High Glucose Concentration Increases the M2 Profile and Reduces the Microbicidal Activity of Macrophages Challenged With Encephalitozoon Cuniculi

Hyperglycemia, an alteration seen in diabetes, causes changes in the immune response and increases the susceptibility of diabetic individuals to infections. In macrophages cultured in high glucose (HG), changes in metabolism, phenotype, and phagocytic activity have been identified, compromising their function as a primary line of defense. To evaluate the effects of HG on the phenotype and activity of macrophages obtained from adherent peritoneal cells (APerC) challenged with the microsporidium E. cuniculi. APerC were cultured in RPMI medium supplemented with 10% fetal bovine serum (R10) or R10 with 30 mM glucose (R10HG30) and challenged with E. cuniculi spores at a ratio of 4 spores per macrophage for 1, 3, 6, and 24 hours. After these periods, cell viability, median fluorescence intensity (MFI) of CD40 and CD206, fungal burden, and production of Th1, Th2, and Th17 cytokines were measured. Macrophages cultured in R10 and challenged with E. cuniculi for 1 and 3 hours showed an increase in the M2 profile and a decline in the M1/M2 ratio (1:1), with increased production of pro-inflammatory cytokines TNF-α and IL-6 and greater microbicidal activity (lower fungal burden) associated with increased NO production. In the same group, after 24 hours, there was an increase in M1 macrophages, a decrease in the M2 profile with an increase in the M1/M2 ratio (5:1), and increased production of pro-inflammatory cytokines TNF-α, IL-6, IL-17, and IFN-γ. However, microbicidal activity and NO production were similar to those in the R10HG30 group. When challenged with the pathogen for 1 and 3 hours, macrophages cultured in high glucose showed a macrophage profile similar to that observed with R10, with predominance of M2, associated with reduced microbicidal activity (higher fungal burden compared with R10) and lower NO production. After 24 hours, despite an increase in M1 macrophages, M2 macrophages remained elevated and there was a decline in the M1/M2 ratio (1:1). In line with this finding, a mixed cytokine profile was identified, including TNF-α, IL-6, IL-17, IFN-γ, and IL-10. High glucose concentration skewed macrophages toward an M2 profile and reduced NO production and the microbicidal activity of M1 macrophages against E. cuniculi.