Activation of Slit2-Robo1 signaling promotes liver fibrosis.

BACKGROUND & AIMS: The secretory protein Slit2 and its receptor Robo1 are believed to regulate cell growth and migration. Here, we aimed to determine whether Slit2-Robo1 signaling mediates the pathogenesis of liver fibrosis. METHODS: Serum levels of Slit2 in patients with liver fibrosis were determined by ELISA. Liver fibrosis was induced in wild-type (WT), Slit2 transgenic (Slit2-Tg) and Robo1(+/-)Robo2(+/-) double heterozygotes (Robo1/2(+/-)) mice by carbon tetrachloride (CCl4). The functional contributions of Slit2-Robo1 signaling in liver fibrosis and activation of hepatic stellate cells (HSCs) were investigated using primary mouse HSCs and human HSC cell line LX-2. RESULTS: Significantly increased serum Slit2 levels and hepatic expression of Slit2 and Robo1 were observed in patients with liver fibrosis. Compared to WT mice, Slit2-Tg mice were much more vulnerable to CCl4-induced liver injury and more readily develop liver fibrosis. Development of hepatic fibrosis in Slit2-Tg mice was associated with a stronger hepatic expression of collagen I and α-smooth muscle actin (α-SMA). However, liver injury and hepatic expression of collagen I and α-SMA were attenuated in CCl4-treated Robo1/2(+/-) mice in response to CCl4 exposure. In vitro, Robo1 neutralizing antibody R5 and Robo1 siRNA downregulated phosphorylation of Smad2, Smad3, PI3K, and AKT in HSCs independent of TGF-ß1. R5 and Robo1 siRNA also inhibited the expression of α-SMA by HSCs. Finally, the protective effect of R5 on the CCl4-induced liver injury and fibrosis was further verified in mice. CONCLUSIONS: Slit2-Robo1 signaling promotes liver injury and fibrosis through activation of HSCs.

SAP deficiency mitigated atherosclerotic lesions in ApoE(-/-) mice.

OBJECTIVE: Serum amyloid P conpoent (SAP), a member of the pentraxin family, interact with pathogens and cell debris to promote their removal by macrophages and neutrophils and is co-localized with atherosclerotic plaques in patients. However, the exact mechanism of SAP in atherogenesis is still unclear. We investigated whether SAP influence macrophage recruitment and foam cell formation and ultimately affect atherosclerotic progression. METHODS: we generated apoE(-/-); SAP(-/-) (DKO) mice and fed them western diet for 4 and 8 weeks to characterize atherosclerosis development. RESULTS: SAP deficiency effectively reduced plaque size both in the aorta (p = 0.0006 for 4 wks; p = 0.0001 for 8 wks) and the aortic root (p = 0.0061 for 4 wks; p = 0.0079 for 8wks) compared with apoE(-/-) mice. Meanwhile, SAP deficiency inhibited oxLDL-induced foam cell formation (p = 0.0004) compared with apoE(-/-) mice and SAP treatment increases oxLDL-induced foam cell formation (p = 0.002) in RAW cells. Besides, SAP deficiency reduced macrophages recruitment (p = 0.035) in vivo and in vitro (p = 0.026). Furthermore, SAP treatment enhanced CD36 (p = 0.007) and FcγRI (p = 0.031) expression induced by oxLDL through upregulating JNK and p38 MAPK phosphorylation whereas specific JNK1/2 inhibitor reduced CD36 (p = 0.0005) and FcγRI (P = 0.0007) expression in RAW cell. SAP deficiency also significantly decreased the expression of M1 and M2 macrophage markers and inflammatory cytokines in oxLDL-induced macrophages. CONCLUSION: SAP deficiency mitigated foam cell formation and atherosclerotic development in apoE(-/-) mice, due to reduction in macrophages recruitment, polarization and pro-inflammatory cytokines and inhibition the CD36/FcγR-dependent signaling pathway.