Protective effect of reduced glutathione and venous systemic oxygen persufflation on rat steatotic graft following liver transplantation

Taurine as Antioxidant in a Novel Cell- and Oxygen Carrier-Free Perfusate for Normothermic Machine Perfusion of Porcine Kidneys

Donor organ-shortage has resulted in the increased use of marginal grafts; however, normothermic machine perfusion (NMP) holds the potential for organ viability assessment and restoration of marginal grafts prior to transplantation. Additionally, cell-, oxygen carrier-free and antioxidants-supplemented solutions could potentially prevent adverse effects (transfusion reactions, inflammation, hemolysis), associated with the use of autologous packed red blood cell (pRBC)-based perfusates. This study compared 6 h NMP of porcine kidneys, using an established pRBC-based perfusate (pRBC, n = 7), with the novel cell- and oxygen carrier-free organ preservation solution Ecosol, containing taurine (Ecosol, n = 7). Despite the enhanced tissue edema and tubular injury in the Ecosol group, related to a suboptimal molecular mass of polyethylene glycol as colloid present in the solution, functional parameters (renal blood flow, intrarenal resistance, urinary flow, pH) and oxygenation (arterial pO₂, absence of hypoxia-inducible factor 1-alpha) were similar to the pRBC group. Furthermore, taurine significantly improved the antioxidant capacity in the Ecosol group, reflected in decreased lactate dehydrogenase, urine protein and tubular vacuolization compared to pRBC. This study demonstrates the feasibility of 6 h NMP using a taurine containing, cell- and oxygen carrier-free perfusate, achieving a comparable organ quality to pRBC perfused porcine kidneys.

Persufflation—Current State of Play

With the ever-increasing disparity between the number of patients waiting for organ transplants and the number organs available, some patients are unable to receive life-saving transplantation in time. The present, widely-used form of preservation is proving to be incapable of maintaining organ quality during long periods of preservation and meeting the needs of an ever-changing legislative and transplantation landscape. This has led to the need for improved preservation techniques. One such technique that has been extensively researched is gaseous oxygen perfusion or Persufflation (PSF). This method discovered in the early 20th century has shown promise in providing both longer term preservation and organ reconditioning capabilities for multiple organs including the liver, kidneys, and pancreas. PSF utilises the organs own vascular network to provide oxygen to the organ tissue and maintain metabolism during preservation to avoid hypoxic damage. This review delves into the history of this technique, its multiple different approaches and uses, as well as in-depth discussion of work published in the past 15 years. Finally, we discuss exciting commercial developments which may help unlock the potential for this technique to be applied at scale.

l-Cysteine augments microtubule-associated protein 2 levels and enhances antioxidant activity in rats following traumatic brain injury

l-Cysteine is a well-known sulfur-containing non-essential amino acid that can be oxidized to cysteine, which possesses a variety of pharmacological actions, including antioxidant and anti-inflammatory activities. Traumatic brain injury (TBI) is defined as a closed head injury that leads to temporary alterations in neural function and further leads to pathophysiological processes. In the present study, rats were categorized into sham, control, 100 mg/kg l-cysteine, and 200 mg/kg l-cysteine groups and then the levels of lipid peroxidation, reduced glutathione (GSH), catalase, superoxide dismutase (SOD), reactive oxygen species (ROS), and mRNA and protein expression of microtubule-associated protein 2 (MAP2) were determined. Following supplementation with l-cysteine, there were reductions in lipid peroxidation and ROS levels, whereas catalase, SOD, and GSH levels increased. Additionally, the mRNA expression of MAP2 in the control rats was drastically reduced by 67% compared to the sham rats. However, supplementation with 100 mg/kg of l-cysteine and 200 mg/kg of l-cysteine significantly increased MAP2 mRNA expression by 84.8% and 169.7%, respectively. Similarly, MAP2 protein expression was drastically reduced by 61% in control rats compared to sham rats, but supplementation with 100 mg/kg of l-cysteine and 200 mg/kg of l-cysteine significantly increased MAP2 protein expression by 41% and 94.9%, respectively. Taken together, these data suggest that supplementation with l-cysteine significantly reduced lipid peroxidation and ROS levels, but increased antioxidant levels and the mRNA and protein expression of MAP2 in rats following TBI.

L-Lysine protects against sepsis-induced chronic lung injury in male albino rats

Sepsis is a severe, life-threatening condition primarily caused by the cellular response to infection. Sepsis leads to increased tissue damage and mortality in patients in the intensive care unit. L-Lysine is an essential amino acid required for protein biosynthesis and is abundant in lamb, pork, eggs, red meat, fish oil, cheese, beans, peas, and soy. Male albino rats were divided into sham, control, 10-mg/kg bwt L-lysine, and 20-mg/kg bwt L-lysine groups. At the end of treatment, we determined the levels of oxidative and inflammatory markers, myeloperoxidase (MPO) and catalase activities, total cell count, the wet/dry ratio of lung tissue, and total protein content. Furthermore, the effect of L-lysine on the cellular architecture of lung tissue was evaluated. L-Lysine significantly reduced the magnitude of lipid peroxidation; total protein content; wet/dry ratio of lung tissue; tumor necrosis factor-alpha, interleukin-8, and macrophage inhibitory factor levels; MPO activity; and total cell, neutrophil, and lymphocyte counts, and it increased the reduced glutathione levels and the glutathione peroxidase, superoxide dismutase, and catalase activities. A normal cellular architecture was noted in rats in the sham group, whereas proinflammatory changes, such as edema and neutrophilic infiltration, were detected in rats in the control group. L-lysine significantly ameliorated these proinflammatory changes. Thus, L-lysine has the potential for the treatment of sepsis-induced CLI.

Mechanistic evaluation of anti-arthritic activity of β-methylphenylalanine in experimental rats

Arthritis is a common chronic joint disorder, with general symptoms including stiffness and joint pain. β-methylphenylalanine is a well-known non-proteogenic unnatural amino acid. This study analyzes the anti-arthritic activity of β-methylphenylalanine in experimental rats. The experimental groups were as follows: group I, sham; group II, control; group III, 100 mg/kg of β-methylphenylalanine; and group IV, 200 mg/kg of β-methylphenylalanine. Lipid peroxidation, glutathione peroxidase (Gpx), reduced glutathione (GSH), superoxide dismutase (SOD), catalase, prostaglandin E₂ (PGE₂), matrix metalloproteinase-3 (MMP-3), ceruloplasmin, zinc, copper, mRNA, and protein expression of inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-κB) were determined. Supplementation with β-methylphenylalanine significantly reduced lipid peroxidation, copper, PGE₂ and MMP-3 levels, whereas GSH, Gpx, catalase, SOD and zinc levels were increased. Supplementation with β-methylphenylalanine significantly reduced NF-κB mRNA expression by 26% and 47.8% in groups III and IV, respectively (P < 0.045), while iNOS mRNA expression was reduced by 14.3 and 47.6% in groups III and IV, respectively. NF-κB and iNOS protein expression increased by 160% and 120% respectively, in the control rats compared to the sham rats. However, supplementation with β-methylphenylalanine significantly reduced NF-κB protein expression by 27% and 50% in groups III and IV, respectively, while iNOS protein expression was reduced by 22.7% and 45.4% in groups III and IV, respectively. Taken together, our data show that supplementation of β-methylphenylalanine was effective against arthritis in a rat model.

Donor liver quality after hypovolemic shock and venous systemic oxygen persufflation in an experimental animal model

BACKGROUND

The ever growing demand for liver transplantation inevitably necessitates an expansion of the donor pool. Utilization of "shock organs" is considered suboptimal to date while the associated outcome has hardly been investigated.

MATERIALS AND METHODS

Male Wistar rats underwent a period of 30 min of hypovolemic shock. After 24 h livers were explanted and prior to reperfusion underwent either 18 h of cold storage (CS; N = 6) or 17 h of CS followed by 60 min venous systemic oxygen persufflation (VSOP; N = 6). The outcome of "shock organs (SHBD)" was compared to heart-beating donor (HBD; N = 12) as positive control and non-heart-beating donor (NHBD; N = 12) as negative control animal groups. Liver function was assessed by measuring enzyme release (AST, ALT, LDH), bile production, portal vein pressure and hepatic oxygen uptake during reperfusion. For reperfusion, the isolated perfused rat liver system was used.

RESULTS

Liver function was severely limited in NHBD group compared to HBD organs after 18 h of CS (e.g., AST; HBD: 32.25 ± 7.25 U/l vs. NHBD: 790 ± 414.56 U/l; p < 0.005). VSOP improved liver function of NHBD organs significantly (AST; NHBD + VSOP: 333.6 ± 149.1 U/l; p < 0.005). SHBD organs showed a comparable outcome to HBD and clearly better results than NHBD organs after 18 h of CS (AST; SHBD: 76.4 ± 21.9 U/l). After 17 h of CS accompanied by 60 min VSOP, no improvement concerning liver function and integrity of SHBD organs was observed while the results were severely deteriorated by VSOP resulting in higher enzyme release (AST; SHBD + VSOP: 213 ± 61 U/l, p < 0.001), higher portal vein pressure (SHBD: 10.8 ± 1.92 mm Hg vs. SHBD + VSOP: 21.6 ± 8.8 mm Hg; p < 0.05) and lower hepatic oxygen uptake (SHBD: 321.75 ± 3.87 ml/glw/min vs. SHBD + VSOP: 395.8 ± 46.64 ml/glw/min, p < 0.05) at 24 h.

CONCLUSIONS

Our data suggest that the potential of "shock organs" within liver transplantation may be underestimated. If our findings are reproducable in humans, SHBD grafts should be considered as a valuable source for expanding the thus far limited donor pool.

Comparison of Aerobic Preservation by Venous Systemic Oxygen Persufflation or Oxygenated Machine Perfusion of Warm-Ischemia-Damaged Porcine Kidneys

Background/Aim: The global shortage of donor organs for transplantation has necessitated the expansion of the organ pool through increased use of organs from less ideal donors. Venous systemic oxygen persufflation (VSOP) and oxygenated machine perfusion (OMP) have previously demonstrated beneficial results compared to cold storage (CS) in the preservation of warm-ischemia-damaged kidney grafts. The aim of this study was to compare the efficacy of VSOP and OMP for the preservation of warm-ischemia-damaged porcine kidneys using the recently introduced Ecosol preservation solution compared to CS using Ecosol or histidine-tryptophan-ketoglutarate solution (HTK). Materials and Methods: Kidneys from German Landrace pigs (n = 5/group) were retrieved and washed out with either Ecosol or HTK after 45 min of clamping of the renal pedicle. As controls, kidneys without warm ischemia, cold stored for 24 h in HTK, were employed. Following 24 h of preservation by VSOP, OMP, CS-Ecosol, or CS-HTK, renal function and damage were assessed during 1 h using the isolated perfused porcine kidney model. Results: During reperfusion, urine production was significantly higher in the VSOP and OMP groups than in the CS-HTK group; however, only VSOP could demonstrate lower urine protein concentrations and fractional excretion of sodium, which did not differ from the non-warm-ischemia-damaged control group. VSOP, CS-Ecosol, and controls showed better maintenance of the acid-base balance than CS-HTK. Reduced lipid peroxidation, as reflected in postreperfusion tissue thiobarbituric acid-reactive substance levels, was observed in the VSOP group compared to the OMP group, and the VSOP and CS-Ecosol groups had concentrations similar to the controls. The ratio of reduced to oxidized glutathione was higher in the VSOP, OMP, and CS-Ecosol groups than in the CS-HTK group and controls, with a higher ratio in the VSOP than in the OMP group. Conclusion: VSOP was associated with mitigation of oxidative stress in comparison to OMP and CS. Preservation of warm-ischemia-damaged porcine kidneys by VSOP was improved compared to OMP and CS, and was comparable to preservation of non-warm-ischemia-damaged cold-stored kidneys.

Liver protection strategies in liver transplantation

BACKGROUND

Liver transplantation is the therapy of choice for patients with end-stage liver diseases. However, the gap between the low availability of organs and high demand is continuously increasing. Innovative strategies for organ protection are necessary to expand donor pool and to achieve better outcomes for liver transplantation. The present review analyzed and compared various strategies of liver protection.

DATA SOURCES

Databases such as PubMed, Embase and Ovid were searched for the literature related to donor liver protection strategies using following key words: "ischemia reperfusion injury", "graft preservation", "liver transplantation", "machine perfusion" and "conditioning". Of the 146 studies identified, only those with cutting edge strategies were analyzed.

RESULTS

A variety of therapeutic approaches were proposed to alleviate graft ischemia/reperfusion injury, which included static cold storage, machine perfusion (hypothermic, normothermic and subnormothermic), manual conditioning (pre, post and remote), and pharmacological conditioning. Evidences from animal experiments and clinical trials suggested that all these strategies could potentially protect liver graft; however, their clinical applications are limited partially due to their own disadvantages.

CONCLUSIONS

There are a plenty of methods suggested to decrease the degree of donor liver transplantation-related injury. However, none of these approaches is perfect in clinical practice. More translational researches (molecular and clinical studies) are needed to improve the techniques in liver graft protection.

"Resuscitation" of marginal liver allografts for transplantation with machine perfusion technology

As the rate of medically suitable donors remains relatively static worldwide, clinicians have looked to novel methods to meet the ever-growing demand of the liver transplant waiting lists worldwide. Accordingly, the transplant community has explored many strategies to offset this deficit. Advances in technology that target the ex vivo "preservation" period may help increase the donor pool by augmenting the utilization and improving the outcomes of marginal livers. Novel ex vivo techniques such as hypothermic, normothermic, and subnormothermic machine perfusion may be useful to "resuscitate" marginal organs by reducing ischemia/reperfusion injury. Moreover, other preservation techniques such as oxygen persufflation are explored as they may also have a role in improving function of "marginal" liver allografts. Currently, marginal livers are frequently discarded or can relegate the patient to early allograft dysfunction and primary non-function. Bench to bedside advances are rapidly emerging and hold promise for expanding liver transplantation access and improving outcomes.

Strategies to rescue steatotic livers before transplantation in clinical and experimental studies

The shortage of donor livers has led to an increased use of organs from expanded criteria donors. Included are livers with steatosis, a metabolic abnormality that increases the likelihood of graft complications post-transplantation. After a brief introduction on the etiology, pathophysiology, categories and experimental models of hepatic steatosis, we herein review the methods to rescue steatotic donor livers before transplantation applied in clinical and experimental studies. The methods span the spectrum of encouraging donor weight loss, employing drug therapy, heat shock preconditioning, ischemia preconditioning and selective anesthesia on donors, and the treatment on isolated grafts during preservation. These methods work at different stages of transplantation process, although share similar molecular mechanisms including lipid metabolism stimulation through enzymes or nuclear receptor e.g., peroxisomal proliferator-activated receptor, or anti-inflammation through suppressing cytokines e.g., tumor necrosis factor-α, or antioxidant therapies to alleviate oxidative stress. This similarity of molecular mechanisms implies possible future attempts to reinforce each approach by repeating the same treatment approach at several stages of procurement and preservation, as well as utilizing these alternative approaches in tandem.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Multidrug donor preconditioning protects steatotic liver grafts against ischemia-reperfusion injury

BACKGROUND

Graft dysfunction of steatotic livers (SL) still remains a major challenge in liver transplantation. Different mechanisms are thought to be involved in the impaired tolerance of SL to ischemia-reperfusion injury. Thus, different pharmacologic strategies may need to be combined to effectively protect SL and to reduce graft dysfunction after transplantation. Therefore, we analyzed the effectiveness of a multidrug donor preconditioning (MDDP) procedure to protect SL from cold ischemia-reperfusion injury.

METHODS

Liver steatosis was induced by a high-carbohydrate, fat-free diet. A total of 24 Sprague-Dawley rats were divided into 3 groups (n = 8 each), including a control group with nonsteatotic livers (Con), a vehicle-treated SL group (SL-Con), and a SL group undergoing MDDP (SL-MDDP), including pentoxyphylline, glycine, deferoxamine, N-acetylcysteine, erythropoietin, melatonin, and simvastatin. MDDP was applied before liver perfusion with 4°C histidine-tryptophan-ketoglutarate (HTK) solution and organ harvest. After 24 hours of cold storage in HTK, postischemic reperfusion was performed in an isolated liver reperfusion model using 37°C Krebs-Henseleit bicarbonate buffer.

RESULTS

After 60 minutes of reperfusion, SL showed a significant reduction of bile flow as well as a marked increase of liver enzyme levels and apoptotic cell death compared with Con. This was associated with an increased malondialdehyde formation, interleukin-1 production, and leukocytic tissue infiltration. MDDP completely abolished the inflammatory response and was capable of significantly reducing parenchymal dysfunction and injury.

CONCLUSIONS

MDDP decreases SL injury after cold storage and reperfusion. The concept of MDDP as a simple and safe preoperative regime, thus may be of interest in clinical use, expanding the donor pool from marginal donors.