Solar ultraviolet (UV)A radiation is a well known trigger of signaling responses in human skin fibroblasts. One important consequence of this stress response is the increased expression of matrix metalloproteinase-1 (MMP-1), which causes extracellular protein degradation and thereby contributes to photoaging of human skin. In the present study we identify the proteasome as an integral part of the UVA-induced, intracellular signaling cascade in human dermal fibroblasts. UVA-induced singlet oxygen formation was accompanied by protein oxidation, the cross-linking of oxidized proteins, and an inhibition of the proteasomal system. This proteasomal inhibition subsequently led to an accumulation of c-Jun and phosphorylated c-Jun and activation of activator protein-1, i.e. transcription factors known to control MMP-1 expression. Increased transcription factor activation was also observed if the proteasome was inhibited by cross-linked proteins or lactacystin, indicating a general mechanism. Most importantly, inhibition of the proteasome was of functional relevance for UVA-induced MMP-1 expression, because overexpression of the proteasome or the protein repair enzyme methionine sulfoxide reductase prevented the UVA-induced induction of MMP-1. These studies show that an environmentally relevant stimulus can trigger a signaling pathway, which links intracellular and extracellular protein degradation. They also identify the proteasome as an integral part of the UVA stress response.Solar ultraviolet A (UVA; 320 -400 nm) radiation is a well known trigger of signaling responses in human dermal fibroblasts in vitro as well as in vivo in human skin (1-3). One important consequence of this stress response is the increased expression of matrix metalloproteinase-1 (MMP-1), 8 which causes extracellular protein degradation and thereby contributes to photoaging of human skin. In fact, UVA-induced MMP-1 expression and the resulting increased degradation of collagen fibers, which occurs primarily in the upper part of the dermis, is thought to be a major reason for wrinkle formation in photoaged human skin (4 -6).The specific signaling steps involved in UVA radiation-induced MMP-1 expression have been extensively examined in recent years. These studies have identified UVA radiation-induced singlet oxygen formation as the initiating event (for review, see Ref. 7) that triggers a cascade of downstream steps which critically involve the activation of the transcription factor complex AP-1 and the subsequent increase in expression of MMP-1. This signaling model, however, includes a black box, because the precise signaling steps linking singlet oxygen with AP-1 activation are largely unknown.In this regard it is of interest that skin fibroblasts in the upper part of the dermis, i.e. exactly the compartment where collagen degradation takes place, contain increased amounts of oxidized proteins (8). The functional relevance of protein oxidation in human skin is not known. Under normal conditions oxidized proteins are being degraded by the proteas...

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Acrylamide (AA), a widely used industrial chemical, is shown to be neurotoxic, mutagenic and carcinogenic. This study was carried out to investigate the effects of different doses of AA on lipid peroxidation (LPO), haemolysis, methaemoglobin (MetHb) and antioxidant system in human erythrocytes in vitro. Erythrocyte solutions were incubated with 0.10, 0.25, 0.50 and 1.00 mM of AA at 37°C for 1 hour. At the end of the incubation, malondialdehyde (MDA), an end product of LPO, was determined by liquid chromatography (LC) while total glutathione, reduced glutathione (GSH) levels, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzymes and the rates of haemolysis and MetHb were determined by spectrophotometric methods. All of the studied concentrations of AA increased MetHb formation and SOD activity, and induced MDA formation and haemolysis due to the destruction of erythrocyte cell membrane. AA caused a decrease in the activities of GSH-Px, CAT and GSH levels. However, these effects of AA were seen only at higher concentrations than AA intake estimated for populations in many countries. We suggest that LPO process may not be involved in the toxic effects of AA in low concentrations, although the present results showed that the studied concentrations of AA exert deteriorating effects on antioxidant enzyme activities, LPO process and haemolysis.

Methiocarb (MC) is a widely used carbamate pesticide in agriculture and health programs. Although the main molecular mechanism of carbamate toxicity involves acetylcholinesterase inhibition, studies have also implicated the induction of oxidative stress. Therefore, the present study was aimed to evaluate the effect of acute MC exposure on lipid peroxidation, antioxidant defense systems, histological changes in Wistar rats and the protective effect of pretreatment with vitamin E and taurine. A total of 48 rats were randomly divided into six groups. Rats in group I were given corn oil, while those in group III were dosed with vitamin E (100 mg/kg body weight (b.w.)) and in group V were dosed with taurine (50 mg/kg b.w.). Rats in group II were administered with MC only (25 mg/kg b.w., 1/4 of median lethal dose (LD(50))), while those in groups IV and VI were pretreated with vitamin E (100 mg/kg b.w.) and taurine (50 mg/kg b.w.) for 20 days, respectively, and then exposed to MC (25 mg/kg b.w.). The rats administered with MC showed significant increase in the levels of malondialdehyde in the liver and kidney as an index of lipid peroxidation. Levels of glutathione and activities of superoxide dismutase, catalase and glutathione peroxidase were significantly increased, while activity of glutathione reductase remained unchanged in both the tissues after MC treatment. Mild degenerative histological changes were observed in liver tissue, while the changes in kidney tissue were more severe then liver after MC treatment. Pretreatment with vitamin E and taurine resulted in a significant decrease in the lipid peroxidation and alleviating effects on antioxidant defense systems in both the tissues, while protective effects on the histological changes were shown only in kidney when compared with liver. In conclusion, the study has demonstrated that the acute MC exposure in Wistar rats caused oxidative damage on liver and kidney, which were partly ameliorated by the pretreatment of vitamin E and taurine.

These results suggest that the VEGF polymorphisms might play a role in the development of CRC. Therefore, the VEGF polymorphisms might be further investigated to use in the determination of risk factors for CRC and to have a predictive value for anti-VEGF-targeted cancer therapies.