Background Although there are many defence systems that protect cellular macromolecules against oxidation, oxidative DNA and RNA damage still occurs. Oxidative damage to nucleic acids has been found to be associated with etiopathogenesis and disease activity of inflammatory disorders. Oxidised guanine species have been recognized as a biomarker of oxidative DNA and RNA damage by endogenously generated oxygen radicals. Sjögren's syndrome (SS) is an autoimmune disorder and associated with overexpression of proinflammatory cytokines. Related to excess expression of proinflammatory cytokines, a prooxidant state could be postulated in SS.
Objectives We aimed to evaluate levels of nucleic acids oxidative stress products in patients with SS.
Methods 11 patients with SS diagnosed according to 2012 American College of Rheumatology (ACR) Classification Criteria for Sjögren's Syndrome, 19 patients with psoriatic arthritis (PsA), diagnosed according to Classification Criteria for Psoriatic Arthritis (PSARC), 9 patients with rheumatoid arthritis (RA), diagnosed according to 2010 Rheumatoid Arthritis Classification Criteria, and 12 healthy controls were included. All SS patients were on hydroxychloroquine sulphate 400mg/day. All PsA and RA patients were on methotrexate 15–20mg/week and folic acid 5 mg/week. The serum samples were collected from participants and stored at -30 C until assayed. Three oxidised guanine species, 8-hydroxy-2'-deoxyguanosine as a DNA oxidation marker, 8-hydroxyguanosine as a RNA oxidation marker, and 8-hydroxyguanine as a DNA and RNA oxidation marker, were measured using DNA/RNA Oxidative Damage ELISA Kit (Cayman Chemicals, USA).
Statistics: All data are presented as mean and standard deviation (SD). Differences between groups were examined using Kruskal- Wallis tests. The Mann-Whitney U test was performed to test the significance of pairwise differences using Bonferroni correction to adjust for multiple comparisons. A p-value less than 0.05 were considered as statistically significant. Statistical analysis of correlation was performed by using the Spearman rank test.
Results There was no statistically significant difference between the groups in terms of age and gender. The average level of serum oxidised guanine species in the PsA, RA, SS and healthy control groups were 2871.77±336.20, 2672.20±292.04, 3375.57±344.21, 2777.55±237.05 pg/mL respectively. Oxidised guanine species levels were significantly higher in patients with SS and positively correlated with CRP levels (p:0.011, r: 0.726) (table 2).
Conclusions A marked increase in DNA damage leading to oxidative stress may contribute to tissue damage in SS.
Disclosure of Interest None declared