BNIP3 protects HepG2 cells against etoposide-induced cell death under hypoxia by an autophagy-independent pathway

Tumor hypoxia is a common characteristic of most solid tumors and is correlated with poor prognosis for patients partly because hypoxia promotes resistance to cancer therapy. Hypoxia selects cancer cells that are resistant to apoptosis and allows the onset of mechanisms that promote cancer cells survival including autophagy. Previously, we showed that human hepatoma HepG2 cells were protected under hypoxia against the etoposide-induced apoptosis. In this study, respective putative contribution of autophagy and BNIP3 in the protection conferred by hypoxia against the etoposide-induced apoptosis was investigated. We report that autophagy is induced by etoposide, a process that is not affected by hypoxic conditions. Using Atg5 siRNA, we show that etoposide-induced autophagy promotes apoptotic cell death under normoxia but not under hypoxia. Then, we investigated whether the hypoxia-induced protein BNIP3 could explain the different effect of autophagy on cell death under hypoxia or normoxia. We show that the silencing of BNIP3 does not affect autophagy whatever the pO₂ but participates in the protective effect of hypoxia against etoposide-induced apoptosis. Together, these results suggest that autophagy might be involved in etoposide-induced cell death only under normoxia and that BNIP3 is a major effector of the protective mechanism conferred by hypoxia to protect cancer cells against etoposide-induced apoptotic cell death.     

miR-146a-5p regulates autophagy and NLRP3 inflammasome activation in epithelial barrier damage in the in vitro cell model of ulcerative colitis through the RNF8/Notch1/mTORC1 pathway

Ulcerative colitis (UC) is a chronic inflammatory disease affecting the colon that can be influenced by microRNAs (miRNAs). This study aims to investigate the impact of miR-146a-5p on lipopolysaccharide (LPS)-induced Caco-2/HT-29 cell autophagy and NLRP3 inflammasome activation and the underlying mechanism, with the aim of identifying potential therapeutic targets. We used LPS to establish Caco-2/HT-29 cell models and measured cell viability by CCK-8. The levels of miR-146a-5p, RNF8, markers of NLRP3 inflammasome activation and autophagy, proteins involved in the Notch1/mTORC1 pathway, and inflammatory factors were assessed by RT-qPCR, Western blot, and ELISA. Intestinal epithelial barrier function was evaluated by measuring transepithelial electrical resistance. Autophagic flux was measured using tandem fluorescent-labeled LC3. miR-146a-5p was highly-expressed in LPS-induced Caco-2/HT-29 cells, and autophagy flux was blocked at the autolysosomal stage after LPS induction. Inhibition of miR-146a-5p suppressed NLRP3 inflammasome activation, reduced intestinal epithelial barrier damage, and facilitated autophagy inhibition in LPS-induced Caco-2/HT-29 cells. The autophagy inhibitor NH4Cl partially nullified the inhibitory effects of miR-146a-5p inhibition on NLRP3 inflammation activation. miR-146a-5p targeted RNF8, and silencing RNF8 partly abrogated the action of miR-146a-5p inhibition on promoting autophagy and inhibiting NLRP3 inflammasome activation. miR-146a-5p inhibition suppressed the Notch1/mTORC1 pathway activation by upregulating RNF8. Inhibition of the Notch1/mTORC1 pathway partially nullified the function of silencing RNF8 on inhibiting autophagy and bolstering NLRP3 inflammasome activation. In conclusion, miR-146a-5p inhibition may be a potential therapeutic approach for UC, as it facilitates autophagy of LPS-stimulated Caco-2/HT-29 cells, inhibits NLRP3 inflammasome activation, and reduces intestinal epithelial barrier damage by upregulating RNF8 and suppressing the Notch1/mTORC1 pathway.     

T-cell selection in the thymus: New routes toward the identification of the self-peptide ligandome presented by thymic epithelial cells

Within the thymus, thymic epithelial cells (TECs) provide a dedicated niche for the selection of functional T cells expressing a highly variable and self-tolerant T-cell receptor (TCR) repertoire. In this minireview, we start by summarizing recent studies that have improved our understanding on the composition of cortical TEC and medullary TEC microenvironments. Next, we focus on the molecular processes that control the function of TECs in T-cell selection. In particular, we discuss the role of cortical TECs in positive selection and the pathways employed by these cells to generate and present selecting self-peptides:MHC II complexes. Several studies have underscored the role of the β5t-containing thymoproteasome in the production of unique MHC I-bound peptides critical for CD8 T-cell selection. Contrarily, the identity of the molecular determinants that regulate the generation of MHC II-bound self-peptides capable of positive selecting CD4 T cells is far more uncertain. We highlight recent advances that interconnect the autophagy-lysosomal pathway, the presentation of specific sets of self-peptide:MHC II complexes, and the diversification of CD4 TCR repertoire. Lastly, we discuss how these findings may open up new avenues for deciphering the identity of the MHC I and MHC II ligandome in the thymus.     

Autophagy in the placenta of women with hypertensive disorders in pregnancy

IntroductionAutophagy has not been studied extensively in the human placenta. This study was performed to determine whether autophagy is increased in the placentas of women with hypertensive disorders in pregnancy compared to normotensive pregnancies.MethodsLC3-II and p62 protein expression were examined by quantitative Western blotting analysis in 40 placentas from women not experiencing labor pains. The 40 placentas were from 13, 8, and 19 women with preeclampsia, gestational hypertension, and normal pregnancy, respectively. Hypertensive disorders in pregnancy included preeclampsia and gestational hypertension.ResultsLC3-II expression was significantly increased, while that of p62 was significantly reduced in 21 placentas of women with hypertensive disorders compared to those with normal blood pressure irrespective of the presence or absence of fetal growth restriction (FGR). LC3-II expression was also significantly increased in 13 placentas of women with preeclampsia irrespective of the presence or absence of FGR.DiscussionThe results of this study suggested that autophagy is active in the placenta of hypertensive disorders even in the absence of FGR.     

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.     

自噬标志物LC3B表达水平的改变与星形细胞瘤手术患者预后的相关性研究

目的 评估两种自噬标志物LC3B和Beclin-1的蛋白表达水平与星形细胞瘤患者的临床参数之间的关系。方法 回顾性收集2009年12月-2012年12月星形细胞瘤患者的106个薄切片,通过切片染色分析LC3B和Beclin-1与患者生存时间的关系。结果 发现LC3B与蛋白质表达水平与抗辐射或化学疗法显著相关(P=0.02); 高强度的LC3B染色预示着不良的预后(P=0.03); Beclin-1蛋白表达水平与患者的总体生存率不相关; CD133和LC3B高表达的患者的总生存期为38个月,CD133和LC3B两者均为弱表达的患者的总生存期为50个月,CD133和LC3B高表达的患者的生存时间明显短于CD133和LC3B低表达者(P=0.049)。结论 星形细胞瘤癌症干细胞样细胞和增强的自噬可引起对放射疗法/化学疗法的抗性,并且针对星形细胞瘤中的癌症干细胞样细胞可提供可行的治疗方法。     

PAR1对蛛网膜下腔出血大鼠神经细胞自噬、神经肽及BDNF水平的影响

目的 探讨蛋白酶激活受体1(Protease-activated receptors 1,PAR1)对蛛网膜下腔出血(Subarachnoid hemorrhage,SAH)大鼠神经细胞自噬、神经肽及脑源性神经营养因子(Brain-derived neurotrophic factor,BDNF)水平的影响。方法 Sham组(假手术组)、SAH组(SAH模型大鼠10只)、BDNF组(SAH模型大鼠给予BDNF干预)、PAR1抑制剂组(SAH模型大鼠给予PAR1抑制剂干预)和联合组(SAH模型大鼠给予BDNF联合PAR1抑制剂干预)均9只;采用放射免疫法检测血液及脑脊液中神经肽γ(Neuropeptide Y,NPY)水平,苏木精-伊红(Hematoxylin eosin,HE)染色检测脑皮质组织形态,免疫印迹检测自噬蛋白表达水平,缺口末端标记技术(Terminal deoxynucleotidyl transferase-mediated nick end labeling,TUNEL)检测细胞凋亡率,免疫组化检测BDNF及酪氨酸激酶受体B(Tyrosine Kinase recept...     

TWEAK激活自噬增强上皮性卵巢癌顺铂耐药细胞株A2780/DDP顺铂敏感性的研究

目的:观察TWEAK对上皮性卵巢癌顺铂耐药细胞株A2780/DDP的顺铂(DDP)耐药性的影响,并初步探讨其机制。方法:CCK8法测定不同浓度TWEAK刺激后A2780/DDP的顺铂半数细胞致死量(IC50)。Western blot法检测TWEAK刺激A2780/DDP后Beclin-1、微管结合蛋白轻链3(LC3)及成纤维细胞生长因子诱导早期反应蛋白14(Fn14)的表达水平。激光共聚焦显微镜检测绿色荧光-LC3蛋白(GFP-LC3)在A2780/DDP细胞内的分布情况。用TWEAK刺激敲除Fn14表达的A2780/DDP细胞,Western blot法检测Beclin-1、LC3的表达。结果:CCK8检测结果显示,10、100ng/mlTWEAK组的顺铂IC50分别为(31.940±0.118)μg/ml、(28.769±0.090)μg/ml,均显著低于0ng/ml组(36.358±0.106)μg/ml(P均<0.05)。Western blot法结果显示,TWEAK可呈剂量和时间依赖性诱导Beclin-1、LC3及Fn14表达上调,而特异性敲除Fn14表达后,Beclin-1、LC3表达明显下调。激光共聚焦显微镜检测结果显示,TWEAK可诱导GFP-LC3致密斑形成。结论:TWEAK可增强人卵巢癌细胞耐药株A2780/DDP的顺铂敏感性;呈剂量和时间依赖性激活A2780/DDP的自噬活性,且主要通过与其受体Fn14结合介导。     

Temsirolimus诱导的自噬对腺样囊性癌的作用

目的：探讨Temsirolimus对腺样囊性癌ACC-M细胞株自噬水平的影响,以研究该药物诱导的自噬对腺样囊性癌细胞的作用。方法：通过细胞增殖实验研究Temsirolimus对ACC-M细胞增殖的影响;通过Western印迹检测实验组与对照组微管相关蛋白1轻链3（LC3）和Beclin1的表达差异;利用透射电镜观察ACC-M细胞中自噬体的形态及数量,采用SPSS15.0软件包对实验结果进行t检验。结果：Temsirolimus对ACC-M细胞具有明显的生长抑制作用,并呈现出剂量-效应关系;LC3和Beclin1在实验组细胞中表达水平高于对照组（P〈0.05）;透射电镜实验中,实验组细胞胞内自噬体及自噬溶酶体数量明显高于对照组（P〈0.01）。结论：Temsirolimus通过诱导ACC-M细胞自噬,产生了明显的抑制肿瘤细胞生长的作用,提示细胞自噬是Temsirolimus作用于唾液腺腺样囊性癌的重要抗肿瘤机制。     

Protective effect of emodin on renal interstitial fibrosis in mice of unilateral ureteral obstruction via PI3K/Akt/mTOR signaling pathway

Objective To investigate the effect and mechanism of emodin (EM) in renal interstitial fibrosis of unilateral ureteral obstruction (UUO) mice. Methods Male C57BL/6J mice were randomly divided into 4 groups, including sham operation group (n=8), UUO operation group (n=8), UUO operation+losartan (LST) group (n=8) and UUO operation+EM group (n=8). The mice in each group were ingested the suspensions by gavage for 14 days after surgery. Mice in UUO+LST and UUO+EM groups were given 10 mg?kg-1?d-1 LST and 20 mg?kg-1?d-1 EM, respectively. LST and EM were mixed with 0.5% sodium carboxymethyl cellulose. Mice in sham group and UUO group were given 0.5% sodium carboxymethyl cellulose. The mice were sacrificed at the 14th day. Interstitial fibrosis was observed by HE, Masson and PAS stain. Real-time PCR was used to detect LC3, Beclin-1 and mTOR mRNA. Protein expressions of TGF-β1, α-SMA, E-cadherin, LC3, Beclin-1, PI3K, p-Akt and mTOR were detected by Western blotting. The autophagy was observed with transmission electron microscopy in the renal tissue. Results Compared with sham mice, UUO mice at the 14th day displayed obvious renal fibrosis. Meanwhile, UUO mice had increased expressions of TGF-β1 and α-SMA (all P＜0.01), and decreased expressions of E-cadherin (P＜0.01). Their renal expressions of PI3K, p-Akt and mTOR were also raised (all P＜0.01). Compared with those in UUO group, in UUO+LST group and UUO+EM group, expressions of autophagy protein LC3 and Beclin-1 were increased (all P＜0.01), and the number of autophagic was increased. Additionally, expressions of TGF-β1 and α-SMA were reduced in UUO+LST group and UUO+EM group (all P＜0.01), while the expression of E-cadherin was increased by emodin treatment (P＜0.05). And expressions of PI3K, p-Akt and mTOR were decreased in UUO+LST group and UUO+EM group (all P＜0.05), meanwhile renal tissue fibrosis significantly reduced. Conclusions Emodin can promote autophagy, ameliorate renal interstitial fibrosis and protect renal function through PI3K/Akt/mTOR signaling pathway.