Mutations of BMPR2 and other TGF-β superfamily genes have been reported in pulmonary arterial hypertension (PAH). However, 60–90% of idiopathic PAH cases have no mutations in these genes. Recently, the expression of NOTCH3 was shown to be increased in the pulmonary artery smooth muscle cells of PAH patients. We sought to investigate NOTCH3 and its target genes in PAH patients and clarify the role of NOTCH3 signaling. We screened for mutations in NOTCH3, HES1, and HES5 in 41 PAH patients who had no mutations in BMPR2, ALK1, endoglin, SMAD1/4/8, BMPR1B, or Caveolin-1. Two novel missense mutations (c.2519 G>A p.G840E, c.2698 A>C p.T900P) in NOTCH3 were identified in two PAH patients. We performed functional analysis using stable cell lines expressing either wild-type or mutant NOTCH3. The protein-folding chaperone GRP78/BiP was colocalized with wild-type NOTCH3 in the endoplasmic reticulum, whereas the majority of GRP78/BiP was translocated into the nuclei of cells expressing mutant NOTCH3. Cell proliferation and viability were higher for cells expressing mutant NOTCH3 than for those expressing wild-type NOTCH3. We identified novel NOTCH3 mutations in PAH patients and revealed that these mutations were involved in cell proliferation and viability. NOTCH3 mutants induced an impairment in NOTCH3-HES5 signaling. The results may contribute to the elucidation of PAH pathogenesis.

BackgroundPulmonary hypertension (PH) is a serious disease with poor prognosis. Reports show that cells in remodeled pulmonary arteries of PH patients have similar characteristics to cancer cells, such as exuberant inflammation, increased proliferation, and decreased apoptosis. An ideal strategy for developing PH therapies is to directly target pulmonary vascular remodeling. High levels of histone deacetylase (HDAC) expression and activity are found in certain cancers, and research has shown the potential of HDAC inhibitors in repressing tumor growth via anti-inflammatory and anti-proliferative effects. To date, little is known about the effectiveness of HDAC inhibitors against pulmonary vascular remodeling in severe PH.ObjectiveTo investigate whether class I HDAC inhibitors suppress or reverse the development of severe PH in rats.MethodsMale Sprague-Dawley rats were injected with a single, subcutaneous dose of monocrotaline (60mg/kg), and were exposed to chronic hypoxia to induce severe PH. Valproic acid, a class I HDAC inhibitor, was administered to rats daily via gastric gavage (300mg/kg) in a PH prevention study (during the first 3 weeks) or a PH reversal study (from 3 to 5 weeks). At the end of experiment, hemodynamic indices were measured, ventricular hypertrophy indices were calculated and vascular remodeling phenotypes were analyzed. Results: After 3 weeks exposure to a combined stimulation of monocrotaline and chronic hypoxia, rats exhibited a reduced body weight, elevated right ventricular systolic pressure, an increased Fulton index, right ventricle weight ratio, medial wall thickness and muscularized peripheral pulmonary arteries. These parameters for PH evaluation were exacerbated from 3 to 5 weeks. Daily administration of valproic acid therapy prevented and partially reversed the development of severe PH in rats, and decreased inflammation and proliferation in remodeled pulmonary arteries.ConclusionThese data show that class I HDAC inhibitors may be effective for treating severe PH.

The authors apologize for the age of proband B and that of her father were incorrect. The correct information is given below.

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Pulmonary arterial hypertension (PAH) is a severe and fatal clinical syndrome. C-X-C chemokine receptor type 4 (CXCR4) is known to serve a key role in recruiting mesenchymal stem cells (MSCs) from the bone marrow. In the present study, a rat model of PAH induced by 5 weeks of chronic hypoxia and treatment with a single injection of monocrotaline (60 mg/kg) was used to investigate the involvement of CXCR4 in PAH. Successful establishment of the PAH model was confirmed by significant differences between the PAH and control groups in right ventricular systolic pressure, Fulton index, wall thickness, vascular occlusion score determined by immunohistochemical staining and the expression of inflammatory markers measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression of CXCR4 and other stem cell markers were compared in the PAH and control groups. RT-qPCR showed that the expression of CXCR4, SCF, c-Kit, and CD29, which are expressed in MSCs, was significantly higher in the PAH group. Immunohistochemical staining also showed that the numbers of CXCR4-, c-Kit- and CD90-positive cells were significantly higher in the PAH group. These results suggest that CXCR4 is involved in the pathogenesis of PAH and that stem cells may serve an important role in pulmonary vascular remodeling.