Instillation Of Hydrochloric Acid Research Articles

The Synthetic Surfactant CHF5633 Restores Lung Function and Lung Architecture in Severe Acute Respiratory Distress Syndrome in Adult Rabbits

PurposeAcute respiratory distress syndrome (ARDS) is a major cause of hypoxemic respiratory failure in adults. In ARDS extensive inflammation and leakage of fluid into the alveoli lead to dysregulation of pulmonary surfactant metabolism and function. Altered surfactant synthesis, secretion, and breakdown contribute to the clinical features of decreased lung compliance and alveolar collapse. Lung function in ARDS could potentially be restored with surfactant replacement therapy, and synthetic surfactants with modified peptide analogues may better withstand inactivation in ARDS alveoli than natural surfactants.MethodsThis study aimed to investigate the activity in vitro and the bolus effect (200 mg phospholipids/kg) of synthetic surfactant CHF5633 with analogues of SP‐B and SP‐C, or natural surfactant Poractant alfa (Curosurf®, both preparations Chiesi Farmaceutici S.p.A.) in a severe ARDS model (the ratio of partial pressure arterial oxygen and fraction of inspired oxygen, P/F ratio ≤ 13.3 kPa) induced by hydrochloric acid instillation followed by injurious ventilation in adult New Zealand rabbits. The animals were ventilated for 4 h after surfactant treatment and the respiratory parameters, histological appearance of lung parenchyma and levels of inflammation, oxidative stress, surfactant dysfunction, and endothelial damage were evaluated.ResultsBoth surfactant preparations yielded comparable improvements in lung function parameters, reductions in lung injury score, pro-inflammatory cytokines levels, and lung edema formation compared to untreated controls.ConclusionsThis study indicates that surfactant replacement therapy with CHF5633 improves lung function and lung architecture, and attenuates inflammation in severe ARDS in adult rabbits similarly to Poractant alfa. Clinical trials have so far not yielded conclusive results, but exogenous surfactant may be a valid supportive treatment for patients with ARDS given its anti-inflammatory and lung-protective effects.

The effect of budesonide delivered by high-frequency oscillatory ventilation on acute inflammatory response in severe lung injury in adult rabbits.

The inflammation present in acute respiratory distress syndrome (ARDS) and thereby associated injury to the alveolar-capillary membrane and pulmonary surfactant can potentiate respiratory failure. Even considering the high mortality rate of severe ARDS, glucocorticoids appear to be a reasonable treatment option along with an appropriate route of delivery to the distal lung. This study aimed to investigate the effect of budesonide therapy delivered intratracheally by high-frequency oscillatory ventilation (HFOV) on lung function and inflammation in severe ARDS. Adult New Zealand rabbits with respiratory failure (P/F<13.3 kPa) induced by intratracheal instillation of hydrochloric acid (HCl, 3 ml/kg, pH 1.5) followed by high tidal ventilation (VT 20 ml/kg) to mimic ventilator-induced lung injury (VILI) were treated with intratracheal bolus of budesonide (0.25 mg/kg, Pulmicort) delivered by HFOV (frequency 8 Hz, MAP 1 kPa, deltaP 0.9 kPa). Saline instead of HCl without VILI with HFOV delivered air bolus instead of therapy served as healthy control. All animals were subjected to lung-protective ventilation for 4 h, and respiratory parameters were monitored regularly. Postmortem, lung injury, wet-to-dry weight ratio, leukocyte shifts, and levels of cytokines in plasma and lung were evaluated. Budesonide therapy improved the lung function (P/F ratio, oxygenation index, and compliance), decreased the cytokine levels, reduced lung edema and neutrophils influx into the lung, and improved lung architecture in interstitial congestion, hyaline membrane, and atelectasis formation compared to untreated animals. This study indicates that HFOV delivered budesonide effectively ameliorated respiratory function, and attenuated acid-induced lung injury in a rabbit model of severe ARDS.

Improving pulmonary perfusion assessment by dynamic contrast-enhanced computed tomography in an experimental lung injury model.

Pulmonary perfusion has been poorly characterized in acute respiratory distress syndrome (ARDS). Optimizing protocols to measure pulmonary blood flow (PBF) via dynamic contrast-enhanced (DCE) computed tomography (CT) could improve understanding of how ARDS alters pulmonary perfusion. In this study, comparative evaluations of injection protocols and tracer-kinetic analysis models were performed based on DCE-CT data measured in ventilated pigs with and without lung injury. Ten Yorkshire pigs (five with lung injury, five healthy) were anesthetized, intubated, and mechanically ventilated; lung injury was induced by bronchial hydrochloric acid instillation. Each DCE-CT scan was obtained during a 30-s end-expiratory breath-hold. Reproducibility of PBF measurements was evaluated in three pigs. In eight pigs, undiluted and diluted Isovue-370 were separately injected to evaluate the effect of contrast viscosity on estimated PBF values. PBF was estimated with the peak-enhancement and the steepest-slope approach. Total-lung PBF was estimated in two healthy pigs to compare with cardiac output measured invasively by thermodilution in the pulmonary artery. Repeated measurements in the same animals yielded a good reproducibility of computed PBF maps. Injecting diluted isovue-370 resulted in smaller contrast-time curves in the pulmonary artery (P < 0.01) and vein (P < 0.01) without substantially diminishing peak signal intensity (P = 0.46 in the pulmonary artery) compared with the pure contrast agent since its viscosity is closer to that of blood. As compared with the peak-enhancement model, PBF values estimated by the steepest-slope model with diluted contrast were much closer to the cardiac output (R2 = 0.82) as compared with the peak-enhancement model. DCE-CT using the steepest-slope model and diluted contrast agent provided reliable quantitative estimates of PBF.NEW & NOTEWORTHY Dynamic contrast-enhanced CT using a lower-viscosity contrast agent in combination with tracer-kinetic analysis by the steepest-slope model improves pulmonary blood flow measurements and assessment of regional distributions of lung perfusion.

Efficacy of surfactant therapy of ARDS induced by hydrochloric acid aspiration followed by ventilator-induced lung injury - an animal study.

The development of acute respiratory distress syndrome (ARDS) is known to be independently attributable to aspiration-induced lung injury. Mechanical ventilation as a high pressure/volume support to maintain sufficient oxygenation of a patient could initiate ventilator-induced lung injury (VILI) and thus contribute to lung damage. Although these phenomena are rare in the clinic, they could serve as the severe experimental model of alveolar-capillary membrane deterioration. Lung collapse, diffuse inflammation, alveolar epithelial and endothelial damage, leakage of fluid into the alveoli, and subsequent inactivation of pulmonary surfactant, leading to respiratory failure. Therefore, exogenous surfactant could be considered as a therapy to restore lung function in experimental ARDS. This study aimed to investigate the effect of modified porcine surfactant in animal model of severe ARDS (P/F ratio </=13.3 kPa) induced by intratracheal instillation of hydrochloric acid (HCl, 3 ml/kg, pH 1.25) followed by VILI (V(T) 20 ml/kg). Adult rabbits were divided into three groups: untreated ARDS, model treated with a bolus of poractant alfa (Curosurf®, 2.5 ml/kg, 80 mg phospholipids/ml), and healthy ventilated animals (saline), which were oxygen-ventilated for an additional 4 h. The lung function parameters, histological appearance, degree of lung edema and levels of inflammatory and oxidative markers in plasma were evaluated. Whereas surfactant therapy with poractant alfa improved lung function, attenuated inflammation and lung edema, and partially regenerated significant changes in lung architecture compared to untreated controls. This study indicates a potential of exogenous surfactant preparation in the treatment of experimental ARDS.

Angiotensin-(1-7) alleviates acute lung injury by activating the Mas receptor in neutrophil.

Acute lung injury (ALI) is a major cause of mortality and morbidity in the clinic. None of the current pharmacological interventions has achieved a detectable benefit. The renin-angiotensin system (RAS) is a complex humoral system essentially involved in the regulation of ALI. In the RAS family, angiotensin (Ang)-(1-7) was found to provide protection by counteracting the effects of Ang II in various cardiopulmonary disease models. The downstream receptor of Ang-(1-7) is the G protein-coupled receptor (GPCR) Mas. We hypothesize that the Ang-(1-7)-Mas pathway would protect patients from ALI. To establish a 2-hit ALI model, the mice underwent intratracheal instillation of hydrochloric acid followed by ventilator-induced lung injury (VILI). ALI was evaluated based on lung edema, histology, myeloperoxidase activity, and proinflammatory cytokine production. The effects of the infusion or inhalation of Ang-(1-7) and Mas receptor blocker A779 were examined. The human neutrophils were isolated, and Mas receptor expression was examined. The neutrophil responses to platelet-activating factor (PAF) stimulation were tested by measuring the formation of reactive oxygen species (ROS), neutrophil adhesion, and chemotaxis. Next, in the mouse model, the neutrophils were depleted using an anti-ly6G antibody. The infusion or inhalation of Ang-(1-7) protected mice from ALI as evidenced by decreases in lung edema, the histological lung injury score, myeloperoxidase activity, and proinflammatory cytokine production. Such effects were largely blocked by the Mas receptor blocker A779. Mas receptor expression in the neutrophils was identified at both the messenger ribonucleic acid and protein levels. Ang-(1-7) prevented neutrophil responses to PAF stimulation, including the formation of ROS, neutrophil adhesion, and chemotaxis, while A779 alleviated these effects. The importance of neutrophils in ALI was further confirmed by neutrophil depletion using the anti-ly6G antibody; however, A779 partially reversed the protective role of neutrophil depletion in ALI, indicating the critical role of Ang-(1-7)-Mas signaling in other pulmonary cells. Ang-(1-7)/Mas receptor attenuates the key features of ALI by regulating neutrophil activation. Our study provides new evidence of their role in the pathogenesis of ALI and may lead to the development of a promising therapeutic strategy.

The Cholinergic Drug Galantamine Ameliorates Acute Respiratory Distress Syndrome in Mice

Acute respiratory distress syndrome (ARDS) is a life‐threatening form of acute lung injury and respiratory failure. The pandemic of SARS‐CoV‐2 has resulted in over 5 million deaths worldwide and many of those deaths have been attributed to complications associated with ARDS. No efficient pharmacological treatments for ARDS are currently available. In addition to lung injury and pulmonary inflammation, patients with ARDS have increased systemic inflammation. Previous insights have highlighted the role of cholinergic signalling in the vagus nerve‐based inflammatory reflex in controlling inflammation (Annu Rev Immunol, 2018, 36:783). Cholinergic anti‐inflammatory signalling can be activated by galantamine ‐ a centrally acting acetylcholinesterase inhibitor that is also clinically approved (for the treatment of Alzheimer’s disease). Here we examined the efficacy of galantamine in attenuating ARDS severity and inflammation in mice. We used a recently developed model of direct acute lung injury and ARDS, in which intratracheal (i.t.) hydrochloric acid (0.1N HCl, 2ml/kg) instillation is combined with LPS (10 mg/kg, i.t.) instillation 24h later in anesthetized mice. Male, 12‐week‐old C57BL/6 mice (n=7‐9), were subjected to this two hit ARDS model and treated 30 mins prior to each insult with galantamine (4 mg/kg, i.p.) or vehicle. Mice were euthanized 6h after LPS instillation and blood and bronchoalveolar lavage (BAL) fluid were collected. Galantamine significantly lowered the levels of BAL myeloperoxidase – an indicator of the accumulation of activated neutrophils in the airspaces of the lung (p = 0.0021) and the BAL total protein ‐ an indicator of alveolar permeability (p = 0.0076), compared with vehicle‐treated mice. BAL pro‐inflammatory cytokine levels were also reduced by galantamine, compared with vehicle‐treated mice – TNF (p = 0.0274), IL‐6 (p = 0.0009), and IL‐1β (p = 0.0380). In addition, treatment with galantamine significantly lowered the levels of serum pro‐inflammatory cytokines ‐ TNF (p = 0.0015), IL‐6 (p = 0.0089), and IL‐1β (p = 0.0149). In conclusion, galantamine reduced the severity of ARDS in mice and alleviated the local and systemic inflammatory responses. These results are of interest for further preclinical and clinical development of galantamine in the treatment of ARDS.

Halogenated Agent Delivery in Porcine Model of Acute Respiratory Distress Syndrome via an Intensive Care Unit Type Device.

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent need to find effective therapies. Preclinical studies have shown that inhaled halogenated agents may have beneficial effects in animal models of ARDS. The development of new devices to administer halogenated agents using modern intensive care unit (ICU) ventilators has significantly simplified the dispensing of halogenated agents to ICU patients. Because previous experimental and clinical research suggested potential benefits of halogenated volatiles, such as sevoflurane or isoflurane, for lung alveolar epithelial injury and inflammation, two pathophysiologic landmarks of diffuse alveolar damage during ARDS, we designed an animal model to understand the mechanisms of the effects of halogenated agents on lung injury and repair. After general anesthesia, tracheal intubation, and the initiation of mechanical ventilation, ARDS was induced in piglets via the intratracheal instillation of hydrochloric acid. Then, the piglets were sedated with inhaled sevoflurane or isoflurane using an ICU-type device, and the animals were ventilated with lung-protective mechanical ventilation during a 4 h period. During the study period, blood and alveolar samples were collected to evaluate arterial oxygenation, the permeability of the alveolar-capillary membrane, alveolar fluid clearance, and lung inflammation. Mechanical ventilation parameters were also collected throughout the experiment. Although this model induced a marked decrease in arterial oxygenation with altered alveolar-capillary permeability, it is reproducible and is characterized by a rapid onset, good stability over time, and no fatal complications. We have developed a piglet model of acid aspiration that reproduces most of the physiological, biological, and pathological features of clinical ARDS, and it will be helpful to further our understanding of the potential lung-protective effects of halogenated agents delivered through devices used for inhaled ICU sedation.

Pulmonary pyruvate metabolism as an index of inflammation and injury in a rat model of acute respiratory distress syndrome.

Increased pulmonary lactate production is correlated with severity of lung injury and outcome in acute respiratory distress syndrome (ARDS) patients. This study was conducted to investigate the relative contributions of inflammation and hypoxia to the lung's metabolic shift to glycolysis in an experimental animal model of ARDS using hyperpolarized (HP) 13 C MRI. Fifty-three intubated and mechanically ventilated male rats were imaged using HP 13 C MRI before, and 1, 2.5 and 4 hours after saline (sham) or hydrochloric acid (HCl; 0.5 ml/kg) instillation in the trachea, followed by protective and nonprotective mechanical ventilation (HCl-PEEP and HCl-ZEEP) or the start of moderate or severe hypoxia (Hyp90 and Hyp75 groups). Pulmonary and cardiac HP lactate-to-pyruvate ratios were compared among groups for different time points. Postmortem histology and immunofluorescence were used to assess lung injury severity and quantify the expression of innate inflammatory markers and local tissue hypoxia. HP pulmonary lactate-to-pyruvate ratio progressively increased in rats with lung injury and moderate hypoxia (HCl-ZEEP), with no significant change in pulmonary lactate-to-pyruvate ratio in noninjured but moderately hypoxic rats (Hyp90). Pulmonary lactate-to-pyruvate ratio was elevated in otherwise healthy lung tissue only in severe systemic hypoxia (Hyp75 group). ex vivo histological and immunopathological assessment further confirmed the link between elevated glycolysis and the recruitment into and presence of activated neutrophils in injured lungs. HP lactate-to-pyruvate ratio is elevated in injured lungs predominantly as a result of increased glycolysis in activated inflammatory cells, but can also increase due to severe inflammation-induced hypoxia.

Effect of positive end-expiratory pressure on functional residual capacity in two experimental models of acute respiratory distress syndrome.

ObjectiveMeasurement of positive end-expiratory pressure (PEEP)-induced recruitment lung volume using passive spirometry is based on the assumption that the functional residual capacity (FRC) is not modified by the PEEP changes. We aimed to investigate the influence of PEEP on FRC in different models of acute respiratory distress syndrome (ARDS).MethodsA randomized crossover study was performed in 12 pigs. Pulmonary (n = 6) and extra-pulmonary (n = 6) ARDS models were established using an alveolar instillation of hydrochloric acid and a right atrium injection of oleic acid, respectively. Low (5 cmH2O) and high (15 cmH2O) PEEP were randomly applied in each animal. FRC and recruitment volume were determined using the nitrogen wash-in/wash-out technique and release maneuver.ResultsFRC was not significantly different between the two PEEP levels in either pulmonary ARDS (299 ± 92 mL and 309 ± 130 mL at 5 and 15 cmH2O, respectively) or extra-pulmonary ARDS (305 ± 143 mL and 328 ± 197 mL at 5 and 15 cmH2O, respectively). The recruitment volume was not significantly different between the two models (pulmonary, 341 ± 100 mL; extra-pulmonary, 351 ± 170 mL).ConclusionsPEEP did not influence FRC in either the pulmonary or extra-pulmonary ARDS pig model.

Use of Electrical Impedance Tomography (EIT) to Estimate Global and Regional Lung Recruitment Volume (VREC) Induced by Positive End-Expiratory Pressure (PEEP): An Experiment in Pigs with Lung Injury.

BackgroundElectrical impedance tomography (EIT) is a real-time tool used to monitor lung volume change at the bedside, which could be used to measure lung recruitment volume (VREC) for setting positive end-expiratory pressure (PEEP). We assessed and compared the agreement in VREC measurement with the EIT method versus the flow-derived method.Material/MethodsIn 12 Bama pigs, lung injury was induced by tracheal instillation of hydrochloric acid and verified by an arterial partial pressure of oxygen to inspired oxygen fraction ratio below 200 mmHg. During the end-expiratory occlusion, an airway release maneuver was conduct at 5 and 15 cmH2O of PEEP. VREC was measured by flow-integrated PEEP-induced lung volume change (flow-derived method) and end-expiratory lung impedance change (EIT-derived method). Linear regression and Bland-Altman analysis were used to test the correlation and agreement between these 2 measures.ResultsLung injury was successfully induced in all the animals. EIT-derived VREC was significantly correlated with flow-derived VREC (R2=0.650, p=0.002). The bias (the lower and upper limits of agreement) was −19 (−182 to 144) ml. The median (interquartile range) of EIT-derived VREC was 322 (218–469) ml, with 110 (59–142) ml and 194 (157–307) ml in dependent and nondependent lung regions, respectively. Global and regional respiratory system compliance increased significantly at high PEEP compared to those at low PEEP.ConclusionsClose correlation and agreement were found between EIT-derived and flow-derived VREC measurements. The advantages of EIT-derived recruitability assessment included the avoidance of ventilation interruption and the ability to provide regional recruitment information.

Increased expression of CART, nNOS, VIP, PACAP, SP and GAL in enteric neurons of the porcine stomach prepyloric region following hydrochloric acid infusion.

Stomach hyperacidity leads to damage of the mucus/bicarbonate barrier, ulcerations and the development of stomach cancer. Key regulators of the mucosal barrier/luminal acid balance are neurotransmitters secreted by intramural neurons. The aim of the current study was to determine the expression of gastric neuropeptides and nNOS in the porcine stomach following hydrochloric acid instillation. We report on increased expression of enteric neurotransmitters involved in adaptive reaction to an experimentally-induced hyperacidity state. The investigation was conducted on eight 12-18 kg pigs. The influence of intragastric infusion of hydrochloric acid on the expression of cocaine- and amphetamine-regulated transcript peptide (CART), neuronal nitric oxide synthase (nNOS), vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating peptide (PACAP), substance P (SP) and galanin (GAL) in the submucous and myenteric gastric neurons of the pig has been studied with double immunofluorescence. A mimicked hyperacidity state significantly increased the proportion of enteric neurons immunoreactive to CART, nNOS, VIP, PACAP, SP and GAL in the submucous gastric neurons. In the myenteric plexus, a significant increase of the number of VIP-, CART- and GAL-immunoreactive (IR) neurons was found. Similarly, the percentage of myenteric nNOS-IR and PACAP-IR neurons tended to increase, while the fraction of SP-IR cells did not change. Stomach hyperacidity modifies the expression of the studied neurotransmitters in a specific way depending on the location of the neurons in particular plexuses of the stomach. Increased numbers of neurons expressing CART, nNOS, VIP, PACAP, SP and GAL clearly indicate their regulatory engagement in the restoration of the physiological gastric balance following hyperacidity.

A Model of Self-limited Acute Lung Injury by Unilateral Intra-bronchial Acid Instillation.

Selective intra-bronchial instillation of hydrochloric acid (HCl) to the murine left mainstem bronchus causes acute tissue injury with histopathologic findings similar to human acute respiratory distress syndrome (ARDS). The resulting alveolar edema, alveolar-capillary barrier damage, and leukocyte infiltration predominantly affect the left lung, preserving the right lung as an uninjured control and allowing animals to survive. This model of self-limited acute lung injury enables investigation of tissue resolution mechanisms, such as macrophage efferocytosis of apoptotic neutrophils and restitution of alveolar-capillary barrier integrity. This model has helped identify important roles for resolution agonists, including specialized pro-resolving mediators (SPMs), providing a foundation for the development of new therapeutic approaches for patients with ARDS.

Inhibition of the Receptor for Advanced Glycation End-Products in Acute Respiratory Distress Syndrome: A Randomised Laboratory Trial in Piglets

The receptor for advanced glycation end-products (RAGE) modulates the pathogenesis of acute respiratory distress syndrome (ARDS). RAGE inhibition attenuated lung injury and restored alveolar fluid clearance (AFC) in a mouse model of ARDS. However, clinical translation will require assessment of this strategy in larger animals. Forty-eight anaesthetised Landrace piglets were randomised into a control group and three treatment groups. Animals allocated to treatment groups underwent orotracheal instillation of hydrochloric acid (i) alone; (ii) in combination with intravenous administration of a RAGE antagonist peptide (RAP), or (iii) recombinant soluble (s)RAGE. The primary outcome was net AFC at 4 h. Arterial oxygenation was assessed hourly and alveolar-capillary permeability, alveolar inflammation and lung histology were assessed at 4 h. Treatment with either RAP or sRAGE improved net AFC (median [interquartile range], 21.2 [18.8–21.7] and 19.5 [17.1–21.5] %/h, respectively, versus 12.6 [3.2–18.8] %/h in injured, untreated controls), oxygenation and decreased alveolar inflammation and histological evidence of tissue injury after ARDS. These findings suggest that RAGE inhibition restored AFC and attenuated lung injury in a piglet model of acid-induced ARDS.

Distinctive Roles and Mechanisms of Human Neutrophil Peptides in Experimental Sepsis and Acute Respiratory Distress Syndrome.

To examine the effects and mechanisms of human neutrophil peptides in systemic infection and noninfectious inflammatory lung injury. Prospective experimental study. University hospital-based research laboratory. In vitro human cells and in vivo mouse models. Wild-type (Friend virus B-type) and conditional leukocyte human neutrophil peptides transgenic mice were subjected to either sepsis induced by cecal ligation and puncture or acute lung injury by intratracheal instillation of hydrochloric acid followed by mechanical ventilation. Using human neutrophil peptides as bait, the basal cell adhesion molecule (CD239) and the purinergic P2Y purinoceptor 6 receptor were identified as the putative human neutrophil peptides receptor complex in human lung epithelial cells. In the cecal ligation and puncture sepsis model, Friend virus B-type mice exhibited higher systemic bacterial load, cytokine production, and lung injury than human neutrophil peptides transgenic mice. Conversely, an increased lung cytokine production was seen in Friend virus B-type mice, which was further enhanced in human neutrophil peptides transgenic mice in response to two-hit lung injury induced by hydrochloric acid and mechanical ventilation. The human neutrophil peptides-mediated inflammatory response was mediated through the basal cell adhesion molecule-P2Y purinoceptor 6 receptor signal pathway in human lung epithelial cells. Human neutrophil peptides are critical in host defense against infectious sepsis by their cationic antimicrobial properties but may exacerbate tissue injury when neutrophil-mediated inflammatory responses are excessive in noninfectious lung injury. Targeting the basal cell adhesion molecule/P2Y purinoceptor 6 signaling pathway may serve as a novel approach to attenuate the neutrophil-mediated inflammatory responses and injury while maintaining the antimicrobial function of human neutrophil peptides in critical illness.

Inhibition of the Receptor for Advanced Glycation End-Products in Acute Respiratory Distress Syndrome: A Randomised Laboratory Trial in Piglets

Background: The receptor for advanced glycation end products (RAGE) modulates the pathogenesis of acute respiratory distress syndrome (ARDS). RAGE inhibition was recently associated with attenuated lung injury and restored alveolar fluid clearance (AFC) in a mouse model of ARDS. However, clinical translation will first require assessment of this strategy in larger animals. Methods: Forty-eight anaesthetised Landrace piglets were randomised into a control group and three treatment groups. Animals allocated to treatment groups underwent orotracheal instillation of hydrochloric acid i) alone; ii) in combination with intravenous administration of a RAGE antagonist peptide (RAP), a S100P-derived peptide that prevents activation of RAGE by its ligands, or iii) in combination with intravenous administration of recombinant soluble (s)RAGE that acted as a decoy receptor. The primary outcome measure was net AFC at 4 h. Arterial oxygenation was assessed hourly for 4 h and alveolar-capillary permeability, alveolar inflammation, lung histology and lung mRNA expression of the epithelial sodium channel (α1-ENaC), α1-Na,K-ATPase and aquaporin (AQP)-5 were assessed at 4 h. Findings: Treatment with either RAP or sRAGE improved net AFC rates (median [interquartile range], 21.2 [18.8-21.7] and 19.5 [17.1-21.5] %/h, respectively, versus 12.6 [3.2-18.8] %/h in injured, untreated controls), improved oxygenation and decreased alveolar inflammation and histological evidence of tissue injury after acid-induced ARDS. RAGE inhibition also restored lung mRNA expression of α1-Na, K-ATPase and AQP-5. Interpretation: RAGE inhibition restored AFC and attenuated lung injury in a piglet model of acid-induced ARDS. Funding: Auvergne Regional Council, Agence Nationale de la Recherche, Direction Generale de l'Offre de Soins. Declaration of Interest: No conflict of interest, other source of financial support, corporate involvement, patent holdings, etc. is to be declared for all authors. Ethical Approval: Animals were maintained and all procedures were performed with the approval of the ethics committee of the French Ministere de l’Education Nationale, de l’Enseignement Superieur et de la Recherche in the Centre International de Chirurgie Endoscopique, School of Medicine - University of Clermont-Ferrand (approval number 01505.03). All experiments were performed in accordance with the “Animal Research: Reporting In Vivo Experiments” (ARRIVE) guidelines.

Vagotomy decreases the neuronal activities of medulla oblongata and alleviates neurogenic inflammation of airways induced by repeated intra-esophageal instillation of HCl in guinea pigs.

Neuronal activity in the medulla oblongata and neurogenic inflammation of airways were investigated in a guinea pig model induced by repeated intra-esophageal instillation of hydrochloric acid (HCl) after vagotomy. Unilateral vagotomy was performed in the vagotomy group, while a sham-operation was performed in the sham group. Operation was not conducted in sham control group. Airway inflammation was observed with hematoxylin and eosin (HE) staining. C-fos protein was measured by immunohistochemistry (IHC) and Western blot (WB). Substance P was examined by IHC and enzyme-linked immuno sorbent assay (ELISA). Airway microvascular permeability was detected by evans blue dye (EBD) fluorescence. Inflammation of airway was observed in the trachea and bronchi after chronic HCl perfusion into the lower esophagus, and was alleviated after unilateral vagotomy. C-fos expression in the medulla oblongata was lower in the vagotomy group compared to the sham control and sham groups. Substance P-like immunoreactivity (SP-li), concentration and microvascular leakage in airway were lower in the vagotomy group than that in the other groups. Our results suggest that vagotomy improved neurogenic inflammation of airways and decreased neuronal activities, the afferent nerves and neurons in medulla oblongata may be involved in neurogenic inflammation of airways mediated by esophageal-bronchial reflex.

Mapping Regional Differences of Local Pressure-Volume Curves With Electrical Impedance Tomography.

Lung-protective mechanical ventilation aims to prevent alveolar collapse and overdistension, but reliable bedside methods to quantify them are lacking. We propose a quantitative descriptor of the shape of local pressure-volume curves derived from electrical impedance tomography, for computing maps that highlight the presence and location of regions of presumed tidal recruitment (i.e., elastance decrease during inflation, pressure-volume curve with upward curvature) or overdistension (i.e., elastance increase during inflation, downward curvature). Secondary analysis of experimental cohort study. University research facility. Twelve mechanically ventilated pigs. After induction of acute respiratory distress syndrome by hydrochloric acid instillation, animals underwent a decremental positive end-expiratory pressure titration (steps of 2 cm H2O starting from ≥ 26 cm H2O). Electrical impedance tomography-derived maps were computed at each positive end-expiratory pressure-titration step, and whole-lung CT taken every second steps. Airway flow and pressure were recorded to compute driving pressure and elastance. Significant correlations between electrical impedance tomography-derived maps and positive end-expiratory pressure indicate that, expectedly, tidal recruitment increases in dependent regions with decreasing positive end-expiratory pressure (p < 0.001) and suggest that overdistension increases both at high and low positive end-expiratory pressures in nondependent regions (p < 0.027), supporting the idea of two different scenarios of overdistension occurrence. Significant correlations with CT measurements were observed: electrical impedance tomography-derived tidal recruitment with poorly aerated regions (r = 0.43; p < 0.001); electrical impedance tomography-derived overdistension with nonaerated regions at lower positive end-expiratory pressures and with hyperaerated regions at higher positive end-expiratory pressures (r ≥ 0.72; p < 0.003). Even for positive end-expiratory pressure levels minimizing global elastance and driving pressure, electrical impedance tomography-derived maps showed nonnegligible regions of presumed overdistension and tidal recruitment. Electrical impedance tomography-derived maps of pressure-volume curve shapes allow to detect regions in which elastance changes during inflation. This could promote individualized mechanical ventilation by minimizing the probability of local tidal recruitment and/or overdistension. Electrical impedance tomography-derived maps might become clinically feasible and relevant, being simpler than currently available alternative approaches.

Intraperitoneal adoptive transfer of mesenchymal stem cells enhances recovery from acid aspiration acute lung injury in mice

BackgroundMesenchymal stem cells (MSCs) might act as fine-tuners of inflammation during acute lung injury. We assessed the effects of adoptive transfer of MSCs in acid aspiration acute lung injury and explored the role of long pentraxin PTX3.MethodsWe conducted a prospective experimental interventional study on wild-type (WT) and PTX3-deficient (PTX3−/−) mice. Acute lung injury was induced in WT and PTX3−/− mice by instillation of hydrochloric acid into the right bronchus. One hour later, animals received intraperitoneal sterile phosphate-buffered saline (PBS), WT-MSCs (1 × 106) or PTX3−/−-MSCs (1 × 106). Twenty-four hours after injury, we measured the effects of treatments on arterial blood gases, wet/dry lung weight (W/D), CT scan analysis of lung collapse, neutrophils, TNFα and CXCL1 in bronchoalveolar lavage, and plasma PTX3. d-dimer was assayed in 1 week and OH-proline in 2 weeks to track the fibrotic evolution.ResultsIn 24 h, in comparison to PBS, WT-MSCs improved oxygenation and reduced W/D and alveolar collapse. These effects were associated with decreased concentrations of alveolar neutrophils and cytokines. WT-MSCs increased d-dimer concentration and decreased OH-proline levels, too.Treatment with PTX3−/−-MSCs ameliorated oxygenation, W/D, and alveolar TNFα, though to a lesser extent than WT-MSCs. PTX3−/−-MSCs did not improve lung collapse, neutrophil count, CXCL1, d-dimer, and OH-proline concentrations. The protective effects of WT-MSCs were dampened by lack of endogenous PTX3, too.ConclusionsIn acid aspiration acute lung injury, MSCs improve pulmonary function and limit fibrosis by fine-tuning inflammation. The role of PTX3 in determining MSCs’ effects might merit further scrutiny.

Effects of esophageal capsaicin instillation on acid induced excitation of secondary peristalsis in humans.

Esophageal instillation of capsaicin or hydrochloric acid enhances secondary peristalsis. Our aim was to investigate whether intra-esophageal capsaicin infusion can influence symptom perception and physiological alteration of secondary peristalsis subsequent to acid infusion. Secondary peristalsis was induced by mid-esophagus injections of air in 18 healthy subjects. Two different sessions including esophageal infusion of hydrochloric acid (0.1 N) following pretreatment with saline or capsaicin-containing red pepper sauce were randomly performed at least one week apart. Symptoms of heartburn and secondary peristalsis were determined and compared between each study session. The intensity of heartburn symptom subsequent to acid infusion was significantly reduced after capsaicin infusion as compared with saline infusion (54 ± 3 vs 61 ± 3; P = 0.03). Capsaicin infusion significantly increased the threshold volume of secondary peristalsis to rapid air injections subsequent to esophageal acid infusion (8.0 ± 0.5 mL vs 4.4 ± 0.3 mL; P < 0.0001). The frequency of secondary peristalsis subsequent to acid infusion was significantly decreased after capsaicin infusion as compared to saline infusion (70% [60-82.5%] vs 80% [70-90%]; P = 0.03). Capsaicin infusion significantly decreased the pressure wave amplitude of secondary peristalsis subsequent to acid infusion during rapid air injections (90.6 ± 8.7 mmHg vs 111.1 ± 11.1 mmHg; P = 0.03). Capsaicin appears to desensitize the esophagus to acid induced excitation of secondary peristalsis in humans, which is probably mediated by rapidly adapting mucosal mechanoreceptors. High capsaicin-containing diet might attenuate normal physiological response to abrupt acid reflux by inhibiting secondary peristalsis.

Effect of hypertonic saline treatment on the inflammatory response after hydrochloric acid-induced lung injury in pigs

OBJECTIVES:Hypertonic saline has been proposed to modulate the inflammatory cascade in certain experimental conditions, including pulmonary inflammation caused by inhaled gastric contents. The present study aimed to assess the potential anti-inflammatory effects of administering a single intravenous dose of 7.5% hypertonic saline in an experimental model of acute lung injury induced by hydrochloric acid.METHODS:Thirty-two pigs were anesthetized and randomly allocated into the following four groups: Sham, which received anesthesia and were observed; HS, which received intravenous 7.5% hypertonic saline solution (4 ml/kg); acute lung injury, which were subjected to acute lung injury with intratracheal hydrochloric acid; and acute lung injury + hypertonic saline, which were subjected to acute lung injury with hydrochloric acid and treated with hypertonic saline. Hemodynamic and ventilatory parameters were recorded over four hours. Subsequently, bronchoalveolar lavage samples were collected at the end of the observation period to measure cytokine levels using an oxidative burst analysis, and lung tissue was collected for a histological analysis.RESULTS:Hydrochloric acid instillation caused marked changes in respiratory mechanics as well as blood gas and lung parenchyma parameters. Despite the absence of a significant difference between the acute lung injury and acute lung injury + hypertonic saline groups, the acute lung injury animals presented higher neutrophil and tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-8 levels in the bronchoalveolar lavage analysis. The histopathological analysis revealed pulmonary edema, congestion and alveolar collapse in both groups; however, the differences between groups were not significant. Despite the lower cytokine and neutrophil levels observed in the acute lung injury + hypertonic saline group, significant differences were not observed among the treated and non-treated groups.CONCLUSIONS:Hypertonic saline infusion after intratracheal hydrochloric acid instillation does not have an effect on inflammatory biomarkers or respiratory gas exchange.