Background-Mutations in the bmpr2 gene, encoding the type II bone morphogenetic protein (BMP) receptor, have been identified in patients with pulmonary arterial hypertension (PAH), implicating BMP signaling in PAH. The aim of this study was to assess BMP signaling and its physiological effects in a monocrotaline (MCT) model of PAH. Methods and Results-Expression of BMP receptors Ib and II, and Smads 4, 5, 6, and 8, was downregulated in lungs but not kidneys of MCT-treated rats. Smad1 phosphorylation and expression of BMP/Smad target genes id1 and id3 was also reduced, although ERK1/2 and p38 MAPK phosphorylation remained unaffected. BMP receptor and Smad expression, Smad1 phosphorylation, and induction of the BMP/Smad-responsive element of the id1 promoter were reduced in pulmonary artery smooth muscle cells (PASMCs) from MCT-treated rats. As a consequence of impaired BMP/Smad signaling, PASMCs from MCT-treated rats were resistant to apoptosis induced by BMP-4 and BMP-7, and were also resistant to BMP-4 antagonism of proliferation induced by platelet-derived growth factor. Conclusion-BMP signaling and BMP-regulated physiological phenomena are perturbed in MCT-treated rats, lending solid support to the proposed roles for BMP signaling in the pathogenesis of human PAH.

Significance The acute respiratory distress syndrome (ARDS) is a devasting clinical problem with high mortality, no drug therapy, and poorly understood pathogenesis. The hallmark of ARDS is persistent pulmonary edema, attributable in part to impaired Na + and fluid transport across the alveolo-capillary barrier, undertaken by the epithelial sodium channel (ENaC). We describe a unique signaling pathway driven by TGF-β, which acutely dysregulates ENaC trafficking, blocking alveolar Na + transport and edema resolution. This pathway represents a unique pathomechanism in ARDS, highlights potential “druggable” targets, and may represent a physiological means of acutely regulating ENaC in lungs and other organs.

Biotin in breakdown products of biotinylated carboxylases serves as substrate for biotinylation of histones by biotinidase. Here we determined whether biotinylation of histones might play a role in repair of damaged DNA and in apoptosis. Jurkat cells were exposed to UV light to induce DNA damage. Abundance of thymine dimers increased about three times in response to UV exposure, consistent with DNA damage. Biotin-containing carboxylases were degraded in response to UV exposure, as judged by Western blot analysis and carboxylase activities. Mitochondrial integrity decreased in response to UV exposure (as judged by confocal microscopy), facilitating the release of breakdown products of carboxylases from mitochondria. Biotinylation of histones increased in response to UV exposure; biotinylation of histones did not occur specifically at sites of newly repaired DNA. UV exposure triggered apoptosis, as judged by caspase-3 activity and analysis by confocal microscopy. In summary, this study provided evidence that increased biotinylation of histones in DNA-damaged cells might either be a side product of carboxylase degradation or a step during apoptosis.

Nestin, a well-known marker of neuronal stem cells, was recently suggested to characterise stem cell-like progenitors in non-neuronal structures during development and tissue repair. Integrating novel morphological approaches (CLARITY), we investigate whether nestin expression defines the proliferating cell population that essentially drives vascular remodelling during development of pulmonary hypertension. The role of nestin was investigated in lungs of nestin-GFP (green fluorescent protein) mice, models of pulmonary hypertension (rat: monocrotaline, SU5416/hypoxia; mouse: hypoxia), samples from pulmonary hypertension patients and human pulmonary vascular smooth muscle cells (VSMCs). Nestin was solely found in lung vasculature and localised to proliferating VSMCs, but not bronchial smooth muscle cells. Nestin was shown to affect cell number and was significantly enhanced in lungs early during development of pulmonary hypertension, correlating well with increased VSMC proliferation, expression of phosphorylated (activated) platelet-derived growth factor receptor β and downregulation of the smooth muscle cell differentiation marker calponin. At later time points when pulmonary hypertension became clinically evident, nestin expression and proliferation returned to control levels. Increase of nestin-positive VSMCs was also found in human pulmonary hypertension, both in vessel media and neointima. Nestin expression seems to be obligatory for VSMC proliferation, and specifies lung vascular wall cells that drive remodelling and (re-)generation. Our data promise novel diagnostic tools and therapeutic targets for pulmonary hypertension.

Pulmonary hypertension (PH) is a disease with a poor prognosis characterized by a vascular remodeling process and an increase in pulmonary vascular resistance. While a variety of reports demonstrated that exercise training exerts beneficial effects on exercise performance and quality of life in PH patients, it is not known how physical exercise affects vascular remodeling processes occurring in hypoxia-induced PH. Therefore, we investigated the effect of individualized exercise training on the development of hypoxia-induced PH in mice. Training effects were compared with pharmacological treatment with the phosphodiesterase 5 inhibitor Sildenafil or a combination of training plus Sildenafil. Trained mice who received Sildenafil showed a significantly improved walking distance (from 88.9 ± 8.1 to 146.4 ± 13.1 m) and maximum oxygen consumption (from 93.3 ± 2.9 to 105.5 ± 2.2% in combination with Sildenafil, to 102.2 ± 3.0% with placebo) compared with sedentary controls. Right ventricular systolic pressure, measured by telemetry, was at the level of healthy normoxic animals, whereas right heart hypertrophy did not benefit from training. Most interestingly, the increase in small pulmonary vessel muscularization was prevented by training. Respective counterregulatory processes were detected for the nitric oxide-soluble guanylate cyclase-phosphodiesterase system. We conclude that individualized daily exercise can prevent vascular remodeling in hypoxia-induced PH.

Our previous findings demonstrated an increase in pulmonary mast cells (MCs) in idiopathic pulmonary arterial hypertension (IPAH). Also, literature suggests a potential role for MCs in chronic obstructive pulmonary disease (COPD). However, a comprehensive investigation of lungs from patients is still needed. We systematically investigated the presence/expression of MCs/MC chymase in the lungs of IPAH and COPD patients by (immuno)histochemistry and subsequent quantification. We found that total and perivascular chymase-positive MCs were significantly higher in IPAH patients than in donors. In addition, chymase-positive MCs were located in proximity to regions with prominent expression of big-endothelin-1 in the pulmonary vessels of IPAH patients. Total and perivascular MCs around resistant vessels were augmented and a significant majority of them were degranulated (activated) in COPD patients. While the total chymase-positive MC count tended to increase in COPD patients, the perivascular number was significantly enhanced in all vessel sizes analyzed. Surprisingly, MC and chymase-positive MC numbers positively correlated with better lung function in COPD. Our findings suggest that activated MCs, possibly by releasing chymase, may contribute to pulmonary vascular remodeling in IPAH. Pulmonary MCs/chymase may have compartment-specific (vascular vs. airway) functions in COPD. Future studies should elucidate the mechanisms of MC accumulation and the role of MC chymase in pathologies of these severe lung diseases.

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The accuracy of indirect oscillometric blood pressure measurements has been evaluated in 32 infants up to 11 months of age undergoing heart surgery. In a number of 1029 simultaneous measurements the indirect blood pressure was compared with the direct value obtained from a radial artery catheter. Cuffs of different sizes were applied. The main results were as follows: Regarding the ratio of cuff width to arm circumference, the best correlation between oscillometric and direct blood pressure measurements was obtained with a ratio of 0.38-0.41. The value of indirect blood pressure measurements depends on the absolute height of the blood pressure. In low blood pressure there is a tendency to underestimate and in high blood pressure there is a tendency to overestimate by the oscillometric blood pressure measurement. By applying an appropriate cuff size and by using our diagrams it should be possible to derive a direct value for the blood pressure on the basis of indirect oscillometric blood pressure measurements.