Research paperEpidermal long non-coding RNAs are regulated by ultraviolet irradiation
Introduction
The epidermis, the outermost layer of the skin, is the primary protective barrier that shields the internal organs from physical and chemical damage. Exposure to ultraviolet (UV) radiation from sunlight is the main cause of non-melanoma skin cancer, as UV irradiation weakens the protective function of skin (Feehan and Shantz, 2016). According to wavelength, UVs are classified as UVA at 320–400 nm, UVB at 290–320 nm, and UVC at shorter ray. UV exposure damages the cell in various ways (Cornaghi et al., 2016, Zeng et al., 2016). UVB exposure especially causes the damage of epidermal layer and further leads to the development of skin cancer (Bowden, 2004). Exposure to UVB light causes the mutation of DNA by inducing the dimerization of adjacent pyrimidine residues (Ikehata and Ono, 2011). In addition, UVB irradiation alters gene expression patterns by disrupting various cell-signaling pathways (Sesto et al., 2002, El-Abaseri et al., 2006).
In recent years, a large number of non-coding RNAs (ncRNAs)—RNAs that are not translated into proteins—have been identified by transcriptional analysis. Any ncRNAs longer than 200 nucleotides are generally classified as long ncRNAs (lncRNAs), which are emerging as important regulators of several cellular processes such as development and differentiation, as well as multiple pathological processes including tumorigenesis (Fatica and Bozzoni, 2014, Adams et al., 2017).
Although many genes and signaling pathways affected by UV irradiation have been described, there are relatively few studies on the effects of UV irradiation on the expression of lncRNAs in epidermal cells. In this study, we conducted a microarray analysis to evaluate the transcriptional profile of lncRNAs after UVB irradiation in keratinocytes.
Section snippets
Cell culture
Human primary epidermal keratinocytes were obtained from Lonza (Walkersville, MD, USA) and were maintained in serum-free KGM-Gold media with Bullet-kit supplements (Lonza). For UVB irradiation, keratinocytes were grown to 70% confluences, then the culture medium was replaced with phosphate buffered saline. 30 mJ/cm2 UVB irradiation was performed using the BIO-SUN irradiation system (Vilber Lourmat, Torcy, France) with peak wavelength at 312 nm.
Microarray analysis
Total RNAs from two independent biological replicates
Analysis of differentially expressed mRNAs and lncRNAs after UVB irradiation
To investigate the changes in lncRNA expression after UVB irradiation, microarray analysis was then performed. Then, differentially expressed lncRNAs and mRNAs were analyzed after checking the quality of RNAs (Supplementary Table 1) and normalizing the band intensities (Fig. 1A). The expression of several lncRNAs and mRNAs was significantly altered, as shown in heat maps with hierarchical clustering (Fig. 1B). Top 20 mRNAs and lncRNAs changed by UVB irradiation were listed Supplementary Table 2
Discussion
UV irradiation is a major environmental carcinogen for the skin. UVB (~ 280–320 nm) radiation is absorbed by the epidermis, damaging the cells. These damaged cells have the potential to progress to a cancerous state (Ikehata and Ono, 2011). Recently, lncRNAs have gained massive attention as they play critical roles in essential biological processes and pathological conditions (Hombach and Kretz, 2013, Schmitz et al., 2016).
Previous studies have demonstrated that the expression of ncRNAs is
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