The Expression of Proinflammatory Cytokines and Intracellular Minerals in Patients with Ankylosing Spondylitis

Abstract

Objective: Our study aimed to investigate the expression of intracellular proinflammatory cytokines and mineral contents in patients with ankylosing spondylitis (AS). Methods: Serum samples from 40 patients with AS and 19 healthy individuals were collected for this study. Flow cytometry was used to determine the intracellular concentration of interleukin (IL)-1β, interferon (IFN)-γ and tumor necrosis factor (TNF)-α in the CD3–, CD4–, and CD8– bearing T cells. The mass fraction of calcium (Ca(superscript 2+)) and magnesium (Mg(superscript 2+)) in phytohemagglutin (PHA)-stimulated lymphocytes were measured using a spectrofluorometer. Clinical variables, including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath ankylosing spondylitis disease activity index (BASDAI), Bath ankylosing spondylitis functional index (BASFI), age at onset, uveitis and family history were recorded. Results: Intracellular proinflammatory cytokine (IL-1β, TNF-α, & IFN-γ) expression in CD3+ and CD4+ T cells after phorbol myristate acetate (PMA) stimulation was more significantly increased in AS patients than in healthy controls (p＜0.05). Intracellular Ca(superscript 2+) exhibited a significant correlation to the TNF-α level in stimulated CD8+ T cells in AS patients (r=0.439, p＜0.05), but not in healthy controls. Comparison between an increase in cytokine expression and clinical variables showed that the increase in IFN-γ was significantly less prominent in patients with a lower BASFI score (BASFI＜20 vs. ≧20, p＜0.05) and more prominent in patients with uveitis. The IL-1β increase after stimulation was less prominent in patients with a higher age of onset (＞30 years of age, p＜0.05). Conclusion: The increased expression of intracellular proinflammatory cytokines, including IL-1β, TNF-α and IFN-γ after PMA-stimulation was more pronounced in AS patients than in normal individuals. A significant correlation between intracellular TNF-α level and Ca(superscript 2+) was found in AS patients. Whether the elevation of intracellular Ca(superscript 2+) can enhance intracellular TNF-α expression in AS patients requires further study.