Genistein prevents ultraviolet B radiation-induced nitrosative skin injury and promotes cell proliferation.

Nitric oxide (NO) levels increase considerably after 24h of exposure of skin to ultraviolet B (UVB) radiation, which leads to nitrosative skin injury. In addition, increased NO levels after exposure to UVB radiation are associated with inhibition of cell proliferation. Compared to the UV-control group, UV-genistein at 10 mg/kg (UV-GEN10) group showed tissue protection, decreased lipid peroxide and nitrotyrosine formation, and low CAT activity. Furthermore, NO levels and iNOS labeling remained high. In this group, the reduction in lipid peroxides and nitrotyrosine was accompanied by upregulation of cell proliferation factors (Ki67 and PCNA), which indicated that prevention of nitrosative skin injury promoted cell proliferation and DNA repair. Genistein also prevented nitrosative events, inhibited ONOO(-) formation, which leads to tissue protection and cell proliferation. The UV-GEN15 group did not result in a greater protective effect compared to that with UV-GEN10 group. In the UV-GEN15 group, histological examination of the epidermis showed morphological alterations without efficient protection against lipid peroxide formation, as well as inhibition of Ki67 and PCNA, and VEGF labeling, which suggested inhibition of cell proliferation. These results help to elucidate the mechanisms underlying the photoprotective effect of genistein and reveal the importance of UVB radiation-induced nitrosative damage.

Time-dependent reactive species formation and oxidative stress damage in the skin after UVB irradiation.

This study provides evidence that skin oxidative stress injury caused by UVB irradiation is mediated predominantly by reactive oxygen species immediately after irradiation and by reactive nitrogen species at later time points. Animals were pre-treated with free radical scavengers (deferrioxamine, histidine), α-tocopherol, or inhibitors of nitric oxide synthase (NOS) (L-NAME or aminoguanidine) or left untreated and subjected to UVB irradiation. α-Tocopherol inhibited the increase in lipid peroxidation, as evaluated by chemiluminescence at 0 h and 24 h after UVB irradiation. Immediately after UVB irradiation, lipid peroxidation increased moderately and was abolished by free radical scavengers but not by NOS inhibitors. Likewise, the reduction of antioxidant capacity was not reversed by NOS inhibitors. Nitric oxide augmentation was not observed at this time point. Twenty-four hours after irradiation, increased lipid peroxidation levels and nitric oxide elevation were observed and were prevented by NOS inhibitors. Low concentrations of GSH and reduced catalase activity were also observed. Altogether, these data indicate that reactive oxygen species (singlet oxygen and hydroxyl radicals) are the principal mediators of immediate damage and that reactive nitrogen species (*NO and possibly ONOO(-)) seem to be involved later in skin oxidative injury induced by UVB radiation. The reduced catalase activity and low level of GSH suggest that *NO and H(2)O(2) may react to generate ONOO(-), a very strong lipid peroxidant species.

Photoaging and chronological aging profile: Understanding oxidation of the skin.

The impact of chronological aging and photoaging on the skin is particularly concerning, especially when oxidative stress is involved. This article provides evidence of quantitative and qualitative differences in the oxidative stress generated by chronological aging and photoaging of the skin in HRS/J hairless mice. Analysis of the results revealed an increase in lipid peroxides as the skin gets older and in photoaged skin (10.086 ± 0.70 η MDA/mg and 14.303 ± 1.81 η MDA/mg protein, respectively), although protein oxidation was only verified in chronological aged skin (15.449 ± 0.99 η protein/mg protein). The difference between both skin types is the decay in the capacity of lipid membrane turnover revealed by the dislocation of older skin to the left in the chemiluminescence curve. Imbalance between antioxidant and oxidation processes was verified by the decrease in total antioxidant capacity of chronological and photoaged skins. Although superoxide dismutase remained unchanged, catalase increased in the 18 and 48-week-old skin groups and decreased in irradiated mice, demonstrating that neither enzyme is a good parameter to determine oxidative stress. The differences observed between chronological and photoaging skin represent a potential new approach to understanding the phenomenon of skin aging and a new target for therapeutic intervention.

Iron-regulated outer-membrane proteins of strains of avian septicemic Escherichia coli.

1. Outer-membrane protein patterns of Escherichia coli recovered from the peritoneal cavities of infected guinea pigs and grown in medium M9 containing 2,2'-dipyridyl were studied by polyacrylamide gel electrophoresis (SDS-PAGE) to determine whether in vivo conditions of growth affected the expression of these bacterial surface proteins. 2. Eleven strains of septicemic E. coli studied in vitro under conditions of iron restriction expressed iron-regulated outer-membrane proteins, mainly the protein of approximately 74 kDa, whereas avirulent strains grown under similar conditions did not present the 74-kDa protein. 3. These results show the distribution of iron-regulated outer-membrane proteins among avian E. coli and suggest that the protein of approximately 74 kDa may be important for the virulence of these strains.

Iron-regulated outer-membrane proteins of strains of avian septicemic Escherichia coli

1. Outer-membrane protein patterns of Escherichia coli recovered from the peritoneal cavities of infected guinea pigs and grown in medium M9 containing 2,2'-dipyridyl were studied by polyacrylamide gel electrophoresis (SDS-PAGE) to determine whether in vivo conditions of growth affected the expression of these bacterial surface proteins. 2. Eleven strains of septicemic E. coli studied in vitro under conditions of iron restriction expressed iron-regulated outer-membrane proteins, mainly the protein of approximately 74 kDa, whereas avirulent strains grown under similar conditions did not present the 74-kDa protein. 3. These results show the distribution of iron-regulated outer-membrane proteins among avian E. coli and suggest that the protein of approximately 74 kDa may be important for the virulence of these strains.