Radioresistant DNA synthesis in fibroblast cell lines derived from LEC strain rats

Nagata

Endoh

et al. 2002

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ABSTRACT. It is known that physical disruption of cell contacts induces apoptosis of thymocytes. When thymocytes from LEC and WKAH rats were incubated in vitro at 37°C for 0-6 hr and then the proportion of apoptotic cells was determined using a flow cytometer, it was found that the percentages of apoptotic thymocytes from both LEC and WKAH rats increased with incubation time and that the proportion of apoptotic cells from LEC rats was significantly higher than that from WKAH rats at each incubation time. The fact that cycloheximide, an inhibitor of protein synthesis, did not show significant inhibitory effects on induction of apoptosis of thymocytes indicates that induction of apoptosis during in vitro cultivation did not require de novo protein synthesis. When thymocytes from LEC and WKAH rats were X-irradiated in vitro at 4 and 8 Gy, the percentages of radiation-induced apoptotic cells increased with post-incubation time after X-irradiation in both LEC and WKAH rat thymocytes and the proportions of apoptotic cells from LEC rats were significa ntly higher than those from WKAH rat cells at 2 and 4 hr post-incubation after X-irradiation. When thymocytes from LEC and WKAH rats were X-irradiated in the presence of cycloheximide, the induction of apoptosis was substantially inhibited, indicating that radiationinduced apoptosis of thymocytes from LEC and WKAH rats required de novo protein synthesis. The present results showed high sensitivities of thymocytes of LEC rats to induction of apoptosis during in vitro cultivation and by X-irradiation. KEY WORDS: apoptosis, LEC strain rat, protein synthesis, thymocyte, X-irradiation.

Section: Discussionmentioning

confidence: 59%

High Sensitivity of Thymocytes of LEC Strain Rats to Induction of Apoptosis by X-Irradiation.

Nagata

Endoh

et al. 2002

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“…Rats of this strain suffered from spontaneous fulminant hepatitis associated with severe jaundice at about 4 months of age. Other characteristics of LEC rats are a high incidence of spontaneous liver cancer in long-surviving individuals [35] and an increased sensitivity in vivo and in vitro to ionizing radiation [7,8,10]. We have reported that the hypersensitivity of LEC rats to whole-body irradiation is mainly controlled by a single autosomal recessive gene, xhs [9], and that LEC rat cells show high rates of Xirradiation-induced chromosome aberrations [22], and the abnormality of transient cell cycle arrest after X-irradiation [11].…”

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confidence: 99%

Wortmannin, a Radiation Sensitizer, Enhances the Radiosensitivity of WKAH Rat Cells but not That of LEC Rat Cells

Kawana

Endoh

et al. 2000

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ABSTRACT. No significant cytotoxic effect was observed in WKAH rat cells by the treatment of wortmannin, a radiation sensitizer, at concentrations lower than 30 µM for 24 hr. The relative surviving fractions of LEC rat cells were slightly, but significantly, lower than those of WKAH rat cells at each concentration of wortmannin. When the wortmannin-treated WKAH rat cells were X-irradiated, the relative surviving fractions decreased in a wortmannin concentration-dependent manner. On the contrary, no significant difference was observed between the survival curves of untreated and wortmannin-treated LEC rat cells after X-irradiation.-KEY WORDS: DNA-dependent protein kinase, LEC rat cell, wortmannin.

“…We have reported that the hypersensitivity of LEC rats to whole-body irradiation is controlled by a single autosomal recessive gene, xhs [7], and that LEC rat cells also show high rates of X-irradiation-induced chromosome aberrations [23]. The fibroblast cell lines established from LEC rats show a high sensitivity to Xirradiation [8]. Recently, we have shown that radiation-induced delay in the progression from G1 to S phase is not observed in LEC rat cells [9].…”

mentioning

confidence: 99%

“…Thus, LEC rat cells display similar characteristics to AT cells. However, the effect of X-irradiation on G2 delay in LEC rat cells remains unclear.In the present study, we examined the cell cycle progression from G2/M phase in the LEC rat cells irradiated at S phase by X-rays and showed an abnormal accumulation of G2/M-phase cells following X-irradiation.The rat fibroblast cell lines were established from the lungs of LEC and WKAH rats by SV40 immortalization as described previously [8]. Cells were grown in a monolayer culture in Eagle's minimum essential medium containing 10% fetal calf serum (FCS).…”

mentioning

confidence: 99%

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Abnormal Accumulation of G2/M-Phase Cells from LEC Strain Rats after X-Irradiation at S Phase.

Kuzumi

Arai

et al. 1999

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ABSTRACT. The effect of X-irradiation on the progression of the cell cycle in cell lines from LEC and WKAH rats was investigated by a flow cytometer. When the cells were exposed to 5 Gy of X-rays at S phase, the proportion of S-phase cells in both cell populations decreased with incubation time and that of G2/M-phase cells was approximately 80% at 6 hr post-irradiation. At 12 hr post-irradiation, approximately 45% of the WKAH rat cells appeared in the G1 phase. However, 80-90% of LEC rat cells remained in the G2/M phase and less than 5% in the G1 phase during 6-12 hr post-irradiation. Thus, the LEC rat cells irradiated at S phase remained in the G2/M phase for at least 6 hr longer than did the WKAH rat cells.-KEY WORDS: G2/M accumulation, LEC strain rat, X-irradiation.J. Vet. Med. Sci. 61(8): 975-978, 1999 Rats of this strain suffered from spontaneous fulminant hepatitis associated with severe jaundice at about 4 months of age. Other characteristics of LEC rats are a high incidence of spontaneous liver cancer in long-surviving individuals [37] and an increased sensitivity to whole-body irradiation [5,6]. We have reported that the hypersensitivity of LEC rats to whole-body irradiation is controlled by a single autosomal recessive gene, xhs [7], and that LEC rat cells also show high rates of X-irradiation-induced chromosome aberrations [23]. The fibroblast cell lines established from LEC rats show a high sensitivity to Xirradiation [8]. Recently, we have shown that radiation-induced delay in the progression from G1 to S phase is not observed in LEC rat cells [9]. Thus, LEC rat cells display similar characteristics to AT cells. However, the effect of X-irradiation on G2 delay in LEC rat cells remains unclear.In the present study, we examined the cell cycle progression from G2/M phase in the LEC rat cells irradiated at S phase by X-rays and showed an abnormal accumulation of G2/M-phase cells following X-irradiation.The rat fibroblast cell lines were established from the lungs of LEC and WKAH rats by SV40 immortalization as described previously [8]. Cells were grown in a monolayer culture in Eagle's minimum essential medium containing 10% fetal calf serum (FCS). Cell cultures were kept at ambient humidity and 37°C in an atmosphere containing 5% CO2.X-irradiation was carried out using a Hitachi MBR-1520R X-ray generator operated at 150 kV and 15 mA with a 0.5 mm Cu + 1.0 mm Al filter at a dose rate of 0.95 Gy/min.The cells (1 to 3 × 10 6 ) were incubated in the medium containing 10 µM bromodeoxyuridine (BUdR) for 30 min at 37°C, washed twice with PBS, and then exposed to 5 Gy of X-rays. After X-irradiation, the cells were incubated at 37°C for 0-16 hr, harvested by trypsinization, washed with PBS containing 2% FCS and 0.1% NaN3, and then pelleted by centrifugation at 500 × g. The cells were fixed in 5 ml Cell cycle checkpoints are crucial points for the integration of external and internal monitoring signals for progression in the cycle. It is well known that defects in the control genes of the checkpoint are assoc...