Paeoniflorin attenuates schistosomiasis japonica-associated liver fibrosis through inhibiting alternative activation of macrophages.

Interleukin (IL)-13 and alternatively activated macrophages (AAMs) play an important role in liver granuloma and fibrosis of schistosomiasis. Paeoniflorin (PAE, C23H28O11) has been reported to have an anti-hepatic fibrosis effect in schistosomiasis; however, the mechanism has not been fully elucidated. In this study, we measured serum hyaluronic acid (HA) concentrations, liver granuloma diameter and volume density, fibrosis degree and expressions of IL-13, arginase-1 (ARG-1), nitric oxide synthase-2 (NOS-2), and phosphorylated signal transducer and activator of transcription 6 (p-STAT6) in mice liver of schistosomiasis. Then we detected expressions of specific biomarkers of AAMs and activity of Arg-1 in Kupffer cells (KCs) from infected and PAE-treated mice, or in KCs from uninfected mice, but exposed to rIL-13 in vitro. Finally, we observed expression of IL-13 signalling molecules in KCs and secretion of IL-13 from lymphocytes of infected and PAE-treated mice. Our results showed that during schistosomiasis, IL-13 expression and secretion increased with liver macrophages activated alternatively. PAE not only directly inhibited alternative activation of macrophages via reducing the phosphorylations of janus-activated kinase 2 (JAK2) and/or STAT6, leading to reduction of AAMs-related markers and Arg-1 activity, but also indirectly suppressed alternative activation of macrophages through decreasing secretion of IL-13. PAE might be a promising prophylactic agent for hepatic granuloma and fibrosis of schistosomiasis japonica.