Donor Hepatic Steatosis Induce Exacerbated Ischemia-Reperfusion Injury Through Activation of Innate Immune Response Molecular Pathways

Abstract

Background Severe liver steatosis is a known risk factor for increased ischemia-reperfusion injury (IRI) and poor outcomes post liver transplantation (LT). This study aimed to identify steatosis-related molecular mechanisms associated with IRI exacerbation post-LT. Methods Paired graft biopsies (n=60) were collected at pre-implantation (L1) and 90 min post-reperfusion (L2). LT recipients (n=30) were classified by graft macrosteatosis: without steatosis or ≤5% (WS, n=13) and with steatosis ≥25% (S, n=17). Plasma samples were collected at L1, L2, and 1-day post-LT (POD1) for cytokines evaluation. Tissue RNA was isolated for gene expression microarrays. Probeset summaries were obtained using RMA algorithm. Pairwise comparisons were fit using two-sample t-test. P-values ≤0.01 were significant (FDR <5%). Molecular pathway analyses were conducted using IPA tool. Results Significantly differentially expressed genes were identified for WS and S grafts, post-reperfusion. Comprehensive comparison analysis of molecular profiles revealed significant association of S grafts molecular profile with innate immune response activation, macrophages production of nitric oxide and reactive oxygen species, IL-6, IL-8, IL-10 signaling activation, recruitment of granulocytes, and accumulation of myeloid cells. Post-reperfusion histological patterns of S grafts revealed neutrophilic infiltration surrounding fat accumulation. Circulating pro-inflammatory cytokines at post-reperfusion and 24 hours post-LT concurred with intra-graft deregulated molecular pathways. All tested cytokines were significantly increased in plasma of S grafts recipients at post-reperfusion when compared with WS group at same time. Conclusions Increases of graft steatosis exacerbate IRI by exacerbation of innate immune response post-LT. Preemptive strategies should consider it for safety usage of steatotic livers.

Peripheral Blood Gene Expression Changes Associated With Primary Graft Dysfunction After Lung Transplantation

“…Likewise, other organs have shown a similar response. Biopsy samples of liver allografts 90 minutes after reperfusion demonstrate significant upregulation of genes in the allograft involved in activation and function of innate immune cells 17 . Similarly, elevated peripheral blood gene expression of the innate immune receptors toll-like receptor 2 and 4 (TLR2 and TLR4) measured 3 to 6 days after reperfusion is associated with delayed kidney graft function 18 .…”

ROS homeostasis, a key determinant in liver ischemic-preconditioning

“…Importantly, in the steatotic liver PGC-1α levels are reduced [48] and this downregulation results in a reduction of antioxidant systems in the liver [49]. This fact, together with the observation of a protective role of PGC-1α in IR tolerance in the liver [49] and several other tissues (ie heart, kidney, the central nervous system (CNS)) [50], [51], [52] suggest that PGC-1α regulation of antioxidant systems can be relevant in the enhanced sensitivity of the steatotic liver to IR. This concept is supported by the observation that in terms of liver damage following IR, PGC-1α KO mice behave similarly to WT mice with steatotic livers [49].…”

Innate Immune Regulations and Liver Ischemia-Reperfusion Injury

“…Furthermore, enhanced TLR4 activation was implicated to be responsible for the increased susceptibilities of steatotic livers to IRI in both animal models and clinical patients 4,5 . Recently, the utility of TLR4 targeted therapy was demonstrated in an animal model in which TLR4 antagonist eritoran tetrasodium effectively attenuated liver IRI 6 .…”