Amifostine induces antioxidant enzymatic activities in normal tissues and a transplantable tumor that can affect radiation response.

Purpose: To determine whether amifostine can induce elevated manganese superoxide dismutase (SOD2) in murine tissues and a transplantable SA-NH tumor, resulting in a delayed tumor cell radioprotective effect.

Methods And Materials: SA-NH tumor-bearing C3H mice were treated with a single 400 mg/kg or three daily 50 mg/kg doses of amifostine administered intraperitoneally. At selected time intervals after the last injection, the heart, liver, lung, pancreas, small intestine, spleen, and SA-NH tumor were removed and analyzed for SOD2, catalase, and glutathione peroxidase (GPx) enzymatic activity.

Maintenance of manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by repeated administration of the free thiol form of amifostine.

Thiol-containing drugs such as WR1065, the free thiol form of amifostine, have been shown to induce a delayed radioprotective effect in both malignant and non-malignant cells. In mammalian cells exposed to a dose as low as 40 microM WR1065, the redox-sensitive nuclear transcription factor kappaB (NFkappaB) is activated, leading to an elevation in the expression of the antioxidant gene manganese superoxide dismutase (SOD2) and a concomitant increase in active SOD2 enzyme levels that peaks 24 to 32 h later. Exposure of cells to ionizing radiation during the period of elevated SOD2 enzymatic activity results in an enhanced radiation resistance.

Relationship between phosphorylated histone H2AX formation and cell survival in human microvascular endothelial cells (HMEC) as a function of ionizing radiation exposure in the presence or absence of thiol-containing drugs.

Human microvascular endothelial cells (HMEC) were exposed to ionizing radiation at doses ranging from 0 to 16 Gy in either the presence or absence of the active thiol forms of amifostine (WR1065), phosphonol (WR255591), N-acetyl-l-cysteine (NAC), captopril or mesna. Each of these clinically relevant thiols, administered to HMEC at a dose of 4 mM for 30 min prior to irradiation, is known to exhibit antioxidant properties. The purpose of this investigation was to determine the relationship(s), if any, between the frequency of radiation-induced histone H2AX phosphorylation at serine 139 (gamma-H2AX) in cells and subsequent survival, as assessed by colony-forming ability, in exposed cell populations as a function of the presence or absence of each of the five thiol compounds during irradiation.

Manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by the free thiol form of amifostine and tumor necrosis factor alpha.

RKO36 cells, a subclone of RKO colorectal carcinoma cells that have been stably transfected with the pCMV-EGFP2Xho vector, were grown to confluence and then exposed to either the radioprotector WR-1065, i.e. the active thiol form of amifostine, for 30 min at doses of 40 microM and 4 mM or the cytokine tumor necrosis factor alpha (TNFalpha, TNFA) for 30 min at a concentration of 10 ng/ml and then washed.