Mechanical Stress and the Induction of Lung Fibrosis via the Midkine Signaling Pathway

MBD2 promotes epithelial-to-mesenchymal transition (EMT) and ARDS-related pulmonary fibrosis by modulating FZD2

OBJECTIVE

To investigate the role and underlying mechanism of Methyl-CpG binding domain protein 2 (MBD2) in the pathogenesis of acute respiratory distress syndrome (ARDS)-related pulmonary fibrosis.

METHODS

Murine models for ARDS-related pulmonary fibrosis were established in wildtype or MBD2 knockout mice, expressions of MBD2 were determined with immunohistochemistry (IHC), immunofluorescence, and western blot. Epithelial-to-mesenchymal transition (EMT) was detected with determined with decreased expression of E-cadherin and increased expressions of N-cadherin, Vimentin, and α-smooth muscle actin (α-SMA). Transforming growth factor β (TGF-β) treated mouse lung epithelial-12 (MLE-12) cells and primary human type II alveolar epithelial cells were applied to establish in vitro model for EMT. Transcriptional sequencing with RNA-Seq and Chromatin immunoprecipitation (ChIP) assay were used to explore the potential targets of MBD2. Single cell sequencing data and Human pulmonary fibrosis samples were analyzed.

RESULTS

Bleomycin (BLM) and lipopolysaccharide (LPS) induced EMT, pulmonary fibrosis, and increased expression of MBD2 in alveolar epithelial cells of mice, and MBD2 knockout significantly alleviated BLM- and LPS-induced pulmonary fibrosis and EMT. TGF-β induced EMT and elevated MBD2 expressions in alveolar epithelial cells, which was mitigated by MBD2 knockdown and aggravated by MBD2 overexpression. Frizzled 2 (FZD2) was found to be the potential target of MBD2. Single-cell sequencing analysis of ARDS patients suggested elevated expression of MBD2 in alveolar epithelial cells, and MBD2 expression was elevated in the lungs of patients with pulmonary fibrosis.

CONCLUSION

Our results indicated that MBD2 could promote EMT and ARDS-related pulmonary fibrosis, potentially by modulating the expression of FZD2.

Midkine, a novel MCP-1 activator mediated PM2.5-aggravated experimental pulmonary fibrosis

Exposure to fine particulate matter (PM2.5) is associated with increased morbidity and mortality among patients with idiopathic pulmonary fibrosis (IPF). Pathological alterations in IPF typically originate in the subpleural regions of the lungs. However, it was unclear how PM2.5 affected subpleural pulmonary fibrosis. In this study, atmospheric PM2.5 and carbon blacks were utilized as representative particulate matter to investigate these effects. Mouse models and cell models were made to investigate macrophage chemotaxis changes under PM2.5 exposure in vivo and in vitro. The findings indicated that PM2.5 promoted macrophage aggregation in the subpleural region of lung and aggravated bleomycin-induced pulmonary fibrosis in mice. At the same time, we uncovered for the first time that PM2.5 exposure led to an upregulation of midkine, which subsequently enhanced the production of monocyte chemotactic protein-1 (MCP-1) through the cell surface receptor Syndecan 4 (SDC4) in pleural mesothelial cells (PMCs), thereby, inducing macrophage aggregation in subpleural region of lung. Furthermore, our results indicated that PM2.5 and bleomycin facilitated macrophage M1 polarization and the production of profibrotic inflammatory factors, culminating in fibrotic alterations in PMCs, lung fibroblasts, and alveolar epithelial cells. Finally, we demonstrated that inhibition of midkine ameliorated lung function and mitigated pulmonary fibrosis in vivo. In conclusion, our findings elucidated that midkine acted as a novel MCP-1 activator, mediating PM2.5-aggravated experimental pulmonary fibrosis, and suggested that the midkine/SDC4/MCP-1 signal should be a new therapeutic target for the treatment of PM2.5-related IPF.

Mechanical Stretch Induces Senescence of Lung Epithelial Cells and Drives Fibroblast Activation by Paracrine Mechanisms

Severe lung injury requiring mechanical ventilation may lead to secondary fibrosis. Senescence, a cell response characterized by cell cycle arrest and a shift toward a proinflammatory/profibrotic phenotype, is one of the involved mechanisms. In this study, we explore the contribution of mechanical stretch as a trigger of senescence of the respiratory epithelium and its link with fibrosis. Human lung epithelial cells and fibroblasts were exposed in vitro to mechanical stretch, and senescence was assessed. In addition, fibroblasts were exposed to culture media preconditioned by senescent epithelial cells, and their activation was studied. Transcriptomic profiles from stretched, senescent epithelial cells and activated fibroblasts were combined to identify potential activated pathways. Finally, the senolytic effects of digoxin were tested in these models. Mechanical stretch induced senescence in lung epithelial cells, but not in fibroblasts. This stretch-induced senescence has specific features compared with senescence induced by doxorubicin. Fibroblasts were activated after exposure to supernatants conditioned by epithelial senescent cells. Transcriptomic analyses revealed Notch signaling as potentially responsible for the epithelial-mesenchymal cross-talk, because blockade of this pathway inhibits fibroblast activation. Treatment with digoxin reduced the percentage of senescent cells after stretch and ameliorated the fibroblast response to preconditioned media. These results suggest that lung fibrosis in response to mechanical stretch may be caused by the paracrine effects of senescent cells. This pathogenetic mechanism can be pharmacologically manipulated to improve lung repair.

A particle of concern: explored and proposed underlying mechanisms of microplastic-induced lung damage and pulmonary fibrosis

PURPOSE

In the past decade, microplastics (MPs) have drawn significant attention as widespread environmental contaminants, with research increasingly highlighting their harmful effects on respiratory health in aquatic and terrestrial organisms. Findings revealed microplastics in human lung tissues, raising concerns about their potential role in damaging lung tissue integrity and contributing to pulmonary fibrosis-a chronic inflammatory condition characterized by scarring of lung epithelial tissues due to accumulated extracellular matrix, triggered by factors such as alcohol, pathogens, genetic mutations, and environmental pollutants.

OBJECTIVE

In this review, we explore both well-studied and lesser-studied mechanisms and signaling pathways, aiming to shed light on how microplastics might act as mediators that activate distinct, often overlooked signaling cascades.

MATERIALS AND METHODS

This review searched PubMed and Google Scholar using keywords like "plastic," "microplastic," "lung fibrosis," "pulmonary system," "exposure route," and "signaling pathways," combined with "OR" and "AND" in singular and plural forms.

RESULTS

These pathways could not only induce lung damage but also play a significant role in the development of pulmonary fibrosis.

DISCUSSION AND CONCLUSIONS

These signaling pathways could also be targeted to reduce microplastic-induced pulmonary fibrosis, opening new avenues for future treatments.

Mechanisms of mechanical stimulation in the development of respiratory system diseases

During respiration, mechanical stress can initiate biological responses that impact the respiratory system. Mechanical stress plays a crucial role in the development of the respiratory system. However, pathological mechanical stress can impact the onset and progression of respiratory diseases by influencing the extracellular matrix and cell transduction processes. In this article, we explore the mechanisms by which mechanical forces communicate with and influence cells. We outline the basic knowledge of respiratory mechanics, elucidating the important role of mechanical stimulation in influencing respiratory system development and differentiation from a microscopic perspective. We also explore the potential mechanisms of mechanical transduction in the pathogenesis and development of respiratory diseases such as asthma, lung injury, pulmonary fibrosis, and lung cancer. Finally, we look forward to new research directions in cellular mechanotransduction, aiming to provide fresh insights for future therapeutic research on respiratory diseases.

Neutrophil dynamics in pulmonary fibrosis: pathophysiological and therapeutic perspectives

The shared pathobiological mechanisms driving progressive fibrosis in interstitial lung diseases (ILDs) remain unclear. Neutrophils, the most common immune cells in the human body, contain an extensive array of proteinases that are important for cell function, including tissue repair and remodelling. Increasing observational studies have reported elevated neutrophil counts in the respiratory tract and circulation of patients with ILD and suggest a role as a biomarker of disease severity. Neutrophils and their contents (including the formation of neutrophil extracellular traps (NETs)) are present in fibrotic lung tissue. Proteinases and NETs may drive fibrogenesis in animal and in vitro models and may impact transforming growth factor-β1 activation. However, the effect of neutrophil action, whether reparative or pathologically destructive to the delicate lung architecture, has yet to be determined. This review aims to summarise the current literature surrounding the potential role of the neutrophil as a biomarker and contributor to the pathogenesis of ILD. There is currently a paucity of treatment options in ILD driven by the knowledge gap underlying the overall disease mechanisms. This review concludes that neutrophils warrant further evaluation as manipulation of recruitment and function could provide a novel and much needed therapeutic strategy.

Ventilatory pressure parameters impact the association between acute gastrointestinal injury and all-cause mortality in mechanically ventilated patients

Acute gastrointestinal injury (AGI) is common in mechanically ventilated (MV) patients, but the potential association between ventilatory pressure parameters and AGI grade and their impact on mortality remains unclear. This study aimed to explore the association between ventilatory pressure parameters and AGI grade, and their interaction on all-cause mortality in MV patients. This study was a secondary analysis of a multicenter, prospective, observational study that enrolled adult patients with an expected duration of mechanical ventilation ≥ 48 h from 14 general intensive care units in Zhejiang Province between March and August 2014. The AGI grade was assessed daily on the basis of gastrointestinal symptoms, intra-abdominal pressures, and feeding intolerance in the first week of admission to the ICU. This study included 331 patients (69.2% men; mean age, 64.6 ± 18.9 years). Multivariate regression analysis showed that plateau pressure (Pplat) (OR 1.044, 95% CI 1.009-1.081, P = 0.013), serum creatinine (OR 1.003, 95% CI 1.001-1.006, P = 0.042) and APACHE II score (OR 1.035, 95% CI 1.021-1.072, P = 0.045) were independently associated with global AGI grade III/IV within 7 days of ICU admission. Moreover, global AGI grade (HR 2.228, 95% CI 1.561-3.182, P < 0.001), serum creatinine (HR 1.002, 95% CI 1.001-1.003, P = 0.012) and APACHE II score (HR 1.039, 95% CI 1.015-1.063, P = 0.001) were independently associated with 60-day mortality. In addition, there were significant (Pint ≤ 0.028) interactions of Pplat and DP with AGI grade in relation to 60-days mortality, whereas no interaction (Pint = 0.061) between PEEP and AGI grade on 60-days mortality was observed. In the presence of Pplat ≥ 19 cmH2O, the patients with AGI grade III/IV had 60-day mortality rate of 72.2%, significantly higher than those with AGI grade I/II (48.7%, P = 0.018), whereas there were no significant differences (27.9% vs. 33.7%, P = 0.39) in 60-days mortality between AGI grade I/II and III/IV among the patients with Pplat < 19 cmH2O. In comparison with Pplat, DP had a similar interaction (Pint = 0.028) with AGI grade on 60-day mortality. Ventilatory pressure parameters (Pplat and DP) are independent risk factors of AGI grade III/IV. Pplat and DP interact with AGI grade on 60-days mortality, highlighting the importance of optimizing ventilatory pressure parameters to improve gastrointestinal function and survival outcomes of MV patients.Trial registration: ChiCTR-OCS-13003824.

Inhibition of SMYD2 attenuates paraquat-induced pulmonary fibrosis by inhibiting the epithelial-mesenchymal transition through the GLIPR2/ERK/p38 axis

Paraquat (PQ) poisoning leads to irreversible fibrosis in the lungs with high mortality and no known antidote. In this study, we investigated the effect of the SET and MYND domain containing 2 (SMYD2) on PQ-induced pulmonary fibrosis (PF) and its potential mechanisms. We established an in vivo PQ-induced PF mouse model by intraperitoneal injection of PQ (20 mg/kg) and in vitro PQ (25 μM)-injured MLE-12 cell model. On the 15th day of administration, tissue injury, inflammation, and fibrosis in mice were evaluated using various methods including routine blood counts, blood biochemistry, blood gas analysis, western blotting, H&E staining, ELISA, Masson staining, and immunofluorescence. The findings indicated that AZ505 administration mitigated tissue damage, inflammation, and collagen deposition in PQ-poisoned mice. Mechanistically, both in vivo and in vitro experiments revealed that AZ505 treatment suppressed the PQ-induced epithelial-mesenchymal transition (EMT) process by downregulating GLI pathogenesis related 2 (GLIPR2) and ERK/p38 pathway. Further investigations demonstrated that SMYD2 inhibition decreased GLIPR2 methylation and facilitated GLIPR2 ubiquitination, leading to GLIPR2 destabilization in PQ-exposed MLE-12 cells. Moreover, rescue experiments conducted in vitro demonstrated that GLIPR2 overexpression eliminated the inhibitory effect of AZ505 on the ERK/p38 pathway and EMT. Our results reveal that the SMYD2 inhibitor AZ505 may act as a novel therapeutic candidate to suppress the EMT process by modulating the GLIPR2/ERK/p38 axis in PQ-induced PF.

Pharmacological inhibition of the ACE/Ang-2/AT1 axis alleviates mechanical ventilation-induced pulmonary fibrosis

Mechanical ventilation (MV) is an essential therapy for acute respiratory distress syndrome (ARDS) and pulmonary fibrosis. However, it can also induce mechanical ventilation-induced pulmonary fibrosis (MVPF) and the underlying mechanism remains unknown. Based on a mouse model of MVPF, the present study aimed to explore the role of the angiotensin-converting enzyme/angiotensin II/angiotensin type 1 receptor (ACE/Ang-2/AT1R) axis in the process of MVPF. In addition, recombinant angiotensin-converting enzyme 2(rACE2), AT1R inhibitor valsartan, AGTR1-directed shRNA and ACE inhibitor perindopril were applied to verify the effect of inhibiting ACE/Ang-2/AT1R axis in the treatment of MVPF. Our study found MV induced an inflammatory reaction and collagen deposition in mouse lung tissue accompanied by the activation of ACE in lung tissue, increased concentration of Ang-2 in bronchoalveolar lavage fluid (BALF), and upregulation of AT1R in alveolar epithelial cells. The process of pulmonary fibrosis could be alleviated by the application of the ACE inhibitor perindopril, ATIR inhibitor valsartan and AGTR1-directed shRNA. Meanwhile, rACE2 could also alleviate MVPF through the degradation of Ang-2. Our finding indicated the ACE/Ang-2/AT1R axis played an essential role in the pathogenesis of MVPF. Pharmacological inhibition of the ACE/Ang-2/AT1R axis might be a promising strategy for the treatment of MVPF.

Toxic epidermal necrolysis complicated with respiratory failure in children: A case report

Stevens-Johnson syndrome or toxic epidermal necrolysis (TEN) is a severe skin and mucosal reaction that develops rapidly and has a high mortality rate. Its early identification and proper treatment are crucial to lowering the risk of death. Severe TEN can also lead to acute respiratory failure. This study probed the effect of early treatment on chronic airway damage in children with TEN complicated by respiratory failure. Three children diagnosed with TEN complicated by respiratory failure received interventions including high-dose glucocorticoids, gamma-globulin pulse therapy, and plasma exchange. One patient experienced recurrent lung infections, developed secondary chronic obstructive pulmonary disease, and eventually succumbed to respiratory failure despite skin improvement. The other two patients showed improvement after receiving combination treatment with a tumor necrosis factor-α (TNF-α) inhibitor. However, they also had concurrent chronic airway disease during the follow-up period. The exact mechanism underlying TEN remains uncertain. Children with TEN complicated by respiratory failure continue to experience chronic airway damage even after standard treatment. In future, multi-center clinical studies are warranted to investigate the impact of TNF-α inhibitors in children with TEN. Assessing the effectiveness and safety of targeted medications for TEN will provide more evidence regarding the prognosis of this disease.

A longitudinal molecular and cellular lung atlas of lethal SARS-CoV-2 infection in K18-hACE2 transgenic mice

BACKGROUND

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to approximately 500 million cases and 6 million deaths worldwide. Previous investigations into the pathophysiology of SARS-CoV-2 primarily focused on peripheral blood mononuclear cells from patients, lacking detailed mechanistic insights into the virus's impact on inflamed tissue. Existing animal models, such as hamster and ferret, do not faithfully replicate the severe SARS-CoV-2 infection seen in patients, underscoring the need for more relevant animal system-based research.

METHODS

In this study, we employed single-cell RNA sequencing (scRNA-seq) with lung tissues from K18-hACE2 transgenic (TG) mice during SARS-CoV-2 infection. This approach allowed for a comprehensive examination of the molecular and cellular responses to the virus in lung tissue.

FINDINGS

Upon SARS-CoV-2 infection, K18-hACE2 TG mice exhibited severe lung pathologies, including acute pneumonia, alveolar collapse, and immune cell infiltration. Through scRNA-seq, we identified 36 different types of cells dynamically orchestrating SARS-CoV-2-induced pathologies. Notably, SPP1+ macrophages in the myeloid compartment emerged as key drivers of severe lung inflammation and fibrosis in K18-hACE2 TG mice. Dynamic receptor-ligand interactions, involving various cell types such as immunological and bronchial cells, defined an enhanced TGFβ signaling pathway linked to delayed tissue regeneration, severe lung injury, and fibrotic processes.

INTERPRETATION

Our study provides a comprehensive understanding of SARS-CoV-2 pathogenesis in lung tissue, surpassing previous limitations in investigating inflamed tissues. The identified SPP1+ macrophages and the dysregulated TGFβ signaling pathway offer potential targets for therapeutic intervention. Insights from this research may contribute to the development of innovative diagnostics and therapies for COVID-19.

FUNDING

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2020M3A9I2109027, 2021R1A2C2004501).

Machine learning identified MDK score has prognostic value for idiopathic pulmonary fibrosis based on integrated bulk and single cell expression data

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease that poses a significant challenge to medical professionals due to its increasing incidence and prevalence coupled with the limited understanding of its underlying molecular mechanisms. In this study, we employed a novel approach by integrating five expression datasets from bulk tissue with single-cell datasets; they underwent pseudotime trajectory analysis, switch gene selection, and cell communication analysis. Utilizing the prognostic information derived from the GSE47460 dataset, we identified 22 differentially expressed switch genes that were correlated with clinical indicators as important genes. Among these genes, we found that the midkine (MDK) gene has the potential to serve as a marker of Idiopathic pulmonary fibrosis because its cellular communicating genes are differentially expressed in the epithelial cells. We then utilized midkine and its cellular communication-related genes to calculate the midkine score. Machine learning models were further constructed through midkine and related genes to predict Idiopathic pulmonary fibrosis disease through the bulk gene expression datasets. The midkine score demonstrated a correlation with clinical indexes, and the machine learning model achieved an AUC of 0.94 and 0.86 in the Idiopathic pulmonary fibrosis classification task based on lung tissue samples and peripheral blood mononuclear cell samples, respectively. Our findings offer valuable insights into the pathogenesis of Idiopathic pulmonary fibrosis, providing new therapeutic directions and target genes for further investigation.

Mechanosensitive ion channel Piezo1 mediates mechanical ventilation-exacerbated ARDS-associated pulmonary fibrosis

INTRODUCTION

Pulmonary fibrosis is a major cause of the poor prognosis of acute respiratory distress syndrome (ARDS). While mechanical ventilation (MV) is an indispensable life-saving intervention for ARDS, it may cause the remodeling process in lung epithelial cells to become disorganized and exacerbate ARDS-associated pulmonary fibrosis. Piezo1 is a mechanosensitive ion channel that is known to play a role in regulating diverse physiological processes, but whether Piezo1 is necessary for MV-exacerbated ARDS-associated pulmonary fibrosis remains unknown.

OBJECTIVES

This study aimed to explore the role of Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis.

METHODS

Human lung epithelial cells were stimulated with hydrochloric acid (HCl) followed by mechanical stretch for 48 h. A two-hitmodel of MV afteracidaspiration-inducedlunginjuryin mice was used. Mice were sacrificed after 14 days of MV. Pharmacological inhibition and knockout of Piezo1 were used to delineate the role of Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis. In some experiments, ATP or the ATP-hydrolyzing enzyme apyrase was administered.

RESULTS

The stimulation of human lung epithelial cells to HCl resulted in phenotypes of epithelial-mesenchymal transition (EMT), which were enhanced by mechanical stretching. MV exacerbated pulmonary fibrosis in mice exposed to HCl. Pharmacologicalinhibitionorknockout of Piezo1 attenuated the MV-exacerbated EMT process and lung fibrosis in vivo and in vitro. Mechanistically, the observed effects were mediated by Piezo1-dependent Ca2+ influx and ATP release in lung epithelial cells.

CONCLUSIONS

Our findings identify a key role for Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis that is mediated by increased ATP release in lung epithelial cells. Inhibiting Piezo1 may constitute a novelstrategyfor the treatment of MV-exacerbated ARDS-associated pulmonary fibrosis.

Nasopharynx Battlefield: Cellular Immune Responses Mediated by Midkine in Nasopharyngeal Carcinoma and COVID-19

Clinical evidence suggests that the severe respiratory illness coronavirus disease 2019 (COVID-19) is often associated with a cytokine storm that results in dysregulated immune responses. Prolonged COVID-19 positivity is thought to disproportionately affect cancer patients. With COVID-19 disrupting the delivery of cancer care, it is crucial to gain momentum and awareness of the mechanistic intersection between these two diseases. This review discusses the role of the cytokine midkine (MK) as an immunomodulator in patients with COVID-19 and nasopharyngeal carcinoma (NPC), both of which affect the nasal cavity. We conducted a review and analysis of immunocellular similarities and differences based on clinical studies, research articles, and published transcriptomic datasets. We specifically focused on ligand-receptor pairs that could be used to infer intercellular communication, as well as the current medications used for each disease, including NPC patients who have contracted COVID-19. Based on our findings, we recommend close monitoring of the MK axis to maintain the desirable effects of therapeutic regimens in fighting both NPC and COVID-19 infections.

Mechanical stretch promotes apoptosis and impedes ciliogenesis of primary human airway basal stem cells

BACKGROUND

Airway basal stem cells (ABSCs) have self-renewal and differentiation abilities. Although an abnormal mechanical environment related to chronic airway disease (CAD) can cause ABSC dysfunction, it remains unclear how mechanical stretch regulates the behavior and structure of ABSCs. Here, we explored the effect of mechanical stretch on primary human ABSCs.

METHODS

Primary human ABSCs were isolated from healthy volunteers. A Flexcell FX-5000 Tension system was used to mimic the pathological airway mechanical stretch conditions of patients with CAD. ABSCs were stretched for 12, 24, or 48 h with 20% elongation. We first performed bulk RNA sequencing to identify the most predominantly changed genes and pathways. Next, apoptosis of stretched ABSCs was detected with Annexin V-FITC/PI staining and a caspase 3 activity assay. Proliferation of stretched ABSCs was assessed by measuring MKI67 mRNA expression and cell cycle dynamics. Immunofluorescence and hematoxylin-eosin staining were used to demonstrate the differentiation state of ABSCs at the air-liquid interface.

RESULTS

Compared with unstretched control cells, apoptosis and caspase 3 activation of ABSCs stretched for 48 h were significantly increased (p < 0.0001; p < 0.0001, respectively), and MKI67 mRNA levels were decreased (p < 0.0001). In addition, a significant increase in the G0/G1 population (20.2%, p < 0.001) and a significant decrease in S-phase cells (21.1%, p < 0.0001) were observed. The ratio of Krt5+ ABSCs was significantly higher (32.38% vs. 48.71%, p = 0.0037) following stretching, while the ratio of Ac-tub+ cells was significantly lower (37.64% vs. 21.29%, p < 0.001). Moreover, compared with the control, the expression of NKX2-1 was upregulated significantly after stretching (14.06% vs. 39.51%, p < 0.0001). RNA sequencing showed 285 differentially expressed genes, among which 140 were upregulated and 145 were downregulated, revealing that DDIAS, BIRC5, TGFBI, and NKX2-1 may be involved in the function of primary human ABSCs during mechanical stretch. There was no apparent difference between stretching ABSCs for 24 and 48 h compared with the control.

CONCLUSIONS

Pathological stretching induces apoptosis of ABSCs, inhibits their proliferation, and disrupts cilia cell differentiation. These features may be related to abnormal regeneration and repair observed after airway epithelium injury in patients with CAD.

COVID-19 and interstitial lung diseases: A multifaceted look at the relationship between the two diseases

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although it has been a fatal disease for many patients, the development of treatment strategies and vaccines have progressed over the past 3 years, and our society has become able to accept COVID-19 as a manageable common disease. However, as COVID-19 sometimes causes pneumonia, post-COVID pulmonary fibrosis (PCPF), and worsening of preexisting interstitial lung diseases (ILDs), it is still a concern for pulmonary physicians. In this review, we have selected several topics regarding the relationships between ILDs and COVID-19. The pathogenesis of COVID-19-induced ILD is currently assumed based mainly on the evidence of other ILDs and has not been well elucidated specifically in the context of COVID-19. We have summarized what has been clarified to date and constructed a coherent story about the establishment and progress of the disease. We have also reviewed clinical information regarding ILDs newly induced or worsened by COVID-19 or anti-SARS-CoV-2 vaccines. Inflammatory and profibrotic responses induced by COVID-19 or vaccines have been thought to be a risk for de novo induction or worsening of ILDs, and this has been supported by the evidence obtained through clinical experience over the past 3 years. Although COVID-19 has become a mild disease in most cases, it is still worth looking back on the above-reviewed information to broaden our perspectives regarding the relationship between viral infection and ILD. As a representative etiology for severe viral pneumonia, further studies in this area are expected.

Inhalation of ACE2 as a therapeutic target on sex-bias differences in SARS-CoV-2 infection and variant of concern

Despite similar infection rates, COVID-19 has resulted in more deaths in men than women. To understand the underlying mechanisms behind this sex-biased difference in disease severity, we infected K18-human angiotensin converting enzyme 2 (ACE2) mice of both sexes with SARS-CoV-2. Our study revealed a unique protein expression profile in the lung microenvironment of female mice. As a result, they were less vulnerable to severe infection, with higher ACE2 expression and a higher estrogen receptor α (ERα)/androgen receptor (AR) ratio that led to increased antiviral factor levels. In male mice, inhaling recombinant ACE2 neutralized the virus and maintained the ERα/AR ratio, thereby protecting the lungs. Our findings suggest that inhaling recombinant ACE2 could serve as a decoy receptor against SARS-CoV-2 and protect male mice by offsetting ERα-associated protective mechanisms. Additionally, our study supports the potential effectiveness of recombinant ACE2 therapy in human lung organoids infected with the Delta variant.

Fibrotic extracellular vesicles contribute to mechanical ventilation-induced pulmonary fibrosis development by activating lung fibroblasts via JNK signalling pathway: an experimental study

Recent research has revealed that mechanical ventilation (MV) could initiate ventilator-induced lung injury along with the initiation of the process of pulmonary fibrosis (PF), leading to MV-induced PF (MVPF). However, the underlying mechanism remains unclear. This study aimed to explore the role of MV-induced extracellular vesicles (MV-EVs) and the c-Jun N-terminal kinase (JNK) signalling pathway in the pathogenesis of MVPF in vivo and in vitro. The process of MV is accompanied by the secretion of MV-EVs, which could induce lung fibroblast activation. Furthermore, single-cell RNA-sequencing analysis revealed that the JNK pathway in lung fibroblasts was activated after MV initiation. Inhibiting the JNK pathway could both restrain MV-EV-induced lung fibroblast activation in vitro or reduce the severity of MVPF in vivo. In conclusion, this study demonstrated that MV-EVs contribute to MVPF progression by activating lung fibroblasts via the JNK signalling pathway and that inhibiting the secretion of EV and the activation of the JNK signalling pathway is a promising strategy for treating MVPF.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

WFDC3 inhibits tumor metastasis by promoting the ERβ-mediated transcriptional repression of TGFBR1 in colorectal cancer

Estrogen plays a protective role in colorectal cancer (CRC) and primarily functions through estrogen receptor β (ERβ). However, clinical strategies for CRC therapy associated with ERβ are still under investigation. Our discoveries identified WFDC3 as a tumor suppressor that facilitates estrogen-induced inhibition of metastasis through the ERβ/TGFBR1 signaling axis. WFDC3 interacts with ERβ and increases its protein stability by inhibiting its proteasome-dependent degradation. WFDC3 represses TGFBR1 expression through ERβ-mediated transcription. Blocking TGFβ signaling with galunisertib, a drug used in clinical trials that targets TGFBR1, impaired the migration of CRC cells induced by WFDC3 depletion. Moreover, there was clinical significance to WFDC3 in CRC, as CRC patients with high WFDC3 expression in tumor cells had favorable prognoses. Therefore, this work suggests that WFDC3 could be an indicator for therapies targeting the estrogen/ERβ pathway in CRC patients.

The Protective Potential Role of ACE2 against COVID-19

Due to the coronavirus disease 2019 (COVID-19), researchers all over the world have tried to find an appropriate therapeutic approach for the disease. The angiotensin-converting enzyme 2 (ACE2) has been shown as a necessary receptor to cell fusion, which is involved in infection due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is commonly crucial for all organs and systems. When ACE2 is downregulated via the SARS-CoV-2 spike protein, it results in the angiotensin II (Ang II)/angiotensin type 1 receptor axis overactivation. Ang II has harmful effects, which can be evidenced by dysfunctions in many organs experienced by COVID-19 patients. ACE2 is the SARS-CoV-2 receptor and has an extensive distribution; thus, some COVID-19 cases experience several symptoms and complications. We suggest strategy for the potential protective effect of ACE2 to the viral infection. The current review will provide data to develop new approaches for preventing and controlling the COVID-19 outbreak.

Attenuation of Ventilation-Enhanced Epithelial–Mesenchymal Transition through the Phosphoinositide 3-Kinase-γ in a Murine Bleomycin-Induced Acute Lung Injury Model

Mechanical ventilation (MV) used in patients with acute lung injury (ALI) induces lung inflammation and causes fibroblast proliferation and excessive collagen deposition—a process termed epithelial–mesenchymal transition (EMT). Phosphoinositide 3-kinase-γ (PI3K-γ) is crucial in modulating EMT during the reparative phase of ALI; however, the mechanisms regulating the interactions among MV, EMT, and PI3K-γ remain unclear. We hypothesized that MV with or without bleomycin treatment would increase EMT through the PI3K-γ pathway. C57BL/6 mice, either wild-type or PI3K-γ-deficient, were exposed to 6 or 30 mL/kg MV for 5 h after receiving 5 mg/kg AS605240 intraperitoneally 5 days after bleomycin administration. We found that, after bleomycin exposure in wild-type mice, high-tidal-volume MV induced substantial increases in inflammatory cytokine production, oxidative loads, Masson’s trichrome staining level, positive staining of α-smooth muscle actin, PI3K-γ expression, and bronchial epithelial apoptosis (p < 0.05). Decreased respiratory function, antioxidants, and staining of the epithelial marker Zonula occludens-1 were also observed (p < 0.05). MV-augmented bleomycin-induced pulmonary fibrogenesis and epithelial apoptosis were attenuated in PI3K-γ-deficient mice, and we found pharmacological inhibition of PI3K-γ activity through AS605240 (p < 0.05). Our data suggest that MV augmented EMT after bleomycin-induced ALI, partially through the PI3K-γ pathway. Therapy targeting PI3K-γ may ameliorate MV-associated EMT.

Non-coding RNA alterations in extracellular vesicles from bronchoalveolar lavage fluid contribute to mechanical ventilation-induced pulmonary fibrosis

Objective

For respiratory failure patients, mechanical ventilation (MV) is a life-saving therapy to maintain respiratory function. However, MV could also cause damage to pulmonary structures, result in ventilator-induced lung injury (VILI) and eventually progress to mechanical ventilation-induced pulmonary fibrosis (MVPF). Mechanically ventilated patients with MVPF are closely related to increased mortality and poor quality of life in long-term survival. Thus, a thorough understanding of the involved mechanism is necessary.

Methods

We used next-generation sequencing to identify differentially expressed non-coding RNAs (ncRNAs) in BALF EVs which were isolated from Sham and MV mice. Bioinformatics analysis was conducted to identify the engaged ncRNAs and related signaling pathways in the process of MVPF.

Results

We found 1801 messenger RNAs (mRNA), 53 micro RNAs (miRNA), 273 circular RNAs (circRNA) and 552 long non-coding RNAs (lncRNA) in mice BALF EVs of two groups, which showed significant differential expression. TargetScan predicted that 53 differentially expressed miRNAs targeted 3105 mRNAs. MiRanda revealed that 273 differentially expressed circRNAs were associated with 241 mRNAs while 552 differentially expressed lncRNAs were predicated to target 20528 mRNAs. GO, KEGG pathway analysis and KOG classification showed that these differentially expressed ncRNA-targeted mRNAs were enriched in fibrosis related signaling pathways and biological processes. By taking the intersection of miRNAs target genes, circRNAs target genes and lncRNAs target genes, we found 24 common key genes and 6 downregulated genes were confirmed by qRT-PCR.

Conclusions

Changes in BALF-EV ncRNAs may contribute to MVPF. Identification of key target genes involved in the pathogenesis of MVPF could lead to interventions that slow or reverse fibrosis progression.

Post-COVID Interstitial Lung Disease—The Tip of the Iceberg

The proportion of symptomatic patients with post-coronavirus 2019 (COVID-19) condition (long COVID) represents a significant burden on the individual as well as on the health care systems. A greater understanding of the natural evolution of symptoms over a longer period and the impacts of interventions will improve our understanding of the long-term impacts of the COVID-19 disease. This review will discuss the emerging evidence for the development of post-COVID interstitial lung disease focusing on the pathophysiological mechanisms, incidence, diagnosis, and impact of this potentially new and emerging respiratory disease.

Serum Biomarkers in Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening complication of connective tissue diseases (CTDs) characterised by increased pulmonary arterial pressure and pulmonary vascular resistance. CTD-PAH is the result of a complex interplay among endothelial dysfunction and vascular remodelling, autoimmunity and inflammatory changes, ultimately leading to right heart dysfunction and failure. Due to the non-specific nature of the early symptoms and the lack of consensus on screening strategies-except for systemic sclerosis, with a yearly transthoracic echocardiography as recommended-CTD-PAH is often diagnosed at an advanced stage, when the pulmonary vessels are irreversibly damaged. According to the current guidelines, right heart catheterisation is the gold standard for the diagnosis of PAH; however, this technique is invasive, and may not be available in non-referral centres. Hence, there is a need for non-invasive tools to improve the early diagnosis and disease monitoring of CTD-PAH. Novel serum biomarkers may be an effective solution to this issue, as their detection is non-invasive, has a low cost and is reproducible. Our review aims to describe some of the most promising circulating biomarkers of CTD-PAH, classified according to their role in the pathophysiology of the disease.

Ephedrine alleviates bleomycin-induced pulmonary fibrosis by inhibiting epithelial-mesenchymal transition and restraining NF-κB signaling

Pulmonary fibrosis is a lethal and progressive pulmonary disorder in human beings. Ephedrine is a compound isolated from Ephedra and plays a regulatory role in inflammatory response. This study focused on the anti-pulmonary fibrosis effect of ephedrine and its potential molecular mechanism. After a mouse model of pulmonary fibrosis was established through bleomycin (BLM) induction, the survival percentage, body weight, and pulmonary index were measured. Hematoxylin-eosin staining and Masson's trichrome staining for lung tissues were performed to observe the pathological alterations. The viability of lung epithelial BEAS-2B cells, intracellular production of reactive oxygen species, and the levels of pro-inflammatory cytokines were examined by cell counting kit-8 assays, 2',7'-dichlorofluorescein diacetate (DCF-DA) staining, and enzyme-linked immunosorbent assay, respectively. Immunofluorescence staining was performed to determine E-cadherin and vimentin expression after BLM or ephedrine treatment. The mRNA and protein levels of cytokeratin-8, E-cadherin, α-SMA, and vimentin were subjected to quantitative polymerase chain reaction and immunoblotting. Experimental results revealed that ephedrine treatment rescued the repressive impact of BLM on BEAS-2B cell viability, and ephedrine inhibited BLM-induced overproduction of reactive oxygen species and inflammatory response in BEAS-2B cells. Additionally, ephedrine suppressed epithelial-mesenchymal transition (EMT) process stimulated by BLM treatment, as demonstrated by the reduced α-SMA and vimentin levels together with the increased cytokeratin-8 and E-cadherin levels in BLM + Ephedrine group. In addition, ephedrine inhibited NF-κB and activated Nrf-2 signaling in BLM-treated BEAS-2B cells. Moreover, ephedrine ameliorated pulmonary fibrosis in BLM-induced mice and improved the survival of model mice. In conclusion, ephedrine attenuates BLM-evoked pulmonary fibrosis by repressing EMT process via blocking NF-κB signaling and activating Nrf-2 signaling, suggesting that ephedrine might become a potential anti-pulmonary fibrosis agent in the future.

Decellularized Spinach Biomaterials Support Physiologically Relevant Mechanical Cyclic Strain and Prompt a Stretch-Induced Cellular Response

Recently, decellularized plant biomaterials have been explored for their use as tissue engineered substitutes. Herein, we expanded upon the investigation of the mechanical properties of these materials to explore their elasticity as many anatomical areas of the body require biomechanical dynamism. We first constructed a device to secure the scaffold and induce a strain within the physiological range of the normal human adult lung during breathing (12-20 movements/min; 10-20% elongation). Results showed that decellularized spinach leaves can support cyclic strain for 24 h and displayed heterogeneous local strain values (7.76-15.88%) as well as a Poisson's ratio (0.12) similar to that of mammalian lungs (10.67-19.67%; 0.01), as opposed to an incompressible homogeneous standard polymer (such as PDMS (10.85-12.71%; 0.4)). Imaging and mechanical testing showed that the vegetal scaffold exhibited strain hardening but maintained its structural architecture and water retention capacity, suggesting an unaltered porosity. Interestingly, we also showed that cells seeded on the scaffold can also sense the mechanical strain as demonstrated by a nuclear reorientation perpendicular to strain direction (63.3° compared to 41.2° for nonstretched cells), a nuclear location of YAP and increased expression of YAP target genes, a high cytoplasmic calcium level, and an elevated expression level of collagen genes (COL1A1, COL3A1, COL4A1, and COL6A) with an increased collagen secretion at the protein level. Taken together, these data demonstrated that decellularized plant leaf tissues have an inherent elastic property similar to that found in the mammalian system to which cells can sense and respond.

ASK1-ER stress pathway-mediated fibrotic-EV release contributes to the interaction of alveolar epithelial cells and lung fibroblasts to promote mechanical ventilation-induced pulmonary fibrosis

Recent clinical research has revealed that mechanical ventilation (MV) can initiate pulmonary fibrosis and induce mechanical ventilation-induced pulmonary fibrosis (MVPF). However, the underlying mechanism remains largely uncharacterized. Based on a mouse model of MVPF and an alveolar epithelial cell cyclic strain model, the present study explores the possible mechanism of MVPF. Single-cell RNA-sequencing and EV RNA-sequencing analysis revealed that MV promoted apoptosis signal-regulating kinase 1 (ASK1)-mediated endoplasmic reticulum (ER) stress pathway activation and extracellular vesicle (EV) release from alveolar epithelial cells. Furthermore, the ASK1-ER stress pathway was shown to mediate mechanical stretch (MS)- or MV-induced EV release and lung fibroblast activation in vivo and in vitro. These processes were suppressed by ER stress inhibitors or by silencing ASK1 with ASK1- short hairpin RNA (shRNA). In addition, MVPF was suppressed by inhibiting ASK1 and ER stress in vivo. Therefore, the present study demonstrates that ASK1-ER stress pathway-mediated fibrotic-EV release from alveolar epithelial cells contributes to fibroblast activation and the initiation of pulmonary fibrosis during MV. The inhibited release of EVs targeting the ASK1-ER stress pathway might be a promising treatment strategy for MVPF.

Host-Cell Surface Binding Targets in SARS-CoV-2 for Drug Design

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a major public health threat to all countries worldwide. SARS-CoV-2 interactions with its receptor are the first step in the invasion of the host cell. The coronavirus spike protein (S) is crucial in binding to receptors on host cells. Additionally, targeting the SARS-CoV-2 viral receptors is considered a therapeutic option in this regard. In this review of literature, we summarized five potential host cell receptors, as host-cell surface bindings, including angiotensin-converting enzyme 2 (ACE2), neuropilin 1 (NRP-1), dipeptidyl peptidase 4 (DPP4), glucose regulated protein-78 (GRP78), and cluster of differentiation 147 (CD147) related to the SARS-CoV-2 infection. Among these targets, ACE2 was recognized as the main SARS-CoV-2 receptor, expressed at a low/moderate level in the human respiratory system, which is also involved in SARS-CoV-2 entrance, so the virus may utilize other secondary receptors. Besides ACE2, CD147 was discovered as a novel SARS-CoV-2 receptor, CD147 appears to be an alternate receptor for SARSCoV- 2 infection. NRP-1, as a single-transmembrane glycoprotein, has been recently found to operate as an entrance factor and enhance SARS Coronavirus 2 (SARS-CoV-2) infection under in-vitro. DPP4, which was discovered as the first gene clustered with ACE2, may serve as a potential SARS-CoV-2 spike protein binding target. GRP78 could be recognized as a secondary receptor for SARS-CoV-2 because it is widely expressed at substantially greater levels, rather than ACE2, in bronchial epithelial cells and the respiratory mucosa. This review highlights recent literature on this topic.

Intersection of stem cell biology and engineering towards next generation in vitro models of human fibrosis

Human fibrotic diseases constitute a major health problem worldwide. Fibrosis involves significant etiological heterogeneity and encompasses a wide spectrum of diseases affecting various organs. To date, many fibrosis targeted therapeutic agents failed due to inadequate efficacy and poor prognosis. In order to dissect disease mechanisms and develop therapeutic solutions for fibrosis patients, in vitro disease models have gone a long way in terms of platform development. The introduction of engineered organ-on-a-chip platforms has brought a revolutionary dimension to the current fibrosis studies and discovery of anti-fibrotic therapeutics. Advances in human induced pluripotent stem cells and tissue engineering technologies are enabling significant progress in this field. Some of the most recent breakthroughs and emerging challenges are discussed, with an emphasis on engineering strategies for platform design, development, and application of machine learning on these models for anti-fibrotic drug discovery. In this review, we discuss engineered designs to model fibrosis and how biosensor and machine learning technologies combine to facilitate mechanistic studies of fibrosis and pre-clinical drug testing.

Midkine-A novel player in cardiovascular diseases

Midkine (MK) is a 13-kDa heparin-binding cytokine and growth factor with anti-apoptotic, pro-angiogenic, pro-inflammatory and anti-infective functions, that enable it to partake in a series of physiological and pathophysiological processes. In the past, research revolving around MK has concentrated on its roles in reproduction and development, tissue protection and repair as well as inflammatory and malignant processes. In the recent few years, MK's implication in a wide scope of cardiovascular diseases has been rigorously investigated. Nonetheless, there is still no broadly accepted consensus on whether MK exerts generally detrimental or favorable effects in cardiovascular diseases. The truth probably resides somewhere in-between and depends on the underlying physiological or pathophysiological condition. It is therefore crucial to thoroughly examine and appraise MK's participation in cardiovascular diseases. In this review, we introduce the MK gene and protein, its multiple receptors and signaling pathways along with its expression in the vascular system and its most substantial functions in cardiovascular biology. Further, we recapitulate the current evidence of MK's expression in cardiovascular diseases, addressing the various sources and modes of MK expression. Moreover, we summarize the most significant implications of MK in cardiovascular diseases with particular emphasis on MK's advantageous and injurious functions, highlighting its ample diagnostic and therapeutic potential. Also, we focus on conflicting roles of MK in a number of cardiovascular diseases and try to provide some clarity and guidance to MK's multifaceted roles. In summary, we aim to pave the way for MK-based diagnostics and therapies that could present promising tools in the diagnosis and treatment of cardiovascular diseases.

Elevated serum midkine levels in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected patients

BACKGROUND

The coronavirus disease-2019 (COVID-19) pandemic has caused important health, economic, social, and cultural problems worldwide. Recent findings demonstrate an excessive cytokine release during the disease development, especially in the seriously life-threatening form of COVID-19. Among other chemokines and cytokines that are released in high amounts at the infection site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), midkine (MK), which is a potent pro-inflammatory growth factor/ cytokine, can be also overexpressed and contribute to the pathophysiological process in patients infected with SARS-CoV-2.

MATERIALS AND METHOD

Serum was collected from 87 intensive care unit (ICU) patients that are COVID-19 positive and 50 healthy volunteers in the control group with a negative PCR test and without disease symptoms. Circulating MK concentration was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

COVID-19 patients had a significantly higher serum MK concentration compared to non-COVID-19 control subjects (1892.8 ± 1615.8 pg/mL versus 680.7 ± 907.6 pg/mL, respectively; P < 0.001). The cut-off MK concentration was 716.7 pg/ mL, with the sensitivity and specificity of 75.9 % and 76.0 %, respectively. The area under the receiver operating characteristic (ROC) curve of MK was = 0.827. Our findings showed that circulating MK levels are significantly increased in SARS-CoV-2 infected patients.

CONCLUSION

We suggest that MK is involved in the pathogenesis of COVID-19 and may be a part of hypercytokinaemia. Therefore, MK may serve as a supporting biomarker in the diagnosis of COVID-19, and blocking MK actions or its targets may attenuate the inflammatory process and the severity of the disease.

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.

Targeting of midkine alleviates cardiac hypertrophy via attenuation of oxidative stress and autophagy

Midkine levels are related to various diseases, including cardiovascular disease, renal disease and autoimmune disease. The research aimed to investigate the mitigation influence of downregulation of intermediate factors on myocardial hypertrophy induced by angiotensin Ⅱ (Ang), and whether downregulation of midkine could attenuate oxidative stress and autophagy. Induced myocardial hypertrophy of the mice model and treated HL-1 cells with Ang Ⅱ in vitro. The expressions of midkine were increased in the model and HL-1 cells with Ang II treatment. Midkine silence alleviated cardiac hypertrophy induced by Ang II, and inhibited the increases of atrial natriuretic peptide (ANP), Brain natriuretic peptide (BNP) and beta-myosin heavy chain (β-MHC) in the heart of mice. The raises of ANP, BNP and β-MHC in Ang II-induced HL-1 cells were also suppressed after midkine downregulation. Downregulating of midkine inhibited the increases of oxidative stress markers 8-OHdG, superoxide anions and MDA in the heart of mice or in the Ang II-treated HL-1 cells. The raises of LC3B, Atg3, Atg5 and Beclin1 in mice heart and in the Ang II.-induced HL-1 cells were attenuated after midkine silence. These outcomes showed that midkine was upregulated in myocardial hypertrophy mice. Targeting of midkine could alleviate cardiac hypertrophy via attenuation of oxidative stress and autophagy.

Midkine-Notch2 Pathway Mediates Excessive Proliferation of Airway Smooth Muscle Cells in Chronic Obstructive Lung Disease

Inflammation-induced proliferation of airway smooth muscle cells (ASMCs) and subsequent airway remodeling is a hallmark of chronic obstructive lung disease (COPD). The role of midkine (MK) in COPD is unclear. In this work, we explored the role of MK-Notch2 signaling in COPD by inhibiting the expression of MK using lentivirus shRNA in ASMCs in vitro and instillation of AAV9-MK in the airway of a COPD rat model in vivo. The results demonstrated that LPS decreased ASMC migration and proliferation, increased apoptosis and induced the expression of MK and Notch2 signaling molecules. Inhibition of MK exacerbated the changes in migration and proliferation but decreased the expression of MK and Notch2 signaling molecules. Rats treated with smoke fumigation and LPS showed features of COPD. The small airways of COPD rats were remodeled and lung function was significantly reduced. The expressions of TGF-β, ICAM-1, HA, MMP-9, PC-III, and LN in BALF and the expression of MK and Notch2 signaling molecules were significantly increased in the COPD rats compared with controls. Inhibition of MK reversed these changes. In conclusion, the MK-Notch2 pathway plays a key role in airway remodeling induced by ASMC proliferation. Targeting the MK-Notch2 pathway may be a new strategy for improving airway remodeling and preventing progressive decline of pulmonary function in COPD.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

Angiotensin-Converting Enzyme 2 Inhibits Lipopolysaccharide-Caused Lung Fibrosis via Downregulating the Transforming Growth Factor β-1/Smad2/Smad3 Pathway

BACKGROUND

In our previous studies, angiotensin-converting enzyme 2 (ACE2) was shown to alleviate the severity of acute lung injury, but its effects on the development of lung injury-caused lung fibrosis have not been studied.

METHODS

In the present study, the effects of ACE2 on lipopolysaccharide (LPS)-induced fibrosis in the lung were studied. The role of epithelial-mesenchymal transition (EMT) and that of the transforming growth factor β-1 (TGF-β1)/Smad2/Smad3 pathway in LPS-induced fibrosis in the lung were investigated.

RESULTS

ACE2 expression in the mouse model of LPS-induced lung fibrosis was significantly increased. ACE2 activator diminazene aceturate (DIZE) significantly reduced pulmonary fibrosis, decreased alpha-smooth muscle actin expression, collagen I, hydroxyproline, and TGF-β1 in the lung. DIZE significantly decreased TGF-β1 expression and the activation of Smad2 and Smad3. ACE2 overexpression inhibited the LPS-induced EMT in MLE-12 cells (lung epithelial cells) and small interfering RNA treatment of ACE2 stimulated EMT. ACE2 overexpression also inhibited TGF-β1 expression and activation of Smad2 and Smad3 in MLE-12 cells. Finally, after MLE-12 cells were treated with both ACE2 and TGF-β1 plasmid, TGF-β1 plasmid significantly abolished the effect of ACE2 plasmid on the EMT in MLE-12 cells.

CONCLUSION

Combined with the in vivo study, it was revealed that ACE2 can suppress the TGF-β1/Smad2/Smad3 pathway in lung type II epithelial cells, thus reversing their EMT and lung fibrosis. The present study provides basic research data for the application of ACE2 in lung injury-caused lung fibrosis treatment and clarifies the intervention mechanism of ACE2 in pulmonary fibrosis, which has potential value for clinical application.

SIGNIFICANCE STATEMENT

Angiotensin-converting enzyme 2 (ACE2) can inhibit the epithelial-mesenchymal transition (EMT) in lung type II epithelial cells and lung fibrosis. ACE2 can regulate the transforming growth factor β-1/Smad2/Smad3 pathway in lung type II epithelial cells, which may be the underlying mechanism of ACE2's effect on EMT and lung fibrosis.

NecroX-5 ameliorates bleomycin-induced pulmonary fibrosis via inhibiting NLRP3-mediated epithelial-mesenchymal transition

Background

Pulmonary fibrosis is a progressive and usually lethal pulmonary disease. Despite considerable research efforts, no effective therapeutic strategy for pulmonary fibrosis has been developed. NecroX-5 has been reported to possess anti-inflammatory, anti-oxidative and anti-tumor activities. In the present study, we aimed to determine whether NecroX-5 exhibits antifibrotic property in bleomycin (BLM)-induced pulmonary fibrosis.

Results

We found that pre-treatment with NecroX-5 alleviated inflammatory response, reduced oxidative stress, inhibited epithelial–mesenchymal transition (EMT), and ameliorated pulmonary fibrosis in vivo and in vitro. Our data further indicated that NecroX-5 substantially reduced activation of NLRP3 inflammasome and TGF-β1/Smad2/3 signaling in vivo and in vitro. Additionally, NLRP3 overexpression significantly reversed the protective effects of NecroX-5 in lung epithelial cells exposed to BLM.

Conclusions

Overall, our results demonstrate the potent antifibrotic properties of NecroX-5 and its therapeutic potential for pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02044-3.

Functional ACE2 deficiency leading to angiotensin imbalance in the pathophysiology of COVID-19

SARS-CoV-2, the virus responsible for COVID-19, uses angiotensin converting enzyme 2 (ACE2) as its primary cell-surface receptor. ACE2 is a key enzyme in the counter-regulatory pathway of the broader renin-angiotensin system (RAS) that has been implicated in a broad array of human pathology. The RAS is composed of two competing pathways that work in opposition to each other: the "conventional" arm involving angiotensin converting enzyme (ACE) generating angiotensin-2 and the more recently identified ACE2 pathway that generates angiotensin (1-7). Following the original SARS pandemic, additional studies suggested that coronaviral binding to ACE2 resulted in downregulation of the membrane-bound enzyme. Given the similarities between the two viruses, many have posited a similar process with SARS-CoV-2. Proponents of this ACE2 deficiency model argue that downregulation of ACE2 limits its enzymatic function, thereby skewing the delicate balance between the two competing arms of the RAS. In this review we critically examine this model. The available data remain incomplete but are consistent with the possibility that the broad multisystem dysfunction of COVID-19 is due in large part to functional ACE2 deficiency leading to angiotensin imbalance with consequent immune dysregulation and endothelial cell dysfunction.

The effect of N6-methyladenosine (m6A) factors on the development of acute respiratory distress syndrome in the mouse model

Acute respiratory distress syndrome (ARDS) can cause loss of alveolar-capillary membrane integrity and life-threatening immune responses. The underlying molecular mechanisms of ARDS remain unclear. N6-methyladenosine (m6A)-RNA modification plays an important part in many biological processes. However, it is not clear whether ARDS alters RNA methylation in lung tissue. We tried to investigate the changes of m6A-RNA methylation in lung tissues of lipopolysaccharide (LPS)-induced ARDS mice. Lung tissue samples were collected to detect the expression of m6A factors through hematoxylin and eosin (HE) staining, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), immunohistochemical analysis and western blot. The overall m6A levels in lung tissue of ARDS in mouse were detected by UPLC-UV-MS. HE staining showed that the degree of the inflammatory response was more severe in the LPS-3 h group. The mRNA expression of YTHDF1, YTHDC1 and IGFBP3 was remarkably up-regulated at, respectively, 6, 6 and 12 h after LPS treatment. The mRNA expression of METTL16, FTO, METTL3, KIAA1429, RBM15, ALKBH5, YTHDF2, YTHDF3, YTHDC2 and IGFBP2 was significantly down-regulated at 24 h after LPS treatment. The protein expression of METTL16 and FTO increased, YTHDC1, IGFBP3 YTHDF1 and YTHDF3 showed a down-regulation trend after LPS induction. Overall m6A-RNA methylation levels were significantly increased at 6 h after LPS induction. In ARDS mice, LPS-induced m6A methylation may be involved in the expression regulation of inflammatory factors and may play important roles in the occurrence and development of lung tissue. It is suggested that m6A modification may be a promising therapeutic target for ARDS.

Mechanotransduction Regulates the Interplays Between Alveolar Epithelial and Vascular Endothelial Cells in Lung

Mechanical stress plays a critical role among development, functional maturation, and pathogenesis of pulmonary tissues, especially for the alveolar epithelial cells and vascular endothelial cells located in the microenvironment established with vascular network and bronchial-alveolar network. Alveolar epithelial cells are mainly loaded by cyclic strain and air pressure tension. While vascular endothelial cells are exposed to shear stress and cyclic strain. Currently, the emerging evidences demonstrated that non-physiological mechanical forces would lead to several pulmonary diseases, including pulmonary hypertension, fibrosis, and ventilation induced lung injury. Furthermore, a series of intracellular signaling had been identified to be involved in mechanotransduction and participated in regulating the physiological homeostasis and pathophysiological process. Besides, the communications between alveolar epithelium and vascular endothelium under non-physiological stress contribute to the remodeling of the pulmonary micro-environment in collaboration, including hypoxia induced injuries, endothelial permeability impairment, extracellular matrix stiffness elevation, metabolic alternation, and inflammation activation. In this review, we aim to summarize the current understandings of mechanotransduction on the relation between mechanical forces acting on the lung and biological response in mechanical overloading related diseases. We also would like to emphasize the interplays between alveolar epithelium and vascular endothelium, providing new insights into pulmonary diseases pathogenesis, and potential targets for therapy.

Antioxidants as Therapeutic Agents in Acute Respiratory Distress Syndrome (ARDS) Treatment-From Mice to Men

Acute respiratory distress syndrome (ARDS) is a major cause of patient mortality in intensive care units (ICUs) worldwide. Considering that no causative treatment but only symptomatic care is available, it is obvious that there is a high unmet medical need for a new therapeutic concept. One reason for a missing etiologic therapy strategy is the multifactorial origin of ARDS, which leads to a large heterogeneity of patients. This review summarizes the various kinds of ARDS onset with a special focus on the role of reactive oxygen species (ROS), which are generally linked to ARDS development and progression. Taking a closer look at the data which already have been established in mouse models, this review finally proposes the translation of these results on successful antioxidant use in a personalized approach to the ICU patient as a potential adjuvant to standard ARDS treatment.

Role of NRF2 and Sirtuin activators in COVID-19

COVID-19 is a pandemic requiring immediate solution for treatment because of its complex pathophysiology. Exploration of novel targets and thus treatment will be life savers which is the need of the hour. 2 host factors- TMPRSS2 and ACE2 are responsible for the way the virus will enter and replicate in the host. Also NRF2 is an important protein responsible for its anti-inflammatory role by multiple mechanisms of action like inhibition of NF-kB, suppression of pro-inflammatory genes, etc. NRF2 is deacetylated by Sirtuins and therefore both have a direct association. Absence of SIRT indicates inhibition of NRF2 expression and thus no anti-oxidative and anti-inflammatory protection for the cell. Therefore, we propose that NRF2 activators and/or SIRT activators can be evaluated to check their efficacy in ameliorating the symptoms of COVID-19.

Serum midkine level might be a diagnostic tool for COVID19 disease in pregnancy: From the disease severity, hospitalization and disease progression respects

BACKGROUND

New biomarkers for diagnosis and monitoring the COVID-19 disease are the most important topics to be studied recently. We aimed to investigate the association between midkine levels and disease severity in pregnant women with COVID-19.

METHODS

Totally 186 pregnant women were participated in this study. 96 of them were healthy pregnant women, 90 of them were pregnant women with COVID19. Pregnant women were evaluated according to their trimesters. Serum midkine level, biochemical profile clinical and disease severity outcomes of pregnant women were obtained.

RESULTS

Our results showed that pregnant women with COVID19 have significantly increased serum midkine level compared to healthy pregnant women (1.801 ± 0.977 vs 0.815 ± 0.294 ng/dL). According to the data among each trimester, it was shown that there were significant increase in serum midkine level during all pregnancy trimesters (1st trimester Control Group: 0.714 ± 0.148, COVID-19 group 1.623 ± 0.824, p < 0.0001; 2nd trimester Control Group: 0.731 ± 0.261, COVID-19 group 2.059 ± 1.146, p < 0.0001; 3rd trimester Control Group: 1.0 ± 0.35, COVID-19 group 1.723 ± 0.907, p = 0.001). Serum midkine levels were significantly different between disease severity subgroups of pregnant women with COVID19; moderate and severe/critic groups had significantly higher serum midkine level than mild group. There was also significant correlation between serum midkine level and severity status (p:0.0001, r: 0.468). The most striking results of serum midkine levels were corelation between length of hospitalization (p: 0.01, r: 0.430) and O² saturation (p < 0.0001, r: -0.521). ROC curve analysis showed that serum midkine level might be a tool for predicting COVID-19 in pregnant women with COVID-19 (AUC: 0.912, 95% CI: [0.871, 0.952], p < 0.0001) CONCLUSION: Our data showed that there is an obvious relation between COVID19 progression and serum midkine level for the first time which might be used for monitoring the disease process.

Binding of SARS-COV-2 (COVID-19) and SARS-COV to human ACE2: Identifying binding sites and consequences on ACE2 stiffness

The SARS-CoV-2 coronavirus (COVID-19) that is causing the massive global pandemic exhibits similar human cell invasion mechanism as the coronavirus SARS-CoV, which had significantly lower fatalities. The cell membrane protein Angiotensin-converting enzyme 2 (ACE2) is the initiation point for both the coronavirus infections in humans. Here, we model the molecular interactions and mechanical properties of ACE2 with both SARS-CoV and COVID-19 spike protein receptor-binding domains (RBD). We report that the COVID-19 spike RBD interacts with ACE2 more strongly and at only two protein residues, as compared to multi-residue interaction of the SARS-CoV. Although both coronaviruses stiffen the ACE2, the impact of COVID-19 is six times larger, which points towards differences in the severity of the reported respiratory distress. The recognition of specific residues of ACE2 attachments to coronaviruses is important as the residues suggest potential sites of intervention to inhibit attachment and subsequent entry of the COVID-19 into human host cells

The growth factor/cytokine midkine may participate in cytokine storm and contribute to the pathogenesis of severe acute respiratory syndrome coronavirus 2-infected patients

Background

The current coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged in Wuhan, China, and has rapidly become a global challenge, creating major challenges to health systems in almost every country in the world it has turned into a pandemic. COVID-19 poses a risky clinical situation that can range from mild illness to severe respiratory failure, requiring admission to intensive care.

Main body

It is known that SARS-CoV-2 infection causes a cytokine storm in some critically ill patients. However, more and more evidence showed that there is a dramatic increase in cytokine levels in patients diagnosed with COVID-19. Midkine (MK) is involved in various physiological and pathological processes, which some of them are desired and beneficial such as controlling tissue repair and antimicrobial effects, but some others are harmful such as promoting inflammation, carcinogenesis, and chemoresistance. Also, MK is expressed in inflammatory cells and released by endothelial cells under hypoxic conditions.

Conclusions

Considering all this information, there are strong data that midkine, an important cytokine known to increase in inflammatory diseases, may be overexpressed in patients who are positive for COVID-19. The overexpression of MK reveals a picture leading to fibrosis and damage in the lung. Therefore, questions arise about how the expression  of  MK  changes in COVID-19 patients and can we use it as an inflammation biomarker or in the treatment protocol in the future.

Six-Month Pulmonary Impairment after Severe COVID-19: A Prospective, Multicentre Follow-Up Study

BACKGROUND

Long-term pulmonary sequelae following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia are not yet confirmed; however, preliminary observations suggest a possible relevant clinical, functional, and radiological impairment.

OBJECTIVES

The aim of this study was to identify and characterize pulmonary sequelae caused by SARS-CoV-2 pneumonia at 6-month follow-up.

METHODS

In this multicentre, prospective, observational cohort study, patients hospitalized for SARS-CoV-2 pneumonia and without prior diagnosis of structural lung diseases were stratified by maximum ventilatory support ("oxygen only," "continuous positive airway pressure," and "invasive mechanical ventilation") and followed up at 6 months from discharge. Pulmonary function tests and diffusion capacity for carbon monoxide (DLCO), 6-min walking test, chest X-ray, physical examination, and modified Medical Research Council (mMRC) dyspnoea score were collected.

RESULTS

Between March and June 2020, 312 patients were enrolled (83, 27% women; median interquartile range age 61.1 [53.4, 69.3] years). The parameters that showed the highest rate of impairment were DLCO and chest X-ray, in 46% and 25% of patients, respectively. However, only a minority of patients reported dyspnoea (31%), defined as mMRC ≥1, or showed restrictive ventilatory defects (9%). In the logistic regression model, having asthma as a comorbidity was associated with DLCO impairment at follow-up, while prophylactic heparin administration during hospitalization appeared as a protective factor. The need for invasive ventilatory support during hospitalization was associated with chest imaging abnormalities.

CONCLUSIONS

DLCO and radiological assessment appear to be the most sensitive tools to monitor patients with the coronavirus disease 2019 (COVID-19) during follow-up. Future studies with longer follow-up are warranted to better understand pulmonary sequelae.

LncRNA-ATB regulates epithelial-mesenchymal transition progression in pulmonary fibrosis via sponging miR-29b-2-5p and miR-34c-3p

Dysregulation of non‐coding RNAs (ncRNAs) has been proved to play pivotal roles in epithelial‐mesenchymal transition (EMT) and fibrosis. We have previously demonstrated the crucial function of long non‐coding RNA (lncRNA) ATB in silica‐induced pulmonary fibrosis‐related EMT progression. However, the underlying molecular mechanism has not been fully elucidated. Here, we verified miR‐29b‐2‐5p and miR‐34c‐3p as two vital downstream targets of lncRNA‐ATB. As opposed to lncRNA‐ATB, a significant reduction of both miR‐29b‐2‐5p and miR‐34c‐3p was observed in lung epithelial cells treated with TGF‐β1 and a murine silicosis model. Overexpression miR‐29b‐2‐5p or miR‐34c‐3p inhibited EMT process and abrogated the pro‐fibrotic effects of lncRNA‐ATB in vitro. Further, the ectopic expression of miR‐29b‐2‐5p and miR‐34c‐3p with chemotherapy attenuated silica‐induced pulmonary fibrosis in vivo. Mechanistically, TGF‐β1‐induced lncRNA‐ATB accelerated EMT as a sponge of miR‐29b‐2‐5p and miR‐34c‐3p and shared miRNA response elements with MEKK2 and NOTCH2, thus relieving these two molecules from miRNA‐mediated translational repression. Interestingly, the co‐transfection of miR‐29b‐2‐5p and miR‐34c‐3p showed a synergistic suppression effect on EMT in vitro. Furthermore, the co‐expression of these two miRNAs by using adeno‐associated virus (AAV) better alleviated silica‐induced fibrogenesis than single miRNA. Approaches aiming at lncRNA‐ATB and its downstream effectors may represent new effective therapeutic strategies in pulmonary fibrosis.

H. sinensis mycelium inhibits epithelial-mesenchymal transition by inactivating the midkine pathway in pulmonary fibrosis

The medical fungus Hirsutella sinensis has been used as a Chinese folk health supplement because of its immunomodulatory properties. Our previous studies established the antifibrotic action of Hirsutella sinensis mycelium (HSM) in the lung. The epithelial-mesenchymal transition (EMT) is involved in the pathogenesis of idiopathic pulmonary fibrosis. The present study investigates the role of HSM in mediating EMT during the development of pulmonary fibrosis. HSM significantly inhibits bleomycin (BLM)-induced pulmonary fibrosis by blocking the EMT. In addition, the expression levels of midkine are increased in the lungs of the BLM-induced group. Further analysis of the results indicates that the mRNA level of midkine correlated positively with EMT. HSM markedly abrogates the transforming growth factor β-induced EMT-like phenotype and behavior in vitro. The activation of midkine related signaling pathway is ameliorated following HSM treatment, whereas this extract also caused an effective attenuation of the induction of EMT (caused by midkine overexpression) in vitro. Results further confirm that oral medication of HSM disrupted the midkine pathway in vivo. Overall, findings suggest that the midkine pathway and the regulation of the EMT may be considered novel candidate therapeutic targets for the antifibrotic effects caused by HSM.