Switch regulation of interleukin-1 beta in downstream of inflammatory cytokines induced by two micro-sized silica particles on differentiated THP-1 macrophages

• Inflammation responses of Si1 μm were more potent than Si3–5 μm at low concentration.
• IL-1β antibody greatly blocked IL-1β, TNF-α and IL-6 expressions induced by silica.
• Neutralization of IL-1β antibody was more effective in Si1 μm than that of Si3–5 μm.
• Recombinant human IL-1β protein strikingly augment TNF-α and IL-6 expressions.
• IL-1β could be a switching regulation in the downstream inflammation by silica.

To investigate the regulated role of IL-1β in initiating and maintaining inflammation, PMA-differentiated THP-1 macrophages were exposed to two micro-sized crystalline silica particles (Si3–5 μm and Si1 μm) from 3 h to 24 h, respectively. Cytotoxicity and inflammatory cytokines (IL-1β, TNF-α and IL-6) expressions measured showed that they were induced by both silica particles in positive dose-dependent manners. The levels of inflammatory cytokines induced by Si1 μm were higher than those induced by Si3–5 μm at low concentration. When pretreated with anti-human IL-1β, not only the high levels of IL-1β but also elevated TNF-α and IL-6 induced by both silica particles were remarkably blocked, especially Si1 μm particle. In addition, recombinant human IL-1β protein could induce macrophages to strikingly augment TNF-α and IL-6 expressions. Our data suggest that IL-1β could play a critical role of switching regulation in the downstream inflammation induced by micro-sized silica particles.