1
|
Fontes FL, Rooker SA, Lynn-Barbe JK, Lyons MA, Crans DC, Crick DC. Pyrazinoic acid, the active form of the anti-tuberculosis drug pyrazinamide, and aromatic carboxylic acid analogs are protonophores. Front Mol Biosci 2024; 11:1350699. [PMID: 38414662 PMCID: PMC10896915 DOI: 10.3389/fmolb.2024.1350699] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 01/16/2024] [Indexed: 02/29/2024] Open
Abstract
Pyrazinoic acid is the active form of pyrazinamide, a first-line antibiotic used to treat Mycobacterium tuberculosis infections. However, the mechanism of action of pyrazinoic acid remains a subject of debate, and alternatives to pyrazinamide in cases of resistance are not available. The work presented here demonstrates that pyrazinoic acid and known protonophores including salicylic acid, benzoic acid, and carbonyl cyanide m-chlorophenyl hydrazone all exhibit pH-dependent inhibition of mycobacterial growth activity over a physiologically relevant range of pH values. Other anti-tubercular drugs, including rifampin, isoniazid, bedaquiline, and p-aminosalicylic acid, do not exhibit similar pH-dependent growth-inhibitory activities. The growth inhibition curves of pyrazinoic, salicylic, benzoic, and picolinic acids, as well as carbonyl cyanide m-chlorophenyl hydrazone, all fit a quantitative structure-activity relationship (QSAR) derived from acid-base equilibria with R2 values > 0.95. The QSAR model indicates that growth inhibition relies solely on the concentration of the protonated forms of these weak acids (rather than the deprotonated forms). Moreover, pyrazinoic acid, salicylic acid, and carbonyl cyanide m-chlorophenyl hydrazone all caused acidification of the mycobacterial cytoplasm at concentrations that inhibit bacterial growth. Thus, it is concluded that pyrazinoic acid acts as an uncoupler of oxidative phosphorylation and that disruption of proton motive force is the primary mechanism of action of pyrazinoic acid rather than the inhibition of a classic enzyme activity.
Collapse
Affiliation(s)
- Fabio L. Fontes
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Steven A. Rooker
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Jamie K. Lynn-Barbe
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Michael A. Lyons
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Debbie C. Crans
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Dean C. Crick
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| |
Collapse
|
2
|
Ramey ME, Kaya F, Bauman AA, Massoudi LM, Sarathy JP, Zimmerman MD, Scott DWL, Job AM, Miller-Dawson JA, Podell BK, Lyons MA, Dartois V, Lenaerts AJ, Robertson GT. Drug distribution and efficacy of the DprE1 inhibitor BTZ-043 in the C3HeB/FeJ mouse tuberculosis model. Antimicrob Agents Chemother 2023; 67:e0059723. [PMID: 37791784 PMCID: PMC10648937 DOI: 10.1128/aac.00597-23] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/04/2023] [Indexed: 10/05/2023] Open
Abstract
BTZ-043, a suicide inhibitor of the Mycobacterium tuberculosis cell wall synthesis decaprenylphosphoryl-beta-D-ribose 2' epimerase, is under clinical development as a potential new anti-tuberculosis agent. BTZ-043 is potent and bactericidal in vitro but has limited activity against non-growing bacilli in rabbit caseum. To better understand its behavior in vivo, BTZ-043 was evaluated for efficacy and spatial drug distribution as a single agent in the C3HeB/FeJ mouse model presenting with caseous necrotic pulmonary lesions upon Mycobacterium tuberculosis infection. BTZ-043 promoted significant reductions in lung and spleen bacterial burdens in the C3HeB/FeJ mouse model after 2 months of therapy. BTZ-043 penetrates cellular and necrotic lesions and was retained at levels above the serum-shifted minimal inhibitory concentration in caseum. The calculated rate of kill was found to be highest and dose-dependent during the second month of treatment. BTZ-043 treatment was associated with improved histology scores of pulmonary lesions, especially compared to control mice, which experienced advanced fulminant neutrophilic alveolitis in the absence of treatment. These positive treatment responses to BTZ-043 monotherapy in a mouse model of advanced pulmonary disease can be attributed to favorable distribution in tissues and lesions, retention in the caseum, and its high potency and bactericidal nature at drug concentrations achieved in necrotic lesions.
Collapse
Affiliation(s)
- Michelle E. Ramey
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Firat Kaya
- Center for Discovery and Innovation, Hackensack Meridian School of Medicine, Nutley, New Jersey, USA
| | - Allison A. Bauman
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Lisa M. Massoudi
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Jansy P. Sarathy
- Center for Discovery and Innovation, Hackensack Meridian School of Medicine, Nutley, New Jersey, USA
| | - Matthew D. Zimmerman
- Center for Discovery and Innovation, Hackensack Meridian School of Medicine, Nutley, New Jersey, USA
| | - Dashick W. L. Scott
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Alyx M. Job
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Jake A. Miller-Dawson
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Brendan K. Podell
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Michael A. Lyons
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Véronique Dartois
- Center for Discovery and Innovation, Hackensack Meridian School of Medicine, Nutley, New Jersey, USA
| | - Anne J. Lenaerts
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Gregory T. Robertson
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| |
Collapse
|
3
|
Lyons MA, Obregon-Henao A, Ramey ME, Bauman AA, Pauly S, Rossmassler K, Reid J, Karger B, Walter ND, Robertson GT. Use of Multiple Pharmacodynamic Measures to Deconstruct the Nix-TB Regimen in a Short-Course Murine Model of Tuberculosis. bioRxiv 2023:2023.11.08.566205. [PMID: 37986955 PMCID: PMC10659381 DOI: 10.1101/2023.11.08.566205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
A major challenge for tuberculosis (TB) drug development is to prioritize promising combination regimens from a large and growing number of possibilities. This includes demonstrating individual drug contributions to the activity of higher-order combinations. A BALB/c mouse TB infection model was used to evaluate the contributions of each drug and pairwise combination in the clinically relevant Nix-TB regimen (bedaquiline-pretomanid-linezolid [BPaL]) during the first three weeks of treatment at human equivalent doses. RS ratio, an exploratory pharmacodynamic (PD) marker of ongoing Mycobacterium tuberculosis rRNA synthesis, to-gether with solid culture CFU and liquid culture time to positivity (TTP) were used as PD markers of treatment response in lung tissue; and their time course profiles were mathematically modeled using rate equations with pharmacologically interpretable parameters. Antimicrobial interactions were quantified using Bliss independence and Isserlis formulas. Subadditive (or antagonistic) and additive effects on bacillary load, assessed by CFU and TTP, were found for bedaquiline-pretomanid and linezolid-containing pairs, respectively. In contrast, subadditive and additive effects on rRNA synthesis were found for pretomanid-linezolid and bedaquiline-containing pairs, respectively. Additionally, accurate predictions of the response to BPaL for all three PD markers were made using only the single-drug and pairwise effects together with an assumption of negligible three-way drug interactions. The results represent an experimental and PD modeling approach aimed at reducing combinatorial complexity and improving the cost-effectiveness of in vivo systems for preclinical TB regimen development.
Collapse
|
4
|
Lyons MA, Malhotra R, Thompson CW. Investigating the free-roaming dog population and gastrointestinal parasite diversity in Tulúm, México. PLoS One 2022; 17:e0276880. [PMID: 36301991 PMCID: PMC9612467 DOI: 10.1371/journal.pone.0276880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/13/2022] [Indexed: 11/29/2022] Open
Abstract
Free-roaming domestic dogs (Canis lupus familiaris) pose major conservation and public health risks worldwide. To better understand the threat of domestic dogs to wildlife and people and add to the growing literature on free-roaming dog ecology, a study was conducted to estimate the dog population in Tulúm, México. A modified mark-recapture technique and program MARK were used to obtain dog population estimates along six different transects dividing the city. Population estimates ranged from 19.75 dogs in one transect to 101.841 dogs in another, with 150 total dogs identified throughout the study and an estimated minimum population density of 48.57 dogs/km2. Fecal samples were also opportunistically collected for parasite identification through fecal flotation analysis using the McMaster technique. Out of 25 samples collected, 19 tested positive for gastrointestinal parasites with the most common species found being Ancylostoma caninum, followed by Toxocara canis, Dipylidium caninum, and Cystoisospora spp. Parasite loads ranged from 50 to 10,700 ova per gram of feces. The large population of free-roaming dogs and the prevalence of three zoonotic parasites highlight the importance of understanding free-roaming dog ecology and educating the public on the health risks free-roaming dogs pose. Los perros callejeros (Canis lupus familiaris) representan un gran riesgo para la conservación de animales y la salud pública mundialmente. Para comprender mejor la amenaza que significan los perros domésticos para la fauna silvestre y los humanos y aportar a la creciente bibliografía sobre la ecología de los perros callejeros, se realizó una investigación para estimar la población de los perros en Tulúm, México. Se utilizó una técnica modificada de marcado y recaptura junto con el programa MARK para estimar la población canina en seis transectos de la ciudad. Los estimados varían desde 19.75 perros en un transecto hasta 101,841 en otro, con un total de 150 perros identificados en el transcurso de la investigación y una densidad mínima estimada de 48,57 perros/km2. Además, se hizo una recolección oportunista de muestras de heces para la identificación de parásitos por medio del análisis de flotacíon fecal, con el método McMaster. De las 25 muestras recolectadas, 19 resultaron positivas para parásitos gastrointestinales, de las cuales las especies más comunes fueron Ancylostomoa caninum, seguida por Toxocara canis, Dipylidium caninum, y Cystoisospora spp. Las cargas parasitarias variaron desde 50 hasta 10.700 óvulos por gramo de heces. La alta población de perros callejeros y la prevalencia de tres enfermedades zoonóticas resaltan la importancia de entender la ecología de los perros callejeros y educar al público sobre los riesgos que significan los perros callejeros para la salud.
Collapse
Affiliation(s)
- Michael A. Lyons
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Museum of Zoology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Rumaan Malhotra
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Museum of Zoology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Cody W. Thompson
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Museum of Zoology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| |
Collapse
|
5
|
Lyons MA. Pretomanid dose selection for pulmonary tuberculosis: An application of multi-objective optimization to dosage regimen design. CPT Pharmacometrics Syst Pharmacol 2021; 10:211-219. [PMID: 33440076 PMCID: PMC7965837 DOI: 10.1002/psp4.12591] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/27/2020] [Accepted: 12/07/2020] [Indexed: 12/18/2022]
Abstract
Clinical development of combination chemotherapies for tuberculosis (TB) is complicated by partial or restricted phase II dose‐finding. Barriers include a propensity for drug resistance with monotherapy, practical limits on numbers of treatment arms for component dose combinations, and limited application of current dose selection methods to multidrug regimens. A multi‐objective optimization approach to dose selection was developed as a conceptual and computational framework for currently evolving approaches to clinical testing of novel TB regimens. Pharmacokinetic‐pharmacodynamic (PK‐PD) modeling was combined with an evolutionary algorithm to identify dosage regimens that yield optimal trade‐offs between multiple conflicting therapeutic objectives. The phase IIa studies for pretomanid, a newly approved nitroimidazole for specific cases of highly drug‐resistant pulmonary TB, were used to demonstrate the approach with Pareto optimized dosing that best minimized sputum bacillary load and the probability of drug‐related adverse events. Results include a population‐typical characterization of the recommended 200 mg once daily dosage, the optimality of time‐dependent dosing, examples of individualized therapy, and the determination of optimal loading doses. The approach generalizes conventional PK‐PD target attainment to a design problem that scales to drug combinations, and provides a benefit‐risk context for clinical testing of complex drug regimens.
Collapse
Affiliation(s)
- Michael A Lyons
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| |
Collapse
|
6
|
Lyons MA. Modeling and Simulation of Pretomanid Pharmacokinetics in Pulmonary Tuberculosis Patients. Antimicrob Agents Chemother 2018; 62:e02359-17. [PMID: 29661865 PMCID: PMC6021621 DOI: 10.1128/aac.02359-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 04/09/2018] [Indexed: 01/28/2023] Open
Abstract
Pretomanid is a nitroimidazole antibiotic in late-phase clinical testing as a component of several novel antituberculosis (anti-TB) regimens. A population pharmacokinetic model for pretomanid was constructed using a Bayesian analysis of data from two phase 2 studies, PA-824-CL-007 and PA-824-CL-010, conducted with adult (median age, 27 years) patients in Cape Town, South Africa, with newly diagnosed pulmonary TB. Combined, these studies included 63 males and 59 females administered once-daily oral pretomanid doses of 50, 100, 150, 200, 600, 1,000, or 1,200 mg for 14 days. The observed pretomanid plasma concentration-time profiles for all tested doses were described by a one-compartment model with first-order absorption and elimination and a sigmoidal bioavailability dependent on dose, time, and the predose fed state. Allometric scaling with body weight (normalized to 70 kg) was used for volume of distribution and clearance, with the scaling exponents equal to 1 and 3/4, respectively. The posterior population geometric means for the clearance and volume of distribution allometric constants were 4.8 ± 0.2 liters/h and 130 ± 5 liters, respectively, and the posterior population geometric mean for the half-maximum-effect dose for the reduction of bioavailability was 450 ± 50 mg. Interindividual variability, described by the percent coefficient of variation, was 32% ± 3% for clearance, 17% ± 4% for the volume of distribution, and 74% ± 9% for the half-maximum-effect dose. This model provides a dose-exposure relationship for pretomanid in adult TB patients with potential applications to dose selection in individuals and to further clinical testing of novel pretomanid-containing anti-TB regimens.
Collapse
Affiliation(s)
- Michael A Lyons
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| |
Collapse
|
7
|
Irwin SM, Prideaux B, Lyon ER, Zimmerman MD, Brooks EJ, Schrupp CA, Chen C, Reichlen MJ, Asay BC, Voskuil MI, Nuermberger EL, Andries K, Lyons MA, Dartois V, Lenaerts AJ. Bedaquiline and Pyrazinamide Treatment Responses Are Affected by Pulmonary Lesion Heterogeneity in Mycobacterium tuberculosis Infected C3HeB/FeJ Mice. ACS Infect Dis 2016; 2:251-267. [PMID: 27227164 PMCID: PMC4874602 DOI: 10.1021/acsinfecdis.5b00127] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [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: 10/26/2015] [Indexed: 12/31/2022]
Abstract
![]()
BALB/c and Swiss mice are routinely
used to validate the effectiveness of tuberculosis drug regimens,
although these mouse strains fail to develop human-like pulmonary
granulomas exhibiting caseous necrosis. Microenvironmental conditions
within human granulomas may negatively impact drug efficacy, and this
may not be reflected in non-necrotizing lesions found within conventional
mouse models. The C3HeB/FeJ mouse model has been increasingly utilized
as it develops hypoxic, caseous necrotic granulomas which may more
closely mimic the pathophysiological conditions found within human
pulmonary granulomas. Here, we examined the treatment response of
BALB/c and C3HeB/FeJ mice to bedaquiline (BDQ) and pyrazinamide (PZA)
administered singly and in combination. BALB/c mice consistently displayed
a highly uniform treatment response to both drugs, while C3HeB/FeJ
mice displayed a bimodal response composed of responsive and less-responsive
mice. Plasma pharmacokinetic analysis of dissected lesions from BALB/c
and C3HeB/FeJ mice revealed that PZA penetrated lesion types from
both mouse strains with similar efficiency. However, the pH of the
necrotic caseum of C3HeB/FeJ granulomas was determined to be 7.5,
which is in the range where PZA is essentially ineffective under standard
laboratory in vitro growth conditions. BDQ preferentially accumulated
within the highly cellular regions in the lungs of both mouse strains,
although it was present at reduced but still biologically relevant
concentrations within the central caseum when dosed at 25 mg/kg. The
differential treatment response which resulted from the heterogeneous
pulmonary pathology in the C3HeB/FeJ mouse model revealed several
factors which may impact treatment efficacy, and could be further
evaluated in clinical trials.
Collapse
Affiliation(s)
- Scott M. Irwin
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Brendan Prideaux
- Public Health Research Institute, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, United States
| | - Edward R. Lyon
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Matthew D. Zimmerman
- Public Health Research Institute, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, United States
| | - Elizabeth J. Brooks
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Christopher A. Schrupp
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Chao Chen
- Public Health Research Institute, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, United States
| | - Matthew J. Reichlen
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80045, United States
| | - Bryce C. Asay
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Martin I. Voskuil
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80045, United States
| | - Eric L. Nuermberger
- Center
for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, United States
| | - Koen Andries
- Department
of Infectious Diseases, Janssen Pharmaceutica, 2340 Beerse, Belgium
| | - Michael A. Lyons
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Véronique Dartois
- Public Health Research Institute, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, United States
| | - Anne J. Lenaerts
- Mycobacteria
Research Laboratories, Department of Microbiology, Immunology and
Pathology, Colorado State University, Fort Collins, Colorado 80523, United States
| |
Collapse
|
8
|
Lyons MA, Lenaerts AJ. Computational pharmacokinetics/pharmacodynamics of rifampin in a mouse tuberculosis infection model. J Pharmacokinet Pharmacodyn 2015; 42:375-89. [PMID: 26026426 DOI: 10.1007/s10928-015-9419-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 05/25/2015] [Indexed: 11/30/2022]
Abstract
One critical approach to preclinical evaluation of anti-tuberculosis (anti-TB) drugs is the study of correlations between drug exposure and efficacy in animal TB infection models. While such pharmacokinetic/pharmacodynamic (PK/PD) studies are useful for the identification of optimal clinical dosing regimens, they are resource intensive and are not routinely performed. A mathematical model capable of simulating the PK/PD properties of drug therapy for experimental TB offers a way to mitigate some of the practical obstacles to determining the PK/PD index that best correlates with efficacy. Here, we present a preliminary physiologically based PK/PD model of rifampin therapy in a mouse TB infection model. The computational framework integrates whole-body rifampin PKs, cell population dynamics for the host immune response to Mycobacterium tuberculosis infection, drug-bacteria interactions, and a Bayesian method for parameter estimation. As an initial application, we calibrated the model to a set of available rifampin PK/PD data and simulated a separate dose fractionation experiment for bacterial killing kinetics in the lungs of TB-infected mice. The simulation results qualitatively agreed with the experimentally observed PK/PD correlations, including the identification of area under the concentration-time curve as best correlating with efficacy. This single-drug framework is aimed toward extension to multiple anti-TB drugs in order to facilitate development of optimal combination regimens.
Collapse
Affiliation(s)
- Michael A Lyons
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA,
| | | |
Collapse
|
9
|
Lyons MA. Computational pharmacology of rifampin in mice: an application to dose optimization with conflicting objectives in tuberculosis treatment. J Pharmacokinet Pharmacodyn 2014; 41:613-23. [PMID: 25173151 DOI: 10.1007/s10928-014-9380-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/19/2014] [Indexed: 10/24/2022]
Abstract
Dose selection for rifampin in the treatment of active pulmonary tuberculosis (TB) illustrates some of the challenges for dose optimization within multidrug therapies. Rifampin-based anti-TB regimens are often combined with antiretroviral therapies to treat human immunodeficiency virus (HIV) coinfection. The potent cytochrome P450 (CYP) enzyme inducing properties of rifampin give rise to significant drug-drug interactions, the minimization of which by limiting the dose, conflicts with the maximization of bacterial killing by increasing the dose. Such multiple and conflicting objectives lead to a set of trade-off optimal solutions for dose optimization rather than a single best solution. Here, we combine pharmacokinetic/pharmacodynamic (PK/PD) modeling with multiobjective optimization to quantitatively explore trade-offs between therapeutic and adverse effects of optimal dosing for the example of rifampin in TB-infected mice. The PK/PD model describes rifampin concentrations in plasma and liver following oral administration together with hepatic CYP enzyme induction and bacterial killing kinetics. We include optimization objectives descriptive of antimicrobial efficacy, CYP-mediated drug-drug interactions, and drug exposure-dependent toxicity. Results show non-conventional dosing scenarios that allow for increased efficacy relative to uniform dosing without increasing drug-drug interactions. Additionally, we find currently employed dosages for rifampin to be nearly optimal with respect to trade-offs between efficacy and toxicity. While limited by the accuracy and applicability of the PK/PD model, these results provide an avenue for experimental investigation of complex dose optimization problems. This method can be extended to include additional drugs and optimization objectives, and may provide a useful tool for individualized medicine.
Collapse
Affiliation(s)
- Michael A Lyons
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA,
| |
Collapse
|
10
|
Diaz HL, Karnati SKR, Lyons MA, Dehority BA, Firkins JL. Chemotaxis toward carbohydrates and peptides by mixed ruminal protozoa when fed, fasted, or incubated with polyunsaturated fatty acids. J Dairy Sci 2014; 97:2231-43. [PMID: 24534499 DOI: 10.3168/jds.2013-7428] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [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: 08/27/2013] [Accepted: 11/25/2013] [Indexed: 12/16/2023]
Abstract
In contrast to the well-characterized chemotaxis and migratory behavior between the dorsal and ventral locations of the rumen by isotrichids, we hypothesized that chemotaxis toward soluble nutrients maintains entodiniomorphid protozoa in the particulate fraction. The objectives of these experiments were to compare the dose-responsive chemotaxis (1) toward different glucose concentrations when ruminal samples were harvested from fed versus fasted cows; (2) toward increasing concentrations of glucose compared with xylose when protozoa were harvested from a fed cow; (3) toward peptides of bacterial, protozoal, and soy origin; and (4) toward glucose when mixed ruminal protozoa were previously incubated for 0, 3, or 6h in the presence of emulsified polyunsaturated fatty acids (PUFA; Liposyn II, Hospira, Lake Forest, IL). In experiment 1, isotrichid protozoa decreased chemotaxis toward increasing glucose concentration when cows were fasted. Entodiniomorphids exhibited chemotaxis to similar concentrations of glucose as did isotrichids, but to a lesser magnitude of response. In experiment 2, xylose was chemotactic to both groups. Xylose might draw fibrolytic entodiniomorphid protozoa toward newly ingested feed. In contrast, even though isotrichids should not use xylose as an energy source, they were highly chemoattracted to xylose. In experiment 3, entodiniomorphids were not selectively chemoattracted toward bacterial or protozoal peptides compared with soy peptides. In experiment 4, despite isotrichid populations decreasing in abundance with increasing time of incubation in PUFA, chemotaxis to glucose remained unchanged. In contrast, entodiniomorphids recovered chemotaxis to glucose with increased time of PUFA incubation. Current results support isotrichid chemotaxis to sugars but also our hypothesis that a more moderate chemotaxis toward glucose and peptides explains how they swim in the fluid but pass from the rumen with the potentially digestible fraction of particulates.
Collapse
Affiliation(s)
- H L Diaz
- Department of Animal Sciences, The Ohio State University, Columbus 43210
| | - S K R Karnati
- Department of Animal Sciences, The Ohio State University, Columbus 43210
| | - M A Lyons
- Department of Animal Sciences, The Ohio State University, Columbus 43210
| | - B A Dehority
- Department of Animal Sciences, The Ohio State University, Columbus 43210
| | - J L Firkins
- Department of Animal Sciences, The Ohio State University, Columbus 43210.
| |
Collapse
|
11
|
Reisfeld B, Ivy JH, Lyons MA, Wright JM, Rogers JL, Mayeno AN. DoseSim: a tool for pharmacokinetic/pharmacodynamic analysis and dose reconstruction. Bioinformatics 2013; 29:400-1. [PMID: 23162056 DOI: 10.1093/bioinformatics/bts671] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
UNLABELLED Assessing and improving the safety of chemicals and the efficacy of drugs depends on an understanding of the biodistribution, clearance and biological effects of the chemical(s) of interest. A promising methodology for the prediction of these phenomena is physiologically based pharmacokinetic/pharmacodynamic modeling, which centers on the prediction of chemical absorption, distribution, metabolism and excretion (pharmacokinetics) and the biological effects (pharmacodynamics) of the chemical on the organism. Strengths of this methodology include modeling across multiple scales of biological organization and facilitate the extrapolation of results across routes of exposure, dosing levels and species. It is also useful as the foundation for tools to (i) predict biomarker levels (concentrations of chemical species found in the body that indicate exposure to a foreign chemical), given a chemical dose or exposure; (ii) reconstruct a dose, given the levels of relevant biomarkers; and (iii) estimate population variability. Despite the importance and promise of physiologically based pharmacokinetic /pharmacodynamics-based approaches to forward and reverse dosimetry, there is currently a lack of user-friendly, freely available implementations that are accessible and useful to a broad range of users. DoseSim was developed to begin to fill this gap. AVAILABILITY The application is available under the GNU General Public License from http://scb.colostate.edu/dosesim.html.
Collapse
Affiliation(s)
- Brad Reisfeld
- Department of Chemical and Biological Engineering, School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA.
| | | | | | | | | | | |
Collapse
|
12
|
Lyons MA, Yang RS, Mayeno AN, Reisfeld B. Computational toxicology of chloroform: reverse dosimetry using Bayesian inference, Markov chain Monte Carlo simulation, and human biomonitoring data. Environ Health Perspect 2008; 116:1040-6. [PMID: 18709138 PMCID: PMC2516557 DOI: 10.1289/ehp.11079] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Accepted: 04/24/2008] [Indexed: 05/26/2023]
Abstract
BACKGROUND One problem of interpreting population-based biomonitoring data is the reconstruction of corresponding external exposure in cases where no such data are available. OBJECTIVES We demonstrate the use of a computational framework that integrates physiologically based pharmacokinetic (PBPK) modeling, Bayesian inference, and Markov chain Monte Carlo simulation to obtain a population estimate of environmental chloroform source concentrations consistent with human biomonitoring data. The biomonitoring data consist of chloroform blood concentrations measured as part of the Third National Health and Nutrition Examination Survey (NHANES III), and for which no corresponding exposure data were collected. METHODS We used a combined PBPK and shower exposure model to consider several routes and sources of exposure: ingestion of tap water, inhalation of ambient household air, and inhalation and dermal absorption while showering. We determined posterior distributions for chloroform concentration in tap water and ambient household air using U.S. Environmental Protection Agency Total Exposure Assessment Methodology (TEAM) data as prior distributions for the Bayesian analysis. RESULTS Posterior distributions for exposure indicate that 95% of the population represented by the NHANES III data had likely chloroform exposures < or = 67 microg/L [corrected] in tap water and < or = 0.02 microg/L in ambient household air. CONCLUSIONS Our results demonstrate the application of computer simulation to aid in the interpretation of human biomonitoring data in the context of the exposure-health evaluation-risk assessment continuum. These results should be considered as a demonstration of the method and can be improved with the addition of more detailed data.
Collapse
Affiliation(s)
- Michael A. Lyons
- Quantitative and Computational Toxicology Group
- Department of Environmental and Radiological Health Sciences and
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado, USA
| | - Raymond S.H. Yang
- Quantitative and Computational Toxicology Group
- Department of Environmental and Radiological Health Sciences and
| | - Arthur N. Mayeno
- Quantitative and Computational Toxicology Group
- Department of Environmental and Radiological Health Sciences and
| | - Brad Reisfeld
- Quantitative and Computational Toxicology Group
- Department of Environmental and Radiological Health Sciences and
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado, USA
| |
Collapse
|
13
|
Abstract
The individual risk for developing cholesterol gallstones in response to specific environmental factors is determined by complex genetics involving multiple genes. In this review, we introduce inbred mice as a model to localise and identify the murine genes that harbour cholesterol gallstone susceptibility alleles (Lith genes). These genes are associated with increased risk of gallstone formation when mice are fed a lithogenic diet containing cholesterol and cholic acid. We summarise the steps involved in localising the chromosomal regions that harbour Lith genes, focusing particularly on the initial step known as quantitative trait locus mapping, which employs breeding crosses of gallstone-susceptible and gallstone-resistant inbred mouse strains. Subsequent steps to narrow the chromosomal regions of the quantitative trait loci and identify the underlying Lith genes are outlined, with particular reference to the examples of Lith1 and Lith2, the first discovered quantitative trait loci associated with murine cholesterol cholelithiasis. We have now reported five quantitative trait loci for murine cholelithogenesis, which are officially named Lith1 through Lith5. Once the genes underlying these quantitative trait loci and other chromosomal loci from ongoing mouse crosses are identified and confirmed, the 'road-map' for discovery of orthologous human LITH genes will be available and, thereafter, their putative roles in cholesterol gallstone formation can be tested in selected human populations.
Collapse
Affiliation(s)
- H Wittenburg
- Department of Medicine, Harvard Medical School, Gastroenterology Division, Brigham and Women's Hospital, and Harvard Digestive Diseases Center, Boston, MA 02115, USA
| | | | | | | |
Collapse
|
14
|
Abstract
This study was designed to investigate the effects of oleic (CIS), palmitic (SAT) and trans fatty acids (TRANS) on cholesterol metabolism. Rats fed the TRANS diet had lower plasma total cholesterol (P < 0.005) and non-HDL-cholesterol (non HDL-C) concentrations (P < 0.005) compared with their CIS-fed counterparts. Plasma HDL-C was highest in rats fed the SAT diet (P = 0.01). An in vivo assay of reverse cholesterol transport (RCT) was performed whereby radiolabeled cholesterol was delivered to the liver as acetylated LDL and the reappearance of label into plasma and HDL was determined. Plasma radioactivity in TRANS-fed rats was lower than in their SAT-fed counterparts (P = 0.01), and consistent with the cholesterol distribution in plasma, the difference was due to lower [(3)H]-cholesterol in lower density lipoproteins. Despite diet-induced differences in the cholesterol and phospholipid concentrations and fatty acid composition of HDL, the amount of label in HDL did not differ among groups, suggesting that consumption of these diets resulted in HDL populations with similar capacity to participate in RCT. The present findings suggest that dietary trans fatty acids regulate the metabolism of apolipoprotein B-containing lipoproteins in rats and that the effect may be masked in species possessing high plasma cholesteryl ester transfer protein (CETP) activity. These results reinforce the important role of CETP activity in determining the distribution of plasma cholesterol in response to dietary trans fatty acids.
Collapse
Affiliation(s)
- L M Gatto
- Human Nutrition Unit, School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW 2006, Australia
| | | | | | | |
Collapse
|
15
|
Gatto LM, Lyons MA, Brown AJ, Samman S. Trans fatty acids and cholesterol metabolism: mechanistic studies in rats and rabbits fed semipurified diets. Int J Food Sci Nutr 2001; 52:435-41. [PMID: 11517736 DOI: 10.1080/09637480120078320] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [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: 10/16/2022]
Abstract
Studies were conducted in rabbits and rats to investigate the effects of diets rich in oleic (CIS diet), palmitic (SAT diet) and trans fatty acids (TRANS diet) on plasma lipids and lipoprotein metabolism. An important difference between these species is that rabbits possess plasma cholesteryl ester transfer protein (CETP) activity while rats are devoid of transfer activity. In the presence of dietary cholesterol (0.2% w/w) the change in plasma low density lipoprotein-cholesterol (LDL-C) concentration from baseline was significantly higher in rabbits fed the TRANS diet compared with those fed the CIS diet (P < 0.01). Despite this difference, the hepatic LDL-receptor activity was similar in all groups. Also, the fatty acid composition of hepatic phospholipids was affected by diet with lower proportion of palmitic (11%) and higher (19%) linoleic acid despite a similar content in the diet. These effects may represent the maintenance of membrane fluidity within narrow limits to ensure optimal function. The studies in rats showed that the plasma total cholesterol concentration was 20% lower (P < 0.01) in TRANS-fed rats compared with those fed the CIS diet. The results of an in vivo assay of reverse cholesterol transport (RCT) suggested that the three diets gave rise to high density lipoprotein (HDL) particles with similar capacity to accept cellular cholesterol. The differential effects of dietary trans fatty acids in these animal models provide another line of evidence that reinforces the significant role of CETP activity in determining the distribution of plasma cholesterol in response to dietary trans fatty acids.
Collapse
Affiliation(s)
- L M Gatto
- Human Nutrition Unit, Department of Biochemistry, University of Sydney, Sydney, NSW, 2006, Australia
| | | | | | | |
Collapse
|
16
|
Abstract
7-Ketocholesterol (7K) is a quantitatively important oxysterol in both atherosclerotic lesions and macrophage foam cells. We reported recently that radiolabeled 7K delivered to rodents in a modified lipoprotein or chylomicron remnant-like emulsion, both cleared predominantly by the liver, was rapidly excreted into the intestine as water-soluble products, presumably bile acids. Herein, we aimed to elucidate the early or initial reactions in 7K metabolism. The hypothesis was tested that sterol 27-hydroxylase, a mitochondrial cytochrome P450 and the first enzyme of the acidic bile acid pathway, is responsible for the initial metabolism of 7K by HepG2 cells, a human hepatoblastoma cell-line. The 27-hydroxylated product of 7K (27OH-7K) was shown to be the initial, lipid-soluble product of 7K metabolism. It was produced in mitochondrial incubations and whole cells and was readily released into the media from cells. Intact cells generated metabolites of 7K that had undergone conversion from lipid-soluble precursors to water-soluble products rapidly and extensively. Their production was ablated with cyclosporin A, a sterol 27-hydroxylase inhibitor. Furthermore, we demonstrated the effectiveness of two novel selective inhibitors of this enzyme, GW273297X and GI268267X. These inhibitors also ablated the production of water-soluble products by cells; and the inhibitor of choice, GW273297X, decreased the production of 27OH-7K in mitochondrial preparations. This is the first study to demonstrate that sterol 27-hydroxylase plays an important role in the metabolism of oxysterols such as 7K in liver cells.
Collapse
Affiliation(s)
- M A Lyons
- Cell Biology Group, Heart Research Institute, Sydney, New South Wales, Australia
| | | |
Collapse
|
17
|
Abstract
AIM OF THE STUDY This phenomenological study examined what it was like for the wives/female partners to live with a Vietnam veteran who suffers from post-traumatic stress disorder (PTSD). PROCEDURE Audio-taped interviews were conducted with 10 women and data were examined from three overlapping phases of the veteran/partner relationship: the early phase, the middle phase and the later phase. FINDINGS The early phase was conceptualized as a period of adjustment in which three themes were identified: (1) attractors, (2) feelings and (3) communication. The middle phase, one of enmeshment, was characterized by six themes: (1) dealing with veteran PTSD symptoms, (2) substance abuse, (3) physical and/or emotional abuse, (4) roles, (5) feelings and (6) coping techniques. Three themes depicted the later phase of resolution/healing: (1) stress related symptoms, (2) staying or leaving and (3) activities that promoted an ongoing process of resolution/healing. CONCLUSIONS The central meaning statement that best described the experience of wives/female partners who live with a Vietnam veteran with PTSD is that the experience is a gradual process of becoming enmeshed in the veteran's pathology, with all energies being directed at minimizing the effect on self and family, culminating in intermittent movement towards resolution/healing. This study has implications for practitioners who treat Vietnam PTSD veterans and their wives or female partners.
Collapse
Affiliation(s)
- M A Lyons
- University of Alabama, Capstone College of Nursing, Tuscaloosa 35487-0358, USA.
| |
Collapse
|
18
|
Lyons MA, Brown AJ. 7-Ketocholesterol delivered to mice in chylomicron remnant-like particles is rapidly metabolised, excreted and does not accumulate in aorta. Biochim Biophys Acta 2001; 1530:209-18. [PMID: 11239823 DOI: 10.1016/s1388-1981(01)00083-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cholesterol oxidation products (oxysterols) have been implicated in atherogenesis due to their presence in atherosclerotic tissue and their potent effects in vitro. One of the major oxysterols currently of interest is 7-ketocholesterol (7K) and it has been suggested that the diet is an important source of this oxysterol. This investigation tested the hypothesis that 7K, delivered in a physiologically relevant vehicle, chylomicron remnant-like emulsion (CMR), would be metabolised and excreted by mice in a similar manner and to a similar extent as previously observed in rats when delivered in a chemically modified lipoprotein, acetylated low-density lipoprotein (acLDL). Indeed, the metabolism of 14C-7K delivered in CMR mirrored that of acLDL and was much more rapid than (3)H-cholesterol delivered simultaneously. The 7K-derived (14)C was cleared from the liver, appeared in the intestine and was excreted in the faeces. A substantial proportion of the 7K-derived (14)C in the intestine and faeces was aqueous-soluble, indicating metabolism to polar products, presumably bile acids. Moreover, while cholesterol-derived (3)H increased in the aorta, (14)C appeared transiently and there was no observable accumulation within 24 h. The data confirm our previous findings of rapid hepatic metabolism of 7K when delivered in acLDL and demonstrate that 7K delivered in a vehicle of dietary significance is similarly metabolised and excreted. Indeed, the data encourage further investigation into the contribution that dietary oxysterols may or may not make to atherogenesis.
Collapse
Affiliation(s)
- M A Lyons
- Cell Biology Group, Heart Research Institute, 145 Missenden Road, Camperdown, 2050, Sydney, N.S.W., Australia
| | | |
Collapse
|
19
|
Lyons MA, Samman S, Gatto L, Brown AJ. Rapid hepatic metabolism of 7-ketocholesterol in vivo: implications for dietary oxysterols. J Lipid Res 1999; 40:1846-57. [PMID: 10508204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Abstract
7-Ketocholesterol is a major dietary oxysterol and the predominant non-enzymically formed oxysterol in human atherosclerotic plaque. We tested the hypothesis that 7-ketocholesterol is preferentially retained by tissues relative to cholesterol in vivo. To ensure rapid tissue uptake, acetylated low density lipoprotein, labeled with esters of [(14)C]-7-ketocholesterol and [(3)H]cholesterol, was injected into rats via a jugular catheter. At timed intervals (2 min to 24 h) rats (n = 48 total) were exsanguinated and tissues were dissected and assayed for radioactivity. In two experiments the majority of both radiolabels appeared in the liver after 2 min. In all tissues, (14)C appeared transiently and did not accumulate. Rather, it was metabolized in the liver and excreted into the intestine mainly as aqueous-soluble metabolites (presumably bile acids). By 9 h, (14)C in the liver had decreased to 10% of the injected dose while 36% was present in the intestine. In contrast, at 9 h 38% of (3)H was evident in the liver while only 5% was found in the intestine. Unlike [(3)H]cholesterol, little (14)C was found to re-enter the circulation, indicating that enterohepatic recycling of 7-ketocholesterol was negligible. This is the first report of the distribution of an oxysterol relative to cholesterol, administered simultaneously, in a whole animal model. The finding that [(14)C]-7-ketocholesterol is rapidly metabolized and excreted by the liver suggests that diet may not be a major source of oxysterols in atherosclerotic plaque, and that perhaps dietary oxysterols make little or no contribution to atherogenesis.
Collapse
Affiliation(s)
- M A Lyons
- Cell Biology Group, Heart Research Institute, Camperdown, New South Wales, 2050, Australia
| | | | | | | |
Collapse
|
20
|
Abstract
This study tested the hypothesis that the inhibition of acetylcholinesterase is greater when the insecticide chlorpyrifos (CPF) is in the presence of several polycyclic aromatic hydrocarbons (PAHs) found in house dust. CPF-oxon (CPFO) inhibition curves of purified AChE (electric eel) were generated in the presence or absence of different concentrations of the PAHs pyrene, benzo(a)pyrene, anthracene, and fluoranthene. Without CPF-oxon, all four PAHs themselves inhibited AChE activity with IC50 values in the range 8.2-17 microM. The IC50 for benzo(a)pyrene with human recombinant AChE was 1.5 microM. When AChE was incubated with CPF-oxon together with the PAHs, the inhibitory effect on AChE was additive. This was exemplified by large (60-80%) and significant (P<0.01) inhibition in AChE activity by the PAHs when combined with nanomolar concentrations of CPF-oxon. Kinetic studies indicated that benzo(a)pyrene inhibited AChE in a noncompetitive manner, and the reduction in maximal velocity (Vmax) by benzo(a)pyrene and CPFO together was the sum of the inhibitory effect of the two inhibitors alone, further supporting an additive effect. These data suggest that some PAHs have anticholinesterase activity, and contribute in an additive manner to the inhibitory effect of CPFO on AChE in vitro. Further research is needed to determine the toxicological relevance of these findings.
Collapse
Affiliation(s)
- D A Jett
- Department of Environmental Health Sciences, Johns Hopkins University, Baltimore, MD 21205, USA.
| | | | | |
Collapse
|
21
|
Abstract
7-Ketocholesterol is a major oxidation product of cholesterol found in human atherosclerotic plaque and is more atherogenic than cholesterol in some animal studies. 7-Ketocholesterol can inhibit cholesterol 7 alpha-hydroxylase, the rate-limiting step in bile acid biosynthesis, as well as strongly inhibiting HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis. It has even been suggested that 7-ketocholesterol is formed enzymically as an endogenous regulator of cholesterol biosynthesis. However, when tested as a pharmacological cholesterol-lowering agent, inhibition of HMG-CoA reductase was rapidly overcome and the 7-ketocholesterol metabolised. In vitro, 7-ketocholesterol has wide-ranging and potent effects, most of which have the potential to contribute to atherosclerosis. For example, 7-ketocholesterol can be cytotoxic and can induce apoptosis in vascular cells. These effects, either individually or more likely, in combination, all implicate 7-ketocholesterol in the initiation and development of atherosclerosis, but further work is needed to establish whether or not its role is a direct causal one.
Collapse
Affiliation(s)
- M A Lyons
- Cell Biology Group, Heart Research Institute, Camperdown, NSW, Australia
| | | |
Collapse
|
22
|
Lyons MA. Re: Robinson SP. Road traffic act: expert's dilemmas. Journal of clinical forensic medicine 1998; 5(2): 104-106. J Clin Forensic Med 1998; 5:217. [PMID: 15335525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
|
23
|
Abstract
Many data have been generated concerning individuals with eating disorders such as anorexia and bulimia. However, few data exist that have explored the phenomenon of compulsive overeating or binge eating. The purpose of this study was to determine the meaning of compulsive overeating, or binge eating, in the lives of adult professional women. Six adult women from the south-east United States were interviewed using an open-ended interview format. Interviews were audio-taped and analysed using the Giorgi (1979) method of phenomenology. Recurrent themes that emerged from data collection included those pertaining to childhood experiences with food, descriptions of the types of food most often eaten during the adult years, eating behaviours in the adult years, perceptions of loss of control, reasons for overeating, emotional consequences of overeating, compensatory behaviours, and prevention strategies. The synthesis of meaning statement elicited was that of a personal struggle to achieve or maintain an acceptable weight and gain mastery over binge eating behaviours. This struggle can be likened to an addictive process in which the individual thinks about food constantly, consciously or unconsciously, and eats compulsively in spite of the consequences.
Collapse
Affiliation(s)
- M A Lyons
- The University of Alabama, Capstone College of Nursing, Tuscaloosa 35487-0358, USA
| |
Collapse
|
24
|
Zirvi KA, Dasmahapatra KS, Atabek U, Lyons MA. alpha-Difluoromethylornithine inhibits liver metastasis produced by intrasplenic injection of human tumor cells into nude mice. Clin Exp Metastasis 1989; 7:591-8. [PMID: 2505959 DOI: 10.1007/bf01753670] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [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: 01/01/2023]
Abstract
The purpose of these studies was to examine metastatic potentials of a human colon tumor xenograft (T6) and three different human tumor cell lines (LS174T, HT29 and A549) using the intrasplenic-nude mouse model system (ISMS model system). A further objective was to study the activity of alpha-difluoromethyl-ornithine (DFMO) against primary and metastatic growth of the xenograft and the three cell lines. DFMO is an irreversible inhibitor of ornithine decarboxylase, a rate-limiting step in polyamine biosynthesis. Tumor burdens in the liver of nude mice were observed 6 weeks after the intrasplenic injection with LS174T and 12-14 weeks after intrasplenic injections with T6, HT29 and A549. Most of the mice developed primary tumor growth in the spleens. DFMO showed significant activity against liver metastases but had little or no activity against primary tumor growth in the spleens of the ISMS model and against s.c. growth of the xenograft. The studies demonstrated that the ISMS model system is an excellent system for studying metastatic behavior of human tumors and for studying the antimetastatic activity of experimental drugs.
Collapse
Affiliation(s)
- K A Zirvi
- Surgical Service, VA Medical Center, East Orange, NJ 07019
| | | | | | | |
Collapse
|