Extracellular HtrA2 Induces Apoptosis in Human Umbilical Vein Endothelial Cells.

Kaur Kaur,Duerschmied Duerschmied,Stallmann Stallmann,Moser Moser,Ahrens Ahrens,Peter Peter,Laumann Laumann,Bode Bode,Stachon Stachon,Steinfurt Steinfurt,Hortmann Hortmann,Schanze Schanze,Heger Heger

doi:10.3390/ijms20215446

Abstract

The serine protease high-temperature-required protein A2 (HtrA2) has been identified as a key intracellular molecule promoting apoptosis in cells during ischemia reperfusion (IR) injury. IR injury in ST-segment elevation myocardial infarction (STEMI) contributes to overall myocardial damage. HtrA2 has further been shown to be significantly increased in the serum of patients with STEMI. In the present pilot study, we use human umbilical vein endothelial cells (HUVECs) to investigate whether extracellular HtrA2 induces apoptosis using Annexin V staining. Furthermore, we examine whether HtrA2 is released extracellularly after staurosporine-induced apoptosis using ELISA. We find that HtrA2 is released upon induction of apoptosis by staurosporine into the cell culture medium. Furthermore, treatment of HUVECs with extracellular HtrA2-induces apoptosis, while the addition of anti-HtrA2 antibodies reduces both HtrA2- and staurosporine-induced endothelial cell apoptosis. In conclusion, we show here that extracellular HtrA2 induces apoptosis in human endothelial cells, although the exact molecular mechanisms have to be investigated in future.

Highlights

According to the World Health Organization’s report of 2016 ischemic heart disease is the major cause of death globally [1]
Staurosporine induction of apoptosis significantly increased high-temperature-required protein A2 (HtrA2) in the culture medium of human umbilical vein endothelial cells (HUVECs) (Figure 1A), whereas HtrA2 was absent after vehicle treatment at every time point
We investigated whether extracellular HtrA2 led to an upregulation of vascular adhesion molecule (VCAM) and intracellular adhesion molecule (ICAM)

Summary

Introduction

According to the World Health Organization’s report of 2016 ischemic heart disease is the major cause of death globally [1]. To prevent the death of cardiomyocytes caused by myocardial infarction, early intervention against ischemia is extremely important, using either thrombolytic therapy or percutaneous coronary intervention for reperfusion [2]. As a consequence of the reinitiated blood flow further cardiomyocyte death is induced by ischemia reperfusion (IR) injury. During IR injury, cardiac cell death is mediated by different mechanisms [10,11]. Necrosis as a passive mechanism causes unregulated cell death and a loss of plasma membrane integrity. Necrosis is primarily involved in ischemia, whereas apoptosis has been described as the main mechanism in reperfusion injury in a murine model of acute myocardial infarction [12]. The quantitative contribution of apoptosis and necrosis to the death of cardiomyocytes remains unclear. Mitochondria play a pivotal role in apoptosis induction, as Bcl-2 proteins and calcium overload promote mitochondrial membrane permeabilization and cause the release of apoptotic factors into the cytosol [6,7,8,13]

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