Ausência da óxido nítrico sintase induzível em modelo murino de carcinogênese bucal com n-óxido de 4-nitroquinolina: alterações em marcadores histopatológicos, inflamatórios sistêmicos e epigenéticos

Abstract

Nitric oxide is a signaling molecule involved in several physiological and pathological conditions, including cancer. During carcinogenesis, it plays a dichotomous role, acting both as a tumorigenic and antitumor agent. Its effects in oral cancer development are, however, not sufficiently explored. This study purposed to analyze the influence of inducible nitric oxide synthase (iNOS) on histopathological, systemic inflammatory, and epigenetic biomarkers in Nos2+/+ (wild-type) and Nos2-/- (knockout) mice treated for 16 weeks with a 50ug/mL solution of 4-nitroquinoline N-oxide (4NQO). After an 8-week observation period, tongues were collected and evaluated for the presence of epithelial hypotrophy, hyperplasia, squamous papilloma, epithelial dysplasia and oral squamous cell carcinoma, in which the depth of invasion (DOI) was measured. Red blood cell, white blood cell, and platelet cell parameters were analyzed in blood samples. Immunostaining for H3K9ac and H3K27ac expression was evaluated with the quickscore method (QS). Nos2+/+ and Nos2-/- mice had similar incidence of tongue lesions, but depth of invasion was lower in Nos2-/- (p=0.018). Strong correlations were found between DOI and neutrophil count (ρ=-0.68, p=0.017), lymphocyte count (ρ=0.72, p=0.011), neutrophil-tolymphocyte ratio (ρ=-0.65, p=0.025), platelet-to-lymphocyte ratio (ρ=-0.73, p=0.013), and systemic immune-inflammation index (ρ=-0.67, p=0.037) in Nos2-/- mice. For H3K9ac, QS values were higher in moderate dysplasia of Nos2-/- (p=0.025) when compared to Nos2+/+. Mild dysplasias had lower values of H3K9ac when compared to moderate and severe in Nos2-/- group (p=0.015). H3K27ac increased from normal mucosa to mild dysplasia in Nos2+/+ mice (p=0.007). Nos2+/+ mice also had a higher number of H3K27ac-positive dysplasias when compared to Nos2-/- (p=0.023). These results suggest that iNOS has an important role in OSCC invasion and progression, which might be associated to alterations in immune-inflammatory cell dynamics evidenced by peripheral blood biomarkers. Additionally, epigenetic alteration in early stages of oral carcinogenesis, mainly changes in histone acetylation pattern of epithelial dysplasia, might be iNOS-mediated.