Effect of the cross‐talk between autophagy and endoplasmic reticulum stress on Mn‐induced alpha‐synuclein oligomerization

Overexposure to manganese (Mn) has been known to induce alpha‐synuclein (α‐Syn) oligomerization, which is degraded mainly depending on endoplasmic reticulum stress (ER stress) and autophagy pathways. However, little data reported the cross‐talk between ER stress and autophagy on Mn‐induced α‐Syn oligomerization. To explore the relationship between ER stress and autophagy, we used 4‐phenylbutyric acid (4‐PBA, the ER stress inhibitor), rapamycin (Rap, autophagy activator) and 3‐methyladenine (3‐MA, autophagy inhibitor) in mice model of manganism. After 4 weeks of treatment with Mn, both ER stress and autophagy were activated. Exposed to Mn also resulted in α‐Syn oligomerization and neuronal cell damage in the brain tissue of mice, which could be relieved by 4‐PBA pretreatment. Moreover, when the ER stress was inhibited, the activation of autophagy was also inhibited. Rap pretreatment significantly activated autophagy and decreased α‐Syn oligomers. However, 3‐MA pretreatment inhibited autophagy resulting in increase of α‐Syn oligomers, and compensatorily activated PERK signaling pathway. Our results also demonstrated that the inhibition of autophagy by 3‐MA aggravated neuronal cell damage. The findings clearly demonstrated that the cross‐talking between autophagy and ER stress might play an important role in the α‐Syn oligomerization and neurotoxicity by Mn.     

Effect of trehalose on manganese‐induced mitochondrial dysfunction and neuronal cell damage in mice

Chronic overexposure to manganese (Mn) has been verified to induce mitochondrial dysfunction, which is related to oxidative damage. The autophagic‐lysosomal degradation pathway plays a vital role in the removal of impaired mitochondria through a specific quality control mechanism termed mitophagy. However, trehalose functions as an inducer of autophagy by an mTOR‐independent mechanism, and little data report its effect on Mn‐induced mitochondrial dysfunction. To explore the possibility that trehalose could be effective in interfering with the Mn‐induced mitochondrial dysfunction, we used trehalose (2% and 4% (g/vol (mL))) in a mouse model of manganism. Our data showed that mice developed weary motor and behavioural deficits after exposure to Mn for 6 weeks. Overexposure to Mn resulted in mitochondrial dysfunction and neuronal cell damage in the basal nuclei of mice, which could be ameliorated by trehalose pre‐treatment. Moreover, our results indicated that trehalose pre‐treatment significantly reduced the oxidative damage and enhanced the activation of mitophagy. The findings clearly demonstrated that trehalose could relieve Mn‐induced mitochondrial and neuronal cell damage through its antioxidative and mitophagy‐inducing effects.     

Tri‐ortho‐cresyl phosphate (TOCP)‐induced reproductive toxicity involved in placental apoptosis,autophagy and oxidative stress in pregnant mice

Tri‐ortho‐cresyl phosphate (TOCP) has been widely used as plasticizers, and reported causing reproductive toxicity in mammals. However, little is known about the toxic effect on the placenta. In this study, dams were orally administered different doses of TOCP to explore the effect of TOCP on placental development. Results showed that TOCP exposure significantly reduced numbers of implanted embryo, caused atrophy and collapse of ectoplacental cone, and decreased total areas of placenta and numbers of PCNA‐positive cells. Expression levels of placental development genes were prominently downregulated in the TOCP‐treated groups. Moreover, TOCP administration induced placental apoptosis and autophagy by upregulating P53, Bax, Beclin‐1, ratio of LC3 II/LC3 I and Atg5 and downregulating Bcl‐2 protein. In addition, TOCP exposure markedly inhibited activities of catalase and superoxide dismutase and increased the production of H₂O₂ and malondialdehyde. Collectively, these findings suggest that apoptosis, autophagy and oxidative stress may be involved in the TOCP‐induced reproductive toxicity.     

大蒜素对慢性铁中毒大鼠氧化应激与肝细胞自噬的抑制作用

目的探讨大蒜素(allicin)对慢性铁中毒大鼠氧化应激与肝细胞自噬的抑制作用及可能机制。方法 36只SD大鼠按体质量随机分为6组,即正常对照(饲喂基础饲料)、慢性铁中毒模型(饲喂高铁饲料)、正常+大蒜素40 mg·kg-1、慢性铁中毒+大蒜素30,40和60 mg·kg-1组,每组6只。持续饲喂6周后,取血及肝、结肠和肾组织用试剂盒测定铁含量、总铁结合力、丙二醛(MDA)含量及总超氧化物歧化酶(T-SOD)活性。透射电镜和免疫组织化学方法观察肝细胞形态结构、自噬以及胱天蛋白酶3凋亡蛋白、Ki-67细胞增殖抗原和LC3-B微管相关蛋白表达的变化。结果与正常对照组比较,模型组血清铁含量增加(P<0.01),总铁结合力下降(P<0.01),肝和结肠组织铁含量增加(P<0.05)。与模型组比较,饲喂不同剂量大蒜素大鼠血清铁含量显著下降(P<0.05),总铁结合力显著增加(P<0.05),结肠组织铁含量显著下降(P<0.05);饲喂大蒜素40和60 mg·kg-1肝组织铁含量显著下降(P<0.05)。与正常对照组比较,模型组肝和结肠组织MDA含量显著增加(P<0.05),肝组织T-SOD活性增加(P<0.01),结肠组织T-SOD活性下降(P<0.01)。与模型组比较,饲喂大蒜素组肝组织MDA含量显著下降(P<0.05),结肠和肾组织T-SOD活性显著增加(P<0.05)。与正常对照组比较,模型组肝实质细胞和肝非实质细胞Ki-67增殖抗原表达显著增加(P<0.05),胱天蛋白酶3凋亡蛋白表达无明显变化(P>0.05)。观察肝细胞超微结构,模型组大鼠肝细胞有大量铁蛋白颗粒累积,线粒体和内质网膜膨胀,胞质中形成自噬前体。模型组大鼠肝细胞LC3-B微管相关蛋白有较强表达,正常对照和正常+大蒜素组肝细胞未发现LC3-B免疫阳性染色。结论大蒜素能有效清除体内自由基,增强机体抗氧化能力,降低肝中铁诱导的氧化压力、线粒体膜的改变和细胞自噬,对慢性铁中毒肝细胞具有一定的保护作用。     

Protective role of silymarin against manganese‐induced nephrotoxicity and oxidative stress in rat

Metal toxicity may occur after exposure from many sources. Oxidative stress is thought to be involved in manganese‐induced toxicity and leads to various health disorders. Silymarin (SIL), a natural flavonoid, has been reported to have many benefits and medicinal properties. The aim of this study was to assess the toxicity of manganese (Mn) on oxidative stress and DNA damage in the kidney of rats and its alleviation by SIL. Manganese was given orally in drinking water (20 mg MnCl₂/mL) with or without SIL administration (100 mg /kg intraperitoneally) for 30 days. Our data showed that SIL significantly prevented Mn induced nephrotoxicity, indicated by both diagnostic indicators of kidney injury like plasma urea, uric acid and creatinine and urinary electrolyte levels and by histopathological analysis. Moreover, Mn‐induced profound elevation of the production of reactive oxygen species (ROS) and altered the levels of oxidative stress related biomarkers in kidney tissue. This is evidenced by the increase of lipid peroxidation, protein carbonylation, DNA fragmentation and urinary hydrogen peroxide, while, the activities of enzymatic antioxidant and glutathione level were decreased. Treatment with SIL reduced the alterations in the renal and urine markers, decreasing lipid peroxidation markers, increasing the antioxidant cascade and decreasing the Mn‐induced damage. All these changes were supported by histopathological observations. These findings suggested that the inhibition of Mn‐induced damage by SIL was due at least in part to its antioxidant activity and its capacity to modulate the oxidative damage. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1147–1154, 2014.     

Overexpression of miR‐138‐5p suppresses MnCl2‐induced autophagy by targeting SIRT1 in SH‐SY5Y cells

The mechanism of manganism caused by manganese (Mn), an important environmental risk factor for Parkinson's disease, is still unclear. Recent evidence suggested that autophagy participated in neurodegenerative diseases, in which microRNA played a crucial role. However, roles of microRNA in the aberrant autophagy that occurs in neurodegenerative diseases remains controversial. In nervous system, miRNA‐138‐5p is highly expressed and plays a key role in regulating memory and axon regeneration. Importantly, we also found that miR‐138‐5p expression decreased significantly after SH‐SY5Y cells exposed to manganese chloride (MnCl₂) in previous study. To explore the role of miR‐138‐5p in Mn‐induced autophagy, autophagy associated indicators were detected. And we found that MnCl₂ could induce autophagic dysregulation and inhibit expression of miR‐138‐5p. While the levels of LC3‐II/LC3‐I, Beclin1, and p62, the number of autophagosome formation significantly decreased after miR‐138‐5p over‐expression, which demonstrated that miR‐138‐5p could clearly retard Mn‐induced autophagy. In additional, we found there were classical and evolutionarily conserved miR‐138‐5p binding sites in 3′‐UTR region of SIRT1, which was inhibited when overexpression of miR‐138‐5p. Therefore, it was speculated that elevated expression of SIRT1 may be resulted from inhibition of miR‐138‐5p after cells exposed to MnCl₂. Finally, we found that SIRT1 inhibitor EX‐527 suppressed Mn‐induced autophagy as well as miR‐138‐5p, while the suppression was reversed by SIRT1‐specific activator SRT1720. These results indicated that overexpression of miR‐138‐5p suppressed Mn‐induced autophagy by targeting SIRT1.     

Protective effects of β‐sheet breaker α/β‐hybrid peptide against amyloid β‐induced neuronal apoptosis in vitro

Alzheimer's disease is most common neurodegenerative disorder and is characterized by increased production of soluble amyloid‐β oligomers, the main toxic species predominantly formed from aggregation of monomeric amyloid‐β (Aβ). Increased production of Aβ invokes a cascade of oxidative damages to neurons and eventually leads to neuronal death. This study was aimed to investigate the neuroprotective effects of a β‐sheet breaker α/β‐hybrid peptide (BSBHp) and the underlying mechanisms against Aβ₄₀‐induced neurotoxicity in human neuroblastoma SH‐SY5Y cells. Cells were pretreated with the peptide Aβ₄₀ to induce neurotoxicity. Assays for cell viability, cell membrane damage, cellular apoptosis, generation of reactive oxygen species (ROS), intracellular free Ca²⁺, and key apoptotic protein levels were performed in vitro. Our results showed that pretreatment with BSBHp significantly attenuates Aβ₄₀‐induced toxicity by retaining cell viability, suppressing generation of ROS, Ca²⁺ levels, and effectively protects neuronal apoptosis by suppressing pro‐apoptotic protein Bax and up‐regulating antiapoptotic protein Bcl‐2. These results suggest that α/β‐hybrid peptide has neuroprotective effects against Aβ₄₀‐induced oxidative stress, which might be a potential therapeutic agent for treating or preventing neurodegenerative diseases.     

Influence of EGCG on α‐synuclein (αS) aggregation and identification of their possible binding mode: A computational study using molecular dynamics simulation

The accumulation of intrinsically disordered α‐synuclein (αS) protein that can form β‐sheet‐rich fibrils is linked to Parkinson's disease. (−)‐Epigallocatechin‐3‐gallate (EGCG) is the most abundant active component in green tea and can inhibit the fibrillation of αS. The elucidation of this molecular mechanism will be helpful to understand the inhibition mechanism of EGCG to the fibrillation of αS and also to find more potential small molecules that can inhibit the aggregation of αS. In this work, to study the influence of EGCG on the structure of β‐sheet‐rich fibrils of αS and identification of their possible binding mode, molecular dynamics simulations of pentamer and decamer aggregates of αS in complex with EGCG were performed. The obtained results indicate that EGCG can remodel the αS fibrils and break the initial ordered pattern by reducing the β‐sheet content. EGCG can also break the Greek conformation of αS by the disappeared H‐bond in the secondary structure of turn. The results from our study can not only reveal the specific interaction between EGCG and β‐sheet‐rich fibrils of αS, but also provide the useful guidance for the discovery of other potential inhibitors.     

The role of GSH in microcystin‐induced apoptosis in rat liver: Involvement of oxidative stress and NF‐κB

Microcystins (MCs) are potent and specific hepatotoxins produced by cyanobacteria in eutrophic waters, representing a health hazard to animals and humans. The objectives of this study are to determine the relationship between oxidative stress and NF‐κB activity in MC‐induced apoptosis in rat liver and the role of glutathione (GSH). Sprague‐Dawley rats were intraperitoneally (i.p.) injected with microcystin‐LR (MC‐LR) at 0.25 and 0.5 LD₅₀ with or without pretreatment of buthionine‐(S,R)‐sulfoximine (BSO), a specific GSH synthesis inhibitor. MC‐LR induced time‐dependent alterations of GSH levels in rat liver. Increased malondialdehyde (MDA) and significant changes of antioxidant enzymes including GSH peroxidase (GPX) and GSH reductase (GR) were also observed, particularly at 24 h post‐exposure. The results indicated that acute exposure to MC‐LR induced oxidative stress, and GSH depletion (BSO pretreatment) enhanced the level of oxidative stress. Furthermore, the modulation of pro‐apoptotic gene p53 and Bax and anti‐apoptotic gene Bcl‐2 was observed in 0.5 LD₅₀ group at 24 h, and the alteration was more pronounced by BSO injection before MC‐LR treatment, suggesting that GSH played a protective role against MC‐induced toxicity. Additionally, electrophoretic mobility shift assay (EMSA) showed that NF‐κB was induced at 0.25 LD₅₀ but inhibited at 0.5 LD₅₀. The above results indicated that the possible crosstalk of oxidative stress and NF‐κB activity was associated with MC‐LR‐induced hepatocytes apoptosis in vivo. Our data will provide a new perspective for understanding the mechanisms of MC‐induced liver injury. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 552–560, 2016.     

Endotoxin‐induced acute lung injury in mice is protected by 5,7‐dihydroxy‐8‐methoxyflavone via inhibition of oxidative stress and HIF‐1α

Up to date, the morbidity and mortality rates of acute lung injury (ALI) still rank high among clinical illnesses. Endotoxin, also called lipopolysaccharide (LPS), induced sepsis is the major cause for ALI. Beneficial biological effects, such as antioxidation, anti‐inflammation, and neuroprotection was found to express by 5,7‐dihydroxy‐8‐methoxyflavone (DHMF). The purpose of present study was to investigate the potential protective effects of DHMF and the possibile mechanisms involved in LPS‐induced ALI. In our experimental model, ALI was induced in mice by intratracheal injection of LPS, and DHMF at various concentrations was injected intraperitoneally for 30 min prior to LPS administration. Pretreatment with DHMF inhibited not only the histolopatholgical changes occurred in lungs but also leukocytes infiltration in LPS‐induced ALI. Decreased activity of antioxidative enzymes (AOE) such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) caused by LPS was reversed by DHMF. LPS‐induced lipid peroxidation HIF‐1α accumulation, NF‐κB phosphorylation, and IκBα degradation were all inhibited by DHMF. In addition, LPS‐induced expression of proinflammatory mediators such as TNF‐α and IL‐1β were also inhibited by 5,7‐dihydroxy‐8‐methoxyflavone. These results suggested that the protective mechanisms of DHMF on endotoxin‐induced ALI might be via up‐regulation of antioxidative enzymes, inhibition of NFκB phosphorylation, and HIF‐1α accumulation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1700–1709, 2016.     

α‐Lipoic acid protects against microcystin‐LR induced hepatotoxicity through regeneration of glutathione via activation of Nrf2

Microcystins (MCs), as the most dominant bloom‐forming strains in eutrophic surface water, can induce hepatotoxicity by oxidative stress. Alpha‐lipoic acid (α‐LA) is a super antioxidant that can induce the synthesis of antioxidants, such as glutathione (GSH), by nuclear factor erythroid 2‐related factor 2 (Nrf2). However, the potential molecular mechanism of α‐LA regeneration of GSH remains unclear. The present study aimed to investigate whether α‐LA could reduce the toxicity of MCs induced in human hepatoma (HepG2), Bel7420 cells, and BALB/c mice by activating Nrf2 to regenerate GSH. Results showed that exposure to 10 μM microcystin‐leucine arginine (MC‐LR) reduced viability of HepG2 and Bel7402 cells and promoted the formation of reactive oxygen species (ROS) compared with untreated cells. Moreover, the protection of α‐LA included reducing the level of ROS, increasing superoxide dismutase activity, and decreasing malondialdehyde. Levels of reduced glutathione (rGSH) and rGSH/oxidized glutathione were significantly increased in cells cotreated with α‐LA and MC‐LR compared to those treated with MC‐LR alone, indicating an ability of α‐LA to attenuate oxidative stress and MC‐LR‐induced cytotoxicity by increasing the amount of rGSH. α‐LA can mediate GSH regeneration through the Nrf2 pathway under the action of glutathione reductase in MC‐LR cell lines. Furthermore, the data also showed that α‐LA‐induced cytoprotection against MC‐LR is associated with Nrf2 mediate pathway in vivo. These findings demonstrated the potential of α‐LA to resist MC‐LR‐induced oxidative damage of liver.     

The role S‐nitrosylation in manganese‐induced autophagy dysregulation in SH‐SY5Y cells

Overexposure to manganese (Mn) has been known to induce nitrosative stress. The dysregulation of autophagy has implicated in nitric oxide (NO) bioactivity alterations. However, the mechanism of Mn‐induced autophagic dysregulation is unclear. The protein of Bcl‐2 was considered as a key role that could participate to the autophagy signaling regulation. To further explore whether S‐nitrosylation of Bcl‐2 involved in Mn‐induced autophagy dysregulation, we treated human neuroblastoma (SH‐SY5Y) cells with Mn and pretreated cells with 1400 W, a selective iNOS inhibitor. After cells were treated with 400 μM Mn for 24 h, there were significant increases in production of NO, inducible NO synthase (iNOS) activity, the mRNA and protein expressions of iNOS. Interestingly, autophagy was activated after cells were treated with Mn for 0–12 h; while the degradation process of autophagy‐lysosome pathway was blocked after cells were treated with Mn for 24 h. Moreover, S‐nitrosylated JNK and Bcl‐2 also increased and phospho‐JNK and phospho‐Bcl‐2 reduced in Mn‐treated cells. Then, the affinity between Bcl‐2 and Beclin‐1 increased significantly in Mn‐treated cells. We used the 1400 W to neutralize Mn‐induced nitrosative stress. The results showed that S‐nitrosylated JNK and Bcl‐2 reduced while their phosphorylation were recovered to some extent. The findings revealed that NO‐mediated S‐nitrosylation of Bcl‐2 directly affected the interaction between Beclin‐1 and Bcl‐2 leading to autophagy inhibition.     

β‐asarone and levodopa co‐administration protects against 6‐hydroxydopamine‐induced damage in parkinsonian rat mesencephalon by regulating autophagy: down‐expression Beclin‐1 and light chain 3B and up‐expression P62

In this study, we investigated Beclin‐1, light chain (LC)3B, and p62 expression in 6‐hydroxydopamine (6‐OHDA)‐induced parkinsonian rats after β‐asarone and levodopa (l ‐dopa) co‐administration. Unilateral 6‐OHDA injection into the medial forebrain bundle was used to create the models, except in sham‐operated rats. Rats were divided into eight groups: sham‐operated group; 6‐OHDA model group; madopar group (75 mg/kg, per os (p.o.)); l ‐dopa group (60 mg/kg, p.o.); β‐asarone group (15 mg/kg, p.o.); β‐asarone + l ‐dopa co‐administered group (15 mg/kg + 60 mg/kg, p.o.); 3‐methyladenine group (500 nmol, intraperitoneal injection); and rapamycin group (1 mg/kg, intraperitoneal injection). Then, Beclin‐1, LC3B, and p62 expression in the mesencephalon were detected. The mesencephalon was also observed by transmission electron microscope. The results showed that Beclin‐1 and LC3B expression decreased and that p62 expression increased significantly in the madopar, l ‐dopa, β‐asarone, and co‐administered groups when compared with the 6‐OHDA model. Beclin‐1 and LC3B expression in the β‐asarone and co‐administered groups were less than in the madopar or l ‐dopa groups, whereas p62 expression in the β‐asarone and co‐administered groups was higher than in the madopar or l ‐dopa groups. In addition, a significant decrease in autophagosome was exhibited in the β‐asarone and co‐administered groups when compared with the 6‐OHDA group. Our findings indicate that Beclin‐1 and LC3B expression decreased, whereas p62 expression increased after co‐administration treatment. In sum, all data suggest that the co‐administration of β‐asarone and l ‐dopa may contribute to the treatment of 6‐OHDA‐induced damage in rats by inhibiting autophagy activity.     

3‐Methyladenine alleviates excessive iodine‐induced cognitive impairment via suppression of autophagy in rat hippocampus

Drinking water with high levels of iodine has been identified as the key contributor to iodine excess, but the mechanisms of neurotoxicity induced by excessive iodine remain elusive. The present study aimed to explore the role of autophagy in the neurotoxic effect induced by excessive iodine in vivo. The Morris water maze test results demonstrated that excessive iodine impaired the learning and memory capabilities of rats, which were associated with marked body weight and brain weight abnormalities. In addition, iodine treatment increased malondialdehyde accumulation, decreased superoxide dismutase activity and glutathione (GSH) level, and enhanced levels of autophagy markers in the hippocampus. Notably, inhibition of autophagy with 3‐methyladenine (3‐MA) could significantly alleviate excessive iodine‐induced cognitive impairment. These data imply that autophagy is involved in the cognitive impairment elicited by excessive iodine as a pathway of cell death, and inhibition of autophagy via 3‐MA may significantly alleviate the above damage.     

α,β‐Unsaturated aldehyde pollutant acrolein suppresses cardiomyocyte contractile function: Role of TRPV1 and oxidative stress

Air pollution is associated with an increased prevalence of heart disease and is known to trigger a proinflammatory response via stimulation of transient receptor potential vanilloid cation channels (TRPV1, also known as the capsaicin receptor). This study was designed to examine the effect of acrolein, an essential α,β‐unsaturated aldehyde pollutant, on myocardial contractile function and the underlying mechanism involved with a focus on TRPV1 and oxidative stress. Cardiomyocyte mechanical and intracellular Ca²⁺ properties were evaluated using an IonOptix MyoCam® system including peak shortening (PS), maximal velocity of shortening/relengthening (± dL/dt), time‐to‐PS (TPS), time‐to‐90% relengthening (TR₉₀), fura‐2 fluorescence intensity (FFI) and intracellular Ca²⁺ decay. Changes in apoptosis and TRPV1 were evaluated using Western blot analysis. The degree of oxidative stress was assessed using the ratio between reduced and oxidized glutathione. Results obtained revealed that exposure of cardiomyocytes to acrolein acutely compromised contractile and intracellular Ca²⁺ properties including depressed PS, ± dL/dt and ΔFFI, as well as prolonged TR₉₀ and intracellular Ca²⁺ decay. In addition, acrolein exposure upregulated TRPV1 associated with an increase in both apoptosis and oxidative stress. However, the acrolein‐induced cardiomyocyte contractile and intracellular Ca²⁺ anomalies, as well as apoptosis (as evidenced by Bcl‐2, Bax, FasL, Caspase‐3 and ?8), were negated by the reactive oxygen species (ROS) scavenger glutathione or the TRPV1 antagonist capsazepine. Collectively these data suggest that the α,β‐unsaturated aldehyde pollutant acrolein may play a role in the pathogenesis and sequelae of air pollution‐induced heart disease via a TRPV1‐ and oxidative stress‐dependent mechanism. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 638–647, 2015.     

Protective effects of emodin against cisplatin‐induced oxidative stress in cultured human kidney (HEK 293) cells

Emodin (a rhubarb anthraquinone) has strong antioxidant and anticancer actions, and recent studies indicated that it reduces cellular oxidative stress induced by various insults and drugs. Cisplatin is an anticancer drug that is associated with nephrotoxicity and induces oxidative stress in cultured human kidney (HEK 293) cells. This study aimed to assess the in‐vitro antioxidant properties of the emodin against cisplatin‐induced oxidative stress in HEK 293 cells. Our study revealed that emodin acted as a potent free radical scavenger and provided nephroprotection against cisplatin‐induced oxidative stress. Emodin as low as 0.5 µm did not decrease cell viability and restored the cisplatin‐induced glutathione depletion and total antioxidant capacity in a dose‐dependent manner. Emodin augmented the cisplatin‐induced inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S‐transferase, glutathione reductase and superoxide dismutase). These results suggest that emodin has the potential to be used as an adjunct therapeutic agent in patients receiving cisplatin treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Epitope region identification challenges of intrinsically disordered proteins in neurodegenerative diseases: Secondary structure dependence of α‐synuclein on simulation techniques and force field parameters

Due to fast aggregation processes of many disordered proteins in neurodegenerative diseases, it is difficult to study their epitope regions at the monomeric and oligomeric levels. Computer simulations complement experiments and have been used to identify the epitope regions of proteins. Residues that adopt β‐sheet conformation play a central role in the oligomerization and aggregation mechanisms of such proteins, including α‐synuclein, which is at the center of Parkinson's and Alzheimer's diseases. In this study, we simulated the monomeric α‐synuclein protein in an aqueous environment to evaluate its secondary structure properties, including β‐sheet propensity, and radius of gyration by replica exchange molecular dynamics simulations. We also obtained the molecular dynamics simulation trajectories of α‐synuclein that were conducted using various force field parameters by the David E. Shaw group. Using these trajectories, we calculated the impacts of force field parameters on α‐synuclein secondary structure properties and radius of gyration values and obtained results are compared with our data from REMD simulations. This study shows that the chosen force field parameters and computer simulation techniques effect the predicted secondary structure properties and radius of gyration values of α‐synuclein in water. Herewith, we illustrate the challenges in epitope region identification of intrinsically disordered proteins in neurodegenerative diseases by current computer simulations.     

Protective effects of Sesamum indicum extract against oxidative stress induced by vanadium on isolated rat hepatocytes

Vanadium toxicity is a challenging problem to human and animal health with no entirely understanding cytotoxic mechanisms. Previous studies in vanadium toxicity showed involvement of oxidative stress in isolated liver hepatocytes and mitochondria via increasing of ROS formation, release of cytochrome c and ATP depletion after incubation with different concentrations (25–200 µM). Therefore, we aimed to investigate the protective effects of Sesamum indicum seed extract (100–300 μg/mL) against oxidative stress induced by vanadium on isolated rat hepatocytes. Our results showed that quite similar to Alpha‐tocopherol (100 µM), different concentrations of extract (100–300 μg/mL) protected the isolated hepatocyte against all oxidative stress/cytotoxicity markers induced by vanadium in including cell lysis, ROS generation, mitochondrial membrane potential decrease and lysosomal membrane damage. Besides, vanadium induced mitochondrial/lysosomal toxic interaction and vanadium reductive activation mediated by glutathione in vanadium toxicity was significantly (P < 0.05) ameliorated by Sesamum indicum extracts. These findings suggested a hepato‐protective role for extracts against liver injury resulted from vanadium toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 979–985, 2016.