N6-methyladenosine of Spi2a attenuates inflammation and sepsis-associated myocardial dysfunction in mice.

ABSTRACT

Bacteria-triggered sepsis is characterized by systemic, uncontrolled inflammation in affected individuals. Controlling the excessive production of pro-inflammatory cytokines and subsequent organ dysfunction in sepsis remains challenging. Here, we demonstrate that Spi2a upregulation in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages reduces the production of pro-inflammatory cytokines and myocardial impairment. In addition, exposure to LPS upregulates the lysine acetyltransferase, KAT2B, to promote METTL14 protein stability through acetylation at K398, leading to the increased m6A methylation of Spi2a in macrophages. m6A-methylated Spi2a directly binds to IKKß to impair IKK complex formation and inactivate the NF-κB pathway. The loss of m6A methylation in macrophages aggravates cytokine production and myocardial damage in mice under septic conditions, whereas forced expression of Spi2a reverses this phenotype. In septic patients, the mRNA expression levels of the human orthologue SERPINA3 negatively correlates with those of the cytokines, TNF, IL-6, IL-1ß and IFNγ. Altogether, these findings suggest that m6A methylation of Spi2a negatively regulates macrophage activation in the context of sepsis.