An autophagic switch in the response of tumor cells to radiation and chemotherapy

Four different functional forms of autophagy have been observed to occur in tumor cells in response to chemotherapeutic drugs and radiation. Currently the different forms of autophagy are distinguished almost exclusively by determining the impact of autophagy inhibition on drug and radiation sensitivity. That is, it cannot otherwise be predicted whether the autophagy induced by radiation or chemotherapy is associated with resistance and the circumstances under which autophagy inhibition might be a useful strategy for enhancing sensitivity to therapy. This commentary highlights an additional level of complexity in the autophagy landscape, specifically that autophagy can switch its function even within the context of a specific external stress and/or a biological cancer model.     

The protective effect of autophagy on mouse spermatocyte derived cells exposure to 1800 MHz radiofrequency electromagnetic radiation

The increasing exposure to radiofrequency (RF) radiation emitted from mobile phone use has raised public concern regarding the biological effects of RF exposure on the male reproductive system. Autophagy contributes to maintaining intracellular homeostasis under environmental stress. To clarify whether RF exposure could induce autophagy in the spermatocyte, mouse spermatocyte-derived cells (GC-2) were exposed to 1800 MHz Global System for Mobile Communication (GSM) signals in GSM-Talk mode at specific absorption rate (SAR) values of 1 w/kg, 2 w/kg or 4 w/kg for 24 h, respectively. The results indicated that the expression of LC3-II increased in a dose- and time-dependent manner with RF exposure, and showed a significant change at the SAR value of 4 w/kg. The autophagosome formation and the occurrence of autophagy were further confirmed by GFP-LC3 transient transfection assay and transmission electron microscopy (TEM) analysis. Furthermore, the conversion of LC3-I to LC3-II was enhanced by co-treatment with Chloroquine (CQ), indicating autophagic flux could be enhanced by RF exposure. Intracellular ROS levels significantly increased in a dose- and time-dependent manner after cells were exposed to RF. Pretreatment with anti-oxidative NAC obviously decreased the conversion of LC3-I to LC3-II and attenuated the degradation of p62 induced by RF exposure. Meanwhile, phosphorylated extracellular-signal-regulated kinase (ERK) significantly increased after RF exposure at the SAR value of 2 w/kg and 4 w/kg. Moreover, we observed that RF exposure did not increase the percentage of apoptotic cells, but inhibition of autophagy could increase the percentage of apoptotic cells. These findings suggested that autophagy flux could be enhanced by 1800 MHz GSM exposure (4 w/kg), which is mediated by ROS generation. Autophagy may play an important role in preventing cells from apoptotic cell death under RF exposure stress.     

A newly synthesized platinum-based compound (PBC-II) increases chemosensitivity of HeLa ovarian cancer cells via inhibition of autophagy

There are many mechanisms of resistance, chemoresistance of HeLa cells to anti-cancer agents seems to be autophagy-mediated. While using very effective anti-cancers such as Doxorubicin and cisplatin, cells overcome the cytotoxicity of these drugs through promotion of what so-called cytoprotective autophagy. Here in this study, we sought to introduce a novel platinum-based compound PBC-II that possesses anti-cancer activity. Our data showed that PBC-II is able to induce apoptosis at relatively low concentrations, with no detectable reactive oxygen species (ROS). However, further experiments demonstrated that exposure of HeLa cells to PBC-II did not promote autophagy; rather, it resulted in accumulation of p62 and decrease in LC3-II levels. Autophagy was then promoted in HeLa cells pharmacologically by Doxorubicin and genetically by siRNA IL-10. In order to confirm promotion of autophagy in our model, we performed acridine orange staining to assess for autophagy under microscope as well as via flow cytometry. We then measured protein level of autophagy markers p62 and LC3 by western blot. Our data indicated that PBC-II interferes with therapy-induced autophagy. We also determined PI3K activity while co-incubation of PBC-II with autophagy inducers. It was clear that PI3K activation decreased when PBC-II was co-administered with autophagy inducers. Collectively, PBC-II exerts unique anti-proliferative effects associated with inhibition of autophagy, which indicates that PBC-II is potentially a promising agent to be used in resistant ovarian tumors.     

自噬与糖尿病骨骼肌病变

骨骼肌占人类体成分的40％～ 50％,是摄取和利用葡萄糖的重要组织,70％的葡萄糖通过胰岛素依赖的方式被骨骼肌摄取;同时骨骼肌也是2型糖尿病患者发生胰岛素抵抗的重要靶组织.现有研究发现,2型糖尿病患者骨骼肌内细胞器发生重构、外膜细胞退化及凋亡、肌膜下线粒体减少、肌细胞内脂质沉积、慢肌纤维与快肌纤维比值降低等,在临床上表现为胰岛素抵抗、骨骼肌萎缩等糖尿病骨骼肌肌病特征.糖尿病骨骼肌病变的发病机制至今不甚明确,自噬可能是主要原因之一.     

Targeting autophagy in osteoporosis: From pathophysiology to potential therapy

Osteoporosis is a highly prevalent disorder characterized by the loss of bone mass and microarchitecture deterioration of bone tissue, attributed to various factors, including menopause (primary), aging (primary) and adverse effects of relevant medications (secondary). In recent decades, knowledge regarding the etiological mechanisms underpinning osteoporosis emphasizes that bone cellular homeostasis, including the maintenance of cell functions, differentiation, and the response to stress, is tightly regulated by autophagy, which is a cell survival mechanism for eliminating and recycling damaged proteins and organelles. With the important roles in the maintenance of cellular homeostasis and organ function, autophagy has emerged as a potential target for the prevention and treatment of osteoporosis. In this review, we update and discuss the pathophysiology of autophagy in normal bone cell life cycle and metabolism. Then, the alternations of autophagy in primary and secondary osteoporosis, and the accompanied pathological process are discussed. Finally, we discuss current strategies, limitations, and challenges involved in targeting relevant pathways and propose strategies by which such hurdles may be circumvented in the future for their translation into clinical validations and applications for the prevention and treatment of osteoporosis.     

Clarithromycin effectively enhances doxorubicin-induced cytotoxicity and apoptosis in MCF7 cells through dysregulation of autophagy

PurposeUse of autophagy inhibitors in combination with chemotherapy has become a novel chemotherapeutic strategy. In this study, we aimed to determine whether the effectiveness of doxorubicin (DOX) is augmented by clarithromycin (CAM) in MCF7 cells and the molecular mechanisms involved.Materials and methodsCombined cytotoxicity of CAM and DOX was assessed by MTT assay and was analyzed using the Chou-Talalay's method. To clarify the underlying mechanisms, several factors, including apoptosis (Annexin V/propidium iodide staining), intracellular level of DOX (spectrofluorimetry) and P-glycoprotein activity (Rhodamin 123 efflux assay) were measured. In addition, autophagy was evaluated by intracellular labeling with anti-LC3II and LysoTrackerGreen (LTG) staining and analyzed by flowcytometry.ResultsThe anti-proliferation effect of DOX was synergistically enhanced by CAM in MCF7 cells and was associated with an increase in the apoptotic cell death. However, the intracellular level of DOX remained unchanged in the presence of CAM. Based on the findings, 100 μM of CAM did not exhibit any inhibitory effects on P-glycoprotein activity. Flow cytometric analysis indicated that DOX at IC₂₀ concentration induced the autophagy flux, as confirmed by the increased level of LC3II and LTG signals. Moreover, combined treatment with DOX and CAM resulted in more pronounced LTG signals, but no change in LC3II. These results indicate that CAM blocks the autophagy flux induced by DOX.ConclusionsThese findings suggest that suppression of autophagy by CAM may promote chemotherapeutic outcome in breast cancer. However, further investigations are needed to evaluate the application of CAM in adjuvant breast cancer therapy.     

山药多糖延缓秀丽隐杆线虫衰老的药效评价及作用机制研究

目的：基于秀丽隐杆线虫模型考察山药多糖的抗衰老药效并探究其作用机制。方法：基于秀丽隐杆线虫模型,利用寿命、咽泵频率、身体活动频率、脂褐素荧光、抗压性实验、活性氧荧光、抗氧化酶活性等指标考察山药多糖的抗衰老药理活性;通过转录组数据分析,探究山药多糖的抗衰老药效机制。结果：山药多糖可以显著延长线虫的寿命,缓解衰老过程中咽泵频率以及身体活动频率的下降,降低衰老过程中脂褐素及活性氧积累并提高线虫的抗压能力和抗氧化活性。转录组学京都基因和基因组百科全书(KEGG)通路分析发现,内分泌系统、细胞的生长和凋亡通路发生了显著的变化。山药多糖调控了30个与衰老相关的基因表达,且差异基因主要显著富集在自噬、哺乳动物雷帕霉素靶蛋白(mTOR)及胰岛素信号通路。结论：山药多糖具有抗衰老药理活性,转录组学数据揭示这种抗衰老作用可能与自噬、mTOR及胰岛素信号通路有关。     

快速动眼睡眠剥夺对大鼠学习、记忆能力及海马组织自噬的影响

目的 探讨快速动眼(rapid eye movement,REM)睡眠剥夺后与大鼠认知相关的行为学变化及脑内海马组织中自噬相关蛋白的表达水平。方法 健康成年雄性大鼠经过筛选后分为空白对照组(CC组)、环境对照组(TC组)、睡眠剥夺组(SD组),每组各6只; 采用改良多平台睡眠剥夺法(modified multiple platform method,MMPM)建立睡眠剥夺模型,连续剥夺5 d后利用Morris水迷宫检测大鼠认知功能; 用蛋白质印记法(Western Blot,WB)检测自噬相关微管蛋白(LC3)及SQSTM1/P62的表达水平变化。结果 与CC组和TC组比较,SD组大鼠毛色无光泽、易激惹、体重下降(P<0.05)。SD组与其他2组比较,逃逸潜伏期延长、目标象限时间减少(P<0.05)。WB显示SD组与其他2组比较,大鼠脑内海马组织自噬相关蛋白LC3-II表达水平上升,P62水平下降(P<0.05)。CC组与TC组大鼠比较,体重、学习记忆能力、海马组织自噬蛋白表达水平均无明显差异(P>0.05)。结论 睡眠剥夺后可损害大鼠学习及记忆功能,海马组织中自噬水平上调提示自噬活动可能参与睡眠剥夺介导的认知功能障碍过程。