CEACAM1 Alternative Splicing in Liver Ischemia-Reperfusion Injury

PROJECT 1 – SUMMARY/ABSTRACT Project 1 competitive renewal addresses the unmet clinical and scientific needs to enhance donor liver supply through organ “rejuvenation.” We reported that hepatic CEACAM1 (encoded by CC1 gene; CD66a) dictates donor liver quality, and prevents early OLT injury in mice and humans. CC1 mRNA undergoes alternative splicing (AS) to generate splice variants, characterized by the inclusion (CC1-L; long) or exclusion (CC1-S; short) of exon 7. Hypothesis: Hepatocyte CC1-S functions as a cytoprotective sentinel, while CC1-L in OLT-infiltrating recipient- derived neutrophils, regulates liver IR-inflammation and fine-tunes its resolution. Aim 1: Delineate mechanisms by which hepatic CC1-S isoform promotes cellular protection in IR- stressed mouse OLT. Hypothesis: Antisense oligomer morpholinos (MOs)-enforced AS of hepatic CC1 generates CC1-S isoform in the donor mouse liver, which under the control of HIF-1α, stimulates cytoprotection by blocking p-p38 (under cold IR-stress) while promoting GPX4 and targeting ferroptosis (under warm IR-stress). Here, we will ascertain whether 1.1: CC1-AS accelerates otherwise impaired hepatic recovery in the acute and the resolution phase of IR-inflammation. 1.2: CC1-S controls IRI-OLT by regulating hepatic cell death pathways. 1.3: CC1-S-mediated cytoprotection is controlled by HIF-1α signaling under warm vs. cold hepatic IR-stress. Aim 2: Define mechanisms by which neutrophil CC1-L isoform exerts anti-inflammatory and cytoprotective functions in IR-stressed mouse OLT. Hypothesis: Recipient CC1-L neutrophils counteract acute IRI-OLT, and stimulate inflammation resolution by orchestrating N1/N2 polarization, with resultant liver homeostatic/regenerative remodeling. We will study whether 2.1: Recipient CC1-L deficient immune cells exacerbate hepatic IRI-OLT. 2.2: CC1-L polarizes N2 neutrophils to promote an anti-inflammatory phenotype/ improve OLT outcomes. 2.3: CC1-L proficient neutrophils polarize M2 macrophages/promote hepatic autophagy. Aim 3: Elucidate mechanisms by which hepatic CC1-S isoform rejuvenates discarded human livers subjected to normothermic machine preservation (NMP). Hypothesis: NMP, supplemented with HIF-1α – CC1- S axis modifiers, improves the function of discarded human livers by mitigating ferroptosis while promoting autophagy. We will incorporate the emerging NMP strategy with adjunctive CC1-intervention to assess whether 3.1: MOs-conditioned humanized CC1 transgenic mice (huCC1-Tg) mimic the effects of CC1-AS upon liver IR- stress in normal mice but be translatable to the human liver. 3.2: CC1-S isoform synergizes with HIF-1α to improve liver function. 3.3: CC1-S synergizes with HIF-1α to enhance cytoprotection in human livers. Integration with PPG: Project 1 complements studies assessing homeostatic mechanisms in the resolution of IRI-OLT in Project 2. Aim 1-2 in Project 1 will be validated by the screening of human OLT biopsies to accelerate assessments of clinical innate immune phenotypes in Project 3. Project 1 is dependent on Core A (Administrative), Core B (Mouse and Human OLT Surgery), and Core C (Computational and Biostatistics).