Toll-like receptor-4, but not toll-like receptor-2 mediates secretion of tumour necrosis factor α and interleukin-8 in lipopolysaccharide-stimulated mouse mammary epithelial cells

Mammary epithelial cells (MECs) from Kunming mice were isolated and stimulated in vitro with 10 mu g/mL of Escherichia coli lipopolysaccharide (LPS). The release of tumour necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8) into culture supernatants was measured by ELISA. Furthermore, blocking experiments with Toll-like receptor 2 (TLR2) and TLR4 antibodies were performed to verify whether cytokine secretion depended on LPS-induced activation of TLR2 or TLR4. The results revealed that LPS-stimulated mouse MECs significantly secreted TNF-alpha and IL-8. Blocking of the TLR4 pathway inhibited the secretion of TNF-alpha and IL-8, while inhibition of LPS-induced TNF-alpha and IL-8 production was not observed when TLR2 was blocked. Thus, TLR4 can mediate the LPS-induced expression of cytokines such as TNF-alpha and IL-8 in mouse MECs.