15 - SIRTUIN 1 REDUCES CARDIOVASCULAR INFLAMMATION IN A MURINE MODEL OF KAWASAKI DISEASE

Background: The overactivation of NLRP3 inflammasome and the production of bioactive IL-1β are critical for the development of cardiovascular lesions in KD. The nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase Sirtuin 1 (SIRT1) is crucial for cellular responses to stress and regulates NLRP3 inflammasome activation, as well as the clearance of damaged mitochondria. However, its potential implication in KD pathophysiology remains unknown.

Methods: We used the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis to determine the role of SIRT1 on the development of cardiovascular lesions. SRT1720, a pharmacological SIRT1 activator, was used to activate SIRT1 in LCWE-injected mice. Metabolomics analysis was performed on the serum of LCWE-injected mice to measure metabolites related to NAD⁺ production, which are directly linked to SIRT1 activity. Furthermore, to assess the effect of boosting NAD⁺ production during LCWE-induced KD vasculitis, mice were orally supplemented with the NAD⁺ precursors β-nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR). The severity of LCWE-induced KD vasculitis was also determined in mice either overexpressing SIRT1 (Sirt1^Super) or lacking Sirt1 expression in vascular smooth muscle cells (VSMCs). To further determine the role of SIRT1 in autophagy/mitophagy, coronary smooth muscle cells were stimulated in vitro with LCWE and/or SRT1720 and the expression of mitophagy/autophagy proteins was analyzed by western blot analysis.

Results: The expression of Sirt1 is downregulated in cardiovascular lesions of LCWE-injected mice. Furthermore, treatment with SRT1720 alleviated the development of LCWE-induced KD vascular inflammation. Metabolomics analysis showed a significant reduction of nicotinamide (NAM), a product resulting from NAD⁺ degradation by SIRT1 activity, in the serum of LCWE-injected mice. Oral supplementation of NMN or NR significantly reduced the development of LCWE-induced cardiovascular lesions. Furthermore, KD vasculitis development was less severe in SIRT1 overexpressing mice and exacerbated in mice with specific Sirt1 deletion in VSMCs. In vitro treatment of LCWE-stimulated coronary smooth muscle cells with SRT1720 promoted localization of p62 and LC3-II to mitochondria and favored mitophagy by inhibiting ribosomal S6 phosphorylation.

Conclusion: These results indicate an impaired NAD⁺/SIRT1 axis in LCWE-induced KD vasculitis and demonstrate that modulation of SIRT1 or NAD⁺ biosynthesis can be targeted to reduce LCWE-induced KD vasculitis. Overall, these findings contribute to our understanding of KD pathogenesis and identify potentially novel therapeutic approaches for KD treatment via targeting the SIRT1 pathway.