Implications of alpha-synuclein nitration at tyrosine 39 in methamphetamine-induced neurotoxicity in vitro and in vivo

Methamphetamine is an amphetamine-type psychostimulant that can damage dopaminergic neurons and cause characteristic pathological changes similar to neurodegenerative diseases such as Parkinson's disease. However, its specific mechanism of action is still unclear. In the present study, we established a Parkinson's disease pathology model by exposing SH-SY5 Y cells and C57 BL/6 J mice to methamphetamine. In vitro experiments were performed with 0, 0.5, 1.0, 1.5, 2.0 or 2.5 mM methamphetamine for 24 hours or 2.0 mM methamphetamine for 0-, 2-, 4-, 8-, 16-, and 24-hour culture of SH-SY5 Y cells. Additional experimental groups of SH-SY5 Y cells were administered a nitric oxide inhibitor, 0.1 mM N-nitro-L-arginine, 1 hour before exposure to 2.0 mM methamphetamine for 24 hours. In vivo experiments: C57 BL/6 J mice were intraperitoneally injected with N-nitro-L-arginine(8 mg/kg), eight times, at intervals of 12 hours. Methamphetamine 15 mg/kg was intraperitoneally injected eight times, at intervals of 12 hours, but 0.5-hour after each N-nitro-L-arginine injection in the combined group. Western blot assay was used to determine the expression of nitric oxide synthase, α-synuclein(α-Syn), 5 G4, nitrated α-synuclein at the residue Tyr39(nT39 α-Syn), cleaved caspase-3, and cleaved poly ADP-ribose polymerase(PARP) in cells and mouse brain tissue. Immunofluorescence staining was conducted to measure the positive reaction of NeuN, nT39 α-Syn and 5 G4. Enzyme linked immunosorbent assay was performed to determine the dopamine levels in the mouse brain. After methamphetamine exposure, α-Syn expression increased; the aggregation of α-Syn 5 G4 increased; nT39 α-Syn, nitric oxide synthase, cleaved caspase-3, and cleaved PARP expression increased in the cultures of SH-SY5 Y cells and in the brains of C57 BL/6 J mice; and dopamine levels were reduced in the mouse brain. These changes were markedly reduced when N-nitro-L-arginine was administered with methamphetamine in both SH-SY5 Y cells and C57 BL/6 J mice. These results suggest that nT39 α-Syn aggregation is involved in methamphetamine neurotoxicity.

Protective effect of alpha-synuclein knockdown on methamphetamine-induced neurotoxicity in dopaminergic neurons

The over-expression of α-synuclein is a major factor in the death of dopaminergic neurons in a methamphetamine-induced model of Parkinson’s disease. In the present study, α-synuclein knockdown rats were created by injecting α-synuclein-shRNA lentivirus stereotaxically into the right striatum of experimental rats. At 2 weeks post-injection, the rats were injected intraper-itoneally with methamphetamine to establish the model of Parkinson’s disease. Expression of α-synuclein mRNA and protein in the right striatum of the injected rats was significantly down-regulated. Food intake and body weight were greater in α-synuclein knockdown rats, and water intake and stereotyped behavior score were lower than in model rats. Striatal dopamine and tyrosine hydroxylase levels were significantly elevated in α-synuclein knockdown rats. Moreover, superoxide dismutase activity was greater in α-synuclein knockdown rat striatum, but the levels of reactive oxygen species, malondialdehyde, nitric oxide synthase and nitrogen monoxide were lower compared with model rats. We also found that α-synuclein knockdown inhibited metham-phetamine-induced neuronal apoptosis. These results suggest that α-synuclein has the capacity to reverse methamphetamine-induced apoptosis of dopaminergic neurons in the rat striatum by inhibiting oxidative stress and improving dopaminergic system function.

Distinguished biological adaptation architecture aggravated population differentiation of Tibeto-Burman-speaking people

Tibeto-Burman(TB)people have endeavored to adapt to the hypoxic,cold,and high-UV high-altitude environments in the Tibetan Plateau and complex disease exposures in lowland rainforests since the late Paleolithic period.However,the full landscape of genetic history and biological adaptation of geographically diverse TB-speaking people,as well as their interaction mechanism,remain unknown.Here,we generate a whole-genome meta-database of 500 individuals from 39 TB-speaking populations and present a comprehensive landscape of genetic diversity,admixture history,and differentiated adaptative features of geographically different TB-speaking people.We identify genetic differentiation related to geography and language among TB-speaking people,consistent with their differentiated admixture process with incoming or indigenous ancestral source populations.A robust genetic connection between the Tibetan-Yi corridor and the ancient Yellow River people supports their Northern China origin hypothesis.We finally report substructure-related differentiated biological adaptative signatures between highland Tibetans and Loloish speakers.Adaptative signatures associated with the physical pigmentation(EDAR and SLC24A5)and metabolism(ALDH9A1)are identified in Loloish people,which differed from the high-altitude adaptative genetic architecture in Tibetan.TB-related genomic resources provide new insights into the genetic basis of biological adaptation and better reference for the anthropologically informed sampling design in biomedical and genomic cohort research.

Perspectives on the Construction of Forensic Autopsy Laboratories Designed to Handle Infectious Diseases

Coronavirus disease 2019 has already infected tens of thousands of people in China.The existing autopsy laboratories are not qualified to perform autopsies on individuals confirmed or suspected to have died from an infectious disease.When dealing with corpses with uncertain health conditions or unknown contact with a pathogen,the forensic medical practitioners face severe risks of being infected.To meet the requirements of performing autopsies on such bodies,ensure the health and safety of forensic medical practitioners,and study the pathophysiological changes of infected patients,it is necessary to improve the construction requirements and regulations for forensic autopsy laboratories.

Characteristics of Mechanical Asphyxia:A Retrospective Epidemiological Study in Two Developed Cities in China

Background:Mechanical asphyxia(MA)is multi-classified.Some epidemiological characteristics are shared and the others different among different MA types.Aims and Objectives:To reveal the characteristics of different types of MA and provide reference data for forensic identification of MA.Materials and Methods:We analyzed 913 cases to reveal the epidemiological characteristics of MA in Dongguan and Guangzhou,China.Results:Seven types of MA were identified and strangulation accounted for up to 89.2%.Those aged 20-29 were the most susceptible to all types,except for traumatic and positional asphyxia.Suicide accounted for 96.6%of hanging cases,and accident was the main manner of death in cases of choking,traumatic,and positional asphyxia.Homicide was the most common in cases of ligature strangulation(LS),manual strangulation(MS),smothering,and asphyxia concomitant with lethal mechanical injury.The homicide rate in LS was positively correlated with the rate of female victims(P<0.001,OR=21.14).In MS,the ratio of female:male was 101:15 in homicide.Compared to native residents,migrant workers were more likely to suffer from LS and MS.Rope was used in 50.8%of hanging cases,while LS tools were evenly distributed.Ligature marks were mostly found above the thyroid cartilage in both hanging and LS cases.The U shaped marks were shown in 51.01%of hanging cases but absent in LS cases.In LS,ligature marks completely encircling the neck,discontinuous marks,as well as≥two marks,were more(P<0.001)than in hanging.In LS and MS cases,abrasion and subcutaneous hemorrhages on the neck were more frequent than in hanging cases(P=0.004 and P<0.001),but the difference in frequency of blister marks was opposite(P<0.001).Conclusion:In summary,this study revealed the epidemiological characteristics of the MA cases in Guangzhou and Dongguan cities.The characteristics of death scene and autopsy findings are important in differentiation of different types of MA,especially between suicide and homicide.