PhD, National University of Singapore, Singapore, 2002
Postdoctoral Fellowship, University of Pittsburgh, 2005
Autophagy and Apoptosis in liver injury and cancer therapy; Redox Signaling and Mitochondrial damage; Mitophagy
1. Mechanisms of autophagy in alcoholic liver disease.
Macroautophagy (referred to as autophagy hereafter) is a major intracellular degradation system that is responsible for the degradation of long-lived proteins and other cellular contents. It is usually activated in response to adverse environment, such as the deprivation of nutrients or growth factors. Autophagy plays a role in development, in defending against microbial infections, in regulating lipid homeostasis and organelles turn over such as mitochondria, and in the pathogenesis of a number of diseases including cancer. In October 2016, The Noble Prize for Physiology and Medicine was given to Professor Yoshinori Ohsumi for his discovery of the mechanisms that regulate autophagy.
Alcohol abuse is a major cause of liver injury. The pathology of alcoholic liver disease develops over a prolonged period. However, the cellular defense mechanisms against the detrimental effects of alcohol are not well understood. We recently demonstrated that autophagy is activated and protects against acute ethanol-induced liver injury and steatosis in mice. Specifically, we found that ethanol-induced autophagy may selectively remove damaged mitochondria (mitophagy) and lipid droplets (lipophagy). The research work in this laboratory is to study the mechanisms by which ethanol induces autophagy and to explore potential therapeutic drugs for alcoholic diseases by inducing autophagy. We are also interested in studying how autophagy would help to reduce alcohol-induced fatty liver (steatosis) and non-alcoholic fatty liver (NASH). Furthermore, we would also apply our autophagy liver model to other drug-induced and bile acids-induced liver injury models.
Ethanol induces mitophagy in mouse hepatocytes. (A) Confocal microscopy images of ethanol-treated mouse hepatocytes (green: GFP-LC3; Red: Mitotracker red). (B) Electron microscopy images of ethanol-treated mouse hepatocytes. Be noted double membrane enveloped mitochondria.
Ding et al., Gastroenterology 2010; Ding et al., EBM 2011; Ni et al Pharm Res. 2012; Ni et al AJP 2013; Williams et al., WJG 2014, Li Y et al., BioMedical Research International 2014; Williams et al., AJP 2015; Wang et al, Oncotarget 2016; Wang et al, ACER, 2016, Nagy et al Gastroenterology 2016, Wang & Ding, Gut 2016
Using the recently established chronic plus acute binge alcohol (Gao-binge) model, we found that Gao-binge alcohol inhibits TFEB, a master regulator and transcription factor for the gene expression of lysosomal biogenesis and autophagy-related genes, resulting impaired autophagy in the liver. We have generated several genetic mouse models (liver-specific TFEB and TFE3 knockout mice) and are currently investigating the role of TFEB in alcohol-induced liver injury.
ROS: reactive oxygen species, ADH: alcohol dehydrogenase, LD: lipid droplets
2. Mechanisms of mitochondria autophagy (mitophagy) and mitochondria dynamics and biogenesis
Mitochondria are dynamic organelles that are responsible for creating more than 90% of the energy needed by the body. Mitochondria are also the central-regulators for apoptosis and the major sources for the production of reactive oxygen species. Many environmental toxicants and chemotherapeutic drugs can damage mitochondria. Damaged mitochondria have been involved in cell death, ischemia and reperfusion injury, aging and many neurodegenerative conditions such as Alzheimer's and Parkinson's disease. It is thus important to eliminate damaged and aged mitochondria to protect the cells against its detrimental effects on the cells. It is now known that autophagy plays an important role to remove these damaged mitochondria, a process, called mitophagy. However, it is not known how damaged mitochondria are eventually recognized by the autophagosomes in mammalian cells although it has recently been reported that Atg32 is required for mitophagy in yeast. We and others recently found that Parkin, an E3 ligase which is commonly mutated in Parkinson's disease, promotes damaged mitochondria ubiquitination and p62 targeting and subsequent mitophagy. Our current research work is to study the molecular signals that could be involved in this process such as redox signaling and mitochondrial fission and fusion machinery. We are also using Parkin knockout mice to investigate the role of Parkin in mitophagy in vivo.
Mitochondria are dynamic organelles and constantly undergo fission and fusion. Fragmented mitochondria may favor autophagic removal due to its small size. We are currently investigating mitochondrial fission and fusion machinery in drug-induced mitophagy and its implication in liver injury.
CCCP induces Parkin-mediated mitophagy. Hela cells were transfected with mCherry parkin and treated with CCCP for 6 hrs.
Ding et al., JBC 2010 Ding et al., JBC 2012; Ding et al Biol Chem. 2012; Williams et al JBC 2015; Williams et al AJP 2015; Ni et al, Redox Biology 2015, Williams et al, Pharm Res 2015,
3. Targeting autophagy for drug-induced liver injury.
The liver is a vital organ that has a wide range of functions. One of the major functions of the liver is to metabolize and detoxify drugs. Consequently, liver is also often the major target to be damaged by drugs. Drug-induced liver injury is one of the most frequent reasons for the withdrawal of an approved drug from the market, and it accounts for up to 50% of acute liver failure cases. Acetaminophen (APAP) is a safe drug at therapeutic levels, but an overdose can cause severe liver injury in animals and man. We recently demonstrated that pharmacological induction of autophagy significantly inhibits APAP-induced liver injury in mouse by removing APAP-induced damaged mitochondria, a process called mitophagy. Induction of mitophagy can attenuate APAP-induced mitochondrial-mediated oxidative stress. Mechanistically, we demonstrated that acetaminophen administration activates Parkin, an E3 ubiquitin ligase, resulting in Parkin mitochondrial translocation and mitophagy in wild type mice. Intriguingly, we found that Parkin knockout mice are not more susceptible but rather are resistant to acetaminophen-induced liver injury due to compensatory effects. Acute knockdown of Parking using an adenovirus shRNA Parkin can overcome the compensatory effects of chronic genetic loss of Parkin. Our studies also raised concerns on the data interpretation for using genetic knockout mice. We are currently actively in investigating the role of Pink1, an upstream kinase of Parkin, in acetaminophen-induced liver injury. We are also investigating the role of mitochondria dynamics in acetaminophen-induced liver injury. With the rapid progress in the discovery of autophagy inducers rather than rapamycin, targeting autophagy could be a novel avenue for treating the APAP overdose patients.
Ni et al., Hepatology 2012; Ni et al., Autophagy, 2012; Ni et al., Toxi Sciences 2012; Ni et al., Pharm. Res. 2012; Ni et al., Redox Biology 2013, Williams, et al JBC, 2015,
We recently also made another important contribution to demonstrate that autophagy is important to remove acetaminophen protein adducts, in particular mitochondrial protein adducts, which are believed to be the initial trigger to induce mitochondria damage and subsequent necrosis. We also found that p62/SQSTM1, an autophagy receptor protein, is important for selective removal of APAP-adducts by autophagy.
4. SQSTM1/p62 mediated-Nrf2 activation promotes liver injury and tumorigenesis in Atg5 liver-specific knockout mice
Autophagy-deficient livers have increased accumulation of p62/SQSTM1, an autophagy substrate and receptor protein. p62 competes with Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) for binding to Keap1 (Kelch-like ECH-associated protein 1) resulting in dissociation of Nrf2 from Keap1 and activation of Nrf2, a transcription factor which regulates expression of cytoprotective genes and hepatic detoxification enzymes. Accumulation of p62 and activation of Nrf2 have been found in human HCCs. Interestingly, we recently demonstrated that p62/SQSTM1-mediated Nrf2 activation is the detrimental factor for the loss of hepatocyte Atg5-induced liver injury, fibrosis and eventual tumorigenesis. Ongoing work is aimed to determine how Nrf2, a traditional thought "good transcriptional factor" for antioxidant genes protecting against oxidative stress, actually cause cell death and tumorigenesis in Atg5-deficient liver. We are currently actively investigating the role of mTOR in Atg5-defiiency-induced liver injury and liver tumorigenesis.
Selected Publications (recent 3 years)
Ding, W.X. (2014) Drinking Coffee Burns Hepatic Fat by Inducing Lipophagy Coupled with Mitochondrial ß-Oxidation. Hepatology. 59(4):1235-8. PMID:24114874.
Manley, S., Woolright, B., Apte, U., Jaeschke, H., Guo, G and Ding, W.X. (2014) Suppression of Autophagic Process by Bile Acids in Hepatocytes. Toxi Sci .137(2):478-90. PMID: 24189133.
Ni, H.M., Woolbright, B., Copple, B, Luyendyke, J., Cui, W., Jaeschke, H and Ding, W.X. (2014) Nrf2 promotes the development of fibrosis and tumorigenesis in mice with defective hepatic autophagy. J of Hepatology 61(3):617-25. PMID: 24815875. PMCID: PMC4143992.
*Commentary: Scott L Friedman. Tracking HCC pathogenesis but not the tumor cells after biopsy. J of Hepatology 61(3):589-93.
Williams, J, Manley, S and Ding, W.X. (2014) New advances and therapeutic targets for alcoholic liver diseases. World J of Gastroenterology 20(36):12908-12933. PMID: 25278688. PMCID: PMC4177473.
Li Y., Wang S., Ni, H.M., Huang H. and Ding, W.X. (2014) Autophagy in alcohol-induced multi-organ injury: mechanisms and potential therapeutic targets. BioMed Research International. 2014:498491. PMID: 25140315. PMCID: PMC4124834
McGill MR, Du K, Xie Y, Bajt ML, Ding WX, Jaeschke H. (2014) The role of the c-Jun N-terminal kinases 1/2 and receptor-interacting protein kinase 3 in furosemide-induced liver injury. Xenobiotica. Nov 25: 1-8. PMID: 25423287. PMCID: PMC4442771.
Manley S., Ni, H.M, Williams, J.A., Guo, G, and Ding, W.X. (2014) Farnesoid X receptor regulates Fork head Box O3a activation in ethanol-induced autophagy and hepatotoxicity. Redox Biology 28;2C:991-1002. PMID: 25460735. PMCID: PMC4215528.
Ni, H.M., Bhakta, A., Wang, S.G., Li, Z., Manley, S., Huang H., Copple, B., and Ding, W.X. (2014) Role of hypoxia inducing factor-1β in Alcohol-induced autophagy, steatosis and liver injury in mice. PLoS ONE. 23;9(12):e115849. PMID: 25536043. PMCID: PMC4275262.
Ding, W.X and Eskelinen, E.L. (2014) Do mitochondria donate membrane to form autophagosomes or undergo remodeling to form mitochondrial spheroids? Cell & Bioscience 14;4(1):65. PMID: 25436108. PMCID: PMC4247758.
Ni, H.M., Williams, J.A., and Ding, W.X. (2015) Mitochondrial dynamics and mitochondrial quality control. Redox Biology 20;4C:6-13. PMID: 25479550. PMCID: PMC4309858.
Ding, W.X. (2015) Uncoupling AMPK from autophagy: a foe that hinders the beneficial effects of metformin treatment on metabolic syndrome-associated atherosclerosis? American J Physiol-Cell Physiol. 308(3):C246-8. PMID:25500743. PMCID: PMC4312841.
Williams, J, Ni, H.M., Hayness, A, Manley, S., Li, Y., Jaeschke, H. and Ding, W.X. (2015) Chronic deletion and acute knockdown of Parkin have differential responses in acetaminophen-induced mitophagy and liver injury in mice. J. Biol. Chem. 290(17):10934-46. PMID: 25752611. PMCID: PMC4409255.
Yang, H., Peng, Y.F., Ni, H.M., Li, Y., Shi, Y.H, Ding, W.X*. and Fan,J. (2015) Basal autophagy and feed back activation of Akt are associated with resistance to metformin-induced inhibition of hepatic tumor cell growth. PloS One. 2015 Jun 25;10(6):e0130953. eCollection 2015. PMID 26111001. PMCID: PMC4482411.
Williams, J, Ni, H.M., and Ding, W.X. (2015) Parkin Regulates Mitophagy and Mitochondrial Function to Protect Against Alcohol induced Liver Injury and Steatosis in Mice. American J Physiol-Gastrointestinal and Liver Physiology. 309(5):G324-40. PMID: 26159696. PMCID:PMC4556950.
Manley, S., and Ding, W.X. (2015) Role of farnesoid X receptor and bile acids in alcoholic liver disease. Acta Pharmaceutica Sinica B 5 (2), 158-167. PMID: 26579442. PMCID: PMC4629219.
Williams, J. and Ding, W.X. (2015). Mitophagy, mitochondrial spheroids and mitochondrial derived vesicles in alcohol-induced liver injury. American J Physiol-Gastrointestinal and Liver Physiology. 15;309(6):G515. PMID: 26374876.
Yang, X., Chao, X., Wang, Z.T and Ding, W.X. (2015) The end of RIPK1-RIPK3-MLKL-mediated necroptosis in acetaminophen-induced hepatotoxicity? Hepatology. PMID: 26418225.
Xie Y, McGill MR, Du K, Dorko K, Kumer SC, Schmitt TM, Ding WX, Jaeschke H (2015). Mitochondrial protein adducts formation and mitochondrial dysfunction during N-acetyl-m-aminophenol (AMAP)-induced hepatotoxicity in primary human hepatocytes. Toxicol Appl Pharmacol. 289(2):213-22. PMID: 26431796. PMCID PMC4651811.
Williams, J. and Ding, W.X. (2015). A mechanistic review of mitophagy and its role in protection against alcoholic liver disease. Biomolecules. 16; 5(4):2619-42. PMID: 26501336. PMCID: PMC4693250.
Williams, J. and Ding, W.X. (2015). Targeting Pink1-Parkin-mediated mitophagy for treating liver injury. Pharm Res. 102:264-9. PMID: 26655101. PMCID: PMC4684418.
Ding, W.X. and Jaeschke, H. (2016) Autophagy in Macrophages Regulates the Inflammasome and Protects Against Liver Injury. J Hepatology. 64(1): 16-8. PMID: 26456339. PMC4888871.
Xiong X, Wang G, Tao R, Wu P, Kono T, Li K, Ding WX, Tong X, Tersey SA, Harris RA, Mirmira RG, Evans-Molina C, Dong XC (2015). Sirtuin 6 regulates glucose-stimulated insulin secretion in mouse pancreatic beta cells. Diabetologia. PMID26471901.
Li, Y and Ding, W.X. (2016) A Gene Transcription Program Decides the Differential Regulation of Autophagy by acute vs Chronic Ethanol? Alcohol Clin Exp Res. 40(1):47-9. PMID: 26727521.
Wang S., Ni, H.M., Dorko, K., Kumer, S.C., Schmitt, T.M., Nawabi, A., Huang H and Ding, W.X. (2016) Increased hepatic expression of receptor interacting protein 3 due to impaired proteasomal functions contributes to Alcohol-induced steatosis and liver injury. Oncotarget 7(14):17681-98. PMID. 26769816. PMCID: PMC4951242.
Qian P, He XC, Paulson A, Li Z, Tao F, Perry JM, Guo F, Zhao M, Zhi L, Venkatraman A, Haug JS, Parmely T, Li H, Dobrowsky RT, Ding WX, Kono T, Ferguson-Smith AC, Li L. (2016) The Dlk1-Gtl2 Locus Preserves LT-HSC Function by Inhibiting the PI3K-mTOR Pathway to Restrict Mitochondrial Metabolism. Cell Stem Cell. 18(2):214-228. PMID: 26627594.
Klionsky, D., ..., Ding, W.X., ..et al. (2016) Guidelines for the Use and Interpretation of Assays for Monitoring Autophagy (3rd edition). Autophagy. 12(1):1-222. PMID: 26799652. PMCID: PMC in progress.
Ni, H.M., McGill., M.R, Chao, X., Du, K., Williams, J.A., Xie, Y., Jaeschke, H., and Ding W.X. (2016) Removal of Acetaminophen-Protein Adducts by Autophagy Protects Against Acetaminophen-Induced Liver Injury in Mice. J of Hepatology. 65(2):354-62. PMID: 27151180. PMCID: PMC4955750.
Nagy, L.E., Ding, W.X., Cresci, G., Saikia, P and Shah, V. (2016) Linking pathogenic mechanisms of alcoholic liver disease with clinical phenotypes. Gastroenterology. 150(8):1756-68. PMID: 26919968. PMCID: PMC4887335.
Pan, J.A., Sun, Y., Jaber, N., Dou, Z., Yang, B., Chen, J.S., Catanzaro, J.M., Du, C., Ding, W.X., Moscat, J., Ozato, K., and Zong, W.X. (2016) TRIM21 suppresses protein sequestration and anti-oxidant response by ubiquitylating SQSTM1/p62. Mol Cell. 3;61(5):720-33. PMID: 26942676. PMCID; PMC4779181.
Li Y., McGreal S., Zhao, J., Huang, R., Zhou, Y., Zhong, H., Xia M and Ding, W.X. A cell-based quantitative high-throughput imaging screening identified novel autophagy modulators. (2016) Pharm. Res. 110:35-49. PMID: 27168224. PMCID PMC4995889.
Wang S.G., Pacher, P., De Lisle, R.C., Huang, H., and Ding, W.X. (2016) A mechanistic review of cell death in alcohol-induced liver injury. Alcohol Clin Exp Res. 2016 Apr 30. PMID: 27130888.
Ni, H.M., McGill, M.R, Chao, X., Woolbright, B., Jaeschke, H., and Ding W.X. (2016). Caspase inhibition prevents TNF-α-induced apoptosis and promotes necrotic cell death in mouse hepatocytes in vivo and in vitro. Am J. Pathol. 186(10):2623-36. PMID: 27616656. Selected as AJP Press Release.
Yang, H, Ni, HM, Guo, F, Ding, Y, Shi, YH, Lahiri, P, Fröhlich, LF, Rülicke, T, Smole, C, Schmidt, VC, Zatloukal, K, Cui, Y, Komatsu, M, Fan, J, Ding, WX. (2016) Sequestosome-1/p62 is associated with autophagic removal of excess endoplasmic reticulum in mice. J Biol Chem. 291(36):18663-74. PMID: 27325701. PMCID: PMC5009243.
Zhou, Y., Li, Y., Ni, H.M., Ding, W.X. and Zhong, H. (2016) Nrf2 but not autophagy inhibition is associated with the survival of wild-type epidermal growth factor receptor non-small lung cancer cells. Toxicol Appl Pharmacol. 310:140-149. PMID: 27639429. PMCID:
Wang, S. and Ding, W.X. (2016) A small RNA in neutrophils protects against acute-on-chronic liver injury. Gut (in press).
Li, Y. and Ding, W.X. (2016) Does genetic loss of immunoglobulin A have no impact on alcoholic liver disease? Alcohol Clin Exp Res. (in press).