Superoxide radicals scavenging and xanthine oxidase inhibitory activity of magnesium lithospermate B from Salvia miltiorrhiza

In this study we investigated the superoxide radicals scavenging effect and xanthine oxidase inhibitory activity by magnesium lithospermate B, which was originally isolated from the roots of Salvia miltiorrhiza (also named Danshen or Dansham), an important herb in Oriental medicine. Superoxide radicals were generated both in β-NADH/PMS system and xanthine/ xanthine oxidase system. Magnesium lithospermate B significantly inhibited the reduction of NBT induced by superoxide radicals with an IC₅₀ of 29.8 μg/mL and 4.06 μg/mL respectively in the two systems. Further study suggested that magnesium lithospermate B can directly inhibit xanthine oxidase and exhibits competitive inhibition. Magnesium lithospermate B was also found to have the hypouricemic activity in vivo against potassium oxonate-induced hyperuricaemia in mice. After oral administration of magnesium lithospermate B at doses of 10, 20 and 30 mg/kg, there was a significant decrease in the serum urate level when compared to the hyperuricemia control. In addition, magnesium lithospermate B significantly protected HL-60 cells from superoxide radicals-induced apoptosis in the xanthine/ xanthine oxidase reactions. This study provided evidence that magnesium lithospermate B exhibits direct superoxide radicals scavenging and xanthine oxidase inhibitory activity.     

Recombinant protein composed of Pseudomonas exotoxin A, outer membrane proteins I and F as vaccine against P. aeruginosa infection

We have constructed a chimeric protein composed of the receptor binding and membrane translocation domains of Pseudomonas exotoxin A (PE) with the outer membrane proteins I and F, together designated as PEIF. The potential of PEIF as a vaccine against Pseudomonas infection was evaluated in BALB/c mice and New Zealand white rabbits. We examined titers of anti-PE and anti-OprF antibodies, and the ability both to neutralize PE cytotoxicity and to increase opsonophagocytic uptake of Pseudomonas aeruginosa strain PAO1, serogroups 2 and 6. The results showed that PEIF can induce antibodies not only to neutralize the PE cytotoxicity but also to promote the uptake of various strains of P. aeruginosa by murine peritoneal macrophages. In a burned mouse model, PEIF afforded significant protection against infection by the homologous P. aeruginosa strain PAO1, heterologous serogroup 2, and the PE hyperproducing strain PA103. These observations thus indicate that PEIF may be used as a novel vaccine against P. aeruginosa infection. Received: 10 March 1999 / Received revision: 21 April 1999 / Accepted: 16 May 1999     

Engineering of enhanced glycine betaine synthesis improves drought tolerance in maize

Glycine betaine plays an important role in some plants, including maize, in conditions of abiotic stress, but different maize varieties vary in their capacity to accumulate glycine betaine. An elite maize inbred line DH4866 was transformed with the betA gene from Escherichia coli encoding choline dehydrogenase (EC 1.1.99.1), a key enzyme in the biosynthesis of glycine betaine from choline. The transgenic maize plants accumulated higher levels of glycine betaine and were more tolerant to drought stress than wild-type plants (non-transgenic) at germination and the young seedling stage. Most importantly, the grain yield of transgenic plants was significantly higher than that of wild-type plants after drought treatment. The enhanced glycine betaine accumulation in transgenic maize provides greater protection of the integrity of the cell membrane and greater activity of enzymes compared with wild-type plants in conditions of drought stress.     

植物热激蛋白的功能及其基因表达的调控

本文介绍了植物热激蛋白的产生、分布和分类。着重论述了热激反应的特点、植物热激蛋白的功能、热激基因表达与调控的研究进展     

家族性高胆固醇血症患者低密度脂蛋白受体基因新突变位点的鉴定

家族性高胆固醇血症(hypercholesterolemia familial,FH)是由于低密度脂蛋白受体(low density lipoprotein receptor,LDLR)基因突变导致的常染色体显性遗传性疾病,临床上表现为多发黄色瘤、高水平血浆LDL、早发性冠心病及有阳性家族史。本研究通过临床症状结合血脂测定诊断出一个FH家系,其纯合子FH患者的血浆总胆固醇水平高达19．05mmol／L,LDL达17．06mmol／L,并有黄色瘤;而杂合子FH患者的血浆总胆固醇水平为7．96mmol／L,LDL为5．55mmol/L,并有心绞痛症状和黄色瘤。我们对该FH家系患者LDLR基因的PCR扩增DNA片段进行测序,发现纯合子FH患者LDLR基因Exon4区域内发生了GAG683GCG突变,即编码LDLR第683位的谷氨酸被丙氨酸替换,而杂合子FH患者该位点呈现杂合突变。此基因型与临床诊断遗传谱完全一致。同时,利用获得Epstein-Barr(EB)病毒转化型人永生淋巴细胞株(EBV-Ls)与荧光探针DiI标记的LDL结合反应,再通过流式细胞仪检测结果显示,具有功能性LDLR的EBV-Ls细胞比例,在纯合子FH患者(7．02％)和杂合子FH患者(62．64％)均比健康对照者(84．69％)低,纯合子FH患者LDLR活性仅为健康对照者的8．29％、而杂合子FH患者LDLR活性约为健康对照者的73．96％,前者呈现非常显著的降低。这些EBV-Ls细胞LDLR的功能变化分析,有力地支持了该FH家系的临床诊断和DNA测序结果。经查阅最新的UMD-LDLR完全版证实,本研究发现鉴定的GAG683GCG突变是人LDLR基因的新突变位点。     

The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis

The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (−1872 bp to −1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as “positive and negative regulation.”