Parnasse, Jennyfer Célia;
(2024)
Exploring the molecular mechanisms of aldehyde
dehydrogenase (ALDH)/retinoic acid (RA)-mediated extracellular matrix (ECM) production in activated mucous membrane pemphigoid
(MMP) conjunctival fibroblasts.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Ocular mucous membrane pemphigoid (MMP) is a leading cause of conjunctival scarring resulting in blindness in 20% of cases. Our recent data suggest that the aldehyde dehydrogenase (ALDH)/retinoic acid (RA) pathway constitutes a promising novel therapeutic target as the isoenzyme ALDH1A3 is up-regulated in ocular MMP fibroblasts and ALDH1 inhibition is anti-fibrotic in vitro and in vivo. This study was carried out in vitro using human primary conjunctival fibroblasts from healthy subjects and ocular MMP patients and aimed to decipher the molecular mechanisms underlying the pro-fibrotic effect of the ALDH/RA pathway. Determination of the effect of pharmacological inhibitors and gene silencing (siRNA) on relative gene and protein expression indicated that the canonical and non-canonical RA signalling pathways are not involved in the fibrotic phenotype of ocular MMP fibroblasts but suggested that the ALDH1-mediated increase in COL1 expression may be induced by FABP5/PPARβ/δ signalling. Metabolic studies indicated decreased energy metabolism with reduced oxidative phosphorylation and glycolysis in ocular MMP fibroblasts. Furthermore, decreased secreted levels of active TGF-β and phosphorylation array data also indicated the down-regulation of TGF-β signalling in ocular MMP fibroblasts. In contrast, increased expression of the glutaminolytic enzyme glutamate dehydrogenase, and pharmacological inhibition of the rate-limiting enzyme glutaminase, showed that glutaminolysis is most likely up-regulated in MMP fibroblasts and promotes increased COL1 protein levels. Additionally, comparison of the phosphorylation status of mRNA translation markers (p-4E-BP1, p-eIF2α) between normal and ocular MMP fibroblasts, and further investigation suggested that the ALDH/RA pathway may up-regulate p-4E-BP1 thus increasing COL1 protein synthesis in diseased cells. Surprisingly, investigation of ECM protein degradation via autophagy showed that increased autophagy promotes COL1 accumulation in ocular MMP fibroblasts. Therefore, autophagy does not mediate collagen degradation in MMP fibroblasts. Taken together, the data identified ALDH/RA mediated pro-fibrotic mechanisms and potential targets for novel anti-scarring strategies in ocular MMP.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Exploring the molecular mechanisms of aldehyde dehydrogenase (ALDH)/retinoic acid (RA)-mediated extracellular matrix (ECM) production in activated mucous membrane pemphigoid (MMP) conjunctival fibroblasts |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10198378 |
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