Cellular response to hypoxia involves signaling via Smad proteins

Biomimetic Hydrogels as the Inductive Endochondral Ossification Template for Promoting Bone Regeneration

Repairing critical size bone defects (CSBD) is a major clinical challenge and requires effective intervention by biomaterial scaffolds. Inspired by the fact that the cartilaginous template-based endochondral ossification (ECO) process is crucial to bone healing and development, developing biomimetic biomaterials to promote ECO is recognized as a promising approach for repairing CSBD. With the unique highly hydrated 3D polymeric network, hydrogels can be designed to closely emulate the physiochemical properties of cartilage matrix to facilitate ECO. In this review, the various preparation methods of hydrogels possessing the specific physiochemical properties required for promoting ECO are introduced. The materiobiological impacts of the physicochemical properties of hydrogels, such as mechanical properties, topographical structures and chemical compositions on ECO, and the associated molecular mechanisms related to the BMP, Wnt, TGF-β, HIF-1α, FGF, and RhoA signaling pathways are further summarized. This review provides a detailed coverage on the materiobiological insights required for the design and preparation of hydrogel-based biomaterials to facilitate bone regeneration.

Forces at play: exploring factors affecting the cancer metastasis

Metastatic disease, a leading and lethal indication of deaths associated with tumors, results from the dissemination of metastatic tumor cells from the site of primary origin to a distant organ. Dispersion of metastatic cells during the development of tumors at distant organs leads to failure to comply with conventional treatments, ultimately instigating abrupt tissue homeostasis and organ failure. Increasing evidence indicates that the tumor microenvironment (TME) is a crucial factor in cancer progression and the process of metastatic tumor development at secondary sites. TME comprises several factors contributing to the initiation and progression of the metastatic cascade. Among these, various cell types in TME, such as mesenchymal stem cells (MSCs), lymphatic endothelial cells (LECs), cancer-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), T cells, and tumor-associated macrophages (TAMs), are significant players participating in cancer metastasis. Besides, various other factors, such as extracellular matrix (ECM), gut microbiota, circadian rhythm, and hypoxia, also shape the TME and impact the metastatic cascade. A thorough understanding of the functions of TME components in tumor progression and metastasis is necessary to discover new therapeutic strategies targeting the metastatic tumor cells and TME. Therefore, we reviewed these pivotal TME components and highlighted the background knowledge on how these cell types and disrupted components of TME influence the metastatic cascade and establish the premetastatic niche. This review will help researchers identify these altered components' molecular patterns and design an optimized, targeted therapy to treat solid tumors and restrict metastatic cascade.

Lactate acidosis and simultaneous recruitment of TGF-β leads to alter plasticity of hypoxic cancer cells in tumor microenvironment

Lactate acidosis is often observed in the tumor microenvironment (TME) of solid tumors. This is because glucose breaks down quickly via glycolysis, causing lactate acidity. Lactate is harmful to healthy cells, but is a major oncometabolite for solid cancer cells that do not receive sufficient oxygen. As an oncometabolite, it helps tumor cells perform different functions, which helps solid hypoxic tumor cells spread to other parts of the body. Studies have shown that the acidic TME contains VEGF, Matrix metalloproteinases (MMPs), cathepsins, and transforming growth factor-β (TGF-β), all of which help spread in direct and indirect ways. Although each cytokine is important in its own manner in the TME, TGF-β has received much attention for its role in metastatic transformation. Several studies have shown that lactate acidosis can cause TGF-β expression in solid hypoxic cancers. TGF-β has also been reported to increase the production of fatty acids, making cells more resistant to treatment. TGF-β has also been shown to control the expression of VEGF and MMPs, which helps solid hypoxic tumors become more aggressive by helping them spread and create new blood vessels through an unknown process. The role of TGF-β under physiological conditions has been described previously. In this study, we examined the role of TGF-β, which is induced by lactate acidosis, in the spread of solid hypoxic cancer cells. We also found that TGF-β and lactate work together to boost fatty acid production, which helps angiogenesis and invasiveness.

Small Molecules Targeting the RNA-Binding Protein HuR Inhibit Tumor Growth in Xenografts

The RNA-binding protein Hu antigen R (HuR) is a post-transcriptional regulator critical in several types of diseases, including cancer, making it a promising therapeutic target. We have identified small-molecule inhibitors of HuR through a screening approach used in combination with fragment analysis. A total of 36 new compounds originating from fragment linking or structural optimization were studied to establish structure-activity relationships in the set. Two top inhibitors, 1c and 7c, were further validated by binding assays and cellular functional assays. Both block HuR function by directly binding to the RNA-binding pocket, inhibit cancer cell growth dependence of HuR, and suppress cancer cell invasion. Intraperitoneal administration of inhibitor 1c inhibits tumor growth as a single agent and shows a synergistic effect in combination with chemotherapy docetaxel in breast cancer xenograft models. Mechanistically, 1c interferes with the HuR-TGFB/THBS1 axis.

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.

Cell-Type Dependent Regulation of the Electrogenic Na+/HCO3- Cotransporter 1 (NBCe1) by Hypoxia and Acidosis in Glioblastoma

Glioblastoma multiforme (GBM) is the most common and malignant brain tumour. It is characterised by transcriptionally distinct cell populations. In tumour cells, physiological pH gradients between the intracellular and extracellular compartments are reversed, compared to non-cancer cells. Intracellular pH in tumour cells is alkaline, whereas extracellular pH is acidic. Consequently, the function and/or expression of pH regulating transporters might be altered. Here, we investigated protein expression and regulation of the electrogenic sodium/bicarbonate cotransporter 1 (NBCe1) in mesenchymal (MES)-like hypoxia-dependent and -independent cells, as well as in astrocyte-like glioblastoma cells following chemical hypoxia, acidosis and elucidated putative underlying molecular pathways. Immunoblotting, immunocytochemistry, and intracellular pH recording with the H⁺-sensitive dye 2′,7′-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein were applied. The results show NBCe1 protein abundance and active NBCe1 transport. Hypoxia upregulated NBCe1 protein and activity in MES-like hypoxia-dependent GBM cells. This effect was positively correlated with HIF-1α protein levels, was mediated by TGF-β signalling, and was prevented by extracellular acidosis. In MES-like hypoxia-independent GBM cells, acidosis (but not hypoxia) regulated NBCe1 activity in an HIF-1α-independent manner. These results demonstrate a cell-specific adaptation of NBCe1 expression and activity to the microenvironment challenge of hypoxia and acidosis that depends on their transcriptional signature in GBM.

Hypoxia Selectively Increases a SMAD3 Signaling Axis to Promote Cancer Cell Invasion

Transforming growth factor β (TGFβ) plays a paradoxical role in cancer, first inhibiting then promoting its progression, a duality that poses a real challenge for the development of effective TGFβ-targeted therapies. The major TGFβ downstream effectors, SMAD2 and SMAD3, display both distinct and overlapping functions and accumulating evidence suggests that their activation ratio may contribute to the dual effect of TGFβ. However, the mechanisms responsible for their selective activation remain poorly understood. Here, we provide experimental evidence that hypoxia induces the pro-invasive arm of TGFβ signaling through a selective increase in SMAD3 interaction with SMAD-Anchor for Receptor Activation (SARA). This event relies on HDAC6-dependent SMAD3 bioavailability, as well as increased SARA recruitment to EEA1+ endosomes. A motility gene expression study indicated that SMAD3 selectively increased the expression of ITGB2 and VIM, two genes that were found to be implicated in hypoxia-induced cell invasion and associated with tumor progression and metastasis in cohorts of cancer patients. Furthermore, CAM xenograft assays show the significant benefit of selective inhibition of the SMAD3 signaling pathway as opposed to global TGFβ inhibition in preventing tumor progression. Overall, these results suggest that fine-tuning of the pro-invasive HDAC6-SARA-SMAD3 axis could be a better strategy towards effective cancer treatments.

Hyperoxia induces alveolar epithelial cell apoptosis by regulating mitochondrial function through small mothers against decapentaplegic 3 (SMAD3) and extracellular signal-regulated kinase 1/2 (ERK1/2)

Oxygen therapy and mechanical ventilation are widely used to treat and manage neonatal emergencies in critically ill newborns. However, they are often associated with adverse effects and result in conditions such as chronic lung disease and bronchopulmonary dysplasia. Hence, aclear understanding of the mechanisms underlying hyperoxia-induced lung damage is crucial in order to mitigate the side effects of oxygen-based therapy. Here, we have established an in vitro model of hyperoxia-induced lung damage in type II alveolar epithelial cells (AECIIs) and delineated the molecular basis of oxygen therapy-induced impaired alveolar development. Thus, AECIIs were exposed to a hyperoxic environment and their cell viability, cell cycle progression, apoptosis, mitochondrial integrity and dynamics, and energy metabolism were assessed. The results showed that hyperoxia has no significant effect as an inhibitor of SMAD3 and ERK1/2 in AECIIs, but leads to significant inhibition of cell viability. Further, hyperoxia was found to promote AECII apoptosis and mitochondrial, whereas chemical inhibition of SMAD3 or ERK1/2 further exacerbated the detrimental effects of hyperoxia in AECIIs. Overall, these findings presented herein demonstrate the critical role of SMAD/ERK signaling in the regulation of AECII behavior in varying oxygen environments. Thus, this study offers novel insights for the prevention of neonatal lung dysfunction in premature infants.

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

Partial EMT in head and neck cancer biology: a spectrum instead of a switch

Our understanding of epithelial-to-mesenchymal transition (EMT) has slowly evolved from a simple two state, binary model to a multi-step, dynamic continuum of epithelial-to-mesenchymal plasticity, with metastable intermediate transition states that may drive cancer metastasis. Head and neck cancer is no exception, and in this review, we use head and neck as a case study for how partial-EMT (p-EMT) cell states may play an important role in cancer progression. In particular, we summarize recent in vitro and in vivo studies that uncover these intermediate transition states, which exhibit both epithelial and mesenchymal properties and appear to have distinct advantages in migration, survival in the bloodstream, and seeding and propagation within secondary metastatic sites. We then summarize the common and distinct regulators of p-EMT as well as methodologies for identifying this unique cellular subpopulation, with a specific emphasis on the role of cutting-edge technologies, such as single cell approaches. Finally, we propose strategies to target p-EMT cells, highlighting potential opportunities for therapeutic intervention to specifically target the process of metastasis. Thus, although significant challenges remain, including numerous gaps in current knowledge, a deeper understanding of EMT plasticity and a genuine identification of EMT as spectrum rather than a switch will be critical for improving patient diagnosis and treatment across oncology.

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.

Preventive but nontherapeutic effect of danshensu on hypoxic pulmonary hypertension

OBJECTIVES

Danshensu is a traditional Chinese medicine that is used for treatment of cardiovascular diseases. We previously demonstrated its preventive effect against early-stage hypoxic pulmonary hypertension (HPH) in a rat model. To determine whether danshensu treatment might be useful for patients with chronic HPH, we examined its therapeutic effect in rats with prolonged HPH.

METHODS

Adult Sprague-Dawley rats received danshensu (80, 160, and 320 mg/kg) during or after hypoxia exposure to assess preventive and therapeutic effects, respectively. Right ventricle systolic pressure (RVSP), right ventricle hypertrophy index (RVHI), and mean left carotid artery pressure (mCAP) were measured in each group. Western blotting was used to assess transforming growth factor (TGF)-β expression levels in rats and cultured cells exposed to hypoxia.

RESULTS

Preventive danshensu treatment significantly reduced the elevation of RVSP and RVHI in rats exposed to hypoxia, whereas therapeutic danshensu treatment did not; mCAP did not change in any treatment group. The increased expression levels of TGF-β induced by hypoxia were inhibited by preventive danshensu treatment, but not by therapeutic danshensu treatment.

CONCLUSIONS

Although danshensu treatment could prevent HPH, it had no obvious therapeutic effect after development of HPH. Therefore, danshensu might be suitable for clinical treatment of early-stage HPH.

TGF-β: The missing link in obesity-associated airway diseases?

Obesity is emerging as a global public health epidemic. The co-morbidities associated with obesity significantly contribute to reduced quality of life, mortality, and global healthcare burden. Compared to other asthma comorbidities, obesity prominently engenders susceptibility to inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), contributes to greater disease severity and evokes insensitivity to current therapies. Unlike in other metabolic diseases associated with obesity, the mechanistic link between obesity and airway diseases is only poorly defined. Transforming growth factor-β (TGF-β) is a pleiotropic inflammatory cytokine belonging to a family of growth factors with pivotal roles in asthma. In this review, we summarize the role of TGF-β in major obesity-associated co-morbidities to shed light on mechanisms of the diseases. Literature evidence shows that TGF-β mechanistically links many co-morbidities with obesity through its profibrotic, remodeling, and proinflammatory functions. We posit that TGF-β plays a similar mechanistic role in obesity-associated inflammatory airway diseases such as asthma and COPD. Concerning the role of TGF-β on metabolic effects of obesity, we posit that TGF-β has a similar mechanistic role in obesity-associated inflammatory airway diseases in interplay with different comorbidities such as hypertension, metabolic diseases like type 2 diabetes, and cardiomyopathies. Future studies in TGF-β-dependent mechanisms in obesity-associated inflammatory airway diseases will advance our understanding of obesity-induced asthma and help find novel therapeutic targets for prevention and treatment.

SARS-CoV-2 and Glutamine: SARS-CoV-2 Triggered Pathogenesis via Metabolic Reprograming of Glutamine in Host Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as coronavirus disease 2019 (COVID-19) pandemic, has killed more than a million people worldwide, and researchers are constantly working to develop therapeutics in the treatment and prevention of this new viral infection. To infect and induced pathogenesis as observed in other viral infections, we postulated that SARS-CoV-2 may also require an escalation in the anabolic metabolism, such as glucose and glutamine, to support its energy and biosynthetic requirements during the infection cycle. Recently, the requirement of altered glucose metabolism in SARS-CoV-2 pathogenesis was demonstrated, but the role of dysregulated glutamine metabolism is not yet mentioned for its infection. In this perspective, we have attempted to provide a summary of possible biochemical events on putative metabolic reprograming of glutamine in host cells upon SARS-CoV-2 infection by comparison to other viral infections/cancer metabolism and available clinical data or research on SARS-CoV-2 pathogenesis. This systematic hypothesis concluded the vital role of glutaminase-1 (GLS1), phosphoserine aminotransferase (PSAT1), hypoxia-inducible factor-1 alpha (HIF-1α), mammalian target of rapamycin complex 1 (mTORC1), glutamine-fructose amidotransferase 1/2 (GFAT1/2), and transcription factor Myc as key cellular factors to mediate and promote the glutamine metabolic reprogramming in SARS-CoV-2 infected cells. In absence of concrete data available for SARS-CoV-2 induced metabolic reprogramming of glutamine, this study efforts to connect the gaps with available clinical shreds of evidence in SARS-CoV-2 infection with altered glutamine metabolism and hopefully could be beneficial in the designing of strategic methods for therapeutic development with elucidation using in vitro or in vivo approaches.

Roles of Hydrogen Sulfide Donors in Common Kidney Diseases

Hydrogen sulfide (H2S) plays a key role in the regulation of physiological processes in mammals. The decline in H2S level has been reported in numerous renal disorders. In animal models of renal disorders, treatment with H2S donors could restore H2S levels and improve renal functions. H2S donors suppress renal dysfunction by regulating autophagy, apoptosis, oxidative stress, and inflammation through multiple signaling pathways, such as TRL4/NLRP3, AMP-activated protein kinase/mammalian target of rapamycin, transforming growth factor-β1/Smad3, extracellular signal-regulated protein kinases 1/2, mitogen-activated protein kinase, and nuclear factor kappa B. In this review, we summarize recent developments in the effects of H2S donors on the treatment of common renal diseases, including acute/chronic kidney disease, renal fibrosis, unilateral ureteral obstruction, glomerulosclerosis, diabetic nephropathy, hyperhomocysteinemia, drug-induced nephrotoxicity, metal-induced nephrotoxicity, and urolithiasis. Novel H2S donors can be designed and applied in the treatment of common renal diseases.

Hypoxia, partial EMT and collective migration: Emerging culprits in metastasis

Epithelial-mesenchymal transition (EMT) is a cellular biological process involved in migration of primary cancer cells to secondary sites facilitating metastasis. Besides, EMT also confers properties such as stemness, drug resistance and immune evasion which can aid a successful colonization at the distant site. EMT is not a binary process; recent evidence suggests that cells in partial EMT or hybrid E/M phenotype(s) can have enhanced stemness and drug resistance as compared to those undergoing a complete EMT. Moreover, partial EMT enables collective migration of cells as clusters of circulating tumor cells or emboli, further endorsing that cells in hybrid E/M phenotypes may be the 'fittest' for metastasis. Here, we review mechanisms and implications of hybrid E/M phenotypes, including their reported association with hypoxia. Hypoxia-driven activation of HIF-1α can drive EMT. In addition, cyclic hypoxia, as compared to acute or chronic hypoxia, shows the highest levels of active HIF-1α and can augment cancer aggressiveness to a greater extent, including enriching for a partial EMT phenotype. We also discuss how metastasis is influenced by hypoxia, partial EMT and collective cell migration, and call for a better understanding of interconnections among these mechanisms. We discuss the known regulators of hypoxia, hybrid EMT and collective cell migration and highlight the gaps which needs to be filled for connecting these three axes which will increase our understanding of dynamics of metastasis and help control it more effectively.

Knockout of TRPV1 Exacerbates Ischemia-reperfusion-induced Renal Inflammation and Injury in Obese Mice

BACKGROUND/AIM

Transient receptor potential vanilloid type 1 (TRPV1) has anti-inflammatory properties. The present study aimed to investigate the role of TRPV1 in renal inflammatory responses and tissue injury following renal ischemia-reperfusion (I/R) in diet-induced obese mice.

MATERIALS AND METHODS

TRPV1 knockout and wild type mice were fed a normal or western diet (WD) for 23 weeks and were then subjected to renal I/R injury.

RESULTS

TRPV1 knockout mice showed enhanced WD-induced renal macrophage infiltration and collagen deposition. Knocking out TRPV1 exacerbated renal I/R-induced increase of malondialdehyde, interleukin-6, monocyte chemoattractant protein-1, and NF-ĸB in obese mice. Similar results were observed in the expression of phosphorylated Smad1 and Smad2/3. Blockade of calcitonin gene-related peptide (CGRP) receptors with CGRP8-37 worsened the I/R-induced renal inflammation and injury.

CONCLUSION

Our data indicate that preserving TRPV1 expression and function may prevent renal I/R injury in obesity likely through alleviating inflammatory responses.

Hypoxia-Induced Epithelial-Mesenchymal Transition in Cancers: HIF-1α and Beyond

Metastasis is the main cause of cancer-related mortality. Although the actual process of metastasis remains largely elusive, epithelial-mesenchymal transition (EMT) has been considered as a major event in metastasis. Besides, hypoxia is common in solid cancers and has been considered as an important factor for adverse treatment outcomes including metastasis. Since EMT and hypoxia potentially share several signaling pathways, many recent studies focused on investigate the issue of hypoxia-induced EMT. Among all potential mediators of hypoxia-induced EMT, hypoxia-inducible factor-1α (HIF-1α) has been studied extensively. Moreover, there are other potential mediators that may also contribute to the process. This review aims to summarize the recent reports on hypoxia-induced EMT by HIF-1α or other potential mediators and provide insights for further investigations on this issue. Ultimately, better understanding of hypoxia-induced EMT may allow us to develop anti-metastatic strategies and improve treatment outcomes.

Hypoxia and transforming growth factor β1 regulation of long non-coding RNA transcriptomes in human pulmonary fibroblasts

One of the key characteristics of idiopathic pulmonary fibrosis (IPF) is accumulation of excess fibrous tissue in the lung, which leads to hypoxic conditions. Transforming growth factor (TGF) β is a major mediator that promotes the differentiation of fibroblasts to myofibroblasts. However, how hypoxia and TGFβ together contribute the pathogenesis of IPF is poorly understood. Long non-coding RNAs (lncRNAs) have regulatory effects on certain genes and are involved in many diseases. In this study, we determined the effects of hypoxia and/or TGFβ on mRNA and lncRNA transcriptomes in pulmonary fibroblasts. Hypoxia and TGFβ1 synergistically increased myofibroblast marker expression. RNA sequencing revealed that hypoxia and TGFβ1 treatment resulted in significant changes in 669 lncRNAs and 2,676 mRNAs compared to 150 lncRNAs and 858 mRNAs in TGFβ1 alone group and 222 lncRNAs and 785 mRNAs in hypoxia alone group. TGFβ1 induced the protein expression of HIF-1α, but not HIF-2α. On the other hand, hypoxia enhanced the TGFβ1-induced phosphorylation of Smad3, suggesting a cross-talk between these two signaling pathways. In all, 10 selected lncRNAs (five-up and five-down) in RNA sequencing data were validated using real-time PCR. Two lncRNAs were primarily located in cytoplasm, three in nuclei and five in both nuclei and cytoplasm. The silencing of HIF-1α and Smad3, but not Smad2 and HIF-2α rescued the downregulation of FENDRR by hypoxia and TGFβ1. In conclusion, hypoxia and TGFβ1 synergistically regulate mRNAs and lncRNAs involved in several cellular processes, which may contribute to the pathogenesis of IPF.

Role of hypoxia in skeletal muscle fibrosis: Synergism between hypoxia and TGF-β signaling upregulates CCN2/CTGF expression specifically in muscle fibers

Several skeletal muscle diseases are characterized by fibrosis, the excessive accumulation of extracellular matrix. Transforming growth factor-β (TGF-β) and connective tissue growth factor (CCN2/CTGF) are two profibrotic factors augmented in fibrotic skeletal muscle, together with signs of reduced vasculature that implies a decrease in oxygen supply. We observed that fibrotic muscles are characterized by the presence of positive nuclei for hypoxia-inducible factor-1α (HIF-1α), a key mediator of the hypoxia response. However, it is not clear how a hypoxic environment could contribute to the fibrotic phenotype in skeletal muscle. We evaluated the role of hypoxia and TGF-β on CCN2 expression in vitro. Fibroblasts, myoblasts and differentiated myotubes were incubated with TGF-β1 under hypoxic conditions. Hypoxia and TGF-β1 induced CCN2 expression synergistically in myotubes but not in fibroblasts or undifferentiated muscle progenitors. This induction requires HIF-1α and the Smad-independent TGF-β signaling pathway. We performed in vivo experiments using pharmacological stabilization of HIF-1α or hypoxia-induced via hindlimb ischemia together with intramuscular injections of TGF-β1, and we found increased CCN2 expression. These observations suggest that hypoxic signaling together with TGF-β signaling, which are both characteristics of a fibrotic skeletal muscle environment, induce the expression of CCN2 in skeletal muscle fibers and myotubes.

Endothelial-to-Mesenchymal Transition (EndoMT): Roles in Tumorigenesis, Metastatic Extravasation and Therapy Resistance

Cancer cells evolve in a very complex tumor microenvironment, composed of several cell types, among which the endothelial cells are the major actors of the tumor angiogenesis. Today, these cells are also characterized for their plasticity, as endothelial cells have demonstrated their potential to modify their phenotype to differentiate into mesenchymal cells through the endothelial-to-mesenchymal transition (EndoMT). This cellular plasticity is mediated by various stimuli including transforming growth factor-β (TGF-β) and is modulated dependently of experimental conditions. Recently, emerging evidences have shown that EndoMT is involved in the development and dissemination of cancer and also in cancer cell to escape from therapeutic treatment. In this review, we summarize current updates on EndoMT and its main induction pathways. In addition, we discuss the role of EndoMT in tumorigenesis, metastasis, and its potential implication in cancer therapy resistance.

Interactions between TGF-β type I receptor and hypoxia-inducible factor-α mediates a synergistic crosstalk leading to poor prognosis for patients with clear cell renal cell carcinoma

To investigate the significance of expression of HIF-1α, HIF-2α, and SNAIL1 proteins; and TGF-β signaling pathway proteins in ccRCC, their relation with clinicopathological parameters and patient's survival were examined. We also investigated potential crosstalk between HIF-α and TGF-β signaling pathway, including the TGF-β type 1 receptor (ALK5-FL) and the intracellular domain of ALK5 (ALK5-ICD). Tissue samples from 154 ccRCC patients and comparable adjacent kidney cortex samples from 38 patients were analyzed for HIF-1α/2α, TGF-β signaling components, and SNAIL1 proteins by immunoblot. Protein expression of HIF-1α and HIF-2α were significantly higher, while SNAIL1 had similar expression levels in ccRCC compared with the kidney cortex. HIF-2α associated with poor cancer-specific survival, while HIF-1α and SNAIL1 did not associate with survival. Moreover, HIF-2α positively correlated with ALK5-ICD, pSMAD2/3, and PAI-1; HIF-1α positively correlated with pSMAD2/3; SNAIL1 positively correlated with ALK5-FL, ALK5-ICD, pSMAD2/3, PAI-1, and HIF-2α. Intriguingly, in vitro experiments performed under normoxic conditions revealed that ALK5 interacts with HIF-1α and HIF-2α, and promotes their expression and the expression of their target genes GLUT1 and CA9, in a VHL dependent manner. We found that ALK5 induces expression of HIF-1α and HIF-2α, through its kinase activity. Under hypoxic conditions, HIF-α proteins correlated with the activated TGF-β signaling pathway. In conclusion, we reveal that ALK5 plays a pivotal role in synergistic crosstalk between TGF-β signaling and hypoxia pathway, and that the interaction between ALK5 and HIF-α contributes to tumor progression.

Hypoxia mimicking hydrogels to regulate the fate of transplanted stem cells

Controlling the phenotype of transplanted stem cells is integral to ensuring their therapeutic efficacy. Hypoxia is a known regulator of stem cell fate, the effects of which can be mimicked using hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors such as dimethyloxalylglycine (DMOG). By releasing DMOG from mesenchymal stem cell (MSC) laden alginate hydrogels, it is possible to stabilize HIF-1α and enhance its nuclear localization. This correlated with enhanced chondrogenesis and a reduction in the expression of markers associated with chondrocyte hypertrophy, as well as increased SMAD 2/3 nuclear localization in the encapsulated MSCs. In vivo, DMOG delivery significantly reduced mineralisation of the proteoglycan-rich cartilaginous tissue generated by MSCs within alginate hydrogels loaded with TGF-β3 and BMP-2. Together these findings point to the potential of hypoxia mimicking hydrogels to control the fate of stem cells following their implantation into the body. STATEMENT OF SIGNIFICANCE: There are relatively few examples where in vivo delivery of adult stem cells has demonstrated a true therapeutic benefit. This may be attributed, at least in part, to a failure to control the fate of transplanted stem cells in vivo. In this paper we describe the development of hydrogels that mimic the effects of hypoxia on encapsulated stem cells. In vitro, these hydrogels enhance chondrogenesis of MSCs and suppress markers associated with chondrocyte hypertrophy. In an in vivo environment that otherwise supports progression along an endochondral pathway, we show that these hydrogels will instead direct mesenchymal stem cells (MSCs) to produce a more stable, cartilage-like tissue. In addition, we explore potential molecular mechanisms responsible for these phenotypic changes in MSCs.

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

The role of HIF-1α-VEGF pathway in bronchiolitis obliterans after lung transplantation

Background

Graft function may be affected if the organ is exposed to hypoxia. We hypothesized that bronchiolitis obliterans (BO) after lung transplantation is associated with hypoxia-inducible factor-1α (HIF-1α). This study compares the expression of HIF-1α and its downstream proteins in allograft and isograft to explore the relationship between this pathway and BO in rats.

Material and methods

We performed an orthotopic left pulmonary transplant model using the tri-cuff vascular anastomosis method and evaluated the histopathology, including the severity of fibrosis (SF). The expression of HIF-1α, VEGF-A, and VEGFR-2 was accessed by immunohistochemistry.

Results

The imageology and pathology showed that the allogenic model developed BO 90 days after the operation. The percentages of a high expression of HIF-1α, VEGF-A, and VEGFR-2 in the allogeneic group were 77.27, 63.64, and 68.18% higher than in the isogeneic group, respectively. The SF score was highest in the allograft and was positively correlated with the expression of the proteins.

Conclusion

This model can simulate human BO after lung transplantation. The expression of HIF-1α and its downstream proteins in post-transplantation was up-regulated, suggesting that activation of the HIF-1α-VEGF pathway might be involved in the occurrence and prognosis of BO.

Analysis of Hypoxiamir-Gene Regulatory Network Identifies Critical MiRNAs Influencing Cell-Cycle Regulation Under Hypoxic Conditions

BACKGROUND

Hypoxia is a pathophysiological condition which arises due to low oxygen concentration in conditions like cardiovascular diseases, inflammation, ascent to higher altitude, malignancies, deep sea diving, prenatal birth, etc. A number of microRNAs (miRNAs), Transcription Factors (TFs) and genes have been studied separately for their role in hypoxic adaptation and controlling cell-cycle progression and apoptosis during this stress.

OBJECTIVE

We hypothesize that miRNAs and TFs may act in conjunction to regulate a multitude of genes and play a crucial and combinatorial role during hypoxia-stress-responses and associated cellcycle control mechanisms.

METHOD

We collected a comprehensive and non-redundant list of human hypoxia-responsive miRNAs (also known as hypoxiamiRs). Their experimentally validated gene-targets were retrieved from various databases and a comprehensive hypoxiamiR-gene regulatory network was built.

RESULTS

Functional characterization and pathway enrichment of genes identified phospho-proteins as enriched nodes. The phospho-proteins which were localized both in the nucleus and cytoplasm and could potentially play important role as signaling molecules were selected; and further pathway enrichment revealed that most of them were involved in NFkB signaling. Topological analysis identified several critical hypoxiamiRs and network perturbations confirmed their importance in the network. Feed Forward Loops (FFLs) were identified in the subnetwork of enriched genes, miRNAs and TFs. Statistically significant FFLs consisted of four miRNAs (hsa-miR-182-5p, hsa- miR-146b-5p, hsa-miR-96, hsa-miR-20a) and three TFs (SMAD4, FOXO1, HIF1A) both regulating two genes (NFkB1A and CDKN1A).

CONCLUSION

Detailed BioCarta pathway analysis identified that these miRNAs and TFs together play a critical and combinatorial role in regulating cell-cycle under hypoxia, by controlling mechanisms that activate cell-cycle checkpoint protein, CDKN1A. These modules work synergistically to regulate cell-proliferation, cell-growth, cell-differentiation and apoptosis during hypoxia. A detailed mechanistic molecular model of how these co-regulatory FFLs may regulate the cell-cycle transitions during hypoxic stress conditions is also put forth. These biomolecules may play a crucial and deterministic role in deciding the fate of the cell under hypoxic-stress.

MiR-425 expression profiling in acute myeloid leukemia might guide the treatment choice between allogeneic transplantation and chemotherapy

Background

Acute myeloid leukemia (AML) is a highly heterogeneous disease. MicroRNAs function as important biomarkers in the clinical prognosis of AML.

Methods

This study identified miR-425 as a prognostic factor in AML by screening the TCGA dataset. A total of 162 patients with AML were enrolled for the study and divided into chemotherapy and allogeneic hematopoietic stem cell transplantation (allo-HSCT) groups.

Results

In the chemotherapy group, patients with high miR-425 expression had significantly longer overall survival (OS) and event-free survival (EFS) compared with patients with low miR-425 expression. In multivariate analyses, high miR-425 expression remained independently predictive of a better OS (HR = 0.502, P = 0.005) and EFS (HR = 0.432, P = 0.001) compared with patients with low miR-425 expression. Then, all patients were divided into two groups based on the median expression levels of miR-425. Notably, the patients undergoing allo-HSCT had significantly better OS (HR = 0.302, P < 0.0001) and EFS (HR = 0.379, P < 0.0001) compared with patients treated with chemotherapy in the low-miR-425-expression group. Mechanistically, high miR-425 expression levels were associated with a profile significantly involved in regulating cellular metabolism. Among these genes, MAP3K5, SMAD2, and SMAD5 were predicted targets of miR-425.

Conclusions

The expression of miR-425 may be useful in identifying patients in need of strategies to select the optimal therapy between chemotherapy and allo-HSCT treatment regimens. Patients with low miR-425 expression may consider early allo-HSCT.

A Comprehensive Roadmap of Murine Spermatogenesis Defined by Single-Cell RNA-Seq

Spermatogenesis requires intricate interactions between the germline and somatic cells. Within a given cross section of a seminiferous tubule, multiple germ and somatic cell types co-occur. This cellular heterogeneity has made it difficult to profile distinct cell types at different stages of development. To address this challenge, we collected single-cell RNA sequencing data from ∼35,000 cells from the adult mouse testis and identified all known germ and somatic cells, as well as two unexpected somatic cell types. Our analysis revealed a continuous developmental trajectory of germ cells from spermatogonia to spermatids and identified candidate transcriptional regulators at several transition points during differentiation. Focused analyses delineated four subtypes of spermatogonia and nine subtypes of Sertoli cells; the latter linked to histologically defined developmental stages over the seminiferous epithelial cycle. Overall, this high-resolution cellular atlas represents a community resource and foundation of knowledge to study germ cell development and in vivo gametogenesis.

2-Methoxyestradiol Attenuates Testosterone-Induced Benign Prostate Hyperplasia in Rats through Inhibition of HIF-1α/TGF-β/Smad2 Axis

Benign prostatic hyperplasia (BPH) is a common disorder in the male population. 2-Methoxyestradiol (2ME) is an end metabolite of estrogens with pleiotropic pharmacological properties. This study aimed to explore the potential ameliorative effects of 2ME against testosterone-induced BPH in rats. 2-Methoxyestradiol (50 and 100 mg/kg, dissolved in DMSO) prevented the rise in prostatic index and weight in comparison to testosterone-alone-treated animals for 2 weeks. Histological examination indicated that 2ME ameliorated pathological changes in prostate architecture. This was confirmed by the ability of 2ME to decrease the glandular epithelial height when compared to the testosterone group. Also, 2ME improved testosterone-induced oxidative stress as it inhibited the rise in lipid peroxide content and the exhaustion of superoxide dismutase (SOD) activity. The beneficial effects of 2ME against the development of BPH were substantiated by assessing proliferation markers, preventing the rise in cyclin D1 protein expression and enhancing Bax/Bcl2 mRNA ratio. It significantly reduced prostate content of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), nuclear factor κB (NF-κB), and transforming growth factor β (TGF-β). In addition, 2ME reduced hypoxia-inducible factor 1-α (HIF-1α) and phospho-Smad2 (p-Smad2) protein expression compared to the testosterone group. In conclusion, 2ME attenuates experimentally induced BPH by testosterone in rats through, at least partly, inhibition of HIF-1α/TGF-β/Smad2 axis.

Thrombospondin-1 regulation of latent TGF-β activation: A therapeutic target for fibrotic disease

Transforming growth factor-β (TGF-β) is a central player in fibrotic disease. Clinical trials with global inhibitors of TGF-β have been disappointing, suggesting that a more targeted approach is warranted. Conversion of the latent precursor to the biologically active form of TGF-β represents a novel approach to selectively modulating TGF-β in disease, as mechanisms employed to activate latent TGF-β are typically cell, tissue, and/or disease specific. In this review, we will discuss the role of the matricellular protein, thrombospondin 1 (TSP-1), in regulation of latent TGF-β activation and the use of an antagonist of TSP-1 mediated TGF-β activation in a number of diverse fibrotic diseases. In particular, we will discuss the TSP-1/TGF-β pathway in fibrotic complications of diabetes, liver fibrosis, and in multiple myeloma. We will also discuss emerging evidence for a role for TSP-1 in arterial remodeling, biomechanical modulation of TGF-β activity, and in immune dysfunction. As TSP-1 expression is upregulated by factors induced in fibrotic disease, targeting the TSP-1/TGF-β pathway potentially represents a more selective approach to controlling TGF-β activity in disease.

Novel microtubule inhibitor MPT0B098 inhibits hypoxia-induced epithelial-to-mesenchymal transition in head and neck squamous cell carcinoma

Background

Tumor hypoxia-induced epithelial–mesenchymal transition (EMT) is critical in promoting cancer metastasis. We recently discovered a novel microtubule inhibitor, MPT0B098, that employs a novel antitumor mechanism. It destabilizes hypoxia-inducible factor (HIF)-1α mRNA by blocking the function of human antigen R. Thus, we proposed that MPT0B098 modulates hypoxia-induced EMT.

Methods

In vitro IC₅₀ values were determined through the methylene blue dye assay. To investigate molecular events, reverse transcriptase-polymerase chain reaction, Western blotting, immunofluorescence staining, and wound healing assay were employed.

Results

MPT0B098 significantly inhibited HIF-1α expression, epithelial-to-mesenchymal morphology changes, and migratory ability in the human head and neck squamous cell carcinoma cell line OEC-M1. Furthermore, after MPT0B098 treatment, the expression of two mesenchymal markers, vimentin and N-cadherin, was downregulated under hypoxic conditions. Moreover, MPT0B098 suppressed hypoxia-induced EMT in part by inhibiting EMT-activating transcription factors, Twist and SNAI2/Slug. In addition, the inhibition of hypoxia-induced F-actin rearrangement and focal adhesion kinase phosphorylation may have contributed to suppression of EMT by MPT0B098in OEC-M1 cells. MPT0B098 significantly inhibited transforming growth factor(TGF)-β-induced phosphorylation of receptor-associated Smad2/3 by downregulating TGF-β mRNA and protein expression.

Conclusions

Taken together, this study provides a novel insight into the role of MPT0B098 in inhibiting hypoxia-induced EMT, suggesting its potential use for treating head and neck cancers.

Electronic supplementary material

The online version of this article (10.1186/s12929-018-0432-6) contains supplementary material, which is available to authorized users.

Bisecting N-Acetylglucosamine Structures Inhibit Hypoxia-Induced Epithelial-Mesenchymal Transition in Breast Cancer Cells

The epithelial-mesenchymal transition (EMT) process plays a key role in many biological processes, including tissue fibrosis, metastatic diseases, and cancer progression. EMT can be induced by certain factors, notably hypoxia, in the tumor microenvironment. Aberrant levels of certain N-glycans is associated with cancer progression. We used an integrated strategy (mass spectrometry in combination with lectin microarray analysis) to elucidate aberrant glycosylation in a hypoxia-induced EMT model using breast cancer cell lines MCF7 and MDA-MB-231. The model showed reduced levels of bisecting GlcNAc structures, and downregulated expression of the corresponding glycosyltransferase MGAT3. MGAT3 overexpression in MCF7 suppressed cell migration, proliferation, colony formation, expression of EMT markers, and AKT signaling pathway, whereas MGAT3 knockdown (shRNA silencing) had opposite effects. Our findings clearly demonstrate the functional role (and effects of dysregulation) of bisecting GlcNAc structures in hypoxia-induced EMT, and provide a useful basis for further detailed studies of physiological functions of these structures in breast cancer.

Hypoxia mimetic activity of VCE-004.8, a cannabidiol quinone derivative: implications for multiple sclerosis therapy

Background

Multiple sclerosis (MS) is characterized by a combination of inflammatory and neurodegenerative processes variously dominant in different stages of the disease. Thus, immunosuppression is the goal standard for the inflammatory stage, and novel remyelination therapies are pursued to restore lost function. Cannabinoids such as ⁹Δ-THC and CBD are multi-target compounds already introduced in the clinical practice for multiple sclerosis (MS). Semisynthetic cannabinoids are designed to improve bioactivities and druggability of their natural precursors. VCE-004.8, an aminoquinone derivative of cannabidiol (CBD), is a dual PPARγ and CB₂ agonist with potent anti-inflammatory activity. Activation of the hypoxia-inducible factor (HIF) can have a beneficial role in MS by modulating the immune response and favoring neuroprotection and axonal regeneration.

Methods

We investigated the effects of VCE-004.8 on the HIF pathway in different cell types. The effect of VCE-004.8 on macrophage polarization and arginase 1 expression was analyzed in RAW264.7 and BV2 cells. COX-2 expression and PGE₂ synthesis induced by lipopolysaccharide (LPS) was studied in primary microglia cultures. The efficacy of VCE-004.8 in vivo was evaluated in two murine models of MS such as experimental autoimmune encephalomyelitis (EAE) and Theiler’s virus-induced encephalopathy (TMEV).

Results

Herein, we provide evidence that VCE-004.8 stabilizes HIF-1α and HIF-2α and activates the HIF pathway in human microvascular endothelial cells, oligodendrocytes, and microglia cells. The stabilization of HIF-1α is produced by the inhibition of the prolyl-4-hydrolase activity of PHD1 and PDH2. VCE-004.8 upregulates the expression of HIF-dependent genes such as erythropoietin and VEGFA, induces angiogenesis, and enhances migration of oligodendrocytes. Moreover, VCE-004.8 blunts IL-17-induced M1 polarization, inhibits LPS-induced COX-2 expression and PGE₂ synthesis, and induces expression of arginase 1 in macrophages and microglia. In vivo experiments showed efficacy of VCE-004.8 in EAE and TMEV. Histopathological analysis revealed that VCE-004.8 treatments prevented demyelination, axonal damage, and immune cells infiltration. In addition, VCE-004.8 downregulated the expression of several genes closely associated with MS physiopathology, including those underlying the production of chemokines, cytokines, and adhesion molecules.

Conclusions

This study provides new significant insights about the potential role of VCE-004.8 for MS treatment by ameliorating neuroinflammation and demyelination.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1103-y) contains supplementary material, which is available to authorized users.

Targeting the microenvironment in solid tumors

Tumorigenesis is a complex and dynamic process involving different cellular and non-cellular elements composed of tumor microenvironment (TME). The interaction of TME with cancer cells is responsible for tumor development, progression and drug resistance. TME consists of non malignant cells of the tumor such as cancer associated fibroblasts (CAFs), endothelial cells and pericytes composing tumor vasculature, immune and inflammatory cells, bone marrow derived cells, and the extracellular matrix (ECM) establishing a complex cross-talk with tumor. These interactions contribute towards proliferation and invasion of the tumor by producing growth factors, chemokines and matrix-degrading enzymes. ECM is a complex system containing macromolecules with distinctive physical, biochemical and biomechanical properties. During tumorigenesis this system is deregulated favoring the generation of tumorigenic microenvironment enhancing tumor-associated angiogenesis and inflammation. An important step of anticancer treatment is the identification of the biological alterations present in TME in order to target these key molecular players. Multitargeted approaches, providing a simultaneous inhibition of TME components, may offer a more efficient way to treat cancer. In this manuscript we overview the function of each components of TME and the treatments targeting the key players.

Glutaminolysis is required for transforming growth factor-β1-induced myofibroblast differentiation and activation

Myofibroblasts participate in physiological wound healing and pathological fibrosis. Myofibroblast differentiation is characterized by the expression of α-smooth muscle actin and extracellular matrix proteins and is dependent on metabolic reprogramming. In this study, we explored the role of glutaminolysis and metabolites of TCA in supporting myofibroblast differentiation. Glutaminolysis converts Gln into α-ketoglutarate (α-KG), a critical intermediate in the TCA cycle. Increases in the steady-state concentrations of TCA cycle metabolites including α-KG, succinate, fumarate, malate, and citrate were observed in TGF-β1-differentiated myofibroblasts. The concentration of glutamate was also increased in TGF-β1-differentiated myofibroblasts compared with controls, whereas glutamine levels were decreased, suggesting enhanced glutaminolysis. This was associated with TGF-β1-induced expression of the glutaminase (GLS) isoform, GLS1, which converts Gln into glutamate, at both the mRNA and protein levels. The stimulation of GLS1 expression by TGF-β1 was dependent on both SMAD3 and p38 mitogen-activated protein kinase activation. Depletion of extracellular Gln prevented TGF-β1-induced myofibroblast differentiation. The removal of extracellular Gln postmyofibroblast differentiation decreased the expression of the profibrotic markers fibronectin and hypoxia-inducible factor-1α and reversed TGF-β1-induced metabolic reprogramming. Silencing of GLS1 expression, in the presence of Gln, abrogated TGF-β1-induced expression of profibrotic markers. Treatment of GLS1-deficient myofibroblasts with exogenous glutamate or α-KG restored TGF-β1-induced expression of profibrotic markers in GLS1-deficient myofibroblasts. Together, these data demonstrate that glutaminolysis is a critical component of myofibroblast metabolic reprogramming that regulates myofibroblast differentiation.

Effects of Acute Confinement Stress-induced Hypothalamic-Pituitary Adrenal Axis Activation and Concomitant Peripheral and Central Transforming Growth Factor-β1 Measures in Nonhuman Primates

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine with anti-inflammatory, immunosuppressive, and neuroprotective properties. The hypothalamic-pituitary-adrenal axis and immune system exert bidirectional influences on each other, via cortisol and TGF-β1, but the exact nature of the interaction is not well characterized. The current study examined the effects, in bonnet macaques (Macaca radiata), of two consecutive acute confinement stress periods in an unfamiliar room while mildly restrained, first without and then with dexamethasone pretreatment (0.01 mg/kg intramuscular). Preceding the confinement studies, a non-stress control condition obtained contemporaneous levels of cortisol and TGF-β1 in both plasma and cerebrospinal fluid to match the confinement stress studies. Subjects were reared under either normative or variable foraging demand conditions. Since there were no rearing effects at baseline or for any of the conditions tested—either for cortisol or TGF-β—the study analyses were conducted on the combined rearing groups. The stress condition increased both plasma and cerebrospinal fluid cortisol levels whereas dexamethasone pretreatment decreased cortisol concentrations to below baseline levels despite stress. The stress condition decreased TGF-β1 concentrations only in cerebrospinal fluid but not in serum. Together, the data suggested that stress-induced reductions of a centrally active neuroprotective cytokine occur in the face of hypothalamic-pituitary-adrenal axis activation, potentially facilitating glucocortoid-induced neurotoxicity. Stress-induced reductions of neuroprotective cytokines prompt exploration of protective measures against glucocorticoid-induced neurotoxicity.

Reactive oxygen species and fibrosis: further evidence of a significant liaison

Age-related diseases such as obesity, diabetes, non-alcoholic fatty liver disease, chronic kidney disease and cardiomyopathy are frequently associated with fibrosis. Work within the last decade has improved our understanding of the pathophysiological mechanisms contributing to fibrosis development. In particular, oxidative stress and the antioxidant system appear to be crucial modulators of processes such as transforming growth factor-β1 (TGF-β1) signalling, metabolic homeostasis and chronic low-grade inflammation, all of which play important roles in fibrosis development and persistence. In the current review, we discuss the connections between reactive oxygen species, antioxidant enzymes and TGF-β1 signalling, together with functional consequences, reflecting a concept of redox-fibrosis that can be targeted in future therapies.

Graphical abstract

Hypoxia-induced endothelial-mesenchymal transition is associated with RASAL1 promoter hypermethylation in human coronary endothelial cells

Cardiac fibrosis is integral in chronic heart disease, and one of the cellular processes contributing to cardiac fibrosis is endothelial-to-mesenchymal transition (EndMT). We recently found that hypoxia efficiently induces human coronary artery endothelial cells (HCAEC) to undergo EndMT through a hypoxia inducible factor-1α (HIF1α)-dependent pathway. Promoter hypermethylation of Ras-Gap-like protein 1 (RASAL1) has also been recently associated with EndMT progression and cardiac fibrosis. Our findings suggest that HIF1α and transforming growth factor (TGF)/SMAD signalling pathways synergistically regulate hypoxia-induced EndMT through both DNMT3a-mediated hypermethylation of RASAL1 promoter and direct SNAIL induction. The findings indicate that multiple cascades may be activated simultaneously to mediate hypoxia-induced EndMT.

Targeting the microenvironment in acute myeloid leukemia

The bone marrow microenvironment plays a critical role in the development, progression, and relapse of acute myeloid leukemia (AML). Similar to normal hematopoietic stem cells, AML blasts express receptors on their surface, allowing them to interact with specific components of the marrow microenvironment. These interactions contribute to both chemotherapy resistance and disease relapse. Preclinical studies and early phase clinical trials have demonstrated the potential for targeting the tumor-microenvironment interactions in AML. Agents currently under investigation include hypoxia-inducible agents and inhibitors of CXCR4 and adhesion molecules such as VLA-4 and E-selectin.

Targeting the leukemia-stroma interaction in acute myeloid leukemia: rationale and latest evidence

The concept of 'niche' has become a focus of attention in hematologic malignancies including acute myeloid leukemia (AML). Similar to normal hematopoietic stem cells, AML cells interact both anatomically and functionally with the stroma within the marrow microenvironment. These interactions have a critical role in the development, progression, and relapse of AML. Chemotherapy resistance is another feature that is at least partially related to AML-stroma interactions. The evidence for safety and efficacy of agents targeting AML-niche interactions is currently limited to preclinical and early phase clinical studies. Examples include CXCR4 inhibitors, hypoxia-inducible agents, and adhesion molecule inhibitors. Agents that target AML-stroma interactions differ from mutation-specific approaches that tend to be limited due to within-individual and between-individual genetic heterogeneity. These agents may be used alone or as chemosensitizers in AML. This novel and rapidly advancing strategy is likely to become an important part of our armamentarium of anti-leukemia treatments in the near future.

Transcriptomic analysis provides insight into high-altitude acclimation in domestic goats

Domestic goats are distributed in a wide range of habitats and have acclimated to their local environmental conditions. To investigate the gene expression changes of goats that are induced by high altitude stress, we performed RNA-seq on 27 samples from the three hypoxia-sensitive tissues (heart, lung, and skeletal muscle) in three indigenous populations from distinct altitudes (600 m, 2000 m, and 3000 m). We generated 129Gb of high-quality sequencing data (~4Gb per sample) and catalogued the expression profiles of 12,421 annotated hircine genes in each sample. The analysis showed global similarities and differences of high-altitude transcriptomes among populations and tissues as well as revealed that the heart underwent the most high-altitude induced expression changes. We identified numerous differentially expressed genes that exhibited distinct expression patterns, and nonsynonymous single nucleotide variant-containing genes that were highly differentiated between the high- and low-altitude populations. These genes have known or potential roles in hypoxia response and were enriched in functional gene categories potentially responsible for high-altitude stress. Therefore, they are appealing candidates for further investigation of the gene expression and associated regulatory mechanisms related to high-altitude acclimation.

Tissue injury and hypoxia promote malignant progression of prostate cancer by inducing CXCL13 expression in tumor myofibroblasts

Prostate cancer (PC) is a slowly progressing malignancy that often responds to androgen ablation or chemotherapy by becoming more aggressive, acquiring a neuroendocrine phenotype, and undergoing metastatic spread. We found that B lymphocytes recruited into regressing androgen-deprived tumors by C-X-C motif chemokine 13 (CXCL13), a chemokine whose expression correlates with clinical severity, play an important role in malignant progression and metastatic dissemination of PC. We now describe how androgen ablation induces CXCL13 expression. In both allografted and spontaneous mouse PC, CXCL13 is expressed by tumor-associated myofibroblasts that are activated on androgen ablation through a hypoxia-dependent mechanism. The same cells produce CXCL13 after chemotherapy. Myofibroblast activation and CXCL13 expression also occur in the normal prostate after androgen deprivation, and CXCL13 is expressed by myofibroblasts in human PC. Hypoxia activates hypoxia-inducible factor 1 (HIF-1) and induces autocrine TGF-β signaling that promotes myofibroblast activation and CXCL13 induction. In addition to TGF-β receptor kinase inhibitors, myofibroblast activation and CXCL13 induction are blocked by phosphodiesterase 5 (PDE5) inhibitors. Both inhibitor types and myofibroblast immunodepletion block the emergence of castration-resistant PC in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model of spontaneous metastatic PC with neuroendocrine differentiation.

Regulation of wound healing and fibrosis by hypoxia and hypoxia-inducible factor-1

Wound healing is a complex multi-step process that requires spatial and temporal orchestration of cellular and non-cellular components. Hypoxia is one of the prominent microenvironmental factors in tissue injury and wound healing. Hypoxic responses, mainly mediated by a master transcription factor of oxygen homeostasis, hypoxia-inducible factor-1 (HIF-1), have been shown to be critically involved in virtually all processes of wound healing and remodeling. Yet, mechanisms underlying hypoxic regulation of wound healing are still poorly understood. Better understanding of how the wound healing process is regulated by the hypoxic microenvironment and HIF-1 signaling pathway will provide insight into the development of a novel therapeutic strategy for impaired wound healing conditions such as diabetic wound and fibrosis. In this review, we will discuss recent studies illuminating the roles of HIF-1 in physiologic and pathologic wound repair and further, the therapeutic potentials of HIF-1 stabilization or inhibition.