Culley, Miranda
(2020)
Frataxin deficiency coordinates iron-sulfur-dependent metabolic and genomic stress to promote endothelial senescence in pulmonary hypertension.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Pulmonary hypertension (PH) is a heterogeneous, fatal disease of the lung vasculature with incompletely defined molecular underpinnings. Specifically, the pathological contributions of endothelial cells to this panvasculopathy remain controversial and unresolved. Endothelial mitochondrial dysfunction and DNA damage have been separately linked to PH, but any shared mechanistic regulation, joint contribution to shifting endothelial phenotypes, and relevance across PH subtypes are unknown. Mutations in the iron-sulfur (Fe-S) biogenesis gene frataxin (FXN) disrupt metabolism and genomic integrity, causing Friedreich’s ataxia (FRDA). This multisystem disease is defined by neurodegeneration and hypertrophic cardiomyopathy (HCM) with the latter driving patient mortality. HCM is often complicated by PH but few studies have interrogated pulmonary vascular phenotypes in FRDA. Separately, deficiencies of other Fe-S cluster assembly genes induced endothelial mitochondrial dysfunction and PH development in vivo. Therefore, we hypothesized that endothelial FXN deficiency and its metabolic and genomic consequences may predispose to PH. Here, we demonstrated acute FXN knockdown abrogated Fe-S biogenesis to attenuate mitochondrial respiration and induce replication stress and growth arrest. Sustained FXN deficiency led to inhibition of Fe-S-containing nuclear proteins, persistent DNA damage response, and apoptosis resistance, culminating in increased vasomotor tone and senescence. Consequently, endothelial FXN deficiency in hypoxic mice increased senescence and worsened PH, which could be prevented with senolytic treatment. Supporting this mechanism, reduced FXN expression alongside elevated senescence markers were observed in animal and patient lung tissues representing multiple PH etiologies. Specifically, we defined HIF--dependent epigenetic reduction of FXN, illustrating the relevance of acquired FXN deficiency in the pulmonary endothelium. Notably, FXN-dependent endothelial senescence was also demonstrated in inducible pluripotent stem cells-derived endothelial cells from patients with FRDA, offering a plausible explanation for a predisposition to PH, independent of or additive to left ventricular dysfunction. Altogether, these data demonstrate that epigenetic or genetic FXN deficiency orchestrates Fe-S-dependent metabolic and replication stress which converge on irreversible senescence, signifying a novel endothelial-specific mechanism across PH subtypes, including PH due to left heart disease. In doing so, this work offers foundational evidence for the identification of a cohort of FRDA patients at risk for PH and endorse several Fe-S-related treatment options including senotherapies.
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| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
1 October 2020 |
| Date Type: |
Publication |
| Defense Date: |
3 August 2020 |
| Approval Date: |
1 October 2020 |
| Submission Date: |
18 August 2020 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
183 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Cellular and Molecular Pathology |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Pulmonary hypertension, endothelium, senescence, metabolism, replication stress, Friedreich's ataxia |
| Date Deposited: |
01 Oct 2020 15:44 |
| Last Modified: |
01 Oct 2020 15:44 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/39644 |
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