蜂毒素微球经动脉介入治疗大鼠肝癌的实验研究

目的:观察蜂毒素微球(M-MS)经动脉介入对大鼠肝癌的治疗作用.方法:采用改良的复乳-液中干燥法制备蜂毒素-聚乳酸/羟乙酸微球,建立大鼠移植性肝癌模型并随机分为四组,分别经肝动脉灌注生理盐水(NS,1.5ml/kg)、蜂毒素(Melittin,0.35mg/kg)、空白微球(B-MS,10mg/kg)和蜂毒素-聚乳酸/羟乙酸微球(10mg/kg).比较治疗后各组大鼠的肿瘤生长情况、肿瘤坏死程度和生存时间.结果:与生理盐水组比较,Melittin组、B-MS组肿瘤生长受到明显抑制(P<0.01),肿瘤坏死程度以轻中度为主,但两组动物生存时间均未能明显延长(P>0.05).M-MS组与NS组、Melittin组及B-MS组相比,肿瘤生长抑制显著(P<0.01),肿瘤坏死更广泛、更彻底,且经蜂毒素微球治疗的大鼠生存期显著延长(P<0.01).结论:蜂毒素以药物微球的剂型经肝动脉给药,抗肿瘤效果明显优于单纯的蜂毒素和空白微球.     

Influence of preformed α-helix and α-helix induction on the activity of cationic antimicrobial peptides

One prominent class of cationic antibacterial peptides comprises the α-helical class, which is unstructured in free solution but folds into an amphipathic α-helix upon insertion into the membranes of target cells. To investigate the importance of α-helicity and its induction on interaction with membranes, a series of peptides was constructed based on a hybrid of moth cecropin (amino acids 1-8) and bee melittin (amino acids 1-18) peptides. The new peptides were predicted to have a high tendency to form α-helices or to have preformed α-helices by virtue of construction of a lactam bridge between glutamate and lysine side-chains at positions i and i+ 4 at various locations along the primary sequence. In two examples where the use of lactam bridge constraints induced and stabilized α-helical structure in benign (aqueous buffer) and/or hydrophobic medium, there was a decrease in antibacterial activity relative to the linear counterparts. Thus the preformation of α-helix in solution was not necessarily beneficial to antimicrobial activity. In the one case where the lactam bridge did result in increased antibacterial activity (lower minimal inhibitory concentration values) it did not increase α-helical content in benign or hydrophobic medium. Broadly speaking, good activity of the peptides against Pseudomonas aeruginosa correlated best (r²= 0.88) with a helican parameter which was calculated as the induction of α-helix in α membrane-mimicking environment divided by the α-helix formation under benign conditions. Interestingly, the activity of the lactam bridge peptide constructs correlated in part with alterations in bacterial outer or cytoplasmic membrane permeability.     

Generation of the eosinophil chemotactic factor (ECF) from various cell types by melittin

The peptide melittin, the main constituent of bee venom is a potent stimulus for the generation of an eosinophil chemotactic factor (ECF) from human polymorphonuclear neutrophils, rat mast cells and rat peritoneal cells depleted in mast cells. Optimal EFC induction required a sublytic activation of the cells. With each cell type the kinetics of ECF generation were similar in that after an early rise in activity a steep fall off occurred at later times of incubation suggesting a mechanism of inactivation. The induction of ECF by melittin is increased in the presence of calcium. The polar portion of the melittin molecule (aminoacids 20–26) is responsible for the generation of the chemotactic activity. Other peptides of honey bee venom such as the mast cell degranulating peptide (MCD) or apamine do not initiate ECF release. It appears that melittin leads to ECF induction via the phospholipase A₂-arachidonic acid dependent pathway of cell activation. Our data suggests that the lipid mediator ECF can be obtained from phagocytes and mast cells thus indicating the interdependence of inflammatory reactions.     

蜂毒素体外抑瘤作用的实验研究

目的：研究蜂毒素对建系肿瘤细胞体外生长的抑制作用。方法：通过凝胶色谱法从蜜蜂毒中纯化得高纯度蜂毒素,分别选取SMMC－7721、BEL－7402和Hep-3B三种肿瘤细胞系,以四甲基偶氮唑盐（MTT）比色法观察蜂毒素对3种肿瘤细胞系的生物抑制作用,以丝裂霉素、长春新碱、华蟾素为对照;并考察了蜂毒素对SMMC－7721细胞系的生长抑制作用的时效关系。结果：蜂毒素的抑瘤作用与剂量呈正相关,抑制率优于对照组药物,蜂毒素对SMMC－7721细胞系各时间点的抑瘤率无显性差异。结论：蜂毒素的体外抑瘤作用明显,而且作用发生迅速。     

Involvement of oxidative stress in bee venom-induced inhibition of Na+/glucose cotransporter in renal proximal tubule cells

1. The present study was conducted to examine the involvement of oxidative stress in bee venom-induced inhibition of the Na+/glucose cotransporter (alpha-methyl-d-glucopyranoside (alpha-MG) uptake), a typical functional marker of proximal tubules, in primary cultured rabbit renal proximal tubule cells (PTC). 2. Bee venom (> or = 1 microg/mL) increased lipid peroxide (LPO) formation over 30 min. The increase in [(3)H]-arachidonic acid (AA) release and LPO formation and the inhibition of alpha-MG uptake induced by bee venom (1 microg/mL) and melittin (a major component of bee venom; 0.5 microg/mL) were blocked by N-acetyl-l-cysteine, vitamin C and vitamin E, anti-oxidants. 3. Bee venom- and melittin-induced increases in LPO formation and inhibition of alpha-MG uptake were significantly prevented by mepacrine and AACOCF(3), phospholipase A(2) inhibitors. In addition, nordihydroguaiareic acid (a lipoxygenase inhibitor) and econazole (a cytochrome P-450 epoxygenase inhibitor), but not indomethacin (a cyclo-oxygenase inhibitor), prevented bee venom- and melittin-induced increases in LPO formation and inhibition of alpha-MG uptake. 4. Nordihydroguaiareic acid prevented bee venom- and melittin-induced increases in Ca(2+) uptake. Moreover, anti- oxidants significantly prevented bee venom- and melittin-induced increases in Ca(2+) uptake. 5. In conclusion, bee venom inhibits alpha-MG uptake via the phospholipase A(2)-oxidative stress-Ca(2+) signalling cascade in primary cultured rabbit renal proximal tubule cells.     

甲胎蛋白启动子驱动的蜂毒基因对肝癌细胞的特异性杀伤作用

目的：构建携蜂毒素基因及甲胎蛋白(AFP)启动子的重组腺病毒栽体,探讨AFP启动子驱动的蜂毒素基因在体外对肝癌细胞的特异性杀伤作用。方法：采用细茵内高效同源重组法构建携蜂毒素基因及甲胎蛋白(AFP)启动子的重组腺病毒栽体,X-gal染色测定重组腺病毒对肝癌细胞的转染效率,MTT法测定蜂毒素基因转染对AFP阳性、阴性肝癌细胞及正常肝细胞增殖的影响。结果：重组腺病毒对肝癌细胞具有较高的转染率,MTT法证明携AFP启动子和蜂毒素基因重组腺病毒转染后,AFP阳性肝癌细胞的增殖受到明显抑制,而对AFP阴性肝癌细胞及正常肝细胞无明显影响;含巨细胞病毒启动子和蜂毒素基因的重组腺病毒转染,则对AFP阳性及阴性肝癌细胞增殖均有抑制作用。结论：AFP启动子驱动的蜂毒素基因在体外可特异性地杀伤AFP阳性肝癌细胞。     

蜂毒素对人肝癌细胞中HMGB1及VEGF-C表达的影响

目的观察蜂毒素对人肝癌细胞株HepG2中高迁移率族蛋白B1(high mobility group box1,HMGB1)及血管内皮生长因子C(vascular endothelial growth factors C,VEGF-C)表达的影响,探讨其抑制肝癌细胞的作用机制。方法肝癌细胞HepG2体外培养,经蜂毒素处理后,采用四甲基偶氮唑蓝(MTT)法了解蜂毒素对肝癌细胞增殖的影响,用Western-blotting、qRT-PCR方法检测HMGB1、VEGF-C的表达。结果蜂毒素在体外能够抑制肝癌细胞的增殖活性;Western-blotting结果显示,蜂毒素可抑制HMGB1的表达,且呈浓度依赖性,但对VEGF-C的蛋白表达无明显影响;qRT-PCR结果显示,蜂毒素在mRNA水平均具有抑制HMGB1、VEGF-C表达的作用。结论蜂毒素可降低肝癌细胞的增殖活性,并可能通过HMGB1、VEGF-C的表达发挥抗肝癌作用。     

融合蛋白AnxB1-MLT的表达、纯化及其对肝癌细胞SMMC7721和HepG2增殖的抑制作用

目的 以膜联蛋白B1(AnxB1)为导向分子,与蜂毒素(MLT)基因融合,制备AnxB1-MLT融合蛋白,探讨其对磷脂酰丝氨酸脂质体的结合活性及对肝癌细胞SMMC7721和HepG2增殖的抑制作用。方法 利用重叠延伸PCR技术构建AnxB1和MLT的融合基因AnxB1-MLT,克隆至原核表达载体pGEX-5T,转化至宿主菌K802,用异丙基-β-D-硫代半乳糖苷(IPTG)诱导AnxB1-MLT融合蛋白表达,优化表达条件,用谷胱甘肽-S-转移酶(GST)亲和色谱纯化柱纯化融合蛋白。采用磷脂结合实验验证AnxB1-MLT融合蛋白的钙依赖性磷脂结合活性,采用CCK-8方法分别检测AnxB1-MLT融合蛋白对肝癌细胞系SMMC7721和HepG2细胞增殖的影响。结果 AnxB1-MLT融合蛋白在宿主菌K802中能够表达,在菌液生长至D₆₀₀为0.6时,加入诱导剂IPTG至终浓度0.2 mmol/L,低温(22～24℃)诱导表达4 h,可使蛋白表达量较高且在上清有表达。通过GST亲和色谱纯化柱纯化融合蛋白,SDS-PAGE结果显示在63 000处可见单一目的条带,纯度>95%。AnxB1-MLT融合蛋白保留了AnxB1的钙依赖性磷脂结合活性,并能显著抑制肝癌细胞系SMMC7721和HepG2的增殖。结论 成功制备了AnxB1-MLT融合蛋白,该融合蛋白具有AnxB1的钙依赖性磷脂结合活性,可抑制肝癌细胞SMMC7721和HepG2的增殖,为进一步利用动物实验研究AnxB1-MLT的抗肿瘤效果奠定了基础。     

蜂毒素对小鼠肝癌H22细胞增殖的影响

目的 观察蜂毒素对小鼠肝癌H22细胞增殖的影响，探讨其抗肿瘤的可能作用环节。方法 以MTT法测定蜂毒素体外对小鼠肝癌H22细胞增殖的影响，运用流式细胞术分析增殖细胞核抗原(PCNA)的表达，并观察iv蜂毒素对荷瘤小鼠的抑瘤作用。结果蜂毒素对H22细胞的抑制作用随药物浓度增加而增强；蜂毒素作用于H22细胞后，细胞PCNA平均荧光强度低于对照组；iv蜂毒素对小鼠皮下H22肝癌细胞具有明显的抑制作用，抑瘤作用随浓度增加而增强。结论蜂毒素在体内外对小鼠肝癌H22细胞增殖均有明显的抑制作用，下调细胞PCNA表达可能是其作用环节之一。     

Bilirubin binding to polypeptides and chiral amines. Induced circular dichroism and fluorescence studies

Induced Cotton effects have been observed in the visible region on interaction of bilirubin with chiral mono- and diamines and poly-l -lysine. At alkaline pH distinct CD spectra are observed for bilirubin bound to the α-helical and β-sheet conformation of poly-l -lysine, which differ from that observed for the pigment bound to human serum albumin. The CD pattern observed on binding to N-acetyl-Lys-N¹-methylamide in CH₂Cl₂ and dioxane is different from that observed in the presence of l -Ala-NH-(CH₂)₆-NH-l -Ala in dioxane. The latter case resembles the spectrum observed in the presence of human serum albumin. Binding to the helical polypeptide melittin and the antiparallel β-sheet peptide, gramicidin S, in aqueous solutions results in opposite signs of the bilirubin CD bands. The quenching of tryptophan fluorescence in melittin, in aqueous solution and enhancement of bilirubin fluorescence in dioxane on binding to gramicidin S have been used to monitor pigment-peptide interactions. The results suggest the utility of bilirubin as a conformational probe.