Silencing of Gal-7 inhibits TGF-β1-induced apoptosis of human airway epithelial cells through JNK signaling pathway

The Role of Galectins in Asthma Pathophysiology: A Comprehensive Review

Galectins are a group of β-galactoside-binding proteins with several roles in immune response, cellular adhesion, and inflammation development. Current evidence suggest that these proteins could play a crucial role in many respiratory diseases such as pulmonary fibrosis, lung cancer, and respiratory infections. From this standpoint, an increasing body of evidence have recognized galectins as potential biomarkers involved in several aspects of asthma pathophysiology. Among them, galectin-3 (Gal-3), galectin-9 (Gal-9), and galectin-10 (Gal-10) are the most extensively studied in human and animal asthma models. These galectins can affect T helper 2 (Th2) and non-Th2 inflammation, mucus production, airway responsiveness, and bronchial remodeling. Nevertheless, while higher Gal-3 and Gal-9 concentrations are associated with a stronger degree of Th-2 phlogosis, Gal-10, which forms Charcot-Leyden Crystals (CLCs), correlates with sputum eosinophilic count, interleukin-5 (IL-5) production, and immunoglobulin E (IgE) secretion. Finally, several galectins have shown potential in clinical response monitoring after inhaled corticosteroids (ICS) and biologic therapies, confirming their potential role as reliable biomarkers in patients with asthma.

The interrelation of galectins and autophagy

Autophagy is a vital physiological process that maintains intracellular homeostasis by removing damaged organelles and senescent or misfolded molecules. However, excessive autophagy results in cell death and apoptosis, which will lead to a variety of diseases. Galectins are a type of animal lectin that binds to β-galactosides and can bind to the cell surface or extracellular matrix glycans, affecting a variety of immune processes in vivo and being linked to the development of many diseases. In many cases, galectins and autophagy both play important regulatory roles in the cellular life course, yet our understanding of the relationship between them is still incomplete. Galectins and autophagy may share common etiological cofactors for some diseases. Hence, we summarize the relationship between galectins and autophagy, aiming to draw attention to the existence of multiple associations between galectins and autophagy in a variety of physiological and pathological processes, which provide new ideas for etiological diagnosis, drug development, and therapeutic targets for related diseases.

Galectin functions in cancer-associated inflammation and thrombosis

Galectins are carbohydrate-binding proteins that regulate many cellular functions including proliferation, adhesion, migration, and phagocytosis. Increasing experimental and clinical evidence indicates that galectins influence many steps of cancer development by inducing the recruitment of immune cells to the inflammatory sites and modulating the effector function of neutrophils, monocytes, and lymphocytes. Recent studies described that different isoforms of galectins can induce platelet adhesion, aggregation, and granule release through the interaction with platelet-specific glycoproteins and integrins. Patients with cancer and/or deep-venous thrombosis have increased levels of galectins in the vasculature, suggesting that these proteins could be important contributors to cancer-associated inflammation and thrombosis. In this review, we summarize the pathological role of galectins in inflammatory and thrombotic events, influencing tumor progression and metastasis. We also discuss the potential of anti-cancer therapies targeting galectins in the pathological context of cancer-associated inflammation and thrombosis.

Medawar's PostEra: Galectins Emerged as Key Players During Fetal-Maternal Glycoimmune Adaptation

Lectin-glycan interactions, in particular those mediated by the galectin family, regulate many processes required for a successful pregnancy. Over the past decades, increasing evidence gathered from in vitro and in vivo experiments indicate that members of the galectin family specifically bind to both intracellular and membrane bound carbohydrate ligands regulating angiogenesis, immune-cell adaptations required to tolerate the fetal semi-allograft and mammalian embryogenesis. Therefore, galectins play important roles in fetal development and placentation contributing to maternal and fetal health. This review discusses the expression and role of galectins during the course of pregnancy, with an emphasis on maternal immune adaptions and galectin-glycan interactions uncovered in the recent years. In addition, we summarize the galectin fingerprints associated with pathological gestation with particular focus on preeclampsia.

CCCTC-binding factor transcriptionally regulates Galectin-7 and activates the JNK/STAT3 axis to aggravate bronchial epithelial cell injury

OBJECTIVE

Studies have shown that the expression of CCCTC-binding factor (CTCF) is significantly upregulated in the airway epithelial cells of asthmatic patients, suggesting that CTCF may play an important role in the progression of asthma.

MATERIAL/METHODS

Human bronchial epithelial cells BEAS-2B were stimulated with transforming growth factor-β1 (TGF-β1) at a concentration of 10 ng/ml, and CTCF overexpression plasmid and CTCF small interfering RNA were transfected into the cells. The proliferation, apoptosis, inflammatory factor secretion, and airway remodeling marker protein expression of injured cells were detected. We bidirectionally regulated Galectin-7 expression in TGF-β1-induced BEAS-2B cells and overexpress CTCF, while interfering with Galectin-7 to further explore the regulatory effect of CTCF on Galectin-7. We introduced SP600125, a c-Jun N-terminal kinase c-Jun (JNK) pathway inhibitor, to investigate whether CTCF affects asthma progression through the JNK pathway.

RESULTS

The expression of CTCF in BEAS-2B cells induced by TGF-β1 was significantly upregulated, interfering with CTCF expression promoted cell proliferation, inhibited apoptosis, reduced inflammatory factors secretion, and decreased the expression of airway remodeling marker protein. Luciferase reporter gene analysis and chromatin immunoprecipitation verified that CTCF directly bound to Galectin-7 promoter. The effect of Galectin-7 on cells is consistent with the effect of CTCF on cells. The regulatory effect of CTCF on injured cells was indeed mediated by activation of the JNK/STAT3 axis.

CONCLUSIONS

CTCF transcriptionally regulated Galectin-7 and activated JNK/STAT3 axis to aggravate bronchial epithelial cell injury.

Functions and Inhibition of Galectin-7, an Emerging Target in Cellular Pathophysiology

Galectin-7 is a soluble unglycosylated lectin that is able to bind specifically to β-galactosides. It has been described to be involved in apoptosis, proliferation and differentiation, but also in cell adhesion and migration. Several disorders and diseases are discussed by covering the aforementioned biological processes. Structural features of galectin-7 are discussed as well as targeting the protein intracellularly or extracellularly. The exact molecular mechanisms that lie behind many biological processes involving galectin-7 are not known. It is therefore useful to come up with chemical probes or tools in order to obtain knowledge of the physiological processes. The objective of this review is to summarize the roles and functions of galectin-7 in the human body, providing reasons why it is necessary to design inhibitors for galectin-7, to give the reader structural insights and describe its current inhibitors.

Mitochondrial-Targeting Antioxidant SS-31 Suppresses Airway Inflammation and Oxidative Stress Induced by Cigarette Smoke

This study investigated whether the mitochondrial-targeted peptide SS-31 can protect against cigarette smoke- (CS-) induced airway inflammation and oxidative stress in vitro and in vivo. Mice were exposed to CS for 4 weeks to establish a CS-induced airway inflammation model, and those in the experimental group were pretreated with SS-31 1 h before CS exposure. Pathologic changes and oxidative stress in lung tissue, inflammatory cell counts, and proinflammatory cytokine levels in bronchoalveolar lavage fluid (BALF) were examined. The mechanistic basis for the effects of SS-31 on CS extract- (CSE-) induced airway inflammation and oxidative stress was investigated using BEAS-2B bronchial epithelial cells and by RNA sequencing and western blot analysis of lung tissues. SS-31 attenuated CS-induced inflammatory injury of the airway and reduced total cell, neutrophil, and macrophage counts and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 6, and matrix metalloproteinase (MMP) 9 levels in BALF. SS-31 also attenuated CS-induced oxidative stress by decreasing malondialdehyde (MDA) and myeloperoxidase (MPO) activities and increasing that of superoxide dismutase (SOD). It also reversed CS-induced changes in the expression of mitochondrial fission protein (MFF) and optic atrophy (OPA) 1 and reduced the amount of cytochrome c released into the cytosol. Pretreatment with SS-31 normalized TNF-α, IL-6, and MMP9 expression, MDA and SOD activities, and ROS generation in CSE-treated BEAS-2B cells and reversed the changes in MFF and OPA1 expression. RNA sequencing and western blot analysis showed that SS-31 inhibited CS-induced activation of the mitogen-activated protein kinase (MAPK) signaling pathway in vitro and in vivo. Thus, SS-31 alleviates CS-induced airway inflammation and oxidative stress via modulation of mitochondrial function and regulation of MAPK signaling and thus has therapeutic potential for the treatment of airway disorders caused by smoking.

P53 in the impaired lungs

Our laboratory is focused on investigating the supportive role of P53 towards the maintenance of lung homeostasis. Acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, pulmonary fibrosis, bronchial asthma, pulmonary arterial hypertension, pneumonia and tuberculosis are respiratory pathologies, associated with dysfunctions of this endothelium defender (P53). Herein we review the evolving role of P53 towards the aforementioned inflammatory disorders, to potentially reveal new therapeutic possibilities in pulmonary disease.

Dual role of RACK1 in airway epithelial mesenchymal transition and apoptosis

Airway epithelial apoptosis and epithelial mesenchymal transition (EMT) are two crucial components of asthma pathogenesis, concomitantly mediated by TGF‐β1. RACK1 is the downstream target gene of TGF‐β1 shown to enhancement in asthma mice in our previous study. Balb/c mice were sensitized twice and challenged with OVA every day for 7 days. Transformed human bronchial epithelial cells, BEAS‐2B cells were cultured and exposed to recombinant soluble human TGF‐β1 to induced apoptosis (30 ng/mL, 72 hours) and EMT (10 ng/mL, 48 hours) in vitro, respectively. siRNA and pharmacological inhibitors were used to evaluate the regulation of RACK1 protein in apoptosis and EMT. Western blotting analysis and immunostaining were used to detect the protein expressions in vivo and in vitro. Our data showed that RACK1 protein levels were significantly increased in OVA‐challenged mice, as well as TGF‐β1‐induced apoptosis and EMT of BEAS‐2B cells. Knockdown of RACK1 (siRACK1) significantly inhibited apoptosis and decreased TGF‐β1 up‐regulated EMT related protein levels (N‐cadherin and Snail) in vitro via suppression of JNK and Smad3 activation. Moreover, siSmad3 or siJNK impaired TGF‐β1‐induced N‐cadherin and Snail up‐regulation in vitro. Importantly, JNK gene silencing (siERK) also impaired the regulatory effect of TGF‐β1 on Smad3 activation. Our present data demonstrate that RACK1 is a concomitant regulator of TGF‐β1 induces airway apoptosis and EMT via JNK/Smad/Snail signalling axis. Our findings may provide a new insight into understanding the regulation mechanism of RACK1 in asthma pathogenesis.

MiR-20a-5p suppressed TGF-β1-triggered apoptosis of human bronchial epithelial BEAS-2B cells by targeting STAT3

Apoptosis of bronchial epithelial cells contributes to lung diseases, including asthma. Although miR-20a-5p is reportedly downregulated in the bronchial epithelia of asthmatic patients, its function and mechanism still need to be explored. Here, we explored how miR-20a-5p affects human bronchial epithelial cells stimulated with transforming growth factor (TGF)-β₁. Using qRT-PCR, we observed downregulated miR-20a-5p levels in these cells. After transfecting miR-20a-5p mimics or inhibitors into human bronchial epithelium BEAS-2B cells, a Cell Counting Kit-8 assay and flow cytometry analysis showed that the mimics mitigated suppression of cell viability and acceleration of apoptosis that was triggered by TGF-β₁, whereas the inhibitors exerted the opposite effects. TGF-β₁ induced a decrease in expression of Bcl-2 and an increase in expression of Bax, both of which were inhibited by miR-20a-5p mimics and further enhanced by miR-20a-5p inhibitors. Further study verified that miR-20a-5p targeted the signal transducer and activator of transcription 3 (STAT3) and the STAT3 level was inversely related to the miR-20a-5p level. Furthermore, STAT3 overexpression partly counteracted the miR-20a-5p-induced anti-apoptotic effect in TGF-β1-treated BEAS-2B cells. In summary, this study suggested that miR-20a-5p restrained apoptosis in TGF-β1-stimulated BEAS-2B cells by targeting STAT3. MiR-20a-5p thus may be a novel therapeutic target for asthma treatment.

Targeting cell signaling in allergic asthma

Asthma is chronic inflammation of the airways characterized by airway hyper-responsiveness, wheezing, cough, and dyspnea. Asthma affects >350 million people worldwide. The Th2 immune response is a major contributor to the pathophysiology of asthma. Targeted therapy modulating cell signaling pathways can be a powerful strategy to design new drugs to treat asthma. The potential molecular pathways that can be targeted include IL-4-IL-13-JAK-STAT-MAP kinases, adiponectin-iNOS-NF-κB, PGD2-CRTH2, IFNs-RIG, Wnt/β-catenin-FAM13A, FOXC1-miR-PI3K/AKT, JNK-Gal-7, Nrf2-ROS, Foxp3-RORγt, CysLTR, AMP, Fas-FasL, PTHrP/PPARγ, PAI-1, FcɛRI-LAT-SLP-76, Tim-3-Gal-9, TLRs-MyD88, PAR2, and Keap1/Nrf2/ARE. Therapeutic drugs can be designed to target one or more of these pathways to treat asthma.