AbstractBackgroundQihuzha granule (QHZG) is a Chinese patent medicine, composed of 11 kinds of edible medicinal plants, which is used to treat dyspepsia and anorexia in children caused by spleen and stomach deficiency syndrome. However, its role and mechanism in immunosuppression induced by cyclophosphamide remained unclear. The purpose of this study is to investigate the effect of QHZG on immunosuppression induced by cyclophosphamide in mice and its possible mechanism.MethodsThe immunosuppression injury model was induced by intraperitoneal injection of cyclophosphamide (100 mg/kg); the mRNA level of cytokines (IL-2/4/6, IFN-γ) and critical targets of signaling pathways related to immune regulation (JNK, ERK, P38, JAK2, SRC and STAT3) were tested by QPCR; related protein levels were detected by western blotting; hematoxylin-eosin (HE) staining was employed to observe the histological alterations; macrophages and neutrophils in the mouse spleen were examined by immunofluorescence analysis. ResultsQHZG significantly increased the spleen index and thymus index of mice with immunodeficiency induced by cyclophosphamide and up-regulated the mRNA expression of cytokines (IL-2/4/6, IFN-γ) and critical targets of signaling pathways related to immune regulation (JNK, ERK, P38, JAK2, SRC and STAT3), which were decreased by cyclophosphamide treatment. The results of immunofluorescence staining and histological analysis showed that QHZG could also protect mice from immunosuppressive injury caused by cyclophosphamide via keeping structural integrity of spleen, and partially restoring the production levels of macrophages and monocytes in the spleen. Further studies indicated that QHZG could significantly counter the decline of phosphorylated protein levels of JAK2/SRC-STAT3 axes (P-JAK2, P-SRC and P-STAT3), and MAPK pathways (P-JNK, P-ERK and P-P38) induced by cyclophosphamide, suggesting that the protective effects of QHZG on immunosuppressive injury triggered by cyclophosphamide were involved in JAK2/SRC-STAT3 axes, and MAPK pathways. Meanwhile, we also found that QHZG could partially restore the vital phosphorylated proteins of PI3K/Akt/mTOR signaling pathway (P-Akt, P-mTOR), which were reduced by cyclophosphamide. The data implied that PI3K signaling pathway was also responsible for the protection of QHZG against the immunosuppression induced by cyclophosphamide in mice. ConclusionsOur study demonstrated that QHZG protected mice from cyclophosphamide-triggered immunosuppressive injury via IL-6 and its downstream signaling pathways including PI3K/Akt/mTOR signal pathway and JAK2-SRC/MAPK/STAT3 axes. These results suggested that QHZG might serve as a new drug for the treatment of the immunosuppression caused by cyclophosphamide therapy.