【作者】 许玉杰；

【导师】 范我；

【作者基本信息】 苏州大学 ， 放射医学， 2008， 博士

【摘要】 研究背景:紫杉醇是从短叶红豆杉(Taxus brevifolia)的树皮中分离出的新型抗肿瘤药物,其抗肿瘤机制是通过作用于微管抑制增殖细胞的有丝分裂,导致细胞周期阻断于G2/M期,快速分裂的癌细胞因出现生长抑制进而死亡。但因紫杉醇极难溶于水,其溶媒聚氧乙基代蓖麻油长导致严重的过敏反应及超敏反应。所以国内外学者均在致力于紫杉醇的新制剂形式的研究研究。为此,本课题组研究设计将紫杉醇用生物可降解脂质材料包裹,制备成了新型紫杉醇脂质纳米粒子(TAX-NLC),具有具有较高的水溶性和载药量,不含聚氧乙基代蓖麻油与无水乙醇等混合溶媒。初步的研究证实其具有较好的靶向肿瘤特征,可以迅速载带药物进入细胞内,并在胞内浓聚,对肿瘤细胞生长的抑制作用要比游离紫杉醇强,表现出良好的发展前景。因此有必要进一步研究其在体内的分布和代谢特征,评价其抗肿瘤效果,为进入临床研究作准备。研究目的:建立放射性核素125I标记游离紫杉醇的新方法,将标记物作为示踪剂研究新型紫杉醇脂质纳米粒子(TAX-NLC)在荷瘤鼠和猕猴体内的药代动力学,获得其在体内的分布和代谢特征,并与游离紫杉醇进行对比。在此基础上评价其抗肿瘤疗效。研究方法:①改良Ch-T标记紫杉醇的方法,先用稳定碘标记后,再用放射性碘去替代,以获得稳定的高放射性比活度的标记物。②制备包含有高放射性比活度标记物的125I标记的新型紫杉醇纳米粒(125I-TAX-NLC),用于动物体内药代动力学研究。③给正常昆明小鼠单次尾静脉注射65mg/m2的125I-TAX后的不同时间点采集静脉血,并解剖动物获得主要的脏器,经过放射性核素示踪结合TCA沉淀法获得各样品的药物浓度,根据荷瘤鼠血液药物浓度与时间的关系通过DAS2.1分析普通游离TAX的药代动力学参数,根据各器官每克组织所含药物量来评价普通游离TAX在体内的分布特征。④给荷瘤鼠单次尾静脉注射75mg/m2的125I-TAX-NLC后的不同时间点采集静脉血,并解剖动物获得主要的脏器,经过放射性核素示踪结合TCA沉淀法获得各样品的药物浓度,根据荷瘤鼠血液药物浓度与时间的关系通过DAS2.1分析TAX-NLC的药代动力学参数,根据各器官每克组织所含药物量来评价TAX-NLC在体内的分布特征,同时用放射自显影术直接观察肿瘤部位的药物蓄积。⑤从左前臂尾静脉单次给猕猴注射75mg/m2的125I-TAX-NLC,在不同时间点从右前臂静脉采集血液,同样经过经过放射性核素示踪结合TCA沉淀法获得各样品的药物浓度,根据荷瘤鼠血液药物浓度与时间的关系,通过DAS2.1分析TAX-NLC的药代动力学参数。使用SPECT显像对125I-TAX-NLC在猕猴的体内分布特征进行动态观察,并通过对各组织器官ROI的半定量分析,计算各主要脏器的药物分布。⑥通过观察荷瘤鼠用TAX-NLC治疗后不同时间点肿瘤的体积变化和肿瘤重量的变化,评价TAX-NLC的抗肿瘤疗效,并使用HE染色和Tunnel方法观察肿瘤组织的死亡与凋亡率,同时体外实验观察新型紫杉醇纳米粒(TAX-NLC)对肿瘤细胞的靶向性。研究结果:本课题在充分调研的基础上,系统开展了新型紫杉醇纳米粒(TAX-NLC)在动物体内的药代动力学研究,初步开展了对荷瘤鼠的治疗研究,得到了以下结果:①通过方法学研究,改良Ch-T法标记紫杉醇,标记率可达达60%以上,经过简单的PB液的清洗、离心沉淀纯化后,标记物的放化纯度达95%以上,纯化后的标记产物在血清、乙醇中有较好的稳定性。说明改良Ch-T法是一个合适的标记方法,标记产物能满足动物体内示踪实验。②采用放射性核素标记示踪结合TCA沉淀实验进行紫杉醇的代谢动力学分析,是一可靠、简便而灵敏的方法,可以将血液中新型紫杉醇纳米粒(TAX-NLC)中的紫杉醇与释放出来的游离状态的紫杉醇一并测出,它反映的是血浆中紫杉醇的真实水平,所以更加符合实际状况,因此得出的结果更加可靠。游离紫杉醇在体内的分布相半衰期0.183h,消除相半衰期为3.295小时,分布体积V1为0.887 L/m2,清除速率CL为0.356 L/h/m2,AUC(0-t)为172.365 mg/L*h。分布的主要器官是肺、肝、肾、脾等,其中肺部的分布呈现过度高的现象。药物不能通过血脑屏障。③与游离紫杉醇比较,新型紫杉醇脂质纳米粒子(TAX-NLC)改变了药物在体内的分布和代谢特征,其在荷瘤鼠体内的代谢符合三室模型,分布相半衰期延长到0.399小时,而消除相的半衰期相似,均为3-4小时;但后者出现了一个缓慢消除相,并且半衰期长达60天,从1室到3室的转移速率常数K13为0.1451/h,比从3室到1室的转移速率常数K31(0.0231/h)要高得多。说明新型紫杉醇脂质纳米粒子(TAX-NLC)确实具备缓慢释放紫杉醇的能力。两者的V1相同,但清除速率CL有较大的变化,从0.356 L/h/m2减少到0.137 L/h/m2,所以AUC(0-∞) 182.64上升到546.135 mg/L*h。主要的分布器官是肝、脾、肺,特别是药物能够通过TAX-NLC的载带,在肿瘤的部位有高度的蓄积分布,最高可达对侧组织的9倍以上,并具备一定的缓释能力,这对于未来用于肿瘤的治疗,具有重大的意义。④新型紫杉醇脂质纳米粒(TAX-NLC)在猕猴体内的代谢动力学符合三室代谢模型,分布相半衰期分别是0.105和0.158,比其在荷瘤鼠体内的分布相半衰期要短一倍左右;猕猴体内的分布体积V1分别为1.422和2.678 L/m2,清除速率CL分别为0.1和0.194 L/h/m2,AUC(0-t)分别是614.105、310.473 mg/L*h,两者相差近1倍,有较大的个体差异,比在荷瘤鼠体内的清除速率快、分布容积增加。与荷瘤鼠体内的分布特征一样,肝、脾、肾是主要的分布器官,但与之不同的是肺部的分布较少;未能发现TAX-NLC能通过血脑屏障。胆汁与尿液是主要的排泄途径,两者比例相当。⑤TAX-NLC具有较高的载带药物进入细胞能力,随着时间的延长,细胞内TAX浓度明显增加,大概在2小时达到饱和,细胞内外的TAX浓度比值在25倍以上。与游离紫杉醇相比较,新型紫杉醇脂质纳米粒子(TAX-NLC)具有较好的生物适应性,减少了普通紫杉醇制剂对动物的刺激作用。两者的抗肿瘤治疗效果相当,均可以显著抑制肿瘤的生长,但TAX-NLC具有一定的体内控释作用,在停药后,TAX-NLC在体内可以缓慢释放TAX,继续发挥着抗肿瘤的作用,结果与TAX-NLC在荷瘤鼠体内存在三室代谢模型相互吻合。研究结论:TAX-NLC是一个有临床应用前景的抗肿瘤新药系统。TAX-NLC在体内具有更长的生物半衰期,能够向肿瘤部位靶向富集,但其与一般游离紫杉醇具有相类似的抗肿瘤作用。主要的排泄途径是胆汁和尿液。TAX-NLC有望在更深入的研究基础上,发展成抗肿瘤新药系统。更多还原

【Abstract】 BACKGROUND Paclitaxel is the diterpene product obtained from the needles and bark of the Pacific Yew (Taxus brevifolia ) to be used as a potent anti-tumor drug. It can block cells in the late G2-mitotic phase of the cell cycle by stabilizing the microtubule cytoskeleton. Because Paclitaxel is lipophilic and possesses very low water solubility (less than 2μg/mL), the drug is dissolved in a 50:50 mixture of Cremophor EL and ethanol. However, Cremophor may induce the hypersensitivity and many other serious side effects, it is necessary to develop the Cremophor EL-free formulations to overcome these problems. In the present study we have developed a new carrier system of nanostructure lipid particle to delivery paclitaxel (TAX-NLC) for improving the solubility of paclitaxel, increasing the enveloping efficiency and enhancing drug loading capacity.OBJECTIVE to get the higher qualified 125I labeled TAX tracer for the radionuclide trace experiment, to investigate the pharmacokinetics and the tissue distributions of the TAX-NLC in nude mice bearing human KB tumor cells and in macaques, to evaluate the anti-tumor efficacy of TAX-NLC initially.METHODS The modified Ch-T labeling method will be used for getting high qualified 125I-TAX tracer. The IR was used to identify the product. HPLC and paper chromatography were used to determine its radiochemical purities. The stabilities of 125I-TAX in vitro were monitored by trichloroacetic acid (TCA) precipitation. The 125I -TAX-NLC was prepared by high pressure homogenization-hot homogenization by entrapped 125I- TAX. The TAX-NLC labeled with 125I - paclitaxel at the dose 75 mg/m2 were injected to nude mice bearing human tumor (KB cell line) xenografts and macaques via tail vein and left forelimb vein, respectively. After the injection, serial blood samples and organs of mice were collected at various time intervals, and the 125I activities in the organs, including blood and tumor, were counted. The serial blood samples of macaques were collected from right forelimb vein at various time intervals too, but the distribution of TAX-NLC in macaques was imaged by SPECT (IRIX, Marconi). The pharmacokinetics parameters were calculated by DAS 2.1 software. Furthermore, the comparable anti-tumor efficacy of TAX-NLC was observed by calculating the weights and volumes of xenografts initially.RESULTS The labeled products has been identified by IR spectra, and the radio chemical purity was more than 95%, the tracer was stable in the serum and ethanol. at room temperature and 4℃. The blood pharmacokinetics of TAX-NLC exhibited a characteristic distribution and elimination response for macromolecules in mice and macaques, which could be described by a bi-exponential process. The plasma concentration of the TAX-NLC in nude mice and macaques was declined as a three-compartment model. The parameters in nude mice were below: half-lives 0.399 h(t1/2α), 3.711 h( t1/2β), 60.117 h( t1/2γ), AUC(0-∞) 546.135 mg/L*h. Because of the big difference between the macaques, the parameters in macaques were below respectively: t1/2αwere 0.105h and 0.158h,the t1/2βwere 6.845 and 3.128h, and the t1/2γwere 72.66 and 29.27. AUC(0-t) were 614.105 and 310.473 mg/L*h. CL were 0.1 and 0.194 L/h/m2. The main tissues distribution of TAX-NLC were live, spleen, lung in nude mice, and the concentration of TAX-NLC in tumor (KB cell line) xenografts reached to 9.6 ug per gram tumor, it was three times more than opposite muscles. However, the main tissues distributions of TAX-NLC in macaques scanned by SPECT were gallbladder, live, urinary bladder, spleen, and heart. The excretion of TAX in the macaques was by bile and urine.The anti-tumor efficacy of TAX-NLC was similar as free TAX, but the TAX-NLC was better about the bioavailability.CONCLUSIONS These studies indicate that The TAX-NLC was a perspective carrier system. The TAX-NLC had a prolonged circulating time, and the main elimination organs were gallbladder and kidneys. The Paclitaxel could be concentrated on the tumor xenografts by the TAX-NLC carrier system. This formulation could serve as a promising approach for cancer therapy.更多还原