Image: Titanium dioxide is a white pigment used increasingly as a food additive (Photo courtesy of UZH).
Nanoparticles of titanium dioxide (TiO2), a white pigment used in medicines, toothpaste, and as a food additive (E171), can cause increased inflammation and damage to the intestinal mucosa, according to a new study.
Researchers at the University of Zurich (UZH; Switzerland) conducted a study in wild-type mice in order to investigate the effects of TiO2 on the development of colitis. The proinflammatory effects of TiO2 nanoparticles in cultured human intestinal epithelial cells (IECs) and macrophages were also studied, as well as the ability of TiO2 crystals to traverse IEC monolayers and accumulate in the blood of patients with inflammatory bowel disease (IBD). To do so, the researchers used inductively coupled plasma mass spectrometry.
The researchers concentrated on a specific protein complex found inside cells, the nucleotide-binding oligomerisation domain receptor, pyrin domain containing (NLRP3) inflammasome, a protein complex that is part of the non-specific immune system. If the NLRP3 inflammasome is activated by bacterial components, it can trigger an inflammatory reaction that protects against infective agents. But in the same way, NLRP3 can be activated by small inorganic particles, with potentially negative outcomes. For example, if uric acid crystals form in the cells, the inflammation leads to gout.
The results showed that TiO2 can penetrate accumulate both in human IECs and in macrophages, and can trigger inflammatory messengers. In addition, patients with ulcerative colitis IBD, whose intestinal barrier is disrupted, have an increased concentration of TiO2 in their blood. When TiO2 nanoparticles were administered to mice, the NLRP3 complex was activated, leading to strong intestinal inflammation and greater damage to the intestinal mucosa. In addition, TiO2 crystals accumulated in the animals' spleens. The study was published in the July 2017 issue of Gut.
“Titanium dioxide induces reactive oxygen species (ROS) formation, as well as inflammation in vitro and in vivo,” concluded senior author professor of gastroenterology and hepatology Gerhard Rogler, MD, and colleagues. “These particles can be absorbed from food under certain disease conditions. Based on our results, patients with an intestinal barrier dysfunction as found in colitis should abstain from foods containing titanium dioxide.”
The prevalence of IBD, including Crohn's disease and ulcerative colitis, has been on the rise in many Western countries for decades. The illnesses are caused by an excessive autoimmune reaction against the intestinal flora. In addition to genetic factors, environmental factors such as the Western lifestyle, especially nutrition, play an essential role in the development of these chronic intestinal diseases.
University of Zurich