Circular RNAs Regulate Vascular Remodelling in Pulmonary Hypertension.

Circular RNAs (circRNAs) are a newly identified type of noncoding RNA molecule with a unique closed-loop structure. circRNAs are widely expressed in different tissues and developmental stages of many species, participating in many important pathophysiological processes and playing an important role in the occurrence and development of diseases. This article reviews the discovery, characteristics, formation, and biological function of circRNAs. The relationship between circRNAs and vascular remodelling, as well as the current status of research and potential application value in pulmonary hypertension (PH), is discussed to promote a better understanding of the role of circRNAs in PH. circRNAs are closely related to the remodelling of vascular endothelial cells and vascular smooth muscle cells. circRNAs have potential application prospects for in-depth research on the possible pathogenesis and mechanism of PH. Future research on the role of circRNAs in the pathogenesis and mechanism of PH will provide new insights and promote screening, diagnosis, prevention, and treatment of this disease.

Sialic acid-binding immunoglobulin-like lectin 9 as a potential therapeutic target for chronic obstructive pulmonary disease.

ABSTRACT: Chronic obstructive pulmonary disease (COPD) has become the third-leading cause of death worldwide, which is a severe economic burden to the healthcare system. Chronic bronchitis is the most common condition that contributes to COPD, both locally and systemically. Neutrophilic inflammation predominates in the COPD airway wall and lumen. Logically, repression of neutrophilia is an essential fashion to COPD treatment. However, currently available anti-neutrophilic therapies provide little benefit in COPD patients and may have serious side effects. Thus, there is an urgent need to explore an effective and safe anti-neutrophilic approach that might delay progression of the disease. Sialic acid-binding immunoglobulin-like lectin (Siglec)-9 is a member of the Siglec cell surface immunoglobulin family. It is noteworthy that Siglec-9 is highly expressed on human neutrophils and monocytes. Ligation of Siglec-9 by chemical compounds or synthetic ligands induced apoptosis and autophagic-like cell death in human neutrophils. Furthermore, administration of antibody to Siglec-E, mouse functional ortholog of Siglec-9, restrained recruitment and activation of neutrophils in mouse models of airway inflammation in vivo. Given the critical role that neutrophils play in chronic bronchitis and emphysema, targeting Siglec-9 could be beneficial for the treatment of COPD, asthma, fibrosis, and related chronic inflammatory lung diseases.

Regulation of circular RNAs act as ceRNA in a hypoxic pulmonary hypertension rat model.

To explore potential critical genes and identify circular RNAs (circRNAs) that act as the competitive endogenous RNA (ceRNA) in a hypoxic pulmonary hypertension (HPH) rat model. Constructed rat model, and a bioinformatics method was used to analyse differentially expressed (DE) genes and construct a circRNA-miRNA-mRNA ceRNA regulatory network. Then, qRT-PCR was used to verify. The significant DEcircRNAs/DEmiRNAs/DEmRNAs was showed, and a ceRNA network with 8 DEcircRNAs, 9 DEmiRNAs and 46 DEmRNAs were constructed. The functional enrichment suggested the inflammatory response, NF-κB signalling, MAPK cascade and Toll-like receptor were associated with HPH. Further assessment confirmed that circ_002723, circ_008021, circ_016925 and circ_020581 could have a potential ceRNA mechanism by sponging miR-23a or miR-21 to control downstream target gene and be involved in the pathophysiology of HPH. The qRT-PCR validation results were consistent with the RNA-Seq results. This study revealed potentially important genes, pathways and ceRNA regulatory networks in HPH.

PDGF mediates pulmonary arterial smooth muscle cell proliferation and migration by regulating NFATc2.

The reconstruction of pulmonary vascular structure caused by the proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) is the central link in the formation of pulmonary arterial hypertension (PAH). Platelet­derived growth factor (PDGF) can regulate the proliferation and migration of PASMCs. At the same time, nuclear factor of activated T cells (NFATs) plays an important role in the development of PAH. To the best of our knowledge, there are no reports yet regarding whether PDGF regulates NFATc2 to increase the proliferation of PASMCs. The present study aimed to investigate whether PDGF affects the proliferation and migration of PASMCs by regulating NFAT, and to study the pathogenesis of PAH. PASMCs were treated with recombinant PDGF; Cell Counting Kit­8 and clone formation experiments showed that PDGF enhanced the cell viability and proliferation of PASMCs. Cell cycle distribution and molecular markers related to cell proliferation (cyclin D1, CDK4 and Proliferating Cell Nuclear Antigen) were detected by flow cytometry, and the results indicated that PDGF promoted the division of PAMSCs. The scratch migration and Transwell migration assays showed that the migratory ability of PASMCs was enhanced following PDGF treatment. Changes in NFATs (NFATc1­5) after PDGF treatment were evaluated by reverse transcription­quantitative PCR and western blotting; NFATc2 showed the most significant results. Finally, PDGF­treated cells were treated with an NFAT pathway inhibitor, cyclosporin A, or a small interfering RNA targeting NFATc2, and changes in cell proliferation and migration were evaluated to assess the role of NFATc2 in PDGF­induced cell proliferation and migration. In conclusion, PDGF may regulate PASMC proliferation and migration by regulating the expression of NFAT, further leading to the occurrence of PAH. It is proposed that NFATc2 could be used as a potential target for PAH treatment.

MicroRNA-214-3p Regulates Hypoxia-Mediated Pulmonary Artery Smooth Muscle Cell Proliferation and Migration by Targeting ARHGEF12.

BACKGROUND miR-214-3p has been found to inhibit proliferation and migration in cancer cells. The objective of this study was to determine whether ARHGEF12 is involved in miR-214-3p-mediated suppression of proliferation and migration of pulmonary artery smooth muscle cells (PASMCs). MATERIAL AND METHODS PASMCs were cultured under normoxia or hypoxia. miR-214-3p mimics or inhibitors were transiently transfected into PASMCs. Proliferation, apoptosis, and migration of PASMCs were evaluated using MTT assay, flow cytometry, and Boyden chamber apparatus. Western blot analysis was used to examine expression of Rho guanine nucleotide exchange factor 12 (ARHGEF12), c-fos, c-jun, and caspase-3. Luciferase reporter assay was used to test the direct regulation of miR-214-3p on the 3'-untranslated region (UTR) of ARHGEF12. RESULTS miR-214-3p was significantly upregulated in hypoxia-treated PASMCs. Knockdown of miR-214-3p significantly attenuated hypoxia-induced proliferation and migration in PASMCs and promoted apoptosis, whereas this effect was aggravated by overexpression of miR-214-3p. In addition, dual-luciferase reporter assay demonstrated that ARHGEF12 is a direct target gene of miR-214-3p. The protein levels of ARHGEF12 were downregulated after knockdown of miR-214-3p in PASMCs. Rescue experiment results indicated that decreased proliferation of PASMCs resulted from knockdown of miR-214-3p were partially reversed by silencing of ARHGEF12 by siRNA. Furthermore, knockdown of miR-214-3p reduced expression of c-jun and c-fos, but increased expression of caspase-3 in PASMCs under hypoxia. CONCLUSIONS In conclusion, these results indicate that miR-214-3p acts as a novel regulator of hypoxia-induced proliferation and migration by directly targeting ARHGEF12 and dysregulating c-jun and c-fos in PASMCs, and may be a potential therapeutic target for treating pulmonary hypertension.

5-Aza-2'-deoxycytidine, a DNA methylation inhibitor, attenuates hypoxic pulmonary hypertension via demethylation of the PTEN promoter.

Phosphatase and tensin homolog (PTEN) plays an important role in the pathogenesis of hypoxic pulmonary hypertension (HPH). A decrease in PTEN expression is associated with the hypermethylation of its promoter. However, whether the demethylation of the PTEN gene could attenuate HPH remains unknown. 5-Aza-2'-deoxycytidine (5-Aza-dC) is a DNA methyltransferase (DNMT) inhibitor. The present study was designed to investigate the effects and mechanisms of 5-Aza-dC on HPH. The proliferation, migration and apoptosis of rat pulmonary artery smooth muscle cells (PASMCs) induced by hypoxia and treated with 5-Aza-dC were detected. The expression of PTEN and DNMTs and the PTEN methylation status of PASMCs were detected. SD rats were randomly divided into normal group, hypoxia group and hypoxia + 5-Aza-dC group. The expression of PTEN was decreased, the expression of DNMTs was increased, and the methylation status of PTEN was increased in hypoxia-induced PASMCs. However, 5-Aza-dC can rescue the decreased PTEN, inhibit DNMT levels in a dose-dependent manner and suppress PTEN methylation. Furthermore, the demethylation of PTEN, which was induced by 5-Aza-dC, inhibited the proliferation, migration and promoted apoptosis in PASMCs. In vivo studies further demonstrated that the expression of PTEN, mean pulmonary artery pressure and right ventricular hypertrophy index in HPH rats was attenuated by 5-Aza-dC. 5-Aza-dC also suppressed the expression of DNMTs and PTEN methylation in the lungs of HPH rats. These results indicated that PTEN promoter methylation status is involved in HPH. 5-Aza-dC, as a DNMT inhibitor, has the potential to attenuate HPH via demethylation of the PTEN promoter.

Autophagy in pulmonary hypertension: Emerging roles and therapeutic implications.

Autophagy is an important mechanism for cellular self-digestion and basal homeostasis. This gene- and modulator-regulated pathway is conserved in cells. Recently, several studies have shown that autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy-related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy-related drugs, such as chloroquine, 3-methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.

Serum cardiac troponin elevation predicts mortality in patients with pulmonary hypertension: A meta-analysis of eight cohort studies.

OBJECTIVE: To determine the association of serum cardiac troponin (cTn) with the mortality of pulmonary hypertension (PH) patients via a meta-analysis. DATE SOURCE: We searched PubMed and EMBASE from inception to October 25, 2017. STUDY SELECTION: The reference lists of the retrieved articles were also consulted. The Q test and I2 test were used for to assess heterogeneity. The relationship between cTn elevation and mortality was analysed. Studies were stratified according to type of troponin (cTnT vs cTnI), region (Europe vs America) and follow-up length (≤3 years vs >3 years). RESULTS: Eight studies with 739 patients were included in the meta-analysis. Cardiac troponin elevation ranged from 14.3% to 94.5%. Overall, 48.8% (39/80) of patients with elevated cTn died compared to 18.6% (45/242) of patients with normal cTn levels. These findings showed cTn elevation was significantly related to an increased mortality risk in PH patients [hazard ratio (HR) = 3.05, 95% confidence interval (95% CI) = 2.16-4.32, I2  = 24.9%]. cTnI was better at predicting mortality than cTnT (HR = 3.37, 95%CI = 2.05-5.55 vs HR = 2.80, 95%CI = 1.97-3.98, respectively). American populations had increased mortality compared to European populations (HR = 4.23, 95%CI = 2.29-7.80 vs HR = 2.70, 95% CI = 1.95-3.74, respectively). This finding was independent of the follow-up length of the studies (≤3 years: HR = 2.36, 95%CI = 1.65-3.38; >3 years: HR = 4.55, 95%CI = 2.80-7.39). CONCLUSIONS: Although different studies detected the expression cTnT or cTnI by various methods, the mortality in the cTn-positive group was higher than that in the cTn-negative group. Serum cTn elevation emerged as an independent predictor of increased risk of mortality in PH patients.