Inhaled β2 Adrenergic Agonists and Other cAMP-Elevating Agents: Therapeutics for Alveolar Injury and Acute Respiratory Disease Syndrome?

Using the sympathetic system, beta blockers and alpha-2 agonists, to address acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) manifests as an acute inflammatory lung injury characterized by persistent hypoxemia, featuring a swift onset, high mortality, and predominantly supportive care as the current therapeutic approach, while effective treatments remain an area of active investigation. Adrenergic receptors (AR) play a pivotal role as stress hormone receptors, extensively participating in various inflammatory processes by initiating downstream signaling pathways. Advancements in molecular biology and pharmacology continually unveil the physiological significance of distinct AR subtypes. Interventions targeting these subtypes have the potential to induce specific alterations in cellular and organismal functions, presenting a promising avenue as a therapeutic target for managing ARDS. This article elucidates the pathogenesis of ARDS and the basic structure and function of AR. It also explores the relationship between AR and ARDS from the perspective of different AR subtypes, aiming to provide new insights for the improvement of ARDS.

Cyclic Adenosine Monophosphate in Cardiac and Sympathoadrenal GLP-1 Receptor Signaling: Focus on Anti-Inflammatory Effects

Glucagon-like peptide-1 (GLP-1) is a multifunctional incretin hormone with various physiological effects beyond its well-characterized effect of stimulating glucose-dependent insulin secretion in the pancreas. An emerging role for GLP-1 and its receptor, GLP-1R, in brain neuroprotection and in the suppression of inflammation, has been documented in recent years. GLP-1R is a G protein-coupled receptor (GPCR) that couples to Gs proteins that stimulate the production of the second messenger cyclic 3',5'-adenosine monophosphate (cAMP). cAMP, acting through its two main effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac), exerts several anti-inflammatory (and some pro-inflammatory) effects in cells, depending on the cell type. The present review discusses the cAMP-dependent molecular signaling pathways elicited by the GLP-1R in cardiomyocytes, cardiac fibroblasts, central neurons, and even in adrenal chromaffin cells, with a particular focus on those that lead to anti-inflammatory effects by the GLP-1R. Fully elucidating the role cAMP plays in GLP-1R's anti-inflammatory properties can lead to new and more precise targets for drug development and/or provide the foundation for novel therapeutic combinations of the GLP-1R agonist medications currently on the market with other classes of drugs for additive anti-inflammatory effect.

Medium-Dose Formoterol Attenuated Abdominal Aortic Aneurysm Induced by EPO via β2AR/cAMP/SIRT1 Pathway

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease but effective drugs for treatment of AAA are still lacking. Recently, erythropoietin (EPO) is reported to induce AAA formation in apolipoprotein-E knock out (ApoE-/-) mice but an effective antagonist is unknown. In this study, formoterol, a β2 adrenergic receptor (β2AR) agonist, is found to be a promising agent for inhibiting AAA. To test this hypothesis, ApoE-/- mice are treated with vehicle, EPO, and EPO plus low-, medium-, and high-dose formoterol, respectively. The incidence of AAA is 0, 55%, 35%,10%, and 55% in these 5 groups, respectively. Mechanistically, senescence of vascular smooth muscle cell (VSMC) is increased by EPO while decreased by medium-dose formoterol both in vivo and in vitro, manifested by the altered expression of senescence biomarkers including phosphorylation of H2AXserine139, senescence-associated β-galactosidase activity, and P21 protein level. In addition, expression of sirtuin 1 (SIRT1) in aorta is decreased in EPO-induced AAA but remarkably elevated by medium-dose formoterol. Knockdown of β2AR and blockage of cyclic adenosine monophosphate (cAMP) attenuate the inhibitory role of formoterol in EPO-induced VSMC senescence. In summary, medium-dose formoterol attenuates EPO-induced AAA via β2AR/cAMP/SIRT1 pathways, which provides a promising medication for the treatment of AAA.

Regulation of Inflammation by IRAK-M Pathway Can Be Associated with nAchRalpha7 Activation and COVID-19

In spite of the vaccine development and its importance, the SARS-CoV-2 pandemic is still impacting the world. It is known that the COVID-19 severity is related to the cytokine storm phenomenon, being inflammation a common disease feature. The nicotinic cholinergic system has been widely associated with COVID-19 since it plays a protective role in inflammation via nicotinic receptor alpha 7 (nAchRalpha7). In addition, SARS-CoV-2 spike protein (Spro) subunits can interact with nAchRalpha7. Moreover, Spro causes toll-like receptor (TLR) activation, leading to pro- and anti-inflammatory pathways. The increase and maturation of the IL-1 receptor-associated kinase (IRAK) family are mediated by activation of membrane receptors, such as TLRs. IRAK-M, a member of this family, is responsible for negatively regulating the activity of other active IRAKs. In addition, IRAK-M can regulate microglia phenotype by specific protein expression. Furthermore, there exists an antagonist influence of SARS-CoV-2 Spro and the cholinergic system action on the IRAK-M pathway and microglia phenotype. We discuss the overexpression and suppression of IRAK-M in inflammatory cell response to inflammation in SARS-CoV-2 infection when the cholinergic system is constantly activated via nAchRalpha7.

Bisdemethoxycurcumin alleviates LPS-induced acute lung injury via activating AMPKα pathway

OBJECTIVE

Inflammation and oxidative stress contribute to the pathogenesis of acute lung injury (ALI), and subsequently result in rapid deterioration in health. Considering the indispensable role of bisdemethoxycurcumin (BDMC) in inflammation and oxidative stress, the present study aims to examine the effect of BDMC on sepsis-related ALI.

METHODS

C57BL/6 mice were administered with BDMC (100 mg/kg) or an equal volume of vehicle, and then injected with lipopolysaccharides (LPS) to induce ALI. We assessed the parameters of lung injury, inflammatory response and oxidative stress in lung tissues. Consistently, the macrophages with or without BDMC treatment were exposed to LPS to verify the effect of BDMC in vitro.

RESULTS

BDMC suppressed LPS-induced lung injury, inflammation and oxidative stress in vivo and in vitro. Mechanistically, BDMC increased the phosphorylation of AMPKα in response to LPS stimulation, and AMPK inhibition with Compound C almost completely blunted the protective effect of BDMC in LPS-treated mice and macrophages. Moreover, we demonstrated that BDMC activated AMPKα via the cAMP/Epac pathway.

CONCLUSION

Our study identifies the protective effect of BDMC against LPS-induced ALI, and the underlying mechanism may be related to the activation of cAMP/Epac/AMPKα signaling pathway.

Sepsis-Induced Acute Lung Injury Is Alleviated by Small Molecules from Dietary Plants via Pyroptosis Modulation

Sepsis-induced acute respiratory distress syndrome (ARDS) has high morbidity and mortality, and it has three major pathogeneses, namely alveolar-capillary barrier destruction, elevated gut permeability, and reduced neutrophil extracellular traps (NETS), all of which are pyroptosis-involved. Due to limitations of current agents like adverse reaction superposition, inevitable drug resistance, and relatively heavier financial burden, naturally extracted small-molecule compounds have a broad market even though chemically modified drugs have straightforward efficacy. Despite increased understanding of the molecular biology and mechanism underlying sepsis-induced ARDS, there are no specific reviews concerning how small molecules from dietary plants alleviate sepsis-induced acute lung injury (ALI) via regulating pyroptotic cell death. Herein, we traced and reviewed the molecular underpinnings of sepsis-induced ALI with a focus on small-molecule compounds from dietary plants, the top three categories of which are respectively flavonoids and flavone, terpenoids, and polyphenol and phenolic acids, and how they rescued septic ALI by restraining pyroptosis.

Psychological distress influences lung cancer: Advances and perspectives on the immune system and immunotherapy

Lung cancer has the highest incidence rate and mortality worldwide. Moreover, multiple factors may cause heterogeneity in the efficacy of immunotherapy for lung cancer, and preclinical studies have gradually uncovered the promotive effects of psychological distress (PD) on tumor hallmarks. Therefore, treatment targeted at PD may be a vital factor in adjusting and improving immunotherapy for lung cancer. Here, by focusing on the central nervous system, as well as stress-related crucial neurotransmitters and hormones, we highlight the effects of PD on the lung immune system, the lung tumor microenvironment (TME) and immunotherapy, which brings a practicable means and psychosocial perspective to lung cancer treatment.

Identification and validation of metabolism-related hub genes in idiopathic pulmonary fibrosis

Background: Idiopathic pulmonary fibrosis (IPF) is a fatal and irreversible interstitial lung disease. The specific mechanisms involved in the pathogenesis of IPF are not fully understood, while metabolic dysregulation has recently been demonstrated to contribute to IPF. This study aims to identify key metabolism-related genes involved in the progression of IPF, providing new insights into the pathogenesis of IPF. Methods: We downloaded four datasets (GSE32537, GSE110147, GSE150910, and GSE92592) from the Gene Expression Omnibus (GEO) database and identified differentially expressed metabolism-related genes (DEMRGs) in lung tissues of IPF by comprehensive analysis. Then, we performed GO, KEGG, and Reactome enrichment analyses of the DEMRGs. Subsequently, key DEMRGs were identified by machine-learning algorithms. Next, miRNAs regulating these key DEMRGs were predicted by integrating the GSE32538 (IPF miRNA dataset) and the miRWalk database. The Cytoscape software was used to visualize miRNA-mRNA regulatory networks. In addition, the relative levels of immune cells were assessed by the CIBERSORT algorithm, and the correlation of key DEMRGs with immune cells was calculated. Finally, the mRNA expression of the key DEMRGs was validated in two external independent datasets and an in vivo experiment. Results: A total of 101 DEMRGs (51 upregulated and 50 downregulated) were identified. Six key DEMRGs (ENPP3, ENTPD1, GPX3, PDE7B, PNMT, and POLR3H) were further identified using two machine-learning algorithms (LASSO and SVM-RFE). In the lung tissue of IPF patients, the expression levels of ENPP3, ENTPD1, and PDE7B were upregulated, and the expression levels of GPX3, PNMT, and POLR3H were downregulated. In addition, the miRNA-mRNA regulatory network of key DEMRGs was constructed. Then, the expression levels of key DEMRGs were validated in two independent external datasets (GSE53845 and GSE213001). Finally, we verified the key DEMRGs in the lung tissue of bleomycin-induced pulmonary fibrosis mice by qRT-PCR. Conclusion: Our study identified key metabolism-related genes that are differentially expressed in the lung tissue of IPF patients. Our study emphasizes the critical role of metabolic dysregulation in IPF, offers potential therapeutic targets, and provides new insights for future studies.

Ex Vivo Pulmonary Oedema after In Vivo Blast-Induced Rat Lung Injury: Time Dependency, Blast Intensity and Beta-2 Adrenergic Receptor Role

Objective: Current treatments for blast-induced lung injury are limited to supportive procedures including mechanical ventilation. The study aimed to investigate the role of post-trauma-induced oedema generation in the function of time and trauma intensity and the probable role of beta 2-adrenergic receptors (β2-ARs) agonists on pulmonary oedema. The study is conducted using an ex vivo model after an experimental in vivo blast-induced thorax trauma in rats. Methods: Rats were randomised and divided into two groups, blast and sham. The blast group were anaesthetised and exposed to the blast wave (3.16 ± 0.43 bar) at a distance of 3.5 cm from the thorax level. The rats were sacrificed 10 min after the blast, the lungs explanted and treated with terbutaline, formoterol, propranolol or amiloride to assess the involvement of sodium transport. Other groups of rats were exposed to distances of 5 and 7 cm from the thorax to reduce the intensity of the injury. Further, one group of rats was studied after 180 min and one after 360 min after a 3.5 cm blast injury. Sham controls were exposed to identical procedures except for receiving blast overpressure. Results: Lung injury and oedema generation depended on time after injury and injury intensity. Perfusion with amiloride resulted in a further increase in oedema formation as indicated by weight gain (p < 0.001), diminished tidal volume (Tv) (p < 0.001), and increased airway resistance (p < 0.001). Formoterol caused a significant increase in the Tv (p < 0.001) and a significant decrease in the airway resistance (p < 0.01), while the lung weight was not influenced. Trauma-related oedema was significantly reduced by terbutaline in terms of lung weight gain (p < 0.01), Tv (p < 0.001), and airway resistance (p < 0.01) compared to control blast-injured lungs. Terbutaline-induced effects were completely blocked by the β-receptor antagonist propranolol (p < 0.05). Similarly, amiloride, which was added to terbutaline perfusion, reversed terbutaline-induced weight gain reduction (p < 0.05). Conclusions: β2-adrenoceptor stimulation had a beneficial impact by amiloride-dependent sodium and therefore, fluid transport mechanisms on the short-term ex vivo oedema generation in a trauma-induced in vivo lung injury of rats.

Advances in the Regulation of Macrophage Polarization by Mesenchymal Stem Cells and Implications for ALI/ARDS Treatment

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a common condition with high mortality. ALI/ARDS is caused by multiple etiologies, and the main clinical manifestations are progressive dyspnea and intractable hypoxemia. Currently, supportive therapy is the main ALI/ARDS treatment, and there remains a lack of targeted and effective therapeutic strategies. Macrophages are important components of innate immunity. M1 macrophages are pro-inflammatory, while M2 macrophages are anti-inflammatory and promote tissue repair. Mesenchymal stem cells (MSCs) are stem cells with broad application prospects in tissue regeneration due to their multi-directional differentiation potential along with their anti-inflammatory and paracrine properties. MSCs can regulate the balance of M1/M2 macrophage polarization to improve the prognosis of ALI/ARDS. In this paper, we review the mechanisms by which MSCs regulate macrophage polarization and the signaling pathways associated with polarization. This review is expected to provide new targets for the treatment of ALI/ARDS.