Methamphetamine-induced oxidative stress in cultured mouse astrocytes

Evaluating the Protective Effects of Thymoquinone on Methamphetamine-induced Toxicity in an In Vitro Model Based on Differentiated PC12 Cells

Methamphetamine (Meth) is a highly addictive stimulant. Its potential neurotoxic effects are mediated through various mechanisms, including oxidative stress and the initiation of the apoptotic process. Thymoquinone (TQ), obtained from Nigella sativa seed oil, has extensive antioxidant and anti-apoptotic properties. This study aimed to investigate the potential protective effects of TQ against Meth-induced toxicity by using an in vitro model based on nerve growth factor-differentiated PC12 cells. Cell differentiation was assessed by detecting the presence of a neuronal marker with flow cytometry. The effects of Meth exposure were evaluated in the in vitro neuronal cell-based model via the determination of cell viability (in an MTT assay) and apoptosis (by annexin/propidium iodide staining). The generation of reactive oxygen species (ROS), as well as the levels of glutathione (GSH) and dopamine, were also determined. The model was used to determine the protective effects of 0.5, 1 and 2 μM TQ against Meth-induced toxicity (at 1 mM). The results showed that TQ reduced Meth-induced neurotoxicity, possibly through the inhibition of ROS generation and apoptosis, and by helping to maintain GSH and dopamine levels. Thus, the impact of TQ treatment on Meth-induced neurotoxicity could warrant further investigation.

Dynamic changes in global methylation and plant cell death mechanism in response to NiO nanoparticles

This report is a first comprehensive work on the potential of engineered nickel oxide nanoparticles affecting the epigenome and modulating global methylation leading to retention of transgenerational footprints. Nickel oxide nanoparticles (NiO-NPs) are known to instigate extensive phenotypic and physiological damage to plants. In the present work, it was shown that exposure to increasing concentrations of NiO-NP-induced cell death cascades in model systems, Allium cepa and tobacco BY-2 cells. NiO-NP also generated variation in global CpG methylation; its transgenerational transmission was shown in affected cells. Plant tissues exposed to NiO-NP showed progressive replacement of essential cations, like Fe and Mg, as seen in XANES and ICP-OES data, providing earliest signs of disturbed ionic homeostasis. Fluorescent staining based confocal microscopy confirmed upsurge of H₂O₂ and nitric oxide after NiO-NP exposure. A NiO-NP concentration gradient-based switching-on of the cell death cascades was observed when autophagosomes were seen in samples exposed to lower and median concentrations of NiO-NP (10-125 mg L^-1). The apoptotic cell death marker, caspase-3 like protein, was noted in the median to higher doses (50-500 mg L^-1), and leakage of lactate dehydrogenase marking necrotic cell death was observed in samples exposed to the highest doses (125-500 mg L^-1) of NiO-NP. Concomitant increase of DNA hypermethylation (quantified by ELISA-based assay) and genomic DNA damage (evaluated through Comet-based analyses) was recorded at higher doses of NiO-NP. MSAP profiles confirmed that global methylation changes incurring in the parental generation upon NiO-NP exposure were transmitted through the two subsequent generations of BY-2 cells which was supported by data from A. cepa, too. Thus, it was evident that NiO-NP exposure incited DNA hypermethylation, as an aftermath of oxidative burst, and led to induction of autophagy, apoptotic and necrotic cell death pathways. Global methylation changes induced by NiO-NP exposure can be transmitted through subsequent cell generations.

Mechanism of SET8 Activates the Nrf2-KEAP1-ARE Signaling Pathway to Promote the Recovery of Motor Function after Spinal Cord Injury

Background

Spinal cord injury (SCI) is a common injury of the central nervous system (CNS), and astrocytes are relatively abundant glial cells in the CNS that impairs the recovery of motor function after SCI. It was confirmed that the oxidative stress of mitochondria leads to the accumulation of reactive oxygen species (ROS) in cells, which plays a key role in the motor function of astrocytes. However, the mechanism by which oxidative stress affects astrocyte motility after SCI is still unexplained. Therefore, this study investigated the influence of SET8-regulated oxidative stress on astrocyte autophagy levels after SCI in rats and the potential mechanisms of action.

Methods

We used real-time quantitative PCR, western blotting, and immunohistochemical staining to analyze SET8, Keap1, and Nrf2 expression at the cellular level and in SCI tissues. ChIP to detect H4K20me1 enrichment in the Keap1 promoter region under OE-SET8 (overexpression of SET8) conditions. Western blotting was used to assess the expression of signature proteins of astrocytes, proteins associated with autophagy, proteins associated with glial scar formation, reactive oxygen species (ROS) levels in cells using DHE staining, and astrocyte number, morphological alterations, and induction of glial scar formation processes using immunofluorescence. In addition, the survival rate of neurons after SCI in rats was examined by using NiSSl staining.

Results

OE-SET8 upregulates the enrichment of H4K20me1 in Keap1, inhibits Keap1 expression, activates the Nrf2-ARE signaling pathway to suppress ROS accumulation, inhibits oxidative stress-induced autophagy and glial scar formation in astrocytes, and leads to reduced neuronal loss, which promoted the recovery and improvement of motor function after SCI in rats.

Conclusion

Overexpression of SET8 alleviated oxidative stress by regulating Keap1/Nrf2/ARE, inhibited astrocyte autophagy levels, and reduced glial scar formation as well as neuronal loss, thereby promoting improved recovery of motor function after SCI. Thus, the SET8/H4K20me1 regulatory function may be a promising cellular therapeutic intervention point after SCI.

Methamphetamine-induced dopaminergic neurotoxicity as a model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with a high prevalence, approximately 1 % in the elderly population. Numerous studies have demonstrated that methamphetamine (MA) intoxication caused the neurological deficits and nigrostriatal damage seen in Parkinsonian conditions, and subsequent rodent studies have found that neurotoxic binge administration of MA reproduced PD-like features, in terms of its symptomatology and pathology. Several anti-Parkinsonian medications have been shown to attenuate the motor impairments and dopaminergic damage induced by MA. In addition, it has been recognized that mitochondrial dysfunction, oxidative stress, pro-apoptosis, proteasomal/autophagic impairment, and neuroinflammation play important roles in inducing MA neurotoxicity. Importantly, MA neurotoxicity has been shown to share a common mechanism of dopaminergic toxicity with that of PD pathogenesis. This review describes the major findings on the neuropathological features and underlying neurotoxic mechanisms induced by MA and compares them with Parkinsonian pathogenesis. Taken together, it is suggested that neurotoxic binge-type administration of MA in rodents is a valid animal model for PD that may provide knowledge on the neuropathogenesis of PD.

Epigallocatechin Gallate Mitigates the Methamphetamine-Induced Striatal Dopamine Terminal Toxicity by Preventing Oxidative Stress in the Mouse Brain

Methamphetamine (METH) is a popular psychostimulant due to its long-lasting effects and inexpensive production. METH intoxication is known to increase oxidative stress leading to neuronal damage. Thus, preventing the METH-induced oxidative stress can potentially mitigate neuronal damage. Previously, our laboratory found that epigallocatechin gallate (EGCG), a strong antioxidant found in green tea, can protect against the METH-induced apoptosis and dopamine terminal toxicity in the striatum of mice. In the present study, we evaluated the anti-oxidative properties of EGCG on the METH-induced oxidative stress using CD-1 mice. First, we demonstrated that mice pretreated with EGCG 30 min prior to the METH injection (30 mg/kg, ip) showed protection against the striatal METH-induced reduction of tyrosine hydroxylase without mitigating hyperthermia. In addition, injecting a single high dose of METH caused the reduction of striatal glutathione peroxidase activity at 24 h after the METH injection. Interestingly, pretreatment with EGCG 30 min prior to the METH injection prevented the METH-induced reduction of glutathione peroxidase activity. Moreover, we utilized Western blots to quantify the glutathione peroxidase 4 protein level in the striatum. The results showed that METH decreased striatal glutathione peroxidase 4 protein level, and the reduction was prevented by EGCG pretreatment. Finally, we observed that the METH-induced increase of striatal catalase and copper/zinc superoxide dismutase protein levels were also attenuated by pretreatment with EGCG. Taken together, our data indicate that EGCG is an effective agent that can be used to mitigate the METH-induced striatal toxicity in the mouse brain.

The role of astrocytes in oxidative stress of central nervous system: A mixed blessing

Central nervous system (CNS) maintains a high level of metabolism, which leads to the generation of large amounts of free radicals, and it is also one of the most vulnerable organs to oxidative stress. Emerging evidences have shown that, as the key homeostatic cells in CNS, astrocytes are deeply involved in multiple aspects of CNS function including oxidative stress regulation. Besides, the redox level in CNS can in turn affect astrocytes in morphology and function. The complex and multiple roles of astrocytes indicate that their correct performance is crucial for the normal functioning of the CNS, and its dysfunction may result in the occurrence and progression of various neurological disorders. To date, the influence of astrocytes in CNS oxidative stress is rarely reviewed. Therefore, in this review we sum up the roles of astrocytes in redox regulation and the corresponding mechanisms under both normal and different pathological conditions.

Evaluation of Microglia/Macrophage Cells from Rat Striatum and Prefrontal Cortex Reveals Differential Expression of Inflammatory-Related mRNA after Methamphetamine

RNA sequencing (RNAseq) can be a powerful tool in the identification of transcriptional changes after drug treatment. RNAseq was utilized to determine expression changes in Fluorescence-activated cell sorted (FACS) CD11b/c+ cells from the striatum (STR) and prefrontal cortex (PFC) of male Sprague-Dawley rats after a methamphetamine (METH) binge dosing regimen. Resident microglia and infiltrating macrophages were collected 2 h or 3 days after drug administration. Gene expression changes indicated there was an increase toward an overall pro-inflammatory state, or M1 polarization, along with what appears to be a subset of cells that differentiated toward the anti-inflammatory M2 polarization. In general, there were significantly more mRNA expression changes in the STR than the PFC and more at 2 h post-binge METH than at 3 days post-binge METH. Additionally, Ingenuity^® Pathway Analysis along with details of RNA expression changes revealed cyclo-oxygenase 2 (COX2)-driven prostaglandin (PG) E2 synthesis, glutamine uptake, and the Nuclear factor erythroid2-related factor 2 (NRF2) canonical pathway in microglia were associated with the binge administration regimen of METH.

Apelin-13 Protects PC12 Cells Against Methamphetamine-Induced Oxidative Stress, Autophagy and Apoptosis

Methamphetamine (METH) is a potent psychomotor stimulant that has a high potential for abuse in humans. In addition, it is neurotoxic, especially in dopaminergic neurons. Long-lasting exposure to METH causes psychosis and increases the risk of Parkinson's disease. Apelin-13 is a novel endogenous ligand which studies have shown that may have a neuroprotective effect. Therefore, we hypothesized that Apelin-13 might adequately prevent METH-induced neurotoxicity via the inhibition of apoptotic, autophagy, and ROS responses. In this study, PC12 cells were exposed to both METH (0.5, 1, 2, 3, 4, 6 mmol/L) and Apelin-13 (0.5, 1.0, 2.0, 4.0, 8.0 μmol/L) in vitro for 24 h to measure determined dose, and then downstream pathways were measured to investigate apoptosis, autophagy, and ROS responses. The results have indicated that Apelin-13 decreased the apoptotic response post-METH exposure in PC12 cells by increasing cell viability, reducing apoptotic rates. In addition, the study has revealed Apelin-13 decreased gene expression of Beclin-1 by Real-Time PCR and LC3-II by western blotting in METH-induced PC12 cells, which demonstrated autophagy is reduced. In addition, this study has shown that Apelin-13 reduces intracellular ROS of METH-induced PC12 cells. These results support Apelin-13 to be investigated as a potential drug for treatment of neurodegenerative diseases. It is suggested that Apelin-13 is beneficial in reducing oxidative stress, which may also play an important role in the regulation of METH-triggered apoptotic response. Hence, these data indicate that Apelin-13 could potentially alleviate METH-induced neurotoxicity via the reduction of oxidative damages, apoptotic, and autophagy cell death.

Identification of cytotoxic markers in methamphetamine treated rat C6 astroglia-like cells

Methamphetamine (METH) is a powerfully addictive psychostimulant that has a pronounced effect on the central nervous system (CNS). The present study aimed to assess METH toxicity in differentiated C6 astroglia-like cells through biochemical and toxicity markers with acute (1 h) and chronic (48 h) treatments. In the absence of external stimulants, cellular differentiation of neuronal morphology was achieved through reduced serum (2.5%) in the medium. The cells displayed branched neurite-like processes with extensive intercellular connections. Results indicated that acute METH treatment neither altered the cell morphology nor killed the cells, which echoed with lack of consequence on reactive oxygen species (ROS), nitric oxide (NO) or inhibition of any cell cycle phases except induction of cytoplasmic vacuoles. On the other hand, chronic treatment at 1 mM or above destroyed the neurite-like processors and decreased the cell viability that paralleled with increased levels of ROS, lipid peroxidation and lactate, depletion in glutathione (GSH) level and inhibition at G0/G1 phase of cell cycle, leading to apoptosis. Pre-treatment of cells with N-acetyl cysteine (NAC, 2.5 mM for 1 h) followed by METH co-treatment for 48 h rescued the cells completely from toxicity by decreasing ROS through increased GSH. Our results provide evidence that increased ROS and GSH depletion underlie the cytotoxic effects of METH in the cells. Since loss in neurite connections and intracellular changes can lead to psychiatric illnesses in drug users, the evidence that we show in our study suggests that these are also contributing factors for psychiatric-illnesses in METH addicts.

Trace amine-associated receptor 1 regulation of methamphetamine-induced neurotoxicity

Trace amine-associated receptor 1 (TAAR1) is activated by methamphetamine (MA) and modulates dopaminergic (DA) function. Although DA dysregulation is the hallmark of MA-induced neurotoxicity leading to behavioral and cognitive deficits, the intermediary role of TAAR1 has yet to be characterized. To investigate TAAR1 regulation of MA-induced neurotoxicity, Taar1 transgenic knock-out (KO) and wildtype (WT) mice were administered saline or a neurotoxic regimen of 4 i.p. injections, 2h apart, of MA (2.5, 5, or 10mg/kg). Temperature data were recorded during the treatment day. Additionally, striatal tissue was collected 2 or 7days following MA administration for analysis of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and tyrosine hydroxylase (TH) levels, as well as glial fibrillary acidic protein (GFAP) expression. MA elicited an acute hypothermic drop in body temperature in Taar1-WT mice, but not in Taar1-KO mice. Two days following treatment, DA and TH levels were lower in Taar1-KO mice compared to Taar1-WT mice, regardless of treatment, and were dose-dependently decreased by MA. GFAP expression was significantly increased by all doses of MA at both time points and greater in Taar1-KO compared to Taar1-WT mice receiving MA 2.5 or 5mg/kg. Seven days later, DA levels were decreased in a similar pattern: DA was significantly lower in Taar1-KO compared to Taar1-WT mice receiving MA 2.5 or 5mg/kg. TH levels were uniformly decreased by MA, regardless of genotype. These results indicate that activation of TAAR1 potentiates MA-induced hypothermia and TAAR1 confers sustained neuroprotection dependent on its thermoregulatory effects.

Methamphetamine Augments Concurrent Astrocyte Mitochondrial Stress, Oxidative Burden, and Antioxidant Capacity: Tipping the Balance in HIV-Associated Neurodegeneration

Methamphetamine (METH) use, with and without human immunodeficiency virus (HIV)-1 comorbidity, exacerbates neurocognitive decline. Oxidative stress is a probable neurotoxic mechanism during HIV-1 central nervous system infection and METH abuse, as viral proteins, antiretroviral therapy and METH have each been shown to induce mitochondrial dysfunction. However, the mechanisms regulating mitochondrial homeostasis and overall oxidative burden in astrocytes are not well understood in the context of HIV-1 infection and METH abuse. Here, we report METH-mediated dysregulation of astrocyte mitochondrial morphology and function during prolonged exposure to low levels of METH. Mitochondria became larger and more rod shaped with METH when assessed by machine learning, segmentation analyses. These changes may be mediated by elevated mitofusin expression coupled with inhibitory phosphorylation of dynamin-related protein-1, which regulate mitochondrial fusion and fission, respectively. While METH decreased oxygen consumption and ATP levels during acute exposure, chronic treatment of 1 to 2 weeks significantly enhanced both when tested in the absence of METH. Together, these changes significantly increased not only expression of antioxidant proteins, augmenting the astrocyte's oxidative capacity, but also oxidative damage. We propose that targeting astrocytes to reduce their overall oxidative burden and expand their antioxidant capacity could ultimately tip the balance from neurotoxicity towards neuroprotection.

Circular RNA HIPK2 regulates astrocyte activation via cooperation of autophagy and ER stress by targeting MIR124-2HG

Circular RNAs are a subclass of noncoding RNAs in mammalian cells; however, whether these RNAs are involved in the regulation of astrocyte activation is largely unknown. Here, we have shown that the circular RNA HIPK2 (circHIPK2) functions as an endogenous microRNA-124 (MIR124-2HG) sponge to sequester MIR124-2HG and inhibit its activity, resulting in increased sigma non-opioid intracellular receptor 1 (SIGMAR1/OPRS1) expression. Knockdown of circHIPK2 expression significantly inhibited astrocyte activation via the regulation of autophagy and endoplasmic reticulum (ER) stress through the targeting of MIR124-2HG and SIGMAR1. These findings were confirmed in vivo in mouse models, as microinjection of a circHIPK2 siRNA lentivirus into mouse hippocampi inhibited astrocyte activation induced by methamphetamine or lipopolysaccharide (LPS). These findings provide novel insights regarding the specific contribution of circHIPK2 to astrocyte activation in the context of drug abuse as well as for the treatment of a broad range of neuroinflammatory disorders.

Role of Mitochondria in Methamphetamine-Induced Dopaminergic Neurotoxicity: Involvement in Oxidative Stress, Neuroinflammation, and Pro-apoptosis-A Review

Methamphetamine (MA), an amphetamine-type psychostimulant, is associated with dopaminergic toxicity and has a high abuse potential. Numerous in vivo and in vitro studies have suggested that impaired mitochondria are critical in dopaminergic toxicity induced by MA. Mitochondria are important energy-producing organelles with dynamic nature. Evidence indicated that exposure to MA can disturb mitochondrial energetic metabolism by inhibiting the Krebs cycle and electron transport chain. Alterations in mitochondrial dynamic processes, including mitochondrial biogenesis, mitophagy, and fusion/fission, have recently been shown to contribute to dopaminergic toxicity induced by MA. Furthermore, it was demonstrated that MA-induced mitochondrial impairment enhances susceptibility to oxidative stress, pro-apoptosis, and neuroinflammation in a positive feedback loop. Protein kinase Cδ has emerged as a potential mediator between mitochondrial impairment and oxidative stress, pro-apoptosis, or neuroinflammation in MA neurotoxicity. Understanding the role and underlying mechanism of mitochondrial impairment could provide a molecular target to prevent or alleviate dopaminergic toxicity induced by MA.

Possible involvement of CREB/BDNF signaling pathway in neuroprotective effects of topiramate against methylphenidate induced apoptosis, oxidative stress and inflammation in isolated hippocampus of rats: Molecular, biochemical and histological evidences

Chronic abuse of methylphenidate (MPH) can cause serious neurotoxicity. The neuroprotective effects of topiramate (TPM) were approved, but its putative mechanism remains unclear. In current study the role of CREB/BDNF signaling pathway in TPM protection against methylphenidate-induced neurotoxicity in rat hippocampus was evaluated. 60 adult male rats were divided randomly into six groups. Groups received MPH (10mg/kg) only and concurrently with TPM (50mg/kg and 100mg/kg) and TPM (50 and 100mg/kg) only for 14 days. Open field test (OFT) was used to investigate motor activity. Some biomarkers of apoptotic, anti-apoptotic, oxidative, antioxidant and inflammatory factors were also measured in hippocampus. Expression of total (inactive) and phosphorylated (active) CREB and BDNF were also measured in gene and protein levels in dentate gyrus (DG) and CA1 areas of hippocampus. MPH caused significant decreases in motor activity in OFT while TPM (50 and 100mg/kg) inhibited MPH-induced decreases in motor activity. On the other hand, MPH caused remarkable increases in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels in hippocampal tissue. MPH also caused significant decreases of superoxide dismutase, activity and also decreased CREB, in both forms, BDNF and Bcl-2 protein levels. TPM, by the mentioned doses, attenuated these effects and increased superoxide dismutase, glutathione peroxidase and glutathione reductase activities and also increased CREB, in both forms, BDNF and Bcl-2 protein levels and inhibited MPH induced increase in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels. TPM also inhibited MPH induced decreases in cell number and changes in cell shapes in DG and CA1 areas. TPM can probably act as a neuroprotective agent against MPH induced neurotoxicity and this might have been mediated by CREB/BDNF signaling pathway.

Neurotoxicity of β-Keto Amphetamines: Deathly Mechanisms Elicited by Methylone and MDPV in Human Dopaminergic SH-SY5Y Cells

Synthetic cathinones (β-keto amphetamines) act as potent CNS stimulants similarly to classical amphetamines, which raise concerns about their potential neurotoxic effects. The present in vitro study aimed to explore and compare the mechanisms underlying the neurotoxicity of two commonly abused cathinone derivatives, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV), with those of 3,4-methylenedioxymethamphetamine (MDMA), using undifferentiated and differentiated SH-SY5Y cells. Following a 24 h exposure period, methylone and MDPV induced loss of cell viability in a concentration-dependent manner, in the following order of potency: MDPV ≈ MDMA > methylone. Dopaminergic differentiated cells evidenced higher sensitivity to the neurotoxic effects of both cathinones and MDMA than the undifferentiated ones, but this effect was not inhibited by the DAT inhibitor GBR 12909. Intracellular oxidative stress mediated by methylone and MDPV was demonstrated by the increase in reactive oxygen and nitrogen species (ROS and RNS) production, depletion of intracellular reduced glutathione and increased oxidized glutathione levels. All three drugs elicited mitochondrial impairment, characterized by the mitochondrial membrane potential (Δψm) dissipation and intracellular ATP depletion. Apoptosis was found to be a common mechanism of cell death induced by methylone and MDPV, with evident chromatin condensation and formation of pyknotic nuclei, and activation of caspases 3, 8, and 9. In conclusion, the present data shows that oxidative stress and mitochondrial dysfunction play a role in cathinones-induced neuronal damage, ultimately leading to cell death by apoptosis.

The neurotoxic mechanisms of amphetamine: Step by step for striatal dopamine depletion

Amphetamine (AMPH) is a commonly abused psychostimulant that induces neuronal cell death/degeneration in humans and experimental animals. Although multiple neurotoxic mechanisms of AMPH have been intensively investigated, the interplay between these mechanisms has remained elusive. In this study, we used a rat model of AMPH-induced long-lasting striatal dopamine (DA) depletion and identified mechanisms of neurotoxicity, energy failure, excitotoxicity, and oxidative stress. Pretreatment with nicotinamide (NAM, a co-factor for the electron transport chain) blocked AMPH-induced free radical formation, energy failure, and striatal DA decrease. Also, MK-801 (a NMDA receptor antagonist) blocked AMPH-induced free radical formation and striatal DA but not energy failure decrease, indicating excitotoxicity may occur before free radical formation and after energy failure. Thus, these results show that during AMPH intoxication, energy failure, excitotoxicity, and free radical formation are orchestrated consecutively to mediate the depletion of striatal DA.

Neuroprotective effects of various doses of topiramate against methylphenidate induced oxidative stress and inflammation in rat isolated hippocampus

Methylphenidate (MPH) abuse causes neurodegeneration. The neuroprotective effects of topiramate (TPM) have been reported but its putative mechanism remains unclear. The current study evaluates the role of various doses of TPM on protection of rat hippocampal cells from MPH-induced oxidative stress and inflammation in vivo. Seventy adult male rats were divided into six groups. Group 1 received normal saline (0.7 mL/rat) and group 2 was injected with MPH (10 mg/kg) for 21 days. Groups 3, 4, 5, 6 and 7 concurrently were treated by MPH (10 mg/kg) and TPM (10, 30, 50, 70 and 100 mg/kg, intraperitoneally (i.p.)), respectively for 21 days. After drug administration, the open field test (OFT) was used to investigate motor activity. Oxidative, antioxidant and inflammatory factors were measured in isolated hippocampus. Also, the brain-derived neurotrophic factor (BDNF) level was measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. Cresyl violet staining of Dentate Gyrus (DG) and CA1 cell layers of the hippocampus were also performed. MPH significantly disturbs motor activity in OFT and TPM (70 and 100 mg/kg) decreased this disturbance. Also MPH significantly increased lipid peroxidation, mitochondrial reduced state of glutathione (GSH) level, interleukin (IL)-1β and tumour necrosis factor (TNF)-α and BDNF level in isolated hippocampal cells. Also superoxide dismutase, glutathione peroxidase and glutathione reductase activity significantly decreased. Various doses of TPM attenuated these effects and significantly decreased MPH-induced oxidative damage, inflammation and hippocampal cell loss and increased BDNF level. This study suggests that TPM has the potential to be used as a neuroprotective agent against oxidative stress and neuroinflammation induced by frequent use of MPH.

Neuroprotective effects of various doses of topiramate against methylphenidate-induced oxidative stress and inflammation in isolated rat amygdala: the possible role of CREB/BDNF signaling pathway

Methylphenidate (MPH) abuse damages brain cells. The neuroprotective effects of topiramate (TPM) have been reported previously, but its exact mechanism of action still remains unclear. This study investigated the in vivo role of various doses of TPM in the protection of rat amygdala cells against methylphenidate-induced oxidative stress and inflammation. Seventy adult male rats were divided into seven groups. Groups 1 and 2 received normal saline (0.7 ml/rat) and MPH (10 mg/kg), respectively, for 21 days. Groups 3, 4, 5, 6, and 7 were concurrently treated with MPH (10 mg/kg) and TPM (10, 30, 50, 70, and 100 mg/kg), respectively, for 21 days. elevated plus maze (EPM) was used to assess motor activity disturbances. In addition, oxidative, antioxidantand inflammatory factors and CREB, Ak1, CAMK4, MAPK3, PKA, BDNF, and c FOS gene levels were measured by RT-PCR, and also, CREB and BDNF protein levels were measured by WB in isolated amygdalae. MPH significantly disturbed motor activity and TPM (70 and 100 mg/kg) neutralized its effects. MPH significantly increased lipid peroxidation, mitochondrial GSSG levels and IL-1β and TNF-α level and CAMK4 gene expression in isolated amygdala cells. In contrast, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities and CREB, BDNF Ak1, MAPK3, PKA, BDNF, and c FOS expression significantly decreased. The various doses of TPM attenuated these effects of MPH. It seems that TPM can be used as a neuroprotective agent and is a good candidate against MPH-induced neurodegeneration.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.

Characterization of binge-dosed methamphetamine-induced neurotoxicity and neuroinflammation

Methamphetamine (MA) is a potent, highly addictive psychostimulant abused by millions of people worldwide. MA induces neurotoxicity, damaging striatal dopaminergic terminals, and neuroinflammation, with striatal glial activation leading to pro-inflammatory cytokine and reactive oxygen species production. It is unclear whether MA-induced neuroinflammation contributes to MA-induced neurotoxicity. In the current study, we examined the linkage between the time course and dose response of MA-induced neurotoxicity and neuroinflammation. Adult male mice underwent a binge dosing regimen of four injections given every 2h with doses of 2, 4, 6, or 8 mg/kg MA per injection, and were sacrificed after 1, 3, 7, or 14 days. Binge MA treatment dose-dependently caused hyperthermia and induced hypoactivity after one day, though activity returned to control levels within one week. Striatal dopamine (DA) was diminished one day after treatment with at least 4 mg/kg MA, while DA turnover rates peaked after seven days. Although striatal tyrosine hydroxylase and DA transporter levels were also decreased one day after treatment with at least 4 mg/kg MA, they trended toward recovery by day 14. All doses of MA activated striatal glia within one day. While astrocyte activation persisted, microglial activation was attenuated over the two weeks of the study. These findings help clarify the relationship between MA-induced neuroinflammation and neurotoxicity, particularly regarding their temporal and dose-specific dynamics.

Mitochondria: key players in the neurotoxic effects of amphetamines

Amphetamines are a class of psychotropic drugs with high abuse potential, as a result of their stimulant, euphoric, emphathogenic, entactogenic, and hallucinogenic properties. Although most amphetamines are synthetic drugs, of which methamphetamine, amphetamine, and 3,4-methylenedioxymethamphetamine ("ecstasy") represent well-recognized examples, the use of natural related compounds, namely cathinone and ephedrine, has been part of the history of humankind for thousands of years. Resulting from their amphiphilic nature, these drugs can easily cross the blood-brain barrier and elicit their well-known psychotropic effects. In the field of amphetamines' research, there is a general consensus that mitochondrial-dependent pathways can provide a major understanding concerning pathological processes underlying the neurotoxicity of these drugs. These events include alterations on tricarboxylic acid cycle's enzymes functioning, inhibition of mitochondrial electron transport chain's complexes, perturbations of mitochondrial clearance mechanisms, interference with mitochondrial dynamics, as well as oxidative modifications in mitochondrial macromolecules. Additionally, other studies indicate that amphetamines-induced neuronal toxicity is closely regulated by B cell lymphoma 2 superfamily of proteins with consequent activation of caspase-mediated downstream cell death pathway. Understanding the molecular mechanisms at mitochondrial level involved in amphetamines' neurotoxicity can help in defining target pathways or molecules mediating these effects, as well as in developing putative therapeutic approaches to prevent or treat the acute- or long-lasting neuropsychiatric complications seen in human abusers.

Prior methamphetamine self-administration attenuates the dopaminergic deficits caused by a subsequent methamphetamine exposure

Others and we have reported that prior methamphetamine (METH) exposure attenuates the persistent striatal dopaminergic deficits caused by a subsequent high-dose "binge" METH exposure. The current study investigated intermediate neurochemical changes that may contribute to, or serve to predict, this resistance. Rats self-administered METH or saline for 7 d. On the following day (specifically, 16 h after the conclusion of the final METH self-administration session), rats received a binge exposure of METH or saline (so as to assess the impact of prior METH self-administration), or were sacrificed without a subsequent METH exposure (i.e., to assess the status of the rats at what would have been the initiation of the binge METH treatment). Results revealed that METH self-administration per se decreased striatal dopamine (DA) transporter (DAT) function and DA content, as assessed 16 h after the last self-administration session. Exposure to a binge METH treatment beginning at this 16-h time point decreased DAT function and DA content as assessed 1 h after the binge METH exposure: this effect on DA content (but not DAT function) was attenuated if rats previously self-administered METH. In contrast, 24 h after the binge METH treatment prior METH self-administration: 1) attenuated deficits in DA content, DAT function and vesicular monoamine transporter-2 function; and 2) prevented increases in glial fibrillary acidic protein and DAT complex immunoreactivity. These data suggest that changes 24 h, but not 1 h, after binge METH exposure are predictive of tolerance against the persistence of neurotoxic changes following binge METH exposures.

Drug abuse and the neurovascular unit

Drug abuse continues to create a major international epidemic affecting society. A great majority of past drug abuse research has focused mostly on the mechanisms of addiction and the specific effects of substance use disorders on brain circuits and pathways that modulate reward, motivation, craving, and decision making. Few studies have focused on the neurobiology of acute and chronic substance abuse as it relates to the neurovascular unit (brain endothelial cell, neuron, astrocyte, microglia, and pericyte). Increasing research indicates that all cellular components of the neurovascular unit play a pivotal role in both the process of addiction and how drug abuse affects the brain response to diseases. This review will focus on the specific effects of opioids, amphetamines, alcohol, and nicotine on the neurovascular unit and its role in addiction and adaption to brain diseases. Elucidation of the role of the neurovascular unit on the neurobiology associated with drug addiction will help to facilitate the development of better therapeutic approaches for drug-dependent individuals.

SN79, a sigma receptor antagonist, attenuates methamphetamine-induced astrogliosis through a blockade of OSMR/gp130 signaling and STAT3 phosphorylation

Methamphetamine (METH) exposure results in dopaminergic neurotoxicity in striatal regions of the brain, an effect that has been linked to an increased risk of Parkinson's disease. Various aspects of neuroinflammation, including astrogliosis, are believed to be contributory factors in METH neurotoxicity. METH interacts with sigma receptors at physiologically relevant concentrations and treatment with sigma receptor antagonists has been shown to mitigate METH-induced neurotoxicity in rodent models. Whether these compounds alter the responses of glial cells within the central nervous system to METH however has yet to be determined. Therefore, the purpose of the current study was to determine whether the sigma receptor antagonist, SN79, mitigates METH-induced striatal reactive astrogliosis. Male, Swiss Webster mice treated with a neurotoxic regimen of METH exhibited time-dependent increases in striatal gfap mRNA and concomitant increases in GFAP protein, indicative of astrogliosis. This is the first report that similar to other neurotoxicants that induce astrogliosis through the activation of JAK2/STAT3 signaling by stimulating gp-130-linked cytokine signaling resulting from neuroinflammation, METH treatment also increases astrocytic oncostatin m receptor (OSMR) expression and the phosphorylation of STAT3 (Tyr-705) in vivo. Pretreatment with SN79 blocked METH-induced increases in OSMR, STAT3 phosphorylation and astrocyte activation within the striatum. Additionally, METH treatment resulted in striatal cellular degeneration as measured by Fluoro-Jade B, an effect that was mitigated by SN79. The current study provides evidence that sigma receptor antagonists attenuate METH-induced astrocyte activation through a pathway believed to be shared by various neurotoxicants.

ROS and Sympathetically Mediated Mitochondria Activation in Brown Adipose Tissue Contribute to Methamphetamine-Induced Hyperthermia

Methamphetamine (Meth) abuse has been shown to induce alterations in mitochondrial function in the brain as well as to induce hyperthermia, which contributes to neurotoxicity and Meth-associated mortality. Brown adipose tissue (BAT), a thermogenic site known to be important in neonates, has recently regained importance since being identified in significant amounts and in correlation with metabolic balance in human adults. Given the high mitochondrial content of BAT and its role in thermogenesis, we aimed to investigate whether BAT plays any role in the development of Meth-induced hyperthermia. By ablating or denervating BAT, we identified a partial contribution of this organ to Meth-induced hyperthermia. BAT ablation decreased temperature by 0.5°C and reduced the length of hyperthermia by 1 h, compared to sham-operated controls. BAT denervation also affected the development of hyperthermia in correlation with decreased the expression of electron transport chain molecules, and increase on PCG1a levels, but without affecting Meth-induced uncoupling protein 1 upregulation. Furthermore, in isolated BAT cells in culture, Meth, but not Norepinephrine, induced H2O2 upregulation. In addition, we found that in vivo Reactive Oxygen Species (ROS) play a role in Meth hyperthermia. Thus, sympathetically mediated mitochondrial activation in the BAT and Meth-induced ROS are key components to the development of hyperthermia in Meth abuse.

Methamphetamine alters occludin expression via NADPH oxidase-induced oxidative insult and intact caveolae

Methamphetamine (METH) is a drug of abuse with neurotoxic and vascular effects that may be mediated by reactive oxygen species (ROS). However, potential sources of METH-induced generation of ROS are not fully understood. This study is focused on the role of NAD(P)H oxidase (NOX) in METH-induced dysfunction of brain endothelial cells. Treatment with METH induced a time-dependent increase in phosphorylation of NOX subunit p47, followed by its binding with gp91 and p22, and the formation of an active NOX complex. An increase in NOX activity was associated with elevated production of ROS, alterations of occludin levels and increased transendothelial migration of monocytes. Inhibition of NOX by NSC 23766 attenuated METH-induced ROS generation, changes in occludin protein levels and monocyte migration. Because an active NOX complex is localized to caveolae, we next evaluated the role of caveolae in METH-mediated toxicity to brain endothelial cells. Treatment with METH induced phosphorylation of ERK1/2 and caveolin-1 protein. Inhibition of ERK1/2 activity or caveolin-1 silencing protected against METH-induced alterations of occludin levels. These findings indicate an important role of NOX and functional caveolae in METH-induced oxidative stress in brain endothelial cells that contribute to the subsequent alterations of occludin levels and transendothelial migration of inflammatory cells.

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

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

Methamphetamine-induced neurotoxicity: the road to Parkinson's disease

Studies have implicated methamphetamine exposure as a contributor to the development of Parkinson's disease. There is a significant degree of striatal dopamine depletion produced by methamphetamine, which makes the toxin useful in the creation of an animal model of Parkinson's disease. Parkinson's disease is a progressive neurodegenerative disorder associated with selective degeneration of nigrostriatal dopaminergic neurons. The immediate need is to understand the substances that increase the risk for this debilitating disorder as well as these substances'neurodegenerative mechanisms. Currently, various approaches are being taken to develop a novel and cost-effective anti-Parkinson's drug with minimal adverse effects and the added benefit of a neuroprotective effect to facilitate and improve the care of patients with Parkinson's disease. Amethamphetamine-treated animal model for Parkinson's disease can help to further the understanding of the neurodegenerative processes that target the nigrostriatal system. Studies on widely used drugs of abuse, which are also dopaminergic toxicants, may aid in understanding the etiology, pathophysiology and progression of the disease process and increase awareness of the risks involved in such drug abuse. In addition, this review evaluates the possible neuroprotective mechanisms of certain drugs against methamphetamine-induced toxicity.

Methamphetamine disrupts blood-brain barrier function by induction of oxidative stress in brain endothelial cells

Methamphetamine (METH), a potent stimulant with strong euphoric properties, has a high abuse liability and long-lasting neurotoxic effects. Recent studies in animal models have indicated that METH can induce impairment of the blood-brain barrier (BBB), thus suggesting that some of the neurotoxic effects resulting from METH abuse could be the outcome of barrier disruption. In this study, we provide evidence that METH alters BBB function through direct effects on endothelial cells and explore possible underlying mechanisms leading to endothelial injury. We report that METH increases BBB permeability in vivo, and exposure of primary human brain microvascular endothelial cells (BMVEC) to METH diminishes the tightness of BMVEC monolayers in a dose- and time-dependent manner by decreasing the expression of cell membrane-associated tight junction (TJ) proteins. These changes were accompanied by the enhanced production of reactive oxygen species, increased monocyte migration across METH-treated endothelial monolayers, and activation of myosin light chain kinase (MLCK) in BMVEC. Antioxidant treatment attenuated or completely reversed all tested aspects of METH-induced BBB dysfunction. Our data suggest that BBB injury is caused by METH-mediated oxidative stress, which activates MLCK and negatively affects the TJ complex. These observations provide a basis for antioxidant protection against brain endothelial injury caused by METH exposure.

Methamphetamine induces heme oxygenase-1 expression in cortical neurons and glia to prevent its toxicity

The impairment of cognitive and motor functions in humans and animals caused by methamphetamine (METH) administration underscores the importance of METH toxicity in cortical neurons. The heme oxygenase-1 (HO-1) exerts a cytoprotective effect against various neuronal injures; however, it remains unclear whether HO-1 is involved in METH-induced toxicity. We used primary cortical neuron/glia cocultures to explore the role of HO-1 in METH-induced toxicity. Exposure of cultured cells to various concentrations of METH (0.1, 0.5, 1, 3, 5, and 10 mM) led to cytotoxicity in a concentration-dependent manner. A METH concentration of 5 mM, which caused 50% of neuronal death and glial activation, was chosen for subsequent experiments. RT-PCR and Western blot analysis revealed that METH significantly induced HO-1 mRNA and protein expression, both preceded cell death. Double and triple immunofluorescence staining further identified HO-1-positive cells as activated astrocytes, microglia, and viable neurons, but not dying neurons. Inhibition of the p38 mitogen-activated protein kinase pathway significantly blocked HO-1 induction by METH and aggravated METH neurotoxicity. Inhibition of HO activity using tin protoporphyrine IX significantly reduced HO activity and exacerbated METH neurotoxicity. However, prior induction of HO-1 using cobalt protoporphyrine IX partially protected neurons from METH toxicity. Taken together, our results suggest that induction of HO-1 by METH via the p38 signaling pathway may be protective, albeit insufficient to completely protect cortical neurons from METH toxicity.

Methamphetamine downregulates peroxiredoxins in rat pheochromocytoma cells

Methamphetamine (METH) is an abusive psychostimulant that induces neuronal cell death/degeneration in experimental animals and humans. METH-induced apoptosis in rat pheochromocytoma cells was utilized to study the neurotoxic mechanism. During METH intoxication, we found that peroxiredoxins and thioredoxins/thioredoxin reductases (peroxiredoxin reducing systems) which are known to prevent oxidative stress and apoptosis were differentially downregulated and upregulated, respectively. We also found not only the free radicals but also the oxidative forms of peroxiredoxin and thioredoxin were increased, indicating the dysfunction of these enzymes. Thus, METH-induced differential regulation and oxidation of peroxiredoxins and thioredoxin may be an important mechanism for apoptosis.

Protective effect of the radical scavenger edaravone against methamphetamine-induced dopaminergic neurotoxicity in mouse striatum

The administration of high doses of methamphetamine causes the degeneration of striatal dopaminergic fibers in the brains of rodents, and oxidative stress appears to be one of the main factors of neurotoxicity. This study examined whether edaravone, a radical scavenger, protects against methamphetamine-induced neurotoxicity in mice. Methamphetamine treatment (4 mg/kg, s.c. x 4 with 2 h intervals) showed striatal dopaminergic degeneration as observed by decreases in dopamine levels and tyrosine hydroxylase immunoreactivity in the striatum. The neurotoxicity was reduced by edaravone (3 mg/kg, i.p.), when it was administered four times 30 min before methamphetamine at 2 h intervals and additionally four times after methamphetamine at 12 h intervals. An immunohistochemical study showed that methamphetamine increased 3-nitrotyrosine immunoreactivity, an in vivo marker of peroxynitrite production, and activated microglia and astrocytes in the striatum. Edaravone blocked the increase in 3-nitrotyrosine immunoreactivity and the activation of astrocytes, but it did not affect the activation of microglia. Edaravone did not affect methamphetamine-induced hyperthermia and striatal dopamine release. These results suggest that edaravone protects against methamphetamine-induced neurotoxicity in the striatum by blocking peroxynitrite production. This study also suggests that methamphetamine activates microglia in a radical-independent mechanism.

Methamphetamine and human immunodeficiency virus protein Tat synergize to destroy dopaminergic terminals in the rat striatum

Dysfunction of the dopaminergic system accompanied by loss of dopamine in the striatum is a major feature of human immunodeficiency virus-1-associated dementia. Previous studies have shown that human immunodeficiency virus-1-associated dementia patients with a history of drug abuse have rapid neurological progression, prominent psychomotor slowing, more severe encephalitis and more severe dendritic and neuronal damage in the frontal cortex compared with human immunodeficiency virus-1-associated dementia patients without a history of drug abuse. In a previous study, we showed that methamphetamine and human immunodeficiency virus-1 protein Tat interact to produce a synergistic decline in dopamine levels in the rat striatum. The present study was carried out to understand the underlying cause for the loss of dopamine. Male Sprague-Dawley rats were administered saline, methamphetamine, Tat or Tat followed by methamphetamine 24 h later. Two and seven days later the animals were killed and tissue sections from striatum were processed for silver staining to examine terminal degeneration while sections from striatum and substantia nigra were processed for tyrosine hydroxylase immunoreactivity. Striatal tissue was also analyzed by Western blotting for tyrosine hydroxylase protein levels. Compared with controls, methamphetamine+Tat-treated animals showed extensive silver staining and loss of tyrosine hydroxylase immunoreactivity and protein levels in the ipsilateral striatum. There was no apparent loss of tyrosine hydroxylase in the substantia nigra. Markers for oxidative stress were significantly increased in striatal synaptosomes from Tat+methamphetamine group compared with controls. The results indicate that methamphetamine and Tat interact to produce an enhanced injury to dopaminergic nerve terminals in the striatum with sparing of the substantia nigra by a mechanism involving oxidative stress. These findings suggest a possible mode of interaction between methamphetamine and human immunodeficiency virus-1 infection to produce enhanced dopaminergic neurotoxicity in human immunodeficiency virus-1 infected/methamphetamine-abusing patients.

Patterns of Selective Neuronal Damage in Methamphetamine-User AIDS Patients

The risk for HIV infection attributable to methamphetamine (METH) use continues to increase. The combined effect of HIV and METH in the pathogenesis of HIV encephalitis (HIVE) is unclear, however. To better understand the neuropathology associated with HIV and METH use, the patterns of neurodegeneration were assessed in HIV-positive METH users and in HIV-positive non-METH users. Patients in the study met criteria for inclusion and received neuromedical and postmortem neuropathologic examinations. Immunocytochemical and polymerase chain reaction analyses were performed to determine brain HIV levels and to exclude the presence of other viruses. METH-using patients with HIVE showed significantly lower gp41 scores and less severe forms of encephalitis but a higher frequency of ischemic events, a more pronounced loss of synaptophysin immunoreactivity, and a more severe microglial reaction than HIVE non-METH users. Furthermore, in METH-using patients with HIVE, extensive loss of calbindin (CB)-immunoreactive interneurons displaying phylopodial neuritic processes suggestive of aberrant sprouting was observed. Taken together, these studies indicate that the combined effects of METH and HIV selectively damage CB immunoreactive nonpyramidal neurons. In combination, METH and HIV may increase neuronal cell injury and death, thereby enhancing brain metabolic disturbances observed in clinical populations of HIV-positive METH abusers.

Enhanced P2Y1 receptor expression in the brain after sensitisation with d-amphetamine

RATIONALE AND OBJECTIVES

Many pathological and physiological processes are associated with the transcriptional induction of specific receptors. The aim of the present study was to examine whether the development of d-amphetamine (AMPH)-induced sensitisation is related to an altered P2Y(1) receptor expression.

METHODS

Rats, treated for 5 successive days with AMPH (1.5 mg/kg, i.p.), alone or after pre-treatment with the non-specific P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2,4-disulphonic acid (PPADS, 0.6 nmol, i.c.v.) and tested in an open field system with respect to locomotor response, were studied immunocytochemically 5 days after the last AMPH injection.

RESULTS

In the behaviourally sensitised animals, astrogliosis, characterised by hypertrophy, increase in glial fibrillary acidic protein (GFAP) immunoreactivity (IR) and astrocytic proliferation in striatal areas and the nucleus accumbens were observed. Quantification of the P2Y(1) receptor stained cells revealed an increase in the receptor expression after AMPH-induced sensitisation in the studied regions. Pre-treatment with PPADS prior to each AMPH administration prevented the development of sensitisation, astrogliosis and P2Y(1) receptor up-regulation. PPADS failed to alter the number of P2Y(1) receptor-labelled cells when given alone. Confocal laser scanning microscopy indicated the localisation of P2Y(1) receptors on GFAP-labelled astrocytes as well as on tubulin (betaIII)-labelled neurones, under control conditions and after AMPH administration.

CONCLUSION

The present results confirm the existence of P2Y(1) receptors on astrocytes and neurones as possible targets of endogenous ATP and in addition show their up-regulation as a consequence of P2Y(1) receptor-involvement in AMPH-induced sensitisation in vivo.

Structural and functional cellular alterations underlying the toxicity of methamphetamine in rat retina and prefrontal cortex

The consumption of illicit drugs is an increasing problem in contemporary societies, and is one of the major causes of death and illness all over the world. Methamphetamine is among the drugs more widely used. Although evidence for a role of reactive species--especially reactive oxygen species (ROS) and apoptotic events--has been shown, the mechanism(s) underlying the cellular toxicity induced by this drug is not yet fully identified. In this context the elucidation of the cytotoxic effects induced by methamphetamine in rat frontal cortex and retina, which compromise cell viability and ultimately result in cell death, can further contribute to the understanding of its mechanism of action. This knowledge may provide new insights into the development of new therapeutic approaches to prevent or ameliorate deleterious alterations of the nervous system. The use of epifluorescence microscopy associated with different fluorescent probes, markers of structural and/or functional cell parameters, can be used as a powerful tool to carry out those studies, in particular, the viability probes propidium iodide (PI) to assess plasma membrane integrity and fluorescein diacetate (FDA), which can monitor intracellular esterase activity and/or pH. In a preliminary study, the kinetic assessment of cellular changes induced by different drug concentrations (0, 1.2, 3, and 6 mM) allowed detection of dose-dependent alterations that are observed earlier in the retina. In fact, in the retina it was possible to monitor alterations (at 4 h of incubation) both in plasma membrane integrity and in esterase activity and/or pH for the lowest drug concentration (1.2 mM). In the prefrontal cortex these changes were only visible for drug concentrations > or = 3 mM. This work is a novel approach to the mechanisms of action of illicit drugs in the central nervous system and will provide the foundations and guidelines for further investigations in the context of tolerance, dependence, and addiction.