Early treatment with fumagillin, an inhibitor of methionine aminopeptidase-2, prevents Pulmonary Hypertension in monocrotaline-injured rats.

Pulmonary Hypertension (PH) is a pathophysiologic condition characterized by hypoxemia and right ventricular strain. Proliferation of fibroblasts, smooth muscle cells, and endothelial cells is central to the pathology of PH in animal models and in humans. Methionine aminopeptidase-2 (MetAP2) regulates proliferation in a variety of cell types including endothelial cells, smooth muscle cells, and fibroblasts. MetAP2 is inhibited irreversibly by the angiogenesis inhibitor fumagillin. We have previously found that inhibition of MetAP2 with fumagillin in bleomycin-injured mice decreased pulmonary fibrosis by selectively decreasing the proliferation of lung myofibroblasts. In this study, we investigated the role of fumagillin as a potential therapy in experimental PH. In vivo, treatment of rats with fumagillin early after monocrotaline injury prevented PH and right ventricular remodeling by decreasing the thickness of the medial layer of the pulmonary arteries. Treatment with fumagillin beginning two weeks after monocrotaline injury did not prevent PH but was associated with decreased right ventricular mass and decreased cardiomyocyte hypertrophy, suggesting a direct effect of fumagillin on right ventricular remodeling. Incubation of rat pulmonary artery smooth muscle cells (RPASMC) with fumagillin and MetAP2-targeting siRNA inhibited proliferation of RPASMC in vitro. Platelet-derived growth factor, a growth factor that is important in the pathogenesis of PH and stimulates proliferation of fibroblasts and smooth muscle cells, strongly increased expression of MetP2. By immunohistochemistry, we found that MetAP2 was expressed in the lesions of human pulmonary arterial hypertension. We propose that fumagillin may be an effective adjunctive therapy for treating PH in patients.

Functional effects of the TMEM43 Ser358Leu mutation in the pathogenesis of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: The Ser358Leu mutation in TMEM43, encoding an inner nuclear membrane protein, has been implicated in arrhythmogenic right ventricular cardiomyopathy (ARVC). The pathogenetic mechanisms of this mutation are poorly understood. METHODS: To determine the frequency of TMEM43 mutations as a cause of ARVC, we screened 11 ARVC families for mutations in TMEM43 and five desmosomal genes previously implicated in the disease. Functional studies were performed in COS-7 cells transfected with wildtype, mutant, and 1:2 wildtype:mutant TMEM43 to determine the effect of the Ser358Leu mutation on the stability and cellular localization of TMEM43 and other nuclear envelope and desmosomal proteins, assessed by solubility assays and immunofluorescence imaging. mRNA expression was assessed of genes potentially affected by dysfunction of the nuclear lamina. RESULTS: Three novel mutations in previously documented desmosomal genes, but no mutations in TMEM43, were identified. COS-7 cells transfected with mutant TMEM43 exhibited no change in desmosomal stability. Stability and nuclear membrane localization of mutant TMEM43 and of lamin B and emerin were normal. Mutant TMEM43 did not alter the expression of genes located on chromosome 13, previously implicated in nuclear envelope protein mutations leading to skeletal muscular dystrophies. CONCLUSIONS: Mutant TMEM43 exhibits normal cellular localization and does not disrupt integrity and localization of other nuclear envelope and desmosomal proteins. The pathogenetic role of TMEM43 mutations in ARVC remains uncertain.

Genomewide RNA expression profiling in lung identifies distinct signatures in idiopathic pulmonary arterial hypertension and secondary pulmonary hypertension.

Idiopathic pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by pulmonary arteriolar remodeling. This investigation aimed to identify genes involved specifically in the pathogenesis of PAH and not other forms of pulmonary hypertension (PH). Using genomewide microarray analysis, we generated the largest data set to date of RNA expression profiles from lung tissue specimens from 1) 18 PAH subjects and 2) 8 subjects with PH secondary to idiopathic pulmonary fibrosis (IPF) and 3) 13 normal subjects. A molecular signature of 4,734 genes discriminated among these three cohorts. We identified significant novel biological changes that were likely to contribute to the pathogenesis of PAH, including regulation of actin-based motility, protein ubiquitination, and cAMP, transforming growth factor-beta, MAPK, estrogen receptor, nitric oxide, and PDGF signaling. Bone morphogenic protein receptor type II expression was downregulated, even in subjects without a mutation in this gene. Women with PAH had higher expression levels of estrogen receptor 1 than normal women. Real-time quantitative PCR confirmed differential expression of the following genes in PAH relative to both normal controls and PH secondary to IPF: a disintegrin-like and metalloprotease with thrombospondin type 1 motif 9, cell adhesion molecule with homology to L1CAM, cytochrome b(558) and beta-polypeptide, coagulation factor II receptor-like 3, A-myb myeloblastosis viral oncogene homolog 1, nuclear receptor coactivator 2, purinergic receptor P2Y, platelet factor 4, phospholamban, and tropomodulin 3. This study shows that PAH and PH secondary to IPF are characterized by distinct gene expression signatures, implying distinct pathophysiological mechanisms.