Titanium Nanoparticle Inhalation Induces Renal Fibrosis in Mice via an Oxidative Stress Upregulated Transforming Growth Factor-β Pathway

Abstract

Titanium dioxide nanoparticles (Nano-TiO2) are gradually being used extensively in clinical settings, industry, and daily life. Accumulation studies showed that Nano-TiO2 exposure is able to cause injuries in various animal organs, including the lung, liver, spleen, and kidney. However, it remains unclear whether exposure of Nano-TiO2 by inhalation causes renal fibrosis. Here, we investigated the role of reactive oxygen species (ROS)/reactive nitrogen species (RNS) related signaling molecules in chronic renal damage after Nano-TiO2 inhalation in mice. Mice were treated with Nano-TiO2 (0.1, 0.25, and 0.5 mg/week) or microparticle-TiO2 (0.5 mg/week) by nonsurgical intratracheal instillation for 4 weeks. The results showed that Nano-TiO2 inhalation increased renal pathological changes in a dose-dependent manner. No renal pathological changes were observed in microparticle-TiO2-instilled mice. Nano-TiO2 (0.5 mg/week) possessed the ability to precipitate in the kidneys, determined by transmission electron microscopy and increased serum levels of blood urea nitrogen. The expressions of markers of ROS/RNS and renal fibrosis markers, including nitrotyrosine, inducible nitric oxide synthase, hypoxia inducible factor-1α (HIF-1α), heme oxygenase 1, transforming growth factor-β (TGFβ), and collagen I, determined by immunohistochemical staining were increased in the kidneys. Furthermore, Nano-TiO2-induced renal injury could be mitigated by iNOS inhibitor aminoguanidine and ROS scavenger N-acetylcysteine treatment in transcription level. The in vitro experiments showed that Nano-TiO2 significantly and dose-dependently increased the ROS production and the expressions of HIF-1α and TGFβ in human renal proximal tubular cells, which could be reversed by N-acetylcysteine treatment. Taken together, these results suggest Nano-TiO2 inhalation might induce renal fibrosis through a ROS/RNS-related HIF-1α-upregulated TGF-β signaling pathway.

Review: the potential impact of surface crystalline states of titanium for biomedical applications

“…Consistently with in vitro studies, experiments in mice also showed that titanium induces increased expression of pro-inflammatory cytokines (TNFα, IL-1β and IL-6), chemokines (CCL2 and CCL3), NLPR3, ROS and RNS (Huang et al, 2015, Jovanovic, 2015, Sang et al, 2012, Warme et al, 2004, Yazdi et al, 2010.…”

Nanosized titanium dioxide resulted in the activation of TGF‐β/Smads/p38MAPK pathway in renal inflammation and fibration of mice

“…Our previous studies suggested that exposure to anatase TiO 2 NPs (5–6 nm) for 2 weeks, 3, or 6 months caused significant elevations in serum Cr and proteinuria in mice, and renal inflammation in female mice, but we did not observe renal fibration . Recently, intratracheal exposure to TiO 2 NPs (21 nm with 35 − 65 m 2 /g surface area, 0.25, and 0.5 mg/week) for four weeks or gavage exposure to TiO 2 NPs (5–6 nm with 174.8 m 2 /g surface area, 1.25, 2.5, or 5 mg/kg body weight) for 9 months was found to result in renal inflammation and fibrosis of male, or female mice . However, bulk TiO 2 (5 μm) did not increase renal histopathological changes in mice .…”

“…TiO 2 was previously considered to be nontoxic in particle toxicology; however, it has been recently classified by the International Agency for Research on Cancer as “possibly carcinogenic to humans” by inhalation, and its multiple specific characteristics coupled with unknown risks to human health and the environment have been reported . While TiO 2 NPs inhalation exposure has been suggested to cause renal damage in mice …”

“…Particularly, oral gavage exposure to 1.25, 5, or 5 mg/kg body weight TiO 2 NPs for 9 months was demonstrated to increased urinary levels of kidney injury molecule‐1, clusterin, and osteopontin, and to cause renal inflammation and fibrosis, which associated with increased expression of Wnt ligands, Wnt receptors Frizzled, co‐receptors low‐density lipoprotein receptor‐related proteins 5/6, Wnt target genes and epithelial‐to‐mesenchymal transition (EMT) markers, and decreased expression of Wnt antagonist‐related markers in mouse kidney . Recently, Huang et al also demonstrated that nonsurgical intratracheal instillation with TiO 2 NPs (0.1, 0.25, and 0.5 mg/week) for 4 weeks resulted in renal fibrosis of male mice, with increases of expressions of nitrotyrosine, inducible nitric oxide synthase, hypoxia inducible factor‐1α (HIF‐1α), heme oxygenase 1, TGFβ, and collagen I, and considered that TiO 2 NPs inhalation might induce renal fibrosis through a ROS/reactive nitrogen species (RNS)‐related HIF‐1α‐upregulated TGF‐β signaling pathway in mice . However, molecular mechanisms of chronic nephritis and renal fibration caused by long‐term TiO 2 NPs exposure in mice are not well understood.…”

Toxicokinetics and tissue distribution of titanium in ionic form after intravenous and oral administration

“…Today the mechanism of action of titanium on the human body is not yet fully understood, but it is known that metal can cause adverse health effects as a result of, for example, inhalation (Grassian et al, 2007;Huang et al, 2015;Ma-Hock et al, 2007;Wang et al, 2007;Warheit et al, 2007). Titanium alloys are of great value in orthopedic surgery due to their significant resistance to the attack of body fluids, strength, flexibility, biocompatibility, or lack of allergenicity (Niinomi, 2008).…”