Myeloid Cell PKM2 Deletion Enhances Efferocytosis and Reduces Atherosclerosis

Abstract

Background: The glycolytic enzyme PKM2 (pyruvate kinase muscle 2) is upregulated in monocytes/macrophages of patients with atherosclerotic coronary artery disease. However, the role of cell type-specific PKM2 in the setting of atherosclerosis remains to be defined. We determined whether myeloid cell-specific PKM2 regulates efferocytosis and atherosclerosis. Methods: We generated myeloid cell-specific PKM2 −/− mice on Ldlr (low-density lipoprotein receptor)-deficient background (PKM2 mye-KO Ldlr −/− ). Controls were littermate PKM2 WT Ldlr −/− mice. Susceptibility to atherosclerosis was evaluated in whole aortae and cross sections of the aortic sinus in male and female mice fed a high-fat Western diet for 14 weeks, starting at 8 weeks. Results: PKM2 was upregulated in macrophages of Ldlr −/− mice fed a high-fat Western diet compared with chow diet. Myeloid cell-specific deletion of PKM2 led to a significant reduction in lesions in the whole aorta and aortic sinus despite high cholesterol and triglyceride levels. Furthermore, we found decreased macrophage content in the lesions of myeloid cell-specific PKM2 −/− mice associated with decreased MCP-1 (monocyte chemoattractant protein 1) levels in plasma, reduced transmigration of macrophages in response to MCP-1, and impaired glycolytic rate. Macrophages isolated from myeloid-specific PKM2 −/− mice fed the Western diet exhibited reduced expression of proinflammatory genes, including MCP-1, IL (interleukin)-1β, and IL-12. Myeloid cell-specific PKM2 −/− mice exhibited reduced apoptosis concomitant with enhanced macrophage efferocytosis and upregulation of LRP (LDLR-related protein)-1 in macrophages in vitro and atherosclerotic lesions in vivo. Silencing LRP-1 in PKM2-deficient macrophages restored inflammatory gene expression and reduced efferocytosis. As a therapeutic intervention, inhibiting PKM2 nuclear translocation using a small molecule reduced glycolytic rate, enhanced efferocytosis, and reduced atherosclerosis in Ldlr −/− mice. Conclusions: Genetic deletion of PKM2 in myeloid cells or limiting its nuclear translocation reduces atherosclerosis by suppressing inflammation and enhancing efferocytosis.

Mechanisms of efferocytosis in determining inflammation resolution: Therapeutic potential and the association with cardiovascular disease

“…As has been well documented in multiple studies, efferocytosis targeting ACs markedly protects against atherosclerosis in animal models (Doddapattar et al, 2022;Mueller et al, 2022). In LDL receptordeficient (LdlrÀ/À) mice, MerTK-dependent efferocytosis could increase the production of SPMs and lead to smaller necrotic cores and thicker fibrous caps in plaques (Cai et al, 2017).…”

“…In addition, fatty acids derived from ACs promote IL‐10 production and macrophage reprogramming to an anti‐phenotype through the mitochondrial β‐oxidation/coenzyme NAD + /SIRT1 pathway but not through glycolysis (Zhang et al, 2019). Pyruvate kinase muscle 2 (PKM2), a glycolytic enzyme regulating energy metabolism, plays a critical role in the macrophage inflammatory response since the depletion of PKM2 can up‐regulate LRP‐1 and enhance subsequent efferocytosis, which results in the inhibition of MCP‐1, IL‐1β and IL‐12 (Doddapattar et al, 2022). This finding indicates that energy‐mediated efferocytosis may have an adequate ability to regulate the macrophage phenotype.…”

“…In macrophages of patients with atherosclerotic coronary artery disease, elevated PKM2, an enzyme regulating energy metabolism, has been reported. In Ldlr −/− mice fed a high‐fat Western diet for 14 weeks, myeloid cell‐specific deletion of PKM2 resulted in the upregulation of LRP‐1 and enhancement of macrophage efferocytosis, contributing to the regression of lesions in the whole aorta and aortic sinus (Doddapattar et al, 2022). As a consequence, the depletion of PKM2 inhibited the expression of MCP‐1, IL‐1β and IL‐12, suggesting that the depletion of PKM2 dampens the macrophage proinflammatory phenotype (Doddapattar et al, 2022).…”

“…In Ldlr −/− mice fed a high‐fat Western diet for 14 weeks, myeloid cell‐specific deletion of PKM2 resulted in the upregulation of LRP‐1 and enhancement of macrophage efferocytosis, contributing to the regression of lesions in the whole aorta and aortic sinus (Doddapattar et al, 2022). As a consequence, the depletion of PKM2 inhibited the expression of MCP‐1, IL‐1β and IL‐12, suggesting that the depletion of PKM2 dampens the macrophage proinflammatory phenotype (Doddapattar et al, 2022). As described above (Ampomah et al, 2022), AC‐derived methionine is metabolized to methionine‐derived SAM, which is used by DNMT3A to methylate Dusp4.…”

Immune Cell Activation in Obesity and Cardiovascular Disease

“…For example, clearance of dead cells results in the upregulation of oxidative phosphorylation, glucose uptake, and aerobic glycolysis, with a corresponding change in metabolic intermediates. In recent studies, deletion of the glycolytic enzyme pyruvate kinase muscle 2 in myeloid cells enhanced efferocytosis, resulting in decreased ASCVD [ 32 •]. In contrast, deletion of aldehyde dehydrogenase 2 in the hematopoietic compartment impaired efferocytosis, resulting in increased plaque formation [ 33 ].…”