Neurotoxicity of artemether and its mechanism

It was reported that artemisinin derivatives in high does could lead to neurotoxicity in rat,dog and monkey.Using artemether as a representative,neurotoxicity and its mechanism of artemisinin derivatives was studied in vitro.MTT assay showed that artemether could affect MTT transformation of pheochromocytoma cell significantly.The morphologic result showed that artemisinin mainly injured mitochondria of pheochromocytoma cells and primary cultured rat neural cells with mitochondrial swelling and mitochondrial crista decreasing,rupturing and disappearing,and degeneration.Artemisinin could decrease mitochondrial transmembrane potential in both cell types in a dose-dependent manner and inhibit activity of the complex I and Ⅳ of mitochondria respiratory chain of rat brain.but the production of malondialdehyde in rat cerebral cortex mitochondria wasn‘t increased by artemether.Based on these experiments,it may infer that one of the neurotoxic mechanism of arfemether lies on its effects on the structure and function of mitochondria of neural cell.     

Procyanidins from grape seeds protect against phorbol ester-induced oxidative cellular and genotoxic damage

AIM: To evaluate the inhibitory effects of Vitis vinifera procyanidins (PAs) on carcinogen-induced oxidative stress. METHODS: The single cell gel electrophoresis technique (comet assay) was employed to detect DNA damage induced by the carcinogen phorbol-12-myristate-13-acetate (PMA), The release of hydrogen peroxidase from polymorphonuclear leukocytes (PMNs) was assayed by the horseradish peroxidase-mediated oxidation of phenol red. The microplate assay was used to detect the presence of oxidative products by means of 2‘,7‘-dichlorofluorescindiacetate (DCFH-DA). The superoxide dismutase (SOD) activity of liver mitochondria was assayed, based on the ability of SOD to inhibit the generation of superoxidate anions by the xanthine-xanthine oxidase system. The malondialdehyde (MDA) level was determined by the thiobarbituric acid (TBA) assay. RESULTS: DNA of NIH3T3 cells was significantly damaged after addition of PMA. The length of the comet tail was observed ,while in normal cells the comet tail could not be observed. PAs showed significant protective effects on carcinogen PMA-induced DNA damage. Through assessment of DCFH-DA oxidation, PAs were shown to inhibit the PMA-induced release of hydrogen peroxide by PMNs, and to inhibit respiratory burst activity in NIH3T3 mouse fibroblasts. Ex vivo study showed that serum from rats administered with PAs displayed similar effects in a dose-dependent manner. In addition, PAs suppressed liver mitochondrial lipid peroxidation induced by PMA. PAs protected the activity of SOD and decreased the level of MDA in liver mitochondria damaged by PMA. CONCLUSION: Dietary PAs from grape seeds protect against carcinogen-induced oxidative cellular and genotoxic damage,     

Protective effects of compound FLZ,a novel synthetic analogue of squamosamide,on β-amyloid-induced rat brain mitochondrial dysfunction in vitro

Aim： The aim of the present study was to assess the effects of N-[2-（4-hydroxyphenyl）ethyl]-2-（2,5-dimethoxyphenyl）-3-（3- methoxy-4-hydroxyphenyl） acrylamide （compound FLZ）, a novel synthetic analogue of squamosamide, on the dysfunction of rat brain mitochondria induced by Aβ25-35 in vitro. Methods： Isolated rat brain mitochondria were incubated with aged Aβ25-35 for 30 rain in the presence and absence of FLZ （1-100 μmol/L）. The activities of.key mitochondrial enzymes, the production of hydrogen peroxide （H2O2） and superoxide anion （O2^-）, and the levels of glutathione （GSH） in mitochondria were examined. Mitochondrial swelling and the release of cytochrome c from mitochondria were assessed by biochemical and Western blot methods, respectively. Results： Incubation of mitochondria with aged Aβ25-35 inhibited the activities of α-ketoglutarate dehydrogenase （α-KGDH）, pyruvate dehydrogenase （PDH） and respiratory chain complex IV. It also resulted in increased H2O2 and O2^- production, and decreased the GSH level in mitochondria. Furthermore, it induced mitochondrial swelling and cytochrome c release from the mitochondria. The addition of FLZ （100 μmol/L） prior to treatment with Aβ25-35 significantly prevented these toxic effects of Aβ25-35 on the mitochondria. Conclusion： FLZ has a protective effect against Aβ25-35-induced mitochondrial dysfunction in vitro.     

一叶萩碱对5种神经递质受体和蛙脊髓膜电位的影响

Using radioligand binding assay method, securinine was shown to be specifically bound to GABA receptors of rat brain with IC₅₀ of 10^(-4)～10^-5mol/L. However, securinine did not exhibit affinity for a₁-, a₂- adrenoceptors and M-cholinergic receptors of rat brain and the β-adrenoceptors of duck erythrocyte membrane. In isolated and perfused bullfrog spinal cord experiment, the depolarization induced by GABA was slightly depressed by securinine (1 mmol/L), but no antagonistic effect on glycine or taurine evoked depolarization was observed with securinine. These results indicate that securinine is a weak GABA antagonist.     

Metabolism of risperidone to 9-hydroxyrisperidone by human cytochromes P450 2D6 and 3A4

Risperidone is a relatively new antipsychotic drug that has been reported to improve both the positive and the negative symptoms of schizophrenia and produces relatively few extrapyramidal side effects at low doses. Formation of 9-hydroxyrisperidone, an active metabolite, is the most important metabolic pathway of risperidone in human. In the present study, in vitro metabolism of risperidone (100 μM) was investigated using the recombinant human cytochrome P450 (CYP) enzymes CYP1A1, CYP1A2, CYP2C8, CYP2C9-arg₁₄₄, CYP2C9-cys₁₄₄, CYP2C19, CYP2D6, CYP3A4 and CYP3A5 supplemented with an NADPH-generating system. 9-Hydroxyrisperidone was determined by a new HPLC method with an Hypersil CN column and a UV detector. Of these enzymes, CYPs 2D6, 3A4 and 3A5 were found to be the ones capable of metabolising risperidone to 9-hydroxyrisperidone, with activities of 7.5, 0.4 and 0.2 pmol pmol^–1 CYP min^–1, respectively. A correlation study using a panel of human liver microsomes showed that the formation of 9-hydroxyrisperidone is highly correlated with CYP2D6 and 3A activities. Thus, both CYP2D6 and 3A4 are involved in the 9-hydroxylation of risperidone at the concentration of risperidone used in this study. This observation is confirmed by the findings that both quinidine (inhibitor of CYP2D6) and ketoconazole (inhibitor of CYP3A4) can inhibit the formation of 9-hydroxyrisperidone. Furthermore, inducers of CYP can significantly increase the formation of 9-hydroxyrisperidone in rat. The formation of 9-hydroxyrisperidone is highly correlated with testosterone 6β-hydroxylase activities, suggesting that inducible CYP3A contributes significantly to the metabolism of risperidone in rat. Received: 4 May 1998 / Accepted: 26 October 1998     

黄芪皂苷甲对血浆cAMP及再生肝DNA合成的影响

Astragalus saponin 1, one of the components isolated from Astragalus membranaceus Bge was found to induce accumulation of cAMP in rabbit plasma at the ip dose of 10mg/kg. The increase of cAMP started at 30 rain and reached maximum in 0.5～4h after a single injection. The effect of the component on DNA biosynthesis in partially hepatectomized mice seemed to be significant. The component was also shown to enhance the incorporation of [³H] TdR into the regenerating liver in mice.     

Assay of mitochondrial functions by resazurin in vitro

AIM: To study the mechanism of resazurin as indicator of mitochondrial function and to develop a rapid and sensitive assay for measuring metabolic activity of isolated mitochondria from rat liver in vitro. METHODS: The screening was carried out on 96-well microtitre plates by monitoring fluorescence intensity of resazurin reduced by mitochondria. Experimental conditions were optimized and influences of several inhibitors on mitochondrial function were observed. RESULTS: Fluorescence intensity increased in a linear manner when the mitochondrial protein concentration from 5 to 50 μg protein per well was incubated with resazurin (5μmol/L) during 230 min period at 37℃. Edetic acid could promote the reduction of resazurin in mitochondria. The fluorescence intensity decreased greatly after pretreatment with NAN3, antimycin A, carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP),and oligomycin compared with the control. However, the typical complex I inhibitor, rotenone enhanced the fluorescence intensity without mitochondria. CONCLUSION: Using resazurin to determine mitochondrial function is sensitive, inexpensive and could be easily automated for high throughput screening.     

Synergistic enhancement of the acoustic startle reflex by dopamine D1 and 5-HT1A agonists and corresponding changes in c-Fos expression in the dorsal raphe of rats

Rationale: Although there is evidence that central opioid receptors are involved in immunomodulation, it has been only recently that an endogenous agonist, designated endomorphin-1, possessing high selectivity and affinity for the mu opioid receptor has been identified. Objective: The present study assesses the immunomodulatory effects of endomorphin-1 in the rat and provides further evaluation of the antinociceptive effects of endomorphin-1. Methods: Rats were surgically implanted with cannulae directed at the lateral cerebral ventricle. Animals received vehicle or endomorphin-1 at doses of 31.63 or 56.23 μg (ICV) and were tested for antinociception in two different assays, the warm water tail withdrawal procedure and the hotplate assay. Additional studies assessed the effect of naltrexone on the antinociception produced by endomorphin-1 in both antinociceptive assessments. Assessments of immune status following endomorphin-1 treatment included measurements of splenic natural killer cell activity, production of interferon-γ, and lymphocyte proliferative responses to mitogenic stimulation by Con-A, LPS, and the microbial superantigen, TSST-1. Results: Endomorphin-1 induced significant and naltrexone reversible antinociception 30 and 60 min following drug administration, as measured by the hotplate assay and warm water tail withdrawal procedure. In marked contrast, endomorphin-1 did not produce immunomodulatory effects up to 120 min following ICV administration. Conclusions: Endomorphin-1 produces antinociception but does not induce immunomodulatory effects in the rat. These findings suggest that it is possible to develop therapeutic strategies for separating antinociception and immunomodulatory properties through the mu opioid receptor. Electronic Publication     

4-氨基吡啶对牛磺酸调节突触体氨基酸释放的影响

AIM　To elucidate the mechanism of taurine-regulated amino acid release from synaptosomes. METHODS　Endogenous aspartate, glutamate and GABA release from cortical synaptosomes were measured by high performance liquid chromatography using stepwise elution system, Glutamate release was monitored by continuous fluorometry. RESULTS　4-Aminopyridine (3.0×10^-2 mol*L^-1) counteracted the taurine-induced inhibition of glutamate overflow (P<0.05), while aspartate and GABA release was not affected. Nimodipine (10^-5 mol*L^-1) combined with 4-aminopyridine was shown to decrease glutamate release (P<0.05). CONCLUSION　Taurine may regulate glutamate release through presynaptic L-type calcium channel and aslo act on Asp-and GABA-nereve terminal to regulate Asp and GABA release in rat cortex.     

Naltrexone and β-funaltrexamine antagonism of the antinociceptive and response rate-decreasing effects of morphine, dezocine, and d-propoxyphene

  Rationale: Patterns of competitive and insurmountable antagonism provide important data to guide the classification and characterization of different types of opioid agonists as well as infer the mechanism of action for agonists. Objective: Experiments with the competitive antagonist, naltrexone, and the insurmountable antagonist, β-funaltrexamine (β-FNA), were conducted to determine whether the antinociceptive and rate-decreasing effects of the opioid agonists dezocine and d-propoxyphene are 1) mediated through μ opioid receptors in rats, and 2) differ from morphine with respect to relative efficacy. Methods: The rat tail-withdrawal assay was used to measure antinociception and a fixed ratio 20 (FR20) schedule of food delivery was used to measure rate suppression. Results: Naltrexone (0.01–1.0 mg/kg) was approximately equipotent as an antagonist of the antinociceptive and rate-decreasing effects of both morphine and dezocine and as an antagonist of the antinociceptive effects of d-propoxyphene. Naltrexone failed to block the rate-decreasing effects of d-propoxyphene. β-FNA (5 and 10 mg/kg) also antagonized the antinociceptive and rate-decreasing effects of morphine and dezocine as well as the antinociceptive effects of d-propoxyphene. β-FNA failed to produce a dose-dependent antagonism of the rate-decreasing effects of d-propoxyphene. Conclusions: These data suggest that the antinociceptive effects of morphine, dezocine, and d-propoxyphene and the rate-decreasing effects of morphine and dezocine are mediated through μ opioid receptors. Overall, high doses of β-FNA produced a greater degree of antagonism of the behavioral effects of dezocine than morphine or d-propoxyphene, confirming other reports that dezocine is a lower efficacy agonist than morphine. Additionally, the degree of antagonism produced by β-FNA was greater for the antinociceptive effects of all three compounds than for the rate-decreasing effects. Received: 14 August 1998 / Final version: 4 December 1998     

阿魏酸钠对大鼠肝线粒体氧化性损伤的保护作用

观察到阿魏酸钠有明显抑制硫酸亚铁和维生素C系统诱导的脂质过氧化反应和线粒体膨胀作用,且呈量效关系,并缓解丙二醛(脂质过氧化产物之一)对线粒体氧化磷酸化过程的解偶联反应。线粒体膜蛋白电泳图谱呈现阿魏酸钠有抑制丙二醛与膜蛋白交联作用。上述结果提示阿魏酸钠可缓解自由基损伤反应,有益机体能量合成代谢。     

没食子酸丙脂对乙醇诱导鼠肝急性损伤的保护作用

本文研究没食子酸丙酯对乙醇塑造鼠急性肝损伤模型的影响。结果证实该化合物具有抑制肝组织脂质过氧化、维持鼠肝线粒体氧化磷酸化、保护其形态结构的完整性等作用。为阐明赤芍的生化药理作用提供资料。     

N-甲基-4-苯基1,2,3,6-四氢吡啶及多巴胺体外引起大鼠脑线粒体损伤作用

目的：观察1-甲基,4-苯基1,2,3,6-四氢吡啶（MPTP）和多巴胺对大鼠脑线粒体损伤作用。方法：大鼠脑线粒体与MPTP和多巴胺温孵后测定膜流动性、膜电位、线粒体肿胀、总ATP酶、呼吸链复合酶活性及线粒体H₂O₂, 和丙二醛（MDA）含量。结果：二者可降低线粒体膜流动性,MPTP损伤线粒体膜电位,对线粒体肿胀、总ATP酶活性无影响;多巴胺不改变膜电位,却抑制总ATP酶活性,导致线粒体肿胀。二者均增加线粒体中MDA含量。多巴胺使H₂O₂和生成增加,MPTP仅增加H₂O₂生成。多巴胺抑制呼吸链复合酶活性,MPTP略有激活作用。结论：MPTP与多巴胺损伤线粒体作用的不同, 可能与通过不同途径刺激氧自由基生成有关。     

淫羊藿苷对氧自由基所致大鼠脑线粒体损伤的保护作用

目的设想神经元缺氧损伤与自由基损伤线粒体有关,由此探讨淫羊藿苷的保护作用机制。方法采用Fe2+/维生素C(VitC)为氧自由基生成系统建立氧自由基损伤线粒体的体外模型。观察淫羊藿苷对线粒体肿胀度、呼吸链复合体酶Ⅰ～Ⅳ活性、丙二醛(MDA)含量的影响。结果Fe2+/VitC(1mmol·L-1/1mmol·L-1,10mmol·L-1/10mmol·L-1)可使线粒体的肿胀度和MDA含量显著增加,呼吸链复合体酶Ⅱ～Ⅳ活性不同程度下降。预先加入淫羊藿苷(0.03和0.1mg·L-1)能显著抑制线粒体肿胀,减少MDA含量,提高呼吸链复合体酶Ⅱ～Ⅳ的活性。结论淫羊藿苷对氧自由基损伤的大鼠脑线粒体呼吸链具有保护作用。     

Contribution of liver mitochondrial membrane-bound glutathione transferase to mitochondrial permeability transition pores

We recently reported that the glutathione transferase in rat liver mitochondrial membranes (mtMGST1) is activated by S-glutathionylation and the activated mtMGST1 contributes to the mitochondrial permeability transition (MPT) pore and cytochrome c release from mitochondria [Lee, K.K., Shimoji, M., Quazi, S.H., Sunakawa, H., Aniya, Y., 2008. Novel function of glutathione transferase in rat liver mitochondrial membrane: role for cytochrome c release from mitochondria. Toxcol. Appl. Pharmacol. 232, 109-118]. In the present study we investigated the effect of reactive oxygen species (ROS), generator gallic acid (GA) and GST inhibitors on mtMGST1 and the MPT. When rat liver mitochondria were incubated with GA, mtMGST1 activity was increased to about 3 fold and the increase was inhibited with antioxidant enzymes and singlet oxygen quenchers including 1,4-diazabicyclo [2,2,2] octane (DABCO). GA-mediated mtMGST1 activation was prevented by GST inhibitors such as tannic acid, hematin, and cibacron blue and also by cyclosporin A (CsA). In addition, GA induced the mitochondrial swelling which was also inhibited by GST inhibitors, but not by MPT inhibitors CsA, ADP, and bongkrekic acid. GA also released cytochrome c from the mitochondria which was inhibited completely by DABCO, moderately by GST inhibitors, and somewhat by CsA. Ca²⁺-mediated mitochondrial swelling and cytochrome c release were inhibited by MPT inhibitors but not by GST inhibitors. When the outer mitochondrial membrane was isolated after treatment of mitochondria with GA, mtMGST1 activity was markedly increased and oligomer/aggregate of mtMGST1 was observed. These results indicate that mtMGST1 in the outer mitochondrial membrane is activated by GA through thiol oxidation leading to protein oligomerization/aggregation, which may contribute to the formation of ROS-mediated, CsA-insensitive MPT pore, suggesting a novel mechanism for regulation of the MPT by mtMGST1.     

丹酚酸A对大鼠脑突触体和线粒体氧应激损伤的体外保护作用

利用蔗糖梯度法分离大鼠脑突触体和线粒体，以Fe^2＋-半胱氨酸（Cys）为氧自由基生成系统造成大鼠脑突触体和线粒体氧应激损伤模型. 在体外Fe^2＋-Cys与脑突触体和线粒体共同温孵可使丙二醛(MDA)生成量显著增加，线粒体ATP酶活性下降. 预先加入丹酚酸 A(Sal A)可显著抑制MDA生成，恢复线粒体 ATP酶活性，防止线粒体肿胀和膜流动性的降低. 通过电镜照片可看到Fe^2＋-Cys引起的线粒体和突触体结构病理性改变，预先加入Sal A可减轻Fe^2＋-Cys造成的这一损伤. 此外，Sal A可阻抑H₂O₂引起的脑突触体GSH含量的降低. 由此可见，Sal A体外对氧应激引起的大鼠脑突触体和线粒体脂质过氧化损伤有明显的保护作用.     

Toxic effects of carvacrol, caryophyllene oxide, and ascaridole from essential oil of Chenopodium ambrosioides on mitochondria

Chenopodium ambrosioides have been used for centuries in the Americas as a popular remedy for parasitic diseases. The essential oil of this plant possesses anthelmintic activity and is still used in some regions to treat parasitosis and leishmaniasis. However, the Chenopodium oil caused also some fatalities, leading to its commercial disuse. In this work, we studied the mechanism of toxicity of the essential oil and its major pure ingredients (carvacrol, caryophyllene oxide, and ascaridole, which was synthesized from α-terpinene) with respect to mammalian cells and mitochondria. We observed that all products, but especially caryophyllene oxide, inhibited the mitochondrial electron transport chain. This effect for carvacrol and caryophyllene oxide was mediated via direct complex I inhibition. Without Fe²⁺, ascaridole was less toxic to mammalian mitochondria than other major ingredients. However, evidence on the formation of carbon-centered radicals in the presence of Fe²⁺ was obtained by ESR spin-trapping. Furthermore, it was shown that Fe²⁺ potentiated the toxicity of ascaridole on oxidative phosphorylation of rat liver mitochondria. The increase of the α-tocopherol quinone/α-tocopherol ratio under these conditions indicated the initiation of lipid peroxidation by Fe²⁺-mediated ascaridole cleavage. Further ESR spin-trapping experiments demonstrated that in addition to Fe²⁺, reduced hemin, but not mitochondrial cytochrome c can activate ascaridole, explaining why ascaridole in peritoneal macrophages from BALB/c mice exhibited a higher toxicity than in isolated mitochondria.     

Arsenic-induced hepatic mitochondrial toxicity in rats and its amelioration by diallyl trisulfide

The present investigation was aimed to investigate the possible protective role of diallyl trisulfide (DATS) against arsenic (As)-induced hepatic mitochondrial toxicity in rats. Mitochondria were isolated from the liver tissue of rats from all the groups. Lipid profile, lipid peroxidation, antioxidant enzyme activities, hepatic function enzymes, mitochondrial swelling, cytochrome c oxidase activity, mitochondrial Ca⁺-ATPase and Na⁺/K⁺-ATPase activity, mitochondrial calcium content and mitochondrial enzyme activities were measured. Short-term As exposure (5?mg/kg?bw/d for 28?d) caused liver damage as evidenced by changes in activities of liver enzymes. The effects of As were coupled with enhanced reactive oxygen species generation, mitochondrial swelling, inhibition of cytochrome c oxidase, complex I-mediated electron transfer, decreased Ca²⁺-ATPase and Na⁺/K⁺-ATPase activity, a reduction in mitochondrial calcium content, changes in indices of hepatic mitochondrial oxidative stress, significant increase in mitochondrial lipid peroxidation products and alterations in mitochondrial lipid profile. Significant decreases in mitochondrial antioxidants and tricarboxylic acid cycle enzymes were also found in the liver mitochondria of As-induced hepatic mitochondrial toxicity in rats. As also increased hepatic caspase-3 activity and DNA fragmentation. All these apoptosis-related molecular changes caused by As could be alleviated by supplementation with DATS, which likely suggests a protective role against As-induced hepatotoxic changes and hepatic mitochondrial toxicity. The protective effect of DATS on the liver mitochondria was evidenced by altering all the changes induced by As. Free radical scavenging and metal chelating activities of DATS may be the mechanism, responsible for the protective action against As-induced mitochondrial damage in liver.     

Hydroxyl scavenging activity accounts for differential antioxidant protection of Plantago major against oxidative toxicity in isolated rat liver mitochondria

Objectives The aim of this work was to study the effects of P. major against the oxidative damage of isolated rat liver mitochondria. Methods The extracts were obtained using methanol (MeOH), ethyl acetate (EAc), dichloromethane (DCM), and hexane (Hex) as solvents. Key findings Hex, DCM, and EAc totally, and MeOH partially, inhibited ROS generation and lipid peroxidation of membranes induced by Fe²⁺ or t‐BOOH. However, only MeOH was able to prevent the t‐BOOH‐induced glutathione and NAD(P)H oxidation. All extracts chelated Fe²⁺ and reduced DPP Hradicals. EPR analysis revealed that P. major exhibited potent scavenger activity for hydroxyl radicals. Conclusions The potent antioxidant activity exhibited by P. major was able to prevent oxidative mitochondrial damage, contributing to the understanding of its hepatoprotective action against ROS‐mediated toxicity.     

羟基红花黄色素A冻干粉针剂对血小板活化因子致大鼠脑皮质线粒体损伤的保护作用

目的观察羟基红花黄色素A冻干粉针剂对血小板活化因子（PAF）引起的线粒体损伤的保护作用。方法采用PAF诱导剂,对分离的大鼠脑线粒体进行体外损伤试验。损伤后线粒体给予羟基红花黄色素A（HSYA）冻干粉针剂温育,观察试验前后线粒体膜流动性、肿胀度和超氧化物歧化酶（SOD）、丙二醛（MDA）含量的变化。结果PAF可降低线粒体膜流动性、增加线粒体的肿胀度、减少SOD含量、增加MDA含量;给予不同剂量的HSYA冻干粉针剂后,线粒体膜流动性增强、膜肿胀度降低、SOD含量上升、MDA含量下降。结论PAF可使大鼠脑皮质线粒体结构和功能受损,而羟基红花黄色素A冻干粉针剂对其有明显的保护作用。