烹调油烟挥发性有机物对人胚肺成纤维细胞的氧化应激效应研究

目的：探讨烹调油烟挥发性有机物对人胚肺成纤维细胞（HELF）的氧化应激效应。方法：用活性炭采集烹调油烟挥发性有机物（COF VOCs）,通过MTT实验确定COF VOCs暴露对HELF细胞的半数抑制浓度（IC50）;取对数生长期HELF细胞,使其暴露于剂量分别为20、4、0．8μg／mL的COF VOCs,分别于12、24、48h后进行活性氧（ROS）分析、丙二醛（MDA）检测和Comet试验。结果：COF VOCs刺激HELF细胞12、24、48h的IC50分别为104．9、111．9和127．2μg／mL;流式细胞术检测发现细胞胞质和线粒体内ROS平均荧光强度随COF VOCs剂量增加而增高;剂量组MDA水平与阴性对照组相比无统计学差异;剂量组DNA断裂水平与阴性对照组相比,差异有统计学意义;各剂量组引起的细胞ROS、MDA升高和DNA断裂在不同暴露时间之间差别均无统计学意义。结论：在实验剂量水平和暴露时间内,COF VOCs暴露可引起HELF细胞胞质和线粒体内ROS升高、DNA断裂,但并不能引起脂质过氧化损伤。     

Pravastatin激活自噬抑制糖皮质激素引起的髓核细胞凋亡

地塞米松注射可以缓解椎间盘退变引起的腰痛症状,但是具有一定的副作用。普伐他汀(Pravastatin)被发现可以缓解骨关节炎的炎症和症状,但是其对髓核细胞及椎间盘退变的作用及其机制尚不清楚。该文培养SD大鼠原代髓核细胞,用不同浓度地塞米松(dexamethasone,DXM)作用髓核细胞48 h后, DCFH-DA和MitoSOX Red染色分析细胞总活性氧(reactive oxygen species, ROS)和线粒体ROS水平, Annexin V/PI流式和DAPI染色分析细胞凋亡水平, N-acetyl-Lcysteine(NAC)抑制ROS水平。Western blot检测LC3-II、Beclin-1和P62等自噬相关蛋白质水平,ATG5 siRNA转染抑制自噬。结果显示,随着DXM处理浓度的增加,髓核细胞内总ROS和线粒体ROS水平及凋亡率升高(P0.05)。Pravastatin增加DXM处理下髓核细胞中LC3-II和Beclin-1蛋白质水平,降低P62蛋白质水平(P0.05)。Pravastatin可以抑制DXM诱导的髓核细胞中的ROS产生和细胞凋亡,而ATG5 siRNA抑制自噬后,显著逆转Pravastatin对细胞的保护作用(P0.05)。该研究结果提示, Pravastatin可能通过激活髓核细胞自噬抑制DXM诱导的ROS产生从而减少细胞凋亡。     

香鳞毛蕨苷提取物E对人肺癌A549细胞增殖及凋亡的影响

目的:研究香鳞毛蕨苷提取物E(Fragranoside E)对人肺癌A549细胞增殖及凋亡的影响。方法:将体外培养的人肺癌A549细胞分为对照组(0.1%DMSO、100 nM紫杉醇)和实验组,通过CCK-8实验、克隆形成实验检测细胞增殖情况;检测乳酸脱氢酶(LDH)水平以探讨Fragranoside E的细胞毒性;透射电镜及流式细胞术检测A549细胞的凋亡情况。进一步采用5mM N-乙酰半胱氨酸(N-acetylcysteine,NAC)预处理A549细胞2 h后,采用荧光显微镜观察细胞内ROS的释放情况。结果:CCK8及克隆形成实验结果提示Fragranoside E呈浓度和时间依赖性抑制A549细胞增殖(P0.05);≤40μM Fragranoside E处理A549细胞对其LDH的释放无显著影响(P0.05);而40μM Fragranoside E可诱导A549细胞凋亡,细胞内ROS升高,NAC(5 m M)预处理2 h后,细胞内ROS(112.6%±12.3%)较Fragranoside E处理组显著降低(P0.05)。结论:Fragranoside E能够抑制A549细胞增殖,诱导其凋亡,其抗肿瘤活性可能与细胞内ROS释放有关。     

甘草查耳酮A对脑胶质瘤细胞SHG-44凋亡的影响

为了探讨甘草查耳酮A对脑胶质瘤细胞SHG-44凋亡的影响以及其机制,本研究通过CCK-8法检测脑胶质瘤细胞SHG-44细胞活力,使用FITC Annexin/PI双染流式细胞仪检测脑胶质瘤细胞SHG-44凋亡率,通过DCFDA细胞ROS检测试剂盒检测脑胶质瘤细胞SHG-44内活性氧(reactive oxygen species, ROS)水平。结果显示,不同浓度(5μmol/L, 10μmol/L和20μmol/L)甘草查耳酮A能明显降低脑胶质瘤细胞SHG-44细胞活力(p0.05, p0.01),能显著促进脑胶质瘤细胞SHG-44凋亡(p0.05);细胞内ROS水平在甘草查耳酮A处理组中明显高于正常脑胶质瘤细胞SHG-44组,ROS抑制剂、NAC预处理可明显抑制草查耳酮A降低的细胞活力(p0.01, p0.05),且对脑胶质瘤细胞SHG-44凋亡的促进作用(p0.01, p0.05)。本研究结果表明甘草查耳酮A能够通过上调ROS水平促进脑胶质瘤细胞SHG-44凋亡。     

敌敌畏对肾细胞系293T增殖的影响

为了研究敌敌畏(dichlorvos,DDVP)对人肾细胞的毒性效应。应用MTT比色法检测敌敌畏对人肾细胞系293T细胞增殖的影响,流式细胞仪检测293T细胞的凋亡情况,荧光二氯荧光素二乙酸(DCF-DA)测定细胞内的活性氧(reactive oxidative species,ROS)水平。结果表明:用浓度为0.5 mmol/L、1 mmol/L、5 mmol/L、10 mmol/L、15 mmol/L和20 mmol/L的敌敌畏分别处理293T细胞1 h后发现敌敌畏对293T的生长抑制具有剂量效应,计算得到1 h的IC_(50)值为10.406 mmol/L;不同浓度敌敌畏(0.5 mmol/L,5 mmol/L,10 mmol/L)处理1 h 293T细胞发现细胞产生明显的凋亡现象,随着处理浓度的增加,细胞的凋亡率升高,检测细胞内活性氧水平发现细胞内活性氧水平也随之升高。结果提示敌敌畏能够通过凋亡途径抑制293T细胞的增殖,其作用机制可能是通过增加293T细胞内活性氧水平,促进细胞凋亡,进而抑制细胞增殖。     

蛋白酶体抑制剂MG132的浓度对人白血病细胞K562凋亡的影响

探讨蛋白酶体抑制剂MG132 在诱导人白血病K562细胞凋亡过程中作用.分别以不同浓度的蛋白酶体抑制剂MG132 处理人白血病细胞K562,通过MTT法检测K562细胞活力,应用Annexin Ⅴ和PI 双染的细胞流式法检测K562细胞凋亡率和细胞内活性氧(ROS) 水平,应用酶标仪法检测K562细胞内Caspase- 3活性变化的情况.结果表明,随着MG132浓度的增加,各个指标与对照组比较差异均有显著性(P<0.05):K562细胞增殖明显受到抑制;细胞凋亡率明显增加,且当MG132浓度为900 nmol/L时,细胞凋亡率达36.5 %;同时,ROS 水平和caspase- 3活性明显升高.因次,蛋白酶体抑制剂MG132可显著抑制人白血病细胞K562增殖并促进其凋亡.     

3-硝基酪氨酸对HepG2细胞氧化还原状态的影响

为了确定3-硝基酪氨酸是否能促进细胞内产生氧化应激,该文研究了不同浓度3．硝基酪氨酸对HepG2细胞作用不同时间（6-48h）后,其对细胞活力、细胞内ROS（H2O2、O2-）、细胞内总抗氧化能力、细胞内抗氧化酶活力和脂质氧化的影响。结果表明,在高浓度（300μmol／L）3．硝基酪氨酸作用48h后,细胞活力下降至48．5％。同时,3-硝基酪氨酸能显著提升细胞内ROS并降低细胞内抗氧化酶活力,同时造成细胞内脂质过氧化物大量积累,最终使细胞线粒体膜电位去极化,并导致SirT3表达下调。损伤随着3-硝基酪氨酸含量的增加和反应时间的延长而加重。结果发现,3．硝基酪氨酸不仅作为蛋白质氧化产物,还能进一步通过降低机体内抗氧化能力而导致细胞内氧化应激加剧,最终导致细胞凋亡。     

氯仿对非洲绿猴肾细胞损伤机理的研究

目的　实验研究氯仿染毒 2 4h对非洲绿猴肾细胞的损伤及其机理。方法　运用显微荧光术测定了非洲绿猴肾细胞 (Vero细胞 )内活性氧 (ROS)含量及游离Ca2 + 浓度 ,同时 ,测定Vero细胞培养上清液乳酸脱氢酶(LDH)活力用于检查Vero细胞受损情况。结果　接触浓度为 4 0mmol L氯仿的Vero细胞内ROS含量及游离Ca2 +浓度与对照组比较无显著性差异 (P >0 0 5 ) ,同时 ,表示Vero细胞受损指标 (LDH活力 )也无显著性差异 (P >0 0 5 ) ;而接触浓度为 8 0mmol L、12 0mmol L氯仿的Vero细胞内ROS含量显著高于对照组 (P <0 0 1) ,其Vero细胞受损也显著增加 (P <0 0 5、P <0 0 1)。结论　较高浓度的氯仿能损伤Vero细胞 ,其损伤的可能途径是通过提高Vero细胞内ROS含量     

二十二碳六烯酸促进无葡萄糖条件下乳腺癌细胞MDA-MB-231死亡

为了探究二十二碳六烯酸(docosahexaenoic acid,DHA)抗乳腺癌的机制,采用流式细胞术分析细胞死亡率,H2DCFDA探针流式细胞术测定细胞内活性氧(reactive oxygen species,ROS)水平,Western blotting方法检测细胞内剪切型Caspase-3的变化。结果发现在无葡萄糖条件下,DHA以浓度依赖性方式促进乳腺癌细胞MDA-MB-231死亡。在这个过程中,DHA促使细胞内ROS水平明显升高,然而,当DHA和抗氧化剂N-乙酰-半胱氨酸(N-acetyl-L-cystein,NAC)共处理细胞时,细胞死亡率和细胞内ROS水平均明显降低。Western blotting检测结果表明DHA可以引起Caspase-3的切割,同时,这种变化可以被NAC抑制。结果表明在无葡萄糖条件下,DHA可以通过增加细胞内ROS的水平,激活Caspase凋亡通路,进而促进乳腺癌细胞MDA-MB-231死亡。     

胆固醇致人血管内皮细胞DNA损伤

本文研究胆固醇是否通过氧化应激机制损伤人内皮细胞DNA.实验用125 mg/L, 25 mg/L, 50 mg/L胆固醇作用于人内皮细胞12 h,用免疫荧光法观察到不同浓度的胆固醇均可诱导细胞内γH2AX形成焦点,随着胆固醇浓度的增加,γH2AX焦点的荧光强度也逐渐增强.利用Western印迹及流式细胞术检测到细胞内γH2AX的量和ROS水平也随胆固醇浓度增大而增加.彗星电泳实验检测到细胞内拖尾DNA量随胆固醇浓度逐渐增加,DNA损伤加重.用抗氧化剂10 mmol/L N 乙酰半胱氨酸(NAC)预作用细胞1 h后,再用50 mg/L胆固醇作用细胞12 h,细胞内γH2AX焦点的荧光强度明显减弱,γH2AX量减少,ROS的水平下降.结果表明,胆固醇可诱导人脐静脉内皮细胞中ROS升高,导致DNA损伤.     

Niacin, poly(ADP-ribose) polymerase-1 and genomic stability

This study demonstrates that cupric 8-quinolinoxide (CuQ) has induced genetic toxicity in bacteria and mammalian cells through a mechanism of reactive oxygen species (ROS) generation. In the Ames test with rat liver S9, CuQ dose-dependently caused a point mutation in Salmonella typhimurium TA100. The effect of CuQ on DNA damage in HL60 and V79 cells identified in the comet assay is direct and enhanced by the addition of S9. Meanwhile, the tailing length of comet DNA is related to the increasing dosage of CuQ. The genotoxic effect of CuQ on either gene mutation in bacteria or DNA damage in culture cells can be generally blocked by several antioxidants, e.g. pyrrolidinedithiocarbamate, N-acetylcysteine, Vitamins C and E. Supportive of this observation, ROS generation induced by CuQ can be demonstrated both in vitro and in vivo by using the DCFH-DA fluoroprobe. The CuQ-induced intracellular ROS level is also dramatically inhibited by the above antioxidants. Above results imply that the CuQ-induced genotoxicity could be mediated by ROS generation. The nature of ferrous-dependent and S9-enhancing in CuQ-induced ROS generation hints a Fenton-like reaction or some specific enzymes activation could be involved in this process. Furthermore, a DNA damage- and oxidative stress-dependent protein, P53, could also been induced by CuQ treatments in a time-course and dose-dependent manners. Its expression level is recoverable by antioxidants too. In conclusion, our current study strongly suggests that CuQ induces gene mutation, global DNA damage, and P53 expression through a ROS-dependent mechanism.     

巯基物质在氧自由基损伤离体胃粘膜细胞中的作用

本文用离体胃粘膜细胞研究了细胞内流基物质在活性氧诱发细胞损伤中的作用。实验采用pronase-EDTA法分离大鼠胃粘膜细胞并进行短期孵育,以黄嘌呤氧化酶(XO)-黄嘌呤(X)系统产生氧自由基损伤细胞。实验结果表明,用XO-X损伤胃粘膜细胞时,细胞存活率显著降低,乳酸脱氨酶(LDH)漏出量增多,同时细胞内非蛋白质巯基(NPSH)和蛋白质巯基(PSH)含量均不同程度地下降;N-乙基顺丁烯二酰亚胺(NEM)在耗竭细胞内NPSH和PSH的同时,引起细胞死亡和LDH漏出增加,这一作用与NEM的作用时间和浓度是显著依从关系;在细胞孵育液中预先加入含-SH的化合物还原型谷胱甘肽(GSH)或半胱胺,可剂量依赖性地减轻XO-X引起的细胞损伤。上述结果提示,胃粘膜细胞内的巯基物质在自身防御机制中具有重要作用,氧自由基损伤胃粘膜细胞的机制之一可能与破坏细胞内巯基的稳态有夫。     

Ca(2+)]-dependent generation of intracellular reactive oxygen species mediates maitotoxin-induced cellular responses in human umbilical vein endothelial cells

Maitotoxin (MTX) is known as one of the most potent marine toxins involved in Ciguatera poisoning, but intracellular signaling pathways caused by MTX was not fully understood. Thus, we have investigated whether intracellular reactive oxygen species (ROS) are involved in MTX-induced cellular responses in human umbilical vein endothelial cells. MTX induced a dose-dependent increase of intracellular [Ca(2+)]. MTX stimulated the production of intracellular ROS in a dose- and time-dependent manner, which was suppressed by BAPTA-AM, an intracellular Ca(2+) che-lator. Ionomycin also elevated the ROS production in a dose-dependent manner. MTX elevated transamidation activity in a time-dependent manner and the activation was largely inhibited by transfection of tissue transglutaminase siRNA. The activation of tissue transglutaminase and ERK1/2 by MTX was sup-pressed by BAPTA-AM or ROS scavengers. In addition, MTX-induced cell death was significantly de-layed by BAPTA-AM or a ROS scavenger. These results suggest that [Ca(2+)]-dependent generation of in-tracellular ROS, at least in part, play an important role in MTX-stimulated cellular responses, such as activation of tTGase, ERK phosphorylation, and in-duction of cell death, in human umbilical vein endothelial cells.     

Sulfhydryl groups during the S phase: comparison of cells from G 1 , plateau-phase G 1 , and G 0

The non-protein sulfhydryl (NPSH) content of cells moving into S from G₁, plateau phase G₁, and G₀ was measured. Chinese hamster ovary (CHO) cells accumulated in G₁ by growth into plateau phase contain only one-fourth the NPSH concentration of cycling C₁ cells or G₁ cells accumulated by brief growth in isoleucine-deficient medium. Upon dilution of plateau cultures with fresh medium, cellular NPSH content increases rapidly, reaching the same level as that in cycling cells within four hours. This increase is prevented by cycloheximide but not by actinomycin D or hydroxyurea. Neither CHO cells cycling in vitro nor salivary gland G₀ cells stimulated with isoproterenol in vivo show significant changes in intracellular NPSH concentrations during S phase. This suggests that the concentration of intracellular NPSH (glutathione) remains constant during the cell cycle except when cells are grown to plateau phase in exhausted or deficient medium, in which case normal degradation exceeds synthesis and the gross level falls until fresh medium is provided and synthesis, apparently on preexisting RNA templates, accelerates.     

Arsenic trioxide induces the apoptosis in vascular smooth muscle cells via increasing intracellular calcium and ROS formation

The present study was designed to investigate whether arsenic trioxide induced the apoptosis in rat mesenteric arterial smooth muscle cells (SMCs), which provides new insights into mechanisms of arsenic-related vascular diseases. Here, we found that arsenic trioxide significantly decreased the viability of SMCs in a dose-dependent manner. In addition, higher level of arsenic trioxide directly caused cellular necrosis. The Hoechst and AO/EB staining demonstrated that apoptotic morphological change was presented in SMCs exposed to arsenic trioxide. The TUNEL assay displayed that more positive apoptotic signal appeared in SMCs treated with arsenic trioxide. The following result showed that ROS formation was markedly increased in arsenic trioxide-treated SMCs. Pretreatment with N-acetylcysteine, an anti-oxidant reagent, obviously attenuated the enhancement of ROS production and the reduction of cell viability induced by arsenic trioxide in SMCs. Arsenic trioxide also enhanced free intracellular Ca²⁺ level in SMCs. BAPTA also significantly prevented the increased intracellular Ca²⁺ and decreased cell viability induced by arsenic trioxide in SMCs. These results suggested that arsenic trioxide obviously induced apoptosis in SMCs, and its mechanism was partially associated with intracellular ROS formation and free Ca²⁺ increasing.     

2,3,7,8-tetrachlorobenzo-p-dioxin inhibits proliferation of SK-N-SH human neuronal cells through decreased production of reactive oxygen species

Oxidative stress has been known to be involved in the mechanism of toxic effects of various agents on many cellular systems. In this study we investigated the role of reactive oxygen species (ROS) in 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD)-induced neuronal cell toxicity using SK-N-SH human neuroblastoma cells. TCDD inhibited proliferation of the cells in a dose-dependent manner, which was revealed by MTT staining, counting of cells stained with trypan blue and [ 3 H]thymidine uptake assay. TCDD also suppressed the basal generation of ROS in a time- and concentration-dependent manner assessed by 2',7'-dichlorofluorescein fluorescence. In addition, TCDD induced a dose-dependent inhibition of lipid peroxidation, a biomarker of oxidative stress, whereas it significantly increased the level of glutathione (GSH), an intracellular free radical scavenger in the cells. Moreover, TCDD altered the activities of major antioxidant enzymes; increase in superoxide dismutase (SOD) and catalase, but decrease in glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Red). Pretreatment with l -buthionine- S , R -sulfoximine (BSO, 50 μM), an inhibitor of GSH synthesis, significantly prevented the TCDD-induced reduction in lipid peroxidation and cell proliferation. Interestingly, exogenous application of an oxidant, H 2 O 2 (50 μM) markedly restored the inhibited cell proliferation induced by TCDD. Taken together, these results suggest that alteration of cellular redox balance may mediate the TCDD-induced inhibition of proliferation in human neuronal cells.     

Evidences for adduct formation between intracellular non-protein thiols and nitroazoles possessing an alpha,beta-unsaturated carbonyl side chain and the effects on radiosensitization of hypoxic cells

Reactivity of a number of nitroazole derivatives bearing an alpha,beta-unsaturated carbonyl group on the side chain toward non-protein thiols (NPSH) was examined both in the phosphate buffer solution and in the biological system. These alpha,beta-unsaturated compounds reacted with NPSH, such as glutathione (GSH) and L-cysteine (Cys), in the buffer solution to afford the 1,4-addition products. The reaction gave a second-order rate constant. The adducts of methyl 4-(2'-nitroimidazol-1'-yl)crotonate (1) with GSH and Cys were isolated and characterized as two diastereomers (7a,b and 8a,b) in ca. 1:1 ratio, respectively. Similarly, exposure of EMT6/KU cells to 1 at 1.0 mM for 1 h resulted in depletion of the intracellular NPSH by more than 80%. Over 50% of the depleted NPSH was attributed to the formation of the conjugated diastereomeric adducts. On the other hand, incubation of EMT6/KU cells with 1 at 1.0 mM under hypoxic conditions before X-ray irradiation caused concurrently a sharp reduction of the shoulder of the dose-survival curves (reduced the extrapolation number (n) from 8.0 to ca. 1.0) and an increase in the slope (decreased the mean lethal dose (Do) to ca. 50% of the control level). The observed effects of 1 on the dose-survival curves were due to the NPSH depletion through the Michael addition occurred in the cellular system. A fairly linear relationship was obtained between the n value and the reduced intracellular NPSH level. It indicated that the shoulder effect of the dose-survival curves of hypoxic cells should be the result of the NPSH depletion by the alpha,beta-unsaturated carbonyl group attached to the nitroazoles.     

Reactive oxygen species modulates the intracellular level of HBx viral oncoprotein

HBx (hepatitis B virus X) viral oncoprotein is a multifunctional protein of which the cellular level may be one of the important factors in determining HBV-mediated pathological progression of liver diseases, chronic hepatitis, and hepatocellular carcinoma. Our previous work revealed that adriamycin, a chemotherapeutic agent, caused a marked increase in the intracellular level of HBx by retarding its rapid degradation. In the present study, modulation of HBx expression was found to be confined to adriamycin but not to other chemotherapeutic agents, cisplatin and 5-fluorouracil. Interestingly, adriamycin caused a rapid increase of reactive oxygen species (ROS) and its accumulation continued until 24h. In contrast, two other agents had little effect on ROS generation, suggesting the possible involvement of ROS in the HBx regulation. In fact, direct addition of H(2)O(2) to the cells significantly increased the level of HBx protein in HBx-expressing ChangX-34 cells as well as in hepatitis B virus-related hepatoma cells, PLC/PRF/5 and HepG2.2.15 cells. Furthermore, antioxidants, N-acetyl-cysteine and pyrrolidinedithiocarbamate (PDTC), completely abolished the increase of HBx protein induced by adriamycin, indicating that adriamycin modulates the intracellular HBx level via ROS generation. Together, these findings provide a novel aspect of HBx regulation by cellular ROS level. Therefore, intracellular microenvironments generating ROS such as severe inflammation may aggravate the pathogenesis of liver disease by accumulating the HBx level.     

Involvement of ROS/ASMase/JNK signalling pathway in inhibiting UVA-induced apoptosis of HaCaT cells by polypeptide from Chlamys farreri

Polypeptide from Chlamys farreri (PCF), a novel marine active material isolated from gonochoric Chinese scallop C. farreri, has potential antioxidant activity and protective effect against ultraviolet (UV) irradiation. The aim was to investigate whether PCF protects HaCaT cells from apoptosis induced by UVA and explore related molecular mechanisms. The results showed that PCF significantly prevented UVA-induced apoptosis of HaCaT cells. PCF not only strongly reduced the intracellular reactive oxygen species (ROS) production, but also diminished expression of acid sphingomyelinase (ASMase) and phosphorylated JNK in HaCaT cells radiated by UVA in a dose-dependent manner. Pre-treatment with ROS scavenger NAC, ASMase inhibitor Desipramine or JNK inhibitor SP600125 was found to effectively prohibit UVA-induced apoptosis and Desipramine markedly blocked phosphorylation of JNK. So it is concluded that PCF obviously protects HaCaT cells from apoptosis induced by UVA and protective effects may attribute to decreasing intracellular ROS level and blocking ASMase/JNK apoptotic signalling pathway.     

Dieldrin-induced oxidative stress and neurochemical changes contribute to apoptopic cell death in dopaminergic cells.

We examined the acute toxicity of dieldrin, a possible environmental risk factor of Parkinson's disease, in a dopaminergic cell model, PC12 cells, to determine early cellular events underlying the pesticide-induced degenerative processes. EC(50) for 1 h dieldrin exposure was 143 microM for PC12 cells, whereas EC(50) for non-dopaminergic cells was 292-351 microM, indicating that dieldrin is more toxic to dopaminergic cells. Dieldrin also induced rapid, dose-dependent releases of dopamine and its metabolite, DOPAC, resulting in depletion of intracellular dopamine. Additionally, dieldrin exposure caused depolarization of mitochondrial membrane potential in a dose-dependent manner. Flow cytometric analysis showed generation of reactive oxygen species (ROS) within 5 min of dieldrin treatment, and significant increases in lipid peroxidation were also detected following 1 h exposure. ROS generation was remarkably inhibited in the presence of SOD. Dieldrin-induced apoptosis was significantly attenuated by both SOD and MnTBAP (SOD mimetic), suggesting that dieldrin-induced superoxide radicals serve as important signals in initiation of apoptosis. Furthermore, pretreatment with deprenyl (MAO-inhibitor) or alpha-methyl-L-p-tyrosine (TH-inhibitor) also suppressed dieldrin-induced ROS generation and DNA fragmentation. Taken together, these results suggest that rapid release of dopamine and generation of ROS are early cellular events that may account for dieldrin-induced apoptotic cell death in dopaminergic cells.