We examined the effects of VEGFA on damage and regeneration in steatotic and non-steatotic livers of rats submitted to PH under I/R, and characterized the underlying mechanisms involved. Our results indicated that VEGFA levels were decreased in both steatotic and non-steatotic livers after surgery. The administration of VEGFA increased VEGFA levels in non-steatotic livers, reducing the incidence of post-operative complications following surgery through the VEGFR2-Wnt2 pathway, independently of Id1. Unexpectedly, administration of VEGFA notably reduced VEGFA levels in steatotic livers, exacerbating damage and regenerative failure. After exogenous administration of VEGFA in steatotic animals, circulating VEGFA is sequestered by the high circulating levels of sFlt1 released from adipose tissue. Under such conditions, VEGFA cannot reach the steatotic liver to exert its effects. Consequently, the concomitant administration of VEGFA and an antibody against sFlt1 was required to avoid binding of sFlt1 to VEGFA. This was associated with high VEGFA levels in steatotic livers and protection against damage and regenerative failure, plus improvement in the survival rate via up-regulation of PI3K/Akt independently of the Id1-Wnt2 pathway. The current study highlights the different effects and signaling pathways of VEGFA in liver surgery requiring PH and I/R based in the presence of steatosis. Key messages VEGFA administration improves PH+I/R injury only in non-steatotic livers of Ln animals. VEGFA benefits are exerted through the VEGFR2-Wnt2 pathway in non-steatotic livers. In Ob rats, exogenous VEGFA is sequestered by circulating sFlt1, exacerbating liver damage. Therapeutic combination of VEGFA and anti-sFlt1 is required to protect steatotic livers. VEGFA+anti-sFlt1 treatment protects steatotic livers through a VEGFR2-PI3K/Akt pathway. Electronic supplementary material The online version of this article (10.1007/s00109-019-01811-y) contains supplementary material, which is available to authorized users.

† These authors contributed equally to this work.High-mobility group box 1 (HMGB1) has been described in different inflammatory disorders, and the deleterious effects of brain death (BD) may counteract the protection conferred by ischemic preconditioning (IP), the only surgical strategy that is being applied in clinical liver transplantation. Our study examined how HMGB1 may affect preconditioned and unpreconditioned steatotic and nonsteatotic liver grafts from donors after BD (DBDs) for transplantation. HMGB1 was pharmacologically modulated in liver grafts from DBDs, and HMGB1-underlying mechanisms were characterized. We found that BD decreased HMGB1 in preconditioned and unpreconditioned livers and was associated with inflammation and damage. Exogenous HMGB1 in DBDs activates phosphoinositide-3-kinase and Akt and reduces hepatic inflammation and damage, increasing the survival of recipients. Combination of IP and exogenous HMGB1 shows additional benefits compared with HMGB1 alone. This study provides new mechanistic insights into the pathophysiology of BD-derived liver graft damage and contributes to the development of novel and efficient strategies to ultimately improve liver graft quality.

In the present study, we examined the effects of cortisol on steatotic and non-steatotic liver grafts from brain-dead donors and characterized the underlying mechanisms involved. Non-steatotic liver grafts showed reduced cortisol and increased cortisone levels in association with up-regulation of enzymes that inactivate cortisol. Conversely, steatotic liver grafts exhibited increased cortisol and reduced cortisone levels. The enzymes involved in cortisol generation were overexpressed, and those involved in cortisol inactivation or clearance were down-regulated in steatotic liver grafts. Exogenous administration of cortisol negatively affected hepatic damage and survival rate in non-steatotic liver transplantation (LT); however, cortisol treatment up-regulated the phosphoinositide 3-kinase (PI3K)-protein kinase C (PKC) pathway, resulting in protection against the deleterious effects of brain-dead donors on damage and inflammatory response in steatotic LT as well as in increased survival of recipients. The present study highlights the differences in the role of cortisol and hepatic mechanisms that regulate cortisol levels based on the type of liver. Our findings suggest that cortisol treatment is a feasible and highly protective strategy to reduce the adverse effects of brain-dead donor livers in order to ultimately improve liver graft quality in the presence of steatosis, whereas cortisol treatment would not be recommended for non-steatotic liver grafts.

Background. We evaluated the potential dysfunction caused by changes in growth hormone (GH) levels after brain death (BD), and the effects of modulating GH through exogenous epidermal growth factor (EGF) in steatotic and nonsteatotic grafts. Methods. Steatotic and nonsteatotic grafts from non-BD and BD rat donors were cold stored for 6 hours and transplanted to live rats. Administration of GH and EGF and their underlying mechanisms were characterized in recipients of steatotic and nonsteatotic grafts from BD donors maintained normotensive during the 6 hours before donation. Circulating and hepatic GH and EGF levels, hepatic damage, and regeneration parameters were evaluated. Recipient survival was monitored for 14 days. Somatostatin, ghrelin, and GH-releasing hormones that regulate GH secretion from the anterior pituitary were determined. The survival signaling pathway phosphoinositide-3-kinase/protein kinase B that regulates inflammation (suppressors of cytokine signaling, high-mobility group protein B1, oxidative stress, and neutrophil accumulation) was evaluated. Results. BD reduced circulating GH and increased GH levels only in steatotic livers. GH administration exacerbated adverse BD-associated effects in both types of graft. Exogenous EGF reduced GH in steatotic livers, thus activating cell proliferation and survival signaling pathways, ultimately reducing injury and inflammation. However, EGF increased GH in nonsteatotic grafts, which exacerbated damage. The benefits of EGF for steatotic grafts were associated with increased levels of somatostatin, a GH inhibitor, whereas the deleterious effect on nonsteatotic grafts was exerted through increased amounts of ghrelin, a GH stimulator. Conclusions. GH treatment is not appropriate in rat liver transplant from BD donors, whereas EGF (throughout GH inhibition) protects only in steatotic grafts.