Possible repair mechanisms of renin-angiotensin system inhibitors, matrix metalloproteinase-9 inhibitors and protein hormones on methamphetamine-induced neurotoxicity

Protective effect of melatonin against methamphetamine-induced attention deficits through miR-181/SIRT1 axis in the prefrontal cortex

INTRODUCTION

Methamphetamine (METH) is an addictive psychostimulant with deleterious effects on the central nervous system. Chronic use of METH in high doses impairs cognition, attention and executive functions, but the underlying mechanisms are still unclear. Sirtuin 1 (SIRT1) is a post-translational regulator that is downregulated following METH neurotoxicity. Melatonin is a neuroprotective hormone that enhances mitochondrial metabolism. Here, we evaluated the effect of melatonin on METH-induced attention deficits disorder and the involvement of the miR-181/SIRT1 axis in melatonin neuroprotection.

METHODS AND RESULTS

METH at a dose of 5 mg/kg was injected for 21 consecutive days. The animals were assigned to receive either melatonin or the vehicle after METH injections. Attention levels were evaluated with abject-based attention test. In the prefrontal cortex, the expression levels of miR-181a-5p, SIRT1, p53 and CCAR2, as well as the mtDNA copy numbers were evaluated using qRT-PCR and western blotting. The outcomes revealed that melatonin treatment following METH injections improved METH-induced attention deficits. METH toxicity can be associated with changes in the miR-181/SIRT1 axis, elevated levels of p53 and COXII, and decreased levels of mtDNA in the prefrontal cortex of adult rats. Interestingly, administration of melatonin can improve the expression of these molecules and reduces the toxic effects of METH.

CONCLUSION

Melatonin ameliorated the neurotoxicity of METH in the prefrontal cortex and the miR-181/SIRT1 axis is involve in the protective effects of melatonin. However, melatonin can be potentially administrated to improve attention impairment in METH use disorders.

Variations in the oral microbiome and metabolome of methamphetamine users

Drug addiction can seriously damage human physical and mental health, while detoxification is a long and difficult process. Although studies have reported changes in the oral microbiome of methamphetamine (METH) users, the role that the microbiome plays in the process of drug addiction is still unknown. This study aims to explore the function of the microbiome based on analysis of the variations in the oral microbiome and metabolome of METH users. We performed the 16S rRNA sequencing analysis based on the oral saliva samples collected from 278 METH users and 105 healthy controls (CTL). In addition, the untargeted metabolomic profiling was conducted based on 220 samples. Compared to the CTL group, alpha diversity was reduced in the group of METH users and the relative abundances of Peptostreptococcus and Gemella were significantly increased, while the relative abundances of Campylobacter and Aggregatibacter were significantly decreased. Variations were also detected in oral metabolic pathways, including enhanced tryptophan metabolism, lysine biosynthesis, purine metabolism, and steroid biosynthesis. Conversely, the metabolic pathways of porphyrin metabolism, glutathione metabolism, and pentose phosphate were significantly reduced. It was speculated that four key microbial taxa, i.e., Peptostreptococcus, Gemella, Campylobacter, and Aggregatibacter, could be involved in the toxicity and addiction mechanisms of METH by affecting the above metabolic pathways. It was found that with the increase of drug use years, the content of tryptamine associated with neuropsychiatric disorders was gradually increased. Our study provides novel insights into exploring the toxic damage and addiction mechanisms underlying the METH addiction.IMPORTANCEIt was found that with the increase of drug use years, the content of tryptamine associated with neuropsychiatric disorders gradually increased. The prediction models based on oral microbiome and metabolome could effectively predict the methamphetamine (METH) smoking. Our study provides novel insights into the exploration of the molecular mechanisms regulating the toxic damage and addiction of METH as well as new ideas for early prevention and treatment strategies of METH addiction.

Methamphetamine induced neurotoxic diseases, molecular mechanism, and current treatment strategies

Methamphetamine (MA) is a extremely addictive psychostimulant drug with a significant abuse potential. Long-term MA exposure can induce neurotoxic effects through oxidative stress, mitochondrial functional impairment, endoplasmic reticulum stress, the activation of astrocytes and microglial cells, axonal transport barriers, autophagy, and apoptosis. However, the molecular and cellular mechanisms underlying MA-induced neurotoxicity remain unclear. MA abuse increases the chances of developing neurotoxic conditions such as Parkinson's disease (PD), Alzheimer's disease (AD) and other neurotoxic diseases. MA increases the risk of PD by increasing the expression of alpha-synuclein (ASYN). Furthermore, MA abuse is linked to high chances of developing AD and subsequent neurodegeneration due to biological variations in the brain region or genetic and epigenetic variations. To date, there is no Food and Drug Administration (FDA)-approved therapy for MA-induced neurotoxicity, although many studies are being conducted to develop effective therapeutic strategies. Most current studies are now focused on developing therapies to diminish the neurotoxic effects of MA, based on the underlying mechanism of neurotoxicity. This review article highlights current research on several therapeutic techniques targeting multiple pathways to reduce the neurotoxic effects of MA in the brain, as well as the putative mechanism of MA-induced neurotoxicity.

Central nervous system stimulants promote nerve cell death under continuous hypoxia

Intake of central nervous system (CNS) stimulants causes hypoxia and brain edema, which results in nerve cell death. However, no study has yet investigated the direct and continuous effects on nerve cells of CNS stimulants under hypoxia. Thus, based on autopsy cases, the effects of CNS stimulant drugs on the CNS were examined. The pathological changes in cultured nerve cells when various CNS stimulants were added under a hypoxic condition were also investigated. Five groups (Group A, stimulants; Group B, stimulants with psychiatric drugs; Group C, caffeine; Group D, psychiatric drugs; and Group E, no drugs) according to the detected drugs in autopsy cases were compared, and brain edema was evaluated using morphological findings. Furthermore, the number of dead cultured nerve cells was counted after the addition of drugs (4-aminopyridine (4-AP), caffeine, and ephedrine) under hypoxia (3% O2). Staining with anti-receptor-interacting protein 3 (RIP3) and other associated stains was also performed to investigate the neuronal changes in the brain. Group A showed significantly more brain edema than the other groups. In the culture experiments, the ratio of nerve cell death after the addition of 4-AP was the highest in the hypoxic condition. Groups with stimulants detected were stained more strongly by RIP3 immunostaining than by other staining. Addition of stimulants to cultured nerve cells in a persistent hypoxic condition led to severe cytotoxicity and nerve cell death. These findings suggest that necroptosis is involved in nerve cell death due to the addition of CNS stimulants in the hypoxic condition.