Eberlin S1, Facchini G1, Silva MS1, Pinheiro ALTA1, Vieira AS2, Eberlin S3, Pinheiro, AS1
Skin photoaging has been attributed to other spectra of solar radiation such as infrared A (IRA). This fact has aroused the interest of the scientific community to evaluate the biological changes promoted by IRA in the skin. Considering the advent of 3R policy, the need for development of alternative methods which reflects more accurately the effects of a real condition becomes imminent. In this sense, an alternative to study the mechanisms of skin biology is the use of skin explants obtained from plastic surgery. The aim of this study was to investigate the modulation of genes involved with the functional alterations promoted by IRA radiation in human skin explants, through large-scale gene expression using the mRNA sequencing (RNA-seq - next generation sequencing). Skin fragments from ten (10) healthy female subjects, aged 30-60 years, phototype II - IV, submitted to abdominoplasty, were fractionated using a punch nº 5 and cultured overnight. After this time, they were exposed to daily doses of 360 J/cm2 IRA radiation for four consecutive days, using Hydrosun 750 and HBM1 devices (Hydrosun Medizintechnik GmbH, Müllheim, Germany). Tissue viability was measured using MTT assay in all experimental times (24, 48, 72, 96 and 120 hours after surgical procedure). After 24 hours of the last dose of IRA, skin fragments were subjected to a large scale gene expression analysis by sequencing the whole transcriptome (RNA-Seq). RNA was extracted, followed by fractionation of mRNA and cDNA library construction. Differentially expressed genes were submitted to enrichment pathways analyze using the MetaCore® database (Thomas-Reuters). Regarding tissue viability, there was no difference between irradiated skin fragments and control groups throughout the experiment. Comparison between the transcriptome of irradiated fragments and control indicated the existence of 214 differentially expressed genes (9 upregulated and 205 downregulated). Regarding upregulated genes, IRA radiation led to the enrichment of pathways involved with immune response, development and cell signaling related to neoplasms, specifically with progression of melanoma and insulin-like growth factor in cancer. For the downregulated genes, 72 pathways were found to be significantly enriched, such as those involved with cell adhesion, immune response, cell cycle, sphingolipid metabolism, fatty acid biosynthesis, oxidative stress and signaling pathways involving ERK and AKT. These results showed that IRA radiation is able to modulate genes that correlate with neoplasms, such as squamous cell neoplasia and Merkel cell carcinoma. Additionally, hyperalgesia, irritant contact dermatitis and psoriasis presented significant enrichment. Assessments of gene expression on a large scale revealed relevant changes in skin metabolism, development of aesthetic changes and appearance of cutaneous pathologies on the IRA exposed skin. Important changes are associated with an increase in inflammatory profile, immune response, formation of inflammassome and exacerbation of oxidative stress. In addition, genes that directly impact the formation of stratum corneum and structure of cutaneous epidermis were also compromised. The results obtained reveal different ways to better understand the impact of IRA radiation on human skin, allowing the development of more accurately evaluation methods to check the effectiveness of active and products to protect the skin from the deleterious effects of IRA radiation.