Effect of gamma radiation on cytokine expression and cytokine-receptor mediated STAT activation.
OBJECTIVE
The expression of cytokine mRNA and their related transcription factors was examined in order to assess the effects of gamma radiation on the immune function of murine splenocytes.


METHODS
Splenocytes were collected from seven-week-old female Balb/c mice, and then irradiated at a dose of 5 Gy of 60Co gamma-ray at a dose rate of 1.394 Gy/min. Total RNA was extracted from both irradiated and non-irradiated splenocytes at 1/2, 1, 3, 6, and 24 h and analysed by reverse transcription-polymerase chain reaction (RT-PCR).


RESULTS
The mRNA level of interferon (IFN)-gamma, which is a Th1-type (T helper cell type 1) cytokine, was reduced after 3 h post-irradiation, whereas the interleukin (IL)-2 mRNA in the naïve splenocytes had no significant changes within the 24 h after irradiation. Moreover, IFN-gamma and IL-2 mRNA expression in concanavalin A (Con A, 2.5 mug/ml) activated-splenocytes was significantly reduced by gamma irradiation. On the other hand, the mRNA level of the Th2 type (T helper cell type 2) cytokines, such as IL-4, IL-5 and IL-10, was increased both in naïve and activated splenocytes, and pro-inflammatory cytokines were also rapidly induced in response to irradiation in naïve splenocytes. Interestingly, gamma irradiation had no effect on transforming growth factor (TGF)-beta mRNA expression. Moreover, the mRNA levels of the leucine zipper trqnscription factor c-Maf and GATA binding protein-3 (GATA-3), which regulate IL-4 and IL-5 transcription, were found to have been up-regulated. However, the mRNA coding for interferon regulatory factor (IRF)-1, which is involved in IFN-gamma production, was reduced 6 h post-irradiation. The level of signal transducers and activators of transcription (Stat)-1 and Stat-4 phosphorylation, which are activated by IFN-gamma and IL-12, respectively, was significantly reduced by gamma irradiation, but IL-4 receptor mediated Stat-6 activation remained unchanged.


CONCLUSIONS
These results suggest that gamma irradiation may play a role in Th1 and Th2 cytokine expression, via regulation of the level of cytokine-mediators through transcriptional modulation and Stat signaling. These results are helpful to understand general profile of cytokine expression in response to gamma irradiation.
Han
Seon-Kyu
SK
Laboratory of Radiation Immunology, Korea Institute of Radiological and Medical Sciences, Nowon-ku, Seoul.
Song
Jie-Young
JY
Yun
Yeon-Sook
YS
Yi
Seh-Yoon
SY
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D015870:Gene Expression / Q000502:physiology / Q000528:radiation effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D011829:Radiation Dosage; D018121:Receptors, Cytokine / Q000378:metabolism* / Q000528:radiation effects; D050791:STAT Transcription Factors / Q000378:metabolism* / Q000528:radiation effects; D013154:Spleen / Q000276:immunology* / Q000528:radiation effects*
D016207:Cytokines; D018121:Receptors, Cytokine; D050791:STAT Transcription Factors