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-SY5Y cells and C57BL/6J 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-SY5Y cells. Additional experimental groups of SH-SY5Y 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: C57BL/6J 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), 5G4, 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 5G4. 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 5G4 increased; nT39 α-Syn, nitric oxide synthase, cleaved caspase-3, and cleaved PARP expression increased in the cultures of SH-SY5Y cells and in the brains of C57BL/6J 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-SY5Y cells and C57BL/6J mice. These results suggest that nT39 α-Syn aggregation is involved in methamphetamine neurotoxicity.

SUMOylation of Alpha-Synuclein Influences on Alpha-Synuclein Aggregation Induced by Methamphetamine.

Methamphetamine (METH) is an illegal and widely abused psychoactive stimulant. METH abusers are at high risk of neurodegenerative disorders, including Parkinson's disease (PD). Previous studies have demonstrated that METH causes alpha-synuclein (α-syn) aggregation in the both laboratory animal and human. In this study, exposure to high METH doses increased the expression of α-syn and the small ubiquitin-related modifier 1 (SUMO-1). Therefore, we hypothesized that SUMOylation of α-syn is involved in high-dose METH-induced α-syn aggregation. We measured the levels of α-syn SUMOylation and these enzymes involved in the SUMOylation cycle in SH-SY5Y human neuroblastoma cells (SH-SY5Y cells), in cultures of C57 BL/6 primary mouse neurons and in brain tissues of mice exposure to METH. We also demonstrated the effect of α-syn SUMOylation on α-syn aggregation after METH exposure by overexpressing the key enzyme of the SUMOylation cycle or silencing SUMO-1 expression in vitro. Then, we make introduced mutations in the major SUMOylation acceptor sites of α-syn by transfecting a lentivirus containing the sequence of WT α-syn or K96/102R α-syn into SH-SY5Y cells and injecting an adenovirus containing the sequence of WT α-syn or K96/102R α-syn into the mouse striatum. Levels of the ubiquitin-proteasome system (UPS)-related makers ubiquitin (Ub) and UbE1, as well as the autophagy-lysosome pathway (ALP)-related markers LC3, P62 and lysosomal associated membrane protein 2A (LAMP2A), were also measured in SH-SY5Y cells transfected with lentivirus and mice injected with adenovirus. The results showed that METH exposure decreases the SUMOylation level of α-syn, although the expression of α-syn and SUMO-1 are increased. One possible cause is the reduction of UBC9 level. The increase in α-syn SUMOylation by UBC9 overexpression relieves METH-induced α-syn overexpression and aggregation, whereas the decrease in α-syn SUMOylation by SUMO-1 silencing exacerbates the same pathology. Furthermore, mutations in the major SUMOylation acceptor sites of α-syn also aggravate α-syn overexpression and aggregation by impairing degradation through the UPS and the ALP in vitro and in vivo. These results suggest that SUMOylation of α-syn plays a fundamental part in α-syn overexpression and aggregation induced by METH and could be a suitable target for the treatment of neurodegenerative diseases.

[Snitrosylating protein disulphide isomerase mediates increased expression of α synuclein caused by methamphetamine in mouse brain].

OBJECTIVE: To investigate the role of Snitrosylation of protein disulphide isomerasec in methamphetamine (METH)-induced expression of alpha synuclein (αSN) in mouse hippocampus and striatum neurons. METHODS: Forty C57BL/6 mice were randomized equally into saline control group, METH group, L-NNA (a NOS inhibitor) group and L-NNA plus METH group. All the agents were injected intraperitoneally at an interval of 12 h, and a total of 8 injections were administered; in L-NNA plus METH group, METH was injected 30 min after LNNA in each treatment. Western Blotting was used to detect the expression of nitric oxide synthase (NOS), αSN, PDI and Snitrosylation of protein disulphide isomerase (PDI-SNO) in the hippocampus and striatum of the mice, and nitric oxide (NO) levels were determined using a NO assay kit. RESULTS: In METH group, the levels of NOS, PDISNO, αSN and NO all increased significantly compared with those in the control group (P<0.05). Combined treatment with L-NNA and METH, compared with METH alone, resulted in significantly lowered expression of NOS, NO, PDI-SNO and αSN in the hippocampus and striatum of the mice (all P<0.05). No significant differences were found in NOS, NO, PDI-SNO or αSN expressions among METH+L-NNA, L-NNA and control groups (P>0.05). CONCLUSION: METH induces the activation of NOS and increases NO level to cause the occurrence of PDI-SNO, leading subsequently to increased expression of αSN in mouse striatum and hippocampus. L-NNA, the inhibitor of NOS, can partly relieve nervous system toxicity induced by METH.

[Effect of methamphetamine exposure on S-nitrosylation of protein disulphide isomerase in PC12 cells].

OBJECTIVE: To study the effect of methamphetamine (METH) exposure on S-nitrosylation of protein disulphide isomerase and the neurotoxicity of METH in PC12 cells. METHODS: PC12 cells were exposed to different concentrations of METH, and the cell viability was assessed using the cell-counting kit-8. PC12 cells exposed to METH in the presence of the NOS inhibitor N-nitro-L-arginine (L-NNA) were examined for cell viability and S-nitrosylation of protein disulphide isomerase using the biotin-switch method, and the changes in cell morphology were examined with HE staining. RESULTS: METH exposure obviously decreased the cell viability and increased S-nitrosylation of protein disulphide isomerase, and the effect of METH was obviously inhibited by L-NNA treatment. CONCLUSION: METH can cause obvious neurotoxicity and promote S-nitrosylation of protein disulphide isomerase in PC12 cells.

[Polymorphism analysis of 20 autosomal short-tandem repeat loci in southern Chinese Han population].

OBJECTIVE: To evaluate the value of PowerPlex®21 System (Promega) and study the genetic polymorphism of its 20 short-tandem repeat (STR) loci in southern Chinese Han population. METHODS: We conducted genotyping experiments using PowerPlex®21 System on 20 autosomal STR loci (D3S1358, D1S1656, D6S1043, D13S317, Penta E, D16S539, D18S51, D2S1338, CSF1PO, Penta D, TH01, vWA, D21S11, D7S820, D5S818, TPOX, D8S1179, D12S391, D19S433 and FGA) in 2367 unrelated Chinese Han individuals living in South China. The allele frequencies and parameters commonly used in forensic science were statistically analyzed in these individuals and compared with the reported data of other populations. RESULTS: The PowerPlex®21 System had a power of discrimination (PD) ranging from 0.7839 to 0.9852 and a power of exclusion (PE) ranging from 0.2974 to 0.8099 for the 20 loci. No significant deviation from Hardy-Weinberg expectations was found for all the loci except for D5S818. This southern Chinese Han population had significant differences in the allele frequencies from 8 ethnic groups reported in China, and showed significant differences at 8 to 20 STR foci from 5 foreign populations. The allele frequency at the locus D1S1656 in this southern Chinese Han population differed significantly from those in the 5 foreign populations and from 3 reported Han populations in Beijing, Zhejiang Province and Fujian Province of China. The neighbor-joining phylogenetictree showed clustering of all the Asian populations in one branch, while the northern Italian and Argentina populations clustered in a separate branch. This southern Chinese Han population had the nearest affinity with the Yi ethnic population in Yunnan Province of China. CONCLUSION: The 20 STR loci are highly polymorphic in this southern Chinese Han population, suggesting the value of this set of STR loci in forensic personal identification, paternity testing and anthropological study.

S-Nitrosylating protein disulphide isomerase mediates α-synuclein aggregation caused by methamphetamine exposure in PC12 cells.

Methamphetamine (METH) belongs to Amphetamine-type stimulants, METH abusers are at high risk of neurodegenerative disorders, including Parkinson's disease (PD). However, there are still no effective treatments to METH-induced neurodegeneration because its mechanism remains unknown. In order to investigate METH's neurotoxic mechanism, we established an in vitro PD pathology model by exposing PC12 cells to METH. We found the expression of nitric oxide synthase (NOS), nitric oxide (NO) and α-synuclein (α-syn) was significantly increased after METH treatment for 24h, in addition, the aggregattion of α-syn and the S-nitrosylation of protein disulphideisomerase(PDI) were also obviously enhanced. When we exposed PC12 cells to the NOS inhibitor N-nitro-L-arginine(L-NNA) with METH together, the L-NNA obviously inhibited these changes induced by METH. While when we exposed PC12 cells to the precursor of NO L-Arginine together with METH, the L-Arginine resulted in the opposite effect compared to L-NNA. And when we knocked down the PDI gene, the L-NNA did not have this effect. Therefore, PDI plays a significant role in neurological disorders related to α-syn aggregation, and it suggests that PDI could be as a potential target to prevent METH-induced neurodegeneration.

[Comparative proteomic analysis of the prefrontal cortex between normal and heroin-addicted rats].

OBJECTIVE: To obtain two-dimensional gel electrophoresis maps of the prefrontal cortex (PFC) proteins of normal and heroin-addicted rats for identifying the differentially expressed proteins in the addicted rats. METHODS: Rat models of heroin addiction were established, and the proteins in the PFC underwent two-dimensional gel electrophoresis with immobiline pH gradient isoelectric focusing as the first and vertical SDS-PAGE as the second dimension. ImageMaster 2D 5.0 analysis software, matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) or MALDI-TOF-TOF-MS as well as NCBInr database searching were performed to separate and identify the proteome in the rat PFC. RESULTS: Seven protein spots to represent 5 proteins were identified by PMF and MALDI-TOF-TOF-MS. Among those proteins, glucose-regulated protein (58 kD) and 26 S proteasome subunit p40.5 existed only in heroin-addicted rats, in which ATP synthase D chain was down-regulated. Ndufa10 and Eno1 were present in both groups, but their molecular mass and pI were different. CONCLUSION: Immobilized pH gradient two-dimensional gel electrophoresis allows good reproducibility in separation and identification of the proteome in the PDF of heroin-addicted rats, which facilitates further investigation of pathogenic mechanisms of heroin addiction and central nerve injury.

The effect of cerebral lymphatic blockage on cortex regional cerebral blood flow and somatosensory evoked potential.

Disputes on the significance of cerebral lymphatic drainage pathways under physiological and pathophysiological conditions still exist. The purpose of this experiment is to investigate the influence of cerebral lymphatic blockage on cerebral blood flow and cortex somatosensory evoked potential. Wistar rat cerebral lymphatic blockage models were established by removing cervical lymphatic nodes after obstructing their input and output tubes. Animals were divided randomly into a sham-operated group and a cerebral lymphatic-blockage group. Regional cerebral blood flow in different regions of the cortex were detected using a laser-Doppler flowmeter probe, and cortex evoked potential was detected using an electromyogram and evoked potential instrument before the operation, then 1 day, 5 days and 7 days after the operation. Results showed that the sham operation had no obvious effect on regional cerebral blood flow and the latency of somatosensory evoked potential. From 1 day to 7 days after cerebral lymphatic obstruction, regional cerebral blood flow in different cortical regions decreased markedly (P<0.01). Latency of somatosensory evoked potential was significantly delayed on the 5th and 7th day after blockage of cerebral lymphatic drainage (P<0.01). We concluded that cerebral lymphatic drainage may play an important role in maintaining the equilibrium of the internal environment of the brain, and blockage of this pathway results in cerebral ischemia.

Alleviation of brain edema by L-arginine following experimental subarachnoid hemorrhage in a rat model.

Decreased levels of nitric oxide play a role in the development of cerebral ischemia secondary to subarachnoid hemorrhage (SAH). The protective effect of L-arginine on brain edema following SAH was investigated in this study. Rats were divided randomly into a sham-operated, a SAH+saline group and a SAH+L-arginine group. At different time points, brain water content was determined using the wet and dry weight compared method. Brain sodium content, potassium content and calcium content were detected using an atomic absorption spectral photometer. Somatosensory evoked potentials (SEP) were also detected. It was found that rat SAH models were successfully replicated. In the SAH+saline group, brain water and sodium content were significantly higher at 6 h and 24 h than those in the sham-operated group, while brain potassium content was statistically lower than that in the sham-operated group. Brain calcium content increased from 1 h to 24 h after induction of SAH. SEP latency progressively delayed. In the SAH+L-arginine group, increases in brain water content, sodium content and calcium content, as well as decreases in brain potassium content, were not as obvious as in the SAH+saline group. L-arginine partly prevented a delay in SEP latency. In conclusion, L-arginine, a substrate of nitric oxide synthesis, may relieve brain edema in rats with experimental SAH.