Protective role of IL-6 in vascular remodeling in Schistosoma pulmonary hypertension

Preliminary Mechanism of Glial Maturation Factor β on Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension

Recent evidence suggests that glia maturation factor β (GMFβ) is important in the pathogenesis of pulmonary arterial hpertension (PAH), but the underlying mechanism is unknown. To clarify whether GMFβ can be involved in pulmonary vascular remodeling and to explore the role of the IL-6-STAT3 pathway in this process, the expression of GMFβ in PAH rats is examined and the expression of downstream molecules including periostin (POSTN) and interleukin-6 (IL-6) is measured using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The location and expression of POSTN is also tested in PAH rats using immunofluorescence. It is proved that GMFβ is upregulated in the lungs of PAH rats. Knockout GMFβ alleviated the MCT-PAH by reducing right ventricular systolic pressure (RVSP), mean pulmonary arterial pressure (mPAP), and pulmonary vascular remodeling. Moreover, the inflammation of the pulmonary vasculature is ameliorated in PAH rats with GMFβ absent. In addition, the IL-6-STAT3 signaling pathway is activated in PAH; knockout GMFβ reduced POSTN and IL-6 production by inhibiting the IL-6-STAT3 signaling pathway. Taken together, these findings suggest that knockout GMFβ ameliorates PAH in rats by inhibiting the IL-6-STAT3 signaling pathway.

Interstitial macrophage phenotypes in Schistosoma-induced pulmonary hypertension

Background

Schistosomiasis is a common cause of pulmonary hypertension (PH) worldwide. Type 2 inflammation contributes to the development of Schistosoma-induced PH. Specifically, interstitial macrophages (IMs) derived from monocytes play a pivotal role by producing thrombospondin-1 (TSP-1), which in turn activates TGF-β, thereby driving the pathology of PH. Resident and recruited IM subpopulations have recently been identified. We hypothesized that in Schistosoma-PH, one IM subpopulation expresses monocyte recruitment factors, whereas recruited monocytes become a separate IM subpopulation that expresses TSP-1.

Methods

Mice were intraperitoneally sensitized and then intravenously challenged with S. mansoni eggs. Flow cytometry on lungs and blood was performed on wildtype and reporter mice to identify IM subpopulations and protein expression. Single-cell RNA sequencing (scRNAseq) was performed on flow-sorted IMs from unexposed and at day 1, 3 and 7 following Schistosoma exposure to complement flow cytometry based IM characterization and identify gene expression.

Results

Flow cytometry and scRNAseq both identified 3 IM subpopulations, characterized by CCR2, MHCII, and FOLR2 expression. Following Schistosoma exposure, the CCR2+ IM subpopulation expanded, suggestive of circulating monocyte recruitment. Schistosoma exposure caused increased monocyte-recruitment ligand CCL2 expression in the resident FOLR2+ IM subpopulation. In contrast, the vascular pathology-driving protein TSP-1 was greatest in the CCR2+ IM subpopulation.

Conclusion

Schistosoma-induced PH involves crosstalk between IM subpopulations, with increased expression of monocyte recruitment ligands by resident FOLR2+ IMs, and the recruitment of CCR2+ IMs which express TSP-1 that activates TGF-β and causes PH.

Interleukin-6 and pulmonary hypertension: from physiopathology to therapy

Pulmonary hypertension (PH) is a progressive, pulmonary vascular disease with high morbidity and mortality. Unfortunately, the pathogenesis of PH is complex and remains unclear. Existing studies have suggested that inflammatory factors are key factors in PH. Interleukin-6 (IL-6) is a multifunctional cytokine that plays a crucial role in the regulation of the immune system. Current studies reveal that IL-6 is elevated in the serum of patients with PH and it is negatively correlated with lung function in those patients. Since IL-6 is one of the most important mediators in the pathogenesis of inflammation in PH, signaling mechanisms targeting IL-6 may become therapeutic targets for this disease. In this review, we detailed the potential role of IL-6 in accelerating PH process and the specific mechanisms and signaling pathways. We also summarized the current drugs targeting these inflammatory pathways to treat PH. We hope that this study will provide a more theoretical basis for targeted treatment in patients with PH in the future.

Repetitive schistosoma exposure causes perivascular lung fibrosis and persistent pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) can occur as a complication of schistosomiasis. In humans, schistosomiasis-PH persists despite antihelminthic therapy and parasite eradication. We hypothesized that persistent disease arises as a consequence of exposure repetition.

METHODS

Following intraperitoneal sensitization, mice were experimentally exposed to Schistosoma eggs by intravenous injection, either once or three times repeatedly. The phenotype was characterized by right heart catheterization and tissue analysis.

RESULTS

Following intraperitoneal sensitization, a single intravenous Schistosoma egg exposure resulted in a PH phenotype that peaked at 7-14 days, followed by spontaneous resolution. Three sequential exposures resulted in a persistent PH phenotype. Inflammatory cytokines were not significantly different between mice exposed to one or three egg doses, but there was an increase in perivascular fibrosis in those who received three egg doses. Significant perivascular fibrosis was also observed in autopsy specimens from patients who died of this condition.

CONCLUSIONS

Repeatedly exposing mice to schistosomiasis causes a persistent PH phenotype, accompanied by perivascular fibrosis. Perivascular fibrosis may contribute to the persistent schistosomiasis-PH observed in humans with this disease.

Contribution of fatty acid oxidation to the pathogenesis of pulmonary hypertension

Dysregulated metabolism characterizes both animal and human forms of pulmonary hypertension (PH). Enzymes involved in fatty acid metabolism have previously not been assessed in human pulmonary arteries affected by pulmonary arterial hypertension (PAH), and how inhibition of fatty acid oxidation (FAO) may attenuate PH remains unclear. Fatty acid metabolism gene transcription was quantified in laser-dissected pulmonary arteries from 10 explanted lungs with advanced PAH (5 idiopathic, 5 associated with systemic sclerosis), and 5 donors without lung diseases. Effects of oxfenicine, a FAO inhibitor, on female Sugen 5416-chronic hypoxia (SuHx) rats were studied in vivo using right heart catheterization, and ex vivo using perfused lungs and pulmonary artery ring segments. The impact of pharmacologic (oxfenicine) and genetic (carnitine palmitoyltransferase 1a heterozygosity) FAO suppression was additionally probed in mouse models of Schistosoma and hypoxia-induced PH. Potential mechanisms underlying FAO-induced PH pathogenesis were examined by quantifying ATP and mitochondrial mass in oxfenicine-treated SuHx pulmonary arterial cells, and by assessing pulmonary arterial macrophage infiltration with immunohistochemistry. We found upregulated pulmonary arterial transcription of 26 and 13 FAO genes in idiopathic and systemic sclerosis-associated PAH, respectively. In addition to promoting de-remodeling of pulmonary arteries in SuHx rats, oxfenicine attenuated endothelin-1-induced vasoconstriction. FAO inhibition also conferred modest benefit in the two mouse models of PH. Oxfenicine increased mitochondrial mass in cultured rat pulmonary arterial cells, and decreased the density of perivascular macrophage infiltration in pulmonary arteries of treated SuHx rats. In summary, FAO inhibition attenuated experimental PH, and may be beneficial in human PAH.

Role of Gut Microbiota in Pulmonary Arterial Hypertension

Gut microbiota and its metabolites play an important role in maintaining host homeostasis. Pulmonary arterial hypertension (PAH) is a malignant clinical syndrome with a frightening mortality. Pulmonary vascular remodeling is an important feature of PAH, and its pathogenesis is not well established. With the progress of studies on intestinal microbes in different disease, cumulative evidence indicates that gut microbiota plays a major role in PAH pathophysiology. In this review, we will systematically summarize translational and preclinical data on the correlation between gut dysbiosis and PAH and investigate the role of gut dysbiosis in the causation of PAH. Then, we point out the potential significance of gut dysbiosis in the diagnosis and treatment of PAH as well as several problems that remain to be resolved in the field of gut dysbiosis and PAH. All of this knowledge of gut microbiome might pave the way for the extension of novel pathophysiological mechanisms, diagnosis, and targeted therapies for PAH.

Smouldering fire or conflagration? An illustrated update on the concept of inflammation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare condition that is characterised by a progressive increase of pulmonary vascular resistances that leads to right ventricular failure and death, if untreated. The underlying narrowing of the pulmonary vasculature relies on several independent and interdependent biological pathways, such as genetic predisposition and epigenetic changes, imbalance of vasodilating and vasoconstrictive mediators, as well as dysimmunity and inflammation that will trigger endothelial dysfunction, smooth muscle cell proliferation, fibroblast activation and collagen deposition. Progressive constriction of the pulmonary vasculature, in turn, initiates and sustains hypertrophic and maladaptive myocardial remodelling of the right ventricle. In this review, we focus on the role of inflammation and dysimmunity in PAH which is generally accepted today, although existing PAH-specific medical therapies still lack targeted immune-modulating approaches.

KCNK3 Mutation Causes Altered Immune Function in Pulmonary Arterial Hypertension Patients and Mouse Models

Loss of function KCNK3 mutation is one of the gene variants driving hereditary pulmonary arterial hypertension (PAH). KCNK3 is expressed in several cell and tissue types on both membrane and endoplasmic reticulum and potentially plays a role in multiple pathological process associated with PAH. However, the role of various stressors driving the susceptibility of KCNK3 mutation to PAH is unknown. Hence, we exposed kcnk3^fl/fl animals to hypoxia, metabolic diet and low dose lipopolysaccharide (LPS) and performed molecular characterization of their tissue. We also used tissue samples from KCNK3 patients (skin fibroblast derived inducible pluripotent stem cells, blood, lungs, peripheral blood mononuclear cells) and performed microarray, immunohistochemistry (IHC) and mass cytometry time of flight (CyTOF) experiments. Although a hypoxic insult did not alter vascular tone in kcnk3^fl/fl mice, RNASeq study of these lungs implied that inflammatory and metabolic factors were altered, and the follow-up diet study demonstrated a dysregulation of bone marrow cells in kcnk3^fl/fl mice. Finally, a low dose LPS study clearly showed that inflammation could be a possible second hit driving PAH in kcnk3^fl/fl mice. Multiplex, IHC and CyTOF immunophenotyping studies on human samples confirmed the mouse data and strongly indicated that cell mediated, and innate immune responses may drive PAH susceptibility in these patients. In conclusion, loss of function KCNK3 mutation alters various physiological processes from vascular tone to metabolic diet through inflammation. Our data suggests that altered circulating immune cells may drive PAH susceptibility in patients with KCNK3 mutation.

The Role of JAK/STAT Molecular Pathway in Vascular Remodeling Associated with Pulmonary Hypertension

Pulmonary hypertension is defined as a group of diseases characterized by a progressive increase in pulmonary vascular resistance (PVR), which leads to right ventricular failure and premature death. There are multiple clinical manifestations that can be grouped into five different types. Pulmonary artery remodeling is a common feature in pulmonary hypertension (PH) characterized by endothelial dysfunction and smooth muscle pulmonary artery cell proliferation. The current treatments for PH are limited to vasodilatory agents that do not stop the progression of the disease. Therefore, there is a need for new agents that inhibit pulmonary artery remodeling targeting the main genetic, molecular, and cellular processes involved in PH. Chronic inflammation contributes to pulmonary artery remodeling and PH, among other vascular disorders, and many inflammatory mediators signal through the JAK/STAT pathway. Recent evidence indicates that the JAK/STAT pathway is overactivated in the pulmonary arteries of patients with PH of different types. In addition, different profibrotic cytokines such as IL-6, IL-13, and IL-11 and growth factors such as PDGF, VEGF, and TGFβ1 are activators of the JAK/STAT pathway and inducers of pulmonary remodeling, thus participating in the development of PH. The understanding of the participation and modulation of the JAK/STAT pathway in PH could be an attractive strategy for developing future treatments. There have been no studies to date focused on the JAK/STAT pathway and PH. In this review, we focus on the analysis of the expression and distribution of different JAK/STAT isoforms in the pulmonary arteries of patients with different types of PH. Furthermore, molecular canonical and noncanonical JAK/STAT pathway transactivation will be discussed in the context of vascular remodeling and PH. The consequences of JAK/STAT activation for endothelial cells and pulmonary artery smooth muscle cells’ proliferation, migration, senescence, and transformation into mesenchymal/myofibroblast cells will be described and discussed, together with different promising drugs targeting the JAK/STAT pathway in vitro and in vivo.

Animal models of pulmonary hypertension: Getting to the heart of the problem

Despite recent therapeutic advances, pulmonary hypertension (PH) remains a fatal disease due to the development of right ventricular (RV) failure. At present, no treatments targeted at the right ventricle are available, and RV function is not widely considered in the preclinical assessment of new therapeutics. Several small animal models are used in the study of PH, including the classic models of exposure to either hypoxia or monocrotaline, newer combinational and genetic models, and pulmonary artery banding, a surgical model of pure RV pressure overload. These models reproduce selected features of the structural remodelling and functional decline seen in patients and have provided valuable insight into the pathophysiology of RV failure. However, significant reversal of remodelling and improvement in RV function remains a therapeutic obstacle. Emerging animal models will provide a deeper understanding of the mechanisms governing the transition from adaptive remodelling to a failing right ventricle, aiding the hunt for druggable molecular targets.

Perivascular Inflammation in Pulmonary Arterial Hypertension

Perivascular inflammation is a prominent pathologic feature in most animal models of pulmonary hypertension (PH) as well as in pulmonary arterial hypertension (PAH) patients. Accumulating evidence suggests a functional role of perivascular inflammation in the initiation and/or progression of PAH and pulmonary vascular remodeling. High levels of cytokines, chemokines, and inflammatory mediators can be detected in PAH patients and correlate with clinical outcome. Similarly, multiple immune cells, including neutrophils, macrophages, dendritic cells, mast cells, T lymphocytes, and B lymphocytes characteristically accumulate around pulmonary vessels in PAH. Concomitantly, vascular and parenchymal cells including endothelial cells, smooth muscle cells, and fibroblasts change their phenotype, resulting in altered sensitivity to inflammatory triggers and their enhanced capacity to stage inflammatory responses themselves, as well as the active secretion of cytokines and chemokines. The growing recognition of the interaction between inflammatory cells, vascular cells, and inflammatory mediators may provide important clues for the development of novel, safe, and effective immunotargeted therapies in PAH.

Interstitial macrophage-derived thrombospondin-1 contributes to hypoxia-induced pulmonary hypertension

AIMS

Transforming growth factor-β (TGF-β) signalling is required for chronic hypoxia-induced pulmonary hypertension (PH). The activation of TGF-β by thrombospondin-1 (TSP-1) contributes to the pathogenesis of hypoxia-induced PH. However, neither the cellular source of pathologic TSP-1 nor the downstream signalling pathway that link activated TGF-β to PH have been determined. In this study, we hypothesized that circulating monocytes, which are recruited to become interstitial macrophages (IMs), are the major source of TSP-1 in hypoxia-exposed mice, and TSP-1 activates TGF-β with increased Rho-kinase signalling, causing vasoconstriction.

METHODS AND RESULTS

Flow cytometry revealed that a specific subset of IMs is the major source of pathologic TSP-1 in hypoxia. Intravenous depletion and parabiosis experiments demonstrated that these cells are circulating prior to recruitment into the interstitium. Rho-kinase-mediated vasoconstriction was a major downstream target of active TGF-β. Thbs1 deficient bone marrow (BM) protected against hypoxic-PH by blocking TGF-β activation and Rho-kinase-mediated vasoconstriction.

CONCLUSION

In hypoxia-challenged mice, BM derived and circulating monocytes are recruited to become IMs which express TSP-1, resulting in TGF-β activation and Rho-kinase-mediated vasoconstriction.

RNA sequencing analysis of monocrotaline-induced PAH reveals dysregulated chemokine and neuroactive ligand receptor pathways

Pulmonary arterial hypertension (PAH) is a serious disease characterized by elevated pulmonary artery pressure, inflammatory cell infiltration and pulmonary vascular remodeling. However, little is known about the pathogenic mechanisms underlying the disease onset and progression. RNA sequencing (RNA-seq) was used to identify the transcriptional profiling in control and rats injected with monocrotaline (MCT) for 1, 2, 3 and 4 weeks. A total of 23200 transcripts and 280, 1342, 908 and 3155 differentially expressed genes (DEGs) were identified at the end of week 1, 2, 3 and 4, of which Svop was the common top 10 DEGs over the course of PAH progression. Functional enrichment analysis of DEGs showed inflammatory/immune response occurred in the early stage of PAH development. KEGG pathway enrichment analysis of DEGs showed that cytokine-cytokine receptor interaction and neuroactive ligand-receptor interaction were in the initiation and progression of PAH. Further analysis revealed impaired expression of cholinergic receptors, adrenergic receptors including alpha1, beta1 and beta2 receptor, and dysregulated expression of γ-aminobutyric acid receptors. In summary, the dysregulated inflammation/immunity and neuroactive ligand receptor signaling pathways may be involved in the onset and progression of PAH.

Schistosomiasis-associated pulmonary arterial hypertension: a systematic review

Schistosomiasis-associated pulmonary arterial hypertension (Sch-PAH) is a life-threatening complication of chronic hepatosplenic schistosomiasis. It is suggested to be the leading cause of pulmonary arterial hypertension (PAH) worldwide. However, pathophysiological data on Sch-PAH are scarce. We examined the hypothesis that there are pronounced similarities in pathophysiology, haemodynamics, and survival of Sch-PAH and idiopathic PAH (iPAH).

This systematic review and meta-analysis was registered in the PROSPERO database (identifier CRD42018104066). A systematic search and review of the literature was performed according to PRISMA guidelines for studies published between 01 January 1990 and 29 June 2018.

For Sch-PAH, 18 studies evaluating pathophysiological mechanisms, eight studies on haemodynamics (n=277), and three studies on survival (n=191) were identified. 16 clinical registries reporting data on haemodynamics and survival including a total of 5792 patients with iPAH were included for comparison. Proinflammatory molecular pathways are involved in both Sch-PAH and iPAH. The transforming growth factor (TGF)-β signalling pathway is upregulated in Sch-PAH and iPAH. While there was no difference in mean pulmonary artery pressure (54±17 mmHg versus 55±15 mmHg, p=0.29), cardiac output (4.4±1.3 L·min−1versus 4.1±1.4 L·min−1, p=0.046), and cardiac index (2.6±0.7 L·min−1·m−2versus 2.3±0.8 L·min−1·m−2, p<0.001) were significantly higher in Sch-PAH compared to iPAH, resulting in a lower pulmonary vascular resistance in Sch-PAH (10±6 Woods units versus 13±7 Woods units, p<0.001). 1- and 3-year survival were significantly better in the Sch-PAH group (p<0.001).

Sch-PAH and iPAH share common pathophysiological mechanisms related to inflammation and the TGF-β signalling pathway. Patients with Sch-PAH show a significantly better haemodynamic profile and survival than patients with iPAH.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

Can intestinal microbiota and circulating microbial products contribute to pulmonary arterial hypertension?

Pulmonary arterial hypertension (PAH) is a fatal disease with a median survival of only 5-7 yr. PAH is characterized by remodeling of the pulmonary vasculature causing reduced pulmonary arterial compliance (PAC) and increased pulmonary vascular resistance (PVR), ultimately resulting in right ventricular failure and death. Better therapies for PAH will require a paradigm shift in our understanding of the early pathophysiology. PAC decreases before there is an increase in the PVR. Unfortunately, present treatment has little effect on PAC. The loss of compliance correlates with extracellular matrix remodeling and fibrosis in the pulmonary vessels, which have been linked to chronic perivascular inflammation and immune dysregulation. However, what initiates the perivascular inflammation and immune dysregulation in PAH is unclear. Alteration of the gut microbiota composition and function underlies the level of immunopathogenic involvement in several diseases, including atherosclerosis, obesity, diabetes mellitus, and depression, among others. In this review, we discuss evidence that raises the possibility of an etiologic role for changes in the gut and circulating microbiome in the initiation of perivascular inflammation in the early pathogenesis of PAH.

Revealing the pathogenic changes of PAH based on multiomics characteristics

BACKGROUND

Pulmonary artery hypertension (PAH), which is characterized by an increase in pulmonary circulation blood pressure, is a fatal disease, and its pathogenesis remains unclear.

METHODS

In this study, RNA sequencing (RNA-seq), tandem mass tags (TMT) and reduced representation bisulfite sequencing (RRBS) were performed to detect the levels of mRNA, protein, and DNA methylation in pulmonary arteries (PAs), respectively. To screen the possible pathways and proteins related to PAH, pathway enrichment analysis and protein-protein interaction (PPI) network analysis were performed. For selected genes, differential expression levels were confirmed at both the transcriptional and translational levels by real-time PCR and Western blot analyses, respectively.

RESULTS

A total of 362 differentially expressed genes (|Fold-change| > 1.5 and p < 0.05), 811 differentially expressed proteins (|Fold-change| > 1.2 and p < 0.05) and 76,562 differentially methylated regions (1000 bp slide windows, 500 bp overlap, p < 0.05, and |Fold-change| > 1.2) were identified when the PAH group (n = 15) was compared with the control group (n = 15). Through an integrated analysis of the characteristics of the three omic analyses, a multiomics table was constructed. Additionally, pathway enrichment analysis showed that the differentially expressed proteins were significantly enriched in five Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathways and ten Gene Ontology (GO) terms for the PAH group compared with the control group. Moreover, protein-protein interaction (PPI) networks were constructed to identify hub genes. Finally, according to the genes identified in the PPI and the protein expression fold-change, nine key genes and their associated proteins were verified by real-time PCR and Western blot analyses, including Col4a1, Itga5, Col2a1, Gstt1, Gstm3, Thbd, Mgst2, Kng1 and Fgg.

CONCLUSIONS

This study conducted multiomic characteristic profiling to identify genes that contribute to the hypoxia-induced PAH model, identifying new avenues for basic PAH research.

Schistosome infection and its effect on pulmonary circulation

Schistosomiasis is the most common parasitic disease associated with pulmonary hypertension. It induces remodelling via complex inflammatory processes, which eventually produce the clinical manifestation of pulmonary hypertension. The pulmonary hypertension shows clinical signs and symptoms that are not distinguishable from other forms of pulmonary arterial hypertension.

Vascular Adaptation of the Right Ventricle in Experimental Pulmonary Hypertension

Optimal right ventricular (RV) function in pulmonary hypertension (PH) requires structural and functional coupling between the RV cardiomyocyte and its adjacent capillary network. Prior investigations have indicated that RV vascular rarefaction occurs in PH, which could contribute to RV failure by reduced delivery of oxygen or other metabolic substrates. However, it has not been determined if rarefaction results from relative underproliferation in the setting of tissue hypertrophy or from actual loss of vessels. It is also unknown if rarefaction results in inadequate substrate delivery to the RV tissue. In the present study, PH was induced in rats by SU5416-hypoxia-normoxia exposure. The vasculature in the RV free wall was assessed using stereology. Steady-state metabolomics of the RV tissue was performed by mass spectrometry. Complementary studies were performed in hypoxia-exposed mice and rats. Rats with severe PH had evidence of RV failure by decreased cardiac output and systemic hypotension. By stereology, there was significant RV hypertrophy and increased total vascular length in the RV free wall in close proportion, with evidence of vessel proliferation but no evidence of endothelial cell apoptosis. There was a modest increase in the radius of tissue served per vessel, with decreased arterial delivery of metabolic substrates. Metabolomics revealed major metabolic alterations and metabolic reprogramming; however, metabolic substrate delivery was functionally preserved, without evidence of either tissue hypoxia or depletion of key metabolic substrates. Hypoxia-treated rats and mice had similar but milder alterations. There is significant homeostatic vascular adaptation in the right ventricle of rodents with PH.

Correlation between the expression of inflammatory cytokines IL-6, TNF-α and hs-CRP and unfavorable fetal outcomes in patients with pregnancy-induced hypertension

The expression of inflammatory factors, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hs-CRP), in patients with pregnancy-induced hypertension (PIH) was investigated, to analyze correlation of expression levels of these factors in patients with unfavorable fetal outcome. A total of 100 patients diagnosed with PIH treated in Jining First People's Hospital (Jining, China) from January 2012 to October 2017 were selected as the experimental group, while 100 normal pregnant women during the same period were selected as the control group. Results showed that the levels of IL-6, TNF-α and hs-CRP in patients with PIH were significantly higher than those in normal pregnant women (p<0.01). There were significant differences in levels of IL-6, TNF-α and hs-CRP among patients with hypertension in different degrees. The expression levels of IL-6, TNF-α and hs-CRP in PIH patients with favorable pregnancy outcome were lower than those in patients with unfavorable pregnancy outcome (p<0.05). Moreover, the expression levels of IL-6, TNF-α and hs-CRP had a linearly positive correlation with systolic blood pressure in PIH patients. Age, height and weight had no significant correlation with unfavorable pregnancy outcome of PIH patients (p>0.05). Finally, inflammatory factors (TNF-α, IL-6 and hs-CRP) and blood pressure were obviously and positively correlated with unfavorable pregnancy outcome of PIH patients (p<0.05). In conclusion, the expression of inflammatory factors (TNF-α, IL-6 and hs-CRP) in PIH patients are positively correlated with the systolic blood pressure and unfavorable fetal outcome of patients, which can be used as indexes of prognosis evaluation of PIH patients.

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.

Immune cells and autoantibodies in pulmonary arterial hypertension

Analyses of immunity in pulmonary arterial hypertension (PAH) support the notion that maladaptation of the immune response exists. Altered immunity is an increasingly recognized feature of PAH. Indeed, a delicate balance between immunity and tolerance exists and any disturbance may result in chronic inflammation or autoimmunity. This is suggested by infiltration of various immune cells (e.g. macrophages, T and B lymphocytes) in remodeled pulmonary vessels. In addition, several types of autoantibodies directed against antinuclear antigens, endothelial cells (ECs) and fibroblasts have been found in idiopathic and systemic sclerosis-associated PAH. These autoantibodies may play an important role in EC apoptosis and in the expression of cell adhesion molecules. This review article provides an overview of immunity pathways highlighting their potential roles in pulmonary vascular remodeling in PAH and the possibility of future targeted therapy.

TGF-β activation by bone marrow-derived thrombospondin-1 causes Schistosoma- and hypoxia-induced pulmonary hypertension

Pulmonary arterial hypertension (PAH) is an obstructive disease of the precapillary pulmonary arteries. Schistosomiasis-associated PAH shares altered vascular TGF-β signalling with idiopathic, heritable and autoimmune-associated etiologies; moreover, TGF-β blockade can prevent experimental pulmonary hypertension (PH) in pre-clinical models. TGF-β is regulated at the level of activation, but how TGF-β is activated in this disease is unknown. Here we show TGF-β activation by thrombospondin-1 (TSP-1) is both required and sufficient for the development of PH in Schistosoma-exposed mice. Following Schistosoma exposure, TSP-1 levels in the lung increase, via recruitment of circulating monocytes, while TSP-1 inhibition or knockout bone marrow prevents TGF-β activation and protects against PH development. TSP-1 blockade also prevents the PH in a second model, chronic hypoxia. Lastly, the plasma concentration of TSP-1 is significantly increased in subjects with scleroderma following PAH development. Targeting TSP-1-dependent activation of TGF-β could thus be a therapeutic approach in TGF-β-dependent vascular diseases.

Thrombospondin-1 (TSP-1) activates latent TGF-β in the extracellular matrix. Here the authors show that inappropriate activation of latent TGF-β in murine, bovine and human lung by monocyte-produced TSP-1 causes pulmonary hypertension, and that interference with the activation process prevents disease development.

Pulmonary Vascular Diseases Secondary to Schistosomiasis

Schistosomiasis is the most common parasitic disease associated with pulmonary arterial hypertension (PAH). It induces remodeling via complex inflammatory processes produced by the parasite eggs. Changes in the pulmonary vasculature after Schistosoma infection are common, but may not always be associated with a clinical manifestation of PAH. Those patients who presented with PAH show clinical signs and symptoms that are not distinguishable from other forms of PAH.

Comparative Transcriptome Analysis Identifies CCDC80 as a Novel Gene Associated with Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a heterogeneous disorder associated with a progressive increase in pulmonary artery resistance and pressure. Although various therapies have been developed, the 5-year survival rate of PAH patients remains low. There is thus an important need to identify novel genes that are commonly dysregulated in PAH of various etiologies and could be used as biomarkers and/or therapeutic targets. In this study, we performed comparative transcriptome analysis of five mammalian PAH datasets downloaded from a public database. We identified 228 differentially expressed genes (DEGs) from a rat PAH model caused by inhibition of vascular endothelial growth factor receptor under hypoxic conditions, 379 DEGs from a mouse PAH model associated with systemic sclerosis, 850 DEGs from a mouse PAH model associated with schistosomiasis, 1598 DEGs from one cohort of human PAH patients, and 4260 DEGs from a second cohort of human PAH patients. Gene-by-gene comparison identified four genes that were differentially upregulated or downregulated in parallel in all five sets of DEGs. Expression of coiled-coil domain containing 80 (CCDC80) and anterior gradient two genes was significantly increased in the five datasets, whereas expression of SMAD family member six and granzyme A was significantly decreased. Weighted gene co-expression network analysis revealed a connection between CCDC80 and collagen type I alpha 1 (COL1A1) expression. To validate the function of CCDC80 in vivo, we knocked out ccdc80 in zebrafish using the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system. In vivo imaging of zebrafish expressing a fluorescent protein in endothelial cells showed that ccdc80 deletion significantly increased the diameter of the ventral artery, a vessel supplying blood to the gills. We also demonstrated that expression of col1a1 and endothelin-1 mRNA was significantly decreased in the ccdc80-knockout zebrafish. Finally, we examined Ccdc80 immunoreactivity in a rat PAHmodel and found increased expression in the hypertrophied media and adventitia of the pre-acinar pulmonary arteries (PAs) and in the thickened intima, media, and adventitia of the obstructed intra-acinar PAs. These results suggest that increased expression of CCDC80 may be involved in the pathogenesis of PAH, potentially by modulating the expression of endothelin-1 and COL1A1.

Comprehensive Transcriptome Meta-analysis to Characterize Host Immune Responses in Helminth Infections

Helminth infections affect more than a third of the world’s population. Despite very broad phylogenetic differences among helminth parasite species, a systemic Th2 host immune response is typically associated with long-term helminth infections, also known as the “helminth effect”. Many investigations have been carried out to study host gene expression profiles during helminth infections. The objective of this study is to determine if there is a common transcriptomic signature characteristic of the helminth effect across multiple helminth species and tissue types. To this end, we performed a comprehensive meta-analysis of publicly available gene expression datasets. After data processing and adjusting for study-specific effects, we identified ~700 differentially expressed genes that are changed consistently during helminth infections. Functional enrichment analyses indicate that upregulated genes are predominantly involved in various immune functions, including immunomodulation, immune signaling, inflammation, pathogen recognition and antigen presentation. Down-regulated genes are mainly involved in metabolic process, with only a few of them are involved in immune regulation. This common immune gene signature confirms previous observations and indicates that the helminth effect is robust across different parasite species as well as host tissue types. To the best of our knowledge, this study is the first comprehensive meta-analysis of host transcriptome profiles during helminth infections.

Many studies have been conducted to understand the immune modulatory effects in helminth infections. To determine whether there is a common transcriptomic signature characteristic of the helminth effect, we performed a comprehensive meta-analysis of publicly available gene expression datasets. The results revealed a distinct pattern of gene expression that is consistent across multiple helminth species and host tissue types, with upregulated genes dominated by those involved in immune regulation, Th2 immunity and inflammatory responses.

The Causal Role of IL-4 and IL-13 in Schistosoma mansoni Pulmonary Hypertension

RATIONALE

The etiology of schistosomiasis-associated pulmonary arterial hypertension (PAH), a major cause of PAH worldwide, is poorly understood. Schistosoma mansoni exposure results in prototypical type-2 inflammation. Furthermore, transforming growth factor (TGF)-β signaling is required for experimental pulmonary hypertension (PH) caused by Schistosoma exposure.

OBJECTIVES

We hypothesized type-2 inflammation driven by IL-4 and IL-13 is necessary for Schistosoma-induced TGF-β-dependent vascular remodeling.

METHODS

Wild-type, IL-4(-/-), IL-13(-/-), and IL-4(-/-)IL-13(-/-) mice (C57BL6/J background) were intraperitoneally sensitized and intravenously challenged with S. mansoni eggs to induce experimental PH. Right ventricular catheterization was then performed, followed by quantitative analysis of the lung tissue. Lung tissue from patients with schistosomiasis-associated and connective tissue disease-associated PAH was also systematically analyzed.

MEASUREMENTS AND MAIN RESULTS

Mice with experimental Schistosoma-induced PH had evidence of increased IL-4 and IL-13 signaling. IL-4(-/-)IL-13(-/-) mice, but not single knockout IL-4(-/-) or IL-13(-/-) mice, were protected from Schistosoma-induced PH, with decreased right ventricular pressures, pulmonary vascular remodeling, and right ventricular hypertrophy. IL-4(-/-)IL-13(-/-) mice had less pulmonary vascular phospho-signal transducer and activator of transcription 6 (STAT6) and phospho-Smad2/3 activity, potentially caused by decreased TGF-β activation by macrophages. In vivo treatment with a STAT6 inhibitor and IL-4(-/-)IL-13(-/-) bone marrow transplantation also protected against Schistosoma-PH. Lung tissue from patients with schistosomiasis-associated and connective tissue disease-associated PAH had evidence of type-2 inflammation.

CONCLUSIONS

Combined IL-4 and IL-13 deficiency is required for protection against TGF-β-induced pulmonary vascular disease after Schistosoma exposure, and targeted inhibition of this pathway is a potential novel therapeutic approach for patients with schistosomiasis-associated PAH.

A review of recent developments and applications of morphometry/stereology in lung research

Design-based stereology is the gold standard of morphometry in lung research. Here, we analyze the current use of morphometric and stereological methods in lung research and provide an overview on recent methodological developments and biological observations made by the use of stereology. Based on this analysis we hope to provide useful recommendations for a good stereological practice to further the use of advanced and unbiased stereological methods.

Correlation of Interleukin-6 levels and lectins during Schistosoma haematobium infection

Urogenital schistosomiasis caused by Schistosoma haematobium induces a Th2 immune response, including expression of Interleukin-6. IL-6 confers protection from experimental Schistosoma-induced pulmonary hypertension and modulates production of mannose-binding lectin (MBL) and other lectins. We studied IL-6 levels in schistosomiasis and its effect on lectins production. Elevated IL-6 levels occurred in cases, compared to controls. IL-6 correlated with the lectins MBL, ficolin-2 and Collectin Kidney-1 (CL-K1) in cases, but correlated inversely in controls. The study shows that IL-6 levels are elevated in individuals infected with urogenital schistosomiasis. IL-6 was also found to be correlated with the production of lectins in S. haematobium infection. A similar correlation between IL-6 and MBL was observed during visceral leishmaniasis.

Schistosomiasis and the pulmonary vasculature (2013 Grover Conference series)

Inflammation is associated with multiple forms of pulmonary arterial hypertension (PAH), including autoimmune (scleroderma) and infectious (HIV, schistosomiasis) etiologies. More than 200 million people worldwide are infected with Schistosoma, predominantly in Brazil, Africa, the Middle East, and South Asia. Schistosomiasis causes PAH in about 6.1% of those chronically infected and is particularly associated with the species Schistosoma mansoni. Treatment for schistosomiasis-associated PAH includes antihelminthic treatment, if active infection is present (although associated with little immediate benefit to the pulmonary hypertension), and then pharmacologic treatment with targeted pulmonary vascular therapies, including phosphodiesterase type 5 inhibitors and endothelin receptor antagonists. The pathophysiological mechanism by which this parasitic infection causes pulmonary hypertension is unknown but is unlikely to be simple mechanical obstruction of the pulmonary vasculature by parasite eggs. Preexisting hepatosplenic disease due to Schistosoma infection is likely important because of portopulmonary hypertension and/or because it allows egg embolization to the lung by portocaval shunts. Potential immune signaling originating in the periegg granulomas causing the pulmonary vascular disease includes the cytokines interleukin (IL)-4, IL-6, IL-13, and transforming growth factor β. Modulating these pathways may be possible targets for future therapy of schistosomiasis-associated PAH specifically, and study of this disease may provide novel insights into other inflammatory causes of PAH.

Interleukin 13- and interleukin 17A-induced pulmonary hypertension phenotype due to inhalation of antigen and fine particles from air pollution

Pulmonary hypertension has a marked detrimental effect on quality of life and life expectancy. In a mouse model of antigen-induced pulmonary arterial remodeling, we have recently shown that coexposure to urban ambient particulate matter (PM) significantly increased the thickening of the pulmonary arteries and also resulted in significantly increased right ventricular systolic pressures. Here we interrogate the mechanism and show that combined neutralization of interleukin 13 (IL-13) and IL-17A significantly ameliorated the increase in right ventricular systolic pressure, the circumferential muscularization of pulmonary arteries, and the molecular change in the right ventricle. Surprisingly, our data revealed a protective role of IL-17A for the antigen- and PM-induced severe thickening of pulmonary arteries. This protection was due to the inhibition of the effects of IL-13, which drove this response, and the expression of metalloelastase and resistin-like molecule α. However, the latter was redundant for the arterial thickening response. Anti-IL-13 exacerbated airway neutrophilia, which was due to a resulting excess effect of IL-17A, confirming concurrent cross inhibition of IL-13- and IL-17A-dependent responses in the lungs of animals exposed to antigen and PM. Our experiments also identified IL-13/IL-17A-independent molecular reprogramming in the lungs induced by exposure to antigen and PM, which indicates a risk for arterial remodeling and protection from arterial constriction. Our study points to IL-13- and IL-17A-coinduced inflammation as a new template for biomarkers and therapeutic targeting for the management of immune response-induced pulmonary hypertension.

Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension

This review summarizes an expanding body of knowledge indicating that failure to resolve inflammation and altered immune processes underlie the development of pulmonary arterial hypertension. The chemokines and cytokines implicated in pulmonary arterial hypertension that could form a biomarker platform are discussed. Pre-clinical studies that provide the basis for dysregulated immunity in animal models of the disease are reviewed. In addition, we present therapies that target inflammatory/immune mechanisms that are currently enrolling patients, and discuss others in development. We show how genetic and metabolic abnormalities are inextricably linked to dysregulated immunity and adverse remodeling in the pulmonary arteries.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Schistosomiasis and pulmonary arterial hypertension

Schistosomiasis is caused by infection with the parasite Schistosoma, which is a flat-worm or fluke. The dominant species are Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium. Schistosomiasis is the third most common parasitic disease in the world after malaria and amoebiasis. It is endemic in more than 70 countries affecting about 200 million people worldwide, of whom 80% are in sub-Saharan Africa. There are pockets of infection in north-eastern Brazil, near the Yangtze River in China, and some pockets in south East Asia. In the East Mediterranean regions, the Schistosoma have been reported in Iraq and Egypt as well as in Sudan. The latter has the highest infection rate nowadays, particularly in the Al Jazeera area, due to the poor Schistosoma control program. In the Arabian peninsula, schistosomiasis has been reported in southwest part of Saudi Arabia, mainly in the Asir province and Jizan province, which lay in the southwest corner of Saudi Arabia and directly north of the border with Yemen. The efforts to control schistosomiasis have been very successful in Saudi Arabia due to the irrigation system control. However, the infection is prone in Yemen, where the schistosomiasis control is much less strict. Thus as a result, the problem still exists due to transmigration of the populations from both countries.

As a cause of pulmonary arterial hypertension (PAH), schistosomiasis is still under diagnosed and undertreated. This article with give a highlight about the pathophysiology of the disease and both diagnostic and therapeutic strategies.

Role of vascular endothelial growth factor signaling in Schistosoma-induced experimental pulmonary hypertension

There is significant evidence that Th2 (T helper 2)-mediated inflammation supports the pathogenesis of both human and experimental animal models of pulmonary hypertension (PH). A key immune regulator is vascular endothelial growth factor (VEGF), which is produced by Th2 inflammation and can itself contribute to Th2 pulmonary responses. In this study, we interrogated the role of VEGF signaling in a murine model of schistosomiasis-induced PH with a phenotype of significant intrapulmonary Th2 inflammation, vascular remodeling, and elevated right ventricular pressures. We found that VEGF receptor blockade partially suppressed the levels of the Th2 inflammatory cytokines interleukin (IL)-4 and IL-13 in both the lung and the liver after Schistosoma mansoni exposure and suppressed pulmonary vascular remodeling. These findings suggest that VEGF positively contributes to schistosomiasis-induced vascular inflammation and remodeling, and they also provide evidence for a VEGF-dependent signaling pathway necessary for pulmonary vascular remodeling and inflammation in this model.

Adventitial fibroblasts induce a distinct proinflammatory/profibrotic macrophage phenotype in pulmonary hypertension

Macrophage accumulation is not only a characteristic hallmark but is also a critical component of pulmonary artery remodeling associated with pulmonary hypertension (PH). However, the cellular and molecular mechanisms that drive vascular macrophage activation and their functional phenotype remain poorly defined. Using multiple levels of in vivo (bovine and rat models of hypoxia-induced PH, together with human tissue samples) and in vitro (primary mouse, rat, and bovine macrophages, human monocytes, and primary human and bovine fibroblasts) approaches, we observed that adventitial fibroblasts derived from hypertensive pulmonary arteries (bovine and human) regulate macrophage activation. These fibroblasts activate macrophages through paracrine IL-6 and STAT3, HIF1, and C/EBPβ signaling to drive expression of genes previously implicated in chronic inflammation, tissue remodeling, and PH. This distinct fibroblast-activated macrophage phenotype was independent of IL-4/IL-13-STAT6 and TLR-MyD88 signaling. We found that genetic STAT3 haplodeficiency in macrophages attenuated macrophage activation, complete STAT3 deficiency increased macrophage activation through compensatory upregulation of STAT1 signaling, and deficiency in C/EBPβ or HIF1 attenuated fibroblast-driven macrophage activation. These findings challenge the current paradigm of IL-4/IL-13-STAT6-mediated alternative macrophage activation as the sole driver of vascular remodeling in PH, and uncover a cross-talk between adventitial fibroblasts and macrophages in which paracrine IL-6-activated STAT3, HIF1α, and C/EBPβ signaling are critical for macrophage activation and polarization. Thus, targeting IL-6 signaling in macrophages by completely inhibiting C/EBPβ or HIF1α or by partially inhibiting STAT3 may hold therapeutic value for treatment of PH and other inflammatory conditions characterized by increased IL-6 and absent IL-4/IL-13 signaling.

Nuclear factor κ-B is activated in the pulmonary vessels of patients with end-stage idiopathic pulmonary arterial hypertension

OBJECTIVES

To assess activation of the inflammatory transcription factor NF-kappa B (NF-κB) in human idiopathic pulmonary arterial hypertension (PAH).

BACKGROUND

Idiopathic PAH is a severe progressive disease characterized by pulmonary vascular remodeling and excessive proliferation of vascular cells. Increasing evidence indicates that inflammation is important in disease pathophysiology.

METHODS

NF-κB-p65 and CD68, CD20 and CD45 were measured by immunohistochemistry and confocal microscopy on lung specimens from patients with idiopathic PAH (n = 12) and controls undergoing lung surgery (n = 14). Clinical data were recorded for all patients including invasive pulmonary hemodynamics for the PAH patients. Immunohistochemical images were analyzed by blinded observers to include standard pulmonary vascular morphometry; absolute macrophage counts/mm(2) and p65-positivity (p65+) using composite images and image-analysis software; and cytoplasmic:nuclear p65+ of individual pulmonary arterial endothelial and smooth muscle cells (PASMC) in 10-20 pulmonary arteries or arterioles per subject. The expression of ET-1 and CCL5 (RANTES) in whole lung was determined by RT-qPCR.

RESULTS

Macrophage numbers were increased in idiopathic PAH versus controls (49.0±4.5 vs. 7.95±1.9 macrophages/100 mm(2), p<0.0001): these macrophages demonstrated more nuclear p65+ than in macrophages from controls (16.9±2.49 vs. 3.5±1.25%, p<0.001). An increase in p65+ was also seen in perivascular lymphocytes in patients with PAH. Furthermore, NF-κB activation was increased in pulmonary arterial endothelial cells (62.3±2.9 vs. 14.4±3.8, p<0.0001) and PASMC (22.6±2.3 vs. 11.2±2.0, p<0.001) in patients with PAH versus controls, with similar findings in arterioles. Gene expression of both ET-1 mRNA ((0.213±0.069 vs. 1.06±0.23, p<0.01) and CCL5 (RANTES) (0.16±0.045 vs. 0.26±0.039, p<0.05) was increased in whole lung homogenates from patients with PAH.

CONCLUSIONS

NF-κB is activated in pulmonary macrophages, lymphocytes, endothelial and PASMC in patients with end-stage idiopathic PAH. Future research should determine whether NF-κB activation is a driver or bystander of pulmonary vascular inflammation and if the former, its potential role as a therapeutic target.