Background
Takayasu arteritis (TAK) is characterized by pro-inflammatory M1 macrophage infiltration and increased interferon (IFN)-γ expression in vascular lesions. IFN-γ is a key cytokine involved in M1 polarization. Macrophage polarization is accompanied by metabolic changes. However, the metabolic regulation mechanism of IFN-γ in M1 macrophage polarization in TAK remains unclear.
Conclusion
PFKFB3-mediated glycolysis promotes IFN-γ-induced M1 polarization through the JAK2/STAT1 signaling pathway, indicating that PFKFB3 plays an important role in M1 polarization mediated by IFN-γ; thus, PFKFB3 is a potential intervention target in TAK.
Methods
Immunohistochemistry and immunofluorescence were employed to observe the expression of IFN-γ, PFKFB3 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3, the rate-limiting enzyme in glycolysis), and macrophage surface markers in the vascular tissue. Monocyte-derived macrophages from patients with TAK were cultured to examine the role of PFKFB3 in IFN-γ-induced M1 macrophage polarization. Seahorse analysis was used to detect the alterations in glucose metabolism during this process. Quantitative reverse transcription PCR, flow cytometry, and western blot were used to confirm the phenotypes of macrophages and related signaling pathways.
Results
In the vascular adventitia of patients with TAK, an increase in PFKFB3 accompanied by IFN-γ expression was observed in M1 macrophages. In vitro, IFN-γ successfully induced macrophage differentiation into the M1 phenotype, which was manifested as an increase in CD80 and HLA-DR markers and the pro-inflammatory cytokines IL-6 and TNF-α. During this process, PFKFB3 expression and glycolysis levels were significantly increased. However, glycolysis and M1 polarization induced by IFN-γ were suppressed by a PFKFB3 inhibitor. In addition, JAK2/STAT1 phosphorylation was also enhanced in macrophages stimulated by IFN-γ. The effects of IFN-γ on macrophages, including the expression of PFKFB3, glycolysis, and M1 polarization, were also inhibited by the JAK inhibitor tofacitinib or STAT1 inhibitor fludarabine.