Abstract 12420: Interleukin-38 Inhibits Nod-Like Receptor Protein 3 Inflammasomes to Suppress Aortic Valve Calcification

Abstract

Calcific aortic valve disease (CAVD) is common in the elderly. Progressive valvular calcification is a characteristic pathobiology in CAVD, and chronic valvular inflammation is known to promote CAVD progression. Matrilin-2 is an extracellular matrix (ECM) protein. Soluble matrilin-2 can function as a damage - associated molecular pattern to induce the inflammatory and osteogenic responses in aortic valve interstitial cells (AVICs). Interleukin-38 (IL-38) is a novel anti-inflammatory cytokine. Lower IL-38 levels are associated with several chronic inflammatory diseases. Recent studies found that IL-38 limits skin inflammation and nephritis by reducing the inflammatory activity of immune cells. We hypothesized that IL-38 is capable of suppressing AVIC osteogenic activity. Methods and Results: We performed immunoblotting and ELISA to assess IL-38 protein levels in AVICs isolated from normal human aortic valves (normal AVICs) and diseased human aortic valves (diseased AVICs). Diseased AVICs had lower levels of IL-38 compared to normal AVICs. Interestingly, recombinant IL-38 inhibited spontaneous deposition of calcium in diseased AVICs. To determine the effect of recombinant IL-38 on AVIC osteogenic response to soluble matrilin-2, we treated normal AVICs with recombinant IL-38 (0, 1, 5 and 10 ng/ml) prior to an exposure to matrilin-2 for 24-72 hour. IL-38 at 10 ng/ml markedly reduced the expression of RUNX-2 and ALP in normal AVICs exposed to matrilin-2. Further, IL-38 suppressed calcium deposition in normal AVICs exposed to matrilin-2 for a prolonged period. Knockdown of IL-38 by shRNA enhanced the osteogenic responses and exaggerated the calcification deposit formation in normal AVICs exposed to matrilin-2. The anti-osteogenic effect of IL-38 is associated with down-regulation of Nod-like receptor protein 3 (NLRP3) inflammasomes, and inhibition of the NLRP3 inflammasomes also suppresses the osteogenic activity in normal AVICs exposed to matrilin-2. Conclusions: IL-38 suppresses the osteogenic activity in human AVICs by inhibiting NLRP3 inflammasomes. The novel findings of this study suggest that IL-38 may have therapeutic potential for prevention of CAVD progression.