Fournier, C.

Hehlgans, S.

Large, M.

Rödel, C.

Rödel, F.

GSI Repository

A non-linear regulation of the antioxidative system in endothelial cellscontributes to the anti- inflammatory effect of low dose X-irradiation∗M. Large1, S. Hehlgans1, C. Fournier2, C. Ro¨del1, and F. Ro¨del11Goethe-University Frankfurt am Main, Germany; 2GSI, Darmstadt, GermanyIntroductionSince ionizing radiation exerts its cytotoxic activity inlarge parts by the generation of reactive oxygen species(ROS), antioxidant systems to maintain cellular redox bal-ances are relevant for radiation response. Moreover, ROSare involved in immunological defense mechanisms andhave a physiological role in cellular signaling [1]. A ma-jor mechanism in the regulation of oxidative stress/damagehomeostasis is activation of the transcription factor nuclearfactor E2-related factor 2 (Nrf2), which tightly controls theexpression of genes encoding antioxidant proteins [2]. Wehave recently reported on a diminished activity of the en-zyme superoxide dismutase (SOD) and a discontinuous in-duction of ROS in EA.hy926 endothelial cells (ECs) mostpronounced at 24 h after a 0.5 Gy exposure [3]. Based onthese findings, analyses were expanded to Nrf2 as a com-mon regulatory element in the antioxidative defense and onfunctional properties of ROS in the anti-adhesive effects oflow dose X-irradiation [4].Material and MethodsEA.hy926 ECs were either stimulated in a proinflamma-tory manner by tumor necrosis factor-α (TNF-α; 20 ng/ml)4 h before or at 20 h after irradiation with X-ray doses rang-ing from 0.3 to 1 Gy. Expression and DNA binding activityof Nrf2 were analyzed by flow cytometry and colorimetricassays. The impact of ROS on peripheral blood mononu-clear cell (PBMC) adhesion was assayed in the presence ofthe scavenger N-acetyl cysteine (NAC).Results and ConclusionAs depicted in Figure 1, a non-linear dose response re-lationship was evident with a relative minimum of proteindetection at 0.5 Gy (Fig. 1A) in line with a reduction inNrf2 DNA-binding activity as quantitated by colorimetricassays (Fig. 1B). Next, to investigate whether low dose X-irradiation modulated induction of ROS is associated withaltered functional properties of EA.hy926 ECs, leukocyteadhesion was quantitated in the presence of the ROS scav-enger NAC. As shown in figure 1C, PBMC/EA.hy926 ECadhesion was suppressed by more than 50 % after a singledose irradiation with 0.5 Gy in control treated ECs. On thecontrary, ROS scavenging by NAC resulted a pronounced∗This research was supported by grants of BMBF (GREWIS,02NUK017F) and EU (DoReMi, FP7-249689).increase of adhesion events and thus a partial, but signifi-cant (p< 0.05) diminution of the anti-adhesive effect of lowdose exposure.Figure 1: Relative Nrf2 protein detection (A) and colori-metric Nrf2 DNA-binding activity (B) as measured at 24 hafter irradiation with single doses as indicated. Data repre-sent mean ± s.e.m from at least three independent experi-ments. ∗ p< 0.05 versus non irradiated ECs. (C) Adhesionof PBMC to NAC (10 mM) treated and stimulated (TNF-α:20 ng/ml) EA.hy.926 EC subsequent to low-dose irradia-tion. Mock treated cells served as a control. Data are givenas mean relative values (± s.e.m) from three independentexperiments. ∗ p < 0.05 versus mock treated controls.In conclusion, these findings implicate a non-linear ex-pression and activity of a major compound of the antioxida-tive system that may contribute to a differential regulationof ROS production and via modulation of the adhesion pro-cess to the anti-inflammatory effects of low dose radiationtherapy.References[1] C. Nathan, Nat Rev Immunol 2013; 13:349-361[2] T. Nguyen, J Biol Chem 2009; 284:13291-13295[3] F. Ro¨del, Curr Med Chem 2014; 19:1741-1750[4] M. Large, Radiat Oncol 2014; 9:80APPA-HEALTH-19 GSI SCIENTIFIC REPORT 2014310 DOI:10.15120/GR-2015-1-APPA-HEALTH-19

A non-linear regulation of the antioxidative system in endothelial cells contributes to the anti-inflammatory effect of low dose X-irradiation

http://repository.gsi.de/record/184040/files/APPA-HEALTH-19.pdf

A non-linear regulation of the antioxidative system in endothelial cells contributes to the anti-inflammatory effect of low dose X-irradiation

Abstract

Similar works

Full text

Available Versions

GSI Repository