Effect of MacroD1 knockout on gene expression of heart on mouse septic model

Metabolic plasticity of tissues determines the degree and reversibility of organ damage under inflammatory challenges. While treating septic cardiomyopathy (SCM) with high mortality, metabolic management should be considered. Still, similar pan-organ metabolic anomalies usually yield contrasting results in each one, highlighting the necessity to identify cardiac-specific metabolic regulators. Nicotinamide adenine dinucleotide (NAD+) signaling is fundamental to cellular metabolic homeostasis and inflammatory response, and cardiomyocyte-enriched NAD+-consuming enzymes programming metabolism against sepsis and their roles in SCM remain undefined. In this study, we explored the expression patterns of NAD+-consuming enzymes of heart and found Mono-ADP-ribosyl hydrolase MacroD1 protein was distinctly enriched in rodent and AC16 human cardiomyocytes and upregulated during severe endotoxemia. Genetic and pharmacological inactivation of MacroD1 counteracted myocardial metabolic impairment, lipid accumulation, inflammatory infiltrate, cardiac dysfunction, and mortality risk induced by septic challenges in mice. Mechanistically, MacroD1 selectively modulated the activity of mitochondrial complex I (MCI), a proximal respiratory unit most vulnerable to early endotoxemia. Its inhibition enhanced MARylation of NDUFB9, an accessory assembly factor of MCI proton-pumping module ND5, and therefore binding to ND5 for preserving MCI activity in sepsis, restraining bioenergetic deficiency, oxidative stress-coupled NLRP3 inflammasome activation, and pyroptosis of cardiomyocytes. Our research reveals that MacroD1 dictates cardiac tolerance to sepsis by configuring MCI-coupled bioenergetic reserve and pyroptosis of cardiomyocytes. Blockade of MacroD1 promises specific prevention of SCM.