we discussed the effect of antagonizing presynaptic nAChRs in glutamate release, the upregulatory effect in GLT-1 expression and the role of glutamate receptors antagonists in the treatment of nicotine dependence.

Peri-adolescent drinking of ethanol and/or nicotine modulates astroglial glutamate transporters and metabotropic glutamate receptor-1 in female alcohol-preferring rats.

ABSTRACT Impairment in glutamate neurotransmission mediates the development of dependence upon nicotine (NIC) and ethanol (EtOH). Previous work indicates that continuous access to EtOH or phasic exposure to NIC reduces expression of the glutamate transporter‐1 (GLT‐1) and cystine/glutamate antiporter (xCT) but not the glutamate/aspartate transporter (GLAST). Additionally, metabotropic glutamate receptors (mGluRs) expression was affected following exposure to EtOH or NIC. However, little is known about the effects of EtOH and NIC co‐consumption on GLT‐1, xCT, GLAST, and mGluR1 expression. In this study, peri‐adolescent female alcohol preferring (P) rats were given binge‐like access to water, sucrose (SUC), SUC‐NIC, EtOH, or EtOH‐NIC for four weeks. The present study determined the effects of these reinforcers on GLT‐1, xCT, GLAST, and mGluR1 expression in the nucleus accumbens (NAc), hippocampus (HIP) and prefrontal cortex (PFC). GLT‐1 and xCT expression were decreased in the NAc following both SUC‐NIC and EtOH‐NIC. In addition, only xCT expression was downregulated in the HIP in both of these latter groups. Also, glutathione peroxidase (GPx) activity in the HIP was reduced following SUC, SUC‐NIC, EtOH, and EtOH‐NIC consumption. Similar to previous work, GLAST expression was not altered in any brain region by any of the reinforcers. However, mGluR1 expression was increased in the NAc in the SUC‐NIC, EtOH, and EtOH‐NIC groups. These results indicate that peri‐adolescent binge‐like drinking of EtOH or SUC with or without NIC may exert differential effects on astroglial glutamate transporters and receptors. Our data further parallel some of the previous findings observed in adult rats. HighlightsBinge‐like drinking of NIC EtOH or SUC with NIC downregulated GLT‐1 in NAc.Binge‐like drinking of NIC EtOH or SUC with NIC reduced xCT in NAc and HIP.Binge‐like drinking of EtOH with/without NIC upregulated mGluR1in the NAc.Binge‐like drinking of EtOH or SUC with/without NIC did not affect GLAST.Binge‐like drinking of EtOH or SUC with/without NIC reduced GPx activity in HIP.

Modulation of the ATP-binding cassette B1 transporter by neuro-inflammatory cytokines: role in the pathogenesis of Alzheimer’s disease

Inflammation of neuronal tissue, or neuro-inflammation, is associated with neurological diseases, including Alzheimers disease (AD) (Patel et al., 2005; Walters et al., 2016; Wang B. et al., 2016). The exact role of neuro-inflammation in AD remains uncertain as it may be a result of other causative factors in AD, but can subsequently contribute to the course of the disease, or be caused by other factors. Neuro-inflammation is significantly correlated with changes in the expression of brain proteins that regulate the transport or signaling pathways of endogenous and exogenous molecules (Tilleux and Hermans, 2007; Kim et al., 2015; Gao et al., 2017). ATP-binding cassette (ABC) proteins, such as ABCB1 (P-glycoprotein, P-gp), are highly expressed in the brain capillary endothelial cells of the blood - brain barrier (BBB) and limit the uptake of certain endogenous and exogenous compounds into the brain (Loscher and Potschka, 2005; Zhang et al., 2015). Several studies have reported alterations in the expression and functions of ABCB1 in AD models (Wijesuriya et al., 2010; van Assema et al., 2012). The formation of amyloid beta (Aβ) (a substrate of ABCB1) plaques in the brain is a histological hallmark associated with AD (Lee et al., 2004; Wildburger et al., 2017). The ABCB1 transporter removes Aβ from the brain into the circulatory system (Hartz et al., 2010; ElAli and Rivest, 2013). Thus, alterations in the expression or function of ABCB1 may affect the progression of AD. The role of ABCB1 in AD progression and treatment has been recently reviewed, elsewhere (Pahnke et al., 2014; Sita et al., 2017). However, the focus of this opinion article is to discuss the effects of neuro-inflammatory cytokines on ABCB1 function and their role in the pathogenesis of AD.

Role of glutamatergic system and mesocorticolimbic circuits in alcohol dependence

Emerging evidence demonstrates that alcohol dependence is associated with dysregulation of several neurotransmitters. Alterations in dopamine, glutamate and gamma-aminobutyric acid release are linked to chronic alcohol exposure. The effects of alcohol on the glutamatergic system in the mesocorticolimbic areas have been investigated extensively. Several studies have demonstrated dysregulation in the glutamatergic systems in animal models exposed to alcohol. Alcohol exposure can lead to an increase in extracellular glutamate concentrations in mesocorticolimbic brain regions. In addition, alcohol exposure affects the expression and functions of several glutamate receptors and glutamate transporters in these brain regions. In this review, we discussed the effects of alcohol exposure on glutamate receptors, glutamate transporters and glutamate homeostasis in each area of the mesocorticolimbic system. In addition, we discussed the genetic aspect of alcohol associated with glutamate and reward circuitry. We also discussed the potential therapeutic role of glutamate receptors and glutamate transporters in each brain region for the treatment of alcohol dependence. Finally, we provided some limitations on targeting the glutamatergic system for potential therapeutic options for the treatment alcohol use disorders.

A computerized exposure system for animal models to optimize nicotine delivery into the brain through inhalation of electronic cigarette vapors or cigarette smoke.

Pre-clinical studies investigated the effects of chronic exposure to nicotine on lungs, kidneys and brains using animal models. Most of these studies delivered nicotine into the circulatory and central nervous systems (CNS) through intraperitoneal injection or oral consumption methods. Few studies used inhalation machine system for nicotine delivery into brains in rodents to mimic human exposure to cigarettes. However, finding a more accurate and clinically relevant method of nicotine delivery is critical. A computerized inhalation machine has been designed (SciReq) and is currently employed in several institutions. The computerized machine delivers electronic (e)-cigarette vapor as well as tobacco smoke to rodents using marketed e-cigarette devices or tobacco cigarettes. This provides evidence about clinical effects of nicotine delivery by traditional methods (combustible cigarettes) and new methodologies (e-cigarettes) in physiological systems. Potential neurobiological mechanisms for the development of nicotine dependence have been determined recently in mice exposed to e-cigarette vapors in our laboratory using SciReq system. In this review article, the discussion focuses on the efficiency and practical applicability of using this computerized inhalation exposure system in inducing significant changes in brain protein expression and function as compared to other nicotine delivery methods. The SciReq inhalation system utilized in our laboratory and others is a method of nicotine delivery to the CNS, which has physiological relevance and mimics human inhalant exposures. Translation of the effects of inhaled nicotine on the CNS into clinical settings could provide important health considerations.