Reprogramming M1-to-M2 Phenotype to Alleviate Inflammation: Using Liposomal Curcumin as a Tool to Redefine Macrophage Functionality.

Abstract

The versatile nature of macrophages and their ability to switch between various activation states plays a pivotal role in both promoting and inhibiting inflammatory processes. In pathological inflammatory conditions, classically activated M1 macrophages are often associated with initiating and maintaining inflammation, while alternatively activated M2 macrophages are linked to the resolution of chronic inflammation. Achieving a favorable equilibrium between M1 and M2 macrophages is crucial for mitigating inflammatory environments in pathological conditions. Polyphenols are known to have strong inherent antioxidative capabilities, and curcumin has been found to reduce macrophage inflammatory reactions. However, its therapeutic efficacy is compromised due to its poor bioavailability. The present study aims to harness the properties of curcumin by loading it in nanoliposomes and enhancing the M1-to-M2 macrophage polarization. A stable liposome formulation was achieved at 122.1 ± 0.08 nm, and a sustained kinetic release of curcumin was observed within 24 h. The nanoliposomes were further characterized using TEM, FTIR, and XRD, and the morphological changes in macrophage cells, RAW264.7, were observed in SEM, indicating a distinct M2-type phenotype after the treatment with liposomal curcumin. ROS may partially control macrophage polarization and be observed to decrease after treatment with liposomal curcumin. The nanoliposomes were able to successfully internalize in the macrophage cells, and an enhanced expression of ARG-1 and CD206 with a decrease in iNOS, CD80, and CD86 levels suggested the polarization of LPS-activated macrophages toward the M2 phenotype. Also, liposomal curcumin treatment dose-dependently inhibited TNF-α, IL-2, IFN-γ, and IL-17A at secretory levels and simultaneously increased the levels of cytokines like IL-4, IL-6, and IL-10.