Baktybek Kojonazarov

5-HT2B Receptor Antagonists Inhibit Fibrosis and Protect from RV Heart Failure

Objective. The serotonin (5-HT) pathway was shown to play a role in pulmonary hypertension (PH), but its functions in right ventricular failure (RVF) remain poorly understood. The aim of the current study was to investigate the effects of Terguride (5-HT2A and 2B receptor antagonist) or SB204741 (5-HT2B receptor antagonist) on right heart function and structure upon pulmonary artery banding (PAB) in mice. Methods. Seven days after PAB, mice were treated for 14 days with Terguride (0.2 mg/kg bid) or SB204741 (5 mg/kg day). Right heart function and remodeling were assessed by right heart catheterization, magnetic resonance imaging (MRI), and histomorphometric methods. Total secreted collagen content was determined in mouse cardiac fibroblasts isolated from RV tissues. Results. Chronic treatment with Terguride or SB204741 reduced right ventricular fibrosis and showed improved heart function in mice after PAB. Moreover, 5-HT2B receptor antagonists diminished TGF-beta1 induced collagen synthesis of RV cardiac fibroblasts in vitro. Conclusion. 5-HT2B receptor antagonists reduce collagen deposition, thereby inhibiting right ventricular fibrosis. Chronic treatment prevented the development and progression of pressure overload-induced RVF in mice. Thus, 5-HT2B receptor antagonists represent a valuable novel therapeutic approach for RVF.

Noninvasive and invasive evaluation of pulmonary arterial pressure in highlanders.

The purpose of the present study was to evaluate Doppler echocardiography for the detection of pulmonary hypertension in high-altitude inhabitants. In total, 60 (55 male) patients aged 18–71 yrs were recruited from an ECG screening programme applied to 1,430 inhabitants living at an altitude of 2,500–3,600 m in Kyrgyzstan. Of these, 44 met ECG criteria for right ventricular hypertrophy. All underwent Doppler echocardiography followed by a cardiac catheterisation within 7 days of arrival in Bishkek (Kyrgyzstan; altitude 760 m). Pulmonary flow acceleration time and the maximum velocity of tricuspid regurgitation were measured. Sufficient quality tricuspid regurgitant jets were recovered in only 28% of the patients. Therefore, pulmonary artery pressure was estimated from the pulmonary flow acceleration time, which was recovered in 100% of the patients. It was found that 37 (62%) of the patients had pulmonary hypertension on echocardiography. Pulmonary hypertension was confirmed in 29 patients on catheterisation. Pulmonary hypertension was detected with 70% sensitivity and 88% specificity by echocardiography, as compared to 59% sensitivity and 81 % specificity by ECG. The correlation coefficient between echocardiography and catheterisation studies was r2 = 0.78. It is concluded that a combination of ECG and echocardiography may be useful for screening high-altitude pulmonary hypertension.

ASK1 Inhibition Halts Disease Progression in Preclinical Models of Pulmonary Arterial Hypertension

Rationale: Progression of pulmonary arterial hypertension (PAH) is associated with pathological remodeling of the pulmonary vasculature and the right ventricle (RV). Oxidative stress drives the remodeling process through activation of MAPKs (mitogen‐activated protein kinases), which stimulate apoptosis, inflammation, and fibrosis. Objectives: We investigated whether pharmacological inhibition of the redox‐sensitive apical MAPK, ASK1 (apoptosis signal‐regulating kinase 1), can halt the progression of pulmonary vascular and RV remodeling. Methods: A selective, orally available ASK1 inhibitor, GS‐444217, was administered to two preclinical rat models of PAH (monocrotaline and Sugen/hypoxia), a murine model of RV pressure overload induced by pulmonary artery banding, and cellular models. Measurements and Main Results: Oral administration of GS‐444217 dose dependently reduced pulmonary arterial pressure and reduced RV hypertrophy in PAH models. The therapeutic efficacy of GS‐444217 was associated with reduced ASK1 phosphorylation, reduced muscularization of the pulmonary arteries, and reduced fibrotic gene expression in the RV. Importantly, efficacy was observed when GS‐444217 was administered to animals with established disease and also directly reduced cardiac fibrosis and improved cardiac function in a model of isolated RV pressure overload. In cellular models, GS‐444217 reduced phosphorylation of p38 and JNK (c‐Jun N‐terminal kinase) induced by adenoviral overexpression of ASK1 in rat cardiomyocytes and reduced activation/migration of primary mouse cardiac fibroblasts and human pulmonary adventitial fibroblasts derived from patients with PAH. Conclusions: ASK1 inhibition reduced pathological remodeling of the pulmonary vasculature and the right ventricle and halted progression of pulmonary hypertension in rodent models. These preclinical data inform the first description of a causal role of ASK1 in PAH disease pathogenesis.

Amplified canonical transforming growth factor-β signalling via heat shock protein 90 in pulmonary fibrosis

Interstitial lung fibroblast activation coupled with extracellular matrix production is a pathological signature of idiopathic pulmonary fibrosis (IPF), and is governed by transforming growth factor (TGF)-β/Smad signalling. We sought to define the role of heat shock protein (HSP)90 in profibrotic responses in IPF and to determine the therapeutic effects of HSP90 inhibition in a murine model of pulmonary fibrosis. We investigated the effects of HSP90 inhibition in vitro by applying 17-AAG (17-allylamino-17-demethoxygeldanamycin) to lung fibroblasts and A549 cells and in vivo by administering 17-DMAG (17-dimethylaminoethylamino-17-demethoxygeldanamycin) to mice with bleomycin-induced pulmonary fibrosis. HSP90 expression was increased in (myo)fibroblasts from fibrotic human and mouse lungs compared with controls. 17-AAG inhibited TGF-β1-induced extracellular matrix production and transdifferentiation of lung fibroblasts and epithelial–mesenchymal transition of A549 cells. The antifibrotic effects were associated with TGF-β receptor disruption and inhibition of Smad2/3 activation. Co-immunoprecipitation revealed that HSP90β interacted with TGF-β receptor II and stabilised TGF-β receptors. Furthermore, 17-DMAG improved lung function and decreased fibrosis and matrix metalloproteinase activity in the lungs of bleomycin-challenged mice. In conclusion, this is the first study to demonstrate that HSP90 inhibition blocks pulmonary fibroblast activation and ameliorates bleomycin-induced pulmonary fibrosis in mice. HSP90 inhibition might be a promising therapy option for PF by blocking exaggerated TGF-β/Smad signalling http://ow.ly/2iTe304ukgL

Effect of Riociguat and Sildenafil on Right Heart Remodeling and Function in Pressure Overload Induced Model of Pulmonary Arterial Banding

Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by remodeling of the pulmonary vasculature and a rise in right ventricular (RV) afterload. The increased RV afterload leads to right ventricular failure (RVF) which is the reason for the high morbidity and mortality in PAH patients. The objective was to evaluate the therapeutic efficacy and antiremodeling potential of the phosphodiesterase type 5 (PDE5) inhibitor sildenafil and the soluble guanylate cyclase stimulator riociguat in a model of pressure overload RV hypertrophy induced by pulmonary artery banding (PAB). Mice subjected to PAB, one week after surgery, were treated with either sildenafil (100 mg/kg/d, n = 5), riociguat (30 mg/kg/d, n = 5), or vehicle (n = 5) for 14 days. RV function and remodeling were assessed by right heart catheterization, magnetic resonance imaging (MRI), and histomorphometry. Both sildenafil and riociguat prevented the deterioration of RV function, as determined by a decrease in RV dilation and restoration of the RV ejection fraction (EF). Although both compounds did not decrease right heart mass and cellular hypertrophy, riociguat prevented RV fibrosis induced by PAB. Both compounds diminished TGF-beta1 induced collagen synthesis of RV cardiac fibroblasts in vitro. Treatment with either riociguat or sildenafil prevented the progression of pressure overload-induced RVF, representing a novel therapeutic approach.

JDP2 overexpression provokes cardiac dysfunction in mice

The transcriptional regulator JDP2 (Jun dimerization protein 2) has been identified as a prognostic marker for patients to develop heart failure after myocardial infarction. We now performed in vivo studies on JDP2-overexpressing mice, to clarify the impact of JDP2 on heart failure progression. Therefore, during birth up to the age of 4 weeks cardiac-specific JDP2 overexpression was prevented by doxycycline feeding in transgenic mice. Then, JDP2 overexpression was started. Already after 1 week, cardiac function, determined by echocardiography, decreased which was also resembled on the cardiomyocyte level. After 5 weeks blood pressure declined, ejection fraction and cardiac output was reduced and left ventricular dilatation developed. Heart weight/body weight, and mRNA expression of ANP, inflammatory marker genes, collagen and fibronectin increased. Collagen 1 protein expression increased, and fibrosis developed. As an additional sign of elevated extracellular matrix remodeling, matrix metalloproteinase 2 activity increased in JDP2 mice. Thus, JDP2 overexpression is deleterious to heart function in vivo. It can be concluded that JDP2 overexpression provokes cardiac dysfunction in adult mice that is accompanied by hypertrophy and fibrosis. Thus, induction of JDP2 is a maladaptive response contributing to heart failure development.

α1-A680T Variant in GUCY1A3 as a Candidate Conferring Protection From Pulmonary Hypertension Among Kyrgyz HighlandersCLINICAL PERSPECTIVE

Background—Human variation in susceptibility to hypoxia-induced pulmonary hypertension is well recognized. High-altitude residents who do not develop pulmonary hypertension may host protective gene mutations. Methods and Results—Exome sequencing was conducted on 24 unrelated Kyrgyz highlanders living 2400 to 3800 m above sea level, 12 (10 men; mean age, 54 years) with an elevated mean pulmonary artery pressure (mean±SD, 38.7±2.7 mm Hg) and 12 (11 men; mean age, 52 years) with a normal mean pulmonary artery pressure (19.2±0.6 mm Hg) to identify candidate genes that may influence the pulmonary vascular response to hypoxia. A total of 140 789 exomic variants were identified and 26 116 (18.5%) were classified as novel or rare. Thirty-three novel or rare potential pathogenic variants (frameshift, essential splice-site, and nonsynonymous) were found exclusively in either ≥3 subjects with high-altitude pulmonary hypertension or ≥3 highlanders with a normal mean pulmonary artery pressure. A novel missense mutation in GUCY1A3 in 3 subjects with a normal mean pulmonary artery pressure encodes an &agr;1-A680T soluble guanylate cyclase (sGC) variant. Expression of the &agr;1-A680T sGC variant in reporter cells resulted in higher cyclic guanosine monophosphate production compared with the wild-type enzyme and the purified &agr;1-A680T sGC exhibited enhanced sensitivity to nitric oxide in vitro. Conclusions—The &agr;1-A680T sGC variant may contribute to protection against high-altitude pulmonary hypertension and supports sGC as a pharmacological target for reducing pulmonary artery pressure in humans at altitude.

SILDENAFIL AND HYPOXIC PULMONARY HYPERTENSION

We have previously demonstrated that sildenafil inhibits hypoxia-induced pulmonary vasoconstriction in healthy subjects. The aim of this study was to investigate the effects of the PDE5 inhibitor sildena- fil on pulmonary hemodynamics in patients with high altitude pulmonary hypertension (HAPH). Twenty-two patients with HAPH were randomized by age and level of mean pulmonary arterial pressure (PAP) in 3 groups: a first group (n=9) treated with 25 mg of sildenafil 3 times a day; a second group (n=5) - received 100 mg of sildenafil 3 times a day; a third group (n=8) - treated with placebo. Pulmonary hemodynamics was measured by right heart catheterization at baseline and after 12 weeks of sildenafil therapy at, before and 1 hour after taking sildenafil or placebo. In the first group the mean PAP decreased after 12 weeks of sildenafil treatment from 36 ± 8 to 30 ± 8 mm Hg and to 25 ± 7 mm Hg (p <0.007) 1 hour after 25 mg of sildenafil, in the second group, mean PAP decreased after 12 weeks from 32 ± 3 to 26 ± 3 mm Hg (p <0.01) and to 21 ± 2 mm Hg (P <0.001) 1 hour after 100 mg of sildenafil, in the third group the mean PAP did not significantly change. Both doses improved the 6-minute walk distance, in the first group of patients by 45.4 m (p <0.01) and in the second group by 40.0 m (p <0.049). No side effects were observed. We conclude that sildenafil therapy decreases PAP and could be recommended for treatment of HAPH.