Radiation-induced caveolin-1 associated EGFR internalization is linked with nuclear EGFR transport and activation of DNA-PK

<p>Abstract</p> <p>Background</p> <p>To elucidate the role of src kinase in caveolin-1 driven internalization and nuclear transport of EGFR linked to regulation of DNA-repair in irradiated cells.</p> <p>Results</p> <p>Ionizing radiation resulted in src kinase stabilization, activation and subsequent src mediated caveolin-1 Y14- and EGFR Y845-phosphorylations. Both phosphorylations were radiation specific and could not be observed after treatment with EGF. Inhibition of EGFR by the antibody Erbitux resulted in a strong accumulation of caveolin/EGFR complexes within the cytoplasm, which could not be further increased by irradiation. Radiation-induced caveolin-1- and EGFR-phosphorylations were associated with nuclear EGFR transport and activation of DNA-PK, as detected by phosphorylation at T2609. Blockage of src activity by the specific inhibitor PP2, decreased nuclear transport of EGFR and inhibited caveolin-1- and DNA-PK-phosphorylation. Knockdown of src by specific siRNA blocked EGFR phosphorylation at Y845, phosphorylation of caveolin-1 at Y14 and abolished EGFR transport into the nucleus and phosphorylation of DNA-PK. Consequently, both knockdown of src by specific siRNA and also inhibition of src activity by PP2 resulted in an enhanced residual DNA-damage as quantified 24 h after irradiation and increased radiosensitivity.</p> <p>Conclusion</p> <p>Src kinase activation following irradiation triggered caveolin-1 dependent EGFR internalization into caveolae. Subsequently EGFR shuttled into the nucleus. As a consequence, inhibition of internalization and nuclear transport of EGFR blocked radiation-induced phosphorylation of DNA-PK and hampered repair of radiation-induced double strand breaks.</p

Terminal Differentiation of Human Fibroblasts is Induced by Radiation

In order to analyze the effect of various kinds of radiation on the terminal differentiation processes of fibroblasts in culture, both human skin and lung fibroblasts were irradiated with electromagnetic non ionizing as well as ionizing radiation in clonal and sparse mass culture systems. As analyzed by cell biological (cell type frequencies), biochemical (collagen synthesis) and molecular markers (expression of protein PIVa) human skin and lung fibroblasts are induced to differentiate prematurely into terminal postmitotic cells. Thus, both electromagnetic and ionizing radiation induce terminal differentiation in cultured cells. These data add some new aspects for the interpretation of radiation effects on cells, e.g., in clinical therapy, as well as for the development of normal tissue responses during early and late effects after radiotherapy

Biological aspects of radiation and drug-eluting stents for the prevention of restenosis

Based on recent advances, this article aims to review the biological basis for the use of either radiation or drug-eluting stents for the prevention of restenosis, and to elucidate the complementary role that they may play in the future. Vascular restenosis is a multifactorial process primarily driven by the remodeling of the arterial wall, as well as by the hyperproliferation of smooth muscle cells (SMC). These pathophysiological features are the target of therapeutic strategies aimed at inhibiting constrictive remodeling as well as inhibiting SMC proliferation. The success of radiation as well as anti-proliferative drugs such as paclitaxel and sirolimus lies in the primary and/or multifactorial inhibition of cell proliferation. Radiation has the additional feature of preventing constrictive remodeling while sirolimus has the potential property of being anti-inflammatory, which may be a desirable feature. The effects of radiation are not reliant on any uptake and "metabolism” by the target cells, as in the case with drugs, and thus radiation potentially may be more effective as a result of its more-direct action. However, radiation does have some significant drawbacks compared to drug-eluting stents, including a much delayed re-endothelialization resulting in the need for prolonged anti-platelet therapy. Based on recent clinical data, drug-eluting stents have been shown to markedly reduce the likelihood of restenosis, which actually favors this approach for the prevention of restenosis. From a biological perspective, drug-eluting stents and radiation have certain differences, which are reviewed in this articl

Role of Nuclear EGFR During Cellular Radiation Response

Emerging evidence suggests the existence of a new mode of epidermal growth factor receptor (EGFR) signalling in which activated EGFR undergoes nuclear translocation. We provide evidence that the nuclear EGFR transport is a stress specific cellular reaction, which is linked to src dependent EGFR internalization into caveolae. Internalized EGFR is sorted into a peri-nuclear localization. This peri-nuclear EGFR may serve as a reservoir for nuclear transport which is regulated by PKC ε. Nuclear EGFR induces transcription of genes essential for cell proliferation and cell cycle regulation. In addition, nuclear EGFR has physical contact with compounds of the DNA repair machinery and is involved in removal of DNA-damage. The exact role of nuclear EGFR has to be elucidated in future experiments

Vasoactive agents affect growth and protein synthesis of cultured rat mesangial cells

Vasoactive agents affect growth and protein synthesis of cultured rat mesangial cells. Mesangial cell (MC) proliferation and extracellular matrix (ECM) formation are hallmarks of chronic glomerular disease. The present in vitro study examined the effects of the vasoactive agents angiotensin II (Ang II), arginine vasopressin (AVP), and serotonin (5-HT) on growth and protein biosynthesis of cultured rat MCs after 72 hours of incubation. AVP and 5-HT (10-6 M) significantly increased DNA synthesis and growth of quiescent subconfluent MCs to levels of 25 and 45%, respectively, of the optimal stimulatory effect of 10% fetal calf serum (FCS) (both P < 0.001). The mitogenic effect of Ang II was 10% of the 10% FCS effect (P < 0.01). ECM production was studied by ELISA assay for fibronectin (FN) secreted into the culture medium (SeFN) and cell-associated FN, that is, intra- and pericellular FN (CaFN). In all incubations, highly significant negative linear relationships were found between the numbers of MCs per well and quantities of both SeFN and CaFN after normalization of the data by logarithmic transformation (SeFN: r values > -0.9705; CaFN: r < -0.9620; P < 0.001). Thus, increasing cell densities progressively suppressed ECM formation by MCs. The ECM production was found to be independent of growth activity. AVP significantly increased SeFN (P < 0.05) and decreased CaFN (P < 0.001) in subconfluent cultures; Ang II and 5-HT had no effect. Metabolic labeling with 35S-methionine (18 hr, 200 µCi/ml medium) and 2-D electrophoresis of MC lysates resulted in resolution of >500 different radiolabeled intracellular proteins in molecular weight from 110 to 20 Kd over an isoelectric interval of 5.0 to 7.0. Computerized video densitometry and scintillation counting of excised spots revealed prominent upregulation of 10 different MC proteins in response to AVP, and enhanced expression of five proteins in response to 5-HT, events characteristic of cellular activation. Ang II caused weakly increased expression of only one protein. The stimulatory effects of AVP and 5-HT on growth and protein synthesis of MCs in-vitro imply a possible in vivo role for these factors in glomerular disease

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

WSES guidelines for management of Clostridium difficile infection in surgical patients

In the last two decades there have been dramatic changes in the epidemiology of Clostridium difficile infection (CDI), with increases in incidence and severity of disease in many countries worldwide. The incidence of CDI has also increased in surgical patients. Optimization of management of C difficile, has therefore become increasingly urgent. An international multidisciplinary panel of experts prepared evidenced-based World Society of Emergency Surgery (WSES) guidelines for management of CDI in surgical patients.Peer reviewe