Exhaled nitric oxide as biomarker of acute lung injury: an unfulfilled promise?

Nitric Oxide as a Central Molecule in Hypertension: Focus on the Vasorelaxant Activity of New Nitric Oxide Donors

Cardiovascular diseases include all types of disorders related to the heart or blood vessels. High blood pressure is an important risk factor for cardiac complications and pathological disorders. An increase in circulating angiotensin-II is a potent stimulus for the expression of reactive oxygen species and pro-inflammatory cytokines that activate oxidative stress, perpetuating a deleterious effect in hypertension. Studies demonstrate the capacity of NO to prevent platelet or leukocyte activation and adhesion and inhibition of proliferation, as well as to modulate inflammatory or anti-inflammatory reactions and migration of vascular smooth muscle cells. However, in conditions of low availability of NO, such as during hypertension, these processes are impaired. Currently, there is great interest in the development of compounds capable of releasing NO in a modulated and stable way. Accordingly, compounds containing metal ions coupled to NO are being investigated and are widely recognized as having great relevance in the treatment of different diseases. Therefore, the exogenous administration of NO is an attractive and pharmacological alternative in the study and treatment of hypertension. The present review summarizes the role of nitric oxide in hypertension, focusing on the role of new NO donors, particularly the metal-based drugs and their protagonist activity in vascular function.

Thyme oil alleviates Ova-induced bronchial asthma through modulating Th2 cytokines, IgE, TSLP and ROS

Bronchial asthma (BA) is a heterogeneous allergic respiratory disease with diverse inflammatory symptoms, pathology, and responses to treatment. Thyme is a natural product which is consisted of multiple phenolic compounds of therapeutic significance for treatment of cough and bronchitis. This study evaluated the efficacy of thyme oil against ovalbumin (OVA)-induced BA in an experimental rabbit model. Forty male rabbits were divided into four equal groups [control group (G1), OVA (G2), thyme oil (G3), and OVA plus thyme oil (G4)]. Animals were treated for 30 days, and clinical, histopathological (HP), histochemical (HC), immunohistochemical (IHC), morphometric, biochemical and flow cytometry methods were performed, followed by statistical analysis. All used methods revealed normal structure of the lung tissues in rabbits of G1 and G3. In contrast, the clinical examination of G2 rabbits revealed an obvious increase in the respiratory rate, sneezing and wheezing, whereas the HP, HC and IHC techniques exhibited substantial inflammatory changes in the peribronchio-vascular lung tissues with thinning, degeneration, apoptosis (using the TUNEL assay), necrosis, and shedding of the airway epithelium. Furthermore, the morphometric results confirmed significant increases in the numbers of inflammatory cells, goblet cells, eosinophils and apoptotic cells from (12, 0, 2, 2 cells) to (34,10, 16, 18 cells) respectively, as well as the area percentage of collagen fiber deposition and immunoexpression of eotaxin-1/10 high power fields. Additionally, the biochemical results revealed significant increases in the serum levels of TSLP, IL-4, IL-5, IL-9, IL-13, IgE and eotaxin-1 cytokines from (140, 40, 15, 38, 120, 100, 48) pg./ml to (360, 270, 130, 85, 365, 398, 110) pg./ml respectively, while analysis of ROS by flow cytometry revealed remarkable oxidative stress effects in G2 rabbits. On the other hand, treatment of rabbits with thyme oil in G4 substantially alleviated all OVA-induced alterations. Overall, our findings indicate for the first time that thyme oil can ameliorate OVA-induced BA via its immunomodulatory, anti-inflammatory, antiapoptotic, and antioxidant effects on the lung tissues of rabbits.

Monitoring of endogenous nitric oxide exhaled by pig lungs during ex-vivo lung perfusion

In the context of organ shortage for transplantation, new criteria for better organ evaluation should be investigated. Ex-Vivo Lung Perfusion (EVLP) allows extra-corporal lung re-conditioning and evaluation, under controlled parameters of the organ reperfusion and mechanical ventilation. This work reports on the interest of exhaled gas analysis during the EVLP procedure. After a one-hour cold ischemia, the endogenous gas production by an isolated lung of nitric oxide and carbon monoxide is simultaneously monitored in real time. The exhaled gas is analysed with two very sensitive and selective laser spectrometers developed upon the technique of optical-feedback cavity-enhanced absorption spectroscopy. Exhaled gas concentration measured for an ex-vivo lung is compared to the corresponding production by the whole living pig, measured before euthanasia. On-line measurements of the fraction of nitric oxide in exhaled gas (FENO) in isolated lungs are reported here for the first time, allowing to resolve the respiratory cycles. In this study, performed on 9 animals, FENO by isolated lungs range from 3.3 to 10.6 ppb with a median value of 4.4 ppb. Pairing ex-vivo lung and pig measurements allows to demonstrate a systematic increase of FENO in the ex-vivo lung as compared to the living animal, by a factor of 3 ± 1.2. Measurements of the fraction of carbon monoxide in exhaled gas (FECO) confirm levels recorded during previous studies driven to evaluate FECO as a potential marker of ischemia reperfusion injuries. FECO production by ex-vivo lungs ranges from 0.31 to 2.3 ppm with a median value of 0.8 ppm. As expected, these FECO values are lower than the production by the corresponding whole pig body, by a factor of 6.9 ± 2.7.

Protective Effects of Anti-IL17 on Acute Lung Injury Induced by LPS in Mice

Introduction: T helper 17 (Th17) has been implicated in a variety of inflammatory lung and immune system diseases. However, little is known about the expression and biological role of IL-17 in acute lung injury (ALI). We investigated the mechanisms involved in the effect of anti-IL17 in a model of lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Methods: Mice were pre-treated with anti-IL17, 1h before saline/LPS intratracheal administration alongside non-treated controls and levels of exhaled nitric oxide (eNO), cytokine expression, extracellular matrix remodeling and oxidative stress, as well as immune cell counts in bronchoalveolar lavage fluid (BALF), and respiratory mechanics were assessed in lung tissue. Results: LPS instillation led to an increase in multiple cytokines, proteases, nuclear factor-κB, and Forkhead box P3 (FOXP3), eNO and regulators of the actomyosin cytoskeleton, the number of CD4+ and iNOS-positive cells as well as the number of neutrophils and macrophages in BALF, resistance and elastance of the respiratory system, ARG-1 gene expression, collagen fibers, and actin and 8-iso-PGF2α volume fractions. Pre-treatment with anti-IL17 led to a significant reduction in the level of all assessed factors. Conclusions: Anti-IL17 can protect the lungs from the inflammatory effects of LPS-induced ALI, primarily mediated by the reduced expression of cytokines and oxidative stress. This suggests that further studies using anti-IL17 in a treatment regime would be highly worthwhile.

Laser spectroscopy for breath analysis: towards clinical implementation

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.

Perioperative changes in exhaled nitric oxide during oesophagectomy

INTRODUCTION

Oesophagectomy is a major surgical procedure, associated with high rates of postoperative cardiopulmonary morbidity, that is in part due to the frequent requirement for periods of intraoperative one-lung ventilation (OLV). The current pilot study aims to investigate variation in exhaled NO levels during oesophagectomy with emphasis on the response to OLV and correlation to physiological variables and clinical outcomes.

METHODS

Breath-to-breath concentrations of NO were analysed in patients undergoing oesophagectomy at various stages of two-lung ventilation. Furthermore, we also analysed the effects of OLV both in the selectively ventilated and collapsed lungs.

RESULTS

Twenty-four patients were recruited to the study (17 male, 60.2 ± 12.8 years). Regarding two-lung ventilation, the baseline levels of NO (2.9 ppb), tended to increase after re-inflation of the collapsed lung (3.5 ppb, P = 0. 888) and decreased at 2 h (2.1 ppb, P = 0.022) and 12 h (2.2 ppb, P = 0.733) postoperatively. Compared to baseline, selective measurements of NO at the end of OLV demonstrated a significant reduction of NO levels in the ventilated lung (1.6 versus 3.1 ppb, P = 0.028), whereas re-inflation of the collapsed lung revealed higher levels of NO (3.4 versus 2.7 ppb, P = 0.657). Exhaled NO correlated significantly with systolic blood pressure and lactate (P < 0.007). Exhaled NO levels tended to be higher at all perioperative time points in patients who developed postoperative respiratory complications (P > 0.05).

CONCLUSION

This study highlights effects of oesophagectomy and OLV on exhaled concentrations of NO. The observed variations may be related to differential ventilation during OLV altering the complex balance between synthesis and consumption of NO as well as local and generalised tissue injury associated with this surgery. Findings should prompt further larger studies to establish the relationship between exhaled NO and lung injury both during and after oesophagectomy and one-lung ventilation.

Preoperative FeNO as a screening indicator of pulmonary complications after abdominal surgery in patients over 60 years old

The incidence of pulmonary complications after abdominal surgery is higher than that of cardiac complications. The perioperative factors currently used to assess the risk of postoperative pulmonary complications (PPCs) are imperfect. FeNO is a marker of respiratory system disease related to the airway inflammatory response and bronchial hyperresponsiveness; it may be a new indicator to screen PPCs. A total of 162 patients over 60 years old scheduled for major abdominal surgery under general anesthesia were chosen to measure their preoperative FeNO level. Statistical analyses including the receiver operating characteristic (ROC) and general linear regression were used to analyze the relationships of FeNO with PPCs and other parameters. The medians and quartiles of preoperative FeNO were 14.33 (9.67-21.10) ppb; the geometric mean was 14.25 ppb. Preoperative FeNO correlated to age (P <  0.05), and the coefficient of association was 0.267. ROC curve analysis of FeNO and PPCs resulted in a high probability with an area under the curve of 0.747 (p = 0.001, 95% confidence interval =0.602-0.893). The cut-off level was 30.2 ppb, with 47.06% sensitivity and 93.10% specificity. The positive predictive value of the cut-off was 42.11% and negative predictive value was 93.70%. OR value was 10.83. The magnitude of FeNO in the PPCs group was larger than that in the non-PPCs groups 26.20 (11.55 - 39.20) versus 13.50 (9.55-20.00); p = 0.008). Preoperative FeNO levels may be used to screen the patients over 60 years old undergoing abdominal surgery with a lower probability to suffer PPCs whoes FeNO values less than 30.2 ppb.

Assessment of the exhalation kinetics of volatile cancer biomarkers based on their physicochemical properties

The current review provides an assessment of the exhalation kinetics of volatile organic compounds (VOCs) that have been linked with cancer. Towards this end, we evaluate various physicochemical properties, such as 'breath:air' and 'blood:fat' partition coefficients, of 112 VOCs that have been suggested over the past decade as potential markers of cancer. With these data, we show that the cancer VOC concentrations in the blood and in the fat span over 12 and 8 orders of magnitude, respectively, in order to provide a specific counterpart concentration in the exhaled breath (e.g., 1 ppb). This finding suggests that these 112 different compounds have different storage compartments in the body and that their exhalation kinetics depends on one or a combination of the following factors: (i) the VOC concentrations in different parts of the body; (ii) the VOC synthesis and metabolism rates; (iii) the partition coefficients between tissue(s), blood and air; and (iv) the VOCs' diffusion constants. Based on this analysis, we discuss how this knowledge allows modeling and simulating the behavior of a specific VOC under different sampling protocols (with and without exertion of effort). We end this review by a brief discussion on the potential role of these scenarios in screening and therapeutic monitoring of cancer.

Alterations in exhaled breath metabolite-mixtures in two rat models of lipopolysaccharide-induced lung injury

Exhaled breath contains information on systemic and pulmonary metabolism, which may provide a monitoring tool for the development of lung injury. We aimed to determine the effect of intravenous (iv) and intratracheal (IT) lipopolysaccharide (LPS) challenge on the exhaled mixture of volatile metabolites and to assess the similarities between these two models. Male adult Sprague-Dawley rats were anesthetized, tracheotomized, and ventilated for 6 h. Lung injury was induced by iv or IT administration of LPS. Exhaled breath was monitored continuously using an electronic nose (eNose), and hourly using gas chromatography and mass spectrometry (GC-MS). GC-MS analysis identified 34 and 14 potential biological markers for lung injury in the iv and IT LPS models, respectively. These volatile biomarkers could be used to discriminate between LPS-challenged rats and control animals within 1 h after LPS administration. Electronic nose analysis resulted in a good separation 3 h after the LPS challenge. Hexanal, pentadecane and 6,10-dimethyl-5,9-undecadien-2-one concentrations decreased after both iv and IT LPS administration. Nonanoic acid was found in a higher concentration in exhaled breath after LPS inoculation into the trachea but in a lower concentration after iv infusion. LPS-induced lung injury rapidly changes exhaled breath metabolite mixtures in two animal models of lung injury. Changes partly overlap between an iv and an IT LPS challenge. This warrants testing the diagnostic accuracy of exhaled breath analysis for acute respiratory distress syndrome in clinical trials, possibly focusing on biological markers described in this study.

Pulmonary infection, and not systemic inflammation, accounts for increased concentrations of exhaled nitric oxide in patients with septic shock

Nitric oxide (NO) is a key mediator in the pathophysiology of septic shock that can be measured in exhaled breath. To assess whether a pulmonary infection itself or systemic inflammation is responsible for NO production, we determined exhaled NO in ventilated patients with respiratory and non-respiratory septic shock and compared it with the concentration in ventilated intensive care patients without systemic inflammation. In addition, the change of NO production over time and correlations with haemodynamic instability were evaluated. The controls without systemic inflammation, as witnessed by the absence of systemic inflammatory response syndrome criteria and low levels of interleukin-6, had similar concentrations of NO as the patients with non-respiratory septic shock. The respiratory sepsis patients exhaled more NO than the non-respiratory sepsis patients (p = 0.05), and a time dependent decline in time in both groups (p = 0.04). Exhaled NO did not correlate with markers of disease severity, systemic inflammation and haemodynamic instability. These data indicate that the infected lungs are the source of exhaled NO.