Histological and biochemical evaluation of the effects of silver nanoparticles (AgNps) versus titanium dioxide nanoparticles (TiO 2 NPs) on rat parotid gland.

The unlimited use of nanoparticles (NPs) results in toxic impacts on different tissues. The current study aimed to compare the adverse effects of AgNPs and TiO2 NPs on the parotid gland of adult male albino rats as regards the histopathological, immunohistochemical, and biochemical changes, exploring the possible underlying mechanisms and the degree of improvement after cessation of administration. Fifty-four adult male albino rats were divided into control group (I), AgNPs-injected group (II), and TiO2 NPs-injected group (III). We measured the levels of tumor necrosis factor-alpha (TNF-α) and interleukin (IL-6) in the serum, and levels of MDA and GSH in parotid tissue homogenate. Quantitative real-time polymerase-chain reaction (qRT-PCR) was used to measure the expression levels of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1-α), nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), mouse double minute 2 (MDM2), Caspase-3 Col1a1, and Occludin. Parotid tissue sections were examined by light microscope (Hematoxylin & Eosin and Mallory trichrome stains), electron microscope, and immunohistochemical examination of CD68 and anti-caspase-3 antibodies. Both NPs severely affected the acinar cells and damaged the tight junction between them by enhancing expression of the inflammatory cytokines, inducing oxidative stress, and disturbing the expression levels of the studied genes. They also stimulated fibrosis, acinar cell apoptosis, and inflammatory cells infiltration in parotid tissue. TiO2 NPs effects were less severe than AgNPs. Cessation of exposure to both NPs, ameliorated the biochemical and structural findings with more improvement in TiO2 NPs withdrawal. In conclusion: AgNPs and TiO2 NPs adversely affected the parotid gland, but TiO2 NPs were less toxic than AgNPs.