*Purpose: Although CEACAM1 (CM1; carcinoembryonic antigen-related cell adhesion molecule 1; CD66a) regulates hepatic metabolic homeostasis, its role in orthotopic liver transplantation (OLT) remains unknown. A recent study identified ASK1 (Apoptosis signal-regulating kinase 1) – p38 MAPK signaling in the mechanism of cellular death. Here, we analyzed mouse OLT and human OLT biopsies (Bx) to determine as to whether/how hepatocyte CM1-ASK1-p38 axis may contribute to OLT function and outcomes.

*Methods: Donor livers from groups of WT and CM1-deficient (CM1-KO) mice (C57/BL6) with/without adjunctive ASK1 inhibitor treatment were transplanted, after 18h cold storage, to syngeneic WT recipients, and sampled at 6h post-OLT. Separate groups of WT, CM1-KO or CM1-KO + ASK1 inhibitor-pretreated livers were perfused after cold storage with saline to analyze HMGB1 and Histone H3 release in the liver flush (LF). In parallel, primary hepatocytes were tested for cold-stress induced immune responses. In the clinical arm, human cold-stored pre-OLT Bx (n=60) were screened for CM1/ASK1/phosphor-p38 (pP38) expression by Western blots and pro-inflammatory phenotype by RT-PCR.

*Results: In the experimental arm, donor liver CM1 null mutation augmented IRI-OLT (CM1-KO>WT) by enhancing ROS expression/HMGB1 translocation during cold storage, as evidenced by increased sAST/sALT levels (p<0.05), serum HMGB1 release (ELISA, p<0.05) and augmented proinflammatory cytokine/chemokine programs (p<0.05). CM1-deficient cold-stored livers showed enhanced pP38 expression (p<0.05) as compared to WT counterparts. Hepatic CM1-deficiency enhanced cold stress-triggered ASK1/p-p38 upregulation. Adjunctive ASK1 inhibition alleviated IRI and improved OLT survival by suppressing p-p38 upregulation, and ROS induction/HMGB1 translocation (CM1-KO>WT), while ASK1 silencing (siRNA) in vitro promoted cytoprotection in cold-stressed CM1-deficient hepatocyte cultures. Consistent with the mouse data, CM1 expression in human donor liver Bx (n=60) correlated negatively with ASK1 (r=-0.3424, p=0.0074) and p-p38 (r=-0.2947, p=0.0222) expression, while low-CM1 levels associated with increased ROS/cytoplasmic HMGB1 translocation, enhanced innate/adaptive immune responses; and trended towards impaired overall graft survival at 3 yrs (76.7% vs 90.8%, p=0.1219) and rejection-free graft survival at 3 yrs (64.7 vs 81.5%, p=0.1383). Notably, reduced donor liver CM1 expression (pre-transplant CM1/β-actin cut-off value of 0.71 by ROC curve; AUROC=0.604, sensitivity=0.761, specificity=0.643) was identified as an independent predictor for early allograft dysfunction (EAD) in human OLT patients.

*Conclusions: As a checkpoint regulator of IR-stress/sterile inflammation, CM1 may serve as a biomarker of donor tissue quality, and a novel target for therapeutic modulation in OLT recipients.

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