Bombyx mori hemocyte extract has anti-inflammatory effects on human phorbol myristate acetate-differentiated THP-1 cells via TLR4-mediated suppression of the NF-κB signaling pathway

Hemolymph is the circulating fluid of insects and is a key component of their immune system. However, little is known concerning hemocyte identification, development, differentiation and related cellular immune responses. The present study aimed to determine whether a hemocyte extract prepared from Bombyx mori larvae had anti‑inflammatory effects; THP‑1 (a human monocytic leukemia cell line) cells that had been differentiated into macrophage‑like cells by treatment with phorbol myristate acetate (PMA) were used. THP‑1 cells were cultured with different concentrations of a B. mori hemocyte extract prior to exposure to lipopolysaccharide (LPS) to induce an inflammatory response. The effects of the B. mori hemocyte extract on anti‑inflammatory pathways were determined using reverse transcription‑quantitative polymerase chain reaction and western blotting to assess the expression of pro‑inflammatory molecules. The B. mori hemocyte extract inhibited the LPS‑induced mRNA expression of Toll‑like receptor 4 in addition to LPS‑induced interleukin (IL)‑1β, IL‑6, IL‑8 and tumor necrosis factor‑α. Treatment of PMA‑differentiated THP‑1 cells with B. mori hemocyte extract also inhibited inducible nitric oxide synthase and cyclooxygenase‑2 transcription and translation. Nuclear factor‑κB activation and phosphorylation also decreased. Further in‑depth functional studies are required to understand the mechanism underlying the anti‑inflammatory effects of silkworm hemocyte extract.