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Tau truncation is widely detected in Alzheimer’s disease brain. Caspases activation is suggested to play a significant role in tau truncation at Aspartate 421 (D421) according to their ability to cleave recombinant tau in vitro. Ample evidence has shown that caspase-6 is involved in cognitive impairment and expressed in AD brain. Reactive oxygen species (ROS) can lead to caspase-6 activation and correlate with AD. Here, we transfected human embryonic kidney 293 (HEK 293) cells with Tau 441 plasmid and investigated the role of caspase-6 and caspase-3 in ROS-mediated tau truncation. Our data demonstrated that H2O2 induced oxidative stress and increased tau truncation. Caspase-6 and caspase-3 activity also increased in a dose-dependent manner in HEK 293/Tau cells during H2O2 insult. When cells were treated with an ROS inhibitor N-acetyl-l-cysteine, tau truncation was significantly suppressed. Compared with H2O2 (100 μM)/non-inhibitor group or single-inhibitor groups (z-VEID-fmk, caspase-6 inhibitor or z-DEVD-fmk, and caspase-3 inhibitor), tau truncation induced by H2O2 was effectively reduced in the combinative inhibitors group. Similar results were shown when cells were transfected with specific caspase-3 and caspase-6 siRNA. Inhibition of caspase-6 led to decline of caspase-3 activation. Taken together, our results suggest that the combination of caspase-6 and caspase-3 aggravates tau truncation at D421 induced by H2O2. Caspase-6 may play an important part in activating caspase-3. Further investigation of how the synergic role of caspase-6 and caspase-3 affects tau truncation may provide new visions for potential AD therapies.  相似文献   

3.
Esculetin is an antioxidant and anti-inflammatory compound derived from coumarin. Oxidative stress can cause overproduction of reactive oxygen species (ROS), which can lead to the development of chronic kidney failure. In this study, human embryonic kidney 293 (HEK293) cells were treated with tert-butyl hydroperoxide (t-BHP) to determine the antioxidant effects of esculetin. HEK293 cells were treated with t-BHP to validate changes in cell viability, ROS production, and apoptosis, and then treated with esculetin to evaluate the changes. Changes in mRNA and protein levels were analyzed using a proteome kit, PCR, and Western blotting. Esculetin improved HEK293 cell viability and reduced apoptosis caused by t-BHP-induced oxidative stress. At the mRNA and protein levels, esculetin decreased pro-apoptotic factor expression as well as increased anti-apoptotic factor expression. The antioxidant efficacy of esculetin was validated when it inhibited the apoptosis caused by t-BHP-induced oxidative stress in HEK293 cells.  相似文献   

4.
The cellular mechanisms that may underlie the death of dopaminergic neurons in Parkinson's disease are ubiquitin-proteasomal system (UPS) impairment, mitochondrial dysfunction, and oxidative stress. The goal of this work was to elucidate the correlation between mitochondrial dysfunction and UPS impairment, focusing on the role of oxidative stress. Our data revealed that mitochondria-DNA-depleted cells (rho0) are compromised at the mitochondrial and UPS levels and also show an alteration of the oxidative status. In parental cells (rho+), MPP(+) induced a clear inhibition of complex I activity, as well as an increase in ubiquitinylated protein levels, which was not observed in cells treated with lactacystin. Moreover, MPP(+) induced a decreased in the 20S chymotrypsin-like and peptidyl-glutamyl peptide hydrolytic-like proteolytic activities after 24 h of exposure. ROS production was increased in rho+ cells treated with MPP(+) or lactacystin, at early treatment periods. MPP(+) induced an increase in carbonyl group formation in rho+ cells. The results suggest that a mitochondrial alteration leads to an imbalance in the cellular oxidative status, inducing a proteasomal deregulation, which may exacerbate protein aggregation, and consequently degenerative events.  相似文献   

5.
SET protein (I2PP2A) is an inhibitor of PP2A, which regulates the phosphorylated Akt (protein kinase B) levels. We assessed the effects of SET overexpression in HEK293T cells, both in the presence and the absence of mild oxidative stress induced by 50 μM tert-butyl hydroperoxide. Immunoblotting assays demonstrated that SET accumulated in HEK293T cells and increased the levels of phosphorylated Akt and PTEN; in addition, SET decreased glutathione antioxidant defense of cell and increased expression of genes encoding antioxidant defense proteins. Immunofluorescence analysis demonstrated that accumulated SET was equally distributed in cytoplasm and nucleus; however, in cells that had been exposed to oxidative stress, SET was found in large aggregates in the cytoplasm. SET accumulation in HEK293T cells correlated with inhibition of basal apoptosis as evidenced by a decrease in annexin V staining and activity of caspases; under mild oxidative stress, SET accumulation correlated with caspase-independent cell death, as evidenced by increased PI and annexin V/PI double staining. The results suggest that accumulated SET could act via Akt/PTEN either as cell survival signal or as oxidative stress sensor for cell death.  相似文献   

6.

Background

Epidemiological case-control studies have revealed associations between mitochondrial haplogroups and the onset and/or progression of various multifactorial diseases. For instance, mitochondrial haplogroup T was previously shown to be associated with vascular diseases, including coronary artery disease and diabetic retinopathy. In contrast, haplogroup H, the most frequent haplogroup in Europe, is often found to be more prevalent in healthy control subjects than in patient study groups. However, justifications for the assumption that haplogroups are functionally distinct are rare. Therefore, we attempted to compare differences in mitochondrial function between haplogroup H and T cybrids.

Methodology/Principal Findings

Mitochondrial haplogroup H and T cybrids were generated by fusion of HEK293 cells devoid of mitochondrial DNA with isolated thrombocytes of individuals with the respective haplogroups. These cybrid cells were analyzed for oxidative phosphorylation (OXPHOS) enzyme activities, mitochondrial DNA (mtDNA) copy number, growth rate and susceptibility to reactive oxygen species (ROS). We observed that haplogroup T cybrids have higher survival rate when challenged with hydrogen peroxide, indicating a higher capability to cope with oxidative stress.

Conclusions/Significance

The results of this study show that functional differences exist between HEK293 cybrid cells which differ in mitochondrial genomic background.  相似文献   

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Glycogen synthase kinase‐3 beta (GSK‐3β) dysfunction may play an essential role in the pathogenesis of psychiatric, metabolic, neurodegenerative diseases, in which oxidative stress exists concurrently. Some studies have shown that GSK‐3β activity is up‐regulated under oxidative stress. This study evaluated how oxidative stress regulates GSK‐3β activity in human embryonic kidney 293 (HEK293)/Tau cells treated with hydrogen peroxide (H2O2). Here, we show that H2O2 induced an obvious increase of GSK‐3β activity. Surprisingly, H2O2 dramatically increased phosphorylation of GSK‐3β at Ser9, an inactive form of GSK‐3β,while there were no changes of phosphorylation of GSK‐3β at Tyr216. Moreover, H2O2 led to a transient [Ca2+]i elevation, and simultaneously increased the truncation of GSK‐3β into two fragments of 40 kDa and 30 kDa, whereas inhibition of calpain decreased the truncation and recovered the activity of GSK‐3β. Furthermore, tau was hyperphosphorylated at Ser396, Ser404, and Thr231, three most common GSK‐3β targeted sites after 100 μM H2O2 administration in HEK293/Tau cells, whereas inhibition of calpain blocked the tau phosphorylation. In addition, we found that there were no obvious changes of Cyclin‐dependent kinase 5 (CDK5) expression (responsible for tau phosphorylation) and of p35 cleavage, the regulatory subunit of CDK5 in H2O2‐treated HEK293/Tau cells. In conclusion, Ca2+‐dependent calpain activation leads to GSK‐3β truncation, which counteracts the inhibitory effect of Ser9 phosphorylation, up‐regulates GSK‐3β activity, and phosphorylates tau in H2O2‐treated HEK293/Tau cells.  相似文献   

9.
Oxidative stress caused by excess reactive oxygen species (ROS) accelerates telomere erosion and mitochondrial injury, leading to impaired cellular functions and cell death. Whether oxidative stress‐mediated telomere erosion induces mitochondrial injury, or vice versa, in human T cells—the major effectors of host adaptive immunity against infection and malignancy—is poorly understood due to the pleiotropic effects of ROS. Here we employed a novel chemoptogenetic tool that selectively produces a single oxygen (1O2) only at telomeres or mitochondria in Jurkat T cells. We found that targeted 1O2 production at telomeres triggered not only telomeric DNA damage but also mitochondrial dysfunction, resulting in T cell apoptotic death. Conversely, targeted 1O2 formation at mitochondria induced not only mitochondrial injury but also telomeric DNA damage, leading to cellular crisis and apoptosis. Targeted oxidative stress at either telomeres or mitochondria increased ROS production, whereas blocking ROS formation during oxidative stress reversed the telomeric injury, mitochondrial dysfunction, and cellular apoptosis. Notably, the X‐ray repair cross‐complementing protein 1 (XRCC1) in the base excision repair (BER) pathway and multiple mitochondrial proteins in other cellular pathways were dysregulated by the targeted oxidative stress. By confining singlet 1O2 formation to a single organelle, this study suggests that oxidative stress induces dual injury in T cells via crosstalk between telomeres and mitochondria. Further identification of these oxidation pathways may offer a novel approach to preserve mitochondrial functions, protect telomere integrity, and maintain T cell survival, which can be exploited to combat various immune aging‐associated diseases.  相似文献   

10.
Overexpression or mutation of α-Synuclein is associated with protein aggregation and interferes with a number of cellular processes, including mitochondrial integrity and function. We used a whole-genome screen in the fruit fly Drosophila melanogaster to search for novel genetic modifiers of human [A53T]α-Synuclein-induced neurotoxicity. Decreased expression of the mitochondrial chaperone protein tumor necrosis factor receptor associated protein-1 (TRAP1) was found to enhance age-dependent loss of fly head dopamine (DA) and DA neuron number resulting from [A53T]α-Synuclein expression. In addition, decreased TRAP1 expression in [A53T]α-Synuclein-expressing flies resulted in enhanced loss of climbing ability and sensitivity to oxidative stress. Overexpression of human TRAP1 was able to rescue these phenotypes. Similarly, human TRAP1 overexpression in rat primary cortical neurons rescued [A53T]α-Synuclein-induced sensitivity to rotenone treatment. In human (non)neuronal cell lines, small interfering RNA directed against TRAP1 enhanced [A53T]α-Synuclein-induced sensitivity to oxidative stress treatment. [A53T]α-Synuclein directly interfered with mitochondrial function, as its expression reduced Complex I activity in HEK293 cells. These effects were blocked by TRAP1 overexpression. Moreover, TRAP1 was able to prevent alteration in mitochondrial morphology caused by [A53T]α-Synuclein overexpression in human SH-SY5Y cells. These results indicate that [A53T]α-Synuclein toxicity is intimately connected to mitochondrial dysfunction and that toxicity reduction in fly and rat primary neurons and human cell lines can be achieved using overexpression of the mitochondrial chaperone TRAP1. Interestingly, TRAP1 has previously been shown to be phosphorylated by the serine/threonine kinase PINK1, thus providing a potential link of PINK1 via TRAP1 to α-Synuclein.  相似文献   

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A high concentration of glucose has been implicated as a causal factor in initiation and progression of diabetic kidney complications, and there is evidence to suggest that hyperglycemia increases the production of free radicals and oxidant stress. Recently, we demonstrated that the control of mitochondrial redox balance and the cellular defense against oxidative damage is one of the primary functions of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm) to supply NADPH for antioxidant systems. In this report, we demonstrate that modulation of IDPm activity in HEK293 cells, an embryonic kidney cell line, regulates high glucose-induced apoptosis. When we examined the protective role of IDPm against high glucose-induced apoptosis with HEK293 cells transfected with the cDNA for mouse IDPm in sense and antisense orientations, a clear inverse relationship was observed between the amount of IDPm expressed in target cells and their susceptibility to apoptosis. The results suggest that IDPm plays an important protective role in apoptosis of HEK293 cells induced by a high concentration of glucose and may contribute to various pathologies associated with the long-term complications of diabetes.  相似文献   

13.
Oxidative stress contributes to dysfunction of glial cells in the optic nerve head (ONH). However, the biological basis of the precise functional role of mitochondria in this dysfunction is not fully understood. Coenzyme Q10 (CoQ10), an essential cofactor of the electron transport chain and a potent antioxidant, acts by scavenging reactive oxygen species (ROS) for protecting neuronal cells against oxidative stress in many neurodegenerative diseases. Here, we tested whether hydrogen peroxide (100 μM H2O2)-induced oxidative stress alters the mitochondrial network, oxidative phosphorylation (OXPHOS) complex (Cx) expression and bioenergetics, as well as whether CoQ10 can ameliorate oxidative stress-mediated alterations in mitochondria of the ONH astrocytes in vitro. Oxidative stress triggered the activation of ONH astrocytes and the upregulation of superoxide dismutase 2 (SOD2) and heme oxygenase-1 (HO-1) protein expression in the ONH astrocytes. In contrast, CoQ10 not only prevented activation of ONH astrocytes but also significantly decreased SOD2 and HO-1 protein expression in the ONH astrocytes against oxidative stress. Further, CoQ10 prevented a significant loss of mitochondrial mass by increasing mitochondrial number and volume density and by preserving mitochondrial cristae structure, as well as promoted mitofilin and peroxisome-proliferator-activated receptor-γ coactivator-1 protein expression in the ONH astrocyte, suggesting an induction of mitochondrial biogenesis. Finally, oxidative stress triggered the upregulation of OXPHOS Cx protein expression, as well as reduction of cellular adeonsine triphosphate (ATP) production and increase of ROS generation in the ONH astocytes. However, CoQ10 preserved OXPHOS protein expression and cellular ATP production, as well as decreased ROS generation in the ONH astrocytes. On the basis of these observations, we suggest that oxidative stress-mediated mitochondrial dysfunction or alteration may be an important pathophysiological mechanism in the dysfunction of ONH astrocytes. CoQ10 may provide new therapeutic potentials and strategies for protecting ONH astrocytes against oxidative stress-mediated mitochondrial dysfunction or alteration in glaucoma and other optic neuropathies.  相似文献   

14.
Tau amyloid assemblies propagate aggregation from the outside to the inside of a cell, which may mediate progression of the tauopathies. The critical size of Tau assemblies, or “seeds,” responsible for this activity is currently unknown, but this could be important for the design of effective therapies. We studied recombinant Tau repeat domain (RD) and Tau assemblies purified from Alzheimer disease (AD) brain composed largely of full-length Tau. Large RD fibrils were first sonicated to create a range of assembly sizes. We confirmed our ability to resolve stable assemblies ranging from n = 1 to >100 units of Tau using size exclusion chromatography, fluorescence correlation spectroscopy, cross-linking followed by Western blot, and mass spectrometry. All recombinant Tau assemblies bound heparan sulfate proteoglycans on the cell surface, which are required for Tau uptake and seeding, because they were equivalently sensitive to inhibition by heparin and chlorate. However, cells only internalized RD assemblies of n ≥ 3 units. We next analyzed Tau assemblies from AD or control brains. AD brains contained aggregated species, whereas normal brains had predominantly monomer, and no evidence of large assemblies. HEK293 cells and primary neurons spontaneously internalized Tau of n ≥ 3 units from AD brain in a heparin- and chlorate-sensitive manner. Only n ≥ 3-unit assemblies from AD brain spontaneously seeded intracellular Tau aggregation in HEK293 cells. These results indicate that a clear minimum size (n = 3) of Tau seed exists for spontaneous propagation of Tau aggregation from the outside to the inside of a cell, whereas many larger sizes of soluble aggregates trigger uptake and seeding.  相似文献   

15.
Mutation in the transmembrane protein 65 gene (TMEM65) results in mitochondrial dysfunction and a severe mitochondrial encephalomyopathy phenotype. However, neither the function of TMEM65 nor the cellular responses to its depletion have been fully elucidated. Hence, we knocked down TMEM65 in human cultured cells and analyzed the resulting cellular responses. Depletion of TMEM65 led to a mild increase in ROS generation and upregulation of the mRNA levels of oxidative stress suppressors, such as NFE2L2 and SESN3, indicating that TMEM65 knockdown induced an oxidative stress response. A mild induction of apoptosis was also observed upon depletion of TMEM65. Depletion of TMEM65 upregulated protein levels of the mitochondrial chaperone HSPD1 and mitochondrial protease LONP1, indicating that mitochondrial unfolded protein response (UPRmt) was induced in response to TMEM65 depletion. Additionally, we found that the mitochondrial protein import receptor TOMM22 and HSPA9 (mitochondrial Hsp70), were also upregulated in TMEM65-depleted cells. Notably, the depletion of TMEM65 did not lead to upregulation of TOMM22 in an ATF5-dependent manner, although upregulation of LONP1 reportedly occurs in an ATF5-dependent manner. Taken together, our findings suggest that depletion of TMEM65 causes mild oxidative stress and apoptosis, induces UPRmt, and upregulates protein expression of mitochondrial protein import receptor TOMM22 in an ATF5-independent manner.  相似文献   

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帕金森病(Parkinson’s disease,PD)的一个主要病理特征就是中脑黑质多巴胺能神经元的丧失,目前研究认为该病理变化与多种因素有关,包括蛋白质异常积聚、泛素蛋白酶体系统功能异常、神经炎症、线粒体损伤和氧化应激。在帕金森病人和动物模型中,中脑黑质有着明显的氧化改变。帕金森病的遗传和环境因素均会作用于线粒体,尤其对线粒体呼吸链复合体I有着抑制作用,造成线粒体损伤,产生活性氧(ROS)。活性氧的大量产生造成脂类、蛋白质和DNA的氧化,从而加剧多巴胺能神经元的线粒体和细胞损伤。多巴胺代谢过程中会产生活性氧,该自身代谢特点决定了多巴胺能神经元存在有较高的氧化应激,易受环境因素的影响。因而,线粒体的氧化损伤在帕金森病病理发生中起着重要作用。  相似文献   

18.
Amyloid-like inclusions have been associated with Huntington''s disease (HD), which is caused by expanded polyglutamine repeats in the Huntingtin protein. HD patients exhibit a high incidence of cardiovascular events, presumably as a result of accumulation of toxic amyloid-like inclusions. We have generated a Drosophila model of cardiac amyloidosis that exhibits accumulation of PolyQ aggregates and oxidative stress in myocardial cells, upon heart-specific expression of Huntingtin protein fragments (Htt-PolyQ) with disease-causing poly-glutamine repeats (PolyQ-46, PolyQ-72, and PolyQ-102). Cardiac expression of GFP-tagged Htt-PolyQs resulted in PolyQ length-dependent functional defects that included increased incidence of arrhythmias and extreme cardiac dilation, accompanied by a significant decrease in contractility. Structural and ultrastructural analysis of the myocardial cells revealed reduced myofibrillar content, myofibrillar disorganization, mitochondrial defects and the presence of PolyQ-GFP positive aggregates. Cardiac-specific expression of disease causing Poly-Q also shortens lifespan of flies dramatically. To further confirm the involvement of oxidative stress or protein unfolding and to understand the mechanism of PolyQ induced cardiomyopathy, we co-expressed expanded PolyQ-72 with the antioxidant superoxide dismutase (SOD) or the myosin chaperone UNC-45. Co-expression of SOD suppressed PolyQ-72 induced mitochondrial defects and partially suppressed aggregation as well as myofibrillar disorganization. However, co-expression of UNC-45 dramatically suppressed PolyQ-72 induced aggregation and partially suppressed myofibrillar disorganization. Moreover, co-expression of both UNC-45 and SOD more efficiently suppressed GFP-positive aggregates, myofibrillar disorganization and physiological cardiac defects induced by PolyQ-72 than did either treatment alone. Our results demonstrate that mutant-PolyQ induces aggregates, disrupts the sarcomeric organization of contractile proteins, leads to mitochondrial dysfunction and increases oxidative stress in cardiomyocytes leading to abnormal cardiac function. We conclude that modulation of both protein unfolding and oxidative stress pathways in the Drosophila heart model can ameliorate the detrimental PolyQ effects, thus providing unique insights into the genetic mechanisms underlying amyloid-induced cardiac failure in HD patients.  相似文献   

19.
谷氧还蛋白1(glutaredoxin1,Grx1)是细胞内一种重要的巯基 二硫键氧化还原酶,在细胞内氧化还原状态的调控及抵抗氧化应激损伤过程中发挥重要作用.为进一步探讨Grx1的抗氧化机制,本实验将重组质粒pcDNA3.1(+)-hGrx1瞬时转染HEK293T细胞,经RT-PCR和Western印迹验证,细胞转染后实现了Grx1的过表达;以不同浓度H2O2为损伤因素,建立细胞氧化应激模型,检测过表达Grx1后细胞存活率,丙二醛(MDA)含量,超氧化物歧化酶(SOD)活力和乳酸脱氢酶(LDH)漏出率的变化,观察过表达Grx1后细胞的抗氧化能力;用终浓度100 μmol/LH2O2作用于细胞,利用Western 印迹检测120 min内HEK293T细胞中p38MAPK磷酸化水平.实验结果表明,HEK293T细胞过表达Grx1后,缓解了细胞的氧化应激损伤;转染空载体组细胞p38MAPK磷酸化水平在H2O2刺激后5 min开始升高,15 min达到最高值,并可维持至120 min左右;而过表达Grx1组细胞p38MAPK磷酸化水平在H2O2刺激后各时间段没有明显改变,提示Grx1通过抑制H2O2诱导的p38MAPK信号通路激活发挥其抗氧化作用.  相似文献   

20.
Microtubule‐associated protein Tau, abundant in the central nervous system (CNS), plays crucial roles in microtubule assembly and stabilization. Abnormal Tau phosphorylation and aggregation are a common pathogenic hallmark in Alzheimer's disease (AD). Hyperphosphorylation of Tau could change its conformation and result in self‐aggregation, increased oxidative stress, and neuronal death. In this study, we examined the potential of licochalcone A (a natural chalcone) and five synthetic derivatives (LM compounds) for inhibiting Tau misfolding, scavenging reactive oxygen species (ROS) and providing neuroprotection in human cells expressing proaggregant ΔK280 TauRD‐DsRed. All test compounds were soluble up to 100 μM in cell culture media and predicted to be orally bioavailable and CNS‐active. Among them, licochalcone A and LM‐031 markedly reduced Tau misfolding and associated ROS, promoted neurite outgrowth, and inhibited caspase 3 activity in ΔK280 TauRD‐DsRed 293 and SH‐SY5Y cells. Mechanistic studies showed that LM‐031 upregulates HSPB1 chaperone, NRF2/NQO1/GCLC pathway, and CREB‐dependent BDNF/AKT/ERK/BCL2 pathway in ΔK280 TauRD‐DsRed SH‐SY5Y cells. Decreased neurite outgrowth upon induction of ΔK280 TauRD‐DsRed was rescued by LM‐031, which was counteracted by knockdown of NRF2 or CREB. LM‐031 further rescued the downregulated NRF2 and pCREB, reduced Aβ and Tau levels in hippocampus and cortex, and ameliorated cognitive deficits in streptozocin‐induced hyperglycemic 3 × Tg‐AD mice. Our findings strongly indicate the potential of LM‐031 for modifying AD progression by targeting HSPB1 to reduce Tau misfolding and activating NRF2 and CREB pathways to suppress apoptosis and promote neuron survival, thereby offering a new drug development avenue for AD treatment.  相似文献   

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