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Zhang S, Orozco CC, Tang LWT, Racich J, Carlo AA, Chang G, Tess D, Keefer C, Di L. Characterization and Applications of Permeabilized Hepatocytes in Drug Discovery. AAPS J 2024; 26:38. [PMID: 38548986 DOI: 10.1208/s12248-024-00907-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 03/02/2024] [Indexed: 04/02/2024] Open
Abstract
Hepatocytes are one of the most physiologically relevant in vitro liver systems for human translation of clearance and drug-drug interactions (DDI). However, the cell membranes of hepatocytes can limit the entry of certain compounds into the cells for metabolism and DDI. Passive permeability through hepatocytes can be different in vitro and in vivo, which complicates the human translation. Permeabilized hepatocytes offer a useful tool to probe mechanistic understanding of permeability-limited metabolism and DDI. Incubation with saponin of 0.01% at 0.5 million cells/mL and 0.05% at 5 million cells/mL for 5 min at 37°C completely permeabilized the plasma membrane of hepatocytes, while leaving the membranes of subcellular organelles intact. Permeabilized hepatocytes maintained similar enzymatic activity as intact unpermeabilized hepatocytes and can be stored at -80°C for at least 7 months. This approach reduces costs by preserving leftover hepatocytes. The relatively low levels of saponin in permeabilized hepatocytes had no significant impact on the enzymatic activity. As the cytosolic contents leak out from permeabilized hepatocytes, cofactors need to be added to enable metabolic reactions. Cytosolic enzymes will no longer be present if the media are removed after cells are permeabilized. Hence permeabilized hepatocytes with and without media removal may potentially enable reaction phenotyping of cytosolic enzymes. Although permeabilized hepatocytes work similarly as human liver microsomes and S9 fractions experimentally requiring addition of cofactors, they behave more like hepatocytes maintaining enzymatic activities for over 4 h. Permeabilized hepatocytes are a great addition to the drug metabolism toolbox to provide mechanistic insights.
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Affiliation(s)
- Sam Zhang
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Christine C Orozco
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Lloyd Wei Tat Tang
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Jillian Racich
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Anthony A Carlo
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - George Chang
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - David Tess
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Christopher Keefer
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA
| | - Li Di
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, 06340, USA.
- Recursion Pharmaceuticals, Salt Lake City, Utah, 84101, USA.
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Filipski KJ, Edmonds DJ, Garnsey MR, Smaltz DJ, Coffman K, Futatsugi K, Lee J, O’Neil SV, Wright A, Nason D, Gosset JR, Orozco CC, Blackler D, Fakhoury G, Gutierrez JA, Perez S, Ross T, Stock I, Tesz G, Dullea R. Design of Next-Generation DGAT2 Inhibitor PF-07202954 with Longer Predicted Half-Life. ACS Med Chem Lett 2023; 14:1427-1433. [PMID: 37849537 PMCID: PMC10577701 DOI: 10.1021/acsmedchemlett.3c00330] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 07/27/2023] [Accepted: 09/26/2023] [Indexed: 10/19/2023] Open
Abstract
Diacylglycerol O-acyltransferase 2 (DGAT2) inhibitors have been shown to lower liver triglyceride content and are being explored clinically as a treatment for non-alcoholic steatohepatitis (NASH). This work details efforts to find an extended-half-life DGAT2 inhibitor. A basic moiety was added to a known inhibitor template, and the basicity and lipophilicity were fine-tuned by the addition of electrophilic fluorines. A weakly basic profile was required to find an appropriate balance of potency, clearance, and permeability. This work culminated in the discovery of PF-07202954 (12), a weakly basic DGAT2 inhibitor that has advanced to clinical studies. This molecule displays a higher volume of distribution and longer half-life in preclinical species, in keeping with its physicochemical profile, and lowers liver triglyceride content in a Western-diet-fed rat model.
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Affiliation(s)
- Kevin J. Filipski
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - David J. Edmonds
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Michelle R. Garnsey
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Daniel J. Smaltz
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Karen Coffman
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Kentaro Futatsugi
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Jack Lee
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Steven V. O’Neil
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Ann Wright
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Deane Nason
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - James R. Gosset
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Christine C. Orozco
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Dan Blackler
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Guila Fakhoury
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Jemy A. Gutierrez
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Sylvie Perez
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Trenton Ross
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Ingrid Stock
- Pfizer
Research & Development, 558 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Gregory Tesz
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
| | - Robert Dullea
- Pfizer
Research & Development, 1 Portland Street, Cambridge, Massachusetts 02139, United States
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3
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Orozco CC, Neuvonen M, Bi YA, Cerny MA, Mathialagan S, Tylaska L, Rago B, Costales C, King-Ahmad A, Niemi M, Rodrigues AD. Characterization of Bile Acid Sulfate Conjugates as Substrates of Human Organic Anion Transporting Polypeptides. Mol Pharm 2023. [PMID: 37134201 DOI: 10.1021/acs.molpharmaceut.3c00040] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Drug interactions involving the inhibition of hepatic organic anion transporting polypeptides (OATPs) 1B1 and OATP1B3 are considered important. Therefore, we sought to study various sulfated bile acids (BA-S) as potential clinical OATP1B1/3 biomarkers. It was determined that BA-S [e.g., glycochenodeoxycholic acid 3-O-sulfate (GCDCA-S) and glycodeoxycholic acid 3-O-sulfate (GDCA-S)] are substrates of OATP1B1, OATP1B3, and sodium-dependent taurocholic acid cotransporting polypeptide (NTCP) transfected into human embryonic kidney 293 cells, with minimal uptake evident for other solute carriers (SLCs) like OATP2B1, organic anion transporter 2, and organic cation transporter 1. It was also shown that BA-S uptake by plated human hepatocytes (PHH) was inhibited (≥96%) by a pan-SLC inhibitor (rifamycin SV), and there was greater inhibition (≥77% versus ≤12%) with rifampicin (OATP1B1/3-selective inhibitor) than a hepatitis B virus myristoylated-preS1 peptide (NTCP-selective inhibitor). Estrone 3-sulfate was also used as an OATP1B1-selective inhibitor. In this instance, greater inhibition was observed with GDCA-S (76%) than GCDCA-S (52%). The study was expanded to encompass the measurement of GCDCA-S and GDCA-S in plasma of SLCO1B1 genotyped subjects. The geometric mean GDCA-S concentration was 2.6-fold (90% confidence interval 1.6, 4.3; P = 2.1 × 10-4) and 1.3-fold (1.1, 1.7; P = 0.001) higher in individuals homozygous and heterozygous for the SLCO1B1 c.521T > C loss-of-function allele, respectively. For GCDCA-S, no significant difference was noted [1.2-fold (0.8, 1.7; P = 0.384) and 0.9-fold (0.8, 1.1; P = 0.190), respectively]. This supported the in vitro data indicating that GDCA-S is a more OATP1B1-selective substrate (versus GCDCA-S). It is concluded that GCDCA-S and GDCA-S are viable plasma-based OATP1B1/3 biomarkers, but they are both less OATP1B1-selective when compared to their corresponding 3-O-glucuronides (GCDCA-3G and GDCA-3G). Additional studies are needed to determine their utility versus more established biomarkers, such as coproporphyrin I, for assessing inhibitors with different OATP1B1 (versus OATP1B3) inhibition signatures.
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Affiliation(s)
- Christine C Orozco
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Mikko Neuvonen
- Department of Clinical Pharmacology, University of Helsinki, Helsinki FI-00014, Finland
- Individualized Drug Therapy Research Program, University of Helsinki, Helsinki FI-00014, Finland
| | - Yi-An Bi
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Matthew A Cerny
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Sumathy Mathialagan
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Laurie Tylaska
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Brian Rago
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Chester Costales
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Amanda King-Ahmad
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
| | - Mikko Niemi
- Department of Clinical Pharmacology, University of Helsinki, Helsinki FI-00014, Finland
- Individualized Drug Therapy Research Program, University of Helsinki, Helsinki FI-00014, Finland
- Department of Clinical Pharmacology, HUS Diagnostic Center, Helsinki University Hospital, Helsinki FI-00029, Finland
| | - A David Rodrigues
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut 06340, United States
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Lapham K, Callegari E, Cianfrogna J, Lin J, Niosi M, Orozco CC, Sharma R, Goosen TC. In Vitro Characterization of Ertugliflozin Metabolism by UDP-Glucuronosyltransferase and Cytochrome P450 Enzymes. Drug Metab Dispos 2020; 48:1350-1363. [DOI: 10.1124/dmd.120.000171] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 09/22/2020] [Indexed: 12/18/2022] Open
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Orozco CC, Atkinson K, Ryu S, Chang G, Keefer C, Lin J, Riccardi K, Mongillo RK, Tess D, Filipski KJ, Kalgutkar AS, Litchfield J, Scott D, Di L. Structural attributes influencing unbound tissue distribution. Eur J Med Chem 2020; 185:111813. [DOI: 10.1016/j.ejmech.2019.111813] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 09/03/2019] [Accepted: 10/23/2019] [Indexed: 12/26/2022]
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Davoren JE, Nason D, Coe J, Dlugolenski K, Helal C, Harris AR, LaChapelle E, Liang S, Liu Y, O'Connor R, Orozco CC, Rai BK, Salafia M, Samas B, Xu W, Kozak R, Gray D. Discovery and Lead Optimization of Atropisomer D1 Agonists with Reduced Desensitization. J Med Chem 2018; 61:11384-11397. [PMID: 30431269 DOI: 10.1021/acs.jmedchem.8b01622] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The discovery of D1 subtype-selective agonists with drug-like properties has been an enduring challenge for the greater part of 40 years. All known D1-selective agonists are catecholamines that bring about receptor desensitization and undergo rapid metabolism, thus limiting their utility as a therapeutic for chronic illness such as schizophrenia and Parkinson's disease. Our high-throughput screening efforts on D1 yielded a single non-catecholamine hit PF-4211 (6) that was developed into a series of potent D1 receptor agonist leads with high oral bioavailability and CNS penetration. An important structural feature of this series is the locked biaryl ring system resulting in atropisomerism. Disclosed herein is a summary of our hit-to-lead efforts on this series of D1 activators culminating in the discovery of atropisomer 31 (PF-06256142), a potent and selective orthosteric agonist of the D1 receptor that has reduced receptor desensitization relative to dopamine and other catechol-containing agonists.
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Affiliation(s)
| | - Deane Nason
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Jotham Coe
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | | | - Christopher Helal
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Anthony R Harris
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Erik LaChapelle
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Sidney Liang
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | | | - Rebecca O'Connor
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Christine C Orozco
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | | | - Michelle Salafia
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Brian Samas
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
| | - Wenjian Xu
- Medicine Design , Pfizer Worldwide Research and Development , Eastern Point Road , Groton , Connecticut 06340 , United States
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7
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Ballard TE, Orozco CC, Obach RS. Generation of Major Human Excretory and Circulating Drug Metabolites Using a Hepatocyte Relay Method. Drug Metab Dispos 2014; 42:899-902. [DOI: 10.1124/dmd.114.057026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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8
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Di L, Atkinson K, Orozco CC, Funk C, Zhang H, McDonald TS, Tan B, Lin J, Chang C, Obach RS. In vitro-in vivo correlation for low-clearance compounds using hepatocyte relay method. Drug Metab Dispos 2013; 41:2018-23. [PMID: 23857891 DOI: 10.1124/dmd.113.053322] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
In vitro-in vivo correlation (IVIVC) of intrinsic clearance in preclinical species of rat and dog was established using the hepatocyte relay method to support high-confidence prediction of human pharmacokinetics for low-clearance compounds. Good IVIVC of intrinsic clearance was observed for most of the compounds, with predicted values within 2-fold of the observed values. The exceptions involved transporter-mediated uptake clearance or metabolizing enzymes with extensive extrahepatic contribution. This is the first assay available to address low clearance challenges in preclinical species for IVIVC in drug discovery. It extends the utility of the hepatocyte relay method in addressing low clearance issues.
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Affiliation(s)
- Li Di
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Inc., Groton, Connecticut
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9
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Strelevitz TJ, Orozco CC, Obach RS. Hydralazine As a Selective Probe Inactivator of Aldehyde Oxidase in Human Hepatocytes: Estimation of the Contribution of Aldehyde Oxidase to Metabolic Clearance. Drug Metab Dispos 2012; 40:1441-8. [DOI: 10.1124/dmd.112.045195] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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10
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John K, Divi RL, Keshava C, Orozco CC, Schockley ME, Richardson DL, Poirier MC, Nath J, Weston A. CYP1A1 and CYP1B1 gene expression and DNA adduct formation in normal human mammary epithelial cells exposed to benzo[a]pyrene in the absence or presence of chlorophyllin. Cancer Lett 2010; 292:254-60. [PMID: 20163913 DOI: 10.1016/j.canlet.2009.12.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 12/09/2009] [Accepted: 12/11/2009] [Indexed: 01/29/2023]
Abstract
Benzo[a]pyrene (BP) is a potent pro-carcinogen and ubiquitous environmental pollutant. Here, we examined the induction and modulation of CYP1A1 and CYP1B1 and 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPdG) adduct formation in DNA from 20 primary normal human mammary epithelial cell (NHMEC) strains exposed to BP (4muM) in the absence or presence of chlorophyllin (5muM). Real-time polymerase chain reaction (RT-PCR) analysis revealed strong induction of both CYP1A1 and CYP1B1 by BP, with high levels of inter-individual variability. Variable BPdG formation was found in all strains by r7, t8-dihydroxy-t-9, 10 epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence assay (CIA). Chlorophyllin mitigated BP-induced CYP1A1 and CYP1B1 gene expression in all 20 strains when administered with BP. Chlorophyllin, administered prior to BP-exposure, mitigated CYP1A1 expression in 18/20 NHMEC strains (p<0.005) and CYP1B1 expression in 17/20 NHMEC strains (p<0.005). Maximum percent reductions of CYP1A1 and CYP1B1 gene expression and BPdG adduct formation were observed when cells were pre-dosed with chlorophyllin followed by administration of the carcinogen with chlorophyllin (p<0.005 for CYP1A1 and CYP1B1 expression and p<0.0005 for BPdG adducts). Therefore, chlorophyllin is likely to be a good chemoprotective agent for a large proportion of the human population.
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Affiliation(s)
- Kaarthik John
- Genetics and Developmental Biology Program, West Virginia University, Morgantown, WV, United States
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11
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Orozco CC, Risser DD, Callahan SM. Epistasis analysis of four genes from Anabaena sp. strain PCC 7120 suggests a connection between PatA and PatS in heterocyst pattern formation. J Bacteriol 2006; 188:1808-16. [PMID: 16484191 PMCID: PMC1426565 DOI: 10.1128/jb.188.5.1808-1816.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The hetR, patA, hetN, and patS genes are part of a regulatory network that regulates the differentiation and patterning of heterocysts in the filamentous cyanobacterium Anabaena sp. strain PCC 7120. In this report, the epistatic interactions of mutant alleles of these four genes have been used to refine our understanding of their relationships to one another. The hetR gene was necessary for differentiation in genetic backgrounds that normally give rise to excessive differentiation, supporting its role as the master regulator of differentiation and indicating that HetR directly regulates factors in addition to hetR and patS genes that regulate differentiation. A functional patS gene was necessary for the delayed multiple-contiguous-heterocyst phenotype observed in hetN mutants as well as for the relative lack of intercalary heterocysts in patA mutants. Epistasis results with mutant alleles of these three genes suggested that PatA attenuates the negative effects of both PatS and HetN on differentiation and promotes differentiation independent of its antagonistic effects on PatS and HetN activity. Cooverxpression of patS and hetR in a synthetic operon indicated that patS acts at a point downstream of hetR transcription in the regulatory network controlling differentiation. A model for the regulation of differentiation that is consistent with these and previous findings is presented.
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Affiliation(s)
- Christine C Orozco
- University of Hawaii, Department of Microbiology, 2538 McCarthy Mall, 207 Snyder Hall, Honolulu, HI 96822, USA
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12
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Borthakur PB, Orozco CC, Young-Robbins SS, Haselkorn R, Callahan SM. Inactivation of patS and hetN causes lethal levels of heterocyst differentiation in the filamentous cyanobacterium Anabaena sp. PCC 7120. Mol Microbiol 2005; 57:111-23. [PMID: 15948953 DOI: 10.1111/j.1365-2958.2005.04678.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Summary In the filamentous cyanobacterium Anabaena sp. PCC 7120 patS and hetN suppress the differentiation of vegetative cells into nitrogen-fixing heterocysts to establish and maintain a pattern of single heterocysts separated by approximately 10 undifferentiated vegetative cells. Here we show that the patS- and hetN-dependent suppression pathways are the only major factors that prevent vegetative cells from differentiating into heterocysts when a source of ammonia is not present. The patS and hetN pathways are independent of each other, and inactivation of both patS and hetN leads to differentiation of almost all cells of a filament in the absence of a source of fixed nitrogen, compared with approximately 9% in the wild type. Complete differentiation of filaments also occurs when nitrate is supplied as a source of fixed nitrogen, conditions that do not induce differentiation of wild-type filaments. However, ammonia is still capable of suppressing differentiation. The percentage of cells that differentiate into heterocysts appears to be a function of time when a source of fixed nitrogen is absent or a function of growth phase when nitrate is supplied. Although differentiation proceeds unchecked in the absence of patS and hetN expression, differentiation is asynchronous and non-random.
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Affiliation(s)
- Pritty B Borthakur
- Department of Microbiology, University of Hawaii, Honolulu, HI 96822, USA
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13
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Divi RL, Leonard SL, Kuo MM, Walker BL, Orozco CC, St Claire MC, Nagashima K, Harbaugh SW, Harbaugh JW, Thamire C, Sable CA, Poirier MC. Cardiac Mitochondrial Compromise in 1-Yr-Old Erythrocebus patas Monkeys Perinatally- Exposed to Nucleoside Reverse Transcriptase Inhibitors. Cardiovasc Toxicol 2005; 5:333-46. [PMID: 16244378 DOI: 10.1385/ct:5:3:333] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [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: 03/30/2005] [Revised: 05/16/2005] [Accepted: 06/09/2005] [Indexed: 11/11/2022]
Abstract
Hearts from 1-yr-old Erythrocebus patas monkeys were examined after in utero and 6-wk-postbirth exposure to antiretroviral nucleoside reverse transcriptase inhibitors (NRTIs). Protocols were modeled on those given to human immunodeficiency virus (HIV)-1-infected pregnant women. NRTIs were administered daily to the dams for the last 20% or 50% of gestation, and to the infants for 6 wk after birth. Exposures included: no drug (n = 4); Zidovudine, 3'-azido-3'-deoxythymidine (AZT; n = 4); AZT/Lamivudine, (-)-beta-L-2', 3'-Dideoxy-3'-thiacytidine (Epivir, 3TC) (n = 4); AZT/Didanosine (Videx, ddI) (n = 4); and Stavudine (Zerit, d4T)/3TC (n = 4). Echocardiograms and clinical chemistry showed no drug-related changes, but the d4T/3TC-exposed fetuses at 6 and 12 mo had increased white cell counts (p < 0.05). At 1 yr of age, oxidative phosphorylation (OXPHOS) enzyme activities were similar in heart mitochondria from all groups. Mitochondrial pathology, that included clones of damaged mitochondria (p < 0.05), was found in hearts of all 1-yr drug-exposed infants. Levels of mtDNA were elevated (p < 0.05) in hearts of all NRTI-exposed monkeys in the following order: control < d4T/3TC < AZT < AZT/3TC < AZT/ddI. The clinical status of NRTI-exposed infants, as evidenced by behavior, clinical chemistry, OXPHOS activity and echocardiogram, was normal. However, extensive mitochondrial damage with clusters of similar-appearing damaged heart mitochondria observed by electron microscopy, and an increase in mtDNA quantity, that persisted at 1 yr of age, suggest the potential for cardiotoxicity later in life.
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Affiliation(s)
- Rao L Divi
- Center for Cancer Research, National Cancer Institute, NIH, 37 Convent Drive, Bethesda, MD 20892-4255, USA
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