Modulation of Inflammatory Reactions by Low-Dose Ionizing Radiation: Cytokine Release of Murine Endothelial Cells Is Dependent on Culture Conditions

Abstract

Background In many European countries, patients with a variety of chronical inflammatory diseases are treated with low-dose radiotherapy (LD-RT). In contrast to high-dose irradiation given to tumor patients, little is known about radiobiological mechanisms underlying this clinical successful LD-RT application. The objective of this study was to gain a better insight into the modulation of inflammatory reactions after LD-RT on the basis of endothelial cells (EC) as major participants and regulators of inflammation. Methods Three murine EC lines were cultivated under 2D and 3D culture conditions and irradiated with doses from 0.01 Gy to 2 Gy. To simulate an inflammatory situation, cells were activated with TNF-α. After LD-RT, a screening of numerous inflammatory markers was determined by multiplex assay, followed by detailed analyses of four cytokines (KC, MCP-1, RANTES, and G-CSF). Additionally, the monocyte binding to EC was analyzed. Results Cytokine concentrations were dependent on culture condition, IR dose, time point after IR, and EC origin. IR caused nonlinear dose-dependent effects on secretion of the proinflammatory cytokines KC, MCP-1, and RANTES. The monocyte adhesion was significantly enhanced after IR as well as activation. Conclusions The study shows that LD-RT, also using very low radiation doses, has a clear immunomodulatory effect on EC as major participants and regulators of inflammation.

Effect of Ionizing Radiation on Human EA.hy926 Endothelial Cells under Inflammatory Conditions and Their Interactions with A549 Tumour Cells

“…In our earlier studies, we compared the binding of monocytes to three different EC lines (H5V, mlEND1, and bEND3). It has been clearly observed that not only a change in the inflammatory cytokine release but also adhesion capacity like that of monocyte binding to ECs depended on the origin of the ECs [35]. The dependence of IR response on the origin of ECs was also described by Nicolson and his coworkers [21].…”

“…It has also been stated that microvascular endothelial cells from human lungs (HLEC) can secrete chemokines like MCP-1 or IL-8 generally and in higher concentrations after TNF- α stimulation [53]. In our former study in murine EC mlEND.1, the concentration of MCP-1 48 hours after IR with 0.1 Gy was 10-fold (2D) or 5.4-fold (3D) higher in activated cells compared to the nonactivated cells [35].…”

“…The increase of metabolic activity was solely explained by cell growth over the observed time frame and, therefore, the gain of viable cells metabolizing the WST-1. In former studies, too, we observed no significant loss of cell viability in three murine ECs—mlEND1, H5V, and bEND3—caused by IR in the investigated dose range [35]. The analysis of metabolic activity was used by many other authors, e.g., Cervelli and coworkers, who irradiated human umbilical vein endothelial cells (HUVECs) with X-rays and observed no significant loss of cell viability caused by IR [45].…”

“…Moreover, IR with low doses affects EC by modulating inflammatory reactions [35, 36]. A great number of studies have investigated the radiation effects on ECs and their role in the anti-inflammatory cascade for the low-dose area (summarized in [37]).…”

Validation of a Vasculogenesis Microfluidic Model for Radiobiological Studies of the Human Microvasculature

“…However, despite the strong data supporting the use of more physiologically relevant tissue models in radiobiological studies, to date their application to investigate in vitro the effect of ionizing radiation on the microvasculature is scarce. The secretion of inflammatory markers was found to differ significantly for endothelial cells cultured in standard 2D plastic well‐plates and on nonadherent surfaces promoting 3D clustering . On the other hand, the kinetics of p53 binding protein 1 linked to DNA double‐strand breaks were similar for human umbilical vein endothelial cells (HUVECs) cultured either in 2D or within tube‐like vascular structures …”