Defining the role of epidermal lipoxygenases and its lipid products in skin homeostasis and disease

Jones, Iestyn 2022. Defining the role of epidermal lipoxygenases and its lipid products in skin homeostasis and disease. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Healthy skin forms an effective barrier that prevents infection and rapid water loss from the body. Epidermal barrier disruption is evident in common skin conditions such as psoriasis and eczema, along with significantly affecting adequate wound healing. Essential to a competent barrier are lipids which are metabolised by a group of enzymes known as lipoxygenases (LOX’s). The molecular mechanisms by which LOX regulates skin homeostasis and prevent skin disease is unexplored and therefore defining the role of LOX in skin is the primary objective of this study. RNA-sequencing of 12R-LOX deficient and wildtype mouse models was performed and results analysed using various bioinformatics tools, allowing the identification of possible molecular networks and biological processes in which LOX may regulate skin function. Interestingly, Gene Ontology (GO) enrichment analysis identified enriched terms relating to differentiation including “keratinocyte differentiation”, “keratinization”, “peptide cross- linking” and “cornified envelope”. Moreover, the majority of differentially expressed genes (DEGs) following 12R-LOX protein deficiency are localised to stratified epidermal layers, suggesting a possible role for 12R-LOX derived lipids in differentiated layers. Interestingly, upregulated genes with a 1.5 fold change included genes involved in the epidermal differentiation complex (EDC), such as small proline-rich protein 1b (Sprr1b), small proline- rich protein 2d (Sprr2d) and repetin (Rptn). KO vs. WT dataset also identified the statistically significantly downregulation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Pparγc1α), hypothesised to be involved in regulating keratinocyte differentiation. As the RNA-sequencing data pointed towards a possible role for 12R-LOX in keratinocyte differentiation, investigation into the effect of 9R,10R,13R-TriHOME terminal product of the 12R-LOX / eLOX-3 pathway showed an increasing effect on the protein level of important differentiation markers (Ivl and Krt10), whilst further in vitro experiments ruled out a role in proliferation, migration and apoptosis respectively. It was also identified in this thesis that the 9R,10R,13R-TriHOME activates Pparγc1α, which was downregulated in 12R- LOX deficient vs wildtype and has previously been demonstrated to be implicated in the process of differentiation. Bioinformatics and biochemical data indicate a possible role for 12R-LOX derived lipids in keratinocyte differentiation which is an important process for the development of an effective skin barrier. These observations raise the possibility of utilising the 9R,10R,13R- TriHOME as treatment for skin disorders with a defective epidermal barrier function.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Pharmacy
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	31 May 2022
Last Modified:	06 Jul 2023 01:53
URI:	https://orca.cardiff.ac.uk/id/eprint/150144

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