Background/Aim: We have documented crucial role of macrophage Notch1 signaling in a mouse warm hepatic ischemia-reperfusion injury (IRI) model. However, its clinical relevance or therapeutic potential remain unknown. Recent studies have identified serelaxin (SER, a recombinant human relaxin) as a putative Notch1 inducer. We aimed to examine the contribution of Notch1 in human OLT as well as to determine whether SER-induced Notch1 signaling may affect IR-stressed mouse OLT. Methods/Results: C57BL/6 mouse livers with extended (18h) cold storage were transplanted to syngeneic hosts and sampled at 6h post-reperfusion. Treatment with SER at reperfusion (5[mu]g/kg iv) ameliorated IRI as evidenced by sALT/sAST levels; Suzuki's histological scores (n=5/gr, p<0.05); improved post-OLT survival (n=10/gr, p<0.05); and decreased number of Ly6G/CD11b/TUNEL positive cells (p<0.05). Graft RXFP1 (SER cognate receptor) expression was neither affected by IR-stress nor SER treatment, while SER increased Notch1 intracellular domain (NICD), Hes1, pStat3, Arg1 and decreased p-IkBa (Western blot). In parallel, SER decreased mRNA levels coding for MCP1, IL1β, CXCL1, CXCL2, CXCL10 while increasing Arg1 and IL10 (p<0.05). Immunohistochemistry showed Notch1 was predominantly expressed by OLT-infiltrating leukocytes. In bone marrow-derived macrophage cultures, SER adjunct increased NICD, Hes1, pStat3, Arg1, CD163 while decreasing p-IkBa, MCP1, IL1β, CXCL1, CXCL2, CXCL10 (p<0.05). In the clinical arm of the study, human liver biopsies (Bx) collected from 21 adult primary liver transplant patients (2h post-reperfusion) were divided into “high” (n=10) vs. “low” (n=11) NICD expression groups (Western blots). The "high" NICD expression group had decreased cleaved caspase-8 (p<0.05), and lower sALT levels at POD1 (216±46 vs. 517±127, p<0.05) and superior post-transplant survival (2-year: 91.6% vs. 77.9%). OLTs with "high" NICD levels were characterized by decreased mRNA coding for CXCL10 (0.77±0.22 vs. 1.00±0.29), IL1β (0.73±0.25 vs. 1.00±0.18) and simultaneously increased CD163 (1.42±0.69 vs. 1.00±0.24). Conclusion: This translational study documents the significance of Notch1 mediated macrophage M2 polarization for hepatoprotection in OLT; and highlights SER-mediated therapeutic potential of Notch1 activation in organ transplantation.

CITATION INFORMATION: Kageyama S., Nakamura K., Ke B., Sosa R., Reed E., Kaldas F., Busuttil R., Kupiec-Weglinski J. Serelaxin-Notch1 Signaling Promotes Macrophage M2 Differentiation and Alleviates Hepatocellular Damage in Orthotopic Liver Transplantation: From Mouse-to-Human Am J Transplant. 2017;17 (suppl 3).

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