Activating Murine Macrophages In Vitro

Inflammatory macrophage to hepatocyte signals can be prevented by extracellular vesicle reprogramming

Macrophage-derived extracellular vesicles (EVs) play key roles in intercellular communication. Within the liver, they have been linked to several inflammatory diseases including nonalcoholic fatty liver disease (NAFLD). In this study, we found that inflammatory macrophages cause injury to hepatocytes, in part by a cell-cell crosstalk phenomenon involving the secretion of EVs containing pro-inflammatory cargo. Incorporation of these inflammatory signals into EV requires the cleavage of the trafficking adaptor protein RILP, which, as previously shown, results from inflammasome-mediated caspase-1 activation. RILP cleavage can be blocked by overexpressing a dominant negative, non-cleavable form of RILP (ncRILP). EV preparations from ncRILP-expressing cells are, by themselves, sufficient to suppress inflammatory effects in hepatocytes. These results suggest that both direct RILP manipulation and/or supplying ncRILP-modified EVs could be used as a novel therapy for the treatment of inflammatory liver diseases.

The immunoenhancement effects of starfish Asterias rollestoni polysaccharides in macrophages and cyclophosphamide-induced immunosuppression mouse models

The water-soluble polysaccharide, SF-2, obtained from starfish (Asterias rollestoni), belongs to the group of polysaccharides known as mannoglucan sulfate. It is composed of mannose as well as glucose and contains 13.85% SO₄^2-. We aimed to detect the immunoenhancement effects of SF-2 in macrophages and cyclophosphamide (CYP)-induced immunosuppression mouse models. RAW 264.7 macrophage cells were treated with SF-2 for different periods of time (0 h, 0.5 h, 1 h, 3 h, 6 h, and 9 h) and the results showed that SF-2 promoted the production of nitric oxide and up-regulated the levels of pro-inflammatory cytokines and related proteins, such as TNF-α, IL-1β, IL-6, COX-2, MMP-9, and iNOS in a time-dependent manner. In addition, SF-2 activated NLRP3 inflammasome and the MAPK/NF-κB signaling pathway, thus promoting its immunoenhancement effects. Moreover, we co-cultured the primary peritoneal macrophages with SF-2 for 6 h and found that SF-2 enhanced the expression of NLRP3 inflammasome and the release of cytokines. Furthermore, SF-2 significantly increased the body weight, spleen index, thymus index, and inflammatory cell counts in CYP-induced immunosuppression mouse models. These results indicate that SF-2 is a potential immunoenhancement mediator that acts by activating the NLRP3 inflammasome and MAPK/NF-κB pathway.