Abstract P3088: Hexokinase 3 Regulates Macrophage Polarization And Cardiac Remodeling Likely Through Serine Metabolism

Abstract

Myocardial infarction (MI) is associated with activation of macrophages in the myocardium. Hexokinase 3 (HK3) is the mainly expressed hexokinase in macrophage. Along with its role as the first enzyme in glycolysis, HK3 has shown to be involved in the regulation of diverse immune system activities. In this study we studied the role of HK3 in the regulation of macrophage polarization into inflammatory phenotype (termed as M1) and anti-inflammatory and repair phenotype (termed as M2). Using CRISPR-Cas9 technology, we generated mice with deletion of exons 2 and 3 of the Hk3 gene, which are needed for the function of the protein. Bone marrow-derived macrophages (BMDM) isolated from Hk3 -/- mice displayed higher levels of M2 markers, including Arg1, Ym1, Mrc1, PD-L2, IRF4, Mgl2, and Mgl1 compared to BMDMs from wild-type mice. Also, we found that pSTAT6 protein, was higher in BMDMs from Hk3 -/- mice. Furthermore, there was a higher oxygen consumption rate and lower extracellular acidification rate in Hk3 -/- BMDMs. Steady-state metabolomics in BMDMs isolated from WT and Hk3 -/- mice showed that there was a significant increase in metabolites in the serine biosynthesis pathway (SBP), indicating that glucose metabolism is more shunted into the SBP with Hk3 deletion. The removal of serine/glycine from media resulted in a significant decrease in the M2 markers in wild-type BMDMs; However, higher M2 markers were observed in Hk3 -/- BMDMs. This result indicated that the SBP is needed for the polarization of macrophages into the M2 subtype, and HK3 mediated M2 polarization is likely through the SBP. We then subjected Hk3 -/- to LAD and assessed cardiac function after seven days using echocardiography. Result demonstrated that both male and female Hk3 -/- mice display improved cardiac function, as assessed by measurement of ejection fraction (EF), fractional shortening (FS), and interventricular septum thickness in diastole (IVSd). Our results demonstrate that HK3 is a novel regulator of macrophage polarization into the phenotype with more anti-inflammatory and tissue repair characteristic. This study is clinically important by providing a potent novel approach to the treatment of ischemic heart disease.