Although mechanisms of immune activation against liver ischemia-reperfusion injury (IRI) have been studied extensively, questions regarding liver resident Kupffer cells vs. infiltrating macrophages (iM[Oslash]s) remain controversial. This study aims to dissect how KCs respond and function in liver IRI. In a murine liver partial warm ischemia model, we analyzed KCs (F4/80⁺CD11b^–) vs. iM[Oslash]s (F4/80⁺CD11b⁺) at different stages of the disease process (0h, 6h, 24h) by fluorescence-activated cell sorting (FACS) and immunofluorescence staining. We found that liver immune activation by IR was associated with not only accumulation/activations of iM[Oslash]s, but also significant depletion of KCs. Prolonged (90m), but not transient (30m), ischemia triggered KC depletion, leading to iM[Oslash] accumulation, pro-inflammatory immune activation and hepatocellular damages. TIM4^high KCs were preferentially depleted by ischemia, leading to an increase of their pro-inflammatory nature upon activation. Thus, in vitro stimulation with LPS of KCs isolated from ischemic livers resulted in higher TNF-a, but lower IL-10, productions as compared with those from sham livers. Ischemia induced upregulation of the expression of Receptor Interacting Protein 1 and 3 (RIP1, RIP3) in livers. Inhibition of RIP1 by Necrostatin-1s (Nec-1s, 4mg/kg, i.p, at -1h) protected KCs from ischemia-induce depletion, resulting in the reduction of iM[Oslash]s, suppression of pro-inflammatory immune activation and protection of livers from IRI. Interestingly, clodronate-liposome-mediated depletion of KCs abrogated the effect of Nec-1s, indicating that protection of KCs, rather than liver parenchymal cells, was critical for the immune regulation/liver protection of Nec-1s. Additionally, liver reconstitutions with KCs post-ischemia (2×106/mouse via portal vein, at 0h post-reperfusion) exerted similar anti-inflammatory/cytoprotective effects against IRI. These results demonstrated a novel mechanism of liver inflammatory immune activation in the pathogenesis of liver IRI: prolonged liver ischemia triggers an RIP-1-dependent TIM4^high KC necrotic depletion, which facilitates the accumulation and activation of iM[Oslash]s.

CITATION INFORMATION: Wang H, Yue S, Ni M, Busittil R, Kupiec-Weglinski J, Lu L, Zhai Y. Prolonged Liver Ischemia Triggers Necrotic Depletion of TIM4+ Kupffer Cells to Facilitate Tissue Inflammatory Immune Activation in Liver Ischemia-Reperfusion Injury. Am J Transplant. 2017;17 (suppl 3).

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