Single-Cell Transcriptome Analysis of Peripheral Neutrophils From Patients With Idiopathic Pulmonary Arterial Hypertension.

BACKGROUND: Idiopathic pulmonary hypertension (IPAH) is a rare and devastating disease often accompanied by persistent inflammation and immune responses. We aim to provide a reference atlas of neutrophils to facilitate a better understanding of cellular phenotypes and discovery of candidate genes. METHODS: Peripheral neutrophils from naive patients with IPAH and matched controls were profiled. Whole-exon sequencing was performed to exclude known genetic mutations before establishing single-cell RNA sequencing. Marker genes were validated by flow cytometry and histology in a separate validation cohort. RESULTS: Seurat clustering analysis revealed that the landscape of neutrophils encompassed 5 clusters, including 1 progenitor, 1 transition, and 3 functional clusters. The intercorrelated genes in patients with IPAH were mainly enriched in antigen processing presentation and natural killer cell mediated cytotoxicity. We identified and validated differentially upregulated genes, including MMP9 (matrix metallopeptidase 9), ISG15 (ISG15 ubiquitin-like modifier), and CXCL8 (C-X-C motif ligand 8). The positive proportions and fluorescence quantification of these genes were significantly increased in CD16+ neutrophils in patients with IPAH. The higher proportion of positive MMP9 neutrophils increased mortality risk after adjustment for age and sex. Patients with higher proportions of positive MMP9 neutrophils had worse survival, while the fraction of ISG15- or CXCL8-positive expression neutrophils failed to predict outcome. CONCLUSIONS: Our study yields a comprehensive dataset of the landscape of neutrophils in patients with IPAH. The predictive values of a neutrophil cluster characterized by higher MMP9 expression indicate a functional role for neutrophil-specific matrix metalloproteinases in the pathogenesis of pulmonary arterial hypertension.

Spatiotemporal trends of cardiovascular disease burden attributable to ambient PM2.5 from 1990 to 2019: A global burden of disease study.

There is little known about the global burden of CVD attributable to ambient PM2.5 (referred to as CVD burden hereinafter) and its secular trend across different regions and countries. We aimed to evaluate the spatiotemporal trends in CVD burden at the global, regional and national levels from 1990 to 2019. Data on CVD burden including mortality and disability adjusted of life years (DALYs) from 1990 to 2019 were extracted from the Global Burden of Disease Study 2019. Cases, the age-standardized rate of mortality (ASMR) and DALYs (ASDR) were estimated by age, sex and sociodemographic index (SDI). Estimated annual percentage change (EAPC) was calculated to evaluate the temporal changing in ASDR and ASMR from 1990 to 2019. In 2019, 2.48 million deaths and 60.91 million DALYs of CVD were attributed to ambient PM2.5 globally. Most CVD burden occurred in males, elderly and the middle SDI region. At national level, Uzbekistan, Egypt, and Iraq had the highest ASMR and ASDR. Despite remarkable increase in number of DALYs and deaths of CVD worldwide from 1990 to 2019, we observed nonsignificant change in ASMR (EAPC: 0.06, 95 % CI: -0.01, 0.13) and slight increment in ASDR (EAPC: 0.30, 95 % CI: 0.23, 0.37). The EAPCs of ASMR and ASDR were negatively associated with SDI in 2019, while the low-middle SDI region exhibited the fastest growth of ASMR and ASDR with EAPCs of 3.25 (95 % CI: 3.14, 3.37) and 3.36 (95 % CI: 3.22, 3.49), respectively. In conclusion, the global CVD burden attributable to ambient PM2.5 has largely increased over the past three decades. The population growth, aging and SDI contributed to the heterogeneity of spatial and temporal distribution. Enforcing policy to improving air quality is required to halt the growing burden of PM2.5 on health.

Pulmonary hypertension: Linking inflammation and pulmonary arterial stiffening.

Pulmonary hypertension (PH) is a progressive disease that arises from multiple etiologies and ultimately leads to right heart failure as the predominant cause of morbidity and mortality. In patients, distinct inflammatory responses are a prominent feature in different types of PH, and various immunomodulatory interventions have been shown to modulate disease development and progression in animal models. Specifically, PH-associated inflammation comprises infiltration of both innate and adaptive immune cells into the vascular wall of the pulmonary vasculature-specifically in pulmonary vascular lesions-as well as increased levels of cytokines and chemokines in circulating blood and in the perivascular tissue of pulmonary arteries (PAs). Previous studies suggest that altered hemodynamic forces cause lung endothelial dysfunction and, in turn, adherence of immune cells and release of inflammatory mediators, while the resulting perivascular inflammation, in turn, promotes vascular remodeling and the progression of PH. As such, a vicious cycle of endothelial activation, inflammation, and vascular remodeling may develop and drive the disease process. PA stiffening constitutes an emerging research area in PH, with relevance in PH diagnostics, prognostics, and as a therapeutic target. With respect to its prognostic value, PA stiffness rivals the well-established measurement of pulmonary vascular resistance as a predictor of disease outcome. Vascular remodeling of the arterial extracellular matrix (ECM) as well as vascular calcification, smooth muscle cell stiffening, vascular wall thickening, and tissue fibrosis contribute to PA stiffening. While associations between inflammation and vascular stiffening are well-established in systemic vascular diseases such as atherosclerosis or the vascular manifestations of systemic sclerosis, a similar connection between inflammatory processes and PA stiffening has so far not been addressed in the context of PH. In this review, we discuss potential links between inflammation and PA stiffening with a specific focus on vascular calcification and ECM remodeling in PH.

m6A Modification-mediated GRAP Regulates Vascular Remodeling in Hypoxic Pulmonary Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling induced by human pulmonary arterial smooth muscle cell (HPASMC) proliferation, migration, and apoptosis resistance. m6A (N6-methyladenosine) is the most prevalent RNA posttranscriptional modification in eukaryotic cells. However, its role in PAH remains elusive. We designed this study to investigate whether m6A modification and its effector proteins play a role in pulmonary vascular resistance. Lung samples were used to profile m6A concentrations in control subjects and patients with PAH. Bioinformatics analysis, real-time PCR, immunohistochemistry, and Western blotting were used to determine the role of m6A effectors in PAH. The biological effects of GRAP modified by m6A were investigated using in vitro and in vivo models. Furthermore, RIP-PCR was used to assess the writers and readers of GRAP. In this study, we revealed that m6A-modified GRAP mRNA was upregulated in PAH lung samples, cHx/Su-induced mouse models, and hypoxia-stimulated HPASMCs; however, GRAP mRNA and protein were abnormally downregulated. Functionally, overexpression of GRAP drastically alleviated the proliferative and invasive ability of PAH HPASMCs through inhibition of the Ras/ERK signaling pathway in vitro and in vivo. In addition, METTL14 (methyltransferase-like 14) and the m6A binding protein YTHDF2 were significantly increased in PAH. Moreover, we found that m6A-modified GRAP mRNA was recognized by YTHDF2 to mediate the degradation. GRAP expression was consistently negatively correlated with METTL14 and YTHDF2 in vivo and in vitro. Taken together, for the first time, our findings highlight the function and therapeutic target value of GRAP and extend our understanding of the importance of RNA epigenetics in PAH.

Regulatory T Cell-Related Gene Indicators in Pulmonary Hypertension.

Objective: Regulatory T cells (Tregs) are critical immune modulators to maintain immune homeostasis and limit pulmonary hypertension (PH). This study was aimed to identify Treg-related genes (TRGs) in PH. Methods: The gene expression profile from lungs of PH patients was retrieved from the Gene Expression Omnibus (GEO) database. The abundance of Tregs was estimated by the xCell algorithm, the correlation of which with differentially expressed genes (DEGs) was performed. DEGs with a |Pearson correlation coefficient| >0.4 were identified as TRGs. Functional annotation and the protein-protein interaction (PPI) network were analyzed. A gene signature for 25 hub TRGs (TRGscore) was generated by a single sample scoring method to determine its accuracy to distinguish PH from control subjects. TRGs were validated in datasets of transcriptional profiling of PH cohorts and in lung tissues of experimental PH mice. Results: A total of 819 DEGs were identified in lungs of 58 PAH patients compared to that of 25 control subjects of dataset GSE117261. In total, 165 of all these DEGs were correlated with the abundance of Tregs and identified as TRGs, with 90 upregulated genes and 75 downregulated genes compared to that of control subjects. The upregulated TRGs were enriched in negative regulation of multiple pathways, such as cAMP-mediated signaling and I-kappaB kinase/NF-kappaB signaling, and regulated by multiple genes encoding transcriptional factors including HIF1A. Furthermore, 25 hub genes categorized into three clusters out of 165 TRGs were derived, and we identified 27 potential drugs targeting 10 hub TRGs. The TRGscore based on 25 hub TRGs was higher in PH patients and could distinguish PH from control subjects (all AUC >0.7). Among them, 10 genes including NCF2, MNDA/Ifi211, HCK, FGR, CSF3R, AQP9, S100A8, G6PD/G6pdx, PGD, and TXNRD1 were significantly reduced in lungs of severe PH patients of dataset GSE24988 as well as in lungs of hypoxic PH mice compared to corresponding controls. Conclusion: Our finding will shed some light on the Treg-associated therapeutic targets in the progression of PH and emphasize on TRGscore as a novel indicator for PH.

Animal models of pulmonary hypertension due to left heart disease.

Pulmonary hypertension due to left heart disease (PH-LHD) is regarded as the most prevalent form of pulmonary hypertension (PH). Indeed, PH is an independent risk factor and predicts adverse prognosis for patients with left heart disease (LHD). Clinically, there are no drugs or treatments that directly address PH-LHD, and treatment of LHD alone will not also ameliorate PH. To target the underlying physiopathological alterations of PH-LHD and to develop novel therapeutic approaches for this population, animal models that simulate the pathophysiology of PH-LHD are required. There are several available models for PH-LHD that have been successfully employed in rodents or large animals by artificially provoking an elevated pressure load on the left heart, which by transduction elicits an escalated pressure in pulmonary artery. In addition, metabolic derangement combined with aortic banding or vascular endothelial growth factor receptor antagonist is also currently applied to reproduce the phenotype of PH-LHD. As of today, none of the animal models exactly recapitulates the condition of patients with PH-LHD. Nevertheless, the selection of an appropriate animal model is essential in basic and translational studies of PH-LHD. Therefore, this review will summarize the characteristics of each PH-LHD animal model and discuss the advantages and limitations of the different models.

The features of rare pathogenic BMPR2 variants in pulmonary arterial hypertension: Comparison between patients and reference population.

BACKGROUND: Mutations in the gene encoding bone morphogenetic protein receptor type 2 (BMPR2) are the most common genetic risk factors underlying pulmonary arterial hypertension (PAH). However, the features of PAH-related BMPR2 rare variants remain unclear. We propose that the discrepancy of BMPR2 rare variants landscape between patients with PAH and reference population would be important to address the genetic background of PAH-related variants. METHODS: We genotyped BMPR2 rare variants in 670 Chinese patients with pulmonary arterial hypertension. The BMPR2 rare variants were screened in 10,508 reference people from two exome databases. RESULTS: The prevalence of rare BMPR2 variants in patients with PAH was significantly higher compared to the reference population (21.5%, 144/670 vs 0.87%, 91/10508, p = 1.3 × 10-118). In patients with PAH, 49% of identified BMPR2 rare variants were loss-of-function or splicing. These BMPR2 rare variants were only observed in 1% of the reference population (p = 9.0 × 10-12). Arg491, which is absent in the reference population, represented as hot-spot site (14.6%, 21/144) in PAH patients. BMPR2 missense mutations in PAH patients were more likely distributed in extracellular ligand-binding domain (ECD, 29.7% vs 11.1%, p < 0.001). Compared with Non-PAH-related variations, PAH-related missense variants tend to alter the amino acid electric status (51.4% vs 23.3%, p < 0.001). CONCLUSIONS: BMPR2 variants located in extracellular ligand-binding domain or altered the amino acid electric status are more pathogenic.

Germline BMP9 mutation causes idiopathic pulmonary arterial hypertension.

BACKGROUND: Idiopathic pulmonary arterial hypertension (IPAH) is a rare disease with high heritability. Although several predisposing genes have been linked to IPAH, the genetic aetiology remains unknown for a large number of IPAH cases. METHODS: We conducted an exome-wide gene-based burden analysis on two independent case-control studies, including a total of 331 IPAH cases and 10 508 controls. Functional assessments were conducted to analyse the effects of genetic mutations on protein biosynthesis and function. RESULTS: The gene encoding human bone morphogenetic protein 9 (BMP9) was identified as a novel genetic locus displaying exome-wide association with IPAH in the discovery cohort (OR 18.8; p=1.9×10-11). This association was authenticated in the independent replication cohort (p=1.0×10-5). Collectively, the rare coding mutations in BMP9 occurred in 6.7% of cases, ranking this gene second to BMPR2, comprising a combined significance of 2.7×10-19 (OR 21.2). Intriguingly, the patients with BMP9 mutations had lower plasma levels of BMP9 than those without. Functional studies showed that the BMP9 mutations led to reduced BMP9 secretion and impaired anti-apoptosis ability in pulmonary arterial endothelial cells. CONCLUSION: We identify BMP9 as an IPAH culprit gene.

Impact of Pituitary-Gonadal Axis Hormones on Pulmonary Arterial Hypertension in Men.

The association of sex hormone (estradiol, testosterone, and progesterone) with cardiopulmonary disease has already attracted great attention, especially in pulmonary arterial hypertension (PAH). However, the impact of sex hormones and their pituitary stimulators (follicle-stimulating hormone and luteinizing hormone) on PAH in men remains unclear. We conducted a prospective cohort study recruiting 95 patients with idiopathic PAH from 2008 to 2014 and following up for a median of 65 months for death. Compared with control, abnormal plasma levels of sex hormones were more common in patients with PAH. Higher estradiol and estradiol/testosterone levels were associated with risk of PAH diagnosis (odds ratio per ln estradiol, 3.55; P<0.001; odds ratio per ln estradiol/testosterone, 4.30; P<0.001), whereas higher testosterone and progesterone were associated with a reduced risk (odds ratio per ln testosterone, 0.48; P=0.003; odds ratio per ln progesterone, 0.09; P<0.001). Fifty patients died during follow-up. Men with higher estradiol had increased mortality (hazard ratio per ln estradiol, 2.02; P=0.007), even after adjustment for baseline characteristics and PAH treatment. According to receiver operating characteristic analysis, patients with PAH with higher estradiol level (≥145.55 pmol/L) had worse 5-year survival rate compared with those with lower estradiol (38.6% versus 68.2%; log-rank test P=0.001). Therefore, our data show higher estradiol, estradiol/testosterone ratio, lower testosterone, and progesterone were associated with increased risk of PAH. Meanwhile, higher estradiol was independently associated with higher mortality in men with PAH. Further studies are needed to explain the origin of these hormonal derangements and their potential pathophysiological implications in PAH.