Exogenous Clara cell protein 16 attenuates silica particles-induced inflammation in THP-1 macrophages by down-regulating NF-κB and caspase-1 activation

• Published in: Journal of toxicological sciences Vol. 45; no. 10; pp. 651 - 660
• Main Authors: Cui, Xiuqing, Xu, Ruijun, Zhang, Hai, Peng, Zhe, Feng, Min, Yu, Bo, Wang, Yaqi, Shi, Tingming, Zhou, Yun, Liu, Yuewei
• Format: Journal Article
• Language: English
• Published: Suita The Japanese Society of Toxicology 2020; Japan Science and Technology Agency
• Subjects: Activation; Caspase-1; CC16 protein; Clara cell protein16 (CC16); Cytokines; Cytosol; Enzyme-linked immunosorbent assay; Exposure; IL-1β; Immunofluorescence; Inflammation; Inhalation; Interleukin 6; Interleukins; Localization; Lung diseases; Macrophages; mRNA; NF-κB; NF-κB protein; Nuclear transport; Nucleotides; Particulates; Polymerase chain reaction; Proteins; Respiration; Silica; Silica particles; Silicon dioxide; Translocation; Tumor necrosis factor-TNF; Tumor necrosis factor-α
• ISSN: 0388-1350; 1880-3989
• DOI: 10.2131/jts.45.651

Inhalation of silica particles leads to pulmonary inflammatory responses. Clara cell protein 16 (CC16) has been reported to played a protective role in inflammatory lung diseases. However, its role on silica particles-induced inflammation has not been fully clarified. In this study, THP-1 macrophages were exposed to 75 μg/cm2 silica particles with or without 2 μg/mL exogenous CC16 (recombinant CC16, rCC16) for 24 hr. The production of inflammatory cytokines, including interleukin (IL)-1β, tumor necrosis factor (TNF)-α and IL-6, in the cell supernatants of different groups was detected through ELISA kits and real-time RT-PCR, respectively. The nuclear translocation of nuclear factor (NF)-κB, protein levels of pro-IL-1β, the nucleotide-binding domain-like receptor protein 3 (NLRP3) and caspase-1 were evaluated via immunofluorescence or western blot. Results showed that, at 75 μg/cm2 silica particle concentration, the treatment of rCC16 significantly decreased IL-1β, TNF-α and IL-6 protein release and mRNA levels in THP-1 macrophages. Compared to those only exposed to silica particles, THP-1 macrophages exposed to both silica particles and rCC16 showed significantly lower nuclear levels and higher cytosol levels of NF-κB p65, as well as lower co-localization coefficients through immunofluorescence. Additionally, the administration of rCC16 significantly attenuated the increase of pro-IL-1β, NLRP3 and caspase-1 levels induced by silica particle exposure. Our results suggested that exogenous CC16 could inhibit silica particles-induced inflammation in THP-1 macrophages, mainly through suppressing NF-κB pathway and caspase-1 activation.