Interleukin-6 as a potential therapeutic target for pulmonary arterial hypertension

Sex Dimorphism in Pulmonary Arterial Hypertension Associated With Autoimmune Diseases

Pulmonary hypertension is a rare, incurable, and progressive disease. Although there is increasing evidence that immune disorders, particularly those associated with connective tissue diseases, are a strong predisposing factor in the development of pulmonary arterial hypertension (PAH), there is currently a lack of knowledge about the detailed molecular mechanisms responsible for this phenomenon. Exploring this topic is crucial because patients with an immune disorder combined with PAH have a worse prognosis and higher mortality compared with patients with other PAH subtypes. Moreover, data recorded worldwide show that the prevalence of PAH in women is 2× to even 4× higher than in men, and the ratio of PAH associated with autoimmune diseases is even higher (9:1). Sexual dimorphism in the pathogenesis of cardiovascular disease was explained for many years by the action of female sex hormones. However, there are increasing reports of interactions between sex hormones and sex chromosomes, and differences in the pathogenesis of cardiovascular disease may be controlled not only by sex hormones but also by sex chromosome pathways that are not dependent on the gonads. This review discusses the role of estrogen and genetic factors including the role of genes located on the X chromosome, as well as the potential protective role of the Y chromosome in sexual dimorphism, which is prominent in the occurrence of PAH associated with autoimmune diseases. Moreover, an overview of animal models that could potentially play a role in further investigating the aforementioned link was also reviewed.

Current Overview of the Biology and Pharmacology in Sugen/Hypoxia-Induced Pulmonary Hypertension in Rats

The Sugen 5416/hypoxia (Su/Hx) rat model of pulmonary arterial hypertension (PAH) demonstrates most of the distinguishing features of PAH in humans, including increased wall thickness and obstruction of the small pulmonary arteries along with plexiform lesion formation. Recently, significant advancement has been made describing the epidemiology, genomics, biochemistry, physiology, and pharmacology in Su/Hx challenge in rats. For example, there are differences in the overall reactivity to Su/Hx challenge in different rat strains and only female rats respond to estrogen treatments. These conditions are also encountered in human subjects with PAH. Also, there is a good translation in both the biochemical and metabolic pathways in the pulmonary vasculature and right heart between Su/Hx rats and humans, particularly during the transition from the adaptive to the nonadaptive phase of right heart failure. Noninvasive techniques such as echocardiography and magnetic resonance imaging have recently been used to evaluate the progression of the pulmonary vascular and cardiac hemodynamics, which are important parameters to monitor the efficacy of drug treatment over time. From a pharmacological perspective, most of the compounds approved clinically for the treatment of PAH are efficacious in Su/Hx rats. Several compounds that show efficacy in Su/Hx rats have advanced into phase II/phase III studies in humans with positive results. Results from these drug trials, if successful, will provide additional treatment options for patients with PAH and will also further validate the excellent translation that currently exists between Su/Hx rats and the human PAH condition.

Causal effect of interleukin (IL)-6 on blood pressure and hypertension: A mendelian randomization study

To examine whether circulating interleukin-6 (IL-6) levels (CirIL6) have a causal effect on blood pressure using Mendelian randomization (MR) methods. We used data from genome-wide association studies (GWAS) of European ancestry to obtain genetic instruments for circulating IL-6 levels and blood pressure measurements. We applied several robust MR methods to estimate the causal effects and to test for heterogeneity and pleiotropy. We found that circulating IL-6 had a significant positive causal effect on systolic blood pressure (SBP) and pulmonary arterial hypertension (PAH), but not on diastolic blood pressure (DBP) or hypertension. We found that as CirIL6 genetically increased, SBP increased using Inverse Variance Weighted (IVW) method (for ukb-b-20175, β = 0.082 with SE = 0.032, P = 0.011; for ukb-a-360, β = 0.075 with SE = 0.031, P = 0.014) and weighted median (WM) method (for ukb-b-20175, β = 0.061 with SE = 0.022, P = 0.006; for ukb-a-360, β = 0.065 with SE = 0.027, P = 0.014). Moreover, CirIL6 may be associated with an increased risk of PAH using WM method (odds ratio (OR) = 15.503, 95% CI, 1.025-234.525, P = 0.048), but not with IVW method. Our study provides novel evidence that circulating IL-6 has a causal role in the development of SBP and PAH, but not DBP or hypertension. These findings suggest that IL-6 may be a potential therapeutic target for preventing or treating cardiovascular diseases and metabolic disorders. However, more studies are needed to confirm the causal effects of IL-6 on blood pressure and to elucidate the underlying mechanisms and pathways.

Mendelian randomization study on causal association of IL-6 signaling with pulmonary arterial hypertension

BACKGROUND

A recent Mendelian randomization (MR) did not support an effect of the lead interleukin-6 receptor (IL-6 R) variant on risk of pulmonary arterial hypertension (PAH). Thus, we used two sets of genetic instrumental variants (IVs) and publicly available PAH genome-wide association studies (GWAS) to reassess the genetic causal link between IL-6 signaling and PAH.

METHODS

Six independent IL-6 signaling and 34 independent soluble IL-6 receptor (sIL-6 R) genetic IVs from recent MR reports and PAH GWAS including 162,962 European individuals were used to perform this two-sample MR study.

RESULTS

We found that as IL-6 signaling genetically increased, the risk of PAH reduced using IVW (odds ratio [OR] = 0.023, 95% confidence interval [CI]: 0.0013-0.393; p = .0093) and weighted median (OR = 0.033, 95% CI: 0.0024-0.467; p = .0116). Otherwise, as sIL-6 R genetically increased, the risk of PAH increased using IVW (OR = 1.34, 95% CI: 1.16-1.56; p = .0001), weighted median (OR = 1.36, 95% CI: 1.10-1.68; p = .005), MR-Egger (OR = 1.43, 95% CI: 1.05-1.94; p = .03), and weighted mode (OR = 1.35, 95% CI for OR: 1.12-1.63; p = .0035).

CONCLUSION

Our analysis suggested the causal link between genetically increased sIL-6 R and increased risk of PAH and between genetically increased IL-6 signaling and reduced risk of PAH. Thus, higher sIL-6 R levels may be a risk factor for patients with PAH, whereas higher IL-6 signaling may be a protective factor for patients with PAH.

Human iPSCs as Model Systems for BMP-Related Rare Diseases

Disturbances in bone morphogenetic protein (BMP) signalling contribute to onset and development of a number of rare genetic diseases, including Fibrodysplasia ossificans progressiva (FOP), Pulmonary arterial hypertension (PAH), and Hereditary haemorrhagic telangiectasia (HHT). After decades of animal research to build a solid foundation in understanding the underlying molecular mechanisms, the progressive implementation of iPSC-based patient-derived models will improve drug development by addressing drug efficacy, specificity, and toxicity in a complex humanized environment. We will review the current state of literature on iPSC-derived model systems in this field, with special emphasis on the access to patient source material and the complications that may come with it. Given the essential role of BMPs during embryonic development and stem cell differentiation, gain- or loss-of-function mutations in the BMP signalling pathway may compromise iPSC generation, maintenance, and differentiation procedures. This review highlights the need for careful optimization of the protocols used. Finally, we will discuss recent developments towards complex in vitro culture models aiming to resemble specific tissue microenvironments with multi-faceted cellular inputs, such as cell mechanics and ECM together with organoids, organ-on-chip, and microfluidic technologies.

Inhibiting IL-6 in medicine: a new twist to sustain inhibition of his cytokine tin the therapy of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, progressive disease characterized by an increase in blood pressure in the lungs' arteries. It can occur in a variety of species, including humans, dogs, cats, and horses. To date, PAH has a high mortality rate in both veterinary and human medicine, often due to complications such as heart failure. The complex pathological mechanisms of PAH involve multiple cellular signalling pathways at various levels. IL-6 is a powerful pleiotropic cytokine that regulates several phases of immune response, inflammation, and tissue remodelling. The hypothesis of this study was that the use of an IL-6 antagonist in PAH could interrupt or mitigate the cascade of events that leads to the progression of the disease and the worsening of clinical outcome, as well as tissue remodelling. In this study, we used two pharmacological protocols with an IL-6 receptor antagonist in a monocrotaline-induced PAH model in rats. Our results showed that the use of an IL-6 receptor antagonist had a significant protective effect, ameliorating both haemodynamic parameters, lung and cardiac function, tissue remodelling, and the inflammation associated with PAH. The results of this study suggest that the inhibition IL-6 could be a useful pharmacological strategy in PAH, in both human and veterinary medicine.

Emerging biologics for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disorder, wherein mean systemic arterial pressure (mPAP) becomes abnormally high because of aberrant changes in various proliferative and inflammatory signalling pathways of pulmonary arterial cells. Currently used anti-PAH drugs chiefly target the vasodilatory and vasoconstrictive pathways. However, an imbalance between bone morphogenetic protein receptor type II (BMPRII) and transforming growth factor beta (TGF-β) pathways is also implicated in PAH predisposition and pathogenesis. Compared to currently used PAH drugs, various biologics have shown promise as PAH therapeutics that elicit their therapeutic actions akin to endogenous proteins. Biologics that have thus far been explored as PAH therapeutics include monoclonal antibodies, recombinant proteins, engineered cells, and nucleic acids. Because of their similarity with naturally occurring proteins and high binding affinity, biologics are more potent and effective and produce fewer side effects when compared with small molecule drugs. However, biologics also suffer from the limitations of producing immunogenic adverse effects. This review describes various emerging and promising biologics targeting the proliferative/apoptotic and vasodilatory pathways involved in PAH pathogenesis. Here, we have discussed sotatercept, a TGF-β ligand trap, which is reported to reverse vascular remodelling and reduce PVR with an improved 6-minute walk distance (6-MWDT). We also elaborated on other biologics including BMP9 ligand and anti-gremlin1 antibody, anti-OPG antibody, and getagozumab monoclonal antibody and cell-based therapies. Overall, recent literature suggests that biologics hold excellent promise as a safe and effective alternative to currently used PAH therapeutics.

Pulmonary artery smooth muscle cell phenotypic switching: A key event in the early stage of pulmonary artery hypertension

Pulmonary arterial hypertension (PAH) is a currently incurable pulmonary vascular disease. Since current research on PAH is mainly aimed at the middle and late stages of disease progression, no satisfactory results have been achieved. This has led researchers to focus on the early stages of PAH. This review highlights for the first time a key event in the early stages of PAH progression, namely, the occurrence of pulmonary arterial smooth muscle cell (PASMC) phenotypic switching. Summarizing the related reports of performance conversion provides new perspectives and directions for the early pathological progression and treatment strategies for PAH.

Celastrol: The new dawn in the treatment of vascular remodeling diseases

Evidence is mounting that abnormal vascular remodeling leads to many cardiovascular diseases (CVDs). This suggests that vascular remodeling can be a crucial target for the prevention and treatment of CVDs. Recently, celastrol, an active ingredient of the broadly used Chinese herb Tripterygium wilfordii Hook F, has attracted extensive interest for its proven potential to improve vascular remodeling. Substantial evidence has shown that celastrol improves vascular remodeling by ameliorating inflammation, hyperproliferation, and migration of vascular smooth muscle cells, vascular calcification, endothelial dysfunction, extracellular matrix remodeling, and angiogenesis. Moreover, numerous reports have proven the positive effects of celastrol and its therapeutic promise in treating vascular remodeling diseases such as hypertension, atherosclerosis, and pulmonary artery hypertension. The present review summarizes and discusses the molecular mechanism of celastrol regulating vascular remodeling and provides preclinical proof for future clinical applications of celastrol.

Predicting the response to pulmonary vasodilator therapy in systemic sclerosis with pulmonary hypertension by using quantitative chest CT

OBJECTIVE

Systemic sclerosis (SSc) is associated with pulmonary vascular disease (PVD) and interstitial lung disease (ILD), making it difficult to differentiate pulmonary arterial hypertension and pulmonary hypertension (PH) due to lung diseases and/or hypoxia and to decide treatments. We aimed to predict the response to pulmonary vasodilators in patients with SSc and PH.

METHODS

84 SSc patients were included with 47 having PH. Chest CT was evaluated using a software to calculate abnormal lung volume (ALV). To define the response to vasodilators, Δ mean pulmonary artery pressure (mPAP)/basal mPAP was used (cut-off value: 10%). The predictive value was evaluated by using receiver operating characteristic curve.

RESULTS

The mean (±SD) value of ALV was 26.8 (±32.2) %. A weak correlation was observed between ALV and forced vital capacity (FVC) (R = -0.46). The predictive value of ALV (area under curve; AUC = 0.74) was superior to that of FVC (AUC = 0.62) for the response to vasodilators. No hemodynamic parameters differed between patients with high and low ALV, whereas survival was worse in high ALV.

CONCLUSION

Quantitative chest CT well predicted the response to vasodilators in patients with SSc and PH. Our results suggest its utility in differentiating the dominance of PVD or ILD.

An Overview of Circulating Pulmonary Arterial Hypertension Biomarkers

Pulmonary arterial hypertension (PAH), also known as Group 1 Pulmonary Hypertension (PH), is a PH subset characterized by pulmonary vascular remodeling and pulmonary arterial obstruction. PAH has an estimated incidence of 15-50 people per million in the United States and Europe, and is associated with high mortality and morbidity, with patients' survival time after diagnosis being only 2.8 years. According to current guidelines, right heart catheterization is the gold standard for diagnostic and prognostic evaluation of PAH patients. However, this technique is highly invasive, so it is not used in routine clinical practice or patient follow-up. Thereby, it is essential to find new non-invasive strategies for evaluating disease progression. Biomarkers can be an effective solution for determining PAH patient prognosis and response to therapy, and aiding in diagnostic efforts, so long as their detection is non-invasive, easy, and objective. This review aims to clarify and describe some of the potential new candidates as circulating biomarkers of PAH.

COVID-19 and the role of cytokines in this disease

Studies have shown that SARS-CoV-2 has the ability to activate and mature proinflammatory cytokines in the body. Cytokine markers are a group of polypeptide signalling molecules that can induce and regulate many cellular biological processes by stimulating cell receptors at the surface. SARS-CoV-2 has been shown to be associated with activation of innate immunity, and an increase in neutrophils, mononuclear phagocytes, and natural killer cells has been observed, as well as a decrease in T cells including CD4+ and CD8. It is noteworthy that during the SARS-CoV-2 infection, an increase in the secretion or production of IL-6 and IL-8 is seen in COVID-19 patients along with a decrease in CD4+ and CD8+ and T cells in general. SARS-CoV-2 has been shown to significantly increase Th2, Th1/Th17 cells and antibody production in the body of patients with COVID-19. Specific immune profiles of SARS-CoV-2 infection can lead to secondary infections and dysfunction of various organs in the body. It has been shown that Interleukins (such as IL-1, IL-4, IL-6, IL-7, IL-10, IL-12, IL-17, and IL-18), IFN-γ, TNF-α,TGF-β and NF-κB play major roles in the body's inflammatory response to SARS-CoV-2 infection. The most important goal of this review is to study the role of inflammatory cytokines in COVID-19.

Text Mining-Based Drug Discovery for Connective Tissue Disease–Associated Pulmonary Arterial Hypertension

Background: The current medical treatments for connective tissue disease–associated pulmonary arterial hypertension (CTD-PAH) do not show favorable efficiency for all patients, and identification of novel drugs is desired.

Methods: Text mining was performed to obtain CTD- and PAH-related gene sets, and the intersection of the two gene sets was analyzed for functional enrichment through DAVID. The protein–protein interaction network of the overlapping genes and the significant gene modules were determined using STRING. The enriched candidate genes were further analyzed by Drug Gene Interaction database to identify drugs with potential therapeutic effects on CTD-PAH.

Results: Based on text mining analysis, 179 genes related to CTD and PAH were identified. Through enrichment analysis of the genes, 20 genes representing six pathways were obtained. To further narrow the scope of potential existing drugs, we selected targeted drugs with a Query Score ≥5 and Interaction Score ≥1. Finally, 13 drugs targeting the six genes were selected as candidate drugs, which were divided into four drug–gene interaction types, and 12 of them had initial drug indications approved by the FDA. The potential gene targets of the drugs on this list are IL-6 (one drug) and IL-1β (two drugs), MMP9 (one drug), VEGFA (three drugs), TGFB1 (one drug), and EGFR (five drugs). These drugs might be used to treat CTD-PAH.

Conclusion: We identified 13 drugs targeting six genes that may have potential therapeutic effects on CTD-PAH.

Signal Transduction during Metabolic and Inflammatory Reprogramming in Pulmonary Vascular Remodeling

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by (mal)adaptive remodeling of the pulmonary vasculature, which is associated with inflammation, fibrosis, thrombosis, and neovascularization. Vascular remodeling in PAH is associated with cellular metabolic and inflammatory reprogramming that induce profound endothelial and smooth muscle cell phenotypic changes. Multiple signaling pathways and regulatory loops act on metabolic and inflammatory mediators which influence cellular behavior and trigger pulmonary vascular remodeling in vivo. This review discusses the role of bioenergetic and inflammatory impairments in PAH development.

The roles of immune system and autoimmunity in pulmonary arterial hypertension: A Review

Pulmonary arterial hypertension (PAH) is a chronic disease characterized by increased pulmonary artery pressure which if left untreated, can lead to poor quality of life and ultimately death. It is a group of conditions and includes idiopathic PAH, familial/hereditary PAH and associated PAH. The condition has been studied for many years and its association with the immune system and in particular autoimmunity has been investigated. The mechanisms for the pathobiology of PAH are unclear although research has highlighted the role of adaptive and innate immune systems in its development. Diagnostics and therapeutic approaches range from cytokine treatments to the use of immunomodulating drugs, although there is still scope for improvements in the field. This article discusses the mechanisms linked to PAH, its association with other conditions and recent therapeutic interventions.

Interleukin-6 Perpetrator of the COVID-19 Cytokine Storm

COVID-19 has emerged as a global pandemic. It is mainly manifested as pneumonia which may deteriorate into severe respiratory failure. The major hallmark of the disease is the systemic inflammatory immune response characterized by Cytokine Storm (CS). CS is marked by elevated levels of inflammatory cytokines, mainly interleukin-6 (IL-6), IL-8, IL-10, tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Of these, IL-6 is found to be significantly associated with higher mortality. IL-6 is also a robust marker for predicting disease prognosis and deterioration of clinical profile. In this review, the pivotal role played by IL-6 in the immuno-pathology of COVID-19 has been illustrated. The role of IL-6 as a pleiotropic cytokine executing both pro and anti-inflammatory activities has been reviewed. ADAM 10, a metalloproteinase switches the anti-inflammatory pathway of IL-6 to pro inflammatory hence blocking the action of ADAM 10 could be a new therapeutic strategy to mitigate the proinflammatory action of IL-6. Furthermore, we explore the role of anti-IL6 agents, IL-6 receptor antibodies which were being used for autoimmune diseases but now are being repurposed for the therapy of COVID-19.

Mendelian randomisation and experimental medicine approaches to IL-6 as a drug target in PAH

Background

Inflammation and dysregulated immunity are important in the development of pulmonary arterial hypertension (PAH). Compelling preclinical data supports the therapeutic blockade of interleukin-6 (IL-6) signalling.

Methods

We conducted a phase 2 open-label study of intravenous tocilizumab (8 mg·kg⁻¹) over 6 months in patients with group 1 PAH. Co-primary end-points were safety, defined by incidence and severity of adverse events, and change in pulmonary vascular resistance. Separately, a mendelian randomisation study was undertaken on 11 744 individuals with European ancestry including 2085 patients with idiopathic/heritable disease for the IL-6 receptor (IL6R) variant (rs7529229), known to associate with circulating IL-6R levels.

Results

We recruited 29 patients (male/female 10/19; mean±sd age 54.9±11.4 years). Of these, 19 had heritable/idiopathic PAH and 10 had connective tissue disease-associated PAH. Six were withdrawn prior to drug administration; 23 patients received at least one dose of tocilizumab. Tocilizumab was discontinued in four patients owing to serious adverse events. There were no deaths. Despite evidence of target engagement in plasma IL-6 and C-reactive protein levels, both intention-to-treat and modified intention-to-treat analyses demonstrated no change in pulmonary vascular resistance. Inflammatory markers did not predict treatment response. Mendelian randomisation did not support an effect of the lead IL6R variant on risk of PAH (OR 0.99, p=0.88).

Conclusion

Adverse events were consistent with the known safety profile of tocilizumab. Tocilizumab did not show any consistent treatment effect.

Tocilizumab did not block IL-6 signalling in pulmonary arterial hypertension. Multicentre mendelian randomisation studies additionally did not demonstrate evidence for IL-6R in pulmonary arterial hypertension.https://bit.ly/3xkDxS5

Role of the Immune System Elements in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a relatively rare disease, but, today, its incidence tends to increase. The severe course of the disease and poor patient survival rate make PAH a major diagnostic and therapeutic challenge. For this reason, a thorough understanding of the pathogenesis of the disease is essential to facilitate the development of more effective therapeutic targets. Research shows that the development of PAH is characterized by a number of abnormalities within the immune system that greatly affect the progression of the disease. In this review, we present key data on the regulated function of immune cells, released cytokines and immunoregulatory molecules in the development of PAH, to help improve diagnosis and targeted immunotherapy.

Cytokines, Chemokines, and Inflammation in Pulmonary Arterial Hypertension

According to the World Symposium Pulmonary Hypertension (WSPH) classification, pulmonary hypertension (PH) is classified into five categories based on etiology. Among them, Group 1 pulmonary arterial hypertension (PAH) disorders are rare but progressive and often, fatal despite multiple approved treatments. Elevated pulmonary arterial pressure in patients with WSPH Group 1 PAH is mainly caused by increased pulmonary vascular resistance (PVR), due primarily to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Growing evidence indicates that inflammation plays a critical role in the development of pulmonary vascular remodeling associated with PAH. While the role of auto-immunity is unclear, infiltration of inflammatory cells in and around vascular lesions, including T- and B-cells, dendritic cells, macrophages, and mast cells have been observed in PAH patients. Serum and plasma levels of chemokines, cytokines, and autoantibodies are also increased in PAH patients; some of these circulating molecules are correlated with disease severity and survival. Preclinical experiments have reported a key role of the inflammation in PAH pathophysiology in vivo. Importantly, anti-inflammatory and immunosuppressive agents have further exhibited therapeutic effects. The present chapter reviews published experimental and clinical evidence highlighting the canonical role of inflammation in the pathogenesis of PAH and as a major target for the development of anti-inflammatory therapies in patients with PAH.

Effect of EZH2 on pulmonary artery smooth muscle cell migration in pulmonary hypertension

Pulmonary hypertension (PH) is a life‑threatening disease that often involves vascular remodeling. Although pulmonary arterial smooth muscle cells (PASMCs) are the primary participants in vascular remodeling, their biological role is not entirely clear. The present study analyzed the role of enhancer of zeste homolog 2 (EZH2) in vascular remodeling of PH by investigating the behavior of PASMCs. The expression levels of EZH2 in PASMCs in chronic thromboembolic pulmonary hypertension (CTEPH), a type of PH, were detected. The role of EZH2 in PASMC migration was investigated by wound‑healing assay following overexpression and knockdown. Functional enrichment analysis of the whole‑genome expression profiles of PASMCs with EZH2 overexpression was performed using an mRNA Human Gene Expression Microarray. Quantitative (q)PCR was performed to confirm the results of the microarray. EZH2 expression levels increased in CTEPH cell models. The overexpression of EZH2 enhanced PASMC migration compared with control conditions. Functional enrichment analysis of the differentially expressed genes following EZH2 overexpression indicated a strong link between EZH2 and the immune inflammatory response and oxidoreductase activity in PASMCs. mRNA expression levels of superoxide dismutase 3 were verified by qPCR. The results suggested that EZH2 was involved in the migration of PASMCs in PH, and may serve as a potential target for the treatment of PH.

Pathological Mechanisms and Potential Therapeutic Targets of Pulmonary Arterial Hypertension: A Review

Pulmonary arterial hypertension (PAH) is a progressive cardiovascular disease characterized by pulmonary vasculature reconstruction and right ventricular dysfunction. The mortality rate of PAH remains high, although multiple therapeutic strategies have been implemented in clinical practice. These drugs mainly target the endothelin-1, prostacyclin and nitric oxide pathways. Management for PAH treatment includes improving symptoms, enhancing quality of life, and extending survival rate. Existing drugs developed to treat the disease have resulted in enormous economic and healthcare liabilities. The estimated cost for advanced PAH has exceeded $200,000 per year. The pathogenesis of PAH is associated with numerous molecular processes. It mainly includes germline mutation, inflammation, dysfunction of pulmonary arterial endothelial cells, epigenetic modifications, DNA damage, metabolic dysfunction, sex hormone imbalance, and oxidative stress, among others. Findings based on the pathobiology of PAH may have promising therapeutic outcomes. Hence, faced with the challenges of increasing healthcare demands, in this review, we attempted to explore the pathological mechanisms and alternative therapeutic targets, including other auxiliary devices or interventional therapies, in PAH. The article will discuss the potential therapies of PAH in detail, which may require further investigation before implementation.

LRADO, Cunha EHM, Maioli TU, Vieira AT, Speziali E, Corrêa-Oliveira R, Martins-Filho OA, Teixeira-Carvalho A, Franceschi C, Rampelli S, Turroni S, Brigidi P, Faria AMC. Hypertension Is Associated With Intestinal Microbiota Dysbiosis and Inflammation in a Brazilian Population

Hypertension is a major global health challenge, as it represents the main risk factor for stroke and cardiovascular disease. It is a multifactorial clinical condition characterized by high and sustained levels of blood pressure, likely resulting from a complex interplay of endogenous and environmental factors. The gut microbiota has been strongly supposed to be involved but its role in hypertension is still poorly understood. In an attempt to fill this gap, here we characterized the microbial composition of fecal samples from 48 hypertensive and 32 normotensive Brazilian individuals by next-generation sequencing of the 16S rRNA gene. In addition, the cytokine production of peripheral blood samples was investigated to build an immunological profile of these individuals. We identified a dysbiosis of the intestinal microbiota in hypertensive subjects, featured by reduced biodiversity and distinct bacterial signatures compared with the normotensive counterpart. Along with a reduction in Bacteroidetes members, hypertensive individuals were indeed mainly characterized by increased proportions of Lactobacillus and Akkermansia while decreased relative abundances of well-known butyrate-producing commensals, including Roseburia and Faecalibacterium within the Lachnospiraceae and Ruminococcaceae families. We also observed an inflamed immune profile in hypertensive individuals with an increase in TNF/IFN-γ ratio, and in TNF and IL-6 production when compared to normotensive ones. Our work provides the first evidence of association of hypertension with altered gut microbiota and inflammation in a Brazilian population. While lending support to the existence of potential microbial signatures of hypertension, likely to be robust to age and geography, our findings point to largely neglected bacteria as potential contributors to intestinal homeostasis loss and emphasize the high vulnerability of hypertensive individuals to inflammation-related disorders.

Successful Treatment of Pulmonary Arterial Hypertension in Systemic Sclerosis with Anticentriole Antibody

Systemic sclerosis (SSc) is characterized by skin sclerosis and multiple organ damages which may cause mortality and is usually accompanied with several specific autoantibodies, each of which is associated with characteristic complications. Among them, anticentriole antibody is recently reported to be highly associated with SSc-associated pulmonary arterial hypertension (SSc-PAH). In general, several vasodilators are used as therapeutic drugs for SSc-PAH, whereas immunosuppressive therapies are not. Here, we report the case of a 62-year-old female with anticentriole antibody-positive SSc-PAH treated with immunosuppressants and vasodilators. She presented with two-year exertional dyspnea and was diagnosed with PAH and SSc owing to the centriole staining pattern and other symptoms without digital sclerosis. Oral vasodilators were initially administered but were not sufficiently effective on dyspnea. Immunosuppressants such as prednisolone and cyclophosphamide were started. Both of them improved mean pulmonary arterial pressure and 6-minute walk distance, and the anticentriole antibody also disappeared. In this case, SSc-PAH with anticentriole antibody was properly diagnosed and immunosuppressants and vasodilators improved the hemodynamics of PAH with anticentriole antibody and stably maintained it and, in addition, reduced the titer of anticentriole antibody. This indicates that anticentriole antibody might represent a good responsive group to therapies among subgroups of patients with SSc-PAH.

Kinases as potential targets for treatment of pulmonary hypertension and right ventricular dysfunction

Pulmonary hypertension (PH) is a progressive pulmonary vasculopathy that causes chronic right ventricular pressure overload and often leads to right ventricular failure. Various kinase inhibitors have been studied in the setting of PH and either improved or worsened the disease, highlighting the importance of understanding the specific role of the respective kinases in a spatiotemporal cellular context. In this review, we will summarize the knowledge on the role of kinases in PH and focus on druggable targets for which certain criteria are met: (a) deregulation of the kinase in PH; (b) small-molecule inhibitors are available (e.g. from the oncology field); (c) preclinical studies have shown their efficacy in PH models; and (d) when available, therapeutic exploitation in human PH has been initiated. Along this line, clinical considerations such as personalized medicine approaches to predict therapy response and adverse side events such as cardiotoxicity together with their clinical management are discussed. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Inflammatory Basis of Pulmonary Arterial Hypertension: Implications for Perioperative and Critical Care Medicine

Patients with pulmonary arterial hypertension have exceptionally high perioperative risk. This review summarizes the clinical presentation and therapies for pulmonary arterial hypertension, and it highlights evidence for inflammation as a driver of disease pathogenesis and a therapeutic target.

Focus on Early Events: Pathogenesis of Pulmonary Arterial Hypertension Development

Significance: Pulmonary arterial hypertension (PAH) is a progressive disease of the lung vasculature characterized by the proliferation of all vascular wall cell types, including endothelial, smooth muscle, and fibroblasts. The disease rapidly advances into a form with extensive pulmonary vascular remodeling, leading to a rapid increase in pulmonary vascular resistance, which results in right heart failure. Recent Advances: Most current research in the PAH field has been focused on the late stage of the disease, largely due to an urgent need for patient treatment options in clinics. Further, the pathobiology of PAH is multifaceted in the advanced disease, and there has been promising recent progress in identifying various pathological pathways related to the late clinical picture. Critical Issues: Early stage PAH still requires additional attention from the scientific community, and although the survival of patients with early diagnosis is comparatively higher, the disease develops in patients asymptomatically, making it difficult to identify and treat early. Future Directions: There are several reasons to focus on the early stage of PAH. First, the complexity of late stage disease, owing to multiple pathways being activated in a complex system with intra- and intercellular signaling, leads to an unclear picture of the key contributors to the pathobiology. Second, an understanding of early pathophysiological events can increase the ability to identify PAH patients earlier than what is currently possible. Third, the prompt diagnosis of PAH would allow for the therapy to start earlier, which has proved to be a more successful strategy, and it ensures better survival in PAH patients.

Predictive Value of Novel Inflammation-Based Biomarkers for Pulmonary Hypertension in the Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Recently, there has been an increasing interest in the potential clinical use of several inflammatory indexes, namely, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic-immune-inflammation index (SII). This study aimed at assessing whether these markers could be early indicators of pulmonary hypertension (PH) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). A total of 185 patients were enrolled in our retrospective study from January 2017 to January 2019. Receiver operating characteristic curve (ROC) and area under the curve (AUC) were used to evaluate the clinical significance of these biomarkers to predict PH in patients with AECOPD. According to the diagnostic criterion for PH by Doppler echocardiography, the patients were stratified into two groups. The study group consisted of 101 patients complicated with PH, and the control group had 84 patients. The NLR, PLR, and SII values of the PH group were significantly higher than those of the AECOPD one (p < 0.05). The blood biomarker levels were positively correlated with NT-proBNP levels, while they had no significant correlation with the estimated pulmonary arterial systolic pressure (PASP) other than PLR. NLR, PLR, and SII values were all associated with PH (p < 0.05) in the univariate analysis, but not in the multivariate analysis. The AUC of NLR used for predicting PH was 0.701 and was higher than PLR and SII. Using 4.659 as the cut-off value of NLR, the sensitivity was 81.2%, and the specificity was 59.5%. In conclusion, these simple markers may be useful in the prediction of PH in patients with AECOPD.

Interleukin-6 Receptor Signaling and Abdominal Aortic Aneurysm Growth Rates

BACKGROUND

The Asp358Ala variant (rs2228145; A>C) in the IL (interleukin)-6 receptor ( IL6R) gene has been implicated in the development of abdominal aortic aneurysms (AAAs), but its effect on AAA growth over time is not known. We aimed to investigate the clinical association between the IL6R-Asp358Ala variant and AAA growth and to assess the effect of blocking the IL-6 signaling pathway in mouse models of aortic aneurysm rupture or dissection.

METHODS

Using data from 2863 participants with AAA from 9 prospective cohorts, age- and sex-adjusted mixed-effects linear regression models were used to estimate the association between the IL6R-Asp358Ala variant and annual change in AAA diameter (mm/y). In a series of complementary randomized trials in mice, the effect of blocking the IL-6 signaling pathways was assessed on plasma biomarkers, systolic blood pressure, aneurysm diameter, and time to aortic rupture and death.

RESULTS

After adjusting for age and sex, baseline aneurysm size was 0.55 mm (95% CI, 0.13-0.98 mm) smaller per copy of the minor allele [C] of the Asp358Ala variant. Change in AAA growth was -0.06 mm per year (-0.18 to 0.06) per copy of the minor allele; a result that was not statistically significant. Although all available worldwide data were used, the genetic analyses were not powered for an effect size as small as that observed. In 2 mouse models of AAA, selective blockage of the IL-6 trans-signaling pathway, but not combined blockage of both, the classical and trans-signaling pathways, was associated with improved survival ( P<0.05).

CONCLUSIONS

Our proof-of-principle data are compatible with the concept that IL-6 trans-signaling is relevant to AAA growth, encouraging larger-scale evaluation of this hypothesis.

Ectopic upregulation of membrane-bound IL6R drives vascular remodeling in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by a progressive accumulation of pulmonary artery smooth muscle cells (PA-SMCs) in pulmonary arterioles leading to the narrowing of the lumen, right heart failure, and death. Although most studies have supported the notion of a role for IL-6/glycoprotein 130 (gp130) signaling in PAH, it remains unclear how this signaling pathway determines the progression of the disease. Here, we identify ectopic upregulation of membrane-bound IL-6 receptor (IL6R) on PA-SMCs in PAH patients and in rodent models of pulmonary hypertension (PH) and demonstrate its key role for PA-SMC accumulation in vitro and in vivo. Using Sm22a-Cre Il6rfl/fl, which lack Il6r in SM22A-expressing cells, we found that these animals are protected against chronic hypoxia-induced PH with reduced PA-SMC accumulation, revealing the potent pro-survival potential of membrane-bound IL6R. Moreover, we determine that treatment with IL6R-specific antagonist reverses experimental PH in two rat models. This therapeutic strategy holds promise for future clinical studies in PAH.

Classical IL-6 signaling: a promising therapeutic target for pulmonary arterial hypertension

Current therapies for pulmonary arterial hypertension (PAH) provide symptomatic relief and improve prognosis but fall short of improving long-term survival. There is emerging evidence for a role of inflammatory mediators, primarily IL-6, in the pathogenesis of PAH. However, the mechanisms by which IL-6 potentially affects PAH are unknown. In this issue of the JCI, Tamura, Phan, and colleagues identified ectopic upregulation of the membrane-bound IL-6 receptor (IL6R), indicating classical IL-6 signaling in the smooth muscle layer of remodeled vessels in human and experimental PAH. They performed a series of in vitro and in vivo experiments that provide deeper insights into the mechanisms of classical IL-6 signaling and propose interventions directed against IL6R as a potential therapeutic strategy for PAH.

Pulmonary arterial hypertension associated with connective tissue diseases: A review focusing on distinctive clinical aspects

Recent studies have clarified that pulmonary arterial hypertension associated with connective tissue diseases (CTD-PAH) has some distinctive clinical aspects from other PAH, such as high prevalence, venous and cardiac involvement, less favourable outcome, helpfulness of detection algorithm, response to immunosuppression, pre-PAH conditions in borderline pulmonary arterial pressure and coexistence of interstitial lung disease. In this review, by focusing on these distinctive aspects, we discuss how to provide an efficacious and safe management of CTD-PAH and garner attention to areas where further evidence is desired.

Clinical trial protocol for TRANSFORM-UK: A therapeutic open-label study of tocilizumab in the treatment of pulmonary arterial hypertension

Our aim is to assess the safety and potential efficacy of a novel treatment paradigm in pulmonary arterial hypertension (PAH), immunomodulation by blocking interleukin-6 (IL6) signaling with the IL6 receptor antagonist, tocilizumab. Inflammation and autoimmunity are established as important in PAH pathophysiology. One of the most robust observations across multiple cohorts in PAH has been an increase in IL6, both in the lung and systemically. Tocilizumab is an IL-6 receptor antagonist established as safe and effective, primarily in rheumatoid arthritis, and has shown promise in scleroderma. In case reports where the underlying cause of PAH is an inflammatory process such as systemic lupus erythematosus, mixed connective tissue disease (MCTD), and Castleman's disease, there have been case reports of regression of PAH with tocilizumab. TRANSFORM-UK is an open-label study of intravenous (IV) tocilizumab in patients with group 1 PAH. The co-primary outcome measures will be safety and the change in resting pulmonary vascular resistance (PVR). Clinically relevant secondary outcome measurements include 6-minute walk distance, WHO functional class, quality of life score, and N-terminal pro-brain natriuretic peptide (NT-proBNP). If the data support a potentially useful therapeutic effect with an acceptable risk profile, the study will be used to power a Phase III study to properly address efficacy.

Association of Anemic Hypoxia and Increased Pulmonary Artery Systolic Pressure in Patients With Systemic Lupus Erythematosus

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a rare but serious complication of systemic lupus erythematosus (SLE). Chronic hypoxia is known to cause PAH resulting from pulmonary vascular remodeling. We investigated the association between anemic hypoxia and PAH in SLE patients.

METHODS

Systolic pulmonary artery pressure (PAP) was measured in 132 SLE patients by echocardiography. Increased PAP was defined as resting PAP > 40 mm Hg. Oxygen delivery (DO2) was estimated as the product of cardiac output and arterial oxygen content.

RESULTS

Of 132 patients, 17 (12.9%) had increased PAP, and these patients had significantly lower DO2 values than patients with normal PAP (P = 0.002). The DO2 values inversely correlated with PAP values (γ = -0.308, P < 0.001) and plasma N-terminal pro-brain natriuretic peptide levels (γ = -0.323, P = 0.001), but positively correlated with hemoglobin levels (γ = 0.402, P < 0.001). Compared to those with normal PAP, patients with increased PAP had significantly longer durations of anemia over the preceding 6-24 months. Patients with anemia of longer durations (≥3 months) in the preceding 6 months had a higher risk of increased PAP compared to those with shorter durations (P < 0.001). When SLE patients were divided into 3 groups according to hemoglobin and PAP, serum interleukin-6 (IL-6) levels increased across groups with higher PAP (P = 0.001 for trend), but decreased across tertiles of hemoglobin levels (P = 0.008 for trend).

CONCLUSION

Our data indicate an association between chronic anemic hypoxia and increased PAP in SLE patients and suggest that increased IL-6 might participate in this process.

Bone morphogenetic protein receptor type II deficiency and increased inflammatory cytokine production. A gateway to pulmonary arterial hypertension

RATIONALE

Mutations in bone morphogenetic protein receptor type II (BMPR-II) underlie most cases of heritable pulmonary arterial hypertension (PAH). However, disease penetrance is only 20-30%, suggesting a requirement for additional triggers. Inflammation is emerging as a key disease-related factor in PAH, but to date there is no clear mechanism linking BMPR-II deficiency and inflammation.

OBJECTIVES

To establish a direct link between BMPR-II deficiency, a consequentially heightened inflammatory response, and development of PAH.

METHODS

We used pulmonary artery smooth muscle cells from Bmpr2(+/-) mice and patients with BMPR2 mutations and compared them with wild-type controls. For the in vivo model, we used mice heterozygous for a null allele in Bmpr2 (Bmpr2(+/-)) and wild-type littermates.

MEASUREMENTS AND MAIN RESULTS

Acute exposure to LPS increased lung and circulating IL-6 and KC (IL-8 analog) levels in Bmpr2(+/-) mice to a greater extent than in wild-type controls. Similarly, pulmonary artery smooth muscle cells from Bmpr2(+/-) mice and patients with BMPR2 mutations produced higher levels of IL-6 and KC/IL-8 after lipopolysaccharide stimulation compared with controls. BMPR-II deficiency in mouse and human pulmonary artery smooth muscle cells was associated with increased phospho-STAT3 and loss of extracellular superoxide dismutase. Chronic lipopolysaccharide administration caused pulmonary hypertension in Bmpr2(+/-) mice but not in wild-type littermates. Coadministration of tempol, a superoxide dismutase mimetic, ameliorated the exaggerated inflammatory response and prevented development of PAH.

CONCLUSIONS

This study demonstrates that BMPR-II deficiency promotes an exaggerated inflammatory response in vitro and in vivo, which can instigate development of pulmonary hypertension.

Enhanced IL-6 trans-signaling in pulmonary arterial hypertension and its potential role in disease-related systemic damage

BACKGROUND

The role of IL-6 in pulmonary arterial hypertension (PAH) has been reported but the prevalence of soluble receptors for IL-6: sIL-6R and sgp130 and its potential role in PAH have not been studied.Our aim was to examine the IL-6 together with the soluble receptors and to assess its relationship with clinical status of PAH patients as well as to assess its potential prognostic significance.

METHODS

Serum concentrations of IL-6, sIL-6R and sgp130 were quantified by ELISA in 26 patients with PAH and 27 healthy controls and related to functional and biochemical parameters and clinical outcome in PAH group. The PAH patients were followed up for 1 year, noting the end point of clinical deterioration (WHO class change, the need for escalation of therapy) or death.

RESULTS

The PAH group was characterized by higher median serum IL-6 [2.38 (IQR 1.56-3.75) vs 0.87 (0.63-1.3) pg/ml, p=0.000003] and sIL-6R concentrations [69.7 (IQR 60.4-84.4 vs 45.7 (34.6-70.3) ng/ml, p=0.0036] compared to control subjects. Both groups did not differ in sgp130 concentrations. There were significant correlations in PAH group between IL-6 levels and uric acid, parameters of ventilatory efficiency in cardiopulmonary exercise testing: VE/VO2, VE/VCO2, VE/VCO2 slope and peak PetCO2. sIL-6R levels inversely correlated with LDL cholesterol. After 1 year the clinical deterioration occurred in 11 patients, 15 remained stable. Patients in whom the clinical deterioration occurred showed significantly higher baseline concentrations of IL-6 [3.25 (IQR 2.46-5.4) pg/ml vs 1.68 (1.38-2.78) pg/ml, p=0.004], but not sIL-6R. Median IL-6 ⩾ 2.3 pg/ml (91% sensitivity, 73% specificity) identified subjects with worse clinical course. In the univariate analysis, higher IL-6 level at baseline was associated with increased risk and earlier occurrence of clinical deterioration (HR 1.42, 95%CI 1.08-1.85, p=0.015).

CONCLUSIONS

IL-6 trans-signaling is enhanced in PAH. Elevated concentration of sIL-6R suggests its potential unfavorable role in systemic amplification of IL-6 signaling in PAH. Levels of IL-6 are associated with clinical indicators of disease severity as well as indirectly with systemic metabolic alterations. IL-6 shows prognostic value regarding predicting clinical deterioration.

Inflammation and hypertension: new understandings and potential therapeutic targets

Research studying the role of inflammation in hypertension and cardiovascular disease has flourished in recent years; however, the exact mechanisms by which the activated immune cells lead to the development and maintenance of hypertension remain to be elucidated. The objectives of this brief review are to summarize and discuss the most recent findings in the field, with special emphasis on potential therapeutics to treat or prevent hypertension. This review will cover novel immune cell subtypes recently associated to the disease including the novel role of cytokines, toll-like receptors, and inflammasomes in hypertension.

Existing drugs and agents under investigation for pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive and debilitating disorder with an associated high morbidity and mortality rate. Significant advances in our understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary hypertension have occurred over the past several decades. This has allowed the development of new therapeutic options in this disease. Today, our selection of therapeutic modalities is broader, including calcium channel blockers, prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, and soluble guanylate cyclase stimulators, but the disease remains fatal. This underscores the need for a continued search for novel therapies. Several potential pharmacologic agents for the treatment of pulmonary arterial hypertension are under clinical development and some promising results with these treatments have been reported. These agents include rho-kinase inhibitors, long-acting nonprostanoid prostacyclin receptor agonists, tyrosine protein kinase inhibitors, endothelial nitric oxide synthase couplers, synthetically produced vasoactive intestinal peptide, antagonists of the 5-HT2 receptors, and others. This article will review several of these promising new therapies and will discuss the current evidence regarding their potential benefit in pulmonary arterial hypertension.

The role of the osteoprotegerin/tumor necrosis factor related apoptosis-inducing ligand axis in the pathogenesis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a fatal condition driven by a progressive remodelling of the small pulmonary arteries through sustained vasoconstriction, and vascular cell proliferation. This process causes a substantial reduction in luminal area increasing pulmonary vascular resistance and blood pressure leading to right heart failure. Current medical therapies can alleviate some symptoms and reduce the vasoconstrictive aspects of disease but new treatments are required that target the vascular cell proliferation if we are to develop new therapies. Expression of the tumour necrosis factor related apoptosis-inducing ligand (TRAIL) and osteoprotegerin (OPG) proteins are increased in IPAH. Specifically OPG is increased within the serum of patients with idiopathic pulmonary arterial hypertension (IPAH) and has prognostic utility, and both OPG and TRAIL are increased within pulmonary vascular lesions of patients with IPAH, and are mitogens for pulmonary artery smooth muscle cells in vitro. We have demonstrated that genetic deletion, or antibody blockade of TRAIL prevents, and critically reverses the development of PAH in multiple rodent models. The role OPG plays in this process both through interacting with TRAIL, and indirectly through other mechanisms is currently unclear these but data highlight the critical importance of this pathway in PAH pathogenesis, and its potential for future therapies.

A novel ACE2 activator reduces monocrotaline-induced pulmonary hypertension by suppressing the JAK/STAT and TGF-β cascades with restored caveolin-1 expression

INTRODUCTION

Pulmonary hypertension (PH) is characterized by increased pressure in the pulmonary artery and right ventricular hypertrophy (RVH). Recently, angiotensin-converting enzyme 2 (ACE2), which converts angiotensin (Ang) II into Ang-(1-7), was shown to inhibit experimental PH. Here we identified a novel ACE2 activator and investigated how the compound reduced monocrotaline (MCT)-induced PH.

METHODS

To induce PH, Sprague-Dawley rats were injected subcutaneously with MCT, followed by the continuous administration of NCP-2454, an ACE2 activator, using osmotic pumps. Pulmonary arterial compliance was monitored every week until 4 weeks post-injection (wpi). RVH and lung remodeling was evaluated using lung tissue at 4 wpi.

RESULTS

NCP-2454 upregulated the production of Ang-(1-7) when incubated with ACE2 and Ang II. Notably, a continuous infusion of NCP-2454 significantly improved pulmonary arterial compliance, right ventricular systolic pressure, and RVH in MCT-treated rats. Interestingly, NCP-2454 increased the relative expression of ACE2 and MAS mRNA in lung tissue, especially in MCT-treated rats. In addition, the compound inhibited the MCT-induced overexpression of transforming growth factor β, phosphorylation of signal transducer and activator of transcription-3 (STAT3), and interleukin-6 production. The compound also restored the expression of caveolin-1 (Cav-1), which negatively regulates the Janus kinase-STAT signaling cascade.

CONCLUSIONS

NCP-2454 prevented MCT-induced PH by suppressing intracellular inflammatory cascades, an upstream molecular change of which is the disruption of Cav-1 expression.

Differential contribution of FXa and thrombin to vascular inflammation in a mouse model of sickle cell disease

Activation of coagulation and vascular inflammation are prominent features of sickle cell disease (SCD). Previously, we have shown that inhibition of tissue factor (TF) attenuates activation of coagulation and vascular inflammation in mouse models of SCD. In this study, we examined the mechanism by which coagulation proteases enhance vascular inflammation in sickle BERK mice. To specifically investigate the contribution of FXa and thrombin, mice were fed chow containing either rivaroxaban or dabigatran, respectively. In addition, we used bone marrow transplantation to generate sickle mice deficient in either protease activated receptor-1 (PAR-1) or protease activated receptor-2 (PAR-2) on nonhematopoietic cells. FXa inhibition and PAR-2 deficiency in nonhematopoietic cells attenuated systemic inflammation, measured by plasma levels of interleukin-6 (IL-6). In contrast, neither thrombin inhibition nor PAR-1 deficiency in nonhematopoietic cells affected plasma levels of IL-6 in sickle mice. However, thrombin did contribute to neutrophil infiltration in the lung, independently of PAR-1 expressed by nonhematopoietic cells. Furthermore, the TF-dependent increase in plasma levels of soluble vascular cell adhesion molecule-1 in sickle mice was not mediated by FXa or thrombin. Our data indicate that TF, FXa, and thrombin differentially contribute to vascular inflammation in a mouse model of SCD.

A comprehensive review: the evolution of animal models in pulmonary hypertension research; are we there yet?

Pulmonary hypertension (PH) is a disorder that develops as a result of remodeling of the pulmonary vasculature and is characterized by narrowing/obliteration of small pulmonary arteries, leading to increased mean pulmonary artery pressure and pulmonary vascular resistance. Subsequently, PH increases the right ventricular afterload, which leads to right ventricular hypertrophy and eventually right ventricular failure. The pathophysiology of PH is not fully elucidated, and current treatments have only a modest impact on patient survival and quality of life. Thus, there is an urgent need for improved treatments or a cure. The use of animal models has contributed extensively to the current understanding of PH pathophysiology and the investigation of experimental treatments. However, PH in current animal models may not fully represent current clinical observations. For example, PH in animal models appears to be curable with many therapeutic interventions, and the severity of PH in animal models is also believed to correlate poorly with that observed in humans. In this review, we discuss a variety of animal models in PH research, some of their contributions to the field, their shortcomings, and how these have been addressed. We highlight the fact that the constant development and evolution of animal models will help us to more closely model the severity and heterogeneity of PH observed in humans.