Clara Cell 10 kDa Protein Alleviates Murine Hepatitis Virus Strain 3-Induced Fulminant Hepatitis by Inhibiting Fibrinogen-Like Protein 2 Expression

Abstract

Background: Fulminant hepatitis (FH) is a serious threat to human life, accompanied by massive and rapid necroinflammation. Kupffer cells, the major immune cell population involved in innate immune responses, are considered to be central for FH. Fibrinogen-like protein 2 (Fgl2) is a pro-coagulant protein that is substantially induced in macrophages upon viral infection, and Fgl2 depletion represses murine hepatitis virus strain 3 (MHV-3) infection. Clara cell 10 kDa (CC10) protein is a secretory protein with anti-inflammatory properties in allergic rhinitis and asthma. However, its mechanisms of action and pathogenic roles in other disease are still unclear. In this study, we aimed to determine the role of CC10 in FH and the regulation of Fgl2 by CC10.Methods: A mouse FH model was established by peritoneal injection of MHV-3. The mice received CC10 protein through tail vein injection before viral infection. Survival rate, liver function, liver histology, fibrin deposition, and necrosis were examined. The regulatory effect of CC10 on Fgl2 expression was investigated using THP-1 cells and mouse peritoneal macrophages in vitro.Results: In the mouse FH model induced by MHV-3, the survival rate increased from 0 to 12.5% in the CC10 group compared to that in the saline-only control group. Meanwhile, the levels of ALT and AST in serum were significantly decreased and liver damage was reduced. Furthermore, hepatic Fgl2, TNF-α, and IL-1β expression was obviously downregulated together with fibrin deposition, and hepatocyte apoptosis was reduced after administration of CC10 protein. In vitro, CC10 was found to significantly inhibit the expression of Fgl2 in IFN-γ-treated THP-1 cells and MHV-3-infected mouse peritoneal macrophages by western blot and real-time PCR. However, there was no direct interaction between CC10 and Fgl2 as shown by co-immunoprecipitation. Microarray investigations suggested that HMG-box transcription factor 1 (HBP1) was significantly low in CC10-treated and IFN-γ-primed THP-1 cells. HBP1-siRNA treatment abrogated the inhibitory effect of CC10 on Fgl2 expression in Human Umbilical Vein Endothelial cells (HUVECs).Conclusion:CC10 protects against MHV-3-induced FH via suppression of Fgl2 expression in macrophages. Such effects may be mediated by the transcription factor HBP1.

Fibrinogen-like protein 2 aggravates nonalcoholic steatohepatitis via interaction with TLR4, eliciting inflammation in macrophages and inducing hepatic lipid metabolism disorder

“…mFgl2 mediates macrophage activation 18 , cell adhesion, trans-endothelial migration 19 and tumor growth 20 while sFgl2 inhibits the proliferation of effector T cells 21 and maintains the immunosuppressive activity of Tregs 22 . Previous work from our group indicated that interference with fgl2 expression significantly increased the survival rate and alleviated liver injury in a murine model of fulminant hepatic failure 23 , 24 . Furthermore, mfgl2 is directly related to the progression of hepatic inflammation in patients with severe hepatitis B 25 .…”

Pyrroloquinoline quinone protects against murine hepatitis virus strain 3-induced fulminant hepatitis by inhibiting the Keap1/Nrf2 signaling

“…Group 1 was transfected with NC small interfering RNA (siRNA). Group 2 was transfected with NC-siRNA and exposed to 1,000 PFUs of MHV-3 for 4 h (Yu et al 2018 ). Group 3 was exposed to PQQ (0.1 μM) for 6 h, transfected with NC-siRNA, and exposed to 1,000 PFUs of MHV-3 for 4 h. Group 4 was exposed to PQQ (0.1 μM) for 6 h, transfected with Nrf2-siRNA, and exposed to 1,000 PFUs of MHV-3 for 4 h. All transfection experiments were performed using Lipofectamine 2000 (#11668027; Thermo Fisher Scientific) according to the manufacturer’s instructions.…”