Hepatocyte growth factor-mediated apoptosis mechanisms of cytotoxic CD8+ T cells in normal and cirrhotic livers

Abstract

Intrahepatic stem/progenitor cells and cytotoxic CD8+ T cells (CD8+ T cells) in the cirrhotic liver undergo apoptosis, which potentially facilitates progression to cancer. Here, we report that hepatocyte growth factor (HGF) signaling plays an important role in promoting normal and damaged liver CD8+ T cell Fas-mediated apoptosis through its only receptor, c-Met. In addition to binding with HGF, c-Met also binds to Fas to form a complex. Using a diethylnitrosamine (DEN)-induced liver fibrosis/cirrhosis mouse model, immunostaining, and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, we found that HGF secretion was significantly higher at 10 weeks post-DEN, the liver cirrhotic phase (LCP), than at 3 weeks post-DEN, the liver fibrotic phase (LFP). Correspondingly, differences in CD8+ T cell proliferation and apoptosis were noted between the two phases. Interestingly, staining and TUNEL assays revealed lower smooth muscle actin (α-SMA)+ cell apoptosis, a marker for hepatic stellate cells (HSCs), in the LFP group than in the LCP group, which suggested a beneficial correlation among HGF, CD8+ T cells and HSCs in improving the fibrotic load during damaged liver repair. In cultures, when met different concentrations of recombinant HGF (rHGF), phytohemagglutinin (PHA)-stimulated naive mouse splenic CD8+ T cells (pn-msCD8+ T cells) responded differently; as increases in rHGF increased were associated with decreases in the clonal numbers of pn-msCD8+ T cells, and when the rHGF dose was greater than 200 ng/mL, the clonal numbers significantly decreased. In the presence of 400 ng/mL rHGF, the death-inducing signaling complex (DISC) can be directly activated in both nsCD8+ T cells and healthy human peripheral blood CD8+ T cells (hp-CD8+ T cells), as indicated by recruitment of FADD and caspase-8 because DISC forms via the recruitment of FADD and caspase-8, among others. These findings suggest that Fas-mediated apoptosis, may also indicate a regulatory role of HGF signaling in hepatic homeostasis.

In vitro differentiated human CD4+ T cells produce hepatocyte growth factor

“…Meanwhile, ligation of c-Met by HGF causes the release of sequestered Fas and increased susceptibility to Fas mediated apoptosis (57). A recent study by Chen et al suggests that the same mechanisms described by Wang et al are functional in CD8 + T cells isolated from the blood of healthy human donors (58). They show that in vitro culture of CD8 + T cells with a high concentration of HGF protein causes release of c-Met sequestered Fas, and then results in Fas mediated apoptosis over a 72-hour culturing period.…”

Comparative effects of hepatocyte growth factor and tacrolimus on acute liver allograft early tolerance

“…Using a WSI automatic image scanner, we found Fas (green) antagonism by cMet (pink) in mouse liver allograft aCD8 + T cells (red), as shown by the merged brick color ( Figure 7A i, bottom panel, box; Supplementary Figure 6A , indicated by an arrow) which was stronger in the allo-liver grafts on POD 7 than that from naive ones ( Figure 7A i, top panel, box, ** p < 0.05), and the merged color changed to a lighter shade from the OLT group ( Figure 7A ii, top panel, box) to the cHGF-treated group ( Figure 7A ii, bottom panel; the boxes indicate a quarter of one field, ** p < 0.001). When analyzing the relationship of two molecules using Co-IP, we, for the first time, find the association of cMet and FAS with MACS-purified naive splenic mouse CD8 + T cells ( Figure 7B ) ( 51 ). These findings may suggest that FAS antagonism by cMet on aCD8 + T cells correlates with aCD8 + T cells/higher activity/tolerance failure/rejection; we deduced that HGF/cHGF activated cMet through its ligand HGF from cHGF, parting the association, FAS-free and aggregation, and then undergo FAS-mediated apoptosis.…”

“…(Ei, ii) Analysis of the IF staining of Ki-67 (green) within CD8 + T cells (red) in liver allografts from the allo-OLT and cHGF groups on POD 7 and 10-12 shown in Supplementary Figures S4D-i, ii (i, **p < 0.001 vs. allo-OLT); analysis of TUNEL staining (green) within CD8 + T cells (red) in liver allografts from the allo-OLT and cHGF groups on POD 7 and 10-12 shown in Supplementary Figures S4E-i, ii (ii, **p < 0.001 vs. allo-OLT). Analysis of cHGF plus anti-cMet-Ab (solid blue bars) for CD8 + T cell proliferation (Ki-67) and apoptosis (TUNEL) in Supplementary Figures S4D-iii of two molecules using Co-IP, we, for the first time, find the of cMet and FAS with MACS-purified naive splenic mouse CD8 + T cells (Figure 7B) (51). These findings may suggest that FAS antagonism by cMet on aCD8 + T cells correlates with aCD8 + T cells/higher activity/tolerance failure/rejection; we deduced that HGF/cHGF activated cMet through its ligand HGF from cHGF, parting the association, FAS-free and aggregation, and then undergo FAS-mediated apoptosis.…”