High-Mobility Group Box 1 Mediates Epithelial-to-Mesenchymal Transition in Pulmonary Fibrosis Involving Transforming Growth Factor-β1/Smad2/3 Signaling

HMGB1 regulates the activation of dendritic cells and CD4+ T cell responses through the modulation of autophagy in bleomycin-induced pulmonary fibrosis

BACKGROUND

The role of HMGB1 in inflammation and autophagy has garnered increasing attention; however, its impact on the activation of dendritic cells (DCs) and autophagy remains unclear. This study aims to explore the effects of HMGB1 on DC activation, autophagy, and its influence on CD4+ T cell responses in a bleomycin-induced pulmonary fibrosis (PF) mouse model.

METHODS

Thirty mice were randomly divided into control and model groups. The model group was established by intratracheal injection of bleomycin to induce PF. Flow cytometry was used to detect DC surface markers, and western blot was employed to assess the expression of autophagy-related protein LC3. Lung DCs and peripheral blood CD14+ monocytes were sorted using magnetic beads and differentiated into M0-DCs, which were then subjected to HMGB1 stimulation experiments to assess activation and cytokine secretion. HMGB1-stimulated or untreated M0-DCs were co-cultured with CFSE-labeled naive CD4+ T cells to evaluate T cell proliferation and differentiation. The effects of HMGB1 on DCs activation, cytokine secretion, and autophagy-related protein expression were assessed after treatment with autophagy regulators.

RESULTS

The model group showed significantly elevated levels of HMGB1 in serum and lung tissues, accompanied by upregulated activation markers of DCs and increased expression of autophagy-related protein LC3. HMGB1 stimulation significantly enhanced the activation of M0-DCs and the secretion of pro-inflammatory cytokines, promoting the proliferation of CD4+ T cells and their differentiation into Th1 and Th17 subsets. Rapamycin, which enhances autophagy, potentiated HMGB1-mediated DC activation, while 3-MA, which inhibits autophagy, suppressed the effects of HMGB1, further influencing CD4+ T cell differentiation.

CONCLUSION

HMGB1 modulates DC autophagy, thereby affecting their activation and immune responses of CD4+ T cells in bleomycin-induced PF. Targeting HMGB1 and the autophagy pathway may provide new strategies for the treatment of PF.

Recent advances in TGF-β signaling pathway in COVID-19 pathogenesis: A review

The coronavirus disease 2019 (COVID-19) has resulted in approximately 7.0 million fatalities between 2019 and 2022, underscoring a pressing need for comprehensive research into its underlying mechanisms and therapeutic avenues. A distinctive feature of severe COVID-19 is the dysregulated immune response characterized by excessive activation of immune cells and the consequent cytokine storms. Recent advancements in our understanding of cellular signaling pathways have illuminated the role of Transforming Growth Factor Beta (TGF-β) as a pivotal signaling molecule with significant implications for the pathogenesis of infectious diseases, including COVID-19. Emerging evidence reveals that TGF-β signaling, when activated by viral components or secondary pathways, adversely affects diverse cell types, particularly immune cells, and lung tissue, leading to complications such as pulmonary fibrosis. In our review article, we critically evaluate recent literature on the involvement of TGF-β signaling in the progression of COVID-19. We discuss a range of pharmacological interventions, including nintedanib, pirfenidone, corticosteroids, proton pump inhibitors, and histone deacetylase inhibitors, and their potential to modulate the TGF-β pathway in the context of COVID-19 treatment. Additionally, we explore ongoing clinical trials involving mesenchymal stem cells, low-dose radiation therapy, and artemisinin derivatives to assess their impact on TGF-β levels and subsequent clinical outcomes in COVID-19 patients. This review is particularly relevant at this juncture as the global health community continues to grapple with the ramifications of the COVID-19 pandemic, highlighting the urgent need for targeted therapeutic strategies aimed at TGF-β modulation to mitigate disease severity and improve patient outcomes.

A Multifunctional Nanocomposite Hydrogel Delivery System Based on Dual-Loaded Liposomes for Scarless Wound Healing

Increased inflammatory responses and oxidative stress at the wound site following skin trauma impair healing. Furthermore, skin scarring places fibroblasts under severe mechanical stress and aggravates pathological fibrosis. A novel liposomal composite hydrogel is engineered for wound microenvironment remodeling, incorporating dual-loaded liposomes into gelatin methacrylate to create a nanocomposite hydrogel. Notably, tetrahydrocurcumin (THC) and hepatocyte growth factor (HGF) are encapsulated in the hydrophobic and hydrophilic layers of liposomes, respectively. The composite hydrogel maintains porous nanoarchitecture, demonstrating sustainable THC and HGF release and enhanced mechanical properties and biocompatibility. This system effectively promotes cell proliferation and angiogenesis and attenuates apoptosis. It decreases the expression of the inflammatory factors by inhibiting the high-mobility group box /receptor for advanced glycation end product/NF-κB (HMGB1/RAGE/NF-κB)pathway and increases macrophage polarization from M1 to M2 in vitro, effectively controlling inflammatory responses. It exhibits remarkable antioxidant properties by scavenging excess reactive oxygen species and free radicals. Most importantly, it effectively prevents scar formation by restraining the transforming growth factor beta (TGF-β)/Smads pathway that downregulates associated fibrotic factors. It demonstrates strong therapeutic effects against inflammation and fibrosis in a rat skin wound model with biosafety, advancing the development of innovative hydrogel-based therapeutic delivery strategies for clinical scarless wound therapy.

HMGB1 as an extracellular pro-inflammatory cytokine: Implications for drug-induced organic damage

Drug-induced organic damage encompasses various intricate mechanisms, wherein HMGB1, a non-histone chromosome-binding protein, assumes a significant role as a pivotal hub gene. The regulatory functions of HMGB1 within the nucleus and extracellular milieu are interlinked. HMGB1 exerts a crucial regulatory influence on key biological processes including cell survival, inflammatory regulation, and immune response. HMGB1 can be released extracellularly from the cell during these processes, where it functions as a pro-inflammation cytokine. HMGB1 interacts with multiple cell membrane receptors, primarily Toll-like receptors (TLRs) and receptor for advanced glycation end products (RAGE), to stimulate immune cells and trigger inflammatory response. The excessive or uncontrolled HMGB1 release leads to heightened inflammatory responses and cellular demise, instigating inflammatory damage or exacerbating inflammation and cellular demise in different diseases. Therefore, a thorough review on the significance of HMGB1 in drug-induced organic damage is highly important for the advancement of pharmaceuticals, ensuring their effectiveness and safety in treating inflammation as well as immune-related diseases. In this review, we initially outline the characteristics and functions of HMGB1, emphasizing their relevance in disease pathology. Then, we comprehensively summarize the prospect of HMGB1 as a promising therapeutic target for treating drug-induced toxicity. Lastly, we discuss major challenges and propose potential avenues for advancing the development of HMGB1-based therapeutics.

Human umbilical cord-derived mesenchymal stromal cells improve myocardial fibrosis and restore miRNA-133a expression in diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is a serious health-threatening complication of diabetes mellitus characterized by myocardial fibrosis and abnormal cardiac function. Human umbilical cord mesenchymal stromal cells (hUC-MSCs) are a potential therapeutic tool for DCM and myocardial fibrosis via mechanisms such as the regulation of microRNA (miRNA) expression and inflammation. It remains unclear, however, whether hUC-MSC therapy has beneficial effects on cardiac function following different durations of diabetes and which mechanistic aspects of DCM are modulated by hUC-MSC administration at different stages of its development. This study aimed to investigate the therapeutic effects of intravenous administration of hUC-MSCs on DCM following different durations of hyperglycemia in an experimental male model of diabetes and to determine the effects on expression of candidate miRNAs, target mRNA and inflammatory mediators.

METHODS

A male mouse model of diabetes was induced by multiple low-dose streptozotocin injections. The effects on severity of DCM of intravenous injections of hUC-MSCs and saline two weeks previously were compared at 10 and 18 weeks after diabetes induction. At both time-points, biochemical assays, echocardiography, histopathology, polymerase chain reaction (PCR), immunohistochemistry and enzyme-linked immunosorbent assays (ELISA) were used to analyze blood glucose, body weight, cardiac structure and function, degree of myocardial fibrosis and expression of fibrosis-related mRNA, miRNA and inflammatory mediators.

RESULTS

Saline-treated diabetic male mice had impaired cardiac function and increased cardiac fibrosis after 10 and 18 weeks of diabetes. At both time-points, cardiac dysfunction and fibrosis were improved in hUC-MSC-treated mice. Pro-fibrotic indicators (α-SMA, collagen I, collagen III, Smad3, Smad4) were reduced and anti-fibrotic mediators (FGF-1, miRNA-133a) were increased in hearts of diabetic animals receiving hUC-MSCs compared to saline. Increased blood levels of pro-inflammatory cytokines (IL-6, TNF, IL-1β) and increased cardiac expression of IL-6 were also observed in saline-treated mice and were reduced by hUC-MSCs at both time-points, but to a lesser degree at 18 weeks.

CONCLUSION

Intravenous injection of hUC-MSCs ameliorated key functional and structural features of DCM in male mice with diabetes of shorter and longer duration. Mechanistically, these effects were associated with restoration of intra-myocardial expression of miRNA-133a and its target mRNA COL1AI as well as suppression of systemic and localized inflammatory mediators.

Jiawei Maxing Shigan Tang alleviates radiation-induced lung injury via TGF-β1/Smad signaling pathway mediated by regulatory T cells

ETHNOPHARMACOLOGICAL RELEVANCE

Radiation-induced lung injury (RILI) is a common complication during thoracic radiotherapy which impairs the quality of life in patients and limits radiation doses. Jiawei Maxing Shigan Tang (JMST), which is a modified decoction made of Ephedra, Apricot Kernel, Gypsum, and Licorice, can alleviate the symptoms of RILI in patients. Previous studies and preliminary findings suggested a potential molecular mechanism of JMST in the treatment of RILI. Further studies are needed.

AIM OF THE STUDY

To elucidate the mechanisms of how regulatory T cells (Tregs) promote RILI and the effect of JMST on Tregs, as well as the corresponding pathway.

MATERIALS AND METHODS

CD4+CD25+ Tregs were isolated from rats, and the supernatant's TGF-β1 level was examined by using enzyme-linked immunosorbent assay (ELISA). Type II alveolar epithelial cells (AECs) were co-cultured with the supernatant of Tregs, and the expression levels of epithelial-to-mesenchymal transition (EMT)-related and TGF-β1/Smad signaling pathway-related proteins were analyzed by using western blotting (WB). Afterward, the Tregs were incubated with different concentrations of JMST. The cell viability and TGF-β1 concentration were confirmed by cell counting kit-8 (CCK-8) assay and ELISA, respectively. The optimized concentration of JMST was applied in vitro and vivo experiments. The specific mechanism was investigated through the combination of using flow cytometry, lung histopathology analysis, ELISA, and WB.

RESULTS

Radiation could promote Tregs to secrete TGF-β1. After radiation, the expression levels of Smad2/3, phosphorylated Smad2/3 (p-Smad2/3), Smad4 and mesenchymal markers Vimentin and α-SMA were all increased, while the expression level of epithelial markers E-cadherin was decreased. The expression levels of these proteins were reversed after interventions involving Treg cell activation inhibition or TGF-β1 receptor inhibitor. JMST reduced the number of Tregs in lung tissue and alleviated the degree of pulmonary fibrosis. The expression of Smad2/3, p-Smad2/3, Smad4, TGF-β1, Vimentin, and α-SMA were significantly downregulated, while the E-cadherin was upregulated, through the intervention of JMST.

CONCLUSION

Tregs could mediate EMT through TGF-β1/Smad pathway. JMST inhibits EMT via TGF-β1/Smad pathway by regulating Tregs, therefore alleviating RILI.

mRNA Levels of Epithelial and Mesenchymal Markers in Lung Epithelial Cell Lines

Background

Epithelial-mesenchymal transition (EMT) is an important physiologic process that determines the outcome of lung tissue healing after injury. Stimuli and molecular cascades inducing EMT lead to up-regulation of the mesenchymal-specific genes in the alveolar epithelial cells and to down-regulation of the genes coding for epithelial markers. Alveolar epithelial cell lines are commonly used as in vitro models to study processes occurring in the lung tissue. The aim of this study is to quantify and compare mRNA expression levels of epithelial and mesenchymal markers in a number of lung epithelial cell lines.

Methods

Lung epithelial cell lines L2, R3/1 and RLE-6TN were cultured. Repeated mRNA isolation, reverse transcription, and quantitative PCR with primers to epithelial (E-cadherin, occludin, and ZO-2) and mesenchymal (α-SMA, collagen III, and vimentin) markers were performed.

Results

First, our study revealed a higher level of epithelial transcripts in the RLE-6TN cell line compared to L2 and R3/1 cells. Secondly, we have found simultaneous mRNA expression of both epithelial (E-cadherin, occludin and ZO-2) and mesenchymal (α-SMA, collagen III and vimentin) markers in all cell lines studied.

Conclusions

Our data indicate that at the transcriptional level the L2, R3/1, and RLE-6TN cell lines are at one of the intermediate stages of EMT, which opens new possibilities for the study of EMT on cell lines. Determination of the direction of changes in epithelial and mesenchymal markers will make it possible to establish the factors responsible for both EMT and reverse mesenchymal-epithelial transition.

Modulatory effect of rupatadine on mesenchymal stem cell-derived exosomes in hepatic fibrosis in rats: A potential role for miR-200a

AIMS

Mesenchymal stem cell-derived exosomes (MSC-EXOs) have emerged as a promising approach in regenerative medicine for management of different diseases. However, the maintenance of their efficacy after in vivo transplantation is still a major concern. The present investigation aimed to assess the modulatory effect of rupatadine (RUP) on MSC-EXOs in diethylnitrosamine (DEN)-induced liver fibrosis (LF), and to explore the possible underlying mechanism.

MAIN METHODS

LF was induced in rats by i.p. injection of DEN (100 mg/kg) once per week for 6 successive weeks. Rats were then treated with RUP (4 mg/kg/day, p.o.) for 4 weeks with or without a single i.v. administration of MSC-EXOs. At the end of the experiment, animals were euthanized and serum and liver were separated for biochemical, and histological measurements.

KEY FINDINGS

The combined MSC-EXOs/RUP therapy provided an additional improvement towards inhibition of DEN-induced LF compared to MSC-EXOs group alone. These outcomes could be mediated through antioxidant, anti-inflammatory, and anti-fibrotic effects of RUP which created a more favorable environment for MSC-EXOs homing, and action. This in turn would enhance more effectively miR-200a expression which reduced oxidative stress, inflammation, necroptosis pathway, and subsequently fibrosis as revealed by turning off TGF-β1/α-SMA expression, and hedgehog axis.

SIGNIFICANCE

The present findings reveal that RUP enhanced the anti-fibrotic efficacy of MSC-EXOs when used as a combined therapy. This was revealed through attenuation of PAF/RIPK3/MLKL/HMGB1, and TGF-β1/hedgehog signaling pathways with a significant role for miR-200a.

HMGB1 coordinates with Brahma-related gene 1 to promote epithelial-mesenchymal transition via the PI3K/Akt/mTOR pathway in BEAS-2B cells

High mobility group protein B1 (HMGB1), a highly conserved non-histone nuclear protein, is highly expressed in fibrotic diseases; however, the role of HMGB1 in pulmonary fibrosis has not been fully elucidated. In this study, an epithelial-mesenchymal transition (EMT) model was constructed using transforming growth factor-β1 (TGF-β1) to stimulate BEAS-2B cells in vitro, and HMGB1 was knocked down or overexpressed to observe its effects on cell proliferation, migration and EMT. Meanwhile, string system, immunoprecipitation and immunofluorescence analyses were applied to identify and examine the relationship between HMGB1 and its potential interacting protein Brahma-related gene 1 (BRG1), and to explore the mechanism of interaction between HMGB1 and BRG1 in EMT. The results indicate that exogenous increase in HMGB1 promotes cell proliferation and migration and facilitates EMT by enhancing the PI3K/Akt/mTOR signaling pathway, whereas silencing HMGB1 has the opposite effect. Mechanistically, HMGB1 exerts these functions by interacting with BRG1, which may enhance BRG1 function and activate the PI3K/Akt/mTOR signaling pathway, thereby promoting EMT. These results suggest that HMGB1 is important for EMT and is a potential therapeutic target for the treatment of pulmonary fibrosis.

Dang Gui Bu Xue Tang, a conventional Chinese herb decoction, ameliorates radiation-induced heart disease via Nrf2/HMGB1 pathway

Introduction: Radiation-induced heart disease (RIHD), characterized by cardiac dysfunction and myocardial fibrosis, is one of the most common complications after cardiothoracic radiotherapy. Dang Gui Bu Xue Tang (DBT) is a conventional Chinese herb decoction composed of Radix Astragali membranaceus (RAM) and Radix Angelicae sinensis (RAS) at a ratio of 5:1, famous for its "blood-nourishing" effect. In this study, we aimed to investigate the cardioprotective effect of DBT on RIHD. Methods: C57BL mice at 8 weeks of age were divided into five groups, namely Control, Radiation, RDBT51 (Radiation with DBT, RAM:RAS = 5:1), RDBT11 (Radiation with DBT, RAM:RAS = 1:1), and RDBT15 (Radiation with DBT, RAM:RAS = 1:5). Results: We mainly found that radiation in the cardiothoracic region led to significant left ventricular systolic dysfunction, myocardial fibrotic lesions and cardiac injury accompanied by abnormally increased myocardial HMGB1 protein levels. Administration of conventional DBT significantly ameliorated left ventricular systolic dysfunction, alleviated myocardial fibrosis, and counteracted cardiac injury, all of which supported the protective effect of DBT on RIHD, involving upregulation of myocardial Nrf2 protein levels and downregulation of HMGB1 protein levels as underlying mechanisms. Conclusions: DBT exerts a significant protective effect on RIHD, and the Nrf2/ HMGB1 pathway probably plays an important role in this protective effect.

Discovery of pulmonary fibrosis inhibitor targeting TGF-β RI in Polygonum cuspidatum by high resolution mass spectrometry with in silico strategy

Pulmonary fibrosis (PF) is an irreversible lung disease that is characterized by excessive scar tissue with a poor median survival rate of 2-3 years. The inhibition of transforming growth factor-β receptor type-I (TGF-β RI) by an appropriate drug may provide a promising strategy for the treatment of this disease. Polygonum cuspidatum (PC) is a well-known traditional Chinese herbal medicine which has an anti-PF effect. Accordingly, a combination of high resolution mass spectrometry with an in silico strategy was developed as a new method to search for potential chemical ingredients of PC that target the TGF-β RI. Based on this strategy, a total of 24 ingredients were identified. Then, absorption, distribution, metabolism, and excretion (ADME)-related properties were subsequently predicted to exclude compounds with potentially undesirable pharmacokinetics behaviour. Molecular docking studies on TGF-β RI were adopted to discover new PF inhibitors. Eventually, a compound that exists in PC known as resveratrol was proven to have excellent biological activity on TGF-β RI, with an IC₅₀ of 2.211 μM in vitro. Furthermore, the complex formed through molecular docking was tested via molecular dynamics simulations, which revealed that resveratrol had strong interactions with residues of TGF-β RI. This study revealed that resveratrol has significant potential as a treatment for PF due to its ability to target TGF-β RI. In addition, this research demonstrated the exploration of natural products with excellent biological activities toward specific targets via high resolution mass spectrometry in combination with in silico technology is a promising strategy for the discovery of novel drugs.

Glycyrrhizic Acid Attenuates Pulmonary Fibrosis of Silicosis by Inhibiting the Interaction between HMGB1 and BRG1 through PI3K/Akt/mTOR Pathway

Purpose: High mobility group protein 1 (HMGB1) is a highly conserved DNA-binding nuclear protein that participates in the occurrence and development of silicosis. HMGB1 binds to its specific receptor and activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B, (PKB; Akt)/mammalian target of rapamycin (mTOR) pathway. Brahma-related genes 1 (BRG1; SMARCA4) is the core subunit of SWI/SNF. HMGB1 activates the Akt pathway through BRG1 to promote the proliferation of prostate cancer. Glycyrrhizic acid is a new pharmacological inhibitor of HMGB1, which may inhibit the occurrence and development of silicosis. We speculate that glycyrrhizic acid inhibits the interaction between HMGB1 and BRG1 through the PI3K/Akt/mTOR pathway to affect the progression of silicosis. Methods: We carried out an in vitro study and stimulated A549 with TGF-β1 to establish an epithelial–mesenchymal transition (EMT) model, knocked down the HMGB1 and BRG1 genes in cells, observed the expression of EMT markers, and detected the interaction between HMGB1 and BRG1 by co-immunoprecipitation. In vivo, we injected glycyrrhizic acid into the mouse silicosis model to inhibit the expression of HMGB1. Results: Both HMGB1 and BRG1 were highly expressed in the process of EMT. After knocking down HMGB1 and BRG1, the process of EMT was inhibited through the PI3K/Akt/mTOR pathway, and their expressions were influenced by each other. HMGB1 and BRG1 interact with each other in A549 cells. HMGB1 and BRG1 are also highly expressed in the mouse silicosis model, and glycyrrhizic acid can inhibit the expression of HMGB1/BRG1 through the PI3K/Akt/mTOR pathway. Conclusion: Glycyrrhizic acid can inhibit the interaction between HMGB1 and BRG1 through the PI3K/Akt/mTOR pathway to affect the progression of silicosis.

Association of the RAGE/RAGE-ligand axis with interstitial lung disease and its acute exacerbation

The receptor for advanced glycation end product (RAGE) is a transmembrane receptor highly expressed in type 1 pneumocytes of healthy lungs. RAGE is considered to play a homeostatic role in the lung, as RAGE knockout mice develop lung fibrosis as they age. In contrast, RAGE can bind numerous ligands, including high-mobility group box 1 (HMGB1). These interactions initiate pro-inflammatory signaling associated with the pathogenesis of lung injury and interstitial lung disease (ILD), including idiopathic pulmonary fibrosis (IPF). ILD is a broad category of diffuse parenchymal lung disease characterized by various extents of lung fibrosis and inflammation, and IPF is a common and progressive ILD of unknown cause. The prognosis of patients with IPF is poor, and acute exacerbation of IPF (AE-IPF) is one of the main causes of death. Recent reports indicate that acute exacerbations can occur in other ILDs (AE-ILD). Notably, ILD is frequently observed in patients with lung cancer, and AE-ILD after surgical procedures or the initiation of chemotherapy for concomitant lung cancer are clinically important due to their association with increased mortality. In this review, we summarize the associations of RAGE/soluble RAGE (sRAGE)/RAGE ligands with the pathogenesis and clinical course of ILD, including IPF and AE-IPF. Additionally, the potential use of sRAGE and RAGE ligands as predictive markers of AE-IPF and cancer treatment-triggered AE-ILD is also discussed.

Polyphenols from Chinese Herbal Medicine: Molecular Mechanisms and Therapeutic Targets in Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a highly confounding and fatal pathological process with finite treatment options. Multiple factors such as oxidative and immune/inflammation involve key pathological processes in chronic lung disease, and their intimate interactions mediate chronic lung damage, denudation of the alveolar epithelium, hyperproliferation of type II alveolar epithelial cells (AECIIs), proliferation and differentiation of fibroblasts, and the permeability of microvessels. We reviewed the classic mechanism of PF and highlighted a few emerging mechanisms for studying complex networks in lung disease pathology. Polyphenols, as a multi-target drug, has excellent potential in the treatment of pulmonary fibrosis. We then reviewed recent advances in discovering phenolic compounds from fruits, tea, and medical herbs with the bioactivities of simultaneously regulating multiple factors (e.g., oxidative stress, inflammation, autophagy, apoptosis, pyroptosis) for minimizing pulmonary fibrosis injury. These compounds include resveratrol, curcumin, salvianolic acid B, epigallocatechin-3-gallate, gallic acid, corilagin. Each phenolic compound can exert its anti-PF effect through various mechanisms, and the signaling pathways involved in different phenolic compounds are not the same. This review summarized the available evidence on phenolic compounds' effectiveness in pulmonary diseases and explored the molecular mechanisms and therapeutic targets of phenolic compounds from Chinese herbal medicine with the properties of inhibition of ongoing fibrogenesis and resolution of existing fibrosis.

The Role of Epithelial Damage in the Pulmonary Immune Response

Pulmonary epithelial cells are widely considered to be the first line of defence in the lung and are responsible for coordinating the innate immune response to injury and subsequent repair. Consequently, epithelial cells communicate with multiple cell types including immune cells and fibroblasts to promote acute inflammation and normal wound healing in response to damage. However, aberrant epithelial cell death and damage are hallmarks of pulmonary disease, with necrotic cell death and cellular senescence contributing to disease pathogenesis in numerous respiratory diseases such as idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and coronavirus disease (COVID)-19. In this review, we summarise the literature that demonstrates that epithelial damage plays a pivotal role in the dysregulation of the immune response leading to tissue destruction and abnormal remodelling in several chronic diseases. Specifically, we highlight the role of epithelial-derived damage-associated molecular patterns (DAMPs) and senescence in shaping the immune response and assess their contribution to inflammatory and fibrotic signalling pathways in the lung.

Dysfunction of epithelial permeability barrier induced by HMGB1 in 2.5D cultures of human epithelial cells

Airway and intestinal epithelial permeability barriers are crucial in epithelial homeostasis. High mobility group box 1 (HMGB1), increased by various stimuli, is involved in the induction of airway inflammation, as well as the pathogenesis of inflammatory bowel disease. HMGB1 enhances epithelial hyperpermeability. Two-and-a-half dimensional (2.5D) culture assays are experimentally convenient and induce cells to form a more physiological tissue architecture than 2D culture assays for molecular transfer mechanism analysis. In 2.5D culture, treatment with HMGB1 induced permeability of FITC-dextran into the lumen formed by human lung, nasal and intestinal epithelial cells. The tricellular tight junction molecule angulin-1/LSR is responsible for the epithelial permeability barrier at tricellular contacts and contributes to various human airway and intestinal inflammatory diseases. In this review, we indicate the mechanisms including angulin-1/LSR and multiple signaling in dysfunction of the epithelial permeability barrier induced by HMGB1 in 2.5D culture of human airway and intestinal epithelial cells.

Reactive oxygen species-evoked endoplasmic reticulum stress mediates 1-nitropyrene-induced epithelial-mesenchymal transition and pulmonary fibrosis

1-Nitropyrene (1-NP) is one component of atmospheric fine particles. Previous report revealed that acute 1-NP exposure induced respiratory inflammation. This study aimed to investigate whether chronic 1-NP exposure induces pulmonary fibrosis. Male C57BL6/J mice were intratracheally instilled to 1-NP (20 μg/mouse/week) for 6 weeks. Diffuse interstitial inflammation, a-smooth muscle actin (a-SMA)-positive cells, a marker of epithelial-mesenchymal transition (EMT), and an extensive collagen deposition, measured by Masson staining, were observed in 1-NP-exposed mouse lungs. Pulmonary function showed that lung dynamic compliance (Cydn-min) was reduced in 1-NP-exposed mice. Conversely, inspiratory resistance (Ri) and expiratory resistance (Re) were elevated in 1-NP-exposed mice. Mechanistically, cell migration and invasion were accelerated in 1-NP-exposed pulmonary epithelial cells. In addition, E-cadherin, an epithelial marker, was downregulated, and vimentin, a-SMA and N-cadherin, three mesenchymal markers, were upregulated in 1-NP-exposed pulmonary epithelial cells. Although TGF-β wasn't altered, phosphorylated Smad2/3 were enhanced in 1-NP-exposed pulmonary epithelial cells. Moreover, reactive oxygen species (ROS) were increased and endoplasmic reticulum (ER) stress was activated in 1-NP-exposed pulmonary epithelial cells. N-Acetylcysteine (NAC), an antioxidant, attenuated 1-NP-evoked excess ROS, ER stress and EMT in pulmonary epithelial cells. Similarly, pretreatment with NAC alleviated 1-NP-caused pulmonary EMT and lung fibrosis in mice. These results demonstrate that ROS-evoked ER stress contributes, at least partially, to 1-NP-induced EMT and pulmonary fibrosis.

TGF‑β1: Gentlemanly orchestrator in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a worldwide disease characterized by the chronic and irreversible decline of lung function. Currently, there is no drug to successfully treat the disease except for lung transplantation. Numerous studies have been devoted to the study of the fibrotic process of IPF and findings showed that transforming growth factor‑β1 (TGF‑β1) plays a central role in the development of IPF. TGF‑β1 promotes the fibrotic process of IPF through various signaling pathways, including the Smad, MAPK, and ERK signaling pathways. There are intersections between these signaling pathways, which provide new targets for researchers to study new drugs. In addition, TGF‑β1 can affect the fibrosis process of IPF by affecting oxidative stress, epigenetics and other aspects. Most of the processes involved in TGF‑β1 promote IPF, but TGF‑β1 can also inhibit it. This review discusses the role of TGF‑β1 in IPF.

Verbascoside inhibits the epithelial-mesenchymal transition of prostate cancer cells through high-mobility group box 1/receptor for advanced glycation end-products/TGF-β pathway

INTRODUCTION

Prostate cancer has significant mortality and metastasis rate in the male. Unfortunately, effective treatment for patients with advanced prostate cancer is still lacking. Verbascoside, a phenylethanoid glycoside, displays various pharmacological properties, such as the anti-cancer activities. The present study aimed to evaluate the effects of purified verbascoside on human prostate cancer and the associated molecular mechanisms.

MATERIALS AND METHODS

The human prostate cancer cell lines, Du-145 and PC-3, were treated with various concentrations of verbascoside (0.1, 1, 10 μM) for 24 h followed by the examination of cell viability using MTT and trypan blue exclusion assays. Cell migration and invasion capacities were assessed by wound healing assay and transwell system. Western blot and immunofluorescence staining were used to detect the expression of epithelial-mesenchymal transition (EMT)-associated factors, components of transforming growth factor (TGF-β)/Smad signaling, and high-mobility group box (HMGB)/receptor for advanced glycation end-products (RAGE) axis.

RESULTS

Verbascoside treatment significantly inhibited cell proliferation, migration, and invasion abilities of Du-145 and PC-3 cells. We showed that verbascoside decreased the expression of EMT promotors, Snail and Slug, and increased the expression of E-cadherin. Moreover, the expression level of alpha-smooth muscle actin was downregulated by verbascoside as well. Besides, we found that the TGF-β pathway was suppressed, which was demonstrated by the diminished expression of type I and II TGF-β receptors and phosphorylated Smad2/3 along with the upregulated Smad7. Our data suggested that this downregulation of TGF-β signaling was mediated by repression of HMGB 1 (HMGB1)/RAGE axis.

CONCLUSION

Verbascoside mitigated the cell proliferation and aggressiveness of prostate cancer via downregulation of TGF-β-associated EMT progression through HMGB1/RAGE suppression. Collectively, our findings revealed that verbascoside may be a beneficial dietary supplement for prostate cancer patients.

Tauroursodeoxycholic acid alleviates pulmonary endoplasmic reticulum stress and epithelial-mesenchymal transition in bleomycin-induced lung fibrosis

Background

Several studies demonstrate that endoplasmic reticulum (ER) stress-mediated epithelial-mesenchymal transition (EMT) is involved in the process of bleomycin (BLM)-induced pulmonary fibrosis. Tauroursodeoxycholic acid (TUDCA), a bile acid with chaperone properties, is an inhibitor of ER stress. This study aimed to investigate the preventive effects of TUDCA on BLM-induced EMT and lung fibrosis.

Methods

The model of lung fibrosis was established by intratracheal injection with a single dose of BLM (3.0 mg/kg). In TUDCA + BLM group, mice were intraperitoneally injected with TUDCA (250 mg/kg) daily.

Results

BLM-induced alveolar septal destruction and inflammatory cell infiltration were alleviated by TUDCA. BLM-induced interstitial collagen deposition, as determined by Sirius Red staining, was attenuated by TUDCA. BLM-induced elevation of pulmonary α-smooth muscle actin (α-SMA) and reduction of pulmonary E-cadherin were attenuated by TUDCA. BLM-induced pulmonary Smad2/3 phosphorylation was suppressed by TUDCA. BLM-induced elevation of Ki67 and PCNA was inhibited by TUDCA in mice lungs. In addition, BLM-induced elevation of HO-1 (heme oxygenase-1) and 3-NT (3-nitrotyrosine) was alleviated by TUDCA. Finally, BLM-induced upregulation of pulmonary GRP78 and CHOP was attenuated by TUDCA.

Conclusions

These results provide evidence that TUDCA pretreatment inhibits Smad2/3-medited EMT and subsequent lung fibrosis partially through suppressing BLM-induced ER stress and oxidative stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01514-6.

Exosomal HMGB1 Promoted Cancer Malignancy

Reciprocal crosstalk between platelets and malignancies underscores the potential of antiplatelet therapy in cancer treatment. In this study, we found that human chronic myeloid leukemia K562 cell-differentiated megakaryocytes and murine platelets produced bioactive substances and these are released into the extracellular space, partly in their exosomal form. High-mobility group box 1 (HMGB1) is a type of exosomal cargo, and the antiplatelet drugs aspirin and dipyridamole interfered with its incorporation into the exosomes. Those released substances and exosomes, along with exogenous HMGB1, promoted cancer cell survival and protected cells from doxorubicin cytotoxicity. In a tumor-bearing model established using murine Lewis lung carcinoma (LLC) cells and C57BL/6 mice, the tumor suppressive effect of dipyridamole correlated well with decreased circulating white blood cells, soluble P-selectin, TGF-β1 (Transforming Growth Factor-β1), exosomes, and exosomal HMGB1, as well as tumor platelet infiltration. Exosome release inhibitor GW4869 exhibited suppressive effects as well. The suppressive effect of dipyridamole on cancer cell survival was paralleled by a reduction of HMGB1/receptor for advanced glycation end-products axis, and proliferation- and migration-related β-catenin, Yes-associated protein 1, Runt-related transcription factor 2, and TGF- β1/Smad signals. Therefore, exosomes and exosomal HMGB1 appear to have roles in platelet-driven cancer malignancy and represent targets of antiplatelet drugs in anticancer treatment.

The UFSP2/UFMylation Pathway Is Involved in Silica-Induced Pulmonary Injury

Silicosis is an irreversible occupational pulmonary disease that is characterized as progressed pulmonary fibrosis. In this study, we investigated the changes of UFSP2 and the related UFMylation in silica-induced pulmonary injury mice models. The experimental silicosis models were prepared by intratracheal injection of silica particles, and the lung samples were harvested at the first or the seventh day after treatment. We found that the UFSP2 expression in the 1-day models was comparable, whereas it was upregulated in the 7-day models. Consistently, the UFMylation in the lung tissues of the 7-day models was activated. In addition, we observed the CADM2, an adhesion molecule, was reported to associate with epithelial-mesenchymal transition, was upregulated in the lungs of 7-day models. In contrast, it remained comparable in the 1-day models. Our data indicated that the UFSP2/UFMylation pathway and the CADM2 might be involved in the silica-induced pulmonary injury.

Inhibiting TGF-[Formula: see text] 1-Mediated Cellular Processes as an Effective Strategy for the Treatment of Pulmonary Fibrosis with Chinese Herbal Medicines

Pulmonary fibrosis (PF) is a chronic and irreversible interstitial lung disease that even threatens the lives of some patients infected with COVID-19. PF is a multicellular pathological process, including the initial injuries of epithelial cells, recruitment of inflammatory cells, epithelial-mesenchymal transition, activation and differentiation of fibroblasts, etc. TGF-[Formula: see text]1 acts as a key effect factor that participates in these cellular processes of PF. Recently, much attention was paid to inhibiting TGF-[Formula: see text]1 mediated cell processes in the treatment of PF with Chinese herbal medicines (CHM), an important part of traditional Chinese medicine. Here, this review first summarized the effects of TGF-[Formula: see text]1 in different cellular processes of PF. Then, this review summarized the recent research on CHM (compounds, multi-components, single medicines and prescriptions) to directly and/or indirectly inhibit TGF-[Formula: see text]1 signaling (TLRs, PPARs, micrRNA, etc.) in PF. Most of the research focused on CHM natural compounds, including but not limited to alkaloids, flavonoids, phenols and terpenes. After review, the research perspectives of CHM on TGF-[Formula: see text]1 inhibition in PF were further discussed. This review hopes that revealing the inhibiting effects of CHM on TGF-[Formula: see text]1-mediated cellular processes of PF can promote CHM to be better understood and utilized, thus transforming the therapeutic activities of CHM into practice.

Deciphering the cellular mechanisms underlying fibrosis-associated diseases and therapeutic avenues

Fibrosis is the excessive deposition of extracellular matrix components, which results in disruption of tissue architecture and loss of organ function. Fibrosis leads to high morbidity and mortality worldwide, mainly due to the lack of effective therapeutic strategies against fibrosis. It is generally accepted that fibrosis occurs during an aberrant wound healing process and shares a common pathogenesis across different organs such as the heart, liver, kidney, and lung. A better understanding of the fibrosis-related cellular and molecular mechanisms will be helpful for development of targeted drug therapies. Extensive studies revealed that numerous mediators contributed to fibrogenesis, suggesting that targeting these mediators may be an effective therapeutic strategy for antifibrosis. In this review, we describe a number of mediators involved in tissue fibrosis, including aryl hydrocarbon receptor, Yes-associated protein, cannabinoid receptors, angiopoietin-like protein 2, high mobility group box 1, angiotensin-converting enzyme 2, sphingosine 1-phosphate receptor-1, SH2 domain-containing phosphatase-2, and long non-coding RNAs, with the goal that drugs targeting these important mediators might exhibit a beneficial effect on antifibrosis. In addition, these mediators show profibrotic effects on multiple tissues, suggesting that targeting these mediators will exert antifibrotic effects on different organs. Furthermore, we present a variety of compounds that exhibit therapeutic effects against fibrosis. This review suggests therapeutic avenues for targeting organ fibrosis and concurrently identifies challenges and opportunities for designing new therapeutic strategies against fibrosis.

Role of Alarmins in the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare chronic autoimmune disease associated with significant morbidity and mortality. Two main subsets of SSc are recognized: (i) diffuse cutaneous SSc with rapidly progressive fibrosis of the skin, lungs, and other internal organs; and (ii) limited cutaneous SSc, which is dominated by vascular manifestations, with skin and organ fibrosis generally limited and slowly progressing. In spite of intense investigation, both etiology and pathogenesis of SSc are still unknown. Genetic and environmental factors, as well as abnormalities of immune functions, are strongly suggested for etiology, while microvascular abnormalities, immune system activation, and oxidative stress are suggested for the pathogenesis. Recently, it has been found that a multitude of mediators and cytokines are implicated in the fibrotic processes observed in SSc. Among these, a central role could be exerted by “alarmins”, endogenous and constitutively expressed proteins/peptides that function as an intercellular signal defense. This review describes, in a detailed manner, the role of alarmins in the pathogenesis of scleroderma.

Aqueous humor interleukin-6 levels in primary open-angle glaucoma (POAG): A systematic review and meta-analysis

OBJECTIVE

To determine the change in aqueous humor interleukin-6 (IL-6) levels among primary open-angle glaucoma (GPAA) patients.

METHODS

Studies that investigated IL-6 level in the aqueous humor in GPAA patients using the detección methods of enzyme-linked immunosorbent assay (ELISA) y multiplex bead immunoassay were retrieved. A meta-analysis was performed a determine the overall change in IL-6 of GPAA patients compared a controls.

RESULTS

A total of 14 studies were selected. Analysis combining the results of studies using both detección approaches did not show any changes in the level of IL-6 in GPAA (SMD=-0,07, 95%IC -0,73 - 0,59, P=0,83), possibly due a the heterogeneity of ELISA data. Since multiplex bead immunoassay is more sensitive than convenciónal ELISA in detecting antibodies, further isolated analysis of multiplex bead immunoassay results revealed that GPAA patients had a lower level of IL-6 in the aqueous humor compared a controls (SMD=-0,40, 95%IC -0,70 - 0,09, P=0,01). Moreover, a sensitivity test also confirmed that no alteracións of results were observed in all pooled studies y pooled studies from multiplex bead immunoassay, suggesting the stabilities of our synthetic results.

CONCLUSION

Because of its robustness, the pooled data from multiplex bead immunoassay was used a draw a conclusion in this study, showing that the reducción of IL-6 levels in aqueous humor was observed in patients with GPAA. Further studies are still warranted a confirm our findings.

High-mobility group box 1 promotes epithelial-to-mesenchymal transition in crystalline silica induced pulmonary inflammation and fibrosis

Silicosis is an inflammatory and fibrotic lung disease caused by prolonged inhalation of silica. The potential role of high-mobility group box-1 (HMGB-1) and its underlying mechanisms in silicosis remain unclear. In this study, intratracheal instillation of a silica suspension was used to establish silicosis in male C57BL/6 mice. To elucidate the effects of HMGB-1 on the pathogenesis of silicosis, we used HMGB-1 neutralizing antibody (anti-HMGB-1) and recombinant HMGB-1 (rmHMGB-1) to abrogate or increase the HMGB-1 levels, respectively. At days 7, 28, and 84, the accumulation of macrophages and neutrophils decreased by anti-HMGB-1 treatment. The expression levels of interleukin-6 and tumor necrosis factor-α in lung increased in response to silica exposure across three time points; anti-HMGB-1 could alleviate those expressions at day 28 and 84. In contrast, rmHMGB-1 aggravated this process. At days 28 and 84, the protein expression of fibronectin and col1a1 decreased in the silica + anti-HMGB-1 groups but increased in silica + rmHMGB-1 groups compared to mice with silica alone. Further study suggested that HMGB-1-mediated epithelial-mesenchymal transition participated in the development of silicosis. In conclusion, the findings demonstrate that HMGB-1 participates in the pathogenesis of silicosis and may represent a potential therapeutic target for the treatment of silicosis.

HMGB1-downregulated angulin-1/LSR induces epithelial barrier disruption via claudin-2 and cellular metabolism via AMPK in airway epithelial Calu-3 cells

A non-histone chromatin-associated protein, high mobility group box 1 (HMGB1), which impairs the airway epithelial barrier, is involved in the induction of airway inflammation in patients with allergy, asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Tricellular tight junctions (tTJs) form at the convergence of bicellular tight junctions (bTJs). Angulin-1/lipolysis-stimulated lipoprotein receptor (LSR) is a novel molecule present at tricellular contacts and contributes to the epithelial barrier and cellular metabolism. Adenosine monophosphate-activated protein kinase (AMPK) is a central metabolic regulator and has a reciprocal association with TJs. In the present study, to examine how HMGB1 contributes to airway epithelial barrier disruption and the cellular metabolism indicated as mitochondrial respiration, bronchial epithelial Calu-3 cells were transfected with siRNAs of angulin-1/LSR or treated with HMGB1 and the relationship between HMGB1 and angulin-1/LSR was investigated. Knockdown of angulin-1/LSR upregulated the expression of the tight junction molecule claudin-2, AMPK activity, and mitochondrial respiration, and downregulated the epithelial barrier. Treatment with HMGB1 downregulated angulin-1/LSR expression and the epithelial barrier, and upregulated claudin-2 expression, AMPK activity and mitochondrial respiration. Treatment with EW-7197, a transforming growth factor-β (TGF-β) type I receptor kinase inhibitor, prevented all the effects of HMGB1 in Calu-3 cells. HMGB1-downregulated angulin-1/LSR induced epithelial barrier disruption via claudin-2 and cellular metabolism via AMPK in airway epithelial Calu-3 cells. The effects of HMGB1 contribute to TGF-β signaling and EW-7197 shows potential for use in therapy for HMGB1-induced airway inflammation.

HIP/PAP protects against bleomycin-induced lung injury and inflammation and subsequent fibrosis in mice

Hepatocarcinoma‐intestine‐pancreas/pancreatitis‐associated protein (HIP/PAP), a C‐type lectin, exerts anti‐oxidative, anti‐inflammatory, bactericidal, anti‐apoptotic, and mitogenic functions in several cell types and tissues. In this study, we explored the role of HIP/PAP in pulmonary fibrosis (PF). Expression of HIP/PAP and its murine counterpart, Reg3B, was markedly increased in fibrotic human and mouse lung tissues. Adenovirus‐mediated HIP/PAP expression markedly alleviated bleomycin (BLM)‐induced lung injury, inflammation, and fibrosis in mice. Adenovirus‐mediated HIP/PAP expression alleviated oxidative injury and lessened the decrease in pulmonary superoxide dismutase (SOD) activity in BLM‐treated mice, increased pulmonary SOD expression in normal mice, and HIP/PAP upregulated SOD expression in cultured human alveolar epithelial cells (A549) and human lung fibroblasts (HLF‐1). Moreover, in vitro experiments showed that HIP/PAP suppressed the growth of HLF‐1 and ameliorated the H₂O₂‐induced apoptosis of human alveolar epithelial cells (A549 and HPAEpiC) and human pulmonary microvascular endothelial cells (HPMVEC). In HLF‐1, A549, HPAEpiC, and HPMVEC cells, HIP/PAP did not affect the basal levels, but alleviated the TGF‐β1‐induced down‐regulation of the epithelial/endothelial markers E‐cadherin and vE‐cadherin and the over‐expression of mesenchymal markers, such as α‐SMA and vimentin. In conclusion, HIP/PAP was found to serve as a potent protective factor in lung injury, inflammation, and fibrosis by attenuating oxidative injury, promoting the regeneration of alveolar epithelial cells, and antagonizing the pro‐fibrotic actions of the TGF‐β1/Smad signaling pathway.

Effects of gastrodin against carbon tetrachloride induced kidney inflammation and fibrosis in mice associated with the AMPK/Nrf2/HMGB1 pathway

Gastrodin (GAS), the main phenolic glycoside extracted from Gastrodia elata Blume, exhibits potential renoprotective properties.

GSPE alleviates renal fibrosis by inhibiting the activation of C3/ HMGB1/ TGF-β1 pathway

Grape seed proanthocyanidin extract (GSPE) has been reported to exhibit a variety of protective effects, such as antioxidant, anti-atherosclerosis and other pharmacological effects. As a member of the complement system, complement component 3 (C3) deposition in the glomerulus is recognized as an important causative mediator of various kidney diseases. In this study, we aimed to identify the effect of GSPE on C3 in the chronic kidney fibrosis and evaluate the possible mechanism. We observed that administration of GSPE relieves inflammation and chronic renal fibrosis in mouse models of UUO. GSPE inhibited C3 secreted by macrophages to relieve renal interstitial inflammation. In vitro, we found that C3 stimulated HMGB1 translocation form nucleus to cytoplasm and promote the expression of pro-inflammatory cytokines including TGF-β1 in primary renal tubular epithelial cells (PTEC), which could be inhibited by GSPE. Meanwhile, GSPE could also decreased HMGB1-induced EMT of PTEC through suppresses the HMGB1/TLR4/p65/TGF-β1 pathway. In addition, the myofibroblast activation was inhibited by GSPE via TGF-β1/Smad2/3 signaling pathways in normal rat kidney fibroblast (NRK-49F) cells. Overall, these observations provide that GSPE alleviates renal fibrosis by inhibiting the C3/HMGB1/TGF-β1 pathway and could thus lead to find the potential therapy for the suppression of renal fibrosis.

MicroRNA-31/184 is involved in transforming growth factor-β-induced apoptosis in A549 human alveolar adenocarcinoma cells

AIMS

TGF-β-induced alveolar epithelial cells apoptosis were involved in idiopathic pulmonary fibrosis (IPF). This study aimed to explore potential targets and mechanisms of IPF.

MAIN METHODS

mRNA and microRNA arrays were used to analyze differentially expressed genes and miRNAs. Several essential targets of TGF-β-SMADs and TGF-β-PI3K-AKT pathways were detected.

KEY FINDINGS

miR-31 and miR-184 expression levels were positively correlated with smad6 and smad2/akt expression levels in IPF patients. TGF-β could induce miR-31 and suppress miR-184 levels in A549 cells. miR-31 was confirmed to bind to the smad6-3'UTR and functionally suppress its expression. Down-regulated SMAD6 enhanced SMAD2/SMAD4 dimer formation and translocation due to its failure to prevent SMAD2 phosphorylation. In contrast, anti-fibrotic functions of miR-184 were abolished due to TGF-β directly suppressing miR-184 levels in A549 cells. When A549 was stimulated by TGF-β combined with or without miR-31 inhibitor/miR-184 mimic, it was showed that depleted miR-31 and/or increased miR-184 significantly ameliorated TGF-β-induced viability of A549 cells, as well as inhibited the expression of profibrotic factors, MMP7 and RUNX2.

SIGNIFICANCE

Inhibiting miR-31 and/or promoting miR-184 protect against TGF-β-induced fibrogenesis by respectively repressing the TGF-β-SMAD2 and TGF-β-PI3K-AKT signaling pathways, implying that miR-31/184 are potential targets and suggesting a new management strategy for IPF.

The Role of HMGB1, a Nuclear Damage-Associated Molecular Pattern Molecule, in the Pathogenesis of Lung Diseases

Significance: High-mobility group protein box 1 (HMGB1), a ubiquitous nuclear protein, regulates chromatin structure and modulates the expression of many genes involved in the pathogenesis of lung cancer and many other lung diseases, including those that regulate cell cycle control, cell death, and DNA replication and repair. Extracellular HMGB1, whether passively released or actively secreted, is a danger signal that elicits proinflammatory responses, impairs macrophage phagocytosis and efferocytosis, and alters vascular remodeling. This can result in excessive pulmonary inflammation and compromised host defense against lung infections, causing a deleterious feedback cycle. Recent Advances: HMGB1 has been identified as a biomarker and mediator of the pathogenesis of numerous lung disorders. In addition, post-translational modifications of HMGB1, including acetylation, phosphorylation, and oxidation, have been postulated to affect its localization and physiological and pathophysiological effects, such as the initiation and progression of lung diseases. Critical Issues: The molecular mechanisms underlying how HMGB1 drives the pathogenesis of different lung diseases and novel therapeutic approaches targeting HMGB1 remain to be elucidated. Future Directions: Additional research is needed to identify the roles and functions of modified HMGB1 produced by different post-translational modifications and their significance in the pathogenesis of lung diseases. Such studies will provide information for novel approaches targeting HMGB1 as a treatment for lung diseases.

HMGB1-Induced p62 Overexpression Promotes Snail-Mediated Epithelial-Mesenchymal Transition in Glioblastoma Cells via the Degradation of GSK-3β

Rationale: Glioblastoma (GBM) is the most common and aggressive brain tumor, characterized by its propensity to invade the surrounding brain parenchyma. The effect of extracellular high-mobility group box 1 (HMGB1) protein on glioblastoma (GBM) progression is still controversial. p62 is overexpressed in glioma cells, and has been associated with the malignant features and poor prognosis of GBM patients. Hence, this study aimed to clarify the role of p62 in HMGB1-induced epithelial-mesenchymal transition (EMT) of GBM both in vitro and in vivo.

Methods: Immunoblotting, immunofluorescence and qRT-PCR were performed to evaluate EMT progression in both human GBM cell line and primary GBM cells. Transwell and wound healing assays were used to assess the invasion and migration of GBM cells. shRNA technique was used to investigate the role of p62 in HMGB1-induced EMT both in vitro and in vivo orthotopic tumor model. Co-immunoprecipitation assay was used to reveal the interaction between p62 and GSK-3β (glycogen synthase kinase 3 beta). Immunohistochemistry was performed to detect the expression levels of proteins in human GBM tissues.

Results: In this study, GBM cells treated with recombinant human HMGB1 (rhHMGB1) underwent spontaneous EMT through GSK-3β/Snail signaling pathway. In addition, our study revealed that rhHMGB1-induced EMT of GBM cells was accompanied by p62 overexpression, which was mediated by the activation of TLR4-p38-Nrf2 signaling pathway. Moreover, the results demonstrated that p62 knockdown impaired rhHMGB1-induced EMT both in vitro and in vivo. Subsequent mechanistic investigations showed that p62 served as a shuttling factor for the interaction of GSK-3β with proteasome, and ultimately activated GSK-3β/Snail signaling pathway by augmenting the degradation of GSK-3β. Furthermore, immunohistochemistry analysis revealed a significant inverse correlation between p62 and GSK-3β, and a combination of the both might serve as a more powerful predictor of poor survival in GBM patients.

Conclusions: This study suggests that p62 is an effector for HMGB1-induced EMT, and may represent a novel therapeutic target in GBM.

Captopril attenuates TAC-induced heart failure via inhibiting Wnt3a/β-catenin and Jak2/Stat3 pathways

Captopril (Cap) as angiotensin-converting enzyme inhibitor (ACEi) is commonly used to treat hypertension and some types of congestive heart failure. However, few studies reported on whether Cap exerts a protective effect on myocardial apoptosis induced by transverse aortic constriction (TAC). This study aimed at investigating the possible mechanism of Cap on myocardial apoptosis induced by pressure overload. Results showed that Cap significantly decreased heart-to-body weight ratios (HBWR). Cap markedly improved cardiac function, and reduced inner diameter of ascending aorta (Asc Ao) in TAC mice as shown by echocardiography. Enzyme-linked immunosorbent assay (ELISA) results demonstrated that Cap treatment also markedly decreased the level of N-terminal pro-B-type natriuretic peptide (NT-proBNP), atrial natriuretic peptide (ANP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Cardiac pathological changes and fibrosis have been improved after Cap treatment as shown by hematoxylin-eosin (H&E) staining and Masson's trichrome staining. Moreover, Terminal deoxynucleotidyl transferase-mediated dexoxyuridine triphosphate nick-end labeling (TUNEL) staining result indicated Cap treatment also significantly inhibited cardiac apoptosis. Western Blot results showed that Cap obviously decreased the expression of cleaved capase-3, Bax, phosphorylated Jak2 (p-Jak2), phosphorylated Stat3 (p-Stat3), Wnt3a and β-catenin proteins, as well as increased Bcl-2 expression. In conclusion, Cap showed a protective effect on TAC-induced cardiac apoptosis, which could be attributed to the inhibition of Wnt3a/β-catenin signaling pathway. Cap also attenuated myocardial hypertrophy induced by TAC via suppression of Jak2/Stat3 pathway.

Macrophage-secreted TSLP and MMP9 promote bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis is a pathological result of dysfunctional repair response to tissue injury, leading to chronically impaired gas exchange and death. Macrophages are believed to be critical in this disease pathogenesis; However, the exact mechanisms remain enigmatic. Here, we demonstrated that macrophages might contribute to pulmonary fibrosis at the early stage because the aggregation of macrophages appeared earlier than epithelial-mesenchymal transition and fibrosis in mouse and rat experimental models of pulmonary fibrosis. It has been found that macrophages could promote epithelial-mesenchymal transition of alveolar epithelial cells and fibroblast migration in co-culture models between macrophages and alveolar epithelial cells/fibroblasts. Importantly, we used protein micro array to analyze the cytokines that were altered after bleomycin treatment. Only thymic stromal lymphopoietin and matrix metalloproteinase 9 were significantly increased. We further confirmed that TSLP participated in the macrophage-induced epithelial-mesenchymal transition of alveolar epithelial cells using a TSLP recombinant protein. MMP9 was also involved in macrophage-induced fibroblast migration, which can be reversed by an inhibitor of MMP9. Collectively, these findings explained the underlying mechanisms of macrophage-promoted pulmonary fibrosis.

miR-627/HMGB1/NF-κB regulatory loop modulates TGF-β1-induced pulmonary fibrosis

Pulmonary fibrosis (PF) is a fibroproliferative disease that can eventually lead to fatal lung failure. It is characterized by abnormal proliferation of fibroblasts, dysregulated fibroblast differentiation to myofibroblast, and disorganized collagen and extracellular matrix production, deposition and degradation. There is still a lack of effective treatment strategies for PF. Extracellular high-mobility group box protein 1 (HMGB1) induces PF through NF-κB-mediated TGF-β1 release. Herein, we first validate the suppressive effect of HMGB1 knockdown on TGF-β1-induced α-smooth muscle actin (α-SMA) and collagen I protein expression. In PF, miRNAs exert different effects through targeting various downstream target messenger RNAs. We searched an online database for dysregulated miRNAs in PF tissues; among them, miR-627 was predicted by online tools to target HMGB1 to inhibit its expression. miR-627 overexpression could partially reverse TGF-β1-induced normal human lung fibroblast proliferation, as well as α-SMA and collagen I protein expression. miR-627 inhibition could partially reverse the suppressive effect of HMGB1 knockdown on TGF-β1-induced α-SMA and collagen I protein expression through direct binding to the 3'-untranslated region of HMGB1. Moreover, miR-627/HMGB1 affected TGF-β1 release through RAGE/NF-κB signaling; miR-627/HMGB1 and RAGE/NF-κB signaling formed a regulatory loop to modulate TGF-β1-induced PF in vitro. In conclusion, miR-627 may be a potential agent that targets HMGB1 to inhibit its expression, thereby improving TGF-β1-induced PF in vitro.

Amiodarone induces epithelial-mesenchymal transition in A549 cells via activation of TGF-β1

Amiodarone is a high effectiveness anti-arrhythmia agent which is able to induce pulmonary fibrosis. Many studies have shown that the epithelial-mesenchymal transition (EMT) was a significant process in pulmonary fibrosis. So far, there are no studies about whether EMT was associated with amiodarone-induced pulmonary fibrosis, which was therefore explored in this study. In addition, the underlying mechanisms of amiodarone-induced pulmonary fibrosis were examined in vitro. We found the EMT marker (α-SMA) was significantly increased, while the E-cadherin was significantly decreased in adenocarcinomic human alveolar basal epithelial cells (A549) after amiodarone treatment, suggesting that the epithelial cells were an important source of mesenchymal cells. Transforming growth factor beta1 (TGF-β1) was also increased significantly after amiodarone treatment. In conclusion, this study suggested amiodarone could induce pulmonary fibrosis via EMT, and the TGF-β1 may be a key profibrotic cytokine in mechanisms of amiodarone-induced pulmonary fibrosis.

Regulation of Tumor Progression by Programmed Necrosis

Rapidly growing malignant tumors frequently encounter hypoxia and nutrient (e.g., glucose) deprivation, which occurs because of insufficient blood supply. This results in necrotic cell death in the core region of solid tumors. Necrotic cells release their cellular cytoplasmic contents into the extracellular space, such as high mobility group box 1 (HMGB1), which is a nonhistone nuclear protein, but acts as a proinflammatory and tumor-promoting cytokine when released by necrotic cells. These released molecules recruit immune and inflammatory cells, which exert tumor-promoting activity by inducing angiogenesis, proliferation, and invasion. Development of a necrotic core in cancer patients is also associated with poor prognosis. Conventionally, necrosis has been thought of as an unregulated process, unlike programmed cell death processes like apoptosis and autophagy. Recently, necrosis has been recognized as a programmed cell death, encompassing processes such as oncosis, necroptosis, and others. Metabolic stress-induced necrosis and its regulatory mechanisms have been poorly investigated until recently. Snail and Dlx-2, EMT-inducing transcription factors, are responsible for metabolic stress-induced necrosis in tumors. Snail and Dlx-2 contribute to tumor progression by promoting necrosis and inducing EMT and oncogenic metabolism. Oncogenic metabolism has been shown to play a role(s) in initiating necrosis. Here, we discuss the molecular mechanisms underlying metabolic stress-induced programmed necrosis that promote tumor progression and aggressiveness.

Nrf2 antioxidant pathway suppresses Numb-mediated epithelial-mesenchymal transition during pulmonary fibrosis

Epithelial mesenchymal transition (EMT) is a key progression that promotes pulmonary fibrosis (PF). Numb, a phosphotyrosine-binding domain (PTB) protein, is implicated with EMT. Nuclear factor erythroid 2-related factor2 (Nrf2) and its downstream proteins heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) constitute an important pathway of antioxidant defense signal for protecting against PF. It remains elusive whether Nrf2 antioxidant pathway and Numb have a potential relationship in EMT-mediated PF. Here, we observed the effects of Nrf2 pathway and Numb on bleomycin(BLM)-induced PF in Nrf2-knockout (Nrf2-/-) and wild-type (WT) mice. Meanwhile, rat type II alveolar epithelial cells line (RLE-6TN) and human epithelial cells line (A549) were both treated with an Nrf2 activator sulforaphane (SFN), or transfected siRNAs of Nrf2 and Numb to unravel roles of Nrf2 pathway, Numb and the link between them on transforming growth factor β1 (TGF-β1)-induced EMT. We found BLM-induced lung fibrosis were more severe in Nrf2-/- mice compared to WT mice with reduced expressions of HO-1 and NQO1. Numb was enhanced with down-regulated expressions of Nrf2 in BLM groups and further increased in Nrf2-/- groups. In vitro, given exogenous TGF-β1 on RLE-6TN and A549 up-regulated Numb expressions, accompanied with down-regulations of Nrf2 and its target proteins HO-1 and NQO1. Transfected with Nrf2 and Numb siRNAs further aggravated and relieved the progression of EMT, respectively. Inversely, activating Nrf2 pathway by SFN reduced the expression of Numb and EMT-related protein. Moreover, Numb deficiency by siRNA relieved the protection of activating Nrf2 against EMT. In conclusion, activating Nrf2 antioxidant pathway suppresses EMT during PF via inhibiting the abnormal expression of Numb. These findings provide insight into PF pathogenesis and a basis for novel treatment approaches.

Endogenous ligands of TLR4 promote unresolving tissue fibrosis: Implications for systemic sclerosis and its targeted therapy

Fibrosis, the hallmark of scleroderma or systemic sclerosis (SSc), is a complex, dynamic and generally irreversible pathophysiological process that leads to tissue disruption, and lacks effective therapy. While early-stage fibrosis resembles normal wound healing, in SSc fibrosis fails to resolve. Innate immune signaling via toll-like receptors (TLRs) has recently emerged as a key driver of persistent fibrotic response in SSc. Recurrent injury in genetically predisposed individual causes generation of "damage-associated molecular patterns" (DAMPs) such as fibronectin-EDA and tenascin-C. Sensing of these danger signals by TLR4 on resident cells elicits potent stimulatory effects on fibrotic gene expression and myofibroblast differentiation, and appears to sensitize fibroblasts to the profibrotic stimulatory effect of TGF-β. Thus, DAMPs induce TLR4-mediated innate immune signaling on resident mesenchymal cells which drives the emergence and persistence of fibrotic cells in tissues, and underlies the switch from a self-limited repair response to non-resolving pathological fibrosis characteristic of SSc. In this review, we present current views of the DAMP-TLR4 axis in driving sustained fibroblasts activation and its pathogenic roles in fibrosis progression in SSc, and potential anti-fibrotic approaches for selective therapeutic targeting of TLR4 signaling.

Protective Effect of Atazanavir Sulphate Against Pulmonary Fibrosis In Vivo and In Vitro

Atazanavir sulphate, an antiretroviral protease inhibitor, has been used to treat HIV/AIDS, but its ability to serve as an antipulmonary fibrosis (PF) agent remains unknown. In this study, the effects of atazanavir sulphate on various aspects of PF were examined and CoCl₂ was used to induce the hypoxia-mimicking condition in vitro, including epithelial-mesenchymal transition (EMT) in A549 cells, endothelial-mesenchymal transition (EndMT) in human pulmonary microvascular endothelial cells (HPMECs), proliferation in human lung fibroblasts (HLF-1) and potential protective effects in human type I alveolar epithelial cells (AT I). Additionally, the effects of atazanavir sulphate were examined using a bleomycin (BLM)-induced pulmonary fibrosis model. After atazanavir sulphate treatment, in A549 cells and HPMECs, the expression of vimentin, HMGB1, Toll-like receptor 4 (TLR-4) and p-NF-κB decreased, while the expression of E-cadherin and VE-cadherin increased. In AT I cells, the expression of aquaporin 5 and RAGE were increased after atazanavir treatment. Proliferation of HLF-1 was reduced after atazanavir treatment, meanwhile the expression of hypoxia-inducible factor-1α (HIF-1α), prolyl hydroxylase domain protein 2 (PHD-2), HMGB1, TLR-9, p-NF-κB, collagen I and collagen III was decreased. In the BLM-induced pulmonary fibrosis rat model, atazanavir sulphate ameliorated PF by reducing pathological score, collagen deposition and the expression of α-SMA, HIF-1α, PHD-2, HMGB1, TLR-4, TLR-9 and p-NF-κB. In summary, our study supports the proposal that atazanavir sulphate may have a therapeutic potential in reducing the progression of pulmonary fibrosis by suppressing HMGB1/TLR signalling.

Astragaloside IV Improves Bleomycin-Induced Pulmonary Fibrosis in Rats by Attenuating Extracellular Matrix Deposition

Pulmonary fibrosis is a devastating lung disorder with mysterious pathogenesis and limited treatment options. It is well-recognized that the uncontrolled proliferation of lung fibroblasts and differentiation of fibroblasts into myofibroblasts excessively produce extracellular matrix (ECM) proteins which contribute to the fibrosis change of the lungs. Thus, blocking ECM accumulation would delay fibrosis progression. In this study, we observed the effects of astragaloside IV (ASV) (10 mg/kg/d) on ECM proteins in bleomycin (BLM, 5 mg/kg)-treated rats. Our results showed that ASV not only ameliorated BLM-induced body weight loss, lung coefficient increase, histological changes and collagen secretion, but also reduced the levels of type III collagen (Col-III) in lung homogenate, laminin (LN) and hyaluronic acid (HA) in serum, as well as hydroxyproline (HYP) in lung tissue. Besides, ASV significantly down-regulated the levels of high-mobility group box1 (HMGB1) in serum and lung tissue, and inhibited the up-regulated expression of α-SMA (marker of myofibroblasts) in the lungs. Taken together, these findings indicate that ASV attenuates BLM-induced ECM deposition, supporting its use as a promising candidate to treat lung fibrosis.

HMGB1 promotes HLF-1 proliferation and ECM production through activating HIF1-α-regulated aerobic glycolysis

Aerobic glycolysis is a crucial event in fibroblast differentiation, and extracellular matrix (ECM) production in the progression of pulmonary fibrosis (PF). Abnormal high mobility group protein B1 (HMGB1) activation is involved in the pathogenesis of PF. However, whether aerobic glycolysis contributes to HMGB1-induced fibroblast proliferation and ECM production in PF has not yet been determined. In this study, we investigated the effects of HMGB1 on human embryonic lung fibroblast (HLF-1) proliferation, ECM production, and aerobic glycolysis. The lactate dehydrogenase inhibitor oxamic acid (OA), and PFKFB3 inhibitor 3PO were used to block certain crucial steps of aerobic glycolysis. As a result, we observed an increase of HMGB1 in bronchoalveolar lavage fluid (BALF) in bleomycin (BLM)-treated rats as compared to non-treated rats (control group). A concentration-dependent increase of HLF-1 proliferation and expression of α-SMA and α-collagen I were observed in the HMGB1 group, as well as increases of LDHA activation, glucose uptake levels, glycolytic rate, lactate level, and ATP production. OA and 3PO, or suppression of HIF1-α, blocked the effects of HMGB1. In summary, HMGB1 promotes fibroblast proliferation and ECM production though upregulating expression of HIF1-α to induce an increase of aerobic glycolysis.