Deferoxamine-induced cytotoxicity in human neuronal cell lines: protection by free radical scavengers

Deferoxamine (DFO) caused decreased viability of human neuronal tumor cells (SK-N-MC neuroblastoma and U-373 MG astrocytoma) in a dose-dependent manner. The addition of stoichiometric amounts of ferric ions did not decrease the cytotoxic effect of DFO on the neuroblastoma cells. However, the cotreatments with various antioxidants, hydroxyl radical scavengers or intracellular Ca²⁺ release blockers significantly protected against the effects of DFO. These results suggest that DFO-induced cytoxicity may be not due to chelating iron, but due to the production of hydroxyl radicals and that intracellular Ca²⁺ may play a role in the cytotoxic effects of DFO.     

Deferoxamine decreases the excitatory amino acid levels and improves the histological outcome in the hippocampus of neonatal rats after hypoxia-ischemia.

Hypoxic-ischemic encephalopathy is a severe complication of perinatal asphyxia and causes lifelong deficits in infants and children. Multiple mechanisms acting in serial or parallel fashion are likely to be involved in this procedure. The neuronal injury is strongly related to iron-catalysed oxygen radical production and subsequent peroxidative damage to lipids and protein. Excessive release of excitatory amino acids (EAA) glutamate and aspartate, with consequent overstimulation of glutamate receptors, is also thought to be an important mechanism in this brain injury. Deferoxamine (DFO), a chelator of non-protein-bound iron, has been shown to inhibit lipid peroxidation and hydroxyl radical production via the Fenton reaction and to decrease hypoxic-ischemic and reperfusion associated brain injury. However, the exact mechanism of neuroprotection of DFO and its possible effect on the neurotransmitters' release is currently being investigated. In the present study, a well-established model of perinatal asphyxia was used to investigate the effect of DFO on hypoxic-ischemic-induced damage to different hippocampal brain structures. DFO was administrated subcutaneously immediately after the asphyctic insult. Histological examination of the hippocampus was conducted and the tissue levels of glutamate and aspartate in the same area were determined. A remarkable reduction of hypoxia-ischemia-evoked neurons in the CA1 hippocampal region and a decrease in the asphyxia-induced hippocampal tissue levels of glutamate and aspartate was noted after DFO treatment. These findings suggest a complex action of DFO, which could be neuroprotective when administrated in the immature brain immediately after hypoxia-ischemia.     

Sodium salicylate is a novel catalytic inhibitor of human DNA topoisomerase II alpha

We have previously reported that pretreatment of human lymphoblastoid cells with the hydroxyl radical scavenger, N-acetyl cysteine, attenuates doxorubicin-induced DNA damage signalling through the ATM protein kinase. We sought to extend these studies to examine the effects of other hydroxyl radical scavengers in human breast cancer cells. Using MCF-7 cells, we observed that doxorubicin treatment triggered autophosphorylation of ATM on serine 1981 and the ATM-dependent activation of its downstream effectors p53, Chk2, and SMC1. Furthermore, we demonstrate that this effect was attenuated by pretreatment of cells with the hydroxyl radical scavengers sodium benzoate, sodium salicylate and, to a lesser extent, N-acetyl cysteine, but not Trolox™. Intriguingly, these effects were independent of doxorubicin's ability to redox cycle, were observed with multiple classes of topoisomerase II poisons, but did not represent a general damage-attenuating response. In addition, the observed effects were independent of the ability of sodium salicylate to inhibit cyclooxygenase-2 or NFκB. We demonstrate that sodium salicylate prevented doxorubicin-induced DNA double-strand break generation, which was attributable to inhibition of doxorubicin-stabilized topoisomerase IIα-DNA cleavable complex formation in vivo. Using topoisomerase IIα-DNA cleavage and decatenation assays, we determined that sodium salicylate is a catalytic inhibitor of topoisomerase IIα. Consistent with the observed inhibition of double-strand break formation, pretreatment of cells with sodium salicylate attenuated doxorubicin and etoposide cytotoxicity. These results demonstrate a novel mechanism of action for sodium salicylate and suggest that further study on the mechanism of topoisomerase II inhibition and the effects of related therapeutics on doxorubicin and etoposide cytotoxicity are warranted.     

Alaternin and emodin with hydroxyl radical inhibitory and/or scavenging activities and hepatoprotective activity on tacrine-induced cytotoxicity in HepG2 cells

The antioxidative and hepatoprotective potentials of two anthraquinones, alaternin (2-hydroxyemodin) and emodin, to scavenge and/or inhibit hydroxyl radicals generated by the Fenton reaction and to protect tacrine-induced cytotoxicity in human liver derived HepG2 cells were evaluated, respectively. The inhibitory activity on hydroxyl radical generated in a cell-free chemical system (FeSO4/H2O2) was investigated by a fluorescence spectrophotometer using a highly fluorescent probe, 2',7'-dichlorofluorescein. The hydroxyl radical scavenging activity was determined by electron spin resonance spectroscopy using 5,5-dimethy-1-pyrroline-N-oxide as hydroxyl radicals trapping agents. Tacrine-induced HepG2 cell toxicity was determined by a 3-[4,5-dimethylthiazole-2yl]-2,5-diphenyltertrazolium bromide assay. Although the scavenging activity of alaternin on hydroxyl radical was similar to that of emodin in dose-dependent patterns, the inhibitory activity exhibited by the former on hydroxyl radical generation was stronger than that of the latter, with IC50 values of 3.05 +/- 0.26 microM and 13.29 +/- 3.20 microM, respectively. In addition, the two anthraquinones, alaternin and emodin showed their hepatoprotective activities on tacrine-induced cytotoxicity, and the EC50 values were 4.02 microM and 2.37 microM, respectively. Silymarin, an antihepatotoxic agent used as a positive control exhibited the EC50 value of 2.00 microM. These results demonstrated that both alaternin and emodin had the simultaneous antioxidant and hepatoprotective activities.     

Modulating activity of fullerol C60(OH)22 on doxorubicin-induced cytotoxicity.

Paper presents the effects of the newly synthesized fullerol C60(OH)22 on the growth of tumor cells in vitro and its modulating activity on doxorubicin (DOX)-induced cytotoxicity in human breast cancer cell lines. Cell growth inhibition was evaluated by tetrazolium colorimetric WST1 assay. Electron spin resonance (ESR) "trapping" method was used to investigate OH-radical scavenger activity of fullerol during Fenton's reaction. At a range of nanomolar concentrations fullerol induced cell growth inhibition, which was cell line, dose and time dependent. Fullerol also strongly suppressed DOX-induced cytotoxicity at all concentrations regardless the time of fullerol addition. Proanthocyanidins added as single agent to MCF-7 cell culture for 48 h induced low growth inhibition but in combination with DOX strongly decreased DOX cytotoxicity. Fullerol was found to be a potent hydroxyl radical scavenger: the relative intensity of ESR signals of DMPO-hydroxyl radical (DMPO-OH) spin adduct decreased by 88% in the presence of 0.5 microg/ml of fullerol. The obtained results suggest that antiproliferative effect of the fullerol and its protective effect on DOX-induced cytotoxicity might be mediated through hydroxyl-radical scavenger activity of C60(OH)22.     

Elevation of intracellular Zn level by nanomolar concentrations of triclocarban in rat thymocytes

It was recently reported that nanomolar concentrations of triclocarban, an antimicrobial agent, were detected in human blood after the use of soap containing triclocarban. Due to the widespread use of triclocarban in adult and infant personal care products, the report prompted us to study its cytotoxicity. The cytotoxicity of triclocarban was examined in rat thymocytes by using a cytometric technique with propidium iodide for examining cell lethality, FluoZin-3-AM for monitoring the intracellular Zn²⁺ level, and 5-chloromethylfluorescencein diacetate for estimating the cellular content of non-protein thiol. The incubation with triclocarban at nanomolar concentrations (50–500 nM) for 1 h did not affect cell lethality but significantly elevated the intracellular Zn²⁺ level. The elevation of the intracellular Zn²⁺ level by triclocarban was not significantly dependent on external Zn²⁺ level. There was a negative correlation (r = −0.9225) between the effect on the intracellular Zn²⁺ level and that on the cellular content of non-protein thiol. These results suggest that nanomolar concentrations of triclocarban decrease the cellular content of non-protein thiol, leading to intracellular Zn²⁺ release. Since zinc plays physiological roles in mammalian cells, the percutaneous absorption of triclocarban from soap may, therefore, affect some cellular functions.     

Role of hydrogen peroxide in cyclosporine-induced renal tubular cell (LLC-PK1) injury

We examined the role of hydrogen peroxide production in cyclosporine A (CsA)-induced LLC-PK1 injury. After exposure to CsA (0.1 microM - 100 microM), cytotoxicity assessed by lactate dehydrogenase release to the media increased dose-dependently. LLC-PK1 cells produced hydrogen peroxide, visualized by 2,7-dichlorodihydrofluorescein assay by the treatment with 100 microM CsA, that was blocked by the treatment with catalase. The cytotoxicity of CsA significantly decreased either by the treatment with catalase, mannitol, or deferoxamine, but not with superoxide dismutase. These results suggest the role of hydrogen peroxide as the source of hydroxyl radical, which mainly contributes to CsA-induced LLC-PK1 injury.     

Oxidative stress-dependent toxicity of silver nanoparticles in human hepatoma cells

Cytotoxicity induced by silver nanoparticles (AgNPs) and the role that oxidative stress plays in this process were demonstrated in human hepatoma cells. Toxicity induced by silver (Ag⁺) ions was studied in parallel using AgNO₃ as the Ag⁺ ion source. Using cation exchange treatment, we confirmed that the AgNP solution contained a negligible amount of free Ag⁺ ions. Metal-responsive metallothionein 1b (MT1b) mRNA expression was not induced in AgNP-treated cells, while it was induced in AgNO₃-treated cells. These results indicate that AgNP-treated cells have limited exposure to Ag⁺ ions, despite the potential release of Ag⁺ ions from AgNPs in cell culture. AgNPs agglomerated in the cytoplasm and nuclei of treated cells, and induced intracellular oxidative stress. AgNPs exhibited cytotoxicity with a potency comparable to that of Ag⁺ ions in in vitro cytotoxicity assays. However, the toxicity of AgNPs was prevented by use of the antioxidant N-acetylcysteine, and AgNP-induced DNA damage was also prevented by N-acetylcysteine. AgNO₃ treatment induced oxidative stress-related glutathione peroxidase 1 (GPx1) and catalase expression to a greater extent than AgNP exposure, but treatment with AgNO₃ and AgNPs induced comparable superoxide dismutase 1 (SOD1) expression levels. Our findings suggest that AgNP cytotoxicity is primarily the result of oxidative stress and is independent of the toxicity of Ag⁺ ions.     

Iron chlorin e6 scavenges hydroxyl radical and protects human endothelial cells against hydrogen peroxide toxicity

Iron chlorin e6 (FeCe6) has recently been proposed to be potentially antimutagenic and antioxidative. However, the antioxidant property of FeCe6 has not been elucidated in detail. In this study, we investigated the ability of FeCe6 to scavenge hydroxyl radical and to protect biomolecules and mammalian cells from oxidative stress-mediated damage. In electron spin resonance (ESR) experiments, FeCe6 showed excellent hydroxyl radical scavenging activity, whereas its iron-deficient molecule, chlorin e6 (Ce6) showed little effect. FeCe6 also significantly reduced hydroxyl radical-induced thiobarbituric acid reactive substance (TBARS) formation and benzoate hydroxylation in a dose-dependent manner. The rate constant for reaction between FeCe6 and hydroxyl radical was measured as 8.5 x 10(10) M(-1) s(-1) by deoxyribose degradation method, and this value was much higher than that of most hydroxyl radical scavengers. Superoxide dismutase (SOD) activity of FeCe6 was also confirmed by ESR study and cytochrome c reduction assay, but its in vitro activity appeared to be less efficient in comparison with other well-known SOD mimics. In addition, FeCe6 appreciably diminished hydroxyl radical-induced DNA single-strand breakage and protein degradation in Fe-catalyzed and Cu-catalyzed Fenton systems, and it significantly protected human endothelial cells against hydrogen peroxide (H2O2) toxicity. These results suggest that FeCe6 is a novel hydroxyl radical scavenger and may be useful for preventing oxidative injury in biological systems.     

Cytotoxicity of synthetic cannabinoids on primary neuronal cells of the forebrain: the involvement of cannabinoid CB1 receptors and apoptotic cell death

The abuse of herbal products containing synthetic cannabinoids has become an issue of public concern. The purpose of this paper was to evaluate the acute cytotoxicity of synthetic cannabinoids on mouse brain neuronal cells. Cytotoxicity induced by synthetic cannabinoid (CP-55,940, CP-47,497, CP-47,497-C8, HU-210, JWH-018, JWH-210, AM-2201, and MAM-2201) was examined using forebrain neuronal cultures. These synthetic cannabinoids induced cytotoxicity in the forebrain cultures in a concentration-dependent manner. The cytotoxicity was suppressed by preincubation with the selective CB₁ receptor antagonist AM251, but not with the selective CB₂ receptor antagonist AM630. Furthermore, annexin-V-positive cells were found among the treated forebrain cells. Synthetic cannabinoid treatment induced the activation of caspase-3, and preincubation with a caspase-3 inhibitor significantly suppressed the cytotoxicity. These synthetic cannabinoids induced apoptosis through a caspase-3-dependent mechanism in the forebrain cultures. Our results indicate that the cytotoxicity of synthetic cannabinoids towards primary neuronal cells is mediated by the CB₁ receptor, but not by the CB₂ receptor, and further suggest that caspase cascades may play an important role in the apoptosis induced by these synthetic cannabinoids. In conclusion, excessive synthetic cannabinoid abuse may present a serious acute health concern due to neuronal damage or deficits in the brain.     

Effect of squalene monohydroperoxide on cytotoxicity and cytokine release in a three-dimensional human skin model and human epidermal keratinocytes

In order to clarify that squalene monohydroperoxide (SQOOH) correlates with changes in morphology through cytotoxicity and establish in vitro evaluation of the cytotoxicity of lipid hydroperoxide, the effect of SQOOH on cytotoxicity and morphology in normal human epidermal keratinocytes (NHEK(B)) and the Gunze three-dimensional cultured human skin model (Vitrolife-skin) was investigated. Additionally, the effect of radical scavengers (mannitol, vitamin C and (+)-catechin) on the cytotoxicity in Vitrolife-skin was studied. The level of lipid hydroperoxide (phoshatidylcholine hydroperoxide: PCOOH) in the cellular membrane was increased with the concentration of SQOOH, and the rise in cytotoxicitv in NHEK(B) was associated with changes to the cellular membrane. A concentration-dependent and protective effect on the increase in cytotoxicity and PCOOH content was observed. To clarify the effect of SQOOH on the release of cytokine from cells, IL-2 level from NHEK(B) and Vitrolife-skin were investigated. IL-2 release from the cells was enhanced by SQOOH and increased at a non-cytotoxic dose. These results suggest that the increase in lipid hydroperoxides resulting from the auto-oxidation of lipids within cellular membranes in the presence of SQOOH correlates with changes in morphology due to cytotoxicity. SQOOH enhanced the release from cells at a non-cytotoxic dose. A method for assessing the protective effect on the cytotoxicity of lipid hydroperoxides using cells would be useful for in vitro evaluation of the cytotoxicity.     

Detection of dichromate (VI)-induced DNA strand breaks and formation of paramagnetic chromium in multiple mouse organs

DNA single-strand breaks (and/or alkali-labile sites) induced by Cr(VI) were evaluated with the alkaline single cell gel electrophoresis (SCG) (Comet) assay in five organs (liver, kidney, spleen, lung, and brain) of male mice dosed with K(2)Cr(2)O(7) (20 mg Cr/kg) by a single ip injection in vivo, and the formation of paramagnetic Cr(V) in these organs was investigated by electron spin resonance (ESR) spectrometry. Furthermore, the in vivo effects of deferoxamine (DFO), an iron chelator, and dimethylthiourea (DMTU), a hydroxyl radical scavenger, on the formation of Cr(V) and DNA strand breaks induced by the metal in the liver and kidney were examined. SCG assay detected DNA strand breaks were detected in the liver and kidney at 15 min and showed that they were being repaired at 3 h after Cr(VI) injection. The ESR spectra of paramagnetic Cr(V) were also observed in the liver and kidney for 15 min to 24 h after Cr(VI) injection. In contrast, there were no significant levels of DNA strand breaks and Cr(V) in the spleen, lung, or brain. The pretreatment of mice with DFO reduced the formation of Cr(VI)-induced DNA strand breaks and Cr(V) complexes as well as the total contents of Cr in the liver and kidney at 15 min after the metal injection. In the case of the pretreatment with DMTU, DNA strand breaks induced by Cr(VI) were suppressed in the liver and kidney at 15 min, without any influence on the levels of Cr(V) complexes and total Cr contents in the organs. The in vitro study showed that DFO decreased the levels of Cr(V)-GSH complexes and Cr(V)-mediated hydroxyl radicals, while DMTU reduced only the levels of Cr(V)-mediated hydroxyl radicals without affecting the formation of Cr(V)-GSH complexes. These results demonstrated that the SCG assay may be useful for detecting DNA strand breaks and/or alkali-labile sites caused by Cr(VI) in vivo. The results also indicated that the in vivo formation of hydroxyl radicals during the reduction of Cr(VI) may play an important role in the induction of the DNA strand breaks caused by this metal and implied that the levels of Cr(V) inside the cells may not always be related to the induction of DNA strand breaks.     

Effects of an epidermal growth factor receptor inhibitor on arsenic associated toxicity in the rat bladder epithelium

Arsenite (As^III), an inorganic arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is known to be metabolized to organic methylated arsenicals in vivo. As^III has been reported to have the ability to up-regulate the epidermal growth factor receptor (EGFR)-associated pathway in epithelial cells, including human urothelial cells in vitro. EGFR is a cell-surface receptor belonging to the ErbB family of receptor tyrosine kinases, and the EGFR-associated signaling pathway has been reported to play an important role in carcinogenesis and cancer progression, including in bladder cancer. In this study, we investigated the growth effects of As^III and an organic trivalent arsenical, dimethylarsinous acid (DMA^III), and the effects of co-exposure of gefitinib, an EGFR inhibitor, with As^III to a rat urothelial cell line (MYP3). We also investigated the effects of co-administration of dietary As^III and gefitinib in vivo. In vitro, concentrations of 1.0 μM As^III or 0.5 μM DMA^III induced cytotoxicity. However, lower concentrations of As^III treatment had a slight mitogenic growth effect whereas lower concentrations of DMA^III did not. Gefitinib blocked As^III-induced cell growth in vitro. In vivo, a high dose of gefitinib alone induced slight urothelial cytotoxicity, and did not reduce cytotoxicity and regenerative cell proliferation when co-administered with As^III. The majority of arsenic metabolites present in the urine of As^III-treated rats were organic arsenicals, mainly dimethylarsinic acid (DMA^V). As^III was also present, and its concentration was higher than the concentration required to produce cytotoxicity in vitro. These data suggest that an EGFR inhibitor has the ability to block As^III-induced cell proliferation in vitro but not in vivo in a short-term study.     

Protective effect of deferoxamine on chromium(VI)-induced DNA single-strand breaks, cytotoxicity, and lipid peroxidation in primary cultures of rat hepatocytes

Incubation of primary cultures of rat hepatocytes with K₂Cr₂O₇ and deferoxamine (DFO), an iron chelator, resulted in a marked decrease in cellular levels of DNA single-strand breaks caused by K₂Cr₂O₇. Cellular treatment with DFO also suppressed both dichromate-induced cytotoxicity – evaluated by the leakage of lactate dehydrogenase, and lipid peroxidation – as monitored by malondialdehyde formation. In addition, treatment with DFO attenuated the suppression of the levels of vitamin E and C as well as the inhibition of alkaline phosphatase and glutathione peroxidase activity attributed to K₂Cr₂O₇. However, DFO had no influence on the cellular level of glutathione or the activity of glutathione reductase and superoxide dismutase suppressed by dichromate. Under the same experimental conditions, cellular uptake and distribution of chromium were not affected by DFO. These results indicate that DFO protects cells from chromium(VI)-induced DNA strand breaks, cytotoxicity, lipid peroxidation, vitamin E and C depression, and glutathione peroxidase inhibition. The role of antioxidants in chromium(VI)-induced cytotoxicity, DNA breaks, and lipid peroxidation is discussed. Received: 17 September 1996 / Accepted: 25 November 1996     

Effects of glutathione depletion and induction of metallothioneins on the cytotoxicity of an organic hydroperoxide in cultured mammalian cells

The effects of glutathione depletion and induction of metallothioneins (MTs) on the cytotoxicity of t-butyl hydroperoxide (t-BHP) were investigated in cultured Chinese hamster V79 cells.

The cytotoxicity of t-BHP was enhanced with increasing duration of the pretreatment with -buthionine-SR-sulfoximine (BSO), a selective inhibitor of γ-glutamylcysteine synthetase, and was correlated with the decrease of cell glutathione, indicating that glutathione constitutes a cellular defence against toxicity by t-BHP.

Desferrioxamine, a specific iron chelator, suppressed partly inhibition of cell growth induced by t-BHP and suppressed completely the increase of the cytotoxicity caused by glutathione depletion. Butylated hydroxytoluene, a diffusible radical scavenger, showed almost the same suppressive effect as desferrioxamine. These results suggest that the cytotoxicity of t-BHP enhanced by the depletion of glutathione is attributed to an action of iron-mediated reactive radical species.

Pretreatment with zinc (10⁻⁴ M) suppressed the cytotoxicity of t-BHP that was enhanced by depletion of glutathione and the extent of suppression was paralleled with increasing duration of zinc pretreatment that correlated with increased synthesis of metallothioneins (MTs). Maximum induction of MTs also suppressed the t-BHP-induced inhibition of cell growth at 4°C in glutathione-depleted cells. These results suggest that MTs act as a scavenger for the reactive radical species which are formed in an iron-mediated manner.     

Lipid Peroxidation of Rat Erythrocyte Membrane Induced by Adriamycin-Fe3+

Adriamycin-Fe³⁺ caused lipid peroxidation of erythrocyte membrane in relation to its concentration. Adriamycin-Fe³⁺ had a high affinity for membrane and the adriamycin-Fe³⁺-binding membranes was also found to cause lipid peroxidation. Under aerobic conditions, adriamycin-Fe³⁺ caused a reduction of cytochrome c and ferrous iron formed spontaneously. Superoxide dismutase (EC 1.15.1.1) (SOD) strongly inhibited the reduction of cytochrome c; however, the enzyme promoted formation of ferrous iron independent of enzymatic action. These results suggest that cytochrome c was reduced by superoxide radical (O₂ ^?) or an adriamycin-iron-O₂ complex such as adriamycin-Fe³⁺–O₂ ^?, but not by adriamycin-Fe²⁺. The ferrous iron chelator bathophenanthroline sulfonate (BPS) completely inhibited oxygen consumption caused by adriamycin-Fe³⁺, indicating that ferrous iron is absolutely required for the lipid peroxidation. SOD and hydroxyl radical scanvengers did not inhibit the lipid peroxidation, indicating that O₂ ^? and hydroxyl radical were not involved in membrane peroxidation. The peroxidation reaction was dramatically inhibited by Tris buffer (2-amino-2-hydroxymethyl-1,3-propanediol). However, hydroxyl radical generation and lipid peroxidation in Tris buffer were not related obviously, indicating that Tris did not act as a hydroxyl radical scavenger. The initial rate of TBARS (thiobarbituric acid reactive substances) formation induced by a mixture of adriamycin-Fe³⁺ and adriamycin-Fe²⁺ was much faster than that indcued by adriamycin-Fe²⁺ or adriamycin-Fe³⁺ alone. These results made it became possible to speculate that the lipid peroxidation might be initiated by an adriamycin-Fe³⁺-oxygen-adriamycin-Fe²⁺ complex.     

活性氧自由基对膀胱癌患者淋巴因子激活的杀伤细胞的作用

目的:探讨活性氧自由基对膀胱癌患者淋巴因子激活的杀伤(LAK)细胞的增殖和抗膀胱癌细胞系活性的作用.方法:分别用细胞计数和MTT法测定LAK细胞的增殖和细胞毒作用.结果:羟自由基浓度依赖性地抑制IL-2所诱导的LAK细胞增殖.用抗坏血酸400μmol·L~(-1)和硫酸亚铁40μmol·L~(-1)培养细胞96h,细胞增殖被抑制34.5％.这种抑制可被一定浓度的甘露醇和依地酸(edetic acid)扭转.一定浓度的超氧阴离子或一氧化氮释放剂硝普钠可刺激由IL-2所诱导的LAK细胞的增殖.超氧化物歧化酶(SOD)可抵消超氧阴离子的刺激作用.外源性超氧阴离子可加强LAK细胞对BIU-87和EJ细胞的杀伤.羟自由基和SOD对LAK细胞杀伤作用则影响不明显.结论:超氧阴离子和一氧化氮可增强膀胱癌患者LAK细胞的增殖、激活和抗肿瘤的细胞毒,而羟自由基对此起抑制作用.这两种活性氧自由基对IL-2诱导的LAK细胞增殖的作用是不同的.     

Reactive oxygen species and non-peroxidative mechanisms of cocaine-induced cytotoxicity in rat hepatocyte cultures

Primary short-term cultures of hepatocytes derived from phenobarbital-induced male Sprague-Dawley rats were used to investigate the mechanisms of cocaine-induced cytotoxicity. Exposure of cells to cocaine resulted in a time and concentration-dependent release of lactate dehydrogenase (LDH) into the culture medium which became evident after 7 h of incubation. Over the course of 24 h incubation with cocaine (0.3 mM) there was no significant lipid peroxidation (measured as the formation of thiobarbituric acid-reactive substances. TBA-RS). The addition of the ferric iron chelator, deferoxamine (DFO), prevented in part cocaine-induced LDH release. Alternatively, addition of the antioxidant, alpha-tocopherol polyethylene glycol 1000 succinate (TPGS), did not protect against hepatocyte injury. Depletion of the intracellular glutathione (GSH) with diethyl maleate (DEM) to below critical levels for antioxidative protection markedly accelerated the onset and increased the extent of cocaine-induced LDH release, concomitant with massive production of lipid peroxidation. During the first four hours of incubation DFO and TPGS protected against cocaine-induced cytotoxicity in GSH-depleted cells. However, at later stages (24 h), the protective effect was lost even in the absence of lipid peroxidation. These results suggest that reactive oxygen species are involved in cocaine-mediated hepatocyte injury. However, lipid peroxidation can be dissociated from other, non-peroxidative, iron-dependent mechanisms of oxidative cell injury.