A Synthetic Superoxide Dismutase/Catalase Mimetic (EUK-134) Inhibits Membrane-Damage-Induced Activation of Mitogen-Activated Protein Kinase Pathways and Reduces p53 Accumulation in Ultraviolet B-Exposed Primary Human Keratinocytes

Abstract

Salen-manganese complexes exhibit powerful superoxide dismutase and catalase activity, with pharmacologic efficacy in several oxidative-stress-associated disease models. Ultraviolet (UV) B not only induces direct DNA damage, but also generates oxidative stress. EUK-134, a salen-manganese complex, might therefore confer a direct protection against UVB-induced oxidative stress and consequently alleviate UVB-damage-induced signal transduction. We investigated the effect of EUK-134 on the UVB-induced accumulation and stabilization of the p53 protein. p53 plays a central role in the UVB response, both as sensor of UVB damage and as a mediator of a protective response. Cells treated with EUK-134 before UVB irradiation showed a significantly lower accumulation of the p53 protein in a concentration-dependent fashion. Furthermore, EUK-134 severely reduced N-terminal phosphorylation of p53. The extracellular signal-regulated kinase ERK and the stress-activated kinases JNK and p38 have been implicated in the UVB-induced N-terminal phosphorylation and accumulation of p53. Pre-treatment with EUK-134 inhibited the UVB-induced activation of these mitogen-activated protein kinase (MAPK) pathways. We hypothesize that EUK-134, by direct protection of the membrane from UVB-induced oxidative damage, reduces oxidative stress induced MAPK signaling and consequently lowers the level of p53 induction. The protection conferred by EUK-134 resulted in a significant increase in cell survival following UVB irradiation.

A Low UVB Dose, with the Potential to Trigger a Protective p53-Dependent Gene Program, Increases the Resilience of Keratinocytes against Future UVB Insults

“…Consistent with earlier observations (Courtois et al, 1997;Decraene et al, 2004), p53 protein levels accumulated in UVB-exposed cells. Phosphorylation of p53 at serine 15, which is required for p53 stabilization (She et al, 2000), was readily observable both after irradiation with a low (8 mJ per cm 2 ) or a high (32 mJ per cm 2 ) UVB dose.…”

“…p53, a nuclear phosphoprotein, functions as a transcription factor with a central role in the stress-response of keratinocytes (Decraene et al, 2004). In its wild-type form, the p53 protein becomes activated in response to a myriad of stress types, not in the least genotoxic stress (through either ultraviolet radiation, ionizing radiation, or chemical agents).…”

Superoxide Dismutase Mimics: Chemistry, Pharmacology, and Therapeutic Potential

“…The effect of Mn salens in neurodegenerative disorders was summarized in a review by Patel (133). The effect on the inhibition of MAPK signaling pathways and decrease in p53 accumulation in ultraviolet B-exposed primary human keratinocytes, leading to increased cell survival, was reported with EUK-134 (84). A rather unexpected effect of EUK-8 as well as of the NADPH oxidase inhibitor, diphenyleneiodonium, on promoting the induction of TGF-b, was observed (339).…”

Targeting the Overproduction of Peroxynitrite for the Prevention and Reversal of Paclitaxel-Induced Neuropathic Pain

“…The SOD activity of PNDCs was determined by their competitive inhibition of luminal oxidation by xanthine/xanthine oxidase-derived superoxide (Bensinger and Johnson, 1981;Kimura and Nakano, 1988;Decraene et al, 2004). Serially diluted compounds were tested in duplicate by adding 50 l of compound/vehicle [4ϫ in TE buffer: 50 mM Tris-HCl, pH 7.8, and 1 mM EDTA] and 50 l of xanthine oxidase from bovine milk, Grade III (0.4 U/ml in TE) to a 96-well white-walled microplate.…”