Lipopolysaccharide mitagates methamphetamine-induced striatal dopamine depletion via modulating local TNF-alpha and dopamine transporter expression

Role of Microglia in Psychostimulant Addiction

The use of psychostimulant drugs can modify brain function by inducing changes in the reward system, mainly due to alterations in dopaminergic and glutamatergic transmissions in the mesocorticolimbic pathway. However, the etiopathogenesis of addiction is a much more complex process. Previous data have suggested that microglia and other immune cells are involved in events associated with neuroplasticity and memory, which are phenomena that also occur in addiction. Nevertheless, how dependent is the development of addiction on the activity of these cells? Although the mechanisms are not known, some pathways may be involved. Recent data have shown psychoactive substances may act directly on immune cells, alter their functions and induce various inflammatory mediators that modulate synaptic activity. These could, in turn, be involved in the pathological alterations that occur in substance use disorder. Here, we extensively review the studies demonstrating how cocaine and amphetamines modulate microglial number, morphology, and function. We also describe the effect of these substances in the production of inflammatory mediators and a possible involvement of some molecular signaling pathways, such as the toll-like receptor 4. Although the literature in this field is scarce, this review compiles the knowledge on the neuroimmune axis that is involved in the pathogenesis of addiction, and suggests some pharmacological targets for the development of pharmacotherapy.

Gut microbiota dysbiosis: The potential mechanisms by which alcohol disrupts gut and brain functions

Alcohol use disorder (AUD) is a high-risk psychiatric disorder and a key cause of death and disability in individuals. In the development of AUD, there is a connection known as the microbiota-gut-brain axis, where alcohol use disrupts the gut barrier, resulting in changes in intestinal permeability as well as the gut microbiota composition, which in turn impairs brain function and worsens the patient’s mental status and gut activity. Potential mechanisms are explored by which alcohol alters gut and brain function through the effects of the gut microbiota and their metabolites on immune and inflammatory pathways. Alcohol and microbiota dysregulation regulating neurotransmitter release, including DA, 5-HT, and GABA, are also discussed. Thus, based on the above discussion, it is possible to speculate on the gut microbiota as an underlying target for the treatment of diseases associated with alcohol addiction. This review will focus more on how alcohol and gut microbiota affect the structure and function of the gut and brain, specific changes in the composition of the gut microbiota, and some measures to mitigate the changes caused by alcohol exposure. This leads to a potential intervention for alcohol addiction through fecal microbiota transplantation, which could normalize the disruption of gut microbiota after AUD.

Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap?

The number of individuals affected by psychostimulant use disorder (PSUD) has increased rapidly over the last few decades resulting in economic, emotional, and physical burdens on our society. Further compounding this issue is the current lack of clinically approved medications to treat this disorder. The dopamine transporter (DAT) is a common target of psychostimulant actions related to their use and dependence, and the recent availability of atypical DAT inhibitors as a potential therapeutic option has garnered popularity in this research field. Modafinil (MOD), which is approved for clinical use for the treatment of narcolepsy and sleep disorders, blocks DAT just like commonly abused psychostimulants. However, preclinical and clinical studies have shown that it lacks the addictive properties (in both behavioral and neurochemical studies) associated with other abused DAT inhibitors. Clinical availability of MOD has facilitated its off-label use for several psychiatric disorders related to alteration of brain dopamine (DA) systems, including PSUD. In this review, we highlight clinical and preclinical research on MOD and its R-enantiomer, R-MOD, as potential medications for PSUD. Given the complexity of PSUD, we have also reported the effects of MOD on psychostimulant-induced appearance of several symptoms that could intensify the severity of the disease (i.e., sleep disorders and impairment of cognitive functions), besides the potential therapeutic effects of MOD on PSUD.

Mitigating Effects of Liriope platyphylla on Nicotine-Induced Behavioral Sensitization and Quality Control of Compounds

In this study we investigated the mitigating effects of Liriope platyphylla Wang et Tang extract on behavioral sensitization and the quantification of its major compounds. The extract of L. platyphylla reduces the expression of tyrosine hydroxylase (TH) protein, which is increased by nicotine, back to normal levels, and increases the expression of dopamine transporter (DAT) protein, which is reduced by nicotine, back to normal levels in PC12 cells. In this study, rats received nicotine (0.4 mg/kg, subcutaneously) only for seven days and then received extract of L. platyphylla (200 or 400 mg/kg, oral) 1 h prior to nicotine administration for an additional seven days. The extract of L. platyphylla reduced locomotor activity compared to the nicotine control group in rats. The extract of L. platyphylla significantly attenuated the repeated nicotine-induced DAT protein expression in the nucleus accumbens (NAc), but there was no effect on increased TH protein expression in the dorsal striatum. These findings suggest that L. platyphylla extract has a mitigating effect on nicotine-induced behavioral sensitization by modulating DAT protein expression in the NAc. For quality control of L. plathyphylla, spicatoside A and D, which are saponin compounds, were quantified in the L. platyphylla extract. The amounts of spicatoside A and D in L. platyphylla extract obtained from ultra-high-performance liquid chromatography with tandem mass spectrometry were 0.148 and 0.272 mg/g, respectively. The identification of these compounds in L. platyphylla, which can be used for quality control, provides important information for the development of drugs to treat nicotine dependence.

Substance Use Disorder in the COVID-19 Pandemic: A Systematic Review of Vulnerabilities and Complications

As the world endures the coronavirus disease 2019 (COVID-19) pandemic, the conditions of 35 million vulnerable individuals struggling with substance use disorders (SUDs) worldwide have not received sufficient attention for their special health and medical needs. Many of these individuals are complicated by underlying health conditions, such as cardiovascular and lung diseases and undermined immune systems. During the pandemic, access to the healthcare systems and support groups is greatly diminished. Current research on COVID-19 has not addressed the unique challenges facing individuals with SUDs, including the heightened vulnerability and susceptibility to the disease. In this systematic review, we will discuss the pathogenesis and pathology of COVID-19, and highlight potential risk factors and complications to these individuals. We will also provide insights and considerations for COVID-19 treatment and prevention in patients with SUDs.

Assessment of Striatal Dopamine Transporter Binding in Individuals With Major Depressive Disorder: In Vivo Positron Emission Tomography and Postmortem Evidence

IMPORTANCE

Major depressive disorder (MDD) might involve dopamine (DA) reductions. The DA transporter (DAT) regulates DA clearance and neurotransmission and is sensitive to DA levels, with preclinical studies (including those involving inescapable stressors) showing that DAT density decreases when DA signaling is reduced. Despite preclinical data, evidence of reduced DAT in MDD is inconclusive.

OBJECTIVE

Using a highly selective DAT positron emission tomography (PET) tracer ([11C] altropane), DAT availability was probed in individuals with MDD who were not taking medication. Levels of DAT expression were also evaluated in postmortem tissues from donors with MDD who died by suicide.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional PET study was conducted at McLean Hospital (Belmont, Massachusetts) and Massachusetts General Hospital (Boston) and enrolled consecutive individuals with MDD who were not taking medication and demographically matched healthy controls between January 2012 and March 2014. Brain tissues were obtained from the Douglas-Bell Canada Brain Bank. For the PET component, 25 individuals with current MDD who were not taking medication and 23 healthy controls recruited from McLean Hospital were included (all provided usable data). For the postmortem component, 15 individuals with depression and 14 healthy controls were considered.

INTERVENTION

PET scan.

MAIN OUTCOMES AND MEASURES

Striatal and midbrain DAT binding potential was assessed. For the postmortem component, tyrosine hydroxylase and DAT levels were evaluated using Western blots.

RESULTS

Compared with 23 healthy controls (13 women [56.5%]; mean [SD] age, 26.49 [7.26] years), 25 individuals with MDD (19 women [76.0%]; mean [SD] age, 26.52 [5.92] years) showed significantly lower in vivo DAT availability in the bilateral putamen and ventral tegmental area (Cohen d range, -0.62 to -0.71), and both reductions were exacerbated with increasing numbers of depressive episodes. Unlike healthy controls, the MDD group failed to show an age-associated reduction in striatal DAT availability, with young individuals with MDD being indistinguishable from older healthy controls. Moreover, DAT availability in the ventral tegmental area was lowest in individuals with MDD who reported feeling trapped in stressful circumstances. Lower DAT levels (and tyrosine hydroxylase) in the putamen of MDD compared with healthy controls were replicated in postmortem analyses (Cohen d range, -0.92 to -1.15).

CONCLUSIONS AND RELEVANCE

Major depressive disorder, particularly with recurring episodes, is characterized by decreased striatal DAT expression, which might reflect a compensatory downregulation due to low DA signaling within mesolimbic pathways.

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

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

Kinase-dependent Regulation of Monoamine Neurotransmitter Transporters

Modulation of neurotransmission by the monoamines dopamine (DA), norepinephrine (NE), and serotonin (5-HT) is critical for normal nervous system function. Precise temporal and spatial control of this signaling in mediated in large part by the actions of monoamine transporters (DAT, NET, and SERT, respectively). These transporters act to recapture their respective neurotransmitters after release, and disruption of clearance and reuptake has significant effects on physiology and behavior and has been linked to a number of neuropsychiatric disorders. To ensure adequate and dynamic control of these transporters, multiple modes of control have evolved to regulate their activity and trafficking. Central to many of these modes of control are the actions of protein kinases, whose actions can be direct or indirectly mediated by kinase-modulated protein interactions. Here, we summarize the current state of our understanding of how protein kinases regulate monoamine transporters through changes in activity, trafficking, phosphorylation state, and interacting partners. We highlight genetic, biochemical, and pharmacological evidence for kinase-linked control of DAT, NET, and SERT and, where applicable, provide evidence for endogenous activators of these pathways. We hope our discussion can lead to a more nuanced and integrated understanding of how neurotransmitter transporters are controlled and may contribute to disorders that feature perturbed monoamine signaling, with an ultimate goal of developing better therapeutic strategies.

The danger-associated molecular pattern HMGB1 mediates the neuroinflammatory effects of methamphetamine

Methamphetamine (METH) induces neuroinflammatory effects, which may contribute to the neurotoxicity of METH. However, the mechanism by which METH induces neuroinflammation has yet to be clarified. A considerable body of evidence suggests that METH induces cellular damage and distress, particularly in dopaminergic neurons. Damaged neurons release danger-associated molecular patterns (DAMPs) such as high mobility group box-1 (HMGB1), which induces pro-inflammatory effects. Therefore, we explored the notion here that METH induces neuroinflammation indirectly through the release of HMGB1 from damaged neurons. Adult male Sprague-Dawley rats were injected IP with METH (10mg/kg) or vehicle (0.9% saline). Neuroinflammatory effects of METH were measured in nucleus accumbens (NAcc), ventral tegmental area (VTA) and prefrontal cortex (PFC) at 2h, 4h and 6h after injection. To assess whether METH directly induces pro-inflammatory effects in microglia, whole brain or striatal microglia were isolated using a Percoll density gradient and exposed to METH (0, 0.1, 1, 10, 100, or 1000μM) for 24h and pro-inflammatory cytokines measured. The effect of METH on HMGB1 and IL-1β in striatal tissue was then measured. To determine the role of HMGB1 in the neuroinflammatory effects of METH, animals were injected intra-cisterna magna with the HMGB1 antagonist box A (10μg) or vehicle (sterile water). 24h post-injection, animals were injected IP with METH (10mg/kg) or vehicle (0.9% saline) and 4h later neuroinflammatory effects measured in NAcc, VTA, and PFC. METH induced robust pro-inflammatory effects in NAcc, VTA, and PFC as a function of time and pro-inflammatory analyte measured. In particular, METH induced profound effects on IL-1β in NAcc (2h) and PFC (2h and 4h). Exposure of microglia to METH in vitro failed to induce a pro-inflammatory response, but rather induced significant cell death as well as a decrease in IL-1β. METH treatment increased HMGB1 in parallel with IL-1β in striatum. Pre-treatment with the HMGB1 antagonist box A blocked the neuroinflammatory effects (IL-1β) of METH in NAcc, VTA and PFC. The present results suggest that HMGB1 mediates, in part, the neuroinflammatory effects of METH and thus may alert CNS innate immune cells to the toxic effects of METH.

Amphetamine- and methamphetamine-induced hyperthermia: Implications of the effects produced in brain vasculature and peripheral organs to forebrain neurotoxicity

The adverse effects of amphetamine- (AMPH) and methamphetamine- (METH) induced hyperthermia on vasculature, peripheral organs and peripheral immune system are discussed. Hyperthermia alone does not produce amphetamine-like neurotoxicity but AMPH and METH exposures that do not produce hyperthermia (≥40°C) are minimally neurotoxic. Hyperthermia likely enhances AMPH and METH neurotoxicity directly through disruption of protein function, ion channels and enhanced ROS production. Forebrain neurotoxicity can also be indirectly influenced through the effects of AMPH- and METH- induced hyperthermia on vasculature. The hyperthermia and the hypertension produced by high doses amphetamines are a primary cause of transient breakdowns in the blood-brain barrier (BBB) resulting in concomitant regional neurodegeneration and neuroinflammation in laboratory animals. This BBB breakdown can occur in the amygdala, thalamus, striatum, sensory and motor cortex and hippocampus. Under these conditions, repetitive seizures greatly enhance neurodegeneration in hippocampus, thalamus and amygdala. Even when the BBB is less disrupted, AMPH- or METH- induced hyperthermia effects on brain vasculature may play a role in neurotoxicity. In this case, striatal and cortical vascular function are adversely affected, and even greater ROS, immune and damage responses are seen in the meninges and cortical surface vasculature. Finally, muscle and liver damage and elevated cytokines in blood can result when amphetamines produce hyperthermia. Proteins, from damaged muscle may activate the peripheral immune system and exacerbate liver damage. Liver damage can further increase cytokine levels, immune system activation and increase ammonia levels. These effects could potentially enhance vascular damage and neurotoxicity.

Lipopolysaccharide increases degradation of central monoamines: an in vivo microdialysis study in the nucleus accumbens and medial prefrontal cortex of mice

Peripheral administration of lipopolysaccharide (LPS) in rodents induces anhedonia, i.e. the inability to experience pleasure. Recently, we reported that serotonin transporter (SERT) function is required for LPS-induced anhedonia. Less is known about the effect of LPS on the biological activity of dopamine transporters (DAT) and norepinephrine transporters (NET). Therefore, in vivo microdialysis was performed in the nucleus accumbens and medial prefrontal cortex of C57BL6/J mice exposed to saline or LPS (133 µg/kg i.p.). To investigate the possible involvement of different monoamine transporters, the triple reuptake inhibitor DOV 216,303 or saline was i.p. injected 30 min before the saline/LPS injection. The dose of LPS, shown to decrease responding for brain stimulation reward in mice, significantly increased extracellular levels of monoamine metabolites (5-HIAA, DOPAC and HVA) in the nucleus accumbens and medial prefrontal cortex. Remarkably, DOV 216,303 abolished LPS-induced DOPAC and HVA formation in the nucleus accumbens, suggesting that LPS increases DAT activity in this brain area. DOV 216,303 also inhibited LPS-induced DOPAC and HVA formation in the medial prefrontal cortex. Since DAT density is very low in this brain structure, reuptake of DA predominantly takes place via NET, suggesting that LPS increases DAT and NET activity in the medial prefrontal cortex. Furthermore, DOV 216,303 pretreatment prevented LPS-induced 5-HIAA formation only in the medial prefrontal cortex, indicating that LPS increases prefrontal SERT activity. In conclusion, the present findings suggest that peripheral LPS increases DAT activity in the nucleus accumbens and increases NET and SERT activity in the medial prefrontal cortex of mice.

Sigma receptor antagonists attenuate acute methamphetamine-induced hyperthermia by a mechanism independent of IL-1β mRNA expression in the hypothalamus

Methamphetamine is currently one of the most widely abused drugs worldwide, with hyperthermia being a leading cause of death in methamphetamine overdose situations. Methamphetamine-induced hyperthermia involves a variety of cellular mechanisms, including increases in hypothalamic interleukin-1 beta (IL-1β) expression. Methamphetamine also interacts with sigma receptors and previous studies have shown that sigma receptor antagonists mitigate many of the behavioral and physiological effects of methamphetamine, including hyperthermia. The purpose of the current study was to determine if the attenuation of methamphetamine-induced hyperthermia by the sigma receptor antagonists, AZ66 and SN79, is associated with a concomitant attenuation of IL-1β mRNA expression, particularly in the hypothalamus. Methamphetamine produced dose- and time-dependent increases in core body temperature and IL-1β mRNA expression in the hypothalamus, striatum, and cortex in male, Swiss Webster mice. Pretreatment with the sigma receptor antagonists, AZ66 and SN79, significantly attenuated methamphetamine-induced hyperthermia, but further potentiated IL-1β mRNA in the mouse hypothalamus when compared to animals treated with methamphetamine alone. These findings suggest sigma receptor antagonists attenuate methamphetamine-induced hyperthermia through a different mechanism from that involved in the modulation of hypothalamic IL-1β mRNA expression.

The effects of psychostimulant drugs on blood brain barrier function and neuroinflammation

The blood brain barrier (BBB) is a highly dynamic interface between the central nervous system (CNS) and periphery. The BBB is comprised of a number of components and is part of the larger neuro(glio)vascular unit. Current literature suggests that psychostimulant drugs of abuse alter the function of the BBB which likely contributes to the neurotoxicities associated with these drugs. In both preclinical and clinical studies, psychostimulants including methamphetamine, MDMA, cocaine, and nicotine, produce BBB dysfunction through alterations in tight junction protein expression and conformation, increased glial activation, increased enzyme activation related to BBB cytoskeleton remodeling, and induction of neuroinflammatory pathways. These detrimental changes lead to increased permeability of the BBB and subsequent vulnerability of the brain to peripheral toxins. In fact, abuse of these psychostimulants, notably methamphetamine and cocaine, has been shown to increase the invasion of peripheral bacteria and viruses into the brain. Much work in this field has focused on the co-morbidity of psychostimulant abuse and human immunodeficiency virus (HIV) infection. As psychostimulants alter BBB permeability, it is likely that this BBB dysfunction results in increased penetration of the HIV virus into the brain thus increasing the risk of and severity of neuro AIDS. This review will provide an overview of the specific changes in components within the BBB associated with psychostimulant abuse as well as the implications of these changes in exacerbating the neuropathology associated with psychostimulant drugs and HIV co-morbidity.

Nrf2 deficiency potentiates methamphetamine-induced dopaminergic axonal damage and gliosis in the striatum

Oxidative stress that correlates with damage to nigrostriatal dopaminergic neurons and reactive gliosis in the basal ganglia is a hallmark of methamphetamine (METH) toxicity. In this study, we analyzed the protective role of the transcription factor Nrf2 (nuclear factor-erythroid 2-related factor 2), a master regulator of redox homeostasis, in METH-induced neurotoxicity. We found that Nrf2 deficiency exacerbated METH-induced damage to dopamine neurons, shown by an increase in loss of tyrosine hydroxylase (TH)- and dopamine transporter (DAT)-containing fibers in striatum. Consistent with these effects, Nrf2 deficiency potentiated glial activation, indicated by increased striatal expression of markers for microglia (Mac-1 and Iba-1) and astroglia (GFAP) one day after METH administration. At the same time, Nrf2 inactivation dramatically potentiated the increase in TNFα mRNA and IL-15 protein expression in GFAP+ cells in the striatum. In sharp contrast to the potentiation of striatal damage, Nrf2 deficiency did not affect METH-induced dopaminergic neuron death or expression of glial markers or proinflammatory molecules in the substantia nigra. This study uncovers a new role for Nrf2 in protection against METH-induced inflammatory and oxidative stress and striatal degeneration.

Stress- and glucocorticoid-induced priming of neuroinflammatory responses: potential mechanisms of stress-induced vulnerability to drugs of abuse

Stress and stress-induced glucocorticoids (GCs) sensitize drug abuse behavior as well as the neuroinflammatory response to a subsequent pro-inflammatory challenge. Stress also predisposes or sensitizes individuals to develop substance abuse. There is an emerging evidence that glia and glia-derived neuroinflammatory mediators play key roles in the development of drug abuse. Drugs of abuse such as opioids, psychostimulants, and alcohol induce neuroinflammatory mediators such as pro-inflammatory cytokines (e.g. interleukin (IL)-1β), which modulate drug reward, dependence, and tolerance as well as analgesic properties. Drugs of abuse may directly activate microglial and astroglial cells via ligation of Toll-like receptors (TLRs), which mediate the innate immune response to pathogens as well as xenobiotic agents (e.g. drugs of abuse). The present review focuses on understanding the immunologic mechanism(s) whereby stress primes or sensitizes the neuroinflammatory response to drugs of abuse and explores whether stress- and GC-induced sensitization of neuroimmune processes predisposes individuals to drug abuse liability and the role of neuroinflammatory mediators in the development of drug addiction.

Cerebral microglia mediate sleep/wake and neuroinflammatory effects of methamphetamine

Methamphetamine and modafinil exert their wake-promoting effects by elevating monoaminergic tone. The severity of hypersomnolence that occurs subsequent to induced wakefulness differs between these two agents. Microglia detects and modulates CNS reactions to agents such as D-methamphetamine that induce cellular stress. We therefore hypothesized that changes in the sleep/wake cycle that occur subsequent to administration of D-methamphetamine are modulated by cerebral microglia. In CD11b-herpes thymidine kinase transgenic mice (CD11b-TK(mt-30)), activation of the inducible transgene by intracerebroventricular (icv) ganciclovir results in toxicity to CD11b-positive cells (i.e. microglia), thereby reducing cerebral microglial cell counts. CD11b-TK(mt-30)and wild type mice were subjected to chronic icv ganciclovir or vehicle administration with subcutaneous mini-osmotic pumps. D-methamphetamine (1 and 2 mg/kg), modafinil (30 and 100 mg/kg) and vehicle were administered intraperitoneally to these animals. In CD11b-TK(mt-30) mice, but not wild type, icv infusion of ganciclovir reduced the duration of wake produced by D-methamphetamine at 2 mg/kg by nearly 1h. Nitric oxide synthase (NOS) activity, studied ex vivo, and NOS expression were elevated in CD11b-positive cerebral microglia from wild type mice acutely exposed to d-methamphetamine. Additionally, CD11b-positive microglia, but not other cerebral cell populations, exhibited changes in sleep-regulatory cytokine expression in response to d-METH. Finally, CD11b-positive microglia exposed to d-methamphetamine in vitro exhibited increased NOS activity relative to pharmacologically-naïve cells. CD11b-positive microglia from the brains of neuronal NOS (nNOS)-knockout mice failed to exhibit this effect. We propose that the effects of D-METH on sleep/wake cycles are mediated in part by actions on microglia, including possibly nNOS activity and cytokine synthesis.

A neurotoxic regimen of methamphetamine exacerbates the febrile and neuroinflammatory response to a subsequent peripheral immune stimulus

Methamphetamine (MA) use is associated with activation of microglia and, at high doses, can induce neurotoxicity. Given the changes in the neuroinflammatory environment associated with MA, we investigated whether MA administration would interfere with the thermoregulatory and neuroinflammatory response to a subsequent peripheral immune stimulus. C57BL6/J mice were given four i.p. injections of either 5 mg/kg MA or saline at two hour intervals. Twenty-four hours following the first MA injection, mice were given 100 μg/kg LPS or saline i.p. and blood and brains were collected. Here we report that mice exposed to MA developed higher fevers in response to LPS than did those given LPS alone. MA also exacerbated the LPS-induced increase in central cytokine mRNA. MA alone increased microglial Iba1 expression and expression was further increased when mice were exposed to both MA and LPS, suggesting that MA not only activated microglia but also influenced their response to a peripheral immune stimulus. Taken together, these data show that MA administration exacerbates the normal central immune response, most likely by altering microglia.

Neurotrophic and neurorescue effects of Echinacoside in the subacute MPTP mouse model of Parkinson's disease

Many experiments support the notion that augmentation of neurotrophic factors' (NTFs) activity, especially glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) could prevent or halt the progress of neurodegeneration in Parkinson's disease (PD). However, application of NTFs as therapeutic agents for PD is hampered by the difficulty in delivering them to specific brain regions safely and effectively. Another potential strategy is to stimulate the endogenous expression of NTFs. In this study, we investigated the effects of Echinacoside (ECH), a monomer extracted from herbs, on rescuing dopaminergic function in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-lesioned mice. We found that oral administration of ECH (30 mg/kg/day for 14 days) to MPTP-treated mice, commencing after impairment of the nigrstriatal system, suppressed the reduction of nigral dopaminergic neurons, striatal fibers, dopamine and dopamine transporter to 134.24%, 203.17%, 147.25% and 154.72 of MPTP-lesioned animals respectively (p<0.05). There was a relative elevation in expression of GDNF and BDNF mRNA (2.94 and 3.75-fold) and protein (184.34% and 185.93%) in ECH treated mice compared with vehicle-treated MPTP-lesioned mice (p<0.05). In addition, the apoptosis cells and Bax/Bcl-2 ratio of mRNA and protein in MPTP-lesioned mice significantly increased, and these effects could be prevented by ECH. At the 7th and 14th days of ECH treatment, the gait disorder displayed obvious improvement (p<0.05). These findings demonstrate that ECH is probably a novel, orally active, non-peptide inducer of NTFs and inhibitor of apoptosis, and they provide preclinical support for therapeutic potential of this compound in the treatment of PD.

Prosurvival effect of human wild-type alpha-synuclein on MPTP-induced toxicity to central but not peripheral catecholaminergic neurons isolated from transgenic mice

In the present work we report the generation of a new line of alpha-synuclein (alpha-SYN) transgenic mice in which the human wild-type alpha-SYN cDNA is expressed under the control of a tyrosine hydroxylase (TH) promoter. We provide evidence that the ectopic protein is found in TH expressing neurons of both central and peripheral nervous systems. The transgene is expressed very early in development coinciding with the activity of the TH promoter and in the adult brain the human protein distributes normally to the nerve endings and cell bodies of dopaminergic nigral neurons without any evidence of abnormal aggregation. Our results indicate that expression of human wild-type alpha-SYN does not affect normal development or maintenance of TH immunoreactive nigral neurons, striatal dopamine content, or locomotor activity. Systemic administration of the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces a loss of TH immunoreactive nigral neurons and terminals and of dopamine levels to the same degree in both transgenic and non-transgenic adult mice. Intoxication also results in a similar loss of cardiac noradrenaline in both genotypes. Surprisingly, cultured transgenic ventral mesencephalic fetal dopaminergic neurons exhibit complete resistance to cell death induced by 1-methyl-4-phenylpyridinium ion (MPP(+)) intoxication, without changes in dopamine transporter (DAT) surface levels. Interestingly, this protection is not observed in other populations of catecholaminergic neurons such as peripheral sympathetic neurons, despite their high sensitivity to MPP(+)in vitro.

Methamphetamine-induced neuroinflammation and neuronal dysfunction in the mice hippocampus: preventive effect of indomethacin

Methamphetamine (METH) causes irreversible damage to brain cells leading to neurological and psychiatric abnormalities. However, the mechanisms underlying life-threatening effects of acute METH intoxication remain unclear. Indeed, most of the hypotheses focused on intra-neuronal events, such as dopamine oxidation, oxidative stress and excitotoxicity. Yet, recent reports suggested that glia may contribute to METH-induced neuropathology. In the present study, we investigated the hippocampal dysfunction induced by an acute high dose of METH (30 mg/kg; intraperitoneal injection), focusing on the inflammatory process and changes in several neuronal structural proteins. For that, 3-month-old male wild-type C57BL/6J mice were killed at different time-points post-METH. We observed that METH caused an inflammatory response characterized by astrocytic and microglia reactivity, and tumor necrosis factor (TNF) system alterations. Indeed, glial fibrillary acidic protein (GFAP) and CD11b immunoreactivity were upregulated, likewise TNF-alpha and TNF receptor 1 protein levels. Furthermore, the effect of METH on hippocampal neurons was also investigated, and we observed a downregulation in beta III tubulin expression. To clarify the possible neuronal dysfunction induced by METH, several neuronal proteins were analysed. Syntaxin-1, calbindin D28k and tau protein levels were downregulated, whereas synaptophysin was upregulated. We also evaluated whether an anti-inflammatory drug could prevent or diminish METH-induced neuroinflammation, and we concluded that indomethacin (10 mg/kg; i.p.) prevented METH-induced glia activation and both TNF system and beta III tubulin alterations. In conclusion, we demonstrated that METH triggers an inflammatory process and leads to neuronal dysfunction in the hippocampus, which can be prevented by an anti-inflammatory treatment.