Single-cell imaging of normal and malignant cell engraftment into optically clear prkdc-null SCID zebrafish

Cell transplantation into immunodeficient mice has revolutionized our understanding of regeneration, stem cell self-renewal, and cancer; yet models for direct imaging of engrafted cells has been limited. Here, we characterize zebrafish with mutations in recombination activating gene 2 (rag2), DNA-dependent protein kinase (prkdc), and janus kinase 3 (jak3). Histology, RNA sequencing, and single-cell transcriptional profiling of blood showed that rag2 hypomorphic mutant zebrafish lack T cells, whereas prkdc deficiency results in loss of mature T and B cells and jak3 in T and putative Natural Killer cells. Although all mutant lines engraft fluorescently labeled normal and malignant cells, only the prkdc mutant fish reproduced as homozygotes and also survived injury after cell transplantation. Engraftment into optically clear casper, prkdc-mutant zebrafish facilitated dynamic live cell imaging of muscle regeneration, repopulation of muscle stem cells within their endogenous niche, and muscle fiber fusion at single-cell resolution. Serial imaging approaches also uncovered stochasticity in fluorescently labeled leukemia regrowth after competitive cell transplantation into prkdc mutant fish, providing refined models to assess clonal dominance and progression in the zebrafish. Our experiments provide an optimized and facile transplantation model, the casper, prkdc mutant zebrafish, for efficient engraftment and direct visualization of fluorescently labeled normal and malignant cells at single-cell resolution.

Microbial light-activatable proton pumps as neuronal inhibitors to functionally dissect neuronal networks in C. elegans

Essentially any behavior in simple and complex animals depends on neuronal network function. Currently, the best-defined system to study neuronal circuits is the nematode Caenorhabditis elegans, as the connectivity of its 302 neurons is exactly known. Individual neurons can be activated by photostimulation of Channelrhodopsin-2 (ChR2) using blue light, allowing to directly probe the importance of a particular neuron for the respective behavioral output of the network under study. In analogy, other excitable cells can be inhibited by expressing Halorhodopsin from Natronomonas pharaonis (NpHR) and subsequent illumination with yellow light. However, inhibiting C. elegans neurons using NpHR is difficult. Recently, proton pumps from various sources were established as valuable alternative hyperpolarizers. Here we show that archaerhodopsin-3 (Arch) from Halorubrum sodomense and a proton pump from the fungus Leptosphaeria maculans (Mac) can be utilized to effectively inhibit excitable cells in C. elegans. Arch is the most powerful hyperpolarizer when illuminated with yellow or green light while the action spectrum of Mac is more blue-shifted, as analyzed by light-evoked behaviors and electrophysiology. This allows these tools to be combined in various ways with ChR2 to analyze different subsets of neurons within a circuit. We exemplify this by means of the polymodal aversive sensory ASH neurons, and the downstream command interneurons to which ASH neurons signal to trigger a reversal followed by a directional turn. Photostimulating ASH and subsequently inhibiting command interneurons using two-color illumination of different body segments, allows investigating temporal aspects of signaling downstream of ASH.

[Influence of N-acylethanolamines on embryonic cell culture survival under the effect of irradiation]

The effects of the N-stearoylethanolamine (NSE), N-oleoylethanolamine (OEA) and N-acylethanolamine (NAE) mixture on the cell survival, apoptosis and activity of mitochondrial succinate dehydrogenase (SDG) and glycerophosphate dehydrogenase (GFDG) in embryonic cell culture under normal conditions and irradiation were compared in the work. It was shown, that all investigated NAE were able to modulate the proliferative activity of intact cells as well as irradiation-exposed cells in concentration-depended manner. The most pronounced effect was observed under the NAE mixture action. It was established, that NAE prevented the damage effects of the irradiation and diminished the activation of apoptotic cell death. It was found that NSE and OEA decreased the activity of the SDG (42.3 and 44.14%, accordingly) and the GFDG activity (14.67 and 17.33%, accordingly) in embryonic cell culture, while addition of the NAE mixture decreased SDG activity by 20%, at the same time GFDG activity increased by 20%. Our findings suggested that antiproliferative effects of NAE depended on their influence on mitochondrial functioning.

Effects of multiple doses of ionizing radiation on cytokine expression in rat and human cells

PURPOSE

To determine the effect of daily fractionated irradiation on the expression of growth factors and cytokines in different cardiac and vascular cell types.

MATERIALS AND METHODS

Cell cultures of rat cardiac myocytes, fibroblasts, a rat cardiac microvascular endothelial cell line and human artery endothelial cells were irradiated with doses of 2 Gy, given daily during 5 consecutive days. Twenty-four hours after each fraction, gene expression was determined by competitive or semiquantitative polymerase chain reaction. Protein secretion into culture media was determined by enzyme-linked immunoabsorbant assay.

RESULTS

Of all investigated mRNA levels, transforming growth factor (TGF)-ss1 and fibroblast growth factor (FGF)-2 were slightly upregulated in the rat cardiac endothelial cell line after irradiation. TGF-ss1 protein secretion by these cells was slightly, but non-significantly, elevated. Interleukin 1ss protein levels in myocyte culture media were decreased in control cultures at days 3 and 4 compared with day 2. No significant changes were observed in expression of FGF-2 in either of the four cell types. Moreover, no changes were observed in gene expression of platelet-derived growth factors A, B and interleukin 8 in the human artery endothelial cells.

CONCLUSIONS

Fractionated irradiation leads to minor changes in the expression of specific cytokines in cardiac myocytes, fibroblasts and endothelial cells.

Theoretical evaluation of dielectric absorption of microwave energy at the scale of nucleic acids

A theoretical model is proposed for the evaluation of dielectric properties of the cell nucleus between 0.3 and 3 GHz, as a function of its nucleic acids (NA) concentration (CNA). It is based on literature data on dielectric properties of DNA solutions and nucleoplasm. In skeletal muscle cells, the specific absorption rate (SAR) ratio between nucleoplasm and cytoplasm is found to be larger than one for CNA above 30 mg/ml. A nearly linear relationship is found between CNA and this nucleocytoplasmic SAR ratio. Considering the nanoscale of the layer of condensed counterions and bound water molecules at the NA-solution interface, the power absorption per unit volume is evaluated at this precise location. It is found to be between one and two orders of magnitude above that in muscle tissue as a whole. Under realistic microwave (MW) exposure conditions, however, these SAR inhomogeneities do not generate any significant thermal gradient at the scale considered here. Nevertheless, the question arises of a possible biological relevance of nonnegligible and preferential heat production at the location of the cell nucleus and of the NA molecules.

Differentiation-induced radioresistance in muscle cells

DNA damage induces cell cycle arrest and DNA repair or apoptosis in proliferating cells. Terminally differentiated cells are permanently withdrawn from the cell cycle and partly resistant to apoptosis. To investigate the effects of genotoxic agents in postmitotic cells, we compared DNA damage-activated responses in mouse and human proliferating myoblasts and their differentiated counterparts, the myotubes. DNA double-strand breaks caused by ionizing radiation (IR) induced rapid activating autophosphorylation of ataxia-teleangiectasia-mutated (ATM), phosphorylation of histone H2AX, recruitment of repair-associated proteins MRE11 and Nbs1, and activation of Chk2 in both myoblasts and myotubes. However, IR-activated, ATM-mediated phosphorylation of p53 at serine 15 (human) or 18 (mouse) [Ser15(h)/18(m)], and apoptosis occurred in myoblasts but was impaired in myotubes. This phosphorylation could be enforced in myotubes by the anthracycline derivative doxorubicin, leading to selective activation of proapoptotic genes. Unexpectedly, the abundance of autophosphorylated ATM was indistinguishable after exposure of myotubes to IR (10 Gy) or doxorubicin (1 microM/24 h) despite efficient phosphorylation of p53 Ser15(h)/18(m), and apoptosis occurred only in response to doxorubicin. These results suggest that radioresistance in myotubes might reflect a differentiation-associated, pathway-selective blockade of DNA damage signaling downstream of ATM. This mechanism appears to preserve IR-induced activation of the ATM-H2AX-MRE11/Rad50/Nbs1 lesion processing and repair pathway yet restrain ATM-p53-mediated apoptosis, thereby contributing to life-long maintenance of differentiated muscle tissues.

Deficient global genome repair of UV-induced cyclobutane pyrimidine dimers in terminally differentiated myocytes and proliferating fibroblasts from the rat heart

Nucleotide excision repair (NER) is the principal pathway for the removal of a wide range of DNA helix-distorting lesions. Two NER subpathways have been identified, i.e. global genome repair (GGR) and transcription-coupled repair (TCR). Little is known about the expression of NER pathways in differentiated cells. We assessed the repair of UV-induced cyclobutane pyrimidine dimers (CPD) and 6-4-photoproducts (6-4 PP) in terminally differentiated myocytes and proliferating fibroblasts isolated from the hearts of neonatal rats. Myocytes and fibroblasts were found to carry out efficient removal of 6-4 PP but display poor repair of CPD by GGR. Furthermore, both cell types were found to carry out TCR of CPD, thus mimicking the repair phenotype of established rodent cell lines. The inefficient repair of CPD at the genome overall level occurs in the absence of massive apoptosis, but goes along with an undetectable level of transcription of the p48 gene, known to be mutated in xeroderma pigmentosum group E (XP-E) patients and recently proposed to be essential for repair of CPD in nonexpressed DNA. Taken together, the results suggest that primary non-dividing cardiac myocytes and proliferating fibroblasts from rat heart selectively remove CPD from the transcribed strand of transcriptionally active genes. GGR of CPD is poor due to the absence of p48 expression.

[Hormonal regulation of the function of the myocyte intracellular membranes under radiation influence]

It was shown that the experimental hypofunction of thyroid, induced by thyroidectomy and strong gamma-irradiation with a dose of 1 Gy lead to disturbance of function and structure of membranes of sarcoplasmic reticulum of myocites in rats. Introduction in vivo of L-thyroxine rose functional capacity of membranes with insignificaut changes in their lipid bilayer.

Reoxygenation of hypoxic coronary smooth muscle cells amplifies growth-retarding effects of ionizing irradiation

BACKGROUND

Hypoxic human coronary smooth muscle cells (HCSMCs) are possible targets for brachytherapy to prevent restenosis after percutaneous transluminal coronary angiography. It is unclear whether growth kinetics and gene expression of these cells undergoing gamma-irradiation are changed by reoxygenation.

METHODS AND RESULTS

Hypoxic (H) and hypoxia-reoxygenated (H-R) HCSMCs were irradiated with gamma-radiation at single doses of 4, 8, and 16 Gy using a 60Co-source. Vascular endothelial growth factor gene expression of HCSMCs was dramatically suppressed in H-R versus H cells independent of the radiation dose (15+/-7% versus 2183+/-2023%, P<0.01, H-R versus H cells). An oxygen enhancement ratio of 1.8 was calculated after irradiation from the retarded growth of H-R versus hypoxic HCSMCs. Production of reactive oxygen species by HCSMCs after irradiation increased by 15+/-2% in H-R cells versus 7+/-1% in H cells (P<0.05).

CONCLUSIONS

Reoxygenation of hypoxic HCSMCs markedly amplifies growth-retarding effects of ionizing irradiation. On the basis of these findings, oxygenating radiosensitizers should be analyzed with regard to suitability for coronary brachytherapy to prevent restenosis.

Effects of cobalt-60 ?-radiation on the synthesis of adrenomedullin and endothelin in rat vascular smooth muscle cells

We studied the effects of cobalt-60 Gamma-radiation on the gene expression and secretion of adrenomedullin (Adm) and endothelin (ET) in cultured rat vascular smooth muscle cells (VSMCs). Rat VSMCs cultured in Dulbecoo's modified Eagle's medium containing 10% FBS were radiated with cobalt-60 Gamma-radiation at doses of 1, 14, and 25 Gy, respectively. Then the mRNA of Adm and ET in VSMCs were detected by the reverse-transcriptative competitive polymerase chain reaction. Adm and ET levels in rat VSMCs were measured by radioimmunoassay. As compared with that of the control, the secretions of Adm in rat VSMCs radiated at doses of 14 and 25 Gy were increased by 270% (P < 0.05) and 233% (P < 0.05), respectively. The mRNA levels of Adm were increased by 82.4% (P < 0.01) and 101% (P <0.01), respectively. Meanwhile, the secretions of ET were decreased by 27.3% (P < 0.01) and 58.0% (P < 0.01) in VSMCs radiated at doses of 14 and 25 Gy, respectively. In parallel, the mRNA levels of ET were decreased by 47.1% (P < 0.01) and 40.2% (P < 0.01), respectively. Radiation at a dose of 1 Gy had no significant effect on Adm and ET at the gene and protein levels. As compared with the control, the Adm/ET ratios in VSMCs increased by 65% (P > 0.05), 409% (P < 0.01), and 693% (P < 0.01), respectively, with radiation at doses of 1,14 and 25 Gy, respectively. The balance of Adm/ET in VSMCs could be changed by cobalt-60 Gamma-radiation, which might play an important role in the use of radiotherapy for restenosis.