Antiplasmodial activity of chloroquine analogs against chloroquine-resistant parasites, docking studies and mechanisms of drug action

Submitted by Nuzia Santos ([email protected]) on 2015-03-02T17:19:49Z No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2015-03-02T17:19:57Z (GMT) No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2015-03-02T17:23:45Z (GMT) No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Made available in DSpace on 2015-03-02T17:23:45Z (GMT). No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5) Previous issue date: 2014Fundação Oswaldo Cruz. Centro de Pesquisas René Rachou. Laboratório de Malária. Belo Horizonte, MG, BrazilUniversidade Federal de Juiz de Fora. Instituto de Ciências Exatas. Departamento de Química. Juiz de Fora, MG, BrazilUniversidade Federal de Juiz de Fora. Instituto de Ciências Exatas. Departamento de Química. Juiz de Fora, MG, BrazilInstituto Militar de Engenharia. Laboratório de Modelagem Molecular Aplicada à Defesa Química e Biológica. Rio de Janeiro, RJ, BrazilFundação Oswaldo Cruz. Centro de Pesquisas René Rachou. Laboratório de Malária. Belo Horizonte, MG, BrazilBackground: Given the threat of resistance of human malaria parasites, including to artemisinin derivatives, new agents are needed. Chloroquine (CQ) has been the most widely used anti-malarial, and new analogs (CQAns) presenting alkynes and side chain variations with high antiplasmodial activity were evaluated. Methods: Six diaminealkyne and diaminedialkyne CQAns were evaluated against CQ-resistant (CQ-R) (W2) and CQ-sensitive (CQ-S) (3D7) Plasmodium falciparum parasites in culture. Drug cytotoxicity to a human hepatoma cell line (HepG2) evaluated, allowed to calculate the drug selectivity index (SI), a ratio of drug toxicity to activity in vitro. The CQAns were re-evaluated against CQ-resistant and -sensitive P. berghei parasites in mice using the suppressive test. Docking studies with the CQAns and the human (HssLDH) or plasmodial lactate dehydrogenase (PfLDH) enzymes, and, a β-haematin formation assay were performed using a lipid as a catalyst to promote crystallization in vitro. Results: All tested CQAns were highly active against CQ-R P. falciparum parasites, exhibiting half-maximal inhibitory concentration (IC50) values below 1 μΜ. CQAn33 and CQAn37 had the highest SIs. Docking studies revealed the best conformation of CQAn33 inside the binding pocket of PfLDH; specificity between the residues involved in H-bonds of the PfLDH with CQAn37. CQAn33 and CQAn37 were also shown to be weak inhibitors of PfLDH. CQAn33 and CQAn37 inhibited β-haematin formation with either a similar or a 2-fold higher IC50 value, respectively, compared with CQ. CQAn37 was active in mice with P. berghei, reducing parasitaemia by 100%. CQAn33, -39 and -45 also inhibited CQ-resistant P. berghei parasites in mice, whereas high doses of CQ were inactive. Conclusions: The presence of an alkyne group and the size of the side chain affected anti-P. falciparum activityin vitro. Docking studies suggested a mechanism of action other than PfLDH inhibition. The β-haematin assay suggested the presence of an additional mechanism of action of CQAn33 and CQAn37. Tests with CQAn34, CQAn37, CQAn39 and CQAn45 confirmed previous results against P. berghei malaria in mice, and CQAn33, 39 and 45 were active against CQ-resistant parasites, but CQAn28 and CQAn34 were not. The result likely reflects structure-activity relationships related to the resistant phenotype

Synthesis, antimalarial activity in vitro, and docking studies of novel neolignan derivatives

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESThe absence of effective vaccines against malaria and the difficulties associated with controlling mosquito vectors have left chemotherapy as the primary control measure against malaria. However, the emergence and spread of parasite resistance to conventi903464472CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESSEM INFORMAÇÃOSEM INFORMAÇÃOSEM INFORMAÇÃOThe authors thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES (CAPES) for financial suppor

Anti-malarial activity of indole alkaloids isolated from Aspidosperma olivaceum

Background: Several species of Aspidosperma (Apocynaceae) are used as treatments for human diseases in the tropics. Aspidosperma olivaceum, which is used to treat fevers in some regions of Brazil, contains the monoterpenoid indole alkaloids (MIAs) aspidoscarpine, uleine, apparicine, and N-methyl-tetrahydrolivacine. Using bio-guided fractionation and cytotoxicity testing in a human hepatoma cell line, several plant fractions and compounds purified from the bark and leaves of the plant were characterized for specific therapeutic activity (and selectivity index, SI) in vitro against the blood forms of Plasmodium falciparum. Methods: The activity of A. olivaceum extracts, fractions, and isolated compounds was evaluated against chloroquine (CQ)-resistant P. falciparum blood parasites by in vitro testing with radiolabelled [3H]-hypoxanthine and a monoclonal anti-histidine-rich protein (HRPII) antibody. The cytotoxicity of these fractions and compounds was evaluated in a human hepatoma cell line using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, and the SI was calculated as the ratio between the toxicity and activity. Two leaf fractions were tested in mice with Plasmodium berghei. Results: All six fractions from the bark and leaf extracts were active in vitro at low doses (IC50 < 5.0 μg/mL) using the anti-HRPII test, and only two (the neutral and basic bark fractions) were toxic to a human cell line (HepG2). The most promising fractions were the crude leaf extract and its basic residue, which had SIs above 50. Among the four pure compounds evaluated, aspidoscarpine in the bark and leaf extracts showed the highest SI at 56; this compound, therefore, represents a possible anti-malarial drug that requires further study. The acidic leaf fraction administered by gavage to mice with blood-induced malaria was also active. Conclusion: Using a bio-monitoring approach, it was possible to attribute the anti-P. falciparum activity of A. olivaceum to aspidoscarpine and, to a lesser extent, N-methyl-tetrahydrolivacine; other isolated MIA molecules were active but had lower SIs due to their higher toxicities. These results stood in contrast to previous work in which the anti-malarial activity of other Aspidosperma species was attributed to uleine

Effects of levamisole on experimental infections by Plasmodium berghei in mice

Levamisole (phenylimidothiazol), considered a strong immunostimulant, when administered to healthy Swiss mice did not cause a significant increase in -the weight of their thymus, liver and spleen, even though the drug was used at different times before removing such organs. High doses ofdrug used in the 4-day prophylactic scheme had no antimalarial effect. However, when given to malaria infected mice 24 hours before, at the same time, and 24 hours after the inoculation of a chloroquine-sensitive or a chloroquine-resistant strain of Plasmodium berghei small doses of the drug induced a somewhat decreased parasitemia, the dose of 1 mg/kg body weight before the inoculum being the best scheme. The mortality rates by malaria in the levamisole treated groups were also delayed although all mice finally died. The data suggest that levamisole may display a stimulant effect on the depressed immune response caused by malaria

Hemocultura: técnica sensível na detecção do Trypanosoma cruzi em pacientes chagásicos na fase crônica da doença de Chagas

A sensibilidade de hemoculturas, realizadas uma ou três vezes, foi estudada em 52 pacientes na fase crônica da doença de Chagas. Modificações foram introduzidas na técnica tais como, diminuição do período de processamento do sangue, homogeneização suave e exame até 120 dias do cultivo. Os resultados mostram alto percentual de positividade, ou seja, 79% e 94% dos pacientes foram positivos, respectivamente, com um ou três testes. A julgar pela número de tubos positivos, em cada paciente, a parasitemia foi baixa em 59% deles, média em 16% e alta em 25%. Não houve diferenças significativas nos resultados positivos em função da idade dos pacientes, que variou de 14 a 82 anos. Nossos resultados demonstram que a hemocultura é uma metodologia sensível para o diagnóstico parasitológico da doença de Chagas e ideal para monitorar cura em pacientes submetidos a tratamento