{"id":{"repo_id":"buffalo","oai_identifier":"oai:ubir.buffalo.edu:10477/79863"},"canonical_url":"https://search.dev.ndltd.org/etd/buffalo/oai:ubir.buffalo.edu:10477/79863","repository":{"repo_id":"buffalo","name":"Buffalo","base_url":"https://ubir.buffalo.edu/oai/request"},"display":{"title":"Pharmacokinetics and Receptor-Mediated Pharmacodynamics of Methylprednisolone","abstract":"Ph.D.","abstract_html":"Ph.D.","abstract_has_math":false,"creators":["Ayyar, Vivaswath"],"institution":"State University of New York at Buffalo","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Jusko, William","Pharmaceutical Sciences"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-07-30T15:10:35Z","date_published":"2019-07-30T15:10:35Z","updated_at":"2026-07-27T19:05:19Z","subjects":["pharmaceutical sciences","pharmacology","systems science"],"languages":["eng"],"rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10477/79863","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Jusko, William","Pharmaceutical Sciences"]},{"key":"dc:creator","label":"Author","values":["Ayyar, Vivaswath"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2019-07-30T15:10:35Z","2019","2019-03-12 16:12:58"]},{"key":"dc:publisher","label":"Institution","values":["State University of New York at Buffalo"]},{"key":"dc:type","label":"Dc Type","values":["Text","Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["pharmaceutical sciences","pharmacology","systems science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/10477/79863"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Ph.D.","The corticosteroids possess substantial anti-inflammatory and immunomodulatory activity. Prolonged use of these drugs are, however, associated with adrenal suppression and other dose-limiting metabolic toxicities, manifested as osteoporosis, hyperglycemia, dyslipidemia, and muscle wasting. Most beneficial and adverse effects stem from coupled receptor-mediated genomic actions. The establishment of quantitative pharmacokinetic and pharmacodynamic (PK/PD) relationships for drugs with complex mechanisms, such as corticosteroids, are complicated by various characteristics of the biological systems they interact with. Hence, establishment of a global understanding of corticosteroid action requires systematic studies and measurements to identify the major determinants of steroid responses in the body along with mechanistic and quantitative models for the prediction of their responses. It is hypothesized that a systems approach to PK/PD modeling offers a rational strategy to develop complex – yet mechanistic and useful – multiscale models which reliably predict drug disposition and actions under scenarios of physiologic or pathophysiologic relevance. The major goal of this work was to investigate the pharmacokinetic/pharmacodynamic/pharmacogenomic (PK/PD/PG) relationships of corticosteroid actions in relation to circadian gene expression and inter-tissue responses (Section-I), biological signaling networks (Section-II), and sex differences (Section-III) using integrated PK/PD and systems modeling approaches, supported with data from microarray and proteomics analysis, systemic physiological measurements, and/or more focused quantitation of useful biomarker(s). Methylprednisolone (MPL), a corticosteroid of intermediate potency, was chosen as a model drug for these studies.Inter-tissue responses of MPL were examined in normal male rats. To that end, the identification, assay development, and application of a sensitive, ubiquitous, and pharmacologically relevant biomarker of corticosteroid actions was pursued. Available tissue microarray data were mined to identify a subset of candidate genes, of which the glucocorticoid-induced leucine zipper (GILZ) was selected for further study. Tissue-wide characterization of GILZ was performed through the development of a GILZ-specific quantitative real-time polymerase chain reaction (PCR) assay. Robust circadian oscillations in basal GILZ gene expression were documented in tissues. Tissue expression of GILZ was strongly enhanced (500 – 1080%) in rats dosed with a 50 mg/kg intramuscular bolus of MPL. Simultaneous modeling of baseline and treatment data elucidated mechanistic features of GILZ regulation in tissues. Consideration of tissue-specific baselines and receptor dynamics enabled the prediction of GILZ responses in lung and fat under chronic dosing of MPL.Modeling the nonstationary behavior of GILZ using circadian input rates prompted a different line of questioning; do circadian removal mechanisms contribute to the emergence of oscillations of endogenous substances? An extension to indirect response models was derived by incorporating periodic removal of the response variable. Mathematical behaviors of this model were tested using simulations and compared to circadian input models. The developed model captured applicable PD biomarkers such as plasma uric acid, brain amyloid beta, and dopamine. This type of model provides a mechanistic basis and utility for capturing drug responses displaying nonstationary baselines controlled by removal mechanisms.Attempts were made to extend the laboratory’s long-standing interests in linking the time course of gene-mediated corticosteroid effects from the transcriptome to systemic end-point responses. Combined data mining and systems modeling approaches were employed to connect corticosteroid actions from the scale of molecular events in tissues to clinically measureable responses. Rich, parallel transcriptomic and proteomic time-series data obtained from livers of adrenalectomized rats dosed with a single bolus of MPL permitted an in-depth analysis of MPL actions at the ‘proteome’ level – understanding protein function(s), relationships to transcriptional circuitry, and interactive signaling mechanisms. Functional proteomic strategies were employed to annotate, cluster, and discuss important drug-regulated signaling proteins in liver. In addition to isolating critical protein clusters, this analysis revealed that functionally clustered proteins displayed marked diversity in temporal profiles, underscoring inherent complexities in the dynamic modeling of such systems. Modeling of transcriptomic and proteomic data was performed using two parallel approaches. Data-driven, mechanism-based models assuming drug effects acting on mRNA and protein turnover were proposed to capture the emergent temporal patterns of over 60 genes perturbed by MPL at the mRNA and protein levels. In addition, a model-based platform that connected MPL exposure, hepatic receptor dynamics, and temporal changes in important mRNA and protein mediators with clinically-relevant responses (liver enzyme activity, hyperglycemia, and lymphocyte dynamics) via distinct signaling mechanisms was also developed. Model-based predictions of end-point responses under different doses and regimens were validated using external data sets.Sex is a relevant factor influencing the PK/PD of drugs. However, few preclinical studies to date include sex as a biological variable. The laboratory’s general study paradigm in male rats was extended to females with the hypothesis that comparative PK/PD assessments of MPL disposition and actions in both sexes will provide insights into factors controlling sex differences in steroid responses. Female rats were dosed with MPL within either the proestrus or estrus stage of the four-day rodent reproductive cycle. A specific hypothesis that elevated 17β-estradiol (E2) in females during proestrus would antagonize CS actions in tissues with estrogen receptors (ER) was evaluated. Higher exposures of total MPL were documented in females, regardless of estrous stage, compared to males. Plasma protein binding was the same in both sexes with linear binding at 60%. An extended minimal physiologically-based pharmacokinetic (mPBPK) model was developed to jointly describe the plasma and tissue PK of MPL in both sexes. In vitro measurements of MPL tissue binding using homogenates were used to predict in vivo tissue distribution of MPL within the mPBPK framework. The enhancement of GILZ by MPL in uterus (high ER) from estrus-staged females (negligible E2) was significantly higher than from proestrus females (elevated E2), despite no differences in drug PK and GR availability, supporting the sex hormone-dependent hypothesis of CS antagonism. An mPBPK/PD/PG model for MPL considering circadian rhythms, receptor dynamics, and the rodent estrous cycle was developed and applied to delineate the multi-factorial control of genomic steroid responses in vivo.In summary, this dissertation has broadened current knowledge on the PK and receptor-mediated PD actions of MPL. Fundamental insights gained from more focused assessments of corticosteroid actions were assimilated to transition towards a global systems PK/PD understanding of MPL. The approaches taken in this work for modeling in vivo systems pharmacology can be generalizable to other drugs acting through similar mechanisms."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Pharmacokinetics and Receptor-Mediated Pharmacodynamics of Methylprednisolone"]}]}],"canonical_facts":{"dc:contributor":["Jusko, William","Pharmaceutical Sciences"],"dc:creator":["Ayyar, Vivaswath"],"dc:date":["2019-07-30T15:10:35Z","2019","2019-03-12 16:12:58"],"dc:description":["Ph.D.","The corticosteroids possess substantial anti-inflammatory and immunomodulatory activity. Prolonged use of these drugs are, however, associated with adrenal suppression and other dose-limiting metabolic toxicities, manifested as osteoporosis, hyperglycemia, dyslipidemia, and muscle wasting. Most beneficial and adverse effects stem from coupled receptor-mediated genomic actions. The establishment of quantitative pharmacokinetic and pharmacodynamic (PK/PD) relationships for drugs with complex mechanisms, such as corticosteroids, are complicated by various characteristics of the biological systems they interact with. Hence, establishment of a global understanding of corticosteroid action requires systematic studies and measurements to identify the major determinants of steroid responses in the body along with mechanistic and quantitative models for the prediction of their responses. It is hypothesized that a systems approach to PK/PD modeling offers a rational strategy to develop complex – yet mechanistic and useful – multiscale models which reliably predict drug disposition and actions under scenarios of physiologic or pathophysiologic relevance. The major goal of this work was to investigate the pharmacokinetic/pharmacodynamic/pharmacogenomic (PK/PD/PG) relationships of corticosteroid actions in relation to circadian gene expression and inter-tissue responses (Section-I), biological signaling networks (Section-II), and sex differences (Section-III) using integrated PK/PD and systems modeling approaches, supported with data from microarray and proteomics analysis, systemic physiological measurements, and/or more focused quantitation of useful biomarker(s). Methylprednisolone (MPL), a corticosteroid of intermediate potency, was chosen as a model drug for these studies.Inter-tissue responses of MPL were examined in normal male rats. To that end, the identification, assay development, and application of a sensitive, ubiquitous, and pharmacologically relevant biomarker of corticosteroid actions was pursued. Available tissue microarray data were mined to identify a subset of candidate genes, of which the glucocorticoid-induced leucine zipper (GILZ) was selected for further study. Tissue-wide characterization of GILZ was performed through the development of a GILZ-specific quantitative real-time polymerase chain reaction (PCR) assay. Robust circadian oscillations in basal GILZ gene expression were documented in tissues. Tissue expression of GILZ was strongly enhanced (500 – 1080%) in rats dosed with a 50 mg/kg intramuscular bolus of MPL. Simultaneous modeling of baseline and treatment data elucidated mechanistic features of GILZ regulation in tissues. Consideration of tissue-specific baselines and receptor dynamics enabled the prediction of GILZ responses in lung and fat under chronic dosing of MPL.Modeling the nonstationary behavior of GILZ using circadian input rates prompted a different line of questioning; do circadian removal mechanisms contribute to the emergence of oscillations of endogenous substances? An extension to indirect response models was derived by incorporating periodic removal of the response variable. Mathematical behaviors of this model were tested using simulations and compared to circadian input models. The developed model captured applicable PD biomarkers such as plasma uric acid, brain amyloid beta, and dopamine. This type of model provides a mechanistic basis and utility for capturing drug responses displaying nonstationary baselines controlled by removal mechanisms.Attempts were made to extend the laboratory’s long-standing interests in linking the time course of gene-mediated corticosteroid effects from the transcriptome to systemic end-point responses. Combined data mining and systems modeling approaches were employed to connect corticosteroid actions from the scale of molecular events in tissues to clinically measureable responses. Rich, parallel transcriptomic and proteomic time-series data obtained from livers of adrenalectomized rats dosed with a single bolus of MPL permitted an in-depth analysis of MPL actions at the ‘proteome’ level – understanding protein function(s), relationships to transcriptional circuitry, and interactive signaling mechanisms. Functional proteomic strategies were employed to annotate, cluster, and discuss important drug-regulated signaling proteins in liver. In addition to isolating critical protein clusters, this analysis revealed that functionally clustered proteins displayed marked diversity in temporal profiles, underscoring inherent complexities in the dynamic modeling of such systems. Modeling of transcriptomic and proteomic data was performed using two parallel approaches. Data-driven, mechanism-based models assuming drug effects acting on mRNA and protein turnover were proposed to capture the emergent temporal patterns of over 60 genes perturbed by MPL at the mRNA and protein levels. In addition, a model-based platform that connected MPL exposure, hepatic receptor dynamics, and temporal changes in important mRNA and protein mediators with clinically-relevant responses (liver enzyme activity, hyperglycemia, and lymphocyte dynamics) via distinct signaling mechanisms was also developed. Model-based predictions of end-point responses under different doses and regimens were validated using external data sets.Sex is a relevant factor influencing the PK/PD of drugs. However, few preclinical studies to date include sex as a biological variable. The laboratory’s general study paradigm in male rats was extended to females with the hypothesis that comparative PK/PD assessments of MPL disposition and actions in both sexes will provide insights into factors controlling sex differences in steroid responses. Female rats were dosed with MPL within either the proestrus or estrus stage of the four-day rodent reproductive cycle. A specific hypothesis that elevated 17β-estradiol (E2) in females during proestrus would antagonize CS actions in tissues with estrogen receptors (ER) was evaluated. Higher exposures of total MPL were documented in females, regardless of estrous stage, compared to males. Plasma protein binding was the same in both sexes with linear binding at 60%. An extended minimal physiologically-based pharmacokinetic (mPBPK) model was developed to jointly describe the plasma and tissue PK of MPL in both sexes. In vitro measurements of MPL tissue binding using homogenates were used to predict in vivo tissue distribution of MPL within the mPBPK framework. The enhancement of GILZ by MPL in uterus (high ER) from estrus-staged females (negligible E2) was significantly higher than from proestrus females (elevated E2), despite no differences in drug PK and GR availability, supporting the sex hormone-dependent hypothesis of CS antagonism. An mPBPK/PD/PG model for MPL considering circadian rhythms, receptor dynamics, and the rodent estrous cycle was developed and applied to delineate the multi-factorial control of genomic steroid responses in vivo.In summary, this dissertation has broadened current knowledge on the PK and receptor-mediated PD actions of MPL. Fundamental insights gained from more focused assessments of corticosteroid actions were assimilated to transition towards a global systems PK/PD understanding of MPL. The approaches taken in this work for modeling in vivo systems pharmacology can be generalizable to other drugs acting through similar mechanisms."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/10477/79863"],"dc:language":["eng"],"dc:publisher":["State University of New York at Buffalo"],"dc:rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"dc:subject":["pharmaceutical sciences","pharmacology","systems science"],"dc:title":["Pharmacokinetics and Receptor-Mediated Pharmacodynamics of Methylprednisolone"],"dc:type":["Text","Dissertation"]},"updated_at":"2026-07-27T19:05:19Z"}