Effects of normal and high circulating concentrations of activin A on vascular endothelial cell functions and vasoactive factor production

Sotatercept in pulmonary hypertension and beyond

Sotatercept binds free activins by mimicking the extracellular domain of the activin receptor type IIA (ACTRIIA). Additional ligands are BMP/TGF-beta, GDF8, GDF11 and BMP10. The binding with activins leads to the inhibition of the signalling pathway and the deactivation of the bone morphogenic protein (BMP) receptor type 2. In this way, sotatercept activates an antiproliferative signalling to the cells of the pulmonary arteries and arterioles with the aim of rebalancing the proliferative and antiproliferative pathway that characterizes the pulmonary arterial hypertension (PAH). Sotatercept is indicated for the treatment of group 1 PAH in combination with drugs that act through the endothelin receptor, nitric oxide or prostacyclin. Its effects, demonstrated in the STELLAR study, are the improvement of exercise capacity and the FC-WHO functional class, together with the reduction of the risk of clinical worsening events. In addition to its antiremodeling effects on the pulmonary circulation, sotatercept has several haematological effects that could suggest its use in the treatment of some blood disorders other than PAH. In this review, we will discuss the effects of the drug on PAH and in parallel provide an in-depth overview of its application in haematological disorders, focusing on clinical and preclinical studies.

Sotatercept: New drug on the horizon of pulmonary hypertension

Sotatercept (brand name WINREVAIR, developed by Merck) is an activin receptor type IIA-Fc (ActRIIA-Fc), working by sequestering free activins. Sotatercept restores the balance between the activin proliferative pathway and the bone morphogenic protein (BMP) antiproliferative pathway in the pulmonary arterial cirulation. Sotatercept recently received approval in the USA and in Europe for the treatment of adults with pulmonary arterial hypertension (PAH) Group 1, on top of background PAH therapy to increase exercise capacity, improve WHO functional class and reduce the risk of clinical worsening events. Nevertheless, several studies are ongoing to investigate the potential adverse reactions of the drug especially at the haematological level. We provide an overview of the clinical and preclinical evidence of the targeting the activing pathway through sotatercept on the treatment of PAH. We also discuss what other possibilities there are for the application of sotatercept in the setting of pulmonary hypertension other than PAH Group 1.

Follistatin lowers blood pressure and improves vascular structure and function in essential and secondary hypertension

Hypertension is characterized by resistance artery remodeling driven by oxidative stress and fibrosis. We previously showed that an activin A antagonist, follistatin, inhibited renal oxidative stress and fibrosis in a model of hypertensive chronic kidney disease. Here, we investigate the effects of follistatin on blood pressure and vascular structure and function in models of essential and secondary hypertension. 5/6 nephrectomised mice, a model of secondary hypertension, were treated with either exogenous follistatin or with a follistatin miRNA inhibitor to increase endogenous follistatin for 9 weeks. Blood pressure in mice was measured by tail cuff. Spontaneously hypertensive rats, a model of essential hypertension, were treated with follistatin for 8 weeks. Wistar Kyoto (WKY) rats were used as the normotensive control. Blood pressure in rats was measured by radiotelemetry. Mouse superior mesenteric arteries and rat first branch mesenteric arteries were isolated for structural and functional analyses. In both models, follistatin significantly lowered blood pressure and improved vascular structure, decreasing medial thickness and collagen content. Follistatin also reduced agonist-induced maximum contraction and improved endothelium-dependent relaxation. Increased vessel oxidative stress was attenuated by follistatin in both models. In ex vivo WKY vessels, activin A increased oxidative stress, augmented constriction, and decreased endothelium-dependent relaxation. Inhibition of oxidative stress restored vessel relaxation. This study demonstrates that follistatin lowers blood pressure and improves vascular structure and function in models of essential and secondary hypertension. Effects were likely mediated through its inhibition of activin A and oxidative stress. These data suggest a potential therapeutic role for follistatin as a novel antihypertensive agent. Follistatin, through antagonization of activin A, inhibits oxidative stress and improves vascular structure and function in resistance arteries from models of essential and secondary HTN. FST decreases collagen content and vascular ROS. Functionally, FST improves endothelium-dependent relaxation and decreases maximal vasoconstriction. Improved resistance artery structure and function are correlated with a decrease in BP in both models.

Perspectives on Sotatercept in Pulmonary Arterial Hypertension

Sotatercept acts as a type IIA-Fc activin receptor, thereby scavenging free activin from its physiological membrane receptor. Through this type of action, sotaterpect leads to a rebalancing of the proliferation and antiproliferation pathways of pulmonary smooth muscle cells in response to bone morphogenic protein (BMP). Although sotatercept has been approved as the fourth pillar of therapy for group 1 pulmonary arterial hypertension (PAH) in the United States and Europe, several studies are ongoing to broaden the application of the drug to non-Group 1 PAH. We provide an overview of the clinical and preclinical evidence of targeting the activation pathway by sotatercept in the treatment of PAH. We also discuss other potential applications of sotatercept in the context of pulmonary hypertension other than PAH group 1.

Quantifying Trophoblast Function Using the xCELLigence System

Analyses of trophoblast behavior in vitro are widely used to investigate and understand the trophoblast dysfunction associated with pregnancy pathologies. Key behaviors critical for trophoblast function include adhesion, proliferation, migration, and invasion. Traditionally, these behaviors have been measured using time-consuming single timepoint or endpoint assays. xCELLigence is a breakthrough technology that utilizes gold electrodes embedded in cell culture plates to collect electrical impedance measurements and monitor cell attachment, spreading, movement, and growth. It enables trophoblast functions to be quantitatively monitored in real-time, providing new insights into trophoblast behavior.

Association of activin A and postpartum blood pressure in peripartum cardiomyopathy

BACKGROUND

Activin A has been implicated in the pathogenesis of patients with chronic hypertension and heart failure as well as patients with hypertensive disorders of pregnancy (HDP). Whether activin A correlates with blood pressure in patients with peripartum cardiomyopathy (PPCM) and HDP history has not previously been explored.

METHODS AND RESULTS

82 women with PPCM w/ and w/out HDP or hypertension history were selected for analysis from the Investigations in Pregnancy Associated Cardiomyopathy (IPAC) study. Serum biomarkers and blood pressure were assessed at the time of enrollment (median postpartum day 24). Levels of both sFlt-1 (SBP: r 0.47, p = 0.008; DBP: r 0.57, p < 0.001) and activin A (SBP: r 0.59, p < 0.001;DBP: r 0.68, p < 0.001) were noted to significantly correlate with blood pressure in patients with a history of HDP who went on to develop PPCM, but not in patients with chronic hypertension or no hypertensive history. The strongest correlation was between activin A levels and postpartum diastolic blood pressure for the subset with preeclampsia (DBP: r0.82, p < 0.001). This remained significant in multivariable linear regression analysis (DBP: β = 0.011, p = 0.015).

CONCLUSION

In patients with PPCM, activin A and sFlt-1 levels had direct correlations with both systolic (SBP) and diastolic blood pressures (DBP), but only in participants with history of HDP. This correlation was more evident for activin A and strongest with a history of preeclampsia. Our findings suggest that activin A may play an important role in blood pressure modulation in women with HDP who subsequently develop PPCM.

Immune Markers, Blood Pressure Severity, and Cardiac Remodeling 1 to 2 Years After Hypertensive Disorders of Pregnancy

Background Cardiovascular dysfunction and hypertension can persist postpartum following hypertensive disorders of pregnancy (HDPs). This study hypothesized that activin A, proinflammatory markers and concentric remodeling by echo would be higher 1-2 years postpartum following HDP with persistent hypertension compared to HDP with normalized blood pressure (BP). We further hypothesized correlations between biomarkers with BP and echocardiographic indices. Methods and Results This study enrolled participants with HDPs but no prepregnancy hypertension followed 1 to 2 years after delivery. Activin A and inflammatory cytokines, BP, and echocardiograms were obtained. Biomarker concentrations and echocardiographic parameters were compared between HDP with and without persistent hypertension. Individuals with persistent hypertension at a mean of 1.6 years postpartum had significantly higher activin A concentrations (median[interquartile range 25-75] 230.6 [196.0-260.9] versus 175.3 pg/mL [164.3-188.4]; P<0.01), more concentric left ventricular concentric remodeling (relative wall thickness >0.42, 48% versus 7%; P<0.01), and worse peak left atrial strain (33.4% versus 39.3%; P<0.05) as compared with those whose BP normalized. Higher activin A and interleukin-6 concentrations correlated with higher systolic (activin A: r=0.43, P=0.01) and diastolic BP (activin A: r=0.58, P<0.01; interleukin-6: r=0.36; P<0.05), as well as greater left ventricular thickness (activin A and interventricular septal thickness: r=0.41, interleukin-6 and interventricular septal thickness: r=0.36; both P<0.05). Conclusions Individuals with HDPs and persistent hypertension had significantly higher activin A and greater concentric remodeling compared with those with HDPs and normalized BP at 1 to 2 years postpartum. Activin A was positively correlated with both BP and echocardiographic indices (left ventricular thickness), suggesting overlapping processes between persistent hypertension and cardiac remodeling.

Pressure Overload-Mediated Sustained PKR2 (Prokineticin-2 Receptor) Signaling in Cardiomyocytes Contributes to Cardiac Hypertrophy and Endotheliopathies

[Figure: see text].

Predictive and diagnostic biomarkers for gestational diabetes and its associated metabolic and cardiovascular diseases

Gestational diabetes mellitus (GDM) is defined as the presence of high blood glucose levels with the onset, or detected for the first time during pregnancy, as a result of increased insulin resistance. GDM may be induced by dysregulation of pancreatic β-cell function and/or by alteration of secreted gestational hormones and peptides related with glucose homeostasis. It may affect one out of five pregnancies, leading to perinatal morbidity and adverse neonatal outcomes, and high risk of chronic metabolic and cardiovascular injuries in both mother and offspring. Currently, GDM diagnosis is based on evaluation of glucose homeostasis at late stages of pregnancy, but increased age and body-weight, and familiar or previous occurrence of GDM, may conditionate this criteria. In addition, an earlier and more specific detection of GDM with associated metabolic and cardiovascular risk could improve GDM development and outcomes. In this sense, 1st-2nd trimester-released biomarkers found in maternal plasma including adipose tissue-derived factors such as adiponectin, visfatin, omentin-1, fatty acid-binding protein-4 and retinol binding-protein-4 have shown correlations with GDM development. Moreover, placenta-related factors such as sex hormone-binding globulin, afamin, fetuin-A, fibroblast growth factors-21/23, ficolin-3 and follistatin, or specific micro-RNAs may participate in GDM progression and be useful for its recognition. Finally, urine-excreted metabolites such as those related with serotonin system, non-polar amino-acids and ketone bodies, may complete a predictive or early-diagnostic panel of biomarkers for GDM.

Circulating Activin A Is a Surrogate for the Incidence of Diastolic Dysfunction and Heart Failure in Patients With Preserved Ejection Fraction

BACKGROUND

Diastolic dysfunction (DD) is a characteristic of heart failure with preserved ejection fraction (HFpEF), which is thought to be caused by cardiac hypertrophy or fibrosis. Activin A is involved in the inflammatory response and myocardial fibrosis, but the relationship between the activin A level and DD remains unclear.

METHODS AND RESULTS

A total of 209 patients with stable angina were enrolled. Serum activin A levels were assessed, and echocardiography and cross-sectional analysis were performed. Among the subjects (65% male; mean age, 70±13 years), 84 (40%) subjects had DD. The subjects were divided into tertiles based on activin A levels. Patients in the high activin A group had enhanced left ventricular mass indexes, medial E/e' ratios, left atrial diameter, and right ventricular systolic pressure compared with those in the lower activin A groups (all P<0.001). Prevalence of DD (P=0.001), HFpEF at enrollment (P=0.007), and the composite endpoints including new-onset heart failure (HF) or death within 3 years (P<0.001) correlated positively with high activin A levels. After adjusting for confounding factors, high activin A levels remained significantly associated with DD (P=0.036) and the composite endpoints (P=0.012).

CONCLUSIONS

Enhanced serum activin A levels were associated with the incidence of DD and development of HF.

The Role of Placental Hormones in Mediating Maternal Adaptations to Support Pregnancy and Lactation

During pregnancy, the mother must adapt her body systems to support nutrient and oxygen supply for growth of the baby in utero and during the subsequent lactation. These include changes in the cardiovascular, pulmonary, immune and metabolic systems of the mother. Failure to appropriately adjust maternal physiology to the pregnant state may result in pregnancy complications, including gestational diabetes and abnormal birth weight, which can further lead to a range of medically significant complications for the mother and baby. The placenta, which forms the functional interface separating the maternal and fetal circulations, is important for mediating adaptations in maternal physiology. It secretes a plethora of hormones into the maternal circulation which modulate her physiology and transfers the oxygen and nutrients available to the fetus for growth. Among these placental hormones, the prolactin-growth hormone family, steroids and neuropeptides play critical roles in driving maternal physiological adaptations during pregnancy. This review examines the changes that occur in maternal physiology in response to pregnancy and the significance of placental hormone production in mediating such changes.

The Association Between Serum Activin A Levels and Hypertension in the Elderly: A Cross-Sectional Analysis From I-Lan Longitudinal Aging Study

BACKGROUND

Hypertension is an important risk factor for cardiovascular disease. Activin A, a member of the transforming growth factor-β cytokine family, has been shown to regulate blood pressure through the renin-angiotensin system. However, the relationship between activin A and blood pressure remains uncertain. The objective of this study was to determine whether serum activin A levels are associated with blood pressure.

METHOD

A total of 470 participants of I-Lan longitudinal Aging Study (ILAS) were eligible for this study. Serum levels of activin A were assessed by enzyme-linked immunosorbent assay. Cross-sectional analyses were performed, including comparisons of demographic characteristics, hypertensive status, and activin A levels.

RESULTS

Among the study participants (50% men, mean age, 69 years), 236 (50.2%) were hypertensive and 234 (49.8%) were normotensive. Hypertensive patients had significantly higher serum activin A levels than normotensives (normotensive vs. hypertensive: 507 ± 169 vs. 554 ± 176 pg/ml, mean ± SD, P < 0.001). All subjects were divided into 3 tertiles on the basis of serum activin A levels. Increasing tertiles of activin A were associated with higher systolic blood pressure (SBP), diastolic blood pressure and pulse pressure (PP) (all P < 0.001). After adjusting for all the potential confounding factors, serum activin A concentration was still significantly associated with SBP (P = 0.02) and PP (P = 0.03).

CONCLUSIONS

Serum activin A level was associated with SBP and PP. Further studies are required to assess their causal relationship and the clinical relevance.

Decidual ACVR2A regulates extravillous trophoblast functions of adhesion, proliferation, migration and invasion in vitro

Decidual stromal cells form the largest proportion of maternal cells at the maternal-fetal interface. Our aim was to investigate the role of the pre-eclampsia associated decidual activin receptor, ACVR2A, in regulating trophoblast functions at this interface. St-T1b and HTR-8/SVneo cell lines were used to model decidual stromal and trophoblast cells respectively. St-T1b conditioned medium inhibited HTR-8/SVneo adhesion, proliferation, migration and invasion; all effects that were attenuated by decidual ACVR2A siRNA transfection. These findings suggest that altered decidual ACVR2A expression perturbs the maternal-fetal crosstalk involved in regulating trophoblast function at the interface, which may affect placentation and lead to pre-eclampsia.