Inhaled nitric oxide attenuates apoptosis in ischemia-reperfusion injury of the rabbit lung

Myrtenol-loaded niosomes can prevent lung ischemia-reperfusion injury model in rats by balancing the Nrf2/Keap1 and NF-κB signaling pathways

Lung Ischemia-reperfusion injury (LIRI) is a risk during lung transplantation that can cause acute lung injury and organ failure. In LIRI, the NF-E2-related factor 2(Nrf2)/ Kelch-like ECH-associated protein 1 (Keap1) signaling pathway and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway are two major pathways involved in regulating oxidative stress and inflammation, respectively. Myrtenol, a natural compound with anti-inflammatory and antioxidant properties, has potential protective effects against IRI. This study aimed to explore the impact of myrtenol encapsulated within niosomes on the prevention of LIRI and examine the role of the two pathways mentioned in this process. Wistar rats were segregated into four groups. Animals received the myrtenol (MN) (32 mg/kg) or vehicle through daily inhalation for a week before LIRI. Expression of IκB, p-IκB, Nrf2, Keap1, Heme Oxygenase-1(HO-1), NF-κB signaling proteins, reactive oxygen species (ROS) level, caspase-3 expression, arterial blood gases, lung edema, and histopathological indices were assessed. Niosomal myrtenol significantly reduced lung edema, ROS, Keap1, p-IκB, NF-kB, Caspase-3, PaCO2 (the carbon dioxide pressure in arterial blood), and histopathological indices. Additionally, the expression of IκB, Nrf2, HO-1, and PaO2 (the oxygen pressure in arterial blood) increased significantly in the pretreated group compared to the IR group. Overall, inhalation of the niosomal myrtenol protects against lung ischemia-reperfusion injury, presumably through the balance between Nrf2/Keap1 and NF-κB pathways. The findings suggest that the niosomal form of myrtenol may be a potential candidate for developing new drugs to prevent and treat LIR damage.

Inhaled nitric oxide and postoperative outcomes in cardiac surgery with cardiopulmonary bypass: A systematic review and meta-analysis

Cardiac surgeries under cardiopulmonary bypass (CPB) are complex procedures with high incidence of complications, morbidity and mortality. The inhaled nitric oxide (iNO) has been frequently used as an important composite of perioperative management during cardiac surgery under CPB. We conducted a meta-analysis of published randomized clinical trials (RCTs) to assess the effects of iNO on reducing postoperative complications, including the duration of postoperative mechanical ventilation, length of intensive care unit (ICU) stay, length of hospital stay, mortality, hemodynamic improvement (the composite right ventricular failure, low cardiac output syndrome, pulmonary arterial pressure, and vasoactive inotropic score) and myocardial injury biomarker (postoperative troponin I levels). Subgroup analyses were performed to assess the effect of modification and interaction. These included iNO dosage, the timing and duration of iNO therapy, different populations (children and adults), and comparators (other vasodilators and placebo or standard care). A comprehensive search for iNO and cardiac surgery was performed on online databases. Twenty-seven studies were included after removing the duplicates and irrelevant articles. The results suggested that iNO could reduce the duration of mechanical ventilation, but had no significance in the ICU stay, hospital stay, and mortality. This may be attributed to the small sample size of the most included studies and heterogeneity in timing, dosage and duration of iNO administration. Well-designed, large-scale, multicenter clinical trials are needed to further explore the effect of iNO in improving postoperative prognosis in cardiovascular surgical patients.

Preparation and Evaluation of Preventive Effects of Inhalational and Intraperitoneal Injection of Myrtenol Loaded Nano-Niosomes on Lung Ischemia-Reperfusion Injury in Rats

INTRODUCTION

Ischemia-reperfusion injury (IRI) is directly related to forming reactive oxygen species, endothelial cell injury, increased vascular permeability, and the activation of neutrophils and cytokines. Niosomes are nanocarriers and an essential part of drug delivery systems. We aimed to investigate the effects of myrtenol's inhaled and intraperitoneal niosomal form, compared to its simple form, on lung ischemia reperfusion injury (LIRI).

MATERIAL AND METHOD

Wistar rats were divided into ten groups. Simple and niosomal forms of myrtenol were inhaled or intraperitoneally injected daily for one week prior to LIRI. We evaluated oxidative stress, apoptotic, and inflammatory indices, nitric oxide, inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS) and histopathological indices.

RESULTS

Pretreatment with simple and niosomal forms of myrtenol significantly inhibited the indices of pulmonary edema, pro-inflammatory cytokines and proteins, oxidant agents, nitric oxide, iNOS, apoptotic proteins, congestion of capillaries, neutrophil infiltration, and bleeding in the alveoli. Furthermore, myrtenol increased anti-inflammatory cytokines, anti-oxidants agents, eNOS, anti-apoptotic proteins and the survival time of animals. The niosomal form of myrtenol showed a more ameliorative effect than its simple form.

CONCLUSION

The results showed the superior protective effect of the inhalation of myrtenol niosomal form against LIRI compared to its simple form and systemic use.

Pulmonary reperfusion injury in post-palliative intervention of oligaemic cyanotic CHD: a new catastrophic consequence or just revisiting the same old story?

Pulmonary reperfusion injury is a well-recognised clinical entity in the setting pulmonary artery angioplasty for pulmonary artery stenosis or chronic thromboembolic disease, but not much is known about this complication in post-palliative intervention of oligaemic cyanotic CHD. The pathophysiology of pulmonary reperfusion injury in this population consists of both ischaemic and reperfusion injury, mainly resulting in oxidative stress from reactive oxygen species generation, followed by endothelial dysfunction, and cytokine storm that may induce multiple organ dysfunction. Other mechanisms of pulmonary reperfusion injury are "no-reflow" phenomenon, overcirculation from high pressure in pulmonary artery, and increased left ventricular end-diastolic pressure. Chronic hypoxia in cyanotic CHD eventually depletes endogenous antioxidant and increased the risk of pulmonary reperfusion injury, thus becoming a concern for palliative interventions in the oligaemic subgroup. The incidence of pulmonary reperfusion injury varies depending on multifactors. Despite its inconsistence occurrence, pulmonary reperfusion injury does occur and may lead to morbidity and mortality in this population. The current management of pulmonary reperfusion injury is supportive therapy to prevent deterioration of lung injury. Therefore, a general consensus on pulmonary reperfusion injury is necessary for the diagnosis and management of this complication as well as further studies to establish the use of novel and potential therapies for pulmonary reperfusion injury.

Nitric Oxide in Cardiac Surgery: A Review Article

Perioperative organ injury remains a medical, social and economic problem in cardiac surgery. Patients with postoperative organ dysfunction have increases in morbidity, length of stay, long-term mortality, treatment costs and rehabilitation time. Currently, there are no pharmaceutical technologies or non-pharmacological interventions that can mitigate the continuum of multiple organ dysfunction and improve the outcomes of cardiac surgery. It is essential to identify agents that trigger or mediate an organ-protective phenotype during cardiac surgery. The authors highlight nitric oxide (NO) ability to act as an agent for perioperative protection of organs and tissues, especially in the heart-kidney axis. NO has been delivered in clinical practice at an acceptable cost, and the side effects of its use are known, predictable, reversible and relatively rare. This review presents basic data, physiological research and literature on the clinical application of NO in cardiac surgery. Results support the use of NO as a safe and promising approach in perioperative patient management. Further clinical research is required to define the role of NO as an adjunct therapy that can improve outcomes in cardiac surgery. Clinicians also have to identify cohorts of responders for perioperative NO therapy and the optimal modes for this technology.

Minimizing Ischemia Reperfusion Injury in Xenotransplantation

The recent dramatic advances in preventing "initial xenograft dysfunction" in pig-to-non-human primate heart transplantation achieved by minimizing ischemia suggests that ischemia reperfusion injury (IRI) plays an important role in cardiac xenotransplantation. Here we review the molecular, cellular, and immune mechanisms that characterize IRI and associated "primary graft dysfunction" in allotransplantation and consider how they correspond with "xeno-associated" injury mechanisms. Based on this analysis, we describe potential genetic modifications as well as novel technical strategies that may minimize IRI for heart and other organ xenografts and which could facilitate safe and effective clinical xenotransplantation.

Inhaled pulmonary vasodilators: a narrative review

Pulmonary hypertension (PH) is a severe disease that affects people of all ages. It can occur as an idiopathic disorder at birth or as part of a variety of cardiovascular and pulmonary disorders. Inhaled pulmonary vasodilators (IPV) can reduce pulmonary vascular resistance (PVR) and improve RV function with minimal systemic effects. IPV includes inhaled nitric oxide (iNO), inhaled aerosolized prostacyclin, or analogs, including epoprostenol, iloprost, treprostinil, and other vasodilators. In addition to pulmonary vasodilating effects, IPV can also be used to improve oxygenation, reduce inflammation, and protect cell. Off-label use of IPV is common in daily clinical practice. However, evidence supporting the inhalational administration of these medications is limited, inconclusive, and controversial regarding their safety and efficacy. We conducted a search for relevant papers published up to May 2020 in four databases: PubMed, Google Scholar, EMBASE and Web of Science. This review demonstrates that the clinical using and updated evidence of IPV. iNO is widely used in neonates, pediatrics, and adults with different cardiopulmonary diseases. The limitations of iNO include high cost, flat dose-response, risk of significant rebound PH after withdrawal, and the requirement of complex technology for monitoring. The literature suggests that inhaled aerosolized epoprostenol, iloprost, treprostinil and others such as milrinone and levosimendan may be similar to iNO. More research of IPV is needed to determine acceptable inclusion criteria, long-term outcomes, and management strategies including time, dose, and duration.

Oxymatrine on Hsp90a expression and apoptosis in a model of lung ischemia-reperfusion injury

The protective effects of oxymatrine (OMT) on apoptosis and heat shock protein 90a (Hsp90a) expression in a rabbit model of lung ischemia-reperfusion injury (LIRI) were investigated. The model of LIRI was established in rabbits and they were randomly divided into two groups: The control group (group C, n=10), and experimental group (further divided into groups E1, n=10; and group E2, n=10), to measure the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) activity in lung tissue homogenates at several time points (T₀, 0 min; T₁, 60 min; T₂, 120 min; T₃, 180 min; and T₄, 240 min), and to measures changes in lung tissue wet/dry weight ratio (W/D), apoptosis index (AI), and Hsp90a expression and organization at T₂, T₃ and T₄. Comparing group C with groups E1 and E2, the levels of SOD activity and MDA were not significantly different at T₀ and T₁ (P>0.05); W/D ratio and AI were significantly higher than in groups E1 and E2 (P<0.05, P<0.01); 120 min after LIR, MDA, W/D ratio, and AI were lower than in groups E1 and E2 (P<0.05, P<0.01). MDA, W/D ratio and AI were lower in E2 than in E1 (P<0.05), and SOD and Hsp90a expression increased (P<0.05). The ultrastructure in group E showed less injury compared with group C. In conclusion, by scavenging oxygen free radicals, OMT can inhibit apoptosis, increase Hsp90a expression, and reduce the injury caused by lung ischemia reperfusion.

The attenuation of lung ischemia reperfusion injury by oxymatrine

To investigate the protective effects of oxymatrine (OMT) on lung ischemia reperfusion injury (LIRI) in rabbits, models of LIRI in rabbit were used. Thirty-two rabbits were randomly divided into four groups: control group (n = 8), ischemia reperfusion group (I/R group, n = 8), OMTl group (n = 8), OMT2 group (n = 8). Lung tissue samples were collected at 40, 80, 120 min time-points after lung ischemia reperfusion. TNF-α, 1I-8, IL-10, apoptosis index (AI), and index of quantitative assessment of histologic lung injury (IQA) were measured in each group. TNF-α and IL-8 in I/R group were significantly higher than those of the control group and OMT2 group (P < 0.01), but in OMT2 group they were significantly lower than those of OMTl group (P < 0.05). IL-10 in OMT2 group and OMTl group was significantly higher than that of I/R group (P < 0.01). But in OMTl group it was significantly lower than that of OMT2 group (P < 0.05). AI in I/R group was significantly higher than that of OMT2 group and the control group at 80 min after lung ischemia reperfusion (P < 0.01). IQA in OMTl group and OMT2 group was significantly lower than that of the I/R group (P < 0.01). Oxymatrine can protect against LIRI in rabbits by upregulating levels of IL-10 and downregulating levels of TNF-α and IL-8, inhibiting the alveolar cells apoptosis and inflammatory response, and attenuating the acute LIRI.

Inhaled nitric oxide therapy for extrapulmonary inflammation

Inhaled nitric oxide (iNO) has been used extensively to treat pulmonary hypertension primarily in newborns. This therapy is a safe and effective therapy to improve the matching between airway ventilation and blood oxygenation. A key conceptual component of iNO therapy is that effects are limited to the pulmonary compartment thereby avoiding unwanted systemic effects. The mechanism underlying this model is that any NO entering the blood stream is rapidly oxidized to nitrate, a relatively inert anion that is excreted. Mediating this oxidation is oxyhemoglobin that becomes oxidized to methemoglobin, accumulation of which is limited by erythrocyte methemoglobin reductase. In this article, we discuss studies that dismiss the notion that once in the blood stream iNO is inactivated and show that a surprising result of iNO therapy is the formation of stable NO-derived products that circulate and can elicit NO-dependent signaling in extra-pulmonary tissues. This pathway has the potential to open up new applications for iNO for treatment of systemic diseases associated with loss of NO signaling.

Investigation of the role of nitric oxide/soluble guanylyl cyclase pathway in ascorbic acid-mediated protection against acute kidney injury in rats

The present study investigated the possible involvement of nitric oxide/soluble guanylyl cyclase (NO/sGC) pathway in ascorbic acid (AA)-mediated protection against acute kidney injury (AKI) in rats. The rats were subjected to bilateral renal ischemia by occluding renal pedicles for 40 min followed by reperfusion for 24 h. The AKI was assessed in terms of measuring creatinine clearance (CrCl), blood urea nitrogen (BUN), plasma uric acid, potassium level, fractional excretion of sodium (FeNa), and microproteinuria. The NO level and oxidative stress in renal tissues were assessed by measuring myeloperoxidase activity, thiobarbituric acid reactive substances, superoxide anion generation, and reduced glutathione level. AA (50 and 100 mg/kg, p.o.) was administered for 3 days before subjecting rats to AKI. In separate groups, the nitric oxide synthase inhibitor, L-NAME (20 mg/kg, i.p.) and sGC inhibitor, methylene blue (50 mg/kg, i.p.) was administered prior to AA treatment in rats. The significant decrease in CrCl and increase in BUN, plasma uric acid, potassium, FeNa, microproteinuria, and oxidative stress in renal tissues demonstrated ischemia-reperfusion-induced AKI in rats. The AA treatment ameliorated ischemia-reperfusion-induced AKI along with the increase in renal NO level. The pretreatment with L-NAME and methylene blue abolished protective effect of AA. It is concluded that AA protects against ischemia-reperfusion-induced AKI. Moreover, the NO/sGC pathway finds its definite involvement in AA-mediated reno-protective effect.

Oxidative Stress and Lung Ischemia-Reperfusion Injury

Ischemia-reperfusion (IR) injury is directly related to the formation of reactive oxygen species (ROS), endothelial cell injury, increased vascular permeability, and the activation of neutrophils and platelets, cytokines, and the complement system. Several studies have confirmed the destructiveness of the toxic oxygen metabolites produced and their role in the pathophysiology of different processes, such as oxygen poisoning, inflammation, and ischemic injury. Due to the different degrees of tissue damage resulting from the process of ischemia and subsequent reperfusion, several studies in animal models have focused on the prevention of IR injury and methods of lung protection. Lung IR injury has clinical relevance in the setting of lung transplantation and cardiopulmonary bypass, for which the consequences of IR injury may be devastating in critically ill patients.

Beneficial effects of inhaled NO on apoptotic pneumocytes in pulmonary thromboembolism model

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) may occur in the region of the affected lung after reperfusion therapy. Inhaled NO may be useful in treating acute and chronic pulmonary thromboembolism (PTE) due to the biological effect property of NO.

METHODS

A PTE canine model was established through selectively embolizing blood clots to an intended right lower lobar pulmonary artery. PaO2/FiO2, the mPAP and PVR were investigated at the time points of 2, 4, 6 hours after inhaled NO. Masson's trichrome stain, apoptotic pneumocytes and lung sample ultrastructure were also investigated among different groups.

RESULTS

The PaO2/FiO2 in the Inhaled NO group increased significantly when compared with the Reperfusion group at time points of 4 and 6 hours after reperfusion, mPAP decreased significantly at point of 2 hours and the PVR decreased significantly at point of 6 hours after reperfusion. The amounts of apoptotic type II pneumocytes in the lower lobar lung have negative correlation trend with the arterial blood PaO2/FiO2 in Reperfusion group and Inhaled NO group. Inhaled nitric oxide given at 20 ppm for 6 hours can significantly alleviate the LIRI in the model.

CONCLUSIONS

Dramatic physiological improvements are seen during the therapeutic use of inhaled NO in pulmonary thromboembolism canine model. Inhaled NO may be useful in treating LIRI in acute or chronic PTE by alleviating apoptotic type II pneumocytes. This potential application warrants further investigation.

A randomized clinical trial testing the anti-inflammatory effects of preemptive inhaled nitric oxide in human liver transplantation

Decreases in endothelial nitric oxide synthase derived nitric oxide (NO) production during liver transplantation promotes injury. We hypothesized that preemptive inhaled NO (iNO) would improve allograft function (primary) and reduce complications post-transplantation (secondary). Patients at two university centers (Center A and B) were randomized to receive placebo (n = 20/center) or iNO (80 ppm, n = 20/center) during the operative phase of liver transplantation. Data were analyzed at set intervals for up to 9-months post-transplantation and compared between groups. Patient characteristics and outcomes were examined with the Mann-Whitney U test, Student t-test, logistic regression, repeated measures ANOVA, and Cox proportional hazards models. Combined and site stratified analyses were performed. MELD scores were significantly higher at Center B (22.5 vs. 19.5, p<0.0001), surgical times were greater at Center B (7.7 vs. 4.5 hrs, p<0.001) and warm ischemia times were greater at Center B (95.4 vs. 69.7 min, p<0.0001). No adverse metabolic or hematologic effects from iNO occurred. iNO enhanced allograft function indexed by liver function tests (Center B, p<0.05; and p<0.03 for ALT with center data combined) and reduced complications at 9-months (Center A and B, p = 0.0062, OR = 0.15, 95% CI (0.04, 0.59)). ICU (p = 0.47) and hospital length of stay (p = 0.49) were not decreased. iNO increased concentrations of nitrate (p<0.001), nitrite (p<0.001) and nitrosylhemoglobin (p<0.001), with nitrite being postulated as a protective mechanism. Mean costs of iNO were $1,020 per transplant. iNO was safe and improved allograft function at one center and trended toward improving allograft function at the other. ClinicalTrials.gov with registry number 00582010 and the following URL:http://clinicaltrials.gov/show/NCT00582010.

Inhaled Nitric Oxide Reduces Brain Damage by Collateral Recruitment in a Neonatal Stroke Model

Background and Purpose—

We recently demonstrated that endogenous nitric oxide (NO) modulates collateral blood flow in a neonatal stroke model in rats. The inhalation of NO (iNO) has been found to be neuroprotective after ischemic brain damage in adults. Our objective was to examine whether iNO could modify cerebral blood flow during ischemia–reperfusion and reduce lesions in the developing brain.

Methods—

In vivo variations in cortical NO concentrations occurring after 20-ppm iNO exposure were analyzed using the voltammetric method in P7 rat pups. Inhaled NO-mediated blood flow velocities were measured by ultrasound imaging with sequential Doppler recordings in both internal carotid arteries and the basilar trunk under basal conditions and in a neonatal model of ischemia–reperfusion. The hemodynamic effects of iNO (5 to 80 ppm) were correlated with brain injury 48 hours after reperfusion.

Results—

Inhaled NO (20 ppm) significantly increased NO concentrations in the P7 rat cortex and compensated for the blockade of endogenous NO synthesis under normal conditions. Inhaled NO (20 ppm) during ischemia increased blood flow velocities and significantly reduced lesion volumes by 43% and cellular damage. In contrast, both 80 ppm iNO given during ischemia and 5 or 20 ppm iNO given 30 minutes after reperfusion were detrimental.

Conclusions—

Our findings strongly indicate that, with the appropriate timing, 20 ppm iNO can be transported into the P7 rat brain and mediated blood flow redistribution during ischemia leading to reduced infarct volume and cell injury.

Emergent role of gasotransmitters in ischemia-reperfusion injury

Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are lipid-soluble, endogenously produced gaseous messenger molecules collectively known as gasotransmitters. Over the last several decades, gasotransmitters have emerged as potent cytoprotective mediators in various models of tissue and cellular injury. Specifically, when used at physiological levels, the exogenous and endogenous manipulation of these three gases has been shown to modulate ischemia/reperfusion injury by inducing a number of cytoprotective mechanisms including: induction of vasodilatation, inhibition of apoptosis, modulation of mitochondrial respiration, induction of antioxidants, and inhibition of inflammation. However, while the actions are similar, there are some differences in the mechanisms by which these gasotransmitters induce these effects and the regulatory actions of the enzyme systems can vary depending upon the gas being investigated. Furthermore, there does appear to be some crosstalk between the gases, which can provide synergistic effects and additional regulatory effects. This review article will discuss several models and mechanisms of gas-mediated cytoprotection, as well as provide a brief discussion on the complex interactions between the gasotransmitter systems.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Nitric oxide mechanism of protection in ischemia and reperfusion injury

In 1992 nitric oxide (NO) was declared molecule of the year by Science magazine, and ever since research on this molecule continues to increase. Following this award, NO was shown to be a mediator/protector of ischemia and reperfusion injury in many organs, such as the heart, liver, lungs, and kidneys. Controversy has existed concerning the actual protective effects of NO. However, literature from the past 15 years seems to reinforce the consensus that NO is indeed protective. Some of the protective actions of NO in ischemia and reperfusion are due to its potential as an antioxidant and anti-inflammatory agent, along with its beneficial effects on cell signaling and inhibition of nuclear proteins, such as NF-kappa B and AP-1. New therapeutic potentials for this drug are also continuously emerging. Exogenous NO and endogenous NO may both play protective roles during ischemia and reperfusion injury. Sodium nitroprusside and nitroglycerin have been used clinically with much success; though only recently have they been tested and proven effective in attenuating some of the injuries associated with ischemia and reperfusion. NO inhalation has, in the past, mostly been used for its pulmonary effects, but has also recently been shown to be protective in other organs. The potential of NO in the treatment of ischemic disease is only just being realized. Elucidation of the mechanism by which NO exerts its protective effects needs further investigation. Therefore, this paper will focus on the mechanistic actions of NO in ischemia and reperfusion injury, along with the compound's potential therapeutic benefits.

Pulmonary macrophage inhibition and inhaled nitric oxide attenuate lung ischemia-reperfusion injury

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is postulated to occur biphasically. Donor pulmonary macrophages mediate early injury, and neutrophil-dependent injury predominates in the later phase of LIRI. We hypothesized that the biphasic response to LIRI would be attenuated by the administration of gadolinium, a known pulmonary macrophage inhibitor, and inhaled nitric oxide (NO), a pulmonary vasodilator that also interferes with neutrophil chemotaxis.

METHODS

Using our isolated, ventilated, blood-perfused rabbit lung model, study groups (n = 10 per group) underwent two hours of reperfusion after 18 hours of cold ischemia (4 degrees C). Lungs received gadolinium alone, or inhaled NO in the presence or absence of macrophage inhibition with gadolinium.

RESULTS

Compared with control animals, pulmonary macrophage inhibition with the concurrent administration of inhaled NO increased lung compliance (p < 0.01) and oxygenation (p = 0.03), while also decreasing pulmonary artery pressure (p < 0.01), myeloperoxidase content by 63% (p < 0.01), wet to dry ratios by 23% (p < 0.01), and lung tissue (p < 0.01) and bronchoalveolar lavage tumor necrosis factor-alpha (TNF-alpha) protein levels (p < 0.01).

CONCLUSIONS

The severity of LIRI was most significantly reduced by the inhibition of pulmonary macrophages and the concomitant use of inhaled NO. Pulmonary macrophages, likely through the elaboration of proinflammatory cytokines such as TNF-alpha, not only cause early injury themselves but also prime cells such as neutrophils to injure lungs in the later stages of LIRI. The LIRI was effectively blunted by the reduction of macrophage-dependent injury by gadolinium while inhaled NO also attenuated injury by reducing pulmonary hypertension and minimizing neutrophil sequestration.

Mitochondrial nitric oxide in the signaling of cell integrated responses

Mitochondria are the specialized organelles for energy metabolism, but, as a typical example of system biology, they also activate a multiplicity of pathways that modulate cell proliferation and mitochondrial biogenesis or oppositely promote cell arrest and programmed cell death by a limited number of oxidative or nitrosative reactions. These reactions are influenced by matrix nitric oxide (NO) steady-state concentration, either from local production or by gas diffusion to mitochondria from the canonical sources. Likewise, in a range of ∼30–200 nM, NO turns mitochondrial O2utilization down by binding to cytochrome oxidase and elicits a burst of superoxide anion and hydrogen peroxide that diffuses outside mitochondria. Depending on NO levels and antioxidant defenses, more or less H2O2accumulates in cytosol and nucleus, and the resulting redox grading contributes to dual activation of proliferating and proapoptotic cascades, like ERK1/2 or p38 MAPK. Moreover, these sequential activating pathways participate in rat liver and brain development and in thyroid modulation of mitochondrial metabolism and contribute to hypothyroid phenotype through complex I nitration. On the contrary, lack of NO disrupts pathways like S-nitrosylation or H2O2production and likewise is a gateway to disease in amyotrophic lateral sclerosis with superoxide dismutase 1 mutations or to cancer proliferation.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Cardiopulmonary bypass for lung transplantation in cystic fibrosis: pilot evaluation of perioperative outcome

OBJECTIVE

The purpose of this study was to determine whether cardiopulmonary bypass (CPB) reduces the incidence of perioperative graft infection after lung transplantation in adults with cystic fibrosis (CF).

DESIGN

Retrospective and observational.

SETTING

University hospital.

PARTICIPANTS

Adults with CF who underwent lung transplantation (1998-2003).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cohort size was 26: group A (n = 10) who underwent CPB for implantation of both lungs, group B (n = 8) who underwent CPB only for implantation of the second lung, and group C (n = 8) who did not undergo CPB. The 3 cohort subgroups were similar (p > 0.05) in demographics, preoperative lung function, and anesthetic management. Group A had a lower incidence of perioperative pneumonia (p = 0.02). CPB exposure increased transfusion (B > A > C) of fresh frozen plasma and platelets but not packed red blood cells. There were no differences (p > 0.05) in clinical outcome as reflected by duration of mechanical ventilation, tracheal re-intubation, re-exploration for bleeding, sepsis, primary graft dysfunction, renal dysfunction, length of stay, and mortality.

CONCLUSIONS

CPB is associated with decreased incidence of early graft infection after lung transplantation for adult CF when used for implantation of both lungs. This may be because of improved decontamination of the operative field before graft implantation.

Immunoregulatory and antimicrobial effects of nitrogen oxides

The therapeutic effects of inhaled nitric oxide (NO) therapy are thought to be restricted to the pulmonary vasculature because of rapid inactivation of NO by hemoglobin in the bloodstream. However, recent data suggest that inhaled NO may not only be scavenged by the heme iron of hemoglobin but also may react with protein thiols in the bloodstream, including cysteine-93 of the hemoglobin B subunit. Reaction of NO with protein or peptide thiols is termed S-nitrosylation and results in the formation of relatively stable protein S-nitrosothiols that carry NO bioactivity to distal organs. Thus, inhaled NO-induced protein S-nitrosylation may allow inhaled NO to have multiple as yet undiscovered physiologic and pathophysiologic effects outside of the lung. Here we review the immunoregulatory and antimicrobial functions of NO and the potential effects of inhaled NO therapy on host defense.

Inhaled nitric oxide effects on lung structure and function in chronically ventilated preterm lambs

RATIONALE

Inhaled nitric oxide (iNO) can reverse neonatal pulmonary hypertension and bronchoconstriction and reduce proliferation of cultured arterial and airway smooth muscle cells.

OBJECTIVES

To see if continuous iNO from birth might reduce pulmonary vascular and respiratory tract resistance (PVR, RE) and attenuate growth of arterial and airway smooth muscle in preterm lambs with chronic lung disease.

METHODS

Eight premature lambs received mechanical ventilation for 3 weeks, four with and four without iNO (5-15 ppm). Four term lambs, mechanically ventilated without iNO for 3 weeks, served as additional control animals.

MEASUREMENTS

PVR and RE were measured weekly. After 3 weeks, lung tissue was processed for quantitative image analysis of smooth muscle abundance around small arteries (SMart) and terminal bronchioles (SMtb). Radial alveolar counts were done to assess alveolar number. Endothelial NO synthase (eNOS) protein in arteries and airways was measured by immunoblot analysis.

MAIN RESULTS

At study's end, PVR was similar in iNO-treated and untreated preterm lambs; PVR was less in iNO-treated preterm lambs compared with term control animals. RE in iNO-treated lambs was less than 40% of RE measured in preterm control animals. SMart was similar in iNO-treated and both groups of control lambs; SMtb in lambs given iNO was significantly less (approximately 50%) than in preterm control animals. Radial alveolar counts of iNO-treated lambs were more than twice that of preterm control animals. eNOS was similar in arteries and airways of iNO-treated preterm lambs compared with control term lambs.

CONCLUSIONS

iNO preserves structure and function of airway smooth muscle and enhances alveolar development in preterm lambs with chronic lung disease.