Gansui Banxia decoction modulates immune-inflammatory homeostasis to ameliorate malignant ascites in rats

“Gansui Banxia decoction” (GBD) is a classical traditional Chinese medicine formula for treating abnormal accumulation of fluid, such as malignant ascites (MA). Although GBD has shown definite water-expelling effects, its exact underlying mechanism has not been elucidated. This study aimed to investigate the drug effects of GBD on MA rats and its underlying mechanisms. The main chemical composition was determined by ultra-high performance liquid chromatography. The drug effects of GBD was evaluated in the established cancer cell-induced MA rat model. The symptoms were analyzed, and biological samples were collected for detecting immune and inflammation-related indicators by enzyme-linked immunosorbent assays, western blot, and flow cytometry. GBD increased urine discharge, decreased ascites production, and alleviated cachexia. After GBD treatment, the expression of TLR4, MyD88, and NF-кB and the release of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were reduced. In addition, GBD increased G1 phase arrest and inhibit excessive proliferation of cells in bone marrow while alleviating G1 phase arrest and increasing proliferation of cells in the thymus. Correspondingly, the development and maturation of T cells also changed. GBD increased the proportion of mature T-cells (CD4+CD8− and CD4−CD8+ single-positive (SP) T-cells), and decrease the proportion of immature cells (CD4+CD8+ double-positive (DP) T-cells and CD4−CD8− double-negative (DN) T-cells) in the blood or tumor microenvironment (TME, the ascites microenvironment). Finally, we further analysis of immune cell subsets, GBD decreased the proportion of immunosuppressive T-cells in the blood (CD4+CD25+Foxp3+ T-cells) and TME (CD8+CD25+Foxp3+ T-cells), and increased the proportion of anti-tumor immune cells (CD8+CD28+ T-cells and NK cells) in the TME. These findings indicated that the drug effects of GBD were attributed to regulating the immune-inflammatory homeostasis, thereby mitigating the destruction of cancer cells and reducing the generation of ascites, which provided theoretical support for the clinical rational application and extended the scientific connotation of “water-expelling” of GBD.