Real-Ambient Particulate Matter Exposure-Induced Cardiotoxicity in C57/B6 Mice

Lianhua Cui; Limei Shi; Daochuan Li; Xiaobo Li; Xuan Su; Liping Chen; Qixiao Jiang; Menghui Jiang; Jing Luo; Andong Ji; Chen Chen; Jianxun Wang; JingLong Tang; Jingbo Pi; Rui Chen; Wen Chen; Rong Zhang; Yuxin Zheng

doi:10.3389/fphar.2020.00199

Real-Ambient Particulate Matter Exposure-Induced Cardiotoxicity in C57/B6 Mice

Front Pharmacol. 2020 Mar 31:11:199. doi: 10.3389/fphar.2020.00199. eCollection 2020.

Authors

Lianhua Cui¹, Limei Shi¹, Daochuan Li², Xiaobo Li³, Xuan Su⁴, Liping Chen², Qixiao Jiang¹, Menghui Jiang¹, Jing Luo¹, Andong Ji¹, Chen Chen¹, Jianxun Wang⁵, JingLong Tang¹, Jingbo Pi⁶, Rui Chen³, Wen Chen², Rong Zhang⁴, Yuxin Zheng¹

Affiliations

¹ Department of Toxicology, School of Public Health, Qingdao University, Qingdao, China.
² Department of Toxicology, School of Public Health, Sun Yat-sen University, Guangzhou, China.
³ Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, China.
⁴ Department of Toxicology, School of Public Health, Hebei Medical University, Shijiazhuang, China.
⁵ School of Basic Medicine, Qingdao University, Qingdao, China.
⁶ School of Public Health, China Medical University, Shenyang, China.

Abstract

It is generally accepted that exposure to particulate matter (PM) increases the risk of cardiovascular-related morbidity and mortality, though the exact mechanism behind this has yet to be elucidated. Oxidative stress plays a potentially important role in the mechanism of toxicity, with Nrf2 serving as a major antioxidant gene. In the current study, a Nrf2 knockout mouse model was used in combination with an individual ventilated cage (IVC)-based real-ambient PM exposure system to assess the potential cardiotoxicity induced by real-ambient PM exposure and the potential role of Nrf2 and related signaling in this endpoint. After 6- or 11-weeks exposure to PM, ICP-mass spectrometry was used to assess the metal depositions in the heart tissue following PM exposure. Functional and morphological changes in the hearts were investigated with echocardiography and histopathology, and oxidative stress levels were assessed with a serum malondialdehyde content assay. In the further mechanistic study, an RNA-seq technique was utilized to assess the gene transcription status in the hearts of C57/B6 mice exposed to PM with or without Nrf2 knockout. The expression levels of genes of interest were then further investigated with quantitative real-time PCR and western blotting. The results indicated that PM exposure resulted in significant elevation of sodium, potassium, selenium, and ferrum levels in mouse heart tissue. Meanwhile, significantly altered heart function and morphology were observed. Interestingly, Nrf2 knockout led to abolishment of PM-induced effects in several functional parameters but not the morphological changes. Meanwhile, elevated malondialdehyde content was observed in Nrf2 knockout animals. RNA-seq results revealed thousands of genes altered by PM exposure and/or Nrf2 knockout, and this affected several pathways, such as MAPK, phagosome, calcium signaling, and JAK-STAT. In subsequent molecular studies, enhanced nuclear translocation of Nrf2 was also observed following PM exposure, while the MAPK signaling pathway along with related JAK-STAT and TGF-β1 pathway genes, such as p38MAPK, AKT, TAK1, JAK1, STAT3, GRB2, TGFb1, and SMAD2, were confirmed to be affected by PM exposure and/or Nrf2 knockout. The data suggested that PM may induce cardiotoxicity in C57/B6 mice in which Nrf2 plays both protective and detrimental roles involving cardiac-related pathways, such as MAPK, JAK-STAT, and TGF-β1.

Keywords: C57/B6 mouse; cardiotoxicity; individual ventilated cages; molecular mechanism; particulate matter; real-life exposure.