JS-K抗肿瘤效果机制的研究进展

研究显示一氧化氮(NO)在体内参与多种信号通路的传导,在机体的肿瘤形成等多种病理和生理过程中发挥着重要作用。谷胱甘肽-S-转移酶(GSTs)在很多肿瘤的表达都是升高的,在肿瘤细胞中发挥着维持氧化还原平衡、解毒和促使肿瘤细胞发生耐药等方面的的作用;而JS-K是近年来新合成的一种一氧化氮(NO)前体药,其可以在体内被谷胱甘肽-S-转移酶(GSTs)酶解生成NO,进而发挥抗肿瘤效应。研究显示JS-K对机体的多种肿瘤都表现出明显的抑制作用,而对正常的组织则没有明显的损伤作用。由于肿瘤的组织来源不同,JS-K表现出的杀伤肿瘤的机制也不尽相同。本课题组通过广泛的文献阅读,系统地综述JS-K杀伤各系统肿瘤的作用机制,为JS-K杀伤肿瘤的进一步的机制研究提供一些有益的思路,和为将来JS-K的临床应用提供理论基础。     

作物籽粒中NO3--N和NO2--N的积累与氮肥种类和数量的关系

1996～1997在芸豆(云南)、红小豆(河北)、大豆(黑龙江)和花生(山东)绿色食品产地,研究了施用有机肥和化肥对这些作物籽粒中NO₃^-、NO₂^-的累积特点.结果表明,芸豆和红小豆不论施用有机肥还是尿素,土壤中的速效氮与籽粒中NO₂^-的灰色关联最好;施用有机肥的最大关联度分别出现在土壤库内部(全氮与速效氮之间)或籽粒库内部(NO₃^-、NO₂^-之间);而施用化肥的最大关联度分别出现在土壤库与籽粒库的全氮与NO₃^-之间.芸豆和红小豆随着施肥水平的提高,籽粒中NO₃^-/NO₂^-比值动态变化趋势因施用有机肥和施用化肥而不同.这4类作物籽粒中的NO₃^-与NO₂^-存在着极显著的负直线相关关系和极显著的直线回归关系.     

Distribution of NO3− reduction between roots and shoots of peachtree seedlings as affected by NO3− uptake rate

The distribution of NO₃^? reduction between roots and shoots was studied in hydro-ponically-grown peach-tree seedlings (Prunus persica L.) during recovery from N starvation. Uptake, translocation and reduction of NO₃^?, together with transport through xylem and phloem of the newly reduced N were estimated, using ¹⁵N labellings, in intact plants supplied for 90 h with 0.5 mM NH₄⁺ and 0.5, 1.5 or 10 mM NO₃^?. Xylem transport of NO₃^? was further investigated by xylem sap analysis in a similar experiment. The roots were the main site of NO₃^? reduction at all 3 levels of NO₃^? nutrition. However, the contribution of the shoots to the whole plant NO₃^? reduction increased with increasing external NO₃^? availability. This contribution was estimated to be 20, 23 and 42% of the total assimilation at 0.5, 1.5 and 10 mM NO₃^?, respectively. Both ¹⁵N results and xylem sap analysis confirmed that this trend was due to an enhancement of NO₃^? translocation from roots to shoots. It is proposed that the lack of NO₃^? export to the shoots at low NO₃^? uptake rate resulted from a competition between NO₃^? reduction in the root epidermis/cortex and NO₃^? diffusion to the stele. On the other hand, net xylem transport of newly reduced N was very efficient since ca 70% of the amino acids synthesized in the roots were translocated to the shoots, regardless of the level of NO₃^? nutrition. This net xylem transport by far exceeded the net downward phloem transport of the reduced N assimilated in shoots. As a consequence, the reduced N resulting from NO₃^? assimilation, principally occurring in the roots, was mainly incorporated in the shoots.     

Mutagenic selectivity of carcinogenic nitroso compounds I. N-methyl-N-nitrosourethane

The mutagenicity of the carcinogen methylnitrosourethane (MNUr) was examined in Drosophila with a view to the determination of its activity on heterochromatic loci (especially rDNA) relative to those in the euchromatin. Assays were made of the yield of rDNA mutations (bobbed: bb) relative to other X-chromosome recessive lethals and visibles [X(l + v)] in the same male germ cells after treatment with different doses (1–10 mM) and at various stages in spermatogenesis.Dose dependence followed the same pattern for all genic loci and germ cell stages. In all instances, the regression of mutation frequency on injected molar dose was approximately linear, but could better be described by a quadratic dose curve. In contrast, the mutagenicity pattern during spermatogenesis varied according to the target genes. The response of the euchromatic loci reached a peak among the earlier germ cells (probably the spermatocytes), whereas that for the heterochromatic sites (including rDNA) was maximal in mature sperm.Mutagenic selectivity for rDNA with MNUr, as indicated by the percentage bb/X-mutations, was among the highest for the intrinsically reactive carcinogens (alkylating and arylating agents). This correlates with the strong carcinogenicity of MNUr and adds further support to the concept that rDNA mutations might well be a crucial step in cancer initiation.     

Effects of genetic modification of nitrate reductase expression on 15NO3– uptake and reduction in Nicotiana plants

The physiological consequences for NO₃^– utilization by the plant of underexpression and overexpression of nitrate reductase (NR) were investigated in nine transformants of Nicotiana tabacum and Nicotiana plumbaginifolia. The in vitro NR activities (NRAs) in both roots and leaves of low- and high-NR tobacco transformants ranged from 5–10% to 150–200%, respectively, of those measured in wild-type plants. The level of NR expression markedly affected the NO₃^– reduction efficiency in detached leaves and intact plants. In both species, ¹⁵NO₃^– reduction ranged from 15–45% of ¹⁵NO₃^– uptake in the low-NR plants, to 40–80% in the wild-type, and up to 95% in high-NR plants. In the high-NR genotypes, however, total ¹⁵NO₃^– assimilation was not significantly increased when compared with that in wild-type plants, because the higher ¹⁵NO₃^– reduction efficiency was offset by lower ¹⁵NO₃^– uptake by the roots. The inhibition of NO₃^– uptake appeared to be the result of negative feedback regulation of NO₃^– influx, and is interpreted as an adjustment of NO₃^– uptake to prevent excessive amino acid synthesis. In genotypes underexpressing NR, the low ¹⁵NO₃^– reduction efficiency also was generally associated with a decrease in net ¹⁵NO₃^– uptake as compared with the wild type. Thus, underexpression of NR resulted in an inhibition of reduced ¹⁵N synthesis in the plant, although the effect was much less pronounced than that expected from the very low NRAs. The restricted NO₃^– uptake in low-NR plants emphasizes the point that the products of NO₃^– assimilation are not the only factors responsible for down-regulation of the NO₃^– uptake system.     

In vivo effects of the controlled NO donor/scavenger ruthenium cyclam complexes on blood pressure

Ruthenium(II/III) complexes able to bind and release NO* were tested in vivo, in conscious Wistar rats instrumented for continuous blood pressure (BP) measurement and administration of in bolus injections (5 to 100 nmol/Kg i.v.) of trans-[Ru(II)Cl(NO+)(cyclam)](PF6)2 (cyclam-NO) or sodium nitroprusside (SNP). For normotensive rats, cyclam-NO produced a sustained 10% BP reduction of basal MAP during 7 +/- 0.4 to 11 +/- 0.3 min. In acute hypertensive rats, cyclam-NO produced BP reduction 3-fold larger than in normotensive rats and similar to that of SNP (maximal effect: 41 +/- 1.3 vs. 45 +/- 2.2 mmHg, respectively). However, the duration of the effect of cyclam-NO was 13 to 21-fold longer than that of SNP. The hypotensive effect of cyclam-NO was fully blocked in presence of continuous infusion of a NO* scavenger, carboxy-PTIO (6 mmol/Kg/min), or of the inhibitor of cGMP activation, methylene blue (83 nmol/Kg/min), or of the cyclam-NO precursor, trans-[RuCl(tfins)(cyclam)](tfms) (cyclam-tfms) (500 mmol/Kg/min). The long lasting BP reduction of cyclam-NO can be interpreted in terms of a slower rate of NO* release (k-NO = 2.2 x 10(-3) S(-1) at 35 degrees C) following chemical reduction (E(0') = 0.10 V vs NHE). In summary, cyclam-NO showed an hypotensive effect around 20 times longer than SNP in either normotensive or hypertensive rats, which was completely inhibited by methylene blue or carboxy-PTIO. Continuous infusion of cyclam-tfms completely blocked the hypotensive effect of cyclam-NO by scavenging the NO* released by the reduced cyclam-NO.     

Lactones from the pericarps of Litsea japonica and their anti-inflammatory activities

Five new lactones, litsenolide F₁ (1), lisealactone H₁ (10), lisealactone H₂ (11), akolactone D (13), and akolactone E (14), along with thirteen known compounds were isolated from the pericarps of Litsea japonica (Thunb.) Jussieu. Their chemical structures were elucidated by extensive spectroscopic analyses, including 1D and 2D NMR, HRMS, and chemical methods. The isolated compounds were evaluated for their inhibitory effects on NO production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Among them, 2-alkylidene-3-hydroxy-4-methylbutanolide derivatives (compounds 1–9) exhibited the most potent activity, with IC₅₀ values in the range of 2.9–12.8?μM. In additon, compounds 1, 3, 4, and 6 showed inhibition of iNOS and COX-2 expression in concentration-dependent manner. Compound 3 suppresses mRNA expression of iNOS, COX-2, IL-6, and TNF-α in LPS-stimulated RAW264.7 cells. Based on these evidence, the isolated lactones from L. japonica could be promissing candidates for the development of new anti-inflammatory agents.     

Mutations et altérations dans la transmission des informations génétiques chez la drosophile par injection d'extraits de chrysalide diapausantes (Pieris brassicae) traitées par des ptérines

The injection of a pterinic growth factor (folic acid) to insects in diapause under hormone-deficient conditions induced the formation of tumors. From these tumours, artificially induced in chrysalids of Pieris brassicae, a factor causing tumours was extracted which could be isolated by ultracentrifugation. The factor induced by the pterins (folic acid) is made up of light particles which contain DNA, and this DNA is the active constituent. It is a 4–8 S component after breakdown of the light particles.     

Giardia lamblia encodes a functional flavohemoglobin

Giardia lamblia is a pathogenic protist that infects the small intestine of mammals. As a facultative anaerobe, Giardia obtains all of its energy by substrate-level phosphorylation, lacks a functioning respiratory chain, and is not thought to require heme. However, sequencing of the G. lamblia genome has identified several putative heme proteins, one of which shares high sequence similarity to flavohemoglobins found in bacteria and some single-celled eukaryotes. We have cloned and characterized the functional properties of the G. lamblia flavohemoglobin. The protein is monomeric, binds heme and flavin adenine dinucleotide, and exhibits similar behavior to known flavohemoglobins, including NADH and NADPH oxidase activity, which is stimulated by addition of the nitric oxide donor DEA/NO. Based on its structural and functional properties, the likely role of this protein is to protect Giardia against oxygen, nitric oxide, or both. The presence of a Giardia gene encoding a functional heme protein raises questions on how this organism acquires the heme cofactor, which hitherto have been unexplored.     

Hcn and Hnc in Comets C/2000 Wm1 (Linear) and C/2002 C1 (Ikeya-Zhang)

Comets have been suggested as a possibly significant source of organic molecules to the early Earth. Hydrogen cyanide (HCN) is important in models of prebiotic chemistry, but may be difficult to form in the early terrestrial environment, while hydrogen isocyanide (HNC) is a `classical' tracer of interstellar ion-molecule chemistry. We have observed both HCN and HNC in 2 recent comets, bringing the number of comets with published measurements of the HNC/HCN abundance ratio to 6. The HNC/HCN ratio in comet Ikeya-Zhang appears to increase with decreasing heliocentric distance, as was previously observed for comet Hale-Bopp, indicating that the HNC is produced at least in part by processes in the cometary coma (atmosphere) and is not simply a constituent of the nuclear ices. Both comets C/2000 WM1 (Linear) and C/2002 C1 (Ikeya-Zhang) exhibit values of the HNC/HCN ratio that appear to be too large (0.09–0.19) tobe matched by current models of coma chemistry. Cometary HNC maybe a photodissociation product of organic grains or large organic polymers stored in the nucleus. We have also set a limit on the emission from the NO radical in comet WM1.     

Oxidized LDL at low concentration promotes in-vitro angiogenesis and activates nitric oxide synthase through PI3K/Akt/eNOS pathway in human coronary artery endothelial cells

It has long been considered that oxidized low-density lipoprotein (oxLDL) causes endothelial dysfunction and is remarkably related to the development of atherosclerosis. However, the effect of oxLDL at very low concentration (<10 μg/ml) on the endothelial cells remains speculative. Nitric oxide (NO) has a crucial role in the endothelial cell function. In this study, we investigated the effect of oxLDL at low concentration on NO production and proliferation, migration, tube formation of the human coronary artery endothelial cells (HCAEC). Results showed that oxLDL at 5 μg/ml enhanced HCAEC proliferation, migration and tube formation. These phenomena were accompanied by an increased intracellular NO production. l-NAME (a NOS inhibitor), LY294002 and wortmannin (PI3K inhibitors) could abolish oxLDL-induced angiogenic effects and prevent NO production in the HCAEC. The phosphorylation of Akt, PI3K and eNOS were up-regulated by oxLDL, which was attenuated by LY294002. Our results suggested that oxLDL at low concentration could promote in-vitro angiogenesis and activate nitric oxide synthesis through PI3K/Akt/eNOS pathway in HCAEC.     

A GAF domain in the hypoxia/NO-inducible Mycobacterium tuberculosis DosS protein binds haem

The majority of the Mycobacterium tuberculosis response to hypoxia and nitric oxide is through the DosRS (DevRS) two-component regulatory system. The N-terminal input domain of the DosS sensor contains two GAF domains. We demonstrate here that the proximal GAF domain binds haem, and identified histidine 149 of DosS as critical to haem-binding; the location of this histidine residue is similar to the cGMP-binding site in a crystal structure of cyclic nucleotide phosphodiesterase 2A. GAF domains are frequently involved in binding cyclic nucleotides, but this is the first GAF domain to be identified that binds haem. In contrast, PAS domains (similar to GAF domains in structure but not primary sequence) frequently use haem cofactors, and these findings further illustrate how the functions of these domains overlap. We propose that the activation of the DosS sensor is controlled through the haem binding of molecular oxygen or nitric oxide.     

干旱胁迫对玉米幼苗根系中NO信号转导的影响

以玉米(Zea mays L.)幼苗根系为材料,研究其生长发育对内外源NO的感应及在干旱条件下内外源NO对其生长发育的影响.结果表明:干旱抑制根系NO释放,NO的产生可能不依赖于NO合酶系统,而依赖于NADPH硝酸还原酶的酶促反应;用活性氧清除剂NAC、NAC与干旱复合处理均能促使内源NO的产生和释放:其根系生物量的分析表明内源NO的释放明显抑制根系的生长发育.     

植物中一氧化氮的生理作用

No是一种易扩散的生物活性分子,是生物体内重要的信号分子。植物细胞通过NO合酶,硝酸还原酶,或非生化反应途径产生NO。NO参与植物生长发育调控和对生物和非生物胁迫的应答反应。主要通过讨论No的产生,对植物生长发育的影响及在抗逆反应中的信号调节来阐述No在植物中的作用。     

植物中一氧化氮与园艺产品的成熟和衰老

概述了一氧化氮(NO)的生物学特性、植物中NO的来源、NO对园艺产品成熟保鲜的作用及其生理机制研究的新进展.