Abstract
BackgroundLiver fibrosis is an excessive wound-healing reaction that requires the participation of inflammatory cells and hepatic stellate cells (HSCs). The pathogenesis of liver fibrosis caused by viruses and alcohol has been well characterized, but the molecular mechanisms underlying liver fibrosis induced by the liver fluke Clonorchis sinensis are poorly understood. Lysophospholipase A (LysoPLA), which deacylates lysophospholipids, plays a critical role in mediating the virulence and pathogenesis of parasites and fungi; however, the roles of C. sinensis lysophospholipase A (CsLysoPLA) in C. sinensis-induced liver fibrosis remain unknown.MethodsA mouse macrophage cell line (RAW264.7) was cultured and treated with CsLysoPLA. IL-25 and members of its associated signaling pathway were detected by performing quantitative real-time PCR, Western blotting and immunofluorescent staining. A human hepatic stellate cell line (LX-2) was cultured and exposed to IL-25. LX-2 cell activation markers were examined via quantitative real-time PCR, Western blotting and immunofluorescent staining. Migration was analyzed in transwell plates.ResultsTreating RAW264.7 cells with CsLysoPLA significantly induced IL-25 expression. Elevated PKA, B-Raf, and ERK1/2 mRNA levels and phosphorylated B-Raf and ERK1/2 were detected in CsLysoPLA-stimulated RAW264.7 cells. The PKA inhibitor H-89 weakened B-Raf and ERK1/2 phosphorylation whereas the AKT activator SC79 attenuated ERK1/2 phosphorylation in RAW264.7 cells. Both H-89 and SC79 inhibited CsLysoPLA-induced IL-25 upregulation. In addition, stimulation of LX-2 cells with IL-25 upregulated the expression of mesenchymal cell markers, including α-smooth muscle actin (α-SMA) and collagen type I (Collagen-I), and promoted cell migration.ConclusionsCsLysoPLA activates HSCs by upregulating IL-25 in macrophages through the PKA-dependent B-Raf/ERK1/2 pathway and potentially promotes hepatic fibrosis during C. sinensis infection.
Highlights
Liver fibrosis is an excessive wound-healing reaction that requires the participation of inflammatory cells and hepatic stellate cells (HSCs)
To confirm the specificity of this CsLysoPLA-induced IL-25 transcription, CsFBPase, a member of the C. sinensis excretory/ secretory proteins (CsESPs), and Mouse serum albumin (MSA) were applied as controls
Stronger green fluorescence emitted by an anti-IL-25 monoclonal antibody was observed in RAW264.7 cells incubated with CsLysoPLA compared with the phosphate-buffered saline (PBS) group (Fig. 1e, f )
Summary
Liver fibrosis is an excessive wound-healing reaction that requires the participation of inflammatory cells and hepatic stellate cells (HSCs). The pathogenesis of liver fibrosis caused by viruses and alcohol has been well characterized, but the molecular mechanisms underlying liver fibrosis induced by the liver fluke Clonorchis sinensis are poorly understood. Mechanical damage caused by the adult C. sinensis worm and excretory/secretory proteins (ESPs) as well as the interplay between worms and the host immune system are responsible for pathological changes [6, 7]. The exact molecular mechanisms involved in C. sinensis-induced liver fibrosis remain unclear. The intranasal administration or forced expression of IL-25 induces pulmonary inflammation similar to asthma [12, 13]. IL-25 administration in mouse xenograft models of human melanoma, breast, lung, colon, and pancreatic cancers induces antitumor activity that requires the presence of B cells and eosinophil infiltration [15]. IL-25, which is essential for host defense, is induced at high levels following helminth infection [16, 17]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
