Significance of cyclic adenosine monophosphate and nitroglycerin in ET-Kyoto solution for lung preservation

Global expression profiling and pathway analysis in two different population groups in relation to high altitude

High altitude (HA) is associated with number of stresses. Response of these stresses may vary in different populations depending upon altitude, duration of residency, ancestry, geographical variation, lifestyle, and ethnicities. For understanding population variability in transcriptome, array-based global gene expression profiling was performed on extracted RNA of male volunteers of two different lowland population groups, i.e., Indians and Kyrgyz, at baseline and day 7 of HA exposure (3200 m). A total of 97 genes were differentially expressed at basal in Kyrgyz as compared to Indians (82 downregulated and 15 upregulated), and 196 were differentially expressed on day 7 of HA (118 downregulated and 78 upregulated). Ingenuity Pathway Analysis and gene ontology highlighted eIF2 signaling with most significant negative activation z score at basal in Kyrgyz compared to Indians with downregulation of various L- and S-ribosomal proteins indicating marked translational repression. On day 7, cAMP-mediated signaling is most enriched with positive activation z score in Kyrgyz compared to Indians. Plasma cAMP levels were higher in Kyrgyz on day 7 compared to Indians. Extracellular adenosine levels were elevated in both the groups upon HA, but higher in Kyrgyz compared to Indians. Valedictory qRT-PCR showed upregulation of ADORA2B and CD73 along with downregulation of ENTs in Kyrgyz compared to Indians indicating elevated levels of extracellular nucleotides mainly adenosine and activation of extracellular cAMP-adenosine pathway which as per literature triggers endogenous protective mechanisms under stress conditions like hypoxia. Thus, transcriptome changes at HA are population-specific, and it may be necessary to take care while interposing similar results in different populations.

Reconditioning of lungs donated after circulatory death with normothermic ex vivo lung perfusion

BACKGROUND

The use of donation-after-circulatory-death (DCD) donors for lung transplantation has come into practice. In this study we investigated whether DCD lungs can be resuscitated after warm ischemia with normothermic ex vivo lung perfusion (EVLP).

METHODS

Four hours after cardiac arrest, beagle dogs were divided into two groups (n = 6 each): those with static cold storage (SCS group) and those with normothermic EVLP (EVLP group), for 3.5 hours. Physiologic lung functions were evaluated during EVLP. In both groups, the left lungs were then transplanted and reperfused for 4 hours to evaluate post-transplant lung functions. Lung tissue adenosine triphosphate (ATP) levels were measured at given time-points.

RESULTS

Lung oxygenation was significantly improved with EVLP (p < 0.01), and lung oxygenation at the end of EVLP significantly reflected post-transplant lung oxygenation (r = 0.99, p < 0.01). Post-transplant lung oxygenation was significantly better in the EVLP group than in the SCS group (p < 0.05). Both dynamic pulmonary compliance and wet-to-dry lung weight ratio 4 hours after transplantation were also significantly better in the EVLP group than in the SCS group (p < 0.05). Microthrombi in the donor lungs before transplantation were microscopically detected more often in the SCS group. The lung tissue ATP levels 4 hours after transplantation were significantly higher in the EVLP group compared with the SCS group (p = 0.03).

CONCLUSIONS

Normothermic ex vivo lung perfusion could resuscitate DCD lungs injured by warm ischemia, and may ameliorate ischemia-reperfusion injury.

Hypothermic machine perfusion ameliorates ischemia-reperfusion injury in rat lungs from non-heart-beating donors

BACKGROUND

The use of non-heart-beating donors (NHBD) has come into practice to resolve the shortage of donor lungs. This study investigated whether hypothermic machine perfusion (HMP) can improve the quality of NHBD lungs.

METHODS

An uncontrolled NHBD model was achieved in male Lewis rats. Ninety minutes after cardiac arrest, HMP was performed for 60 min at 6°C to 10°C. The first study investigated the physiological lung functions during HMP and the lung tissue energy levels before and after HMP. The second study divided the rats into three groups (n=6 each): no ischemia group; 90-min warm ischemia+60-min HMP+120-min static cold storage (SCS) (HMP group); and 90-min warm ischemia+180-min SCS group. All lungs were reperfused for 60 min at 37°C. Lung functions were evaluated at given timings throughout the experiments. Oxidative damage during reperfusion was evaluated immunohistochemically with a monoclonal antibody against 8-hydroxy-2'-deoxyguanosine.

RESULTS

The first study revealed that lung functions were stable during HMP. Lung tissue energy levels decreased during warm ischemia but were significantly increased by HMP (P<0.05). The second study confirmed that HMP significantly decreased pulmonary vascular resistance, increased pulmonary compliance, and improved pulmonary oxygenation. The ratio of 8-hydroxy-2'-deoxyguanosine positive cells to total cells significantly increased in the SCS group (P<0.01).

CONCLUSIONS

Short-term HMP improved lung tissue energy levels that decreased during warm ischemia and ameliorated ischemia-reperfusion injury with decreased production of reactive oxygen species.

Experimental orthotopic lung transplantation model in rats with cold storage

This report describes a new experimental procedure, a rat unilateral, orthotopic lung transplantation with cold storage, and evaluates its relevancy and reliability to study the early events during cold ischemia/reperfusion (I/R) injury. This model, using the cuff technique, does not require extensive training and is relatively easy to be established. The model can induce reproducible degrees of pulmonary graft injury including impaired gas exchange, proinflammatory cytokine upregulation, or inflammatory infiltrates, depending on the preservation time. The results are consistent with the previous clinical evidence, thus suggesting that this model is a valid and reliable animal model of cold I/R injury.

ET-Kyoto solution plus dibutyryl cyclic adenosine monophosphate is superior to University of Wisconsin solution in rat liver preservation

ET-Kyoto solution (ET-K) is an extracellular-type organ preservation solution containing the cytoprotective disaccharide, trehalose. A previous study reported the supplement of dibutyryl cyclic adenosine monophosphate (db-cAMP) in conventional ET-K to attenuate lung ischemia-reperfusion injury. In this study, the efficacy of this modified ET-K for liver preservation was investigated by comparison with University of Wisconsin solution (UW). ET-K was supplemented with db-cAMP (2 mmol/L). Lewis rats were randomly assigned to two groups, and liver grafts were flushed and stored at 40C for 24 h with ET-K or UW before syngeneic liver transplantation. The graft function and histological changes at 4 h posttransplant as well as 7-day survival were evaluated. Recipient rat survival rate was significantly higher in the ET-K group than in the UW group. Preservation in ET-K resulted in a significant reduction in serum parenchymal transaminase level and promotion of bile production in comparison with UW. The serum hyaluronic acid level, an indicator of sinusoidal endothelial cell injury, was significantly lower after ET-K preservation than that in UW. Histologically, at 4 h after transplantation, the liver grafts preserved in UW solution demonstrated a greater degree of injury than those in ET-K, which appeared to be apoptosis, rather than necrosis. The continuity of the sinusoidal lining was better preserved in ET-K than in UW. In conclusion, ET-K supplemented with db-cAMP is superior to UW in rat liver preservation. This modified ET-K might therefore be a novel candidate for the procurement and preservation of multiple organs.

Dose-related effects of theophylline added to modified euro-collins solution used for hypothermic preservation of lung

OBJECTIVE

To investigate the dose-related effects of theophylline in prevention of ischemia-reperfusion injury of the lung.

DESIGN

Experimental study.

SETTINGS

University hospital.

PARTICIPANTS

Thirty Wistar rats.

INTERVENTIONS

In experimental group 1 (G-I) (n = 5) 20 mg/L, in G-II (n = 5) 100 mg/L, in G-III (n = 5) 400 mg/L, and in G-IV (n = 5) 1000 mg/L of theophylline was added to modified Euro-Collins solution and perfused the lungs. Lungs were extracted without an ischemic period in control group 1 (C-I) and perfused with modified Euro-Collins solution in control group 2 (C-II). Lungs were kept in a hypothermic state for 6 hours and then ventilated for 30 minutes with 100% O(2).

MEASUREMENTS AND MAIN RESULTS

Tissue levels of dien congugate (DC) and malonylaldehyde (MDA) were measured. Comparison of 6 groups revealed statistically significant differences for DC and MDA (p < 0.0001 for both comparisons). Both DC and MDA levels of C-II were found to be higher than G-III and G-IV (p = 0.008). DC and MDA levels of G-III and G-IV were significantly lower than G-I and G-II (p = 0.008 for all comparisons).

CONCLUSION

The results of this study showed that 400 mg/L and 1000 mg/L of theophylline added to the modified Euro-Collins solution decreased the intermediate products of lipid peroxidation. Theophylline merits further investigation in ischemia-reperfusion studies as a potentially beneficial agent.

Experimental lung preservation with Perfadex: effect of the NO-donor nitroglycerin on postischemic outcome

OBJECTIVE

Optimal preservation of postischemic graft function is essential in lung transplantation. Antegrade flush perfusion with modified Euro-Collins solution represents the standard technique worldwide. However, growing evidence suggests the superiority of extracellular-type Perfadex solution (Vitrolife AB, Gothenburg, Germany) over Euro-Collins solution. During ischemia and reperfusion, endogenous pulmonary nitric oxide synthesis is decreased, and therefore therapeutic stimulation of the nitric oxide pathway might be beneficial in ameliorating ischemia-reperfusion damage. However, research mainly focuses on nitric oxide supplementation of intracellular solutions, and no studies exist in which the effect of nitroglycerin on Perfadex preservation quality is evaluated.

METHODS

Eight rat lungs each were preserved with Perfadex solution with or without nitroglycerin (0.1 mg/mL) and compared with low-potassium Euro-Collins solution. Postischemic lungs were reventilated and reperfused, and oxygenation capacity, pulmonary vascular resistance, and peak inspiratory pressures were monitored continuously. Stereological analysis was used for evaluation of pulmonary edema and assessment of the vasculature. Statistics were performed by using different analysis of variance models.

RESULTS

The oxygenation capacity of the Perfadex-preserved groups was higher compared with that of the low-potassium Euro-Collins solution group (P <.03). By using nitroglycerin, flush-perfusion time was reduced, and Perfadex solution with nitroglycerin-protected lungs showed superior oxygenation capacity compared with that seen in Perfadex solution-protected organs (P <.01). Furthermore, pulmonary vascular resistance and peak inspiratory pressures were improved in the nitroglycerin group (P <.01). Stereology revealed comparable intrapulmonary edema between groups and a trend toward less vasoconstricted vasculature in Perfadex with nitroglycerin-protected lungs.

CONCLUSIONS

Perfadex solution provides superior lung preservation in terms of postischemic oxygenation capacity than Euro-Collins solution. Supplementation of the nitric oxide pathway by nitroglycerin further enhances functional outcome of Perfadex-preserved organs and might be an easily applicable tool in clinical lung transplantation.

Subthreshold doses of nebulized prostacyclin and rolipram synergistaically protect against lung ischemia-reperfusion

BACKGROUND

Pulmonary edema caused by increased microvascular permeability is an important feature of lung ischemia-reperfusion (I/R) injury.

METHODS

We investigated the impact of co-aerosolized prostaglandin (PG)I(2) and the 3',5-cyclic adenosine monophosphate (cAMP)-specific phosphodiesterase inhibitor rolipram on microvascular leakage following I/R injury. Buffer-perfused rabbit lungs were exposed to 270 minutes of warm ischemia while anoxic ventilation and a positive intravascular pressure were maintained.

RESULTS

On reperfusion, a massive increase of the capillary filtration coefficient and severe edema formation were noted, whereas microvascular pressures displayed only minor changes. Short-time aerosolization of subthreshold doses of either rolipram (33 microg) or PGI(2) (2.6 microg) at the beginning of ischemia did not attenuate the leakage response, whereas the co-aerosolization of both agents largely blocked any permeability increase and edema formation, independent of hemodynamic effects. The same was true when the co-aerosolization was undertaken before onset of ischemia. Similarly, the intravascular administration of rolipram and PGI(2) showed a synergistic reduction of I/R-induced vascular leak but demanded 10-fold higher doses. Intravascular release of cAMP was markedly enhanced on combined PGI(2)-rolipram administration but depended on the mode of delivery of these agents.

CONCLUSIONS

Low doses of aerosolized prostacyclin and rolipram synergistically protect against severe lung I/R injury and can be used independently of lung perfusion. This strategy may be suitable for an improvement of organ preservation in lung transplantation including early management of non-heart-beating donors.

Influence of high molecular dextrans on lung function in an ex vivo porcine lung model

BACKGROUND

Extracellular preservation solutions utilizing high molecular agents can reduce intracellular edema during ischemia/reperfusion in lung transplantation. A solution of 40,000 dalton molecular weight (DMW) has already been clinically established (Perfadex). However, it is unclear whether dextrans of this particular size represent the optimal additive for lung preservation solutions.

MATERIALS AND METHODS

In a new ex vivo porcine lung model, lungs were each preserved with low-potassium solutions containing 5% dextran with 90,000 DMW (Dex 90) and 160,000 DMW (Dex 160) and with Perfadex (40,000 DMW). After 24 h of cold ischemia, reperfusion was performed employing a roller pump with a pulsatile module. Lungs were perfused with deoxygenated perfusate and ventilated with room air. The oxygenation capacity (Delta pO(2)), peak inspiratory pressure (PIP), and mean pulmonary artery pressure (PAP) were monitored for 60 min. Net weight gain (NWG) and wet-to-dry ratio (W/D ratio) were determined. Free-radical generation was assessed by measuring malondialdehyde (MDA) at 10, 30, and 50 min.

RESULTS

PIP and PAP increased in all groups significantly during reperfusion. However, Dex 160-perfused lungs exhibited significantly higher values than those with Dex 90 and Perfadex. Perfadex showed the highest Delta pO(2) throughout the entire reperfusion, while Delta pO(2) was slightly reduced in Dex 160 and significantly lower in Dex 90. In Perfadex the lowest water content was observed assessed by NWG and W/D ratio. The highest MDA values were observed in Dex 90, followed by Dex 160, while the lowest values were seen in Perfadex.

CONCLUSIONS

Preservation of the lung with Perfadex exhibited superior postischemic function in contrast to preservation solutions containing dextrans with a higher molecular weight.