Investigating the Role of Quercetin, an Active Ingredient in Bazhen Decoction, in Targeting CXCL8 to Inhibit Macrophage M2 Polarization and Reshape the Immunological Microenvironment of Colorectal Cancer.

Abstract

Bazhen Decoction (Eight Treasures Decoction) has demonstrated efficacy in the treatment of colorectal cancer (CRC), yet the active ingredients in it and the mechanisms underlying their anti-cancer properties are not well understood. Through network pharmacology, the effective components of Bazhen Decoction against CRC and their corresponding key genes were delineated. Molecular docking was executed to identify the active component targeting the key gene CXCL8, which led to the discovery of Quercetin. The cellular thermal shift assay method was then used to verify the binding interaction. CRC cells were treated with incremental concentrations of Quercetin, cell viability was evaluated by the Cell Counting Kit-8 assay to calculate the IC₅₀, and apoptosis rates were determined by flow cytometry. Expression of the apoptosis-related proteins Bcl-2 and Cleaved caspase-3 was measured using western blot. The impact of Quercetin on macrophage polarization was studied by co-culturing the treated CRC cells with macrophages, assessing M1 and M2 macrophage distribution via flow cytometry, and quantifying cytokine levels (IL-6, IL-10, IL-12, and CXCL8) with enzyme-linked immunosorbent assay (ELISA). The active ingredient Quercetin from Bazhen Decoction exhibited a targeted binding affinity with the key gene CXCL8, which enabled it to inhibit the proliferation of CRC cells and induce cell apoptosis. The overexpression of CXCL8 was associated with the promotion of CRC malignancy, yet the presence of Quercetin could lessen the impact of CXCL8 overexpression on CRC cells. Moreover, the treatment with Quercetin leads to a diminished abundance of M2 macrophages and an increase in the levels of cytokines IL-6 and IL-12, while reducing the levels of IL-10 and CXCL8, which indicates that Quercetin has an inhibitory effect on macrophage M2 polarization. Quercetin, the active component in Bazhen Decoction that is known for anti-CRC effects, targets and inhibits CXCL8 to impede the malignant behaviors and the M2 polarization of macrophages. Thus, Quercetin may be utilized as an immunomodulatory agent in CRC treatment.