Young-Sook Lee

Role of protein kinase C delta in X‐ray‐induced apoptosis of keratinocyte

Abstract:u2002 In this study, we investigated the process of X‐ray‐induced apoptosis of skin keratinocyte, and the functional role of protein kinase C delta (PKCδ) and downstream signalling cascade. High‐dose X‐ray irradiation (10u2003Gy) led to the apoptosis of HaCaT keratinocyte, accompanied by PKCδ cleavage. Treatment with PKCδ inhibitor and adenoviral transduction of dominant‐negative PKCδ clearly inhibited the X‐ray‐induced apoptosis of keratinocyte. In addition, X‐ray induced the phosphorylation of extracellular signal‐regulated kinases 1/2 (ERK1/2) and inhibition by ERK1/2 inhibitor abrogated the X‐ray‐induced apoptosis. Interestingly, overexpression of dominant‐negative PKCδ markedly blocked the X‐ray‐induced phosphorylation of ERK1/2, suggesting that ERK1/2 is the functional downstream effector of PKCδ. Next, we investigated the difference between UVB and X‐ray response. UVB induced the apoptosis of keratinocyte in a PKCδ‐dependent manner, similar to X‐ray response. However, UVB irradiation induced the phosphorylation of c‐jun N‐terminal kinases (JNK) and inhibition of JNK significantly protected the UVB‐induced apoptosis. These results demonstrate that PKCδ is a key regulator in X‐ray‐induced apoptosis of keratinocyte and suggest that there is subtle difference in downstream signalling cascade between UVB and X‐ray response of keratinocyte.

ID3 mediates X-ray-induced apoptosis of keratinocytes through the regulation of β-catenin

BACKGROUNDnIonizing radiation is used to treat many of cancers, however, it also produces unwanted side effect on normal tissues, such as radiodermatitis. We previously established an animal model for radiodermatitis, and found that X-ray irradiation induced the expression of ID3 in hairless mouse skin by cDNA microarray.nnnOBJECTIVEnThe aim of this study is to investigate the functional role of ID3 in X-ray irradiated keratinocytes.nnnMETHODSnImmunohistochemistry, RT-PCR and Western blot were performed to demonstrate the ID3 induction by X-ray irradiation. HaCaT keratinocytes were transduced with the recombinant adenovirus expressing HA-ID3, and then effects on apoptosis were analyzed.nnnRESULTSnX-ray irradiation increased markedly the ID3 protein level in epidermis of mouse skin. X-ray irradiation also induced the expression of ID3 in HaCaT keratinocytes cultured in vitro, at both mRNA and protein levels. When ID3 was overexpressed by recombinant adenovirus, apoptosis of keratinocytes were induced even in the absence of X-ray irradiation. Furthermore, overexpression of ID3 sensitized X-ray-induced apoptosis. Interestingly, X-ray irradiation significantly reduced the endogenous β-catenin level, which was related with induction of apoptosis. Similarly, overexpression of ID3 led to remarkable reduction in β-catenin level.nnnCONCLUSIONnThese results suggest that ID3 plays a role as an apoptosis inducer in response to X-ray irradiation via the regulation of endogenous β-catenin level.

Gene expression analysis of toxicological pathways in TM3 leydig cell lines treated with Ethane dimethanesulfonate

Ethane dimethanesulfonate (EDS), a well‐known alkylating agent, selectively destroys Leydig cells. To clarify the molecular pathways underlying EDS action on Leydig cells, we analyzed gene expression profiles of an EDS‐treated TM3 Leydig cell line. In this study, we analyzed the representative canonical pathways and toxicity pathways/gene lists using the Ingenuity Pathways Analysis program. In TM3 cells, 677 and 6756 genes were identified as being up‐ or downregulated after 3 and 24 h EDS treatments, respectively, (>1.3‐fold changes, p < 0.05). Toxicological pathway analysis revealed that expression of genes related to Nrf2‐mediated oxidative stress response showed remarkable changes in early or later stage of EDS‐treated TM3 cells. Several genes related to steroidogenesis and apoptosis were also differentially expressed at 24 h in EDS‐treated TM3 cells. Overall, toxicological pathway analysis using gene expression profiling showed that oxidative stress might be an important factor in cell death in TM3 cells affected by EDS treatment.

EISCAT Observation of Wave‐Like Fluctuations in Vertical Velocity of Polar Mesospheric Summer Echoes Associated With a Geomagnetic Disturbance

By analyzing a data set from the European Incoherent SCATter (EISCAT) Very High Frequency (VHF) radar at Tromsø, we find that both radar reflectivity and upward ion velocity in a polar mesospheric summer echo (PMSE) layer simultaneously increased at the commencement of a local geomagnetic disturbance, which occurred at midnight on 9 July 2013. The onset of the upward velocity was followed by periodic repetition of ~5 min during the initial 30-min stage, and then at later stage the vertical velocity oscillated with ~7and ~20-min periodicities at 85to 90-km altitudes. The ~5-min periodicity is close to the buoyancy period, and the ~7and ~20min periodicities are consistent with gravity waves, thus suggesting that gravity waves can be generated by the effects of the geomagnetic disturbance. On the other hand, the variation of PMSE intensity (85–90 km) was in phase with fluctuations of electron densities (90–110 km) with ~12and ~13-min periodicities at the initial and later stages, respectively. The initial creation of PMSE can be attributed to both the sudden onset of particle precipitation and ice particles produced by adiabatic cooling during the rapid updraft, as detected by large upward velocity. Our periodogram analysis suggests that variations of PMSE intensity seem to follow the same periods with E region electron density, which is moduled by energetic electron precipitation, while vertical velocity oscillates at atmospheric gravity wave periods.

Detection of RTP801, a Gene That is Differentially Expressed in Irradiated HeLa Cells

PURPOSEnTo quantify the effects of irradiation on the expression levels of a differentially expressed gene, RTP801, in HeLa cells.nnnMATERIALS AND METHODSnTotal RNA was isolated from irradiated and non-irradiated HeLa cells. A subtraction library was constructed, from which 88 random clones were screened. The expression patterns of one clone, detected by reverse Northern blotting, were quantified by real time RT-PCR, using CYBR green I dye.nnnRESULTSnRTP801, a hypoxia-inducible factor-I-responsive gene, was identified as a differentially expressed gene in HeLa cells exposed to X-ray. Real time RT-PCR showed that the mRNA levels of RTP801 were greatly diminished by radiation.nnnCONCLUSIONSnThese results suggest that down-regulation of hypoxia-inducible factor-I-responsive genes, such as RTP801, in irradiated HeLa cells may result in reductions in the radiotherapy resistance of tumor cells.