Autophagy in 5-Fluorouracil Therapy in Gastrointestinal Cancer: Trends and Challenges

Objective:

5-Fluorouracil (5-FU)-based combination therapies are standard treatments for gastrointestinal cancer, where the modulation of autophagy is becoming increasingly important in offering effective treatment for patients in clinical practice. This review focuses on the role of autophagy in 5-FU-induced tumor suppression and cancer therapy in the digestive system.

Data Sources:

All articles published in English from 1996 to date those assess the synergistic effect of autophagy and 5-FU in gastrointestinal cancer therapy were identified through a systematic online search by use of PubMed. The search terms were “autophagy” and “5-FU” and (“colorectal cancer” or “hepatocellular carcinoma” or “pancreatic adenocarcinoma” or “esophageal cancer” or “gallbladder carcinoma” or “gastric cancer”).

Study Selection:

Critical reviews on relevant aspects and original articles reporting in vitro and/or in vivo results regarding the efficiency of autophagy and 5-FU in gastrointestinal cancer therapy were reviewed, analyzed, and summarized. The exclusion criteria for the articles were as follows: (1) new materials (e.g., nanomaterial)-induced autophagy; (2) clinical and experimental studies on diagnostic and/or prognostic biomarkers in digestive system cancers; and (3) immunogenic cell death for anticancer chemotherapy.

Results:

Most cell and animal experiments showed inhibition of autophagy by either pharmacological approaches or via genetic silencing of autophagy regulatory gene, resulting in a promotion of 5-FU-induced cancer cells death. Meanwhile, autophagy also plays a pro-death role and may mediate cell death in certain cancer cells where apoptosis is defective or difficult to induce. The dual role of autophagy complicates the use of autophagy inhibitor or inducer in cancer chemotherapy and generates inconsistency to an extent in clinic trials.

Conclusion:

Autophagy might be a therapeutic target that sensitizes the 5-FU treatment in gastrointestinal cancer.     

AMPK-mTOK信号通路参与百草枯致PC12细胞的自噬抑制作用

目的探讨AMPK-mTOR信号转导通路在百草枯(paraquat,PQ)诱导大鼠肾上腺髓质嗜铬细胞瘤细胞(PC12)自噬异常中的调控作用。方法用终浓度0、25、50、100、200、300、400 μmol/L PQ处理PC12细胞24 h,300 μmol/L PQ处理细胞不同时间(6、12、24、48 h),四甲基偶氮唑蓝(MTT)检测细胞相对存活率,确定剂量/时间-效应关系;终浓度0、100、200、300 μmol/L PQ处理细胞24 h,分光光度法检测培养上清中乳酸脱氢酶(LDH)活力;二氯荧光素双醋酸盐(DCFH-DA)法检测细胞内活性氧(ROS)水平;单丹磺酰尸胺(MDC)染色法观察自噬溶酶体的表达及分布变化;免疫荧光(IF)检测微管相关蛋白1轻链3(LC3)表达水平;免疫印迹法(Western blot)检测自噬相关蛋白LC3Ⅱ、p62、Beclin1及AMPK-mTOR信号通路蛋白p-AMPK、p-mTOR表达水平。结果与对照组比较,100、200、300、400 μmol/L PQ染毒组的细胞存活率明显降低,且呈剂量依赖关系,差异有统计学意义(P<0.05)。300 μmol/L PQ处理细胞不同时间(6、12、24、48 h),细胞存活率随染毒时间的延长而下降,其中12、24、48 h染毒组的差异有统计学意义(P<0.05)。与对照组比较,100、200、300 μmol/L PQ染毒组细胞上清液中LDH活力明显升高,细胞内ROS荧光强度明显增高,差异有统计学意义(P<0.05);MDC染色结果显示,PQ染毒组的自噬溶酶体在核周分布密度降低、荧光强度减弱、自噬水平降低;免疫荧光结果显示,PQ染毒组的LC3荧光强度减弱,细胞自噬水平下降,与MDC染色结果一致。Western blot结果显示,与对照组比较,PQ染毒组的自噬相关蛋白LC3Ⅱ、Beclin1表达水平均明显降低,而p62蛋白表达水平升高,差异有统计学意义(P<0.05)。200、300 μmol/L PQ染毒组的p-AMPK蛋白表达水平降低,p-mTOR蛋白表达水平升高,差异有统计学意义(P<0.05)。结论PQ致PC12细胞损伤过程中,细胞自噬水平降低,AMPK-mTOR信号通路发挥调节作用。     

番茄红素通过上调Beclin1-Atg 5通路激活自噬发挥对脊髓损伤大鼠的神经保护作用

目的 探讨番茄红素对大鼠脊髓损伤后的神经保护机制。方法 27只（6~8周龄）雌性SD大鼠随机分为假手术组、模型组和实验组各9只。大鼠麻醉清醒后,实验组20 mg/kg番茄红素玉米油溶液灌胃,假手术组和模型组等体积玉米油灌胃,每天1次,共14 d。分别于术后1、3、7、14 d,采用斜板试验评估各组大鼠后肢运动功能变化;术后7 d,采用qRT-PCR和Western blot检测大鼠脊髓组织自噬相关因子Beclin1、Atg 5的表达水平。结果 斜板试验结果显示,术后1、3、7、14 d模型组和实验组大鼠后肢运动功能低于假手术组（P<0.05）;术后7、14 d,实验组较模型组大鼠后肢运动功能提高,差异有统计学意义（P<0.05）;实时荧光定量PCR（quantitative real-time,qRT-PCR）和蛋白质印迹法（western blot）结果显示,术后7 d模型组和实验组Beclin1、Atg 5的mRNA和蛋白质表达均较假手术组升高,实验组与模型组比较显著升高,差异具有统计学意义（P<0.05）。结论 番茄红素可能通过上调Beclin1-Atg 5通路激活自噬发挥对脊髓损伤大鼠的神经保护作用。     

自噬在骨骼肌质量维持中的作用

作为人体重要的运动和能量代谢器官,骨骼肌质量的正常维持对于机体发挥正常的生理功能至关重要。自噬-溶酶体(autophagy-lysosome,AL)途径是一种在正常和病态细胞中普遍存在的生理或病理机制,对于维持细胞内蛋白质平衡,清除细胞内受损的细胞器,及维持内环境稳定起到关键作用。自噬过程的顺利进行需要经历多个步骤,在多重因子的协调作用下完成。自噬通过清除受损的肌原纤维和隔离的胞浆蛋白等细胞成分来维持健康机体的肌肉内稳态。自噬还可以提供细胞增殖所需的初始能量,促进损伤后肌肉的再生和重塑。同时,自噬失调也是导致年龄相关性骨骼肌萎缩的一个重要诱因。自噬可以影响骨骼肌对运动的反应,增加基础自噬水平有利于提高骨骼肌对运动的适应性。本文将自噬在骨骼肌质量维持中的作用与通路进行总结,以便为临床预防和治疗肌萎缩提供有效的康复策略。     

mTOR通路对癫痫的影响及中医药干预作用研究进展

癫痫是常见的神经系统疾病,其发病机制复杂,病理改变亦多样化,以海马神经元细胞凋亡、胶质细胞增生、苔藓纤维出芽等为主要病理表现。近年来,国内外对于抗癫痫治疗专注于分子水平及其信号通路的研究,其中哺乳动物雷帕霉素靶蛋白(mTOR)这一信号通路通过细胞生长增殖、蛋白质代谢、细胞凋亡自噬、突触可塑性等对抗癫痫发挥重要的作用。中医药在治疗癫痫上疗效明显,大量实验证明中医药干预,包括中药单体、中药复方等治疗,能够通过mTOR信号通路发挥抗癫痫作用,从而减少癫痫发作频率、保护神经元细胞、改善癫痫症状等。mTOR信号通路也成为中医药治疗癫痫的重要靶点。现综述mTOR通路对癫痫的影响及中医药干预作用的研究进展。     

自噬在急性胰腺炎中的研究新进展

自噬是细胞清除胞质中受损、缺陷或无用的细胞器、长寿命蛋白质和脂质,并回收其成分以满足生物新陈代谢的营养和能量需要的主要分解代谢过程。急性胰腺炎(AP)是常见临床急症,其发病率也逐年升高。研究显示,自噬在AP的发病过程中起到重要作用,可以导致胰腺腺泡细胞内胰蛋白酶原的激活,腺泡细胞内大液泡积聚,诱发促炎介质的释放,引起胰腺炎症细胞浸润和全身性炎症反应。笔者就自噬的分子机制以及自噬在AP发生、发展中作用机制的研究进展进行综述。     

Bromelain activates the AMP-activated protein kinase-autophagy pathway to alleviate hepatic lipid accumulation

Bromelain, a cysteine protease found in pineapple, is known to exert protective effects against non-alcoholic fatty liver disease (NAFLD); however, the underlying mechanism is unclear. In this study, we aimed to investigate the molecular mechanisms underlying the beneficial effects of bromelain using in vivo and in vitro models. C57BL/6 mice were fed a high-fat diet (HFD) with or without bromelain (20 mg/kg/day) for 12 weeks. We found that treatment with bromelain alleviated hepatic lipid accumulation accompanied by the activation of AMP-activated protein kinase (AMPK) and autophagy flux, as evidenced by the elevated levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and lysosome-associated membrane protein 2 (LAMP2), and the decreased levels of p62 in the liver of HFD-fed mice. In human hepatoma Huh 7 cells, bromelain prevented oleic acid (OA)-induced lipid accumulation and increased the levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and LAMP2 but decreased the levels of p62. Inhibition of AMPK and autophagy flux by specific inhibitors or small interfering RNAs suppressed bromelain-mediated protective effect on lipid accumulation. Moreover, inhibition of AMPK activity abolished the activation of autophagy flux in OA-treated hepatocytes. Collectively, these findings suggest a new molecular mechanism involving the AMPK-autophagy pathway through which bromelain confers protection against the deregulation of lipid metabolism in the liver.