Estrogen receptors orchestrate cell growth and differentiation to facilitate liver regeneration.

Background and Aims: Improving liver regeneration (LR) capacity and thereby liver function reserve is a critical bridging strategy for managing liver failure patients. Since estrogen signaling may participate in LR, our aim was to characterize the roles of ERα and ERß in LR. Methods: LR capacity and estradiol levels following 2/3rd partial hepatectomy (PHx) were compared in ERα-KO or ERß-KO vs. wildtype mice. The ERα- or ERß-related transcriptome and interactome were analyzed from regenerating livers, and then bioinformatics was used for pathway discovery and analysis of interactome-transcriptome relationships. Human hepatic progenitors (HepRG cells) and mouse Hepa1-6 hepatocytes were used to elucidate molecular interactions and functions. Results: This paper demonstrated that estrogen signals orchestrate hepatic repopulation and differentiation via distinct transcriptome patterns governed by ERα or ERß. Cell repopulation pathway was associated with the ERα-transcriptome, but cell differentiation and metabolic function were associated with the ERß transcriptome. Mechanistic studies linking ERs interactomes and transcriptomes discovered that ERα-Chd1 interaction promoted cell growth by upregulating Ssxb6, Crygc, and Cst1; and, ERß-Ube3a interaction facilitated hepatic progenitor cell differentiation to hepatocytes and cholangiocytes, specifically by upregulating Ifna5. Conclusions: ERα and ERß orchestrate liver cell proliferation and differentiation respectively, thereby promoting LR.

Estrogen-Estrogen Receptor α Signaling Facilitates Bilirubin Metabolism in Regenerating Liver Through Regulating Cytochrome P450 2A6 Expression.

BACKGROUND: After living donor liver transplantation (LDLT), rising serum bilirubin levels commonly indicate insufficient numbers of hepatocytes are available to metabolize bilirubin into biliverdin. Recovery of bilirubin levels is an important marker of hepatocyte repopulation after LDLT. Cytochrome P450 (CYP) 2A6 in humans (or cyp2a4 in rodents) can function as "bilirubin oxidase." Functional hepatocytes contain abundant CYP2A6, which is considered a marker for hepatocyte function recovery. The aim of our study was to determine the impact of estradiol/estrogen receptor signaling on bilirubin levels during liver function recovery. METHODS: We conducted a hospital-based cohort study of bilirubin levels after LDLT surgery in both liver graft donors and recipients, performed a transcriptome comparison of wild-type versus estrogen receptor (ER)α knockout mice and a bioinformatics analysis of transcriptome changes in their regenerating liver after two-third partial hepatectomy (PHx), and assayed in vitro expression of cytochrome (CYP2A6) in human hepatic progenitor cells (HepRG) treated with 17ß-estradiol (E2). RESULTS: The latency of bilirubin level reduction was shorter in women than in men, suggesting that a female factor promotes bilirubin recovery after liver transplantation surgery. In the PHx mouse model, the expression of the cyp2a4 gene was significantly lower in livers from the knockout ERα mice than in livers from their wild-type littermates; but the expression of other bilirubin metabolism-related genes were similar between these groups. Moreover, E2 or bilirubin treatments significantly promoted CYP2A6 expression in hepatocyte progenitor cells (HepRG cells). Sequence analysis revealed similar levels of aryl hydrocarbon receptor (AhR; bilirubin responsive nuclear receptor) and ESR1 binding to the promoter region of CYP2A6. CONCLUSIONS: This is the first report to demonstrate, on a molecular level, that E2/ERα signaling facilitates bilirubin metabolism in regenerating liver. Our findings contribute new knowledge to our understanding of why the latency of improved bilirubin metabolism and thereby liver function recovery is shorter in females than in males.

Aerosolized human extracellular superoxide dismutase prevents hyperoxia-induced lung injury.

An important issue in critical care medicine is the identification of ways to protect the lungs from oxygen toxicity and reduce systemic oxidative stress in conditions requiring mechanical ventilation and high levels of oxygen. One way to prevent oxygen toxicity is to augment antioxidant enzyme activity in the respiratory system. The current study investigated the ability of aerosolized extracellular superoxide dismutase (EC-SOD) to protect the lungs from hyperoxic injury. Recombinant human EC-SOD (rhEC-SOD) was produced from a synthetic cassette constructed in the methylotrophic yeast Pichia pastoris. Female CD-1 mice were exposed in hyperoxia (FiO2>95%) to induce lung injury. The therapeutic effects of EC-SOD and copper-zinc SOD (CuZn-SOD) via an aerosol delivery system for lung injury and systemic oxidative stress at 24, 48, 72 and 96 h of hyperoxia were measured by bronchoalveolar lavage, wet/dry ratio, lung histology, and 8-oxo-2'-deoxyguanosine (8-oxo-dG) in lung and liver tissues. After exposure to hyperoxia, the wet/dry weight ratio remained stable before day 2 but increased significantly after day 3. The levels of oxidative biomarker 8-oxo-dG in the lung and liver were significantly decreased on day 2 (P<0.01) but the marker in the liver increased abruptly after day 3 of hyperoxia when the mortality increased. Treatment with aerosolized rhEC-SOD increased the survival rate at day 3 under hyperoxia to 95.8%, which was significantly higher than that of the control group (57.1%), albumin treated group (33.3%), and CuZn-SOD treated group (75%). The protective effects of EC-SOD against hyperoxia were further confirmed by reduced lung edema and systemic oxidative stress. Aerosolized EC-SOD protected mice against oxygen toxicity and reduced mortality in a hyperoxic model. The results encourage the use of an aerosol therapy with EC-SOD in intensive care units to reduce oxidative injury in patients with severe hypoxemic respiratory failure, including acute respiratory distress syndrome (ARDS).