Protein kinase Cδ mediates methamphetamine-induced dopaminergic neurotoxicity in mice via activation of microsomal epoxide hydrolase

HDAC6 inhibitor-loaded brain-targeted nanocarrier-mediated neuroprotection in methamphetamine-driven Parkinson's disease

The dynamic equilibrium between acetylation and deacetylation is vital for cellular homeostasis. Parkinson's disease (PD), a neurodegenerative disorder marked by α-synuclein (α-syn) accumulation and dopaminergic neuron loss in the substantia nigra, is associated with a disruption of this balance. Therefore, correcting this imbalance with histone deacetylase (HDAC) inhibitors represents a promising treatment strategy for PD. CAY10603 (CAY) is a potent and selective HDAC6 inhibitor. However, because of its poor water solubility and short biological half-life, it faces clinical limitations. Herein, we engineered lactoferrin-decorated CAY-loaded poly(lactic-co-glycolic acid) nanoparticles (denoted as PLGA@CAY@Lf NPs) to effectively counter methamphetamine (Meth)-induced PD. PLGA@CAY@Lf NPs showed enhanced blood-brain barrier crossing and significant brain accumulation. Notably, CAY released from PLGA@CAY@Lf NPs restored the disrupted acetylation balance in PD, resulting in neuroprotection by reversing mitochondrial dysfunction, suppressing reactive oxygen species, and inhibiting α-syn accumulation. Additionally, PLGA@CAY@Lf NPs treatment normalized dopamine and tyrosine hydroxylase levels, reduced neuroinflammation, and improved behavioral impairments. These findings underscore the potential of PLGA@CAY@Lf NPs in treating Meth-induced PD and suggest that an innovative HDAC6-inhibitor-based strategy can be used to treat PD.

Identifying methamphetamine use predictors in HIV infection: Immune-dopaminergic signatures in peripheral leukocytes and the role of COMT genotype

The pursuit of translational biomarkers is complex due to the heterogeneous human pathophysiology, but critical for disease diagnosis, prognosis, monitoring therapeutic efficacy, and for patient stratification. In HIV-associated neurocognitive impairment (NCI), biomarkers that delineate the trajectory of neuropathogenesis and neurocognitive sequelae are critical, particularly considering confounders such as substance use, including Methamphetamine (METH). METH use is a significant health concern among persons living with HIV (PWH), aggravating cognitive deficits and neuroinflammation despite of antiretrovirals, introducing elements in the microenvironment that are fundamentally differerent in relation to non-METH users, such as high levels of dopamine (DA) affecting HIV-innate immune targets. Yet, current biomarkers do not detect these differences. We hypothesized that predefined DA-induced signatures detectable in peripheral blood leukocytes, can distinguish HIV+ METH users compared to HIV-negative or PWH that are non METH users. The elevated expression of CD8A, CREBBP, CCL5, and combinations of dopaminergic pathway transcripts clustered METH users with detectable CSF viral load and major depressive disorder (MDD), indicating neuroimmune-mechanistic links. Cathecol-o-methyltransferase (COMT) gene polymorphisms affecting DA metabolism improved the identification of PWH using METH with biomarkers. The results indicate that underlying immunedopaminergic mechanisms provide signatures and genotypes that can identify PWH that are METH users and their attributes.

Brain dysfunctions and neurotoxicity induced by psychostimulants in experimental models and humans: an overview of recent findings

Preclinical and clinical studies indicate that psychostimulants, in addition to having abuse potential, may elicit brain dysfunctions and/or neurotoxic effects. Central toxicity induced by psychostimulants may pose serious health risks since the recreational use of these substances is on the rise among young people and adults. The present review provides an overview of recent research, conducted between 2018 and 2023, focusing on brain dysfunctions and neurotoxic effects elicited in experimental models and humans by amphetamine, cocaine, methamphetamine, 3,4-methylenedioxymethamphetamine, methylphenidate, caffeine, and nicotine. Detailed elucidation of factors and mechanisms that underlie psychostimulant-induced brain dysfunction and neurotoxicity is crucial for understanding the acute and enduring noxious brain effects that may occur in individuals who use psychostimulants for recreational and/or therapeutic purposes.

Application of mesenchymal stem cells for neurodegenerative diseases therapy discovery

Neurodegenerative diseases are central or peripheral nervous system disorders associated with progressive brain cell degeneration. Common neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis have been widely studied. However, current therapeutics only reduce the symptoms and do not ameliorate the pathogenesis of these diseases. Recent studies suggested the roles of neuroinflammation, apoptosis, and oxidative stress in neurodegenerative diseases. Mesenchymal stem cells (MSCs) exert anti-apoptotic, anti-inflammatory, and antioxidative effects. Therefore, investigating the effects of MSCs and their applications may lead to the discovery of more effective therapies for neurodegenerative diseases. In this study, we review different approaches used to identify therapies for neurodegenerative diseases using MSCs.

Ginsenoside Re blocks Bay k-8644-induced neurotoxicity via attenuating mitochondrial dysfunction and PKCδ activation in the hippocampus of mice: Involvement of antioxidant potential

Although the anticonvulsant effects of ginsenosides are recognized, little is known about their effects on the convulsive behaviors induced by the activation of L-type Ca²⁺ channels. Here, we investigated whether ginsenoside Re (GRe) modulates excitotoxicity induced by the L-type Ca²⁺ channel activator Bay k-8644. GRe significantly attenuated Bay k-8644-induced convulsive behaviors and hippocampal oxidative stress in mice. GRe-mediated antioxidant potential was more pronounced in the mitochondrial fraction than cytosolic fraction. As L-type Ca²⁺ channels are thought to be targets of protein kinase C (PKC), we investigated the role of PKC under excitotoxic conditions. GRe attenuated Bay k-8644-induced mitochondrial dysfunction, PKCδ activation, and neuronal loss. The PKCδ inhibition and neuroprotection mediated by GRe were comparable to those by the ROS inhibitor N-acetylcysteine, the mitochondrial protectant cyclosporin A, the microglial inhibitor minocycline, or the PKCδ inhibitor rottlerin. Consistently, the GRe-mediated PKCδ inhibition and neuroprotection were counteracted by the mitochondrial toxin 3-nitropropionic acid or the PKC activator bryostatin-1. GRe treatment did not have additional effects on PKCδ gene knockout-mediated neuroprotection, suggesting that PKCδ is a molecular target of GRe. Collectively, our results suggest that GRe-mediated anticonvulsive/neuroprotective effects require the attenuation of mitochondrial dysfunction and altered redox status and inactivation of PKCδ.

Nanowired Delivery of Curcumin Attenuates Methamphetamine Neurotoxicity and Elevates Levels of Dopamine and Brain-Derived Neurotrophic Factor

Curcumin is a well-known antioxidant used as traditional medicine in China and India since ages to treat variety of inflammatory ailments as a food supplement. Curcumin has antitumor properties with neuroprotective effects in Alzheimer's disease. Curcumin elevates brain-derived neurotrophic factor (BDNF) and dopamine (DA) levels in the brain indicating its role in substance abuse. Methamphetamine (METH) is one of the most abused substances in the world that induces profound neurotoxicity by inducing breakdown of the blood-brain barrier (BBB), vasogenic edema and cellular injuries. However, influence of curcumin on METH-induced neurotoxicity is still not well investigated. In this investigation, METH neurotoxicity and neuroprotective effects of curcumin nanodelivery were examined in a rat model. METH (20 mg/kg, i.p.) neurotoxicity is evident 4 h after its administration exhibiting breakdown of BBB to Evans blue albumin in the cerebral cortex, hippocampus, cerebellum, thalamus and hypothalamus associated with vasogenic brain edema as seen measured using water content in all these regions. Nissl attaining exhibited profound neuronal injuries in the regions of BBB damage. Normal curcumin (50 mg/kg, i.v.) 30 min after METH administration was able to reduce BBB breakdown and brain edema partially in some of the above brain regions. However, TiO₂ nanowired delivery of curcumin (25 mg/kg, i.v.) significantly attenuated brain edema, neuronal injuries and the BBB leakage in all the brain areas. BDNF level showed a significant higher level in METH-treated rats as compared to saline-treated METH group. Significantly enhanced DA levels in METH-treated rats were also observed with nanowired delivery of curcumin. Normal curcumin was able to slightly elevate DA and BDNF levels in the selected brain regions. Taken together, our observations are the first to show that nanodelivery of curcumin induces superior neuroprotection in METH neurotoxicity probable by enhancing BDNF and DA levels in the brain, not reported earlier.

Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.

Neurotoxicity of methamphetamine: Main effects and mechanisms

Methamphetamine (METH) is an illicit psychostimulant that is abused throughout the world. METH addiction is also a major public health concern and the abuse of large doses of the drug is often associated with serious neuropsychiatric consequences that may include agitation, anxiety, hallucinations, paranoia, and psychosis. Some human methamphetamine users can also suffer from attention, memory, and executive deficits. METH-associated neurological and psychiatric complications might be related, in part, to METH-induced neurotoxic effects. Those include altered dopaminergic and serotonergic functions, neuronal apoptosis, astrocytosis, and microgliosis. Here we have endeavored to discuss some of the main effects of the drug and have presented the evidence supporting certain of the molecular and cellular bases of METH neurotoxicity. The accumulated evidence suggests the involvement of transcription factors, activation of dealth pathways that emanate from mitochondria and endoplasmic reticulum (ER), and a role for neuroinflammatory mechanisms. Understanding the molecular processes involved in METH induced neurotoxicity should help in developing better therapeutic approaches that might also serve to attenuate or block the biological consequences of use of large doses of the drug by some humans who meet criteria for METH use disorder.

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.

Ginsenoside Re Protects against Serotonergic Behaviors Evoked by 2,5-Dimethoxy-4-iodo-amphetamine in Mice via Inhibition of PKCδ-Mediated Mitochondrial Dysfunction

It has been recognized that serotonin 2A receptor (5-HT_2A) agonist 2,5-dimethoxy-4-iodo-amphetamine (DOI) impairs serotonergic homeostasis. However, the mechanism of DOI-induced serotonergic behaviors remains to be explored. Moreover, little is known about therapeutic interventions against serotonin syndrome, although evidence suggests that ginseng might possess modulating effects on the serotonin system. As ginsenoside Re (GRe) is well-known as a novel antioxidant in the nervous system, we investigated whether GRe modulates 5-HT_2A receptor agonist DOI-induced serotonin impairments. We proposed that protein kinase Cδ (PKCδ) mediates serotonergic impairments. Treatment with GRe or 5-HT_2A receptor antagonist MDL11939 significantly attenuated DOI-induced serotonergic behaviors (i.e., overall serotonergic syndrome behaviors, head twitch response, hyperthermia) by inhibiting mitochondrial translocation of PKCδ, reducing mitochondrial glutathione peroxidase activity, mitochondrial dysfunction, and mitochondrial oxidative stress in wild-type mice. These attenuations were in line with those observed upon PKCδ inhibition (i.e., pharmacologic inhibitor rottlerin or PKCδ knockout mice). Furthermore, GRe was not further implicated in attenuation mediated by PKCδ knockout in mice. Our results suggest that PKCδ is a therapeutic target for GRe against serotonergic behaviors induced by DOI.

GPx-1-encoded adenoviral vector attenuates dopaminergic impairments induced by methamphetamine in GPx-1 knockout mice through modulation of NF-κB transcription factor

We suggested that selenium-dependent glutathione peroxidase (GPx) plays a protective role against methamphetamine (MA)-induced dopaminergic toxicity. We focused on GPx-1, a major selenium-dependent enzyme and constructed a GPx-1 gene-encoded adenoviral vector (Ad-GPx-1) to delineate the role of GPx-1 in MA-induced dopaminergic neurotoxicity. Exposure to Ad-GPx-1 significantly induced GPx activity and GPx-1 protein levels in GPx-1-knockout (GPx-1-KO) mice. MA-induced dopaminergic impairments [i.e., hyperthermia; increased nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) DNA-binding activity; and decreased dopamine levels, TH activity, and behavioral activity] were more pronounced in GPx-1-KO mice than in WT mice. In contrast, exposure to Ad-GPx-1 significantly attenuated MA-induced dopaminergic loss in GPx-1-KO mice. The protective effect exerted by Ad-GPx-1 was comparable to that exerted by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor against MA insult. Consistently, GPx-1 overexpression significantly attenuated MA dopaminergic toxicity in mice. PDTC did not significantly impact the protective effect of GPx-1 overexpression, suggesting that interaction between NF-κB and GPx-1 is critical for dopaminergic protection. Thus, NF-κB is a potential therapeutic target for GPx-1-mediated dopaminergic protective activity. This study for the first time demonstrated that Ad-GPx-1 rescued dopaminergic toxicity in vivo following MA insult. Furthermore, GPx-1-associated therapeutic interventions may be important against dopaminergic toxicity.

5-HT2A receptor-mediated PKCδ phosphorylation is critical for serotonergic impairments induced by p-chloroamphetamine in mice

p-Chloroamphetamine (PCA), an amphetamine derivative, has been shown to induce serotonergic toxicity. However, the precise mechanism of serotonergic toxicity induced by PCA remains unclear. In this study, PCA treatment (20 mg/kg, i.p.) did not significantly change 5-HT_1A receptor gene expression, but significantly increased 5-HT_2A receptor gene expression. Furthermore, 5-HT_2A receptor antagonist MDL11939, but not 5-HT_1A receptor antagonist WAY100635, significantly attenuated PCA-induced serotonergic impairments. We investigated whether PCA activated a specific isoform of protein kinase C (PKC), since previous evidence indicated the involvement of PKC in neurotoxicity induced by amphetamines. We observed that PCA treatment significantly increased the expression levels of PKCδ among all PKC isoforms. MDL11939 treatment significantly attenuated PCA-induced phosphorylation of PKCδ. However, PCA-induced increase in 5-HT_2A receptor gene expression was not altered by rottlerin (a pharmacological inhibitor of PKCδ) in mice, suggesting that 5-HT_2A receptor is an upstream molecule for the activation of PKCδ. Rottlerin or PKCδ knockout significantly attenuated serotonergic behaviors. However, MDL11939 did not show any additional effects against the attenuation caused by PKCδ knockout in mice, suggesting that PKCδ gene is a molecular target for 5-HT_2A receptor-mediated serotonergic effects. Our results suggest that 5-HT_2A receptor mediates PCA-induced serotonergic impairments via activation of PKC.δ.