Abstract 13994: PKM2 Ablation Increases Pro-Inflammatory Signaling in Mice

Abstract

Introduction: The predominant isoform of pyruvate kinase (PKM1) promotes oxidative metabolism in the healthy heart. We previously described a hypoxia and ischemia-mediated switch to the alternatively spliced isoform PKM2, known to promote glycolysis. Pkm2 has also been shown to reduce oxidative damage and promote cardiomyocyte cell proliferation after myocardial infarction (MI). PKM2 is also a metabolic regulator of immune cell differentiation. Hypothesis: We hypothesize that PKM2 has a role in limiting inflammatory stress by regulating the migration and activity of immune cells. Methods: PKM2 control and global KO mice were subjected to permanent ligation of the left anterior descending coronary artery to mimic an MI (n=3). Hearts were excised after 3 days and the transcriptomes and gene ontologies (GO) were then assessed by RNA-sequencing and pathway analysis. Circulating C-reactive protein (CRP) was assessed using an ELISA (n=12) and cytokines in plasma and heart tissue were assessed using a multiplex assay (n=3-5). Neutrophil myeloperoxidase secretion and differentiated cardiac macrophages were analyzed by immunofluorescent staining (n=3). Results: GO term enrichment analysis of RNA-seq results showed increased abundance of genes for neutrophil chemotaxis and apoptosis, regulation of cytokine production, and the inflammatory response in PKM2 KO hearts after MI compared to controls. PKM2 KO hearts showed increased neutrophil myeloperoxidase secretion and Ly6G/C staining for neutrophils and monocytes compared to controls. Similarly, M1 macrophages appeared to be more abundant in PKM2 KO hearts compared to controls. IL-6 levels were elevated in PKM2 KO plasma at baseline compared to controls, while CRP was elevated in PKM2 KO plasma across all conditions. IL-6 was also substantially elevated in PKM2 KO hearts after MI compared to controls. Conclusions: Loss of PKM2 increased pro-inflammatory signaling in the heart of KO mice. We saw increased cardiac and plasma IL-6 and CRP, likely related to the polarization of macrophages towards the M1 phenotype, and increased neutrophil activity in PKM2 KO hearts. We suggest that PKM2, induced by a hypoxia-related splicing event, protects the heart against the inflammation that accompanies infarction.