Immunotoxicity of titanium dioxide nanoparticles via simultaneous induction of apoptosis and multiple toll-like receptors signaling through ROS-dependent SAPK/JNK and p38 MAPK activation

Abstract

Madhusmita Dhupal,1,2 Jae-Min Oh,3 Dipti Ranjan Tripathy,4 Soo-Ki Kim,2 Sang Baek Koh,5 Kyu-Sang Park6 1Department of Global Medical Science, Wonju College of Medicine, Yonsei University, Wonju, Republic of Korea; 2Department of Microbiology, Wonju College of Medicine, Yonsei University, Wonju, Republic of Korea; 3Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Republic of Korea; 4Department of Neurology, Gauhati Medical College and Hospital, Gauhati, India; 5Department of Preventive Medicine, Wonju College of Medicine, Yonsei University, Wonju, Republic of Korea; 6Department of Physiology, Wonju College of Medicine, Yonsei University, Wonju, Republic of Korea Background: Titanium dioxide nanoparticles (TiO2 NPs) represent a scientific breakthrough in the areas of biological and medicinal applications. Interaction of TiO2 NPs with components of innate immune system remains elusive. Aim: This study explored in vitro immunotoxicity of murine macrophage RAW 264.7 to TiO2 NPs (20 nm, negative charge) and its underlying molecular mechanism by way of immunoredox profiling. Materials and methods: In this study, chemically synthesized BSA-functionalized TiO2 NPs (20 nm, negative charge) were characterized and immunotoxicity was investigated on RAW 264.7 cells. Results: We found that reactive oxygen species levels significantly increased with increasing nitric oxide production, whereas depleting endogenous antioxidant super oxide dismutase as well as nuclear factor erythroid 2-related factor 2 (Nrf2) protein levels. Furthermore, NPs exposure increased the expression of apoptotic factors such as BAX, BIM, and PUMA with disruption of mitochondrial membrane potential (ΔΨm) that lead to decrease in immunocytes. Molecular immune profiling revealed the activation of multiple toll-like receptors (TLRs) 4/9/12/13 simultaneously with the phosphorylation of p-p38MAPK and p-SAPK/c-Jun N-terminal kinase (JNK) compared to untreated control. Conclusion: Collectively, this study shows that the molecular nature of TiO2SA20(-) NP-induced immunotoxicity in RAW 264.7 macrophage is simultaneous induction of immunocyte apoptosis and multiple TLRs signaling through oxidative stress-dependent SAPK/JNK and p38 mitogen-associated protein kinase activation. This is the first study to address newer molecular mechanism of TiO2SA20(-) NP-induced immunotoxicity. Keywords: titanium dioxide, toll-like receptors, MAPK pathways, apoptosis, nanoparticles, oxidative stress

Keywords

• Titanium dioxide
• Toll-like receptors
• MAPK pathways
• Apoptosis
• Nanoparticles
• Oxidative stress.