Argon reduces the pulmonary vascular tone in rats and humans by GABA-receptor activation

Precision cut lung slices: an integrated ex vivo model for studying lung physiology, pharmacology, disease pathogenesis and drug discovery

Precision Cut Lung Slices (PCLS) have emerged as a sophisticated and physiologically relevant ex vivo model for studying the intricacies of lung diseases, including fibrosis, injury, repair, and host defense mechanisms. This innovative methodology presents a unique opportunity to bridge the gap between traditional in vitro cell cultures and in vivo animal models, offering researchers a more accurate representation of the intricate microenvironment of the lung. PCLS require the precise sectioning of lung tissue to maintain its structural and functional integrity. These thin slices serve as invaluable tools for various research endeavors, particularly in the realm of airway diseases. By providing a controlled microenvironment, precision-cut lung slices empower researchers to dissect and comprehend the multifaceted interactions and responses within lung tissue, thereby advancing our understanding of pulmonary pathophysiology.

Clinical Diagnostic Value of Serum GABA, NE, ET-1, and VEGF in Chronic Obstructive Pulmonary Disease with Pulmonary Hypertension

Background

Pulmonary hypertension (PH) is the one of the most common complications of chronic obstructive pulmonary disease (COPD). Whereas, the associated diagnostic factors are uncertain. The present study aims to investigate useful diagnostic factors in patients with COPD and PH (COPD-PH).

Patients and Methods

A total of 111 patients with COPD in Shanxi Bethune Hospital from December 2019 to December 2020 were divided into COPD (PASP≤50 mmHg) and COPD-PH groups (PASP>50 mmHg). Pulmonary function and chest CT results were collected. Routine blood, biochemical, and blood coagulation function indices were examined for all patients. Arterial blood gas analysis and serum cytokines were also measured. Differences in the distribution of the above indicators between the two groups were analyzed using binary logistic regression analysis to identify the risk factors of COPD-PH, and multiple linear regression analysis to determine the factors affecting PASP. The influencing factors and joint predictive factors of the above linear regression analysis were analyzed using the ROC curve. The area under the curve and the best cut-off value were calculated, and their predictive value and clinical significance in disease diagnosis were discussed.

Results

A total of 27 indexes with statistically significant differences between the two groups were identified (P < 0.05). Binary Logistic regression analysis showed that the factors influencing the diagnosis of pulmonary hypertension were serum GABA, NE, VEGF, BUN, and LYM% levels (P < 0.05). Multiple linear regression showed that the factors influencing PASP were serum NE, ET-1, GABA, and VEGF levels, and the goodness of fit of the model was 0.748 (P < 0.001). ROC curve showed that the AUC of the combined diagnosis of serum NE, ET-1, GABA, and VEGF levels was 0.966 (sensitivity, 87.5%; specificity, 93.65%).

Conclusion

Serum NE and ET-1 are risk factors for COPD-PH, whereas serum GABA and VEGF are protective factors against COPD-PH. The combined diagnostic value of serum NE, ET-1, GABA, and VEGF levels was the highest.

Application of Precision-Cut Lung Slices as an In Vitro Model for Research of Inflammatory Respiratory Diseases

The leading cause of many respiratory diseases is an ongoing and progressive inflammatory response. Traditionally, inflammatory lung diseases were studied primarily through animal models, cell cultures, and organoids. These technologies have certain limitations, despite their great contributions to the study of respiratory diseases. Precision-cut lung slices (PCLS) are thin, uniform tissue slices made from human or animal lung tissue and are widely used extensively both nationally and internationally as an in vitro organotypic model. Human lung slices bridge the gap between in vivo and in vitro models, and they can replicate the living lung environment well while preserving the lungs' basic structures, such as their primitive cells and trachea. However, there is no perfect model that can completely replace the structure of the human lung, and there is still a long way to go in the research of lung slice technology. This review details and analyzes the strengths and weaknesses of precision lung slices as an in vitro model for exploring respiratory diseases associated with inflammation, as well as recent advances in this field.

Platelet-derived growth factor (PDGF)-BB regulates the airway tone via activation of MAP2K, thromboxane, actin polymerisation and Ca2+-sensitisation

BACKGROUND

PDGFR-inhibition by the tyrosine kinase inhibitor (TKI) nintedanib attenuates the progress of idiopathic pulmonary fibrosis (IPF). However, the effects of PDGF-BB on the airway tone are almost unknown. We studied this issue and the mechanisms beyond, using isolated perfused lungs (IPL) of guinea pigs (GPs) and precision-cut lung slices (PCLS) of GPs and humans.

METHODS

IPL: PDGF-BB was perfused after or without pre-treatment with the TKI imatinib (perfused/nebulised) and its effects on the tidal volume (TV), the dynamic compliance (Cdyn) and the resistance were studied.

PCLS (GP)

The bronchoconstrictive effects of PDGF-BB and the mechanisms beyond were evaluated. PCLS (human): The bronchoconstrictive effects of PDGF-BB and the bronchorelaxant effects of imatinib were studied. All changes of the airway tone were measured by videomicroscopy and indicated as changes of the initial airway area.

RESULTS

PCLS (GP/human): PDGF-BB lead to a contraction of airways. IPL: PDGF-BB decreased TV and Cdyn, whereas the resistance did not increase significantly. In both models, inhibition of PDGFR-(β) (imatinib/SU6668) prevented the bronchoconstrictive effect of PDGF-BB. The mechanisms beyond PDGF-BB-induced bronchoconstriction include activation of MAP2K and TP-receptors, actin polymerisation and Ca²⁺-sensitisation, whereas the increase of Ca²⁺ itself and the activation of EP_1-4-receptors were not of relevance. In addition, imatinib relaxed pre-constricted human airways.

CONCLUSIONS

PDGFR regulates the airway tone. In PCLS from GPs, this regulatory mechanism depends on the β-subunit. Hence, PDGFR-inhibition may not only represent a target to improve chronic airway disease such as IPF, but may also provide acute bronchodilation in asthma. Since asthma therapy uses topical application. This is even more relevant, as nebulisation of imatinib also appears to be effective.

Never Change a Flowing System? The Effects of Retrograde Flow on Isolated Perfused Lungs and Vessels

Retrograde perfusion may occur during disease, surgery or extracorporeal circulation. While it is clear that endothelial cells sense and respond to changes in blood flow, the consequences of retrograde perfusion are only poorly defined. Similar to shear stress or disturbed flow, retrograde perfusion might result in vasomotor responses, edema formation or inflammation in and around vessels. In this study we investigated in rats the effects of retrograde perfusion in isolated systemic vessels (IPV) and in pulmonary vessels of isolated perfused lungs (IPL). Anterograde and retrograde perfusion was performed for 480 min in IPV and for 180 min in the IPL. Perfusion pressure, cytokine levels in perfusate and bronchoalveolar lavage fluid (BALF), edema formation and mRNA expression were studied. In IPV, an increased perfusion pressure and initially also increased cytokine levels were observed during retrograde perfusion. In the IPL, increased edema formation occurred, while cytokine levels were not increased, though dilution of cytokines in BALF due to pulmonary edema cannot be excluded. In conclusion, effects of flow reversal were visible immediately after initiation of retrograde perfusion. Pulmonary edema formation was the only effect of the 3 h retrograde perfusion. Therefore, further research should focus on identification of possible long-term complications of flow reversal.

Argon Attenuates Multiorgan Failure in Relation with HMGB1 Inhibition

Argon inhalation attenuates multiorgan failure (MOF) after experimental ischemic injury. We hypothesized that this protection could involve decreased High Mobility Group Box 1 (HMGB1) systemic release. We investigated this issue in an animal model of MOF induced by aortic cross-clamping. Anesthetized rabbits were submitted to supra-coeliac aortic cross-clamping for 30 min, followed by 300 min of reperfusion. They were randomly divided into three groups (n = 7/group). The Control group inhaled nitrogen (70%) and oxygen (30%). The Argon group was exposed to a mixture of argon (70%) and oxygen (30%). The last group inhaled nitrogen/oxygen (70/30%) with an administration of the HMGB1 inhibitor glycyrrhizin (4 mg/kg i.v.) 5 min before aortic unclamping. At the end of follow-up, cardiac output was significantly higher in Argon and Glycyrrhizin vs. Control (60 ± 4 and 49 ± 4 vs. 33 ± 8 mL/kg/min, respectively). Metabolic acidosis was attenuated in Argon and Glycyrrhizin vs. Control, along with reduced amount of norepinephrine to reverse arterial hypotension. This was associated with reduced interleukin-6 and HMGB1 plasma concentration in Argon and Glycyrrhizin vs. Control. End-organ damages were also attenuated in the liver and kidney in Argon and Glycyrrhizin vs. Control, respectively. Argon inhalation reduced HMGB1 blood level after experimental aortic cross-clamping and provided similar benefits to direct HMGB1 inhibition.

Update of the organoprotective properties of xenon and argon: from bench to beside

The growth of the elderly population has led to an increase in patients with myocardial infarction and stroke (Wajngarten and Silva, Eur Cardiol 14: 111–115, 2019). Patients receiving treatment for ST-segment-elevation myocardial infarction (STEMI) highly profit from early reperfusion therapy under 3 h from the onset of symptoms. However, mortality from STEMI remains high due to the increase in age and comorbidities (Menees et al., N Engl J Med 369: 901–909, 2013). These factors also account for patients with acute ischaemic stroke. Reperfusion therapy has been established as the gold standard within the first 4 to 5 h after onset of symptoms (Powers et al., Stroke 49: e46-e110, 2018). Nonetheless, not all patients are eligible for reperfusion therapy. The same is true for traumatic brain injury patients. Due to the complexity of acute myocardial and central nervous injury (CNS), finding organ protective substances to improve the function of remote myocardium and the ischaemic penumbra of the brain is urgent. This narrative review focuses on the noble gases argon and xenon and their possible cardiac, renal and neuroprotectant properties in the elderly high-risk (surgical) population. The article will provide an overview of the latest experimental and clinical studies. It is beyond the scope of this review to give a detailed summary of the mechanistic understanding of organ protection by xenon and argon.

Embedding of Precision-Cut Lung Slices in Engineered Hydrogel Biomaterials Supports Extended Ex Vivo Culture

Maintaining the three-dimensional architecture and cellular complexity of lung tissue ex vivo can enable elucidation of the cellular and molecular pathways underlying chronic pulmonary diseases. Precision-cut lung slices (PCLS) are one human-lung model with the potential to support critical mechanistic studies and early drug discovery. However, many studies report short culture times of 7-10 days. Here, we systematically evaluated poly(ethylene glycol)-based hydrogel platforms for the encapsulation of PCLS. We demonstrated the ability to support ex vivo culture of embedded PCLS for at least 21 days compared with control PCLS floating in media. These customized hydrogels maintained PCLS architecture (no difference), viability (4.7-fold increase, P < 0.0001), and cellular phenotype as measured by SFTPC (1.8-fold increase, P < 0.0001) and vimentin expression (no change) compared with nonencapsulated controls. Collectively, these results demonstrate that hydrogel biomaterials support the extended culture times required to study chronic pulmonary diseases ex vivo using PCLS technology.

γ-aminobutyric acid alleviates LPS-induced acute lung injury in mice through upregulating type B receptors

INTRODUCTION

In recent years, studies have shown that GABA has a certain therapeutic effect on acute lung injury (ALI), but its specific mechanism has not been fully elucidated. The study was designed to investigate the protective effect and mechanism of γ-aminobutyric acid (GABA) on ALI induced by lipopolysaccharide (LPS) in mice.

MATERIAL AND METHODS

C57BL/6 mice were randomly divided into a control group, LPS group, LPS + GABA (10 mg/kg) group and LPS + dexamethasone (Dex, 5 mg/kg) group. The survival rate of each group was observed at different time points after modeling. The levels of tumor necrosis factor α (TNF-α), interleukin (IL) 1β, 10, myeloperoxidase (MPO) and the cell count and protein concentration in bronchoalveolar lavage fluid (BALF) were measured. Lung histopathology and the expression of GABA receptors were observed by HE staining and immunohistochemistry respectively. Lung water content was assessed by wet-dry weight ratio.

RESULTS

GABA could significantly improve the survival rate and prolong the survival time of animals, alleviate the degree of inflammatory injury and pulmonary edema, reduce the content of MPO, down-regulate the levels of pro-inflammatory cytokines IL-1β and TNF-α, and up-regulate the expression of anti-inflammatory cytokine IL-10. Moreover, GABA could significantly decrease the expression of type A receptors and enhance type B receptors.

CONCLUSIONS

GABA can effectively alleviate ALI induced by LPS in mice, and its effect may be related to the upregulation of type B receptors.