Challenges and perspectives in porcine model of acute lung injury using oleic acid

Differential changes in expression of inflammatory mRNA and protein after oleic acid-induced acute lung injury

Background: Acute Respiratory Distress syndrome (ARDS) is a clinical syndrome of noncardiac pulmonary edema and inflammation leading to acute respiratory failure. We used the oleic acid infusion pig model of ARDS resembling human disease to explore cytokine changes in white blood cells (WBC) and plasma proteins, comparing baseline to ARDS values. Methods: Nineteen juvenile female swine were included in the study. ARDS defined by a PaO2/FiO2 ratio < 300 was induced by continuous oleic acid infusion. Arterial blood was drawn before and during oleic acid infusion, and when ARDS was established. Cytokine expression in WBC was analyzed by RT-qPCR and plasma protein expression by ELISA. Results: The median concentration of IFN-γ mRNA was estimated to be 59% (p = 0.006) and of IL-6 to be 44.4% (p = 0.003) of the baseline amount. No significant changes were detected for TNF-α, IL-17, and IL-10 mRNA expression. In contrast, the concentrations of plasma IFN-γ and IL-6 were significantly higher (p = 0.004 and p = 0.048 resp.), and TNF-α was significantly lower (p = 0.006) at ARDS compared to baseline. Conclusions: The change of proinflammatory cytokines IFN-γ and IL-6 expression is different comparing mRNA and plasma proteins at oleic acid-induced ARDS compared to baseline. The migration of cells to the lung may be the cause for this discrepancy.

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

Therapeutic effects of minocycline on oleic acid-induced acute respiratory distress syndrome (ARDS) in rats

Acute respiratory distress syndrome (ARDS) is a serious intensive care condition. Despite advances in treatment over the previous few decades, ARDS patients still have high fatality rates. Thus, more research is needed to improve the outcomes for people with ARDS. Minocycline is an antibiotic with antioxidant, anti-inflammatory, and anti-apoptotic effects. In the current investigation, the therapeutic effects of minocycline on oleic acid-induced ARDS were evaluated. Male rats were classified into 6 groups, 1. control (normal saline), 2. oleic acid (100 µL, i.v.), 3-5. oleic acid + minocycline (50, 100, 200 mg/kg, i.p.), and 6. minocycline (200 mg/kg, i.p.) alone. Twenty-four hours after the oleic acid injection, the lung tissue is isolated, weighed, and the middle part of the right lung is immediately placed in the freezer, while the middle part of the left lung is placed in formalin and sent to the laboratory for pathology testing. Then, the amounts of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), cytokines (interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α)), B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X (Bax), and cleaved caspase-3 were determined in lung tissue. Administration of oleic acid increased emphysema, inflammation, vascular congestion, hemorrhage, MDA amount, Bax/Bcl-2 ratio, cleaved caspase-3, IL-1β, TNF-α levels, and decreased GSH, SOD, and CAT levels in comparison with the control group. The administration of minocycline could significantly reduce pathological and biochemical alterations induced by oleic acid. Minocycline has a therapeutic effect on oleic acid-induced ARDS through antioxidant, anti-inflammatory, and anti-apoptotic properties.

A long-lasting porcine model of ARDS caused by pneumonia and ventilator-induced lung injury

BACKGROUND

Animal models of acute respiratory distress syndrome (ARDS) do not completely resemble human ARDS, struggling translational research. We aimed to characterize a porcine model of ARDS induced by pneumonia-the most common risk factor in humans-and analyze the additional effect of ventilator-induced lung injury (VILI).

METHODS

Bronchoscopy-guided instillation of a multidrug-resistant Pseudomonas aeruginosa strain was performed in ten healthy pigs. In six animals (pneumonia-with-VILI group), pulmonary damage was further increased by VILI applied 3 h before instillation and until ARDS was diagnosed by PaO2/FiO2 < 150 mmHg. Four animals (pneumonia-without-VILI group) were protectively ventilated 3 h before inoculum and thereafter. Gas exchange, respiratory mechanics, hemodynamics, microbiological studies and inflammatory markers were analyzed during the 96-h experiment. During necropsy, lobar samples were also analyzed.

RESULTS

All animals from pneumonia-with-VILI group reached Berlin criteria for ARDS diagnosis until the end of experiment. The mean duration under ARDS diagnosis was 46.8 ± 7.7 h; the lowest PaO2/FiO2 was 83 ± 5.45 mmHg. The group of pigs that were not subjected to VILI did not meet ARDS criteria, even when presenting with bilateral pneumonia. Animals developing ARDS presented hemodynamic instability as well as severe hypercapnia despite high-minute ventilation. Unlike the pneumonia-without-VILI group, the ARDS animals presented lower static compliance (p = 0.011) and increased pulmonary permeability (p = 0.013). The highest burden of P. aeruginosa was found at pneumonia diagnosis in all animals, as well as a high inflammatory response shown by a release of interleukin (IL)-6 and IL-8. At histological examination, only animals comprising the pneumonia-with-VILI group presented signs consistent with diffuse alveolar damage.

CONCLUSIONS

In conclusion, we established an accurate pulmonary sepsis-induced ARDS model.

Pterostilbene pre-treatment reduces LPS-induced acute lung injury through activating NR4A1

CONTEXT

Pterostilbene (PTE), a common polyphenol compound, exerts an anti-inflammatory effect in many diseases, including acute lung injury (ALI).

OBJECTIVE

This study explores the potential mechanism of PTE pre-treatment against lipopolysaccharide (LPS)-induced ALI.

MATERIALS AND METHODS

Sixty Sprague-Dawley rats were divided into control, ALI, 10 mg/kg PTE + LPS, 20 mg/kg PTE + LPS, and 40 mg/kg PTE + LPS groups. At 24 h before LPS instillation, PTE was administered orally. At 2 h before LPS instillation, PTE was again administered orally. After 24 h of LPS treatment, the rats were euthanized. The levels of inflammatory cells and inflammatory factors in the bronchoalveolar lavage fluid (BALF), the expression of nuclear receptor subfamily 4 group A member 1 (NR4A1), and the nuclear factor (NF)-κB pathway-related protein levels were detected. NR4A1 agonist was used to further investigate the mechanism of PTE pre-treatment.

RESULTS

After PTE pre-treatment, the LPS induced inflammation was controlled and the survival rate was increased to 100% from 70% after LPS treatment 24 h. For lung injury score, it decreased to 1.5 from 3.5 after treating 40 mg/kg PTE. Compared with the control group, the expression of NR4A1 in the ALI group was decreased by 20-40%. However, the 40 mg/kg PTE pre-treatment increased the NR4A1 expression by 20-40% in the lung tissue. The results obtained with pre-treatment NR4A1 agonist were similar to those obtained by pre-treatment 40 mg/kg PTE.

CONCLUSIONS

PTE pre-treatment might represent an appropriate therapeutic target and strategy for preventing ALI induced by LPS.

Prevention of mortality in acute lung injury induced by oleic acid: Application of polyherbal decoction (bronco T)

Acute lung injury (ALI) is a lethal respiratory disorder; directed uncontrolled inflammation, sloughing of the alveolar cells and their diffusion, and altered cardiorespiratory parameters with a global mortality rate of 40%. This study was designed to assess the preventive effect of a polyherbal decoction (Bronco T, 1.5 g/kg b. w.) on cardiorespiratory variables in oleic acid-induced ALI in rats. Oleic acid increases the level of neutrophil infiltration leading to pulmonary edema and alters the cardiorespiratory dynamics. The adult male rats were surgically cannulated and treated with intravenous oleic acid (0.38 ml/kg b. w.) to establish the ALI model. Bronco T was pre-administered orally 3 hours before oleic acid. The biophysical, histological, biochemical, and molecular effects were compared with dexamethasone (5 mg/kg b. w. i. p.). The animals were randomly divided into control, lethal, standard, and treatment groups. Respiratory frequency (RF), heart rate (HR), and mean arterial pressure (MAP) were recorded on a computerized chart recorder; arterial blood sample was collected to determine PaO₂/FiO₂, TNF-α, and MPO. Lipid peroxidation, superoxide dismutase, and catalase activity were evaluated to measure oxidative stress in bronchoalveolar lavage. Additionally, the pulmonary water content, COX-2 expression and histological examination were determined in the lung. A molecular docking study of the active phytoconstituent of BT obtained from HR-LCMS analysis against reported targets (IL-6, COX-2, TNFα, MPO and ENaC) of ALI was carried out. The B.T. pretreatment prevents mortality in comparison to the oleic acid group. It protects the lungs and heart from the detrimental effect of oleic acid, on par with dexamethasone. COX-2 mRNA expression was significantly down-regulated in the treatment group. The reduced level of TNF-α, MPO, SOD and catalase supported the protective effect of B.T. The in silico study revealed strong binding interaction between the phytoconstituent (Galangin 3- [galactosyl-(1–4)-rhamnoside and Beta solamarine] of BT and the reported target. The B.T. pre-administration attenuates the oleic acid-induced mortality and cardiorespiratory toxicity.

A clinically relevant model of acute respiratory distress syndrome in human-size swine

Despite over 30 years of intensive research for targeted therapies, treatment of acute respiratory distress syndrome (ARDS) remains supportive in nature. With mortality upwards of 30%, a high-fidelity pre-clinical model of ARDS, on which to test novel therapeutics, is urgently needed. We used the Yorkshire breed of swine to induce a reproducible model of ARDS in human-sized swine to allow the study of new therapeutics, from both mechanistic and clinical standpoints. For this, animals were anesthetized, intubated and mechanically ventilated, and pH-standardized gastric contents were delivered bronchoscopically, followed by intravenous infusion of Escherichia coli-derived lipopolysaccharide. Once the ratio of arterial oxygen partial pressure (PaO2) to fractional inspired oxygen (FIO2) had decreased to <150, the animals received standard ARDS treatment for up to 48 h. All swine developed moderate to severe ARDS. Chest radiographs taken at regular intervals showed significantly worse lung edema after induction of ARDS. Quantitative scoring of lung injury demonstrated time-dependent increases in interstitial and alveolar edema, neutrophil infiltration, and mild to moderate alveolar membrane thickening. This pre-clinical model of ARDS in human-sized swine recapitulates the clinical, radiographic and histopathologic manifestations of ARDS, providing a tool to study therapies for this highly morbid lung disease.

Biphasic positive airway pressure spontaneous breathing attenuates lung injury in an animal model of severe acute respiratory distress syndrome

OBJECTIVE

To compare the effects of unassisted spontaneous breathing (SB) and complete muscle paralysis (PC) on early severe acute respiratory distress syndrome (ARDS) in an animal model, and to explore the possibility of biphasic positive airway pressure (BIPAP) as lung protective ventilation support for patients in the early stage of severe ARDS.

METHODS

Twelve healthy beagle dogs between the ages of 10 and 15 months were randomly divided into two groups: the SB group (BIPAP_SB) and the PC group (BIPAP_PC). Arterial blood samples were drawn before modelling. Arterial blood gas analysis and mechanical tests were conducted. The animal model of severe ARDS was established using a deep intravenous injection of oleic acid, and BIPAP ventilation was performed for 8 hours. Lung tissue and blood were taken to detect lung function, inflammatory reactions and degree of pathological damage.

RESULTS

At the beginning of the experiment, there was no significant difference in the arterial blood gas analysis between the two groups (p > 0.05). After successful modelling, the oxygenation index and the end-expiratory lung volume in the SB group were significantly higher than those in the PC group 8 hours after MV. Pathologically, the wet-dry ratio and pathological score of the PC group were higher than those of the SB group; the lung injury in the gravity-dependent area in the SB group was less than that in the PC group (p< 0.05).

CONCLUSIONS

In the early stage of severe ARDS induced by oleic acid, compared with PC, retention of the BIPAP mode of SB can reduce the risk of lung injury and improve respiratory function.

Towards Biohybrid Lung Development: Establishment of a Porcine In Vitro Model

Lung transplantation (LTx) is the only curative therapy option for patients with end-stage lung diseases, though only available for chosen patients. To provide an alternative treatment option to LTx, we aim for the development of an implantable biohybrid lung (BHL) based on hollow fiber membrane (HFM) technology used in extracorporeal membrane oxygenators. Crucial for long-lasting BHL durability is complete hemocompatibility of all blood contacting surfaces, which can be achieved by their endothelialization. In continuation to successful in vitro investigations using human endothelial cells (ECs), indicating general feasibility, the appropriate porcine in vivo model needs to be prepared and established to fill the translational data gap prior to patient’s application. Therefore, isolation of porcine ECs from carotid arteries (pCECs) was established. Following, pCECs were used for HFM endothelialization and examined under static and dynamic conditions using cell medium or heparinized blood, to assess their proliferation capacity, flow resistance and activation state, especially under clinically relevant conditions. Additionally, comparative hemocompatibility tests between native and endothelialized HFMs were performed. Overall, pure pCECs formed a viable and confluent monolayer, which resisted applied flow conditions, in particular due to physiological extracellular matrix synthesis. Additionally, pCECs remained the non-inflammatory and anti-thrombogenic status, significantly improving the hemocompatibility of endothelialized HFMs. Finally, as relevant for reliable porcine to human translation, pCECs behaved in the same way as human ECs. Concluding, generated in vitro data justify further steps towards pre-clinical BHL examination, in particular BHL application to porcine lung injury models, reflecting the clinical scenario with end-stage lung-diseased patients.

In Vivo Assessment of Lung Ultrasound Features Mimicking Viral Pneumonia Using a Large Animal Model

Lung ultrasound (LUS) is a practical tool for lung diagnosis when computer tomography (CT) is not available. Recent findings suggest that LUS diagnosis is highly advantageous because of its mobility and correlation with radiological findings for viral pneumonia. Simple models for both educational evaluation and technical evaluation are needed. Therefore, this work investigates the usability of a large animal model under aspects of LUS features of viral pneumonia using saline one lung flooding. Six pigs were intubated with a double-lumen tube, and the left lung was instilled with saline. During the instillation of up to 12.5 ml/kg, the sonographic features were assessed. All features present during viral pneumonia were found, such as B-lines, white lung syndrome, pleural thickening, and the formation of pleural consolidations. Sonographic findings correlate well with current LUS scores for COVID19. The scores of 1, 2, and 3 were dominantly present at 1-4-, 4-8-, and 8-12-ml/kg saline instillation, respectively. The noninfective animal model can be used for further investigation of the LUS features and can serve in education, by helping with the appropriate handling of LUS in clinical practice during management of viral pneumonia.