Inhibition of FGFR Signaling With PD173074 Ameliorates Monocrotaline-induced Pulmonary Arterial Hypertension and Rescues BMPR-II Expression

Receptor Tyrosine Kinase: Still an Interesting Target to Inhibit the Proliferation of Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) proliferation is a critical event that contributes to the pathogenesis of vascular remodeling such as hypertension, restenosis, and pulmonary hypertension. Increasing evidences have revealed that VSMCs proliferation is associated with the activation of receptor tyrosine kinases (RTKs) by their ligands, including the insulin-like growth factor receptor (IGFR), fibroblast growth factor receptor (FGFR), epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor (VEGFR), and platelet-derived growth factor receptor (PDGFR). Moreover, some receptor tyrosinase inhibitors (TKIs) have been found and can prevent VSMCs proliferation to attenuate vascular remodeling. Therefore, this review will describe recent research progress on the role of RTKs and their inhibitors in controlling VSMCs proliferation, which helps to better understand the function of VSMCs proliferation in cardiovascular events and is beneficial for the prevention and treatment of vascular disease.

Upregulation of miR-335-5p Contributes to Right Ventricular Remodeling via Calumenin in Pulmonary Arterial Hypertension

Right ventricular (RV) failure determines the prognosis in pulmonary arterial hypertension (PAH), but the underlying mechanism is still unclear. Growing evidence has shown that microRNAs participate in RV remodeling. This study is undertaken to explore the role of miR-335-5p in regulating RV remodeling induced by PAH. Two PAH models were used in the study, including the monocrotaline rat model and hypoxia/su5416 mouse model. miRNA sequencing and RT-qPCR validation identified that miR-335-5p was elevated in the RV of PAH rats. In vitro, miR-335-5p expression was increased after angiotensin II treatment, and miR-335-5p inhibition relieved angiotensin II-induced cardiomyocyte hypertrophy. The luciferase reporter assay showed that calumenin was a target gene for miR-335-5p. Pretreatment with miR-335-5p inhibitors could rescue calumenin downregulation induced by angiotensin II in H9C2 cells. Moreover, intracellular Ca²⁺ concentration and apoptosis were increased after angiotensin II treatment, and miR-335-5p inhibition decreased intracellular Ca²⁺ accumulation and apoptosis. Finally, in vivo miR-335-5p downregulation (antagomir miR-335-5p) attenuated RV remodeling and rescued calumenin downregulation under conditions of hypoxia/su5416 exposure. Our work highlights the role of miR-335-5p and calumenin in RV remodeling and may lead to the development of novel therapeutic strategies for right heart failure.

Growth factors in pulmonary arterial hypertension: Focus on preserving right ventricular function

Pulmonary arterial hypertension (PAH) is a rare and progressive disease, characterized by increased vascular resistance leading to right ventricle (RV) failure. The extent of right ventricular dysfunction crucially influences disease prognosis; however, currently no therapies have specific cardioprotective effects. Besides discussing the pathophysiology of right ventricular adaptation in PAH, this review focuses on the roles of growth factors (GFs) in disease pathomechanism. We also summarize the involvement of GFs in the preservation of cardiomyocyte function, to evaluate their potential as cardioprotective biomarkers and novel therapeutic targets in PAH.

Tie-2 Cre-Mediated Deficiency of Extracellular Signal-Regulated Kinase 2 Potentiates Experimental Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension in Neonatal Mice

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a significant lung morbidity of infants, and disrupted lung angiogenesis is a hallmark of this disease. We observed that extracellular signal-regulated kinases (ERK) 1/2 support angiogenesis in vitro, and hyperoxia activates ERK1/2 in fetal human pulmonary microvascular endothelial cells (HPMECs) and in neonatal murine lungs; however, their role in experimental BPD and PH is unknown. Therefore, we hypothesized that Tie2 Cre-mediated deficiency of ERK2 in the endothelial cells of neonatal murine lungs would potentiate hyperoxia-induced BPD and PH. We initially determined the role of ERK2 in in vitro angiogenesis using fetal HPMECs. To disrupt endothelial ERK2 signaling in the lungs, we decreased ERK2 expression by breeding ERK2^flox/flox mice with Tie-Cre mice. One-day-old endothelial ERK2-sufficient (eERK2^+/+) or –deficient (eERK2^+/−) mice were exposed to normoxia or hyperoxia (FiO₂ 70%) for 14 d. We then performed lung morphometry, gene and protein expression studies, and echocardiography to determine the extent of inflammation, oxidative stress, and development of lungs and PH. The knockdown of ERK2 in HPMECs decreased in vitro angiogenesis. Hyperoxia increased lung inflammation and oxidative stress, decreased lung angiogenesis and alveolarization, and induced PH in neonatal mice; however, these effects were augmented in the presence of Tie2-Cre mediated endothelial ERK2 deficiency. Therefore, we conclude that endothelial ERK2 signaling is necessary to mitigate hyperoxia-induced experimental BPD and PH in neonatal mice. Our results indicate that endothelial ERK2 is a potential therapeutic target for the management of BPD and PH in infants.

Effects of the FGF receptor-1 inhibitor, infigratinib, with or without sildenafil, in experimental pulmonary arterial hypertension

BACKGROUND AND PURPOSE

Pulmonary arterial hypertension (PAH) is a progressive disease associated with high morbidity and mortality, despite advances in medical therapy. We compared the effects of infigratinib (NVP-BGJ398), a new FGF receptor-1 inhibitor, with or without the PDE-5 inhibitor sildenafil, on vascular function and remodelling as well as on gene expression of signal transducers for receptors of TGF-β (Smads-1/2/4) and transcription factor of endothelial-mesenchymal transition (Twist-1) in established experimental PAH. Types I and III pro-collagen and TGF-β expressions in lung fibroblasts were analysed in vitro after the different treatments.

EXPERIMENTAL APPROACH

PAH was induced in male Wistar rats with monocrotaline. 14 days later, treatments [sildenafil (SIL), infigratinib (INF) or their combination (SIL+INF)] were given for another 14 days. On Day 28, echocardiography and haemodynamic assays were performed, and lungs and pulmonary vessels were removed for analysis by histology, immunohistochemistry and RT-PCR. Fibroblasts prepared from PAH lungs were also analysed for TGF-β and pro-collagen.

KEY RESULTS

Only the combination of infigratinib and sildenafil significantly improved right ventricular systolic pressure and vascular remodelling parameters (right ventricular hypertrophy, smooth muscle α-actin, vessel wall thickness, and vascular collagen content). Infigratinib may act by reducing gene expression of Smads-1/4 and Twist-1 in lung tissue, as well as TGF-β and types I and III pro-collagen in lung fibroblasts.

CONCLUSIONS AND IMPLICATIONS

In this model of monocrotaline-induced PAH, the combination of the new inhibitor of FGF receptor-1, infigratinib, and sildenafil effectively improved haemodynamics and decreased vascular remodelling.

FGF21 Protects the Blood-Brain Barrier by Upregulating PPARγ via FGFR1/β-klotho after Traumatic Brain Injury

Blood-brain barrier (BBB) disruption and dysfunction result in brain edema, which is responsible for more than half of all deaths after severe traumatic brain injury (TBI). Fibroblast growth factor 21 (FGF21) has a potential neuroprotective function in the brain. However, the effects and underlying possible mechanism of action on BBB integrity following TBI remain unknown. The purpose of the current study was to determine the effects of FGF21 on BBB protection and TBI treatment. The effects of recombinant human FGF21 (rhFGF21) on BBB integrity and on tight junction (TJ) and adhesion junction (AJ) proteins were investigated both in a TBI mouse model and an in vitro BBB disruption model established with tumor necrosis factor alpha (TNF-α)-induced human brain microvascular endothelial cells (HBMECs). The ability of rhFGF21 to form an FGF21/FGFR1/β-klotho complex was confirmed by in vitro β-klotho small interfering RNA (siRNA) transfection and FGFR1 co-immunoprecipitation. In addition, the specific FGFR1 and peroxisome proliferator-activated receptor gamma (PPARγ) inhibitors PD173074 and GW9662, respectively, were applied to further explore the possible mechanism of rhFGF21 in BBB maintenance after TBI. rhFGF21 markedly reduced neurofunctional behavior deficits and cerebral edema degree, preserved BBB integrity, and recued brain tissue loss and neuron apoptosis in the mouse model after TBI. Both in vivo and in vitro, rhFGF21 upregulated TJ and AJ proteins, thereby preserving the BBB. Moreover, rhFGF21 activated PPARγ in TNF-α-induced HBMECs through formation of an FGF21/FGFR1/β-klotho complex. rhFGF21 protected the BBB through FGF21/FGFR1/β-klotho complex formation and PPARγ activation, which upregulated TJ and AJ proteins.

MiR-339 inhibits proliferation of pulmonary artery smooth muscle cell by targeting FGF signaling

Pulmonary artery hypertension (PAH) is a fatal disorder. Recent studies suggest that microRNA (miRNA) plays an important role in regulating proliferation of pulmonary artery smooth muscle cells (PASMC), which underlies the pathology of PAH. However, the exact mechanism of action of miRNAs remains elusive. In this study, we found that miR‐339 was highly expressed in the cardiovascular system and was downregulated by a group of cytokines and growth factors, especially PDGF‐BB and FGF2. Functional analyses revealed that miR‐339 can inhibit proliferation of PASMC. Also, miR‐339 inhibited FGF2‐induced proliferation, but had no effect on proliferation induced by PDGF‐BB. The fibroblast growth factor receptor substrate 2 (FRS2) was identified as a potential direct target of miR‐339. Consistent with the actions of miR‐339, knockdown of FRS2 only inhibited FGF2‐ but not PDGF‐BB‐induced proliferation of PASMC. In addition, our results showed that inhibition of ERK and PI3K abrogated the downregulation of miR‐339 induced by PDGF‐BB. Finally, miR‐339 expression was found to be decreased in the pulmonary arteries of rats with MCT‐induced PAH. Our study is the first report on the biological role of miR‐339 in regulating proliferation of PASMC by targeting FGF signaling, providing new mechanistic insights into PASMC proliferation and pathogenesis of PAH.

Dihydromyricetin prevents monocrotaline-induced pulmonary arterial hypertension in rats

Pulmonary artery hypertension (PAH) is a chronic and deadly disease, for which effective medical treatments are lacking. Here, we investigated whether 2R,3R-dihydromyricetin (DHM) could prevent monocrotaline (MCT)-induced PAH in rats. The MCT-injected rats were treated with normal saline or DHM (100mg/kg body weight/d) for 4 weeks, followed by measurements of right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), pulmonary arterial remodeling (PAR), and expression levels of IL-6, TNF-α, and IL-10. In vitro, we assessed the role of DHM on IL-6-induced migration of primary human pulmonary arterial smooth muscle cells (HPASMCs). We found that DHM treatment attenuated changes in RVSP, RVHI, and PAR in MCT-injected PAH rats. The observed increase of IL-6 levels in PAH rats was inhibited by DHM treatment. In vitro, DHM pretreatment reduced IL-6-induced HPASMC migration. Furthermore, MCT- and IL-6-mediated increases in MMP9 and P-STAT3 (tyr705) PY-STAT3 levels were suppressed by DHM treatment in vivo and in vitro. These results suggest that DHM could prevent MCT-induced rat PAH and IL-6-induced HPASMC migration through a mechanism involving inhibiting of the STAT3/MMP9 axis.

Prediction of target genes for miR-140-5p in pulmonary arterial hypertension using bioinformatics methods

The expression of microRNA (miR)-140-5p is known to be reduced in both pulmonary arterial hypertension (PAH) patients and monocrotaline-induced PAH models in rat. Identification of target genes for miR-140-5p with bioinformatics analysis may reveal new pathways and connections in PAH. This study aimed to explore downstream target genes and relevant signaling pathways regulated by miR-140-5p to provide theoretical evidences for further researches on role of miR-140-5p in PAH. Multiple downstream target genes and upstream transcription factors (TFs) of miR-140-5p were predicted in the analysis. Gene ontology (GO) enrichment analysis indicated that downstream target genes of miR-140-5p were enriched in many biological processes, such as biological regulation, signal transduction, response to chemical stimulus, stem cell proliferation, cell surface receptor signaling pathways. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway analysis found that downstream target genes were mainly located in Notch, TGF-beta, PI3K/Akt, and Hippo signaling pathway. According to TF-miRNA-mRNA network, the important downstream target genes of miR-140-5p were PPI, TGF-betaR1, smad4, JAG1, ADAM10, FGF9, PDGFRA, VEGFA, LAMC1, TLR4, and CREB. After thoroughly reviewing published literature, we found that 23 target genes and seven signaling pathways were truly inhibited by miR-140-5p in various tissues or cells; most of these verified targets were in accordance with our present prediction. Other predicted targets still need further verification in vivo and in vitro.

Therapeutic and pathological roles of fibroblast growth factors in pulmonary diseases

Fibroblast growth factors (FGFs) constitute a large family of polypeptides that are involved in many biological processes, ranging from prenatal cell-fate specification and organogenesis to hormonal and metabolic regulation in postnatal life. During embryonic development, these growth factors are important mediators of the crosstalk among ectoderm-, mesoderm-, and endoderm-derived cells, and they instruct the spatial and temporal growth of organs and tissues such as the brain, bone, lung, gut, and others. The involvement of FGFs in postnatal lung homeostasis is a growing field, and there is emerging literature about their roles in lung pathophysiology. In this review, the involvement of FGF signaling in a wide array of lung diseases will be summarized. Developmental Dynamics 246:235-244, 2017. © 2016 Wiley Periodicals, Inc.