Mechanism of uptake of ZnO nanoparticles and inflammatory responses in macrophages require PI3K mediated MAPKs signaling

•Effect of ZNPs on cytotoxicity & functional responses of macrophages was studied.•ZNPs induced RNS generation and pro-inflammatory cytokines and chemokines.•TEM results showed that ZNPs concentrate within late endosomes and lysosomes.•Majorly clathrin, caveolae & SR pathways were involved i...

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Published in:Toxicology in vitro Vol. 28; no. 3; pp. 457 - 467
Main Authors: Roy, Ruchi, Parashar, Vyom, Chauhan, L.K.S., Shanker, Rishi, Das, Mukul, Tripathi, Anurag, Dwivedi, Premendra Dhar
Format: Journal Article
Language:English
Published: England Elsevier Ltd 01-04-2014
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Summary:•Effect of ZNPs on cytotoxicity & functional responses of macrophages was studied.•ZNPs induced RNS generation and pro-inflammatory cytokines and chemokines.•TEM results showed that ZNPs concentrate within late endosomes and lysosomes.•Majorly clathrin, caveolae & SR pathways were involved in uptake of ZNPs.•Inflammatory responses involve PI3K mediated MAPKs signaling cascade. The inflammatory responses after exposure to zinc oxide nanoparticles (ZNPs) are known, however, the molecular mechanisms and direct consequences of particle uptake are still unclear. Dose and time-dependent increase in the uptake of ZNPs by macrophages has been observed by flow cytometry. Macrophages treated with ZNPs showed a significantly enhanced phagocytic activity. Inhibition of different internalization receptors caused a reduction in uptake of ZNPs in macrophages. The strongest inhibition in internalization was observed by blocking clathrin, caveolae and scavenger receptor mediated endocytic pathways. However, FcR and complement receptor-mediated phagocytic pathways also contributed significantly to control. Further, exposure of primary macrophages to ZNPs (2.5μg/ml) caused (i) significant enhancement of Ras, PI3K, (ii) enhanced phosphorylation and subsequent activation of its downstream signaling pathways via ERK1/2, p38 and JNK MAPKs (iii) overexpression of c-Jun, c-Fos and NF-κB. Our results demonstrate that ZNPs induce the generation of reactive nitrogen species and overexpression of Cox-2, iNOS, pro-inflammatory cytokines (IL-6, IFN-γ, TNF-α, IL-17 and regulatory cytokine IL-10) and MAPKs which were found to be inhibited after blocking internalization of ZNPs through caveolae receptor pathway. These results indicate that ZNPs are internalized through caveolae pathway and the inflammatory responses involve PI3K mediated MAPKs signaling cascade.
ISSN:0887-2333
1879-3177
DOI:10.1016/j.tiv.2013.12.004