Browsing by Author "Chen, Xiaoyun"
Now showing 1 - 10 of 16
Results Per Page
Sort Options
Item AMDE-1 is a dual function chemical for autophagy activation and inhibition(PLoS, 2015-04-20) Li, Min; Yang, Zuolong; Vollmer, Laura L.; Gao, Ying; Fu, Yuanyuan; Lui, Cui; Chen, Xiaoyun; Liu, Peiqing; Vogt, Andreas; Yin, Xiao-Ming; Department of Pathology and Laboratory Medicine, IU School of MedicineAutophagy is the process by which cytosolic components and organelles are delivered to the lysosome for degradation. Autophagy plays important roles in cellular homeostasis and disease pathogenesis. Small chemical molecules that can modulate autophagy activity may have pharmacological value for treating diseases. Using a GFP-LC3-based high content screening assay we identified a novel chemical that is able to modulate autophagy at both initiation and degradation levels. This molecule, termed as Autophagy Modulator with Dual Effect-1 (AMDE-1), triggered autophagy in an Atg5-dependent manner, recruiting Atg16 to the pre-autophagosomal site and causing LC3 lipidation. AMDE-1 induced autophagy through the activation of AMPK, which inactivated mTORC1 and activated ULK1. AMDE-1did not affect MAP kinase, JNK or oxidative stress signaling for autophagy induction. Surprisingly, treatment with AMDE-1 resulted in impairment in autophagic flux and inhibition of long-lived protein degradation. This inhibition was correlated with a reduction in lysosomal degradation capacity but not with autophagosome-lysosome fusion. Further analysis indicated that AMDE-1 caused a reduction in lysosome acidity and lysosomal proteolytic activity, suggesting that it suppressed general lysosome function. AMDE-1 thus also impaired endocytosis-mediated EGF receptor degradation. The dual effects of AMDE-1 on autophagy induction and lysosomal degradation suggested that its net effect would likely lead to autophagic stress and lysosome dysfunction, and therefore cell death. Indeed, AMDE-1 triggered necroptosis and was preferentially cytotoxic to cancer cells. In conclusion, this study identified a new class of autophagy modulators with dual effects, which can be explored for potential uses in cancer therapy.Item Autophagy induced by calcium phosphate precipitates targets damaged endosomes(ASBMB, 2014-04-18) Chen, Xi; Khambu, Bilon; Zhang, Hao; Gao, Wentao; Li, Min; Chen, Xiaoyun; Yoshimori, Tamotsu; Yin, Xiao-Ming; Department of Pathology & Laboratory Medicine, IU School of MedicineCalcium phosphate precipitates (CPPs) form complexes with DNA, which enter cells via endocytosis. Under this condition CPPs induce autophagy via the canonic autophagy machinery. Here we showed that CPP-induced autophagy was also dependent on endocytosis as the process was significantly inhibited by methyl-β-cyclodextrin and dynasore, which suppress clathrin-dependent endocytosis. Consistently, CPP treatment triggered the formation of filipin-positive intracellular vesicles whose membranes are rich in cholesterol. Unexpectedly, these vesicles were also positive for galectin 3, suggesting that they were damaged and the membrane glycans became accessible to galectins to bind. Endosome damage was caused by endocytosis of CPPs and was reversed by calcium chelators or by endocytosis inhibitors. Notably, CPP-induced LC3-positive autophagosomes were colocalized with galectin 3, ubiquitin, and p62/SQSTM1. Inhibition of galectin 3 reduced p62 puncta and autophagosome formation. Knockdown of p62 additionally inhibited the colocalization of autophagosomes with galectins. Furthermore, most of the galectin 3-positive vesicles were colocalized with Rab7 or LAMP1. Agents that affect endosome/lysosome maturation and function, such as bafilomycin A1, also significantly affected CPP-induced tubulovesicular autophagosome formation. These findings thus indicate that endocytosed CPPs caused endosome damage and recruitment of galectins, particularly at the later endosome stage, which led to the interaction of the autophagosomal membranes with the damaged endosome in the presence of p62.Item Diverse Consequences in Liver Injury in Mice with Different Autophagy Functional Status Treated with Alcohol(Elsevier, 2019) Yan, Shengmin; Zhou, Jun; Chen, Xiaoyun; Dong, Zheng; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of MedicineAlcoholic fatty liver disease is often complicated by other pathologic insults, such as viral infection or high-fat diet. Autophagy plays a homeostatic role in the liver but can be compromised by alcohol, high-fat diet, or viral infection, which in turn affects the disease process caused by these etiologies. To understand the full impact of autophagy modulation on alcohol-induced liver injury, several genetic models of autophagy deficiency, which have different levels of functional alterations, were examined after acute binge or chronic-plus-binge treatment. Mice given alcohol with either mode and induced with deficiency in liver-specific autophagy-related protein (Atg)-7 shortly after the induction of Atg7 deletion had elevated liver injury, indicating the protective role of autophagy. Constitutive hepatic Atg7–deficient mice, in which Atg7 was deleted in embryos, were more susceptible with chronic-plus-binge but not with acute alcohol treatment. Constitutive hepatic Atg5–deficient mice, in which Atg5 was deleted in embryos, were more susceptible with acute alcohol treatment, but liver injury was unexpectedly improved with the chronic-plus-binge regimen. A prolonged Atg deficiency may complicate the hepatic response to alcohol treatment, likely in part due to endogenous liver injury. The complexity of the relationship between autophagy deficiency and alcohol-induced liver injury can thus be affected by the timing of autophagy dysfunction, the exact autophagy gene being affected, and the alcohol treatment regimen.Item Dynamic MTORC1-TFEB feedback signaling regulates hepatic autophagy, steatosis and liver injury in long-term nutrient oversupply(Taylor & Francis, 2018) Zhang, Hao; Yan, Shengmin; Khambu, Bilon; Ma, Fengguang; Li, Yong; Chen, Xiaoyun; Puertollano, Rosa; Li, Yu; Chalasani, Naga; Yin, Xiao-Ming; Martina, Jose A.; Pathology & Laboratory Medicine, IU School of MedicineNormal metabolism requires a controlled balance between anabolism and catabolism. It is not completely known how this balance can be retained when the level of nutrient supply changes in the long term. We found that in murine liver anabolism, as represented by the phosphorylation of RPS6KB (ribosomal protein S6 kinase), was soon elevated while catabolism, as represented by TFEB (transcription factor EB)-directed gene transcription and lysosomal activities, was downregulated after the administration of a high-fat diet (HFD). Surprisingly, neither the alteration in RPS6KB phosphorylation nor that in TFEB functions was static over the long course of HFD feeding. Instead, the 2 signals exhibited dynamic alterations in opposite directions, which could be explained by the dependence of MTORC1 (MTOR complex 1) activation on TFEB-supported lysosome function and the feedback suppression of TFEB by MTORC1. Disruption of the dynamics by enforced expression of TFEB in HFD-fed mice at the peaks of MTORC1 activation restored lysosome function. Consistently, interference of MTORC1 activation with rapamycin or with a constitutively activated RRAGA mutant at the peak or nadir of MTORC1 oscillation enhanced or reduced the lysosome function, respectively. These treatments also improved or exacerbated hepatic steatosis and liver injury, respectively. Finally, there was a significant inverse correlation between TFEB activation and steatosis severity in the livers of patients with non-alcohol fatty liver diseases, supporting the clinical relevance of TFEB-regulated events. Thus, maintaining catabolic function through feedback mechanisms during enhanced anabolism, which is caused by nutrient oversupply, is important for reducing liver pathology.Item Endoplasmic Reticulum Stress Activates the Inflammasome via NLRP3- and Caspase-2-Driven Mitochondrial Damage(Elsevier, 2015-09-15) Bronner, Denise N.; Abuaita, Basel H.; Chen, Xiaoyun; Fitzgerald, Katherine A.; Nuñez, Gabriel; He, Yongqun; Yin, Xiao-Ming; O’Riordan, Mary X.D.; Department of Pathology and Laboratory Medicine, IU School of MedicineEndoplasmic reticulum (ER) stress is observed in many human diseases, often associated with inflammation. ER stress can trigger inflammation through nucleotide-binding domain and leucine-rich repeat containing (NLRP3) inflammasome, which might stimulate inflammasome formation by association with damaged mitochondria. How ER stress triggers mitochondrial dysfunction and inflammasome activation is ill defined. Here we have used an infection model to show that the IRE1α ER stress sensor regulates regulated mitochondrial dysfunction through an NLRP3-mediated feed-forward loop, independently of ASC. IRE1α activation increased mitochondrial reactive oxygen species, promoting NLRP3 association with mitochondria. NLRP3 was required for ER stress-induced cleavage of caspase-2 and the pro-apoptotic factor, Bid, leading to subsequent release of mitochondrial contents. Caspase-2 and Bid were necessary for activation of the canonical inflammasome by infection-associated or general ER stress. These data identify an NLRP3-caspase-2-dependent mechanism that relays ER stress to the mitochondria to promote inflammation, integrating cellular stress and innate immunity.Item Gene Expression Analysis Indicates Divergent Mechanisms in DEN-Induced Carcinogenesis in Wild Type and Bid-Deficient Livers(Public Library of Science (PLoS), 2016) Yu, Changshun; Yan, Shengmin; Khambu, Bilon; Chen, Xiaoyun; Dong, Zheng; Luo, Jianhua; Michalopoulos, George K.; Wu, Shangwei; Yin, Xiao-Ming; Department of Pathology & Laboratory Medicine, IU School of MedicineBid is a Bcl-2 family protein. In addition to its pro-apoptosis function, Bid can also promote cell proliferation, maintain S phase checkpoint, and facilitate inflammasome activation. Bid plays important roles in tissue injury and regeneration, hematopoietic homeostasis, and tumorigenesis. Bid participates in hepatic carcinogenesis but the mechanism is not fully understood. Deletion of Bid resulted in diminished tumor burden and delayed tumor progression in a liver cancer model. In order to better understand the Bid-regulated events during hepatic carcinogenesis we performed gene expression analysis in wild type and bid-deficient mice treated with a hepatic carcinogen, diethylnitrosamine. We found that deletion of Bid caused significantly fewer alterations in gene expression in terms of the number of genes affected and the number of pathways affected. In addition, the expression profiles were remarkably different. In the wild type mice, there was a significant increase in the expression of growth regulation-related and immune/inflammation response-related genes, and a significant decrease in the expression of metabolism-related genes, both of which were diminished in bid-deficient livers. These data suggest that Bid could promote hepatic carcinogenesis via growth control and inflammation-mediated events.Item Golgi-associated LC3 lipidation requires V-ATPase in noncanonical autophagy(Nature Publishing Group, 2016-08-11) Gao, Ying; Liu, Yajun; Hong, Liang; Yang, Zuolong; Cai, Xinran; Chen, Xiaoyun; Fu, Yuanyuan; Lin, Yujie; Wen, Weijie; Li, Sitong; Liu, Xingguo; Huang, Heqing; Vogt, Andreas; Liu, Peiqing; Yin, Xiao-Ming; Li, Min; Department of Pathology and Laboratory Medicine, School of MedicineAutophagy is an evolutionarily conserved catabolic process by which cells degrade intracellular proteins and organelles in the lysosomes. Canonical autophagy requires all autophagy proteins (ATGs), whereas noncanonical autophagy is activated by diverse agents in which some of the essential autophagy proteins are dispensable. How noncanonical autophagy is induced and/or inhibited is still largely unclear. In this study, we demonstrated that AMDE-1, a recently identified chemical that can induce canonical autophagy, was able to elicit noncanonical autophagy that is independent of the ULK1 (unc-51-like kinase 1) complex and the Beclin1 complex. AMDE-1-induced noncanonical autophagy could be specifically suppressed by various V-ATPase (vacuolar-type H(+)-ATPase) inhibitors, but not by disturbance of the lysosome function or the intracellular ion redistribution. Similar findings were applicable to a diverse group of stimuli that can induce noncanonical autophagy in a FIP200-independent manner. AMDE-1-induced LC3 lipidation was colocalized with the Golgi complex, and was inhibited by the disturbance of Golgi complex. The integrity of the Golgi complex was also required for multiple other agents to stimulate noncanonical LC3 lipidation. These results suggest that the Golgi complex may serve as a membrane platform for noncanonical autophagy where V-ATPase is a key player. V-ATPase inhibitors could be useful tools for studying noncanonical autophagy.Item Hepatic Autophagy Deficiency Compromises FXR Functionality and Causes Cholestatic Injury(AASLD, 2019) Khambu, Bilon; Li, Tiangang; Yan, Shengmin; Yu, Changshun; Chen, Xiaoyun; Goheen, Michael; Li, Yong; Lin, Jingmei; Cummings, Oscar W.; Lee, Youngmin A.; Friedman, Scott; Dong, Zheng; Feng, Gen-Sheng; Wu, Shangwei; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of MedicineAutophagy is important for hepatic homeostasis, nutrient regeneration and organelle quality control. We investigated the mechanisms by which liver injury occurred in the absence of autophagy function. We found that mice deficient in autophagy due to the lack of Atg7 or Atg5, key autophagy‐related genes, manifested intracellular cholestasis with increased levels of serum bile acids, a higher ratio of TMCA/TCA in the bile, increased hepatic bile acid load, abnormal bile canaliculi and altered expression of hepatic transporters. In determining the underlying mechanism, we found that autophagy sustained and promoted the basal and upregulated expression of Fxr in the fed and starved conditions, respectively. Consequently, expression of Fxr and its downstream genes, particularly Bsep, and the binding of FXR to the promoter regions of these genes, were suppressed in autophagy‐deficient livers. In addition, co‐deletion of Nrf2 in autophagy deficiency status reversed the FXR suppression. Furthermore, the cholestatic injury of autophagy‐deficient livers was reversed by enhancement of FXR activity or expression, or by Nrf2 deletion.Item Hepatic Autophagy Deficiency Remodels Gut Microbiota for Adaptive Protection via FGF15-FGFR4 Signaling(Elsevier, 2021) Yan, Shengmin; Khambu, Bilon; Chen, Xiaoyun; Dong, Zheng; Guo, Grace; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of MedicineBackground & aims: The functions of the liver and the intestine are closely tied in both physiological and pathologic conditions. The gut microbiota (GM) often cause deleterious effects during hepatic pathogenesis. Autophagy is essential for liver homeostasis, but the impact of hepatic autophagy function on liver-gut interaction remains unknown. Here we investigated the effect of hepatic autophagy deficiency (Atg5Δhep) on GM and in turn the effect of GM on the liver pathology. Methods: Fecal microbiota were analyzed by 16S sequencing. Antibiotics were used to modulate GM. Cholestyramine was used to reduce the enterohepatic bile acid (BA) level. The functional role of fibroblast growth factor 15 (FGF15) and ileal farnesoid X receptor (FXR) was examined in mice overexpressing FGF15 gene or in mice given a fibroblast growth factor receptor-4 (FGFR4) inhibitor. Results: Atg5Δhep causes liver injury and alterations of intestinal BA composition, with a lower proportion of tauro-conjugated BAs and a higher proportion of unconjugated BAs. The composition of GM is significantly changed with an increase in BA-metabolizing bacteria, leading to an increased expression of ileal FGF15 driven by FXR that has a higher affinity to unconjugated BAs. Notably, antibiotics or cholestyramine treatment decreased FGF15 expression and exacerbated liver injury. Consistently, inhibition of FGF15 signaling in the liver enhances liver injury. Conclusions: Deficiency of autophagy function in the liver can affect intestinal environment, leading to gut dysbiosis. Surprisingly, such changes provide an adaptive protection against the liver injury through the FGF15-FGFR4 signaling. Antibiotics use in the condition of liver injury may thus have unexpected adverse consequences via the gut-liver axis.Item HMGB1 promotes ductular reaction and tumorigenesis in autophagy-deficient livers(American Society for Clinical Investigation, 2018-06-01) Khambu, Bilon; Huda, Nazmul; Chen, Xiaoyun; Antoine, Daniel J.; Li, Yong; Dai, Guoli; Köhler, Ulrike A.; Zong, Wei-Xing; Waguri, Satoshi; Werner, Sabine; Oury, Tim D.; Dong, Zheng; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of MedicineAutophagy is important for liver homeostasis, and the deficiency leads to injury, inflammation, ductular reaction (DR), fibrosis, and tumorigenesis. It is not clear how these events are mechanistically linked to autophagy deficiency. Here, we reveal the role of high-mobility group box 1 (HMGB1) in two of these processes. First, HMGB1 was required for DR, which represents the expansion of hepatic progenitor cells (HPCs) implicated in liver repair and regeneration. DR caused by hepatotoxic diets (3,5-diethoxycarbonyl-1,4-dihydrocollidine [DDC] or choline-deficient, ethionine-supplemented [CDE]) also depended on HMGB1, indicating that HMGB1 may be generally required for DR in various injury scenarios. Second, HMGB1 promoted tumor progression in autophagy-deficient livers. Receptor for advanced glycation end product (RAGE), a receptor for HMGB1, was required in the same two processes and could mediate the proliferative effects of HMBG1 in isolated HPCs. HMGB1 was released from autophagy-deficient hepatocytes independently of cellular injury but depended on NRF2 and the inflammasome, which was activated by NRF2. Pharmacological or genetic activation of NRF2 alone, without disabling autophagy or causing injury, was sufficient to cause inflammasome-dependent HMGB1 release. In conclusion, HMGB1 release is a critical mechanism in hepatic pathogenesis under autophagy-deficient conditions and leads to HPC expansion as well as tumor progression.