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

Cannabinoids Δ9-tetrahydrocannabinol and cannabidiol may be effective against methamphetamine induced mitochondrial dysfunction and inflammation by modulation of Toll-like type-4(Toll-like 4) receptors and NF-κB signaling

The neurodegeneration, neuro-inflammation and mitochondrial dysfunction which occur by methamphetamine (METH) abuse or administration are serious and motivation therapeutic approaches for inhibition of these types of neurodegeneration. As we know, METH through Toll-like receptors (TLRs), specially type 4, and NF-κB signaling pathway causes neuro-inflammation and mitochondrial dysfunction. Neuroprotective approach for management of METH-induced neurodegeneration, inflammation and mitochondrial dysfunction, through a novel neuroprotective agent is continuously being superior to any kind of other therapeutic strategy. Therefore, the clarification, introduction and development of efficacious novel neuroprotective agent are demanded. During recent years, using new neuroprotective agent with therapeutic probability for treatment of METH-induced neuro-inflammation and mitochondrial dysfunction has been astoundingly increased. Previous studies have stated the neuroprotective and anti-inflammatory roles ofcannabinoid derivate such as cannabidiol (CBD) and delta-9-tetrahydrocannabinol (Δ⁹-THC) in multiple neurodegenerative events and diseases. According to literature cannabinoid derivate, by inhibition of TLR4 and activation of NF-κB signaling pathway, exerts their anti-inflammatory and neuroprotective effects and cause mitochondrial biogenesis. Thus we hypothesized that by using cannabinoids in METH dependent subject it would provide neuroprotection against METH-induced neurodegeneration, neuro-inflammation and mitochondrial dysfunction and probably can manage sequels of METH-induced neurochemical abuses via modulation of TLR4/NF-κB signaling pathway. In this article, we tried to discuss our hypothesis regarding the possible role of CBD and Δ⁹-THC, as a potent neuroprotective and anti-inflammatory agents, in inhibition or treatment of METH-induced neurodegeneration, neuro-inflammation and mitochondrial dysfunction through its effects on TLR4/NF-κB signaling pathway.

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

We previously demonstrated that activation of protein kinase Cδ (PKCδ) is critical for methamphetamine (MA)-induced dopaminergic toxicity. It was recognized that microsomal epoxide hydrolase (mEH) also induces dopaminergic neurotoxicity. It was demonstrated that inhibition of PKC modulates the expression of mEH. We investigated whether MA-induced PKCδ activation requires mEH induction in mice. MA treatment (8 mg/kg, i.p., × 4; 2 h interval) significantly enhanced the level of phosphorylated PKCδ in the striatum of wild type (WT) mice. Subsequently, treatment with MA resulted in significant increases in the expression of cleaved PKCδ and mEH. Treatment with MA resulted in enhanced interaction between PKCδ and mEH. PKCδ knockout mice exhibited significant attenuation of the enhanced mEH expression induced by MA. MA-induced hyperthermia, oxidative stress, proapoptotic potentials, and dopaminergic impairments were attenuated by PKCδ knockout or mEH knockout in mice. However, treating mEH knockout in mice with PKCδ inhibitor, rottlerin did not show any additive beneficial effects, indicating that mEH is a critical mediator of neurotoxic potential of PKCδ. Our results suggest that MA-induced PKCδ activation requires mEH induction as a downstream signaling pathway and that the modulation of the PKCδ and mEH interaction is important for the pharmacological intervention against MA-induced dopaminergic neurotoxicity.

Eckol Inhibits Particulate Matter 2.5-Induced Skin Keratinocyte Damage via MAPK Signaling Pathway

Toxicity of particulate matter (PM) towards the epidermis has been well established in many epidemiological studies. It is manifested in cancer, aging, and skin damage. In this study, we aimed to show the mechanism underlying the protective effects of eckol, a phlorotannin isolated from brown seaweed, on human HaCaT keratinocytes against PM_2.5-induced cell damage. First, to elucidate the underlying mechanism of toxicity of PM_2.5, we checked the reactive oxygen species (ROS) level, which contributed significantly to cell damage. Experimental data indicate that excessive ROS caused damage to lipids, proteins, and DNA and induced mitochondrial dysfunction. Furthermore, eckol (30 μM) decreased ROS generation, ensuring the stability of molecules, and maintaining a steady mitochondrial state. The western blot analysis showed that PM_2.5 promoted apoptosis-related protein levels and activated MAPK signaling pathway, whereas eckol protected cells from apoptosis by inhibiting MAPK signaling pathway. This was further reinforced by detailed investigations using MAPK inhibitors. Thus, our results demonstrated that inhibition of PM_2.5-induced cell apoptosis by eckol was through MAPK signaling pathway. In conclusion, eckol could protect skin HaCaT cells from PM_2.5-induced apoptosis via inhibiting ROS generation.

Effects of Molecular Hydrogen on Methamphetamine-Induced Neurotoxicity and Spatial Memory Impairment

Methamphetamine (METH) is a highly addictive stimulant, and METH exposure can induce irreversible neuronal damage and cause neuropsychiatric and cognitive disorders. The ever-increasing levels of METH abuse worldwide have necessitated the identification of effective intervention strategies to protect the brain against METH-induced neurotoxicity. The protective effects of molecular hydrogen on oxidative stress and related neurodegenerative diseases have been recently elucidated. Herein, we investigated whether treatment with molecular hydrogen ameliorated the METH-induced neurotoxicity and spatial learning and memory impairments. Male C57BL/6 mice received four intraperitoneal METH injections (10 mg/kg, 3-h interval), and stereotypic behaviors and hyperthermia were observed. After METH treatment and behavioral observation, the mice were returned to their home cages, where they received water or hydrogen-rich water (HRW) ad libitum for 7 days. We found that the molecular hydrogen delivered by ad libitum HRW consumption significantly inhibited the METH-induced spatial learning impairment and memory loss evidenced in the Barnes maze and Morris water maze tests. Furthermore, molecular hydrogen significantly restrained the neuronal damage in the hippocampus after high-dose METH exposure. Ad libitum HRW consumption also had an inhibitory effect on the METH-induced increase in the expression of Bax/Bcl-2, cleaved caspase-3, glucose-related protein 78 (GRP 78), CCAAT/enhancer-binding protein homologous protein (CHOP), and p-NF-kB p65 expression and elevation of interleukin (IL)-6 and tumor necrosis factor (TNF)-α levels in the hippocampus. These are the first findings to indicate that hydrogen might ameliorate METH-induced neurotoxicity and has a potential application in reducing the risk of neurodegeneration frequently observed in METH abusers.

Paris saponin VII extracted from trillium tschonoskii suppresses proliferation and induces apoptosis of human colorectal cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Saponins of many herbs could inhibit the growth of colorectal cancer cells. In the study, we investigated the effects of Paris saponin Ⅶ (PSⅦ), and elucidated its mechanism in colorectal carcinoma cells and a xenograft mouse model.

MATERIALS AND METHODS

HT-29 and HCT-116 cells were treated with different concentrations of PSⅦ (0-100 μM). The effects of PSⅦ on HCT-116 cells were assessed using a microarray. Then, apoptotic cells were detected by flow cytometric analysis and apoptosis related protein expression was evaluated by Western blot. A xenograft model of nude mice was used to assess the effect of PSⅦ in vivo.

RESULTS

MTT assay showed the IC₅₀ values of PSⅦ for growth inhibition of HT-29 and HCT-116 cells were 1.02 ± 0.05 μM and 3.50 ± 0.79 μM respectively. Edu assay demonstrated that PSⅦ effectively suppressed the growth of HT-29 and HCT-116 cells. Treatment with 0-3 μM PSⅦ not only triggered apoptosis, but also activated caspase-3 and caspase-9 of HT-29 and HCT-116 cells in a concentration dependent manner. In parallel to the alterations, Bax and Cyto-c expression increased while Bcl-2 decreased. In nude mice, PSⅦ reduced the tumor size and induced the apoptosis of tumor cells. PSVII could suppress IL-6-induced phosphorylation of STAT3 in vitro and blocked STAT3 phosphorylation in vivo.

CONCLUSION

Our results suggest that PSVII suppressed the activation of IL-6/STAT3 pathway, consequently suppressed the growth and proliferation and triggered the apoptosis of CRC cells. These findings indicate that PSⅦ might be an effective tumouristatic agent for the treatment of colorectal cancer.

Involvement of C/EBPβ-related signaling pathway in methamphetamine-induced neuronal autophagy and apoptosis

Methamphetamine (METH) is a widely abused illicit psychoactive drug. Our previous study has shown that CCAAT-enhancer binding protein β (C/EBPβ) is an important regulator in METH-induced neuronal autophagy and apoptosis. However, the detailed molecular mechanisms underlying this process remain poorly understood. Previous studies have demonstrated that DNA damage-inducible transcript 4 (DDIT4), Trib3 (tribbles pseudo kinase 3), alpha-synuclein (α-syn) are involved in METH-induced dopaminergic neurotoxicity. We hypothesized that C/EBPβ is involved in METH-induced DDIT4-mediated neuronal autophagy and Trib3-mediated neuronal apoptosis. We tested our hypothesis by examining the effects of silencing C/EBPβ, DDIT4, Trib3 or α-syn with small interfering ribonucleic acid (siRNA) on METH-induced autophagy and apoptosis in the human neuroblastoma SH-SY5Y cells. We also measured the levels of phosphorylated tuberous sclerosis complex 2 (TSC2) protein and Parkin protein level in SH-SY5Y cells. Furthermore, we demonstrated the effect of silencing C/EBPβ on METH-caused neurotoxicity in the striatum of rats by injecting LV-shC/EBPβ lentivirus using a stereotaxic positioning system. The results showed that METH exposure increased C/EBPβ, DDIT4 protein expression. Elevated DDIT4 expression raised up p-TSC2/TSC2 protein expression ratio, inhibited mTOR signaling pathway, activating cell autophagy. We also found that METH exposure increased the expression of Trib3, α-syn, decreased the Parkin protein expression. Lowering levels of Parkin raised up α-syn expression, which initiated mitochondrial apoptosis by down-regulating anti-apoptotic Bcl-2, followed by up-regulation of pro-apoptotic Bax, resulting in translocation of cytochrome c (cyto c), an apoptogenic factor, from the mitochondria to cytoplasm and activation of caspase-dependent pathways. These findings were supported by data showing METH-induced autophagy and apoptosis was significantly inhibited by silencing C/EBPβ, DDIT4, Trib3 or α-syn, or by Parkin over-expression. Based on the present data, a novel of mechanism on METH-induced cell toxicity is proposed, METH exposure increased C/EBPβ protein expression, triggered DDIT4/TSC2/mTOR signaling pathway, and evoked Trib3/Parkin/α-syn-related mitochondrial apoptotic signaling pathway. Collectively, these results suggest that C/EBPβ plays an important role in METH-triggered autophagy and apoptosis and it may be a potential target for therapeutics in METH-caused neurotoxicity.

Methiopropamine, a methamphetamine analogue, produces neurotoxicity via dopamine receptors

Methiopropamine (MPA) is structurally categorized as a thiophene ring-based methamphetamine (MA) derivative. Although abusive potential of MPA was recognized, little is known about the neurotoxic potential of MPA up to now. We investigated whether MPA induces dopaminergic neurotoxicity, and whether MPA activates a specific dopamine receptor. Here, we observed that treatment with MPA resulted in dopaminergic neurotoxicity in a dose-dependent manner. MPA treatment potentiated oxidative parameters (i.e., increases in the level of reactive oxygen species, 4-hydroxynonenal, and protein carbonyl), M1 phenotype-related microglial activity, and pro-apoptotic property (i.e., increases in Bax- and cleaved caspase-3-expressions, while a decrease in Bcl-2-expression). Moreover, treatment with MPA resulted in significant impairments in dopaminergic parameters [i.e., changes in dopamine level, dopamine turnover rate, tyrosine hydroxylase (TH) levels, dopamine transporter (DAT) expression, and vesicular monoamine transporter-2 (VMAT-2) expression], and in behavioral deficits. Both dopamine D1 receptor antagonist SCH23390 and D2 receptor antagonist sulpiride protected from these neurotoxic consequences. Therefore, our results suggest that dopamine D1 and D2 receptors simultaneously mediate MPA-induced dopaminergic neurodegeneration in mice via oxidative burdens, microgliosis, and pro-apoptosis.

Neuroinflammation in addiction: A review of neuroimaging studies and potential immunotherapies

Addiction is a worldwide public health problem and this article reviews scientific advances in identifying the role of neuroinflammation in the genesis, maintenance, and treatment of substance use disorders. With an emphasis on neuroimaging techniques, this review examines human studies of addiction using positron emission tomography to identify binding of translocator protein (TSPO), which is upregulated in reactive glial cells and activated microglia during pathological states. High TSPO levels have been shown in methamphetamine use but exhibits variable patterns in cocaine use. Alcohol and nicotine use, however, are associated with lower TSPO levels. We discuss how mechanistic differences at the neurotransmitter and circuit level in the neural effects of these agents and subsequent immune response may explain these observations. Finally, we review the potential of anti-inflammatory drugs, including ibudilast, minocycline, and pioglitazone, to ameliorate the behavioral and cognitive consequences of addiction.

Effect of methamphetamine on the fasting blood glucose in methamphetamine abusers

Methamphetamine is a popular psychostimulant worldwide which causes neurotoxicity and neuroinflammation. Although previous studies have characterized potential associations between addictive drugs and fasting blood glucose, the influence of methamphetamine on the blood glucose is still largely unknown. The present study was designed to investigate the change of fasting blood glucose of methamphetamine abusers and to confirm the impairment of liver and kidney. Fasting blood glucose was significantly decreased in methamphetamine abusers and in a high-fat diet mouse model with methamphetamine treatment discontinuation. Serum level of ALT, creatine kinase and creatinine were increased in methamphetamine abusers. Serum level of ALT and AST were increased in a high-fat diet mouse model after methamphetamine injection, but there was no significant difference in the anatomy of the liver and kidney in high-fat diet treated mice with or without methamphetamine. The levels of ALT and creatinine were also increased in the methamphetamine abusers. This study demonstrated that the level of glucose was decreased in methamphetamine abusers and in high-fat diet-fed mice after methamphetamine treatment discontinuation. The effect of methamphetamine on the levels of blood glucose may provide the evidence that methamphetamine abusers should be keep energy balance due to the low blood glucose.

The Main Molecular Mechanisms Underlying Methamphetamine- Induced Neurotoxicity and Implications for Pharmacological Treatment

Methamphetamine (METH) is a popular new-type psychostimulant drug with complicated neurotoxicity. In spite of mounting evidence on METH-induced damage of neural cell, the accurate mechanism of toxic effect of the drug on central nervous system (CNS) has not yet been completely deciphered. Besides, effective treatment strategies toward METH neurotoxicity remain scarce and more efficacious drugs are to be developed. In this review, we summarize cellular and molecular bases that might contribute to METH-elicited neurotoxicity, which mainly include oxidative stress, excitotoxicity, and neuroinflammation. We also discuss some drugs that protect neural cells suffering from METH-induced neurotoxic consequences. We hope more in-depth investigations of exact details that how METH produces toxicity in CNS could be carried out in future and the development of new drugs as natural compounds and immunotherapies, including clinic trials, are expected.

The Role of Mitochondria in Methamphetamine-induced inhibitory effects on osteogenesis of Mesenchymal Stem Cells

Methamphetamine (METH) abuse causes significant physical, psychological, and social concerns. Therefore, in this study, we investigated its effects on osteogenic differentiation of mesenchymal stem cells (MSCs). We found that METH dose-dependently affected MSCs viability. Upon osteogenic induction, the 3 and 30 µmol/l METH dosages without deleterious effects on MSCs viability resulted in the down-regulation of osteoblastic marker genes (Alp, Bglap, and Runx2), suppression of the protein expression of RUNX2, and decreased ALP activity and mineralization ability. Mitochondria are essential during osteogenesis of MSCs. Our analysis on mitochondrial function revealed that METH decreased ATP production, suppressed the oxygen consumption rate, and depolarized the mitochondrial membrane potential, but it had no significant effects on the protein expression of the five complexes on the respiratory chain. Additionally, METH could impair mitochondrial biogenesis, as demonstrated by decreased mtDNA and down-regulated biogenesis factors. Mitochondrial fusion regulators were also decreased at the mRNA and protein levels. However, mitochondrial fission and mitophagy were not affected. In conclusion, our study revealed that exposure to METH could result in decreased mitochondrial biogenesis and fusion as well as mitochondrial dysfunction, and thus it suppressed the osteogenesis of MSCs.

Ginsenoside Re protects methamphetamine-induced dopaminergic neurotoxicity in mice via upregulation of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated neurokinin 1 receptor

BACKGROUND

We previously reported that ginsenoside Re (GRe) attenuated against methamphetamine (MA)-induced neurotoxicity via anti-inflammatory and antioxidant potentials. We also demonstrated that dynorphin possesses anti-inflammatory and antioxidant potentials against dopaminergic loss, and that balance between dynorphin and substance P is important for dopaminergic neuroprotection. Thus, we examined whether GRe positively affects interactive modulation between dynorphin and substance P against MA neurotoxicity in mice.

METHODS

We examined changes in dynorphin peptide level, prodynorphin mRNA, and substance P mRNA, substance P-immunoreactivity, homeostasis in enzymatic antioxidant system, oxidative parameter, microglial activation, and pro-apoptotic parameter after a neurotoxic dose of MA to clarify the effects of GRe, prodynorphin knockout, pharmacological inhibition of κ-opioid receptor (i.e., nor-binaltorphimine), or neurokinin 1 (NK1) receptor (i.e., L-733,060) against MA insult in mice.

RESULTS

GRe attenuated MA-induced decreases in dynorphin level, prodynorphin mRNA expression in the striatum of wild-type (WT) mice. Prodynorphin knockout potentiated MA-induced dopaminergic toxicity in mice. The imbalance of enzymatic antioxidant system, oxidative burdens, microgliosis, and pro-apoptotic changes led to the dopaminergic neurotoxicity. Neuroprotective effects of GRe were more pronounced in prodynorphin knockout than in WT mice. Nor-binaltorphimine, a κ-opioid receptor antagonist, counteracted against protective effects of GRe. In addition, we found that GRe significantly attenuated MA-induced increases in substance P-immunoreactivity and substance P mRNA expression in the substantia nigra. These increases were more evident in prodynorphin knockout than in WT mice. Although, we observed that substance P-immunoreactivity was co-localized in NeuN-immunreactive neurons, GFAP-immunoreactive astrocytes, and Iba-1-immunoreactive microglia. NK1 receptor antagonist L-733,060 or GRe selectively inhibited microgliosis induced by MA. Furthermore, L-733,060 did not show any additive effects against GRe-mediated protective activity (i.e., antioxidant, antimicroglial, and antiapoptotic effects), indicating that NK1 receptor is one of the molecular targets of GRe.

CONCLUSIONS

Our results suggest that GRe protects MA-induced dopaminergic neurotoxicity via upregulatgion of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated NK1 R.

Intranasal insulin treatment restores cognitive deficits and insulin signaling impairment induced by repeated methamphetamine exposure

Long-term use of methamphetamine (MA) causes a broad range of cognitive deficits. Recently, it has been reported insulin signaling and mitochondrial biogenesis are involved in cognitive processes. This study aimed to examine whether MA induces cognitive deficits concomitant with insulin signaling impairment and mitochondrial dysfunctions and also intranasal (IN) insulin treatment can reverse cognitive deficits caused by MA. Rats were repeatedly treated with increasing doses of MA (1-10 mg/kg) twice a day for 10 days, and their cognitive functions were assessed using Y-maze, novel object recognition and passive avoidance tasks. The expression of components involved in insulin signaling (IR/IRS2/PI3K/Akt/GSK3β) and mitochondrial biogenesis (PGC-1α, NRF1, and TFAM) was measured in the hippocampus. Therapeutic effects of IN insulin delivery (0.5- IU/day, for 7 days after MA discontinuation) were also investigated in MA-treated animals. Our results showed that repeated MA exposure induced cognitive deficits, and led to insulin signaling impairment and mitochondrial dysfunction. Interestingly, IN insulin treatment reduced MA-induced cognitive impairments possibly through activating insulin signaling, particularly PI3K/Akt/GSK3β pathway, and mitochondrial biogenesis. Thus, insulin and insulin signaling pathway can be considered as useful targets for the treatment of abnormalities associated with MA abuse.