RESUMO
BACKGROUND: Karwinskia humboldtiana (Kh) is a poisonous plant of the rhamnacea family. To elucidate some of the subcellular effects of Kh toxicity, membrane fluidity and ATPase activities as hydrolytic and as proton-pumping activity were assessed in rat liver submitochondrial particles. Rats were randomly assigned into control non-treated group and groups that received 1, 1.5 and 2 g/Kg body weight of dry powder of Kh fruit, respectively. Rats were euthanized at day 1 and 7 after treatment. RESULTS: Rats under Kh treatment at all dose levels tested, does not developed any neurologic symptoms. However, we detected alterations in membrane fluidity and ATPase activity. Lower dose of Kh on day 1 after treatment induced higher mitochondrial membrane fluidity than control group. This change was strongly correlated with increased ATPase activity and pH gradient driven by ATP hydrolysis. On the other hand, membrane fluidity was hardly affected on day 7 after treatment with Kh. Surprisingly, the pH gradient driven by ATPase activity was significantly higher than controls despite an diminution of the hydrolytic activity of ATPase. CONCLUSIONS: The changes in ATPase activity and pH gradient driven by ATPase activity suggest an adaptive condition whereby the fluidity of the membrane is altered.
Assuntos
Adenosina Trifosfatases/metabolismo , Karwinskia/toxicidade , Fluidez de Membrana/efeitos dos fármacos , Mitocôndrias Hepáticas/efeitos dos fármacos , Animais , Frutas/toxicidade , Masculino , Mitocôndrias Hepáticas/enzimologia , Força Próton-Motriz/efeitos dos fármacos , Distribuição Aleatória , Ratos Sprague-Dawley , Frações Subcelulares/efeitos dos fármacos , Partículas Submitocôndricas/efeitos dos fármacosRESUMO
BACKGROUND: Karwinskia humboldtiana (Kh) is a poisonous plant of the rhamnacea family. To elucidate some of the subcellular effects of Kh toxicity, membrane fluidity and ATPase activities as hydrolytic and as proton-pumping activity were assessed in rat liver submitochondrial particles. Rats were randomly assigned into control non-treated group and groups that received 1,1.5 and 2 g/Kg body weight of dry powder of Kh fruit, respectively. Rats were euthanized at day 1 and 7 after treatment. RESULTS: Rats under Kh treatment at all dose levels tested, does not developed any neurologic symptoms. However, we detected alterations in membrane fluidity and ATPase activity. Lower dose of Kh on day 1 after treatment induced higher mitochondrial membrane fluidity than control group. This change was strongly correlated with increased ATPase activity and pH gradient driven by ATP hydrolysis. On the other hand, membrane fluidity was hardly affected on day 7 after treatment with Kh. Surprisingly, the pH gradient driven by ATPase activity was significantly higher than controls despite an diminution of the hydrolytic activity of ATPase. CONCLUSIONS: The changes in ATPase activity and pH gradient driven by ATPase activity suggest an adaptive condition whereby the fluidity of the membrane is altered.
Assuntos
Animais , Masculino , Ratos , Mitocôndrias Hepáticas/efeitos dos fármacos , Adenosina Trifosfatases/metabolismo , Karwinskia/toxicidade , Fluidez de Membrana/efeitos dos fármacos , Frações Subcelulares/efeitos dos fármacos , Partículas Submitocôndricas/efeitos dos fármacos , Mitocôndrias Hepáticas/enzimologia , Distribuição Aleatória , Ratos Sprague-Dawley , Força Próton-Motriz/efeitos dos fármacos , Frutas/toxicidadeRESUMO
Bacterial resistance to antibiotics has become a serious problem of public health. Along with the controlled permeability by the cell-wall, active efflux systems can provide resistance by extruding antibiotics. Carnosic acid is capable to potentiate the antimicrobial activity of several antibiotics. However, the underlying molecular mechanism governing this effect remains unclear. The present study aims to investigate the effect of carnosic acid on the transport of ethidium bromide, on the permeability or the membrane potential in Enterococcus faecalis and Staphylococcus aureus. By using fluorimetric assays it was demonstrated that in E. faecalis, carnosic acid is a modulator of the uptake and efflux of ethidium bromide which does not induce cell membrane permeabilization phenomena. Such effect was sensitive to the inhibition caused by both the proton-motive force carbonyl cyanide m-chlorophenylhydrazone and the calcium antagonist verapamil, but not to vanadate, an ATPase inhibitor. In this work it was demonstrated, for the first time, that the activity of carnosic acid on the uptake/efflux of ethidium bromide is correlated with its capacity to change the membrane potential gradient in S. aureus and E. faecalis. In conclusion, carnosic acid is a natural compound, structurally unrelated to known antibiotics, which can function as an efflux pump modulator by dissipation of the membrane potential. Therefore, carnosic acid would be a good candidate to be employed as a novel therapeutic agent to be used in combination therapies against drug-resistant enterococci and S. aureus infections.
Assuntos
Abietanos/farmacologia , Enterococcus faecalis/efeitos dos fármacos , Extratos Vegetais/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Antibacterianos/farmacologia , Transporte Biológico/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Farmacorresistência Bacteriana Múltipla , Enterococcus faecalis/metabolismo , Etídio/metabolismo , Etídio/farmacocinética , Potenciais da Membrana/efeitos dos fármacos , Permeabilidade/efeitos dos fármacos , Força Próton-Motriz/efeitos dos fármacos , Staphylococcus aureus/metabolismoRESUMO
An active chloramphenicol efflux system was demonstrated in a multiresistant E. coli isolated from poultry carcass. The effect of different concentrations of chloramphenicol on the original strain and on the plasmid-cured strain was determined in the presence and in the absence of CCCP, an uncoupler of the proton-motive force. Minimal inhibitory concentration (MIC) was lower in the presence of CCCP in the original strain. The plasmid-cured strain displayed lower resistance for chloramphenicol than the wild type, but the MIC was not affected by CCCP. The combined results indicate a plasmid encoded energy dependent resistance mechanism. 3H-chloramphenicol accumulation within the cells was measured by scintillation counting. The uptake or the efflux of 3H-chloramphenicol was influenced by CCCP in the original strain, but not in the plasmid-cured strain. More than one chloramphenicol resistance mechanism may exist in this strain. E. coli is an important commensal or pathogen that inhabits the gastrointestinal tracts of humans and animals, so a plasmid encoded active drug resistance mechanism can be a potential source of horizontal transfer of resistance.