Targeting Hypoxia Inducible Factors-1α As a Novel Therapy in Fibrosis

The hippo-YAP1/HIF-1α pathway mediates arsenic-induced renal fibrosis

Epidemiological evidence reveals that arsenic increases the risk of chronic kidney disease (CKD) in humans, but its mechanism of action has so far been unclear. Fibrosis is the manifestation of end-stage renal disease. Hypoxia is recognized as a vital event accompanying the progression of renal fibrosis. KM mice were exposed to 0, 20, 40, and 80 mg/L NaAsO2 for 12 weeks. HK-2 cells were treated with 1 μM NaAsO2 for 4 weeks. The results showed that arsenic increased the expression of hypoxia-inducible factor 1α (HIF-1α) (P < 0.05), which is involved in inorganic arsenic-induced renal fibrosis. The Hippo signaling pathway is the upstream signal of HIF-1α and the kinase cascade of Large tumor suppressor kinase 1 (LATS1) and Yes-associated protein 1 (YAP1) is the heart of the Hippo pathway. Our results showed that protein expressions of LATS1 and phosphorylated YAP1 were decreased, and dephosphorylated YAP1 expression increased in arsenic-treated mouse kidneys and human HK-2 cells (P < 0.05). Our research manifested that arsenic treatment suppressed the Hippo signaling and induced high expression of YAP1 into the nucleus. We also found that YAP1 was involved in arsenic-induced renal fibrosis by forming a complex with HIF-1α and maintaining HIF-1α stability. Our findings indicate that YAP1 is a potential target for molecular-based therapy for arsenic-mediated renal fibrosis.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

Targeting Pulmonary Fibrosis by SLC1A5-Dependent Glutamine Transport Blockade

The neutral amino acid glutamine plays a central role in TGF-β (transforming growth factor-β)-induced myofibroblast activation and differentiation. Cells take up glutamine mainly through a transporter expressed on the cell surface known as solute carrier SLC1A5 (solute carrier transporter 1A5). In the present work, we demonstrated that profibrotic actions of TGF-β are mediated, at least in part, through a metabolic maladaptation of SLC1A5 and that targeting SLC1A5 abrogates multiple facets of fibroblast activation. This approach could thus represent a novel therapeutic strategy to treat patients with fibroproliferative diseases. We found that SLC1A5 was highly expressed in fibrotic lung fibroblasts and fibroblasts isolated from idiopathic pulmonary fibrosis lungs. The expression of profibrotic targets, cell migration, and anchorage-independent growth by TGF-β required the activity of SLC1A5. Loss or inhibition of SLC1A5 function enhanced fibroblast susceptibility to autophagy; suppressed mTOR, HIF (hypoxia-inducible factor), and Myc signaling; and impaired mitochondrial function, ATP production, and glycolysis. Pharmacological inhibition of SLC1A5 by the small-molecule inhibitor V-9302 shifted fibroblast transcriptional profiles from profibrotic to fibrosis resolving and attenuated fibrosis in a bleomycin-treated mouse model of lung fibrosis. This is the first study, to our knowledge, to demonstrate the utility of a pharmacological inhibitor of glutamine transport in fibrosis, providing a framework for new paradigm-shifting therapies targeting cellular metabolism for this devastating disease.

Hybrid computational modeling highlights reverse warburg effect in breast cancer-associated fibroblasts

Cancer-associated fibroblasts (CAFs) are amongst the key players of the tumor microenvironment (TME) and are involved in cancer initiation, progression, and resistance to therapy. They exhibit aggressive phenotypes affecting extracellular matrix remodeling, angiogenesis, immune system modulation, tumor growth, and proliferation. CAFs phenotypic changes appear to be associated with metabolic alterations, notably a reverse Warburg effect that may drive fibroblasts transformation. However, its precise molecular mechanisms and regulatory drivers are still under investigation. Deciphering the reverse Warburg effect in breast CAFs may contribute to a better understanding of the interplay between TME and tumor cells, leading to new treatment strategies. In this regard, dynamic modeling approaches able to span multiple biological layers are essential to capture the emergent properties of various biological entities when complex and intertwined pathways are involved. This work presents the first hybrid large-scale computational model for breast CAFs covering major cellular signaling, gene regulation, and metabolic processes. It was generated by combining a cell- and disease-specific asynchronous Boolean model with a generic core metabolic network leveraging both data-driven and manual curation approaches. This model reproduces the experimentally observed reverse Warburg effect in breast CAFs and further identifies Hypoxia-Inducible Factor 1 (HIF-1) as its key molecular driver. Targeting HIF-1 as part of a TME-centered therapeutic strategy may prove beneficial in the treatment of breast cancer by addressing the reverse Warburg effect. Such findings in CAFs, in light of our previously published results in rheumatoid arthritis synovial fibroblasts, point to a common HIF-1-driven metabolic reprogramming of fibroblasts in breast cancer and rheumatoid arthritis.

EP300 as a Molecular Integrator of Fibrotic Transcriptional Programs

Fibrosis is a condition characterized by the excessive accumulation of extracellular matrix proteins in tissues, leading to organ dysfunction and failure. Recent studies have identified EP300, a histone acetyltransferase, as a crucial regulator of the epigenetic changes that contribute to fibrosis. In fact, EP300-mediated acetylation of histones alters global chromatin structure and gene expression, promoting the development and progression of fibrosis. Here, we review the role of EP300-mediated epigenetic regulation in multi-organ fibrosis and its potential as a therapeutic target. We discuss the preclinical evidence that suggests that EP300 inhibition can attenuate fibrosis-related molecular processes, including extracellular matrix deposition, inflammation, and epithelial-to-mesenchymal transition. We also highlight the contributions of small molecule inhibitors and gene therapy approaches targeting EP300 as novel therapies against fibrosis.

Kidney Damage in Long COVID: Studies in Experimental Mice

Signs and symptoms involving multiple organ systems which persist for weeks or months to years after the initial SARS-CoV-2 infection (also known as PASC or long COVID) are common complications of individuals with COVID-19. We recently reported pathophysiological changes in various organs post-acute infection of mice with mouse hepatitis virus-1 (MHV-1, a coronavirus) (7 days) and after long-term post-infection (12 months). One of the organs severely affected in this animal model is the kidney, which correlated well with human studies showing kidney injury post-SARS-CoV-2 infection. Our long-term post-infection pathological observation in kidneys includes the development of edema and inflammation of the renal parenchyma, severe acute tubular necrosis, and infiltration of macrophages and lymphocytes, in addition to changes observed in both acute and long-term post-infection, which include tubular epithelial cell degenerative changes, peritubular vessel congestion, proximal and distal tubular necrosis, hemorrhage in the interstitial tissue, and vacuolation of renal tubules. These findings strongly suggest the possible development of renal fibrosis, in particular in the long-term post-infection. Accordingly, we investigated whether the signaling system that is known to initiate the above-mentioned changes in kidneys in other conditions is also activated in long-term post-MHV-1 infection. We found increased TGF-β1, FGF23, NGAL, IL-18, HIF1-α, TLR2, YKL-40, and B2M mRNA levels in long-term post-MHV-1 infection, but not EGFR, TNFR1, BCL3, and WFDC2. However, only neutrophil gelatinase-associated lipocalin (NGAL) increased in acute infection (7 days). Immunoblot studies showed an elevation in protein levels of HIF1-α, TLR-2, and EGFR in long-term post-MHV-1 infection, while KIM-1 and MMP-7 protein levels are increased in acute infection. Treatment with a synthetic peptide, SPIKENET (SPK), which inhibits spike protein binding, reduced NGAL mRNA in acute infection, and decreased TGF-β1, BCL3 mRNA, EGFR, HIF1-α, and TLR-2 protein levels long-term post-MHV-1 infection. These findings suggest that fibrotic events may initiate early in SARS-CoV-2 infection, leading to pronounced kidney fibrosis in long COVID. Targeting these factors therapeutically may prevent acute or long-COVID-associated kidney complications.

Role of innate immunity and systemic inflammation in cystic fibrosis disease progression

Pathophysiological manifestations of cystic fibrosis (CF) result from a functional defect in the cystic fibrosis transmembrane conductance regulator (CFTR) paving way for mucus obstruction and pathogen colonization. The role of CFTR in modulating immune cell function and vascular integrity, irrespective of mucus thickening, in determining the host cell response to pathogens/allergens and causing systemic inflammation is least appreciated. Since CFTR plays a key role in the conductance of anions like Cl^-, loss of CFTR function could affect various basic cellular processes, such as cellular homeostasis, lysosome acidification, and redox balance. CFTR aids in endotoxin tolerance by regulating Toll-like receptor-mediated signaling resulting in uncontrolled activation of innate immune cells. Although leukocytes of CF patients are hyperactivated, they exhibit compromised phagosome activity thus favouring the orchestration of sepsis from defective pathogen clearance. This review will emphasize the importance of innate immunity and systemic inflammatory response in the development of CF and other CFTR-associated pathologies.

Polymer-Functionalized Mitochondrial Transplantation to Fibroblasts Counteracts a Pro-Fibrotic Phenotype

Fibroblast-to-myofibroblast transition (FMT) leads to excessive extracellular matrix (ECM) deposition-a well-known hallmark of fibrotic disease. Transforming growth factor-β (TGF-β) is the primary cytokine driving FMT, and this phenotypic conversion is associated with mitochondrial dysfunction, notably a metabolic reprogramming towards enhanced glycolysis. The objective of this study was to examine whether the establishment of favorable metabolic phenotypes in TGF-β-stimulated fibroblasts could attenuate FMT. The hypothesis was that mitochondrial replenishment of TGF-β-stimulated fibroblasts would counteract a shift towards glycolytic metabolism, consequently offsetting pro-fibrotic processes. Isolated mitochondria, functionalized with a dextran and triphenylphosphonium (TPP) (Dex-TPP) polymer conjugate, were administered to fibroblasts (MRC-5 cells) stimulated with TGF-β, and effects on bioenergetics and fibrotic programming were subsequently examined. Results demonstrate that TGF-β stimulation of fibroblasts led to FMT, which was associated with enhanced glycolysis. Dex-TPP-coated mitochondria (Dex-TPP/Mt) delivery to TGF-β-stimulated fibroblasts abrogated a metabolic shift towards glycolysis and led to a reduction in reactive oxygen species (ROS) generation. Importantly, TGF-β-stimulated fibroblasts treated with Dex-TPP/Mt had lessened expression of FMT markers and ECM proteins, as well as reduced migration and proliferation. Findings highlight the potential of mitochondrial transfer, as well as other strategies involving functional reinforcement of mitochondria, as viable therapeutic modalities in fibrosis.

An integrated cell atlas of the lung in health and disease

Single-cell technologies have transformed our understanding of human tissues. Yet, studies typically capture only a limited number of donors and disagree on cell type definitions. Integrating many single-cell datasets can address these limitations of individual studies and capture the variability present in the population. Here we present the integrated Human Lung Cell Atlas (HLCA), combining 49 datasets of the human respiratory system into a single atlas spanning over 2.4 million cells from 486 individuals. The HLCA presents a consensus cell type re-annotation with matching marker genes, including annotations of rare and previously undescribed cell types. Leveraging the number and diversity of individuals in the HLCA, we identify gene modules that are associated with demographic covariates such as age, sex and body mass index, as well as gene modules changing expression along the proximal-to-distal axis of the bronchial tree. Mapping new data to the HLCA enables rapid data annotation and interpretation. Using the HLCA as a reference for the study of disease, we identify shared cell states across multiple lung diseases, including SPP1+ profibrotic monocyte-derived macrophages in COVID-19, pulmonary fibrosis and lung carcinoma. Overall, the HLCA serves as an example for the development and use of large-scale, cross-dataset organ atlases within the Human Cell Atlas.

Recent Advances (2015-2020) in Drug Discovery for Attenuation of Pulmonary Fibrosis and COPD

A condition of scarring of lung tissue due to a wide range of causes (such as environmental pollution, cigarette smoking (CS), lung diseases, some medications, etc.) has been reported as pulmonary fibrosis (PF). This has become a serious problem all over the world due to the lack of efficient drugs for treatment or cure. To date, no drug has been designed that could inhibit fibrosis. However, few medications have been reported to reduce the rate of fibrosis. Meanwhile, ongoing research indicates pulmonary fibrosis can be treated in its initial stages when symptoms are mild. Here, an attempt is made to summarize the recent studies on the effects of various chemical drugs that attenuate PF and increase patients' quality of life. The review is classified based on the nature of the drug molecules, e.g., natural/biomolecule-based, synthetic-molecule-based PF inhibitors, etc. Here, the mechanisms through which the drug molecules attenuate PF are discussed. It is shown that inhibitory molecules can significantly decrease the TGF-β1, profibrotic factors, proteins responsible for inflammation, pro-fibrogenic cytokines, etc., thereby ameliorating the progress of PF. This review may be useful in designing better drugs that could reduce the fibrosis process drastically or even cure the disease to some extent.

Involvement of lysyl oxidase in the pathogenesis of arterial stiffness in chronic kidney disease

Patients with chronic kidney disease (CKD) are at increased risk for adverse cardiovascular events. CKD is associated with increases in arterial stiffness, whereas improvements in arterial stiffness correlate with better survival. However, arterial stiffness is increased early in CKD, suggesting that there might be additional factors, unique to kidney disease, that increase arterial stiffness. Lysyl oxidase (LOX) is a key mediator of collagen cross linking and matrix remodeling. LOX is predominantly expressed in the cardiovascular system, and its upregulation has been associated with increased tissue stiffening and extracellular matrix remodeling. Thus, this study was designed to evaluate the role of increased LOX activity in inducing aortic stiffness in CKD and whether β-aminopropionitrile (BAPN), a LOX inhibitor, could prevent aortic stiffness by reducing collagen cross linking. Eight-week-old male C57BL/6 mice were subjected to 5/6 nephrectomy (Nx) or sham surgery. Two weeks after surgery, mice were randomized to BAPN (300 mg/kg/day in water) or vehicle treatment for 4 wk. Aortic stiffness was assessed by pulse wave velocity (PWV) using Doppler ultrasound. Aortic levels of LOX were assessed by ELISA, and cross-linked total collagen levels were analyzed by mass spectrometry and Sircol assay. Nx mice showed increased PWV and aortic wall remodeling compared with control mice. Collagen cross linking was increased in parallel with the increases in total collagen in the aorta of Nx mice. In contrast, Nx mice that received BAPN treatment showed decreased cross-linked collagens and PWV compared with that received vehicle treatment. Our results indicated that LOX might be an early and key mediator of aortic stiffness in CKD.NEW & NOTEWORTHY Arterial stiffness in CKD is associated with adverse cardiovascular outcomes. However, the mechanisms underlying increased aortic stiffness in CKD are unclear. Herein, we demonstrated that 1) increased aortic stiffness in CKD is independent of hypertension and calcification and 2) LOX-mediated changes in extracellular matrix are at least in part responsible for increased aortic stiffness in CKD. Prevention of excess LOX may have therapeutic potential in alleviating increased aortic stiffness and improving cardiovascular disease in CKD.

Endothelial-to-Mesenchymal Transition: Potential Target of Doxorubicin-Induced Cardiotoxicity

The use of chemotherapeutic agents is becoming more frequent as the proportion of new oncology patients increases worldwide, with prolonged survival after treatment. As one of the most popular chemotherapy drugs, doxorubicin plays a substantial role in the treatment of tumors. Unfortunately, the use of doxorubicin is associated with several adverse effects, particularly severe cardiotoxicity that can be life-threatening, which greatly limits its clinical use. For decades, scientists have tried to explore many cardioprotective agents and therapeutic approaches, but their efficacy remains controversial, and some drugs have even brought about significant adverse effects. The concrete molecular mechanism of doxorubicin-induced cardiotoxicity is still to be unraveled, yet endothelial damage is gradually being identified as an important mechanism triggering the development and progression of doxorubicin-induced cardiotoxicity. Endothelial-to-mesenchymal transition (EndMT), a fundamental process regulating morphogenesis in multicellular organisms, is recognized to be associated with endothelial damage repair and acts as an important factor in the progression of cardiovascular diseases, tumors, and rheumatic immune diseases. Mounting evidence suggests that endothelial-mesenchymal transition may play a non-negligible role in doxorubicin-induced cardiotoxicity. In this paper, we reviewed the molecular mechanisms and signaling pathways of EndMT and outlined the molecular mechanisms of doxorubicin-induced cardiotoxicity and the current therapeutic advances. Furthermore, we summarized the basic principles of doxorubicin-induced endothelial-mesenchymal transition that lead to endothelial dysfunction and cardiotoxicity, aiming to provide suggestions or new ideas for the prevention and treatment of doxorubicin-induced endothelial and cardiac injury.

Glycolytic reprogramming is involved in tissue remodeling on chronic rhinosinusitis

BACKGROUND

Glycolytic reprogramming is a key feature of chronic inflammatory disease. Extracellular matrix (ECM) produced by myofibroblasts plays an important role in tissue remodeling of nasal mucosa in chronic rhinosinusitis (CRS). This study aimed to determine whether glycolytic reprogramming contributes to myofibroblast differentiation and ECM production in nasal fibroblasts.

METHODS

Primary nasal fibroblasts were isolated from the nasal mucosa of patients with CRS. Glycolytic reprogramming was assessed by measuring the extracellular acidification and oxygen consumption rates in nasal fibroblast, with and without transforming growth factor beta 1 (TGF-β1) treatment. Expression of glycolytic enzymes and ECM components was measured by real-time polymerase chain reaction, western blotting, and immunocytochemical staining. Gene set enrichment analysis was performed using whole RNA-sequencing data of nasal mucosa of healthy donors and patients with CRS.

RESULT

Glycolysis of nasal fibroblasts stimulated with TGF-B1 was upregulated along with glycolytic enzymes. Hypoxia-inducing factor (HIF)-1α was a high-level regulator of glycolysis, and increased HIF-1α expression promoted glycolysis of nasal fibroblasts, and inhibition of HIF-1α down-regulated myofibroblasts differentiation and ECM production.

CONCLUSION

This study suggests that inhibition of the glycolytic enzyme and HIF-1α in nasal fibroblasts regulates myofibroblast differentiation and ECM generation associated with nasal mucosa remodeling.

Implantation and tracing of green fluorescent protein-expressing adipose-derived stem cells in peri-implant capsular fibrosis

BACKGROUND

Adipose-derived stem cells (ASCs) have been reported to reduce fibrosis in various tissues. In this study, we investigated the inhibitory role of ASCs on capsule formation by analyzing the histologic, cellular, and molecular changes in a mouse model of peri-implant fibrosis. We also investigated the fate and distribution of ASCs in the peri-implant capsule.

METHODS

To establish a peri-implant fibrosis model, customized silicone implants were inserted into the dorsal site of C57BL/6 wild-type mice. ASCs were harvested from the fat tissues of transgenic mice that express a green fluorescent protein (GFP-ASCs) and then injected into the peri-implant space of recipient mice. The peri-implant tissues were harvested from postoperative week 2 to 8. We measured the capsule thickness, distribution, and differentiation of GFP-ASCs, as well as the cellular and molecular changes in capsular tissue following ASC treatment.

RESULTS

Injected GFP-ASCs were distributed within the peri-implant capsule and proliferated. Administration of ASCs reduced the capsule thickness, decreased the number of myofibroblasts and macrophages in the capsule, and decreased the mRNA level of fibrogenic genes within the peri-implant tissue. Angiogenesis was enhanced due to trans-differentiation of ASCs into vascular endothelial cells, and tissue hypoxia was relieved upon ASC treatment.

CONCLUSIONS

We uncovered that implanted ASCs inhibit capsule formation around the implant by characterizing a series of biological alterations upon ASC treatment and the fate of injected ASCs. These findings highlight the value of ASCs for future clinical applications in the prevention of capsular contracture after implant-based reconstruction surgery.

Metabolic regulation of the proteasome under hypoxia by Poldip2 controls fibrotic signaling in vascular smooth muscle cells

The polymerase delta interacting protein 2 (Poldip2) is a nuclear-encoded mitochondrial protein required for oxidative metabolism. Under hypoxia, Poldip2 expression is repressed by an unknown mechanism. Therefore, low levels of Poldip2 are required to maintain glycolytic metabolism. The Cellular Communication Network Factor 2 (CCN2, Connective tissue growth factor, CTGF) is a profibrogenic molecule highly expressed in cancer and vascular inflammation in advanced atherosclerosis. Because CCN2 is upregulated under hypoxia and is associated with glycolytic metabolism, we hypothesize that Poldip2 downregulation is responsible for the upregulation of profibrotic signaling under hypoxia. Here, we report that Poldip2 is repressed under hypoxia by a mechanism that requires the activation of the enhancer of zeste homolog 2 repressive complex (EZH2) downstream from the Cyclin-Dependent Kinase 2 (CDK2). Importantly, we found that Poldip2 repression is required for CCN2 expression downstream of metabolic inhibition of the ubiquitin-proteasome system (UPS)-dependent stabilization of the serum response factor. Pharmacological or gene expression inhibition of CDK2 under hypoxia reverses Poldip2 downregulation, the inhibition of the UPS, and the expression of CCN2, collagen, and fibronectin. Thus, our findings connect cell cycle regulation and proteasome activity to mitochondrial function and fibrotic responses under hypoxia.

Ochratoxin A induces endoplasmic reticulum stress and fibrosis in the kidney via the HIF-1α/miR-155-5p link

Ochratoxin A (OTA) is a ubiquitous fungal toxin found in agricultural products and foods that is toxic to both humans and animals. OTA mainly affects kidney, but the mechanisms underlying OTA-induced nephrotoxicity remain not fully understood. MicroRNA (miRNA) is involved in key cellular processes. The toxic mechanism and regulatory effects of miRNAs on OTA toxicity in kidney, and particularly the role of HIFα-1/miR-155-5p on OTA-caused ER stress and fibrosis, were investigated in this study. OTA induced hypoxia-like conditions such as ER stress and fibrosis in HK-2 cells and renal tissues via modulating HIF-1α, which was followed by regulation of ER stress-related proteins (GRP78 and ATF-4), as well as fibrosis-related markers (fibronectin, α-SMA, and E-cadherin). Notably, a total of 62 miRNAs showed significant differential expression in kidney of OTA-treated mice. Under OTA exposure, HIF-1α enhanced miR-155-5p expression, causing ER stress and fibrosis in HK-2 cells. HIF-1α knockdown decreased OTA-induced miR-155-5p expression as well as ER stress and fibrotic responses, whereas miR-155-5p overexpression restored this. Our data suggest that OTA enhances ER stress and fibrosis in the kidney through upregulating the HIF-1α/miR-155-5p link.

Bioinformatic Exploration of Hub Genes and Potential Therapeutic Drugs for Endothelial Dysfunction in Hypoxic Pulmonary Hypertension

Hypoxic pulmonary hypertension (HPH) is a fatal chronic pulmonary circulatory disease, characterized by hypoxic pulmonary vascular constriction and remodeling. Studies performed to date have confirmed that endothelial dysfunction plays crucial roles in HPH, while the underlying mechanisms have not been fully revealed. The microarray dataset GSE11341 was downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) between hypoxic and normoxic microvascular endothelial cell, followed by Gene Ontology (GO) annotation/Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA) pathway enrichment analysis, and protein-protein interaction (PPI) network construction. Next, GSE160255 and RT-qPCR were used to validate hub genes. Meanwhile, GO/KEGG and GSEA were performed for each hub gene to uncover the potential mechanism. A nomogram based on hub genes was established. Furthermore, mRNA-miRNA network was predicted by miRNet, and the Connectivity Map (CMAP) database was in use to identify similarly acting therapeutic candidates. A total of 148 DEGs were screened in GSE11341, and three hub genes (VEGFA, CDC25A, and LOX) were determined and validated via GSE160255 and RT-qPCR. Abnormalities in the pathway of vascular smooth muscle contraction, lysosome, and glycolysis might play important roles in HPH pathogenesis. The hub gene-miRNA network showed that hsa-mir-24-3p, hsa-mir-124-3p, hsa-mir-195-5p, hsa-mir-146a-5p, hsa-mir-155-5p, and hsa-mir-23b-3p were associated with HPH. And on the basis of the identified hub genes, a practical nomogram is developed. To repurpose known and therapeutic drugs, three candidate compounds (procaterol, avanafil, and lestaurtinib) with a high level of confidence were obtained from the CMAP database. Taken together, the identification of these three hub genes, enrichment pathways, and potential therapeutic drugs might have important clinical implications for HPH diagnosis and treatment.

MYBPC3 deficiency in cardiac fibroblasts drives their activation and contributes to fibrosis

Genetic mutations in the MYBPC3 gene encoding cardiac myosin binding protein C (cMyBP-C) are the most common cause of hypertrophic cardiomyopathy (HCM). Myocardial fibrosis (MF) plays a critical role in the development of HCM. However, the mechanism for mutant MYBPC3-induced MF is not well defined. In this study, we developed a R495Q mutant pig model using cytosine base editing and observed an early-onset MF in these mutant pigs shortly after birth. Unexpectedly, we found that the "cardiac-specific" MYBPC3 gene was actually expressed in cardiac fibroblasts from different species as well as NIH3T3 fibroblasts at the transcription and protein levels. CRISPR-mediated disruption of Mybpc3 in NIH3T3 fibroblasts activated nuclear factor κB (NF-κB) signaling pathway, which increased the expression of transforming growth factor beta (TGF-β1) and other pro-inflammatory genes. The upregulation of TGF-β1 promoted the expression of hypoxia-inducible factor-1 subunit α (HIF-1α) and its downstream targets involved in glycolysis such as GLUT1, PFK, and LDHA. Consequently, the enhanced aerobic glycolysis with higher rate of ATP biosynthesis accelerated the activation of cardiac fibroblasts, contributing to the development of HCM. This work reveals an intrinsic role of MYBPC3 in maintaining cardiac fibroblast homeostasis and disruption of MYBPC3 in these cells contributes to the disease pathogenesis of HCM.

Intimate intertwining of the pathogenesis of hypoxia and systemic sclerosis: A transcriptome integration analysis

OBJECTIVES

Systemic sclerosis (SSc) is an autoimmune disease caused by various pathogenic factors, including hypoxia. Hypoxia stimulates the production of the extracellular matrix to promote fibrosis. However, the integrated function and the underlying mechanism of hypoxia in SSc are unclear.

METHODS

In the present study, we used Agilent SurePrint G3 Human Gene Expression v3 for the transcriptional sequencing of fibroblasts with and without hypoxia to detect differentially expressed genes (DEGs) in hypoxia. We analyzed the results with the transcriptome data of SSc lesions (GSE95065) to select the co-DEGs. Then, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed on the basis of the co-DEGs using the R package ClusterProfiler, which showed that hypoxia and cross talk of hypoxia with other pathogenic factors are involved in the pathogenesis of SSc. Furthermore, we constructed a protein-protein interaction (PPI) network of co-DEGs and screened two significant functional expression modules.

RESULTS

We identified nine hub genes (ALDH1A1, EGF, NOX4, LYN, DNTT, PTGS2, TKT, ACAA2, and ALDH3A1). These genes affect the pentose phosphate pathway, oxidative stress, and lipolysis.

CONCLUSION

Our study provides insights into the mechanisms underlying the effects of hypoxia on SSc pathogenesis, which will help to better understand SSc pathogenesis and develop new therapeutic strategies for SSc.

Modeling Kaempferol as a Potential Pharmacological Agent for COVID-19/PF Co-Occurrence Based on Bioinformatics and System Pharmacological Tools

Objective: People suffering from coronavirus disease 2019 (COVID-19) are prone to develop pulmonary fibrosis (PF), but there is currently no definitive treatment for COVID-19/PF co-occurrence. Kaempferol with promising antiviral and anti-fibrotic effects is expected to become a potential treatment for COVID-19 and PF comorbidities. Therefore, this study explored the targets and molecular mechanisms of kaempferol against COVID-19/PF co-occurrence by bioinformatics and network pharmacology.

Methods: Various open-source databases and Venn Diagram tool were applied to confirm the targets of kaempferol against COVID-19/PF co-occurrence. Protein-protein interaction (PPI), MCODE, key transcription factors, tissue-specific enrichment, molecular docking, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to clarify the influential molecular mechanisms of kaempferol against COVID-19 and PF comorbidities.

Results: 290 targets and 203 transcription factors of kaempferol against COVID-19/PF co-occurrence were captured. Epidermal growth factor receptor (EGFR), proto-oncogene tyrosine-protein kinase SRC (SRC), mitogen-activated protein kinase 3 (MAPK3), mitogen-activated protein kinase 1 (MAPK1), mitogen-activated protein kinase 8 (MAPK8), RAC-alpha serine/threonine-protein kinase (AKT1), transcription factor p65 (RELA) and phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform (PIK3CA) were identified as the most critical targets, and kaempferol showed effective binding activities with the above critical eight targets. Further, anti-COVID-19/PF co-occurrence effects of kaempferol were associated with the regulation of inflammation, oxidative stress, immunity, virus infection, cell growth process and metabolism. EGFR, interleukin 17 (IL-17), tumor necrosis factor (TNF), hypoxia inducible factor 1 (HIF-1), phosphoinositide 3-kinase/AKT serine/threonine kinase (PI3K/AKT) and Toll-like receptor signaling pathways were identified as the key anti-COVID-19/PF co-occurrence pathways.

Conclusion: Kaempferol is a candidate treatment for COVID-19/PF co-occurrence. The underlying mechanisms may be related to the regulation of critical targets (EGFR, SRC, MAPK3, MAPK1, MAPK8, AKT1, RELA, PIK3CA and so on) and EGFR, IL-17, TNF, HIF-1, PI3K/AKT and Toll-like receptor signaling pathways. This study contributes to guiding development of new drugs for COVID-19 and PF comorbidities.

Effects of Ultrafine Single-Nanometer Oxygen Bubbles on Radiation Sensitivity in a Tumor-Bearing Mouse Model

Radiation therapy against cancer cells often causes radiation resistance via accumulation of hypoxia-inducible factor 1 subunit alpha (HIF-1α) under hypoxic conditions and severe side effects. Radiation sensitizers without side effects are required to overcome hypoxia-induced radiation resistance and decrease radiation-related side effects in patients with refractory cancer. We previously developed oxygen nanobubble water (NBO₂ water) and demonstrated that it suppresses hypoxia-induced radiation resistance in cancer cell lines within the single-nanometer range. This study aimed to elucidate whether NBO₂ water could act as a radiosensitizer via regulation of HIF-1α in a tumor-bearing mouse model. Six-week-old female BALB/c mice subcutaneously injected with tumor cells received control water or NBO₂ water for 28 days, after which biochemical examinations and radiation treatment were performed. Hypoxic tumor regions were detected immunohistochemically. We found that NBO₂ water sensitized radiation reactivity in the xenografted tumors. Notably, NBO₂ water administration downregulated the accumulation of HIF-1α in xenografted tumors and did not affect the vital organs of healthy mice. The combination of radiation and single-nanometer NBO₂ water without severe side effects may be a promising therapeutic option to improve radiation sensitivity in cancer patients without tolerance to invasive treatments.

Hypoxia and Hypoxia-Inducible Factors in Lymphedema

Lymphedema is a chronic inflammatory disorder characterized by edema, fat deposition, and fibrotic tissue remodeling. Despite significant advances in lymphatic biology research, our knowledge of lymphedema pathology is incomplete. Currently, there is no approved pharmacological therapy for this debilitating disease. Hypoxia is a recognized feature of inflammation, obesity, and fibrosis. Understanding hypoxia-regulated pathways in lymphedema may provide new insights into the pathobiology of this chronic disorder and help develop new medicinal treatments.

A New Hypothetical Concept in Metabolic Understanding of Cardiac Fibrosis: Glycolysis Combined with TGF-β and KLF5 Signaling

The accumulation of fibrosis in cardiac tissues is one of the leading causes of heart failure. The principal cellular effectors in cardiac fibrosis are activated fibroblasts and myofibroblasts, which serve as the primary source of matrix proteins. TGF-β signaling pathways play a prominent role in cardiac fibrosis. The control of TGF-β by KLF5 in cardiac fibrosis has been demonstrated for modulating cardiovascular remodeling. Since the expression of KLF5 is reduced, the accumulation of fibrosis diminishes. Because the molecular mechanism of fibrosis is still being explored, there are currently few options for effectively reducing or reversing it. Studying metabolic alterations is considered an essential process that supports the explanation of fibrosis in a variety of organs and especially the glycolysis alteration in the heart. However, the interplay among the main factors involved in fibrosis pathogenesis, namely TGF-β, KLF5, and the metabolic process in glycolysis, is still indistinct. In this review, we explain what we know about cardiac fibroblasts and how they could help with heart repair. Moreover, we hypothesize and summarize the knowledge trend on the molecular mechanism of TGF-β, KLF5, the role of the glycolysis pathway in fibrosis, and present the future therapy of cardiac fibrosis. These studies may target therapies that could become important strategies for fibrosis reduction in the future.

Hypoxia-induced interstitial transformation of microvascular endothelial cells by mediating HIF-1α/VEGF signaling in systemic sclerosis

Objective

The aim of this research was to systematically investigate the effects of endothelial mesenchymal transition (EndMT) induced by hypoxia on the skin microvascular remodeling of systemic sclerosis (SSc) and the underlying mechanism.

Methods

Skin tissues from SSc patients and controls were collected for isobaric tags for the relative and absolute quantification (iTRAQ)-based proteomics and immunohistochemical test. Human microvascular endothelial cell line-1 (HMEC-1) cultured in hypoxic or normal conditions was treated by tamoxifen or bevacizumab.

Results

The iTRAQ-based proteomics indicated a significantly upregulated hypoxia-inducible factor-1 (HIF-1) signal in SSc samples. The immunohistochemical results demonstrated the significant downregulation of CD31, the positive staining of α-smooth muscle actin (α-SMA), HIF-1α, and vascular endothelial growth factor (VEGF-a) in SSc skin tissues, compared with control samples. Consistent with these observations, HMEC-1 cells cultured under hypoxic conditions exhibited a significant decrease in CD31 and VE-cadherin expression, alongside a marked increase in the expression of α-SMA and fibronectin, as well as a distinct upregulation of HIF-1α and VEGF-a, when compared with those under normal conditions. It is noteworthy that the inhibition of HIF-1α by tamoxifen effectively downregulated the hypoxic induction of VEGF-a and α-SMA while rescuing the hypoxic suppression of CD31. In addition, the VEGF-a inhibitor bevacizumab treatment had the same effect on the hypoxic expression of α-SMA and CD31, as a tamoxifen intervention, but did not reduce HIF-1α.

Conclusion

These results suggest that the HIF-1α/VEGF signaling pathway can have a critical role in mediating the effect of hypoxia-induced EndMT on the skin microvascular remodeling of SSc.

Circular RNA Plasmacytoma Variant Translocation 1 (CircPVT1) knockdown ameliorates hypoxia-induced bladder fibrosis by regulating the miR-203/Suppressor of Cytokine Signaling 3 (SOCS3) signaling axis

The effects of circular RNAs (circRNAs) on bladder outlet obstruction (BOO)-induced hypertrophy and fibrogenesis in rats and hypoxia-induced bladder smooth muscle cell (BSMC) fibrosis remain unclear. This study aimed to determine the regulatory role of circRNAs in the phenotypic changes in BSMCs in BOO-induced rats.circRNAmicroarray and real-time PCR were used to explore differentiated expressed circRNAs. Bioinformatics analyses and dual-luciferase reporter were performed to identify the targets for circRNA PVT1 (circPVT1). BOO was performed to establish a bladder fibrosis animal model. The circPVT1 and suppressor of cytokine signaling 3 (SOCS3) expression levels were upregulated (p = 0.0061 and 0.0328, respectively), whereas the microRNA-203a (miR-203) level was downregulated in rats with bladder remodeling (p=0.0085). Bioinformatics analyses and dual-luciferase reporter assay results confirmed that circPVT1 sponges miR-203 and that the latter targets the 3'-untranslated region of SOCS3. Additionally, circPVT1 knockdown alleviated BOO-induced bladder hypertrophy and fibrogenesis. Furthermore, hypoxia was induced in BSMCs to establish a cell model of bladder fibrosis. Hypoxia induction in BSMCs resulted in upregulated circPVT1 and SOCS3 levels (p = 0.0052) and downregulated miR-203 levels. Transfection with circPVT1 and SOCS3 shRNA ameliorated hypoxia-induced transforming growth factor-β (TGF-β1), TGFβR1, α-smooth muscle actin, fibrotic growth factor, extracellular matrix subtypes, BSMC proliferation, and apoptosis-associated cell injury, whereas co-transfection with miR-203 inhibitor counteracted the effect of circPVT1 shRNA on these phenotypes.These findings revealed a novel circRNA regulator of BOO-associated bladder wall remodeling and hypoxia-induced phenotypic changes in BMSCs by targeting the miR-203-SOCS3 signaling axis.

GATA4 induces liver fibrosis regression by deactivating hepatic stellate cells

In response to liver injury, hepatic stellate cells activate and acquire proliferative and contractile features. The regression of liver fibrosis appears to involve the clearance of activated hepatic stellate cells, either by apoptosis or by reversion toward a quiescent-like state, a process called deactivation. Thus, deactivation of active hepatic stellate cells has emerged as a novel and promising therapeutic approach for liver fibrosis. However, our knowledge of the master regulators involved in the deactivation and/or activation of fibrotic hepatic stellate cells is still limited. The transcription factor GATA4 has been previously shown to play an important role in embryonic hepatic stellate cell quiescence. In this work, we show that lack of GATA4 in adult mice caused hepatic stellate cell activation and, consequently, liver fibrosis. During regression of liver fibrosis, Gata4 was reexpressed in deactivated hepatic stellate cells. Overexpression of Gata4 in hepatic stellate cells promoted liver fibrosis regression in CCl4-treated mice. GATA4 induced changes in the expression of fibrogenic and antifibrogenic genes, promoting hepatic stellate cell deactivation. Finally, we show that GATA4 directly repressed EPAS1 transcription in hepatic stellate cells and that stabilization of the HIF2α protein in hepatic stellate cells leads to liver fibrosis.

Conditional Antisense Oligonucleotides Triggered by miRNA

Antisense oligonucleotides (ASOs) are single-stranded short nucleic acids that silence the expression of target mRNAs and show increasing therapeutic potential. Since ASOs are internalized by many cell types, both normal and diseased cells, gene silencing in unwanted cells is a significant challenge for their therapeutic use. To address this challenge, we created conditional ASOs that become active only upon detecting transcripts unique to the target cell. As a proof-of-concept, we modified an HIF1α ASO (EZN2968) to generate miRNA-specific conditional ASOs, which can inhibit HIF1α in the presence of a hepatocyte-specific miRNA, miR-122, via a toehold exchange reaction. We characterized a library of nucleic acids, testing how the conformation, thermostability, and chemical composition of the conditional ASO impact the specificity and efficacy in response to miR-122 as a trigger signal. Optimally designed conditional ASOs demonstrated knockdown of HIF1α in cells transfected with exogenous miR-122 and in hepatocytes expressing endogenous miR-122. We confirmed that conditional ASO activity was mediated by toehold exchange between miR-122 and the conditional ASO duplex, and the magnitude of the knockdown depended on the toehold length and miR-122 levels. Using the same concept, we further generated another conditional ASO that can be triggered by miR-21. Our results suggest that conditional ASOs can be custom-designed with any miRNA to control ASO activation in targeted cells while reducing unwanted effects in nontargeted cells.

Impairment of the Hif-1α regulatory pathway in Foxn1-deficient (Foxn1-/- ) mice affects the skin wound healing process

Hypoxia and hypoxia-regulated factors (eg, hypoxia-inducible factor-1α [Hif-1α], factor inhibiting Hif-1α [Fih-1], thioredoxin-1 [Trx-1], aryl hydrocarbon receptor nuclear translocator 2 [Arnt-2]) have essential roles in skin wound healing. Using Foxn1^-/- mice that can heal skin injuries in a unique scarless manner, we investigated the interaction between Foxn1 and hypoxia-regulated factors. The Foxn1^-/- mice displayed impairments in the regulation of Hif-1α, Trx-1, and Fih-1 but not Arnt-2 during the healing process. An analysis of wounded skin showed that the skin of the Foxn1^-/- mice healed in a scarless manner, displaying rapid re-epithelialization and an increase in transforming growth factor β (Tgfβ-3) and collagen III expression. An in vitro analysis revealed that Foxn1 overexpression in keratinocytes isolated from the skin of the Foxn1^-/- mice led to reduced Hif-1α expression in normoxic but not hypoxic cultures and inhibited Fih-1 expression exclusively under hypoxic conditions. These data indicate that in the skin, Foxn1 affects hypoxia-regulated factors that control the wound healing process and suggest that under normoxic conditions, Foxn1 is a limiting factor for Hif-1α.

Noscapine Acts as a Protease Inhibitor of In Vitro Elastase-Induced Collagen Deposition in Equine Endometrium

Endometrosis is a reproductive pathology that is responsible for mare infertility. Our recent studies have focused on the involvement of neutrophil extracellular traps enzymes, such as elastase (ELA), in the development of equine endometrosis. Noscapine (NOSC) is an alkaloid derived from poppy opium with anticough, antistroke, anticancer, and antifibrotic properties. The present work investigates the putative inhibitory in vitro effect of NOSC on collagen type I alpha 2 chain (COL1A2) mRNA and COL1 protein relative abundance induced by ELA in endometrial explants of mares in the follicular or mid-luteal phases at 24 or 48 h of treatment. The COL1A2 mRNA was evaluated by qPCR and COL1 protein relative abundance by Western blot. In equine endometrial explants, ELA increased COL 1 expression, while NOSC inhibited it at both estrous cycle phases and treatment times. These findings contribute to the future development of new endometrosis treatment approaches. Noscapine could be a drug capable of preventing collagen synthesis in mare’s endometrium and facilitate the therapeutic approach.

Myofibroblast-Derived Exosome Induce Cardiac Endothelial Cell Dysfunction

Background: Endothelial cells (ECs) play a critical role in the maintenance of vascular homeostasis and in heart function. It was shown that activated fibroblast-derived exosomes impair cardiomyocyte function in hypertrophic heart, but their effect on ECs is not yet clear. Thus, we hypothesized that activated cardiac fibroblast-derived exosomes (FB-Exo) mediate EC dysfunction, and therefore modulation of FB-exosomal contents may improve endothelial function. Methods and Results: Exosomes were isolated from cardiac fibroblast (FB)-conditioned media and characterized by nanoparticle tracking analysis and electron microscopy. ECs were isolated from mouse heart. ECs were treated with exosomes isolated from FB-conditioned media, following FB culture with TGF-β1 (TGF-β1-FB-Exo) or PBS (control) treatment. TGF-β1 significantly activated fibroblasts as shown by increase in collagen type1 α1 (COL1α1), periostin (POSTN), and fibronectin (FN1) gene expression and increase in Smad2/3 and p38 phosphorylation. Impaired endothelial cell function (as characterized by a decrease in tube formation and cell migration along with reduced VEGF-A, Hif1α, CD31, and angiopoietin1 gene expression) was observed in TGF-β1-FB-Exo treated cells. Furthermore, TGF-β1-FB-Exo treated ECs showed reduced cell proliferation and increased apoptosis as compared to control cells. TGF-β1-FB-Exo cargo analysis revealed an alteration in fibrosis-associated miRNAs, including a significant increase in miR-200a-3p level. Interestingly, miR-200a-3p inhibition in activated FBs, alleviated TGF-β1-FB-Exo-mediated endothelial dysfunction. Conclusions: Taken together, this study demonstrates an important role of miR-200a-3p enriched within activated fibroblast-derived exosomes on endothelial cell biology and function.

Engineering Advanced In Vitro Models of Systemic Sclerosis for Drug Discovery and Development

Systemic sclerosis (SSc) is a complex multisystem disease with the highest case-specific mortality among all autoimmune rheumatic diseases, yet without any available curative therapy. Therefore, the development of novel therapeutic antifibrotic strategies that effectively decrease skin and organ fibrosis is needed. Existing animal models are cost-intensive, laborious and do not recapitulate the full spectrum of the disease and thus commonly fail to predict human efficacy. Advanced in vitro models, which closely mimic critical aspects of the pathology, have emerged as valuable platforms to investigate novel pharmaceutical therapies for the treatment of SSc. This review focuses on recent advancements in the development of SSc in vitro models, sheds light onto biological (e.g., growth factors, cytokines, coculture systems), biochemical (e.g., hypoxia, reactive oxygen species) and biophysical (e.g., stiffness, topography, dimensionality) cues that have been utilized for the in vitro recapitulation of the SSc microenvironment, and highlights future perspectives for effective drug discovery and validation.

Hypoxia Inducible Factor 1A Supports a Pro-Fibrotic Phenotype Loop in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with poor prognosis. The IPF-conditioned matrix (IPF-CM) system enables the study of matrix–fibroblast interplay. While effective at slowing fibrosis, nintedanib has limitations and the mechanism is not fully elucidated. In the current work, we explored the underlying signaling pathways and characterized nintedanib involvement in the IPF-CM fibrotic process. Results were validated using IPF patient samples and bleomycin-treated animals with/without oral and inhaled nintedanib. IPF-derived primary human lung fibroblasts (HLFs) were cultured on Matrigel and then cleared using NH₄OH, creating the IPF-CM. Normal HLF-CM served as control. RNA-sequencing, PCR and western-blots were performed. HIF1α targets were evaluated by immunohistochemistry in bleomycin-treated rats with/without nintedanib and in patient samples with IPF. HLFs cultured on IPF-CM showed over-expression of ‘HIF1α signaling pathway’ (KEGG, p < 0.0001), with emphasis on SERPINE1 (PAI-1), VEGFA and TIMP1. IPF patient samples showed high HIF1α staining, especially in established fibrous tissue. PAI-1 was overexpressed, mainly in alveolar macrophages. Nintedanib completely reduced HIF1α upregulation in the IPF-CM and rat-bleomycin models. IPF-HLFs alter the extracellular matrix, thus creating a matrix that further propagates an IPF-like phenotype in normal HLFs. This pro-fibrotic loop includes the HIF1α pathway, which can be blocked by nintedanib.

Role of the ROS-JNK Signaling Pathway in Hypoxia-Induced Atrial Fibrotic Responses in HL-1 Cardiomyocytes

By promoting atrial structural remodeling, atrial hypoxia contributes to the development of the atrial fibrillation substrate. Our study aimed to investigate the modulatory effect of hypoxia on profibrotic activity in cultured HL-1 cardiomyocytes and explore the possible signaling transduction mechanisms of profibrotic activity in vitro. Hypoxia (1% O₂) significantly and time-dependently increased the expression of hypoxia-inducible factor (HIF)-1α and fibrotic marker proteins collagen I and III (COL1A and COL3A), transforming growth factor (TGF)-β1 and α-smooth muscle actin (SMA). Western blot or immunohistochemistry analysis showed that hypoxia-induced increase in COL1A and COL3A was significantly attenuated by the addition of SP600125 (a specific c-Jun N-terminal kinase [JNK] inhibitor) or expression of dominant-negative JNK before hypoxia treatment. The inhibition of hypoxia-activated phosphorylation of JNK signal components (JNK, MKK4, nuclear c-Jun and ATF-2) by pre-treatment with SP600125 could suppress hypoxia-stimulated HIF-1α upregulation and fibrotic marker proteins expression. Hypoxia significantly increased reactive oxygen species (ROS) production in cultured HL-1 atrial cells. Pre-treatment with N-acetylcysteine significantly abrogated the expression of nuclear HIF-1α, JNK transduction components and fibrotic marker proteins. Taken together, these findings indicated that the hypoxia-induced atrial profibrotic response occurs mainly via the ROS/JNK pathway, its downstream upregulation of HIF-1α and c-Jun/ATF2 phosphorylation and nuclear translocation to up-regulate the expression of fibrosis-related proteins (COL1A, COL3A, TGF-β1 and α-SMA). Our result suggests that suppression of ROS/JNK signaling pathway is a critical mechanism for developing a novel therapeutic strategy against atrial fibrillation.

Angiotensin II blockers improve cardiac coronary flow under hemodynamic pressure overload

Coronary flow velocity (CFV) is reduced in pathologic cardiac hypertrophy. This functional reduction is linked to adverse cardiac remodeling, hypertension and fibrosis, and angiotensin II (AngII) is a key molecular player. Angiotensin receptor blockers (ARBs) are known to attenuate adverse cardiac remodeling and fibrosis following increased afterload, while the mechanism by which these drugs offer clinical benefits and regulate hemodynamics remains unknown. To establish a direct connection between coronary flow changes and angiotensin-induced hypertension, we used a Doppler echocardiographic method in two distinct disease models. First, we performed serial echocardiography to visualize coronary flow and assess heart function in patients newly diagnosed with hypertension and currently on ARBs or calcium channel blockers (CCBs). CFV improved significantly in the hypertensive patients after 12 weeks of ARB treatment but not in those treated with CCBs. Second, using murine models of pressure overload, including Ang II infusion and aortic banding, we mimicked the clinical conditions of Ang II- and mechanical stress-induced hypertension, respectively. Both Ang II infusion and aortic banding increased the end-systolic pressure-volume relationship and cardiac fibrosis, but interestingly, only Ang II infusion resulted in a significant reduction in CFV and corresponding activation of pressure-sensitive proteins, including connective tissue growth factor, hypoxia-inducible factor 1α and signal transducer and activator of transcription 3. These data support the existence of a molecular and functional link between AngII-induced hemodynamic remodeling and alterations in coronary vasculature, which, in part, can explain the clinical benefit of ARB treatment in hypertensive patients.

Astragaloside IV improves angiogenesis under hypoxic conditions by enhancing hypoxia‑inducible factor‑1α SUMOylation

Improving angiogenic capacity under hypoxic conditions is essential for improving the survival of skin grafts, as they often lack the necessary blood supply. The stable expression levels of hypoxia‑inducible factor‑1α (HIF‑1α) in the nucleus directly affect the downstream vascular endothelial growth factor (VEGF) signaling pathway and regulate angiogenesis in a hypoxic environment. Astragaloside IV (AS‑IV), an active component isolated from Astragalus membranaceus, has multiple biological effects including antioxidant and anti‑diabetic effects, and the ability to provide protection from cardiovascular damage. However, the mechanisms underlying these effects have not previously been elucidated. The present study investigated whether AS‑IV promotes angiogenesis via affecting the balance between ubiquitination and small ubiquitin‑related modifier (SUMO) modification of HIF‑1α. The results demonstrated that persistent hypoxia induces changes in expression levels of HIF‑1α protein and significantly increases the proportion of dysplastic blood vessels. Further western blotting experiments showed that rapid attenuation and delayed compensation of SUMO1 activity is one of the reasons for the initial increase then decrease in HIF‑1α levels. SUMO1 overexpression stabilized the presence of HIF‑1α in the nucleus and decreased the extent of abnormal blood vessel morphology observed following hypoxia. AS‑IV induces vascular endothelial cells to continuously produce SUMO1, stabilizes the HIF‑1α/VEGF pathway and improves angiogenesis in hypoxic conditions. In summary, the present study confirmed that AS‑IV stimulates vascular endothelial cells to continuously resupply SUMO1, stabilizes the presence of HIF‑1α protein and improves angiogenesis in adverse hypoxic conditions, which may improve the success rate of flap graft surgery following trauma or burn.

Notch3 Modulates Cardiac Fibroblast Proliferation, Apoptosis, and Fibroblast to Myofibroblast Transition via Negative Regulation of the RhoA/ROCK/Hif1α Axis

Cardiac fibrosis is a common pathological process in multiple cardiovascular diseases, including myocardial infarction (MI). Abnormal cardiac fibroblast (CF) activity is a key event in cardiac fibrosis. Although the Notch signaling pathway has been reported to play a vital role in protection from cardiac fibrosis, the exact mechanisms underlying cardiac fibrosis and protection from it have not yet been elucidated. Similarly, Hif1α and the RhoA/ROCK signaling pathway have been shown to participate in cardiac fibrosis. The RhoA/ROCK signaling pathway has been reported to be an upstream pathway of Hif1α in several pathophysiological processes. In the present study, we aimed to determine the effects of notch3 on CF activity and its relationship with the RhoA/ROCK/Hif1α signaling pathway. Using in vitro experiments, we demonstrated that notch3 inhibited CF proliferation and fibroblast to myofibroblast transition (FMT) and promoted CF apoptosis. A knockdown of notch3 using siRNAs had the exact opposite effect. Next, we found that notch3 regulated CF activity by negative regulation of the RhoA/ROCK/Hif1α signaling pathway. Extending CF-based studies to an in vivo rat MI model, we showed that overexpression of notch3 by the Ad-N3ICD injection attenuated the increase of RhoA, ROCK1, ROCK2, and Hif1α levels following MI and further prevented MI-induced cardiac fibrosis. On the basis of these results, we conclude that notch3 is involved in the regulation of several aspects of CF activity, including proliferation, FMT, and apoptosis, by inhibiting the RhoA/ROCK/Hif1α signaling pathway. These findings are significant to further our understanding of the pathogenesis of cardiac fibrosis and to ultimately identify new therapeutic targets for cardiac fibrosis, potentially based on the RhoA/ROCK/Hif1α signaling pathway.

Roxadustat attenuates experimental pulmonary fibrosis in vitro and in vivo

Roxadustat is the first orally administered, small-molecule hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor that has been submitted for FDA regulatory approval to treat anemia secondary to chronic kidney diseases. Its usage has also been suggested for pulmonary fibrosis; however, the corresponding therapeutic effects remain to be investigated. The in vitro effects of roxadustat on cobalt chloride (CoCl₂)-stimulated pulmonary fibrosis with L929 mouse fibroblasts as well as on an in vivo pulmonary fibrosismice model induced with bleomycin (BLM; intraperitoneal injection, 50 mg/kg twice a week for 4 continuous weeks) were investigated. It found that the proliferation of L929 cells was inhibited and the production of collagen I, collagen III, prolyl hydroxylase domain protein 2 (PHD2), HIF-1α, α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), transforming growth factor-β1 (TGF-β1) and p-Smad3 were reduced relative to that in the CoCl₂ or BLM group after roxadustat treatment. Roxadustat ameliorated pulmonary fibrosis by reducing the pathology score and collagen deposition as well as decreasing the expression of collagen I, collagen III, PHD2, HIF-1α, α-SMA, CTGF, TGF-β1 and p-Smad3/Smad3. Our cumulative results demonstrate that roxadustat administration can attenuate experimental pulmonary fibrosis via the inhibition of TGF-β1/Smad activation.

Autophagy mediates 2-methoxyestradiol-inhibited scleroderma collagen synthesis and endothelial-to-mesenchymal transition induced by hypoxia

OBJECTIVES

To investigate whether autophagy mediates 2-methoxyestradiol (2-ME)-inhibited hypoxia-induced fibrosis and endothelial-to-mesenchymal transition (endoMT) in SSc.

METHODS

Autophagy in the skin of SSc patients was assessed by transmission electron microscopy. SSc skin fibroblasts and human umbilical vein endothelial cells (HUVECs) were cultured under hypoxic (1% O2) conditions with 2-ME or autophagy inhibitor. Collagen I and connective tissue growth factor (CTGF) in fibroblasts and vascular endothelial (VE)-cadherin, CD31, vimentin and α-smooth muscle actin (α-SMA) in HUVECs were examined by western blotting. Autophagic markers were evaluated by confocal microscopy and immunofluorescence.

RESULTS

SSc skins presented increased autolysosomes, LC3-II, collagen I and CTGF. Hypoxia-challenged fibroblasts and HUVECs formed more autophagosomes and autolysosomes, with increased LC3 and decreased P62. Meanwhile, hypoxia increased collagen I and CTGF in fibroblasts and increased vimentin and α-SMA but decreased VE-cadherin and CD31 in HUVECs. Bafilomycin A1 increased LC3-II and P62 in fibroblasts and HUVECs and decreased collagen I and CTGF in fibroblasts and vimentin and α-SMA in HUVECs, while upregulating VE-cadherin and CD31. 3-methyladenine decreased autophagy and fibrosis in fibroblasts and endothelial-to-mesenchymal transition in HUVECs. 2-ME-treated HUVECs showed more autophagosomes and fewer autolysosomes while 2-ME-treated fibroblasts showed fewer of both. Moreover, 2-ME decreased LC3-II and increased P62 in fibroblasts and increased both in HUVECs. Inhibition of autophagy by 2-ME showed the same effect with bafilomycin A1 on fibroblast collagen synthesis as well as endothelial and mesenchymal markers in HUVECs.

CONCLUSION

Autophagy mediated hypoxia-induced fibroblast collagen synthesis and endoMT in SSc, which could be reversed by 2-ME.

Exogenous hydrogen sulfide protects against high glucose-induced apoptosis and oxidative stress by inhibiting the STAT3/HIF-1α pathway in H9c2 cardiomyocytes

Hydrogen sulfide (H2S), an endogenous gasotransmitter, possesses multiple physiological and pharmacological properties including anti-apoptotic, anti-oxidative stress and cardiac protective activities in diabetic cardiomyopathy. An increasing body of evidence has suggested that signal transducer and activator of transcription 3 (STAT3) has beneficial effects in the heart. However, the effect of diabetes on the phosphorylation or activation of cardiac STAT3 appears to be controversial. The present study was designed to investigate the precise function of the STAT3/hypoxia-inducible factor-1α (HIF-1α) signaling pathway in high glucose (HG)-induced H9c2 cardiomyocyte injury and the function of the STAT3/HIF-1α pathway in the cardioprotective action of H2S. The results revealed that GYY4137 pretreatment substantially ameliorated the HG-induced decrease in cell viability and the increase in lactate dehydrogenase (LDH) release in H9c2 cells. Additionally, HG treatment resulted in the upregulation of the phosphorylated (p)-STAT3/STAT3 ratio and HIF-1α protein expression in H9c2 cells, indicating that the activation of the STAT3/HIF-1α pathway was induced by HG. STAT3/HIF-1α pathway inhibition induced by transfection with STAT3 small interfering (si)-RNA attenuated the HG-induced downregulation of cell viability and the upregulation of LDH release. Furthermore, STAT3 siRNA transfection and GYY4137 pretreatment combined attenuated HG-induced apoptosis as illustrated by the decrease in the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells, caspase-3 activity, apoptosis ratio and BCL2 associated X, apoptosis regulator/BCL2 apoptosis regulator ratio in H9c2 cells. In addition, STAT3 siRNA transfection and GYY4137 blocked HG-induced oxidative stress as evidenced by the decrease in reactive oxygen species generation, malondialdehyde content and NADPH oxidase 2 expression, and the increase in superoxide dismutase activity and glutathione level. Notably, GYY4137 pretreatment was revealed to reduce the p-STAT3/STAT3 ratio and HIF-1α protein expression, resulting in the inhibition of the STAT3/HIF-1α signaling pathway in HG-treated H9c2 cells. Altogether, the present results demonstrated that H2S mitigates HG-induced H9c2 cell damage, and reduces apoptosis and oxidative stress by suppressing the STAT3/HIF-1α signaling pathway.

Raltegravir Attenuates Experimental Pulmonary Fibrosis In Vitro and In Vivo

Raltegravir, an inhibitor of human immunodeficiency virus-1 (HIV-1) integrase, has been used to treat HIV/acquired immunodeficiency syndrome; however, its therapeutic effects on pulmonary fibrosis have not been investigated. In this study, the in vitro effects of raltegravir (RAV) on transforming growth factor beta 1 (TGF-β1)-induced pulmonary fibrosis on L929 mouse fibroblasts were investigated. In addition, the effects of RAV on an in vivo pulmonary fibrosis model induced by intratracheal instillation of bleomycin were investigated. The proliferation of L929 cells was inhibited after RAV treatment. Meanwhile, the in vitro and in vivo protein expression of nucleotide-binding oligomerization domain-like receptor 3 (NLRP3), high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), prolyl hydroxylase domain protein 2, phosphorylated nuclear factor-κB (p-NF-κB), hypoxia-inducible factor-1α (HIF-1α), collagens I and III was reduced relative to TGF-β1 or the bleomycin group. Raltegravir ameliorated pulmonary fibrosis by reducing the pathology score, collagen deposition, and expression of α-smooth muscle actin, NLRP3, HMGB1, TLR4, inhibitor of kappa B, p-NF-κB, HIF-1α, collagen I, and collagen III. The results of this study demonstrate that RAV attenuated experimental attenuates pulmonary fibrosis by inhibiting NLRP3 activation.

Hypoxia-adaptive pathways: A pharmacological target in fibrotic disease?

Wound healing responses are physiological reactions to injuries and share common characteristics and phases independently of the injured organ or tissue. A major hallmark of wound healing responses is the formation of extra-cellular matrix (ECM), mainly consisting of collagen fibers, to restore the initial organ architecture and function. Overshooting wound healing responses result in unphysiological accumulation of ECM and collagen deposition, a process called fibrosis. Importantly, hypoxia (oxygen demand exceeds supply) plays a significant role during wound healing responses and fibrotic diseases. Under hypoxic conditions, cells activate a gene program, including the stabilization of hypoxia-inducible factors (HIFs), which induces the expression of HIF target genes counteracting hypoxia. In contrast, in normoxia, so-called HIF-prolyl hydroxylases (PHDs) oxygen-dependently hydroxylate HIF-α, which marks it for proteasomal degradation. Importantly, PHDs can be pharmacologically inhibited (PHI) by so-called PHD inhibitors. There is mounting evidence that the HIF-pathway is continuously up-regulated during the development of tissue fibrosis, and that pharmacological (HIFI) or genetic inhibition of HIF can prevent organ fibrosis. By contrast, initial (short-term) activation of the HIF pathway via PHI during wound healing seems to be beneficial in several models of inflammation or acute organ injury. Thus, timing and duration of PHI and HIFI treatment seem to be crucial. In this review, we will highlight the role of hypoxia-adaptive pathways during wound healing responses and development of fibrotic disease. Moreover, we will discuss whether PHI and HIFI might be a promising treatment option in fibrotic disease, and consider putative pitfalls that might result from this approach.

Hypoxia-induced epithelial-mesenchymal transition and fibrosis for the development of breast capsular contracture

Fibrosis has been considered as a major cause of capsular contracture. Hypoxia has widely emerged as one of the driving factors for fibrotic diseases. The aim of this study was to examine the association between hypoxia-induced fibrosis and breast capsular contracture formation. Fibrosis, epithelial-mesenchymal transition (EMT), expression levels of hypoxia-inducible factor-1α (HIF-1α), vimentin, fibronectin, and matrix metalloproteinase-9 (MMP-9) in tissues from patients with capsular contracture were determined according to the Baker classification system. Normal breast skin cells in patients with capsular contracture after implant-based breast surgery and NIH3T3 mouse fibroblasts were cultured with cobalt chloride (CoCl₂) to mimic hypoxic conditions. Treatment responses were determined by detecting the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, occludin, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and -2, as well as phosphorylated ERK. The expression levels of HIF-1α, vimentin, fibronectin, and fibrosis as well as EMT were positively correlated with the severity of capsular contracture. MMP-9 expression was negatively correlated the Baker score. Hypoxia up-regulated the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, TIMP-1 and -2, as well as phosphorylated ERK in normal breast skin cells and NIH3T3. Nonetheless, the expression levels of MMP-9 and occludin were down-regulated in response to CoCl₂ treatment. This study is the first to demonstrate the association of hypoxia-induced fibrosis and capsular contracture.

An integrative computational approach for a prioritization of key transcription regulators associated with nanomaterial-induced toxicity

A rapid increase of new nanomaterial products poses new challenges for their risk assessment. Current traditional methods for estimating potential adverse health effect of nanomaterials (NMs) are complex, time consuming and expensive. In order to develop new prediction tests for nanotoxicity evaluation, a systems biology approach and data from high-throughput omics experiments can be used. We present a computational approach that combines reverse engineering techniques, network analysis and pathway enrichment analysis for inferring the transcriptional regulation landscape and its functional interpretation. To illustrate this approach, we used published transcriptomic data derived from mice lung tissue exposed to carbon nanotubes (NM-401 and NRCWE-26). Because fibrosis is the most common adverse effect of these NMs, we included in our analysis the data for bleomycin (BLM) treatment, which is a well-known fibrosis inducer. We inferred gene regulatory networks for each NM and BLM to capture functional hierarchical regulatory structures between genes and their regulators. Despite the different nature of the lung injury caused by nanoparticles and BLM, we identified several conserved core regulators for all agents. We reason that these regulators can be considered as early predictors of toxic responses after NMs exposure. This integrative approach, which refines traditional methods of transcriptomic analysis, can be useful for prioritization of potential core regulators and generation of new hypothesis about mechanisms of nanoparticles toxicity.

Probucol ameliorates EMT and lung fibrosis through restoration of SIRT3 expression

Pulmonary fibrosis is a progressive fibrotic lung disease with a paucity of therapeutic options. Here we investigated the potential roles of probucol, a cholesterol-lowering drug with potent anti-oxidation properties, on pulmonary epithelial-mesenchymal transition (EMT) and fibrosis. We found that bleomycin-induced lung fibrosis was associated with increased transforming growth factor (TGF)-β1, α-smooth muscle actin (α-SMA) and decreased E-cadherin expression in lung tissues, indicating EMT formation. Bleomycin treatment resulted in an induction of oxidative stress in lung tissues. Probucol treatment attenuated bleomycin-induced TGF-β1 production, EMT and pulmonary fibrosis, meanwhile it suppressed bleomycin-induced oxidative stress. Bleomycin treatment resulted in decreases in protein expressions of Sirtuin 3 (SIRT3) in the lung, which were restored by ROS scavenger NAC and probucol treatment, suggesting that probucol might restore SIRT3 expression by suppressing bleomycin-induced oxidative stress. In the mouse alveolar type II epithelial cell line MLE-12, probucol treatment leads to an increase in SIRT3 expression in bleomycin-treated AT-II cells, which might contribute to the inhibitory effect of probucol on EMT through suppressing hypoxia inducible factor (HIF)-1α/TGF-β1 pathway. In addition, probucol inhibited bleomycin-induced macrophage infiltration in the lung. Bleomycin decreased SIRT3 protein expression, whereas increased HIF-1α activation and TGF-β1 release in the mouse macrophage cell line RAW264.7, which were attenuated by probucol treatment. Taken together, the present study suggests that probucol may ameliorate EMT and lung fibrosis through restoration of SIRT3 expression. The data obtained in this study provides proof for the idea that probucol may be a potential therapeutic option for the treatment of pulmonary fibrosis.

Hypoxia-inducible factor 1-alpha (HIF-1α) as a factor mediating the relationship between obesity and heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF), a common condition with an increased mortality, is strongly associated with obesity and the metabolic syndrome. The latter two conditions are associated with increased epicardial fat that can extend into the heart. This review advances the proposition that hypoxia-inhibitory factor-1α (HIF-1α) maybe a key factor producing HFpEF. HIF-1α, a highly conserved transcription factor that plays a key role in tissue response to hypoxia, is increased in adipose tissue in obesity. Increased HIF-1α expression leads to expression of a potent profibrotic transcriptional programme involving collagen I, III, IV, TIMP, and lysyl oxidase. The net effect is the formation of collagen fibres leading to fibrosis. HIF-1α is also responsible for recruiting M1 macrophages that mediate obesity-associated inflammation, releasing IL-6, MCP-1, TNF-α, and IL-1β with increased expression of thrombospondin, pro α2 (I) collagen, transforming growth factor β, NADPH oxidase, and connective tissue growth factor. These factors can accelerate cardiac fibrosis and impair cardiac diastolic function. Inhibition of HIF-1α expression in adipose tissue of mice fed a high-fat diet suppressed fibrosis and reduces inflammation in adipose tissue. Delineation of the role played by HIF-1α in obesity-associated HFpEF may lead to new potential therapies.

Hypoxia suppresses myofibroblast differentiation by changing RhoA activity

Fibroblasts show a high range of phenotypic plasticity, including transdifferentiation into myofibroblasts. Myofibroblasts are responsible for generation of the contraction forces that are important for wound healing and scar formation. Overactive myofibroblasts, by contrast, are involved in abnormal scarring. Cell stretching and extracellular signals such as transforming growth factor β can induce the myofibroblastic program, whereas microenvironmental conditions such as reduced tissue oxygenation have an inhibitory effect. We investigated the effects of hypoxia on myofibroblastic properties and linked this to RhoA activity. Hypoxia reversed the myofibroblastic phenotype of primary fibroblasts. This was accompanied by decreased αSMA (ACTA2) expression, alterations in cell contractility, actin reorganization and RhoA activity. We identified a hypoxia-inducible induction of ARHGAP29, which is critically involved in myocardin-related transcription factor-A (MRTF-A) signaling, the differentiation state of myofibroblasts and modulates RhoA activity. This novel link between hypoxia and MRTF-A signaling is likely to be important for ischemia-induced tissue remodeling and the fibrotic response.This article has an associated First Person interview with the first author of the paper.

MicroRNA-101 protects bladder of BOO from hypoxia-induced fibrosis by attenuating TGF-β-smad2/3 signaling

Bladder outlet obstruction is a common disease, which always evokes urinary bladder wall remodeling significantly. It has been suggested that bladder outlet obstruction can make the bladder progression from inflammation to fibrosis, and hypoxia may play a vital role. It has been found the expression of microRNA-101 varied in bladder after BOO. But what role microRNA-101 and hypoxia play in bladder is not well known. This study is to investigate the mechanism of microRNA-101 and hypoxia in fibrosis of bladder after BOO. We found the expression of microRNA-101 and hif-1α increased in bladder after BOO. Hypoxia could promote the expression of extracellular matrix subtypes and microRNA-101 in BSMCs. When microRNA-101b was translated into BSMCs, the smad2/3 signaling pathway was found to repress. Dual luciferase reporter detected that microRNA-101b attenuated the TGF-β signaling pathway by inhibiting the expression of TGFβR1. Then, we conclude microRNA-101b is induced by hypoxia and represses fibrosis of BSMCs by inhibiting the expression of TGFβR1 through TGF-β signaling pathway, and it may be an anti-fibrotic miRNA for therapy. © 2018 IUBMB Life, 71(1):235-243, 2019.