Radiotherapy Suppresses Angiogenesis in Mice through TGF-βRI/ALK5-Dependent Inhibition of Endothelial Cell Sprouting

BACKGROUND: Radiotherapy is widely used to treat cancer. While rapidly dividing cancer cells are naturally considered the main target of radiotherapy, emerging evidence indicates that radiotherapy also affects endothelial cell functions, and possibly also their angiogenic capacity. In spite of its clinical relevance, such putative anti-angiogenic effect of radiotherapy has not been thoroughly characterized. We have investigated the effect of ionizing radiation on angiogenesis using in vivo, ex vivo and in vitro experimental models in combination with genetic and pharmacological interventions. PRINCIPAL FINDINGS: Here we show that high doses ionizing radiation locally suppressed VEGF- and FGF-2-induced Matrigel plug angiogenesis in mice in vivo and prevented endothelial cell sprouting from mouse aortic rings following in vivo or ex vivo irradiation. Quiescent human endothelial cells exposed to ionizing radiation in vitro resisted apoptosis, demonstrated reduced sprouting, migration and proliferation capacities, showed enhanced adhesion to matrix proteins, and underwent premature senescence. Irradiation induced the expression of P53 and P21 proteins in endothelial cells, but p53 or p21 deficiency and P21 silencing did not prevent radiation-induced inhibition of sprouting or proliferation. Radiation induced Smad-2 phosphorylation in skin in vivo and in endothelial cells in vitro. Inhibition of the TGF-beta type I receptor ALK5 rescued deficient endothelial cell sprouting and migration but not proliferation in vitro and restored defective Matrigel plug angiogenesis in irradiated mice in vivo. ALK5 inhibition, however, did not rescue deficient proliferation. Notch signaling, known to hinder angiogenesis, was activated by radiation but its inhibition, alone or in combination with ALK5 inhibition, did not rescue suppressed proliferation. CONCLUSIONS: These results demonstrate that irradiation of quiescent endothelial cells suppresses subsequent angiogenesis and that ALK5 is a critical mediator of this suppression. These results extend our understanding of radiotherapy-induced endothelial dysfunctions, relevant to both therapeutic and unwanted effects of radiotherapy

Outcome predictors for status epilepticus-what really counts

In adult patients with status epilepticus (SE)-a life-threatening state of ongoing or repetitive seizures-the current evidence regarding outcome prediction is based on clinical, biochemical and EEG determinants. These predictors of outcome involve clinical features such as age, history of prior seizures or epilepsy, SE aetiology, level of consciousness, and seizure type at SE onset. The clinical risk-benefit calculation between the danger of undertreated persistent seizure activity and, conversely, the potential damage from unwarranted aggressive treatments remains a constant challenge. Improved knowledge of outcome determinants, as well as increased availability of reliable outcome prediction models early in the course of SE, is paramount for optimization of treatment of patients who develop this disorder. In this Review, we discuss the major prognostic determinants of outcome in SE. Through consideration of studies that provide measures of association between predictors of SE outcome and death, we propose a detailed-but as yet unvalidated-paradigm for assessment of these predictors during the course of SE. Such an algorithm could guide the organization of results from existing trials and provide direction with regard to the parameters that should be monitored in future studies of SE