Raffinose improves the function of rat pulmonary grafts stored for twenty-four hours in low-potassium dextran solution

L-Alanyl-L-Glutamine Alleviated Ischemia-Reperfusion Injury and Primary Graft Dysfunction in Rat Lung Transplants

BACKGROUND

Concern of ischemia-reperfusion injury reduces utilization of donor lungs. We hypothesized adding L-alanyl-L-glutamine (L-AG) to preservation solution may protect donor lungs from ischemia-reperfusion injury through its multiple cytoprotective effects.

METHODS

A lung transplantation cell culture model was used on human lung epithelial cells and pulmonary microvascular endothelial cells, and the effects of adding different concentrations of L-AG on basic cellular function were tested. Rat donor lungs were preserved at 4 °C with 8 mmol/L L-AG for 12 h followed by 4 h reperfusion or monitored for 3 d. Lung function, lung histology, inflammation, and cell death biomarker were tested. Computerized tomography scan was used and metabolomic analysis was performed on lung tissues.

RESULTS

Cold preservation with L-AG improved cell viability and inhibited apoptosis in cell culture. Rat donor lungs treated with L-AG during cold storage showed decreased peak airway pressure, higher dynamic compliance and oxygenation ability, reduced lung injury, apoptosis, and oxidative stress during reperfusion. L-AG treatment significantly changed 130 metabolites during reperfusion, with enhanced amino acid biosynthesis and tricarboxylic acid cycle. Furthermore, cold storage with L-AG decreased primary graft dysfunction grade, improved oxygenation, reduced pulmonary atelectasis, sign of infection, and pneumothorax in a rat left lung transplant 3-d survival model.

CONCLUSIONS

Adding L-AG to cold preservation solution reduced lung injury and alleviated primary graft dysfunction by inhibiting inflammation, oxidative stress, and cell death with modified metabolic activities.

Therapeutic benefits of nitric oxide in lung transplantation

Lung transplantation is an evolutionary procedure from its experimental origin in the twentieth century and is now recognized as an established and routine life-saving intervention for a variety of end-stage pulmonary diseases refractory to medical management. Despite the success and continuous refinement in lung transplantation techniques, the widespread application of this important life-saving intervention is severely hampered by poor allograft quality offered from donors-after-brain-death. This has necessitated the use of lung allografts from donors-after-cardiac-death (DCD) as an additional source to expand the pool of donor lungs. Remarkably, the lung exhibits unique properties that may make it ideally suitable for DCD lung transplantation. However, primary graft dysfunction (PGD), allograft rejection and other post-transplant complications arising from unavoidable ischemia-reperfusion injury (IRI) of transplanted lungs, increase morbidity and mortality of lung transplant recipients annually. In the light of this, nitric oxide (NO), a selective pulmonary vasodilator, has been identified as a suitable agent that attenuates lung IRI and prevents PGD when administered directly to lung donors prior to donor lung procurement, or to recipients during and after transplantation, or administered indirectly by supplementing lung preservation solutions. This review presents a historical account of clinical lung transplantation and discusses the lung as an ideal organ for DCD. Next, the author highlights IRI and its clinical effects in lung transplantation. Finally, the author discusses preservation solutions suitable for lung transplantation, and the protective effects and mechanisms of NO in experimental and clinical lung transplantation.

Using nutrient-rich solutions and adding multiple cytoprotective agents as new strategies to develop lung preservation solutions

Commonly, donor lungs are preserved with low-potassium dextran glucose solution at low temperature. We hypothesized that adding nutrients and/or cytoprotective agents to preservation solutions improves donor lung quality. Human lung epithelial cells and human pulmonary microvascular endothelial cells cultured at 37°C with serum containing medium were switched to designated testing solutions at 4°C with 50% O2 for different cold ischemic time, followed by switching back to serum containing culture medium at 37°C to simulate reperfusion. We found that bicarbonate buffer system should be avoided in preservation solution. When pH was maintained at physiological levels, cell culture media showed better cell survival than in low-potassium dextran glucose solution. Phosphate-buffered cell culture media were further improved by adding colloid dextran 40. When rat donor lungs were preserved at 4°C for 24 h, phosphate-buffered Roswell Park Memorial Institute-1640 medium [RPMI-1640(p)] plus dextran 40 or adding cytoprotective agents (alpha 1 antitrypsin, raffinose, and glutathione) to low-potassium dextran glucose solution prevented alveolar wall swelling, apoptosis, activation of endothelial cells, and cellular edema. Using nutrient-rich solution and/or adding multiple cytoprotective agents is a new direction for designing and developing organ preservation solutions. Cell culture model, as a screening tool, reduces the use of animals and provides potential underlying mechanisms.

Importance of Tumor Necrosis Factor-α Cleavage Process in Post-Transplantation Lung Injury in Rats

Tumor necrosis factor-alpha (TNF-alpha) has two forms with apparently different biological activities: a membrane-associated form and a soluble form. TNF-alpha-converting enzyme (TACE) mediates a cleavage of membrane-associated TNF-alpha to induce its bioactive soluble form. We hypothesized that inhibition of TACE might prevent TNF-alpha-induced tissue injury while preserving the benefits of TNF-alpha. In this study, we evaluated the role of TACE in acute inflammation using an inhibitor of the enzyme in a rat model of lung transplantation. Inbred Lewis rats underwent left lung isotransplantation, and the donor lungs were kept in Euro-Collins solution with or without the inhibitor. After 6 hours of ischemia, the left lung was transplanted into the recipient rat and reperfused for 4 hours. Inhibition of TACE significantly attenuated endothelial and alveolar septal damage, as assessed by radiolabeled albumin leakage after transplantation. The inhibition also attenuated neutrophil accumulation in the alveolar space and other histopathologic findings, including intercellular adhesion molecule-1 expression. In addition, significantly lower levels of monocyte chemotactic protein-1, cytokine-induced neutrophil chemoattractant-1, high mobility group box-1, and soluble epithelial cadherin and decreased neutrophil elastase activity were observed in bronchoalveolar lavage fluid from the rats treated with the inhibitor. We conclude that TACE mediates a critical step in the development of post-transplantation lung injury.

Endothelium-dependent relaxation of canine pulmonary artery after prolonged lung graft preservation in University of Wisconsin solution: role of L-arginine supplementation

BACKGROUND

The University of Wisconsin (UW) solution has been demonstrated to enhance pulmonary allograft preservation. Endothelial nitric oxide (NO) production has been shown to be significantly impaired after ischemia and reperfusion (I/R) injury. The present experiments aimed to determine the protective effects of pulmonary endothelium-dependent function by using supplemental NO in University of Wisconsin (UW) solution following prolonged lung graft preservation.

METHODS

Thirty-six healthy mongrel dogs underwent thoracotomy to expose the left lung. In addition to a group given UW solution (n = 4), 100 micromol/liter l-arginine, (n = 7), 100 micromol/liter N(G)-monomethyl-l-arginine (l-NMMA n = 7) and 1.0 micromol/liter 3-morpholinosydnonimine (SIN-1, n = 18 respectively, were added to UW solution, and infused from the aortic root and pulmonary artery to the pulmonary vein. The perfused lung was then allowed to inflate to its maximum volume for 24-hour oxygenated preservation in each supplemented condition of UW solution at 4 degrees C. In the SIN-1 group, the preservation period was further divided into 8 hours and 16 hours, respectively. Rings of the third-order pulmonary artery of the inflated lung were then suspended in organ chambers to measure isometric force.

RESULTS

Endothelium-dependent relaxation (EDR) to acetylcholine, adenosine diphosphate and sodium fluoride of the pulmonary rings in the l-arginine group was significantly preserved compared with UW-solution-only group. The l-NMMA group showed significant EDR impairment after 24-hour preservation compared with the UW solution group. Similar to the l-arginine group, the SIN-1 group showed significant EDR protection with 8-hour preservation, but not with 24-hour preservation. In contrast, EDR to calcium ionophore A23187 showed no EDR changes after 24-hour preservation in any of the supplemented groups.

CONCLUSIONS

Supplemental l-arginine in UW solution ameliorates impaired pulmonary EDR following prolonged lung preservation of up to 24 hours.

Lung transplantation. Lung preservation

Over the past decade, improvements in the technique of lung preservation have led to significant reduction in the incidence of ischemia-reperfusion-induced lung injury after lung transplantation. The challenge remains to improve the number of donor lungs available for transplantation. While the number of patients on the waiting list is constantly increasing, only 10% to 30% of donor lungs are currently being used for transplantation. Hence, the development of new strategies to assess, repair, and improve the quality of the lungs could have a tremendous impact on the number of transplants performed. In addition, an improved understanding of the mechanisms involved in lung preservation might help elucidate the potential link between acute lung injury and chronic graft dysfunction. In the future, genetic analysis using novel technologies such as microarray analysis will help researchers determine which genes control the injury seen in the transplantation process. Hopefully, this information will provide new insights into the mechanisms of injury and reveal potential new strategies and targets for therapies to improve lung preservation.

Ischemia-reperfusion decreases protein tyrosine phosphorylation and p38 mitogen-activated protein kinase phosphorylation in rat lung transplants

BACKGROUND

Dramatic alterations of protein tyrosine phosphorylation have been found during the ischemia-reperfusion (IR) period of human lung transplantation. IR also induces activation of p38 mitogen-activated protein kinase (p38) in the heart and kidney. The objective of the present study was to determine whether these changes exist in a rat single-lung transplant model for further mechanistic investigations.

METHODS

Isogeneic lung transplantation was performed from Lewis (LEW) to LEW rats, whereas allogeneic transplantation was from LEW to Brown Norway (BN) rats. Blood gases and peak airway pressure were monitored. Lung tissues were collected after 6 hours of cold ischemic preservation, after 30 minutes of warm ischemia for lung implantation, and after 2 hours of reperfusion. Protein tyrosine kinase (PTK) and phosphatase (PTP) activities were measured. Protein tyrosine phosphorylation, Src PTK and p38 expression and p38 phosphorylation were examined by western blotting.

RESULTS

In both iso- and allografts, the lung function of transplants was very well preserved. Protein tyrosine phosphorylation, PTK and PTP activities were decreased significantly after 2 hours of reperfusion. Src protein level and phosphorylation of p38 were reduced after 2 hours of reperfusion.

CONCLUSIONS

During the early IR period of lung transplantation, decreased protein tyrosine phosphorylation may be involved in apoptosis and other biologic changes. The lack of p38 activation suggests that activity of mitogen-activated protein kinase pathways in the lung transplantation setting may be different from other IR processes.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Trimetazidine protects the energy status after ischemia and reduces reperfusion injury in a rat single lung transplant model

BACKGROUND

Ischemia-reperfusion injury involves free radical generation and polymorphonuclear neutrophil chemotaxis. Trimetazidine is an anti-ischemic drug that restores the ability of the ischemic cells to produce energy and reduces the generation of oxygen-derived free radicals. We evaluated the effect of trimetazidine against ischemia-reperfusion injury after lung transplantation.

METHODS

Rat single lung transplantation was performed in 3 experimental groups (n = 5): (1) the immediate transplantation group was defined as animals undergoing transplantation immediately after harvest without treatment; (2) the ischemic control group was defined as animals undergoing transplantation after 18 hours of cold (4 degrees C) ischemia without treatment; and (3) the trimetazidine-treated group was defined as animals undergoing transplantation after 18 hours of cold (4 degrees C) ischemia and donor and recipient treatment with 5 mg/kg intravenous trimetazidine 10 minutes before harvest and reperfusion, respectively. All donor lungs were flushed with low-potassium dextran-glucose solution. After 2 hours of reperfusion, oxygenation was measured, and lung tissue was frozen and assessed for adenosine triphosphate content, myeloperoxidase activity, and thiobarbituric acid-reactive substances. Peak airway pressure was recorded throughout the reperfusion period.

RESULTS

The trimetazidine group showed significantly higher levels of adenosine triphosphate content (1.73 +/- 0.8 pmol vs 0.72 +/- 0.2 pmol [ischemic control], P =.008), better oxygenation (238.82 +/- 113.9 mm Hg vs 89.39 +/- 14.7 mm Hg [ischemic control], P =.008), and reduced lipid peroxidation (1.28 +/- 0.1 nmol/g vs 2.09 +/- 0.4 nmol/g [ischemic control], P =.008). Adenosine triphosphate levels of the trimetazidine group were comparable with those of the immediate transplantation group (1.73 +/- 0.8 pmol vs 1.89 +/- 0.5 pmol, respectively; P =.31). Peak airway pressure and myeloperoxidase activity were comparable among groups.

CONCLUSION

Donor and recipient treatment with trimetazidine provided a significant protection of the energy status, better oxygenation, and reduced lipid peroxidation in this experimental model. Our data suggest that trimetazidine may be an important adjunct to prolong ischemic time safely and to decrease lung ischemia-reperfusion injury.

Recipient treatment with trimetazidine improves graft function and protects energy status after lung transplantation

BACKGROUND

Ischemia-reperfusion injury remains an important obstacle to successful lung transplantation. Trimetazidine is an anti-ischemic drug that restores the ability of ischemic cells to produce energy and reduces the generation of oxygen-derived free radicals. The aim of this study was to assess the protective effect of trimetazidine after prolonged ischemia in lung transplantation.

METHODS

Rat single-lung transplantation was performed in 4 experimental groups (n = 5 each). In all groups, transplantation was performed after 18 hours of cold (4 degrees C) ischemia. All donor lungs were flushed with low-potassium dextran-glucose (LPDG) solution that also contained 500 microg/liter prostaglandin estradiol (E(1)). Groups studied included: Group I: flush solution was administered containing 10(-6) mol/liter trimetazidine (TMZ), neither donor nor recipient treatment given; Group II: donors were treated with 5 mg/kg intravenous TMZ 10 minutes prior to harvest, but the flush solution did not contain TMZ; Group III: recipients treated with 5 mg/kg intravenous TMZ 10 minutes before reperfusion, and flush solution contained 10(-6) mol/liter trimetazidine; Group IV: ischemic control group. After 2 hours of reperfusion, oxygenation was measured and lung tissue was frozen and assessed for adenosine triphosphate (ATP) content, myeloperoxidase (MPO) activity and thiobarbituric acid-reactive substances (TBARS). Peak airway pressure (PawP) was recorded throughout the reperfusion period.

RESULTS

Group III showed significantly higher levels of ATP content (11.1 +/- 5.01 pmol vs Group I, 3.36 +/- 1.8 pmol, p = 0.008; vs Group II, 4.7 +/- 1.9 pmol, p = 0.03; vs Group IV, 0.7 +/- 0.2 pmol, p = 0.008), better oxygenation (442.5 +/- 26.5 mm Hg, vs Group I, 161.06 +/- 54.5 mm Hg; vs Group II, 266.02 +/- 76.9 mm Hg; vs Group IV, 89.4 +/- 14.7 mm Hg, p = 0.008) and reduced lipid peroxidation (TBARS) (0.15 +/- 0.03 nmol/g; vs Group I, 1.04 +/- 0.76 nmol/g; vs Group II, 0.69 +/- 0.4 nmol/g; vs Group IV, 2.29 +/- 0.4 nmol/g, p = 0.008). PawP and MPO activity were comparable in the 4 study groups.

CONCLUSION

Recipient treatment with TMZ provided significant protection of energy status, better oxygenation and reduced lipid peroxidation. Our data suggest that TMZ may be an important adjunct in the prevention of post-transplant lung ischemia-reperfusion injury.

In vivo transtracheal adenovirus-mediated transfer of human interleukin-10 gene to donor lungs ameliorates ischemia-reperfusion injury and improves early posttransplant graft function in the rat

We examined the effect of adenovirus-mediated transtracheal transfer of the human interleukin 10 (hIL-10) gene on lung ischemia-reperfusion (IR) injury, which is the insult due to hypothermic preservation plus graft reperfusion, and posttransplant lung function in Lewis rat lungs. Thirty rats were divided into 6 groups (n = 5). Groups 1 and 4 received 5 x 10(9) PFU of Ad5E1RSVhIL-10, groups 2 and 5 received 5 x 10(9) PFU of Ad5BGL2 ("empty" vector), and groups 3 and 6 received 3% sucrose (diluent). After 24 hr of in vivo transfection, lungs were stored at 4 degrees C (cold ischemic time, CIT) for 6 hr (groups 1-3) or 24 hr (groups 4-6) before transplantation. After 2 hr of reperfusion, lung function was assessed by oxygenation (FIO2, 1.0), airway pressure (AwP), and wet-to-dry (W/D) weight ratios. Rat tumor necrosis factor alpha (rTNF-alpha), interferon gamma (IFN-gamma), IL-10, and hIL-10 were measured in graft tissue and recipient plasma by ELISA and detected by immunohistochemistry (IHC). Partial pressure of oxygen (PaO2) levels in the hIL-10 group (6 hr of CIT) were higher than in empty vector and diluent groups (PaO2, 530 +/- 23 vs. 387 +/- 31 and 439 +/- 27 mmHg, respectively, p < 0.05). IL-10 rats after 24 hr of CIT showed higher PaO2 levels (260 +/- 29 mmHg) than empty vector (96 +/- 24 mmHg) or diluent (133 +/- 10 mmHg) lungs (p < 0.05). AwP and W/D ratios were reduced in hIL10 lungs (p < 0.05) compared with the other groups. rTNF-alpha and INF-gamma were reduced in tissue and plasma in groups 1 and 4 (p < 0.05). rIL-10 was reduced in the tissue of hIL-10 lungs (p < 0.05). IHC showed equal distribution of cytokines in tissue and abundant transgene expression in large and small airway epithelium in hIL-10 lungs.

Raffinose improves 24-hour lung preservation in low potassium dextran glucose solution: a histologic and ultrastructural analysis

BACKGROUND

We have previously shown that the addition of raffinose to low potassium dextran (LPD) preservation solution improves transplanted rat lung function after 24 hours of storage. The mechanisms by which raffinose acts are unclear. The aim of this study was to examine the histologic and ultrastructural correlates of this enhanced pulmonary function after preservation with raffinose.

METHODS

In a randomized, blinded study, rat lungs were flushed with LPD, or LPD containing 30 mmol/L of raffinose, and stored for 24 hours at 4 degrees C. Control lungs were flushed with LPD but not stored (n = 5 each group). Changes in postpreservation edema were determined. In addition, lungs were flushed with a trypan blue solution to quantify cell death, and examined using both light and electron microscopy.

RESULTS

The LPD lungs gained significantly more weight (25.5%+/-5.5%) compared with raffinose-LPD lungs (5.2%+/-5.3%; p < 0.0001). There were higher percentages of dead cells in the LPD lungs (29%+/-0.3% of total cells) compared with raffinose-LPD lungs (14%+/-1.4%; p < 0.001) and control lungs (0.2%+/-5%; p < 0.001). Control lungs maintained normal ultrastructure, whereas LPD lungs showed a decreased number of intact type II pneumocytes and significant cellular necrosis. Interstitial and alveolar edema with interstitial macrophage infiltration was also observed. Alveolar capillaries were collapsed. In contrast, raffinose-LPD lungs showed only mild alterations such as minimal interstitial edematous expansion, fewer damaged cells, and minimal capillary injury.

CONCLUSIONS

Raffinose exerts a cytoprotective effect on pulmonary grafts during preservation, which explains the previously documented improved function. This simple modification of LPD with raffinose may provide clinical benefit in extended pulmonary preservation.