RESUMO
Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is a worldwide disease whose clinical manifestations include encephalitis and congenital malformations in newborns. Previously, we described the synthesis of new ethyl-ester derivatives of the antibiotic ciprofloxacin with ~40-fold increased activity against T. gondii in vitro, compared with the original compound. Cipro derivatives are expected to target the parasite's DNA gyrase complex in the apicoplast. The activity of these compounds in vivo, as well as their mode of action, remained thus far uncharacterized. Here, we examined the activity of the Cipro derivatives in vivo, in a model of acute murine toxoplasmosis. In addition, we investigated the cellular effects T. gondii tachyzoites in vitro, by immunofluorescence and transmission electron microscopy (TEM). When compared with Cipro treatment, 7-day treatments with Cipro derivatives increased mouse survival significantly, with 13-25% of mice surviving for up to 60 days post-infection (vs. complete lethality 10 days post-infection, with Cipro treatment). Light microscopy examination early (6 and 24h) post-infection revealed that 6-h treatments with Cipro derivatives inhibited the initial event of parasite cell division inside host cells, in an irreversible manner. By TEM and immunofluorescence, the main cellular effects observed after treatment with Cipro derivatives and Cipro were cell scission inhibition--with the appearance of 'tethered' parasites--malformation of the inner membrane complex, and apicoplast enlargement and missegregation. Interestingly, tethered daughter cells resulting from Cipro derivatives, and also Cipro, treatment did not show MORN1 cap or centrocone localization. The biological activity of Cipro derivatives against C. parvum, an apicomplexan species that lacks the apicoplast, is, approximately, 50 fold lower than that in T. gondii tachyzoites, supporting that these compounds targets the apicoplast. Our results show that Cipro derivatives improved the survival of mice acutely infected with T. gondii and inhibited parasite replication early in the first cycle of infection in vitro, highlighting their therapeutic potential for the treatment of toxoplasmosis.
Assuntos
Ciprofloxacina/agonistas , Ésteres/administração & dosagem , Toxoplasma/efeitos dos fármacos , Toxoplasmose Animal/tratamento farmacológico , Animais , Antimaláricos/administração & dosagem , Antimaláricos/farmacologia , Divisão Celular/efeitos dos fármacos , Ciprofloxacina/administração & dosagem , Ciprofloxacina/farmacologia , Ésteres/farmacologia , Feminino , Camundongos , Análise de Sobrevida , Toxoplasma/fisiologia , Toxoplasmose Animal/parasitologiaRESUMO
A bioorganometallic approach to malaria therapy led to the discovery of ferroquine (FQ, SSR97193). To assess the importance of the electronic properties of the ferrocenyl group, cyclopentadienyltricarbonylrhenium analogues related to FQ, were synthesized. The reaction of [N-(7-chloro-4-quinolinyl)-1,2-ethanodiamine] with the cyrhetrenylaldehyde complexes (η(5)-C(5)H(4)CHO)Re(CO)(3) and [η(5)-1,2-C(5)H(3)(CH(2)OH)(CHO)]Re(CO)(3) produces the corresponding imine derivatives [η(5)-1,2-C(5)H(3)(R)(CHN-CH(2)CH(2)NH-QN)]Re(CO)(3) R=H 3a; R=CH(2)OH 3b; QN=N-(7-Cl-4-quinolinyl). Reduction of 3a and 3b with sodium borohydride in methanol yields quantitatively the amine complexes [η(5)-1,2-C(5)H(3)(R)(CH(2)-NH-CH(2)CH(2)NH-QN)]Re(CO)(3) R=H 4a; R=CH(2)OH 4b. To establish the role of the cyrethrenyl moiety in the antimalarial activity of this series, purely organic parent compounds were also synthesized and tested. Evaluation of antimalarial activity measured in vitro against the CQ-resistant strains (W2) and the CQ-susceptible strain (3D7) of Plasmodium falciparum indicates that these cyrhetrene conjugates are less active compared to their ferrocene and organic analogues. These data suggest an original mode-of-action of FQ and ferrocenyl analogues in relationship with the redox pharmacophore.