Research Paper
Subject Category: Drug Discovery
British Journal of Pharmacology (2007) 152, 112–121; doi:10.1038/sj.bjp.0707363; published online 2 July 2007
In vitro and in vivo antiproliferative and trypanocidal activities of ruthenium NO donors
J J N Silva1,, A L Osakabe2, W R Pavanelli2, J S Silva2 and D W Franco1
- 1Departamento de Química e Física Molecular, Instituto de Química de São Carlos – Universidade de São Paulo (USP), São Carlos, SP, Brazil
- 2Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil
Correspondence: Dr DW Franco, Departamento de Química e Física Molecular, Universidade de São Paulo, Av Trbalhador Sãocarlence, 400, São Carlos, São Paulo, CP 780, Brazil. E-mail: douglas@iqsc.usp.br
This work, which is the main part of JJN Silva Ph.D. thesis, is dedicated to the memory of our master and friend Henry Taube.
Received 22 March 2007; Revised 21 May 2007; Accepted 22 May 2007; Published online 2 July 2007.
Abstract
Background and purpose:
Many compounds liberating NO (NO donors) have been used as therapeutic agents. Here we test two ruthenium nitrosyls, which release NO when activated by biological reducing agents, for their effects in vitro and in vivo against Trypanasoma cruzi, the agent responsible for the American trypanosomiasis (Chagas' disease).
Experimental approach:
Ruthenium NO donors were incubated with a partially drug-resistant strain of T. cruzi and the anti-proliferative and trypanocidal activities evaluated. In a mouse model of acute Chagas' disease, trypanocidal activity was evaluated by measuring parasitemia, survival rate of infected mice and elimination of amastigotes in myocardial tissue.
Key results:
In vitro, the observed anti-proliferative and trypanocidal activities of trans-[Ru(NO)(NH3)4isn](BF4)3 and trans-[Ru(NO)(NH3)4imN](BF4)3 were due to NO liberated upon reduction of these nitrosyls. Ru(NO)isn had a lower IC50epi (67 
M) than the NO donor, sodium nitroprusside (IC50epi=244 M) and Ru(NO)imN (IC50try=52 M) was more potent than gentian violet (IC50try=536 M), currently used in the treatment of blood. Both ruthenium nitrosyls eliminated, in vivo, extracellular as well as intracellular forms of T. cruzi in the bloodstream and myocardial tissue and allowed survival of up to 80% of infected mice at a dose (100 nmol kg-1 day-1) much lower than the optimal dose for benznidazole (385 mol kg-1 day-1).
Conclusions and implications:
Our data strongly suggest that NO liberated is responsible for the anti-proliferative and trypanocidal activities of the ruthenium NO donors and that these compounds are promising leads for novel and effective anti-parasitic drugs.
Keywords:
ruthenium nitrosyl, NO donors, nitric oxide, trypanosomiasis, Trypanosoma cruzi, Chagas' disease, inorganic medicinal chemistry, benznidazole, cytotoxicity, Y strain
Abbreviations:
BT, bloodstream trypomastigote forms of Trypanosoma cruzi; E(NO+/NO0), reduction potential of the RuNO+/RuNO0 couple; % GI, percentage of growth inhibition on epimastigote forms; IC50try, inhibitory concentration on trypomastigotes forms; IC50V79, inhibitory concentration on V-79 cells; imC, imidazole coordinated by carbon; imN, imidazole coordinated by nitrogen; ina, isonicotinic acid; isn, isonicotinamide; k-NO, specific rate constant for NO release; L, trans ligand; L-hist, L-histidine; NHE, normal hydrogen electrode; nic, nicotinamide; PBS, phosphate-buffered saline; 4-pic, 4-picoline; [P(OEt)3], triethylphosphite; py, pyridine; pz, pyrazine; Ru(NO)imN, trans-[RuII(NO+)(NH3)4imN](BF4)3; Ru(NO)isn, trans-[RuII(NO+)(NH3)4isn](BF4)3; SNAP, S-nitroso-acetyl-penicillamine; SNP, sodium nitroprusside; % TA, percentage of trypanocidal activity; T. cruzi, Trypanosoma cruzi; TNF-
, tumour necrosis factor-
