Selective thromboxane A2 synthase inhibition by OKY-046 prevents cardiopulmonary dysfunction after ovine smoke inhalation injury

An in silico approach to understanding the interaction between cardiovascular and pulmonary lymphatic dysfunction

The lung is extremely sensitive to interstitial fluid balance, yet the role of pulmonary lymphatics in lung fluid homeostasis and its interaction with cardiovascular pressures is poorly understood. In health, there is a fine balance between fluid extravasated from the pulmonary capillaries into the interstitium and the return of fluid to the circulation via the lymphatic vessels. This balance is maintained by an extremely interdependent system governed by pressures in the fluids (air and blood) and tissue (interstitium), lung motion during breathing, and the permeability of the tissues. Chronic elevation in left atrial pressure (LAP) due to left heart disease increases the capillary blood pressure. The consequent fluid accumulation in the delicate lung tissue increases its weight, decreases its compliance, and impairs gas exchange. This interdependent system is difficult, if not impossible, to study experimentally. Computational modeling provides a unique perspective to analyze fluid movement in the cardiopulmonary vasculature in health and disease. We have developed an initial in silico model of pulmonary lymphatic function using an anatomically structured model to represent ventilation and perfusion and underlying biophysical laws governing fluid transfer at the interstitium. This novel model was tested against increased LAP and noncardiogenic effects (increased permeability). The model returned physiologically reasonable values for all applications, predicting pulmonary edema when LAP reached 25 mmHg and with increased permeability.NEW & NOTEWORTHY This model presents a novel approach to understanding the interaction between cardiac dysfunction and pulmonary lymphatic function, using anatomically structured models and biophysical equations to estimate regional variation in fluid transport from blood to interstitial and lymphatic flux. This fluid transport model brings together advanced models of ventilation, perfusion, and lung mechanics to produce a detailed model of fluid transport in health and various altered pathological conditions.

Club Cell Protein, CC10, Attenuates Acute Respiratory Distress Syndrome Induced by Smoke Inhalation

OBJECTIVES

To evaluate the dose effects of Recombinant human Club cell 10-kDa protein (rhCC10) on lung function in a well-characterized ovine model of acute respiratory distress syndrome (ARDS) induced by smoke inhalation injury (SII); specifically, the potential of rhCC10 protein to control the inflammatory response and protect pulmonary tissue and function following SII.

DESIGN

Randomized, controlled, prospective, and large animal translational studies.

SETTING

University large animal intensive care unit.

SUBJECTS

Thirty-six adult female sheep were surgically prepared and allocated into five groups (Sham (no SII), n = 6; 1 mg/kg/d CC10, n = 8; 3 mg/kg/d CC10, n = 7; 10 mg/kg/d CC10, n = 8; Control SII, n = 7).

INTERVENTIONS

All groups except the sham group were subjected to SII with cooled cotton smoke. Then, the animals were placed on a ventilator, treated with 1, 3, and 10 mg/kg/d of intravenous rhCC10 or vehicle, divided evenly into two administrations per day every 12 h, fluid resuscitated, and monitored for 48 h in a conscious state.

MEASUREMENTS AND MAIN RESULTS

The group treated with 10 mg/kg/d rhCC10 attenuated changes in the following variables: PaO2/FiO2 ratio, oxygenation index, and peak inspiratory pressure; neutrophil content in the airway and myeloperoxidase levels; obstruction of the large and small airways; systemic leakage of fluid and proteins, and pulmonary edema.

CONCLUSIONS

In this study, high-dose rhCC10 significantly attenuated ARDS progression and lung dysfunction and significantly reduced systemic extravasation of fluid and proteins, normalizing fluid balance. Based on these results, rhCC10 may be considered a novel therapeutic option for the treatment of SII-induced ARDS.

Polygalasaponin F treats mice with pneumonia induced by influenza virus

BACKGROUND

Influenza is an acute viral respiratory illness that causes high morbidity and mortality globally. Therapeutic actions are limited to vaccines and a few anti-viral drugs. Polygala (P.) japonica herba is rich in Polygalasaponin F (PSF, C₅₃H₈₆O₂₃), used for acute bronchitis, pharyngitis, pneumonia, amygdalitis, and respiratory tract infections treatment in China. Hypercytokinemia is often correlated with severe pneumonia caused by several influenza viruses. PSF was reported to have anti-inflammatory effects and its mechanism is associated with the nuclear factor (NF)-κB signaling pathway. The action of PSF to alleviate pulmonary inflammation caused by influenza A virus (IAV) infection requires careful assessment. In the present study, we evaluated the effect and mechanism of PSF on mice with pneumonia caused by influenza H1N1 (A/FM/1/47).

METHODS

Mice were infected intranasally with fifteen 50% mouse lethal challenge doses (MLD₅₀) of influenza virus. BALB/c mice were treated with PSF or oseltamivir (oral administration) for 2 h post-infection and received concomitant treatment for 5 days after infection. On day 6 post-infection, 10 mice per group were killed to collect related samples, measure body weight and lung wet weight, and detect the viral load, cytokine, prostaglandins, pathological changes, and cell pathway protein expression in the lungs. In addition, the survival experiments were carried out to investigate the survival of mice. The expression profile of cell pathway proteins was detected and analyzed using a broad pathway antibody array and confirmed the findings from the array by western blotting.

RESULTS

Polygalasaponin F and oseltamivir can protect against influenza viral infection in mice. PSF and oseltamivir significantly relieved the signs and symptoms, reduced body weight loss, and improved the survival rate of H1N1-infected mice. Moreover, PSF efficiently decreased the level of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-4, interferon (IFN)-γ, thromboxane A₂ (TXA₂), and prostaglandin E₂ (PGE₂) in lung tissues of mice infected with influenza virus (p < 0.05-0.01). Oseltamivir had a similar effect to lung cytokine of PSF, but did not decrease the levels of TXA₂ and PGE₂. There was a twofold or greater increase in four cell pathway protein, namely NF-κB p65 (2.68-fold), I-kappa-B-alpha (IκBα) (2.56-fold), and MAPK/ERK kinase 1 (MEK1) (7.15-fold) assessed in the array induced by influenza virus. Western blotting showed that the expression of these proteins was significantly decreased in lung after influenza virus challenge in PSF and oseltamivir-treated mice (p < 0.05-0.01).

CONCLUSION

Polygalasaponin F appears to be able to augment protection against IAV infection in mice via attenuation of pulmonary inflammatory responses. Its effect on IAV-induced pulmonary inflammation was associated with suppression of Raf/MEK/ERK and NF-κB expressions.

Positive End-expiratory Pressure Ventilation Increases Extravascular Lung Water Due to a Decrease in Lung Lymph Flow

Positive end-expiratory pressure (PEEP) is used to improve gas exchange, increase functional residual capacity, recruit air spaces, and decrease pulmonary shunt in patients suffering from respiratory failure. The effect of PEEP on extravascular lung water (EVLW), however, is still not fully understood. This study was designed as a prospective laboratory experiment to evaluate the effects of PEEP on EVLW and pulmonary lymph flow (QL) under physiologic conditions.

Twelve adult sheep were operatively prepared to measure haemodynamics of the systemic and pulmonary circulation, and to assess EVLW. In addition, the lung lymphatic duct was cannulated and a tracheostomy performed. The animals were then mechanically ventilated in the awake-state without end-expiratory pressure (PEEP 0). After a two-hour baseline period, PEEP was increased to 10 cmH2O for the duration of two hours, and then reduced back to 0 cmH2O. Cardiopulmonary variables, QL, and arterial blood gases were recorded intermittently; EVLW was determined two hours after each change in PEEP.

The increase in PEEP resulted in a decrease in QL (7±1 vs 5±1 ml/h) and an increase in EVLW (498±40 vs 630±58 ml; P<0.05 each) without affecting cardiac output. As PEEP was decreased back to baseline, QL increased significantly (5±1 vs 10±2 ml/h), whereas EVLW returned back to baseline.

This study suggests that institution of PEEP produces a reversible increase in EVLW that is linked to a decrease in QL.

Metabolic Serum Profiles for Patients Receiving Allogeneic Stem Cell Transplantation: The Pretransplant Profile Differs for Patients with and without Posttransplant Capillary Leak Syndrome

Allogeneic stem cell transplantation is commonly used in the treatment of younger patients with severe hematological diseases, and endothelial cells seem to be important for the development of several posttransplant complications. Capillary leak syndrome is a common early posttransplant complication where endothelial cell dysfunction probably contributes to the pathogenesis. In the present study we investigated whether the pretreatment serum metabolic profile reflects a risk of posttransplant capillary leak syndrome. We investigated the pretransplant serum levels of 766 metabolites for 80 consecutive allotransplant recipients. Patients with later capillary leak syndrome showed increased pretherapy levels of metabolites associated with endothelial dysfunction (homocitrulline, adenosine) altered renal regulation of fluid and/or electrolyte balance (betaine, methoxytyramine, and taurine) and altered vascular function (cytidine, adenosine, and methoxytyramine). Additional bioinformatical analyses showed that capillary leak syndrome was also associated with altered purine/pyrimidine metabolism (i.e., metabolites involved in vascular regulation and endothelial functions), aminoglycosylation (possibly important for endothelial cell functions), and eicosanoid metabolism (also involved in vascular regulation). Our observations are consistent with the hypothesis that the pretransplant metabolic status can be a marker for posttransplant abnormal fluid and/or electrolyte balance.

A dynamic smoke generation and nose-only inhalation exposure system for rats: preliminary results from studies of selected transportation materials

CONTEXT

Smoke inhalation injury is the main cause of fatalities for fire victims. Understanding in the pathophysiology of the injury has not been fully explored in recent years. To further explore the pathophysiological mechanism, a dynamic and controllable animal model is necessary.

OBJECTIVE

To develop a rat model of smoke inhalation injury to simulate human victims in air-restricted vehicle cabin fires.

MATERIALS AND METHODS

Smoke concentration, including CO, O2, VOCs and smoke temperature under different combustion conditions, were detected. Levels of COHb, respiratory function, lung wet-to-dry weight ratio and protein concentration in BALF and blood were measured. Pathological evaluations of lung in tissues were conducted at 1, 6, 24 and 48 h post-exposure.

RESULTS

Smoke concentration rose with the increase of combustion temperature and decrease of oxygen flow. Further, 215 kinds of VOCs in the smoke were detected, and the concentrations of benzene, methylbenzene, ethylbenzene, dimethylbenzene, phenylethylene and trimethylbenzene was 32.93, 402.06, 764.03, 113.73, 1006.61 and 89.28 mg/m(3), respectively. Significant hypoxemia and CO poisoning occurred in rats. The FCOHb after exposure for 14 min immediately rose to (44.2 ± 12.3) % and then gradually decrease to a normal level at 300 min post-exposure. At 24 h post-exposure, Penh increased significantly (p < 0.05), and high pulmonary vascular permeability and significant lung edema (p < 0.05) were observed in the smoke inhalation group.

DISCUSSION AND CONCLUSION

In summary, the novel rat model of smoke inhalation injury system used in the study is dynamic and controllable, and appropriate for use in smoke inhalation injury studies of air-restricted cabins in vehicles.

Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care

Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.

Inhalation injury: epidemiology, pathology, treatment strategies

Lung injury resulting from inhalation of smoke or chemical products of combustion continues to be associated with significant morbidity and mortality. Combined with cutaneous burns, inhalation injury increases fluid resuscitation requirements, incidence of pulmonary complications and overall mortality of thermal injury. While many products and techniques have been developed to manage cutaneous thermal trauma, relatively few diagnosis-specific therapeutic options have been identified for patients with inhalation injury. Several factors explain slower progress for improvement in management of patients with inhalation injury. Inhalation injury is a more complex clinical problem. Burned cutaneous tissue may be excised and replaced with skin grafts. Injured pulmonary tissue must be protected from secondary injury due to resuscitation, mechanical ventilation and infection while host repair mechanisms receive appropriate support. Many of the consequences of smoke inhalation result from an inflammatory response involving mediators whose number and role remain incompletely understood despite improved tools for processing of clinical material. Improvements in mortality from inhalation injury are mostly due to widespread improvements in critical care rather than focused interventions for smoke inhalation.

Morbidity associated with inhalation injury is produced by heat exposure and inhaled toxins. Management of toxin exposure in smoke inhalation remains controversial, particularly as related to carbon monoxide and cyanide. Hyperbaric oxygen treatment has been evaluated in multiple trials to manage neurologic sequelae of carbon monoxide exposure. Unfortunately, data to date do not support application of hyperbaric oxygen in this population outside the context of clinical trials. Cyanide is another toxin produced by combustion of natural or synthetic materials. A number of antidote strategies have been evaluated to address tissue hypoxia associated with cyanide exposure. Data from European centers supports application of specific antidotes for cyanide toxicity. Consistent international support for this therapy is lacking. Even diagnostic criteria are not consistently applied though bronchoscopy is one diagnostic and therapeutic tool. Medical strategies under investigation for specific treatment of smoke inhalation include beta-agonists, pulmonary blood flow modifiers, anticoagulants and antiinflammatory strategies. Until the value of these and other approaches is confirmed, however, the clinical approach to inhalation injury is supportive.

Preclinical evaluation of epinephrine nebulization to reduce airway hyperemia and improve oxygenation after smoke inhalation injury

OBJECTIVE

Acute lung injury secondary to smoke inhalation is a major source of morbidity and mortality in burn patients. We tested the hypothesis that nebulized epinephrine would ameliorate pulmonary dysfunction secondary to acute lung injury by reducing airway hyperemia and edema formation and mediating bronchodilatation in an established, large animal model of inhalation injury.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University research laboratory.

SUBJECTS

Twenty-four chronically instrumented, adult, female sheep.

INTERVENTIONS

Following baseline measurements, the animals were allocated to a sham-injured group (n = 5), an injured and saline-treated group (n = 6), or an injured group treated with 4 mg of nebulized epinephrine every 4 hrs (n = 6). Inhalation injury was induced by 48 breaths of cotton smoke. The dose of epinephrine was derived from dose finding experiments (n = 7 sheep).

MEASUREMENTS AND MAIN RESULTS

The injury induced significant increases in airway blood flows, bronchial wet/dry weight ratio, airway obstruction scores, ventilatory pressures, and lung malondialdehyde content, and contributed to severe pulmonary dysfunction as evidenced by a significant decline in Pao₂/Fio₂ ratio and increase in pulmonary shunt fraction. Nebulization of epinephrine significantly reduced tracheal and main bronchial blood flows, ventilatory pressures, and lung malondialdehyde content. The treatment was further associated with significant improvements of Pao₂/FIO₂ ratio and pulmonary shunting.

CONCLUSIONS

Nebulization of epinephrine reduces airway blood flow and attenuates pulmonary dysfunction in sheep subjected to severe smoke inhalation injury. Future studies will have to improve the understanding of the underlying pathomechanisms and identify the optimal dosing for the treatment of patients with this injury.

QTc interval and neurological outcomes in aneurysmal subarachnoid hemorrhage

BACKGROUND

Prolonged heart rate-corrected QT (QTc) interval is frequently observed in subarachnoid hemorrhage (SAH). This study was conducted to determine the relationship between QTc interval and neurological outcome during the acute posthemorrhagic period after aneurysmal SAH.

METHODS

We studied 71 patients undergoing surgery who were admitted within 24 h after the onset of aneurysmal SAH. Standard 12-lead electrocardiography was performed on admission (T1) and at 1 and 7 days after operation (T2 and T3). QT intervals were corrected by heart rate according to the Fridericia formula. The Glasgow Coma Scale (GCS) score was calculated over the period T1-T3. Neurological outcome was assessed using the Glasgow Outcome Scale at hospital discharge.

RESULTS

Among the 71 patients, 31 had an unfavorable neurological outcome. Although QTc interval prolongation improved in patients with a good outcome, QTc interval prolongation continued in patients with an unfavorable outcome. The areas under the receiver-operator characteristic curves showed that the QTc and GCS score at T3, and the Hunt and Hess grade were significant predictors of an unfavorable neurological outcome. The threshold value, sensitivity, and specificity for the QTc at T3 were 448 ms, 73% [95% confidence interval (CI), 68-78], and 93% (95% CI, 90-96), respectively.

CONCLUSION

This study confirms that QTc interval prolongation continues in the SAH patients with an unfavorable outcome but that QTc interval prolongation improves in patients with a good outcome, suggesting that a QTc interval of more than 448 ms at 7 days after operation is a predictor of neurological outcome after SAH.

Experimental trauma models: an update

Treatment of polytrauma patients remains a medical as well as socioeconomic challenge. Although diagnostics and therapy improved during the last decades, multiple injuries are still the major cause of fatalities in patients below 45 years of age. Organ dysfunction and organ failure are major complications in patients with major injuries and contribute to mortality during the clinical course. Profound understanding of the systemic pathophysiological response is crucial for innovative therapeutic approaches. Therefore, experimental studies in various animal models are necessary. This review is aimed at providing detailed information of common trauma models in small as well as in large animals.

Protective role of simvastatin on lung damage caused by burn and cotton smoke inhalation in rats

BACKGROUND

Smoke inhalation injury is a major comorbid factor in patients with thermal injury and occurs in about 30% of patients with major burns. In addition, inhalation injury reportedly accounts for 20%-84% of the mortality in burned individuals and is associated with higher mortality rates for every age and burn size category. The aim of the present study was to investigate the effects of simvastatin on lung damage with burn and cotton smoke inhalation.

METHODS

Wistar rats were randomly assigned to three groups: saline treated control group, via an orogastric route (group 1, n = 6), burn (30%) and cotton smoke inhalated group (group 2, n = 6), and simvastatin treated (25 mg/kg/d, via an orogastric route) burn (30%) and cotton smoke inhalated group (group 3, n = 6). Rats were sacrificed at 48 h of the treatments and the trachea and lungs were removed completely. Tissue samples were taken for histopathologic, immunohistopathologic, and biochemical analyses. Univariate analysis of variance coupled with Duncan's post-hoc test was performed for statistical evaluation.

RESULTS

Lung parenchymal and tracheoepithelial damage was confirmed in group 2 by histopathologic examination. Lung malonedialdehyde (MDA) levels were significantly decreased (P < 0.001), while glutathione (GSH) concentration did not alter in group 2 compared with group 1. Also, immunopathologic data revealed that epithelial iNOS level was elevated, while no modulation was detected in the level of myeloperoxidase (MPO). Simvastatin administration resulted in decreasing the lung parenchymal and tracheoepithelial damage. Tissue MDA levels were decreased significantly (P < 0.001), whereas GSH concentrations were elevated in group 3 compared with group 1 and group 2 (P < 0.001). Simvastatin treatment caused a decrease in epithelial iNOS levels, while MPO levels were not modulated. In addition, simvastatin significantly reduced pulmonary apoptosis in lung injury.

CONCLUSIONS

Our results have indicated that simvastatin administration seems to play beneficial role in lung injury of rats promoted by combined burn and smoke inhalation. Thus, simvastatin may represent a potential approach to prevent smoke inhalation-associated lung dysfunction. However, the significant decrease in basal oxidant production may cause impairment in cellular signalling processes.

Ozagrel reverses streptozotocin-induced constriction of arterioles in rat retina

Retinal blood flow decreases early in the progression of diabetic retinopathy; however, the mediators and mechanisms responsible for this decrease have yet to be determined. In this study, diabetes was induced by streptozotocin in rats, and retinal blood flow was measured via intravital microscopy 1 or 3 weeks following the induction of hyperglycemia. Additionally, retinal arteriolar diameters and flow were measured prior to and following acute administration of the thromboxane synthase inhibitor ozagrel to investigate the potential role of thromboxane in the observed constriction. Minimal changes in the retinal diameters and flow were observed at 1 week of diabetes; however, at 3 weeks of diabetes, arteriolar constriction and decreases in blood flow were significant. Notably, the constriction occurred only in the arterioles that were in closer proximity to the venules draining the retina. Acute administration of ozagrel reversed the constriction of the closely venule-paired arterioles. In summary, the results suggest that thromboxane mediates localized, venule-dependent arteriolar constriction induced by streptozotocin-induced diabetes in rats.

Neuronal nitric oxide synthase inhibition attenuates cardiopulmonary dysfunctions after combined burn and smoke inhalation injury in sheep

OBJECTIVE

We hypothesized that nitric oxide derived from the neuronal nitric oxide synthase (NOS) is responsible for much of the injury resulting from skin burn and smoke inhalation. Therefore, we aimed to examine the effects of selective neuronal NOS inhibition on cardiopulmonary functions and cellular injury in sheep with acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury.

DESIGN

Prospective, randomized, controlled laboratory experiment.

SETTING

Investigational intensive care unit.

SUBJECTS

A total of 22 chronically instrumented adult ewes.

INTERVENTIONS

Sheep were randomly assigned to either healthy controls (sham), injured controls (40% third-degree flame burn; 48 breaths of cotton smoke), or an injury group treated with the specific neuronal NOS inhibitor 7-nitroindazole (1 mg x kg(-1) x hr(-1)) from 1 hr postinjury to the end of the 48-hr study period. Hypoxic pulmonary vasoconstriction was assessed as decrease in left pulmonary blood flow in response to single-lung hypoxic challenges (100% nitrogen) at baseline, 24 hrs, and 48 hrs.

MEASUREMENTS AND MAIN RESULTS

The combination injury contributed to a approximately 90% loss of hypoxic pulmonary vasoconstriction and was associated with significant pulmonary shunting and death of one animal. The increase in nitrate/nitrite plasma levels in injured controls (12 hrs: 17 +/- 2 vs. 6 +/- 1 microM in sham animals; p < .001) was linked to increases in inducible NOS messenger RNA and 3-nitrotyrosine formation in lung tissue (48 hrs: 22 +/- 1 vs. 0.8 +/- 0.3 nM in sham animals; p < .001). 7-Nitroindazole treatment prevented the injury-associated changes in inducible NOS messenger RNA, nitrate/nitrite, and 3-nitrotyrosine, thereby attenuating the loss of hypoxic pulmonary vasoconstriction and improving gas exchange. In addition, 7-nitroindazole decreased lung tissue concentrations of hemoxygenase-1 and ameliorated myocardial depression, airway obstruction, pulmonary edema, ventilatory pressures, and histopathologic changes seen in injured controls.

CONCLUSIONS

The present study provides evidence that neuronal NOS-derived nitric oxide plays a pivotal role in the pathogenesis of acute respiratory distress syndrome resulting from combined burn and smoke inhalation injury.