Oral and Poster Presentation 18th International Congress on Photobiology 2024

Endogenous photosensitizers (EP) are responsive to solar photon absorption, leading to oxidative stress upon prolonged sun exposure. Among these, 6-formylindole [3,2-b] carbazole (FICZ) (fig.1A) stands out for its potent properties as an aryl hydrocarbon receptor (AhR) agonist¹, but it’s role in photooxidative stress remains incompletely understood². To elucidate the impact on cellular lipids, we examined the photophysical and photochemical characteristics of FICZ and compared them with indole [3,2-b] carbazole (ICZ), a non-typical EP lacking triplet species and singlet oxygen formation. Our objective was to investigate FICZ's oxidative stress on giant unilamellar vesicles (GUVs). To investigate the role of FICZ on oxidative stress, GUVs were prepared via the natural swelling method with EP and DOPC, and then examined using epifluorescence microscopy. Previous photochemical and photophysical assays showed that FICZ has ΦΔ of 0.53 and Φf of 0.15, contrasting ICZ with ΦΔ of 0.05 and Φf of 0.30.³ In HaCaT cells, FICZ induced phototoxicity and AhR translocation, while GUVs photosensitized with FICZ exhibited hydroperoxide formation (fig.1C), consistent with its ΦΔ, whereas ICZ led to instability due to its rigid structure. 

Figure 1. Molecular structure of FICZ (A) and ICZ (B). GUV of FICZ:DOPC (1:100) observed over 158 seconds under UVA irradiation. Scale 10µm.