Transcription and activity of antioxidant enzymes after ionizing irradiation in radiation-resistant and radiation-sensitive mice

Abstract

The involvement of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase in radiobiological processes has been described at the enzyme activity level. We irradiated radiationresistant (RR) and radiation-sensitive (RS) mice and studied antioxidant enzymes at the transcriptional and activity level. In addition, aromatic hydroxylation and lipid peroxidation parameters were determined to study radiation resistance at the oxidation level. RS BALB͞c͞J Him mice and RR C3H He͞Him mice were whole-body-irradiated with x-rays at 2, 4, and 6 Gy and killed 5, 15, and 30 min after irradiation. mRNA was isolated from liver and hybridized with probes for antioxidant enzymes and ␤-actin as a housekeeping gene control. Antioxidant enzyme activities were determined by standard assays. Parameters for aromatic hydroxylation (o-tyrosine) and lipid peroxidation (malondialdehyde) were determined by HPLC methods. Antioxidant transcription was unchanged in contrast to antioxidant activities; SOD and CAT activities were elevated within 15 min in RR animals but not in RS mice, at all doses studied. Glutathione peroxidase activity was not different between RR and RS mice and was only moderately elevated after irradiation. No significant differences were found between RR and RS animals at the oxidation level, although a radiation dose-dependent increase of oxidation products was detected in both groups. We found that ionizing irradiation led to increased antioxidant activity only minutes after irradiation in the absence of increased transcription of these antioxidant enzymes. RR animals show higher antioxidant enzyme activities than do RS mice, but oxidation products are comparable in RS and RR mice. As unchanged transcription of antioxidant enzymes could not have been responsible for the increased antioxidant enzyme activities, preformed antioxidant enzymes should have been released by the irradiation process. This would be in agreement with previous studies of preformed, stored SOD. The finding of higher SOD and CAT activities in RR than in RS animals could point to a role for these antioxidant enzymes for the process of radiation sensitivity.

Synergistic activation of p53-dependent transcription by two cooperating damage recognition pathways

“…p53 protein can activate an ionizing radiation-dependent apoptotic pathway in tissue known to be acutely sensitive to radiation in vivo (Macleod et al, 1995). In addition to p53 and other components of the DNA-damage repair pathway including scid and PARP (Biedermann et al, 1991;Wesierska-Gadek et al, 1999), two factors implicated in oxidative stress-responses and which regulate the rates of irradiation injury include Superoxide Dismutase and Catalase (Hardmeier et al, 1997). Ionizing radiation induces damage not only to DNA but to lipids and proteins in part from the generation of highly reactive oxygen intermediates.…”

Cell phenotype specific kinetics of expression of intratracheally injected manganese superoxide dismutase–plasmid/liposomes (MnSOD–PL) during lung radioprotective gene therapy

“…Previous data indicated that irradiation results in increased endogenous MnSOD-mRNA as well as increased MnSOD biochemical activity following irradiation. 19,20 Ionizing irradiation induces expression of NFk-B, and its activation of the promoter for the MnSOD gene may be the mechanism of increased endogenous MnSOD expression. 21,22 Administration of HA-MnSOD-PL in previous studies was as protective as non-tagged MnSOD with respect to decreased irradiation relative to organizing alveolitis and persistent biochemical activity.…”

Positive and negative regulatory elements in the upstream region of the rat Cu/Zn-superoxide dismutase gene

“…Other studies have demonstrated that extracellular SOD is up-regulated along with inducible nitric oxide synthase after nuclear factor-κB (NF-κB) activation [12]. Hardmeier et al [13] reported that SOD activities were also increased at a very early post-irradiation period. The ACE1…”