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Int. J. Mol. Sci. 2017, 18(11), 2290; https://doi.org/10.3390/ijms18112290

Endothelial Mesenchymal Transition in Hypoxic Microvascular Endothelial Cells and Paracrine Induction of Cardiomyocyte Apoptosis Are Mediated via TGFβ1/SMAD Signaling

Institute of Physiology, Justus Liebig University, 35392 Giessen, Germany
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Received: 30 September 2017 / Revised: 24 October 2017 / Accepted: 30 October 2017 / Published: 31 October 2017
(This article belongs to the Special Issue TGF-beta Family in Fibrosis and Cancer)
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Abstract

Cardiac remodeling plays a crucial role in the development of heart failure after mycocardial infarction. Besides cardiomyocytes, endothelial cells are recognized to contribute to cardiac remodeling. We now investigated processes of endothelial mesenchymal transition (EndoMT) in microvascular endothelial cells of rat (MVEC) under hypoxia and paracrine effects on ventricular cardiomyocytes of adult rat. Exposure of MVECs to hypoxia/reoxygenation enhanced TGFβ/SMAD signaling, since phosphorylation, and thus activation, of SMAD1/5 and SMAD2 increased. This increase was blocked by inhibitors of TGFβ receptor types ALK1 or ALK5. Exposure of ventricular cardiomyocytes to conditioned medium from hypoxic/reoxygenated MVECs enhanced SMAD2 phosphorylation and provoked apoptosis in cardiomyoyctes. Both were blocked by ALK5 inhibition. To analyze autocrine effects of hypoxic TGFβ signaling we investigated EndoMT in MVECs. After 3 days of hypoxia the mesenchymal marker protein α-smooth muscle actin (α-SMA), and the number of α-SMA- and fibroblast specific protein 1 (FSP1)-positive cells increased in MVECs cultures. This was blocked by ALK5 inhibition. Similarly, TGFβ1 provoked enhanced expression of α-SMA and FSP1 in MVECs. In conclusion, hypoxia provokes EndoMT in MVECs via TGFβ1/SMAD2 signaling. Furthermore, release of TGFβ1 from MVECs acts in a paracrine loop on cardiomyocytes and provokes apoptotic death. Thus, in myocardial infarction hypoxic endothelial cells may contribute to cardiac remodeling and heart failure progression by promotion of cardiac fibrosis and cardiomyocytes death. View Full-Text
Keywords: fibrosis; TGFβ; ischemia; cardiac remodeling; endothelial cells; cardiomyocytes; apoptosis fibrosis; TGFβ; ischemia; cardiac remodeling; endothelial cells; cardiomyocytes; apoptosis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Sniegon, I.; Prieß, M.; Heger, J.; Schulz, R.; Euler, G. Endothelial Mesenchymal Transition in Hypoxic Microvascular Endothelial Cells and Paracrine Induction of Cardiomyocyte Apoptosis Are Mediated via TGFβ1/SMAD Signaling. Int. J. Mol. Sci. 2017, 18, 2290.

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