Yang Ting, Chen Jiamao, Gao Lingqiang, Huang Yuanyu, Liao Guochao, Cao Yi
Joint Laboratory for Translational Cancer Research of Chinese Medicine of the Ministry of Education of the People's Republic of China, International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, PR China; Key Laboratory of Environment-Friendly Chemistry and Application of Ministry of Education, Lab of Biochemistry, College of Chemistry, Xiangtan University, Xiangtan 411105, PR China.
Joint Laboratory for Translational Cancer Research of Chinese Medicine of the Ministry of Education of the People's Republic of China, International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, PR China.
Toxicol Lett. 2020 Oct 10;332:65-73. doi: 10.1016/j.toxlet.2020.07.007. Epub 2020 Jul 7.
Exposure to multi-walled carbon nanotubes (MWCNTs) might induce lipid droplet (LD) biogenesis, but the roles of physicochemical properties of MWCNTs, as well as the mechanisms, remain poorly understood. In this study, we investigated lipid laden foam formation in THP-1 macrophages exposed to MWCNTs of different diameters, and attempted transcriptomic analysis to study the possible mechanisms. We observed diameter-dependent cytotoxicity, lipid accumulation and intracellular reactive oxygen species production that were more pronounced for MWCNTs with smaller diameters compared with those with larger diameters. However, more MWCNTs with larger diameters were retained in macrophages after 24 h exposure. One possible explanation for the inverse relationship between MWCNT bio-effects and internalization is that macrophages altered the expression of exocytotic genes to export toxic MWCNTs. Transcriptomic data showed that MWCNTs with smaller diameters more effectively altered the expression of genes related with cytotoxicity and lipid metabolism, and KEGG pathway analysis suggested that MWCNTs with smaller diameters activated peroxisome proliferator-activated receptor (PPAR) signalling pathway (map03320), leading to over-expression of perilipin 2, the surface proteins of LDs. Western blot confirmed that MWCNTs effectively promoted CD36, PPARγ and perilipin 2, key components in map03320. Moreover, inhibition of PPARγ by chemicals or siRNA significantly inhibited lipid accumulation induced by MWCNTs with smaller diameters, and perilipin 2 proteins in MWCNT-exposed macrophages could be decreased by PPARγ siRNA. In conclusion, the results of this study revealed the induction of LDs by MWCNTs in a diameter-dependent manner through the activation of PPAR signalling pathway.
暴露于多壁碳纳米管（MWCNTs）可能会诱导脂滴（LD）的生物合成，但MWCNTs的物理化学性质的作用以及其机制仍知之甚少。在本研究中，我们调查了暴露于不同直径MWCNTs的THP-1巨噬细胞中富含脂质的泡沫形成情况，并尝试通过转录组分析来研究可能的机制。我们观察到了直径依赖性细胞毒性、脂质积累和细胞内活性氧生成，与较大直径的MWCNTs相比，较小直径的MWCNTs表现得更为明显。然而，暴露24小时后，巨噬细胞中保留了更多较大直径的MWCNTs。MWCNT生物效应与内化之间这种反比关系的一种可能解释是，巨噬细胞改变了胞吐基因的表达以输出有毒的MWCNTs。转录组数据表明，较小直径的MWCNTs更有效地改变了与细胞毒性和脂质代谢相关的基因表达，KEGG通路分析表明，较小直径的MWCNTs激活了过氧化物酶体增殖物激活受体（PPAR）信号通路（map03320），导致脂滴表面蛋白 perilipin 2的过度表达。蛋白质印迹证实，MWCNTs有效地促进了map03320中的关键成分CD36、PPARγ和perilipin 2。此外，用化学物质或小干扰RNA（siRNA）抑制PPARγ可显著抑制较小直径MWCNTs诱导的脂质积累，并且PPARγ siRNA可降低MWCNT暴露的巨噬细胞中的perilipin 2蛋白。总之，本研究结果揭示了MWCNTs通过激活PPAR信号通路以直径依赖性方式诱导脂滴形成。
