Macrophage Stimulating Protein Enhances Hepatic Inflammation in a NASH Model

PLoS One. 2016 Sep 29;11(9):e0163843. doi: 10.1371/journal.pone.0163843. eCollection 2016.

Abstract

Non-alcoholic steatohepatitis (NASH) is a common liver disease characterized by hepatic lipid accumulation (steatosis) and inflammation. Currently, therapeutic options are poor and the long-term burden to society is constantly increasing. Previously, macrophage stimulating protein (MSP)-a serum protein mainly secreted by liver-was shown to inhibit oxidized low-density lipoprotein (OxLDL)/lipopolysaccharides (LPS)-induced inflammation in mouse macrophages. Additionally, MSP could reduce palmitic acid (PA)-induced lipid accumulation and lipogenesis in the HepG2 cell line. Altogether, these data suggest MSP as a suppressor for metabolic inflammation. However, so far the potential of MSP to be used as a treatment for NASH was not investigated. We hypothesized that MSP reduces lipid accumulation and hepatic inflammation. To investigate the effects of MSP in the early stage of NASH, low-density lipoprotein receptor (Ldlr-/-) mice were fed either a regular chow or a high fat, high cholesterol (HFC) diet for 7 days. Recombinant MSP or saline (control) was administrated to the mice by utilizing subcutaneously-implanted osmotic mini-pumps for the last 4 days. As expected, mice fed an HFC diet showed increased plasma and hepatic lipid accumulation, as well as enhanced hepatic inflammation, compared with chow-fed controls. Upon MSP administration, the rise in cholesterol and triglyceride levels after an HFC diet remained unaltered. Surprisingly, while hepatic macrophage and neutrophil infiltration was similar between the groups, MSP-treated mice showed increased gene expression of pro-inflammatory and pro-apoptotic mediators in the liver, compared with saline-treated controls. Contrary to our expectations, MSP did not ameliorate NASH. Observed changes in inflammatory gene expression suggest that further research is needed to clarify the long-term effects of MSP.

Grants and funding

JL is supported by the Chinese Scholarship Council with file number 201307040028. DC is a recipient of a Marie Curie fellowship (Grant PIIF-GA-2012-332230). Research in the DN laboratory is funded by The Netherlands Organization for Scientific Research (NWO) (VIDI grant number 864.10.007). Research in the laboratory of RSS is supported by the Maag Lever Darm Stichting (MLDS) (WO 08-16 and WO 11-35), the Netherlands Organisation for Scientific Research (NWO) (VIDI grant number 016.126.327), and the Cardiovascular Research Netherlands (CVON) IN-CONTROL grant (CVON 2012-03). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.