The administration of low-dose Curcuma longa extract induces M2 polarization in peritoneal macrophage culture

Abstract

Curcuma longa (turmeric) has been widely used to accelerate wound healing, but the underlying mechanism remains unclear. Wound healing consists of four phases which are correlated and overlapping, i.e., coagulation, inflammation, proliferation and remodeling. Macrophages play an important role in most phases. Macrophage polarization to M2 initiates the proliferation phase, which is characterized by the production of several crucial growth factors. Since turmeric has been known to be an herb that accelerates wound closure, we investigated whether Curcuma longa extract administration in macrophage culture induces M2 macrophage switching. An in vitro study was performed using peritoneal macrophages from Swiss Webster strain mice. Peritoneal cells were collected and cultured in a 24-well plate. After 2 hours of incubation, macrophages (adherent cells) were treated with 0.5 ppm, 1.0 ppm and 5.0 ppm of ethanolic extract of Curcuma longa and incubated for 2 days. Quantitative real time PCR was performed to quantify M2 and M1 marker gene expression. The results revealed the upregulation of M2 marker (Arginase-1) expression upon administration of 0.5 ppm of Curcuma longa extract, but not of higher doses (1.0 and 5.0 ppm). In parallel, the ratio of Arg-1/Inos was high upon administration of 0. 5ppm of extract. In conclusion, Curcuma longa extract induces in vitro M2 polarization in low-dose administration.