Altered fibrinogen γ-chain cross-linking in mutant fibrinogen-γΔ5 mice drives acute liver injury

• DOI: 10.1016/j.jtha.2023.04.003
• Publication Date: 2023-04-14T15:19:23Z
• Authors: Lauren G. Poole; Lauren R. Schmitt; Anthony Schulte; Dafna J. Groeneveld; Holly M. Cline; Yaqiu Sang; Woosuk S. Hur; Alisa S. Wolberg; Matthew J. Flick; Kirk C. Hansen; James P. Luyendyk
• Keywords: Mice; Fibrin; Integrins; Chemical and Drug Induced Liver Injury, Chronic; Lysine; Animals; Fibrinogen; Acetaminophen

Hepatic deposition of cross-linked fibrin(ogen) occurs alongside platelet accumulation as a hallmark of acetaminophen (APAP)-induced liver injury.We sought to define the precise role of the fibrinogen γ-chain C-terminal integrin αIIbβ3 binding domain in APAP-induced liver injury.Mice expressing mutant fibrinogen incapable of engaging integrin αIIbβ3 due to a C-terminal fibrinogen γ-chain truncation (mutant fibrinogen-γΔ5 [FibγΔ5] mice) and wild-type mice were challenged with APAP (300 mg/kg, intraperitoneally).We observed an altered pattern of fibrin(ogen) deposition in the livers of APAP-challenged FibγΔ5 mice. This led to the unexpected discovery that fibrinogen γ-chain cross-linking was altered in the livers of APAP-challenged FibγΔ5 mice compared with that in wild-type mice, including absence of γ-γ dimer and accumulation of larger molecular weight cross-linked γ-chain complexes. This finding was not unique to the injured liver because activation of coagulation did not produce γ-γ dimer in plasma from FibγΔ5 mice or purified FibγΔ5 fibrinogen. Sanger sequencing predicted that the fibrinogen-γΔ5 γ-polypeptide would terminate at lysine residue 406, but liquid chromatography tandem mass spectrometry analysis revealed that this critical lysine residue was absent in purified fibrinogen-γΔ5 protein. Interestingly, hepatic deposition of this uniquely aberrantly cross-linked fibrin(ogen) in FibγΔ5 mice was associated with exacerbated hepatic injury, an effect not recapitulated by pharmacologic inhibition of integrin αIIbβ3.The results indicate that fibrinogen-γΔ5 lacks critical residues essential to form γ-γ dimer in response to thrombin and suggest that hepatic accumulation of abnormally cross-linked fibrin(ogen) can exacerbate hepatic injury.