Response of human cord blood cells to styrene exposure: evaluation of its effects on apoptosis and gene expression by genomic technology

Styrene is one of the most important monomers produced worldwide, and it finds major use in the production of polystyrene, acrylonitrile–butadiene–styrene resins and unsaturated polystyrene resins. Epidemiological studies on styrene showed that the malignancies observed most frequently in humans after exposure are related to the lymphatic and haemopoietic system. IARC classified styrene a possible carcinogenic to humans (Group 2B). In this study, we evaluated the effect of styrene on gene expression profiles of human cord blood cells, as well as its activity on the apoptosis and bcl-2 related protein expression. Data demonstrated that, after 24 and 48 h of exposure, styrene (800 μM) induced an increase in the necrosis of mononuclear cord blood cells, whereas it did not cause any increase in the apoptotic process. Western blot analysis revealed a modified expression of Bax, BCl-2, c-Jun, c-Fos and Raf-1 proteins in the human cord blood cells after direct exposure to styrene, whereas p53 expression did not change. Furthermore, Macroarray analysis showed that styrene changed cord blood gene expression, inducing up-regulation of monocyte chemotactic protein 1 (MCP-1), and down-regulation of CC chemokine receptor type 1 (CCR-1) and SLP-76 tyrosine–phosphoprotein.     

葡萄糖对胰岛细胞胰腺-十二指肠同源盒基因-1表达的影响

目的 研究不同浓度葡萄糖对大鼠胰岛细胞胰腺-十二指肠同源盒基因-1(PDX-1)表达的调节作用.方法 用不同浓度葡萄糖分别刺激胰岛细胞1、4、7、14d,运用RT-PCR技术检测PDX-1基因表达的变化.结果 与对照组相比(葡萄糖浓度为5.5mmol/L),刺激胰岛细胞1d时,葡萄糖浓度为2.2mmol/L时,PDX-1表达显著降低,当葡萄糖浓度高于对照组时,PDX-1基因的表达量呈浓度依赖性升高;4d时,低糖浓度仍然显著抑制PDX-1基因表达,浓度升至11.1mmol/L,PDX-1基因表达量呈显著升高,浓度为16.7mmol/L时,PDX-1基因表达量呈下降趋势,浓度升至33.3mmol/L时,PDX-1基因表达量明显降低;7d时,除浓度11.1mmol/L外,其余浓度PDX-1基因表达均降低;刺激时间延长到14d,非生理浓度葡萄糖均表现为对PDX-1基因的抑制作用.结论 低血糖可以抑制PDX-1基因表达.短期的血糖升高可以一定程度地刺激PDX-1基因表达,但长期的高血糖则使PDX-1基因表达明显受抑.     

Indicators of oxidative stress and apoptosis in mouse whole lung and Clara cells following exposure to styrene and its metabolites

In mice, styrene is hepatotoxic, pneumotoxic, and causes lung tumors. One explanation for the mechanism of toxicity is oxidative stress/damage. Previous studies have shown decreased glutathione levels, linked to increased apoptosis, in lung homogenates and isolated Clara cells 3 h following styrene or styrene oxide (SO) administration or in vitro exposure. The objective of the current studies was to determine what effects styrene and its active metabolites, primarily styrene oxide, had on indicators of oxidative stress and attendant apoptosis in order to understand better the mechanism of styrene-induced toxicity. Three hours following in vitro exposure of Clara cells to styrene or SO there were increases in reactive oxygen species (ROS). Following administration of styrene or styrene oxide ip, increases in ROS, superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) formation were observed. Since increases in ROS have been linked to increases in apoptosis ratios of bax/bcl-2, mRNA and protein expression were determined 3–240 h following the administration of styrene and R-styrene oxide (RSO). The bax/bcl-2 mRNA ratio increased 12 and 24 h following R-SO and 120 h following styrene administration. However, the bax/bcl-2 protein ratio was not increased until 240 h following R-SO, and 24 and 240 h following styrene administration. However, only a slight increase in caspase 3 was observed. These results indicated that oxidative stress occurred 3 h following styrene or styrene oxide as evidenced by increased ROS and SOD. This increased ROS may be responsible for the increased 8-OHdG formation. Our findings of limited apoptosis in Clara cells following acute exposure to styrene or SO are in agreement with others and may reflect the minimal extent to which apoptosis plays a role in acute styrene toxicity. It is clear, however, that oxidative stress and oxidative effects on DNA are increased following exposure to styrene or styrene oxide, and these may play a role in the lung tumorigenesis in mice.     

氧化应激与胰岛素抵抗分子机制之联系

氧化应激是体内活性氧化物产生多于清除的氧化还原反应失衡的病理状态.对胰岛素抵抗的发生发展起着关键性作用.本文综述了氧化应激致胰岛素抵抗的信号传导途径,旨在为胰岛素抵抗相关疾病的抗氧化药物治疗及信号途径药物干预治疗提供新的途径或靶点.     

In vitro kinetics of styrene and styrene oxide metabolism in rat,mouse, and human

Styrene oxide (SO), a labile metabolite of styrene, is generally accepted as being responsible for any genotoxicity associated with styrene. To better define the hazard associated with styrene, the activity of the enzymes involved in the formation (monooxygenase) and destruction of SO (epoxide hydrolase and glutathione-S-transferase) were measured in the liver and lungs from naive and styrene-exposed male Sprague-Dawley rats and B6C3F1 mice (three daily 6-h inhalation exposures at up to 600 ppm styrene) and Fischer 344 rats (four daily 6-h inhalation exposures at up to 1000 ppm styrene), and in samples of human liver tissue. Additionally, the time course of styrene and SO in the blood was measured following oral administration of 500 mg styrene/kg body weight to naive Fischer rats and rats previously exposed to 1000 ppm styrene. The affinity of hepatic monooxygenase for styrene, as measured by the Michaelis constant (K _m), was similar in the rat, mouse, and human. Based on theV _max for monooxygenase activity and the relative liver and body size, the mouse had the greatest capacity and humans the lowest capacity to form SO from styrene. In contrast, human epoxide hydrolase had a greater affinity (i. e., lowerK _m) for SO than epoxide hydrolase from rats or mice while the apparent Vmax for epoxide hydrolase was similar in the rat, mouse, and human liver. However, the activity of epoxide hydrolase relative to monooxygenase activity was much greater in the human than in the rodent liver. Hepatic glutathione-S-transferase activity, as indicated by theV _max, was 6- to 33-fold higher than epoxide hydrolase activity. However, the significance of the high glutathione-S-transferase activity is unknown because hydrolysis, rather than conjugation, is the primary pathway for SO detoxification in vivo. Human hepatic glutathione-S-transferase activity was extremely variable between individual human livers and much lower than in rat or mouse liver. Prior exposure to styrene had no effect on monooxygenase activity or on blood styrene levels in rats given a large oral dose of styrene. In contrast, prior exposure to styrene increased hepatic epoxide hydrolase activity 1.6-fold and resulted in lower (0.1>P>0.05) blood SO levels in rats given a large oral dose of styrene. Qualitatively, these data indicate that the mouse has the greatest capacity and the human the lowest capacity to form SO. In addition, human liver should be more effective than rodent liver in hydrolyzing low levels of SO. Quantitative evaluation of the species differences in enzyme levels are being evaluated with the development of a physiologically based pharmacokinetic model for styrene that includes SO.     

The protective effect of silk fibroin on high glucose induced insulin resistance in HepG2 cells

The therapeutic use of silk-derived materials such as fibroin in biomedicine is well-established in Southeast Asian countries. Studies indicated that silk fibroin (SF) peptide enhances insulin sensitivity and glucose metabolism phenomena associated with type 2 diabetes mellitus (T2DM) suggesting this peptide may be beneficial to treat this disease. However, the mechanisms underlying protective effect of SF in insulin-mediated hepatic metabolic dysfunction remains unclear. The aim of this study was to investigate the influence of SF on insulin resistant HepG2 cells which were used a model of T2DM. Treatment of cells with 30 mmol/L of glucose and 10⁻⁶ mol/L insulin for 48 h significantly reduced glucose consumptions and intracellular glycogen levels but increased triglyceride (TG) levels. SF or metformin alone elevated glucose consumptions and glycogen accumulation accompanied by lower TG content. Greater effects in these metabolic parameters were found when SF and metformin were combined. Treatment of insulin resistant cells with SF or metformin alone decreased levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF-α) and interleukin-6 (IL-6); whereas antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity, as well as total antioxidant capacity (T-AOC) ability increased. The combination of SF and metformin produced greater changes in these parameters compared to metformin alone. Data indicated that the protective effect of SF or metformin in insulin resistant HepG2 cells involves inhibition of oxidant processes and that the combination of agents may prove more effective therapeutically.     

Gene expression profiling reveals underlying molecular mechanisms of the early stages of tamoxifen-induced rat hepatocarcinogenesis

Tamoxifen is a widely used anti-estrogenic drug for chemotherapy and, more recently, for the chemoprevention of breast cancer. Despite the indisputable benefits of tamoxifen in preventing the occurrence and re-occurrence of breast cancer, the use of tamoxifen has been shown to induce non-alcoholic steatohepatitis, which is a life-threatening fatty liver disease with a risk of progression to cirrhosis and hepatocellular carcinoma. In recent years, the high-throughput microarray technology for large-scale analysis of gene expression has become a powerful tool for increasing the understanding of the molecular mechanisms of carcinogenesis and for identifying new biomarkers with diagnostic and predictive values. In the present study, we used the high-throughput microarray technology to determine the gene expression profiles in the liver during early stages of tamoxifen-induced rat hepatocarcinogenesis. Female Fisher 344 rats were fed a 420 ppm tamoxifen containing diet for 12 or 24 weeks, and gene expression profiles were determined in liver of control and tamoxifen-exposed rats. The results indicate that early stages of tamoxifen-induced liver carcinogenesis are characterized by alterations in several major cellular pathways, specifically those involved in the tamoxifen metabolism, lipid metabolism, cell cycle signaling, and apoptosis/cell proliferation control. One of the most prominent changes during early stages of tamoxifen-induced hepatocarcinogenesis is dysregulation of signaling pathways in cell cycle progression from the G(1) to S phase, evidenced by the progressive and sustained increase in expression of the Pdgfc, Calb3, Ets1, and Ccnd1 genes accompanied by the elevated level of the PI3K, p-PI3K, Akt1/2, Akt3, and cyclin B, D1, and D3 proteins. The early appearance of these alterations suggests their importance in the mechanism of neoplastic cell transformation induced by tamoxifen.     

Activity and gene expression profile of certain antioxidant enzymes to microcystin-LR induced oxidative stress in mice

Microcystins are cyclic heptapeptide toxins produced by certain strains of Microcystis aeruginosa and microcystin-LR (MC-LR) is the most toxic among the 70 variants isolated so far. These toxins have been implicated in both human and livestock mortality. In the present study we investigated the microcystin-LR induced oxidative stress in mice in terms of its effect on activity and gene expression profile of certain antioxidant enzymes and expression of heat shock protein-70 (HSP-70). Mice were treated with 0.5 LD₅₀ (38.31 μg/kg) and 1 LD₅₀ (76.62 μg/kg) and the biochemical variables were determined at 1, 3, 7 days and 15, 30, 60 and 120 min post-exposure for 0.5 and 1 LD₅₀ dose, respectively. A significant time-dependent increase in HSP-70 expression over control was observed at 1 LD₅₀ dose. The toxin induced significant increase in liver body weight index, hepatic lipid perxoidation and depletion of GSH levels at 1 LD₅₀ compared to control group. There was significant decrease in the activity of antioxidant enzymes glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione-S-transferase (GST) at 1 LD₅₀. Except catalase, there was no effect on other antioxidant enzymes at 0.5 LD₅₀ dose. In contrast to activity of antioxidant enzymes the gene expression profile did not show any significant difference compared to control at 1 LD₅₀. GR showed significant decrease in expression at 1, 3 and 7 days in animals dosed with 0.5 LD₅₀ MC-LR. The results of our in vivo study clearly show the oxidative stress induced by MC-LR, and a correlation with activity and regulation at gene expression level of antioxidant enzymes.     

Molecular mechanisms of action of styrene toxicity in blood plasma and liver

Styrene is an aromatic colorless hydrocarbon available in liquid form and highly volatile. In its pure form, it gives a sweet smell. The primary source of exposure in the environment is from plastic materials, rubber industries, packaging materials, insulations, and fiber glass and carpet industry. Natural sources of styrene include: few metabolites in plants which are transferred through food chain. The current study was designed to evaluate styrene toxicity, including: superoxide dismutase (SOD) and protein carbonyl, oxidative stress, glucose‐6‐phosphatase (G6Pase), glycogen phosphorylase (GP), and phosphoenolpyruvate carboxykinase (PEPCK) activities, adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio, and changes in gene expressions such as glutamate dehydrogenase 1 (GLUD1), glucose transporter 2 (GLUT2), and glucokinase (GCK) in the rat liver tissue. For this purpose, styrene was dissolved in corn oil and was administered via gavage, at doses 250, 500, 1000, 1500, 2000, mg/kg/day per mL and control (corn oil) to each rat with one day off in a week, for 42 days. Plasma SOD and protein carbonyl of plasma were significantly up‐regulated in 1000, 1500, and 2000 mg/kg/day styrene administrated groups (P < .001). In addition, styrene caused an increase in lipid peroxidation (LPO) and reactive oxygen species (ROS) in the dose‐dependent manners in liver tissue (P < .001). Furthermore, the ferrous reducing antioxidant power (FRAP) and total thiol molecules (TTM) in styrene‐treated groups were significantly decreased in liver tissue (P < .001) with increasing doses. In treated rats, styrene significantly increased G6Pase activity (P < .001) and down‐regulated GP activity (P < .001) as compared to the control group. The PEPCK activity was significantly raised in a dose‐dependent manner (P < .001). The ATP/ADP ratio of live cells was significantly raised by increasing the dose (P < .001). There was significantly an up‐regulation of GLUD1 and GCK at 2000 mg/kg group (P < .01) and a down‐regulation for GLUT2 at the same dose. While in the rest of group, GLUT2 showed up‐regulation of relative fold change. By targeting genes such as GLUD1, GLUT2, and GCK, disruption of hepatic gluconeogenesis, glycogenolysis, and insulin secretory functions are obvious. The present study illustrates that induction of oxidative stress followed by changes in G6Pase, GP, and PEPCK activities and the genes responsible for glucose metabolism are the mechanisms of styrene's action in the liver.     

Arsenic-induced alteration in the expression of genes related to type 2 diabetes mellitus

Chronic exposure to high concentrations of arsenic in drinking water is associated with an increased risk for developing type 2 diabetes. The present revision focuses on the effect of arsenic on tissues that participate directly in glucose homeostasis, integrating the most important published information about the impairment of the expression of genes related to type 2 diabetes by arsenic as one of the possible mechanisms by which it leads to the disease. Many factors are involved in the manner in which arsenic contributes to the occurrence of diabetes. The reviewed studies suggest that arsenic might increase the risk for type 2 diabetes via multiple mechanisms, affecting a cluster of regulated events, which in conjunction trigger the disease. Arsenic affects insulin sensitivity in peripheral tissue by modifying the expression of genes involved in insulin resistance and shifting away cells from differentiation to the proliferation pathway. In the liver arsenic disturbs glucose production, whereas in pancreatic beta-cells arsenic decreases insulin synthesis and secretion and reduces the expression of antioxidant enzymes. The consequences of these changes in gene expression include the reduction of insulin secretion, induction of oxidative stress in the pancreas, alteration of gluconeogenesis, abnormal proliferation and differentiation pattern of muscle and adipocytes as well as peripheral insulin resistance.     

A physiologic pharmacokinetic model for styrene and styrene-7,8-oxide in mouse,rat and man

Concern about the carcinogenic potential of styrene (ST) is due to its reactive metabolite, styrene-7,8-oxide (SO). To estimate the body burden of SO resulting from various scenarios, a physiologically based pharmacokinetic (PBPK) model for ST and its metabolite SO was developed. This PBPK model describes the distribution and metabolism of ST and SO in the rat, mouse and man following inhalation, intravenous (i.v.), oral (p.o.) and intraperitoneal (i.p.) administration of ST or i.v., p.o. and i.p. administration of SO. Its structure includes the oxidation of ST to SO, the intracellular first-pass hydrolysis of SO catalyzed by epoxide hydrolase and the conjugation of SO with glutathione. This conjugation is described by an ordered sequential ping-pong mechanism between glutathione, SO and glutathioneS-transferase. The model was based on a PBPK model constructed previously to describe the pharmacokinetics of butadiene with its metabolite butadiene monoxide. The equations of the original model were revised to refer to the actual tissue concentration of chemicals instead of their air equivalents used originally. Blood: air and tissue: blood partition coefficients for ST and SO were determined experimentally and have been published previously. Metabolic parameters were taken from in vitro or in vivo measurements. The model was validated using various data sets of different laboratories describing pharmacokinetics of ST and SO in rodents and man. In addition, the influences of the biochemical parameters, alveolar ventilation and blood: air partition coefficient for ST on the pharmacokinetics of ST and SO were investigated by sensitivity analysis. The PBPK model presented can be used to predict concentration-time curves of ST or SO in blood and different tissues. Results were presented in part at the International Symposium on Health Hazards of Butadiene and Styrence, 1993 Espoo, Finland     

Effects of subchronic exposure to styrene on the extracellular and tissue levels of dopamine, serotonin and their metabolites in rat brain

At present, there is controversy over the neurotoxic potential of styrene. Several epidemiological and clinical studies have shown that styrene exposure causes alterations of central nervous system functions in humans. Neurotransmitters have been implicated in the pathogenesis of styrene neurotoxicity in rodents. Several studies carried out on postmortem brain tissue suggest that styrene may alter dopaminergic neurotransmission in rabbit or rat brain. Moreover, in vitro studies suggest that both styrene and styrene oxide inhibit the uptake of dopamine (DA) in purified synaptic vesicles prepared from rat brain striata. To date, biochemical studies on animals have explored global tissue levels of neurotransmitters with sub-acute exposures to styrene. However, extracellular levels of neurotransmitters are more closely related to behaviour than are global tissue levels. The present study determined changes in the extracellular concentrations of DA, serotonin (5-HT) and their acid metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), in striatal dialysates from freely moving adult male rats after exposure to 750 and 1,000 ppm styrene, 6 h per day, 5 days per week for 4 weeks. We also determined the concentrations of DA, 5-HT and their acid metabolites in striatum, nucleus accumbens and prefrontal cortex obtained postmortem from similarly exposed rats. Exposure to 1,000 ppm of styrene caused a significant decrease in extracellular acid metabolite concentrations. Tissue levels of acid metabolites were also decreased to a lesser extent. The effects were observed 72 h after discontinuing exposure but had vanished 17 days later. There was no change in DA or 5-HT concentrations either in the dialysates or tissues. Exposure to 750 ppm styrene caused no changes in the concentrations of DA, 5-HT and their acid metabolites either in the dialysates or tissues. The possibility that the effect of styrene is mediated by monoamine oxidase (MAO) inhibition is discussed.     

Effect of forskolin on islet cyclic AMP,insulin secretion,blood glucose and intravenous glucose tolerance in rats

Summary The in vivo effect of forskolin on insulin release, blood glucose and intravenous glucose tolerance test has been studied in the rat. In addition in vitro experiments on the effect of forskolin on islet cAMP and insulin release have been performed for comparison purposes.In batch incubated islets forskolin increased cAMP levels concentration dependently, the EC₅₀ being approximately 25 M. The maximal effect occurred after 5 min. In the presence of 2.8 mM glucose 10M forskolin did not stimulate insulin release; however, it potentiated both phase of 11.1 mM glucose induced insulin secretion.I. v. administration of 1.5 mg/kg of forskolin increased blood glocose levels in rats, which was associated with significant elevation of serum insulin. During an i. v. glucose tolerance test forskolin potentiated the insulin releasing capacity of glucose but did not significantly affect blood glucose levels. It is conceivable that cAMP per se does not initiate but rather amplifies insulin release by glucose. Since the synergistic effect of forskolin and glucose on insulin release in vivo is not associated with increased elimination rate it is possible that forskolin exhibits additional effects which counteract the glucose lowering action of insulin.     

Altered gene expression in rat mesenteric tissue following in vivo exposure to a phosphodiesterase 4 inhibitor

Vascular injury is a relatively common finding during the pre-clinical toxicity testing of drugs. The mechanisms of the injury are poorly understood and in turn, sensitive and specific biomarkers for pre-clinical and clinical monitoring do not exist. The present study was undertaken to investigate the molecular mechanisms of drug-induced vascular injury in mesenteric tissue of rats treated with the selective phosphodiesterase 4 (PDE4) inhibitor CI-1044. In a time-course study, male Sprague Dawley rats were given daily doses of 40 or 80 mg/kg for 1, 2 or 3 successive days and were euthanized the following day. Gene expression profiles in mesenteric tissue were determined using Affymetrix RG_U34A microarrays and fibrinogen and cytokine measurements were performed in blood samples. Hierarchical clustering analysis produced a clear pattern separation of the animals with inflammation, animal with inflammation and necrosis and animals without any lesion. Genes associated with inflammation, procoagulation, extracellular matrix remodeling were up-regulated. An altered expression of genes involved in vascular tone regulation, lipid and glucose metabolism was also observed. Selected genes expression changes were confirmed by TaqMan real-time RT-PCR. The inflammatory process was also detected in the bloodstream at the protein level since fibrinogen, IL6 and IL1beta concentrations were increased in treated animals. Overall, the present study reveals several molecular changes supporting the hypothesis by which PDE4 inhibitor-induced vascular lesions in rats are triggered by an inflammatory mechanism and/or a vascular tone dysregulation.     

Effect of blood on styrene oxidation in perfused rat liver

The oxidation of styrene to styrene oxide was studied in the isolated perfused rat liver in the presence and absence of blood at styrene concentrations of 2.5 and 50 mM. Erythrocytes contained in whole blood increased the levels of styrene glycol about 5 times after a short perfusion time with both concentrations. This increase was observed up to 1 h with 2.5 mM styrene. At both styrene concentrations styrene oxide was not detectable, either in the presence or absence of blood indicating that the liver was able completely to detoxify the styrene oxide produced by the mixed-function oxidases (MFO) and the oxyhemoglobin in the erythrocytes.     

Gene expression profile in circulating mononuclear cells after exposure to ultrafine carbon particles

Context: Exposure to particulate matter (PM) is associated with systemic health effects, but the cellular and molecular mechanisms are unclear. Objective: We hypothesized that, if circulating mononuclear cells play an important role in mediating systemic effects of PM, they would show gene expression changes following exposure. Materials and methods: Peripheral blood samples were collected before (0?h) and at 24?h from healthy subjects exposed to filtered air (FA) and ultrafine carbon particles (UFPs, 50 μg/m³) for 2?h in a previous study (n?=?3 each). RNA from mononuclear cell fraction (>85% lymphocytes) was extracted, amplified and hybridized to Affymetrix HU133 plus 2 microarrays. Selected genes were confirmed in five additional subjects from the same study. Results: We identified 1713 genes (UFP 24?h vs. FA 0 and 24?h, P?<?0.05, false discovery rate of 0.01). The top 10 upregulated genes (fold) were CDKN1C (1.86), ZNF12 (1.83), SRGAP2 (1.82), FYB (1.79), LSM14B (1.79), CD93 (1.76), NCSTN (1.70), DUSP6 (1.69), TACC1 (1.68), and H2AFY (1.68). Upregulation of CDKN1C and SRGAP2 was confirmed by real-time-PCR. We entered 1020 genes with a ratio >1.1 or <?1.1 into the Ingenuity Pathway Analysis and identified pathways related to inflammation, tissue growth and host defense against environmental insults, such as, insulin growth factor 1 signaling, insulin receptor signaling and NF-E2-related factor-2-mediated oxidative stress response pathway. Discussion and conclusions: Two-hour exposures to UFP produced gene expression changes in circulating mononuclear cells. These gene changes provide biologically plausible links to PM-induced systemic health effects, especially those in the cardiovascular system and glucose metabolism.     

含绿色荧光蛋白及人胰岛素基因的真核表达载体的构建

目的构建含绿色荧光蛋白(GFP)基因与人胰岛素基因的重组真核表达载体。方法将人胰岛素基因插入到真核表达载体pIRES2-EGFP的EcoRⅠ和BamHⅠ位点中,构建重组质粒pIRES2-EGFP-INS。酶切鉴定,测序证实。结果重组真核表达载体pIRES2-EGFP-INS经限制性内切酶EcoRⅠ和BamHⅠ酶切,电泳后显示360bp的INS的目的片段和5.3kb的pIRES2-EGFP载体片段,进一步测序并证明重组质粒连接正确。结论成功构建了pIRES2-EGFP-INS重组质粒,为简便快速了解胰岛素基因的转染效率奠定了基础。     

Effect of multiple doses of styrene and R-styrene oxide on CC10, bax,and bcl-2 expression in isolated Clara cells of CD-1 mice

Styrene exposure is highest among workers in the reinforced plastics industry with exposure seen for 5 consecutive days during the work week. Styrene is both hepatotoxic and pneumotoxic in mice, in addition to causing lung tumors. Human epidemiological studies are inconclusive as to the carcinogenicity of styrene so it is important to understand the mechanism responsible for styrene tumors in mice. Previous studies showed significant decreases in CC10 protein for 5 days following a single dose of the active metabolite R-styrene oxide (R-SO), yet little change in the bax/bcl-2 protein ratio was seen until 10 days following styrene or R-SO administration. Styrene or R-SO was given to CD-1 mice for 5 consecutive days. Mice were euthanized 24 h, 10 days or 30 days following the last dose, and CC10, bax and bcl-2 mRNA and protein levels were determined in isolated Clara cells. CC10 mRNA levels were decreased at 24 h for both styrene and R-SO. R-SO decreased CC10 protein levels up to 10 days following the last dose. Increases in the bax/bcl-2 mRNA and protein ratio were seen 24 h following R-SO administration. Styrene did not significantly increase the bax/bcl-2 mRNA ratio until 10 days after treatment, with the bax/bcl-2 protein ratio increased at both 10 days and 30 days. It is likely that oxidative stress is involved in the toxicity caused by styrene and that minimal apoptosis may be involved. Chronically decreased CC10 levels may lead to increases in oxidative stress in Clara cells, the main target for styrene toxicity in the lung, and may be an early indicator for lung carcinogenesis in mice.