Thesis

Dysregulation of connexin-43 (cx43) in doxorubicin-induced cardiotoxicity

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Awarding institution
  • University of Strathclyde
Date of award
  • 2024
Thesis identifier
  • T16981
Person Identifier (Local)
  • 201955566
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Qualification Name
Department, School or Faculty
Abstract
  • The chemotherapeutic drug doxorubicin (DOX) is widely used in the treatment of cancer; however patients experience dose-dependent cardiotoxicity that can manifest acute, early- and late-onset chronic and is associated with a decreased contractility and dilated cardiomyopathy. Similar effects have been reported during cardiac malfunction, which have been linked with a disorganisation and dysfunction of gap junctions called connexins in the heart. Here, we examine the effects of the anthracycline DOX on the expression and localisation of connexin-43 (Cx43) in rodent and human cardiac cells and cells of the vasculature to identify if drug treatment impacts this important cardiac connexin. Through investigating the cardiotoxic effects of DOX, this project has shown that total Cx43 protein levels were reduced in human coronary artery endothelial cells (HCAECs), AC16 cardiomyocytes, human umbilical vein endothelial cells (HUVECs), and human cardiac fibroblasts (hCFs) in response to DOX. Interestingly, Langendorff perfusion of rat hearts with clinically relevant concentrations of DOX resulted in increased Cx43 expression in the left ventricle, with lateralisation of Cx43 in ventricular cardiomyocytes. Further investigation of these effects was explored using human 3D cardiac spheroids comprising HUVECs, hCFs, and iCell cardiomyocytes. Unlike the monolayer studies, Cx43 expression levels were not reduced when the cells were co-expressed in the 3D cell model. However, these spheroids were capable of spontaneous contraction and pilot studies using contractile 3D human iCell cardiomyocytes highlighted a change in contractility and calcium handling in spheroids in response to DOX. Interestingly, parallel studies in cancer cells did not reveal significant changes in Cx43 expression in response to DOX, which may indicate that these effects are cardiac and vascular-cell specific. More recently, there has been a growing number of publications focusing on exosomal Cx43 as a biomarker for DOX-induced cardiotoxicity in cancer patients. The potential for indirect DOX effects on the heart mediated through the release of extracellular vesicles (EVs) from cancer cells is in its infancy as most studies have focussed upon direct drug effects on cardiac function. Nanoparticle tracking analysis of DOX-treated MDA-MB-231 cells did indeed result in significantly increased EVs released with no change in particle size (120-250nm). Challenges were experienced when investigating the exosomal Cx43 during DOX treatment therefore independent funding was secured during the PhD period to go on secondment to the Faculty of Medicine at University of Coimbra (FMUC) to work with Professor Henrique Girão, an expert in exosomal Cx43 biology during cardiotoxicity. During this period, molecular and cellular tools were optimised to permit the future study of Cx43 using their established Cx43 knock out and Cx43-GFP cell models. Establishing these models in Strathclyde Institute of Pharmacy & Biomedical Sciences (SIPBS), will now pave the way for more meaningful interrogation of the functional role of Cx43 doxorubicin-induced cardiotoxicity that was unfortunately beyond the timescale of the current investigation. Collectively, the data generated in this thesis suggest that alterations in Cx43 protein expression and subcellular re-localisation, along with alterations in cardiomyocyte calcium handling may contribute to the detrimental effects of DOX on the heart. This research has ignited new venues for follow-up investigation of Cx43 at the molecular level to understand more fully the implications of the direct and indirect effects of DOX upon Cx43 expression, localisation and activity in the cancer and cardiac niche.
Advisor / supervisor
  • Currie, Susan
  • Cunningham, Margaret
Resource Type
DOI
Date Created
  • 2023

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file details PDF of thesis T16981 2024-06-19 公开 下载