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Cunningham RP, Porat-Shliom N. Liver Zonation - Revisiting Old Questions With New Technologies. Front Physiol 2021; 12:732929. [PMID: 34566696 PMCID: PMC8458816 DOI: 10.3389/fphys.2021.732929] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/10/2021] [Indexed: 12/12/2022] Open
Abstract
Despite the ever-increasing prevalence of non-alcoholic fatty liver disease (NAFLD), the etiology and pathogenesis remain poorly understood. This is due, in part, to the liver's complex physiology and architecture. The liver maintains glucose and lipid homeostasis by coordinating numerous metabolic processes with great efficiency. This is made possible by the spatial compartmentalization of metabolic pathways a phenomenon known as liver zonation. Despite the importance of zonation to normal liver function, it is unresolved if and how perturbations to liver zonation can drive hepatic pathophysiology and NAFLD development. While hepatocyte heterogeneity has been identified over a century ago, its examination had been severely hindered due to technological limitations. Recent advances in single cell analysis and imaging technologies now permit further characterization of cells across the liver lobule. This review summarizes the advances in examining liver zonation and elucidating its regulatory role in liver physiology and pathology. Understanding the spatial organization of metabolism is vital to further our knowledge of liver disease and to provide targeted therapeutic avenues.
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Affiliation(s)
- Rory P Cunningham
- Thoracic and GI Malignancies Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
| | - Natalie Porat-Shliom
- Thoracic and GI Malignancies Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
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Berndt N, Kolbe E, Gajowski R, Eckstein J, Ott F, Meierhofer D, Holzhütter HG, Matz-Soja M. Functional Consequences of Metabolic Zonation in Murine Livers: Insights for an Old Story. Hepatology 2021; 73:795-810. [PMID: 32286709 DOI: 10.1002/hep.31274] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 03/13/2020] [Accepted: 04/01/2020] [Indexed: 12/19/2022]
Abstract
BACKGROUND AND AIMS Zone-dependent differences in expression of metabolic enzymes along the portocentral axis of the acinus are a long-known feature of liver metabolism. A prominent example is the preferential localization of the enzyme, glutamine synthetase, in pericentral hepatocytes, where it converts potentially toxic ammonia to the valuable amino acid, glutamine. However, with the exception of a few key regulatory enzymes, a comprehensive and quantitative assessment of zonal differences in the abundance of metabolic enzymes and, much more important, an estimation of the associated functional differences between portal and central hepatocytes is missing thus far. APPROACH AND RESULTS We addressed this problem by establishing a method for the separation of periportal and pericentral hepatocytes that yields sufficiently pure fractions of both cell populations. Quantitative shotgun proteomics identified hundreds of differentially expressed enzymes in the two cell populations. We used zone-specific proteomics data for scaling of the maximal activities to generate portal and central instantiations of a comprehensive kinetic model of central hepatic metabolism (Hepatokin1). CONCLUSIONS The model simulations revealed significant portal-to-central differences in almost all metabolic pathways involving carbohydrates, fatty acids, amino acids, and detoxification.
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Affiliation(s)
- Nikolaus Berndt
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität BerlinHumboldt-Universität zu Berlin, and Berlin Institute of HealthInstitute for Imaging Science and Computational Modelling in Cardiovascular MedicineBerlinGermany
| | - Erik Kolbe
- Rudolf-Schönheimer-Institute of BiochemistryFaculty of MedicineLeipzig UniversityLeipzigGermany
| | - Robert Gajowski
- Max Planck Institute for Molecular GeneticsBerlinGermany.,Department of Biology, Chemistry, PharmacyFreie UniversitätBerlinGermany
| | - Johannes Eckstein
- Charité -Universitätsmedizin Berlin, corporate member of Freie Universität BerlinHumboldt-Universität zu Berlin, and Berlin Institute of HealthInstitute of BiochemistryBerlinGermany
| | - Fritzi Ott
- Rudolf-Schönheimer-Institute of BiochemistryFaculty of MedicineLeipzig UniversityLeipzigGermany
| | | | - Hermann-Georg Holzhütter
- Charité -Universitätsmedizin Berlin, corporate member of Freie Universität BerlinHumboldt-Universität zu Berlin, and Berlin Institute of HealthInstitute of BiochemistryBerlinGermany
| | - Madlen Matz-Soja
- Rudolf-Schönheimer-Institute of BiochemistryFaculty of MedicineLeipzig UniversityLeipzigGermany.,Division of Hepatology, Department of Oncology, Gastroenterology, Hepatology, Pulmonology, and Infectious DiseasesLeipzig University Medical CenterLeipzigGermany
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Taly V, Urban P, Truan G, Pompon D. A combinatorial approach to substrate discrimination in the P450 CYP1A subfamily. Biochim Biophys Acta Gen Subj 2007; 1770:446-57. [PMID: 16996693 DOI: 10.1016/j.bbagen.2006.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Revised: 07/22/2006] [Accepted: 08/08/2006] [Indexed: 11/21/2022]
Abstract
A comparison of all known mammalian CYP1A sequences identifies nineteen sequence regions that are conserved within all 1A1s or within all 1A2s but at the same time systematically differ between any 1A1 and any 1A2. The purpose of this study was to explore links between these specific CYP1A sequence signatures and substrate specificity shift through the kinetic analysis of combinatorial variants of increasing complexity. The less complex variants correspond to multiple mutations within a short segment of their sequence. The more complex variants correspond to mosaic P450s recombining 1A1 and 1A2 sequences (up to 5 crossovers per sequence). Fifty-eight such functional CYP1A variants and parental wild-type enzymes were expressed in yeast and assayed with 7-alkoxyresorufins and ethoxyflurorescein ethyl ester as substrates. Observed kinetic data were analyzed by multivariate statistical analyses and hierarchical clustering in order to highlight correlations and identify potential sequence-activity relationships within the three-dimensional function space investigated. Several variants are outliers in these representations and show a redistribution of their substrate specificity compared to wild-type CYP1As. Some combinations of sequence elements were identified that significantly discriminate between 1A1 and 1A2 for these three substrates. The comparison of this combinatorial approach with previous results of site-directed mutagenesis is discussed.
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Affiliation(s)
- Valérie Taly
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, UPR2167, Avenue de la Terrasse, 91190 Gif-sur-Yvette, France
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Barogi S, Baracca A, Cavazzoni M, Parenti Castelli G, Lenaz G. Effect of the oxidative stress induced by adriamycin on rat hepatocyte bioenergetics during ageing. Mech Ageing Dev 2000; 113:1-21. [PMID: 10708246 DOI: 10.1016/s0047-6374(99)00089-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We have investigated the effect of ageing and of adriamycin treatment on the bioenergetics of isolated rat hepatocytes. Ageing per se, whilst being associated with a striking increase of hydrogen peroxide in the cells, induces only minor changes on mitochondrial functions. The adriamycin treatment induces a decrease of the mitochondrial membrane potential in situ and a consistent increase of the superoxide anion cellular content independently of the donor's age, whilst the hydrogen peroxide is significantly higher in aged than in adult rat hepatocytes. Kinetic studies in isolated mitochondria show that the mitochondrial respiratory chain activity (NADH --> O2) of 50 microM adriamycin-treated hepatocytes is lowered both in adult and aged rats. The same adriamycin concentration induces a slight decrease of the maximal rate of ATP hydrolysis in both young and aged rats, without affecting the Km for the substrate. However, at drug concentrations lower than 50 microM, both ATPase and NADH oxidation activities decrease significantly in aged rats only. The results suggest that free radicals increase during ageing in rat hepatocytes but are unable to induce major modifications of mitochondrial bioenergetics. This contrasts with the damaging effect of adriamycin, suggesting that some effects of the drug may be due to other reasons besides oxidative stress.
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Affiliation(s)
- S Barogi
- Dipartimento di Biochimica G. Moruzzi, Università di Bologna, Italy
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Cavazzoni M, Barogi S, Baracca A, Parenti Castelli G, Lenaz G. The effect of aging and an oxidative stress on peroxide levels and the mitochondrial membrane potential in isolated rat hepatocytes. FEBS Lett 1999; 449:53-6. [PMID: 10225427 DOI: 10.1016/s0014-5793(99)00400-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated the effect of ageing and of adriamycin treatment on the bioenergetics of isolated rat hepatocytes. Ageing per se, whilst being associated with a striking increase of hydrogen peroxide in the cells, induces only minor changes on the mitochondrial membrane potential. The adriamycin treatment induces a decrease of the mitochondrial membrane potential in situ and a consistent increase of the superoxide anion cellular content independently of the donor age. The hydrogen peroxide is significantly increased in both aged and adult rat hepatocytes, however, due to the high basal level in the aged cells, it is higher in aged rat cells not subjected to oxidative stress than that elicited by 50 microM adriamycin in young rat hepatocytes. The results suggest that a hydrogen peroxide increase in hepatocytes of aged rats is unable to induce major modifications of mitochondrial bioenergetics. This contrasts with the damaging effect of adriamycin, suggesting that the effects of the drug may be due to the concomitant high level of both superoxide and hydrogen peroxide.
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Affiliation(s)
- M Cavazzoni
- Dipartimento di Biochimica G. Moruzzi, Università di Bologna, Italy
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Spisni E, Cavazzoni M, Griffoni C, Calzolari E, Tomasi V. Evidence that photodynamic stress kills Zellweger fibroblasts by a nonapoptotic mechanism. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1402:61-9. [PMID: 9551086 DOI: 10.1016/s0167-4889(97)00148-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Zellweger fibroblasts, which are devoid of peroxisomes and fail to synthesize plasmalogens, are very sensitive to the killing effect triggered by UV-activated 12-(1-pyrene) dodecanoic acid (P12). Although in some studied performed, it is assumed that reactive oxygen species (ROS) may damage plasma membrane causing necrosis, other studies suggest that ROS are involved in apoptotic cell death induced by a wide variety of stimuli. Analysing the P12 dose-response in Zellweger fibroblasts, we observed that at high doses (1-2 microM), more than 75% of the cells died after 24 h. This behaviour suggested that, at high doses, P12 kills the cells by unspecific lytic mechanisms or by necrosis, while at low doses (0.1-0.5 microM), an apoptotic mechanism could be involved. Cytofluorimetric analysis of Zellweger fibroblasts-treated with activated P12 (0.5 microM) did not show morphological modifications typical of apoptotic cell death. This was supported by comparative staining of fibroblast nuclei, DNA gel electrophoresis and identification of poly(ADP-ribose) polymerase (PARP) cleavage and Bcl-2 expression, assayed by Western blots. Thus, our results, while confirming the importance of plasmalogens in the protection against ROS, establish that apoptosis is not involved in photodynamic death induced by activated P12. Therefore, we can expect that in gene transfer experiments, the rescue of Zellweger cells will be dependent only on the correction of peroxisomal biogenesis.
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Affiliation(s)
- E Spisni
- Department of Experimental Biology, University of Bologna, Italy
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Beyer RE, Segura-Aguilar J, Di Bernardo S, Cavazzoni M, Fato R, Fiorentini D, Galli MC, Setti M, Landi L, Lenaz G. The role of DT-diaphorase in the maintenance of the reduced antioxidant form of coenzyme Q in membrane systems. Proc Natl Acad Sci U S A 1996; 93:2528-32. [PMID: 8637908 PMCID: PMC39831 DOI: 10.1073/pnas.93.6.2528] [Citation(s) in RCA: 222] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The experiments reported here were designed to test the hypothesis that the two-electron quinone reductase DT-diaphorase [NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2] functions to maintain membrane-bound coenzyme Q (CoQ) in its reduced antioxidant state, thereby providing protection from free radical damage. DT-diaphorase was isolated and purified from rat liver cytosol, and its ability to reduce several CoQ homologs incorporated into large unilamellar vesicles was demonstrated. Addition of NADH and DT-diaphorase to either large unilamellar or multilamellar vesicles containing homologs of CoQ, including CoQ9 and CoQ10, resulted in the essentially complete reduction of the CoQ. The ability of DT-diaphorase to maintain the reduced state of CoQ and protect membrane components from free radical damage as lipid peroxidation was tested by incorporating either reduced CoQ9 or CoQ10 and the lipophylic azoinitiator 2,2'-azobis(2,4-dimethylvaleronitrile) into multilamellar vesicles in the presence of NADH and DT-diaphorase. The presence of DT-diaphorase prevented the oxidation of reduced CoQ and inhibited lipid peroxidation. The interaction between DT-diaphorase and CoQ was also demonstrated in an isolated rat liver hepatocyte system. Incubation with adriamycin resulted in mitochondrial membrane damage as measured by membrane potential and the release of hydrogen peroxide. Incorporation of CoQ10 provided protection from adriamycin-induced mitochondrial membrane damage. The incorporation of dicoumarol, a potent inhibitor of DT-diaphorase, interfered with the protection provided by CoQ. The results of these experiments provide support for the hypothesis that DT-diaphorase functions as an antioxidant in both artificial membrane and natural membrane systems by acting as a two-electron CoQ reductase that forms and maintains the antioxidant form of CoQ. The suggestion is offered that DT-diaphorase was selected during evolution to perform this role and that its conversion of xenobiotics and other synthetic molecules is secondary and coincidental.
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Affiliation(s)
- R E Beyer
- Laboratory of Chemical Biology, Department of Biology, University of Michigan, Ann Arbor 48109, USA
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Juan G, Cavazzoni M, Sáez GT, O'Connor JE. A fast kinetic method for assessing mitochondrial membrane potential in isolated hepatocytes with rhodamine 123 and flow cytometry. CYTOMETRY 1994; 15:335-42. [PMID: 8026223 DOI: 10.1002/cyto.990150409] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Rhodamine 123 (Rh123) is widely used as a flow cytometric probe for mitochondrial membrane potential (MMP) in metabolic, pharmacologic, and toxicological studies. However, the use of relatively high concentrations of Rh123 (up to 10 micrograms/ml) and prolonged incubation times (up to 1 h), including washing steps, may be inconvenient for certain applications in which labile cells are used or which demand rapid or repeated analysis. In this paper we describe a rapid kinetic assay of MMP in isolated rat hepatocytes, based upon the quantitation of the initial rate of Rh123 uptake by living cells, selected by their scattering properties. The results indicate that at an appropriate dye-to-cell ratio (in our experiments, 50 ng Rh123/ml for 250,000-300,000 cells/ml), the initial rate of Rh123 uptake is a highly reproducible and sensitive parameter for estimation of MMP, as demonstrated by the effects of substrates and inhibitors of the glycolytic pathway and mitochondrial respiration. Because of its simplicity, rapidity (about 5 min) and metabolic implications, this assay would be also suitable for the routine evaluation of metabolic state of cell suspensions, as a complementary test to the standard dual-staining tests of viability. Other possible applications in screening pharmacologic and toxicological analysis are discussed.
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Affiliation(s)
- G Juan
- Departamento de Bioquímica, Facultad de Medicina, Universidad de Valencia, Spain
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