Nickel nanoparticles induce epithelial-mesenchymal transition in human bronchial epithelial cells via the HIF-1α/HDAC3 pathway

Nickel induces epithelial-mesenchymal transition in pulmonary fibrosis in mice via activation of the oxidative stress-mediated TGF-β1/Smad signaling pathway

Nickel (Ni) is recognized as a carcinogenic metal, and its widespread use has led to severe environmental and health problems. Although the lung is among the main organs affected by Ni, the precise mechanisms behind this effect remain poorly understood. This study aimed to elucidate the physiological mechanisms underlying Ni-induced pulmonary fibrosis (PF), using various techniques including histopathological detection, biochemical analysis, immunohistochemistry, western blotting, and quantitative real-time PCR. Mice were treated with nickel chloride (NiCl2), which induced PF (detected by Masson staining), up-regulation of α-smooth muscle actin (α-SMA), and collagen-1 mRNA and protein expression. NiCl2 was found to induce PF by: activation of the epithelial-mesenchymal transition (EMT) and the transforming growth factor-β1 (TGF-β1)/Smad signaling pathway; up-regulation of protein and mRNA expression of TGF-β1, p-Smad2, p-Smad3, vimentin, and N-cadherin; and down-regulation of protein and mRNA expression of E-cadherin. In addition, NiCl2 treatment increased malondialdehyde content while inhibiting antioxidant activity, as indicated by decreased catalase, total antioxidant capacity, and superoxide dismutase activities, and glutathione content. Co-treatment with the effective antioxidant and free radical scavenger N-acetyl cysteine (NAC) plus NiCl2 was used to study the effects of oxidative stress in NiCl2-induced PF. The addition of NAC significantly mitigated NiCl2-induced PF, and reversed activation of the TGF-β1/Smad signaling pathway and EMT. NiCl2-induced PF was therefore shown to be due to EMT activation via the TGF-β1/Smad signaling pathway, mediated by oxidative stress.

Nickel nanoparticles induce autophagy and apoptosis via HIF-1α/mTOR signaling in human bronchial epithelial cells

With the rapid development of nanotechnology, the potential adverse health effects of nanoparticles have been caught more attention and become global concerns. However, the underlying mechanisms in metal nanoparticle-induced toxic effects are still largely obscure. In this study, we investigated whether exposure to nickel nanoparticles (Nano-Ni) and titanium dioxide nanoparticles (Nano-TiO₂) would alter autophagy and apoptosis levels in normal human bronchial epithelial BEAS-2B cells and the underlying mechanisms involved in this process. Our results showed that the expressions of autophagy- and apoptosis-associated proteins were dysregulated in cells exposed to Nano-Ni. However, exposure to the same doses of Nano-TiO₂ had no significant effects on these proteins. In addition, exposure to Nano-Ni, but not Nano-TiO₂, led to nuclear accumulation of HIF-1α and decreased phosphorylation of mTOR in BEAS-2B cells. Inhibition of HIF-1α by CAY10585 abolished Nano-Ni-induced decreased phosphorylation of mTOR, while activation of mTOR by MHY1485 did not affect Nano-Ni-induced nuclear accumulation of HIF-1α. Furthermore, both HIF-1α inhibition and mTOR activation abolished Nano-Ni-induced autophagy but enhanced Nano-Ni-induced apoptosis. Blockage of autophagic flux by Bafilomycin A1 exacerbated Nano-Ni-induced apoptosis, while activation of autophagy by Rapamycin effectively rescued Nano-Ni-induced apoptosis. In conclusion, our results demonstrated that Nano-Ni exposure caused increased levels of autophagy and apoptosis via the HIF-1α/mTOR signaling axis. Nano-Ni-induced autophagy has a protective role against Nano-Ni-induced apoptosis. These findings provide us with further insight into Nano-Ni-induced toxicity.