Protective effects of hydrogen inhalation during the warm ischemia phase against lung ischemia-reperfusion injury in rat donors after cardiac death

Background: Successful amelioration of long-term warm ischemia lung injury in donors after cardiac death (DCDs) can remarkably improve outcomes. Hydrogen gas provides potent anti-inflammatory and antioxidant effects against ischemia-reperfusion injury (IRI). This study observed the effects of hydrogen inhalation on lung grafts during the warm ischemia phase in cardiac death donors. Methods: After cardiac death, rat donor lungs (n = 8) underwent mechanical ventilation with 40% oxygen plus 60% nitrogen (control group) or 3% hydrogen and 40% oxygen plus 57% nitrogen (hydrogen group) for 2 h during the warm ischemia phase in situ. Then, lung transplantation was performed after 2 h of cold storage and 3 h of recipient reperfusion prior to lung graft assessment. Rats that underwent left thoracotomy without transplantation served as the sham group (n = 8). The results of static compliance and arterial blood gas analysis were assessed in the recipients. The wet-to-dry weight ratio (W/D), inflammation, oxidative stress, cell apoptosis and histologic changes were evaluated after 3 h of reperfusion. Nuclear factor kappa B (NF-κB) protein expression in the graft was analyzed by Western blotting. Results: Compared with the sham group, lung function, W/D, inflammatory reaction, oxidative stress and histological changes were decreased in both transplant groups (control and hydrogen groups). However, compared with the control group, exposure to 3% hydrogen significantly improved lung graft static compliance and oxygenation and remarkably decreased the wet-to-dry weight ratio, inflammatory reactions, and lipid peroxidation. Furthermore, hydrogen improved the lung graft histological changes, decreased the lung injury score and apoptotic index and reduced NF-κB nuclear accumulation in the lung grafts. Conclusion: Lung inhalation with 3% hydrogen during the warm ischemia phase attenuated lung graft IRI via NF-κB-dependent anti-inflammatory and antioxidative effects in rat donors after cardiac death.

Lung inflation with hydrogen during the cold ischemia phase decreases lung graft injury in rats

Hydrogen has antioxidant and anti-inflammatory effects on lung ischemia-reperfusion injury when it is inhaled by donor or/and recipient. This study examined the effects of lung inflation with 3% hydrogen during the cold ischemia phase on lung graft function in rats. The donor lung was inflated with 3% hydrogen, 40% oxygen, and 57% nitrogen at 5 mL/kg, and the gas was replaced every 20 min during the cold ischemia phase for 2 h. In the control group, the donor lung was inflated with 40% oxygen and 60% nitrogen at 5 mL/kg. The recipient was euthanized 2 h after orthotropic lung transplantation. The hydrogen concentration in the donor lung during the cold ischemia phase was 1.99-3%. The oxygenation indices in the arterial blood and pulmonary vein blood were improved in the hydrogen group. The inflammation response indices, including lung W/D ratio, the myeloperoxidase activity in the grafts, and the levels of IL-8 and TNF-α in serum, were significantly lower in the hydrogen group (5.2 ± 0.8, 0.76 ± 0.32 U/g, 340 ± 84 pg/mL, and 405 ± 115 pg/mL, respectively) than those in the control group (6.5 ± 0.7, 1.1 ± 0.5 U/g, 443 ± 94 pg/mL, and 657 ± 96 pg/mL, respectively (P < 0.05), and the oxidative stress indices, including the superoxide dismutase activity and the level of malonaldehyde in lung grafts were improved after hydrogen application. Furthermore, the lung injury score determined by histopathology, the cell apoptotic index, and the caspase-3 protein expression in lung grafts were decreased after hydrogen treatment, and the static pressure-volume curve of lung graft was improved by hydrogen inflation. In conclusion, lung inflation with 3% hydrogen during the cold ischemia phase alleviated lung graft injury and improved graft function. © 2015 by the Society for Experimental Biology and Medicine.

Protection of donor lung inflation in the setting of cold ischemia against ischemia-reperfusion injury with carbon monoxide, hydrogen, or both in rats

Aims: Lung ischemia-reperfusion injury (IRI) may be attenuated through carbon monoxide (CO)’s anti-inflammatory effect or hydrogen (H2)’s anti-oxidant effect. In this study, the effects of lung inflation with CO, H2, or both during the cold ischemia phase on graft function were observed. Materials and methods: Rat donor lungs, inflated with 40% oxygen (control group), 500ppm CO (CO group), 3% H2 (H2 group) or 500ppm CO+3% H2 (COH group), were kept at 4°C for 180min. After transplantation, the recipients’ artery blood gas and pressure-volume (P-V) curves were analyzed. The inflammatory response, oxidative stress and apoptosis in the recipients were assessed at 180min after reperfusion. Key findings: Oxygenation in the CO and H2 groups were improved compared with the control group. The CO and H2 groups also exhibited significantly improved P-V curves, reduced lung injury, and decreased inflammatory response, malonaldehyde content, and cell apoptosis in the grafts. Furthermore, the COH group experienced enhanced improvements in oxygenation, P-V curves, inflammatory response, lipid peroxidation, and graft apoptosis compared to the CO and H2 groups. Significance: Lung inflation with CO or H2 protected against IRI via anti-inflammatory, anti-oxidant and anti-apoptotic mechanisms in a model of lung transplantation in rats, which was enhanced by combined treatment with CO and H2.

The Anti-inflammatory Effect of Hydrogen on Lung Transplantation Model of Pulmonary Microvascular Endothelial Cells During Cold Storage Period

Background: Lung ischemia-reperfusion injury (LIRI) remains an important factor for the early mortality of lung transplantations. Hydrogen (H2) can attenuate lung injury and improve lung function in animal experiments. In previous studies, pulmonary microvascular endothelial cells (PMVECs) were used to simulate LIRI. We hypothesized that H2 can alleviate inflammatory injury in a PMVECs lung transplantation model in the cold ischemia phase. Methods: PMVECs were divided into 4 groups: Blank, Control, Oxygen (O2), and Hydrogen (H2). The Blank group included PMVECs without treatment. During the cold storage period, the O2 group was aerated with 40% O2 and 60% N2, and the H2 group was aerated with 3% H2, 40% O2 and 57% N2. The Control group was aerated without gases. The mixed gases were replaced every 20 min for 4 h. During the transplantation period, the sealed containers were warmed for 1 h at room temperature. In the reperfusion period, the containers were aerated with 50% O2, 5% CO2 and 45% N2 at 37 °C. Results: The concentrations of IL-6 and TNF-α in the extracellular solutions were significantly decreased, and the concentration of IL-10 was increased in the H2 group. ICAM-1 expression was inhibited by hydrogen. Furthermore, hydrogen decreased the activation of NF-κB and phosphorylation level of p38. Cell apoptosis was alleviated. The pathological changes in the cell and mitochondria were alleviated after hydrogen administration. Conclusion: Hydrogen attenuated inflammatory response in a PMVECs lung transplantation model during cold storage. The effect may be achieved by inhibition of p38 MAPK and NF-κB pathways.