Hepatic ischemia/reperfusion injury (IRI) linked to leukocyte recruitment has a negative impact on graft outcomes. Focal matrix degradation is a key prerequisite for leukocyte transmigration across vascular barriers. Gelatinase A (GelA) and B (GelB) are a family of metalloproteinases (MMPs) known for its ability to degrade vascular basement membrane components. Here we assess the individual contributions of gelatinases to hepatic IRI. Methods: GelA- and GelB-deficient knock-out (KO) mice, matched wild-type (WT) control littermates, and C57BL6 mice treated with anti-GelA and anti-GelB neutralizing antibodies (3mg/kg,i.v.) or isotype-matched IgG were subject to 90 min partial liver ischemia followed by 6h reperfusion. Results: GelAKO mice and mice treated with anti-GelA mAb showed a significantly worse liver function (ALT: ≈2-fold increase; p<0.03) and histological preservation post-IRI, as compared to controls. In contrast, GelBKO mice and mice treated with anti-GelB mAb were characterized by improved liver function (ALT: ≈3-6-fold-decrease; p<0.05) and histology, further supporting a beneficial role for GelB inhibition in liver IRI. While GelAKO mice had enhanced MPO activity (12.63±4.82 vs.7.21±1.58 U/g;p<0.05) and Ly6G-neutrophil (186.6±27.0 vs.125.0±17.7;p<0.01)/Mac-1-macrophage (155.4±31.2 vs.122.9±12.9;p<0.05) infiltration, GelBKO mice showed depressed MPO activity (4.07±1.32 vs. 6.83±1.44 U/g;p<0.002) and leukocyte infiltration (Ly6G: 59.2±23.7 vs. 115.1±20.9,p<0.02; Mac-1: 56.8±14.9 vs.121.2±16.8,p<0.002), compared to respective controls. TNF-Α (p<0.05), IFN-Γ (p<0.01), and IL-6 (p<0.01), otherwise depressed in GelBKO livers, were significantly increased in GelAKO livers post-IRI. Notably, following FMLP stimulation, GeLB activity was markedly upregulated in isolated GelA KO neutrophils (10,682±1,283 vs.5,816±1,527;p<0.01), compared to wild-type cells. Moreover, selective inhibition of GelB significantly depressed GelA KO neutrophil migration across fibronectin-coated-transwell-plates (35.8±9.7 vs. 59.2±15.3;p<0.01). Conclusion: Our novel data support the view that while it is beneficial to inhibit GelB, GelA inhibition worsens liver damage post-IRI. Inhibition of GelA activity in neutrophils results in the upregulation of gelatinase B activity, which facilitates leukocyte recruitment in hepatic IRI. Importantly, our results caution against the use of broad-spectrum MMP inhibitors for the treatment of hepatic IRI.

« Back to 2013 American Transplant Congress