Dexamethasone down-regulates ABCG2 expression levels in breast cancer cells

The breast cancer resistance protein ABCG2 effluxes a variety of drugs and is believed to play an important role in multidrug resistance to chemotherapy. We show here for the first time that dexamethasone (DEX) and progesterone (PROG) are able to strongly inhibit ABCG2 expression in progesterone receptor (PR)-positive MCF7 and PR-negative MDA-MB-231 breast cells. In contrast, in the latter cells stably-transfected with progesterone receptor isoforms A and B, ABCG2 expression was strongly up-regulated by DEX and PROG. In addition, two other ligands of Pregnane X Receptor (PXR) and/or Glucocorticoid Receptor (GR) were also able to down-regulate ABCG2 expression in PXR- and GR-positive MCF7 cells. ABCG2 expression regulation by DEX likely resulted from the activation of PR-, PXR-, and/or GR-signaling pathways. ABCG2 expression inhibition by DEX was associated with increased sensitivity to mitoxantrone, a known ABCG2 substrate. The findings suggest that DEX may be useful in improving drug efficacy under certain conditions.     

Renin angiotensin aldosterone axis, including aldosterone binding globulin and blood pressure in three species of nonhuman primates

Variables of renin-angiotensin-aldosterone axis with inclusion of protein binding to specific plasma globulin (ABG), plasma cortisol, and the blood pressure (BP) were measured in 24 chimpanzees, 4 gorillas, and 16 cynomolgus monkeys. ABG activity was readily detected in plasma from the primates. In chimpanzees and gorillas, all the variables under baseline conditions were similar to those in humans. In cynomolgus (Macaca fascicularis), both the ABG binding capacity for aldosterone and the diastolic or systolic BP were significantly higher (p less than 0.001 and p less than 0.01 respectively) than in chimpanzees and gorillas.     

近10年外来入侵昆虫风险分析的研究现状及主要进展

随着经济全球化的加速发展,外来入侵昆虫对世界各国农林业、生态环境、社会经济和人类健康造成的影响日趋严重。近10年来,关于外来入侵昆虫风险分析的相关研究备受重视,发展迅速;在研究对象类别中,鞘翅目昆虫居多,占所有入侵昆虫的32.21%,其次为双翅目和膜翅目,最小的为缨翅目,仅占1.44%。风险分析主要包括入侵途径、适生范围及风险等级、传播扩散、经济和生态影响等层面;其中以适生性风险分析研究最多,占43.41%。深入开展入侵昆虫的风险分析,对防范和阻截其传入、扩散和蔓延具有重要的理论意义和应用价值。     

Mutation spectrum of phenylketonuria in Syrian population: Genotype–phenotype correlation

Characterization of the molecular basis of phenylketonuria (PKU) in Syria has been accomplished through the analysis of 78 unrelated chromosomes from 39 Syrian patients with PKU. Phenylalanine hydroxylase (PAH) gene mutations have been analyzed by using molecular detection methods based on the restriction fragment length polymorphism (RFLP), artificial constructed restriction sites (ACRS) PCR and direct DNA sequencing. 56.4% of the patients had cPKU. A mutation detection rate of 79.49% was achieved and sixteen different mutations were found: missense 56.25%, splice site 37.5%, and frameshift 6.25%. The predominant mutation in this population sample was p.R261Q G>A, p.F55>Lfs and p.R243Q G>A. No mutation in six PKU patients was observed. In 57.9% of patient genotypes, the metabolic phenotype could be predicted. The identification of the mutations in the PAH gene and the genotype–phenotype correlation should facilitate the evaluation of metabolic phenotypes, diagnosis, implementation of optimal dietary therapy, and determination of prognosis in the patients and genetic counseling for the patient's relatives.     

D-ribose-5-phosphate isomerase B from Escherichia coli is also a functional D-allose-6-phosphate isomerase, while the Mycobacterium tuberculosis enzyme is not

Interconversion of d-ribose-5-phosphate (R5P) and d-ribulose-5-phosphate is an important step in the pentose phosphate pathway. Two unrelated enzymes with R5P isomerase activity were first identified in Escherichia coli, RpiA and RpiB. In this organism, the essential 5-carbon sugars were thought to be processed by RpiA, while the primary role of RpiB was suggested to instead be interconversion of the rare 6-carbon sugars d-allose-6-phosphate (All6P) and d-allulose-6-phosphate. In Mycobacterium tuberculosis, where only an RpiB is found, the 5-carbon sugars are believed to be the enzyme's primary substrates. Here, we present kinetic studies examining the All6P isomerase activity of the RpiBs from these two organisms and show that only the E. coli enzyme can catalyze the reaction efficiently. All6P instead acts as an inhibitor of the M. tuberculosis enzyme in its action on R5P. X-ray studies of the M. tuberculosis enzyme co-crystallized with All6P and 5-deoxy-5-phospho-d-ribonohydroxamate (an inhibitor designed to mimic the 6-carbon sugar) and comparison with the E. coli enzyme's structure allowed us to identify differences in the active sites that explain the kinetic results. Two other structures, that of a mutant E. coli RpiB in which histidine 99 was changed to asparagine and that of wild-type M. tuberculosis enzyme, both co-crystallized with the substrate ribose-5-phosphate, shed additional light on the reaction mechanism of RpiBs generally.     

Characterization of SARS-CoV main protease and identification of biologically active small molecule inhibitors using a continuous fluorescence-based assay

Severe acute respiratory syndrome associated coronavirus main protease (SARS-CoV Mpro) has been proposed as a prime target for anti-SARS drug development. We have cloned and overexpressed the SARS-CoV Mpro in Escherichia coli, and purified the recombinant Mpro to homogeneity. The kinetic parameters of the recombinant SARS-CoV Mpro were characterized by high performance liquid chromatography-based assay and continuous fluorescence-based assay. Two novel small molecule inhibitors of the SARS-CoV Mpro were identified by high-throughput screening using an internally quenched fluorogenic substrate. The identified inhibitors have Ki values at low microM range with comparable anti-SARS-CoV activity in cell-based assays.     

Molecular features of Mycobacterium avium human isolates carrying a single copy of IS1245 and IS1311 per genome

Human clinical isolates of the Mycobacterium avium complex, from hospitals in Bogotá, were studied using a wide range of molecular tests including PCR restriction-enzyme analysis (PRA) of the hsp65 gene. Up to 21 of the isolates were identified as M. avium PRA variant III (Mav III), a variant obtained only from isolates on the American continent. In contrast to previous reports, restriction fragment length polymorphism analysis using IS1245 and IS1311 showed a single copy for each insertion sequence (IS) in the majority (19/21) of the Colombian Mav III isolates under study. In order to analyse whether the ISs were inserted in a relevant genomic region, experimental conditions were established to determine the insertion loci of each single copy of both ISs in the genome. Analysis of genomic insertion loci indicated that both IS1245 and IS1311 were present in areas containing putatively truncated integrases and/or transposases, which may have an influence on the mobility of the inserted IS. In addition, a conserved genomic region was identified for the insertion of IS1311; this region could be part of the IS1311 itself.     

Progressive retinal atrophy in Shetland sheepdog is associated with a mutation in the CNGA1 gene

Progressive retinal atrophy (PRA) is the collective name of a class of hereditary retinal dystrophies in the dog and is often described as the equivalent of retinitis pigmentosa in humans. PRA is characterized by visual impairment due to degeneration of the photoreceptors in the retina, usually leading to blindness. PRA has been reported in dogs from more than 100 breeds and can be genetically heterogeneous both between and within breeds. The disease can be subdivided by age at onset and rate of progression. Using genome‐wide association with 15 Shetland Sheepdog (Sheltie) cases and 14 controls, we identified a novel PRA locus on CFA13 (P_raw = 8.55 × 10^?7, P_genome = 1.7 × 10^?4). CNGA1, which is known to be involved in human cases of retinitis pigmentosa, was located within the associated region and was considered a likely candidate gene. Sequencing of this gene identified a 4‐bp deletion in exon 9 (c.1752_1755delAACT), leading to a frameshift and a premature stop codon. The study indicated genetic heterogeneity as the mutation was present in all PRA‐affected individuals in one large family of Shelties, whereas some other cases in the studied Sheltie population were not associated with this CNGA1 mutation. To our knowledge, this is the first report of a mutation in CNGA1 causing PRA in dogs.     

Development and evaluation of an immuno-MALDI (iMALDI) assay for angiotensin I and the diagnosis of secondary hypertension

Plasma renin activity (PRA) is an essential analytical tool for screening and diagnosis of secondary forms of hypertension. Typically, PRA is measured by competitive radioimmunoassay, but there are significant drawbacks to this technique including non-specificity, long analysis times, narrow calibration range, and the requirement for radionucleotides. In this paper, we report a method for plasma renin activity determination by immuno-MALDI mass spectrometry detection. This method overcomes the issues of non-specificity and long analytical times present with RIA, and does not require the use of radionucleotides. As an initial methodological evaluation, plasma renin activity results obtained by radioimmunoassay, LC/ESI-MS/MS, and immuno-MALDI on 64 samples from an outpatient primary aldosteronism screening program have been compared. A strong correlation was found between immuno-MALDI and radioimmunoassay (R² = 0.9412, 62/64 within the 95% CI of the Bland-Altman plot), and iMALDI and LC/ESI-MS/MS (R² = 0.9471, 62/64 within the 95% CI of the Bland-Altman plot). Technical replicates showed a 4.8% CV, while inter- and intra-day replicates showed CVs of 17.3% and 17.2% respectively. We have developed an assay capable of measuring PRA without the use of radionucleotides. This immuno-MALDI approach affords the specificity of MS while avoiding the long analytical run times and technical problems associated with HPLC. With the use of robotic sample preparation to optimize precision, this assay should be adaptable to clinical environments.