Hypersensitivity of DJ-1-deficient mice to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP) and oxidative stress

Mutations of the DJ-1 (PARK7) gene are linked to familial Parkinson's disease. We used gene targeting to generate DJ-1-deficient mice that were viable, fertile, and showed no gross anatomical or neuronal abnormalities. Dopaminergic neuron numbers in the substantia nigra and fiber densities and dopamine levels in the striatum were normal. However, DJ-1-/- mice showed hypolocomotion when subjected to amphetamine challenge and increased striatal denervation and dopaminergic neuron loss induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine. DJ-1-/-embryonic cortical neurons showed increased sensitivity to oxidative, but not nonoxidative, insults. Restoration of DJ-1 expression to DJ-1-/- mice or cells via adenoviral vector delivery mitigated all phenotypes. WT mice that received adenoviral delivery of DJ-1 resisted 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine-induced striatal damage, and neurons overexpressing DJ-1 were protected from oxidative stress in vitro. Thus, DJ-1 protects against neuronal oxidative stress, and loss of DJ-1 may lead to Parkinson's disease by conferring hypersensitivity to dopaminergic insults.     

黑色素对神经细胞DJ-1基因表达的影响

目的探讨氧化应激对神经黑色素（NM）诱导的多巴胺能神经元细胞或神经胶质细胞DJ-1基因表达的影响。方法选择人类神经元细胞（SK—N-SH）和神经胶质细胞（U373）作为细胞模型,将Fenton试剂（FR）作用于加有人类神经黑色素（hNM）、多巴胺黑色素（DAM）或铁螯合剂去铁胺（DFO）的细胞SK—N-SH或U373中,提取总RNA,用实时定量PCR法观察DJ-1表达的改变。结果在SK-N—SH细胞中,经过FR、DAM和FR＋DAM处理后,DJ-1的基因表达显著升高,而FR＋hNM处理后则无统计学变化;含有DFO处理的细胞与不含DFO处理的细胞比较,DJ-1的基因表达降低（P〈0．05）。在U373细胞中,经FR、NM、DAM和FR＋DAM处理后,DJ-1基因表达明显增高（P〈0．05）。结论DJ-1对细胞有保护作用;hNM生理条件下保护细胞,但在铁浓度升高时对细胞有毒害作用。     

Mutational analysis of DJ-1 in Drosophila implicates functional inactivation by oxidative damage and aging

Inherited mutations in PARK7, the gene encoding DJ-1, are associated with loss of protein function and early-onset parkinsonism. Like human DJ-1 (hDJ-1), Drosophila DJ-1b protects against oxidative insult and is modified with oxidation. We demonstrate that hDJ-1 rescues flies mutant for DJ-1b, and that a conserved cysteine residue in the fly protein (C104, analogous to C106 in hDJ-1) is critical for biological antioxidant function in vivo. Targeted mutagenesis suggests that modification of DJ-1b at this residue inactivates the protective activity of the protein against oxidative stress. Further studies show that DJ-1 modification increases dramatically with age in flies, mice, and humans, with aged flies showing strikingly increased susceptibility to oxidative stress and markedly enhanced DJ-1b modification upon oxidative challenge. Overoxidation of DJ-1 with age and exposure to oxidative toxins may lead to inactivation of DJ-1 function, suggesting a role in susceptibility to sporadic Parkinson's disease.     

红景天苷的神经保护作用

体内外动物模型实验发现,红景天苷对多种原因引起的各种神经细胞和脑组织损伤均有保护作用.其神经保护作用机制涉及多个方面:(1)通过对抗氧化应激、防止细胞内Ca2+超载、抑制胱冬酶-3活化以及抑制缺氧诱导的淀粉样前体蛋白异常代谢,保护神经元免遭凋亡性损伤;(2)促进干细胞定向分化为神经细胞,诱导神经发生;(3)促进红细胞生...     

红景天苷的神经保护作用

体内外动物模型实验发现，红景天苷对多种原因引起的各种神经细胞和脑组织损伤均有保护作用。其神经保护作用机制涉及多个方面：（1）通过对抗氧化应激、防止细胞内Ca2＋超载、抑制胱冬酶-3活化以及抑制缺氧诱导的淀粉样前体蛋白异常代谢，保护神经元免遭凋亡性损伤；（2）促进干细胞定向分化为神经细胞，诱导神经发生；（3）促进红细胞生成素刺激成红细胞分化为红细胞，并降低脑血管阻力，改善脑缺血缺氧。红景天苷有望用于脑缺血性和神经变性疾病（如脑梗死、老年性痴呆、帕金森病、肌萎缩性脊髓侧索硬化和糖尿病性脑病等）的防治。     

The Parkinson's disease protein DJ-1 is neuroprotective due to cysteine-sulfinic acid-driven mitochondrial localization

Loss-of-function DJ-1 mutations can cause early-onset Parkinson's disease. The function of DJ-1 is unknown, but an acidic isoform accumulates after oxidative stress, leading to the suggestion that DJ-1 is protective under these conditions. We addressed whether this represents a posttranslational modification at cysteine residues by systematically mutating cysteine residues in human DJ-1. WT or C53A DJ-1 was readily oxidized in cultured cells, generating a pI 5.8 isoform, but an artificial C106A mutant was not. We observed a cysteine-sulfinic acid at C106 in crystalline DJ-1 but no modification of C53 or C46. Oxidation of DJ-1 was promoted by the crystallization procedure. In addition, oxidation-induced mitochondrial relocalization of DJ-1 and protection against cell death were abrogated in C106A but not C53A or C46A. We suggest that DJ-1 protects against neuronal death, and that this is signaled by acidification of the key cysteine residue, C106.     

Inactivation of Drosophila DJ-1 leads to impairments of oxidative stress response and phosphatidylinositol 3-kinase/Akt signaling

Parkinson's disease (PD) is the most common movement disorder characterized by dopaminergic dysfunction and degeneration. The cause of most PD cases is unknown, although postmortem studies have implicated the involvement of oxidative stress. The identification of familial PD-associated genes offers the opportunity to study mechanisms of PD pathogenesis in model organisms. Here, we show that DJ-1A, a Drosophila homologue of the familial PD-associated gene DJ-1, plays an essential role in oxidative stress response and neuronal maintenance. Inhibition of DJ-1A function through RNA interference (RNAi) results in cellular accumulation of reactive oxygen species, organismal hypersensitivity to oxidative stress, and dysfunction and degeneration of dopaminergic and photoreceptor neurons. To identify other genes that may interact with DJ-1A in regulating cell survival, we performed genetic interaction studies and identified components of the phosphatidylinositol 3-kinase (PI3K)/Akt-signaling pathway as specific modulators of DJ-1A RNAi-induced neurodegeneration. PI3K signaling suppresses DJ-1A RNAi phenotypes at least in part by reducing cellular reactive oxygen species levels. Consistent with the genetic interaction results, we also found reduced phosphorylation of Akt in DJ-1A RNAi animals, indicating an impairment of PI3K/Akt signaling by DJ-1A down-regulation. Together with recent findings in mammalian systems, these results implicate impairments of PI3K/Akt signaling and oxidative stress response in DJ-1-associated disease pathogenesis. We also observed impairment of PI3K/Akt signaling in the fly parkin model of PD, hinting at a common molecular event in the pathogenesis of PD. Manipulation of PI3K/Akt signaling may therefore offer therapeutic benefits for the treatment of PD.     

Amelioration of neurodegenerative changes in cellular and rat models of diabetes-related Alzheimer's disease by exendin-4

Growing evidence suggests that type 2 diabetes mellitus (DM) is associated with age-dependent Alzheimer's disease (AD), the latter of which has even been considered as type 3 diabetes. Several physiopathological features including hyperglycemia, oxidative stress, and dysfunctional insulin signaling relate DM to AD. In this study, high glucose-, oxidative stress-induced neuronal injury and intracerebroventricular-streptozotocin (ICV-STZ) animals as the possible models for diabetes-related AD were employed to investigate the effects of exendin-4 (Ex-4), a long-acting glucagon-like peptide-1 (GLP-1) receptor agonist, on diabetes-associated Alzheimer-like changes as well as the molecular mechanisms involved. Our study demonstrated that GLP-1/Ex-4 could exert a protective effect against reduced viability of PC12 cells caused by high glucose and that this protective effect was mediated via the PI3-kinase pathway. In addition, GLP-1/Ex-4 ameliorated oxidative stress-induced injury in PC12 cells. In rat models, bilateral ICV-STZ administration was used to produce impaired insulin signaling in the brain. Fourteen days following ICV-STZ injection, rats treated with twice-daily Ex-4 had better learning and memory performance in the Morris water maze test compared with rats treated with saline. Additionally, histopathological evaluation confirmed the protective effects of Ex-4 treatment on hippocampal neurons against degeneration. Furthermore, we demonstrated that Ex-4 reversed ICV-STZ-induced tau hyperphosphorylation through downregulation of GSK-3β activity, a key kinase in both DM and AD. Our findings suggests that Ex-4 can protect neurons from diabetes-associated glucose metabolic dysregulation insults in vitro and from ICV-STZ insult in vivo, and that Ex-4 may prove of therapeutic value in the treatment of AD especially DM-related AD.     

融合DJ-1及其活性多肽片段的抗氧化应激作用及机制

目的 探讨融合DJ-1及其活性多肽片段的抗氧化应激作用及其机制。方法在稳定的抗氧化应激实验系统中,分别观察20μmol／LH2O2作用下不同质量浓度His融合DJ-1对钙调神经磷酸酶（CaN）活性的影响;在1．5μmol／LH2O2作用下DJ-1活性多肽片段102—107IAMCA和106—111CAGPTA对乳酸脱氢酶（LDH）活性的影响。结果两种浓度His融合DJ．1均可对抗H20：诱导的氧化应激,恢复CaN活性;DJ-1活性多肽片段102—107IAAICA和106～111CAGPTA均可部分对抗H2O2诱导的氧化应激,提高LDH活性。结论融合DJ-1及其活性多肽片段具有抗氧化应激作用;DJ-1完整蛋白可能通过自身C106残基氧化来对抗氧化应激,此为今后对抗H2O2活性多肽的发展及应用提供了依据。     

RNA binding activity of the recessive parkinsonism protein DJ-1 supports involvement in multiple cellular pathways

Parkinson's disease (PD) is a major neurodegenerative condition with several rare Mendelian forms. Oxidative stress and mitochondrial function have been implicated in the pathogenesis of PD but the molecular mechanisms involved in the degeneration of neurons remain unclear. DJ-1 mutations are one cause of recessive parkinsonism, but this gene is also reported to be involved in cancer by promoting Ras signaling and suppressing PTEN-induced apoptosis. The specific function of DJ-1 is unknown, although it is responsive to oxidative stress and may play a role in the maintenance of mitochondria. Here, we show, using four independent methods, that DJ-1 associates with RNA targets in cells and the brain, including mitochondrial genes, genes involved in glutathione metabolism, and members of the PTEN/PI3K cascade. Pathogenic recessive mutants are deficient in this activity. We show that DJ-1 is sufficient for RNA binding at nanomolar concentrations. Further, we show that DJ-1 binds RNA but dissociates after oxidative stress. These data implicate a single mechanism for the pleiotropic effects of DJ-1 in different model systems, namely that the protein binds multiple RNA targets in an oxidation-dependent manner.     

The Parkinson's disease gene DJ-1 is also a key regulator of stroke-induced damage

Recent evidence has indicated that common mechanisms play roles among multiple neurological diseases. However, the specifics of these pathways are not completely understood. Stroke is caused by the interruption of blood flow to the brain, and cumulative evidence supports the critical role of oxidative stress in the ensuing neuronal death process. DJ-1 (PARK7) has been identified as the gene linked to early-onset familial Parkinson's disease. Currently, our work also shows that DJ-1 is central to death in both in Vitro and in Vivo models of stroke. Loss of DJ-1 increases the sensitivity to excitotoxicity and ischemia, whereas expression of DJ-1 can reverse this sensitivity and indeed provide further protection. Importantly, DJ-1 expression decreases markers of oxidative stress after stroke insult in Vivo, suggesting that DJ-1 protects through alleviation of oxidative stress. Consistent with this finding, we demonstrate the essential role of the oxidation-sensitive cysteine-106 residue in the neuroprotective activity of DJ-1 after stroke. Our work provides an important example of how a gene seemingly specific for one disease, in this case Parkinson's disease, also appears to be central in other neuropathological conditions such as stroke. It also highlights the important commonalities among differing neuropathologies.     

Melatonin alleviates cadmium‐induced liver injury by inhibiting the TXNIP‐NLRP3 inflammasome

Cadmium (Cd) is a persistent environmental and occupational contaminant that accumulates in the liver and induces oxidative stress and inflammation. Melatonin possesses potent hepatoprotective properties against the development and progression of acute and chronic liver injury. Nevertheless, the molecular mechanism underlying the protective effects of melatonin against Cd‐induced hepatotoxicity remains obscure. In this study, we aimed to investigate the effects of melatonin on Cd‐induced liver inflammation and hepatocyte death. Male C57BL/6 mice were intraperitoneally injected with melatonin (10 mg/kg) once a day for 3 days before exposure to CdCl₂ (2.0 mg/kg). We found that Cd induced hepatocellular damage and inflammatory infiltration as well as increased serum ALT/AST enzymes. In addition, we showed that Cd triggered an inflammatory cell death, which is mediated by the NOD‐like receptor pyrin domain containing 3 (NLRP3) inflammasome. Moreover, melatonin treatment significantly alleviated Cd‐induced liver injury by decreasing serum ALT/AST levels, suppressing pro‐inflammatory cytokine production, inhibiting NLRP3 inflammasome activation, ameliorating oxidative stress, and attenuating hepatocyte death. Most importantly, melatonin markedly abrogated Cd‐induced TXNIP overexpression and decreased the interaction between TXNIP and NLRP3 in vivo and in vitro. However, treatment with siRNA targeting TXNIP blocked the protective effects of melatonin in Cd‐treated primary hepatocytes. Collectively, our results suggest that melatonin confers protection against Cd‐induced liver inflammation and hepatocyte death via inhibition of the TXNIP‐NLRP3 inflammasome pathway.     

The Rai (Shc C) adaptor protein regulates the neuronal stress response and protects against cerebral ischemia

Rai (Shc C or N-Shc) is a neuron-specific member of the family of Shc-like adaptor proteins. Rai functions in the cytoplasmic propagation of Ret-dependent survival signals and regulates, in vivo, the number of sympathetic neurons. We report here a function of Rai, i.e., the regulation of the neuronal adaptive response to environmental stresses. We demonstrate that (i) primary cultures of cortical neurons from Rai-/- mice are more sensitive to apoptosis induced by hypoxia or oxidative stress; (ii) in Rai-/- mice, ischemia/reperfusion injury induces severe neurological deficits, increased apoptosis and size of the infarct area, and significantly higher mortality; and (iii) Rai functions as a stress-response gene that increases phosphatidylinositol 3-kinase activation and Akt phosphorylation after hypoxic or oxidation insults. These data suggest that Rai has a functional neuroprotective role in brain injury, with possible implications in the treatment of stroke.     

Melatonin provides neuroprotection by reducing oxidative stress and HSP70 expression during chronic cerebral hypoperfusion in ovariectomized rats

Abstract:  Oxidative stress is believed to contribute to functional and histopathologic disturbances associated with chronic cerebral hypoperfusion (CCH) in rats. Melatonin has protective effects against cerebral ischemia/reperfusion injury. This effect has mainly been attributed to its antioxidant properties. In the present study, we evaluate the effects of melatonin on chronic cerebral hypoperfused rats and examined its possible influence on oxidative stress, superoxide dismutase (SOD) activity, reduced glutathione (GSH) levels, and heat shock protein (HSP) 70 induction. CCH was induced by permanent bilateral common carotid artery occlusion in ovariectomized female rats. Extensive neuronal loss in the hippocampus at day 14 following CCH was observed. The ischemic changes were preceded by increases in malondialdehyde (MDA) concentration and HSP70 induction as well as reductions in GSH and SOD. Melatonin treatment restored the levels of MDA, SOD, GSH, and HSP70 induction as compared to the ischemic group. Histopathologic analysis confirmed the protective effect of melatonin against CCH-induced morphologic alterations. Taken together, our results document that melatonin provides neuroprotective effects in CCH by attenuating oxidative stress and stress protein expression in neurons. This suggests melatonin may be helpful for the treatment of vascular dementia and cerebrovascular insufficiency.     

Melatonin protects against Nickel‐induced neurotoxicity in vitro by reducing oxidative stress and maintaining mitochondrial function

Abstract: Nickel is a potential neurotoxic pollutant. Oxidative stress is supposed to be involved in the mechanism underlying nickel‐induced neurotoxicity. Melatonin has efficient protective effects against various oxidative damages in nervous system. The purpose of this study was to investigate whether melatonin could efficiently protect against neurotoxicity induced by nickel. Here, we exposed primary cultured cortical neurons and mouse neuroblastoma cell lines (neuro2a) to different concentrations of nickel chloride (NiCl₂) (0.125, 0.25, 0.5, and 1 mm ) for 12 hr or 0.5 mm NiCl₂ for various periods (0, 3, 6, 12, and 24 hr). We found that nickel significantly increased reactive oxygen species production and caused the loss of cell viability both in cortical neurons and neuro2a cells. In addition, nickel exposure obviously inhibited the mitochondrial function, disrupted the mitochondrial membrane potential (ΔΨm), reduced ATP production, and decreased mitochondrial DNA (mtDNA) content. However, each of these oxidative damages was efficiently attenuated by melatonin pretreatment. These protective effects of melatonin may be attributable to its roles in reducing oxidative stress and improving mitochondrial function in nickel‐treated nerve cells. Our results suggested that melatonin may have great pharmacological potential in protecting against the adverse effects of nickel in the nervous system.     

Chronic doxorubicin cardiotoxicity is mediated by oxidative DNA damage-ATM-p53-apoptosis pathway and attenuated by pitavastatin through the inhibition of Rac1 activity

Doxorubicin is known to have cumulative dose-dependent cardiotoxicity, and a tumor suppressor protein p53 has been implicated in the pathogenesis of doxorubicin cardiotoxicity. However, how p53 is induced by doxorubicin and mediates the cardiotoxic effects of doxorubicin remains elusive. In cultured cardiac myocytes, doxorubicin induced oxidative stress, DNA damage, ATM activation, and p53 induction. A free radical scavenger NAC attenuated all of these events, whereas an ATM kinase inhibitor wortmannin attenuated doxorubicin-induced ATM activation and p53 induction but not oxidative stress. Doxorubicin treatment in vivo also induced oxidative stress, DNA damage, ATM activation, and p53 accumulation. These observations suggest that p53 induction by doxorubicin is mediated by oxidative DNA damage-ATM pathway. Doxorubicin-induced contractile dysfunction and myocyte apoptosis in vivo were attenuated in heterozygous p53 deficient mice and cardiac-restricted Bcl-2 transgenic mice, suggesting that myocyte apoptosis plays a central role downstream of p53 in doxorubicin cardiotoxicity. We also tested whether pitavastatin exerts protective effects on doxorubicin cardiotoxicity. Pitavastatin attenuated doxorubicin-induced oxidative stress, DNA damage, ATM activation, p53 accumulation, and apoptosis in vitro. Pitavastatin also attenuated myocyte apoptosis and contractile dysfunction in vivo. The beneficial effects of pitavastatin were reversed by intermediate products of the mevalonate pathway that are required for the activation of Rac1, and Rac1 inhibitor exhibited cardioprotective effects comparable to those of pitavastatin. These data collectively suggest that doxorubicin-induced cardiotoxicity is mediated by oxidative DNA damage-ATM-p53-apoptosis pathway, and is attenuated by pitavastatin through its antioxidant effect involving Rac1 inhibition.