George Dikdan

Hepatic steatosis and liver transplantation current clinical and experimental perspectives.

Hepatic steatosis has diverse clinical implications in liver transplantation, hepatology, and hepatic surgery. This review will focus on issues related to liver transplantation; the prevalence and diagnosis of hepatic steatosis in potential donors, the impact of steatosis on graft and recipient survival after transplantation and on donor liver supply. In addition, we will review available animal models to investigate this problem and the data in humans and in experimental animals that help understand how steatosis leads to increased liver ischemia/reperfusion (I/RP) injury.

OXYGEN FREE RADICALS : EFFECT ON RED CELL DEFORMABILITY IN SEPSIS

ObjectiveTo examine the effect of α-tocopherol, a free radical scavenger, on RBC deformability, mixed venous hemoglobin saturation (Svo2), arterial-venous oxygen content difference (C[a-v]o2), pHv, and survival during sepsis. DesignRandomized controlled study. InterventionsSprague-Dawley rats were randomized to three groups: sham, cecal ligation and puncture, or α-tocopherol/cecal ligation and puncture (pretreatment with α-tocopherol before cecal ligation and puncture). Measurements and Main ResultsThe cecal ligation and puncture group had a significantly (p < .05) higher Svo2 and lower C(a-v)o2, pHv, and survival rate when compared with α-tocopherol/cecal ligation and puncture and sham groups. No difference in pHa existed between groups. ConclusionsThe α-tocopherol treatment improves survival in sepsis. RBC deformability during sepsis is prevented by α-tocopherol, suggesting that free radicals may cause the decrease in RBC deformability. This study provides indirect evidence that decreased RBC deformability may play a role in the physiologic peripheral shunting and decreased mi-crocirculatory flow that occurs during sepsis. (Crit Care Med 1991; 19:732)

Trauma-hemorrhagic shock mesenteric lymph from rat contains a modified form of albumin that is implicated in endothelial cell toxicity.

It has been proposed that factors originating from the gut after severe trauma/shock are introduced into the systemic circulation through the mesenteric lymphatics and are responsible for the cellular injury and inflammation that culminates in acute multiple organ dysfunction syndrome (MODS). Indeed, it has been shown that lymph collected from shocked but not sham-shocked animals causes endothelial cell death, neutrophil activation, and bone marrow (BM) colony growth suppression in vitro. In an attempt to isolate the factor(s) in lymph responsible for endothelial cell toxicity, lymph from shock and sham animals was fractionated by solid phase extraction (SPE) and ion exchange chromatography (IEX). The separation of shock lymph by both methodologies yielded two fractions having major detectable toxicity to endothelial cells, whereas no toxicity was detected from sham lymph separations by either method. Subsequent analysis of each SPE toxic fraction by gel electrophoresis and mass spectrometry suggests the toxicity is associated with a modified form of rat serum albumin (mod-RSA) and multiple lipid-based factors. Therefore, we have been able to demonstrate by two different separation techniques that shock lymph contains two or more factors that may account for the toxicity to endothelial cells. Further investigations are needed to determine the type of RSA modification and the identity of the lipid factors and their role in MODS.

Review of randomized clinical trials of donor management and organ preservation in deceased donors: opportunities and issues.

Abstract Given the static number of deceased donors, improvements in donor management and organ preservation to increase the number and quality of organs transplanted per donor are more pressing. Because controlled trials provide the best evidence, we conducted a review of English-language literature of trials in donor management and organ preservation to provide a compendium and to promote additional discussion and studies. Eighty-seven reports were retrieved: 13 on hemodynamic and fluid management, 7 on immunosuppressants, 12 on preconditioning, 34 on preservation fluids, and 21 on pulsatile perfusion. Sixteen studies are ongoing. Although hormonal therapy is used widely, additional studies are needed to determine the benefit of thyroid hormone and insulin replacement and to optimize steroid regimens. Dopamine’s success in reducing kidney delayed graft function highlights the opportunity for additional preconditioning trials of remote ischemia, gases, opioids, and others. More rapid progress requires addressing unique barriers in consent and research approval, legal constraints precluding research in cardiac death donors, and streamlining collaboration of multiple stakeholders. With little interest from industry, federal funding needs to be increased. While the University of Wisconsin solution still reigns supreme, several promising preservative solutions and additives with not only biophysical but also pharmacological effects are on the cusp of phase 1 to 2 trials. After nearly three decades of uncertainty, the recent success of a European trial has reenergized the topic not only of machine preservation of the kidney but also of other organs evident by trials in progress. However, the costs of such technical innovations merit the burden of rigorous proof from controlled trials.

Organ distribution of radiolabeled enteric Escherichia coli during and after hemorrhagic shock

Translocation of intestinal bacteria to the blood during hemorrhagic shock (HS) has been confirmed in rats and humans. The current study was designed to trace the path of translocated intestinal bacteria in a murine HS model. Thirty-one rats were gavaged with 1,000,000 counts of viable 14C oleic acid-labeled Escherichia coli. Forty-eight hours later the animals were bled to 30 mmHg until either 80% of their maximal shed blood was returned or 5 hours of shock had elapsed and they were resuscitated with Ringers lactate as previously described. Control animals were cannulated but not shocked. Eight rats immediately after shock and resuscitation, 6 rats 24 hours after shock, 3 rats 48 hours after shock, and 4 animals that died in shock had their heart, lung, liver, spleen, kidney, and serum harvested, cultured, and radioactive content measured. Translocated enteric bacteria are found primarily in the lung immediately after shock with redistribution to the liver and kidney 24 hours later. Animals surviving to 48 hours were capable of eliminating the majority of the bacteria from their major organ systems. Positive cultures for E. coli were also found in the blood, lung, liver, and kidney. We speculate that the inflammatory response stimulated by the bacteria in these organs may contribute to the multiple-organ failure syndrome seen after HS.

Ischemic preconditioning of the liver: A few perspectives from the bench to bedside translation

Utilization of ischemic preconditioning to ameliorate ischemia/reperfusion injury has been extensively studied in various organs and species for the past two decades. While hepatic ischemic preconditioning in animals has been largely beneficial, translational efforts in the two clinical contexts—liver resection and decreased donor liver transplantation—have yielded mixed results. This review is intended to critically examine the translational data and identify some potential reasons for the disparate clinical results, and highlight some issues for further studies. Liver Transpl 14:1569–1577, 2008.

Albumin peptide : A molecular marker for trauma/hemorrhagic-shock in rat mesenteric lymph

Vascular permeability and endothelial cell damage has been shown to occur in rats subjected to trauma with hemorrhagic-shock. Although the factors responsible for the endothelial cell injury are unknown, it has been hypothesized that toxic factors produced in response to hemorrhagic-shock originate in the gut and are absorbed into the mesenteric lymphatics. Consistent with this hypothesis, it has been shown that lymph collected from animals subjected to trauma with hemorrhagic-shock (T/HS) results in a marked decrease in endothelial cell viability both in vitro and in vivo. We therefore compared the lymph collected pre-T/HS to samples collected during, and up to 3h post-T/HS in order to identify a factor present or increased in post-T/HS lymph. This analysis revealed that a single cationic peptide band was significantly increased in post-T/HS lymph, but not in lymph from control animals subjected to trauma without hemorrhagic-shock (T/SS). This peptide was subsequently identified as the N-terminal 24 amino acids of rat serum albumin (RSA) by mass spectrometry and amino acid sequencing. Although the measured increase in the albumin peptide correlates with detectable shock lymph-induced endothelial cell toxicity, the peptide was not toxic to endothelial cells. We therefore propose that the significant increase in the albumin peptide is a marker for post-T/HS lymph-induced endothelial cell toxicity.

Role of eicosanoids and white blood cells in the beneficial effects of limited reperfusion after ischemia-reperfusion injury in skeletal muscle

Limiting the rate of reperfusion blood flow has been shown to be beneficial locally in models of ischemia-reperfusion injury. We investigated the effects of this on eicosanoids (thromboxane B2, 6-keto-PGF1 alpha, and leukotriene B4), white blood cell activation, and skeletal muscle injury as quantitated by triphenyltetrazolium chloride and technetium-99m pyrophosphate after ischemia-reperfusion injury in an isolated gracilis muscle model in 16 anesthetized dogs. One gracilis muscle in each dog was subjected to 6 hours of ischemia followed by 1 hour of limited reperfusion and then by a second hour of normal reperfusion. The other muscle was subjected to 6 hours of ischemia followed by 2 hours of normal reperfusion. Six dogs each were used as normal reperfusion controls (NR) and limited reperfusion controls (LR), with 5 dogs being treated with a thromboxane synthetase inhibitor (LR/TSI) and another five with a leukotriene inhibitor (LR/LI). LR in all three groups (LR, LR/TSI, and LR/LI) showed a benefit in skeletal muscle injury as measured by triphenyltetrazolim chloride and technetium-99m pyrophosphate when compared with NR. However, there was no significant difference between the groups with LR regarding eicosanoid levels and white blood cell activation when compared with NR. These results demonstrate that LR produces benefits by mechanisms other than those dependent upon thromboxane A2, prostacyclin, or white blood cell activation.

Prerecovery liver biopsy in the brain-dead donor: a case-control study of logistics, safety, precision, and utility.

Prerecovery liver biopsy (PLB) can potentially to decrease futile recovery and increase utilization of marginal brain‐dead donor (BDD) livers. A case‐control study was conducted to examine the logistics, safety, histological precision, and liver utilization associated with PLB in BDDs. Twenty‐three cases between January 2008 and January 2013 were compared to 2 groups: 48 sequential and 69 clinically matched controls. Compared to the sequential controls, the cases were older (53 versus 46 years), heavier (30.2 versus 25.8 kg/m2), had higher prevalences of hypertension (78.3% versus 44.7%) and alcohol use (56.5% versus 23.4%), and a lower United Network for Organ Sharing expected organ yield (0.73 versus 0.81 livers/donor; P < 0.05 for all). Baseline characteristics were similar between cases and clinical controls. Donor management time was longer for the cases (22.4 hours) versus sequential controls (16.5 hours, P = 0.01) and clinical controls (15.9 hours, P = 0.01). Complications for cases (8.7%) were not different from either group of controls (18.8% for sequential controls, P = 0.46; 17.4% for clinical controls, P = 0.50). The agreement between the donor hospital and study pathologists was substantial regarding evaluation of steatosis (κ = 0.623) and fibrosis (κ = 0.627) and moderate regarding inflammation (κ = 0.495). The proportions of livers that were transplanted were similar for the cases and the clinical controls (60.9% versus 59.4%). In contrast, the proportion of donors for whom liver recovery was not attempted was higher (30.4% versus 8.7%), and the proportion of attempted liver recoveries that did not result in transplantation was lower (8.7% versus 31.9%). These differences were significant at P = 0.009. Overall, PLB is logistically feasible with only a minimal delay and is safe, its interpretation at donor hospitals is reproducible, and it appears to decrease futile liver recovery. Liver Transpl 20:237‐244, 2014.

Influence of pH on the modification of thiols by carbamoylating agents and effects on glutathione levels in normal and neoplastic cells

SummaryIn previous studies, we have suggested that the selective inhibitory effect of sodium cyanate (NaOCN) on hepatoma metabolism may be due to the lower pH observed in tumors relative to normal tissues. Lower pH might enhance the action of NaOCN by increasing the formation of isocyanic acid and carbamoylation of sulfhydryl groups. In the present work, studies were conducted on the effect of pH on the carbamoylation of sulfhydryl groups. The data indicated that carbamoylation of the sulfhydryl group of glutathione by NaOCN was enhanced by decreasing the pH from 7.4 to 6.6. A less pH-dependent response was observed with organic isocyanates. However, all reactions were reversible after the pH was increased by the addition of base. Kinetic studies showed that the rate of the reaction is very rapid, a maximal effect occurring within the first 10 min. Dose-dependent modifications of cellular glutathione by NaOCN and organic isocyanates were observed in human HT29 colon tumor cells, rat HTC hepatoma cells, and rat hepatocytes. The rate of carbamoylation of the glutathione sulfhydryl group in cells was similar to that of pure glutathione (GSH). The effect of buthionine sulfoximine on GSH levels in cells was at least as great as that of sodium cyanate, but only the latter showed inhibitory effects on macromolecular synthesis; these were very rapid, pH-dependent, and reversible in tumor cells. Our results suggest that cellular sulfhydryl group(s) other than that of GSH might be involved in the effect of NaOCN on macromolecular synthesis.