Ambient NO2 exposure induced cardiotoxicity associated with gut microbiome dysregulation and glycerophospholipid metabolism disruption

An average daily increase of 10 μg/m3 in NO2 concentrations could lead to an increased mortality in cardiovascular, cerebrovascular of 1.89%, 2.07%, but the mechanism by which NO2 contributes to cardiotoxicity is rarely reported. In order to assess the cardiotoxicity of NO2 inhalation (5 ppm), we firstly investigate the change of gut microbiota, serum metabonomics and cardiac proteome. Non-targeted LC-MS/MS metabonomics showed that NO2 stress could perturb the glycerophospholipid metabolism in the serum, which might destabilize the bilayer configuration of cardiac lipid membranes. Furthermore, we observed that NO2 inhalation caused augmented intercellular gap and inflammatory infiltration in the heart. Although 16 S rRNA gene amplification sequencing demonstrated that NO2 exposure did not influence the intestinal microbial abundance and diversity, but glycerophospholipid metabolism disruption might be finally reflected in gut microbiom dysregulation, such as Sphingomonas, Koribacter, Actinomarina and Bradyrhizobium Turicibacter, Rothia, Globicatella and Aerococcus. Proteome mining revealed that differentially expressed genes (DEGs) in the heart after NO2 stress were involved in necroptosis, mitophagy and ferroptosis. We further revealed that NO2 increased the number of cardiac mitochondria with depletion of cristae by regulating the expression of Mfn2 and Hsp70. This study indicating Mfn2-meidcated imbalanced mitochondrial dynamics as a potential mechanism after NO2-induced heart injury and suggesting microbiome dysregulation/glycerophospholipid metabolism exerts critical roles in cardiotoxicity caused by NO2.