Effects of stilbene-enriched tomato extracts on human skin explant models of ageing

Dillon, Oliver (2024) Effects of stilbene-enriched tomato extracts on human skin explant models of ageing. Doctoral thesis, University of East Anglia.

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Abstract

Skin ageing is caused by several factors, with ultraviolet radiation (UVR) from sunlight being a major factor leading to the accelerated skin ageing phenotype photoageing. Photoageing is characterised by the formation of coarse wrinkles caused by increased production of free radicals leading to inflammation and degradation of structural proteins in the extracellular matrix (ECM) by matrix metalloproteinases (MMPs). Additionally, inflammation caused by chronological age, or UVR, can lead to premature skin ageing by causing a chronic low-grade inflammatory state called inflammageing. Due to the involvement of free radicals in the onset of skin ageing, antioxidants are used as a treatment due to their ability to scavenge free radicals. Persephone Bio has produced transgenic tomato plants with synthetic pathways for the overexpression of antioxidants, and extracts from these tomatoes are tested in this project to treat skin ageing. One of these synthetic antioxidant pathways was for the polyphenolic compound resveratrol, as resveratrol has been highly published for its potential health benefits. This project hypothesised that the resveratrol-expressing tomato (ResTom) may produce benefits due to the unique matrix of resveratrol and the plant compounds naturally present in tomatoes. An ex vivo human skin explant system was established to assess changes caused by ultraviolet B (UVB) irradiation and model inflammageing. The Inflammageing explants were treated with the inflammatory molecules interleukin 1 and oncostatin M (IL1/OSM) to mimic chronic inflammation. There was a significant reduction in the expression of the longevity gene SIRT1 after treatment with IL1/OSM compared to treatment with ResTom extracts. UVB irradiation induced the formation of DNA damage and impacted inflammatory pathways, and skin morphology. Immunofluorescent microscopy and histological analysis showed that UVB irradiation caused thymine dimers, a form of direct DNA damage, and activated the inflammatory NF-ᴋB pathway. UVB irradiation also caused the formation of keratinocytes in the epidermis with pyknotic-like nuclei reminiscent of sunburn cells. RNA-seq data showed that genes involved in the degradation of the ECM are upregulated after irradiation with UVB, while genes involved in immune function and skin barrier function were downregulated. These are well characterised changes caused by UVB irradiation and indicate that this ex vivo model accurately depicts excessive UVB exposure.

Additionally, qRT-PCR and RNA-seq showed UVB induced the expression of MMP1 and 3. Adding ResTom extracts to UVB-exposed skin explants had complex effects, both pro- and anti-ageing. However, a combination of qRT-PCR and RNA-seq showed that water-based ResTom extracts act on the NRF2 pathway as treatment of skin explants with ResTom increased gene expression of the antioxidant enzyme SOD2. Analysis with a proteome profiler also showed ResTom could regulate the secretion of nineteen UVB-induced cytokines, including proteins regulated by the NF-ᴋB pathway, suggesting that ResTom can regulate UVB-induced inflammation.

The effects seen in the ex vivo UVB exposure model were recapitulated in the HaCaT keratinocyte cell line with high doses of UVB, causing decreased cell viability. Irradiation of HaCaT cells with UVB also caused increased expression of MMP1, 3 and 12, and ResTom showed a slight reduction in the expression of these MMPs relative to UVB alone, suggesting that it might combat some UVB-induced damage in HaCaT cells. As keratinocytes are the primary cell type in the epidermis, this reinforces the observations seen in the ex vivo model.

Overall, the impacts of tomato extracts on skin biology suggests novel interventions for skin ageing.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	05 Jun 2025 08:46
Last Modified:	05 Jun 2025 08:46
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99400
DOI:

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