Comparison of poisoning deaths with wastewater-based consumption estimates and assessment of fatal toxicity for amphetamine-type stimulant drugs

Among several established indicators that are used to monitor the illicit drug scene, drug-related deaths and wastewater-based epidemiology (WBE) stand out for population-level coverage. In this study, we aimed to compare temporal trends with respect to amphetamine, methamphetamine and methylenedioxymethamphetamine (MDMA) revealed by these indicators and explore the differences in fatal toxicity between the stimulants. All deaths in which poisoning caused by amphetamine, methamphetamine or MDMA was either the underlying or contributing cause of death in Finland in 2012, 2014, 2016, 2018 and 2020 were included in the study. Consumption of the studied drugs was measured by WBE in the same years. There was a significant correlation between poisoning and drug consumption for all three stimulants, and for amphetamine and MDMA, these figures increased over the study period. The highest fatal toxicity, as expressed by the number of deaths per million doses, was obtained for methamphetamine at an estimated dose of 50 mg, followed by MDMA (100 mg dose) and with amphetamine (50 mg dose). The fatal toxicity found here for the stimulants was close to that previously reported for many prescription opioids and tricyclic antidepressants. Our study is the first to quantitatively investigate the fatal toxicity of amphetamine-type stimulants by comparing deaths with consumption estimates derived from WBE. It shows that amphetamine, methamphetamine and MDMA possess a quite similar capacity to cause death. This new approach adds to the earlier methods of estimating drug-related harm.

Triggering Receptor Expressed on Myeloid Cells 2 Deficiency Exacerbates Methamphetamine-Induced Activation of Microglia and Neuroinflammation

Methamphetamine (METH) is a highly addictive psychostimulant and one of the most widely abused drugs worldwide. The continuous use of METH eventually leads to neurotoxicity and drug addiction. Studies have shown that neurotoxicity is strongly associated with METH-induced neuroinflammation, and microglia are the key drivers of neuroinflammation. Triggering receptor expressed on myeloid cells 2 (TREM2) is reported to play a key role in activation of microglia and neuroinflammation. Yet, the molecular mechanisms by which METH causes neuroinflammation and neurotoxicity remain elusive. In the current study, we investigated the role of TREM2 in neuroinflammation induced by METH in BV2 cells and the wild-type (WT) C57BL/6J mice, CX3CR1GFP/+ transgenic mice, and TREM2 knockout (KO) mice. Postmortem samples from the frontal cortex of humans with a history of METH use were also analyzed to determine the levels of TREM2, TLR4, IBA1, and IL-1β. The expression levels of TREM2, TLR4, IBA1, IL-1β, iNOS, and Arg-1 were then assessed in the BV2 cells and frontal cortex of mice and human METH users. Results revealed that the expression levels of TREM2, TLR4, IBA1, and IL-1β were significantly elevated in METH-using individuals and BV2 cells. Microglia were clearly activated in the frontal cortex of WT C57BL/6 mice and CX3CR1GFP/+ transgenic mice, and the protein levels of IBA1, TREM2, TLR4, and IL-1β were elevated in the METH-induced mouse models. Moreover, TREM2-KO mice showed further increased microglial activation, neuroinflammation, and excitotoxicity induced by METH. Thus, these findings suggest that TREM2 may be a target for regulating METH-induced neuroinflammation.

Daphnia magna an emerging environmental model of neuro and cardiotoxicity of illicit drugs

Cocaine, methamphetamine, ectasy (3,4-methylenedioxy amphetamine (MDMA)) and ketamine are among the most consumed drugs worldwide causing cognitive, oxidative stress and cardiovascular problems in humans. Residue levels of these drugs and their transformation products may still enter the aquatic environment, where concentrations up to hundreds of ng/L have been measured. In the present work we tested the hypothesis that psychotropic effects and the mode of action of these drugs in D. magna cognitive, oxidative stress and cardiovascular responses are equivalent to those reported in humans and other vertebrate models. Accordingly we expose D. magna juveniles to pharmacological and environmental relevant concentrations. The study was complemented with the measurement of the main neurotransmitters involved in the known mechanisms of action of these drugs in mammals and physiological relevant amino acids. Behavioural cognitive patters clearly differentiate the 3 psychostimulant drugs (methamphetamine, cocaine, MDMA) from the dissociative one ketamine. Psychostimulant drugs at pharmacological doses (10-200 μM), increased basal locomotion activities and responses to light, and decreased habituation to it. Ketamine only increased habituation to light. The four drugs enhanced the production of reactive oxygen species in a concentration related manner, and at moderate concentrations (10-60 μM) increased heartbeats, diminishing them at high doses (200 μM). In chronic exposures to environmental low concentrations (10-1000 ng/L) the four drugs did not affect any of the behavioural responses measured but methamphetamine and cocaine inhibited reproduction at 10 ng/L. Observed effects on neurotransmitters and related metabolites were in concern with reported responses in mammalian and other vertebrate models: cocaine and MDMA enhanced dopamine and serotonin levels, respectively, methamphetamine and MDMA decreased dopamine and octopamine, and all but MDMA decreased 3 MT levels. Drug effects on the concentration of up to 10 amino acids evidence disruptive effects on neurotransmitter synthesis, the urea cycle, lipid metabolism and cardiac function.

The Effect of Methamphetamine on Ventricular Myocytes of Neonatal Rats

Objective

The paper studied the effect of Methamphetamine (MDMA) on myocardial gap junction protein to further reveal the molecular toxicological mechanism of Methamphetamine directly inducing cardiotoxicity,does it affect the expression, distribution, and phosphorylation status of connexin 43 in myocardial cells, inducing cardiac dysfunction.

Methods

Select 1-day SPF grade neonatal rats, obtain purified ventricular myocytes, and undergo acute exposure for 1 hour to establish an in vitro model of MDMA acute exposure.An in vitro MDMA acute exposure model was constructed to observe the effects of acute exposure to different concentrations of MDMA on the expression and transcription level of CX43 protein in ventricular myocytes; the effect on the content and distribution of mouse ventricular myocyte Connexin 43; the influence on the phosphorylation status of Ser368 at the phosphorylation site of protein 43; and the effects on the intracellular calcium oscillation mode and the intracellular calcium ion concentration.

Results

The content of total Connexin 43 in cardiomyocytes of the acute MDMA exposure group decreased significantly. Immunofluorescence detection of MDMA found that the content of Connexin 43 in the gap junction decreased with abnormal distribution. MDMA can lead to changes in the phosphorylation status of Connexin 43, which is manifested as an increase in the proportion of non-phosphorylation status, and can also increase the phosphorylation level of site Ser368. MDMA can change the calcium oscillation mode and rise of calcium ion concentration in cardiomyocytes.

Conclusion

MDMA can destroy the calcium homeostasis in cardiomyocytes and affect the expression, distribution, and phosphorylation state of cardiomyocyte Connexin 43. This is also one of the potential mechanisms concerning the direct myocardial toxicity of MDMA.

Practical Application

MDMA is a kind of amphetamine derivative, a class of synthetic non-catecholamine sympathomimetic drugs. It can selectively act on the central nervous system above the brainstem to stimulate the neurosynaptic precursors to release serotonin (5-HT) and the monoamine neurotransmitters dopamine (DA) and norepinephrine (NE). After taking it, people may experience elevated mood, euphoria, sexual impulse, and involuntary head shaking caused by sympathetic nerve excitement.

α-synuclein-lack expression rescues methamphetamine-induced mossy fiber degeneration in dorsal hippocampal CA3

Methamphetamine (METH) - induced cognitive impairments may be related to synaptic degeneration at mossy fiber terminals, critical for spatial memory formation in hippocampal circuits. We have previously found METH-induced neurodegeneration in the striatum by increasing the α-synuclein (α-SYN) level. However, whether and how the METH-induced mossy fiber degeneration is also blamed for the abnormal accumulation of α-SYN remains to be elucidated. Chronic METH exposure decreased mossy fiber density but upregulatedα-SYN and phosphorylated TAU (TAU-pSer396) in hippocampal CA3, associated with glial cell overactivation, axonal neuropathies, and memory impairment. Notably, the knockout of the α-SYN gene significantly alleviated the METH-induced mossy fiber degeneration and memory impairment. Meanwhile, the TAU-pSer396 accumulation and glial activation were ameliorated by α-SYN knockout. Our findings suggest an essential role of α-SYN in mediating METH-induced mossy fiber degeneration, providing promising therapeutic and prophylactic targets for METH-related neurodegenerative diseases.

The neuroprotective effect of LCZ696 on methamphetamine-induced cognitive impairment in mice

OBJECTIVE

Methamphetamine (METH) exposure commonly causes cognitive impairment. An angiotensin II receptor/neprilysin inhibitor (ARNI), LCZ696 has been demonstrated to inhibit inflammation, oxidative stress and apoptosis. The present study was designed to examine the effect of LCZ696 on METH-induced cognitive impairment and the underlying mechanism.

METHODS

Following daily treatment of either saline or METH (5 mg/kg) for 5 consecutive days, the cognitive function was tested using the Y-maze and the Novel Object Recognition (NOR) in Experiment 1. In Experiment 2, mice were initially treated with saline or LCZ696 (60 mg/kg) for 9 consecutive days, followed by LCZ696, METH or saline for 5 days. Cognitive testing was carried out as Experiment 1. In Experiment 3, SH-SY5Y cells were treated with either METH (2.5 Mm) or ddH2O for 12 h. The apoptosis and reactive oxygen species (ROS) level of SH-SY5Y were examined. In Experiment 4, SH-SY5Y cells were pretreated with either ddH2O or LCZ696 (70um) for 30 min, followed by ddH2O or METH treatment for 12 h. Nrf2 and HO-1 protein expression was examined in the ventral tegemental area (VTA) of all the animals and SH-SY5Y cells.

RESULTS

LCZ696 significantly improved METH-induced cognitive impairment, in conjunction with decreased apoptosis and ROS levels in VTA of METH-treated mice and SH-SY5Y cells. METH significantly decreased Nrf2 and HO-1 protein expression in VTA of mice and SH-SY5Y cells, which was reversed by LCZ696 treatment.

CONCLUSION

LCZ696 yields a neuroprotective effect against METH-induced cognitive dysfunction via the Nrf2/HO-1 signaling pathway.

Neuropharmacological Evidence Implicating Drug-Induced Glutamate Receptor Dysfunction in Affective and Cognitive Sequelae of Subchronic Methamphetamine Self-Administration in Mice

Methamphetamine (MA) is a highly addictive drug, and MA use disorder is often comorbid with anxiety and cognitive impairment. These comorbid conditions are theorized to reflect glutamate-related neurotoxicity within the frontal cortical regions. However, our prior studies of MA-sensitized mice indicate that subchronic, behaviorally non-contingent MA treatment is sufficient to dysregulate glutamate transmission in mouse brain. Here, we extend this prior work to a mouse model of high-dose oral MA self-administration (0.8, 1.6, or 3.2 g/L; 1 h sessions × 7 days) and show that while female C57BL/6J mice consumed more MA than males, MA-experienced mice of both sexes exhibited some signs of anxiety-like behavior in a behavioral test battery, although not all effects were concentration-dependent. No MA effects were detected for our measures of visually cued spatial navigation, spatial learning, or memory in the Morris water maze; however, females with a history of 3.2 g/L MA exhibited reversal-learning deficits in this task, and mice with a history of 1.6 g/L MA committed more working-memory incorrect errors and relied upon a non-spatial navigation strategy during the radial-arm maze testing. Relative to naïve controls, MA-experienced mice exhibited several changes in the expression of certain glutamate receptor-related proteins and their downstream effectors within the ventral and dorsal areas of the prefrontal cortex, the hippocampus, and the amygdala, many of which were sex-selective. Systemic pretreatment with the mGlu1-negative allosteric modulator JNJ 162596858 reversed the anxiety-like behavior expressed by MA-experienced mice in the marble-burying test, while systemic pretreatment with NMDA or the NMDA antagonist MK-801 bi-directionally affected the MA-induced reversal-learning deficit. Taken together, these data indicate that a relatively brief history of oral MA is sufficient to induce some signs of anxiety-like behavior and cognitive dysfunction during early withdrawal that reflect, at least in part, MA-induced changes in the corticolimbic expression of certain glutamate receptor subtypes of potential relevance to treating symptoms of MA use disorder.

Paternal methamphetamine exposure differentially affects first and second generations in mice

Amphetamine-type stimulants are abused worldwide, and methamphetamine (METH) accounts for a large majority of seized abused drug cases. Recently, the paternal origin of health and disease theory has been proposed as a concept wherein paternal factors influence descendants. Although METH abuse is more common among males, its effects on their descendants were not examined. Therefore, we investigated the effects of paternal METH exposure on F1 and F2 levels in a mouse model. Sires were administered METH for 21 days and mated with female mice to obtain F1 mice. Growth evaluations (number of births, survival rate, body weight, righting reflex, cliff avoidance tests, and wire-hanging maneuver) were performed on F1 mice. Upon reaching six weeks of age, the mice were subjected to spontaneous locomotion, elevated plus-maze, acute METH treatment, and passive avoidance tests. Additionally, RNA-seq was performed on the striatum of male mice. Male F1 mice were mated with female mice to obtain F2 mice. They were subjected to the same tests as the F1 mice. Paternal METH exposure resulted in delayed growth and decreased memory function in F1 mice, overweight in F2 mice, decreased METH sensitivity, and reduced anxiety-related behaviors in female F2 mice. Enrichment analysis revealed significant enrichment of terms related to behavior in F1 and protein folding in F2. These results indicated that the effects of paternal METH exposure vary across generations. The effects of paternal factors need to be examined not only in F1, but also in F2 and beyond.

Maternal inulin supplementation ameliorates prenatal methamphetamine exposure-induced hepatotoxicity and restores gut microbiota in mouse offspring

Prenatal exposure to methamphetamine (METH) is an issue of global concern due to its adverse effects on offspring, particularly its impact on liver health, an area still not fully understood. Inulin, a recognized prebiotic, is thought to potentially ameliorate these developmental disorders and toxic injuries in progeny. To investigate the effects of prenatal METH exposure on the liver and the role of gut microbiota, we established a murine model, the subjects of which were exposed to METH prenatally and subsequently treated with inulin. Our findings indicate that prenatal METH exposure causes liver damage in offspring, as evidenced by a decreased liver index, histopathological changes, diminished glycogen synthesis, hepatic dysfunction, and alterations in mRNA profiles. Furthermore, it impairs the antioxidant system and induces oxidative stress, possibly due to changes in cecal microbiota and dysregulation of bile acid homeostasis. However, maternal inulin supplementation appears to restore the gut microbiota in offspring and mitigate the hepatotoxic effects induced by prenatal METH exposure. Our study provides definitive evidence of METH's transgenerational hepatotoxicity and suggests that maternal inulin supplementation could be an effective preventive strategy.

The association between neuropsychiatric effects of substance use and occurrence of endoplasmic reticulum and unfolded protein response: A systematic review

INTRODUCTION

This systematic review aimed to assess the association between neuropsychiatric effects of substance use and occurrence of ER stress and unfolded protein response (UPR) through comprehensive electronic search of existing literature and review of their findings.

METHODS

A comprehensive electronic literature search was carried out on research articles published between 1950 to July 2023 through major databases, such as Scopus, Web of Science, Google Scholar, PubMed, PsycINFO, EMBASE, Medline and Cochrane Library.

RESULTS

A total of 21 research articles were selected for review, which were comprised of sixteen animal studies, four human studies and one study on postmortem human brain samples. The selected studies revealed that alcohol, methamphetamine, cocaine, opioid and kratom exposures contributed to neuropsychiatric effects: such as decline in learning and memory function, executive dysfunction, alcohol, methamphetamine, opioid, and kratom dependence. These effects were associated with activation and persistent of ER stress and UPR with elevation of BiP and CHOP expression and the direction of ER stress is progressing towards the PERK-eIF2α-ATF4-CHOP pathway and neuronal apoptosis and neurodegeneration at various regions of the brain. In addition, regular kratom use in humans also contributed to elevation of p-JNK expression, denoting progress of ER stress towards the IRE1-ASK1-JNK-p-JNK pathway which was linked to kratom use disorder. However, treatment with certain compounds or biological agents could reverse the activation of ER stress.

CONCLUSIONS

The neuropsychiatric effects of alcohol, methamphetamine, cocaine, opioid and kratom use may be associated with persistent ER stress and UPR.

Molecular mechanisms and treatment strategies for methamphetamine‑induced neurodegeneration, inflammation and neurotoxicity

Methamphetamine (METH) is a highly addictive psychostimulant known for its profound impact on the nervous system. Chronic METH use leads to neurotoxicity characterized by various molecular and structural alterations in the brain. This review article primarily aims to elucidate the mechanisms underlying METH‑induced neurotoxicity. METH's mechanism of action involves the inhibition of dopamine, serotonin, and norepinephrine reuptake, resulting in altered synaptic function. Prolonged METH exposure triggers oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, impaired axonal transport, autophagy, and programmed cell death, ultimately contributing to neurotoxicity. These neurotoxic effects manifest as increased neuronal firing rate, disruptions in intracellular ion balance (Ca2+ and Na+), energy production imbalances, and excessive reactive oxygen species production. The blood‑brain barrier is compromised, leading to structural, functional, and neurochemical alterations, particularly in the fronto‑striatal circuit. While our comprehensive review addresses these intricate molecular and structural changes induced by METH, we also examined the latest therapeutic strategies designed to mitigate neurotoxicity. Our investigation sheds light on the critical need to comprehend the complex pathways underlying METH‑induced neurotoxicity and develop effective treatment approaches.

Iron chelation prevents nigrostriatal neurodegeneration in a chronic methamphetamine mice model

Methamphetamine (METH) has been established to selectively target and impair dopaminergic neurons through multiple pathways. Ferroptosis is a unique form of non-apoptotic cell death driven by cellular iron accumulation-induced lipid peroxidation. Nonetheless, it remains unclear whether METH can induce ferroptosis. In the present study, we sought to assess alterations in iron levels after chronic METH exposure and reveal the modulatory role of iron on METH-induced pathologies. Importantly, we demonstrated that METH increased iron deposition in the nigrostriatal system, including the substantia nigra (SN) and caudate putamen (CPu). Moreover, decreases in GPx4 levels, increases in lipid peroxidation products, and pathological alterations were observed in the nigrostriatal system as a consequence of chronic METH exposure. The iron chelator deferiprone not only alleviated nigrostriatal iron deposition, dopaminergic cell death, and lipid peroxidation, but alsoattenuated the decreases in GPx4 induced by METH. These findings suggest an alleviation of ferroptosis in dopaminergic neurons. In addition, we found that the ferroptosis inhibitor liproxstatin-1 attenuated METH-induced dopaminergic degeneration in the nigrostriatal system. Our findings corroborated that METH might induce dopaminergic neurodegeneration through iron-dependent ferroptosis. Interestingly, reducing iron levels or inhibiting ferroptosis may alleviate METH-induced dopaminergic neurodegeneration.

Linalool attenuates hypothalamus proteome disturbance facilitated by methamphetamine induced neurotoxicity in rats

BACKGROUND

One of the most powerful stimulants of the central nervous system is methamphetamine (METH). Linalool has a neuroprotective effect against ischemia injury by reducing oxidative stress and apoptosis. The present study investigated whether linalool can reverse the hypothalamus neurotoxicity and proteome disturbance in METH-treated rats.

BRIEF METHOD

A total of 36 male albino rats were split into two equal groups (normal and METH-treated). Three equal subgroups of normal rats were created; Control, Linalool (25 mg/kg), and Linalool (50 mg/kg); Normal rats were given daily oral doses of 1 ml of distilled water, 25 mg/kg linalool, and 50 mg/kg of linalool, respectively. METH groups were divided into 3 equal subgroups; METH-treated rats, Linalool (25 mg/kg)+METH-treated, and Linalool (50 mg/kg)+METH-treated subgroups; METH-treated rats received daily and oral doses of 1 ml distilled water, 25 mg/kg linalool, and 50 mg/kg of linalool, respectively.

RESULTS

According to the data obtained, METH caused a decrease of the sucrose preference test, travel distance test, and center square entries test, superoxide dismutase, glutathione peroxidase, catalase, NADPH oxidase, interleukin-10 but a rise in the center square duration test, tail suspension test, and forced swimming test, malondialdehyde, conjugated dienes, oxidative index, serotonin, dopamine, norepinephrine, γ-aminobutyric acid, tumour necrosis factor-α, interleukin-1β, interleukin-6 levels. When compared to the control group, rats treated with METH had lower sodium/potassium ATPase activity and missing of prothrombin, fibrinogen, and ceruloplasmin protein bands in the hypothalamus. In METH-treated rats, daily and oral co-administration with linalool brought all these parameters back to values that were close to control.

SIGNIFICANCE

According to obtained data, linalool could protect the hypothalamus against METH-induced neurotoxicity and proteome disturbance probably by modifying oxidative stress, neurotransmitters, inflammation, sodium/potassium-ATPase activity, proteome disturbance, and tissue histology in METH-treated rats where higher dose of linalool was more efficient than lower dose.

Melatonin enhances the restoration of neurological impairments and cognitive deficits during drug withdrawal in methamphetamine-induced toxicity and endoplasmic reticulum stress in rats

Methamphetamine (METH) is a psychostimulant with a very high addiction rate. Prolonged use of METH has been observed as one of the root causes of neurotoxicity. Melatonin (Mel) has been found to have a significant role in METH-induced neurotoxicity. This study aimed to investigate the restorative effect of Mel on behavioral flexibility in METH-induced cognitive deficits. Male Sprague-Dawley rats were randomly assigned to be intraperitoneally injected with saline (control) or Meth at 5 mg/kg for 7 consecutive days. Then, METH injection was withdrawn and rats in each group were subcutaneously injected with saline or Mel at 10 mg/kg for 14 consecutive days. The stereotypic behavioral test and attentional set-shifting task (ASST) were used to evaluate neurological functions and cognitive flexibility, respectively. Rats developed abnormal features of stereotyped behaviors and deficits in cognitive flexibility after 7 days of METH administration. However, post-treatment with Mel for 14 days after METH withdrawal dramatically ameliorated the neurological and cognitive deficits in METH-treated rats. Blood biomarkers indicated METH-induced systemic low-grade inflammation. Moreover, METH-induced endoplasmic reticulum (ER) stress in the prefrontal cortex was diminished by melatonin supplementation. These findings might reveal the therapeutic potential of Mel in METH toxicity-induced neurological and cognitive deficits.

Effects of Multiple High-Dose Methamphetamine Administration on Enteric Dopaminergic Neurons and Intestinal Motility in the Rat Model

Several studies have identified the effects of methamphetamine (MA) on central dopaminergic neurons, but its effects on enteric dopaminergic neurons (EDNs) are unclear. The aim of this study was to investigate the effects of MA on EDNs and intestinal motility. Male Sprague-Dawley rats were randomly divided into MA group and saline group. The MA group received the multiple high-dose MA treatment paradigm, while the controls received the same saline treatment. After enteric motility was assessed, different intestinal segments (i.e., duodenum, jejunum, ileum, and colon) were taken for histopathological, molecular biological, and immunological analysis. The EDNs were assessed by measuring the expression of two dopaminergic neuronal markers, dopamine transporter (DAT) and tyrosine hydroxylase (TH), at the transcriptional and protein levels. We also used c-Fos protein, a marker of neural activity, to detect the activation of EDNs. MA resulted in a significant reduction in TH and DAT mRNA expression as well as in the number of EDNs in the duodenum and jejunum (p < 0.05). MA caused a dramatic increase in c-Fos expression of EDNs in the ileum (p < 0.001). The positional variability of MA effects on EDNs paralleled the positional variability of its effect on intestinal motility, as evidenced by the marked inhibitory effect of MA on small intestinal motility (p < 0.0001). This study found significant effects of MA on EDNs with locational variability, which might be relevant to locational variability in the potential effects of MA on intestinal functions, such as motility.

Consecutive treatments of methamphetamine promote the development of cardiac pathological symptoms in zebrafish

Chronic methamphetamine use, a widespread drug epidemic, has been associated with cardiac morphological and electrical remodeling, leading to the development of numerous cardiovascular diseases. While methamphetamine has been documented to induce arrhythmia, most results originate from clinical trials from users who experienced different durations of methamphetamine abuse, providing no documentation on the use of methamphetamine in standardized settings. Additionally, the underlying molecular mechanism on how methamphetamine affects the cardiovascular system remains elusive. A relationship was sought between cardiotoxicity and arrhythmia with associated methamphetamine abuse in zebrafish to identify and to understand the adverse cardiac symptoms associated with methamphetamine. Zebrafish were first treated with methamphetamine 3 times a week over a 2-week duration. Immediately after treatment, zebrafish underwent electrocardiogram (ECG) measurement using an in-house developed acquisition system for electrophysiological analysis. Subsequent analyses of cAMP expression and Ca2+ regulation in zebrafish cardiomyocytes were conducted. cAMP is vital to development of myocardial fibrosis and arrhythmia, prominent symptoms in the development of cardiovascular diseases. Ca2+ dysregulation is also a factor in inducing arrhythmias. During the first week of treatment, zebrafish that were administered with methamphetamine displayed a decrease in heart rate, which persisted throughout the second week and remained significantly lower than the heart rate of untreated fish. Results also indicate an increased heart rate variability during the early stage of treatment followed by a decrease in the late stage for methamphetamine-treated fish over the duration of the experiment, suggesting a biphasic response to methamphetamine exposure. Methamphetamine-treated fish also exhibited reduced QTc intervals throughout the experiment. Results from the cAMP and Ca2+ assays demonstrate that cAMP was upregulated and Ca2+ was dysregulated in response to methamphetamine treatment. Collagenic assays indicated significant fibrotic response to methamphetamine treatment. These results provide potential insight into the role of methamphetamine in the development of fibrosis and arrhythmia due to downstream effectors of cAMP.

Emergency department management of methamphetamine toxicity

Management of patients who are acutely intoxicated with methamphetamine (a member of the substituted amphetamine class of drugs) can be resource-intensive for most emergency departments. Clinical presentations of the methamphetamine sympathomimetic toxidrome range from mild agitation to rhabdomyolysis, acute kidney injury, seizures, and intracranial hemorrhage. High-quality evidence on how to best manage these patients is lacking, and most research focuses on symptomatic interventions to control patients' agitation and hemodynamics. This review analyzes the best available evidence on the diagnosis and management of emergency department patients with substituted amphetamine toxicity and offers best-practice recommendations on treatment and disposition.

Macrophage microvesicle-derived circ_YTHDF2 in methamphetamine-induced chronic lung injury

Long-term abuse of methamphetamine (MA) can cause lung toxicity. Intercellular communication between macrophages and alveolar epithelial cells (AECs) is critical for maintaining lung homeostasis. Microvesicles (MVs) are an important medium of intercellular communication. However, the mechanism of macrophage MVs (MMVs) in MA-induced chronic lung injury remains unclear. This study aimed to investigate if MA can augment the activity of MMVs and if circ_YTHDF2 is a key factor in MMV-mediated macrophage-AEC communication, and to explore the mechanism of MMV-derived circ_YTHDF2 in MA-induced chronic lung injury. MA elevated peak velocity of the pulmonary artery and pulmonary artery accelerate time, reduced the number of alveolar sacs, thickened the alveolar septum, and accelerated the release of MMVs and the uptake of MMVs by AECs. Circ_YTHDF2 was downregulated in lung and MMVs induced by MA. The immune factors in MMVs were increased by si-circ_YTHDF. Circ_YTHDF2 knockdown in MMVs induced inflammation and remodelling in the internalised AECs by MMVs, which was reversed by circ_YTHDF2 overexpression in MMVs. Circ_YTHDF2 bound specifically to and sponged miRNA-145-5p. Runt-related transcription factor 3 (RUNX3) was identified as potential target of miR-145-5p. RUNX3 targeted zinc finger E-box-binding homeobox 1 (ZEB1)-related inflammation and EMT of AECs. In vivo, circ_YTHDF2 overexpression-MMVs attenuated MA-induced lung inflammation and remodelling by the circ_YTHDF2-miRNA-145-5p-RUNX3 axis. Therefore, MA abuse can induce pulmonary dysfunction and alveolus injury. The immunoactivity of MMVs is regulated by circ_YTHDF2. Circ_YTHDF2 in MMVs is the key to communication between macrophages and AECs. Circ_YTHDF2 sponges miR-145-5p targeting RUNX3 to participate in ZEB1-related inflammation and remodelling of AECs. MMV-derived circ_YTHDF2 would be an important therapeutic target for MA-induced chronic lung injury. KEY POINTS: Methamphetamine (MA) abuse induces pulmonary dysfunction and alveoli injury. The immunoactivity of macrophage microvesicles (MMVs) is regulated by circ_YTHDF2. Circ_YTHDF2 in MMVs is the key to MMV-mediated intercellular communication between macrophages and alveolar epithelial cells. Circ_YTHDF2 sponges miR-145-5p targeting runt-related transcription factor 3 (RUNX3) to participate in zinc finger E-box-binding homeobox 1 (ZEB1)-related inflammation and remodelling. MMV-derived circ_YTHDF2 would be an important therapeutic target for MA-induced chronic lung injury.

Proteomic Analysis Reveals the Neurotoxic Effects of Chronic Methamphetamine Self-Administration-Induced Cognitive Impairments and the Role of Melatonin-Enhanced Restorative Process during Methamphetamine Withdrawal

Cognitive flexibility is a crucial ability in humans that can be affected by chronic methamphetamine (METH) addiction. The present study aimed to elucidate the mechanisms underlying cognitive impairment in mice chronically administered METH via an oral self-administration method. Further, the effect of melatonin treatment on recovery of METH-induced cognitive impairment was also investigated. Cognitive performance of the mice was assessed using an attentional set shift task (ASST), and possible underlying neurotoxic mechanisms were investigated by proteomic and western blot analysis of the prefrontal cortex (PFC). The results showed that mice-administered METH for 21 consecutive days exhibited poor cognitive performance compared to controls. Cognitive deficit in mice partly recovered after METH withdrawal. In addition, mice treated with melatonin during METH withdrawal showed a higher cognitive recovery than vehicle-treated METH withdrawal mice. Proteomic and western blot analysis revealed that METH self-administration increased neurotoxic markers, including disruption to the regulation of mitochondrial function, mitophagy, and decreased synaptic plasticity. Treatment with melatonin during withdrawal restored METH-induced mitochondria and synaptic impairments. These findings suggest that METH-induced neurotoxicity partly depends on mitochondrial dysfunction leading to autophagy-dependent cell death and that the recovery of neurological impairments may be enhanced by melatonin treatment during the withdrawal period.

NRF2 Antagonizes HIV-1 Tat and Methamphetamine-Induced BV2 Cell Ferroptosis by Regulating SLC7A11

Methamphetamine (METH) and HIV-1 lead to oxidative stress and their combined effect increases the risk of HIV-associated neurocognitive disorder (HAND), which may be related to the synergistic ferroptotic impairment in microglia. Ferroptosis is a redox imbalance cell damage associated with iron overload that is linked to the pathogenic processes of METH and HIV-1. NRF2 is an antioxidant transcription factor that plays a protective role in METH and HIV-1-induced neurotoxicity, but its mechanism has not been fully elucidated. To explore the role of ferroptosis in METH abuse and HIV-1 infection and the potential role of NRF2 in this process, we conducted METH and HIV-1 Tat exposure models using the BV2 microglia cells. We found that METH and HIV-1 Tat reduced the expression of ferroptotic protein GPX4 and the cell viability and enhanced the expression of P53 and the level of ferrous iron, while the above indices were significantly improved with pretreatment of ferrostatin-1. In addition, NRF2 knockdown accelerated METH and HIV-1 Tat-induced BV2 cell ferroptosis accompanied by decreased expression of SLC7A11. On the contrary, NRF2 stimulation significantly increased the expression of SLC7A11 and attenuated ferroptosis in cells. In summary, our study indicates that METH and HIV-1 Tat synergistically cause BV2 cell ferroptosis, while NRF2 antagonizes BV2 cell ferroptotic damage induced by METH and HIV-1 Tat through regulation of SLC7A11. Overall, this study provides potential therapeutic strategies for the treatment of neurotoxicity caused by METH and HIV-1 Tat, providing a theoretical basis and new targets for the treatment of HIV-infected drug abusers.

Calcitriol protects against reductions in striatal serotonin in rats treated with neurotoxic doses of methamphetamine

The present experiments were designed to examine the ability of calcitriol to protect against methamphetamine (METH)-induced reductions in striatal serotonin (5-HT) release and content. Male Fischer-344 rats were administered vehicle or calcitriol (0.3, 1.0, or 3.0 μg/kg, s.c.) once a day for 8 consecutive days. After the seventh day of treatment the animals were given METH (5 mg/kg, s.c.) or saline 4 times in 1 day at 2 h intervals. Seven days after the METH or saline treatments in vivo microdialysis experiments were conducted to measure potassium and d-amphetamine evoked overflow of 5-HT from the striatum. In animals treated with vehicle and METH there were significant reductions in both potassium and d-amphetamine evoked overflow of 5-HT. The 1.0 and 3.0 μg/kg/day doses of calcitriol provided significant protection against the 5-HT depleting effects of METH. A similar pattern of neuroprotection was found for post-mortem tissue levels of 5-HT. The calcitriol treatments did not prevent hyperthermia during the multiple injections of METH, indicating that the protective effects of calcitriol are not due to prevention of METH-induced increases in body temperature. These results suggest that calcitriol can provide significant protection against the 5-HT depleting effects of neurotoxic doses of METH.

p-Nrf2/HO-1 Pathway Involved in Methamphetamine-induced Executive Dysfunction through Endoplasmic Reticulum Stress and Apoptosis in the Dorsal Striatum

Methamphetamine (METH) abuse is known to cause executive dysfunction. However, the molecular mechanism underlying METH induced executive dysfunction remains unclear. Go/NoGo experiment was performed in mice to evaluate METH-induced executive dysfunction. Immunoblot analysis of Nuclear factor-E2-related factor 2 (Nrf2), phosphorylated Nrf2 (p-Nrf2), heme-oxygenase-1 (HO-1), Glucose Regulated Protein 78(GRP78), C/EBP homologous protein (CHOP), Bcl-2, Bax and Caspase3 was performed to evaluate the levels of oxidative stress, endoplasmic reticulum (ER) stress and apoptosis in the dorsal striatum (Dstr). Malondialdehyde (MDA) levels and glutathione peroxidase (GSH-Px) activity was conducted to evaluate the level of oxidative stress. TUNEL staining was conducted to detect apoptotic neurons. The animal Go/NoGo testing confirmed that METH abuse impaired the inhibitory control ability of executive function. Meanwhile, METH down-regulated the expression of p-Nrf2, HO-1 and GSH-Px and activated ER stress and apoptosis in the Dstr. Microinjection of Tert-butylhydroxyquinone (TBHQ), an Nrf2 agonist, into the Dstr increased the expression of p-Nrf2, HO-1, and GSH-Px, ameliorated ER stress, apoptosis and executive dysfunction caused by METH. Our results indicated that the p-Nrf2/HO-1 pathway was potentially involved in mediating methamphetamine-induced executive dysfunction by inducing endoplasmic reticulum stress and apoptosis in the dorsal striatum.

Methamphetamine-induced region-specific transcriptomic and epigenetic changes in the brain of male rats

Psychostimulant methamphetamine (METH) is neurotoxic to the brain and, therefore, its misuse leads to neurological and psychiatric disorders. The gene regulatory network (GRN) response to neurotoxic METH binge remains unclear in most brain regions. Here we examined the effects of binge METH on the GRN in the nucleus accumbens, dentate gyrus, Ammon's horn, and subventricular zone in male rats. At 24 h after METH, ~16% of genes displayed altered expression and over a quarter of previously open chromatin regions - parts of the genome where genes are typically active - showed shifts in their accessibility. Intriguingly, most changes were unique to each area studied, and independent regulation between transcriptome and chromatin accessibility was observed. Unexpectedly, METH differentially impacted gene activity and chromatin accessibility within the dentate gyrus and Ammon's horn. Around 70% of the affected chromatin-accessible regions in the rat brain have conserved DNA sequences in the human genome. These regions frequently act as enhancers, ramping up the activity of nearby genes, and contain mutations linked to various neurological conditions. By sketching out the gene regulatory networks associated with binge METH in specific brain regions, our study offers fresh insights into how METH can trigger profound, region-specific molecular shifts.

Nrf2 protects against methamphetamine-induced nephrotoxicity by mitigating oxidative stress and autophagy in mice

Methamphetamine (MA) is a widely abused drug that can cause kidney damage. However, the molecular mechanism remains unclear. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates resistance to oxidative and proteotoxic stress. In this study, we investigated the role of Nrf2 in MA-induced renal injury in mice. Nrf2 was pharmacologically activated and genetically knocked-out in mice. The animal model of MA-induced nephrotoxicity was established by injecting MA (2 mg/kg) intraperitoneally twice a day for 5 days. Histopathological alterations were shown in the MA-exposed kidneys. MA significantly increased renal function biomarkers and kidney injury molecule-1 (KIM-1) levels. MA decreased superoxide dismutase activity and increased malondialdehyde levels. Autophagy-related factors (LC3 and Beclin 1) were elevated in MA-treated mice. Furthermore, Nrf2 increased in the MA-exposed kidneys. Activation of Nrf2 may attenuate histopathological changes in the kidneys of MA-treated mice. Pre-administration of Nrf2 agonist significantly decreased KIM-1 expression, oxidative stress, and autophagy in the kidneys after MA toxicity. In contrast, Nrf2 knockout mice treated with MA lost renal tubular morphology. Nrf2 deficiency increased KIM-1 expression, oxidative stress, and autophagy in the MA-exposed kidneys. Our results demonstrate that Nrf2 may protect against MA-induced nephrotoxicity by mitigating oxidative stress and autophagy.

Gut Microbiota Taxon-Dependent Transformation of Microglial M1/M2 Phenotypes Underlying Mechanisms of Spatial Learning and Memory Impairment after Chronic Methamphetamine Exposure

Methamphetamine (METH) exposure may lead to cognitive impairment. Currently, evidence suggests that METH exposure alters the configuration of the gut microbiota. However, the role and mechanism of the gut microbiota in cognitive impairment after METH exposure are still largely unknown. Here, we investigated the impact of the gut microbiota on the phenotype status of microglia (microglial phenotypes M1 and microglial M2) and their secreting factors, the subsequent hippocampal neural processes, and the resulting influence on spatial learning and memory of chronically METH-exposed mice. We determined that gut microbiota perturbation triggered the transformation of microglial M2 to M1 and a subsequent change of pro-brain-derived neurotrophic factor (proBDNF)-p75NTR-mature BDNF (mBDNF)-TrkB signaling, which caused reduction of hippocampal neurogenesis and synaptic plasticity-related proteins (SYN, PSD95, and MAP2) and, consequently, deteriorated spatial learning and memory. More specifically, we found that Clostridia, Bacteroides, Lactobacillus, and Muribaculaceae might dramatically affect the homeostasis of microglial M1/M2 phenotypes and eventually contribute to spatial learning and memory decline after chronic METH exposure. Finally, we found that fecal microbial transplantation could protect against spatial learning and memory decline by restoring the microglial M1/M2 phenotype status and the subsequent proBDNF-p75NTR/mBDNF-TrkB signaling in the hippocampi of chronically METH-exposed mice. IMPORTANCE Our study indicated that the gut microbiota contributes to spatial learning and memory dysfunction after chronic METH exposure, in which microglial phenotype status plays an intermediary role. The elucidated "specific microbiota taxa-microglial M1/M2 phenotypes-spatial learning and memory impairment" pathway would provide a novel mechanism and elucidate potential gut microbiota taxon targets for the no-drug treatment of cognitive deterioration after chronic METH exposure.

Obeticholic acid protects against methamphetamine-induced anxiety-like behavior by ameliorating microbiota-mediated intestinal barrier impairment

Methamphetamine (Meth) abuse can cause severe anxiety disorder and interfere with gut homeostasis. Obeticholic acid (OCA) has emerged as a protective agent against diet-related anxiety that improves gut homeostasis. The potential for OCA to ameliorate Meth-induced anxiety, and the microbial mechanisms involved, remain obscure. Here, C57/BL6 mice were intraperitoneally injected with Meth (15 mg/kg) to induce anxiety-like behavior. 16 S rRNA sequence analysis and fecal microbiome transplantation (FMT) were used to profile the gut microbiome and evaluate its effects, respectively. Orally administered OCA was investigated for protection against Meth-induced anxiety. Results indicated that Meth mediated anxiety-like behavior, aroused hippocampal neuroinflammation through activation of the TLR4/MyD88/NF-κB pathway, weakened intestinal barrier and disturbed the gut microbiome. Specifically, abundance of anxiety-related Rikenella was increased. FMT from Meth-administrated mice also weakened intestinal barrier and elevated serum LPS, inducing hippocampal neuroinflammation and anxiety-like behavior in recipient mice. Finally, OCA pretreatment ameliorated Meth-induced impairment of gut homeostasis by reshaping the microbial composition and improving the intestinal barrier. Meth-induced anxiety-like behavior and hippocampal neuroinflammation were also ameliorated by OCA pretreatment. These preliminary findings reveal the crucial role of gut microbiota in Meth-induced anxiety-like behavior and neuroinflammation, highlighting OCA as a potential candidate for the prevention of Meth-induced anxiety.

Normal Transaminases in Methamphetamine- and Heroin-Associated Hyperammonemic Encephalopathy

Detecting undisclosed methamphetamine and heroin abuse is a challenge for life underwriters and medical directors. A common clinical assumption is that if substance abusers experience liver damage, it will be indicated by elevated serum transaminases. The following case suggests that assumption may not be true for heavy substance abusers who consume no or minimal alcohol. This report describes a 44-year-old male with long-term use of inhaled combined methamphetamine and heroin ("speedballs") and minimal alcohol use, whose transaminases remained normal while episodes of acute liver failure and transient hepatic encephalopathy from hyperammonemia were observed. In this case, a fatal motor vehicle accident occurred following the sudden onset of hepatic encephalopathy hours after consuming a "speedball." Normal transaminases may not be proof of a normal healthy liver among methamphetamine and heroin abusers.

Nrf2 attenuates methamphetamine-induced myocardial injury by regulating oxidative stress and apoptosis in mice

OBJECTIVES

Methamphetamine (MA) abuse is a serious social problem worldwide. Cardiovascular complications were the second leading cause of death among MA abusers. We aimed to clarify the effects of MA on myocardial injury, oxidative stress, and apoptosis in myocardial cells and to explore the potential mechanism of nuclear factor-erythroid factor 2-related factor 2 (Nrf2) in MA-induced oxidative stress and apoptosis.

METHODS

An acute cardiac toxicity model of MA was established by intraperitoneal injection of MA (2 mg/kg) for 5 days. Nrf2 activation (by sulforaphane (SFN) 1 h before MA injection) and Nrf2 gene knockout were performed to explore the regulatory effects of Nrf2 on cardiac toxicity.

RESULTS

The protein expressions of Nrf2 (p < .001) and heme oxygenase-1 (HO-1) were increased (p < .01), suggesting that MA activated the Nrf2/HO-1 pathway. In the MA group, cardiac injury score (p < .001) and cardiac troponin I (cTnI) protein expression increased (p < .01). Malondialdehyde (MDA) content increased (p < .001), superoxide dismutase (SOD) activity decreased (p < .05). Protein expressions of Caspase-3 (p < .001) and Bax (p < .001) increased, and Bcl-2 decreased (p < .001) as well. These changes were reversed by activation of Nrf2 but became more pronounced after Nrf2 knockout, suggested that the activation and knockout of Nrf2 attenuated and aggravated MA-induced myocardial injury, oxidative stress and apoptosis in myocardial cells, respectively.

CONCLUSIONS

MA administration induced myocardial injury, oxidative stress, and apoptosis in mice. Nrf2 attenuated MA-induced myocardial injury by regulating oxidative stress and apoptosis, thus playing a protective role.

Mitochondrial dysfunction and autophagy activation are associated with cardiomyopathy developed by extended methamphetamine self-administration in rats

The recent rise in illicit use of methamphetamine (METH), a highly addictive psychostimulant, is a huge health care burden due to its central and peripheral toxic effects. Mounting clinical studies have noted that METH use in humans is associated with the development of cardiomyopathy; however, preclinical studies and animal models to dissect detailed molecular mechanisms of METH-associated cardiomyopathy development are scarce. The present study utilized a unique very long-access binge and crash procedure of METH self-administration to characterize the sequelae of pathological alterations that occur with METH-associated cardiomyopathy. Rats were allowed to intravenously self-administer METH for 96 h continuous weekly sessions over 8 weeks. Cardiac function, histochemistry, ultrastructure, and biochemical experiments were performed 24 h after the cessation of drug administration. Voluntary METH self-administration induced pathological cardiac remodeling as indicated by cardiomyocyte hypertrophy, myocyte disarray, interstitial and perivascular fibrosis accompanied by compromised cardiac systolic function. Ultrastructural examination and native gel electrophoresis revealed altered mitochondrial morphology and reduced mitochondrial oxidative phosphorylation (OXPHOS) supercomplexes (SCs) stability and assembly in METH exposed hearts. Redox-sensitive assays revealed significantly attenuated mitochondrial respiratory complex activities with a compensatory increase in pyruvate dehydrogenase (PDH) activity reminiscent of metabolic remodeling. Increased autophagy flux and increased mitochondrial antioxidant protein level was observed in METH exposed heart. Treatment with mitoTEMPO reduced the autophagy level indicating the involvement of mitochondrial dysfunction in the adaptive activation of autophagy in METH exposed hearts. Altogether, we have reported a novel METH-associated cardiomyopathy model using voluntary drug seeking behavior. Our studies indicated that METH self-administration profoundly affects mitochondrial ultrastructure, OXPHOS SCs assembly and redox activity accompanied by increased PDH activity that may underlie observed cardiac dysfunction.

Methamphetamine-associated pulmonary arterial hypertension

PURPOSE OF REVIEW

Methamphetamine use is increasing in popularity globally, and chronic users suffer from various drug toxicities, including the development of pulmonary arterial hypertension. Although it was previously thought to be a possible cause of pulmonary arterial hypertension, as of the sixth World Symposium on Pulmonary Hypertension, methamphetamine use is now recognized as a definite cause of pulmonary arterial hypertension. This review will discuss the history of methamphetamine use, the link between methamphetamine use and pulmonary arterial hypertension, and the clinical characteristics of patients with pulmonary hypertension from methamphetamine use.

RECENT FINDINGS

The mechanism by which methamphetamine abuse leads to pulmonary hypertension is unclear. However, recent studies have suggested that reduced expression of carboxylesterase 1 may be implicated due to maladaptation to the environmental injury of methamphetamine abuse. Based on the report of two recent cohort studies, patients with methamphetamine-associated pulmonary arterial hypertension have a worse functional class, less favorable hemodynamics, impaired health-related quality of life, increased health-care utilization, and attenuated survival, as compared to those with idiopathic pulmonary arterial hypertension.

SUMMARY

Future studies are needed to better understand the mechanism by which methamphetamine use leads to pulmonary arterial hypertension. Methamphetamine-associated pulmonary arterial hypertension likely represents a more advanced disease state than idiopathic pulmonary arterial hypertension, however, it is treated less aggressively in clinical practice.

Repeated methamphetamine administration produces cognitive deficits through augmentation of GABAergic synaptic transmission in the prefrontal cortex

Methamphetamine (METH) abuse is associated with the emergence of cognitive deficits and hypofrontality, a pathophysiological marker of many neuropsychiatric disorders that is produced by altered balance of local excitatory and inhibitory synaptic transmission. However, there is a dearth of information regarding the cellular and synaptic mechanisms underlying METH-induced cognitive deficits and associated hypofrontal states. Using PV-Cre transgenic rats that went through a METH sensitization regime or saline (SAL) followed by 7-10 days of home cage abstinence combined with cognitive tests, chemogenetic experiments, and whole-cell patch recordings on the prelimbic prefrontal cortex (PFC), we investigated the cellular and synaptic mechanisms underlying METH-induce hypofrontality. We report here that repeated METH administration in rats produces deficits in working memory and increases in inhibitory synaptic transmission onto pyramidal neurons in the PFC. The increased PFC inhibition is detected by an increase in spontaneous and evoked inhibitory postsynaptic synaptic currents (IPSCs), an increase in GABAergic presynaptic function, and a shift in the excitatory-inhibitory balance onto PFC deep-layer pyramidal neurons. We find that pharmacological blockade of D1 dopamine receptor function reduces the METH-induced augmentation of IPSCs, suggesting a critical role for D1 dopamine signaling in METH-induced hypofrontality. In addition, repeated METH administration increases the intrinsic excitability of parvalbumin-positive fast spiking interneurons (PV + FSIs), a key local interneuron population in PFC that contributes to the control of inhibitory tone. Using a cell type-specific chemogenetic approach, we show that increasing PV + FSIs activity in the PFC is necessary and sufficient to cause deficits in temporal order memory similar to those induced by METH. Conversely, reducing PV + FSIs activity in the PFC of METH-exposed rats rescues METH-induced temporal order memory deficits. Together, our findings reveal that repeated METH exposure increases PFC inhibitory tone through a D1 dopamine signaling-dependent potentiation of inhibitory synaptic transmission, and that reduction of PV + FSIs activity can rescue METH-induced cognitive deficits, suggesting a potential therapeutic approach to treating cognitive symptoms in patients suffering from METH use disorder.

Bacopa Protects against Neurotoxicity Induced by MPP+ and Methamphetamine

The neurotoxins methamphetamine (METH) and 1-methyl-4-phenylpyridinium (MPP⁺) damage catecholamine neurons. Although sharing the same mechanism to enter within these neurons, METH neurotoxicity mostly depends on oxidative species, while MPP⁺ toxicity depends on the inhibition of mitochondrial activity. This explains why only a few compounds protect against both neurotoxins. Identifying a final common pathway that is shared by these neurotoxins is key to prompting novel remedies for spontaneous neurodegeneration. In the present study we assessed whether natural extracts from Bacopa monnieri (BM) may provide a dual protection against METH- and MPP⁺-induced cell damage as measured by light and electron microscopy. The protection induced by BM against catecholamine cell death and degeneration was dose-dependently related to the suppression of reactive oxygen species (ROS) formation and mitochondrial alterations. These were measured by light and electron microscopy with MitoTracker Red and Green as well as by the ultrastructural morphometry of specific mitochondrial structures. In fact, BM suppresses the damage of mitochondrial crests and matrix dilution and increases the amount of healthy and total mitochondria. The present data provide evidence for a natural compound, which protects catecholamine cells independently by the type of experimental toxicity. This may be useful to counteract spontaneous degenerations of catecholamine cells.

New insight into methamphetamine-associated heart failure revealed by transcriptomic analyses: Circadian rhythm disorder

Methamphetamine (METH) abuse is a significant public health concern globally. Cardiac toxicity is one of the important characteristics of METH, in addition to its effects on the nervous system. However, to date, research on the cardiotoxic injury induced by METH consumption has been insufficient. To systematically analyze the potential molecular mechanism of cardiac toxicity in METH-associated heart failure (HF), a rat model was constructed with a dose of 10 mg/kg of METH consumption. Cardiac function was evaluated by echocardiography, and HE staining was used to clarify the myocardial histopathological changes. Integrated analyses, including mRNA, miRNA and lncRNA, was performed to analyze the RNA expression profile and the potential molecular mechanisms involved in METH-associated HF. The results showed that METH caused decreased myocardial contractility, with a decreased percent ejection fraction (%EF). Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses of the RNAs with expression changes revealed abnormal circadian rhythm regulation in the METH groups, with circadian rhythm-related genes and their downstream effectors expressed differentially, especially the aryl hydrocarbon receptor nuclear translocator-like (Arntl). Competing endogenous RNA (ceRNA) networks associated with circadian rhythm, including Arntl, was also observed. Therefore, this study revealed that long-term METH consumption was associated with the HF in a rat model by decreasing the %EF, and that the abnormal circadian rhythm could provide new directions for investigating the METH-associated HF, and that the differentially expressed genes in this model could provide candidate genes for the identification and assessment of cardiac toxicity in METH-associated HF, which is fundamental for further understanding of the disease.

Gut microbiota mediates methamphetamine-induced hepatic inflammation via the impairment of bile acid homeostasis

Methamphetamine (Meth), an addictive psychostimulant of abuse worldwide, has been a common cause of acute toxic hepatitis in adults. Gut microbiota has emerged as a modulator of host immunity via metabolic pathways. However, the microbial mechanism of Meth-induced hepatic inflammation and effective therapeutic strategies remain unknown. Here, mice were intraperitoneally (i.p.) injected with Meth to induce hepatotoxicity. Cecal microbiome and bile acids (BAs) composition were analyzed after Meth administration. Fecal microbiota transplantation (FMT) technology was utilized to investigate the role of microbiota. Additionally, the protective effects of obeticholic acid (OCA), an agonist of farnesoid X receptor (FXR), were evaluated. Results indicated that Meth administration induced hepatic cholestasis, dysfunction and aroused hepatic inflammation by stimulating the TLR4/MyD88/NF-κB pathway in mice. Meanwhile, Meth disturbed the cecal microbiome and impaired the homeostasis of BAs. Interestingly, FMT from Meth administered mice resulted in serum and hepatic BA accumulation and transferred similar phenotypic changes into the healthy recipient mice. Finally, OCA normalized Meth-induced BA accumulation in both serum and the liver, and effectively protected against Meth-induced hepatic dysfunction and inflammation by suppressing the TLR4/MyD88/NF-κB pathway. This study established the importance of microbial mechanism and its inhibition as a potential therapeutic target to treat Meth-related hepatotoxicity.

Dopamine D1 receptors mediate methamphetamine-induced dopaminergic damage: involvement of autophagy regulation via the AMPK/FOXO3A pathway

RATIONALE

Clinical studies have revealed that methamphetamine abuse increases risk for developing Parkinson's diseases. It is thus important to elucidate the mechanisms by which methamphetamine damages dopaminergic neurons.

OBJECTIVES

The present study was designed to elucidate the role of the dopamine D1 receptor in methamphetamine-mediated dopaminergic neuronal damage and its underlying mechanisms.

METHODS

Mice were treated for 4 days with vehicle, methamphetamine, or the D1 agonist SKF38393 and then assessed for locomotion and performance in the pole and rotarod tests. Cellular indices of autophagy, LC3, P62, and Beclin-1, tyrosine hydroxylase, and the AMPK/FOXO3A pathway were analyzed in striatal tissue from treated mice, in PC12 cells, and in D1 receptor mutant mice.

RESULTS

Repeated treatment with a relatively high dose of methamphetamine for 4 days induced both loss of dopaminergic neurons and activation of autophagy in the striatum as evidenced by increased expression of LC3 and P62. However, such treatment did not induce either loss of dopaminergic neurons or activation of autophagy in D1 receptor knockout mice. D1 receptor-mediated activation of autophagy was also confirmed in vitro using dopaminergic neuronal PC12 cells. Further studies demonstrated that the AMPK/FOXO3A signaling pathway is responsible for D1 receptor-mediated activation of autophagy.

CONCLUSIONS

The present data indicate a novel mechanism for methamphetamine-induced dopaminergic neuronal damage and reveal an important role for D1 receptors in the neurotoxicity of this drug.

Prenatal methamphetamine exposure causes dysfunction in glucose metabolism and low birthweight

Methamphetamine (METH) is a psychostimulant drug that induces addiction. Previous epidemiological studies have demonstrated that maternal METH abuse during pregnancy causes low birthweight (LBW) in the offspring. As a source of essential nutrients, in particular glucose, the placenta plays a key role in fetal development. LBW leads to health problems such as obesity, diabetes, and neurodevelopmental disorders (NDDs). However, the detailed mechanism underlying offspring's LBW and health hazards caused by METH are not fully understood. Therefore, we investigated the effects of prenatal METH exposure on LBW and fetal-placental relationship by focusing on metabolism. We found dysfunction of insulin production in the pancreas of fetuses exposed to METH. We also found a reduction of the glycogen cells (GCs) storing glycogens in the junctional zone of placenta, all of which suggest abnormal glucose metabolism affects the fetal development. These results suggest that dysfunction in fetal glucose metabolism may cause LBW and future health hazards. Our findings provide novel insights into the cause of LBW via the fetal-placental crosstalk.

Dopamine and Methamphetamine Differentially Affect Electron Transport Chain Complexes and Parkin in Rat Striatum: New Insight into Methamphetamine Neurotoxicity

Methamphetamine (METH) is a highly abused psychostimulant that is neurotoxic to dopaminergic (DAergic) nerve terminals in the striatum and increases the risk of developing Parkinson’s disease (PD). In vivo, METH-mediated DA release, followed by DA-mediated oxidative stress and mitochondrial dysfunction in pre- and postsynaptic neurons, mediates METH neurotoxicity. METH-triggered oxidative stress damages parkin, a neuroprotective protein involved in PD etiology via its involvement in the maintenance of mitochondria. It is not known whether METH itself contributes to mitochondrial dysfunction and whether parkin regulates complex I, an enzymatic complex downregulated in PD. To determine this, we separately assessed the effects of METH or DA alone on electron transport chain (ETC) complexes and the protein parkin in isolated striatal mitochondria. We show that METH decreases the levels of selected complex I, II, and III subunits (NDUFS3, SDHA, and UQCRC2, respectively), whereas DA decreases the levels only of the NDUFS3 subunit in our preparations. We also show that the selected subunits are not decreased in synaptosomal mitochondria under similar experimental conditions. Finally, we found that parkin overexpression does not influence the levels of the NDUFS3 subunit in rat striatum. The presented results indicate that METH itself is a factor promoting dysfunction of striatal mitochondria; therefore, it is a potential drug target against METH neurotoxicity. The observed decreases in ETC complex subunits suggest that DA and METH decrease activities of the ETC complexes via oxidative damage to their subunits and that synaptosomal mitochondria may be somewhat “resistant” to DA- and METH-induced disruption in mitochondrial ETC complexes than perikaryal mitochondria. The results also suggest that parkin does not regulate NDUFS3 turnover in rat striatum.

Research Progress on the Omics of Methamphetamine Toxic Damage and Addiction

The mechanism of methamphetamine toxicity and addiction is the key research direction of forensic toxicology, and the development of omics technology provides a new platform for further study of this direction. METH toxic damage and addiction are reflected differently in genes, ribonucleic acid (RNA) transcription, protein and metabolism. This article summarizes the achievements and shortcomings of multi-omics technologies such as genome, transcriptome, metabolome and proteome in the study of METH damage and addiction, and discusses the strategies and advantages of multi-omics combined analysis in the study of METH toxic damage and addiction mechanism, in order to provide more useful reference information for forensic toxicology of METH.

In Vitro and In Vivo Sequestration of Methamphetamine by a Sulfated Acyclic CB[n]-Type Receptor

We report the synthesis of two new acyclic sulfated acyclic CB[n]-type receptors (TriM0 and Me4 TetM0) and investigations of their binding properties toward a panel of drugs of abuse (1-13) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry. TetM0 is the most potent receptor with Ka ≥106  M-1 toward methamphetamine, fentanyl, MDMA and mephedrone. TetM0 is not cytotoxic toward HepG2 and HEK 293 cells below 100 μM according to MTS metabolic and adenylate kinase release assays and is well tolerated in vivo when dosed at 46 mg kg-1 . TetM0 does not inhibit the hERG ion channel and is not mutagenic based on the Ames fluctuation test. Finally, in vivo efficacy studies show that the hyperlocomotion of mice treated with methamphetamine can be greatly reduced by treatment with TetM0 up to 5 minutes later. TetM0 has potential as a broad spectrum in vivo sequestrant for drugs of abuse.

A quantitative trait variant in Gabra2 underlies increased methamphetamine stimulant sensitivity

Psychostimulant (methamphetamine, cocaine) use disorders have a genetic component that remains mostly unknown. We conducted genome-wide quantitative trait locus (QTL) analysis of methamphetamine stimulant sensitivity. To facilitate gene identification, we employed a Reduced Complexity Cross between closely related C57BL/6 mouse substrains and examined maximum speed and distance traveled over 30 min following methamphetamine (2 mg/kg, i.p.). For maximum methamphetamine-induced speed following the second and third administration, we identified a single genome-wide significant QTL on chromosome 11 that peaked near the Cyfip2 locus (LOD = 3.5, 4.2; peak = 21 cM [36 Mb]). For methamphetamine-induced distance traveled following the first and second administration, we identified a genome-wide significant QTL on chromosome 5 that peaked near a functional intronic indel in Gabra2 coding for the alpha-2 subunit of the GABA-A receptor (LOD = 3.6-5.2; peak = 34-35 cM [66-67 Mb]). Striatal cis-expression QTL mapping corroborated Gabra2 as a functional candidate gene underlying methamphetamine-induced distance traveled. CRISPR/Cas9-mediated correction of the mutant intronic deletion on the C57BL/6J background to the wild-type C57BL/6NJ allele was sufficient to reduce methamphetamine-induced locomotor activity toward the wild-type C57BL/6NJ-like level, thus validating the quantitative trait variant (QTV). These studies show the power and efficiency of Reduced Complexity Crosses in identifying causal variants underlying complex traits. Functionally restoring Gabra2 expression decreased methamphetamine stimulant sensitivity and supports preclinical and human genetic studies implicating the GABA-A receptor in psychostimulant addiction-relevant traits. Importantly, our findings have major implications for studying psychostimulants in the C57BL/6J strain-the gold standard strain in biomedical research.

Functional and structural alternations in the choroid plexus upon methamphetamine exposure

Choroid plexus (CP) is the principal source of cerebrospinal fluid. CP can produce and release a wide range of materials including growth factors, neurotrophic factors, etc. all of which play an important role in the maintenance and proper functioning of the brain. Methamphetamine (METH) is a CNS neurostimulant that causes brain dysfunction. Herein, we investigated the potential effects of METH exposure on CP structure and function. Stereological analysis revealed a significant alteration in CP volume, epithelial cells and capillary number upon METH treatment. Electron microscopy exhibited changes in ultrastructure. Moreover, the upregulation of neurotrophic factors such as BDNF and VEGF as well as autophagy and apoptosis gene following METH administration were observed. We also identified several signaling cascades related to autophagy. In conclusion, gene expression changes coupled with structural alterations of the CP in response to METH suggested METH-induced autophagy in CP.

Methamphetamine mediates apoptosis of vascular smooth muscle cells via the chop-related endoplasmic reticulum stress pathway

Methamphetamine (METH) is a highly addictive amphetamine-type drug that has caused persistent harm to society and human health in recent years. Most studies have shown that METH severely damages the central nervous system, and this drug has been found to be toxic to the cardiovascular system in recent years. Therefore, we hypothesized that METH may also damage vascular smooth muscle. We examined the expression of the apoptosis-related proteins Caspase 3 and PARP after METH treatment in vivo and in vitro and detected the expression of endoplasmic reticulum stress-related proteins. After treatment with the endoplasmic reticulum stress inhibitor 4-PBA, changes in the above indicators were examined. C/EBP homologous protein (Chop) expression was also detected, and the relationship between endoplasmic reticulum stress and apoptosis was further determined by siRNA silencing of Chop. The results indicated that METH can induce apoptosis of vascular smooth muscle cells (VSMCs) and upregulate the expression of Chop and endoplasmic reticulum stress-related proteins. Chop inhibits protein kinase B phosphorylation and further inhibits forkhead box class O3a (Foxo3a) dephosphorylation, resulting in increased p53 upregulated molecular of apoptosis (PUMA) transcription. Increased PUMA induces apoptosis through the mitochondrial pathway. These results indicate that Chop is involved in the METH-induced endoplasmic reticulum stress and apoptosis in VSMCs and may be a potential therapeutic target for METH-induced VSMC injury.

Lactoferrin Protects against Methamphetamine Toxicity by Modulating Autophagy and Mitochondrial Status

Lactoferrin (LF) was used at first as a vehicle to deliver non-soluble active compounds to the body, including the central nervous system (CNS). Nonetheless, it soon became evident that, apart from acting as a vehicle, LF itself owns active effects in the CNS. In the present study, the effects of LF are assessed both in baseline conditions, as well as to counteract methamphetamine (METH)-induced neurodegeneration by assessing cell viability, cell phenotype, mitochondrial status, and specific autophagy steps. In detail, cell integrity in baseline conditions and following METH administration was carried out by using H&E staining, Trypan blue, Fluoro Jade B, and WST-1. Western blot and immuno-fluorescence were used to assess the expression of the neurofilament marker βIII-tubulin. Mitochondria were stained using Mito Tracker Red and Green and were further detailed and quantified by using transmission electron microscopy. Autophagy markers were analyzed through immuno-fluorescence and electron microscopy. LF counteracts METH-induced degeneration. In detail, LF significantly attenuates the amount of cell loss and mitochondrial alterations produced by METH; and mitigates the dissipation of autophagy-related proteins from the autophagy compartment, which is massively induced by METH. These findings indicate a protective role of LF in the molecular mechanisms of neurodegeneration.

Assessment on the adverse effects on different kinds of fish induced by methamphetamine during the natural attenuation process based on adverse outcome pathway

The adverse effects on model fish induced by methamphetamine (METH) have been revealed. However, the toxicity of METH on different kinds of non-model fish during the natural attenuation remained unclear. Hence, in this study, we for the first time established a static lab-scale aquatic ecosystem spiked with METH (initial levels at 25 μg/L) for 40 days to estimate its metabolism and toxicity in Chinese medaka, rosy bitterling, loach, and mosquito fish. The concentrations of METH in water and fish's brain were detected termly. The physiological functions, histopathology of brain, neurotransmitters contents, and expressions of associated genes of the four kinds of fish were determined at day 0, 20, and 40, respectively. The results indicated METH could be remarkably accumulated in fish brains with the distribution factor vs water (DFw) at 232.5-folds, and attenuated both in water and fish body during the exposure. METH caused physiological functions (i.e., swimming trajectories, locomotion distances, and feeding rates) disorders of the four kinds of fish, and stimulated surfacing behavior of loach. Tissue and macro/micromolecular biomarkers including histopathology, neurotransmitters (i.e., dopamine, serotonin, and norepinephrine), and mRNA, were similarly affected by METH. Mitogen-activated protein kinase (MAPKs) signaling pathway, P53-regulated apoptosis signaling pathway, N-methyl-d-aspartate-dopamine system, and mTOR signaling pathway of different kinds of fish were regulated by METH. Additionally, the impairments of the physiological and macromolecular indicators of fish could be alleviated as the natural attenuation of METH occurred. All the biomarkers, as well as the recovery effects during the exposure were integrated onto an adverse outcome pathway (AOP) framework. The key event was the micromolecular indicators (genes). The adverse outcomes at individual and population levels would result in the ecological consequences, implying the imperative to consider the natural attenuation process while assessing the environmental risk of METH.

Cannabidiol promotes neurogenesis in the dentate gyrus during an abstinence period in rats following chronic exposure to methamphetamine

Chronic methamphetamine (meth) abuse can lead to certain deficits in the hippocampal function by affecting the hippocampal neurogenesis and plasticity. To determine whether cannabidiol (CBD) can promote proliferation and maturation of neuronal progenitor cells, this study investigated the CBD effect on neurogenesis in the hippocampal dentate gyrus (DG) following chronic exposure to meth in rats. The rats received 2 mg/kg of meth twice a day for ten days. Next, immunofluorescence was performed to evaluate the effect of intracerebroventricular (ICV) administration of CBD (50 μg/5 μL) over an abstinence period (ten days) on the expression levels of neurogenesis markers, such as Ki67, NeuN, and doublecortin (DCX). Moreover, neuronal degeneration in the hippocampus was assessed using Nissl staining. According to our findings, repeated ICV administration of CBD improved cell proliferation and neurogenesis and increased the number of Ki-67 and DCX-positive cells in the abstinence period. Meanwhile, meth treatment subjects caused a significant decrease in the number of neurogenesis makers, as compared to the control group. The neurogenesis markers (Ki-67 and DCX) could be somewhat reversed, while NeuN did not show any significant increase in the CBD group. Our findings demonstrated that CBD can induce neuroprotective effects by modulating neurogenesis. Therefore, it can provide a promising therapeutic approach to improve cognitive performance following chronic exposure to psychostimulant drugs, including meth.

Mitochondrial oxidant stress mediates methamphetamine neurotoxicity in substantia nigra dopaminergic neurons

Methamphetamine abuse is associated with an increased risk of developing Parkinson's disease (PD). Recently, it was found that methamphetamine increases mitochondrial oxidant stress in substantia nigra pars compacta (SNc) dopaminergic neurons by releasing vesicular dopamine (DA) and stimulating mitochondrially-anchored monoamine oxidase (MAO). As mitochondrial oxidant stress is widely thought to be a driver of SNc degeneration in PD, these observations provide a potential explanation for the epidemiological linkage. To test this hypothesis, mice were administered methamphetamine (5 mg/kg) for 28 consecutive days with or without pretreatment with an irreversible MAO inhibitor. Chronic methamphetamine administration resulted in the degeneration of SNc dopaminergic neurons and this insult was blocked by pretreatment with a MAO inhibitor - confirming the linkage between methamphetamine, MAO and SNc degeneration. To determine if shorter bouts of consumption were as damaging, mice were given methamphetamine for two weeks and then studied. Methamphetamine treatment elevated both axonal and somatic mitochondrial oxidant stress in SNc dopaminergic neurons, was associated with a modest but significant increase in firing frequency, and caused degeneration after drug cessation. While axonal stress was sensitive to MAO inhibition, somatic stress was sensitive to Cav1 Ca2+ channel inhibition. Inhibiting either MAO or Cav1 Ca2+ channels after methamphetamine treatment attenuated subsequent SNc degeneration. Our results not only establish a mechanistic link between methamphetamine abuse and PD, they point to pharmacological strategies that could lessen PD risk for patients with a methamphetamine use disorder.

Exercise Pills for Drug Addiction: Forced Moderate Endurance Exercise Inhibits Methamphetamine-Induced Hyperactivity through the Striatal Glutamatergic Signaling Pathway in Male Sprague Dawley Rats

Physical exercise reduces the extent, duration, and frequency of drug use in drug addicts during the drug initiation phase, as well as during prolonged addiction, withdrawal, and recurrence. However, information about exercise-induced neurobiological changes is limited. This study aimed to investigate the effects of forced moderate endurance exercise training on methamphetamine (METH)-induced behavior and the associated neurobiological changes. Male Sprague Dawley rats were subjected to the administration of METH (1 mg/kg/day, i.p.) and/or forced moderate endurance exercise (treadmill running, 21 m/min, 60 min/day) for 2 weeks. Over the two weeks, endurance exercise training significantly reduced METH-induced hyperactivity. METH and/or exercise treatment increased striatal dopamine (DA) levels, decreased p(Thr308)-Akt expression, and increased p(Tyr216)-GSK-3β expression. However, the phosphorylation levels of Ser9-GSK-3β were significantly increased in the exercise group. METH administration significantly increased the expression of NMDAr1, CaMKK2, MAPKs, and PP1 in the striatum, and exercise treatment significantly decreased the expression of these molecules. Therefore, it is apparent that endurance exercise inhibited the METH-induced hyperactivity due to the decrease in GSK-3β activation by the regulation of the striatal glutamate signaling pathway.

Norepinephrine Protects against Methamphetamine Toxicity through β2-Adrenergic Receptors Promoting LC3 Compartmentalization

Norepinephrine (NE) neurons and extracellular NE exert some protective effects against a variety of insults, including methamphetamine (Meth)-induced cell damage. The intimate mechanism of protection remains difficult to be analyzed in vivo. In fact, this may occur directly on target neurons or as the indirect consequence of NE-induced alterations in the activity of trans-synaptic loops. Therefore, to elude neuronal networks, which may contribute to these effects in vivo, the present study investigates whether NE still protects when directly applied to Meth-treated PC12 cells. Meth was selected based on its detrimental effects along various specific brain areas. The study shows that NE directly protects in vitro against Meth-induced cell damage. The present study indicates that such an effect fully depends on the activation of plasma membrane β2-adrenergic receptors (ARs). Evidence indicates that β2-ARs activation restores autophagy, which is impaired by Meth administration. This occurs via restoration of the autophagy flux and, as assessed by ultrastructural morphometry, by preventing the dissipation of microtubule-associated protein 1 light chain 3 (LC3) from autophagy vacuoles to the cytosol, which is produced instead during Meth toxicity. These findings may have an impact in a variety of degenerative conditions characterized by NE deficiency along with autophagy impairment.

Evaluation of Cytotoxic and Mutagenic Effects of the Synthetic Cathinones Mexedrone, α-PVP and α-PHP

Mexedrone, α-PVP and α-PHP are synthetic cathinones. They can be considered amphetamine-like substances with a stimulating effect. Actually, studies showing their impact on DNA are totally absent. Therefore, in order to fill this gap, aim of the present work was to evaluate their mutagenicity on TK6 cells. On the basis of cytotoxicity and cytostasis results, we selected the concentrations (35–100 µM) to be used in the further analysis. We used the micronucleus (MN) as indicator of genetic damage and analyzed the MNi frequency fold increase by flow cytometry. Mexedrone demonstrated its mutagenic potential contrary to the other two compounds; we then proceeded by repeating the analyzes in the presence of extrinsic metabolic activation in order to check if it was possible to totally exclude the mutagenic capacity for α-PVP and α-PHP. The results demonstrated instead the mutagenicity of their metabolites. We then evaluated reactive oxygen species (ROS) induction as a possible mechanism at the basis of the highlighted effects but the results did not show a statistically significant increase in ROS levels for any of the tested substances. Anyway, our outcomes emphasize the importance of mutagenicity evaluation for a complete assessment of the risk associated with synthetic cathinones exposure.