Protection against lung damage in reduced-size liver transplantation

Inflammasome-Mediated Inflammation in Liver Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction and liver failure post-transplantation. To date, ischemia-reperfusion injury is an unsolved problem in clinical practice. In this context, inflammasome activation, recently described during ischemia-reperfusion injury, might be a potential therapeutic target to mitigate the clinical problems associated with liver transplantation and hepatic resections. The present review aims to summarize the current knowledge in inflammasome-mediated inflammation, describing the experimental models used to understand the molecular mechanisms of inflammasome in liver ischemia-reperfusion injury. In addition, a clear distinction between steatotic and non-steatotic livers and between warm and cold ischemia-reperfusion injury will be discussed. Finally, the most updated therapeutic strategies, as well as some of the scientific controversies in the field will be described. Such information may be useful to guide the design of better experimental models, as well as the effective therapeutic strategies in liver surgery and transplantation that can succeed in achieving its clinical application.

Propofol attenuated liver transplantation-induced acute lung injury via connexin43 gap junction inhibition

BACKGROUND

Postoperative acute lung injury (ALI) is a severe complication after liver transplantation, which influences patient survival rate obviously. However, its mechanisms are unclear and effective therapies are still lacking. The current study focused on effects of propofol on liver transplantation-induced ALI and whether its underlying mechanism was relative with connexin43 (Cx43) alternation. The authors postulated that endotoxin induced enhancement of Cx43 gap junction (GJ) plays a critical role in mediating post liver transplantation ALI and that pretreatment with the anesthetic propofol, known to inhibit gap junction, can confer effective protection.

METHODS

Male Sprague-Dawley rats underwent autologous orthotopic liver transplantation (AOLT) in the absence or presence of treatments with the selective Cx43 inhibitor, enanthol (0.1 mg/kg) and propofol (50 mg/kg), a commonly used anesthetic in clinical anesthesia. In vitro study, BEAS-2B cells, a kind of lung epithelial cell line expressing Cx43, exposed to lipopolysaccharide (LPS), which mainly contributed to ALI. Function of Cx43 GJ was regulated by Cx43 specific inhibitors, gap26 (300 μM) or enhancer, retinoic acid (10 μM) and two specific siRNAs.

RESULTS

Compared with the sham group, AOLT results in ALI obviously with plasma endotoxin increase. Cx43 inhibition decreased ALI through inflammatory reaction reduction. In vitro studies, LPS-induced BEAS-2B cells damage was attenuated by Cx43 function inhibition, but amplified by enhancement. Another important finding was propofol reduced Cx43 function and protected against LPS-mediated BEAS-2B cells damage or AOLT-induced ALI, mechanisms of which were also associated with inflammatory reaction decrease.

CONCLUSION

Cx43 plays a vital role in liver transplantation-induced ALI. Propofol decreased Cx43 function and protected against ALI in vivo and in vitro. This finding provide a new basis for targeted intervention of organ protection in liver transplantation, even in other kinds of operations.

TLR4 as receptor for HMGB1-mediated acute lung injury after liver ischemia/reperfusion injury

Acute lung injury (ALI) frequently occurs after liver transplantation and major liver surgery. Proinflammatory mediators released by damaged liver after liver ischemia/reperfusion (I/R) injury might contribute to this form of ALI, but the underlying mechanisms have not been well characterized. High-mobility group box protein 1 (HMGB1), a recently identified proinflammatory cytokine, was found to be significantly higher in the serum after liver I/R injury. This study investigated whether HMGB1 was involved as a stimulating factor, and whether its downstream Toll-like receptor 4 (TLR4), p38 mitogen-activated protein kinase (p38MAPK), and activator protein-1 (AP-1) signaling pathways act as mediators in the development of liver I/R injury-induced ALI. Extensive ALI and lung inflammation was induced in a rat model of liver I/R injury. Serum HMGB1 was significantly higher after liver I/R injury, and more importantly, expression of HMGB1 mRNA and protein in the lung tissue was also significantly increased. We further found that liver I/R injury enhanced the expression of TLR4 mRNA and protein, and the activity of p38MAPK and AP-1 in the lung tissue. Inhibition of TLR4 expression in the lung tissue by infection with pGCSIL-GFP-lentivirus-expressing small hairpin RNAs targeting the TLR4 gene (TLR4-shRNA lentivirus) significantly attenuated ALI, lung inflammation, and activity of p38MAPK and AP-1 in the lung tissue. These findings indicate that HMGB1 might contribute to the underlying mechanism for liver I/R injury-induced ALI and that its downstream TLR4, p38MAPK, and AP-1 signaling pathways are potentially important mediators in the development of ALI.

Small-for-Size Liver Transplantation Increases Pulmonary Injury in Rats: Prevention by NIM811

Pulmonary complications after liver transplantation (LT) often cause mortality. This study investigated whether small-for-size LT increases acute pulmonary injury and whether NIM811 which improves small-for-size liver graft survival attenuates LT-associated lung injury. Rat livers were reduced to 50% of original size, stored in UW-solution with and without NIM811 (5 μM) for 6 h, and implanted into recipients of the same or about twice the donor weight, resulting in half-size (HSG) and quarter-size grafts (QSG), respectively. Liver injury increased and regeneration was suppressed after QSG transplantation as expected. NIM811 blunted these alterations >75%. Pulmonary histological alterations were minimal at 5–18 h after LT. At 38 h, neutrophils and monocytes/macrophage infiltration, alveolar space exudation, alveolar septal thickening, oxidative/nitrosative protein adduct formation, and alveolar epithelial cell/capillary endothelial apoptosis became overt in the lungs of QSG recipients, but these alterations were mild in full-size and HSG recipients. Liver pretreatment with NIM811 markedly decreased pulmonary injury in QSG recipients. Hepatic TNFα and IL-1β mRNAs and pulmonary ICAM-1 expression were markedly higher after QSG transplantation, which were all decreased by NIM811. Together, dysfunctional small-for-size grafts produce toxic cytokines, leading to lung inflammation and injury. NIM811 decreased toxic cytokine formation, thus attenuating pulmonary injury after small-for-size LT.

Post liver transplantation acute kidney injury in a rat model of syngeneic orthotopic liver transplantation

Acute kidney injury (AKI) is a frequent complication after liver transplantation (LT). The mechanism of post-LT AKI remains unclear. We used the rat model of syngeneic orthotopic LT (SOLT) to investigate the mechanism of post-LT AKI. We hypothesized that the condition of the graft, rather than intraoperative hemodynamic instability, has an important role in post-LT AKI in the SOLT model. Rats were randomly assigned into four groups: sham-operated group; vessel-clamped group; full-size LT group; and reduced-size LT group. We identified AKI in both full-size and reduced-size LT groups. In addition to renal tubular necrosis and apoptosis, renal peritubular capillary injury was also present. Pathological changes were more severe in the reduced-size than in the full-size LT group. We found that the systemic inflammatory response induced by LT was the initiating factor in post-LT AKI. This is the first study to investigate the pathological mechanism of AKI in an animal model of SOLT. Our results demonstrate that protection of the liver graft and inhibition of the systemic inflammatory response are vital in reducing the risk of post-LT AKI.

Advances in the regulation of liver regeneration

Liver regeneration is known to be a process involving highly organized and ordered tissue growth triggered by the loss of liver tissue, and remains a fascinating topic. A large number of genes are involved in this process, and there exists a sequence of stages that results in liver regeneration, while at the same time inhibitors control the size of the regenerated liver. The initiation step is characterized by priming of quiescent hepatocytes by factors such as TNF-α, IL-6 and nitric oxide. The proliferation step is the step during which hepatocytes enter into the cell cycle's G1 phase and are stimulated by complete mitogens including HGF, TGF-α and EGF. Hepatic stimulator substance, glucagon, insulin, TNF-α, IL-1 and IL-6 have also been implicated in regulating the regeneration process. Inhibitors and stop signals of hepatic regeneration are not well known and only limited information is available. Furthermore, the effects of other factors such as VEGF, PDGF, hypothyroidism, proliferating cell nuclear antigen, heat shock proteins, ischemic-reperfusion injury, steatosis and granulocyte colony-stimulating factor on liver regeneration are also systematically reviewed in this article. A tissue engineering approach using isolated hepatocytes for in vitro tissue generation and heterotopic transplantation of liver cells has been established. The use of stem cells might also be very attractive to overcome the limitation of donor liver tissue. Liver-specific differentiation of embryonic, fetal or adult stem cells is currently under investigation.

Alterations in the proteome of pulmonary alveolar type II cells in the rat after hepatic ischemia-reperfusion

OBJECTIVE

Hepatic ischemia-reperfusion can be associated with acute lung injury. Alveolar epithelial type II cells (ATII) play an important role in maintaining lung homeostasis in acute lung injury.

DESIGN

To study potentially new mechanisms of hepatic ischemia-reperfusion-induced lung injury, we examined how liver ischemia-reperfusion altered the proteome of ATII.

SETTING

Laboratory investigation.

SUBJECTS

Spontaneously breathing male Zucker rats.

INTERVENTIONS

Rats were anesthetized with isoflurane. The vascular supply to the left and medial lobe of the liver was clamped for 75 mins and then reperfused. Sham-operated rats were used as controls. After 8 hrs, rats were killed.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage and differential cell counts were performed, and tumor necrosis factor-alpha and cytokine-induced neutrophil chemotactic factor-1 in plasma were determined by enzyme-linked immunosorbent assay. ATII were isolated, lysed, tryptically digested, and labeled using isobaric tags (iTRAQ). The samples were fractionated by cation exchange chromatography, separated by high-performance liquid-chromatography, and identified using electrospray tandem mass spectrometry. Spectra were interrogated and quantified using ProteinProspector. Quantitative proteomics provided quantitative data for 94 and 97 proteins in the two groups. Significant changes in ATII protein content included 30% to 40% increases in adenosine triphosphate synthases, adenosine triphosphate/adenosine diphosphate translocase, and catalase (all p < .001). Following liver ischemia-reperfusion, there was also a significant increase in the percentage of neutrophils in bronchoalveolar lavage (48% +/- 26%) compared with sham-operated controls (5% +/- 3%) (p < .01), and plasma tumor necrosis factor-alpha levels were also significantly increased.

CONCLUSIONS

The proteins identified by quantitative proteomics indicated significant changes in moderators of cell metabolism and host defense in ATII. These findings provide new insights into possible mechanisms responsible for hepatic ischemia-reperfusion-related acute lung injury and suggest that ATII cells in the lung sense and respond to hepatic injury.

Role of ischaemic preconditioning in liver regeneration following major liver resection and transplantation

Liver ischaemic preconditioning (IPC) is known to protect the liver from the detrimental effects of ischaemic-reperfusion injury (IRI), which contributes significantly to the morbidity and mortality following major liver surgery. Recent studies have focused on the role of IPC in liver regeneration, the precise mechanism of which are not completely understood. This review discusses the current understanding of the mechanism of liver regeneration and the role of IPC in this setting. Relevant articles were reviewed from the published literature using the Medline database. The search was performed using the keywords “liver”, “ischaemic reperfusion”, “ischaemic preconditioning”, “regeneration”, “hepatectomy” and “transplantation”. The underlying mechanism of liver regeneration is a complex process involving the interaction of cytokines, growth factors and the metabolic demand of the liver. IPC, through various mediators, promotes liver regeneration by up-regulating growth-promoting factors and suppresses growth-inhibiting factors as well as damaging stresses. The increased understanding of the cellular mechanisms involved in IPC will enable the development of alternative treatment modalities aimed at promoting liver regeneration following major liver resection and transplantation.

Liver and lung late alterations following hepatic reperfusion associated to ischemic preconditioning orN-acetylcysteine

This study aimed the effect of n-acetylcysteine or ischemic preconditioning in hepatic and pulmonary damage after liver ischemia-reperfusion injury. Twenty-four male Wistar-EPM rats were assigned into four groups: (IR) Hepatic ischemia-reperfusion; (IPC) IPC achieved before hepatic ischemia; (NAC) Animals received NAC pretreatment; and Sham operated group. After 24 h of hepatic reperfusion, blood, liver, and pulmonary samples were evaluated. Nonparametric tests were used (P <or= 0.05). Aspartate aminotransferase levels were similar among experimental groups. Lower alanine aminotrasnferase levels were observed in sham group (P = 0.04). IPC and NAC groups prevented from necrosis (P = 0.027), apoptosis (P = 0.003), and microvesicular steatosis (P = 0.0007), but not from neutrophil infiltration in liver tissue. IPC and NAC treatment reduced alveolar septal edema (P = 0.014), but did not prevent from neutrophil infiltration or vascular congestion. In conclusion, IPC and NAC attenuated hepatic and pulmonary damage after hepatic ischemia-reperfusion injury.