DNA microarray analysis of active- and inactive-adult Still disease (ASD)

Objective: Adult Stills disease (ASD) is a systemic disorder of unknown etiology characterized by high spiking fever, rash and arthritis. The purpose of this study was to determine the pathogenic roles of specific genes in ASD. Methods: Differentially expressed genes (DEGs) were examined by DNA microarray and validated by quantitative PCR using monocytes isolated from patients with active-ASD, inactive-ASD and healthy controls. The correlation between validated DEGs and ASD activity was analyzed. After inflammasome activation with LPS and Nigericin, the production of IL-1, IL-18, inflammasome and autophagy related proteins in DEGs-overexpressing THP-1 cells was carried out by ELISA or western blotting. DEGs-overexpressing THP-1 cells were treated with an inhibitor of autophagy followed by assessment of IL-1 and IL-18 production by ELISA and western blotting method.Conclusions: The overexpression of PLAC8 in monocytes might play a regulatory role in the production of IL-1 and IL-18 by the enhancement of autophagy, resulting in the suppression of ASD. Results:A total of 68 genes were highly expressed in monocytes isolated from active-ASD patients, relative to their expression in inactive-ASD patients and healthy controls. After validation of expression of 13 genes (CLU, FCGR1B, PLAC8, TLR1, S100A12, CD55, PIM1, BCL2A1, SOD2, PLSCR1, CYP1B1, STEAP4, IL1RN), the expression of PLAC8 was significantly higher in active-ASD patients than the other groups. In ASD, PLAC8 expression level correlated with serum levels of CRP, ferritin and IL-18. Stimulation of monocytes with lipopolysaccharide resulted in PLAC8 upregulation. LPS or Nigericin stimulation of PLAC8-overexpressing THP-1, but not THP-1 cells< was associated with significant decrease in IL-1 and IL-18 production. PLAC8 overexpressing in THP-1 cells was associated with enhanced autophagy and suppression of IL-1 and IL-18 production. Conclusions: PLAC8 upregulation in monocytes seemed to play a regulatory role in the production of IL-1 and IL-18 through enhanced autophagy, resulting in suppression of ASD. The results highlight the role of PLAC8 in the pathogenesis of ASD and suggest its potential suitability as a therapeutic target in ASD.

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Segawa S, Kondo Y, Nakai Y, Iizuka A, Kaneko S, Yokosawa M, Furuyama K, Tsuboi H, Goto D, Matsumoto I, Sumida T