Cerium dioxide nanoparticles (CeO2 NPs) have diversified industrial uses and novel therapeutic applications are actively being pursued. There is lack of mechanistic data concerning the effects of CeO2 NPs on primary human cells. We aimed at characterizing the cytotoxic effects of CeO2 NPs in human peripheral blood monocytes. CeO2 NPs and their suspensions were thoroughly characterized, including using transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis. Blood from healthy human volunteers was drawn through phlebotomy and CD14+ cells were isolated. Cells were exposed to CeO2 NPs (0.5–10 μg/mL) for 20 or 40 hours and mechanisms of cell injury were studied. TEM revealed that CeO2 NPs are internalized by monocytes and are found either in vesicles or free in the cytoplasm. CeO2 NP exposure leads to decrease in cell viability and treated cells exhibit characteristic hallmarks of apoptosis (activation of Bax, loss of mitochondrial membrane potential, DNA fragmentation). CeO2 NP toxicity is caused by mitochondrial damage leading to apoptosis inducing factor (AIF) release, but not due to caspase activation or reactive oxygen species production. Moreover, CeO2 NP exposure leads to autophagy, which is further increased after pharmacological inhibition of tumour suppressor protein p53. Inhibition of autophagy partially reverses cell death by CeO2 NPs. It is concluded that CeO2 NPs are toxic to primary human monocytes at relatively low doses.

BackgroundIn vivo studies have demonstrated the ability of multi-walled carbon nanotubes (MWCNT) to induce airway remodeling, a key feature of chronic respiratory diseases like asthma and chronic obstructive pulmonary disease. However, the mechanism leading to remodeling is poorly understood. Particularly, there is limited insight about the role of airway epithelial injury in these changes.ObjectivesWe investigated the mechanism of MWCNT-induced primary human bronchial epithelial (HBE) cell injury and its contribution in inducing a profibrotic response.MethodsPrimary HBE cells were exposed to thoroughly characterized MWCNTs (1.5-24 μg/mL equivalent to 0.37-6.0 μg/cm2) and MRC-5 human lung fibroblasts were exposed to 1:4 diluted conditioned medium from these cells. Flow cytometry, ELISA, immunostainings/immunoblots and PCR analyses were employed to study cellular mechanisms.ResultsMWCNT induced NLRP3 inflammasome dependent pyroptosis in HBE cells in a time- and dose-dependent manner. Cell death and cytokine production were significantly reduced by antioxidants, siRNA to NLRP3, a caspase-1 inhibitor (z-WEHD-FMK) or a cathepsin B inhibitor (CA-074Me). Conditioned medium from MWCNT-treated HBE cells induced significant increase in mRNA expression of pro-fibrotic markers (TIMP-1, Tenascin-C, Procollagen 1, and Osteopontin) in human lung fibroblasts, without a concomitant change in expression of TGF-beta. Induction of pro-fibrotic markers was significantly reduced when IL-1β, IL-18 and IL-8 neutralizing antibodies were added to the conditioned medium or when conditioned medium from NLRP3 siRNA transfected HBE cells was used.ConclusionsTaken together these results demonstrate induction of a NLRP3 inflammasome dependent but TGF-beta independent pro-fibrotic response after MWCNT exposure.

Background: Cerium dioxide (CeO 2 ) nanoparticles have potential therapeutic applications and are widely used for industrial purposes. However, the effects of these nanoparticles on primary human cells are largely unknown. The ability of nanoparticles to exacerbate pre-existing inflammatory disorders is not well documented for engineered nanoparticles, and is certainly lacking for CeO 2 nanoparticles. We investigated the inflammation-modulating effects of CeO 2 nanoparticles at noncytotoxic concentrations in human peripheral blood monocytes. Methods: CD14+ cells were isolated from peripheral blood samples of human volunteers. Cells were exposed to either 0.5 or 1 µg/mL of CeO 2 nanoparticles over a period of 24 or 48 hours with or without lipopolysaccharide (10 ng/mL) prestimulation. Modulation of the inflammatory response was studied by measuring secreted tumor necrosis factor-alpha, interleukin-1beta, macrophage chemotactic protein-1, interferon-gamma, and interferon gamma-induced protein 10. Results: CeO 2 nanoparticle suspensions were thoroughly characterized using dynamic light scattering analysis (194 nm hydrodynamic diameter), zeta potential analysis (−14 mV), and transmission electron microscopy (irregular-shaped particles). Transmission electron microscopy of CD14 + cells exposed to CeO 2 nanoparticles revealed that these nanoparticles were efficiently internalized by monocytes and were found either in vesicles or free in the cytoplasm. However, no significant differences in secreted cytokine profiles were observed between CeO 2 nanoparticletreated cells and control cells at noncytotoxic doses. No significant effects of CeO 2 nanoparticle exposure subsequent to lipopolysaccharide priming was observed on cytokine secretion. Moreover, no significant difference in lipopolysaccharide-induced cytokine production was observed after exposure to CeO 2 nanoparticles followed by lipopolysaccharide exposure. Conclusion: CeO 2 nanoparticles at noncytotoxic concentrations neither modulate pre-existing inflammation nor prime for subsequent exposure to lipopolysaccharides in human monocytes from healthy subjects.

Cystic fibrosis (CF) is a chronic inflammatory disease that is affecting thousands of patients worldwide. Adjuvant anti-inflammatory treatment is an important component of cystic fibrosis treatment, and has shown promise in preserving lung function and prolonging life expectancy. Inhaled high molecular weight hyaluronan (HMW-HA) is reported to improve tolerability of hypertonic saline and thus increase compliance, and has been approved in some European countries for use as an adjunct to hypertonic saline treatment in cystic fibrosis. However, there are theoretical concerns that HMW-HA breakdown products may be pro-inflammatory. In this clinical pilot study we show that sputum cytokines in CF patients receiving HMW-HA are not increased, and therefore HMW-HA does not appear to adversely affect inflammatory status in CF airways.