Emerging role of monocytes and their intracellular calcium pattern in spondyloarthritis

Spondyloarthritis (SpA) comprises multifactorial diseases characterized by a complex interplay between an inherited background and environmental factors that lead to immune response dysregulation and inflammation. Unlike for other rheumatic diseases, no specific biomarkers are available in clinical practice for diagnosing SpA. The aim of the present study was to search new potential biomarkers for SpA diagnosis by focusing on the innate immune response. An evaluation was made of the mRNA expression levels of inflammatory cytokines (TNF-α, IL-1β, TGF-β1, S100A8, S100A9) and matrix metalloproteinases (MMP3, MMP8, MMP9) in blood mononuclear cells of SpA patients (n = 64) with respect to controls (n = 100). In parallel, the pattern of intracellular calcium flows of blood monocytes was verified in order to ascertain whether any specific fingerprint characterizes innate immune cells in SpA patients. Inflammatory cytokines and MMPs expression levels were not correlated with SpA, while in this disease a reduced expression of the S100A8 and a decreased frequency of monocytes showing intracellular calcium flows were observed. In conclusion, no specific signs of systemic inflammation are detectable in SpA, but the disease affects the "on-off" mechanisms that regulate the concentration of intracellular calcium and calcium-related proteins. This potentially pave the way for the discovery of new biomarkers.