1. p62/SQSTM1 accumulation due to degradation inhibition and transcriptional activation plays a critical role in silica nanoparticle-induced airway inflammation via NF-κB activation
- Author
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Yang Jin, Xiaoke Wang, Yifan Wu, Tianyu Sun, Xinyuan Zhao, Jinlong Li, Junkang Jiang, Gang Chen, Qinglin Zhang, and Piaoyu Zhu
- Subjects
Male ,Scaffold protein ,lcsh:Medical technology ,p62 accumulation ,NF-E2-Related Factor 2 ,lcsh:Biotechnology ,Biomedical Engineering ,Pharmaceutical Science ,Medicine (miscellaneous) ,Bioengineering ,Silica nanoparticle ,Applied Microbiology and Biotechnology ,Nrf2 ,Cell Line ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Transcriptional activation ,Downregulation and upregulation ,lcsh:TP248.13-248.65 ,Sequestosome-1 Protein ,Autophagy ,Animals ,Humans ,030304 developmental biology ,Mice, Inbred ICR ,0303 health sciences ,Gene knockdown ,Chemistry ,Research ,NF-kappa B ,Autophagic flux blockade ,Pneumonia ,Silicon Dioxide ,Molecular medicine ,In vitro ,Cell biology ,lcsh:R855-855.5 ,Cytoplasm ,030220 oncology & carcinogenesis ,Nanoparticles ,Molecular Medicine ,Flux (metabolism) ,Signal Transduction ,Airway inflammation - Abstract
Background Most nanoparticles (NPs) reportedly block autophagic flux, thereby upregulating p62/SQSTM1 through degradation inhibition. p62 also acts as a multifunctional scaffold protein with multiple domains, and is involved in various cellular processes. However, the autophagy substrate-independent role of p62 and its regulation at the transcriptional level upon NPs exposure remain unclear. Results In this work, we exposed BEAS-2b cells and mice to silica nanoparticles (SiNPs), and found that SiNPs increased p62 protein levels in vivo and vitro. Then, we further explored the role and mechanism of SiNPs-stimulated p62 in vitro, and found that p62 degradation was inhibited due to autophagic flux blockade. Mechanistically, SiNPs blocked autophagic flux through impairment of lysosomal capacity rather than defective autophagosome fusion with lysosomes. Moreover, SiNPs stimulated translocation of NF-E2-related factor 2 (Nrf2) to the nucleus from the cytoplasm, which upregulated p62 transcriptional activation through direct binding of Nrf2 to the p62 promoter. Nrf2 siRNA dramatically reduced both the mRNA and protein levels of p62. These two mechanisms led to p62 protein accumulation, thus increasing interleukin (IL)-1 and IL-6 expression. SiNPs activated nuclear factor kappa B (NF-κB), and this effect could be alleviated by p62 knockdown. Conclusion SiNPs caused accumulation of p62 through both pre- and post-translational mechanisms, resulting in airway inflammation. These findings improve our understanding of SiNP-induced pulmonary damage and the molecular targets available to mitigate it.
- Published
- 2020
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