Skin Microbiome and Polymorphic Light Eruption

Overview

Polymorphic light eruption (PLE) is the most common form among UV-inducible disorders with a prevalence of approximately 11-21% worldwide and a clear predisposition of women. Usually, within several hours after an intense UV exposure, most likely in spring or early summer, the formation of itchy skin lesions particularly at the upper arms and V-neck and neck is distinctive for PLE. It has been suggested that the development of a potential photo-induced antigen may initiate a delayed-type hypersensitivity reaction in PLE (causing the skin rash) and the microbiota of the skin may be involved. We thus hypothesized that eliminating the microbiota of the skin by disinfection may affect the formation of PLE. The concept of this study covers a combined interindividual and intraindividual half-body comparison of the skin reactions of disinfected and contralateral non-disinfected areas upon UV exposure in PLE patients and healthy subjects.

UV-induced erythema and pigmentation is quantified by visual scoring and reflectance spectroscopy to determine the minimum erythema dose (MED) exploring the fields of an UV test ladder on the dorsal skin of the study subjects. Investigations after determining the MED and consecutive photo provocations on 4 subsequent days (PLE group only) using solar simulated UV radiation with slight dose increments include a half-body site comparison of test areas located on the back of the subjects in a randomized, double blinded manner. The microbiota of a respective test area is removed by the disinfection with Octeniderm (octenidine dihydrochloride, 1-propanol, 2- propanol) whereas a control site remains non-disinfected (sham-treated with physiologic sodium chloride solution). The PLE related symptoms are evaluated by a validated PLE score, which is composed as follows: Affected skin area (AA) \[range, 0-4\] + skin infiltration (SI) \[range, 0-4\] + 0.4 pruritus (P) \[range, 0-10\]; (\[total range 0-12\]. As additional procedures, tape strips and skin swabs are taken immediately after UV exposures. The material is used for shotgun metagenomic sequencing of microbes and further analysis such as quantitative measures of antimicrobial peptides and urocanic acid levels. Furthermore, suction blisters are produced after MED testing and the last day of photo provocation \[Time Frame: At day 3 and 6\] to profile the inflammatory milieu of the skin by transcriptomics. The epidermal blister roof is used together with optional skin biopsies (PLE patients only) for various investigations, including H/E and immunohistochemical stainings and messenger ribonucleic acid (mRNA) analysis.