The heart tissue is a potential target of various noxae contributing to the onset of cardiovascular diseases. However, underlying pathophysiological mechanisms are largely unknown. Human stem cell-derived models are promising, but a major concern is cell immaturity when estimating risks for adults. In this study, 3D aggregates of human embryonic stem cell-derived cardiomyocytes were cultivated for 300 days and characterized regarding degree of maturity, structure, and cell composition. Furthermore, effects of ionizing radiation (X-rays, 0.1–2 Gy) on matured aggregates were investigated, representing one of the noxae that are challenging to assess. Video-based functional analyses were correlated to changes in the proteome after irradiation. Cardiomyocytes reached maximum maturity after 100 days in cultivation, judged by α-actinin lengths, and displayed typical multinucleation and branching. At this time, aggregates contained all major cardiac cell types, proven by the patch-clamp technique. Matured and X-ray-irradiated aggregates revealed a subtle increase in beat rates and a more arrhythmic sequence of cellular depolarisation and repolarisation compared to non-irradiated sham controls. The proteome analysis provides first insights into signaling mechanisms contributing to cardiotoxicity. Here, we propose an in vitro model suitable to screen various noxae to target adult cardiotoxicity by preserving all the benefits of a 3D tissue culture.
Radiation therapy efficiently eliminates cancer cells and reduces tumor growth. To understand collateral agonistic and antagonistic effects of this treatment on the immune system, we examined the impact of x-ray irradiation on human T cells. We find that, in a major population of leukemic Jurkat T cells and peripheral blood mononuclear cells, clinically relevant radiation doses trigger delayed oscillations of the cytosolic Ca2+ concentration. They are generated by store-operated Ca2+ entry (SOCE) following x-ray–induced clustering of Orai1 and STIM1 and formation of a Ca2+ release–activated Ca2+ (CRAC) channel. A consequence of the x-ray–triggered Ca2+ signaling cascade is translocation of the transcription factor nuclear factor of activated T cells (NFAT) from the cytosol into the nucleus, where it elicits the expression of genes required for immune activation. The data imply activation of blood immune cells by ionizing irradiation, with consequences for toxicity and therapeutic effects of radiation therapy.
Radiation therapy is efficiently employed for eliminating cancer cells and reducing tumor growth. To further improving its therapeutic application it is mandatory to unravel the molecular effects of ionizing irradiation and to understand whether they support or counteract tumor therapy. Here we examine the impact of X-ray irradiation on immune activation of human T cells with single doses typically employed in tumor therapy. We discover that exposing cells to radiation triggers in a population of leukemic Jurkat T cells and in peripheral blood mononuclear cells (PBMCs) a canonical Ca2+ signaling cascade, which elicits immune activation of these cells. An early step in the signaling cascade is the initiation of sustained oscillations of the cytosolic Ca2+ concentration, an event mediated by store operated Ca2+ entry (SOCE) via an X-ray induced clustering of the Calcium Release-Activated Calcium Modulator 1 with the stromal interaction molecule 1 (Oari1/STIM1). A functional consequence of the Ca2+ signaling cascade is the translocation of the transcription factor nuclear factor of activated T cells (NFAT) from the cytosol into the nucleus where it elicits the expression of genes required for immune activation. These data imply that a direct activation of blood immune cells by ionizing irradiation has an impact on toxicity and therapeutic effects of radiation therapy.
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