Peroxiredoxin I (Prx-I), a key member of the peroxiredoxin family, reduces peroxides and equiva- lents through the thioredoxin system. Our previous work has shown that expression of Prx-I in mammalian cells increases following ionizing radiation (IR), indicating that Prx-I actively responds to IR-induced reactive oxygen species (ROS) and suggesting that Prx-I plays an important role in protecting cells from IR-induced death. To test this hypothesis, we suppressed the expression of Prx-I in SW480 cells by RNA interference. Our results show that IR induces the expression of Prx-I in SW480 cells in a dose- and time- dependent manner. The recombinant siRNA vector targeting Prx-I dramatically reduced the expression of Prx-I in SW480 cells. When Prx-I was knocked down in SW480 cells, the cells exhibited a decreased growth rate, a reduced antioxidant capability following IR and became more sensitive to IR-induced apo- ptosis. Together, our results demonstrate that Prx-I plays an important role in protecting cells from IR- induced cell death, which might be through scavenging IR-induced ROS in the cells.

AIM: To clone and express mouse peroxiredoxin I in IEC-6 cells. METHODS: Total RNAs were isolated from cultured IEC-6 cells, and the coding region of peroxiredoxin I was amplified by RT-PCR. After it was cloned into T-vector and sequenced, pSG5 was used to transiently express peroxiredoxin I in IEC-6 by liposome-mediated transfection, and the expression of peroxiredoxin I was evaluated by RT-PCR and Western blot. RESULTS: A DNA fragment about 750 bp was amplified from total RNAs of IEC-6 cells using specific primers of peroxiredoxin I. The sequencing confirmed the coding region was successfully cloned into T-vector, which was completely coincident with the sequence in GeneBank. After the EcoRI-BamHI fragment of T-vector containing peroxiredoxin I was inserted into pSG5, the recombinant plasmid was transferred to IEC-6 cells. RT-PCR assay showed that a DNA fragment of 930 bp could be amplified, which indicated the transcription of pSG5-Prx. Western blot confirmed the expression of peroxiredoxin I in IEC-6 cells. CONCLUSION: Mouse peroxiredoxin I can be successfully expressed in IEC-6 cells.

Objective: To investigate the effect of Calpain inhibitor I on glucoconicoid receptor-dependent proteasomal degradation and its transcriptional activity. Methods: After Raw-264.7 cells were treated with Calpain inhibitor I, dexam- ethasone. or both for about 12 h. the change of glucocorticoid receptor was detected by westem blot analysis. COS. -7 cells were transfected with PRsh-GRa expression vector and glucocorticoid-responsive receptor pMAMneo-CAT, then the effect of Calpain inhibitor I on glucocorticoid receptor transcriptional activation ability was detennined by CAT activity. Results: The glucocorticoid receptor levels decreased after RAW-264.7 cells were treated with dexamethasone for 12 hours. which effect can be inhibited by Calpain inhibitor I to some extent. CAT activity assay showed that Calpain inhibitor I enhance glucoconi- coid receptor transcriptional activity. Condusion: Calpain inhibitor I can inhibit the down-regulation of dexamethasone on glucocorticoid receptor, and enhances glucocorticoid receptor transactivation ability.

AIM: To identify the differentially expressed proteins involved in ionizing radiation in mice and to explore new ways forstudying radiation-related proteins.

Preliminaryexperimentsindicatedthattargetcellswereresistanttoglucocorticoid(GC)afterpathologicalstress.Thisstudywasdesigned to investigate the alterations in plasma corticosterone level and GC receptor (GR) of liver cytosols, to assess the relative inflammatory cytokines contribution to GC resistant, and to observe the action of-melanocyte-stimulating hormone (-MSH) on the potential impli-cations of glucocorticord regulatory effects in burned rats. Male Wistar rats (weight range, 180-200g) received a 35% total body surface area immersion scald and were randomly divided to receive either tumor necrosis factor (TNF), interleukin-1 (IL-1), polyclonal antibody(pAb),-MSH,Ac-D-Lys-L-Pro-D-Val(KPVpeptide),orsaline(control).Thebindingcapacity(Rt)ofthesteroid-bindingsites Preliminary experiments indicated that target cells were resistant to glucocorticoid (GC) after pathological stress. This study was designed to investigate the alterations in plasma corticosterone level and GC receptor (GR) of liver cytosols, to assess the relative inflammatory cytokines contribution to GC resistant. and to observe the action of a-melanocyte-stimulating hormone (a-MSH) on the potential impli- cations of glucocorticord regulatory effects in burned rats. Male Wistar rats (weight range, 1 80-200 g) received a 3 5% total body surface area immersion scald and were randomly divided to receive either tumor necrosis factor a (TNFa), interleukin-l [3 (11-1 [3), polyclonal antibody (pAb), a-MSH. Ac-D-Lys-L-Pro-D-Val (KPV peptide), or saline (controD.The binding capacity (Rt) of the steroid-binding sites was measured by radioligand binding assay, using [3H]dexamethasone as the ligand. We examined plasma levels of 11-1 [3, TNFa, IL-10, and corticosterone following scald challenge in rats. The Rt of GR (208.45