Artesunate down-regulates immunosuppression from colorectal cancer Colon26 and RKO cells in vitro by decreasing transforming growth factor ß1 and interleukin-10.

Immunosuppression is the main source of ineffective treatment on tumor, and the study aimed to investigate the effect of artesunate on tumor immunosuppression. Supernatants of re-cultivated murine colorectal cancer cell Colon26 and human colorectal cancer cell RKO after pre-treatment with or without artesunate were enrolled, and their effects on five immune parameters were assessed, including killing activity of natural killer (NK) and lymphocyte proliferation, as measured by MTT, and expressions of interleukin 2 receptor (IL-2R)α, CD3ε(+)ζ(+) and CD3ε(-)ζ(+) on lymphocytes, as analyzed by flow cytometry. Six immunosuppressive factors were measured by ELISA, including transforming growth factor (TGF) ß1, vascular endothelial growth factor (VEGF), IL-4, IL-6, IL-10, and prostaglandin E2 (PGE2). Then, multiple linear regression analysis was applied to reveal the correlation between immunosuppression and immunosuppressive factors, and was used to confirm the findings. It was shown that Colon26 and RKO cells secreted immunosuppressive factors and inhibited these five immune parameters steadily. After pretreatment with artesunate, immunosuppression from the two cells was down-regulated significantly (all P<0.05), and the concentrations of TGF-ß1 and IL-10 decreased greatly (all P<0.001). There were positive correlations between the down-regulation of immunosuppression and the decrease in TGF-ß1 or IL-10. Their combined potency attributed to decreased TGF-ß1 and IL-10 with respect to the down-regulating effect of artesunate on immunosuppression of NK killing, lymphocyte proliferation and expressions of IL-2Rα and CD3ε(+)ζ(+), was about 60%-90%. The present analysis provides clues that artesunate reverses the immunosuppression from Colon26 and RKO colorectal cancer cells by decreasing TGF-ß1 and IL-10. This is probably one of the anti-tumor mechanisms of artesunate.

α-MSH inhibits TNF-α-induced maturation of human dendritic cells in vitro through the up-regulation of ANXA1.

α-Melanocyte-stimulating hormone (α-MSH), an anti-inflammatory and immunomodulatory neuropeptide, has been shown to be effective in the experimental treatment of autoimmune diseases and allograft rejection. However, its regulatory mechanism is still unclear. Mature dendritic cells (DCs) are pivotal initiators of immune response and inflammation. We hypothesized that the regulatory role of α-MSH in DC maturation would contribute to the effects of α-MSH in immune-response-mediated disease models. It was found that α-MSH inhibited tumor necrosis factor-alpha (TNF-α)-induced maturation of human peripheral-monocyte-derived DCs (MoDCs), both phenotypically and functionally. This occurred through the down-regulation of the expression of co-stimulatory molecules CD83 and CD86, the production of IL-12, the promotion of IL-10 secretion, and the MoDC phagocytic activity, suggesting that the inhibition of DC maturation by α-MSH could contribute to the anti-inflammatory effect of this neuropeptide. Furthermore, increased expression of annexin A1 (ANXA1) was found to be responsible for the α-MSH inhibiting effect on TNF-α-induced MoDC maturation, which could be abolished by the treatment of MoDCs with specific, small interfering RNAs targeting ANXA1 (ANXA1-siRNA), suggesting that α-MSH-induced ANXA1 mediates the inhibition. Therefore, α-MSH inhibits TNF-α-induced maturation of human DCs through α-MSH-up-regulated ANXA1, suggesting that inhibition of the maturation of DCs by α-MSH could mediate the anti-inflammatory effect of the neuropeptide. Furthermore, ANXA1 could be identified as a new therapeutic drug target based on the role of DCs in immune-mediated inflammatory diseases.