RESUMO
The UVA component of sunlight induces DNA damage, which are basically responsible for skin cancer formation. Xeroderma Pigmentosum Variant (XP-V) patients are defective in the DNA polymerase pol eta that promotes translesion synthesis after sunlight-induced DNA damage, implying in a clinical phenotype of increased frequency of skin cancer. However, the role of UVA-light in the carcinogenesis of these patients is not completely understood. The goal of this work was to characterize UVA-induced DNA damage and the consequences to XP-V cells, compared to complemented cells. DNA damage were induced in both cells by UVA, but lesion removal was particularly affected in XP-V cells, possibly due to the oxidation of DNA repair proteins, as indicated by the increase of carbonylated proteins. Moreover, UVA irradiation promoted replication fork stalling and cell cycle arrest in the S-phase for XP-V cells. Interestingly, when cells were treated with the antioxidant N-acetylcysteine, all these deleterious effects were consistently reverted, revealing the role of oxidative stress in these processes. Together, these results strongly indicate the crucial role of oxidative stress in UVA-induced cytotoxicity and are of interest for the protection of XP-V patients.
Assuntos
Reparo do DNA/efeitos da radiação , Fibroblastos/efeitos da radiação , Pontos de Checagem da Fase S do Ciclo Celular/efeitos da radiação , Raios Ultravioleta/efeitos adversos , Acetilcisteína/farmacologia , Linhagem Celular Transformada , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Dano ao DNA , Reparo do DNA/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , Replicação do DNA/efeitos da radiação , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Fibroblastos/patologia , Humanos , Nocodazol/farmacologia , Oniocompostos/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/efeitos da radiação , Carbonilação Proteica/efeitos dos fármacos , Carbonilação Proteica/efeitos da radiação , Pontos de Checagem da Fase S do Ciclo Celular/efeitos dos fármacos , Xeroderma Pigmentoso/genética , Xeroderma Pigmentoso/metabolismo , Xeroderma Pigmentoso/patologiaRESUMO
The use of soluble and highly oxidizing Ag(III) in the form of the tetrahydroxoargentate ion Ag(OH)4- is reported for the oxidation of surrogate organic recalcitrant dyes (i.e., rhodamine 6G (Rh6G) and fluorescein (Fl)). The possible use of Ag(OH)4- for the treatment of these and other refractory compounds is assessed. Such dyes were selected due to their common occurrence, stability, refractory nature, the relatively high toxicity of Rh6G, and their structural similarity to Fl. Several reaction intermediates/products were identified. The results showed that the highly oxidizing tetrahydroxoargentate anion was capable of degrading these recalcitrant dyes. Furthermore, the final degradation products do not represent a higher environmental risk than the original surrogates themselves. In addition, the partial mineralization of the dyes was proven.
Assuntos
Corantes/química , Poluentes Ambientais/química , Prata/química , Íons/química , Oxirredução , Rodaminas/químicaRESUMO
Investigations of the redox process and chemical speciation of Hg(II) lead to a better understanding of biogeochemical processes controlling the transformation of Hg(II) into toxic and bioaccumulative monomethyl mercury, mainly in areas contaminated with Hg(0). This study investigates the speciation and redox processes of Hg in soil samples from a small area contaminated with Hg(0) as a result of gold mining activities in the rural municipality of Descoberto (Minas Gerais, Brazil). Soil samples were prepared by adding Hg(0) and HgCl2 separately to dry soil, and the Hg redox process was monitored using thermodesorption coupled to atomic absorption spectrometry. A portion of the Hg(0) added was volatilized (up to 37.4±2.0%) or oxidized (from 36±7% to 88±16%). A correlation with Mn suggests that this oxidation is favored, but many other factors must be evaluated, such as the presence of microorganisms and the types of organic matter present. The interaction of Hg with the matrix is suggested to involve Hg(II)-complexes formed with inorganic and organic sulfur ligands and/or nonspecific adsorption onto oxides of Fe, Al and/or Mn. The kinetics of the oxidation reaction was approximated for two first-order reactions; the faster reaction was attributed to the oxidation of Hg(0)/Hg(I), and the slower reaction corresponded to Hg(I)/Hg(II). The second stage was 43-139 times slower than the first. The samples spiked with Hg(II) showed low volatilization and a shifting of the signal of Hg(II) to lower temperatures. These results show that the extent, rate and type of redox process can be adverse in soils. Descoberto can serve as an example for areas contaminated with Hg(0).