Polyhexamethylene guanidine (PHMG) phosphate was used as a disinfectant for the prevention of microorganism growth in humidifiers, without recognizing that a change of exposure route might cause significant health effects. Epidemiological studies reported that the use of humidifier disinfectant containing PHMG-phosphate can provoke pulmonary fibrosis. However, the pulmonary toxicity of PHMG-phosphate aerosol particles is unknown yet. This study aimed to elucidate the toxicological relationship between PHMG-phosphate aerosol particles and pulmonary fibrosis. An in vivo nose-only exposure system and an in vitro air-liquid interface (ALI) co-culture model were applied to confirm whether PHMG-phosphate induces inflammatory and fibrotic responses in the respiratory tract. Seven-week-old male Sprague-Dawley rats were exposed to PHMG-phosphate aerosol particles for 3 weeks and recovered for 3 weeks in a nose-only exposure chamber. In addition, three human lung cells (Calu-3, differentiated THP-1 and HMC-1 cells) were cultured at ALI condition for 12 days and were treated with PHMG-phosphate at set concentrations and times. The reactive oxygen species (ROS) generation, airway barrier injuries and inflammatory and fibrotic responses were evaluated in vivo and in vitro. The rats exposed to PHMG-phosphate aerosol particles in nanometer size showed pulmonary inflammation and fibrosis including inflammatory cytokines and fibronectin mRNA increase, as well as histopathological changes. In addition, PHMG-phosphate triggered the ROS generation, airway barrier injuries and inflammatory responses in a bronchial ALI co-culture model. Those results demonstrated that PHMG-phosphate aerosol particles cause pulmonary inflammatory and fibrotic responses. All features of fibrogenesis by PHMG-phosphate aerosol particles closely resembled the pathology of fibrosis that was reported in epidemiological studies. Finally, we expected that PHMG-phosphate infiltrated into the lungs in the form of aerosol particles would induce an airway barrier injury via ROS, release fibrotic inflammatory cytokines, and trigger a wound-healing response, leading to pulmonary fibrosis. A simultaneous state of tissue destruction and inflammation caused by PHMG-phosphate had whipped up a "perfect storm" in the respiratory tract.

-Deregulated apoptosis has been associated with many lung diseases. Although many studies have reported the apoptotic effects exhibited by silver nanoparticles (Ag-NPs) in various circumstances, the apoptosis mechanism of Ag-NPs is unclear. We investigated oxidative stress and apoptosis in human normal bronchial epithelial (BEAS-2B) cells to elucidate the role of p53 in apoptosis by Ag-NPs. First, dispersion and stability of Ag-NPs improved using bronchial epithelial cell growth medium with 5% fetal bovine serum. Then, we observed oxidative stress in BEAS-2B cells exposed to Ag-NPs. Second, we carried out a cell death assay to measure DNA fragmentation as a biomarker of apoptosis. BEAS--mentation. We also found that apoptosis-related genes (caspase-3, Bax, and Bcl-2) were regulated by AgNPs, which was detected by mRNA and protein levels. These results suggest that Ag-NPs induced p53-Ag-NPs in pulmonary disease. Original ArticleThe Journal of Toxicological Sciences (J. Toxicol. Sci.) Vol.39, No.3, 401-412, 2014 Vol. 39 No. 3 401 lar and DNA damage (Risom et al., 2005). DNA damage induces extracellular and intracellular signals that trigger the onset of a signaling cascade with characteristic biochemical and morphological features, including nuclear condensation, membrane blebbing, and DNA fragmentation, leading ultimately to cell death (Johnson et al., 1996). This is called apoptosis, which is essential for the normal functioning and survival of multi-cellular organisms. However, deregulated apoptosis has been associated with many lung diseases because toxic contents are released from apoptotic cells unless the cells are quickly recognized or ingested by phagocytes (Pandya et al., 2006).The p53 gene regulates the apoptosis pathway (Korsmeyer, 1995;Yang and Duerksen-Hughes, 1998) and is tightly controlled through a complex series of events including translational regulation, interaction with regu--cations including multisite phosphorylation and acetylation (Giaccia and Kastan, 1998;Meek, 1999;Prives and Hall, 1999). In particular, phosphorylation of the serine-15 (Ser-15) residue due to DNA damage plays an important role in p53-mediated apoptosis (Dumaz and Meek, 1999;Siliciano et al., 1997;Unger et al., 1999). This activation of p53 leads to expression of its downstream effectors such as Bax, Bcl-2 and caspase-3, resulting in apoptosis (Martin and Elkon, 2004).In this study, we hypothesized that Ag-NPs induce apoptosis via the p53 signaling pathway in normal human lung bronchial epithelial (BEAS-2B) cells. Although many reports have shown apoptotic effects of Ag-NPs in various circumstances (Foldbjerg et al., 2009;Li et al., 2010;Miura and Shinohara, 2009;Piao et al., 2011), the were used to elucidate the role of p53 in apoptosis by Ag--sion of TiO 2 NPs improved by adding bovine serum albumin (BSA) or fetal bovine serum (FBS) to the medium (Ji et al., 2010). Thus, Ag-NPs were dispersed in bronchial epithelial growth medium (BEGM) with 5% FBS and were characterized. Then, we observed ROS generation...

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