麦胚黄酮类提取物对荷瘤大鼠的抗氧化作用

为研究由麦胚提取的黄酮类化合物对 7,12 二甲基苯蒽 (DMBA)诱发大鼠乳腺肿瘤的抑制作用 ,将出生 5 0天的雌性SD大鼠随机分为阴性对照组、阳性对照组、低剂量实验组和高剂量实验组。阳性及阴性对照组大鼠喂基础饲料 ,除阴性对照组外的 3组大鼠经灌胃给致癌剂DMBA(每只 15mg溶于 1 5ml的植物油中 ) ,低 高剂量实验组大鼠同时给含麦胚黄酮类提取物的饲料 (分别为 2和 10g kg) ,持续喂养 2 4周。结果表明 ,高剂量组大鼠乳腺肿瘤的发生率较阳性对照组显著降低 ,实验组大鼠血液及肝脏中谷胱甘肽过氧化物酶活性和超氧化物歧化酶活性较阳性对照组大鼠有明显增加 ,丙二醛含量下降。提示麦胚提取的黄酮类化合物对抗过氧化物酶的诱导作用可能是其对乳腺癌具有化学预防作用的机制之一。     

Glutathione S-Transferase P1 Genotypes,Genetic Susceptibility and Outcome of Therapy in Thai Childhood Acute Lymphoblastic Leukemia

Glutathione S-transferases (GSTs) are enzymes that involved in bio- transformation by conjugation ofelectrophillic compounds to glutathione. Polymorphisms within genes that encode GSTs may affect the functionof the enzymes. Polymorphisms of GSTP1 at codon 105 residue forms GSTP1 active site for binding of hydrophobicelectrophiles, and the Ile-Val substitution affect substrate specific catalytic activity of this enzyme andmay associate with susceptibility to malignant human disease, especially acute lymphoblastic leukemia (ALL),which is the most common leukemia in children younger than 15 years old.Genetic polymorphisms within theGSTP1 gene of childhood ALL patients were studied. In addition, the association of genetic polymorphism ofGSTP1 and genetic susceptibility of acute lymphoblastic leukemia (ALL) was also determined using Chi-squareand Odds ratio. PCR-RFLP was used to study genetic polymorphism of GSTP1 in 100 ALL patients and 100healthy individuals.The results show that there is no statistically significant association between each genotypesand genetic susceptibility of acute lymphoblastic leukemia (ALL) (OR=0.92, P –value=0.886). Moreover, thereis no statistically significant association between each genotypes and demographic data of acute lymphoblasticleukemia (ALL). However, there are 2 cases of ALL with BM relapse show the polymorphic genotypes of GSTP1.It may suggest that GSTP1*V105 may be involved in relapse of ALL.     

利福平对鱼藤酮致分化PC12细胞氧化应激的影响

【目的】 探讨利福平对鱼藤酮诱导的分化大鼠嗜铬细胞瘤细胞株(PC12)细胞形态､活性氧(ROS)､还原型谷胱甘肽(GSH)及细胞凋亡的影响｡【方法】 利用鱼藤酮诱导分化PC12细胞建立帕金森病体外细胞模型;显微镜下观察细胞形态,酶标仪检测细胞还原型谷胱甘肽,流式细胞仪检测细胞活性氧和凋亡｡【结果】 鱼藤酮组细胞内还原型谷胱甘肽含量低于两对照组,而活性氧含量及凋亡率均高于两对照组;经100､200和300 μmol/L各浓度利福平预处理后,利福平预防组3组细胞内活性氧含量及凋亡率均低于鱼藤酮组,而细胞内还原型谷胱甘肽含量高于鱼藤酮组,且存在浓度依赖性｡【结论】 利福平可能通过氧化应激途径减轻鱼藤酮诱导的分化PC12细胞的损伤作用,且存在浓度依赖性｡     

A Novel Glutathione S-Transferase Gtt2 Class (VpGSTT2) Is Found in the Genome of the AHPND/EMS Vibrio parahaemolyticus Shrimp Pathogen

Glutathione S-transferases are a family of detoxifying enzymes that catalyze the conjugation of reduced glutathione (GSH) with different xenobiotic compounds using either Ser, Tyr, or Cys as a primary catalytic residue. We identified a novel GST in the genome of the shrimp pathogen V. parahaemolyticus FIM- S1708⁺, a bacterial strain associated with Acute Hepatopancreatic Necrosis Disease (AHPND)/Early Mortality Syndrome (EMS) in cultured shrimp. This new GST class was named Gtt2. It has an atypical catalytic mechanism in which a water molecule instead of Ser, Tyr, or Cys activates the sulfhydryl group of GSH. The biochemical properties of Gtt2 from Vibrio parahaemolyticus (VpGSTT2) were characterized using kinetic and crystallographic methods. Recombinant VpGSTT2 was enzymatically active using GSH and CDNB as substrates, with a specific activity of 5.7 units/mg. Low affinity for substrates was demonstrated using both Michaelis–Menten kinetics and isothermal titration calorimetry. The crystal structure showed a canonical two-domain structure comprising a glutathione binding G-domain and a hydrophobic ligand H domain. A water molecule was hydrogen-bonded to residues Thr9 and Ser 11, as reported for the yeast Gtt2, suggesting a primary role in the reaction. Molecular docking showed that GSH could bind at the G-site in the vicinity of Ser11. G-site mutationsT9A and S11A were analyzed. S11A retained 30% activity, while T9A/S11A showed no detectable activity. VpGSTT2 was the first bacterial Gtt2 characterized, in which residues Ser11 and Thr9 coordinated a water molecule as part of a catalytic mechanism that was characteristic of yeast GTT2. The GTT2 family has been shown to provide protection against metal toxicity; in some cases, excess heavy metals appear in shrimp ponds presenting AHPND/EMS. Further studies may address whether GTT2 in V. parahaemolyticus pathogenic strains may provide a competitive advantage as a novel detoxification mechanism.     

Read-across to rank skin sensitization potential: subcategories for the Michael acceptor domain

Background:  Eliminating animal testing for skin sensitization is a significant challenge in consumer safety risk assessment. To be able to perform resilient risk assessments in the future, one will need alternative approaches to fill the data gaps.
Objectives:  To this end, we propose a subcategory-based read-across approach to estimate and rank skin sensitization potential of chemicals. The example described here is for the mechanism of Michael-type nucleophilic addition with subcategories being limited to carbonyl-containing compounds.
Patients/Methods:  In this approach, in silico tools based on structural alerts were used to determine both the mechanism of protein binding and the relative subcategories within that mechanism.
Results:  Fifty compounds previously evaluated in the in vivo mouse local lymph node assay (LLNA) were placed in 10 subcategories defined by their polarized α,β-unsaturated substructure. To offset the limitations and skewness of the published in vivo data, in chemico glutathione (GSH) depletion data also were included.
Conclusions:  It was shown that the read-across approach can be successfully used to rank qualitatively skin sensitization potential of an untested carbonyl-containing Michael acceptor chemical by using subcategories. Moreover, the use of the more resilient in chemico GSH depletion data added further support to the read-across result.     

Stabilization of HIPK2 by escape from proteasomal degradation mediated by the E3 ubiquitin ligase Siah1

Homeodomain-interacting protein kinase 2 (HIPK2) induces apoptosis and, thus, is maintained at a low level via ubiquitin-mediated proteolysis. In a yeast two-hybrid screen, we identified Siah1, a RING finger E3 ubiquitin ligase, as an interacting protein of HIPK2. Siah1 targeted HIPK2 for poly-ubiquitination-mediated proteasomal degradation. Degradation of HIPK2 by Siah1 was blocked by forced expression of either Mixed Lineage Kinase-3 or Epstein-Barr viral protein LMP-1, as well as by DNA damaging stimuli. These findings effectively illustrate the regulatory mechanisms underlying HIPK2 stabilization by escape from Siah1-mediated degradation, and that Siah1 is an integration target for several internal or external stimuli for HIPK2 stabilization.     

Phase 3 randomised study of canfosfamide (Telcyta, TLK286) versus pegylated liposomal doxorubicin or topotecan as third-line therapy in patients with platinum-refractory or -resistant ovarian cancer

RationaleCanfosfamide HCl (CAN) is a glutathione analogue prodrug that is activated by glutathione S-transferase P1-1 and induces apoptosis. CAN is synergistic in vitro with carboplatin, paclitaxel and anthracyclines.MethodsPatients with platinum-refractory or -resistant ovarian cancer (OC) who had progressed on second-line therapy with pegylated liposomal doxorubicin (PLD) or topotecan (TOPO), were randomised between CAN 1000 mg/m² IV q 3 weeks or to either PLD 50 mg/m² IV q 4 weeks or TOPO 1.5 mg/m² IV d1-5 q 3 weeks.ResultsAbout 461 patients were randomised after stratification for ECOG performance status, prior therapy, and bulky (>5 cm) disease. Groups were well balanced. In the control arm 58% and 42% were treated with PLD and TOPO, respectively. CAN was well tolerated with the most common grade 3–4 toxicities of 5% anaemia, 4% neutropaenia (no febrile neutropaenia), 4% thrombocytopaenia, and 7% vomiting. Progression-free survival (PFS) and overall survival (OS) were significantly higher in the control arm (p < 0.001 and p < 0.01, respectively). In a subgroup analysis PFS and OS tended to be higher with PLD than with TOPO.ConclusionCAN was well tolerated. This is the first randomised study showing an increased OS with third-line therapy. This might have important consequences for other recurrent OC trials.     

Advances in pharmacological strategies for the prevention of cataract development

Cataractous-opacification of the lens is one of the leading causes of blindness in India. The situation can be managed by surgical removal of the cataractous lens. Various pharmacological strategies have been proposed for the prevention and treatment of cataract. Information on possible benefits of putative anticataract agents comes from a variety of approaches, ranging from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients. This review deals with the various mechanisms, and possible pharmacological interventions for the prevention of cataract. The article also reviews research on potential anticataractous agents, including aldose reductase inhibitors, glutathione boosters, antiglycating agents, vitamins and various drugs from indigenous sources.     

Enhancement of cytotoxicity of natural product drugs against multidrug resistant variant cell lines of human head and neck squamous cell carcinoma and breast carcinoma by tesmilifene

N,N-diethyl-2-[4-(phenylmethyl)phenoxyl]ethanamine (tesmilifene), a tamoxifen derivative with antihistamine activity, greatly enhanced the survival of doxorubicin-treated, advanced stage breast cancer patients in a phase III trial. However, the molecular basis of tesmilifene action is not firmly established. The effects of tesmilifene on activity of several anticancer drugs was investigated using human head and neck squamous cell carcinoma (HNSCC) and breast carcinoma cell lines as a model system. Multidrug resistant (MDR) variants of an HNSCC cell line, HN-5a/V15e, and a breast carcinoma cell line, MCF-7/V25a, both highly overexpressed mdr1 (ABCB1) mRNA and the proteins P-glycoprotein and glutathione transferase-pi. Drug sensitivities were measured by a vital stain after 4 days of continuous exposure to anticancer drug in the absence and presence of tesmilifene at a concentration that alone had no antiproliferative effect. Tesmilifene had minimal effect on drug cytotoxicity against the parental cell lines. However, the same tesmilifene treatment enhanced cytotoxicity of docetaxel, paclitaxel, epirubicin, doxorubicin, and vinorelbine against both MDR cell lines by up to 50%. Flow cytometric measurement of annexin V/propidium iodide staining demonstrated that tesmilifene increased the killing of HN-5a/V15e cells caused by docetaxel after 24 and 48h exposure. Tesmilifene increased accumulation of radiolabelled vincristine in HN-5a/V15e cells, over 4h, by up to 100%. The results suggest that tesmilifene might be effective in the treatment of tumors that are resistant to natural product drugs. The mechanism of enhancement appears to be related to expression of an ABC pump-dependent, MDR phenotype.     

GSTM1 and GSTT1 null genotypes as possible heritable factors of rosacea

PURPOSE: Rosacea might be related to an increased activity of reactive oxygen species (ROS) and deficient function of the antioxidant system. Glutathione S-transferases (GSTs) play a primer role in cellular defense against electrophilic chemical species and radical oxygen species. We hypothesized that increased ROS activity or decreased antioxidant potential, possibly induced by GST gene polymorphism, might have a pathogenic role in rosacea. METHODS: The study group consisted of 45 patients with rosacea and 100 control subjects. DNA samples were isolated from blood samples using high pure polymerase chain reaction (PCR) Template preparation Kit. The GSTM1, GSTT1, and P1 polymorphisms were detected using a real-time PCR and fluorescence resonance energy transfer with a Light-Cycler Instrument. Associations between specific genotypes and the development of rosacea were examined using logistic regression analyses to calculate odds ratios (OR) and 95% confidence intervals (CI). RESULTS: GSTM1 and GSTT1 null genotypes were found to be statistically different from control (P=0.005, P=0.009, respectively), and associated with an increased risk of rosacea (OR [95% CI]: 2.84 [1.37-5.89]; OR [95% CI]: 2.68 [1.27-5.67], respectively). There was a statistically significant relationship between both null combination of the GSTM1 and GSTT1 genotype polymorphisms and rosacea (P=0.003, OR [95% CI]: 4.18 [1.57-11.13]). There were no statistically significant differences between patient and control groups for the GSTP1 Ile/Ile, Ile/Val, and Val/Val genotypes (P>0.05). CONCLUSION: We demonstrated a significant association between the GSTT1 and/or GSTM1 null genotypes and rosacea. However, the potential role of GSTs as markers of susceptibility to rosacea needs further studies in larger patient groups.