Análise do estresse oxidativo, reparo do DNA e alterações epigenéticas no líquen plano

Abstract

Lichen planus (LP) is a mucocutaneous, inflammatory disease immunologically mediated by cytotoxic T lymphocytes (CD8+ CTL). While oral lichen planus (OLP) is considered a potentially malignant lesion, cutaneous lichen planus (CLP) is a typically self-limiting condition, suggesting that the pathogenesis of these lesions may be distinct. Thus, the aim of this study was, first, to evaluate the levels of oxidative stress markers in the saliva of patients with OLP and, subsequently, to analyze the expression profile of DNA repair proteins (XRCC1 and APE1) and H3K9 histone acetylation in the OLP and CLP. For the oxidative stress study, 34 individuals participated in the research, of which 22 were clinically and histopathologically diagnosed with OLP (reticular and erosive) and 12 were control cases. Non-stimulated sialometry was performed and, subsequently, oxidative stress (MPO, MDA) and antioxidant action (SOD, GSH) markers were determined. To perform the study on DNA repair and H3K9 histone acetylation, the total sample consisted of 89 cases of LP (66 OLP and 23 CLP). Analysis of APE1 and XRCC1 expression was performed by immunohistochemistry, whereas the analysis of H3K9 acetylation was performed by immunofluorescence. Five representative fields of the lesions were photographed and the analyzes were performed quantitatively. Statistical analysis was performed using SPSS and GraphPad Prism software. In the study related to oxidative stress, among the 22 patients diagnosed with OLP, most were female (n = 19; 86.4%) and reported to have entered menopause (63.2%). In the majority of cases, OLP lesions were in the active phase (77.3%), with a predominance of the reticular OLP (n = 15; 68.2%). Concerning to oxidative stress levels, no statistically significant differences were observed when comparing SOD, GSH, MPO and MDA values between case and control groups, as well as between erosive and reticular OLP (p > 0.05). Individuals with inactive OLP lesions presented higher SOD when compared to those with active lesions (p = 0.031). The study related to DNA repair and H3K9 histone acetylation showed that the immunoreactivity for APE1 and XRCC1 was significantly higher in CLP than in OLP (P = 0.003 and P = 0.034, respectively). There was a significant and moderate positive correlation between APE1 and XRCC1 in the OLP group (Rho=0.544; P<0.0001). Evaluation of H9K3 histone acetylation levels did not reveal significant results comparing OLP to CLP, neither comparing erosive to reticular OLP (P> 0.05). In conclusion, our findings revealed that oxidative stress markers in saliva of patients with OLP was similar to the control cases, which may be related to the high exposure of the oral cavity environment to several physical, chemical and microbiological stimuli, important generators of the oxidative stress. Furthermore, changes in the expression profile of the DNA repair proteins exerted greater influence in the cases of CLP than in the cases of OLP, in addition, H3K9 histone acetylation is an epigenetic event found in both lesions.