Association between 8-OHdG Levels and Eosinophil Counts in Chronic Rhinosinusitis with Nasal Polyps

Oxidative stress plays an important role in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP). The 8-Hydroxydeoxyguanosine (8-OHdG) is a major oxidative DNA adduct, and its levels have been noted as a triggering factor for inflammation-related carcinogenesis, but have not been assessed in CRSwNP. The MAPK/ERK pathway importance in the pathogenesis of CRSwNP has previously been reported. Mutations in RAS family genes occur in neoplastic and non-neoplastic proliferative lesions, and it has been previously demonstrated that KRAS mutations do not occur in CRSwNP. To assess the levels of 8-OHdG in nasal polyps occurring in CRSwNP, to associate these levels with clinicopathological parameters, and to investigate HRAS and NRAS hotspot mutations in the same samples. Both the HRAS (codons 49 and 61) and NRAS (codon 61) mutations were investigated through Sanger sequencing, and the levels of 8-OHdG were determined using ELISA in 14 freshly collected snap-frozen samples of nasal polyps occurring in CRSwNP. The associations between the levels of 8-OHdG and patients' age, presence of asthma, and eosinophil counts in nasal polyps were tested. No mutations were detected. The association between higher levels of 8-OHdG and higher eosinophil counts was observed, whereas there was no association between it and age or the presence of asthma. Based on the results in the present cohort, higher levels of 8-OHdG, indicative of oxidative stress, are associated with higher eosinophil counts in CRSwNP. Additionally, HRAS and NRAS mutations do not occur in nasal polyps or occur at a very low frequency.