Ceftriaxone increases glutamate uptake and reduces striatal tyrosine hydroxylase loss in 6-OHDA Parkinson's model

Ceftriaxone reverses diet-induced deficits in goal-directed control

RATIONALE

Obesity is associated with numerous health risks and ever-increasing rates are a significant global concern. However, despite weight loss attempts many people have difficulty maintaining weight loss. Previous studies in animals have shown that chronic access to an obesogenic diet can disrupt goal-directed behavior, impairing the ability of animals to flexibly adjust food-seeking behavior following changes in the value of earned outcomes. Changes in behavioral control have been linked to disruption of glutamate transmission in the dorsal medial striatum (DMS), a region critical for the acquisition and expression of goal-directed behavior.

OBJECTIVES

The goal of this study was to test whether ceftriaxone, a beta-lactam antibiotic shown elsewhere to upregulate the expression of the glutamate transporter GLT-1, would improve goal-directed control following long-term exposure to an obesogenic diet.

METHODS

Male and female rats were given access to either standard chow or chow plus sweetened condensed milk (SCM) for 6 weeks. Access to SCM was ended and rats received daily injections of either ceftriaxone or saline for 6 days. Rats were then trained to press a lever to earn a novel food reward and, finally, were assessed for sensitivity to outcome devaluation. Histological analyses examined changes to GLT-1 protein levels and morphological changes to astrocytes, within the DMS.

RESULTS

We found that ceftriaxone robustly restored goal-directed behavior in animals following long-term exposure to SCM. While we did not observe changes in protein levels of GLT-1 in the DMS, we observed that SCM induced changes in the morphology of astrocytes in the DMS, and that ceftriaxone mitigated these changes.

CONCLUSIONS

These results demonstrate that long-term access to a SCM diet impairs goal-directed behavior while also altering the morphology of astrocytes in the DMS. Furthermore, these results suggest that ceftriaxone administration can reverse the impairment of goal-directed behavior potentially through its actions on astrocytes in decision-making circuitry.

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.

Dopamine Signaling in Substantia Nigra and Its Impact on Locomotor Function-Not a New Concept, but Neglected Reality

The mechanistic influences of dopamine (DA) signaling and impact on motor function are nearly always interpreted from changes in nigrostriatal neuron terminals in striatum. This is a standard practice in studies of human Parkinson's disease (PD) and aging and related animal models of PD and aging-related parkinsonism. However, despite dozens of studies indicating an ambiguous relationship between changes in striatal DA signaling and motor phenotype, this perseverating focus on striatum continues. Although DA release in substantia nigra (SN) was first reported almost 50 years ago, assessment of nigral DA signaling changes in relation to motor function is rarely considered. Whereas DA signaling has been well-characterized in striatum at all five steps of neurotransmission (biosynthesis and turnover, storage, release, reuptake, and post-synaptic binding) in the nigrostriatal pathway, the depth of such interrogations in the SN, outside of cell counts, is sparse. However, there is sufficient evidence that these steps in DA neurotransmission in the SN are operational and regulated autonomously from striatum and are present in human PD and aging and related animal models. To complete our understanding of how nigrostriatal DA signaling affects motor function, it is past time to include interrogation of nigral DA signaling. This brief review highlights evidence that changes in nigral DA signaling at each step in DA neurotransmission are autonomous from those in striatum and changes in the SN alone can influence locomotor function. Accordingly, for full characterization of how nigrostriatal DA signaling affects locomotor activity, interrogation of DA signaling in SN is essential.

Astrocyte Responses Influence Local Effects of Whole-Brain Magnetic Stimulation in Parkinsonian Rats

BACKGROUND

Excessive glutamatergic transmission in the striatum is implicated in Parkinson's disease (PD) progression. Astrocytes maintain glutamate homeostasis, protecting from excitotoxicity through the glutamate-aspartate transporter (GLAST), whose alterations have been reported in PD. Noninvasive brain stimulation using intermittent theta-burst stimulation (iTBS) acts on striatal neurons and glia, inducing neuromodulatory effects and functional recovery in experimental parkinsonism.

OBJECTIVE

Because PD is associated with altered astrocyte function, we hypothesized that acute iTBS, known to rescue striatal glutamatergic transmission, exerts regional- and cell-specific effects through modulation of glial functions.

METHODS

6-Hydroxydopamine-lesioned rats were exposed to acute iTBS, and the areas predicted to be more responsive by a biophysical, hyper-realistic computational model that faithfully reconstructs the experimental setting were analyzed. The effects of iTBS on glial cells and motor behavior were evaluated by molecular and morphological analyses, and CatWalk and Stepping test, respectively.

RESULTS

As predicted by the model, the hippocampus, cerebellum, and striatum displayed a marked c-FOS activation after iTBS, with the striatum showing specific morphological and molecular changes in the astrocytes, decreased phospho-CREB levels, and recovery of GLAST. Striatal-dependent motor performances were also significantly improved.

CONCLUSION

These data uncover an unknown iTBS effect on astrocytes, advancing the understanding of the complex mechanisms involved in TMS-mediated functional recovery. Data on numerical dosimetry, obtained with a degree of anatomical details never before considered and validated by the biological findings, provide a framework to predict the electric-field induced in different specific brain areas and associate it with functional and molecular changes. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Nigral-specific increase in ser31 phosphorylation compensates for tyrosine hydroxylase protein and nigrostriatal neuron loss: Implications for delaying parkinsonian signs

Compensatory mechanisms that augment dopamine (DA) signaling are thought to mitigate onset of hypokinesia prior to major loss of tyrosine hydroxylase (TH) in striatum that occurs in Parkinson's disease. However, the identity of such mechanisms remains elusive. In the present study, the rat nigrostriatal pathway was unilaterally-lesioned with 6-hydroxydopamine (6-OHDA) to determine whether differences in DA content, TH protein, TH phosphorylation, or D1 receptor expression in striatum or substantia nigra (SN) aligned with hypokinesia onset and severity at two time points. In striatum, DA and TH loss reached its maximum (>90%) 7 days after lesion induction. However, in SN, no DA loss occurred, despite ∼60% TH loss. Hypokinesia was established at 21 days post-lesion and maintained at 28 days. At this time, DA loss was ∼60% in the SN, but still of lesser magnitude than TH loss. At day 7 and 28, ser31 TH phosphorylation increased only in SN, corresponding to less DA versus TH protein loss. In contrast, ser40 TH phosphorylation was unaffected in either region. Despite DA loss in both regions at day 28, D1 receptor expression increased only in lesioned SN. These results support the concept that augmented components of DA signaling in the SN, through increased ser31 TH phosphorylation and D1 receptor expression, contribute as compensatory mechanisms against progressive nigrostriatal neuron and TH protein loss, and may mitigate hypokinesia severity.

Foliglurax, a positive allosteric modulator of the metabotrophic glutamate receptor 4, protects dopaminergic neurons in MPTP-lesioned male mice

Overactivity of the corticostriatal glutamatergic pathway is documented in Parkinson's disease (PD) and stimulation of presynaptic metabotropic glutamate (mGlu) receptors 4 on these striatal afferents inhibits glutamate release normalizing neuronal activity in the basal ganglia. Moreover, mGlu4 receptors are also expressed in glial cells and are able to modulate glial function making this receptor a potential target for neuroprotection. Hence, we investigated whether foliglurax, a positive allosteric modulator of mGlu4 receptors with high brain exposure after oral administration, has neuroprotective effects in MPTP mice to model early PD. Male mice were treated daily from day 1 to 10 with 1, 3 or 10 mg/kg of foliglurax and administered MPTP on the 5th day then euthanized on the 11th day. Dopamine neuron integrity was assessed with measures of striatal dopamine and its metabolites levels, striatal and nigral dopamine transporter (DAT) binding and inflammation with markers of striatal astrocytes (GFAP) and microglia (Iba1). MPTP lesion produced a decrease in dopamine, its metabolites and striatal DAT specific binding that was prevented by treatment with 3 mg/kg of foliglurax, whereas 1 and 10 mg/kg had no beneficial effect. MPTP mice had increased levels of GFAP; foliglurax treatment (3 mg/kg) prevented this increase. Iba1 levels were unchanged in MPTP mice compared to control mice. There was a negative correlation between dopamine content and GFAP levels. Our results show that positive allosteric modulation of mGlu4 receptors with foliglurax provided neuroprotective effects in the MPTP mouse model of PD.

Differential expression of RET and GDNF family receptor, GFR-α1, between striatum and substantia nigra following nigrostriatal lesion: a case for diminished GDNF-signaling

Although glial cell line-derived neurotrophic factor (GDNF) showed efficacy in preclinical and early clinical studies to alleviate parkinsonian signs in Parkinson's disease (PD), later trials did not meet primary endpoints, giving pause to consider further investigation. While GDNF dose and delivery methods may have contributed to diminished efficacy, one crucial aspect of these clinical studies is that GDNF treatment across all studies began ∼8 years after PD diagnosis; a time point representing several years after near 100% depletion of nigrostriatal dopamine markers in striatum and at least 50% in substantia nigra (SN), and is later than the timing of GDNF treatment in preclinical studies. With nigrostriatal terminal loss exceeding 70% at PD diagnosis, we utilized hemi-parkinsonian rats to determine if expression of GDNF family receptor, GFR-α1, and receptor tyrosine kinase, RET, differed between striatum and SN at 1 and 4 weeks following a 6-hydroxydopamine (6-OHDA) lesion. Whereas GDNF expression changed minimally, GFR-α1 expression decreased progressively in striatum and in tyrosine hydroxylase positive (TH+) cells in SN, correlating with reduced TH cell number. However, in nigral astrocytes, GFR-α1 expression increased. RET expression decreased maximally in striatum by 1 week, whereas in the SN, a transient bilateral increase occurred that returned to control levels by 4 weeks. Expression of brain-derived neurotrophic factor (BDNF) or its receptor, TrkB, were unchanged throughout lesion progression. Together, these results reveal that differential GFR-α1 and RET expression between the striatum and SN, and cell-specific differences in GFR-α1 expression in SN, occur during nigrostriatal neuron loss. Targeting loss of GDNF receptors appears critical to enhance GDNF therapeutic efficacy against nigrostriatal neuron loss.

Significance Statement

Although preclinical evidence supports that GDNF provides neuroprotection and improves locomotor function in preclinical studies, clinical data supporting its efficacy to alleviate motor impairment in Parkinson's disease patients remains uncertain. Using the established 6-OHDA hemi-parkinsonian rat model, we determined whether expression of its cognate receptors, GFR-α1 and RET, were differentially affected between striatum and substantia nigra in a timeline study. In striatum, there was early and significant loss of RET, but a gradual, progressive loss of GFR-α1. In contrast, RET transiently increased in lesioned substantia nigra, but GFR-α1 progressively decreased only in nigrostriatal neurons and correlated with TH cell loss. Our results indicate that direct availability of GFR-α1 may be a critical element that determines GDNF efficacy following striatal delivery.

Highlights

GDNF expression was minimally affected by nigrostriatal lesionGDNF family receptor, GFR-α1, progressively decreased in striatum and in TH neurons in SN.GFR-α1 expression decreased along with TH neurons as lesion progressedGFR-α1 increased bilaterally in GFAP+ cells suggesting an inherent response to offset TH neuron lossRET expression was severely reduced in striatum, whereas it increased in SN early after lesion induction.

Astrocytes as a Therapeutic Target in Alzheimer's Disease-Comprehensive Review and Recent Developments

Alzheimer's disease (AD) is a frequent and disabling neurodegenerative disorder, in which astrocytes participate in several pathophysiological processes including neuroinflammation, excitotoxicity, oxidative stress and lipid metabolism (along with a critical role in apolipoprotein E function). Current evidence shows that astrocytes have both neuroprotective and neurotoxic effects depending on the disease stage and microenvironmental factors. Furthermore, astrocytes appear to be affected by the presence of amyloid-beta (Aβ), with alterations in calcium levels, gliotransmission and proinflammatory activity via RAGE-NF-κB pathway. In addition, astrocytes play an important role in the metabolism of tau and clearance of Aβ through the glymphatic system. In this review, we will discuss novel pharmacological and non-pharmacological treatments focused on astrocytes as therapeutic targets for AD. These interventions include effects on anti-inflammatory/antioxidant systems, glutamate activity, lipid metabolism, neurovascular coupling and glymphatic system, calcium dysregulation, and in the release of peptides which affects glial and neuronal function. According to the AD stage, these therapies may be of benefit in either preventing or delaying the progression of the disease.

The Interplay between Gut Microbiota and Parkinson's Disease: Implications on Diagnosis and Treatment

The bidirectional interaction between the gut microbiota (GM) and the Central Nervous System, the so-called gut microbiota brain axis (GMBA), deeply affects brain function and has an important impact on the development of neurodegenerative diseases. In Parkinson’s disease (PD), gastrointestinal symptoms often precede the onset of motor and non-motor manifestations, and alterations in the GM composition accompany disease pathogenesis. Several studies have been conducted to unravel the role of dysbiosis and intestinal permeability in PD onset and progression, but the therapeutic and diagnostic applications of GM modifying approaches remain to be fully elucidated. After a brief introduction on the involvement of GMBA in the disease, we present evidence for GM alterations and leaky gut in PD patients. According to these data, we then review the potential of GM-based signatures to serve as disease biomarkers and we highlight the emerging role of probiotics, prebiotics, antibiotics, dietary interventions, and fecal microbiota transplantation as supportive therapeutic approaches in PD. Finally, we analyze the mutual influence between commonly prescribed PD medications and gut-microbiota, and we offer insights on the involvement also of nasal and oral microbiota in PD pathology, thus providing a comprehensive and up-to-date overview on the role of microbial features in disease diagnosis and treatment.

Amitriptyline Improves Cognitive and Neuronal Function in a Rat Model that Mimics Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB), a highly prevalent neurodegenerative disorder, causes motor and cognitive deficits. The main pathophysiologies of DLB are glutamate excitotoxicity and accumulation of Lewy bodies comprising α-synuclein (α-syn) and β-amyloid (Aβ). Amitriptyline (AMI) promotes expression of glutamate transporter-1 and glutamate reuptake. In this study, we measured the effects of AMI on behavioral and neuronal function in a DLB rat model. We used rivastigmine (RIVA) as a positive control. To establish the DLB rat model, male Wistar rats were stereotaxically injected with recombinant adenoassociated viral vector with the SNCA gene (10μg/10μL) and Aβ (5μg/2.5μL) into the left ventricle and prefrontal cortex, respectively. AMI (10mg/kg/day, i.p.), RIVA (2mg/kg/day, i.p.), or saline was injected intraperitoneally after surgery. From the 29^th day, behavioral tests were performed to evaluate the motor and cognitive functions of the rats. Immunohistochemical staining was used to assess neuronal changes. We measured the α-syn level, number of newborn cells, and neuronal density in the hippocampus and in the nigrostriatal dopaminergic system. The DLB group exhibited deficit in object recognition. Both the AMI and RIVA treatments reversed these deficits. Histologically, the DLB rats exhibited cell loss in the substantia nigra pars compacta and in the hippocampal CA1 area. AMI reduced this cell loss, but RIVA did not. In addition, the DLB rats exhibited a lower number of newborn cells and higher α-syn levels in the dentate gyrus (DG). AMI did not affect α-syn accumulation but recovered neurogenesis in the DG of the rats, whereas RIVA reversed the α-syn accumulation but did not affect neurogenesis in the rats. We suggest that AMI may have potential for use in the treatment of DLB.

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.

Trafficking of the glutamate transporter is impaired in LRRK2-related Parkinson's disease

The Excitatory Amino Acid Transporter 2 (EAAT2) accounts for 80% of brain glutamate clearance and is mainly expressed in astrocytic perisynaptic processes. EAAT2 function is finely regulated by endocytic events, recycling to the plasma membrane and degradation. Noteworthy, deficits in EAAT2 have been associated with neuronal excitotoxicity and neurodegeneration. In this study, we show that EAAT2 trafficking is impaired by the leucine-rich repeat kinase 2 (LRRK2) pathogenic variant G2019S, a common cause of late-onset familial Parkinson’s disease (PD). In LRRK2 G2019S human brains and experimental animal models, EAAT2 protein levels are significantly decreased, which is associated with elevated gliosis. The decreased expression of the transporter correlates with its reduced functionality in mouse LRRK2 G2019S purified astrocytic terminals and in Xenopus laevis oocytes expressing human LRRK2 G2019S. In LRRK2 G2019S knock-in mouse brain, the correct surface localization of the endogenous transporter is impaired, resulting in its interaction with a plethora of endo-vesicular proteins. Mechanistically, we report that pathogenic LRRK2 kinase activity delays the recycling of the transporter to the plasma membrane via Rabs inactivation, causing its intracellular re-localization and degradation. Taken together, our results demonstrate that pathogenic LRRK2 interferes with the physiology of EAAT2, pointing to extracellular glutamate overload as a possible contributor to neurodegeneration in PD.

Neuroprotective Effect of Ceftriaxone on MPTP-Induced Parkinson's Disease Mouse Model by Regulating Inflammation and Intestinal Microbiota

Parkinson's disease (PD) is a common degenerative disease of the central nervous system. Although some drugs can alleviate the progress of PD, their long-term use will lead to complications, so it is still necessary to find new drugs to delay or cure PD effectively. In view of the difficulty in developing new drugs, it is imperative to discover new functions of existing compounds that could be used to treat PD. In this study, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to induce PD symptoms in a mouse model. Subsequently, these mice were treated with the antibiotic ceftriaxone. Ceftriaxone alleviated the behavioural and neuropathological changes induced by MPTP, downregulated the expression of glial fibrillary acidic protein (GFAP) and ionised calcium-binding adapter molecule 1 (Iba1) as markers of astroglia and microglia, respectively, and reduced the expression of neuroinflammation-related Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), and phosphorylated nuclear factor kappa-B (p-NF-κB)/NF-κB in the brain of PD mice. In addition, ceftriaxone reduced the abundance of pathogenic bacteria of the genus Proteus and increased the abundance of probiotic Akkermansia. Finally, ceftriaxone treatment increased the expression of the tight junction proteins zona occludens-1(ZO-1) and occludin in the colon, decreased the expression of the inflammation-related proteins TLR4, MyD88, and NF-κB in the colon, and decreased the serum concentration of the proinflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumour necrosis factor-α (TNF-α). These results indicate that ceftriaxone had a neuroprotective effect on MPTP-induced PD mice, and its neuroprotective effect could be through regulating inflammation and intestinal microbiota. While we showed that ceftriaxone exerts a neuroprotective effect in an MPTP-induced PD mouse model, our findings are limited to the short-term effects of ceftriaxone. Additional work using transgenic mice is required to determine the long-term effects of ceftriaxone. In addition, the dose and frequency of ceftriaxone use should be evaluated.

Induction of Parkinsonian-Like Changes via Targeted Downregulation of Astrocytic Glutamate Transporter GLT-1 in the Striatum

BACKGROUND

Previous investigations have suggested that decreased expression of glutamate transporter-1 (GLT-1) is involved in glutamate excitotoxicity and contribute to the development of Parkinson's disease (PD), GLT-1 is decreased in animal models of PD. GLT-1 is mainly expressed in astrocytes, and the striatum is a GLT-1-rich brain area.

OBJECTIVE

The aim was to explore the function and mechanism of astrocytic GLT-1 in PD-like changes.

METHODS

In the study, PD-like changes and their molecular mechanism in rodents were tested by a behavioral assessment, micro-positron emission tomography/computed tomography (PET/CT), western blotting, immunohistochemical and immunofluorescence staining, and high performance liquid chromatography pre-column derivatization with O-pthaldialdehida after downregulating astrocytic GLT-1 in vivo and in vitro.

RESULTS

In vivo, after 6 weeks of brain stereotactic injection of adeno-associated virus into the striatum, rats in the astrocytic GLT-1 knockdown group showed poorer motor performance, abnormal gait, and depression-like feature; but no olfactory disorders. The results of micro-PET/CT and western blotting indicated that the dopaminergic system was impaired in astrocytic GLT-1 knockdown rats. Similarly, tyrosine hydroxylase (TH) positive immune-staining in neurons of astrocytic GLT-1 knockdown rats showed deficit in cell count. In vitro, knockdown of astrocytic GLT-1 via RNA interference led to morphological injury of TH-positive neurons, which may be related to the abnormal calcium signal induced by glutamate accumulation after GLT-1 knockdown. Furthermore, the GLT-1 agonist ceftriaxone showed a protective effect on TH-positive neuron impairment.

CONCLUSION

The present findings may shed new light on the future prevention and treatment of PD based on blocking glutamate excitotoxicity.

The Role of Pathogens and Anti-Infective Agents in Parkinson's Disease, from Etiology to Therapeutic Implications

Parkinson's disease is a debilitating neurodegenerative disorder whose etiology is still unclear, hampering the development of effective treatments. There is an urgent need to identify the etiology and provide further effective treatments. Recently, accumulating evidence has indicated that infection may play a role in the etiology of Parkinson's disease. The infective pathogens may act as a trigger for Parkinson's disease, the most common of which are hepatitis C virus, influenza virus, and Helicobacter pylori. In addition, gut microbiota is increasingly recognized to influence brain function through the gut-brain axis, showing an important role in the pathogenesis of Parkinson's disease. Furthermore, a series of anti-infective agents exhibit surprising neuroprotective effects via various mechanisms, such as interfering with α-synuclein aggregation, inhibiting neuroinflammation, attenuating oxidative stress, and preventing from cell death, independent of their antimicrobial effects. The pleiotropic agents affect important events in the pathogenesis of Parkinson's disease. Moreover, most of them are less toxic, clinically safe and have good blood-brain penetrability, making them hopeful candidates for the treatment of Parkinson's disease. However, the use of antibiotics and subsequent gut dysbiosis may also play a role in Parkinson's disease, making the long-term effects of anti-infective drugs worthy of further consideration and exploration. This review summarizes the current evidence for the association between infective pathogens and Parkinson's disease and subsequently explores the application prospects of anti-infective drugs in Parkinson's disease treatment, providing novel insights into the pathogenesis and treatment of Parkinson's disease.

The role of hippocampal glial glutamate transporter (GLT-1) in morphine-induced behavioral responses

Opioid abuse modifies synaptic plasticity, which leads to behavioral changes, such as morphine dependence, but the mechanism remains poorly understood. Glial cells play an important role in the modulation of synaptic plasticity and are involved in addictive-like behaviors. The indisputable role of glutamate in opiate addiction has been shown. Astrocytes, a type of glial cells, which are integral functional elements of synapses, modulate the concentration of glutamate in the synaptic space. One of the most important mechanisms for glutamate concentration regulation is its uptake from the synaptic cleft. In this study, we evaluated the role of hippocampal glial glutamate transporter (GLT-1) in morphine dependence. Male rats received subcutaneous (s.c.) morphine sulfate (10 mg/kg) at an interval of 12 h for 9 days. In order to activate GLT-1, animals received an intrahippocampal injection of ceftriaxone (0.5 mmol/0.5 μl) in the CA1 region of the hippocampus, 30 min before each morphine administration. Rats were assessed for morphine dependence by monitoring naloxone hydrochloride-induced morphine withdrawal. Our results showed that hippocampal microinjection of ceftriaxone, as an activator of GLT-1, reduced some signs of morphine withdrawal, such as activity, diarrhea, head tremor, freezing, and ptosis. It seems that hippocampal GLT-1 can be affected by chronic morphine administration and involved in morphine dependence. Therefore, its activation may reduce morphine side effects by reducing hippocampal glutamate.

Exercise increases striatal Glu reuptake and improves motor dysfunction in 6-OHDA-induced Parkinson's disease rats

The purpose of this study is to clarify that exercise may improve the motor dysfunction of Parkinson's disease (PD) model rats by increasing the reuptake of glutamate (Glu) in the striatum. The neurotoxin 6-hydroxydopamine (6-OHDA) was injected into the medial forebrain bundle (MFB) of the rats' right brain to establish PD model rats with unilateral injury, and the sham operation group was given the same dose of normal saline at the same site as the control group. The reliability of the model was evaluated by apomorphine (APO)-induced rotation test combined with tyrosine hydroxylase (TH) immunohistochemical staining in the substantia nigra and striatum. The exercise group started treadmill training intervention (11 m/min, 30 min/day, 5d/week, and 4 weeks in total) 1 week after the operation. The balance bar test, suspension test, and the tail-lifting handstand test were used to evaluate exercise performance of rats; RT-PCR and western blotting were used to detect protein and mRNA expression of glutamate transporter-1 (GLT-1) and glutamine synthetase (GS) in the striatum; and isotope labeling was used to detect the ability of Glu reuptake in the striatum. (1) Compared with PD group, the number of TH immunoreactive cells in the substantia nigra and the content of TH immunoreactive fibers in the striatum did not change significantly in PD + Ex group. (2) Compared with PD group, the latency and total time of crossing the balance beam were significantly shorter (P < 0.01), the retention time of two forepaws on the metal wire was significantly longer (P < 0.01), the maximum lifting of head and trunk was significantly increased (P < 0.01) in PD + Ex group. (3) Compared with PD group, the ability of Glu reuptake in the striatum was significantly increased (P < 0.05), the expression levels of GLT-1 and GS mRNA in the striatum were significantly increased (P < 0.05), the protein expression of GLT-1 and GS in the striatum was significantly upregulated (P < 0.05) in PD + Ex group. Exercise intervention can significantly improve the motor dysfunction of PD model rats, increase the ability of striatal Glu reuptake significantly, and upregulate the expression levels of GLT-1 and GS protein and GS mRNA significantly. Exercise intervention may increase the protein expression level of GLT-1 and increase the reuptake ability of Glu in the striatum, thereby reducing the excitotoxic effect of excessive Glu on the postsynaptic membrane, and ultimately alleviate the motor dysfunction in PD model rats.

Challenges and Opportunities of Targeting Astrocytes to Halt Neurodegenerative Disorders

Neurodegenerative diseases are a heterogeneous group of disorders whose incidence is likely to duplicate in the next 30 years along with the progressive aging of the western population. Non-cell-specific therapeutics or therapeutics designed to tackle aberrant pathways within neurons failed to slow down or halt neurodegeneration. Yet, in the last few years, our knowledge of the importance of glial cells to maintain the central nervous system homeostasis in health conditions has increased exponentially, along with our awareness of their fundamental and multifaced role in pathological conditions. Among glial cells, astrocytes emerge as promising therapeutic targets in various neurodegenerative disorders. In this review, we present the latest evidence showing the astonishing level of specialization that astrocytes display to fulfill the demands of their neuronal partners as well as their plasticity upon injury. Then, we discuss the controversies that fuel the current debate on these cells. We tackle evidence of a potential beneficial effect of cell therapy, achieved by transplanting astrocytes or their precursors. Afterwards, we introduce the different strategies proposed to modulate astrocyte functions in neurodegeneration, ranging from lifestyle changes to environmental cues. Finally, we discuss the challenges and the recent advancements to develop astrocyte-specific delivery systems.

Glutathione Liposomes Carrying Ceftriaxone, FK506, and Nilotinib to Control Overexpressed Dopamine Markers and Apoptotic Factors in Neurons

Advances in liposomal formulation carrying multiple neuroprotective drugs, such as ceftriaxone (CEF), FK506, and nilotinib, can point toward an approach to obviating the difficulties in Parkinson's disease (PD) treatment. We prepared functionalized liposomes decorated with glutathione (GSH) to penetrate the blood-brain barrier (BBB) and cardiolipin (CL) to link up apoptotic neurons. Further, the effect of CEF-FK506-nilotinib-GSH-CL-liposomes on a PD model established by SH-SY5Y cells with 1-methyl-4-phenylpyridinium-induced neurotoxicity was investigated. An increment of the mole percentage of dihexadecyl phosphate and CL increased the particle size and the absolute value of ζ potential, improved the entrapment efficiency of CEF, FK506, and nilotinib, and reduced the drug-releasing rate. The toxicity studies revealed that CEF, FK506, and nilotinib-encapsulated liposomes could enhance the survival of SH-SY5Y cells. Western blot and immunofluorescence revealed that incorporation of CL in a lipid bilayer ameliorated the docking of CEF-FK506-nilotinib-GSH-CL-liposomes at α-synuclein (α-syn), indicating a better targeting capability of the liposomes to degenerated neurons. Treatment with CEF-FK506-nilotinib-GSH-CL-liposomes reduced the expression of Bax and α-syn and promoted the expression of Bcl-2, tyrosine hydroxylase, and the dopamine transporter. GSH- and CL-conjugated liposomes showed combined activity of targeting the BBB and α-syn and augmented the efficiency of the three drugs in rescuing dopaminergic neurons for neurodegenerative therapy.

Targeted overexpression of glutamate transporter-1 reduces seizures and attenuates pathological changes in a mouse model of epilepsy

Astrocytic glutamate transporters are crucial for glutamate homeostasis in the brain, and dysregulation of these transporters can contribute to the development of epilepsy. Glutamate transporter-1 (GLT-1) is responsible for the majority of glutamate uptake in the dorsal forebrain and has been shown to be reduced at epileptic foci in patients and preclinical models of temporal lobe epilepsy (TLE). Current antiepileptic drugs (AEDs) work primarily by targeting neurons directly through suppression of excitatory neurotransmission or enhancement of inhibitory neurotransmission, which can lead to both behavioral and psychiatric side effects. This study investigates the therapeutic capacity of astrocyte-specific AAV-mediated GLT-1 expression in the intrahippocampal kainic acid (IHKA) model of TLE. In this study, we used Western blot analysis, immunohistochemistry, and long-term-video EEG monitoring to demonstrate that cell-type-specific upregulation of GLT-1 in astrocytes is neuroprotective at early time points during epileptogenesis, reduces seizure frequency and total time spent in seizures, and eliminates large behavioral seizures in the IHKA model of epilepsy. Our findings suggest that targeting glutamate uptake is a promising therapeutic strategy for the treatment of epilepsy.

Treatment effects of the combination of ceftriaxone and valproic acid on neuronal and behavioural functions in a rat model of epilepsy

NEW FINDINGS

What is the central question of this study? Imbalance of activities between GABAergic and glutamatergic systems is involved in epilepsy. It is not known whether simultaneously increasing GABAergic and decreasing glutamatergic activity using valproic acid and ceftriaxone, respectively, leads to better seizure control. What is the central question of this study? Ceftriaxone suppressed seizure and cognitive deficits and restored neuronal density and the number of newborn cells in the hippocampus in a rat model of epilepsy. Combined treatment with ceftriaxone and valproic acid showed additive effects in seizure suppression.

ABSTRACT

The pathophysiology of epilepsy is typically considered as an imbalance between inhibitory GABA and excitatory glutamate neurotransmission. Valproic acid (Val), a GABA agonist, is one of the first-line antiepileptic drugs in the treatment of epilepsy, but it exhibits adverse effects. Ceftriaxone (CEF) elevates expression of glutamate transporter-1, enhances the reuptake of synaptic glutamate, increases the number of newborn cells and exhibits neuroprotective effects in animal studies. In this study, we evaluated effects of the combination of CEF and Val on behavioural and neuronal measures in a rat epilepsy model. Male Wistar rats were injected i.p. with pentylenetetrazol (35 mg/kg, every other day for 13 days) to induce the epilepsy model. Ceftriaxone (10 or 50 mg/kg), Val (50 or 100 mg/kg) or the combination of CEF and Val were injected daily after the fourth pentylenetetrazol injection for seven consecutive days. Epileptic rats exhibited seizure and impairments in motor and cognitive functions. Treatment with CEF and Val reduced the seizure and enhanced motor and cognitive functions in a dose-dependent manner. The combination of CEF (10 mg/kg) and Val (50 mg/kg) improved behaviours considerably. Histologically, compared with control animals, epileptic rats exhibited lower neuronal density and a reduction in hippocampal newborn cells but higher apoptosis in the basolateral amygdala, all of which were restored by the treatment with CEF, Val or the combination of CEF and Val. The study findings demonstrated that the combination of low doses of CEF and Val has beneficial effects on seizure suppression, neuroprotection and improvement in motor and cognitive functions in epilepsy.

Modulating neuroinflammation in neurodegeneration-related dementia: can microglial toll-like receptors pull the plug?

Neurodegeneration-associated dementia disorders (NADDs), namely Alzheimer and Parkinson diseases, are developed by a significant portion of the elderly population globally. Extensive research has provided critical insights into the molecular basis of the pathological advancements of these diseases, but an efficient curative therapy seems elusive. A common attribute of NADDs is neuroinflammation due to a chronic inflammatory response within the central nervous system (CNS), which is primarily modulated by microglia. This response within the CNS is positively regulated by cytokines, chemokines, secondary messengers or cyclic nucleotides, and free radicals. Microglia mediated immune activation is regulated by a positive feedback loop in NADDs. The present review focuses on evaluating the crosstalk between inflammatory mediators and microglia, which aggravates both the clinical progression and extent of NADDs by forming a persistent chronic inflammatory milieu within the CNS. We also discuss the role of the human gut microbiota and its effect on NADDs as well as the suitability of targeting toll-like receptors for an immunotherapeutic intervention targeting the deflation of an inflamed milieu within the CNS.

The Effect of GLT-1 Upregulation on Extracellular Glutamate Dynamics

Pharmacological upregulation of glutamate transporter-1 (GLT-1), commonly achieved using the beta-lactam antibiotic ceftriaxone, represents a promising therapeutic strategy to accelerate glutamate uptake and prevent excitotoxic damage in neurological conditions. While excitotoxicity is indeed implicated in numerous brain diseases, it is typically restricted to select vulnerable brain regions, particularly in early disease stages. In healthy brain tissue, the speed of glutamate uptake is not constant and rather varies in both an activity- and region-dependent manner. Despite the widespread use of ceftriaxone in disease models, very little is known about how such treatments impact functional measures of glutamate uptake in healthy tissue, and whether GLT-1 upregulation can mask the naturally occurring activity-dependent and regional heterogeneities in uptake. Here, we used two different compounds, ceftriaxone and LDN/OSU-0212320 (LDN), to upregulate GLT-1 in healthy wild-type mice. We then used real-time imaging of the glutamate biosensor iGluSnFR to investigate functional consequences of GLT-1 upregulation on activity- and regional-dependent variations in glutamate uptake capacity. We found that while both ceftriaxone and LDN increased GLT-1 expression in multiple brain regions, they did not prevent activity-dependent slowing of glutamate clearance nor did they speed basal clearance rates, even in areas characterized by slow uptake (e.g., striatum). Unexpectedly, ceftriaxone but not LDN decreased glutamate release in the cortex, suggesting that ceftriaxone may alter release properties independent of its effects on GLT-1 expression. In sum, our data demonstrate the complexities of glutamate uptake by showing that GLT-1 expression does not necessarily translate to accelerated uptake. Furthermore, these data suggest that the mechanisms underlying activity- and regional-dependent differences in glutamate dynamics are independent of GLT-1 expression levels.

New Avenues for Parkinson's Disease Therapeutics: Disease-Modifying Strategies Based on the Gut Microbiota

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, and for which no disease-modifying treatments exist. Neurodegeneration and neuropathology in different brain areas are manifested as both motor and non-motor symptoms in patients. Recent interest in the gut-brain axis has led to increasing research into the gut microbiota changes in PD patients and their impact on disease pathophysiology. As evidence is piling up on the effects of gut microbiota in disease development and progression, another front of action has opened up in relation to the potential usage of microbiota-based therapeutic strategies in treating gastrointestinal alterations and possibly also motor symptoms in PD. This review provides status on the different strategies that are in the front line (i.e., antibiotics; probiotics; prebiotics; synbiotics; dietary interventions; fecal microbiota transplantation, live biotherapeutic products), and discusses the opportunities and challenges the field of microbiome research in PD is facing.

Astrocyte-specific deletion of the transcription factor Yin Yang 1 in murine substantia nigra mitigates manganese-induced dopaminergic neurotoxicity

Manganese (Mn)-induced neurotoxicity resembles Parkinson's disease (PD), but the mechanisms underpinning its effects remain unknown. Mn dysregulates astrocytic glutamate transporters, GLT-1 and GLAST, and dopaminergic function, including tyrosine hydroxylase (TH). Our previous in vitro studies have shown that Mn repressed GLAST and GLT-1 via activation of transcription factor Yin Yang 1 (YY1). Here, we investigated if in vivo astrocytic YY1 deletion mitigates Mn-induced dopaminergic neurotoxicity, attenuating Mn-induced reduction in GLAST/GLT-1 expression in murine substantia nigra (SN). AAV5-GFAP-Cre-GFP particles were infused into the SN of 8-week-old YY1 ^flox/flox mice to generate a region-specific astrocytic YY1 conditional knockout (cKO) mouse model. 3 weeks after adeno-associated viral (AAV) infusion, mice were exposed to 330 μg of Mn (MnCl₂ 30 mg/kg, intranasal instillation, daily) for 3 weeks. After Mn exposure, motor functions were determined in open-field and rotarod tests, followed by Western blotting, quantitative PCR, and immunohistochemistry to assess YY1, TH, GLAST, and GLT-1 levels. Infusion of AAV5-GFAP-Cre-GFP vectors into the SN resulted in region-specific astrocytic YY1 deletion and attenuation of Mn-induced impairment of motor functions, reduction of TH-expressing cells in SN, and TH mRNA/protein levels in midbrain/striatum. Astrocytic YY1 deletion also attenuated the Mn-induced decrease in GLAST/GLT-1 mRNA/protein levels in midbrain. Moreover, YY1 deletion abrogated its interaction with histone deacetylases in astrocytes. These results indicate that astrocytic YY1 plays a critical role in Mn-induced neurotoxicity in vivo, at least in part, by reducing astrocytic GLAST/GLT-1. Thus, YY1 might be a potential target for treatment of Mn toxicity and other neurological disorders associated with dysregulation of GLAST/GLT-1.

Neuromodulation of Glial Function During Neurodegeneration

Glia, a non-excitable cell type once considered merely as the connective tissue between neurons, is nowadays acknowledged for its essential contribution to multiple physiological processes including learning, memory formation, excitability, synaptic plasticity, ion homeostasis, and energy metabolism. Moreover, as glia are key players in the brain immune system and provide structural and nutritional support for neurons, they are intimately involved in multiple neurological disorders. Recent advances have demonstrated that glial cells, specifically microglia and astroglia, are involved in several neurodegenerative diseases including Amyotrophic lateral sclerosis (ALS), Epilepsy, Parkinson's disease (PD), Alzheimer's disease (AD), and frontotemporal dementia (FTD). While there is compelling evidence for glial modulation of synaptic formation and regulation that affect neuronal signal processing and activity, in this manuscript we will review recent findings on neuronal activity that affect glial function, specifically during neurodegenerative disorders. We will discuss the nature of each glial malfunction, its specificity to each disorder, overall contribution to the disease progression and assess its potential as a future therapeutic target.

Glutamate-induced excitotoxicity in Parkinson's disease: The role of glial cells

Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamate transmission efficiency depends on the correct functionality and expression of a plethora of receptors and transporters, located both on neurons and glial cells. Of note, glutamate reuptake by dedicated transporters prevents its accumulation at the synapse as well as non-physiological spillover. Indeed, extracellular glutamate increase causes aberrant synaptic signaling leading to neuronal excitotoxicity and death. Moreover, extrasynaptic glutamate diffusion is strongly associated with glia reaction and neuroinflammation. Glutamate-induced excitotoxicity is mainly linked to an impaired ability of glial cells to reuptake and respond to glutamate, then this is considered a common hallmark in many neurodegenerative diseases, including Parkinson's disease (PD). In this review, we discuss the function of astrocytes and microglia in glutamate homeostasis, focusing on how glial dysfunction causes glutamate-induced excitotoxicity leading to neurodegeneration in PD.

Molecular changes evoked by the beta-lactam antibiotic ceftriaxone across rodent models of substance use disorder and neurological disease

Ceftriaxone is a beta-lactam antibiotic that increases the expression of the major glutamate transporter, GLT-1. As such, ceftriaxone ameliorates symptoms across multiple rodent models of neurological diseases and substance use disorders. However, the mechanism behind GLT-1 upregulation is unknown. The present review synthesizes this literature in order to identify commonalities in molecular changes. We find that ceftriaxone (200 mg/kg for at least two days) consistently restores GLT-1 expression in multiple rodent models of neurological disease, especially when GLT-1 is decreased in the disease model. The same dose given to healthy/drug-naive rodents does not reliably upregulate GLT-1 in any brain region except the hippocampus. Increased GLT-1 expression does not consistently arise from transcriptional regulation, and is likely to be due to trafficking changes. In addition to altered transporter expression, ceftriaxone ameliorates neuropathologies (e.g. tau, amyloid beta, cell death) and aberrant protein expression associated with a number of neurological disease models. Taken together, these results indicate that ceftriaxone remains a strong candidate for treatment of multiple disorders in the clinic.

Linear Predictive Approaches Separate Field Potentials in Animal Model of Parkinson's Disease

Parkinson's disease (PD) causes impaired movement and cognition. PD can involve profound changes in cortical and subcortical brain activity as measured by electroencephalography or intracranial recordings of local field potentials (LFP). Such signals can adaptively guide deep-brain stimulation (DBS) as part of PD therapy. However, adaptive DBS requires the identification of triggers of neuronal activity dependent on real time monitoring and analysis. Current methods do not always identify PD-related signals and can entail delays. We test an alternative approach based on linear predictive coding (LPC), which fits autoregressive (AR) models to time-series data. Parameters of these AR models can be calculated by fast algorithms in real time. We compare LFPs from the striatum in an animal model of PD with dopamine depletion in the absence and presence of the dopamine precursor levodopa, which is used to treat motor symptoms of PD. We show that in dopamine-depleted mice a first order AR model characterized by a single LPC parameter obtained by LFP sampling at 1 kHz for just 1 min can distinguish between levodopa-treated and saline-treated mice and outperform current methods. This suggests that LPC may be useful in online analysis of neuronal signals to guide DBS in real time and could contribute to DBS-based treatment of PD.

Excitatory Amino Acid Transporters in Physiology and Disorders of the Central Nervous System

Excitatory amino acid transporters (EAATs) encompass a class of five transporters with distinct expression in neurons and glia of the central nervous system (CNS). EAATs are mainly recognized for their role in uptake of the amino acid glutamate, the major excitatory neurotransmitter. EAATs-mediated clearance of glutamate released by neurons is vital to maintain proper glutamatergic signalling and to prevent toxic accumulation of this amino acid in the extracellular space. In addition, some EAATs also act as chloride channels or mediate the uptake of cysteine, required to produce the reactive oxygen speciesscavenger glutathione. Given their central role in glutamate homeostasis in the brain, as well as their additional activities, it comes as no surprise that EAAT dysfunctions have been implicated in numerous acute or chronic diseases of the CNS, including ischemic stroke and epilepsy, cerebellar ataxias, amyotrophic lateral sclerosis, Alzheimer’s disease and Huntington’s disease. Here we review the studies in cellular and animal models, as well as in humans that highlight the roles of EAATs in the pathogenesis of these devastating disorders. We also discuss the mechanisms regulating EAATs expression and intracellular trafficking and new exciting possibilities to modulate EAATs and to provide neuroprotection in course of pathologies affecting the CNS.

GFR-α1 Expression in Substantia Nigra Increases Bilaterally Following Unilateral Striatal GDNF in Aged Rats and Attenuates Nigral Tyrosine Hydroxylase Loss Following 6-OHDA Nigrostriatal Lesion

Glial cell line-derived neurotrophic factor (GDNF) improved motor function in Parkinson's disease (PD) patients in Phase I clinical trials, and these effects persisted months after GDNF discontinuation. Conversely, phase II clinical trials reported no significant effects on motor improvement vs placebo. The disease duration and the quantity, infusion approach, and duration of GDNF delivery may affect GDNF efficacy in PD treatment. However, identifying mechanisms activated by GDNF that affect nigrostriatal function may reveal additional avenues to partially restore nigrostriatal function. In PD and aging models, GDNF affects tyrosine hydroxylase (TH) expression or phosphorylation in substantia nigra (SN), long after a single GDNF injection in striatum. In aged rats, the GDNF family receptor, GFR-α1, increases TH expression and phosphorylation in SN. To determine if GFR-α1 could be a mechanistic link in long-term GDNF impact, we conducted two studies; first to determine if a single unilateral striatal delivery of GDNF affected GFR-α1 and TH over time (1 day, 1 week, and 4 weeks) in the striatum or SN in aged rats, and second, to determine if soluble GFR-α1 could mitigate TH loss following 6-hydroxydopamine (6-OHDA) lesion. In aged rats, GDNF bilaterally increased ser31 TH phosphorylation and GFR-α1 expression in SN at 1 day and 4 weeks after GDNF, respectively. In striatum, GFR-α1 expression decreased 1 week after GDNF, only on the GDNF-injected side. In 6-OHDA-lesioned rats, recombinant soluble GFR-α1 mitigated nigral, but not striatal, TH protein loss following 6-OHDA. Together, these results show GDNF has immediate and long-term impact on dopamine regulation in the SN, which includes a gradual increase in GFR-α1 expression that may sustain TH expression and dopamine function therein.

Study on Effect of Striatal mGluR2/3 in Alleviating Motor Dysfunction in Rat PD Model Treated by Exercise Therapy

Background: Exercise therapy has been widely applied in clinical rehabilitation as an important practical and side effect-free adjuvant therapy, with a significant effect in alleviating motor dysfunction of patients with Parkinson's disease (PD) or animal PD models. This study focuses on the effect of exercise therapy in reducing the concentration of extracellular glutamate (Glu) in the striatum in a rat PD model by upregulating the expression of group II metabotropic Glu receptor (mGluR2/3), so as to alleviate motor dysfunction in the rat PD model. Methods: Neurotoxin 6-hydroxydopamine (6-OHDA) was injected into the right medial forebrain bundle (MFB) of the rats to establish the semi-lateral cerebral damage PD model. The sham-operated group was given an equal amount of normal saline at the same site and taken as the control group. The apomorphine (APO)-induced rotational behavior test combined with immunohistochemical staining with tyrosine hydroxylase (TH) in the substantia nigra (SNc) and striatum was performed to assess the reliability of the model. The exercise group was given treadmill exercise intervention for 4 weeks (11 m/min, 30 min/day, 5 days/week) 1 week after the operation. The open field test (OFT) was performed to assess the locomotor activity of the rats; the Western blot technique was used to detect SNc TH and striatal mGluR2/3 protein expressions; real-time polymerase chain reaction (RT-PCR) was applied to detect striatal mGluR2 and mGluR3 mRNA expressions; the microdialysis-high-performance liquid chromatography (HPLC) method was adopted to detect the concentration of extracellular Glu in striatal neurons. Results: Compared with the control group, the number of rotations of each model group at the first week was significantly increased (P < 0.01); compared with the PD group, the number of rotations of the PD + exercise group at the third week and the fifth week was significantly decreased (P < 0.05, P < 0.01). Compared with the control group, the total movement distance, the total movement time, and the mean velocity of each model group at the first week were significantly reduced (P < 0.05); compared with the PD group, the total movement distance, the total movement time, and the mean velocity of the PD + exercise group at the third week and the fifth week were significantly increased (P < 0.01). Compared with the control group, the count of immunopositive cells and protein expression of SNc TH, and the content of immunopositive fiber terminals in the striatal TH of each model group significantly declined (P < 0.01). Compared with the PD group, the striatal mGluR2/3 protein expression of the PD + exercise group significantly rose (P < 0.01). Compared with the control group, the concentration of extracellular Glu in striatal neurons of each model group at the first week significantly grew (P < 0.05); compared with the PD group, the concentration of extracellular Glu in striatal neurons of the PD + exercise group at the third week and the fifth week was significantly decreased (P < 0.01); compared with the PD + exercise group, the concentration of extracellular Glu in striatal neurons of the group injected with mGluR2/3 antagonist (RS)-1-amino-5-phosphonoindan-1-carboxylic acid (APICA) into the striatum at the third week and the fifth week was significantly increased (P < 0.05, P < 0.01). Compared with the control group, the striatal mGluR2/3 protein expression of the PD group was significantly downregulated (P < 0.01); compared with the PD group, the striatal mGluR2/3 protein expression of the PD + exercise group was significantly upregulated (P < 0.05); compared with the control group, the striatal mGluR3 mRNA expression of the PD group was significantly downregulated (P < 0.01); compared with the PD group, the striatal mGluR3 mRNA expression of the PD + exercise group was significantly upregulated (P < 0.01); 6-OHDA damage and exercise intervention had no significant effect on the striatal mGluR2 mRNA expression (P > 0.05). Compared with the PD + exercise group, the total movement distance, the total movement time, and the mean velocity of the PD + exercise + APICA group were significantly decreased (P < 0.05); compared with the PD group, the PD + exercise + APICA group had no significant change in the total movement distance, the total movement time, and the mean velocity (P > 0.05). Conclusion: These data collectively demonstrate that the mGluR2/3-mediated glutamatergic transmission in the striatum is sensitive to dopamine (DA) depletion and may serve as a target of exercise intervention for mediating the therapeutic effect of exercise intervention in a rat model of PD.

Reversible Choreoathetosis in a Patient with End-stage Renal Disease from Administration of Ceftriaxone

A wide spectrum of neurological manifestations may be induced in patients with impaired renal function when receiving beta-lactam antibiotics due to the altered pharmacokinetics. Beta-lactam antibiotics is commonly chosen for treatment in patients with end-stage renal disease due to its good penetration into the cerebrospinal fluid and long half-life.

Here, we present a case of a 73-year-old Malay lady with end-stage renal disease who was admitted for treatment of gastroenteritis. She presented with acute onset of diarrhoea and vomiting for two days. She was febrile during admission and was prescribed intravenous ceftriaxone 2 grams daily for coverage of bacterial gastroenteritis. Among the investigations done, white cell count were raised together with the C-reactive protein. Stool and blood cultures were also sent for further investigations. Over a three-day period, her general condition improved and she was discharged home. The onset of clinical manifestation of choreoathetosis was noticed by her caregiver on the same day of discharge. She was brought back to the emergency department and was readmitted for further workup of the new presenting complain of abnormal movement and disorientation. Haemodialysis was arranged and immediately commenced during her admission. The renal nurses reported that her neurological symptoms were noticeably improved after completion of the initial dialysis without any treatment.

Ceftriaxone including other beta lactam antibiotics penetrates the blood-brain barrier and induces glutamate in excess in the striatum and cerebral cortex, resulting in neurological hyper excitability disorders despite appropriate renal adjusted dosage for end-stage renal disease patients on haemodialysis.

Moxibustion Exerts a Neuroprotective Effect through Antiferroptosis in Parkinson's Disease

The objective of this study was to explore the neuroprotective effect of moxibustion on rats with Parkinson's disease (PD) and its mechanism. A Parkinson's disease model was established in rats using a two-point stereotactic 6-hydroxydopamine injection in the right substantia nigra (SN) and ventral tegmental area. The rats received moxibustion at the Baihui (GV20) and Sishencong (EX-HN1) acupoints for 20 minutes, six times a week, for 6 weeks. The right SN tissue was histologically and immunohistochemically examined. Differentially expressed genes (DEGs) were identified through RNA sequencing. In addition, the levels of tyrosine hydroxylase (TH), glutathione peroxidase 4 (GPX4), and ferritin heavy chain 1 (FTH1) in SN were measured. In comparison to the model group, the moxibustion group showed a significantly greater TH immunoreactivity and a higher behavioural score. In particular, moxibustion led to an increase in the number and morphological stability of SN neural cells. The functional pathway analysis showed that DEGs are closely related to the ferroptosis pathway. GPX4 and FTH1 in the SN were significantly overexpressed in the moxibustion-treated rats with PD. Moxibustion can effectively reduce the death of SN neurons, decrease the occurrence of ferroptosis, and increase the TH activity to protect the neurons in rats with PD. The protective mechanism may be associated with suppression of the ferroptosis.

1H NMR profiling of the 6-OHDA parkinsonian rat brain reveals metabolic alterations and signs of recovery after N-acetylcysteine treatment

Parkinson's disease is the second most common neurodegenerative disease caused by degeneration of dopamine neurons in the substantia nigra. The origin and causes of dopamine neurodegeneration in Parkinson's disease are not well understood but oxidative stress may play an important role in its onset. Much effort has been dedicated to find biomarkers indicative of oxidative stress and neurodegenerative processes in parkinsonian brains. By using proton nuclear magnetic resonance (¹H NMR) to identify and quantify key metabolites, it is now possible to elucidate the metabolic pathways affected by pathological conditions like neurodegeneration. The metabolic disturbances in the 6-hydroxydopamine (6-OHDA) hemiparkinsonian rat model were monitored and the nature and size of these metabolic alterations were analyzed. The results indicate that a unilateral injection of 6-OHDA into the striatum causes metabolic changes that not only affect the injected hemisphere but also the contralateral, non-lesioned side. We could clearly identify specific metabolic pathways that were affected, which were mostly related with oxidative stress and neurotransmission. In addition, a partial metabolic recovery by carrying out an antioxidant treatment with N-acetylcysteine (NAC) was observable.

Repurposing of the β-Lactam Antibiotic, Ceftriaxone for Neurological Disorders: A Review

To date, there is no cure or disease-modifying agents available for most well-known neurological disorders. Current therapy is typically focused on relieving symptoms and supportive care in improving the quality of life of affected patients. Furthermore, the traditional de novo drug discovery technique is more challenging, particularly for neurological disorders. Therefore, the repurposing of existing drugs for these conditions is believed to be an efficient and dynamic approach that can substantially reduce the investments spent on drug development. Currently, there is emerging evidence that suggests the potential effect of a beta-lactam antibiotic, ceftriaxone (CEF), to alleviate the symptoms of different experimentally-induced neurological disorders: Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, epileptic-seizure, brain ischemia, traumatic brain injuries, and neuropathic pain. CEF also affects the markers of oxidative status and neuroinflammation, glutamatergic systems as well as various aggregated toxic proteins involved in the pathogenesis of different neurological disorders. Moreover, it was found that CEF administration to drug dependent animal models improved the withdrawal symptoms upon drug discontinuation. Thus, this review aimed to describe the effects of CEF against multiple models of neurological illnesses, drug dependency, and withdrawal. It also emphasizes the possible mechanisms of neuroprotective actions of CEF with respective neurological maladies.

Pyridazine-derivatives Enhance Structural and Functional Plasticity of Tripartite Synapse Via Activation of Local Translation in Astrocytic Processes

Excitatory amino acid transporter 2 (EAAT2) is primarily located in perisynaptic astrocytic processes (PAP) where it plays a critical role in synaptic glutamate homeostasis. Dysregulation of EAAT2 at the translational level has been implicated in a myriad of neurological diseases. We previously discovered that pyridazine analogs can activate EAAT2 translation. Here, we sought to further refine the site and mechanism of compound action. We found that in vivo, compound treatment increased EAAT2 expression only in the PAP of astrocytes where EAAT2 mRNA also was identified. Direct application of compound to isolated PAP induced de novo EAAT2 protein synthesis, indicating that compound activates translation locally in the PAP. Using a screening process, we identified a set of PAP proteins that are rapidly up-regulated following compound treatment and a subset of these PAP proteins may be locally synthesized in the PAP. Importantly, these identified proteins are associated with the structural and functional capacity of the PAP, indicating compound enhanced plasticity of the PAP. Concomitantly, we found that pyridazine analogs increase synaptic protein expression in the synapse and enhance hippocampal long-term potentiation. This was not dependent upon compound-mediated local translation in neurons. This suggests that compound enhances the structural and functional capacity of the PAP which in turn facilitates enhanced plasticity of the tripartite synapse. Overall, this provides insight into the mechanism action site of pyridazine derivatives as well as the growing appreciation of the dynamic regulation and functional aspects of the PAP at the tripartite synapse.

Prolonged increase in ser31 tyrosine hydroxylase phosphorylation in substantia nigra following cessation of chronic methamphetamine

Methamphetamine (MA) exposure may increase the risk of motor or cognitive impairments similar to Parkinson's disease (PD) by middle age. Although damage to nigrostriatal or mesoaccumbens dopamine (DA) neurons may occur during or early after MA exposure, overt PD-like symptoms at a younger age may not manifest due to compensatory mechanisms to maintain DA neurotransmission. One possible compensatory mechanism is increased tyrosine hydroxylase (TH) phosphorylation. In the rodent PD 6-OHDA model, nigrostriatal lesion decreases TH protein in both striatum and substantia nigra (SN). However, DA loss in the SN is significantly less than that in the striatum. An increase in ser31 TH phosphorylation in the SN may increase TH activity in response to TH loss. To determine if similar compensatory mechanisms may be engaged in young mice after MA exposure, TH expression, phosphorylation, and DA tissue content were evaluated, along with dopamine transporter expression, 21 days after cessation of MA (24 mg/kg, daily, 14 days). DA tissue content was unaffected by the MA regimen in striatum, nucleus accumbens, SN, or ventral tegmental area (VTA), despite decreased TH protein in SN and VTA. In the SN, but not striatum, ser31 phosphorylation increased over 2-fold. This suggests that increased ser31 TH phosphorylation may be an inherent compensatory mechanism to attenuate DA loss against TH loss, similar to that in an established PD model. These results also indicate the somatodendritic compartments of DA neurons are more vulnerable to TH protein loss than terminal fields following MA exposure.

Ceftriaxone reduces L-dopa-induced dyskinesia severity in 6-hydroxydopamine parkinson's disease model

BACKGROUND

Increased extracellular glutamate may contribute to l-dopa induced dyskinesia, a debilitating side effect faced by Parkinson's disease patients 5 to 10 years after l-dopa treatment. Therapeutic strategies targeting postsynaptic glutamate receptors to mitigate dyskinesia may have limited success because of significant side effects. Increasing glutamate uptake may be another approach to attenuate excess glutamatergic neurotransmission to mitigate dyskinesia severity or prolong the time prior to onset. Initiation of a ceftriaxone regimen at the time of nigrostriatal lesion can attenuate tyrosine hydroxylase loss in conjunction with increased glutamate uptake and glutamate transporter GLT-1 expression in a rat 6-hydroxydopamine model. In this article, we examined if a ceftriaxone regimen initiated 1 week after nigrostriatal lesion, but prior to l-dopa, could reduce l-dopa-induced dyskinesia in an established dyskinesia model.

METHODS

Ceftriaxone (200 mg/kg, intraperitoneal, once daily, 7 consecutive days) was initiated 7 days post-6-hydroxydopamine lesion (days 7-13) and continued every other week (days 21-27, 35-39) until the end of the study (day 39 postlesion, 20 days of l-dopa).

RESULTS

Ceftriaxone significantly reduced abnormal involuntary movements at 5 time points examined during chronic l-dopa treatment. Partial recovery of motor impairment from nigrostriatal lesion by l-dopa was unaffected by ceftriaxone. The ceftriaxone-treated l-dopa group had significantly increased striatal GLT-1 expression and glutamate uptake. Striatal tyrosine hydroxylase loss in this group was not significantly different when compared with the l-dopa alone group.

CONCLUSIONS

Initiation of ceftriaxone after nigrostriatal lesion, but prior to and during l-dopa, may reduce dyskinesia severity without affecting l-dopa efficacy or the reduction of striatal tyrosine hydroxylase loss. © 2017 International Parkinson and Movement Disorder Society.

SSa ameliorates the Glu uptaking capacity of astrocytes in epilepsy via AP-1/miR-155/GLAST

BACKGROUND

Neuronal glutamate (Glu) release has been reported to mediate the neuronal injury of epilepsy, while Saikosaponin a (Ssa) was shown to ameliorate the epilepsy that induced by pentylenetetrazol (PTZ). However, potential interactions between glutamate release and Ssa has not been fully identified.

METHODS

Herein, PTZ-induced rat model were established to evaluate the neuron injury, while Ssa was used to treat the model rat. Rat astrocytes were isolated and induced by PTZ to construct cell models of epilepsy, real-time PCR and western blot were used to determine genes' expression. Luciferase reporter assay were performed to validate the relationship between miR-155-5p and glutamate aspartate transporter (GLAST). The level of Glu was sampled for HPLC measurement.

RESULTS

Ssa treatment could decrease the level of Glu in hippocampus of rat. PTZ-induced astrocytes pretreated with Ssa significantly decreased the expression of AP-1 and miR-155, but increased the expression of GLAST, furthermore, PTZ stimulation enables astrocytes to uptake large amount of extracellular Glu. AP-1 could bind with the promoter of miR-155 to promote its transcription. MiR-155 tragets GLAST to govern its expression.

CONCLUSION

Ssa treatment played pivotal roles in PTZ-induced epilepsy by promoting the expression of GLAT1 and uptaking of Glu, which was mediated by the expression of AP-1 and miR-155.

Choreoathetosis Is a Possible Adverse Event of a Commonly Used Antibiotic

BACKGROUND

Choreoathetosis (CAS) is attributed to a few neuropsychiatric drugs; however, it is scarcely reported with commonly used antibiotics.

AIMS

To present a case of ceftriaxone (CTX)-induced CAS and to perform a literature review.

SETTING

A medical teaching hospital.

CASE HISTORY

An 83-year-old female with end stage renal disease was prescribed CTX 2 g/day intravenously and doxycycline (DXC) 200 mg/day orally for the treatment of acute community-acquired systemic infection. CAS developed 3 days after the administration of both drugs. Withdrawal of CTX and DXC yielded complete resolution of the CAS on the following day. Neither neurological adverse events related to DXC use nor pharmacological interaction between DXC and CTX was reported. Therefore, the CAS development was attributed to CTX.

CONCLUSION

CTX as well as other ß-lactam antibiotics induce glutamate excess in the striatum and cerebral cortex, resulting in neurological hyperexcitability disorders. Dosage adjustment of these antibiotics in relation to the patients' renal clearance is warranted.

Ceftriaxone reverses deficits of behavior and neurogenesis in an MPTP-induced rat model of Parkinson's disease dementia

Hyperactivity of the glutamatergic system is involved in excitotoxicity and neurodegeneration in Parkinson's disease (PD) so that glutamatergic modulation maybe a potential therapeutic target for PD. Ceftriaxone (CEF) has been reported to increase glutamate uptake by increasing glutamate transporter expression and has been demonstrated neuroprotective effects in animal study. The aim of this study was to determine the effects of CEF on behavior and neurogenesis in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD rat model. MPTP was stereotaxically injected into the substantia nigra pars compacta (SNc) of male Wistar rats. Starting on the same day after MPTP lesioning (day 0), the rats were injected daily with either CEF or saline for 14days and underwent a T-maze test on days 8-10 and an object recognition test on days 12-14, then the brain was taken for histological evaluation on day 15. The results showed that MPTP lesioning resulted in decreased motor function, working memory, and object recognition and reduced neurogenesis in the substantial nigra and dentate gyrus of the hippocampus. These behavioral and neuronal changes were prevented by CEF treatment. To our knowledge, this is the first study showing that CEF prevents loss of neurogenesis in the brain of PD rats. CEF may therefore have clinical potential in the treatment of PD.

Ceftriaxone attenuates glutamate-mediated neuro-inflammation and restores BDNF in MPTP model of Parkinson's disease in rats

The present study is designed to investigate the role of glutamate transporter in neuroprotection of ceftriaxone against MPTP induced PD animal model. Young male Wistar rats were subjected to intra-nigral administration of MPTP for the induction of Parkinson's disease. Glutamate modulators like ceftriaxone (CFX), Memantine (MEM) and Dihydrokainate (DHK) were administered to MPTP-lesioned rats. Different behavioral alterations were assessed in between the study period. Animals were sacrificed immediately after behavioral session, and different biochemical parameters were measured. Intranigral administration of MPTP showed significant impairment of motor behavior and marked increase in inflammatory mediators and oxidative stress parameters in rats. In addition, MPTP also produced significant decrease in brain-derived neurotrophic factor (BDNF) in striatum of rats. However, chronic administration of ceftriaxone (200mg/kg) has shown significant improvement in motor behavioral deficits and oxidative damage. In addition, Ceftriaxone also attenuated the marked increase of NFκB, TNF-α and IL-1β in MPTP treated rats thus, conferring its neuro-inflammatory property. Further, Ceftriaxone significantly restored the decreased activity of BDNF in striatum of MPTP treated rats. Moreover, pre-treatment of memantine (20mg/kg) with sub-therapeutic dose of ceftriaxone (100mg/kg) potentiated the protective effect of ceftriaxone. Furthermore, intra-nigral injection of DHK (200 nmol) with lower dose of ceftriaxone (100mg/kg) reversed the protective effect of ceftriaxone in MPTP treated rats. The present study concluded that ceftriaxone produce beneficial effect against MPTP induced PD like symptoms rats through glutamatergic pathways.

Axial levodopa-induced dyskinesias and neuronal activity in the dorsal striatum

Levodopa-induced dyskinesias are abnormal involuntary movements that limit the effectiveness of treatments for Parkinson's disease. Although dyskinesias involve the striatum, it is unclear how striatal neurons are involved in dyskinetic movements. Here we record from striatal neurons in mice during levodopa-induced axial dyskinesias. We developed an automated 3-dimensional motion tracking system to capture the development of axial dyskinesias at ∼10ms resolution, and correlated these movements with neuronal activity of striatal medium spiny neurons and fast-spiking interneurons. The average firing rate of medium spiny neurons increased as axial dyskinesias developed, and both medium spiny neurons and fast-spiking interneurons were modulated around axial dyskinesias. We also found that delta field potential power increased in the striatum with dyskinesia, and that this increased delta power coupled with striatal neurons. Our findings provide insight into how striatal networks change as levodopa-induced dyskinesias develop, and suggest that increased medium spiny neuron firing, increased delta field potential power, and abnormal delta-coupling may be neurophysiological signatures of dyskinesias. These data could be helpful in understanding the role of the striatum in the pathogenesis of dyskinesias in Parkinson's disease.

Native DIGE proteomic analysis of mitochondria from substantia nigra and striatum during neuronal degeneration and its compensation in an animal model of early Parkinson's disease

Cause of Parkinson's disease (PD) is still not understood. Motor symptoms are not observed at early stages of disease due to compensatory processes. Dysfunction of mitochondria was indicated already at preclinical PD. Selective toxin 6-OHDA was applied to kill dopaminergic neurons in substantia nigra and disturb neuronal transmission in striatum. Early phase of active degeneration and later stage, when surviving cells adapted to function normally, were analysed. 2D BN/SDS difference gel electrophoresis (DIGE) of mitochondrial proteome enabled to point out crucial processes involved at both time-points in dopaminergic structures. Marker proteins such as DPYSL2, HSP60, ATP1A3, EAAT2 indicated structural remodelling, cytoskeleton rearrangement, organelle trafficking, axon outgrowth and regeneration. Adaptations in dopaminergic and glutamatergic neurotransmission, recycling of synaptic vesicles, along with enlargement of mitochondria mass were proposed as causative for compensation. Changed expression of carbohydrates metabolism and oxidative phosphorylation proteins were described, including their protein-protein interactions and supercomplex assembly.

Effects of repeated high-dose methamphetamine and ceftriaxone post-treatments on tissue content of dopamine and serotonin as well as glutamate and glutamine

Repeated exposure to high doses of methamphetamine (METH) is known to alter several neurotransmitters in certain brain regions. Little is known about the effects of ceftriaxone (CEF), a β-lactam antibiotic, known to upregulate glutamate transporter subtype 1, post-treatment on METH-induced depletion of dopamine and serotonin (5-HT) tissue content in brain reward regions. Moreover, the effects of METH and CEF post-treatment on glutamate and glutamine tissue content are not well understood. In this study, Wistar rats were used to investigate the effects of METH and CEF post-treatment on tissue content of dopamine/5-HT and glutamate/glutamine in the nucleus accumbens (NAc) and prefrontal cortex (PFC). Rats received either saline or METH (10mg/kg, i.p. every 2h×4) followed by either saline or CEF (200mg/kg, i.p, every day×3) post-treatment. METH induced a significant depletion of dopamine and 5-HT in the NAc and PFC. Importantly, dopamine tissue content was completely restored in the NAc following CEF post-treatment. Additionally, METH caused a significant decrease in glutamate and glutamine tissue content in PFC, and this effect was attenuated by CEF post-treatment. These findings demonstrate for the first time the attenuating effects of CEF post-treatment on METH induced alterations in the tissue contents of dopamine, glutamate, and glutamine.

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.