RESUMO
Sodium-copper chlorophyllin (SCC), a copper-porphyrin complex, has been shown to act as an inhibitor as well as a promoter of DNA-damage induction by a variety of mutagens in several test systems. In order to investigate the basis of this dual effect, experiments were carried out to compare the influence of pretreatment with intact SCC and that of its constituents, the metal-free protoporphyrin (PP-IX) and copper as CuCl(2). The wing-spot test was employed to monitor mutational events in somatic cells of Drosophila melanogaster. Heterozygous mwh+/+flr(3) larvae were treated for 24h with SCC, PP-IX, CuCl(2) or sucrose. Following this treatment, one group of larvae were immediately allowed to feed on instant medium containing 0.5mM N-nitroso-N-ethylurea (ENU) dissolved in phosphate buffer to reach pH 6. The remaining larvae received treatment with ENU with a delay of 1, 2 or 3days (DTD). Results revealed an (a) overall inhibitory effect for 0-DTD and 1-DTD after pretreatment with SCC, (b) only in 0-DTD after PP-IX, and (c) in all DTDs after treatment with CuCl(2). These results provide evidence that the copper ion plays a central role in the antimutagenic effect of SCC, and for a sustained period of time. Pretreatment with SCC and PP-IX produced a promoter effect at 2-DTD and 3-DTD. The results could be explained as an effect of the accumulation of metal-free porphyrin following the dissociation of the copper-porphyrin complex (SCC), the copper-ion reaching proteins to form complexes and participated in anabolic pathways.
Assuntos
Antimutagênicos/farmacologia , Clorofilídeos/toxicidade , Cobre/farmacologia , Etilnitrosoureia/toxicidade , Mutagênicos/farmacologia , Porfirinas/farmacologia , Animais , Clorofilídeos/química , Clorofilídeos/farmacologia , Drosophila/genética , Testes de Mutagenicidade , Relação Estrutura-AtividadeRESUMO
It was first demonstrated in Salmonella that higher and lower concentrations of chlorophyllin (CHLN) may have effects in opposite directions, higher doses inhibiting and lower doses promoting the mutagenic activity of certain tobacco-related nitrosamines. Previous work of our group demonstrated that CHLN may have both a promoter and an inhibitory effect on mutagenesis in Drosophila. The present paper reviews the evidence obtained in our laboratory using gamma rays as the mutagenic agent, that higher and lower pretreatment concentrations of CHLN are associated with inhibitory and promoting effects, respectively, as in Salmonella. Employing the wing spot test, 48h larvae were pretreated with various concentrations of CHLN from 0 to 69 mM and then treated with 10 Gy gamma rays. With the highest concentration of CHLN, an approximate 54% reduction in mutagenesis was observed. At 35 mM a remnant of this inhibitory effect was found in that a significant decrease was limited to the twin spot category. Evidence of promotion was first seen at 4.3mM CHLN, an effect which persisted for the remaining five lower concentrations, the most pronounced evidence of promotion being found at the four lowest concentrations, 0.03-1.1 mM CHLN. It should be noted that no evidence of genotoxicity was found for CHLN alone, an observation consistent with the several reports in the literature. The results are taken as strong evidence that pretreatment with low concentrations of CHLN promotes DNA damage induced by gamma rays in somatic cells of Drosophila.
Assuntos
Clorofilídeos/farmacologia , Clorofilídeos/toxicidade , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/efeitos da radiação , Raios gama/efeitos adversos , Mutagênicos/toxicidade , Animais , Clorofilídeos/administração & dosagem , Relação Dose-Resposta a Droga , Drosophila/genética , Testes de Mutagenicidade , Protetores contra Radiação/farmacologiaRESUMO
AIMS: Chlorophyllin (CHLN) is a synthetic derivative of chlorophyll that possesses antimutagenic activity against several environmental contaminants. In the present study, CHLN was assayed for its capacity to prevent nuclear fragmentation (NF) in HEp-2 cells infected with poliovirus. METHODS AND RESULTS: CHLN was assayed at concentrations of 0.5 and 2.5 microg ml(-1), and NF was monitored using the comet assay and acridine orange staining. We demonstrated that CHLN reduced the percentage of NF in poliovirus-infected HEp-2 cells, when cells were treated with drug before infection or exposed continuously to drug. However, the highest degree of protection was achieved when the virus was exposed to CHLN before infection followed by protocol where infected cultures were continuously exposed to the drug after infection. CONCLUSIONS: It is suggested that CHLN primarily binds to the virus which inhibits cell penetration, thereby maintaining nuclear integrity. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering that CHLN has several beneficial properties and no significant toxic effects in humans and animals, it would be an ideal candidate drug to test for antiviral activity.
Assuntos
Antivirais/toxicidade , Clorofilídeos/toxicidade , Fragmentação do DNA/efeitos dos fármacos , Poliovirus/efeitos dos fármacos , Linhagem Celular Tumoral , Núcleo Celular/efeitos dos fármacos , Ensaio Cometa , HumanosRESUMO
Chlorophyllin, a sodium-copper salt derivative of chlorophyll-a and -b, was evaluated for antimutagenic activity against ethyl methane sulfonate by the hypoxanthin-guanine-phosphoribosyl transferase (HGPRT) assay. The results obtained suggest that this chlorophyllin can potentiate the mutagenicity of an alkylating agent which induces DNA damage.
Assuntos
Clorofilídeos/genética , Clorofilídeos/toxicidade , Hipoxantina Fosforribosiltransferase/efeitos dos fármacos , Testes de Mutagenicidade/métodos , Animais , Células CHO , Clorofilídeos/efeitos adversos , Clorofilídeos/farmacocinética , Cricetinae , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Sinergismo Farmacológico , Metanossulfonato de Etila/efeitos adversos , Feminino , Hipoxantina Fosforribosiltransferase/genética , Mutagênese Sítio-Dirigida , Mutagênicos/efeitos adversosRESUMO
Chlorophyll and its derivatives are examples of plant compounds (purified and/or extracted) which appear to protect DNA from damage caused by chemical or physical agents, although some studies have identified clastogenic activity of these compounds. This study was carried out to assess the genotoxic activity of chlorophyll-a (Chl-a), -b (Chl-b) and chlorophyllin (Chl) and their antigenotoxic activity against the DNA damage induced by methyl methanesulphonate (MMS) under conditions of simultaneous, pre-, post-treatment, and simultaneous treatment after pre-incubation of the chemical with MMS. The micronucleus (MN) test was used in binucleated cells (induced by cytochalasin-B) of a mammalian cell line (V79). The three concentrations of Chl-a, Chl-b or Chl (0.1375, 0.275, 0.55microM) were not genotoxic and the genotoxic action of MMS (400microM) decreased (74-117%) under all treatment conditions. The results showed that there was no significant difference among the treatment types, the concentration or the nature of chlorophyll used. The data obtained suggest that Chl-a, Chl-b and Chl when associated with the DNA damaging agent, MMS, may protect the DNA by desgenotoxic action and/or by bio-antigenotoxic mechanisms, with the similar efficiency.
Assuntos
Antimutagênicos/farmacologia , Clorofila/farmacologia , Clorofila/toxicidade , Clorofilídeos/farmacologia , Clorofilídeos/toxicidade , Mutagênicos/toxicidade , Animais , Linhagem Celular , Clorofila/administração & dosagem , Clorofila A , Clorofilídeos/administração & dosagem , Cricetinae , Dano ao DNA , Metanossulfonato de Metila/antagonistas & inibidores , Metanossulfonato de Metila/toxicidade , Testes para MicronúcleosRESUMO
Irradiation of 96h old Drosophila following a 24h pretreatment with 5% chlorophyllin (CHLN) was delayed 0-4 days. The antimutagenic effect of CHLN in somatic cells monitored by the wing spot test persisted for 3 days after completion of the pretreatment and appeared to terminate at a time corresponding to the cessation of mitotic divisions of wing anlagen cells. Within the same population of cells, CHLN demonstrated both an inhibitory effect as measured in mwh single spot classes, and contrarily, a promoting effect in the class of mwh/flr twin spots and to an extent in the class of large flr spots. The reason for the contrasting effects of CHLN remains to be determined.