Experimental Brain Death Models in Liver Transplantation

Most organs for transplantation are currently procured from brain-dead donors; however, brain death is an important risk factor in liver transplantation. In addition, to counteract the shortage of liver grafts, transplant centers accept the use of sub-optimal livers, which may show higher risk of primary non-function or initial poor function. Very few literatures exist regarding liver transplantation using brain-dead donors, or about brain death and its effects on sub-optimal grafts in such surgical situation. This chapter aims to describe the pathophysiological changes occurring in liver grafts during brain death and focuses on the strengths and limitations of experimental models used to study the effect of brain death on optimal and sub-optimal (specially steatotic) liver grafts. Depending on the use of experimental models that simulate as much as possible the surgical conditions present in clinical practice, therapeutic strategies designed in animal models could be more successfully translated to the bedside

Insights into Growth Factors in Liver Carcinogenesis and Regeneration: An Ongoing Debate on Minimizing Cancer Recurrence after Liver Resection

This research was funded by the Ministerio de Ciencia, Innovacion y Universidades (Project Grant RTI2018-095114-B-I00) Madrid, Spain; European Union (Fondos FEDER, "una manera de hacer Europa"); CERCA Program/Generalitat de Catalunya; the Secretaria d' Universitats I Recerca del Departament d' Economia I Coneixement (Project Grant 2017_SGR_551) Barcelona, Spain, by the COST action Programs CA17103 (DARTER), CA17112 (PRO-EURO-DILI-NET), CA17121 (COMULIS) and CA17126 (TUMIEE), and by the Consejo Nacional de Ciencia y Tecnologia (CONACYT), Fondo Sectorial de Investigacion para la Educacion (Project grant 257743), Mexico. Marc Mico-Carnero is the recipient of a fellowship from FCT (Fundacio Catalana de Trasplantament), Spain.Hepatocellular carcinoma has become a leading cause of cancer-associated mortality throughout the world, and is of great concern. Currently used chemotherapeutic drugs in the treatment of hepatocellular carcinoma lead to severe side effects, thus underscoring the need for further research to develop novel and safer therapies. Liver resection in cancer patients is routinely performed. After partial resection, liver regeneration is a perfectly calibrated response apparently sensed by the body’s required liver function. This process hinges on the effect of several growth factors, among other molecules. However, dysregulation of growth factor signals also leads to growth signaling autonomy and tumor progression, so control of growth factor expression may prevent tumor progression. This review describes the role of some of the main growth factors whose dysregulation promotes liver tumor progression, and are also key in regenerating the remaining liver following resection. We herein summarize and discuss studies focused on partial hepatectomy and liver carcinogenesis, referring to hepatocyte growth factor, insulin-like growth factor, and epidermal growth factor, as well as their suitability as targets in the treatment of hepatocellular carcinoma. Finally, and given that drugs remain one of the mainstay treatment options in liver carcinogenesis, we have reviewed the current pharmacological approaches approved for clinical use or research targeting these factors.Ministerio de Ciencia, Innovacion y Universidades Madrid, Spain RTI2018-095114-B-I00European Union (Fondos FEDER, "una manera de hacer Europa")General ElectricSecretaria d' Universitats I Recerca del Departament d' Economia I Coneixement Barcelona, Spain 2017_SGR_551COST action Programs CA17103 CA17112 CA17121 CA17126Consejo Nacional de Ciencia y Tecnologia (CONACyT)Fondo Sectorial de Investigacion para la Educacion, Mexico 257743FCT (Fundacio Catalana de Trasplantament), Spai

Spironolactone Effect in Hepatic Ischemia/Reperfusion Injury in Wistar Rats

Introduction. Ischemia/reperfusion (IR) injury, often associated with liver surgery, is an unresolved problem in the clinical practice. Spironolactone is an antagonist of aldosterone that has shown benefits over IR injury in several tissues, but its effects in hepatic IR are unknown. Objective. To evaluate the effect of spironolactone on IR-induced damage in liver. Materials and Methods. Total hepatic ischemia was induced in rats for 20 min followed by 60 min of reperfusion. Spironolactone was administered and hepatic injury, cytokine production, and oxidative stress were assessed. Results. After IR, increased transaminases levels and widespread acute inflammatory infiltrate, disorganization of hepatic hemorrhage trabeculae, and presence of apoptotic bodies were observed. Administration of SPI reduced biochemical and histological parameters of liver injury. SPI treatment increased IL-6 levels when compared with IR group but did not modify either IL-1β or TNF-α with respect to IR group. Regarding oxidative stress, increased levels of catalase activity were recorded in IR + SPI group in comparison with group without treatment, whereas MDA levels were similar in IR + SPI and IR groups. Conclusions. Spironolactone reduced the liver damage induced by IR, and this was associated with an increase in IL-6 production and catalase activity

Estrategias para proteger el injerto esteatósico en el trasplante hepático

En trasplante hepático (TH), la lesión por isquemia-reperfusión (I/R) es la causa principal tanto del mal funcionamiento como del fallo primario del injerto hepático. Y si esto ocurre en hígados sanos, aun son mayores los casos de mal función o fallo primario cuando el injerto es esteatósico, ya que estos hígados toleran peor que los normales la lesión por I/R. Además, la esteatosis es la causa del mayor número de hígados no aptos para el trasplante, acentuando la problemática de la falta de injertos para TH. Por ello, es evidente la necesidad de desarrollar estrategias protectoras para minimizar los efectos adversos de la lesión por I/R en hígados esteatósicos. Los efectos perjudiciales del Sistema Renina-Angiotensina (RAS) y de la proteína transportadora de retinol tipo 4 (RBP4) en varias patologías están bien documentados pero no se sabe si estarían implicados en la lesión por I/R en TH. Por otro lado, el precondicionamiento isquémico (PCI) basado en la inducción de breves periodos de I/R, reduce la lesión por I/R asociada a TH, pero se desconocen en gran parte sus mecanismos protectores. En la presente tesis se investigó el papel del RAS y del RBP4 en la lesión por I/R en injertos esteatósicos y no esteatósicos sometidos a TH, así como su implicación en los beneficios del PCI. Además de esto, se evaluaron los mecanismos de protección de estrategias farmacológicas o quirúrgicas, como el PCI capaces de modular el RAS y el RBP4 en ambos tipos de injertos. Para alcanzar estos objetivos, se utilizó el modelo experimental de TH ortotópico utilizando ratas de la cepa Zucker. Los resultados obtenidos indicaron que la Angiotensina II, principal efectora del RAS, está implicada en la lesión por I/R en injertos hepáticos no esteatósicos, pero no en los beneficios del PCI. Asimismo se demostró que los antagonistas de los receptores de la Angiotensina II protegieron a los injertos no esteatósicos a través de la sobrerregulación de la ERK1/2. Estas estrategias no fueron de utilidad en presencia de esteatosis. En el caso de los injertos hepáticos esteatósicos se ha señalado por primera vez la implicación de la Angiotensina 1-7 (Ang 1-7), otro potente efector del RAS, en la lesión por I/R, demostrando propiedades perjudiciales de la Ang 1-7 no conocidas anteriormente. Además se describió un nuevo mecanismo protector del PCI, en el cual el PCI, a través de AMPK, induce la generación de RBP4, que a su vez reduce la sobre-expresión del PPARγ, protegiendo así a los injertos esteatósicos. Esto señaló por primera vez un efecto beneficioso del RBP4 que no había sido descrito anteriormente en ninguna patología. Adicionalmente, se describieron las siguientes estrategias terapéuticas específicas para los injertos esteatósicos: el antagonista del receptor de la Ang 1-7 redujo el daño trasplante, reduciendo asÍ la lista de espera en TH. Estos hallazgos también podrían contribuir a nuevas aplicaciones del PCI en la práctica clínica en TH, ya que los mecanismos protectores descritos del PCI refuerzan su papel como estrategia protectora y muestran al PCI como una estrategia quirúrgica sencilla que puede ejercer los mismos efectos beneficiosos que varias de las estrategias farmacológicas propuestas.Numerous steatotic livers are discarded as unsuitable for transplantation because of their poor tolerance of ischemia-reperfusion (I/R). The injurious effects of renin-angiotensin system (RAS) and retinol-binding protein 4 (RBP4) in various pathologies are well documented. Ischemic preconditioning (PC) based on brief periods of I/R protects steatotic liver grafts against I/R injury, but the responsible mechanism is poorly understood. The aims of this doctoral thesis were: a) to investigate the role of RAS and RBP4 in I/R injury associated with non-steatotic and steatotic liver transplantation and the benefits of PC in such situations, and b) to examine protective mechanisms of pharmacological or surgical strategies such as PC, able to modulate RAS and RBP4 in both type of grafts. For this, Zucker rats were submitted to liver transplantation with or without preconditioning. Our results showed that Angiotensin II, the main effector of RAS, is involved in I/R injury in non-steatotic grafts, but not in the benefits of PC. Thus, Angiotensin II receptor antagonists protected non-steatotic grafts against damage and this protection was associated with ERK 1/2 over-expression. These strategies were ineffective in steatotic grafts. In the presence of steatosis, Angiotensin 1-7 (Ang 1-7), another effector of RAS, played a role in I/R injury in steatotic grafts. Additionally, it has been described that PC through AMPK, induced RBP4 and this in turn reduced PPARγ, thus protecting steatotic grafts against I/R injury. Results obtained herein also led to describe the following therapeutic strategies specific for steatotic grafts: Ang 1-7 receptor antagonists reduced hepatic damage through reduction of peroxynitrite formation; and therapies that induce RBP4, such as PCI of pretreatment with RBP4, as well as PPARγ antagonists, also protected steatotic grafts against I/R injury in liver transplantation. In terms of clinical application, these therapies might open new avenues for steatotic liver transplantation and improve the initial conditions of donor livers with low steatosis that are available for transplantation. Such therapies could also increase the use of numerous steatotic livers currently discarded for transplantation, thus reducing the risk of death of those patients on liver transplant waiting lists

Are angiotensin II receptor antagonists useful strategies in steatotic and nonsteatotic livers in conditions of partial hepatectomy under ischemia-reperfusion?

We examined whether angiotensin (Ang) II receptor antagonists could be considered a therapeutic strategy in steatotic and nonsteatotic livers in conditions of partial hepatectomy under ischemia-reperfusion (I/R), which is commonly applied in clinical practice to reduce blood loss. We report that Ang II type I receptor (AT1R) antagonist, but not Ang II type II receptor (AT2R) antagonist, increased regeneration in nonsteatotic livers. In the presence of steatosis, both AT1R and AT2R antagonists increased liver regeneration. This effect was stronger when the two were combined. Neither of the Ang II receptor antagonists protected nonsteatotic livers against damage. Only the AT1R antagonist, through nitric oxide inhibition, reduced damage in steatotic livers. The combination of the AT1R and AT2R antagonists in steatotic livers conferred a similar degree of protection to AT1R antagonist alone. Herein, we show that p38 mitogen-activated protein kinase (p38) was a key mechanism in the regeneration induced by the Ang II receptor antagonists in both liver types because when this signaling pathway was inhibited, the beneficial effects of the Ang II receptor antagonists on liver regeneration disappeared, regardless of hepatocyte growth factor or transforming growth factor β-hepatic levels. In conclusion, in conditions of partial hepatectomy under I/R, the AT1R antagonist for nonsteatotic livers and the AT1R and AT2R antagonists for steatotic livers improved regeneration in the remnant liver through p38 activation. In addition, the combination of the AT1R and AT2R antagonists in steatotic livers led to stronger liver regeneration than either antagonists used separately and also provided the same protection against damage as that afforded by AT1R antagonist alone.This work was supported by the Ministerio de Educación y Ciencia (Madrid, Spain) [Grant SAF 2005-00385]; the Ministerio de Sanidad y Consumo (Madrid, Spain) [Grant PIO60021]; and the Generalitat de Catalunya (Barcelona, Spain) [Grant 2005 SGR/00781].Peer reviewe

Trimetazidine: Is it a promising drug for use in steatotic grafts?

Aim: Chronic organ-donor shortage has led to the acceptance of steatotic livers for transplantation, despite the higher risk of graft dysfunction or nonfunction associated with the ischemic preservation period of these organs. The present study evaluates the effects of trimetazidine (TMZ) on an isolated perfused liver model. Methods: Steatotic and non-steatotic livers were preserved for 24 h in the University of Wisconsin (UW) solution with or without TMZ. Hepatic injury and function (transaminases, bile production and sulfobromophthalein (BSP) clearance) and factors potentially involved in the susceptibility of steatotic livers to ischemia-reperfusion (I/R) injury, including oxidative stress, mitochondrial damage, microcirculatory diseases, and ATP depletion were evaluated. Results: Steatotic livers preserved in UW solution showed higher transaminase levels, lower bile production and BSP clearance compared with non-steatotic livers. Alterations in perfusion flow rate and vascular resistance, mitochondrial damage, and reduced ATP content were more evident in steatotic livers. TMZ addition to UW solution reduced hepatic injury and ameliorated hepatic functionality in both types of the liver and protected against the mechanisms potentially responsible for the poor tolerance of steatotic livers to I/R. Conclusion: TMZ may constitute a useful approach in fatty liver surgery, limiting the inherent risk of steatotic liver failure following transplantation. © 2006 The WJG Press. All rights reserved.Supported by the Ministerio de Ciencia y Tecnología (project grants HP 2003-0051, BFI 2002-00704 and BFI 2003-00912) and the Agencia Española de Cooperación Internacional (AECI, project grant 25/03/P) (Madrid, Spain)Peer Reviewe

Effects of Gut Metabolites and Microbiota in Healthy and Marginal Livers Submitted to Surgery

We thank Toffa (Language Advisory Service, University of Barcelona, Barcelona, Spain) for revising the English textMicrobiota is defined as the collection of microorganisms within the gastrointestinal ecosystem. These microbes are strongly implicated in the stimulation of immune responses. An unbalanced microbiota, termed dysbiosis, is related to the development of several liver diseases. The bidirectional relationship between the gut, its microbiota and the liver is referred to as the gut–liver axis. The translocation of bacterial products from the intestine to the liver induces inflammation in different cell types such as Kupffer cells, and a fibrotic response in hepatic stellate cells, resulting in deleterious effects on hepatocytes. Moreover, ischemia-reperfusion injury, a consequence of liver surgery, alters the microbiota profile, affecting inflammation, the immune response and even liver regeneration. Microbiota also seems to play an important role in post-operative outcomes (i.e., liver transplantation or liver resection). Nonetheless, studies to determine changes in the gut microbial populations produced during and after surgery, and affecting liver function and regeneration are scarce. In the present review we analyze and discuss the preclinical and clinical studies reported in the literature focused on the evaluation of alterations in microbiota and its products as well as their effects on post-operative outcomes in hepatic surgery.Ministerio de Ciencia, Innovacion y Universidades (MCIU) Madrid, Spain RTI2018-095114-B-I00European Union (Fondos Feder, "Una manera de hacer Europa")CERCA Program/Generalitat de CatalunyaSecretaria d'Universitats i Recerca Barcelona, Spain 2017SGR-551COST action Programs CA17103 CA1712

Past and future approaches to ischemia-reperfusion lesion associated with liver transplantation

Ischemia-reperfusion (I/R) injury associated with liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem. The present review focuses on the complexity of I/R injury, summarizing conflicting results obtained from the literature about the mechanisms responsible for it. We also review the therapeutic strategies designed in past years to reduce I/R injury, attempting to explain why most of them have not been applied clinically. These strategies include improvements in pharmacological treatments, modifications of University of Wisconsin (UW) preservation solution based on a variety of additives, and gene therapy. Finally, we will consider new potential protective strategies using trimetazidine, 5-amino-4-imidazole carboxamide riboside (AICAR), melatonin, modulators of the renin-angiotensin system (RAS) and the phosphatidylinositol-3-OH kinase (PI3K)-Akt and the p42/p44 extracellular signal-regulated kinases (Erk 1/2) pathway. These strategies have shown promising results for I/R injury but have not been tested in experimental liver transplantation to date. Moreover, we will review ischemic preconditioning, taking into account the recent clinical studies that suggest that this surgical strategy could be appropriate for liver transplantation. © 2006 Elsevier Inc. All rights reserved.Supported by the Ministerio de Educación y Ciencia (project grants BFI 2003-00912, SAF 2005-00385, and Ramón y Cajal research contract for Carmen Peralta) (Madrid, Spain), Ministerio de Asuntos Exteriores (hp2003-0051) and Generalitat de Catalunya (2005SGR/00781 project. We would also like to thank the CONACYT (Mexico D.F., Mexico), AECI (Madrid, Spain) and CAPES Ministério de Educaçao (Brasília, Brazil) for the fellowships awarded to A. Casillas-Ramírez, I. Ben Mosbah and Fernando Ramalho, respectivelyPeer Reviewe

The Role of Neuregulin-1 in Steatotic and Non-Steatotic Liver Transplantation from Brain-Dead Donors

Background. Brain death (BD) and steatosis are key risk factors to predict adverse post-transplant outcomes. We investigated the role of Neuregulin-1 (NRG1) in rat steatotic and non-steatotic liver transplantation (LT) from brain death donors (DBD). Methods: NRG1 pathways were characterized after surgery. Results: NRG1 and p21-activated kinase 1 (PAK1) levels increased in steatotic and non-steatotic grafts from DBDs. The abolishment of NRG1 effects reduced PAK1. When the effect of either NRG1 nor PAK1 was inhibited, injury and regenerative failure were exacerbated. The benefits of the NRG-1-PAK1 axis in liver grafts from DBDs were associated with increased vascular endothelial growth factor-A (VEGFA) and insulin growth factor-1 (IGF1) levels, respectively. Indeed, VEGFA administration in non-steatotic livers and IGF1 treatment in steatotic grafts prevented damage and regenerative failure resulting from the inhibition of either NRG1 or PAK-1 activity in each type of liver. Exogenous NRG1 induced greater injury than BD induction. Conclusions: This study indicates the benefits of endogenous NRG1 in liver grafts from DBDs and underscores the specificity of the NRG1 signaling pathway depending on the type of liver: NRG1-PAK1-VEGFA in non-steatotic livers and NRG1-PAK1-IGF1 in steatotic livers. Exogenous NRG1 is not an appropriate strategy to apply to liver grafts from DBD

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery