Toxicity Preventive Potential of Anti-Inflammatory CeO2 Nanoparticles in HUVE Cells

Abstract

The mechanism behind the cytoprotective potential of cerium oxide nanoparticles (CeO2 NPs) against cytotoxic nitric oxide (NO) donors and H2O2 is still not clear. Synthesized and characterized CeO2 NPs significantly ameliorated the lipopolysaccharide (LPS)-induced cytokines IL-1\(\beta\) and TNF-\(\alpha\). The main objective of this study was to determine the capacities of CeO2 NPs regarding their signaling effects that could have occurred due to reactive oxygen species (ROS) and/or NO, since NP-induced ROS/NO did not lead to toxicity in HUVE cells. To achieve this objective, two NO-donors were applied in human umbilical vein-derived endothelial (HUVE) cells in con-junction with CeO2 NPs. To the best of our knowledge, there is limited research regarding modulatory potential of CeO2 NPs against known NO-donors. The two NO donors used in this study were SNP (sodium nitroprusside, #ab145732 from Abcam plc, Cambridge, UK) and DETA-NO (Z)-1-[N-(2-Aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate or DETA-NONOate #ab144627 from Abcam plc, Cambridge, UK). Concentrations that induced 50% cell death (i.e., IC50s) of two NO donors (DETA-NO; 1250 ± 110 µM and sodium nitroprusside (SNP); 950 ± 89 µM) along with the IC50 of H2O2 (120 ± 7 µM) were utilized to evaluate cytoprotective potential and its underlying mechanism. We determined total ROS (as a collective marker of hydrogen peroxide, superoxide radical \(O_2\bullet-\) hydroxyl radical, etc.) by DCFH-DA and used a \(O_2\bullet-\) specific probe DHE to decipher prominent ROS. The findings revealed that signaling effects mediated mainly by \(O_2\bullet-\) and/or NO are responsible for the amelioration of toxicity by CeO2 NPs at 100 µg/mL. The unaltered effect on mitochondrial membrane potential (MMP) due to NP exposure and, again, CeO2 NPs-mediated recovery in the loss of MMP due to exogenous NO donors and H2O2 suggested that NP-mediated \(O_2\bullet-\) production might be extra-mitochondrial. Data on activated glutathione reductase (GR) and unaffected glutathione peroxidase (GPx) activities partially explain the mechanism behind the NP-induced gain in GSH and persistent cytoplasmic ROS. The promoted antioxidant capacity due to non-cytotoxic ROS and/or NO production, rather than inhibition, by CeO2 NP treatment may allow cells to develop the capacity to tolerate exogenously induced toxicity.