Norcantharidin alleviates cyclophosphamide-induced immunosuppression via circBCL2L1/miR-30c-3-3p/TRAF6 axis

Cyclophosphamide is a widely used antitumor drug, with induced adverse effects, such as intestinal mucosal injury and immunosuppression. Norcantharidin possesses anticancer activity through enhancement of antitu-mor immunity. We investigated the role of norcantharidin in cyclophosphamide-induced immunosuppression. Mice were treated with cyclophosphamide, and exposed to norcantharidin. Enzyme-linked-immunosorbent serologic assay was performed to assess the levels of immunoglobulin and cytokines in serum, and the splenic T lymphocytes were analyzed by immunohistochemistry. Incubation with norcantharidin increased the serum levels of immunoglobulin G (IgG), interleukin (IL)-12, interferon-gamma (IFN-gamma), and IL-6, and enhanced the percentage of CD4(+) and CD8(+) T lymphocytes in cyclophosphamide-induced mice. Expression of circBCL2L1 was down-regulated in the spleen of cyclophosphamide-induced mice, while up-regulated by norcantharidin incuba-tion. Norcantharidin attenuated cyclophosphamide-induced up-regulation of miR-30c-3-3p and down-regulation of tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) in mice. Over-expression of circBCL2L1 increased serum levels of immunoglobulin and cytokines, and enhanced the percentage of splenic CD4(+) and CD8(+) T lymphocytes in cyclophosphamide-induced mice. Moreover, over-expression of circBCL2L1 increased TRAF6 in cyclophosphamide-induced mice through down-regulation of miR-30c-3-3p. Knockdown of TRAF6 attenuated norcantharidin-induced increase of serum levels of IgG, IL-12, IFN-gamma, and IL-6, and up-regulation of CD4(+) and CD8(+) T lymphocytes in cyclophosphamide-induced mice. Norcantharidin exhibited protective effect against cyclophosphamide-induced immunosuppression in mice through regulation of circBCL2L1/miR-30c-3-3p/TRAF6 axis.