Methamphetamine Induces Apoptosis of Microglia via the Intrinsic Mitochondrial-Dependent Pathway

The interaction between central and peripheral immune systems in methamphetamine use disorder: current status and future directions

Methamphetamine (METH) use disorder (MUD) is characterized by compulsive drug-seeking behavior and substantial neurotoxicity, posing a considerable burden on individuals and society. Traditionally perceived as a localized central nervous system disorder, recent preclinical and clinical studies have elucidated that MUD is a multifaceted disorder influenced by various biological systems, particularly the immune system. Emerging evidence suggests that both central and peripheral immune responses play a crucial role in the initiation and persistence of MUD. Conceptualizing it as a systemic immune process prompts significant inquiries regarding the mechanisms of communication between peripheral and central compartments. Also, whether this intercommunication could serve as diagnostic biomarkers or therapeutic targets. This review begins by offering an overview of mechanistic studies pertaining to the neuroimmune and peripheral immune systems. Finally, future directions are suggested through the integration of innovative technologies and multidimensional data to promote the translation of basic mechanistic research into clinical diagnostic and therapeutic interventions.

Rotenone and Its Derivative, Rotenoisin A, Induce Neurodegeneration Differentially in SH-SY5Y Cells

Rotenone (ROT), the most significant rotenoid, which has shown anticancer activity, has also been reported to be toxic to normal cells, inducing Parkinson's disease (PD)-like neuronal loss with aggregation of α-synuclein (α-syn). To reduce the adverse effects of ROT, its derivative, rotenoisin A (ROA), is obtained by directly irradiating a ROT solution in methanol using γ-rays, which has been reported for potential anticancer properties. However, its PD-inducing effects have not yet been researched or reported. This study sought to compare the activities of ROA and ROT on the aggregation of α-syn, apoptosis, and autophagy in SH-SY5Y cells. ROA decreased cell survival less when compared with ROT on SH-SY5Y cells at 48 h in a dose-dependent manner. ROT (0.5 and 1 μM) and ROA (4 and 5 μM) decreased the expression of tyrosine hydroxylase. Western blot analysis of the Triton X-100 insoluble fraction revealed that both ROT and ROA significantly increased the levels of oligomeric, dimeric, and monomeric phosphorylated Serine129 α-syn and total monomeric α-syn. Moreover, both compounds decreased the proportion of neuronal nuclei, the neurofilament-heavy chain, and β3-tubulin. The phosphorylation of ERK and SAPK were reduced, whereas ROA did not act on Akt. Additionally, the increased Bax/Bcl-2 ratio further activated the downstream caspases cascade. ROT promoted the LC3BII/I ratio and p62 levels; however, different ROA doses resulted in different effects on autophagy while inducing PD-like impairments in SH-SY5Y cells.

STIM1 Mediates Methamphetamine-Induced Neuronal Autophagy and Apoptosis

Methamphetamine (METH) is a widely abused amphetamine-type psychoactive drug that causes serious health problems. Previous studies have demonstrated that METH can induce neuron autophagy and apoptosis in vivo and in vitro. However, the molecular mechanisms underlying METH-induced neuron autophagy and apoptosis remain poorly understood. Stromal interacting molecule 1 (STIM1) was hypothesized to be involved in METH-induced neuron autophagy and apoptosis. Therefore, the expression of STIM1 protein was measured and the effect of blocking STIM1 expression with siRNA was investigated in cultured neuronal cells, and the hippocampus and striatum of mice exposed to METH. Furthermore, intracellular calcium concentration and endoplasmic reticulum (ER) stress-related proteins were determined in vitro and in vivo in cells treated with METH. The results suggested that STIM1 mediates METH-induced neuron autophagy by activating the p-Akt/p-mTOR pathway. METH exposure also resulted in increased expression of Orai1, which was reversed after STIM1 silencing. Moreover, the disruption of intracellular calcium homeostasis induced ER stress and up-regulated the expression of pro-apoptotic protein CCAAT/enhancer-binding protein homologous protein (CHOP), resulting in classic mitochondria apoptosis. METH exposure can cause neuronal autophagy and apoptosis by increasing the expression of STIM1 protein; thus, STIM1 may be a potential gene target for therapeutics in METH-caused neurotoxicity.

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

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

Neuroprotective activity of green synthesized silver nanoparticles against methamphetamine-induced cell death in human neuroblastoma SH-SY5Y cells

The present study aimed to investigate the neuroprotective activity of the black peel pomegranate extract, and silver nanoparticles (AgNPs) biosynthesized using the extract. We pretreated the human neuroblastoma SH-SY5 cells with the extract and AgNPs and evaluated the neuroprotective activity of these agents against methamphetamine (Meth) cytotoxicity. The NPs were spherical with 19 ± 8 nm size, - 28 mV surface charge, and 0.20 PDI. Meth killed the cells by increasing proapoptotic (Bax, PTEN, AKT, PI3K, NF-κB, P53, TNF-α, Cyt C, and Cas 3) and decreasing the antiapoptotic genes (Bcl-2) expression. Exposure to Meth caused DNA fragmentation and increased the intercellular ROS and malondialdehyde (MDA) levels while reducing the mitochondrial membrane potential (MMP). A 4-h pretreatment of the cells with the extract and AgNPs could retain the viability of the cells above 80% by increasing the Bcl-2 expression up to fourfold and inhibiting the cell death pathways. ROS, MDA, and MMP levels in the pretreated cells were close to the control group. The percentage of necrosis in cells pretreated with the extract and AgNPs declined to 32% and 8%, respectively. Our promising findings indicated that AgNPs could reduce Meth-induced oxidative stress and prevent necrotic and apoptotic cell death by regulating related genes' expression.

MitomiR-504 alleviates the copper-induced mitochondria-mediated apoptosis by suppressing Bak1 expression in porcine jejunal epithelial cells

Copper (Cu), an environmental heavy metal pollutant, has been widely researched in its toxicology. Recently, an increasing number of mitochondrial microRNAs (mitomiRs) have been shown to involve in the metabolic regulation. However, the underlying mechanisms of mitomiRs on regulating apoptosis under Cu exposure are still unclear. Here, we proved that Cu induced mitochondria-mediated apoptosis in porcine jejunal epithelial cells, concomitant with distinct reduction of mitomiR-504 in vivo and in vitro. The miR-504 mimic notably enhanced the mRNA and protein expressions of Bak1, Bax, Cleaved-caspase3 and Caspase-9, and significantly decreased the apoptosis rate and Bcl-2 mRNA and protein levels, indicating that overexpression of mitomiR-504 attenuated the Cu-induced mitochondria-mediated apoptosis. Besides, Bak1 was confirmed as a direct target of mitomiR-504 by the bioinformatics analysis and dual-luciferase reporter assay. Subsequently, transfection of siRNA targeting Bak1 significantly enhanced the alleviating effect of miR-504 mimic on the Cu-induced mitochondria-mediated apoptosis. Overall, these suggested that overexpression of mitomiR-504 alleviated the Cu-induced mitochondria-mediated apoptosis in jejunal epithelial cells by suppressing Bak1 expression. These findings are conducive to elucidating the mechanism of Cu-induced jejunal epithelial pathologies, providing a new research idea for the Cu toxicology.

Role of Microglia in Psychostimulant Addiction

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

Raman spectroscopy based molecular signatures of methamphetamine and HIV induced mitochondrial dysfunction

METH and HIV Tat treatment results in increased oxidative stress which affects cellular metabolism and causes DNA damage in the treated microglia. Both, METH ± HIV Tat impair mitochondrial respiration, leading to dysfunction in bioenergetics and increased ROS in microglial cells. Our data indicate that mitochondrial dysfunction may be key to the METH and/or HIV Tat-induced neuropathology. METH and/or HIV Tat induced changes in the protein, lipid and nucleotide concentration in microglial cells were measured by Raman Spectroscopy, and we speculate that these fundamental molecular-cellular changes in microglial cells contribute to the neuropathology that is associated with METH abuse in HIV patients.

Effects and associated transcriptomic landscape changes of methamphetamine on immune cells

Background

Methamphetamine (METH) abuse causes serious health problems, including injury to the immune system, leading to increased incidence of infections and even making withdrawal more difficult. Of course, immune cells, an important part of the immune system, are also injured in methamphetamine abuse. However, due to different research models and the lack of bioinformatics, the mechanism of METH injury to immune cells has not been clarified.

Methods

We examined the response of three common immune cell lines, namely Jurkat, NK-92 and THP-1 cell lines, to methamphetamine by cell viability and apoptosis assay in vitro, and examined their response patterns at the mRNA level by RNA-sequencing. Differential expression analysis of two conditions (control and METH treatment) in three types of immune cells was performed using the DESeq2 R package (1.20.0). And some of the differentially expressed genes were verified by qPCR. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of differentially expressed genes by the clusterProfiler R package (3.14.3). And gene enrichment analysis was also performed using MetaScape (www.metascape.org).

Results

The viability of the three immune cells was differentially affected by methamphetamine, and the rate of NK-cell apoptosis was significantly increased. At the mRNA level, we found disorders of cholesterol metabolism in Jurkat cells, activation of ERK1 and ERK2 cascade in NK-92 cells, and disruption of calcium transport channels in THP-1 cells. In addition, all three cells showed changes in the phospholipid metabolic process.

Conclusions

The results suggest that both innate and adaptive immune cells are affected by METH abuse, and there may be commonalities between different immune cells at the transcriptome level. These results provide new insights into the potential effects by which METH injures the immune cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01295-9.

Methamphetamine Dysregulation of the Central Nervous System and Peripheral Immunity

Methamphetamine (METH) is a potent psychostimulant that increases extracellular monoamines, such as dopamine and norepinephrine, and affects multiple tissue and cell types in the central nervous system (CNS) and peripheral immune cells. The reinforcing properties of METH underlie its significant abuse potential and dysregulation of peripheral immunity and central nervous system functions. Together, the constellation of METH's effects on cellular targets and regulatory processes has led to immune suppression and neurodegeneration in METH addicts and animal models of METH exposure. Here we extensively review many of the cell types and mechanisms of METH-induced dysregulation of the central nervous and peripheral immune systems. SIGNIFICANCE STATEMENT: Emerging research has begun to show that methamphetamine regulates dopaminergic neuronal activity. In addition, METH affects non-neuronal brain cells, such as microglia and astrocytes, and immunological cells of the periphery. Concurrent disruption of bidirectional communication between dopaminergic neurons and glia in the CNS and peripheral immune cell dysregulation gives rise to a constellation of dysfunctional neuronal, cell, and tissue types. Therefore, understanding the pathophysiology of METH requires consideration of the multiple targets at the interface between basic and clinical neuroscience.

Neural-Induced Human Adipose Tissue-Derived Stem Cells Conditioned Medium Ameliorates Rotenone-Induced Toxicity in SH-SY5Y Cells

Parkinson's disease (PD) is an age-related neurodegenerative disease (NDD) characterized by the degenerative loss of dopaminergic neurons in the substantia nigra along with aggregation of α-synuclein (α-syn). Neurogenic differentiation of human adipose-derived stem cells (NI-hADSCs) by supplementary factors for 14 days activates different biological signaling pathways. In this study, we evaluated the therapeutic role of NI-hADSC-conditioned medium (NI-hADSC-CM) in rotenone (ROT)-induced toxicity in SH-SY5Y cells. Increasing concentrations of ROT led to decreased cell survival at 24 and 48 h in a dose- and time-dependent manner. Treatment of NI-hADSC-CM (50% dilution in DMEM) against ROT (0.5 μM) significantly increased the cell survival. ROT toxicity decreased the expression of tyrosine hydroxylase (TH). Western blot analysis of the Triton X-100-soluble fraction revealed that ROT significantly decreased the oligomeric, dimeric, and monomeric phosphorylated Serine129 (p-S129) α-syn, as well as the total monomeric α-syn expression levels. ROT toxicity increased the oligomeric, but decreased the dimeric and monomeric p-S129 α-syn expression levels. Total α-syn expression (in all forms) was increased in the Triton X-100-insoluble fraction, compared to the control. NI-hADSC-CM treatment enhanced the TH expression, stabilized α-syn monomers, reduced the levels of toxic insoluble p-S129 α-syn, improved the expression of neuronal functional proteins, regulated the Bax/Bcl-2 ratio, and upregulated the expression of pro-caspases, along with PARP-1 inactivation. Moreover, hADSC-CM treatment decreased the cell numbers and have no effect against ROT toxicity on SH-SY5Y cells. The therapeutic effects of NI-hADSC-CM was higher than the beneficial effects of hADSC-CM on cellular signaling. From these results, we conclude that NI-hADSC-CM exerts neuroregenerative effects on ROT-induced PD-like impairments in SH-SY5Y cells.

Therapeutic Effects of Conditioned Medium of Neural Differentiated Human Bone Marrow-Derived Stem Cells on Rotenone-Induced Alpha-Synuclein Aggregation and Apoptosis

Mesenchymal stem cells (MSCs) have been used against several diseases. Their potential mainly appears from its secreted biomolecules. Human bone marrow-derived stem cells (hBMSC) displayed neuronal functional characteristics after differentiation by basic fibroblast growth factor (bFGF) and forskolin. PD is a chronic age-related neurodegenerative disease (NDD) characterized by loss of dopaminergic neurons in the substantia nigra (SN) and abnormal accumulation of α-synuclein (α-syn) aggregations. In this present study, we evaluated the therapeutic effects of neural differentiated hBMSC (NI-hBMSC) conditioned medium (NI-hBMSC-CM) to a rotenone- (ROT-) induced Parkinson's disease (PD) model in SH-SY5Y cells. NI-hBMSC-CM treatment (50% diluted) in the last 24 h of 48 h ROT (0.5 μM) toxicity showed a significant increase in cell survival. The decreased tyrosine hydroxylase (TH) expression as a hallmark of PD was increased by NI-hBMSC-CM. The Triton X-100-soluble and Triton X-100-insoluble cell lysate fractions were used in Western blotting. The oligomeric, dimeric, and monomeric phosphorylated serine129 (p-S129) α-syn and total monomeric α-syn were decreased during ROT toxicity in the Triton X-100-soluble fraction. The Triton X-100-insoluble fraction revealed that ROT toxicity significantly increased the oligomeric but decreased the dimeric and monomeric p-S129 α-syn expressions while all forms of total α-syn were increased in SH-SY5Y cells. NI-hBMSC-CM stabilized the physiological α-syn monomers and reduced aggregated insoluble p-S129 α-syn against ROT. The cytoskeletal proteins, neurofilament-H (NF-H), β3-tubulin (Tuj1), neuronal nuclei (NeuN), and synaptophysin (SYP) were significantly decreased during ROT toxicity. In addition, proapoptotic Bax was increased by ROT with decreased antiapoptotic Bcl-2 and Mcl-1 as well as proforms of caspase-9, caspase-3, caspase-7, and PARP-1. NI-hBMSC-CM ameliorated the neurotrophic protein expressions, controlled the Bax/Bcl-2 ratio, upregulated procaspases, and inactivated PARP-1. From our results, we conclude that NI-hBMSC-CM containing released biomolecules during neural differentiation employs regenerative effects on the ROT model of PD in SH-SY5Y cells.

Suicide Attempts and Perceived Social Support among Chinese Drug Users: The Mediating Role of Self-Esteem and Depression

Suicidal behavior is a severe problem among drug users. This study examines influential factors related to suicide attempts and analyzes possible mediators of the relationship between perceived social support and suicide attempts amongst Chinese drug users under compulsory institutional drug treatment. Taking perceived social support as the independent variable, we found that the relationship between suicide attempts and perceived social support is mediated by self-esteem as a protective factor and depression as a risk factor. Path analysis shows that self-esteem contributes relatively more to the indirect effects than depression does, accounting for 31.1% and 24.2% of the total effect, respectively. Generally speaking, the findings of this study point to an urgent need for addressing suicide attempts among Chinese drug users while treating self-esteem as the protective factor that deserves as substantial attention as depression receives.

TBHQ-Overview of Multiple Mechanisms against Oxidative Stress for Attenuating Methamphetamine-Induced Neurotoxicity

Methamphetamine is a derivative of amphetamines, a highly addictive central stimulant with multiple systemic toxicity including the brain, heart, liver, lung, and spleen. It has adverse effects such as apoptosis and breakdown of the blood-brain barrier. Methamphetamine is a fatal and toxic chemical substance, and its lethal mechanism has been widely studied in recent years. The possible mechanism is that methamphetamine can cause cardiotoxicity and neurotoxicity mainly by inducing oxidative stress so as to generate heat, eliminate people's hunger and thirst, and maintain a state of excitement so that people can continue to exercise. According to many research, there is no doubt that methamphetamine triggers neurotoxicity by inducing reactive oxygen species (ROS) production and redox imbalance. This review summarized the mechanisms of methamphetamine-induced neurotoxicity including apoptosis and blood-brain barrier breakdown through oxidative stress and analyzed several possible antioxidative mechanisms of tert-butylhydroquinone (TBHQ) which is a kind of food additive with antioxidative effects. As a nuclear factor E2-related factor 2 (Nrf2) agonist, TBHQ may inhibit neurotoxicity caused by oxidative stress through the following three mechanisms: the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system, the astrocytes activation, and the glutathione pathway. The mechanism about methamphetamine's toxic effects and its antioxidative therapeutic drugs would become a research hotspot in this field and has very important research significance.

Neuroprotective and neuro-survival properties of safinamide against methamphetamine-induced neurodegeneration: Hypothetic possible role of BDNF/TrkB/PGC-1α signaling pathway and mitochondrial uncoupling protein -2(UCP-2)

Methamphetamine is a behavioral psychostimulant that has a high potential for misuse and induction of neurotoxicity. Safinamide is a novel inhibitor of monoamine oxidase B (MAOB) with neuroprotective properties. Methamphetamine abuse causes dysfunction in the respiratory chain of the mitochondria, but the specific signaling mechanism and role of the uncoupling protein-2(UCP-2) remain unclear. As we know, some indirect evidence indicates that neurodegeneration can be caused by inhibition of the brain-derived neurotrophic factor (BDNF) receptor, TrkB and its downstream signaling pathway, such as the PGC-1α protein. Neuroprotective strategies and approaches to the management, treatment or prevention of methamphetamine-induced neurodegeneration by modulating BDNF / TrkB / PGC-1α-UCP-2 can be considered as novel therapeutic approaches to these psychostimulant neurochemical and neurobehavioral approaches. Previous studies have shown that safinamide, a monoamine oxidase-B (MAOB) inhibitor, can function as a neuroprotective agent and inhibit the neurodegenerative process especially in Parkinson's disease but its impact on other neurodegenerative processes and drug-induced neurotoxicity remain unclear. Although there is some evidence that BDNF / TrkB / PGC-1α-UCP-2 signaling pathway and mitochondrial UCP-2 mediated safinamide induced neuroprotection but it's exact and precise mechanism of action and neuroprotective effects in neurodegenerative disorder and the protective properties against methamphetamine induced neurodegeneration and the role of BDNF / TrkB / PGC-1α signaling pathway and role of mitochondrial UCP-2 in this process have not yet been clarified. Therefore, in subjects addicted to methamphetamine, we hypothesized that safinamide will provide neuroprotection against methamphetamine-prompted neurodegeneration, and it appears that BDNF / TrkB / PGC-1α signaling pathway and mitochondrial UCP-2 are likely to play a critical role.

Methamphetamine induces GSDME-dependent cell death in hippocampal neuronal cells through the endoplasmic reticulum stress pathway

Methamphetamine (METH) is an illegal amphetamine-typed psychostimulant that is abused worldwide and causes serious public health problems. METH exposure induces apoptosis and autophagy in neuronal cells. However, the role of pyroptosis in METH-induced neurotoxicity is still unclear. Here, we investigate whether pyroptosis is involved in METH-induced hippocampal neurotoxicity and the potential mechanisms of Endoplasmic reticulum (ER) stress in hippocampal neuronal cells. For this purpose, the expression levels of pyroptosis-related proteins, GSDMD and GSDME, were analyzed by immunoblotting and immunohistochemistry in the hippocampal neuron cell line HT-22. Next, we explored METH-induced pyroptosis in HT-22 using immunoblotting, LDH assays and SYTOX green acid staining. Further, the relationship between pyroptosis and ER stress in METH-induced hippocampal neuron damage was studied in HT-22 cells using inhibitors including TUDCA, a specific inhibitor of ER stress, GSK-2656157, a PERK pathway inhibitor and STF-0803010, an inhibitor of IRE1α endoribonuclease activity. This relationship was also studied using siRNAs, including siTRAF2, an siRNA against IRE1α kinase activity and siATF6 against the ATF6 pathway, which were analyzed by immunoblotting, LDH assays and SYTOX green acid staining. GSDME but not GSDMD was found to be expressed in HT-22 cells. METH treatment induced the upregulation of cleaved GSDME-NT and LDH release, as well as the increase of SYTOX green positive cells in HT-22 cells, which was partly reversed by inhibitors and siRNAs, indicating that the ER stress signaling pathway was involved in GSDME-dependent cell death induced by METH. In summary, these results revealed that METH induced ER stress that mediated GSDME-dependent cell death in hippocampal neuronal cells. These findings provide novel insight into the mechanisms of METH-induced neurotoxicity.

Methamphetamine alters the TLR4 signaling pathway, NF-κB activation, and pro-inflammatory cytokine production in LPS-challenged NR-9460 microglia-like cells

Methamphetamine (METH) is a major public health and safety problem worldwide. METH is psychostimulant that activates microglia via the toll-like receptor (TLR) 4/MD2 complex, modulating the abundant production of pro-inflammatory cytokines in the central nervous system (CNS). The TLR4/MD2 complex on the surface of microglia recognizes pathogen-associated molecular patterns such as lipopolysaccharide (LPS) resulting in brain tissue inflammation and neuronal damage. Since METH has been associated with microglia-induced neurotoxicity, we hypothesized that METH impairs the expression of TLR4 and activation of NF-κB in NR-9460 microglia-like cells after LPS challenge. We demonstrated that METH decreases the distribution and expression of TLR4 receptors on the surface of microglia-like cells after incubation with endotoxin. Moreover, METH impairs the TLR4/MD2 complex signaling pathways, compromises the activation of NF-κB, and reduces the production of pro-inflammatory mediators in microglia-like cells upon LPS stimulation. Interestingly, microglia-like cells treated with METH and challenged with LPS showed considerable cellular morphological changes including enlarged nuclei and ruffled surface. Our results suggest that METH may have a significant impact on microglial-induced neuroinflammation, neurotoxicity, and the CNS defense against infection. It also highlights the importance of studying the effects of METH on the molecular and cellular components of users' CNS immunity. Finally, animal studies exploring the role of METH on the effectors functions of microglia after antigenic exposure are necessary to understand drug-related inflammation and neural damage in users.

Metformin enhances the sensitivity of colorectal cancer cells to cisplatin through ROS-mediated PI3K/Akt signaling pathway

Metformin and cisplatin have been widely studied as antitumor agents. However, the effect of metformin combined with cisplatin has not been investigated in colorectal cancer (CRC) cells. This study was aimed to explore the effect of metformin or/and cisplatin on cell viability, apoptosis, and the related signaling pathways in CRC SW480 and SW620 cells. We found that metformin or cisplatin inhibited cell viability of SW480 and SW620 cells in a concentration- and time-dependent manner. Furthermore, metformin combined with cisplatin obviously inhibited cell viability, decreased colony formation, induced apoptosis, mediated cleavage of caspase-9, caspase-3 and PARP, activated mitochondrial membrane potential, downregulated Mcl-1 and Bcl-2 expression, upregulated Bak and Bax expression, and increased reactive oxygen species (ROS) production, compared to the individual agent in SW480 and SW620 cells, which were attenuated by N-acetyl-L-cysteine (NAC), a ROS scavenger. Moreover, NAC could recover the downregulation of p-PI3K and p-Akt treated with combination of metformin and cisplatin, which subsequently activated the PI3K/Akt signaling pathway. Taken together, our results demonstrated that metformin enhanced the sensitivity of CRC cells to cisplatin through ROS-mediated PI3K/Akt signaling pathway.

Comparative phase imaging of live cells by digital holographic microscopy and transport of intensity equation methods

We describe a microscopic setup implementing phase imaging by digital holographic microscopy (DHM) and transport of intensity equation (TIE) methods, which allows the results of both measurements to be quantitatively compared for either live cell or static samples. Digital holographic microscopy is a well-established method that provides robust phase reconstructions, but requires a sophisticated interferometric imaging system. TIE, on the other hand, is directly compatible with bright-field microscopy, but is more susceptible to noise artifacts. We present results comparing DHM and TIE on a custom-built microscope system that allows both techniques to be used on the same cells in rapid succession, thus permitting the comparison of the accuracy of both methods.

Tea Polyphenols Attenuate Methamphetamine-Induced Neuronal Damage in PC12 Cells by Alleviating Oxidative Stress and Promoting DNA Repair

DNA integrity plays a crucial role in cell survival. Methamphetamine (METH) is an illegal psychoactive substance that is abused worldwide, and repeated exposure to METH could form mass free radicals and induce neuronal apoptosis. It has been reported that free radicals generated by METH treatment can oxidize DNA and hence produce strand breaks, but whether oxidative DNA damage is involved in the neurotoxicity caused by METH remains unclear. Tea polyphenols exert bioactivities through antioxidant-related mechanisms. However, the potential neuroprotective effect of tea polyphenols on METH-induced nerve cell damage and the underlying mechanism remain to be clarified. In this study, oxidative stress, DNA damage, and cell apoptosis were increased after METH exposure, and the expressions of DNA repair-associated proteins, including the phosphorylation of ataxia telangiectasia mutant (p-ATM) and checkpoint kinase 2 (p-Chk2), significantly declined in PC12 cells after high-dose or long-time METH treatment. Additionally, tea polyphenols could protect PC12 cells against METH-induced cell viability loss, reactive oxide species and nitric oxide production, and mitochondrial dysfunction and suppress METH-induced apoptosis. Furthermore, tea polyphenols could increase the antioxidant capacities and expressions of p-ATM and p-Chk2 and then attenuate DNA damage via activating the DNA repair signaling pathway. These findings indicate that METH is likely to induce neurotoxicity by inducing DNA damage, which can be reversed by tea polyphenols. Supplementation with tea polyphenols could be an effective nutritional prevention strategy for METH-induced neurotoxicity and neurodegenerative disease.

Role of C/EBP-β in Methamphetamine-Mediated Microglial Apoptosis

Methamphetamine (MA) is a widely abused psychoactive drug that primarily damages the nervous system. However, the involvement of MA in the survival of microglia remains poorly understood. CCAAT-enhancer binding protein (C/EBP-β) is a transcription factor and an important regulator of cell apoptosis. Lipocalin2 (lcn2) is a known apoptosis inducer and is involved in many cell death processes. We hypothesized that C/EBP-β is involved in MA-induced lcn2-mediated microglial apoptosis. To test this hypothesis, we measured the protein expression of C/EBP-β after MA treatment and evaluated the effects of silencing C/EBP-β or lcn2 on MA-induced apoptosis in BV-2 cells and the mouse striatum after intrastriatal MA injection. MA exposure increased the expression of C/EBP-β and stimulated the lcn2-mediated modulation of apoptosis. Moreover, silencing the C/EBP-β-dependent lcn2 upregulation reversed the MA-induced microglial apoptosis. The in vivo relevance of these findings was confirmed in mouse models, which demonstrated that the microinjection of anti-C/EBP-β into the striatum ameliorated the MA-induced decrease survival of microglia. These findings provide a new insight regarding the specific contributions of C/EBP-β-lcn2 to microglial survival in the context of MA abuse.

Microglial alterations induced by psychoactive drugs: A possible mechanism in substance use disorder?

Recently, the xenobiotic hypothesis has implicated the immune system in targeting substances of abuse as foreign molecules and stimulating inflammatory responses. Microglial cells are the resident immune cells of the central nervous system and function in homeostatic surveillance. Microglial changes that are induced by exposure to substances of abuse appear to mediate in part the establishment of addiction and the persistence of drug-mediated biological and behavioral changes. In this context, interest in the study of drug-microglia interactions has increased recently. This review summarizes the most recent preclinical rodent and clinical studies on the interaction between microglia and various classes of drugs of abuse, such as ethanol, psychostimulants, and opioids. The principal biological mechanisms of the communication between substances of abuse and microglia will be described to consider putative mechanisms of the establishment of drug addiction and future potential targets for treating substance use disorder.

Methamphetamine-induced apoptosis in glial cells examined under marker-free imaging modalities

We used phase microscopy and Raman spectroscopic measurements to assess the response of in vitro rat C6 glial cells following methamphetamine treatment in real time. Digital holographic microscopy (DHM) and three-dimensional (3-D) tomographic nanoscopy allow measurements of live cell cultures, which yield information about cell volume changes. Tomographic phase imaging provides 3-D information about the refractive index distribution associated with the morphology of biological samples. DHM provides similar information, but for a larger population of cells. Morphological changes in cells are associated with alterations in cell cycle and initiation of cell death mechanisms. Raman spectroscopy measurements provide information about chemical changes within the cells. Our Raman data indicate that the chemical changes in proteins preceded morphological changes, which were seen with DHM. Our study also emphasizes that tomographic phase imaging, DHM, and Raman spectroscopy are imaging tools that can be utilized for noninvasive simultaneous monitoring of morphological and chemical changes in cells during apoptosis and can also be used to monitor other dynamic cell processes.

Methamphetamine regulates βAPP processing in human neuroblastoma cells

Methamphetamine is a potent and highly addictive psychostimulant whose abuse has turned out to be a global health hazard. The multitudinous effects it exerts at the cellular level induces neurotoxic responses in the human brain, ultimately leading to neurocognitive disorders. Strikingly, brain changes, tissue damage and neuropsychological symptoms due to Meth exposure compels and necessitates to link the probability of risk of developing premature Alzheimer's disease, a progressive neurodegenerative disorder characterized by amyloid plaques composed of amyloid-β peptides and clinical dementia. These peptides are derived from sequential cleavages of the β-amyloid precursor protein by β- and γ-secretases. Previous studies reveals evidence for both positive and negative effects of Meth pertaining to cognitive functioning based on the dosage paradigm and duration of exposure revealing a beneficial psychotropic profile under some conditions and deleterious cognitive deficits under some others. In this context, we proposed to examine the effect of Meth on βAPP metabolism and βAPP-cleaving secretases in the human neuroblastoma SH-SY5Y cell line. Our results showed that Meth dose-dependently increases BACE1 expression and catalytic activity, while its effect on the α-cleavage of βAPP and on the expression and catalytic activity of the main α-secretase ADAM10 display a bell-curve shape. To our knowledge, the present study is the first to demonstrate that Meth can control βAPP-cleaving secretases. Moreover, we propose from these findings that the deleterious effect of Meth on cognitive decline might be an outcome of high dosage paradigm whereas acute and short-term drug use which stimulated sAPPα might produce improvements in cognition in disorders such as AD.

Methamphetamine Impairs IgG1-Mediated Phagocytosis and Killing of Cryptococcus neoformans by J774.16 Macrophage- and NR-9640 Microglia-Like Cells

The prevalence of methamphetamine (METH) use is estimated at ∼35 million people worldwide, with over 10 million users in the United States. Chronic METH abuse and dependence predispose the users to participate in risky behaviors that may result in the acquisition of HIV and AIDS-related infections. Cryptococcus neoformans is an encapsulated fungus that causes cryptococcosis, an opportunistic infection that has recently been associated with drug users. METH enhances C. neoformans pulmonary infection, facilitating its dissemination and penetration into the central nervous system in mice. C. neoformans is a facultative intracellular microorganism and an excellent model to study host-pathogen interactions. METH compromises phagocyte effector functions, which might have deleterious consequences on infection control. In this study, we investigated the role of METH in phagocytosis and antigen processing by J774.16 macrophage- and NR-9460 microglia-like cells in the presence of a specific IgG1 to C. neoformans capsular polysaccharide. METH inhibits antibody-mediated phagocytosis of cryptococci by macrophages and microglia, likely due to reduced expression of membrane-bound Fcγ receptors. METH interferes with phagocytic cells' phagosomal maturation, resulting in impaired fungal control. Phagocytic cell reduction in nitric oxide production during interactions with cryptococci was associated with decreased levels of tumor necrosis factor alpha (TNF-α) and lowered expression of Fcγ receptors. Importantly, pharmacological levels of METH in human blood and organs are cytotoxic to ∼20% of the phagocytes. Our findings suggest that METH abrogates immune cellular and molecular functions and may be deadly to phagocytic cells, which may result in increased susceptibility of users to acquire infectious diseases.