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Windoloski KA, Janum S, Berg RMG, Olufsen MS. Characterization of differences in immune responses during bolus and continuous infusion endotoxin challenges using mathematical modelling. Exp Physiol 2024; 109:689-710. [PMID: 38466166 PMCID: PMC11061636 DOI: 10.1113/ep091552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 02/13/2024] [Indexed: 03/12/2024]
Abstract
Endotoxin administration is commonly used to study the inflammatory response, and though traditionally given as a bolus injection, it can be administered as a continuous infusion over multiple hours. Several studies hypothesize that the latter better represents the prolonged and pronounced inflammation observed in conditions like sepsis. Yet very few experimental studies have administered endotoxin using both strategies, leaving significant gaps in determining the underlying mechanisms responsible for their differing immune responses. We used mathematical modelling to analyse cytokine data from two studies administering a 2 ng kg-1 dose of endotoxin, one as a bolus and the other as a continuous infusion over 4 h. Using our model, we simulated the dynamics of mean and subject-specific cytokine responses as well as the response to long-term endotoxin administration. Cytokine measurements revealed that the bolus injection led to significantly higher peaks for interleukin (IL)-8, while IL-10 reaches higher peaks during continuous administration. Moreover, the peak timing of all measured cytokines occurred later with continuous infusion. We identified three model parameters that significantly differed between the two administration methods. Monocyte activation of IL-10 was greater during the continuous infusion, while tumour necrosis factor α $ {\alpha} $ and IL-8 recovery rates were faster for the bolus injection. This suggests that a continuous infusion elicits a stronger, longer-lasting systemic reaction through increased stimulation of monocyte anti-inflammatory mediator production and decreased recovery of pro-inflammatory catalysts. Furthermore, the continuous infusion model exhibited prolonged inflammation with recurrent peaks resolving within 2 days during long-term (20-32 h) endotoxin administration.
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Affiliation(s)
| | - Susanne Janum
- Frederiksberg and Bispebjerg HospitalsFrederiksbergDenmark
- Department of Biomedical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Ronan M. G. Berg
- Department of Biomedical SciencesUniversity of CopenhagenCopenhagenDenmark
- Department of Clinical Physiology and Nuclear Medicine and, Centre for Physical Activity ResearchCopenhagen University HospitalCopenhagenDenmark
- Neurovascular Research LaboratoryUniversity of South WalesPontypriddUK
| | - Mette S. Olufsen
- Department of MathematicsNorth Carolina State UniversityRaleighNorth CarolinaUSA
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Somvanshi PR, Mellon SH, Yehuda R, Flory JD, Makotkine I, Bierer L, Marmar C, Jett M, Doyle FJ. Role of enhanced glucocorticoid receptor sensitivity in inflammation in PTSD: insights from computational model for circadian-neuroendocrine-immune interactions. Am J Physiol Endocrinol Metab 2020; 319:E48-E66. [PMID: 32315214 DOI: 10.1152/ajpendo.00398.2019] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Although glucocorticoid resistance contributes to increased inflammation, individuals with posttraumatic stress disorder (PTSD) exhibit increased glucocorticoid receptor (GR) sensitivity along with increased inflammation. It is not clear how inflammation coexists with a hyperresponsive hypothalamic-pituitary-adrenal (HPA) axis. To understand this better, we developed and analyzed an integrated mathematical model for the HPA axis and the immune system. We performed mathematical simulations for a dexamethasone (DEX) suppression test and IC50-dexamethasone for cytokine suppression by varying model parameters. The model analysis suggests that increasing the steepness of the dose-response curve for GR activity may reduce anti-inflammatory effects of GRs at the ambient glucocorticoid levels, thereby increasing proinflammatory response. The adaptive response of proinflammatory cytokine-mediated stimulatory effects on the HPA axis is reduced due to dominance of the GR-mediated negative feedback on the HPA axis. To verify these hypotheses, we analyzed the clinical data on neuroendocrine variables and cytokines obtained from war-zone veterans with and without PTSD. We observed significant group differences for cortisol and ACTH suppression tests, proinflammatory cytokines TNFα and IL6, high-sensitivity C-reactive protein, promoter methylation of GR gene, and IC50-DEX for lysozyme suppression. Causal inference modeling revealed significant associations between cortisol suppression and post-DEX cortisol decline, promoter methylation of human GR gene exon 1F (NR3C1-1F), IC50-DEX, and proinflammatory cytokines. We noted significant mediation effects of NR3C1-1F promoter methylation on inflammatory cytokines through changes in GR sensitivity. Our findings suggest that increased GR sensitivity may contribute to increased inflammation; therefore, interventions to restore GR sensitivity may normalize inflammation in PTSD.
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Affiliation(s)
- Pramod R Somvanshi
- Harvard John Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
| | - Synthia H Mellon
- Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Francisco, California
| | - Rachel Yehuda
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Janine D Flory
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Iouri Makotkine
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Linda Bierer
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Charles Marmar
- Department of Psychiatry, New York Langone Medical School, New York, New York
| | - Marti Jett
- Integrative Systems Biology, U.S. Army Medical Research and Materiel Command, U.S. Army Center for Environmental Health Research (USACEHR), Fort Detrick, Frederick, Maryland
| | - Francis J Doyle
- Harvard John Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
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Somvanshi PR, Mellon SH, Flory JD, Abu-Amara D, Wolkowitz OM, Yehuda R, Jett M, Hood L, Marmar C, Doyle FJ. Mechanistic inferences on metabolic dysfunction in posttraumatic stress disorder from an integrated model and multiomic analysis: role of glucocorticoid receptor sensitivity. Am J Physiol Endocrinol Metab 2019; 317:E879-E898. [PMID: 31322414 PMCID: PMC6879860 DOI: 10.1152/ajpendo.00065.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 06/28/2019] [Accepted: 07/17/2019] [Indexed: 02/08/2023]
Abstract
Posttraumatic stress disorder (PTSD) is associated with neuroendocrine alterations and metabolic abnormalities; however, how metabolism is affected by neuroendocrine disturbances is unclear. The data from combat-exposed veterans with PTSD show increased glycolysis to lactate flux, reduced TCA cycle flux, impaired amino acid and lipid metabolism, insulin resistance, inflammation, and hypersensitive hypothalamic-pituitary-adrenal (HPA) axis. To analyze whether the co-occurrence of multiple metabolic abnormalities is independent or arises from an underlying regulatory defect, we employed a systems biological approach using an integrated mathematical model and multiomic analysis. The models for hepatic metabolism, HPA axis, inflammation, and regulatory signaling were integrated to perform metabolic control analysis (MCA) with respect to the observations from our clinical data. We combined the metabolomics, neuroendocrine, clinical laboratory, and cytokine data from combat-exposed veterans with and without PTSD to characterize the differences in regulatory effects. MCA revealed mechanistic association of the HPA axis and inflammation with metabolic dysfunction consistent with PTSD. This was supported by the data using correlational and causal analysis that revealed significant associations between cortisol suppression, high-sensitivity C-reactive protein, homeostatic model assessment of insulin resistance, γ-glutamyltransferase, hypoxanthine, and several metabolites. Causal mediation analysis indicates that the effects of enhanced glucocorticoid receptor sensitivity (GRS) on glycolytic pathway, gluconeogenic and branched-chain amino acids, triglycerides, and hepatic function are jointly mediated by inflammation, insulin resistance, oxidative stress, and energy deficit. Our analysis suggests that the interventions to normalize GRS and inflammation may help to manage features of metabolic dysfunction in PTSD.
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Affiliation(s)
- Pramod R Somvanshi
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
| | - Synthia H Mellon
- Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Francisco, California
| | - Janine D Flory
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Duna Abu-Amara
- Department of Psychiatry, New York Langone Medical School, New York, New York
| | - Owen M Wolkowitz
- Department of Psychiatry, University of California, San Francisco, California
| | - Rachel Yehuda
- Department of Psychiatry, James J. Peters Veterans Affairs Medical Center, Bronx, New York
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Marti Jett
- Integrative Systems Biology, US Army Medical Research and Materiel Command, US Army Center for Environmental Health Research, Fort Detrick, Frederick, Maryland
| | - Leroy Hood
- Institute for Systems Biology, Seattle, Washington
| | - Charles Marmar
- Department of Psychiatry, New York Langone Medical School, New York, New York
| | - Francis J Doyle
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
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Ramirez-Zuniga I, Rubin JE, Swigon D, Clermont G. Mathematical modeling of energy consumption in the acute inflammatory response. J Theor Biol 2019; 460:101-114. [PMID: 30149010 PMCID: PMC6690200 DOI: 10.1016/j.jtbi.2018.08.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 08/20/2018] [Accepted: 08/22/2018] [Indexed: 01/20/2023]
Abstract
When a pathogen invades the body, an acute inflammatory response is activated to eliminate the intruder. In some patients, runaway activation of the immune system may lead to collateral tissue damage and, in the extreme, organ failure and death. Experimental studies have found an association between severe infections and depletion in levels of adenosine triphosphate (ATP), increase in nitric oxide production, and accumulation of lactate, suggesting that tissue energetics is compromised. In this work we present a differential equations model that incorporates the dynamics of ATP, nitric oxide, and lactate accompanying an acute inflammatory response and employ this model to explore their roles in shaping this response. The bifurcation diagram of the model system with respect to the pathogen growth rate reveals three equilibrium states characterizing the health, aseptic and septic conditions. We explore the domains of attraction of these states to inform the instantiation of heterogeneous virtual patient populations utilized in a survival analysis. We then apply the model to study alterations in the inflammatory response and survival outcomes in metabolically altered conditions such as hypoglycemia, hyperglycemia, and hypoxia.
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Affiliation(s)
- Ivan Ramirez-Zuniga
- Department of Mathematics, 301 Thackeray Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States.
| | - Jonathan E Rubin
- Department of Mathematics, 301 Thackeray Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - David Swigon
- Department of Mathematics, 301 Thackeray Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Gilles Clermont
- Department of Mathematics, 301 Thackeray Hall, University of Pittsburgh, Pittsburgh, PA 15260, United States; Department of Critical Care Medicine, 3550 Terrace St., University of Pittsburgh Medical Center, Pittsburgh, PA 15261, United States; Department of Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, PA 15260, United States
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