Correlation between TNF-alpha and IL-12p40-containing cytokines in silicosis

The aim of the present study was to investigate the correlation between tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-12p40-containing cytokines, in silicosis patients and healthy donors exposed to silica dust, in an attempt to clarify the reason for variety of clinical outcomes between humans with similar exposure history. Serum levels of TNF-alpha, IL-12p40, IL-12p70 and IL-23 in total group of 62 silicosis patients, 24 healthy donors with similar exposure history like patients and 19 healthy donors without exposure were determined by enzyme-linked-immunosorbent assay (ELISA) method. The serum level of TNF-alpha was significantly higher in healthy donors exposed to SiO(2) (22.4 +/- 11.1 pg/mL) in comparison with non-exposed healthy donors (14.8 +/- 8.8 pg/mL; p = 0.022) and similar to that in silicosis patients. In total, group of silicosis patients significantly elevated levels of TNF-alpha (20.9 +/- 12.9 vs. 14.8 +/- 8.8 pg/mL; p = 0.047) and IL-12p40 (94.5 +/- 51.6 pg/mL vs. 68.7 +/- 26.2 pg/mL; p = 0.029) compared to non-exposed healthy donors were observed. In addition, a strong positive correlation between TNF-alpha and IL-23 levels (r = 0.678; p = 0.022) and between TNF-alpha and IL-12p70 levels (r = 0.75; p = 0.0003) was detected in the group of exposed healthy donors, while in the group of silicosis patients, a significant positive correlation was observed only between TNF-alpha and IL-12p40 (r = 0.434; p = 0.00048), in contrast to other IL-12p40 containing cytokines. In conclusion, we could assume that the elevated serum levels of TNF-alpha are associated with exposition to silica particles, while the elevation of both TNF-alpha and IL-12p40 is associated with silicosis development and severity. Additionally, the balance between IL-12p40-containing cytokines may also contribute to the silicosis progression.