Search

Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and often death. Here we report that deficiency of transcription factor GATA6 is a shared pathological feature of PA endothelial (PAEC) and smooth muscle cells (PASMC) in human PAH and experimental PH, which is responsible for maintenance of hyper-proliferative cellular phenotypes, pulmonary vascular remodeling and pulmonary hypertension. We further show that GATA6 acts as a transcription factor and direct positive regulator of anti-oxidant enzymes, and its deficiency in PAH/PH pulmonary vascular cells induces oxidative stress and mitochondrial dysfunction. We demonstrate that GATA6 is regulated by the BMP10/BMP receptors axis and its loss in PAECs and PASMC in PAH supports BMPR deficiency. In addition, we have established that GATA6-deficient PAEC, acting in a paracrine manner, increase proliferation and induce other pathological changes in PASMC, supporting the importance of GATA6 in pulmonary vascular cell communication. Treatment with dimethyl fumarate resolved oxidative stress and BMPR deficiency, reversed hemodynamic changes caused by endothelial Gata6 loss in mice, and inhibited proliferation and induced apoptosis in human PAH PASMC, strongly suggesting that targeting GATA6 deficiency may provide a therapeutic advance for patients with PAH.

Objective: Rarefaction of blood and lymphatic vessels in the skin has been reported in systemic sclerosis (SSc) (scleroderma). E26 transformation–specific–related factor (ERG) and Friend leukemia virus–induced erythroleukemia 1 (FLI‐1) are important regulators of angiogenesis, but their role in lymphatic vasculature is lesser known. The goal of this study was to determine the role of ERG and FLI‐1 in postnatal lymphangiogenesis and SSc lymphatic system defects. Methods: Immunofluorescence was used to detect ERG and FLI‐1 in skin biopsy samples from patients with SSc and healthy controls. Transcriptional analysis of ERG or FLI‐1–silenced human dermal lymphatic endothelial cells (LECs) was performed using microarrays. Effects of ERG and FLI‐1 deficiency on in vitro tubulogenesis in human dermal LECs were examined using a Matrigel assay. ERG and FLI‐1 endothelial–specific knockouts and ERG lymphatic–specific knockouts were generated to examine vessel regeneration in mice. Results: ERG and FLI‐1 protein levels were reduced in the blood and lymphatic vasculature in SSc skin biopsy samples. ERG levels were shown to regulate genes involved in lymphatic vessel specification, including vascular endothelial growth factor receptor 3/FLT‐4, lymphatic vessel endothelial hyaluronan receptor 1, SOX‐18, and prospero homeobox 1 (PROX‐1), whereas FLI‐1 enhanced the function of ERG. The ERG–FLT‐4 pathway regulated in vitro tubulogenesis in human LECs. Deficiency of ERG or FLI‐1 similarly impaired the function of blood vessels in mice. However, only ERG deficiency affected the regeneration of lymphatic vessels during wound healing. Conclusion: ERG and FLI‐1 are essential regulators of blood and lymphatic vessel regeneration. Deficiency of ERG and FLI‐1 in SSc endothelial cells may contribute to the impairment of blood and lymphatic vasculature in patients with SSc. [ABSTRACT FROM AUTHOR]

Objectives: Friend leukemia integration 1 and erythroblast transformation‐specific, important regulators of endothelial cell homeostasis, are reduced in microvascular endothelial cells in scleroderma patients, and their deficiency has been implicated in disease pathogenesis. The goal of this study was to identify the mechanisms involved in the protein turnover of friend leukemia integration 1 and erythroblast transformation‐specific in microvascular endothelial cells. Methods: The effects of lysosome and proteosome inhibitors on friend leukemia integration 1 and erythroblast transformation‐specific levels were assessed by Western blotting and capillary morphogenesis. The effect of scleroderma and control sera on the levels of friend leukemia integration 1 and erythroblast transformation‐specific was examined. Results: The reduction in the protein levels of friend leukemia integration 1 and erythroblast transformation‐specific in response to interferon α or Poly:(IC) was reversed by blocking either lysosomal (leupeptin and Cathepsin B inhibitor) or proteosomal degradation (MG132). MG132, leupeptin or CTSB‐(i) also counteracted the anti‐angiogenic effects of Poly:(IC) or interferon α. Scleroderma sera reduced protein levels of friend leukemia integration 1 and erythroblast transformation‐specific in comparison to control sera. Treatment with CTSB(i) increased the levels of friend leukemia integration 1 and erythroblast transformation‐specific in a majority of serum‐treated samples. Conclusions: Inhibition of cathepsin B was effective in reversing the reduction of friend leukemia integration 1 and erythroblast transformation‐specific protein levels after treatment with interferon α or scleroderma sera, suggesting that targeting cathepsin B may have a beneficial effect in SSc vascular disease. [ABSTRACT FROM AUTHOR]