Abstract
Multiple exopolysaccharides (EPSs) have been isolated from various organisms in extreme environments and have yielded a variety of activities. The present study evaluated the immunomodulatory capabilities of an EPS (termed PH‑EPS) derived from the fungus Paecilomyces lilacinus PH0016, which was isolated from a tropical and hyperhaline environment in southern China. The macrophage RAW 264.7 cell line was used to investigate the mechanism of PH‑EPS‑induced macrophage activation. The results indicated that RAW 264.7 macrophages were activated by PH‑EPS, in an effect slightly inferior to lipopolysaccharide (LPS), as evidenced by secretion of interleukin (IL)‑1β, tumor necrosis factor (TNF)‑α and nitric oxide (NO), and by significantly increased phagocytosis in the cells treated with PH‑EPS. Nuclear factor (NF)‑κB p65 was significantly translocated into the nucleus in the PH‑EPS‑treated cells. In addition, expression of inducible NO synthase (iNOS) and IκB‑α degradation were enhanced in PH‑EPS‑treated cells. The phosphorylation levels of p38, JNK and ERK were also significantly increased in the PH‑EPS‑treated cells. Furthermore, IL‑1β and TNF‑α production was markedly decreased in PH‑EPS‑treated cells when the mitogen‑activated protein kinase (MAPK) pathways were blocked by the inhibitor Dectin‑1 and by antibodies against Toll‑like receptor 4 (TLR4). The present results indicated that PH‑EPS from Paecilomyces lilacinus possessed the capability of activating RAW 264.7 cells via the TLR4/NF‑κB/MAPKs signaling pathway.