An emerging strategy for targeted therapy of pulmonary arterial hypertension: vasodilation plus vascular remodeling inhibition

Contribution of pressure and flow changes to resistance reduction after pulmonary arterial hypertension treatment: a meta-analysis of 3898 patients

Background

Pulmonary arterial hypertension (PAH)-targeted therapies exert significant haemodynamic changes; however, systematic synthesis is currently lacking.

Methods

We searched PubMed, CENTRAL and Web of Science for studies evaluating mean pulmonary artery pressure (mPAP), cardiac index/cardiac output (CI/CO) and pulmonary vascular resistance (PVR) of PAH-targeted therapies either in monotherapy or combinations as assessed by right heart catheterisation in treatment-naïve PAH patients. We performed a random-effects meta-analysis with meta-regression.

Results

We included 68 studies (90 treatment groups) with 3898 patients (age 47.4±13.2 years, 74% women). In studies with small PVR reduction (<4 WU), CI/CO increase (R2=62%) and not mPAP reduction (R2=24%) was decisive for the PVR reduction (p<0.001 and p=0.36, respectively, in the multivariable meta-regression model); however, in studies with large PVR reduction (>4 WU), both CI/CO increase (R2=72%) and mPAP reduction (R2=35%) contributed significantly to the PVR reduction (p<0.001 and p=0.01, respectively). PVR reduction as a percentage of the pre-treatment value was more pronounced in the oral+prostanoid intravenous/subcutaneous combination therapy (mean difference -50.0%, 95% CI -60.8- -39.2%), compared to oral combination therapy (-41.7%, -47.6- -35.8%), prostanoid i.v./s.c. monotherapy (-31.8%, -37.6- -25.9%) and oral monotherapy (-21.6%, -25.4- -17.8%). Changes in haemodynamic parameters were significantly associated with changes in functional capacity of patients with PAH as expressed by the 6-min walking distance.

Conclusion

Combination therapies, especially with the inclusion of parenteral prostanoids, lead to remarkable haemodynamic improvement in treatment-naïve PAH patients and may unmask the contribution of mPAP reduction to the overall PVR reduction in addition to the increase in CO.

Inhibition of Hsp110-STAT3 interaction in endothelial cells alleviates vascular remodeling in hypoxic pulmonary arterial Hypertension model

BACKGROUND

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary vascular remodeling which is associated with the malignant phenotypes of pulmonary vascular cells. Recently, the effects of heat shock protein 110 (Hsp110) in human arterial smooth muscle cells were reported. However, the underlying roles and mechanisms of Hsp110 in human pulmonary arterial endothelial cells (HPAECs) that was disordered firstly at the early stage of PAH remain unknown.

METHODS

In this research, the expression of Hsp110 in PAH human patients and rat models was investigated, and the Hsp110 localization was determined both in vivo and in vitro. The roles and mechanism of elevated Hsp110 in excessive cell proliferation and migration of HPAECs were assessed respectively exposed to hypoxia. Small molecule inhibitors targeting Hsp110-STAT3 interaction were screened via fluorescence polarization, anti-aggregation and western blot assays. Moreover, the effects of compound 6 on HPAECs abnormal phenotypes in vitro and pulmonary vascular remodeling of hypoxia-indued PAH rats in vivo by interrupting Hsp110-STAT3 interaction were evaluated.

RESULTS

Our studies demonstrated that Hsp110 expression was increased in the serum of patients with PAH, as well as in the lungs and pulmonary arteries of PAH rats, when compared to their respective healthy subjects. Moreover, Hsp110 levels were significantly elevated in HPAECs under hypoxia and mediated its aberrant phenotypes. Furthermore, boosted Hsp110-STAT3 interaction resulted in abnormal proliferation and migration via elevating p-STAT3 and c-Myc in HPAECs. Notably, we successfully identified compound 6 as potent Hsp110-STAT3 interaction inhibitor, which effectively inhibited HPAECs proliferation and migration, and significantly ameliorated right heart hypertrophy and vascular remodeling of rats with PAH.

CONCLUSIONS

Our studies suggest that elevated Hsp110 plays a vital role in HPAECs and inhibition of the Hsp110-STAT3 interaction is a novel strategy for improving vascular remodeling. In addition, compound 6 could serve as a promising lead compound for developing first-in-class drugs against PAH.

Allicin, an Emerging Treatment for Pulmonary Arterial Hypertension: An Experimental Study

We assessed whether allicin, through its antihypertensive and antioxidant effects, relieves vascular remodeling, endothelial function, and oxidative stress (OS), thereby improving experimental pulmonary arterial hypertension (PAH). Allicin (16 mg/kg) was administered to rats with PAH (monocrotaline 60 mg/kg). Allicin encouraged body weight gain and survival rate, and medial wall thickness and the right ventricle (RV) hypertrophy were prevented. Also, angiotensin II concentrations in the lung (0.37 ± 0.01 vs. 0.47 ± 0.06 pmoles/mL, allicin and control, respectively) and plasma (0.57 ± 0.05 vs. 0.75 ± 0.064, allicin and control respectively) and the expressions of angiotensin-converting enzyme II and angiotensin II type 1 receptor in lung tissue were maintained at normal control levels with allicin. In PAH rats treated with allicin, nitric oxide (NO) (31.72 ± 1.22 and 51.4 ± 3.45 pmoles/mL), tetrahydrobiopterin (8.43 ± 0.33 and 10.14 ± 0.70 pmoles/mL), cyclic guanosine monophosphate (5.54 ± 0.42 and 5.64 ± 0.73 pmoles/mL), and Ang-(1-7) (0.88 ± 0.23 and 0.83 ± 0.056 pmoles/mL) concentrations increased in lung tissue and plasma, respectively. In contrast, dihydrobiopterin increase was prevented in both lung tissue and plasma (5.75 ± 0.3 and 5.64 ± 0.73 pmoles/mL); meanwhile, phosphodiesterase-5 was maintained at normal levels in lung tissue. OS in PAH was prevented with allicin through the increased expression of Nrf2 in the lung. Allicin prevented the lung response to hypoxia, preventing the overexpression of HIF-1α and VEGF. Allicin attenuated the vascular remodeling and RV hypertrophy in PAH through its effects on NO-dependent vasodilation, modulation of RAS, and amelioration of OS. Also, these effects could be associated with the modulation of HIF-1α and improved lung oxygenation. The global effects of allicin contribute to preventing endothelial dysfunction, remodeling of the pulmonary arteries, and RV hypertrophy, preventing heart failure, thus favoring survival. Although human studies are needed, the data suggest that, alone or in combination therapy, allicin may be an alternative in treating PAH if we consider that, similarly to current treatments, it improves lung vasodilation and increase survival. Allicin may be considered an option when there is a lack of efficacy, and where drug intolerance is observed, to enhance the efficacy of drugs, or when more than one pathogenic mechanism must be addressed.

TNF-α and IL-8 levels are positively correlated with hypobaric hypoxic pulmonary hypertension and pulmonary vascular remodeling in rats

The expression status of proinflammatory cytokines in high-altitude pulmonary arterial hypertension (PAH) has been well studied. However, the changes in interleukin (IL)-8 and tumor necrosis factor α (TNF-α) during the reversible changes in pulmonary vascular remodeling (PVR) in PAH after detaching from a hypobaric hypoxic environment have not been elucidated. This investigation elucidated a high-altitude PAH rat model. Then, PAH rats in the high-altitude group were maintained in the high-altitude area, and rats in the low-altitude group returned to the low-altitude area. After 0, 10, 20, and 30 days of PAH modeling, right ventricular systolic pressure (RVSP) and the mean pulmonary arterial pressure (mPAP) were assessed. Right ventricular (RV) hypertrophy was reflected by the ratio of RV/[left ventricle + interventricular septum (S)]. Pathological changes in PVR were accessed by hematoxylin-eosin staining, and medial wall thickness (WT%) and medial wall area (WA%) were measured. TNF-α and IL-8 levels in pulmonary artery tissues and blood were measured with Western blot assay and enzyme-linked immunosorbent assay, respectively. Our results showed that PAH rats exhibited a substantial increase in RVSP and mPAP, RV hypertrophy, PVR, and enhanced generation of TNF-α and IL-8. Then, we found that these pathological changes were gradually aggravated and TNF-α and IL-8 levels were increased in rats in the high-altitude group after 10, 20, and 30 days of PAH modeling. In contrast, the mPAP was decreased and PVR was alleviated in rats in the low-altitude group, accompanying with reduced TNF-α and IL-8 production. In conclusion, our study demonstrated that the generation of TNF-α and IL-8 was also reversible during the reversible changes in PVR after detaching from a hypobaric hypoxic environment. Thus, proinflammatory cytokine TNF-α and IL-8 levels are positively correlated with PVR severity.

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

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

Radiation-induced cardiac side-effects: The lung as target for interacting damage and intervention

Radiotherapy is part of the treatment for many thoracic cancers. During this treatment heart and lung tissue can often receive considerable doses of radiation. Doses to the heart can potentially lead to cardiac effects such as pericarditis and myocardial fibrosis. Common side effects after lung irradiation are pneumonitis and pulmonary fibrosis. It has also been shown that lung irradiation has effects on cardiac function. In a rat model lung irradiation caused remodeling of the pulmonary vasculature increasing resistance of the pulmonary vascular bed, leading to enhanced pulmonary artery pressure, right ventricle hypertrophy and reduced right ventricle performance. Even more pronounced effects are observed when both, lung and heart are irradiated.

The effects observed after lung irradiation show striking similarities with symptoms of pulmonary arterial hypertension. In particular, the vascular remodeling in lung tissue seems to have similar underlying features. Here, we discuss the similarities and differences of vascular remodeling observed after thoracic irradiation compared to those in pulmonary arterial hypertension patients and research models. We will also assess how this knowledge of similarities could potentially be translated into interventions which would be beneficial for patients treated for thoracic tumors, where dose to lung tissue is often unavoidable.