28 - TRIMETHYLAMINE N-OXIDE PROMOTES VASCULITIS DEVELOPMENT IN A MURINE MODEL OF KAWASAKI DISEASE VASCULITIS

Background and Aims: Changes in the intestinal microbiota composition have been implicated in the pathogenesis of cardiovascular diseases, including Kawasaki disease (KD), an acute febrile and systemic pediatric vasculitis. Over the last decade, microbial-derived metabolites have emerged as significant contributors to the development of cardiovascular diseases. Among these is the bacteria-derived trimethylamine-N-oxide (TMAO), generated from the dietary precursor choline, phosphatidylcholine, and carnitine, whose plasma levels are associated with increased cardiovascular risks in clinical studies. TMAO promotes vascular inflammation by enhancing cytokine production, reactive oxygen species (ROS), and the activation of platelets, endothelial cells, and vascular smooth muscle cells (VSMCs). However, whether TMAO contributes to the development of KD remains unknown.

Methods: To determine if TMAO contributes to KD development, we used the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, which closely phenocopies the important histological, functional, and immune features of human KD. 16S rRNA gene sequencing was used to characterize the fecal microbiome composition of control and LCWE-injected mice, and TMAO circulating levels were measured by liquid chromatography with tandem mass spectrometry (LC-MS-MS). To modulate the TMAO pathway, mice were orally supplemented with either TMAO, the selective TMAO inhibitor 3,3-dimethyl butanol (DMB), or fluoromethylcholine, a trimethylamine (TMA)-lyase inhibitor, which blocks TMA oxidation into TMAO. Immunofluorescence was used to assess ROS production in the intestinal tissues of control and LCWE-injected mice.

Results: We observed the blooming of Proteobacteria, which are involved in the TMAO anaerobic process, in the fecal pellets of LCWE-injected mice. Compared with control PBS-injected mice, levels of TMAO were significantly increased in the serum of LCWE-injected mice. Furthermore, TMAO supplementation in drinking water exacerbated LCWE-induced cardiovascular inflammation, while oral supplementation with a selective TMAO inhibitor, DMB, reduced the severity of LCWE-induced cardiovascular lesions. Treatment with fluoromethylcholine, a TMA-lyase inhibitor that blocks TMA oxidation and the production of TMAO, also reduced the development of LCWE-induced KD lesions.

Conclusions: Our results indicate that TMAO promotes cardiovascular inflammation in a mouse model of KD vasculitis. Our findings support future research examining the role of microbiota and microbiota-derived metabolites, such as TMAO, in human KD and may reveal novel diagnostic and therapeutic tools for KD.