RESUMO
There is increasing interest in the use of lipophilic copper (Cu)-containing complexes to combat bacterial infections. In this work, we showed that Cu complexes with bis(thiosemicarbazone) ligands [Cu(btsc)] exert antibacterial activity against a range of medically significant pathogens. Previous work using Neisseria gonorrhoeae showed that Cu(btsc) complexes may act as inhibitors of respiratory dehydrogenases in the electron transport chain. We now show that these complexes are also toxic against pathogens that lack a respiratory chain. Respiration in Escherichia coli was slightly affected by Cu(btsc) complexes, but our results indicate that, in this model bacterium, the complexes act primarily as agents that deliver toxic Cu ions efficiently into the cytoplasm. Although the chemistry of Cu(btsc) complexes may dictate their mechanism of action, their efficacy depends heavily on bacterial physiology. This is linked to the ability of the target bacterium to tolerate Cu and, additionally, the susceptibility of the respiratory chain to direct inhibition by Cu(btsc) complexes. The physiology of N. gonorrhoeae, including multidrug-resistant strains, makes it highly susceptible to damage by Cu ions and Cu(btsc) complexes, highlighting the potential of Cu(btsc) complexes (and Cu-based therapeutics) as a promising treatment against this important bacterial pathogen.
Assuntos
Antibacterianos/toxicidade , Complexos de Coordenação/toxicidade , Cobre/toxicidade , Farmacorresistência Bacteriana/efeitos dos fármacos , Tiossemicarbazonas/toxicidade , Antibacterianos/química , Transporte Biológico , Complexos de Coordenação/química , Cobre/química , Citoplasma/efeitos dos fármacos , Citoplasma/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Haemophilus influenzae/efeitos dos fármacos , Haemophilus influenzae/crescimento & desenvolvimento , Haemophilus influenzae/metabolismo , Lactobacillus acidophilus/efeitos dos fármacos , Lactobacillus acidophilus/crescimento & desenvolvimento , Lactobacillus acidophilus/metabolismo , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Neisseria gonorrhoeae/efeitos dos fármacos , Neisseria gonorrhoeae/crescimento & desenvolvimento , Neisseria gonorrhoeae/metabolismo , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/metabolismo , Especificidade da Espécie , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus aureus/metabolismo , Streptococcus pneumoniae/efeitos dos fármacos , Streptococcus pneumoniae/crescimento & desenvolvimento , Streptococcus pneumoniae/metabolismo , Tiossemicarbazonas/químicaRESUMO
Only a few drugs are available for treating sleeping sickness and nagana disease; parasitic infections caused by protozoans of the genus Trypanosoma in sub-Saharan Africa. There is an urgent need for the development of new medicines for chemotherapy of these devastating diseases. In this study, three newly designed thiosemicarbazone iron chelators, TSC24, Dp44mT and 3-AP, were tested for in vitro activity against bloodstream forms of Trypanosoma brucei and human leukaemia HL-60 cells. In addition to their iron chelating properties, TSC24 and Dp44mT inhibit topoisomerase IIα while 3-AP inactivates ribonucleotide reductase. All three compounds exhibited anti-trypanosomal activity, with minimum inhibitory concentration (MIC) values ranging between 1 and 100 µM and 50% growth inhibition (GI50) values of around 250 nM. Although the compounds did not kill HL-60 cells (MIC values >100 µM), TSC24 and Dp44mT displayed considerable cytotoxicity based on their GI50 values. Iron supplementation partly reversed the trypanotoxic and cytotoxic activity of TSC24 and Dp44mT but not of 3-AP. This finding suggests possible synergy between the iron chelating and topoisomerase IIα inhibiting activity of the compounds. However, further investigation using separate agents, the iron chelator deferoxamine and the topoisomerase II inhibitor epirubicin, did not support any synergy for the interaction of iron chelation and topoisomerase II inhibition. Furthermore, TSC24 was shown to induce DNA degradation in bloodstream forms of T. brucei indicating that the mechanism of trypanotoxic activity of the compound is topoisomerase II independent. In conclusion, the data support further investigation of thiosemicarbazone iron chelators with dual activity as lead compounds for anti-trypanosomal drug development.
Assuntos
Quelantes de Ferro/farmacologia , Tiossemicarbazonas/farmacologia , Trypanosoma brucei brucei/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células HL-60 , Humanos , Ferro/metabolismo , Quelantes de Ferro/química , Quelantes de Ferro/toxicidade , Piridinas/química , Piridinas/farmacologia , Piridinas/toxicidade , Tiossemicarbazonas/química , Tiossemicarbazonas/toxicidadeRESUMO
Di-2-pyridylketone-4,4,-dimethyl-3-thiosemicarbazone (Dp44mT) is a potential candidate in chelation therapy as an iron chelator. This study showed that a combined treatment with 2µM easily available Fe(II), Cu(II) and Zn(II) each and 5µM Dp44mT on eight different cancer cell lines resulted in a 10-40-fold increase in the intracellular Cu content compared to control samples. The uptake of Cu and Cu-dependent cytotoxicity strictly depend on the Cu concentration of the culture medium. Even as low concentration of Dp44mT as 0.1µM can transport high amounts of copper inside the cells. The Cu accumulation and toxicity through Dp44mT can hardly be influenced by Fe. Copper uptake and toxicity triggered by 2µM extracellular Cu(II) and 5µM Dp44mT could not be influenced by Fe(II) extracellular concentrations even 50-times higher than that of Cu(II). A 50-times higher Co(II) extracellular concentration hindered the Cu(II) uptake almost completely and a 10-times higher Co(II) concentration already decreased the Dp44mT-mediated Cu toxicity. Conditional complex stability constant determinations for Dp44mT with Cu(II), Co(II), Fe(II), Ni(II) and Zn(II) revealed that the metal-to-ligand ratio is 1:1 in [Cu(II)Dp44mT] complex, while for Co(II), Fe(II) and Ni(II) is 1:2. The highest stability constant was obtained for Cu(II) (lg ß=7.08±0.05) and Co(II) (lg ß2=12.47±0.07). According to our results, Dp44mT in combination with Cu is highly toxic in vitro. Therefore, the use of Dp44mT as an iron chelator is limited if biologically available Cu is also present even at low concentrations.
Assuntos
Quelantes/química , Quelantes/toxicidade , Tiossemicarbazonas/química , Tiossemicarbazonas/toxicidade , Linhagem Celular Tumoral , Cobalto/química , Cobalto/metabolismo , Cobre/metabolismo , Cobre/farmacocinética , Relação Dose-Resposta a Droga , Células HT29/efeitos dos fármacos , Células HT29/metabolismo , Humanos , Ferro/metabolismo , Quelantes de Ferro/química , Quelantes de Ferro/toxicidade , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/metabolismo , Prótons , Tiossemicarbazonas/metabolismo , Tiossemicarbazonas/farmacocinética , Zinco/química , Zinco/metabolismoRESUMO
Various 6-substituted benzothiazolyl-2-thiosemicarbazones were synthesized and screened for anticonvulsant activity in maximal electroshock induced seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) induced seizure models in mice. The neurotoxicity was assessed using the rotorod method. The 6-methyl benzothiazolyl-2-thiosemicarbazones showed anticonvulsant activity in both mice i.p. and rat oral MES screen. The 6-nitro benzothiazolyl thiosemicarbazone derivative 1a emerged as the most promising one with anti-MES activity in mice i.p., rat i.p. and rat p.o. evaluations. All the compounds exhibited lesser or no neurotoxicity compared to phenytoin. The isatinimino derivatives had shown better activity when compared to the benzylidene or acetophenone derivatives.
Assuntos
Anticonvulsivantes/toxicidade , Convulsões/tratamento farmacológico , Tiossemicarbazonas/toxicidade , Animais , Anticonvulsivantes/síntese química , Anticonvulsivantes/uso terapêutico , Convulsivantes/toxicidade , Avaliação Pré-Clínica de Medicamentos , Masculino , Camundongos , Atividade Motora/efeitos dos fármacos , Pentilenotetrazol/toxicidade , Ratos , Ratos Sprague-Dawley , Convulsões/induzido quimicamente , Relação Estrutura-Atividade , Tiossemicarbazonas/síntese química , Tiossemicarbazonas/uso terapêuticoRESUMO
Ten 6-chlorobenzothiazolyl-2-thiosemicarbazones were synthesised and screened for anticonvulsant and neurotoxic properties. Most of the compounds showed anticonvulsant activity against both maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole screens. Eight compounds have shown good protection in the rat p.o. MES test at 30 mg kg(-1). Compound 1 [4-(6-chlorobenzothiazol-2-yl)-1-(3-isatinimino)thiosemicarbazone] emerged as the most promising one with an ED(50) of 17.86 and 6.07 mg kg(-1) in mice i.p. and rat p.o., respectively. Compound 1 showed a weak ability to block the expression of fully kindled seizures.
Assuntos
Anticonvulsivantes/toxicidade , Anticonvulsivantes/uso terapêutico , Convulsões/tratamento farmacológico , Tiossemicarbazonas/toxicidade , Tiossemicarbazonas/uso terapêutico , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/fisiologia , Animais , Anticonvulsivantes/administração & dosagem , Anticonvulsivantes/síntese química , Avaliação Pré-Clínica de Medicamentos , Eletrochoque , Excitação Neurológica/efeitos dos fármacos , Camundongos , Estrutura Molecular , Ratos , Convulsões/induzido quimicamente , Tiossemicarbazonas/administração & dosagem , Tiossemicarbazonas/síntese químicaRESUMO
Metal-binding chelators may interact with biological systems by either of two mechanisms: they may combine with an essential metal, which can be either freely dissociated or part of an enzyme prosthetic group, or they may react with a metal ion to form a biologically reactive metal-chelate complex. As trace metals are always present as contaminants in serum-supplemented culture media used to study chelating agents, it is frequently difficult to distinguish between the two possibilities. Here we describe the use of a nontoxic, copper-specific chelating agent, bathocuproine sulphonate (Fig. 1) which, by combining with available endogenous copper in a tissue culture preparation, abolished the toxicity of three structurally unrelated chelating agents. These three agents may therefore be considered to be biologically active by the second mechanism.
Assuntos
Quelantes , Cobre/toxicidade , Fenantrolinas/toxicidade , Animais , Células Cultivadas , Ditiocarb/toxicidade , Leucemia L1210 , Camundongos , Tiossemicarbazonas/toxicidadeAssuntos
Antivirais , Herpesvirus Galináceo 2/efeitos dos fármacos , Indóis/farmacologia , Isatina/farmacologia , Tiossemicarbazonas/farmacologia , Animais , Galinhas , Avaliação Pré-Clínica de Medicamentos/veterinária , Isatina/análogos & derivados , Doença de Marek/tratamento farmacológico , Tiossemicarbazonas/toxicidade , Replicação Viral/efeitos dos fármacosRESUMO
The effectiveness of chalkones and derivatives as antibacterial and antifungal agents stimulated our interest in the possibility of coupling this type of compound with certain hydrazines and thiosemicarbazides to determine the potential chemotherapeutic activity of these combinations as anticancer and antimalarial agents. Accordingly, 18 hydrazine and thiosemicarbazide derivatives of alpha-methylchalkone (dypnone) have been synthesized for study as potential antitumor agents in animal tumor systems against Walker 256 carcinosarcoma (intramuscular) and leukemia L-1210 and for antimalarial activity against Plasmodium berghei in experimentally infected mice. Of the series of chalkone derivatives, significant inhibition in preliminary tests against the Walker 256 carcinosarcoma (intramuscular) rat tumor system was exhibited by alpha-methylchalkone-1,4-phthalazinediyldihydrazone and showed activity in the leukemia 1210 mouse tumor system. The guanylhydrazone of alpha-methylchalkone showed good inhibition with confirmed activity against Plasmodium berghei in experimentally infected mice.