Elevated APE1/Ref-1 Levels of Synovial Fluids in Patients with Rheumatoid Arthritis: Reflection of Disease Activity

Figures

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  Figure 1. The concentration of apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) was increased in synovial fluid (SF) of rheumatoid arthritis (RA) patients. (a) The serum levels of APE1/Ref-1 in patients with RA (n = 29) were significantly elevated compared to those of the healthy control (HC) (n = 30) and osteoarthritis (OA) patient groups (n = 30). (b) The RA patient group (n = 31) had a significantly higher APE1/Ref-1 concentration in their SF than that of the OA patient group (n = 30). Dot plots represent the mean; bars represent the SD. *** p < 0.001, **** p < 0.0001 vs. RA group based on one-way ANOVA analysis followed by Bonferroni’s multiple comparison test and unpaired t-test. (c,d) Significant correlations were found between serum and SF APE1/Ref-1 levels in paired OA samples (n = 16) (c) and RA samples (n = 13). (d) Statistical significance was determined by paired t-test. * p < 0.05 vs. OA_serum or RA_serum.

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  Figure 2. The receiver operating characteristic (ROC) curve of apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) levels in serum and synovial fluid (SF) of rheumatoid arthritis (RA) patients. (a) The ROC curve from serum samples of patients with osteoarthritis (OA) and RA resulted in an area under the curve (AUC) of 0.73, and that of healthy control (HC) patients and RA patients resulted in an AUC of 0.74. (b) The ROC curve from SF samples of patients with OA and RA resulted in an AUC of 0.92.

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  Figure 3. Correlation between synovial APE1/Ref-1 levels and rheumatoid arthritis (RA) disease activity; (a,b) 28-joint disease activity score (DAS 28), using ESR and CRP (DAS28-ESR/DAS28-CRP). Statistical significance was determined by Pearson’s correlation analysis.

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  Figure 4. The comparison of APE1/Ref-1 levels between the remission group (DAS 28 < 2.6) and the nonremission group (DAS 28 > 2.6). (a) The serum APE1/Ref-1 concentration of the remission group (n = 6) and the nonremission group (n = 23). (b) The synovial APE1/Ref-1 concentration of the remission group (n = 6) and the nonremission group (n = 25). Columns represent the mean; bars represent the SD. ** p < 0.01, vs. remission according to an unpaired t-test.

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  Figure 5. Synovial APE1/Ref-1 levels according to disease activity categories. The synovial APE1/Ref-1 concentrations were associated with disease activity categories. Columns represent the mean; bars represent the SD. * p < 0.05 vs. low based on one-way ANOVA analysis followed by Bonferroni’s multiple comparison test.