KLF5 mediates vascular remodeling via HIF-1α in hypoxic pulmonary hypertension

Hypoxia and inflammation induce synergistic transcriptome turnover in macrophages

Macrophages are effector immune cells that experience substantial changes to oxygenation when transiting through tissues, especially when entering tumors or infected wounds. How hypoxia alters gene expression and macrophage effector function at the post-transcriptional level remains poorly understood. Here, we use TimeLapse-seq to measure how inflammatory activation modifies the hypoxic response in primary macrophages. Nucleoside recoding sequencing allows the derivation of steady-state transcript levels, degradation rates, and transcriptional synthesis rates from the same dataset. We find that hypoxia produces distinct responses from resting and inflammatory macrophages. Hypoxia induces destabilization of mRNA transcripts, though inflammatory macrophages substantially increase mRNA degradation compared to resting macrophages. Increased RNA turnover results in the upregulation of ribosomal protein genes and downregulation of extracellular matrix components in inflammatory macrophages. Pathways regulated by mRNA decay in vitro are differentially regulated in tumor-associated macrophages implying that mixed stimuli could induce post-transcriptional regulation of macrophage function in solid tumors.

Long Noncoding RNA MALAT1: Salt-Sensitive Hypertension

Hypertension stands as the leading global cause of mortality, affecting one billion individuals and serving as a crucial risk indicator for cardiovascular morbidity and mortality. Elevated salt intake triggers inflammation and hypertension by activating antigen-presenting cells (APCs). We found that one of the primary reasons behind this pro-inflammatory response is the epithelial sodium channel (ENaC), responsible for transporting sodium ions into APCs and the activation of NADPH oxidase, leading to increased oxidative stress. Oxidative stress increases lipid peroxidation and the formation of pro-inflammatory isolevuglandins (IsoLG). Long noncoding RNAs (lncRNAs) play a crucial role in regulating gene expression, and MALAT1, broadly expressed across cell types, including blood vessels and inflammatory cells, is also associated with inflammation regulation. In hypertension, the decreased transcriptional activity of nuclear factor erythroid 2-related factor 2 (Nrf2 or Nfe2l2) correlates with heightened oxidative stress in APCs and impaired control of various antioxidant genes. Kelch-like ECH-associated protein 1 (Keap1), an intracellular inhibitor of Nrf2, exhibits elevated levels of hypertension. Sodium, through an increase in Sp1 transcription factor binding at its promoter, upregulates MALAT1 expression. Silencing MALAT1 inhibits sodium-induced Keap1 upregulation, facilitating the nuclear translocation of Nrf2 and subsequent antioxidant gene transcription. Thus, MALAT1, acting via the Keap1-Nrf2 pathway, modulates antioxidant defense in hypertension. This review explores the potential role of the lncRNA MALAT1 in controlling the Keap1-Nrf2-antioxidant defense pathway in salt-induced hypertension. The inhibition of MALAT1 holds therapeutic potential for the progression of salt-induced hypertension and cardiovascular disease (CVD).

SWI/SNF Complex in Vascular Smooth Muscle Cells and Its Implications in Cardiovascular Pathologies

Mature vascular smooth muscle cells (VSMC) exhibit a remarkable degree of plasticity, a characteristic that has intrigued cardiovascular researchers for decades. Recently, it has become increasingly evident that the chromatin remodeler SWItch/Sucrose Non-Fermentable (SWI/SNF) complex plays a pivotal role in orchestrating chromatin conformation, which is critical for gene regulation. In this review, we provide a summary of research related to the involvement of the SWI/SNF complexes in VSMC and cardiovascular diseases (CVD), integrating these discoveries into the current landscape of epigenetic and transcriptional regulation in VSMC. These novel discoveries shed light on our understanding of VSMC biology and pave the way for developing innovative therapeutic strategies in CVD treatment.

Circ_0068481 Affects the Human Pulmonary Artery Smooth Muscle Cells' Progression by miR-361-3p/KLF5 Axis

BACKGROUND

Uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) contributes to the pathogenesis of pulmonary arterial hypertension (PAH). In this work, we defined the precise part of circ_0068481 in PASMC proliferation and migration induced by hypoxia. We hypothesized that circ_0068481 enhanced hypoxia-induced PASMC proliferation, invasion, and migration through the microRNA (miR)-361-3p/Krüppel-like factor 5 (KLF5) pathway.

METHODS

Human PASMCs (hPASMCs) were exposed to hypoxic (3% O2) conditions. Circ_0068481, miR-361-3p, and KLF5 levels were gauged by qRT-PCR and western blot. Cell viability, proliferation, invasion, and migration were detected by XTT, EdU incorporation, transwell, and wound-healing assays, respectively. Dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays were performed to confirm the direct relationship between miR-361-3p and circ_0068481 or KLF5.

RESULTS

Circ_0068481 expression was increased in the serum of PAH patients and hypoxia-induced hPASMCs. Downregulation of circ_0068481 attenuated hypoxia-induced promotion in hPASMC proliferation, invasion, and migration. Circ_0068481 directly targeted miR-361-3p, and miR-361-3p downregulation reversed the inhibitory effects of circ_0068481 silencing on hypoxia-induced hPASMC proliferation, invasion, and migration. KLF5 was a direct miR-361-3p target, and miR-361-3p upregulation mitigated hypoxia-induced hPASMC proliferation, invasion, and migration by inhibiting KLF5 expression. Moreover, circ_0068481-induced KLF5 expression by binding to miR-361-3p in hypoxic hPASMCs.

CONCLUSIONS

Circ_0068481 knockdown ameliorated hypoxia-induced hPASMC proliferation, invasion, and migration at least in part through the miR-361-3p/KLF5 axis.

Transcription factors and potential therapeutic targets for pulmonary hypertension

Pulmonary hypertension (PH) is a refractory and fatal disease characterized by excessive pulmonary arterial cell remodeling. Uncontrolled proliferation and hypertrophy of pulmonary arterial smooth muscle cells (PASMCs), dysfunction of pulmonary arterial endothelial cells (PAECs), and abnormal perivascular infiltration of immune cells result in pulmonary arterial remodeling, followed by increased pulmonary vascular resistance and pulmonary pressure. Although various drugs targeting nitric oxide, endothelin-1 and prostacyclin pathways have been used in clinical settings, the mortality of pulmonary hypertension remains high. Multiple molecular abnormalities have been implicated in pulmonary hypertension, changes in numerous transcription factors have been identified as key regulators in pulmonary hypertension, and a role for pulmonary vascular remodeling has been highlighted. This review consolidates evidence linking transcription factors and their molecular mechanisms, from pulmonary vascular intima PAECs, vascular media PASMCs, and pulmonary arterial adventitia fibroblasts to pulmonary inflammatory cells. These findings will improve the understanding of particularly interactions between transcription factor-mediated cellular signaling pathways and identify novel therapies for pulmonary hypertension.

Bone marrow-derived mesenchymal stem cells accelerate angiogenesis in pregnant experimentally induced deep venous thrombosis rat model via up-regulation of pro-angiogenic secretogranin II

The present study investigated whether bone marrow-derived mesenchymal stem cells (BMMSCs) facilitate angiogenesis and improve outcomes of pregnancy with obstetric deep venous thrombosis (DVT) and explored the underlying mechanism. A pregnant DVT rat model was established using a "stenosis" method on the lower segment of the inferior vena cava (IVC). The extent of vascularization in thrombosed IVC was examined by immunohistochemistry. In addition, the effect of BMMSCs on DVT pregnancy outcomes was evaluated. We also characterized the effect of BMMSC-derived conditioned medium (BM-CM) on the impaired human umbilical vein endothelial cells (HUVECs). Thereafter, transcriptome sequencing was employed to identify the differentially expressed genes in thrombosed IVC tissues of DVT and DVT plus BMMSCs (thrice) groups. Lastly, the candidate gene's role in the promotion of angiogenesis was demonstrated in vitro and in vivo. The DVT model was successfully established using IVC stenosis. The injection of three consecutive BMMSC doses into pregnant SD rats with DVT was demonstrated to be the most effective treatment, which significantly reduced the length and weight of the thrombus, induced the highest level of angiogenesis, and ameliorated the embryo absorption rate. In vitro, BM-CM efficiently increased the abilities of impaired endothelial cells to proliferate, migrate, invade, and form vessel-like tubes, while inhibiting their apoptosis. Transcriptome sequencing revealed that BMMSCs induced a prominent upregulation of a variety of pro-angiogenic genes, including secretogranin II (SCG2). When SCG2 expression was knocked down by lentivirus, the BMMSCs' and BM-CM-induced pro-angiogenic effects on pregnant DVT rats and HUVECs were markedly attenuated. In conclusion, the study results suggest that BMMSCs enhance angiogenesis via up-regulation of SCG2, providing an effective alternative regenerative agent and novel target for the therapy of obstetric DVT.

Transcription factors in the pathogenesis of pulmonary arterial hypertension-Current knowledge and therapeutic potential

Pulmonary arterial hypertension (PAH) is a disease characterized by elevated pulmonary vascular resistance and pulmonary artery pressure. Mortality remains high in severe cases despite significant advances in management and pharmacotherapy. Since currently approved PAH therapies are unable to significantly reverse pathological vessel remodeling, novel disease-modifying, targeted therapeutics are needed. Pathogenetically, PAH is characterized by vessel wall cell dysfunction with consecutive remodeling of the pulmonary vasculature and the right heart. Transcription factors (TFs) regulate the process of transcribing DNA into RNA and, in the pulmonary circulation, control the response of pulmonary vascular cells to macro- and microenvironmental stimuli. Often, TFs form complex protein interaction networks with other TFs or co-factors to allow for fine-tuning of gene expression. Therefore, identification of the underlying molecular mechanisms of TF (dys-)function is essential to develop tailored modulation strategies in PAH. This current review provides a compendium-style overview of TFs and TF complexes associated with PAH pathogenesis and highlights their potential as targets for vasculoregenerative or reverse remodeling therapies.

Focus on long non-coding RNA MALAT1: Insights into acute and chronic lung diseases

Acute lung injury (ALI) is a pulmonary illness with a high burden of morbidity and mortality around the world. Chronic lung diseases also represent life-threatening situations. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a type of long non-coding RNA (lncRNA) and is highly abundant in lung tissues. MALAT1 can function as a competitive endogenous RNA (ceRNA) to impair the microRNA (miRNA) inhibition on targeted messenger RNAs (mRNAs). In this review, we summarized that MALAT1 mainly participates in pulmonary cell biology and lung inflammation. Therefore, MALAT1 can positively or negatively regulate ALI and chronic lung diseases (e.g., chronic obstructive pulmonary disease (COPD), bronchopulmonary dysplasia (BPD), pulmonary fibrosis, asthma, and pulmonary hypertension (PH)). Besides, we also found a MALAT1-miRNA-mRNA ceRNA regulatory network in acute and chronic lung diseases. Through this review, we hope to cast light on the regulatory mechanisms of MALAT1 in ALI and chronic lung disease and provide a promising approach for lung disease treatment.

Long read genome assemblies complemented by single cell RNA-sequencing reveal genetic and cellular mechanisms underlying the adaptive evolution of yak

Wild yak (Bos mutus) and domestic yak (Bos grunniens) are adapted to high altitude environment and have ecological, economic, and cultural significances on the Qinghai-Tibetan Plateau (QTP). Currently, the genetic and cellular bases underlying adaptations of yak to extreme conditions remains elusive. In the present study, we assembled two chromosome-level genomes, one each for wild yak and domestic yak, and screened structural variants (SVs) through the long-read data of yak and taurine cattle. The results revealed that 6733 genes contained high-FST SVs. 127 genes carrying special type of SVs were differentially expressed in lungs of the taurine cattle and yak. We then constructed the first single-cell gene expression atlas of yak and taurine cattle lung tissues and identified a yak-specific endothelial cell subtype. By integrating SVs and single-cell transcriptome data, we revealed that the endothelial cells expressed the highest proportion of marker genes carrying high-FST SVs in taurine cattle lungs. Furthermore, we identified pathways which were related to the medial thickness and formation of elastic fibers in yak lungs. These findings provide new insights into the high-altitude adaptation of yak and have important implications for understanding the physiological and pathological responses of large mammals and humans to hypoxia.

The genetic bases of yak adaptations to extreme conditions remains elusive. This study compares yak and cattle at a genomic and transcriptomic level, revealing a new type of endothelial cell and candidate genes related with elastic fiber formation in yak lungs that might contribute to high altitude adaptation.

Induction of GLI1 by miR-27b-3p/FBXW7/KLF5 pathway contributes to pulmonary arterial hypertension

Glioma-associated oncogene homolog 1 (GLI1), a zinc-finger transcription factor, is upregulated in tumors and promotes cancer cell proliferation and migration. However, whether GLI1 involves in pulmonary artery smooth muscle cells (PASMCs) proliferation and migration and the detailed molecular mechanisms underlying GLI1 in pulmonary arterial hypertension (PAH) are not yet clear. Primary cultured rat PASMCs and monocrotaline (MCT)-induced PAH rats model were applied to address these issues in the present study. We found that the expression of GLI1 was significantly increased in endothelin-1 (ET-1) treated PASMCs, accompanied with the activation of microRNA (miR)-27b-3p/F-box and WD repeat domain containing 7 (FBXW7)/kruppel-like factor 5 (KLF5)/GLI1 pathway through endothelin-1 receptor type A (ETAR). Elevated miR-27b-3p suppressed FBXW7 expression, which led to KLF5 accumulation by decreasing its ubiquitinated degradation, KLF5 further induced GLI1 upregulation leading to PASMCs proliferation and migration. In addition, in MCT-induced PAH rats, targeting ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 pathway effectively prevented the pulmonary vascular remodeling and the development of PAH in rats. Our study indicates that interfering ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 signaling axis might have a potential value in the prevention and treatment of PAH.

Hypoxia-inducible factors: roles in cardiovascular disease progression, prevention, and treatment

Hypoxia-inducible factors (HIF)-1 and HIF-2 are master regulators of oxygen homeostasis that regulate the expression of thousands of genes in order to match O2 supply and demand. A large body of experimental data links HIF activity to protection against multiple disorders affecting the cardiovascular system: ischemic cardiovascular disease (including coronary artery disease and peripheral artery disease), through collateral blood vessel formation and preconditioning phenomena; emphysema; lymphedema; and lung transplant rejection. In these disorders, strategies to increase the expression of one or both HIFs may be of therapeutic utility. Conversely, extensive data link HIFs to the pathogenesis of pulmonary arterial hypertension and drugs that inhibit one or both HIFs may be useful in treating this disease.

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.

Nanoparticle-Delivered microRNA-153-3p Alleviates Myocardial Infarction-Induced Myocardial Injury in a Rat Model

Although microRNA-153-3p (miR-153-3p) has been demonstrated to confer protective roles in ischemia/reperfusion injury, its potential role in myocardial infarction (MI) remains undefined. Small-molecule modifiers and nanoparticles loaded with microRNAs (miRNAs) have emerged as potential therapeutic reagents for MI treatment. In this study, we prepared liposome nanoparticles, hyaluronic acid (HA)-cationic liposomes (CLPs) complex, for the delivery of miR-153-3p and delineated the mechanistic actions of miR-153-3p modified by nHA-CLPs in MI-induced injury. Our data suggested that nHA-CLPs-loaded miR-153-3p protected cardiomyocytes against MI-induced cardiomyocyte apoptosis and myocardial injury. miR-153-3p was bioinformatically predicted and experimentally verified to bind to Krüppel-like factor 5 (KLF5) 3'UTR and negatively regulate its expression. Hypoxia was adopted to stimulate MI-induced injury to cardiomyocytes in vitro, in which miR-153-3p presented anti-apoptotic potential. However, restoration of KLF5 reversed this anti-apoptotic effect of miR-153-3p. Furthermore, KLF5 was demonstrated to be an activator of the NF-κB pathway. KLF5 enhanced cardiomyocyte apoptosis and inflammation under hypoxic conditions through NF-κB pathway activation, while nHA-CLPs-loaded miR-153-3p suppressed inflammation by blocking the NF-κB pathway. Collectively, our findings suggested the cardioprotective role of miR-153-3p against MI and the successful delivery of miR-153-3p by nHA-CLPs. The identification of KLF5-mediated activation of NF-κB pathway as an apoptotic and inflammatory mechanism aids in better understanding of the biology of MI and development of novel therapeutic strategies for MI.

Calpain-1 mediates vascular remodelling and fibrosis via HIF-1α in hypoxia-induced pulmonary hypertension

Calpain‐1, a calcium‐activated neutral cysteine proteases, has been reported to be involved in the formation of pulmonary hypertension. HIF‐1α, an oxygen‐sensitive transcription factor, has been reported to activate genes involved in cell proliferation and extracellular matrix recombination. This study was designed to investigate the effect of calpain‐1 in hypoxic pulmonary hypertension (HPH) and to explore whether there is a relationship between calpain‐1 and HIF‐1α in this disease. In the hypoxia‐induced model of HPH, we found that hypoxia resulted in increased right ventricular systolic pressure, right ventricular hypertrophy, pulmonary vascular remodelling and collagen deposition in lung tissues of mice. The levels of calpain‐1 and HIF‐1α were up‐regulated in the lung tissues of hypoxia‐treated mice and pulmonary arterial smooth muscle cells (PASMCs). Knock‐out of calpain‐1 restrained haemodynamic and histological changes induced by chronic hypoxia in mice, and inhibition of calpain‐1 also repressed the abnormal proliferation and migration of PASMCs. Besides, knock‐out or inhibition of calpain‐1 suppressed hypoxia‐induced expression of HIF‐1α, VEGF, PCNA, TGF‐β1, MMP2 and collagen I in vivo and in vitro. While inhibition of HIF‐1α abolished the above effects of calpain‐1. Furthermore, we found that calpain‐1 mediates the expression of HIF‐1α through NF‐κB (P65) under hypoxia conditions. In conclusion, our results suggest that calpain‐1 plays a pivotal role in hypoxia‐induced pulmonary vascular remodelling and fibrosis through HIF‐1α, providing a better understanding of the pathogenesis of HPH.

Notch4 mediates vascular remodeling via ERK/JNK/P38 MAPK signaling pathways in hypoxic pulmonary hypertension

Background

Hypoxic pulmonary hypertension (HPH) is a chronic progressive advanced disorder pathologically characterized by pulmonary vascular remodeling. Notch4 as a cell surface receptor is critical for vascular development. However, little is known about the role and mechanism of Notch4 in the development of hypoxic vascular remodeling.

Methods

Lung tissue samples were collected to detect the expression of Notch4 from patients with HPH and matched controls. Human pulmonary artery smooth muscle cells (HPASMCs) were cultured in hypoxic and normoxic conditions. Real-time quantitative PCR and western blotting were used to examine the mRNA and protein levels of Notch4. HPASMCs were transfected with small interference RNA (siRNA) against Notch4 or Notch4 overexpression plasmid, respectively. Cell viability, cell proliferation, apoptosis, and migration were assessed using Cell Counting Kit-8, Edu, Annexin-V/PI, and Transwell assay. The interaction between Notch4 and ERK, JNK, P38 MAPK were analyzed by co-immunoprecipitation. Adeno-associated virus 1-mediated siRNA against Notch4 (AAV1-si-Notch4) was injected into the airways of hypoxic rats. Right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular remodeling were evaluated.

Results

In this study, we demonstrate that Notch4 is highly expressed in the media of pulmonary vascular and is upregulated in lung tissues from patients with HPH and HPH rats compared with control groups. In vitro, hypoxia induces the high expression of Delta-4 and Notch4 in HPASMCs. The increased expression of Notch4 promotes HPASMCs proliferation and migration and inhibits cells apoptosis via ERK, JNK, P38 signaling pathways. Furthermore, co-immunoprecipitation result elucidates the interaction between Notch4 and ERK/JNK/P38. In vivo, silencing Notch4 partly abolished the increase in RVSP and pulmonary vascular remodeling caused by hypoxia in HPH rats.

Conclusions

These findings reveal an important role of the Notch4-ERK/JNK/P38 MAPK axis in hypoxic pulmonary remodeling and provide a potential therapeutic target for patients with HPH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-01927-9.

TRB3 mediates vascular remodeling by activating the MAPK signaling pathway in hypoxic pulmonary hypertension

BACKGROUND

Hypoxic pulmonary hypertension (PH) is a refractory pulmonary vascular remodeling disease, and the efficiency of current PH treatment strategies is unsatisfactory. Tribbles homolog 3 (TRB3), a member of the pseudokinase family, is upregulated in diverse types of cellular stresses and functions as either a pro-proliferative or pro-apoptotic factor depending on the specific microenvironment. The regulatory mechanisms of TRB3 in hypoxic PH are poorly understood.

METHODS

We performed studies using TRB3-specific silencing and overexpressing lentiviral vectors to investigate the potential roles of TRB3 on hypoxic pulmonary artery smooth muscle cells (PASMCs). Adeno-associated virus type 1(AVV1) vectors encoding short-hairpin RNAs against rat TRB3 were used to assess the role of TRB3 on hypoxic PH. TRB3 protein expression in PH patients was explored in clinical samples by western blot analysis.

RESULTS

The results of whole-rat genome oligo microarrays showed that the expression of TRB3 and endoplasmic reticulum stress (ERS)-related genes was upregulated in hypoxic PASMCs. TRB3 protein expression was significantly upregulated by hypoxia and thapsigargin. In addition, 4-PBA and 4μ8C, both inhibitors of ERS, decreased the expression of TRB3. TRB3 knockdown promoted apoptosis and damaged the proliferative and migratory abilities of hypoxic PASMCs as well as inhibited activation of the MAPK signaling pathway. TRB3 overexpression stimulated the proliferation and migration of PASMCs but decreased the apoptosis of PASMCs, which was partly reversed by specific inhibitors of ERK, JNK and p38 MAPK. The Co-IP results revealed that TRB3 directly interacts with ERK, JNK, and p38 MAPK. Knockdown of TRB3 in rat lung tissue reduced the right ventricular systolic pressure and decreased pulmonary medial wall thickness in hypoxic PH model rats. Further, the expression of TRB3 in lung tissues was higher in patients with PH compared with those who have normal pulmonary artery pressure.

CONCLUSIONS

TRB3 was upregulated in hypoxic PASMCs and was affected by ERS. TRB3 plays a key role in the pathogenesis of hypoxia-induced PH by binding and activating the ERK, JNK, and p38 MAPK pathways. Thus, TRB3 might be a promising target for the treatment of hypoxic PH.

The roles and regulation of the KLF5 transcription factor in cancers

Krüppel‐like factor 5 (KLF5) is a member of the KLF family. Recent studies have suggested that KLF5 regulates the expression of a large number of new target genes and participates in diverse cellular functions, such as stemness, proliferation, apoptosis, autophagy, and migration. In response to multiple signaling pathways, various transcriptional modulation and posttranslational modifications affect the expression level and activity of KLF5. Several transgenic mouse models have revealed the physiological and pathological functions of KLF5 in different cancers. Studies of KLF5 will provide prognostic biomarkers, therapeutic targets, and potential drugs for cancers.

Role of Krüppel-like factors in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare but deadly disease with a complex pathogenesis. Recent evidence demonstrates that Krüppel-like factors, a diverse family of transcription factors, are involved in several key disease processes such as the phenotypic transition of endothelial cells and smooth muscle cells. Importantly, manipulation of certain Krüppel-like factors enables protection or attenuation against pulmonary arterial hypertension in both animal models and preliminary human studies. In this review, we discuss how Krüppel-like factors, in particular Krüppel-like factors 2, 4 and 5 contribute to the pathological phenomena seen in pulmonary arterial hypertension and how associated signaling and microRNA pathways may be suitable targets for new therapies.

AAV1-Mediated shRNA Knockdown of SASH1 in Rat Bronchus Attenuates Hypoxia-Induced Pulmonary Artery Remodeling

Pulmonary hypertension (PH) is a proliferative disease characterized by pulmonary arterial remodeling (PAR). SAM and SH3 domain containing 1 (SASH1) is a novel tumor suppressor gene whose biological function in PH is unclear. In this study, a hypoxia-induced pulmonary hypertension (HPH) rat model was constructed to explore the role of SASH1 in PAR. Histopathological changes in the lung tissue and hemodynamic alteration were detected in SASH1-knockdown rats through adeno-associated virus type-1 (AAV1) infection. In vitro, primary human pulmonary arterial smooth muscle cells (HPASMCs) were transfected with SASH1siRNA to investigate the effects of SASH1 on hypoxia-induced proliferation and migration. The molecular mechanisms associated with SASH1 were explored through knockdown and overexpression approaches. We found that SASH1 expression was significantly increased in rat pulmonary arteries and HPASMCs after hypoxia exposure. In vivo, silencing the SASH1 gene expression improved HPH in rats. The SASH1 downregulation inhibited proliferation and migration of hypoxia-induced HPASMCs. The protein expression of phospho-AKT (known as protein kinase B), proliferating cell nuclear antigen, and matrix metalloproteinase 9 (MMP9) in HPASMCs were increased after SASH1 overexpression, whereas these effects were inhibited by SASH1 knockdown. In conclusion, SASH1 downregulation improved hypoxia-induced PAR and PH. SASH1 may be a novel target for PH gene therapy in the era of precision medicine.

Hypoxia-inducible factor signaling in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by pulmonary artery remodeling that can subsequently culminate in right heart failure and premature death. Emerging evidence suggests that hypoxia-inducible factor (HIF) signaling plays a fundamental and pivotal role in the pathogenesis of PH. This Review summarizes the regulation of HIF isoforms and their impact in various PH subtypes, as well as the elaborate conditional and cell-specific knockout mouse studies that brought the role of this pathway to light. We also discuss the current preclinical status of pan- and isoform-selective HIF inhibitors, and propose new research areas that may facilitate HIF isoform-specific inhibition as a novel therapeutic strategy for PH and right heart failure.

Current knowledge of Krüppel-like factor 5 and vascular remodeling: providing insights for therapeutic strategies

Vascular remodeling is a pathological basis of various disorders. Therefore, it is necessary to understand the occurrence, prevention, and treatment of vascular remodeling. Krüppel-like factor 5 (KLF5) has been identified as a significant factor in cardiovascular diseases during the last two decades. This review provides a mechanism network of function and regulation of KLF5 in vascular remodeling based on newly published data and gives a summary of its potential therapeutic applications. KLF5 modulates numerous biological processes, which play essential parts in the development of vascular remodeling, such as cell proliferation, phenotype switch, extracellular matrix deposition, inflammation, and angiogenesis by altering downstream genes and signaling pathways. Considering its essential functions, KLF5 could be developed as a potent therapeutic target in vascular disorders.

Identification of a Novel HIF-1α-αMβ2 Integrin-NET Axis in Fibrotic Interstitial Lung Disease

Neutrophilic inflammation correlates with mortality in fibrotic interstitial lung disease (ILD) particularly in the most severe form, idiopathic pulmonary fibrosis (IPF), although the underlying mechanisms remain unclear. Neutrophil function is modulated by numerous factors, including integrin activation, inflammatory cytokines and hypoxia. Hypoxia has an important role in inflammation and may also contribute to pulmonary disease. We aimed to determine how neutrophil activation occurs in ILD and the relative importance of hypoxia. Using lung biopsies and bronchoalveolar lavage (BAL) fluid from ILD patients we investigated the extent of hypoxia and neutrophil activation in ILD lungs. Then we used ex vivo neutrophils isolated from healthy volunteers and BAL from patients with ILD and non-ILD controls to further investigate aberrant neutrophil activation in hypoxia and ILD. We demonstrate for the first time using intracellular staining, HIF-1α stabilization in neutrophils and endothelial cells in ILD lung biopsies. Hypoxia enhanced both spontaneous (+1.31-fold, p < 0.05) and phorbol 12-myristate 13-acetate (PMA)-induced (+1.65-fold, p < 0.001) neutrophil extracellular trap (NET) release, neutrophil adhesion (+8.8-fold, <0.05), and trans-endothelial migration (+1.9-fold, p < 0.05). Hypoxia also increased neutrophil expression of the αM (+3.1-fold, p < 0.001) and αX (+1.6-fold, p < 0.01) integrin subunits. Interestingly, NET formation was induced by αMβ2 integrin activation and prevented by cation chelation. Finally, we observed NET-like structures in IPF lung sections and in the BAL from ILD patients, and quantification showed increased cell-free DNA content (+5.5-fold, p < 0.01) and MPO-citrullinated histone H3 complexes (+21.9-fold, p < 0.01) in BAL from ILD patients compared to non-ILD controls. In conclusion, HIF-1α upregulation may augment neutrophil recruitment and activation within the lung interstitium through activation of β2 integrins. Our results identify a novel HIF-1α- αMβ2 integrin axis in NET formation for future exploration in therapeutic approaches to fibrotic ILD.

Oxygen homeostasis and cardiovascular disease: A role for HIF?

Hypoxia, the decline of tissue oxygen stress, plays a role in mediating cellular processes. Cardiovascular disease, relatively widespread with increased mortality, is closely correlated with oxygen homeostasis regulation. Besides, hypoxia-inducible factor-1(HIF-1) is reported to be a crucial component in regulating systemic hypoxia-induced physiological and pathological modifications like oxidative stress, damage, angiogenesis, vascular remodeling, inflammatory reaction, and metabolic remodeling. In addition, HIF1 controls the movement, proliferation, apoptosis, differentiation and activity of numerous core cells, such as cardiomyocytes, endothelial cells (ECs), smooth muscle cells (SMCs), and macrophages. Here we review the molecular regulation of HIF-1 in cardiovascular diseases, intended to improve therapeutic approaches for clinical diagnoses. Better knowledge of the oxygen balance control and the signal mechanisms involved is important to advance the development of hypoxia-related diseases.

Notch3 signalling and vascular remodelling in pulmonary arterial hypertension

Notch signalling is critically involved in vascular morphogenesis and function. Four Notch isoforms (Notch1–4) regulating diverse cellular processes have been identified. Of these, Notch3 is expressed almost exclusively in vascular smooth muscle cells (VSMCs), where it is critically involved in vascular development and differentiation. Under pathological conditions, Notch3 regulates VSMC switching between the contractile and synthetic phenotypes. Abnormal Notch3 signalling plays an important role in vascular remodelling, a hallmark of several cardiovascular diseases, including pulmonary arterial hypertension (PAH). Because of the importance of Notch3 in VSMC (de)differentiation, Notch3 has been implicated in the pathophysiology of pulmonary vascular remodelling in PAH. Here we review the current literature on the role of Notch in VSMC function with a focus on Notch3 signalling in pulmonary artery VSMCs, and discuss potential implications in pulmonary artery remodelling in PAH.

Identification of Key Players Involved in CoCl2 Hypoxia Induced Pulmonary Artery Hypertension in vitro

Background

The proliferation of human pulmonary artery smooth muscle cells (HPASMCs) induced by hypoxia was considered as the main cause of pulmonary arterial hypertension (PAH). This study aimed to explore potential genes and long non-coding RNAs (lncRNAs) involved in the mechanism of hypoxia-induced PAH.

Methods

CoCl₂ was utilized to induce hypoxia in HPASMCs, and then cell proliferation, apoptosis, and expression of hypoxia-inducible factors (HIF)-1α were determined. Meanwhile, the RNA isolated from CoCl₂-treated cells and control cells were sequenced and differentially expressed genes/lncRNA (DEGs/DELs) were screened, followed by protein-protein interaction (PPI) construction, functional enrichment analyses, and lncRNA-target prediction. Finally, the expression of key genes and lncRNAs were validated using quantitative real-time PCR and western blotting.

Results

CoCl₂ treatment could significantly increase the expression of HIF-1α and the proliferation of HPASMCs. A total of 360 DEGs and 57 DELs were identified between CoCl₂ treated and control cells. Functional enrichment analysis showed that up-regulated DEGs and DELs’ targets, including LDHA, PFKP, and VEGFA, were significantly enriched in biological processes related to hypoxia or oxygen levels, and the downregulated DEGs and DELs’ targets were significantly enriched in extracellular-matrix-related biological processes. In addition, LDHA, PFKP, and VEGFA exhibited a strong relationship with miR-100HG and TSPEAR-AS2 in lncRNA-target network. The protein level of LDHA, PFKP, and VEGFA were all increased.

Conclusion

LDHA, PFKP, VEGFA, and lncRNA miR-100HG and TSPEAR-AS2 probably played crucial roles in the pathogenesis of CoCl₂ hypoxia-induced-HAP, which might serve as promising therapeutic targets for PAH.

The Drug-Resistance Mechanisms of Five Platinum-Based Antitumor Agents

Platinum-based anticancer drugs, including cisplatin, carboplatin, oxaliplatin, nedaplatin, and lobaplatin, are heavily applied in chemotherapy regimens. However, the intrinsic or acquired resistance severely limit the clinical application of platinum-based treatment. The underlying mechanisms are incredibly complicated. Multiple transporters participate in the active transport of platinum-based antitumor agents, and the altered expression level, localization, or activity may severely decrease the cellular platinum accumulation. Detoxification components, which are commonly increasing in resistant tumor cells, can efficiently bind to platinum agents and prevent the formation of platinum–DNA adducts, but the adducts production is the determinant step for the cytotoxicity of platinum-based antitumor agents. Even if adequate adducts have formed, tumor cells still manage to survive through increased DNA repair processes or elevated apoptosis threshold. In addition, autophagy has a profound influence on platinum resistance. This review summarizes the critical participators of platinum resistance mechanisms mentioned above and highlights the most potential therapeutic targets or predicted markers. With a deeper understanding of the underlying resistance mechanisms, new solutions would be produced to extend the clinical application of platinum-based antitumor agents largely.

Metabolism and Redox in Pulmonary Vascular Physiology and Pathophysiology

Significance: This review considers how some systems controlling pulmonary vascular function are potentially regulated by redox processes to examine how and why conditions such as prolonged hypoxia, pathological mediators, and other factors promoting vascular remodeling contribute to the development of pulmonary hypertension (PH). Recent Advances and Critical Issues: Aspects of vascular remodeling induction mechanisms described are associated with shifts in glucose metabolism through the pentose phosphate pathway and increased cytosolic NADPH generation by glucose-6-phosphate dehydrogenase, increased glycolysis generation of cytosolic NADH and lactate, mitochondrial dysfunction associated with superoxide dismutase-2 depletion, changes in reactive oxygen species and iron metabolism, and redox signaling. Future Directions: The regulation and impact of hypoxia-inducible factor and the function of cGMP-dependent and redox regulation of protein kinase G are considered for their potential roles as key sensors and coordinators of redox and metabolic processes controlling the progression of vascular pathophysiology in PH, and how modulating aspects of metabolic and redox regulatory systems potentially function in beneficial therapeutic approaches.

eIF2α promotes vascular remodeling via autophagy in monocrotaline-induced pulmonary arterial hypertension rats

PURPOSE

Eukaryotic initiation factor 2α (eIF2α) plays important roles in the proliferation and survival of pulmonary artery smooth muscle cells (PASMCs) in animal hypoxia-induced pulmonary hypertension models. However, the underlying mechanism remains unknown at large. Autophagy has been reported to play a key role in the vascular remodeling in pulmonary arterial hypertension (PAH). The purposes of this study are to determine the functions of eIF2α and autophagy in the vascular remodeling of the monocrotaline-induced PAH rats and to clarify the correlation between eIF2α and autophagy.

METHODS

We established a rat model of monocrotaline-induced PAH, and we established a cell model of platelet derived growth factor (PDGF)-induced PASMCs proliferation. The vascular morphology and the expression of eIF2α, LC3B, and p62 were assessed in the pulmonary arterial tissue of Sprague-Dawleyrats and PDGF-induced PASMCs.

RESULTS

Autophagy was significantly active in monocrotaline model group (MCT)-induced PAH rats, which obviously promotes vascular remodeling in MCT-induced PAH rats. Furthermore, the proliferation of PASMCs was induced by PDGF in vitro. The expression of LC3B, eIF2α was increased in the PDGF-induced PASMCs proliferation, and the expression of p62 was reduced in the PDGF-induced PASMCs proliferation. Moreover, eIF2α siRNA downregulated the expression of eIF2α and LC3B, and upregulated the expression of p62 in PDGF-induced PASMCs proliferation. eIF2α siRNA inhibited the PDGF-induced PASMCs proliferation. Finally, chloroquine can upregulate the protein expression of LC3B and p62, it also can inhibit proliferation in PDGF-induced PASMCs.

CONCLUSION

Based on these observations, we conclude that eIF2α promotes the proliferation of PASMCs and vascular remodeling in monocrotaline-induced PAH rats through accelerating autophagy pathway.

CD146-HIF-1α hypoxic reprogramming drives vascular remodeling and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease of cardiopulmonary units. No cure is currently available due to an incomplete understanding of vascular remodeling. Here we identify CD146-hypoxia-inducible transcription factor 1 alpha (HIF-1α) cross-regulation as a key determinant in vascular remodeling and PAH pathogenesis. CD146 is markedly upregulated in pulmonary artery smooth muscle cells (PASMCs/SMCs) and in proportion to disease severity. CD146 expression and HIF-1α transcriptional program reinforce each other to physiologically enable PASMCs to adopt a more synthetic phenotype. Disruption of CD146-HIF-1α cross-talk by genetic ablation of Cd146 in SMCs mitigates pulmonary vascular remodeling in chronic hypoxic mice. Strikingly, targeting of this axis with anti-CD146 antibodies alleviates established pulmonary hypertension (PH) and enhances cardiac function in two rodent models. This study provides mechanistic insights into hypoxic reprogramming that permits vascular remodeling, and thus provides proof of concept for anti-remodeling therapy for PAH through direct modulation of CD146-HIF-1α cross-regulation.

Vascular remodelling contributes to the development of pulmonary hypertension (PH). Here Luo and colleagues find that increases in CD146 levels drive vascular remodelling in PH through a cross-talk with hypoxia inducible factor (HIF) signalling, and show that inhibition of CD146 can attenuate disease progression.

NPS2390, a Selective Calcium-sensing Receptor Antagonist Controls the Phenotypic Modulation of Hypoxic Human Pulmonary Arterial Smooth Muscle Cells by Regulating Autophagy

Background and Objectives

Calcium-sensing receptor (CaSR) is known to regulate hypoxia-induced pulmonary hypertension (HPH) and vascular remodeling via the phenotypic modulation of pulmonary arterial smooth muscle cells (PASMCs) in small pulmonary arteries. Moreover, autophagy is an essential modulator of VSMC phenotype. But it is not clear whether CaSR can regulate autophagy involving the phenotypic modulation under hypoxia.

Methods

The viability of human PASMCs was detected by cell cycle and BrdU. The expressions of proliferation protein, phenotypic marker protein, and autophagy protein in human PASMCs were determined by western blot.

Results

Our results showed that hypoxia-induced autophagy was considerable at 24 h. The addition of NPS2390 decreased the expression of autophagy protein and synthetic phenotype marker protein osteopontin and increased the expression of contractile phenotype marker protein SMA-ɑ and calponin via suppressing downstream PI3K/Akt/mTOR signal pathways.

Conclusions

Our study demonstrates that treatment of NPS2390 was conducive to inhibit the proliferation and reverse phenotypic modulation of PASMCs by regulating autophagy levels.

Long non‑coding RNA MALAT1 sponges miR‑124‑3p.1/KLF5 to promote pulmonary vascular remodeling and cell cycle progression of pulmonary artery hypertension

Previous studies have demonstrated that long non-coding RNA (lncRNA) is involved in vascular remodeling. The metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) lncRNA is associated with the proliferation and migration of vascular smooth muscle and endothelial cells; however, its biological role in pulmonary artery hypertension (PAH) is currently unclear. The aim of the present study was to investigate the post-transcriptional regulation of MALAT1 in human pulmonary artery smooth muscle cells (HPASMCs). The results revealed that MALAT1 expression levels were significantly upregulated in the pulmonary arteries (PAs) and HPASMCs obtained from patients with PAH compared with adjacent normal PA tissues and HPASMCs. Knockdown of MALAT1 suppressed the viability and proliferation of HPASMCs and prevented cells entering the G₀/G₁ cell cycle phase. MALAT1 overexpression exerted the opposite effects. Bioinformatics analysis predicted complementary binding of hsa-microRNA (miR)-124-3p.1 with the 3′-untranslated region of MALAT1. Luciferase reporter assays and RNA immunoprecipitation experiments demonstrated molecular binding between MALAT1 and hsa-miR-124-3p.1. This resulted in the formation of an RNA-induced silencing complex. In addition, Kruppel-like factor 5 (KLF5) was confirmed to be a target gene of MALAT1/hsa-miR-124-3p.1. MALAT1 silencing did not inhibit the proliferation and migration of HPASMCs following knockdown of hsa-miR-124-3p.1. In addition, MALAT1 knockdown was demonstrated to attenuate the expression of KLF5. Following MALAT1 knockdown, the expression level of KLF5 was rescued by inhibition of hsa-miR-124-3p.1 expression. The results of the current study indicate that the MALAT1/hsa-miR-124-3p.1/KLF5 axis may serve a key role in HPASMCs. In addition, the results contribute to what is known regarding the role of MALAT1 in PAH development and provide a novel theoretical basis for the development of new therapeutic interventions for patients with PAH.

miR-448-3p controls intracranial aneurysm by regulating KLF5 expression

microRNAs (miRNAs) control several processes known to be involved in progression of aneurysm. Here, intracranial aneurysms (IAs) were surgically induced in Sprague-Dawley rats, and we found that miR-448-3p was downregulated and KLF5 was upregulated in IA rats. We identified Klf5 as a direct target of miR-448-3p in smooth muscle cells (SMCs). In addition, aneurysms size and the lumen area of the aneurysms were smaller 4 weeks after IA induction in the miR-448-3p-treated group. miR-448-3p treatment protected the wall thickness ratio and suppressed macrophage infiltration after IA induction. IAs caused a significant increase in KLF5 expression and were alleviated by miR-448-3p. Moreover, the anti-inflammatory effect of miR-448-3p was verified in lipopolysaccharide -stimulated RAW 264.7 macrophage cells. The expression levels of KLF5, MMP2, and MMP9 levels were elevated by LPS, and were attenuated by miR-448-3p. These data suggest that miR-448-3p plays the inhibitory role in IA progression, indicating that miR-448-3p overexpression is crucial for preventing the development of IA through downregulation of macrophage-mediated inflammation.

Krüppel-like factors and vascular wall homeostasis

Cardiovascular diseases (CVDs) are major causes of death worldwide. Identification of promising targets for prevention and treatment of CVDs is paramount in the cardiovascular field. Numerous transcription factors regulate cellular function through modulation of specific genes and thereby are involved in the physiological and pathophysiological processes of CVDs. Although Krüppel-like factors (KLFs) have a similar protein structure with a conserved zinc finger domain, they possess distinct tissue and cell distribution patterns as well as biological functions. In the vascular system, KLF activities are regulated at both transcriptional and posttranscriptional levels. Growing in vitro, in vivo, and genetic epidemiology studies suggest that specific KLFs play important roles in vascular wall biology, which further affect vascular diseases. KLFs regulate various functional aspects such as cell growth, differentiation, activation, and development through controlling a whole cluster of functionally related genes and modulating various signaling pathways in response to pathological conditions. Therapeutic targeting of selective KLF family members may be desirable to achieve distinct treatment effects in the context of various vascular diseases. Further elucidation of the association of KLFs with human CVDs, their underlying molecular mechanisms, and precise protein structure studies will be essential to define KLFs as promising targets for therapeutic interventions in CVDs.

Knockdown of KLF5 suppresses hypoxia-induced resistance to cisplatin in NSCLC cells by regulating HIF-1α-dependent glycolysis through inactivation of the PI3K/Akt/mTOR pathway

BACKGROUND

Hypoxia-mediated chemoresistance has been regarded as an important obstacle in the development of cancer treatment. Knockdown of krüppel-like factor 5 (KLF5) was reported to inhibit hypoxia-induced cell survival and promote cell apoptosis in non-small cell lung cancer (NSCLC) cells via direct regulation of hypoxia inducible factor-1α (HIF-1α) expression. However, the roles of KLF5 in the development of hypoxia-induced cisplatin (DDP) resistance and its underlying mechanism in NSCLC cells remain to be further elucidated.

METHODS

Western blot was performed to determine the protein levels of KLF5, P-glycoprotein (P-gp) and HIF-1α in treated NSCLC cells. Cell survival was examined by MTT assay. The effect of KLF5 knockdown on hypoxia-induced glycolysis was assessed by measuring glucose consumption and lactate production. The effect of KLF5 knockdown on the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway was analyzed by western blot.

RESULTS

Hypoxia upregulated the expression of KLF5 in NSCLC cells. KLF5 knockdown suppressed hypoxia-induced DDP resistance in NSCLC cells, as demonstrated by the increased cytotoxic effects of DDP and reduced P-gp expression in NSCLC cells in hypoxia. Moreover, KLF5 knockdown inhibited hypoxia-induced HIF-1α expression and glycolysis, and KLF5 knockdown suppressed hypoxia-induced DDP resistance by inhibiting HIF-1α-dependent glycolysis in NSCLC cells. Furthermore, KLF5 knockdown suppressed hypoxia-induced activation of the PI3K/Akt/mTOR pathway in NSCLC cells and KLF5 overexpression promoted hypoxia-induced DDP resistance in NSCLC cells through activation of the PI3K/Akt/mTOR pathway.

CONCLUSIONS

KLF5 knockdown could suppress hypoxia-induced DDP resistance, and its mechanism may be due to the inhibition of HIF-1α-dependent glycolysis via inactivation of the PI3K/Akt/mTOR pathway.

Krüppel-Like Factors in Vascular Inflammation: Mechanistic Insights and Therapeutic Potential

The role of inflammation in vascular disease is well recognized, involving dysregulation of both circulating immune cells as well as the cells of the vessel wall itself. Unrestrained vascular inflammation leads to pathological remodeling that eventually contributes to atherothrombotic disease and its associated sequelae (e.g., myocardial/cerebral infarction, embolism, and critical limb ischemia). Signaling events during vascular inflammation orchestrate widespread transcriptional programs that affect the functions of vascular and circulating inflammatory cells. The Krüppel-like factors (KLFs) are a family of transcription factors central in regulating vascular biology in states of homeostasis and disease. Given their abundance and diversity of function in cells associated with vascular inflammation, understanding the transcriptional networks regulated by KLFs will further our understanding of the pathogenesis underlying several pervasive health concerns (e.g., atherosclerosis, stroke, etc.) and consequently inform the treatment of cardiovascular disease. Within this review, we will discuss the role of KLFs in coordinating protective and deleterious responses during vascular inflammation, while addressing the potential targeting of these critical transcription factors in future therapies.

Mitochondrial dysfunction and pulmonary hypertension: cause, effect, or both

Pulmonary hypertension describes a heterogeneous disease defined by increased pulmonary artery pressures, and progressive increase in pulmonary vascular resistance due to pathologic remodeling of the pulmonary vasculature involving pulmonary endothelial cells, pericytes, and smooth muscle cells. This process occurs under various conditions, and although these populations vary, the clinical manifestations are the same: progressive dyspnea, increases in right ventricular (RV) afterload and dysfunction, RV-pulmonary artery uncoupling, and right-sided heart failure with systemic circulatory collapse. The overall estimated 5-yr survival rate is 72% in highly functioning patients, and as low as 28% for those presenting with advanced symptoms. Metabolic theories have been suggested as underlying the pathogenesis of pulmonary hypertension with growing evidence of the role of mitochondrial dysfunction involving the major proteins of the electron transport chain, redox-related enzymes, regulators of the proton gradient and calcium homeostasis, regulators of apoptosis, and mitophagy. There remain more studies needed to characterize mitochondrial dysfunction leading to impaired vascular relaxation, increase proliferation, and failure of regulatory mechanisms. The effects on endothelial cells and resulting interactions with their microenvironment remain uncharted territory for future discovery. Additionally, on the basis of observations that the "plexigenic lesions" of pulmonary hypertension resemble the unregulated proliferation of tumor cells, similarities between cancer pathobiology and pulmonary hypertension have been drawn, suggesting interactions between mitochondria and angiogenesis. Recently, mitochondria targeting has become feasible, which may yield new therapeutic strategies. We present a state-of-the-art review of the role of mitochondria in both the pathobiology of pulmonary hypertension and potential therapeutic targets in pulmonary vascular processes.

Vascular peroxidase 1 mediates hypoxia-induced pulmonary artery smooth muscle cell proliferation, apoptosis resistance and migration

Aims

Reactive oxygen species (ROS) play essential roles in the pulmonary vascular remodelling associated with hypoxia-induced pulmonary hypertension (PH). Vascular peroxidase 1 (VPO1) is a newly identified haeme-containing peroxidase that accelerates oxidative stress development in the vasculature. This study aimed to determine the potential role of VPO1 in hypoxia-induced PH-related vascular remodelling.

Methods and results

The vascular morphology and VPO1 expression were assessed in the pulmonary arteries of Sprague–Dawley (SD) rats. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) and VPO1 expression and HOCl production were significantly increased in hypoxic rats, which also exhibited obvious vascular remodelling. Furthermore, a hypoxia-induced PH model was generated by exposing primary rat pulmonary artery smooth muscle cells (PASMCs) to hypoxic conditions (3% O2, 48 h), which significantly increased the expression of NOX4 and VPO1 and the production of HOCl. These hypoxic changes were accompanied by enhanced proliferation, apoptosis resistance, and migration. In PASMCs, hypoxia-induced changes, including effects on the expression of cell cycle regulators (cyclin B1 and cyclin D1), apoptosis-related proteins (bax, bcl-2, and cleaved caspase-3), migration promoters (matrix metalloproteinases 2 and 9), and NF-κB expression, as well as the production of HOCl, were all inhibited by silencing VPO1 with small interfering RNAs. Moreover, treatment with HOCl under hypoxic conditions upregulated NF-κB expression and enhanced proliferation, apoptosis resistance, and migration in PASMCs, whereas BAY 11-7082 (an inhibitor of NF-κB) significantly inhibited these effects.

Conclusion

Collectively, these results demonstrate that VPO1 promotes hypoxia-induced proliferation, apoptosis resistance, and migration in PASMCs via the NOX4/VPO1/HOCl/NF-κB signalling pathway.

Hypoxia induces the dysfunction of human endothelial colony-forming cells via HIF-1α signaling

Endothelial injury is considered as a trigger of pulmonary vascular lesions in the pathogenesis of hypoxic pulmonary hypertension (HPH). Although endothelial colony-forming cells (ECFCs) have vascular regeneration potential to maintain endothelial integrity, hypoxia-induced precise alteration in ECFCs function remains controversial. This study investigated the impact of hypoxia on human ECFCs function in vitro and the underlying mechanism. We found that hypoxia inhibited ECFCs proliferation, migration and angiogenesis. Compared with no treatment, the expression of hypoxia inducible factor-1α (HIF-1α) in hypoxia-treated ECFCs was increased, with an up-regulation of p27 and a down-regulation of cyclin D1. The over-secreted vascular endothelial growth factor (VEGF) was detected, with the imbalanced expression of fetal liver kinase 1 (flk-1) and fms related tyrosine kinase 1 (flt-1). Hypoxia-induced changes in ECFCs could be reversed by HIF-1α inhibitor KC7F2. These data suggest that HIF-1α holds the key in regulating ECFCs function which may open a new perspective of ECFCs in HPH management.

Survivin in autoimmune diseases

Survivin is a protein functionally important for cell division, apoptosis, and possibly, for micro-RNA biogenesis. It is an established marker of malignant cell transformation. In non-malignant conditions, the unique properties of survivin make it indispensable for homeostasis of the immune system. Indeed, it is required for the innate and adaptive immune responses, controlling differentiation and maintenance of CD4⁺ and CD8⁺ memory T-cells, and in B cell maturation. Recently, survivin has emerged as an important player in the pathogenesis of autoimmune diseases. Under the conditions of unreserved inflammation, survivin enhances antigen presentation, maintains persistence of autoreactive cells, and supports production of autoantibodies. In this context, survivin takes its place as a diagnostic and prognostic marker in rheumatoid arthritis, psoriasis, systemic sclerosis and pulmonary arterial hypertension, neuropathology and multiple sclerosis, inflammatory bowel diseases and oral lichen planus. In this review, we summarise the knowledge about non-malignant properties of survivin and focus on its engagement in cellular and molecular pathology of autoimmune diseases. The review highlights utility of survivin measures for clinical applications. It provides rational for the survivin inhibiting strategies and presents results of recent reports on survivin inhibition in modern therapies of cancers and autoimmune diseases.

Quercetin induces autophagy via FOXO1-dependent pathways and autophagy suppression enhances quercetin-induced apoptosis in PASMCs in hypoxia

Quercetin, an important dietary flavonoid has been demonstrated to potentially reverse or even prevent pulmonary arterial hypertension (PAH) progression. However, the effects of quercetin on apoptosis and autophagy in pulmonary arterial smooth muscle cells (PASMCs) have not yet been clearly elucidated. The current study found that quercetin significantly induce the apoptotic and autophagic capacities of PASMCs in vitro and in vivo in hypoxia. In addition, we found that quercetin increases FOXO1 (a major mediator in autophagy regulation) expression and transcriptional activity. Moreover, FOXO1 knockdown by siRNAs inhibited the phosphorylation of mTOR and 4E-BPI, which is downstream of P70-S6K, and markedly blocked quercetin-induced autophagy. We also observed that FOXO1-mediated autophagy was achieved via SESN3 not Rictor upregulation and after mTOR suppression. Furthermore, Treatment with autophagy-specific inhibitors could markedly enhance quercetin-induced apoptosis in PASMCs under hypoxia. Finally, quercetin in combination with autophagy inhibition treatment could enhance the therapeutic effects of quercetin in hypoxia-associated PAH in vivo. Taken together, quercetin could enhance hypoxia-induced autophagy through the FOXO1-SENS3-mTOR pathway in PASMCs. Combining quercetin and autophagy inhibitors may be a novel therapeutic strategy for treating hypoxia-associated PAH.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.