22 research outputs found
Validation of biological recognition elements for signal transduction as first step in the development of whole cell biosensors
Choosing the proper combination of receptor element, cell type and measurable signal requires major consideration for developing cell-based biosensors. In order to use physiologically relevant cellular responses towards (geno)toxic conditions, information on the mechanism of action and of the expected outcome of exposure needs to be considered
Radiation Response of Murine Embryonic Stem Cells
To understand the mechanisms of disturbed differentiation and development by
radiation, murine CGR8 embryonic stem cells (mESCs) were exposed to ionizing radiation and
differentiated by forming embryoid bodies (EBs). The colony forming ability test was applied for
survival and the MTT test for viability determination after X-irradiation. Cell cycle progression was
determined by flow cytometry of propidium iodide-stained cells, and DNA double strand break
(DSB) induction and repair by γH2AX immunofluorescence. The radiosensitivity of mESCs was
slightly higher compared to the murine osteoblast cell line OCT-1. The viability 72 h after
X-irradiation decreased dose-dependently and was higher in the presence of leukemia inhibitory
factor (LIF). Cells exposed to 2 or 7 Gy underwent a transient G2 arrest. X-irradiation induced
γH2AX foci and they disappeared within 72 h. After 72 h of X-ray exposure, RNA was isolated and
analyzed using genome-wide microarrays. The gene expression analysis revealed amongst others a
regulation of developmental genes (Ada, Baz1a, Calcoco2, Htra1, Nefh, S100a6 and Rassf6),
downregulation of genes involved in glycolysis and pyruvate metabolism whereas upregulation of
genes related to the p53 signaling pathway. X-irradiated mESCs formed EBs and differentiated
toward cardiomyocytes but their beating frequencies were lower compared to EBs from
unirradiated cells. These results suggest that X-irradiation of mESCs deregulate genes related to the
developmental process. The most significant biological processes found to be altered by
X-irradiation in mESCs were the development of cardiovascular, nervous, circulatory and renal
system. These results may explain the X-irradiation induced-embryonic lethality and
malformations observed in animal studies
The Use of ProteoTuner Technology to Study Nuclear Factor κB Activation by Heavy Ions
Nuclear factor κB (NF-κB) activation might be central to heavy ion-induced detrimental processes such as cancer promotion and progression and sustained inflammatory responses. A sensitive detection system is crucial to better understand its involvement in these processes. Therefore, a DD-tdTomato fluorescent protein-based reporter system was previously constructed with human embryonic kidney (HEK) cells expressing DD-tdTomato as a reporter under the control of a promoter containing NF-κB binding sites (HEK-pNFκB-DD-tdTomato-C8). Using this reporter cell line, NF-κB activation after exposure to different energetic heavy ions (¹⁶O, 95 MeV/n, linear energy transfer—LET 51 keV/µm; ¹²C, 95 MeV/n, LET 73 keV/μm; ³⁶Ar, 95 MeV/n, LET 272 keV/µm) was quantified considering the dose and number of heavy ions hits per cell nucleus that double NF-κB-dependent DD-tdTomato expression. Approximately 44 hits of ¹⁶O ions and ≈45 hits of ¹²C ions per cell nucleus were required to double the NF-κB-dependent DD-tdTomato expression, whereas only ≈3 hits of ³⁶Ar ions were sufficient. In the presence of Shield-1, a synthetic molecule that stabilizes DD-tdTomato, even a single particle hit of ³⁶Ar ions doubled NF-κB-dependent DD-tdTomato expression. In conclusion, stabilization of the reporter protein can increase the sensitivity for NF-κB activation detection by a factor of three, allowing the detection of single particle hits’ effects
Transcription Factors in the Cellular Response to Charged Particle Exposure
Charged particles, such as carbon ions, bear the promise of a more effective cancer therapy. In human spaceflight, exposure to charged particles represents an important risk factor for chronic and late effects such as cancer. Biological effects elicited by charged particle exposure depend on their characteristics, e.g., on linear energy transfer (LET). For diverse outcomes (cell death, mutation, transformation, and cell-cycle arrest), an LET dependency of the effect size was observed. These outcomes result from activation of a complex network of signaling pathways in the DNA damage response, which result in cell-protective (DNA repair and cell-cycle arrest) or cell-destructive (cell death) reactions. Triggering of these pathways converges among others in the activation of transcription factors, such as p53, nuclear factor κB (NF-κB), activated protein 1 (AP-1), nuclear erythroid-derived 2-related factor 2 (Nrf2), and cAMP responsive element binding protein (CREB). Depending on dose, radiation quality, and tissue, p53 induces apoptosis or cell-cycle arrest. In low LET radiation therapy, p53 mutations are often associated with therapy resistance, while the outcome of carbon ion therapy seems to be independent of the tumor’s p53 status. NF-κB is a central transcription factor in the immune system and exhibits pro-survival effects. Both p53 and NF-κB are activated after ionizing radiation exposure in an ataxia telangiectasia mutated (ATM)-dependent manner. The NF-κB activation was shown to strongly depend on charged particles’ LET, with a maximal activation in the LET range of 90–300 keV/μm. AP-1 controls proliferation, senescence, differentiation, and apoptosis. Nrf2 can induce cellular antioxidant defense systems, CREB might also be involved in survival responses. The extent of activation of these transcription factors by charged particles and their interaction in the cellular radiation response greatly influences the destiny of the irradiated and also neighboring cells in the bystander effect
An in-vitro approach for water quality determination: activation of NF-κB as marker for cancer-related stress responses induced by anthropogenic pollutants of drinking water
Epidemiological studies show that there is a link between urban water pollution and increase in human morbidity and mortality. With the increase in number of new substances arising from the chemical, pharmaceutical, and agricultural industries, there is an urgent need to develop biological test systems for fast evaluation of potential risks to humans and the environmental ecosystems. Here, a combined cellular reporter assay based on the cellular survival and the stress-induced activation of the survival-promoting factor nuclear factor κB (NF-κB) and its use for the detection of cytotoxicity and cancer-related stress responses is presented. A total of 14 chemicals that may be found in trace-amounts in ground water levels are applied and tested with the presented assay. The project is embedded within the joint research project TOX-BOX which aims to develop a harmonized testing strategy for risk management of anthropogenic trace substances in potable water. The assay identified carbendazim as a NF-κB-activating agent in mammalian cells
RADIATION RESPONSE OF PORCINE LENS EPITHELIAL CELLS AND EYE LENSES IN ORGAN-CULTURE
Astronauts on long-term space missions have a higher risk for the expression of radiation late effects
such as cancer or sub-capsular cortical eye lens opacities. This is due to higher dose and different patterns of cellular energy deposition from high-linear-energy-transfer (LET) components of galactic cosmic
radiation in space than that of terrestrial low-LET radiation on Earth. The eye lens is a radiation sensitive organ with radiation induced cataract to occur with a threshold absorbed dose of 0.5 Gy (0 - 1
Gy) of sparsely ionizing radiation. Doses perceived by astronauts on the International Space Station
(ISS) are in average 150 mSv per year (Cucinotta et al. (2001) Radiat Res. 156:460-466). Radiationinduced lens opacification is assumed to initiate from post irradiation proliferative activity of genetically
damaged lens epithelial cells with alterations in cell cycle control, apoptosis, differentiation, and cellular
disorganization, or other pathways controlling lens fiber cells’ differentiation. As the porcine eye lens is
similar to the human lens in size and anatomy, DNA damage response was investigated in ex-vivo porcine
lenses in organ culture, in in-vitro cultivated lens epithelial slabs (ES) and in porcine lens epithelial cells
(pLEC). Cell survival of proliferative cells was calculated from colony forming ability (CFA) assay. The
phosphorylated form of H2AX (γH2AX) was used as a molecular marker to visualize DNA double strand
breaks (DSB) and their repair. Propidium iodide based DNA staining for cellular DNA content marked
radiation-induced cell cycle disturbances. In pLEC the cell survival curve of immediate plated cells and
after a recovery period of 24 h follow the equation S=1.40xD+ln 1.47 and S=1.59xD+ln 1.79, respectively.
DNA DSB are induced in a dose-dependent manner ( 18 DSB/cell/Gy) and repaired during successive
recovery ( 5 DSB/cell/Gy residual damage after 24 h). For doses >2 Gy a cell cycle arrest in G2 phase
occurred 24 h after X-irradiation and persisted up to 72 h post-irradiation. DNA DSB induction and
repair could as well be documented for ES and whole lenses after X-irradiation. In whole lenses, the
amount of residual damage (after 24 h and 48 h) was highest in the equatorial zone while in the central
epithelial zone DSB repair seemed to proceed with time in a manner comparable to in-vitro cultivated
pLEC. Lens organ culture allows cellular metabolism and DNA synthesis in whole lenses. Repair of DNA
DSB takes place in the central epithelial layer and is reduced in the equatorial region of cultivated lenses
An in-vitro approach for water quality determination: activation of NF-κB as marker for cancer-related stress responses induced by anthropogenic pollutants of drinking water
Epidemiological studies show that there is a link
between urban water pollution and increase in human morbidity
and mortality. With the increase in number of new substances
arising from the chemical, pharmaceutical, and agricultural
industries, there is an urgent need to develop biological
test systems for fast evaluation of potential risks to
humans and the environmental ecosystems. Here, a combined
cellular reporter assay based on the cellular survival and the
stress-induced activation of the survival-promoting factor nuclear
factor κB (NF-κB) and its use for the detection of cytotoxicity
and cancer-related stress responses is presented. A
total of 14 chemicals that may be found in trace-amounts in
ground water levels are applied and tested with the presented
assay. The project is embedded within the joint research project
TOX-BOX which aims to develop a harmonized testing
strategy for risk management of anthropogenic trace substances
in potable water. The assay identified carbendazim
as a NF-κB-activating agent in mammalian cells
DNA DAMAGE RESPONSE OF EX-VIVO PORCINE EYE LENSES IN ORGANCULTURE AND IN-VITRO CULTURED LENS EPITHELIAL CELLS TO IONIZING RADIATION
Astronauts on space missions, especially on long-term missions to Moon or Mars have a higher
risk for the expression of radiation late effects such as cancer or sub-capsular cortical eye lens
opacities. This is due to higher dose and different patterns of cellular energy deposition from
high-linear-energy-transfer (LET) components of galactic cosmic radiation in space than that
of terrestrial low-LET radiation on Earth. The eye lens is considered to be a radiation sensitive
organ with radiation induced cataract to occur with a threshold absorbed dose of 0.5 Gy of
sparsely ionizing radiation. For terrestrial occupational radiation lens exposure limit is set to
yearly 20 mSv by the International Commission on Radiological Protection (ICRP, Statement
on tissue reactions, Ottawa, Canada, 2011). Doses perceived by astronauts are much higher:
in average 150 mSv per year on the International Space Station (ISS) and 1.2 to 1.4 mSv per
day on Apollo and Skylab missions (Cucinotta FA, Manuel FK, Jones J, Iszard G, Murrey J,
Djojonegro B, Wear M. Space radiation and cataracts in astronauts. Radiat Res. 156:460-466,
2001)
Molecular Signaling in Response to Charged Particle Exposures and its Importance in Particle Therapy
Energetic, charged particles elicit an orchestrated DNA damage response (DDR)
during their traversal through healthy tissues and tumors. Complex DNA damage
formation, after exposure to high linear energy transfer (LET) charged particles, results
in DNA repair foci formation, which begins within seconds. More protein modifications
occur after high-LET, compared with low-LET, irradiation. Charged-particle exposure
activates several transcription factors that are cytoprotective or cytodestructive, or that
upregulate cytokine and chemokine expression, and are involved in bystander
signaling. Molecular signaling for a survival or death decision in different tumor types
and healthy tissues should be studied as prerequisite for shaping sensitizing and
protective strategies. Long-term signaling and gene expression changes were found in
various tissues of animals exposed to charged particles, and elucidation of their role in
chronic and late effects of charged-particle therapy will help to develop effective
preventive measures