Current and future treatments of pulmonary arterial hypertension

Orai1/STIMs modulators in pulmonary vascular diseases

Calcium (Ca2+) is a secondary messenger that regulates various cellular processes. However, Ca2+ mishandling could lead to pathological conditions. Orai1 is a Ca2+channel contributing to the store-operated calcium entry (SOCE) and plays a critical role in Ca2+ homeostasis in several cell types. Dysregulation of Orai1 contributed to severe combined immune deficiency syndrome, some cancers, pulmonary arterial hypertension (PAH), and other cardiorespiratory diseases. During its activation process, Orai1 is mainly regulated by stromal interacting molecule (STIM) proteins, especially STIM1; however, many other regulatory partners have also been recently described. Increasing knowledge about these regulatory partners provides a better view of the downstream signalling pathways of SOCE and offers an excellent opportunity to decipher Orai1 dysregulation in these diseases. These proteins participate in other cellular functions, making them attractive therapeutic targets. This review mainly focuses on Orai1 regulatory partners in the physiological and pathological conditions of the pulmonary circulation and inflammation.

Respiratory, cardiovascular and musculoskeletal mechanisms involved in the pathophysiology of pulmonary hypertension: An updated systematic review of preclinical and clinical studies

BACKGROUND

Progressive exercise intolerance is a hallmark of pulmonary hypertension (pH), severely impacting patients' independence and quality of life (QoL). Accumulating evidence over the last decade shows that combined abnormalities in peripheral reflexes and target organs contribute to disease progression and exercise intolerance.

OBJECTIVE

The aim of this study was to review the literature of the last decade on the contribution of the cardiovascular, respiratory, and musculoskeletal systems to pathophysiology and exercise intolerance in pH.

METHODS

A systematic literature search was conducted using specific terms in PubMed, SciELO, and the Cochrane Library databases for original pre-clinical or clinical studies published between 2013 and 2023. Studies followed randomized controlled/non-randomized controlled and pre-post designs.

RESULTS

The systematic review identified 25 articles reporting functional or structural changes in the respiratory, cardiovascular, and musculoskeletal systems in pH. Moreover, altered biomarkers in these systems, lower cardiac baroreflex, and heightened peripheral chemoreflex activity seemed to contribute to functional changes associated with poor prognosis and exercise intolerance in pH. Potential therapeutic strategies acutely explored involved manipulating the baroreflex and peripheral chemoreflex, improving cardiovascular autonomic control via cardiac vagal control, and targeting specific pathways such as GPER1, GDF-15, miR-126, and the JMJD1C gene.

CONCLUSION

Information published in the last 10 years advances the notion that pH pathophysiology involves functional and structural changes in the respiratory, cardiovascular, and musculoskeletal systems and their integration with peripheral reflexes. These findings suggest potential therapeutic targets, yet unexplored in clinical trials, that could assist in improving exercise tolerance and QoL in patients with pH.

The role of serum sodium in poor prognosis evaluation of pulmonary hypertension associated with left heart disease

BACKGROUND

Previous studies have shown that hyponatremia was strongly associated with a poor prognosis of type 1 pulmonary hypertension, and our team's antecedent studies found that low serum sodium was associated with the severity and the length of hospitalization of pulmonary hypertension associated with left ventricular disease (PH-LHD). However, the relationship between serum sodium and the prognosis of PH-LHD remains unclear. This study aims to determine the clinical value of serum sodium in evaluating poor prognosis in patients with PH-LHD.

METHODS

We successfully followed 716 patients with PH-LHD. Kaplan-Meier was used to plot survival in PH-LHD patients with different serum sodium levels. The effect of serum sodium on poor prognosis was analyzed using a Cox proportional risk model. The trends between patients serum sodium and survival were visualized by restricted cubic spline (RCS).

RESULTS

The survival rates at 1, 2, 3 and 4 years were 52%, 41%, 31% and 31% for the patients with hyponatremia associated with PH-LHD and 71%, 71%, 71% and 54% for the patients with hypernatremia, respectively. The observed mortality rate in the hyponatremia and hypernatremia groups surpassed that of the normonatremic group. The adjusted risks of death (risk ratio) for patients with hyponatremia and hypernatremia were found to be 2.044 and 1.877. Furthermore, the restricted cubic spline demonstrated an L-shaped correlation between serum sodium and all-cause mortality in patients with PH-LHD.

CONCLUSIONS

Abnormal serum sodium level is strongly associated with poor prognosis in PH-LHD. Serum sodium may play an important pathogenic role in PH-LHD occurrence and could be used as a marker to assess the survival in patients.

Mesenchymal stem cell-derived exosomes ameliorate hypoxic pulmonary hypertension by inhibiting the Hsp90aa1/ERK/pERK pathway

Hypoxic pulmonary hypertension (HPH) is a serious and life-threatening chronic cardiopulmonary disease characterized by progressive elevation of pulmonary artery pressure and pulmonary vascular remodeling. Mesenchymal stem cell- derived exosomes (MSC-Exos) can relieve HPH by reversing pulmonary vascular remodeling. The HPH model was established in healthy male Sprague-Dawley (SD) rats aged 6 to 8 weeks. The rats were placed in a room with oxygen concentration of (10 ± 1) % for 8 h a day over 28 days, were then injected intravenously with MSC-Exos (100 ug protein/kg) or equal-volume phosphate buffer saline (PBS) once a day over 1 week. Right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI) and pulmonary vascular remodeling were observed after anesthesia. In addition, platelet-derived growth factor BB (PDGF-BB) were used to stimulate rat pulmonary artery smooth muscle cells (PASMCs) to construct HPH pathological cell models. The results showed that MSC-Exos could not only reduce the elevation of RVSP, right ventricular hypertrophy and the degree of pulmonary vascular remodeling in HPH rats, but also reduce the proliferation, migration and apoptosis resistance of PASMCs. Finally, GSE53408 and GSE113439 datasets were analyzed and showed that the expression of Hsp90aa1 and pERK/ERK were significantly increased in HPH, also could be inhibited by MSC-Exos. Meanwhile, inhibition of Hsp90aa1 also reduced PASMCs migration and pERK/ERK protein level. In conclusion, MSC-Exos alleviated HPH by suppressing PASMCs proliferation, migration and apoptosis resistance through inhibiting the Hsp90aa1/ERK/pERK pathway.

Fluorinated perhexiline derivative attenuates vascular proliferation in pulmonary arterial hypertension smooth muscle cells

Increased proliferation and reduced apoptosis of pulmonary artery smooth muscle cells (PASMCs) is recognised as a universal hallmark of pulmonary arterial hypertension (PAH), in part related to the association with reduced pyruvate dehydrogenase (PDH) activity, resulting in decreased oxidative phosphorylation of glucose and increased aerobic glycolysis (Warburg effect). Perhexiline is a well-recognised carnitine palmitoyltransferase-1 (CPT1) inhibitor used in cardiac diseases, which reciprocally increases PDH activity, but is associated with variable pharmacokinetics related to polymorphic variation of the cytochrome P450-2D6 (CYP2D6) enzyme, resulting in the risk of neuro and hepatotoxicity in 'slow metabolisers' unless blood levels are monitored and dose adjusted. We have previously reported that a novel perhexiline fluorinated derivative (FPER-1) has the same therapeutic profile as perhexiline but is not metabolised by CYP2D6, resulting in more predictable pharmacokinetics than the parent drug. We sought to investigate the effects of perhexiline and FPER-1 on PDH flux in PASMCs from patients with PAH. We first confirmed that PAH PASMCs exhibited increased cell proliferation, enhanced phosphorylation of AKTSer473, ERK 1/2Thr202/Tyr204 and PDH-E1αSer293, indicating a Warburg effect when compared to healthy PASMCs. Pre-treatment with perhexiline or FPER-1 significantly attenuated PAH PASMC proliferation in a concentration-dependent manner and suppressed the activation of the AKTSer473 but had no effect on the ERK pathway. Perhexiline and FPER-1 markedly activated PDH (seen as dephosphorylation of PDH-E1αSer293), reduced glycolysis, and upregulated mitochondrial respiration in these PAH PASMCs as detected by Seahorse analysis. However, both perhexiline and FPER-1 did not induce apoptosis as measured by caspase 3/7 activity. We show for the first time that both perhexiline and FPER-1 may represent therapeutic agents for reducing cell proliferation in human PAH PASMCs, by reversing Warburg physiology.

Corosolic acid attenuates platelet-derived growth factor signaling in macrophages and smooth muscle cells of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease that is characterized by vascular remodeling of the pulmonary artery. Pulmonary vascular remodeling is primarily caused by the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are facilitated by perivascular inflammatory cells including macrophages. Corosolic acid (CRA) is a natural pentacyclic triterpenoid that exerts anti-inflammatory effects. In the present study, the effects of CRA on the viability of macrophages were examined using monocrotaline (MCT)-induced PAH rats and human monocyte-derived macrophages. Although we previously reported that CRA inhibited signal transducer and activator of transcription 3 (STAT3) signaling and ameliorated pulmonary vascular remodeling in PAH, the inhibitory mechanism remains unclear. Therefore, the underlying mechanisms were investigated using PASMCs from idiopathic PAH (IPAH) patients. In MCT-PAH rats, CRA inhibited the accumulation of macrophages around remodeled pulmonary arteries. CRA reduced the viability of human monocyte-derived macrophages. In IPAH-PASMCs, CRA attenuated cell proliferation and migration facilitated by platelet-derived growth factor (PDGF)-BB released from macrophages and PASMCs. CRA also downregulated the expression of PDGF receptor β and its signaling pathways, STAT3 and nuclear factor-κB (NF-κB). In addition, CRA attenuated the phosphorylation of PDGF receptor β and STAT3 following the PDGF-BB simulation. The expression and phosphorylation levels of PDGF receptor β after the PDGF-BB stimulation were reduced by the small interfering RNA knockdown of NF-κB, but not STAT3, in IPAH-PASMCs. In conclusion, CRA attenuated the PDGF-PDGF receptor β-STAT3 and PDGF-PDGF receptor β-NF-κB signaling axis in macrophages and PASMCs, and thus, ameliorated pulmonary vascular remodeling in PAH.

Population pharmacokinetic modeling of sotatercept in healthy participants and patients with pulmonary arterial hypertension

Sotatercept is a breakthrough, first-in-class biologic, that is FDA-approved for the treatment of pulmonary arterial hypertension (PAH). A population pharmacokinetic (PopPK) model was developed using data from two phase 1 studies in healthy participants, and two phase 2 studies and one phase 3 study in participants with PAH. The pooled sotatercept PK data encompassed single intravenous (IV) or subcutaneous (SC) doses ranging from 0.01 to 3.0 mg/kg, as well as multiple SC doses ranging from 0.03 to 1.0 mg/kg, with PK samples collected up to a maximum of ~150 weeks following Q3W and Q4W dosing regimens. The final PopPK analysis included 350 participants, with 30 and 320 participants receiving sotatercept IV and SC, respectively. A two-compartment model with a first-order absorption rate constant and a linear disposition from central compartment well-described sotatercept PK. The estimated bioavailability is ~66%; bioavailability, clearance (CL), and central volume (VC) have low to moderate inter-individual variability. Time-varying body weight and baseline albumin concentration were statistically significant predictors of PK; CL and VC were predicted to increase with increasing body weight, while CL was predicted to decrease with increasing baseline albumin concentration. However, the magnitude of covariate effects is not predicted to meaningfully alter the disposition of sotatercept. Altogether, the PopPK modeling results demonstrate favorable PK characteristics (low to moderate variability and typical bioavailability), supporting sotatercept as a SC biological agent for the treatment of patients with PAH.

Identification of differentially expressed ER stress-related genes and their association with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a complex and progressive illness that has a multifaceted origin, significant fatality rates, and profound effects on health. The pathogenesis of PAH is poorly defined due to the insufficient understanding of the combined impact of endoplasmic reticulum (ER) stress and immune infiltration, both of which play vital roles in PAH development. This study aims to identify potential ER stress-related biomarkers in PAH and investigate their involvement in immune infiltration.

METHODS

The GEO database was used to download gene expression profiles. Genes associated with ER stress were obtained from the MSigDB database. Weighted gene co-expression network analysis (WGCNA), GO, KEGG, and protein-protein interaction (PPI) were utilized to conduct screening of hub genes and explore potential molecular mechanisms. Furthermore, the investigation also delved into the presence of immune cells in PAH tissues and the correlation between hub genes and the immune system. Finally, we validated the diagnostic value and expression levels of the hub genes in PAH using subject-workup characterization curves and real-time quantitative PCR.

RESULTS

In the PAH and control groups, a total of 31 genes related to ER stress were found to be differentially expressed. The enrichment analysis revealed that these genes were primarily enriched in reacting to stress in the endoplasmic reticulum, dealing with unfolded proteins, transporting proteins, and processing proteins within the endoplasmic reticulum. EIF2S1, NPLOC4, SEC61B, SYVN1, and DERL1 were identified as the top 5 hub genes in the PPI network. Immune infiltration analysis revealed that these hub genes were closely related to immune cells. The receiver operating characteristic (ROC) curves revealed that the hub genes exhibited excellent diagnostic efficacy for PAH. The levels of SEC61B, NPLOC4, and EIF2S1 expression were in agreement with the findings of bioinformatics analysis in the PAH group.

CONCLUSIONS

Potential biomarkers that could be utilized are SEC61B, NPLOC4, and EIF2S1, as identified in this study. The infiltration of immune cells was crucial to the development and advancement of PAH. This study provided new potential therapeutic targets for PAH.

Blockage of the adenosine A2B receptor prevents cardiac fibroblasts overgrowth in rats with pulmonary arterial hypertension

Sustained pressure overload and fibrosis of the right ventricle (RV) are the leading causes of mortality in pulmonary arterial hypertension (PAH). Although the role of adenosine in PAH has been attributed to the control of pulmonary vascular tone, cardiac reserve, and inflammatory processes, the involvement of the nucleoside in RV remodelling remains poorly understood. Conflicting results exist on targeting the low-affinity adenosine A2B receptor (A2BAR) for the treatment of PAH mostly because it displays dual roles in acute vs. chronic lung diseases. Herein, we investigated the role of the A2BAR in the viability/proliferation and collagen production by cardiac fibroblasts (CFs) isolated from RVs of rats with monocrotaline (MCT)-induced PAH. CFs from MCT-treated rats display higher cell viability/proliferation capacity and overexpress A2BAR compared to the cells from healthy littermates. The enzymatically stable adenosine analogue, 5'-N-ethylcarboxamidoadenosine (NECA, 1-30 μM), concentration-dependently increased growth, and type I collagen production by CFs originated from control and PAH rats, but its effects were more prominent in cells from rats with PAH. Blockage of the A2BAR with PSB603 (100 nM), but not of the A2AAR with SCH442416 (100 nM), attenuated the proliferative effect of NECA in CFs from PAH rats. The A2AAR agonist, CGS21680 (3 and 10 nM), was virtually devoid of effect. Overall, data suggest that adenosine signalling via A2BAR may contribute to RV overgrowth secondary to PAH. Therefore, blockage of the A2AAR may be a valuable therapeutic alternative to mitigate cardiac remodelling and prevent right heart failure in PAH patients.

Up-regulated expression of two-pore domain K+ channels, KCNK1 and KCNK2, is involved in the proliferation and migration of pulmonary arterial smooth muscle cells in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is a severe and rare disease in the cardiopulmonary system. Its pathogenesis involves vascular remodeling of the pulmonary artery, which results in progressive increases in pulmonary arterial pressure. Chronically increased pulmonary arterial pressure causes right ventricular hypertrophy and subsequent right heart failure. Pulmonary vascular remodeling is attributed to the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are induced by enhanced Ca2+ signaling following the up-/down-regulation of ion channel expression.

Objectives

In the present study, the functional expression of two-pore domain potassium KCNK channels was investigated in PASMCs from idiopathic PAH (IPAH) patients and experimental pulmonary hypertensive (PH) animals.

Results

In IPAH-PASMCs, the expression of KCNK1/TWIK1 and KCNK2/TREK1 channels was up-regulated, whereas that of KCNK3/TASK1 and KCNK6/TWIK2 channels was down-regulated. The similar up-regulated expression of KCNK1 and KCNK2 channels was observed in the pulmonary arterial smooth muscles of monocrotaline-induced PH rats, Sugen 5416/hypoxia-induced PH rats, and hypoxia-induced PH mice. The facilitated proliferation of IPAH-PASMCs was suppressed by the KCNK channel blockers, quinine and tetrapentylammonium. The migration of IPAH-PASMCs was also suppressed by these channel blockers. Furthermore, increases in the proliferation and migration were inhibited by the siRNA knockdown of KCNK1 or KCNK2 channels. The siRNA knockdown also caused membrane depolarization and subsequent decrease in cytosolic [Ca2+]. The phosphorylated level of c-Jun N-terminal kinase (JNK) was elevated in IPAH-PASMCs compared to normal-PASMCs. The increased phosphorylation was significantly reduced by the siRNA knockdown of KCNK1 or KCNK2 channels.

Conclusion

Collectively, these findings indicate that the up-regulated expression of KCNK1 and KCNK2 channels facilitates the proliferation and migration of PASMCs via enhanced Ca2+ signaling and JNK signaling pathway, which is associated with vascular remodeling in PAH.

The nitric oxide-soluble guanylate cyclase-cGMP pathway in pulmonary hypertension: from PDE5 to soluble guanylate cyclase

The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway plays a key role in the pathogenesis of pulmonary hypertension (PH). Targeted treatments include phosphodiesterase type 5 inhibitors (PDE5i) and sGC stimulators. The sGC stimulator riociguat is approved for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). sGC stimulators have a dual mechanism of action, enhancing the sGC response to endogenous NO and directly stimulating sGC, independent of NO. This increase in cGMP production via a dual mechanism differs from PDE5i, which protects cGMP from degradation by PDE5, rather than increasing its production. sGC stimulators may therefore have the potential to increase cGMP levels under conditions of NO depletion that could limit the effectiveness of PDE5i. Such differences in mode of action between sGC stimulators and PDE5i could lead to differences in treatment efficacy between the classes. In addition to vascular effects, sGC stimulators have the potential to reduce inflammation, angiogenesis, fibrosis and right ventricular hypertrophy and remodelling. In this review we describe the evolution of treatments targeting the NO-sGC-cGMP pathway, with a focus on PH.

Expression of Inflammatory Genes in Murine Lungs in a Model of Experimental Pulmonary Hypertension: Effects of an Antibody-Based Targeted Delivery of Interleukin-9

BACKGROUND

Pathogenesis of pulmonary hypertension (PH) is a multifactorial process driven by inflammation and pulmonary vascular remodeling. To target these two aspects of PH, we recently tested a novel treatment: Interleukin-9 (IL9) fused to F8, an antibody that binds to the extra-domain A of fibronectin (EDA+ Fn). As EDA+ Fn is not found in healthy adult tissue but is expressed during PH, IL9 is delivered specifically to the tissue affected by PH. We found that F8IL9 reduced pulmonary vascular remodeling and attenuated PH compared with sham-treated mice.

PURPOSE

To evaluate possible F8IL9 effects on PH-associated inflammatory processes, we analysed the expression of genes involved in pulmonary immune responses.

METHODS

We applied the monocrotaline (MCT) model of PH in mice (n = 44). Animals were divided into five experimental groups: sham-induced animals without PH (control, n = 4), MCT-induced PH without treatment (PH, n = 8), dual endothelin receptor antagonist treatment (dual ERA, n = 8), F8IL9 treatment (n = 12, 2 formats with n = 6 each), or with KSFIL9 treatment (KSFIL9, n = 12, 2 formats with n = 6 each, KSF: control antibody with irrelevant antigen specificity). After 28 days, a RT-PCR gene expression analysis of inflammatory response (84 genes) was performed in the lung.

RESULTS

Compared with the controls, 19 genes exhibited relevant (+2.5-fold) upregulation in the PH group without treatment. Gene expression levels in F8IL9-treated lung tissue were reduced compared to the PH group without treatment. This was the case especially for CCL20, CXCL5, C-reactive protein, pentraxin related (CRPPR), and Kininogen-1 (KNG1).

CONCLUSION

In accordance with the hypothesis stated above, F8IL9 treatment diminished the upregulation of some genes associated with inflammation in a PH animal model. Therefore, we hypothesize that IL9-based immunocytokine treatment will likely modulate various inflammatory pathways.

In Vitro Experimental Approach for Studying Human Pulmonary Artery Smooth Muscle Cells and Endothelial Cells Proliferation and Migration

Pulmonary arterial hypertension (PAH) is a severe vascular disease characterized by persistent precapillary pulmonary hypertension, leading to right heart failure and death. Despite intense research in the last decades, PAH remains an incurable disease with high morbidity and mortality. New directions and therapies to improve understanding and treatment of PAH are desperately needed. The pathological mechanisms leading to this fatal disorder remain mostly undetermined, although structural remodeling of the pulmonary vessels is known to be an early feature of PAH. Pulmonary vascular remodeling includes proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells (PAECs). The use of in vitro approaches is useful to delineate the mechanisms involved in the pathogenesis of PAH and to identify new therapeutic strategies for PAH. In this chapter, we describe protocols for culturing and assessing proliferation and migration of human PASMCs and PAECs.

The novel roles of YULINK in the migration, proliferation and glycolysis of pulmonary arterial smooth muscle cells: implications for pulmonary arterial hypertension

BACKGROUND

Abnormal remodeling of the pulmonary vasculature, characterized by the proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) along with dysregulated glycolysis, is a pathognomonic feature of pulmonary arterial hypertension (PAH). YULINK (MIOS, Entrez Gene: 54468), a newly identified gene, has been recently shown to possess pleiotropic physiologic functions. This study aims to determine novel roles of YULINK in the regulation of PAH-related pathogenesis, including PASMC migration, proliferation and glycolysis.

RESULTS

Our results utilized two PAH-related cell models: PASMCs treated with platelet-derived growth factor (PDGF) and PASMCs harvested from monocrotaline (MCT)-induced PAH rats (PAH-PASMCs). YULINK modulation, either by knockdown or overexpression, was found to influence PASMC migration and proliferation in both models. Additionally, YULINK was implicated in glycolytic processes, impacting glucose uptake, glucose transporter 1 (GLUT1) expression, hexokinase II (HK-2) expression, and pyruvate production in PASMCs. Notably, YULINK and GLUT1 were observed to colocalize on PASMC membranes under PAH-related pathogenic conditions. Indeed, increased YULINK expression was also detected in the pulmonary artery of human PAH specimen. Furthermore, YULINK inhibition led to the suppression of platelet-derived growth factor receptor (PDGFR) and the phosphorylation of focal adhesion kinase (FAK), phosphoinositide 3-kinase (PI3K), and protein kinase B (AKT) in both cell models. These findings suggest that the effects of YULINK are potentially mediated through the PI3K-AKT signaling pathway.

CONCLUSIONS

Our findings indicate that YULINK appears to play a crucial role in the migration, proliferation, and glycolysis in PASMCs and therefore positioning it as a novel promising therapeutic target for PAH.

Whole-genome microRNA sequencing analysis in patients with pulmonary hypertension

Pulmonary hypertension (PH) is a pathological disorder with multiple clinical manifestations that lead to cardiovascular and respiratory diseases in most patients. Recent studies have revealed that microRNAs (miRNAs) play important roles as upstream signaling molecules in several diseases, including PH. However, miRNAs that can be used as diagnostic or prognostic biomarkers for PH have not been identified. Thus, in this study, peripheral blood samples obtained from patients with PH and healthy individuals were subjected to genome-wide miRNA sequencing and transcriptome analysis. We screened 136 differentially expressed miRNAs in patients with PH and verified that four differentially expressed miRNAs, namely, hsa-miR-1304-3p, hsa-miR-490-3p, hsa-miR-11400, and hsa-miR-31-5p, could be used as clinical diagnostic biomarkers for pulmonary arterial hypertension. Our findings provide a basis for further in-depth investigations of the specific mechanisms of miRNAs in PH.

The Emerging Therapeutic Role of Prostaglandin E2 Signaling in Pulmonary Hypertension

Mild-to-moderate pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). It is characterized by narrowing and thickening of the pulmonary arteries, resulting in increased pulmonary vascular resistance (PVR) and ultimately leading to right ventricular dysfunction. Pulmonary vascular remodeling in COPD is the main reason for the increase of pulmonary artery pressure (PAP). The pathogenesis of PH in COPD is complex and multifactorial, involving chronic inflammation, hypoxia, and oxidative stress. To date, prostacyclin and its analogues are widely used to prevent PH progression in clinical. These drugs have potent anti-proliferative, anti-inflammatory, and stimulating endothelial regeneration properties, bringing therapeutic benefits to the slowing, stabilization, and even some reversal of vascular remodeling. As another well-known and extensively researched prostaglandins, prostaglandin E2 (PGE2) and its downstream signaling have been found to play an important role in various biological processes. Emerging evidence has revealed that PGE2 and its receptors (i.e., EP1-4) are involved in the regulation of pulmonary vascular homeostasis and remodeling. This review focuses on the research progress of the PGE2 signaling pathway in PH and discusses the possibility of treating PH based on the PGE2 signaling pathway.

[Genetic diagnostics and molecular approaches in pulmonary arterial hypertension]

The recently published new European guidelines for diagnosis and treatment of pulmonary hypertension now offer the so far most extensive description of genetic testing and counselling for pulmonary arterial hypertension patients. In addition, the importance of a clinical screening of healthy mutation carriers is highlighted as well as the genetic testing of patients with a suspicion of pulmonary veno-occlusive disease. We frame the respective parts of the guidelines on genetic testing and counselling in the context of recent data and provide comments. Finally, we give an outlook on novel molecular approaches starting from Sotatercept, addressing ion channels and novel therapeutic developments.

Therapeutic Approaches in Pulmonary Arterial Hypertension with Beneficial Effects on Right Ventricular Function-Preclinical Studies

Pulmonary hypertension (PH) is a progressive condition that affects the pulmonary vessels, but its main prognostic factor is the right ventricle (RV) function. Many mice/rat models are used for research in PAH, but results fail to translate to clinical trials. This study reviews studies that test interventions on pulmonary artery banding (PAB), a model of isolated RV disfunction, and PH models. Multiple tested drugs both improved pulmonary vascular hemodynamics in PH models and improved RV structure and function in PAB animals. PH models and PAB animals frequently exhibited similar results (73.1% concordance). Macitentan, sildenafil, and tadalafil improved most tested pathophysiological parameters in PH models, but almost none in PAB animals. Results are frequently not consistent with other studies, possibly due to the methodology, which greatly varied. Some research groups start treating the animals immediately, and others wait up to 4 weeks from model induction. Treatment duration and choice of anaesthetic are other important differences. This review shows that many drugs currently under research for PAH have a cardioprotective effect on animals that may translate to humans. However, a uniformization of methods may increase comparability between studies and, thus, improve translation to clinical trials.

Preventive effect of LCZ696 on hypoxic pulmonary hypertension in rats via regulating the PI3K/AKT signaling pathway

Hypoxic pulmonary hypertension (HPH) is a devastating disease worldwide; however, effective therapeutic drugs are lacking. This study investigated the effects and underlying mechanisms of LCZ696 treatment on hypoxia-induced pulmonary hypertension. Male Sprague-Dawley (SD) rats were kept in a hypobaric chamber with an oxygen concentration of 5% for 4 weeks. Rats were treated with either LCZ696 (18 mg/kg, 36 mg/kg, and 72 mg/kg) or sildenafil. The mean pulmonary artery pressure (mPAP), right ventricle hypertrophy index (RVHI), and lung system index were measured. Hematoxylin-eosin (HE) staining, Masson staining, and immunofluorescence staining were used for histological analysis. Enzyme linked immunosorbent assay (ELISA) kits were used to determine the concentrations of inflammatory and hypoxia-related factors. Western blotting was used to examine the expression of apoptotic and PI3K/AKT signaling pathway proteins in rat lung tissue. Hypoxia increased mPAP, RVHI, and lung system index and induced pulmonary vascular remodeling, pulmonary arteriomyosis, and pulmonary artery fibrosis. LCZ696 treatment reduced the increase in mPAP, RVHI, and the lung system index and ameliorated the induced pathological changes. Hypoxia upregulated expression of NF-kB, TNF-α, IL-6, HIF-1α, and Vascular endothelial growth factor (VEGF), decreased the ratio of Bax/Bcl-2, and activated the PI3K/AKT signaling pathway in lung tissue, and these effects were partially reversed by treatment with LCZ696. These results demonstrated that LCZ696 can ameliorate hypoxia-induced HPH by suppressing apoptosis, inhibiting the inflammatory response, and inhibiting the PI3K/AKT signaling pathway. It provides a reference for clinical rational drug use and lays a foundation for the study of HPH therapeutic drugs.

Pulmonary Hypertension: Unveiling Molecular Mechanisms, Diagnosis, and Therapeutic Targets

Pulmonary hypertension (PH) is a progressive and life-threatening disease characterized by increased pulmonary arterial pressure, which leads to right heart hypertrophy and eventually right heart failure [...].

Pulmonary Hypertension: A Contemporary Review

Major advances in pulmonary arterial hypertension, pulmonary hypertension (PH) associated with lung disease, and chronic thromboembolic PH cast new light on the pathogenetic mechanisms, epidemiology, diagnostic approach, and therapeutic armamentarium for pulmonary vascular disease. Here, we summarize key basic, translational, and clinical PH reports, emphasizing findings that build on current state-of-the-art research. This review includes cutting-edge progress in translational pulmonary vascular biology, with a guide to the diagnosis of patients in clinical practice, incorporating recent PH definition revisions that continue emphasis on early detection of disease. PH management is reviewed including an overview of the evolving considerations for the approach to treatment of PH in patients with cardiopulmonary comorbidities, as well as a discussion of the groundbreaking sotatercept data for the treatment of pulmonary arterial hypertension.

The future of group 2 pulmonary hypertension: Exploring clinical trials and therapeutic targets

Pulmonary hypertension due to left heart disease (PH-LHD) or group 2 PH is the most common and lethal form of PH, occurring secondary to left ventricular systolic or diastolic heart failure (HF), left-sided valvular diseases, and congenital abnormalities. It is subdivided into isolated postcapillary PH (IpcPH) and combined pre- and post-capillary PH (CpcPH), with the latter sharing many similarities with group 1 PH. CpcPH is associated with worse outcomes and increased morbidity and mortality when compared to IpcPH. Although IpcPH can be improved by treatment of the underlying LHD, CpcPH is an incurable disease for which no specific treatment exists, likely due to the lack of understanding of its underlying mechanisms. Furthermore, drugs approved for PAH are not recommended for group 2 PH, as they are either ineffective or even deleterious. With this major unmet medical need, a better understanding of mechanisms and the identification of effective treatment strategies for this deadly condition are urgently needed. This review presents relevant background of the molecular mechanisms underlying PH-LHD that could translate into innovative therapeutic targets and explores novel targets currently being evaluated in clinical trials.

Maresin-1 protects against pulmonary arterial hypertension by improving mitochondrial homeostasis through ALXR/HSP90α axis

AIMS

Pulmonary arterial hypertension (PAH) is a progressive and lethal disease characterized by continuous proliferation of pulmonary arterial smooth muscle cell (PASMCs) and increased pulmonary vascular remodeling. Maresin-1 (MaR1) is a member of pro-resolving lipid mediators and exhibits protective effects on various inflammation-related diseases. Here we aimed to study the role of MaR1 in the development and progression of PAH and to explore the underlying mechanisms.

METHODS AND RESULTS

We evaluated the effect of MaR1 treatment on PAH in both monocrotaline (MCT)-induced rat and hypoxia+SU5416 (HySu)-induced mouse models of pulmonary hypertension (PH). Plasma samples were collected from patients with PAH and rodent PH models to examine MaR1 production. Specific shRNA adenovirus or inhibitors were used to block the function of MaR1 receptors. The data showed that MaR1 significantly prevented the development and blunted the progression of PH in rodents. Blockade of the function of MaR1 receptor ALXR, but not LGR6 or RORα, with BOC-2, abolished the protective effect of MaR1 against PAH development and reduced its therapeutic potential. Mechanistically, we demonstrated that the MaR1/ALXR axis suppressed hypoxia-induced PASMCs proliferation and alleviated pulmonary vascular remodeling by inhibiting mitochondrial accumulation of heat shock protein 90α (HSP90α) and restoring mitophagy.

CONCLUSION

MaR1 protects against PAH by improving mitochondrial homeostasis through ALXR/HSP90α axis and represents a promising target for PAH prevention and treatment.

Evidence for Hypoxia-Induced Shift in ATP Production from Glycolysis to Mitochondrial Respiration in Pulmonary Artery Smooth Muscle Cells in Pulmonary Arterial Hypertension

BACKGROUND

The metabolic state of pulmonary artery smooth muscle cells (PASMCs) from patients with pulmonary arterial hypertension (PAH) is not well understood. In this study, we examined the balance between glycolysis and mitochondrial respiration in non-PAH-PASMCs and PAH-PASMCs under normoxia and hypoxia.

METHODS

We investigated the enzymes involved in glycolysis and mitochondrial respiration, and studied the two major energy-yielding pathways (glycolysis and mitochondrial respiration) by measuring extracellular acidification rate (ECAR) and cellular oxygen consumption rate (OCR) using the Seahorse extracellular flux technology.

RESULTS

Under both normoxia and hypoxia, the mRNA and protein levels of pyruvate dehydrogenase kinase 1 and pyruvate dehydrogenase were increased in PAH-PASMCs compared with non-PAH-PASMCs. The mRNA and protein levels of lactate dehydrogenase, as well as the intracellular lactate concentration, were also increased in PAH-PASMCs compared with non-PAH-PASMCs under normoxia. However, these were not significantly increased in PAH-PASMCs compared with non-PAH-PASMCs under hypoxia. Under normoxia, ATP production was significantly lower in PAH-PASMCs (59 ± 5 pmol/min) than in non-PAH-PASMCs (70 ± 10 pmol/min). On the other hand, ATP production was significantly higher in PAH-PASMCs (31 ± 5 pmol/min) than in non-PAH-PASMCs (14 ± 3 pmol/min) under hypoxia.

CONCLUSIONS

There is an underlying change in the metabolic strategy to generate ATP production under the challenge of hypoxia.

Insights into Endothelin Receptors in Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease which affects the cardiopulmonary system; it is defined as a mean pulmonary artery pressure (mPAP) > 20 mmHg as measured by right heart catheterization at rest, and is caused by complex and diverse mechanisms. In response to stimuli such as hypoxia and ischemia, the expression and synthesis of endothelin (ET) increase, leading to the activation of various signaling pathways downstream of it and producing effects such as the induction of abnormal vascular proliferation during the development of the disease. This paper reviews the regulation of endothelin receptors and their pathways in normal physiological processes and disease processes, and describes the mechanistic roles of ET receptor antagonists that are currently approved and used in clinical studies. Current clinical researches on ET are focused on the development of multi-target combinations and novel delivery methods to improve efficacy and patient compliance while reducing side effects. In this review, future research directions and trends of ET targets are described, including monotherapy and precision 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.

Silencing EIF3A ameliorates pulmonary arterial hypertension through HDAC1 and PTEN/PI3K/AKT pathway in vitro and in vivo

Pulmonary vascular remodeling caused by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs) is the hallmark feature of pulmonary arterial hypertension (PAH). Eukaryotic initiation factor 3 subunit A (EIF3A) exhibited proliferative activity in multiple cell types. The present study investigated the role of EIF3A in the progression of PAH. A monocrotaline (MCT)-induced PAH rat model was constructed, and adeno-associated virus type 1 (AAV1) carrying EIF3A shRNA was intratracheally delivered to PAH rats to block EIF3A expression. PASMCs were isolated from rats and treated with PDGF-BB to simulate PASMC proliferation, and shRNA for EIF3 was conducted to investigate the mechanism behind the role of EIF3A in PASMC function in vitro. EIF3A expression was upregulated in pulmonary arteries, and EIF3A inhibition effectively improved pulmonary hypertension and right ventricular hypertrophy and suppressed MCT-induced vascular remodeling in vivo. In addition, we found that genetic knockdown of EIF3A reduced PDGF-triggered proliferation and arrested cell cycle, accompanied by downregulated proliferation-related protein expression in PASMCs. Mechanistically, the histone deacetylase 1 (HDAC1)-mediated PTEN/PI3K/AKT pathway was recognized as a primary mechanism in PAH progression. Silencing EIF3A decreased HDAC1 expression, and further inhibited the excessive proliferation of PASMCs by increasing the phosphatase and tension homolog (PTEN) expression and suppressing the AKT phosphorylation. Notably, HDAC1 expression reversed the effect of silencing EIF3A on PAH and PTEN/PI3K/AKT pathway. Collectively, silencing EIF3A improved PAH by decreasing PASMC proliferation through the HDAC1-mediated PTEN/PI3K/AKT pathway. These findings suggest that targeting EIF3A may represent a potential approach for the treatment of PAH.

Novel Drugs for the Treatment of Pulmonary Arterial Hypertension: Where Are We Going?

Pulmonary arterial hypertension (PAH) is a progressive disease that despite advances in therapy is associated with a 7-year survival of approximately 50%. Several risk factors are associated with developing PAH, include methamphetamine use, scleroderma, human immunodeficiency virus, portal hypertension, and genetic predisposition. PAH can also be idiopathic. There are traditional pathways underlying the pathophysiology of PAH involving nitric oxide, prostacyclin, thromboxane A2, and endothelin-1, resulting in impaired vasodilation, enhanced vasoconstriction and proliferation in the pulmonary vasculature. Established PAH medications targets these pathways; however, this paper aims to discuss novel drugs for treating PAH by targeting new and alternative pathways.

New Drugs and Therapies in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a chronic, progressive disorder of the pulmonary vasculature with associated pulmonary and cardiac remodeling. PAH was a uniformly fatal disease until the late 1970s, but with the advent of targeted therapies, the life expectancy of patients with PAH has now considerably improved. Despite these advances, PAH inevitably remains a progressive disease with significant morbidity and mortality. Thus, there is still an unmet need for the development of new drugs and other interventional therapies for the treatment of PAH. One shortcoming of currently approved vasodilator therapies is that they do not target or reverse the underlying pathogenesis of the disease process itself. A large body of evidence has evolved in the past two decades clarifying the role of genetics, dysregulation of growth factors, inflammatory pathways, mitochondrial dysfunction, DNA damage, sex hormones, neurohormonal pathways, and iron deficiency in the pathogenesis of PAH. This review focuses on newer targets and drugs that modify these pathways as well as novel interventional therapies in PAH.

Natural Products for the Treatment of Pulmonary Hypertension: Mechanism, Progress, and Future Opportunities

Pulmonary hypertension (PH) is a lethal disease due to the remodeling of pulmonary vessels. Its pathophysiological characteristics include increased pulmonary arterial pressure and pulmonary vascular resistance, leading to right heart failure and death. The pathological mechanism of PH is complex and includes inflammation, oxidative stress, vasoconstriction/diastolic imbalance, genetic factors, and ion channel abnormalities. Currently, many clinical drugs for the treatment of PH mainly play their role by relaxing pulmonary arteries, and the treatment effect is limited. Recent studies have shown that various natural products have unique therapeutic advantages for PH with complex pathological mechanisms owing to their multitarget characteristics and low toxicity. This review summarizes the main natural products and their pharmacological mechanisms in PH treatment to provide a useful reference for future research and development of new anti-PH drugs and their mechanisms.

Pharmacology and Emerging Therapies for Group 3 Pulmonary Hypertension Due to Chronic Lung Disease

Pulmonary hypertension (PH) frequently complicates chronic lung disease and is associated with high morbidity and poor outcomes. Individuals with interstitial lung disease and chronic obstructive pulmonary disease develop PH due to structural changes associated with the destruction of lung parenchyma and vasculature with concurrent vasoconstriction and pulmonary vascular remodeling similar to what is observed in idiopathic pulmonary arterial hypertension (PAH). Treatment for PH due to chronic lung disease is largely supportive and therapies specific to PAH have had minimal success in this population with exception of the recently FDA-approved inhaled prostacyclin analogue treprostinil. Given the significant disease burden of PH due to chronic lung diseases and its associated mortality, a great need exists for improved understanding of molecular mechanisms leading to vascular remodeling in this population. This review will discuss the current understanding of pathophysiology and emerging therapeutic targets and potential pharmaceuticals.

A transparent artificial intelligence framework to assess lung disease in pulmonary hypertension

Recent studies have recognized the importance of characterizing the extent of lung disease in pulmonary hypertension patients by using Computed Tomography. The trustworthiness of an artificial intelligence system is linked with the depth of the evaluation in functional, operational, usability, safety and validation dimensions. The safety and validation of an artificial tool is linked to the uncertainty estimation of the model's prediction. On the other hand, the functionality, operation and usability can be achieved by explainable deep learning approaches which can verify the learning patterns and use of the network from a generalized point of view. We developed an artificial intelligence framework to map the 3D anatomical models of patients with lung disease in pulmonary hypertension. To verify the trustworthiness of the framework we studied the uncertainty estimation of the network's prediction, and we explained the learning patterns of the network. Therefore, a new generalized technique combining local explainable and interpretable dimensionality reduction approaches (PCA-GradCam, PCA-Shape) was developed. Our open-source software framework was evaluated in unbiased validation datasets achieving accurate, robust and generalized results.

The role of riociguat in combination therapies for pulmonary arterial hypertension

Effective clinical decision-making in initial treatment selection and switching or escalations of therapy for pulmonary arterial hypertension (PAH) depends on multiple factors including the patient's risk profile. Data from clinical trials suggest that switching from a phosphodiesterase-5 inhibitor (PDE5i) to the soluble guanylate cyclase stimulator riociguat may provide clinical benefit in patients not reaching treatment goals. In this review, we cover the clinical evidence for riociguat combination regimens for patients with PAH and discuss their evolving role in upfront combination therapy and switching from a PDE5i as an alternative to escalating therapy. Specifically, we review current evidence which suggests or provides a hypothesis for 1) the potential use of riociguat plus endothelin receptor antagonist combinations for upfront combination therapy in patients with PAH at intermediate to high risk of 1-year mortality and 2) the benefits of switching to riociguat from a PDE5i in patients who are not achieving treatment goals with PDE5i-based dual combination therapy and at intermediate risk.

Divergent Roles of Ephrin-B2/EphB4 Guidance System in Pulmonary Hypertension

BACKGROUND

Smooth muscle cell (SMC) expansion is one key morphological hallmark of pathologically altered vasculature and a characteristic feature of pulmonary vascular remodeling in pulmonary hypertension. Normal embryonal vessel maturation requires successful coverage of endothelial tubes with SMC, which is dependent on ephrin-B2 and EphB4 ligand-receptor guidance system. In this study, we investigated the potential role of ephrin-B2 and EphB4 on neomuscularization in adult pulmonary vascular disease.

METHODS AND RESULTS

Ephrin-B2 and EphB4 expression is preserved in smooth muscle and endothelial cells of remodeled pulmonary arteries. Chronic hypoxia-induced pulmonary hypertension was not ameliorated in mice with SMC-specific conditional ephrin-B2 knockout. In mice with global inducible ephrin-B2 knockout, pulmonary vascular remodeling and right ventricular hypertrophy upon chronic hypoxia exposure were significantly diminished compared to hypoxic controls, while right ventricular systolic pressure was unaffected. In contrast, EphB4 receptor kinase activity inhibition reduced right ventricular systolic pressure in hypoxia-induced pulmonary hypertension without affecting pulmonary vascular remodeling. Genetic deletion of ephrin-B2 in murine pulmonary artery SMC, and pharmacological inhibition of EphB4 in human pulmonary artery smooth muscle cells, blunted mitogen-induced cell proliferation. Loss of EphB4 signaling additionally reduced RhoA expression and weakened the interaction between human pulmonary artery smooth muscle cells and endothelial cells in a three-dimensional coculture model.

CONCLUSIONS

In sum, pulmonary vascular remodeling was dependent on ephrin-B2-induced Eph receptor (erythropoietin-producing hepatocellular carcinoma receptor) forward signaling in SMC, while EphB4 receptor activity was necessary for RhoA expression in SMC, interaction with endothelial cells and vasoconstrictive components of pulmonary hypertension.

Corosolic acid ameliorates vascular remodeling in pulmonary arterial hypertension via the downregulation of STAT3 signaling

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that is characterized by vascular remodeling of the pulmonary artery. PAH remodeling is primarily caused by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). Therefore, an inhibitory mechanism is expected as a target for the treatment of PAH. Corosolic acid (CRA) is a pentacyclic triterpenoid extracted from the leaves of Banaba (Lagerstroemia speciosa) that exerts anti-diabetic, anti-inflammatory, and anti-tumor effects. In the present study, the effects of CRA on PAH remodeling were examined using PASMCs from idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline (MCT)-induced pulmonary hypertensive (PH) rats. CRA inhibited the excessive proliferation of IPAH-PASMCs in a concentration-dependent manner (IC₅₀ = 14.1 μM). It also reduced the migration of IPAH-PASMCs. The CRA treatment downregulated the expression of signal transducer and activator of transcription 3 (STAT3) in IPAH-PASMCs. In MCT-PH rats, the administration of CRA (1 mg/kg/day) attenuated increases in right ventricular systolic pressure, pulmonary vascular remodeling, and right ventricular hypertrophy. CRA also decreased the expression of STAT3 in pulmonary arterial smooth muscles from MCT-PH rats. In conclusion, the anti-proliferative and anti-migratory effects of CRA in PASMCs ameliorated PAH remodeling by downregulating STAT3 signaling pathways.

Therapeutic targeting of mineralocorticoid receptors in pulmonary hypertension: Insights from basic research

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling and associated with adverse outcomes. In patients with PH, plasma aldosterone levels are elevated, suggesting that aldosterone and its receptor, the mineralocorticoid receptor (MR), play an important role in the pathophysiology of PH. The MR plays a crucial role in adverse cardiac remodeling in left heart failure. A series of experimental studies from the past few years indicate that MR activation promotes adverse cellular processes that lead to pulmonary vascular remodeling, including endothelial cell apoptosis, smooth muscle cell (SMC) proliferation, pulmonary vascular fibrosis, and inflammation. Accordingly, in vivo studies have demonstrated that pharmacological inhibition or cell-specific deletion of the MR can prevent disease progression and partially reverse established PH phenotypes. In this review, we summarize recent advances in MR signaling in pulmonary vascular remodeling based on preclinical research and discuss the potential, but also the challenges, in bringing MR antagonists (MRAs) into clinical application.

Quinazoline-based human phosphodiesterase 5 inhibitors exhibited a selective vasorelaxant effect on rat isolated pulmonary arteries involving NO-sGC-cGMP pathway and calcium inhibitory effects

Phosphodiesterase 5 (PDE5) inhibitors are an attractive option among the currently available therapies in the management of pulmonary arterial hypertension (PAH). Good selectivity for PDE5 is associated with reduced side effects and greater vasorelaxant effect on pulmonary arteries (PA). This study investigated the vasorelaxant effects of a series of quinazoline-based PDE5 inhibitors and their precise mechanisms action using rat isolated PA and aorta, as compared to sildenafil. Their effects on rat hepatocytes (viability and CYP activities) were also evaluated. Compounds 5 and 11 displayed lower human PDE5 IC₅₀ of the analogs studied here and induced a greater relaxant effect on PA (EC₅₀ 0.94 ± 0.30 and 1.03 ± 0.23 μM, respectively). As compared to sildenafil (EC₅₀ = 0.05 ± 0.02 μM on PA), the relaxant effect of 5 and 11 on PA was lower but their selectivity for PA compared to aorta was higher. The effects of 5 and 11 were reduced by N^G-nitro-L-arginine methyl ester, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one, but not by indomethacin or potassium channels blockers. They also enhanced the relaxant effect of sodium nitroprusside, and inhibited extracellular Ca²⁺ influx and intracellular Ca²⁺release. Compounds 5 and 11 did not reduce hepatocyte viability except at concentration > 10 μM, inhibited CYP3A at 10 μM, like sildenafil, but did not induce CYP1A. In conclusion, this study identified 2 quinazoline analogues with good PDE5 inhibitory activity and good selectivity for the pulmonary vasculature. Their relaxant effect involves both the potentiation of nitric oxide-sGC-cGMP pathway and calcium inhibition. These compounds are potential leads for developing new drugs for PAH.

Translational potential of targeting Anoctamin-1-Encoded Calcium-Activated chloride channels in hypertension

Calcium-activated chloride channels (CaCC) provide a depolarizing stimulus to a variety of tissues through chloride efflux in response to a rise in internal Ca²⁺ and voltage. One of these channels, Anoctamin-1 (ANO1 or TMEM16A) is now recognized to play a central role in promoting smooth muscle tone in various types of blood vessels. Its role in hypertension, and thus the therapeutic promise of targeting ANO1, is less straightforward. This review gives an overview of our current knowledge about the potential role ANO1 may play in hypertension within the systemic, portal, and pulmonary vascular systems and the importance of this information when pursuing potential treatment strategies. While the role of ANO1 is well-established in several forms of pulmonary hypertension, its contributions to both the generation of vascular tone and its role in hypertension within the systemic and portal systems are much less clear. This, combined with ANO1's various roles throughout a multitude of tissues throughout the body, command caution when targeting ANO1 as a therapeutic target and may require tissue-selective strategies.

SIRT6 inhibits hypoxia-induced pulmonary arterial smooth muscle cells proliferation via HIF-1α/PDK4 signaling

SIRT6 is an NAD⁺-dependent protein that plays a vital role in regulating the cell proliferation, differentiation and apoptosis. Abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) in peripheral vascular is one of the major pathological findings of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). However, whether SIRT6 is involved in hypoxia-induced proliferation of PASMCs and its possible mechanisms remain unknown. In the present study, we found that the expression of SIRT6 was decreased in both hypoxia-induced PAH rats model and HPASMCs. Hypoxia promoted the proliferation of HPASMCs in a time-dependent manner, inhibited the activity of caspase-3 and the production of PDH, increased the activity of LDH, ROS level, mitochondrial membrane potential(MMP) and the expression of HIF-1α and PDK4, which induced glycolysis. SIRT6 over-expression could inhibit the proliferation of HPASMCs and increase the apoptosis rate, impelled the retardation of cell cycle in phase G1. Meanwhile, SIRT6 over-expression reduced LDH activity, the levels of ROS and MMP, which simultaneously increased the production of PDH, the expression of HIF-1α, PDK4, Cyclin D1 and PCNA in hypoxia-induced HPASMCs. Moreover, SIRT6 over-expression inhibited the transcriptional activation of HIF-1α/PDK4 signaling. In addition, SIRT6 knockdown with SIRT6 siRNA exhibited the same effect as hypoxia. Together, our results indicated that SIRT6 was participant in regulating hypoxia-induced imbalance of proliferation and apoptosis of HPASMCs, which was associated with the activation of HIF-1α/PDK4 signaling pathway. Targeting at SIRT6 gene and regulating the downstream metabolism signaling pathway may be a novel strategy for the treatment of hypoxia-induced PAH.

Characteristics of Patients With Pulmonary Arterial Hypertension in a Pulmonary Hypertension Association-Accredited Comprehensive Care Center: A Contrast in Features When Compared With US National Registry Data

Background Since the initial description in the 1980s, our understanding of the diversity of pulmonary arterial hypertension (PAH) has continued to evolve. In this study, we report the characteristics of patients seen in an academic medical center for PAH from August 2020 through November 2021 and contrast those with nationally reported data from the United States Pulmonary Hypertension Scientific Registry (USPHSR).  Study Design Investigators at the University of Utah Pulmonary Hypertension Program prospectively enrolled adult patients diagnosed with WHO Group 1 PAH, who were evaluated between August 2020 and November 2021 in a program-specific registry. Patient exposure and health histories were collected through structured interviews and questionnaires, along with clinical data and medication use. A total of 242 patients were enrolled in the University of Utah Pulmonary Hypertension Registry (UUPHR).  Results Of the 242 enrolled patients, the most common etiology was associated PAH (APAH), accounting for 71.1% of the population. The second largest etiology was idiopathic PAH (IPAH) at 26.4%. The remaining patients were distributed between familial PAH (FPAH), pulmonary veno-occlusive disease (PVOD), and others. Of the total population classified as APAH, 39% of cases were noted as secondary to connective tissue disease (CTD) and 33% as toxin-induced. These represented 28% and 24% of the total population, respectively.  Conclusions In this US-based accredited academic medical center, the etiology of PAH in our patient population contrasts with national registry data. In the UUPHR, APAH, specifically CTD-PAH and toxin-associated PAH, accounts for the majority of patients with PAH. This contrasts with IPAH, which nationally is the most reported cause of PAH. Differences in our population may reflect the regional variation of the referral site, but it is noteworthy for its contrast with historically reported phenotypes.

Srolo Bzhtang reduces inflammation and vascular remodeling via suppression of the MAPK/NF-κB signaling pathway in rats with pulmonary arterial hypertension

ETHNOPHARMACOLOGICAL RELEVANCE

Srolo Bzhtang (SBT), which consists of Solms-laubachia eurycarpa, Bergenia purpurascens, Glycyrrhiza uralensis, and lac secreted by Laccifer lacca Kerr (Lacciferidae Cockerell), is a well-known traditional Tibetan medicinal formula and was documented to cure "lung-heat" syndrome by eliminating "chiba" in the ancient Tibetan medical work Four Medical Tantras (Rgyud bzhi). Clinically, it is a therapy for pulmonary inflammatory disorders, such as pneumonia, chronic bronchitis, and chronic obstructive pulmonary disease. However, whether and how SBT participates in pulmonary arterial hypertension (PAH) is still unclear.

AIM OF THE STUDY

We aimed to determine the role of SBT in attenuating pulmonary arterial pressure and vascular remodeling caused by monocrotaline (MCT) and hypoxia. To elucidate the potential mechanism underlying SBT-mediated PAH, we investigated the changes in inflammatory cytokines and mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) signaling pathway.

MATERIALS AND METHODS

MCT- and hypoxia-induced PAH rat models were used. After administering SBT for four weeks, the rats were tested for hemodynamic indicators, hematological changes, pulmonary arterial morphological changes, and the levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in serum and lung tissues. Protein expression of the MAPK/NF-κB signaling pathway was determined using western blotting.

RESULTS

SBT reduced pulmonary arterial pressure, vascular remodeling, and the levels of inflammatory cytokines induced by MCT and hypoxia in rats. Furthermore, SBT significantly suppressed the MAPK/NF-κB signaling pathway.

CONCLUSIONS

To our knowledge, this is the first study to demonstrate that SBT alleviates MCT- and hypoxia-induced PAH in rats, which is related to its anti-inflammatory actions involving inhibition of the MAPK/NF-κB signaling pathway.

Sox17 Deficiency Promotes Pulmonary Arterial Hypertension via HGF/c-Met Signaling

BACKGROUND

In large-scale genomic studies, Sox17, an endothelial-specific transcription factor, has been suggested as a putative causal gene of pulmonary arterial hypertension (PAH); however, its role and molecular mechanisms remain to be elucidated. We investigated the functional impacts and acting mechanisms of impaired Sox17 (SRY-related HMG-box17) pathway in PAH and explored its potential as a therapeutic target.

METHODS

In adult mice, Sox17 deletion in pulmonary endothelial cells (ECs) induced PAH under hypoxia with high penetrance and severity, but not under normoxia.

RESULTS

Key features of PAH, such as hypermuscularization, EC hyperplasia, and inflammation in lung arterioles, right ventricular hypertrophy, and elevated pulmonary arterial pressure, persisted even after long rest in normoxia. Mechanistically, transcriptomic profiling predicted that the combination of Sox17 deficiency and hypoxia activated c-Met signaling in lung ECs. HGF (hepatocyte grow factor), a ligand of c-Met, was upregulated in Sox17-deficient lung ECs. Pharmacologic inhibition of HGF/c-Met signaling attenuated and reversed the features of PAH in both preventive and therapeutic settings. Similar to findings in animal models, Sox17 levels in lung ECs were repressed in 26.7% of PAH patients (4 of 15), while those were robust in all 14 non-PAH controls. HGF levels in pulmonary arterioles were increased in 86.7% of patients with PAH (13 of 15), but none of the controls showed that pattern.

CONCLUSIONS

The downregulation of Sox17 levels in pulmonary arterioles increases the susceptibility to PAH, particularly when exposed to hypoxia. Our findings suggest the reactive upregulation of HGF/c-Met signaling as a novel druggable target for PAH treatment.

Urokinase-loaded cyclic RGD-decorated liposome targeted therapy for in-situ thrombus of pulmonary arteriole of pulmonary hypertension

Backgroud:In-situ thrombosis is a significant pathophysiological basis for the development of pulmonary hypertension (PH). However, thrombolytic therapy for in-situ thrombus in PH was often hampered by the apparent side effects and the low bioavailability of common thrombolytic medications. Nanoscale cyclic RGD (cRGD)-decorated liposomes have received much attention thanks to their thrombus-targeting and biodegradability properties. As a result, we synthesized urokinase-loaded cRGD-decorated liposome (UK-cRGD-Liposome) for therapy of in-situ thrombosis as an exploration of pulmonary hypertensive novel therapeutic approaches.

Purpose: To evaluate the utilize of UK-cRGD-Liposome for targeted thrombolysis of in-situ thrombus in PH and to explore the potential mechanisms of in-situ thrombus involved in the development of PH.

Methods: UK-cRGD-Liposome nanoscale drug delivery system was prepared using combined methods of thin-film hydration and sonication. Induced PH via subcutaneous injection of monocrotaline (MCT). Fibrin staining (modified MSB method) was applied to detect the number of vessels within-situ thrombi in PH. Echocardiography, hematoxylin-eosin (H & E) staining, and Masson’s trichrome staining were used to analyze right ventricular (RV) function, pulmonary vascular remodeling, as well as RV remodeling.

Results: The number of vessels with in-situ thrombi revealed that UK-cRGD-Liposome could actively target urokinase to in-situ thrombi and release its payload in a controlled manner in the in vivo environment, thereby enhancing the thrombolytic effect of urokinase. Pulmonary artery hemodynamics and echocardiography indicated a dramatical decrease in pulmonary artery pressure and a significant improvement in RV function post targeted thrombolytic therapy. Moreover, pulmonary vascular remodeling and RV remodeling were significantly restricted post targeted thrombolytic therapy.

Conclusion: UK-cRGD-Liposome can restrict the progression of PH and improve RV function by targeting the dissolution of pulmonary hypertensive in-situ thrombi, which may provide promising therapeutic approaches for PH.

Strategizing Drug Therapies in Pulmonary Hypertension for Improved Outcomes

Pulmonary hypertension (PH) is characterized by a resting mean pulmonary artery pressure (PAP) of 20 mmHg or more and is a disease of multiple etiologies. Of the various types of PH, pulmonary arterial hypertension (PAH) is characterized by elevated resistance in the pulmonary arterial tree. It is a rare but deadly disease characterized by vascular remodeling of the distal pulmonary arteries. This paper focuses on PAH diagnosis and management including current and future treatment options. Over the last 15 years, our understanding of this progressive disease has expanded from the concept of vasoconstrictive/vasodilatory mismatch in the pulmonary arterioles to now a better appreciation of the role of genetic determinants, numerous cell signaling pathways, cell proliferation and apoptosis, fibrosis, thrombosis, and metabolic abnormalities. While knowledge of its pathophysiology has expanded, the majority of the treatments available today still modulate the same three vasodilatory pathways that have been targeted for over 30 years (endothelin, nitric oxide, and prostacyclin). While modifying these pathways may help improve symptoms and quality of life, none of these directly modify the underlying disease pathogenesis. However, there are now studies ongoing with new drugs that can prevent or reverse these underlying causes of PAH. This review discusses the evidence base for the current treatment algorithms for PAH, as well as discusses novel therapies in development.

Salusin-β, a TOR2A gene product, promotes proliferation, migration, fibrosis, and calcification of smooth muscle cells and accelerates the imbalance of vasomotor function and vascular remodeling in monocrotaline-induced pulmonary hypertensive rats

Purpose: The hyper-proliferation, promoted migration, fibrosis, and calcification of pulmonary arterial smooth muscle cells (PASMCs) play critical roles in pulmonary artery (PA) continuous contraction and vascular remodeling, leading to elevated pulmonary arterial resistance and pulmonary hypertension (PH). In this study, we sought to ascertain the effects of a TOR2A gene product, salusin-β, on PASMCs’ proliferation, migration, fibrosis, calcification, and the imbalance of vasomotor function as well as pulmonary vascular remodeling in monocrotaline (MCT)-induced PH rats and their underlying mechanisms.

Methods: Knockdown or overexpression of salusin-β in rats or PASMCs was performed through tail vein injection or cell transfection of virus. The right ventricular systolic pressure (RVSP) of the rat was measured by right ventricle catheterization. Sodium nitroprusside (SNP) or acetylcholine (ACh)-induced dose-dependent relaxation was used to evaluate the vasodilatation function. Primary PASMCs were isolated from the PAs of control and PH rats.

Results: The salusin-β protein expressions were significantly increased in PAs and PASMCs isolated from PH rats compared with control rats. Knockdown of salusin-β in rats decreased high K⁺ solution-induced contraction, RVSP and RV hypertrophy index, improved SNP or ACh-induced vascular relaxation of PAs, and relieved vascular remodeling and calcification of PAs from PH rats. Silencing salusin-β in PASMCs isolated from PH rats alleviated the proliferation, migration, fibrosis, and calcification, as well as the NAD(P)H oxidase activity and reactive oxygen species (ROS) level. Overexpression of salusin-β exerted the opposite effects on vasomotor function and vascular remodeling, and PASMCs proliferation, migration, fibrosis and calcification.

Conclusion: Increased salusin-β activity in PAs from PH rats contributes to PASMCs proliferation, migration, fibrosis, and calcification, leading to the imbalance of vascular contraction and relaxation and vascular remodeling through stimulating the production of NAD(P)H oxidase derived ROS.

Why Multitarget Vasodilatory (Endo)cannabinoids are Not Effective as Antihypertensive Compounds after Chronic Administration: Comparison of Their Effects on Systemic and Pulmonary Hypertension

Systemic and pulmonary hypertension are multifactorial, high-pressure diseases. The first one is a civilizational condition, and the second one is characterized by a very high mortality rate. Searching for new therapeutic strategies is still an important task. (Endo)cannabinoids, known for their strong vasodilatory properties, have been proposed as possible drugs for different types of hypertension. Unfortunately, our review, in which we summarized all publications found in the PubMed database regarding chronic administration of (endo)cannabinoids in experimental models of systemic and pulmonary hypertension, does not confirm any encouraging suggestions, being based mainly on in vitro and acute in vivo experiments. We considered vasodilator or blood pressure (BP) responses and cardioprotective, anti-oxidative, and the anti-inflammatory effects of particular compounds and their influence on the endocannabinoid system. We found that multitarget (endo)cannabinoids failed to modify higher BP in systemic hypertension since they induced responses leading to decreased and increased BP. In contrast, multitarget cannabidiol and monotarget ligands effectively treated pulmonary and systemic hypertension, respectively. To summarize, based on the available literature, only (endo)cannabinoids with a defined site of action are recommended as potential antihypertensive compounds in systemic hypertension, whereas both mono- and multitarget compounds may be effective in pulmonary hypertension.

Mitochondrial Regulation of the Hypoxia-Inducible Factor in the Development of Pulmonary Hypertension

Pulmonary hypertension (PH) is a severe progressive lung disorder characterized by pulmonary vasoconstriction and vascular remodeling, culminating in right-sided heart failure and increased mortality. Data from animal models and human subjects demonstrated that hypoxia-inducible factor (HIF)-related signaling is essential in the progression of PH. This review summarizes the regulatory pathways and mechanisms of HIF-mediated signaling, emphasizing the role of mitochondria in HIF regulation and PH pathogenesis. We also try to determine the potential to therapeutically target the components of the HIF system for the management of PH.

Effects of the peripheral CB1 receptor antagonist JD5037 in mono— and polytherapy with the AMPK activator metformin in a monocrotaline-induced rat model of pulmonary hypertension

Pulmonary hypertension (PH) is a disease leading to increased pressure in the pulmonary artery and right heart failure. The adenosine monophosphate-activated protein kinase (AMPK) activator, metformin, has a protective effect against PH. CB₁ receptor blockade reduces the number of pathological alterations in experimental lung fibrosis. The current study evaluates the effect of the peripheral cannabinoid CB₁ receptor antagonist JD5037 in mono- and polytherapy with metformin in rat monocrotaline-induced mild PH. Animals received metformin (100 mg/kg), JD5037 (3 mg/kg), or a combination of both once daily for 21 days. Monocrotaline (60 mg/kg) increased right ventricular (RV) systolic pressure (RVSP), led to RV and lung hypertrophy and remodeling, and decreased oxygen saturation. Metformin partially restored the monocrotaline-induced effects, i.e., decreased RVSP, increased oxygen saturation, and counteracted cardiac fibrotic, hypertrophic, and inflammatory changes. JD5037 modified parameters related to inflammation and/or fibrosis. Only polytherapy with metformin and JD5037 improved Fulton’s index and coronary artery hypertrophy and tended to be more effective than monotherapy against alterations in RVSP, oxygen saturation and coronary artery tunica media vacuolization. In conclusion, monotherapy with JD5037 does not markedly influence the PH-related changes. However, polytherapy with metformin tends to be more efficient than any of these compounds alone.