Human S100A8 ELISA Matched Antibody Pair

Accumulation of advanced glycation end-products (AGEs) in periodontal tissues of patients with diabetes mellitus aggravates periodontitis, but the mechanisms are unknown. Calprotectin, a heterocomplex of S100A8 and S100A9 proteins, is a constitutive cytoplasmic component of healthy gingival epithelial cells. This study aimed at investigating the effects of AGE and Porphyromonas gingivalis lipopolysaccharide (PgLPS) on calprotectin expression in the human gingival epithelial cell line OBA-9. AGE and PgLPS increased the expression of S100A8 and S100A9 mRNAs, and AGE+PgLPS co-stimulation amplified their expression in OBA-9 cells. A higher concentration of calprotectin in cell lysates was also induced by stimulation with AGE and/or PgLPS. S100A8 was mainly translocated from the nucleus to the cytoplasm by AGE stimulation, while cytoplasmic localization of S100A9 was not altered following stimulation with AGE and/or PgLPS. Calprotectin was found in the cytoplasm of BSA-treated cells, but cytoplasmic and nuclear localization was observed following stimulation with AGE and/or PgLPS. AGE-induced S100A8, and S100A9 mRNA expression was partially suppressed by RAGE-specific siRNA. In contrast, PgLPS-induced S100A8 and S100A9 mRNA expression was strongly suppressed by TLR2-specific siRNA. Furthermore, the inhibition of p38, JNK MAPK, and NF-B attenuated AGE- and PgLPS-induced S100A8 and S100A9 mRNA expression. Taken together, these results demonstrate that AGE acts in synergy with PgLPS to stimulate RAGE and TLR2 expression and activate p38, JNK MAPK, and NF-B signaling pathways, resulting in increased activation of calprotectin (S100A8/S100A9) in human gingival epithelial cells. Our results suggest that calprotectin may be involved in the pathogenesis of diabetic periodontitis.

Objective: To investigate whether calprotectin (S100A8/A9 or MRP8/14), an inflammatory complex released by monocytes, could indicate residual subclinical inflammation in rheumatoid arthritis (RA) patients who are in stable remission on disease-modifying anti-rheumatic drugs (DMARDs) and serve as a marker for disease flare after DMARD tapering. Methods: We used data from two trials. Patients from the IMPROVED study had early (< 2 years) RA, and when they achieved disease activity score remission (DAS44 < 1.6), they stopped methotrexate to attempt drug-free remission. Patients from the RETRO study had established RA in stable remission (DAS28 < 2.6) and either tapered by 50% or stopped (biological or conventional) DMARDs. Circulating calprotectin at the tapering time point was determined by ELISA, and its predictive value for flare (loss of remission) within 12 months of DMARD tapering/stopping was determined. Results: In both IMPROVED (n = 104) and RETRO (n = 57), patients that flared within 12 months had higher calprotectin at the moment of DMARD tapering/stopping. Twofold higher calprotectin at the moment of DMARD tapering/stopping was associated with an increased risk (odds ratio) of flare of 1.07 (95% CI 0.98-1.18, p = 0.14) in the IMPROVED and 3.62 (95% CI 1.76-7.46, p < 0.001) in the RETRO. Correcting for clinical predictors of flare (DAS at study inclusion, anti-CCP2 positivity, gender) did not change these estimates. The area under the receiver operating curve of calprotectin levels for predicting flare within 12 months was 0.63 (95% CIs 0.51-0.76) in the IMPROVED study and 0.80 (95% CIs 0.69 to 0.92) in the RETRO study. Conclusion: Circulating calprotectin levels in RA patients in remission on DMARDs are higher in patients that will flare upon DMARD tapering/stopping. Since the differences between the cohorts precluded definitive conclusions, more research is needed to determine whether calprotectin has prognostic value in predicting flare after attempting drug tapering in RA.