Morphological alterations induced by the exposure to TiO2 nanoparticles in primary cortical neuron cultures and in the brain of rats

Xavier Valentini; Pauline Deneufbourg; Paula Paci; Pascaline Rugira; Sophie Laurent; Annica Frau; Dimitri Stanicki; Laurence Ris; Denis Nonclercq

doi:10.1016/j.toxrep.2018.08.006

Morphological alterations induced by the exposure to TiO₂ nanoparticles in primary cortical neuron cultures and in the brain of rats

Toxicol Rep. 2018 Aug 23:5:878-889. doi: 10.1016/j.toxrep.2018.08.006. eCollection 2018.

Authors

Xavier Valentini¹, Pauline Deneufbourg², Paula Paci², Pascaline Rugira¹, Sophie Laurent^{3

4}, Annica Frau¹, Dimitri Stanicki³, Laurence Ris², Denis Nonclercq¹

Affiliations

¹ Laboratory of Histology, University of Mons, Institute for Health Sciences and Technology, Faculty of Medicine and Pharmacy, 23, Place du Parc, B-7000 Mons, Belgium.
² Laboratory of Neurosciences, University of Mons, Institute for Health Sciences and Technology, Faculty of Medicine and Pharmacy, 23, Place du Parc, B-7000 Mons, Belgium.
³ Laboratory of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Institute for Health Sciences and Technology, Institute of Biosciences, Faculty of Medicine and Pharmacy, 23, Place du Parc, B-7000 Mons, Belgium.
⁴ Center for Microscopy and Molecular Imaging (CMMI), B-6041 Gosselies, Belgium.

Abstract

Nowadays, nanoparticles (NPs) of titanium dioxide (TiO₂) are abundantly produced. TiO₂ NPs are present in various food products, in paints, cosmetics, sunscreens and toothpastes. However, the toxicity of TiO₂ NPs on the central nervous system has been poorly investigated until now. The aim of this study was to evaluate the toxicity of TiO₂ NPs on the central nervous system in vitro and in vivo. In cell cultures derived from embryonic cortical brain of rats, a significant decrease in neuroblasts was observed after 24 to 96 h of incubation with TiO₂ NPs (5 to 20 μg/ml). This phenomenon resulted from an inhibition of neuroblast proliferation and a concomitant increase in apoptosis. In the same time, a gliosis, characterized by an increase in proliferation of astrocytes and the hypertrophy of microglial cells, occurred. The phagocytosis of TiO₂ NPs by microgliocytes was also observed. In vivo, after intraperitoneal injection, the TiO₂ NPs reached the brain through the blood brain barrier and the nanoparticles promoted various histological injuries such as cellular lysis, neuronal apoptosis, and inflammation. A reduction of astrocyte population was observed in some brain area such as plexiform zone, cerebellum and subependymal area. An oxidative stress was also detected by immunohistochemistry in neurons of hippocampus, cerebellum and in subependymal area. In conclusion, our study demonstrated clearly the toxic impact of TiO₂ NPs on rat brain and neuronal cells and pointed about not yet referenced toxicity impacts of TiO2 such as the reduction of neuroblast proliferation both in vitro and in vivo.

Keywords: 4-HNE, 4-hydroxynonenal; ATP, adenosine triphosphate; BBB, blood-brain barrier; Brain; BrdU, 5-Bromo-2′-deoxyuridine; CNS, central nervous system; Cell culture; DLS, dynamic light scattering; FBS, fetal bovine serum; GFAP, glial fibrillary acidic protein; HBSS, Hank's balanced salt solution; IL-10, interleukin-10; IL-1β, interleukin-1β; IP, intraperitoneal; MAP2, microtubule-associated protein 2; MDA, malondialdehyde; NMDA, N-methyl-D-aspartate; NO, nitric oxide; NOS, nitric oxide synthase; NPs, nanoparticles; Nanoparticles; Oxidative stress; Proliferation; ROS, reactive oxygen species; SEM, standard error of the mean; TNF-α, tumor necrosis factor-α.