Exposure to Multiwall Carbon Nanotubes Promotes Fibrous Proliferation by Production of Matrix Metalloproteinase-12 via NF-κB Activation in Chronic Peritonitis.

The toxicologic effects of nanomaterials, such as carbon nanotubes (CNTs), on the immune system are understood well. However, the precise relationship between long-term exposure to CNTs and chronic inflammation remains unclear. In this study, a mouse model of chronic peritonitis was established using i.p. injection of multiwalled CNTs treated by the Taquann method with high dispersion efficiency. Chronic peritonitis with fibrosis was observed in Taquann-treated multiwalled CNT (T-CNT)-injected mice, but not in Taquann-treated titanium dioxide-injected mice. In vivo and in vitro experiments showed that matrix metalloproteinase-12 (MMP-12) of macrophages was up-regulated by T-CNT to enhance fibroblast activation and profibrotic molecule expression in fibroblasts. In addition, T-CNT-induced peritonitis reduced MMP-12 expression in Nfκb1-/- mice, suggesting that MMP-12-producing macrophages play a key role in chronic inflammation due to T-CNT exposure through NF-κB activation. The results of this study could be helpful in understanding the molecular toxicity of nanomaterial and chronic inflammation.