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Badal SS, Al Tuhaifi T, Yu YF, Lopez D, Plato CT, Joly K, Breckenridge DG, Yang HC, Liles JT, Fogo AB. Selonsertib Enhances Kidney Protection Beyond Standard of Care in a Hypertensive, Secondary Glomerulosclerosis CKD Model. Kidney360 2022; 3:1169-1182. [PMID: 35919527 PMCID: PMC9337896 DOI: 10.34067/kid.0001032022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 04/05/2022] [Indexed: 01/12/2023]
Abstract
Background Despite widespread use of renin-aldosterone-angiotensin system inhibitors and the benefits of lowering glomerular pressure in patients with CKD, there remains a major unmet need for therapies targeting underlying causes of CKD progression. Apoptosis signal-regulating kinase 1 (ASK1) promotes apoptosis and glomerulosclerosis, and is implicated in the progression of diabetic kidney disease (DKD), a major cause of CKD. Selonsertib is a selective ASK1 inhibitor currently in clinical development for the treatment of DKD. We examined the added benefits of selonsertib on existing glomerulosclerosis and related molecular pathways in the nondiabetic 5/6 nephrectomy (5/6 Nx) rat model in combination with the angiotensin-converting enzyme inhibitor (ACEI) enalapril. Methods Male Sprague Dawley rats underwent 5/6 Nx with kidney biopsy 8 weeks later for assessment of glomerulosclerosis, and were randomized to four treatment groups with equal glomerulosclerosis: selonsertib, enalapril, combination (selonsertib plus enalapril), and untreated controls. Serum creatinine, systolic BP (SBP), and urinary albumin were measured at intervals. Animals were euthanized at week 12 for histologic, biochemical, and molecular analyses. Results All rats developed hypertension, albuminuria, and glomerulosclerosis by week 8. Kidney function further declined, and glomerulosclerosis and albuminuria progressively increased in controls from week 8 to 12. Enalapril treatment alone from week 8 to 12 reduced SBP versus controls, decreased albuminuria, and resulted in numerically lower glomerulosclerosis. Selonsertib alone had no effect on SBP but preserved kidney function. Combined treatment significantly reduced glomerulosclerosis, with more regression than either monotherapy. Enalapril treatment resulted in fewer interstitial macrophages, whereas selonsertib treatment reduced apoptosis and podocyte loss. RNA-seq revealed that combined treatment influenced pathways related to extracellular matrix and wound healing. Conclusions Selonsertib targets a novel, nonhemodynamic pathway in CKD. Our data suggest that ASK1 inhibition, when combined with ACEI, has additive effects to reduce progression of glomerulosclerosis, attenuate kidney function decline, and reduce podocyte loss.
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Affiliation(s)
| | - Tareq Al Tuhaifi
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Ya-Fen Yu
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
- Fourth Hospital, Wuxi, Anhui, China
| | - David Lopez
- Gilead Sciences, Inc., Foster City, California
| | | | | | | | - Hai-Chun Yang
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | | | - Agnes B. Fogo
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
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2
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Vijayakumar A, Okesli-Armlovich A, Wang T, Olson I, Seung M, Kusam S, Hollenback D, Mahadevan S, Marchand B, Toteva M, Breckenridge DG, Trevaskis JL, Bates J. Combinations of an acetyl CoA carboxylase inhibitor with hepatic lipid modulating agents do not augment antifibrotic efficacy in preclinical models of NASH and fibrosis. Hepatol Commun 2022; 6:2298-2309. [PMID: 35735253 PMCID: PMC9426400 DOI: 10.1002/hep4.2011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 04/17/2022] [Accepted: 05/01/2022] [Indexed: 11/11/2022] Open
Abstract
Dysregulated hepatocyte lipid metabolism is a hallmark of hepatic lipotoxicity and contributes to the pathogenesis of nonalcoholic steatohepatitis (NASH). Acetyl CoA carboxylase (ACC) inhibitors decrease hepatocyte lipotoxicity by inhibiting de novo lipogenesis and concomitantly increasing fatty acid oxidation (FAO), and firsocostat, a liver‐targeted inhibitor of ACC1/2, is under evaluation clinically in patients with NASH. ACC inhibition is associated with improvements in indices of NASH and reduced liver triglyceride (TG) content, but also increased circulating TG in subjects with NASH and preclinical rodent models. Here we evaluated whether enhancing hepatocyte FAO by combining ACC inhibitors with peroxisomal proliferator‐activated receptor (PPAR) or thyroid hormone receptor beta (THRβ) agonists could drive greater liver TG reduction and NASH/antifibrotic efficacy, while ameliorating ACC inhibitor–induced hypertriglyceridemia. In high‐fat diet–fed dyslipidemic rats, the addition of PPAR agonists fenofibrate (Feno), elafibranor (Ela), lanifibranor (Lani), seladelpar (Sela) or saroglitazar (Saro), or the THRb agonist resmetirom (Res), to an analogue of firsocostat (ACCi) prevented ACCi‐induced hypertriglyceridemia. However, only PPARα agonists (Feno and Ela) and Res provided additional liver TG reduction. In the choline‐deficient high‐fat diet rat model of advanced liver fibrosis, neither PPARα (Feno) nor THRβ (Res) agonism augmented the antifibrotic efficacy of ACCi. Conclusion: These data suggest that combination therapies targeting hepatocyte lipid metabolism may have beneficial effects on liver TG reduction; however, they may not be sufficient to drive fibrosis regression.
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Affiliation(s)
| | | | - Ting Wang
- Gilead Sciences, Foster City, California, USA
| | | | - Minji Seung
- Gilead Sciences, Foster City, California, USA
| | | | | | | | | | | | | | | | - Jamie Bates
- Gilead Sciences, Foster City, California, USA
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3
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Cazanave SC, Warren AD, Pacula M, Touti F, Zagorska A, Gural N, Huang EK, Sherman S, Cheema M, Ibarra S, Bates J, Billin AN, Liles JT, Budas GR, Breckenridge DG, Tiniakos D, Ratziu V, Daly AK, Govaere O, Anstee QM, Gelrud L, Luther J, Chung RT, Corey KE, Winckler W, Bhatia S, Kwong GA. Peptide-based urinary monitoring of fibrotic nonalcoholic steatohepatitis by mass-barcoded activity-based sensors. Sci Transl Med 2021; 13:eabe8939. [PMID: 34669440 DOI: 10.1126/scitranslmed.abe8939] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
[Figure: see text].
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Affiliation(s)
| | | | | | | | | | - Nil Gural
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | | | | - Jamie Bates
- Gilead Sciences Inc., Foster City, CA 94404, USA
| | | | - John T Liles
- Gilead Sciences Inc., Foster City, CA 94404, USA
| | | | | | - Dina Tiniakos
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.,Newcastle NIHR Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 7RU, UK
| | - Vlad Ratziu
- Sorbonne Université, ICAN (Institute of Cardiometabolism And Nutrition), Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Sorbonne University, INSERM UMRS 1138 CRC, Paris 75013, France
| | - Ann K Daly
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.,Newcastle NIHR Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 7RU, UK
| | - Olivier Govaere
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.,Newcastle NIHR Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 7RU, UK
| | - Quentin M Anstee
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.,Newcastle NIHR Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 7RU, UK
| | - Louis Gelrud
- Bon Secours St Mary's Hospital, Richmond VA 23226, USA
| | - Jay Luther
- Liver Center, GI Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Raymond T Chung
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA 30332, USA
| | - Kathleen E Corey
- Liver Center, GI Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | | | - Sangeeta Bhatia
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Gabriel A Kwong
- Glympse Bio Inc., Cambridge, MA 02138, USA.,The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA 30332, USA
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4
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Schwabl P, Hambruch E, Budas GR, Supper P, Burnet M, Liles JT, Birkel M, Brusilovskaya K, Königshofer P, Peck-Radosavljevic M, Watkins WJ, Trauner M, Breckenridge DG, Kremoser C, Reiberger T. The Non-Steroidal FXR Agonist Cilofexor Improves Portal Hypertension and Reduces Hepatic Fibrosis in a Rat NASH Model. Biomedicines 2021; 9:biomedicines9010060. [PMID: 33435509 PMCID: PMC7827357 DOI: 10.3390/biomedicines9010060] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/31/2020] [Accepted: 01/05/2021] [Indexed: 02/07/2023] Open
Abstract
Background: The farnesoid X receptor (FXR) influences hepatic metabolism, inflammation and liver fibrosis as key components of non-alcoholic steatohepatitis (NASH). We studied the effects of the non-steroidal FXR agonist cilofexor (formerly GS-9674) on portal pressure and fibrosis in experimental NASH. Methods: NASH was induced in Wistar rats using a choline-deficient high-fat diet plus intraperitoneal sodium nitrite injections. First, a dose-finding study was performed with 10 mg/kg and 30 mg/kg of cilofexor, focusing on histological readouts. Liver fibrosis was assessed by Picro-Sirius-Red, desmin staining and hepatic hydroxyproline content. Gene expression was determined by RT-PCR. In a subsequent hemodynamic study, rats received 30 mg/kg cilofexor with or without propranolol (25 mg/kg). Portal pressure, systemic hemodynamics and splanchnic blood flow were measured. Results: Cilofexor dose-dependently induced FXR target genes shp, cyp7a1 and fgf15 in hepatic and ileal tissues, paralleled by a dose-dependent reduction in liver fibrosis area (Picro-Sirius-Red) of −41% (10 mg/kg) and −69% (30 mg/kg), respectively. The 30 mg/kg cilofexor dose significantly reduced hepatic hydroxyproline content (−41%), expression of col1a1 (−37%) and pdgfr-β (−36%), as well as desmin area (−42%) in NASH rats. Importantly, cilofexor decreased portal pressure (11.9 ± 2.1 vs. 8.9 ± 2.2 mmHg; p = 0.020) without affecting splanchnic blood-flow or systemic hemodynamics. The addition of propranolol to cilofexor additionally reduced splanchnic inflow (−28%) but also mean arterial pressure (−25%) and heart rate (−37%). Conclusion: The non-steroidal FXR agonist cilofexor decreased portal hypertension and reduced liver fibrosis in NASH rats. While cilofexor seems to primarily decrease sinusoidal resistance in cirrhotic portal hypertension, the combination with propranolol additionally reduced mesenteric hyperperfusion.
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Affiliation(s)
- Philipp Schwabl
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Christian Doppler Lab for Portal Hypertension and Liver Fibrosis, Medical University of Vienna, 1090 Vienna, Austria
| | - Eva Hambruch
- Phenex Pharmaceuticals AG, 69123 Heidelberg, Germany; (E.H.); (M.B.); (C.K.)
| | - Grant R. Budas
- Gilead Sciences Inc., Foster City, CA 94404, USA; (G.R.B.); (J.T.L.); (W.J.W.); (D.G.B.)
| | - Paul Supper
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
| | | | - John T. Liles
- Gilead Sciences Inc., Foster City, CA 94404, USA; (G.R.B.); (J.T.L.); (W.J.W.); (D.G.B.)
| | - Manfred Birkel
- Phenex Pharmaceuticals AG, 69123 Heidelberg, Germany; (E.H.); (M.B.); (C.K.)
| | - Ksenia Brusilovskaya
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Christian Doppler Lab for Portal Hypertension and Liver Fibrosis, Medical University of Vienna, 1090 Vienna, Austria
| | - Philipp Königshofer
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Christian Doppler Lab for Portal Hypertension and Liver Fibrosis, Medical University of Vienna, 1090 Vienna, Austria
| | - Markus Peck-Radosavljevic
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Department of Internal Medicine and Gastroenterology (IMuG), Hepatology, Endocrinology, Rheumatology, and Nephrology with Centralized Emergency Service (ZAE), Klinikum Klagenfurt am Wörthersee, 9020 Klagenfurt, Austria
| | - William J. Watkins
- Gilead Sciences Inc., Foster City, CA 94404, USA; (G.R.B.); (J.T.L.); (W.J.W.); (D.G.B.)
| | - Michael Trauner
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
| | - David G. Breckenridge
- Gilead Sciences Inc., Foster City, CA 94404, USA; (G.R.B.); (J.T.L.); (W.J.W.); (D.G.B.)
| | - Claus Kremoser
- Phenex Pharmaceuticals AG, 69123 Heidelberg, Germany; (E.H.); (M.B.); (C.K.)
| | - Thomas Reiberger
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria; (P.S.); (P.S.); (K.B.); (P.K.); (M.P.-R.); (M.T.)
- Vienna Hepatic Experimental Hemodynamic (HEPEX) Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Christian Doppler Lab for Portal Hypertension and Liver Fibrosis, Medical University of Vienna, 1090 Vienna, Austria
- Ludwig Boltzmann Institute for Rare and Undiagnosed Diseases (LBI-RUD), 1090 Vienna, Austria
- CeMM Research Center for Molecular Medicine, The Austrian Academy of Sciences, 1090 Vienna, Austria
- Correspondence: ; Tel.: +43-1-40400-47410
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5
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Bates J, Vijayakumar A, Ghoshal S, Marchand B, Yi S, Kornyeyev D, Zagorska A, Hollenback D, Walker K, Liu K, Pendem S, Newstrom D, Brockett R, Mikaelian I, Kusam S, Ramirez R, Lopez D, Li L, Fuchs BC, Breckenridge DG. Acetyl-CoA carboxylase inhibition disrupts metabolic reprogramming during hepatic stellate cell activation. J Hepatol 2020; 73:896-905. [PMID: 32376414 DOI: 10.1016/j.jhep.2020.04.037] [Citation(s) in RCA: 108] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/22/2020] [Accepted: 04/23/2020] [Indexed: 12/16/2022]
Abstract
BACKGROUND & AIMS Non-alcoholic steatohepatitis (NASH) is a chronic liver disease characterized by hepatic lipid accumulation, inflammation, and progressive fibrosis. Acetyl-CoA carboxylase (ACC) catalyzes the rate-limiting step of de novo lipogenesis and regulates fatty acid β-oxidation in hepatocytes. ACC inhibition reduces hepatic fat content and markers of liver injury in patients with NASH; however, the effect of ACC inhibition on liver fibrosis has not been reported. METHODS A direct role for ACC in fibrosis was evaluated by measuring de novo lipogenesis, procollagen production, gene expression, glycolysis, and mitochondrial respiration in hepatic stellate cells (HSCs) in the absence or presence of small molecule inhibitors of ACC. ACC inhibitors were evaluated in rodent models of liver fibrosis induced by diet or the hepatotoxin, diethylnitrosamine. Fibrosis and hepatic steatosis were evaluated by histological and biochemical assessments. RESULTS Inhibition of ACC reduced the activation of TGF-β-stimulated HSCs, as measured by both α-SMA expression and collagen production. ACC inhibition prevented a metabolic switch necessary for induction of glycolysis and oxidative phosphorylation during HSC activation. While the molecular mechanism by which inhibition of de novo lipogenesis blocks glycolysis and oxidative phosphorylation is unknown, we definitively show that HSCs require de novo lipogenesis for activation. Consistent with this direct antifibrotic mechanism in HSCs, ACC inhibition reduced liver fibrosis in a rat choline-deficient, high-fat diet model and in response to chronic diethylnitrosamine-induced liver injury (in the absence of hepatic lipid accumulation). CONCLUSIONS In addition to reducing lipid accumulation in hepatocytes, ACC inhibition also directly impairs the profibrogenic activity of HSCs. Thus, small molecule inhibitors of ACC may lessen fibrosis by reducing lipotoxicity in hepatocytes and by preventing HSC activation, providing a mechanistic rationale for the treatment of patients with advanced liver fibrosis due to NASH. LAY SUMMARY Hepatic fibrosis is the most important predictor of liver-related outcomes in patients with non-alcoholic steatohepatitis (NASH). Small molecule inhibitors of acetyl-CoA carboxylase (ACC) reduce hepatic fat content and markers of liver injury in patients with NASH. Herein, we report that inhibition of ACC and de novo lipogenesis also directly suppress the activation of hepatic stellate cells - the primary cell responsible for generating fibrotic scar in the liver - and thus fibrosis. These data provide further evidence for the use of ACC inhibitors to treat patients with NASH and advanced fibrosis.
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Affiliation(s)
| | | | - Sarani Ghoshal
- Massachusetts General Hospital, Boston, MA, USA; Synlogic Therapeutics, Cambridge, MA, USA
| | | | - Saili Yi
- Gilead Sciences, Foster City, CA, USA
| | | | | | | | | | - Kathy Liu
- Gilead Sciences, Foster City, CA, USA
| | | | - David Newstrom
- Gilead Sciences, Foster City, CA, USA; Advanced Cell Diagnostics (ACD), Newark, CA, USA
| | - Robert Brockett
- Gilead Sciences, Foster City, CA, USA; Visiopharm, Westminster, CO, USA
| | - Igor Mikaelian
- Gilead Sciences, Foster City, CA, USA; 23andMe, San Mateo, CA, USA
| | | | | | | | - Li Li
- Gilead Sciences, Foster City, CA, USA
| | - Bryan C Fuchs
- Massachusetts General Hospital, Boston, MA, USA; Ferring Pharmaceuticals, San Diego, CA, USA
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6
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Dobie R, Wilson-Kanamori JR, Henderson BEP, Smith JR, Matchett KP, Portman JR, Wallenborg K, Picelli S, Zagorska A, Pendem SV, Hudson TE, Wu MM, Budas GR, Breckenridge DG, Harrison EM, Mole DJ, Wigmore SJ, Ramachandran P, Ponting CP, Teichmann SA, Marioni JC, Henderson NC. Single-Cell Transcriptomics Uncovers Zonation of Function in the Mesenchyme during Liver Fibrosis. Cell Rep 2019; 29:1832-1847.e8. [PMID: 31722201 PMCID: PMC6856722 DOI: 10.1016/j.celrep.2019.10.024] [Citation(s) in RCA: 209] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 08/26/2019] [Accepted: 10/07/2019] [Indexed: 12/11/2022] Open
Abstract
Iterative liver injury results in progressive fibrosis disrupting hepatic architecture, regeneration potential, and liver function. Hepatic stellate cells (HSCs) are a major source of pathological matrix during fibrosis and are thought to be a functionally homogeneous population. Here, we use single-cell RNA sequencing to deconvolve the hepatic mesenchyme in healthy and fibrotic mouse liver, revealing spatial zonation of HSCs across the hepatic lobule. Furthermore, we show that HSCs partition into topographically diametric lobule regions, designated portal vein-associated HSCs (PaHSCs) and central vein-associated HSCs (CaHSCs). Importantly we uncover functional zonation, identifying CaHSCs as the dominant pathogenic collagen-producing cells in a mouse model of centrilobular fibrosis. Finally, we identify LPAR1 as a therapeutic target on collagen-producing CaHSCs, demonstrating that blockade of LPAR1 inhibits liver fibrosis in a rodent NASH model. Taken together, our work illustrates the power of single-cell transcriptomics to resolve the key collagen-producing cells driving liver fibrosis with high precision.
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Affiliation(s)
- Ross Dobie
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - John R Wilson-Kanamori
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Beth E P Henderson
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - James R Smith
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Kylie P Matchett
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Jordan R Portman
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Karolina Wallenborg
- Karolinska Institutet (KI), Science for Life Laboratory, Tomtebodavägen 23, Solna 171 65, Sweden
| | - Simone Picelli
- Karolinska Institutet (KI), Science for Life Laboratory, Tomtebodavägen 23, Solna 171 65, Sweden
| | | | | | | | | | | | | | - Ewen M Harrison
- Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Damian J Mole
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK; Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Stephen J Wigmore
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK; Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Prakash Ramachandran
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Chris P Ponting
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine at the University of Edinburgh, Edinburgh EH4 2XU, UK; Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Sarah A Teichmann
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SA, UK; European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge CB10 1SD, UK; Theory of Condensed Matter Group, The Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - John C Marioni
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SA, UK; European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge CB10 1SD, UK; Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge CB2 0RE, UK
| | - Neil C Henderson
- Centre for Inflammation Research, The Queen's Medical Research Institute, Edinburgh BioQuarter, University of Edinburgh, Edinburgh EH16 4TJ, UK.
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7
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Sperandio D, Aktoudianakis V, Babaoglu K, Chen X, Elbel K, Chin G, Corkey B, Du J, Jiang B, Kobayashi T, Mackman R, Martinez R, Yang H, Zablocki J, Kusam S, Jordan K, Webb H, Bates JG, Lad L, Mish M, Niedziela-Majka A, Metobo S, Sapre A, Hung M, Jin D, Fung W, Kan E, Eisenberg G, Larson N, Newby ZER, Lansdon E, Tay C, Neve RM, Shevick SL, Breckenridge DG. Structure-guided discovery of a novel, potent, and orally bioavailable 3,5-dimethylisoxazole aryl-benzimidazole BET bromodomain inhibitor. Bioorg Med Chem 2018; 27:457-469. [PMID: 30606676 DOI: 10.1016/j.bmc.2018.11.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 12/12/2022]
Abstract
The bromodomain and extra-terminal (BET) family of proteins, consisting of the bromodomains containing protein 2 (BRD2), BRD3, BRD4, and the testis-specific BRDT, are key epigenetic regulators of gene transcription and has emerged as an attractive target for anticancer therapy. Herein, we describe the discovery of a novel potent BET bromodomain inhibitor, using a systematic structure-based approach focused on improving potency, metabolic stability, and permeability. The optimized dimethylisoxazole aryl-benzimidazole inhibitor exhibited high potency towards BRD4 and related BET proteins in biochemical and cell-based assays and inhibited tumor growth in two proof-of-concept preclinical animal models.
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Affiliation(s)
- David Sperandio
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA.
| | - Vangelis Aktoudianakis
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Kerim Babaoglu
- Department of Structural Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Xiaowu Chen
- Department of Structural Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Kristyna Elbel
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Gregory Chin
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Britton Corkey
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Jinfa Du
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Bob Jiang
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Tetsuya Kobayashi
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Richard Mackman
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Ruben Martinez
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Hai Yang
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Jeff Zablocki
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Saritha Kusam
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Kim Jordan
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Heather Webb
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Jamie G Bates
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Latesh Lad
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Michael Mish
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Anita Niedziela-Majka
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Sammy Metobo
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Annapurna Sapre
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Magdeleine Hung
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Debi Jin
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Wanchi Fung
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Elaine Kan
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Gene Eisenberg
- Department of Drug Metabolism, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Nate Larson
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Zachary E R Newby
- Department of Structural Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Eric Lansdon
- Department of Structural Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Chin Tay
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Richard M Neve
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - Sophia L Shevick
- Department of Medicinal Chemistry, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
| | - David G Breckenridge
- Department of Biology, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA
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8
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Liles JT, Corkey BK, Notte GT, Budas GR, Lansdon EB, Hinojosa-Kirschenbaum F, Badal SS, Lee M, Schultz BE, Wise S, Pendem S, Graupe M, Castonguay L, Koch KA, Wong MH, Papalia GA, French DM, Sullivan T, Huntzicker EG, Ma FY, Nikolic-Paterson DJ, Altuhaifi T, Yang H, Fogo AB, Breckenridge DG. ASK1 contributes to fibrosis and dysfunction in models of kidney disease. J Clin Invest 2018; 128:4485-4500. [PMID: 30024858 DOI: 10.1172/jci99768] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 07/13/2018] [Indexed: 12/14/2022] Open
Abstract
Oxidative stress is an underlying component of acute and chronic kidney disease. Apoptosis signal-regulating kinase 1 (ASK1) is a widely expressed redox-sensitive serine threonine kinase that activates p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase kinases, and induces apoptotic, inflammatory, and fibrotic signaling in settings of oxidative stress. We describe the discovery and characterization of a potent and selective small-molecule inhibitor of ASK1, GS-444217, and demonstrate the therapeutic potential of ASK1 inhibition to reduce kidney injury and fibrosis. Activation of the ASK1 pathway in glomerular and tubular compartments was confirmed in renal biopsies from patients with diabetic kidney disease (DKD) and was decreased by GS-444217 in several rodent models of kidney injury and fibrosis that collectively represented the hallmarks of DKD pathology. Treatment with GS-444217 reduced progressive inflammation and fibrosis in the kidney and halted glomerular filtration rate decline. Combination of GS-444217 with enalapril, an angiotensin-converting enzyme inhibitor, led to a greater reduction in proteinuria and regression of glomerulosclerosis. These results identify ASK1 as an important target for renal disease and support the clinical development of an ASK1 inhibitor for the treatment of DKD.
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Affiliation(s)
| | | | | | | | | | | | | | - Michael Lee
- Gilead Sciences, Foster City, California, USA
| | | | - Sarah Wise
- Gilead Sciences, Foster City, California, USA
| | | | | | | | - Keith A Koch
- Consortium for Fibrosis Research and Translation, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | | | | | | | | | | | - Frank Y Ma
- Department of Nephrology and Monash University Centres for Inflammatory Diseases, Monash Medical Centre, Clayton, Victoria, Australia
| | - David J Nikolic-Paterson
- Department of Nephrology and Monash University Centres for Inflammatory Diseases, Monash Medical Centre, Clayton, Victoria, Australia
| | - Tareq Altuhaifi
- College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| | - Haichun Yang
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Agnes B Fogo
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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9
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Amos LA, Ma FY, Tesch GH, Liles JT, Breckenridge DG, Nikolic-Paterson DJ, Han Y. ASK1 inhibitor treatment suppresses p38/JNK signalling with reduced kidney inflammation and fibrosis in rat crescentic glomerulonephritis. J Cell Mol Med 2018; 22:4522-4533. [PMID: 29998485 PMCID: PMC6111820 DOI: 10.1111/jcmm.13705] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 04/29/2018] [Indexed: 12/15/2022] Open
Abstract
Activation of p38 mitogen‐activated protein kinase (MAPK) and c‐Jun amino terminal kinase (JNK) is prominent in human crescentic glomerulonephritis. p38 and JNK inhibitors suppress crescentic disease in animal models; however, the upstream mechanisms inducing activation of these kinases in crescentic glomerulonephritis are unknown. We investigated the hypothesis that apoptosis signal‐regulating kinase 1 (ASK1/MAP3K5) promote p38/JNK activation and renal injury in models of nephrotoxic serum nephritis (NTN); acute glomerular injury in SD rats, and crescentic disease in WKY rats. Treatment with the selective ASK1 inhibitor, GS‐444217 or vehicle began 1 hour before nephrotoxic serum injection and continued until animals were killed on day 1 (SD rats) or 14 (WKY rats). NTN resulted in phosphorylation (activation) of p38 and c‐Jun in both models which was substantially reduced by ASK1 inhibitor treatment. In SD rats, GS‐444217 prevented proteinuria and glomerular thrombosis with suppression of macrophage activation on day 1 NTN. In WKY rats, GS‐444217 reduced crescent formation, prevented renal impairment and reduced proteinuria on day 14 NTN. Macrophage activation, T‐cell infiltration and renal fibrosis were also reduced by GS‐444217. In conclusion, GS‐444217 treatment inhibited p38/JNK activation and development of renal injury in rat NTN. ASK1 inhibitors may have therapeutic potential in rapidly progressive glomerulonephritis.
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Affiliation(s)
- Liv A Amos
- Department of Nephrology, Monash Medical Centre, Clayton, Vic., 3168, Australia.,Monash University Centre for Inflammatory Diseases, Monash Medical Centre, Clayton, Vic., 3168, Australia
| | - Frank Y Ma
- Department of Nephrology, Monash Medical Centre, Clayton, Vic., 3168, Australia.,Monash University Centre for Inflammatory Diseases, Monash Medical Centre, Clayton, Vic., 3168, Australia
| | - Greg H Tesch
- Department of Nephrology, Monash Medical Centre, Clayton, Vic., 3168, Australia.,Monash University Centre for Inflammatory Diseases, Monash Medical Centre, Clayton, Vic., 3168, Australia
| | | | | | - David J Nikolic-Paterson
- Department of Nephrology, Monash Medical Centre, Clayton, Vic., 3168, Australia.,Monash University Centre for Inflammatory Diseases, Monash Medical Centre, Clayton, Vic., 3168, Australia
| | - Yingjie Han
- Department of Nephrology, Monash Medical Centre, Clayton, Vic., 3168, Australia.,Monash University Centre for Inflammatory Diseases, Monash Medical Centre, Clayton, Vic., 3168, Australia
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10
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Yin M, Zhou HJ, Zhang J, Lin C, Li H, Li X, Li Y, Zhang H, Breckenridge DG, Ji W, Min W. ASK1-dependent endothelial cell activation is critical in ovarian cancer growth and metastasis. JCI Insight 2017; 2:91828. [PMID: 28931753 DOI: 10.1172/jci.insight.91828] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 08/11/2017] [Indexed: 02/06/2023] Open
Abstract
We have recently reported that tumor-associated macrophages (TAMs) promote early transcoelomic metastasis of ovarian cancer by facilitating TAM-ovarian cancer cell spheroid formation. ASK1 is known to be important for macrophage activation and inflammation-mediated tumorigenesis. In the present study, we show that ASK1 deficiency attenuates TAM-spheroid formation and ovarian cancer progression in an orthotopic ovarian cancer model. Interestingly, ASK1 in stroma, but not in TAMs, is critical for peritoneal tumor growth of ovarian cancer. Moreover, overexpression of an ASK1 inhibitory protein (suppressor of cytokine signaling-1; SOCS1) in vascular endothelium attenuates vascular permeability, TAM infiltration, and ovarian cancer growth. Mechanistically, we show that ASK1 mediates degradation of endothelial junction protein VE-cadherin via a lysosomal pathway to promote macrophage transmigration. Importantly, a pharmacological ASK1 inhibitor prevents tumor-induced vascular leakage, macrophage infiltration, and tumor growth in two mouse models. Since transcoelomic metastasis is also associated with many other cancers, such as pancreatic and colon cancers, our study provides ASK1 as a therapeutic target for the treatment of ovarian cancer and other transcoelomic metastasis cancers.
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Affiliation(s)
- Mingzhu Yin
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Huanjiao Jenny Zhou
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Jiqin Zhang
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Translational Medicine, The First Affiliated Hospital, and
| | - Caixia Lin
- Center for Translational Medicine, The First Affiliated Hospital, and
| | - Hongmei Li
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Xia Li
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Yonghao Li
- Zhongshan Ophthalmology Hospital, Sun Yat-sen University, Guangzhou, China
| | - Haifeng Zhang
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | | | - Weidong Ji
- Center for Translational Medicine, The First Affiliated Hospital, and
| | - Wang Min
- Department of Pathology and the Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Translational Medicine, The First Affiliated Hospital, and
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11
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Tesch GH, Ma FY, Han Y, Liles JT, Breckenridge DG, Nikolic-Paterson DJ. ASK1 Inhibitor Halts Progression of Diabetic Nephropathy in Nos3-Deficient Mice. Diabetes 2015; 64:3903-13. [PMID: 26180085 DOI: 10.2337/db15-0384] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/06/2015] [Indexed: 01/04/2023]
Abstract
p38 mitogen-activated protein kinase (MAPK) signaling promotes diabetic kidney injury. Apoptosis signal-regulating kinase (ASK)1 is one of the upstream kinases in the p38 MAPK-signaling pathway, which is activated by inflammation and oxidative stress, suggesting a possible role for ASK1 in diabetic nephropathy. In this study, we examined whether a selective ASK1 inhibitor can prevent the induction and progression of diabetic nephropathy in mice. Diabetes was induced in hypertensive endothelial nitric oxide synthase (Nos3)-deficient mice by five low-dose streptozotocin (STZ) injections. Groups of diabetic Nos3(-/-) mice received ASK1 inhibitor (GS-444217 delivered in chow) as an early intervention (2-8 weeks after STZ) or late intervention (weeks 8-15 after STZ). Control diabetic and nondiabetic Nos3(-/-) mice received normal chow. Treatment with GS-444217 abrogated p38 MAPK activation in diabetic kidneys but had no effect upon hypertension in Nos3(-/-) mice. Early intervention with GS-444217 significantly inhibited diabetic glomerulosclerosis and reduced renal dysfunction but had no effect on the development of albuminuria. Late intervention with GS-444217 improved renal function and halted the progression of glomerulosclerosis, renal inflammation, and tubular injury despite having no effect on established albuminuria. In conclusion, this study identifies ASK1 as a new therapeutic target in diabetic nephropathy to reduce renal inflammation and fibrosis independent of blood pressure control.
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Affiliation(s)
- Greg H Tesch
- Department of Nephrology, Monash Medical Centre, Clayton, Victoria, Australia Monash University Department of Medicine, Clayton, Victoria, Australia
| | - Frank Y Ma
- Department of Nephrology, Monash Medical Centre, Clayton, Victoria, Australia Monash University Department of Medicine, Clayton, Victoria, Australia
| | - Yingjie Han
- Department of Nephrology, Monash Medical Centre, Clayton, Victoria, Australia Monash University Department of Medicine, Clayton, Victoria, Australia
| | | | | | - David J Nikolic-Paterson
- Department of Nephrology, Monash Medical Centre, Clayton, Victoria, Australia Monash University Department of Medicine, Clayton, Victoria, Australia
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12
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Xie Y, Ramachandran A, Breckenridge DG, Liles JT, Lebofsky M, Farhood A, Jaeschke H. Inhibitor of apoptosis signal-regulating kinase 1 protects against acetaminophen-induced liver injury. Toxicol Appl Pharmacol 2015; 286:1-9. [PMID: 25818599 DOI: 10.1016/j.taap.2015.03.019] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 03/15/2015] [Accepted: 03/16/2015] [Indexed: 02/08/2023]
Abstract
Metabolic activation and oxidant stress are key events in the pathophysiology of acetaminophen (APAP) hepatotoxicity. The initial mitochondrial oxidative stress triggered by protein adduct formation is amplified by c-jun-N-terminal kinase (JNK), resulting in mitochondrial dysfunction and ultimately cell necrosis. Apoptosis signal-regulating kinase 1 (ASK1) is considered the link between oxidant stress and JNK activation. The objective of the current study was to assess the efficacy and mechanism of action of the small-molecule ASK1 inhibitor GS-459679 in a murine model of APAP hepatotoxicity. APAP (300 mg/kg) caused extensive glutathione depletion, JNK activation and translocation to the mitochondria, oxidant stress and liver injury as indicated by plasma ALT activities and area of necrosis over a 24h observation period. Pretreatment with 30 mg/kg of GS-459679 almost completely prevented JNK activation, oxidant stress and injury without affecting the metabolic activation of APAP. To evaluate the therapeutic potential of GS-459679, mice were treated with APAP and then with the inhibitor. Given 1.5h after APAP, GS-459679 was still protective, which was paralleled by reduced JNK activation and p-JNK translocation to mitochondria. However, GS-459679 treatment was not more effective than N-acetylcysteine, and the combination of GS-459679 and N-acetylcysteine exhibited similar efficacy as N-acetylcysteine monotherapy, suggesting that GS-459769 and N-acetylcysteine affect the same pathway. Importantly, inhibition of ASK1 did not impair liver regeneration as indicated by PCNA staining. In conclusion, the ASK1 inhibitor GS-459679 protected against APAP toxicity by attenuating JNK activation and oxidant stress in mice and may have therapeutic potential for APAP overdose patients.
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Affiliation(s)
- Yuchao Xie
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
| | - Anup Ramachandran
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
| | | | - John T Liles
- Department of Biology, Gilead Sciences, Inc., Foster City, CA, USA
| | - Margitta Lebofsky
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
| | - Anwar Farhood
- Department of Pathology, St. David's North Austin Medical Center, Austin, TX 78756, USA
| | - Hartmut Jaeschke
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
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13
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Toldo S, Breckenridge DG, Mezzaroma E, Van Tassell BW, Shryock J, Kannan H, Phan D, Budas G, Farkas D, Lesnefsky E, Voelkel N, Abbate A. Inhibition of apoptosis signal-regulating kinase 1 reduces myocardial ischemia-reperfusion injury in the mouse. J Am Heart Assoc 2012; 1:e002360. [PMID: 23316291 PMCID: PMC3541620 DOI: 10.1161/jaha.112.002360] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 08/06/2012] [Indexed: 01/08/2023]
Abstract
Background Despite the clear advantages of reperfusion in acute myocardial infarction, part of the myocardium is injured during reperfusion by reactive oxygen species. Reactive oxygen species activate apoptosis signal–regulating kinase-1, a key mediator in cell death. We hypothesized that inhibition of apoptosis signal–regulating kinase-1 at the time of reperfusion would protect the heart from ischemia–reperfusion injury. Methods and Results Male CD1 mice underwent transient coronary artery ligation (30 minutes) followed by reperfusion or underwent sham surgery (n=10 to 12 per group). A selective small-molecule inhibitor of apoptosis signal–regulating kinase-1 (GS-459679) was given immediately after reperfusion (10 or 30 mg/kg IP). Infarct size was measured early (at 24 hours, in a subgroup of mice) by triphenyl tetrazolium chloride staining and late (at 7 days) by Masson's trichrome staining for fibrosis. Apoptosis was assessed by measurement of caspase-3 activity and by determination of DNA fragmentation in cardiomyocytes bordering the infarct. Transthoracic echocardiography was performed before surgery and then at 24 hours and 7 days later. Treatment with GS-459679 at reperfusion led to a significant dose-related reduction in infarct size (31% for 10 mg/kg [P<0.001 versus vehicle] and 60% for 30 mg/kg [P<0.001 versus vehicle]), inhibition of apoptotic cell death, and preservation of left ventricular dimension and systolic function at both 24 hours and 7 days. Conclusions Inhibition of apoptosis signal–regulating kinase-1 at the time of reperfusion limits infarct size and preserves left ventricular function in a model of acute myocardial infarction in the mouse.
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Affiliation(s)
- Stefano Toldo
- VCU Pauley Heart Center, Virginia Commonwealth University, Richmond, VA 23298, USA.
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14
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Gerczuk PZ, Breckenridge DG, Liles JT, Shryock JC, Belardinelli L, Kloner RA, Dai W. An apoptosis signal‐regulating kinase 1 inhibitor reduces cardiomyocyte apoptosis and infarct size in a rat ischemia‐reperfusion model. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.1114.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | | | | | - Wangde Dai
- Heart InstituteGood Samaritan HospitalLos AngelesCA
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15
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Breckenridge DG, Kang BH, Kokel D, Mitani S, Staehelin LA, Xue D. Caenorhabditis elegans drp-1 and fis-2 regulate distinct cell-death execution pathways downstream of ced-3 and independent of ced-9. Mol Cell 2008; 31:586-597. [PMID: 18722182 DOI: 10.1016/j.molcel.2008.07.015] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 05/12/2008] [Accepted: 07/28/2008] [Indexed: 12/31/2022]
Abstract
The dynamin family of GTPases regulate mitochondrial fission and fusion processes and have been implicated in controlling the release of caspase activators from mitochondria during apoptosis. Here we report that profusion genes fzo-1 and eat-3 or the profission gene drp-1 are not required for apoptosis activation in C. elegans. However, minor proapoptotic roles for drp-1 and fis-2, a homolog of human Fis1, are revealed in sensitized genetic backgrounds. drp-1 and fis-2 function independent of one another and the Bcl-2 homolog CED-9 and downstream of the CED-3 caspase to promote elimination of mitochondria in dying cells, an event that could facilitate cell-death execution. Interestingly, CED-3 can cleave DRP-1, which appears to be important for DRP-1's proapoptotic function, but not its mitochondria fission function. Our findings demonstrate that mitochondria dynamics do not regulate apoptosis activation in C. elegans and reveal distinct roles for drp-1 and fis-2 as mediators of cell-death execution downstream of caspase activation.
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Affiliation(s)
- David G Breckenridge
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Byung-Ho Kang
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Department of Microbiology and Cell Science, Integrated Center for Biotechnology Research, University of Florida, Gainesville, FL 32608, USA
| | - David Kokel
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University, School of Medicine, and CREST, JST, Tokyo, 162-8666, Japan
| | - L Andrew Staehelin
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Ding Xue
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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16
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Abstract
Mitochondria play an important role in the integration and transmission of cell death signals, activating caspases and other cell death execution events by releasing apoptogenic proteins from the intermembrane space. The BCL-2 family of proteins localize (or can be targeted) to mitochondria and regulate the permeability of the mitochondrial outer membrane to these apoptotic factors. Recent evidence suggests that multiple mechanisms may regulate the release of mitochondrial factors, some of which depend on the action of caspases.
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Affiliation(s)
- David G Breckenridge
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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17
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Abstract
Apoptotic programmed cell death pathways are activated by a diverse array of cell extrinsic and intrinsic signals, most of which are ultimately coupled to the activation of effector caspases. In many instances, this involves an obligate propagation through mitochondria, causing egress of critical proapoptotic regulators to the cytosol. Central to the regulation of the mitochondrial checkpoint is a complex three-way interplay between members of the BCL-2 family, which are comprised of an antiapoptotic subgroup including BCL-2 itself, and the proapoptotic BAX,BAK and BH3-domain-only subgroups. Constituents of all three of these BCL-2 classes, however, also converge on the endoplasmic reticulum (ER), an organelle whose critical contributions to apoptosis is only now becoming apparent. In addition to propagating death-inducing stress signals itself, the ER also contributes in a fundamental way to Fas-mediated apoptosis and to p53-dependent pathways resulting from DNA damage and oncogene expression. Mobilization of ER calcium stores can initiate the activation of cytoplasmic death pathways as well as sensitize mitochondria to direct proapoptotic stimuli. Additionally, the existence of BCL-2-regulated initiator procaspase activation complexes at the ER membrane has also been described. Here, we review the potential underlying mechanisms involved in these events and discuss pathways for ER-mitochondrial crosstalk pertinent to a number of cell death stimuli.
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Affiliation(s)
- David G Breckenridge
- Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Quebec, Canada H3G 1Y6
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18
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Wang B, Nguyen M, Breckenridge DG, Stojanovic M, Clemons PA, Kuppig S, Shore GC. Uncleaved BAP31 in association with A4 protein at the endoplasmic reticulum is an inhibitor of Fas-initiated release of cytochrome c from mitochondria. J Biol Chem 2003; 278:14461-8. [PMID: 12529377 DOI: 10.1074/jbc.m209684200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BAP31 is a polytopic integral protein of the endoplasmic reticulum membrane and, like BID, is a preferred substrate of caspase-8. Upon Fas/CD95 stimulation, BAP31 is cleaved within its cytosolic domain, generating proapoptotic p20 BAP31. In human KB epithelial cells expressing the caspase-resistant mutant crBAP31, Fas stimulation resulted in cleavage of BID and insertion of BAX into mitochondrial membrane, but subsequent oligomerization of BAX and BAK, egress of cytochrome c to the cytosol, and apoptosis were impaired. Bap31-null mouse cells expressing crBAP31 cannot generate the endogenous p20 BAP31 cleavage product, yet crBAP31 conferred resistance to cellular condensation and cytochrome c release in response to activation of ectopic FKBPcasp8 by FK1012z. Full-length BAP31, therefore, is a direct inhibitor of these caspase-8-initiated events, acting independently of its ability to sequester p20, with which it interacts. Employing a novel split ubiquitin yeast two-hybrid screen for BAP31-interacting membrane proteins, the putative ion channel protein of the endoplasmic reticulum, A4, was detected and identified as a constitutive binding partner of BAP31 in human cells. Ectopic A4 that was introduced into A4-deficient cells cooperated with crBAP31 to resist Fas-induced egress of cytochrome c from mitochondria and cytoplasmic apoptosis.
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Affiliation(s)
- Bing Wang
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y, Canada
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19
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Breckenridge DG, Stojanovic M, Marcellus RC, Shore GC. Caspase cleavage product of BAP31 induces mitochondrial fission through endoplasmic reticulum calcium signals, enhancing cytochrome c release to the cytosol. J Cell Biol 2003; 160:1115-27. [PMID: 12668660 PMCID: PMC2172754 DOI: 10.1083/jcb.200212059] [Citation(s) in RCA: 415] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Stimulation of cell surface death receptors activates caspase-8, which targets a limited number of substrates including BAP31, an integral membrane protein of the endoplasmic reticulum (ER). Recently, we reported that a caspase-resistant BAP31 mutant inhibited several features of Fas-induced apoptosis, including the release of cytochrome c (cyt.c) from mitochondria (Nguyen, M., D.G. Breckenridge, A. Ducret, and G.C. Shore. 2000. Mol. Cell. Biol. 20:6731-6740), implicating ER-mitochondria crosstalk in this pathway. Here, we report that the p20 caspase cleavage fragment of BAP31 can direct pro-apoptotic signals between the ER and mitochondria. Adenoviral expression of p20 caused an early release of Ca2+ from the ER, concomitant uptake of Ca2+ into mitochondria, and mitochondrial recruitment of Drp1, a dynamin-related protein that mediates scission of the outer mitochondrial membrane, resulting in dramatic fragmentation and fission of the mitochondrial network. Inhibition of Drp1 or ER-mitochondrial Ca2+ signaling prevented p20-induced fission of mitochondria. p20 strongly sensitized mitochondria to caspase-8-induced cyt.c release, whereas prolonged expression of p20 on its own ultimately induced caspase activation and apoptosis through the mitochondrial apoptosome stress pathway. Therefore, caspase-8 cleavage of BAP31 at the ER stimulates Ca2+-dependent mitochondrial fission, enhancing the release of cyt.c in response to this initiator caspase.
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Ducret A, Nguyen M, Breckenridge DG, Shore GC. The resident endoplasmic reticulum protein, BAP31, associates with gamma-actin and myosin B heavy chain. Eur J Biochem 2003; 270:342-9. [PMID: 12605685 DOI: 10.1046/j.1432-1033.2003.03395.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulum whose cytosolic domain contains two caspase recognition sites that are preferentially cleaved by initiator caspases, such as caspase-8. Recently, we reported that the caspase-resistant BAP31 inhibited Fas-mediated apoptotic membrane fragmentation and the release of cytochrome c from mitochondria in KB epithelial cells (Nguyen M., Breckenridge G., Ducret A & Shore G. (2000) Mol. Cell. Biol.20, 6731-6740). We describe here the characterization by capillary liquid chromatography microelectrospray tandem MS of a BAP31 immunocomplex isolated from a HepG2 cell lysate in the absence of a death signal. We show that BAP31 specifically associates with nonmuscle myosin heavy chain B and nonmuscle gamma-actin, two components of the cytoskeleton actomyosin complex. Collectively, these data confirm that BAP31, in addition to its potential role as a chaperone, may play a fundamental role in the structural organization of the cytoplasm. Here we also show that Fas stimulation of apoptosis releases BAP31 associations with these motor proteins, a step that may contribute to extranuclear events, such as membrane remodelling, during the execution phase of apoptosis.
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Affiliation(s)
- Axel Ducret
- Merck Frosst Center for Therapeutic Research, Pointe-Claire-Dorval, Québec, Canada.
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Breckenridge DG, Nguyen M, Kuppig S, Reth M, Shore GC. The procaspase-8 isoform, procaspase-8L, recruited to the BAP31 complex at the endoplasmic reticulum. Proc Natl Acad Sci U S A 2002; 99:4331-6. [PMID: 11917123 PMCID: PMC123648 DOI: 10.1073/pnas.072088099] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
BAP31 is an integral protein of the endoplasmic reticulum membrane and a substrate of caspase-8. Here, we describe the procaspase-8 isoform, procaspase-8L, which is ubiquitously expressed and selectively recruited to the BAP31 complex in response to apoptotic signaling by E1A. Procaspase-8L is characterized by the N-terminal extension (Nex) domain, which extends procaspase-8/a at the N terminus and is required for selective association of procaspase-8L with the BAP31 complex. Gene deletion identified BAP31 and related BAP29 as required for processing of procaspase-8L in response to E1A, by a FADD-independent mechanism that was blocked by BCL-2. Further, Bap29,31 deletion, as well as a Nex-domain dominant-negative mutant, curtailed the activation of downstream caspases (IETDase and DEVDase) and cell death in response to E1A. Preferential recruitment of procaspase-8L by the BAP31 complex at the endoplasmic reticulum suggests an additional pathway for regulating initiator caspase-8 during apoptosis.
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Affiliation(s)
- David G Breckenridge
- Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, QC, Canada H3G 1Y6
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Abstract
E1A and c-myc are oncogenes that can deregulate the cell cycle and promote transformation under conditions where normal cell-cycle checkpoints are inactivated. In situations where cell-cycle checkpoints are intact, the E1A and c-Myc proteins potently induce apoptosis, a property that is believed to be the end result of a cellular response to uncontrolled growth-promoting signals. p53 is a key regulator of E1A and c-myc-induced apoptosis and, together with the oncoproteins, may transcriptionally activate numerous genes whose products influence, or are themselves, members of the core apoptotic machinery. The upstream signaling events and the ultimate apoptotic pathways activated by E1A and c-Myc are discussed in this review.
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Affiliation(s)
- D G Breckenridge
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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Ruffolo SC, Breckenridge DG, Nguyen M, Goping IS, Gross A, Korsmeyer SJ, Li H, Yuan J, Shore GC. BID-dependent and BID-independent pathways for BAX insertion into mitochondria. Cell Death Differ 2000; 7:1101-8. [PMID: 11139284 DOI: 10.1038/sj.cdd.4400739] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In the absence of an apoptotic signal, BAX adopts a conformation that constrains the protein from integrating into mitochondrial membranes. Here, we show that caspases, including caspase-8, can initiate BAX insertion into mitochondria in vivo and in vitro. The cleavage product of caspase-8, tBID, induced insertion of BAX into mitochondria in vivo, and reconstitution in vitro showed that tBID, either directly or indirectly, relieved inhibition of the BAX transmembrane signal-anchor by the NH2-terminal domain, resulting in integration of BAX into mitochondrial membrane. In contrast to these findings, however, Bid-null mouse embryo fibroblasts supported Bax insertion into mitochondria in response to death signaling by either TNFalpha or E1A, despite the fact that cytochrome c release from the organelle was inhibited. We conclude, therefore, that a parallel Bid-independent pathway exists in these cells for mitochondrial insertion of Bax and that, in the absence of Bid, cytochrome c release can be uncoupled from Bax membrane insertion.
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Affiliation(s)
- S C Ruffolo
- Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Quebec, Canada H3G 1Y6
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Nguyen M, Breckenridge DG, Ducret A, Shore GC. Caspase-resistant BAP31 inhibits fas-mediated apoptotic membrane fragmentation and release of cytochrome c from mitochondria. Mol Cell Biol 2000; 20:6731-40. [PMID: 10958671 PMCID: PMC86192 DOI: 10.1128/mcb.20.18.6731-6740.2000] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulum whose cytosolic domain contains two identical caspase recognition sites (AAVD.G) that are preferentially cleaved by initiator caspases, including caspase 8. Cleavage of BAP31 during apoptosis generates a p20 fragment that remains integrated in the membrane and, when expressed ectopically, is a potent inducer of cell death. To examine the consequences of maintaining the structural integrity of BAP31 during apoptosis, the caspase recognition aspartate residues were mutated to alanine residues, and Fas-mediated activation of caspase 8 and cell death were examined in human KB epithelial cells stably expressing the caspase-resistant mutant crBAP31. crBAP31 only modestly slowed the time course for activation of caspases, as assayed by the processing of procaspases 8 and 3 and the measurement of total DEVDase activity. As a result, cleavage of the caspase targets poly(ADP-ribosyl) polymerase and endogenous BAP31, as well as the redistribution of phosphatidylserine and fragmentation of DNA, was observed. In contrast, cytoplasmic membrane blebbing and fragmentation and apoptotic redistribution of actin were strongly inhibited, cell morphology was retained near normal, and the irreversible loss of cell growth potential following removal of the Fas stimulus was delayed. Of note, crBAP31-expressing cells also resisted Fas-mediated release of cytochrome c from mitochondria, and the mitochondrial electrochemical potential was only partly reduced. These results argue that BAP31 cleavage is important for manifesting cytoplasmic apoptotic events associated with membrane fragmentation and reveal an unexpected cross talk between mitochondria and the endoplasmic reticulum during Fas-mediated apoptosis in vivo.
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Affiliation(s)
- M Nguyen
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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Breckenridge DG, Shore GC. Regulation of Apoptosis by E1A and Myc Oncoproteins. Crit Rev Eukaryot Gene Expr 2000. [DOI: 10.1615/critreveukargeneexpr.v10.i34.50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Breckenridge DG, Watanabe Y, Greenwood SJ, Gray MW, Schnare MN. U1 small nuclear RNA and spliceosomal introns in Euglena gracilis. Proc Natl Acad Sci U S A 1999; 96:852-6. [PMID: 9927657 PMCID: PMC15314 DOI: 10.1073/pnas.96.3.852] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the flagellated protozoon Euglena gracilis, characterized nuclear genes harbor atypical introns that usually are flanked by short repeats, adopt complex secondary structures in pre-mRNA, and do not obey the GT-AG rule of conventional cis-spliced introns. In the nuclear fibrillarin gene of E. gracilis, we have identified three spliceosomal-type introns that have GT-AG consensus borders. Furthermore, we have isolated a small RNA from E. gracilis and propose, on the basis of primary and secondary structure comparisons, that it is a homolog of U1 small nuclear RNA, an essential component of the cis-spliceosome in higher eukaryotes. Conserved sequences at the 5' splice sites of the fibrillarin introns can potentially base pair with Euglena U1 small nuclear RNA. Our observations demonstrate that spliceosomal GT-AG cis-splicing occurs in Euglena, in addition to the nonconventional cis-splicing and spliced leader trans-splicing previously recognized in this early diverging unicellular eukaryote.
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Affiliation(s)
- D G Breckenridge
- Program in Evolutionary Biology, Canadian Institute for Advanced Research, Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada
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