Abstract 793: Macrophage Transcription Factor EB Attenuates Left Ventricular Remodeling Via Lysosomal Lipolysis

Abstract

Background: Autophagy, lipid metabolism, and inflammation are interrelated cellular processes that implicate lysosomes in human disease. After ischemia reperfusion (IR) injury, inflammasome activation and interleukin 1-beta (IL1-beta) secretion promote heart failure progression. Whether macrophage autophagy and lysosomal biogenesis can attenuate post-IR remodeling and inflammation is unknown. We hypothesized that macrophages exhibit lysosome dysfunction and autophagic impairment after IR injury, and that augmentation of macrophage lysosomal biogenesis via macrophage-specific overexpression of transcription factor EB (Mf-TFEB), a master regulator of autophagy and lysosomal biogenesis, would attenuate myocardial remodeling and inflammation in ischemic cardiomyopathy. Methods and Results: In mice subject to IR injury and humans with ischemic cardiomyopathy, we observed evidence of lysosomal and autophagic impairment. To ameliorate post-IR macrophage lysosomal injury, we expressed Mf-TFEB in a closed-chest IR murine model using a tamoxifen-inducible CX3CR1erCre and TFEB overexpression cassette bearing a Cre-excisable STOP codon. Compared to Cre-only controls, Mf-TFEB mice had significantly increased left ventricular (LV) ejection fraction 28-days post-IR (40% relative increase, p=0.002, n=15-17 per group), decreased abundance of pro-inflammatory macrophages, and reduced levels of IL1-beta in myocardial tissue. Surprisingly, neither inflammasome suppression nor TFEB-mediated attenuation of post-IR remodeling required intact macro-autophagy as evidenced by Mf-TFEB-mediated rescue of post-IR LV dysfunction in mice with concomitant inducible ATG5 ablation. RNA sequencing of flow-sorted macrophages from post-IR mice identified lysosomal acid lipase amongst other lipases regulated by TFEB. Mechanistically, pharmacologic inhibition of lysosomal acid lipase specifically abrogated the in vivo effects of TFEB on post-IR remodeling. Conclusions: Our findings suggest that macrophage TFEB regulates lysosomal lipolysis to attenuate inflammasome activity and protect against post-IR LV dysfunction, suggesting an alternative paradigm for how lysosome function may impact acute inflammation in vivo.