Degradation of the Endoplasmic Reticulum by Autophagy during Endoplasmic Reticulum Stress in Arabidopsis

In this article, we show that the endoplasmic reticulum (ER) in Arabidopsis thaliana undergoes morphological changes in structure during ER stress that can be attributed to autophagy. ER stress agents trigger autophagy as demonstrated by increased production of autophagosomes. In response to ER stress, a soluble ER marker localizes to autophagosomes and accumulates in the vacuole upon inhibition of vacuolar proteases. Membrane lamellae decorated with ribosomes were observed inside autophagic bodies, demonstrating that portions of the ER are delivered to the vacuole by autophagy during ER stress. In addition, an ER stress sensor, INOSITOL-REQUIRING ENZYME-1b (IRE1b), was found to be required for ER stress–induced autophagy. However, the IRE1b splicing target, bZIP60, did not seem to be involved, suggesting the existence of an undiscovered signaling pathway to regulate ER stress–induced autophagy in plants. Together, these results suggest that autophagy serves as a pathway for the turnover of ER membrane and its contents in response to ER stress in plants.     

Norcantharidin Inhibits Renal Interstitial Fibrosis by Blocking the Tubular Epithelial-Mesenchymal Transition

Epithelial–mesenchymal transition (EMT) is thought to contribute to the progression of renal tubulointerstitial fibrosis. Norcantharidin (NCTD) is a promising agent for inhibiting renal interstitial fibrosis. However, the molecular mechanisms of NCTD are unclear. In this study, a unilateral ureteral obstruction (UUO) rat model was established and treated with intraperitoneal NCTD (0.1 mg/kg/day). The UUO rats treated with NCTD showed a reduction in obstruction-induced upregulation of α-SMA and downregulation of E-cadherin in the rat kidney (P<0.05). Human renal proximal tubule cell lines (HK-2) stimulated with TGF-β₁ were treated with different concentrations of NCTD. HK-2 cells stimulated by TGF-β₁ in vitro led to downregulation of E-cadherin and increased de novo expression of α-SMA; co-treatment with NCTD attenuated all of these changes (P<0.05). NCTD reduced TGF-β₁-induced expression and phosphorylation of Smad2/3 and downregulated the expression of Snail1 (P<0.05). These results suggest that NCTD antagonizes tubular EMT by inhibiting the Smad pathway. NCTD may play a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.     

Secretoglobin 3A2 Exhibits Anti-Fibrotic Activity in Bleomycin-Induced Pulmonary Fibrosis Model Mice

Objective

Secretoglobin (SCGB) 3A2 is a novel lung-enriched cytokine, previously shown to exhibit anti-inflammatory, growth factor, and anti-fibrotic activities. The latter activity was demonstrated using exogenously-administered recombinant SCGB3A2 in the bleomycin (BLM)-induced pulmonary fibrosis model. Whether SCGB3A2 exhibits anti-fibrotic activity in vivo is not known.

Methods

Mice null for the Scgb3a2 gene were subjected to the BLM-induced pulmonary fibrosis model, and the severity of pulmonary fibrosis determined using histological and biochemical methods.

Results

BLM treatment caused weight loss of both Scgb3a2-null and wild-type mice, however, the loss was far more pronounced in BLM-treated Scgb3a2-null than wild-type mice, and the weight of day 21 of BLM-treated Scgb3a2-null mice was about half of that of BLM-treated wild-type mice. Hematoxylin & Eosin, Masson Trichrome, and Sirius Red staining of lung sections, Ashcroft fibrosis scores, hydroxyproline contents, and the levels of mRNAs encoding various collagens demonstrated that BLM-treated Scgb3a2-null mouse lungs had more severe fibrosis than those of wild-type mouse lungs. Total and differential inflammatory cell numbers in bronchoalveolar lavage fluids, and levels of lung mRNAs including those encoding Th2 cytokines such as IL-4 and profibrotic cytokines such as TGFβ were higher in BLM-treated Scgb3a2-null mouse lungs as compared to those of wild-type mouse lungs. In contrast, mRNAs encoding surfactant proteins A, B, C, and D, and SCGB1A1 did not differ between BLM-treated Scgb3a2-null and wild-type mouse lungs.

Conclusion

The role of SCGB3A2 in fibrosis was revisited using Scgb3a2-null mice and littermate controls in the BLM-induced pulmonary fibrosis model. The pulmonary fibrosis in the Scgb3a2-null mice was more severe than the wild-type controls, thus establishing that SCGB3A2 has anti-fibrotic activity in vivo. Importantly, surfactant proteins and SCGB1A1 appear not to be involved in the susceptibility of Scgb3a2-null mice to BLM-induced pulmonary fibrosis.     

Kaempferol Inhibits Endoplasmic Reticulum Stress-Associated Mucus Hypersecretion in Airway Epithelial Cells And Ovalbumin-Sensitized Mice

Mucus hypersecretion is an important pathological feature of chronic airway diseases, such as asthma and pulmonary diseases. MUC5AC is a major component of the mucus matrix forming family of mucins in the airways. The initiation of endoplasmic reticulum (ER)-mediated stress responses contributes to the pathogenesis of airway diseases. The present study investigated that ER stress was responsible for airway mucus production and this effect was blocked by the flavonoid kaempferol. Oral administration of ≥10 mg/kg kaempferol suppressed mucus secretion and goblet cell hyperplasia observed in the bronchial airway and lung of BALB/c mice sensitized with ovalbumin (OVA). TGF-β and tunicamycin promoted MUC5AC induction after 72 h in human bronchial airway epithelial BEAS-2B cells, which was dampened by 20 μM kaempferol. Kaempferol inhibited tunicamycin-induced ER stress of airway epithelial cells through disturbing the activation of the ER transmembrane sensor ATF6 and IRE1α. Additionally, this compound demoted the induction of ER chaperones such as GRP78 and HSP70 and the splicing of XBP-1 mRNA by tunicamycin. The in vivo study further revealed that kaempferol attenuated the induction of XBP-1 and IRE1α in epithelial tissues of OVA-challenged mice. TGF-β and tunicamycin induced TRAF2 with JNK activation and such induction was deterred by kaempferol. The inhibition of JNK activation encumbered the XBP-1 mRNA splicing and MUC5AC induction by tunicamycin and TGF-β. These results demonstrate that kaempferol alleviated asthmatic mucus hypersecretion through blocking bronchial epithelial ER stress via the inhibition of IRE1α-TRAF2-JNK activation. Therefore, kaempferol may be a potential therapeutic agent targeting mucus hypersecretion-associated pulmonary diseases.     

细胞内质网应激与糖脂代谢紊乱的机制关联

在真核细胞中,内质网是蛋白质合成、折叠、加工及其质量监控的重要场所。当内质网难以承担蛋白折叠的高负荷时则引发内质网应激(ER stress),激活细胞的未折叠蛋白响应(unfoldedprotein response,UPR)。细胞通过内质网跨膜蛋白ATF6、PERK和IRE1介导的三条极为关键的UPR信号通路,调控下游相关基因的表达,以增强内质网对蛋白折叠的处理能力。因此,UPR通路在细胞的稳态平衡中具有举足轻重的作用,而这一动态过程的调控对于维持机体的正常生理功能至关重要。近来大量研究表明,在哺乳动物中内质网应激与机体的营养感应和糖脂代谢的调控过程密切相关。在肝脏、脂肪、胰岛以及下丘脑等不同的组织器官中,内质网应激均影响代谢通路的调节机制,因此在糖脂代谢紊乱的发生发展中扮演重要的角色。综上所述,进一步深入了解内质网应激引发代谢异常的生理学机制,可以为肥胖、脂肪肝及2型糖尿病等相关代谢性疾病的防治提供新的潜在药物靶点和重要的理论线索。     

内质网应激与肝脏疾病

内质网在细胞内分布广泛,是细胞内蛋白质、脂类和糖类合成的重要场所,是细胞内钙离子的储存场所,与物质运输、交换等作用密切相关。内质网稳态失衡会诱导内质网应激(Endoplasmic reticulum stress,ERS),持久应激会导致细胞凋亡。多项研究显示内质网应激与多种肝脏疾病密切相关。本文就内质网应激与肝脏疾病发病机制作一综述。     

Psychostimulant-Induced Endoplasmic Reticulum Stress and Neurodegeneration

The endoplasmic reticulum (ER) is a subcellular organelle that ensures proper protein folding process. The ER stress is defined as cellular conditions that disturb the ER homeostasis, resulting in accumulation of unfolded and/or misfolded proteins in the lumen of the ER. The presence of these proteins within the ER activates the ER stress response, known as unfolded protein response (UPR), to restore normal functions of the ER. However, under the severe and/or prolonged ER stress, UPR initiates apoptotic cell death. Psychostimulants such as cocaine, amphetamine, and methamphetamine cause the ER stress and/or apoptotic cell death in regions of the brain related to drug addiction. Recent studies have shown that the ER stress in response to psychostimulants is linked to behavioral sensitization and that the psychostimulant-induced ER stress signaling cascades are closely associated with the pathogenesis of the neurodegenerative diseases. Therefore, this review was conducted to improve understanding of the functional role of the ER stress in the addiction as well as neurodegenerative diseases. This would be helpful to facilitate development of new therapeutic strategies for the drug addiction and/or neurodegenerative diseases caused or exacerbated by exposure to psychostimulants.     

内质网应激与心脏疾病

内质网是细胞内蛋白质合成折叠、Ca2+储存和脂质合成的重要部位.内质网稳态的破坏将导致大量错误或者未折叠蛋白质在内质网中的聚集,通过相应的信号通路,引起一系列的细胞反应,即内质网应激.内质网应激参与心脏的发育和多种心脏疾病的发生发展,包括心肌缺血和再灌注损伤、心肌病、心力衰竭等.内质网应激可能是研究心血管疾病发病机制和防治措施的新靶点.     

NGF通过抑制内质网应激途径保护SCs在高糖环境诱导的凋亡

已知神经生长因子 (nerve growth factor, NGF) 对糖尿病外周神经病变 (diabetic peripheral neuropathy, DPN) 患者具有良好的治疗效果,内质网应激 (endoplasmic reticulum stress, ERS) 在调控DPN 的发生发展方面扮演着重要的角色。然而,二者间的关系未知。本研究以30 mmol/L的高糖处理RSC-96大鼠雪旺细胞 (RSC96 Schwann cells, SCs),模拟DPN患者外周神经的内环境。研究结果证实,在高糖条件下,NGF通过抑制SCs内 ERS的过度激活进而保护SCs的存活且这种抑制作用依靠P13K/AKT/GSK-3β和ERK1/2两条信号通路的调节实现。MTT检测细胞的存活率,结果显示高糖环境培养的SCs在24 h发生最佳程度的抑制,且此时间点加入的NGF浓度为50 ng/mL 时,其存活率最高。Western 印迹检测ERS和相关蛋白质的表达揭示,高糖能够过度激活SCs内ERS蛋白 (GRP-78、ATF-6、ATF-4、XBP-1、CHOP),给予 50 ng/mL的NGF处理后,ERS蛋白的表达水平大幅下调并接近正常,且此时p-AKT、p-ERK1/2、p-GSK3β蛋白的检测水平明显升高。流式细胞术检测细胞凋亡显示,NGF能显著抑制SCs的早期凋亡。上述结果证明,高糖诱导SCs的凋亡增加是由于自身的ERS被过度激活,NGF可通过调节P13K/AKT/GSK-3β和ERK1/2两条信号通路来抑制ERS的过度激活,达到保护SCs存活的目的。此机制为临床治疗 DPN 提供新的理论基础。     

内质网应激与阿尔茨海默病

内质网是蛋白质合成、修饰以及折叠的重要场所。内质网内未折叠蛋白堆积,钙离子失稳等可触发内质网应激,通过非折叠蛋白应答纠正这些异常变化。过度的内质网应激或内质网应激机制失常将导致细胞损害和死亡。近年来的研究发现阿尔茨海默病的神经系统损害与内质网应激异常有关。深入研究内质网应激将为进一步探索阿尔茨海默病发病机制和防治基础提供新的方向。     

内质网应激与疾病

内质网是蛋白质合成与折叠、维持Ca²⁺动态平衡及合成脂类和固醇的场所。遗传或环境损伤引起内质网功能紊乱导致内质网应激,激活未折叠蛋白反应。未折叠蛋白反应是一种细胞自我保护性措施,但是内质网应激过强或持续时间过久可引起细胞凋亡。因此,内质网应激与众多人类疾病的发生发展密切相关。最近研究证明,癌症、炎症性疾病、代谢性疾病、骨质疏松症及神经退行性疾病等有内质网应激信号传递参与。然而内质网应激作为一个有效靶点参与各种疾病发挥作用的功能和机制仍然有待进一步研究。在近年来发表的文献基础上对内质网应激与疾病的关系,以及其可能的作用机制进行综述。     

骨关节炎软骨细胞发生内质网应激

目的：研究骨关节炎软骨细胞是否发生内质网应激现象。方法：对关节置换术后的人类骨关节炎软骨标本和正常关节软骨标本切片进行内质网应激标志分子免疫球蛋白重链结合蛋白（BiP）的免疫组织化学检测;对小鼠膝关节进行半月板切断术诱发实验性骨关节炎,在术后1、3和6周取材,对组织切片进行番红花“O”染色、Mankin评分及BiP的免疫组织化学检测。结果：所有人类骨关节炎标本中软骨细胞BiP的表达明显升高。番红花“O”染色结果表明,在小鼠骨关节炎模型中,全部手术侧关节表面发生磨损,且随着术后时间延长关节表面磨损范围逐步扩大,手术侧Mankn分值显著高于对照侧;此外,手术侧的软骨细胞内BiP呈阳性表达,且表达量随术后时间延长而增加。结论：在人类骨关节炎标本和实验性小鼠骨关节炎模型中,关节软骨细胞均发生明显的内质网应激现象。     

内质网应激与哺乳动物雄性生殖

内质网应激 (endoplasmic reticulum stress,ERS) 激活未折叠蛋白反应,维持哺乳动物细胞的胞内稳态,过度持续的ERS导致细胞凋亡。最新研究表明,ERS对哺乳动物雄性生殖有重要的调节作用,包括对精母细胞、睾丸结构及精子发生的影响。ERS是研究生殖细胞生存和凋亡的新通路。雄性不育可能是由过度ERS引起的。本文通过简述ERS的最新研究进展,分析雄性生殖与ERS的关系,并从ERS调控雄性生殖角度提出新的理解和展望。     

炙甘草汤通过抗氧化抑制博莱霉素诱导的小鼠肺纤维化

摘要 目的：探讨炙甘草汤对特发性肺纤维化（Idiopathic pulmonary fibrosis,IPF）小鼠纤维化相关指标的影响,挖掘炙甘草汤治疗IPF的机制。方法：将60只SPF级ICR小鼠随机分为空白组、模型组、吡菲尼酮组和炙甘草汤组,除空白组外,其余组采用气管滴注博莱霉素（5 mg/kg)方法复制IPF小鼠模型,并给予相应的药物治疗。空白组和模型组小鼠灌胃生理盐水,吡菲尼酮组和炙甘草汤组小鼠分别灌胃吡菲尼酮(50 mg/kg)和炙甘草汤（25.4 g/kg）,各组均连续给药4周后取材,记录各组小鼠的死亡情况,计算各组肺系数;观察肺组织切片病理变化;碱水解法检测肺组织羟脯氨酸（HYP）含量;比色法检测肺组织丙二醛（MDA）含量、超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GSH-Px）的活性;免疫组化、荧光定量PCR检测α-SMA、COL1A蛋白和mRNA的表达水平。结果：炙甘草汤组小鼠死亡数减少,肺系数显著降低（P＜0.01）,炎性细胞浸润和胶原沉积面积大量减少,肺泡结构逐渐修复,HYP、MDA含量降低（P＜0.01）,SOD活性（P＜0.05）和GSH-Px活性（P＜0.01）显著增强;α-SMA、COL1A蛋白和mRNA表达均降低（P＜0.01）。结论：炙甘草汤通过抑制氧化应激反应,从而抑制成纤维细胞活化,减少细胞质基质沉积,从而减缓IPF疾病进程。     

Positional Cloning Reveals Strain-Dependent Expression of Trim16 to Alter Susceptibility to Bleomycin-Induced Pulmonary Fibrosis in Mice

Pulmonary fibrosis is a disease of significant morbidity, with no effective therapeutics and an as yet incompletely defined genetic basis. The chemotherapeutic agent bleomycin induces pulmonary fibrosis in susceptible C57BL/6J mice but not in mice of the C3H/HeJ strain, and this differential strain response has been used in prior studies to map bleomycin-induced pulmonary fibrosis susceptibility loci named Blmpf1 and Blmpf2. In this study we isolated the quantitative trait gene underlying Blmpf2 initially by histologically phenotyping the bleomycin-induced lung disease of sublines of congenic mice to reduce the linkage region to 13 genes. Of these genes, Trim16 was identified to have strain-dependent expression in the lung, which we determined was due to sequence variation in the promoter. Over-expression of Trim16 by plasmid injection increased pulmonary fibrosis, and bronchoalveolar lavage levels of both interleukin 12/23-p40 and neutrophils, in bleomycin treated B6.C3H-Blmpf2 subcongenic mice compared to subcongenic mice treated with bleomycin only, which follows the C57BL/6J versus C3H/HeJ strain difference in these traits. In summary we demonstrate that genetic variation in Trim16 leads to its strain-dependent expression, which alters susceptibility to bleomycin-induced pulmonary fibrosis in mice.