Flavonoids from Scutellaria barbata inhibit activation of tumor-associated macrophages by blocking the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor-κB signaling pathway.

OBJECTIVE

To determine the efficacy of Scutellaria barbata flavonoids and polysaccharides on Ishikawa endometrial carcinoma cells co-cultured with U937 macrophages.

METHODS

The presence of CD163 and CD206 was determined by flow cytometry. Thiazolyl Blue Tetrazolium Bromide assays were used to assess the proliferation effect of tumor-associated macrophages (TAMs) on Ishikawa cells. The secretion of interleukin (IL)-10 in the co-culture conditioned media was examined using an enzyme-linked immunosorbent assay. The protein expression levels of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor (NF)-κB p65 were detected by Western blot. The mRNA expression levels of TLR4 and MyD88 were analyzed by real-time polymerase chain reaction (PCR). The expression levels of IL-12, IL-1β and tumor necrosis factor-α (TNF-α) were evaluated with real-time PCR.

RESULTS

Compared with the U937 control group, the expression levels of CD163 and CD206 in the TAM group were higher (P < 0.05). TAMs co-cultured with Ishikawa cells for 24 or 48 h showed higher proliferation rates (P < 0.05). The expression levels of IL-12 decreased than compared with those in the U937 untreated group (P < 0.05) and those of the Scutellaria barbata flavonoids group (P < 0.05). The expression levels of CD206, CD163, IL-10, IL-1β and TNF-α, NF-κB p65 and TLR4/MyD88 in the TAMs control group were greater than those in the U937 untreated group (P < 0.05) and those of the Scutellaria barbata flavonoids group (P < 0.05).

CONCLUSION

Scutellaria barbata flavonoids may inhibit TAM activation by blocking the TLR4/MyD88/NF-κB signaling pathway.