Evaluation of the carcinogenic and genotoxic potential of praziquantel in the Syrian hamster embryo cell transformation assay

Enantiomeric determination of praziquantel and its main metabolite trans-4-hydroxypraziquantel in human plasma by cyclodextrin-modified micellar electrokinetic chromatography

A capillary electrophoresis method for the simultaneous quantitation of praziquantel and its main metabolite trans-4-hydroxypraziquantel enantiomers in human plasma was developed and validated using cyclodextrin-modified micellar electrokinetic chromatography. Sample clean-up involved a single-step liquid-liquid extraction of plasma with toluene after the addition of NaCl. The complete enantioselective analysis was obtained in less than 7 min using 2% w/v sulfated beta-cyclodextrin as chiral selector and 20 mmol/L sodium deoxycholate as surfactant, in 20 mmol/L sodium borate buffer, pH 10. A 50 microm x 42 cm uncoated fused-silica capillary was used for the analysis, performed at a voltage of 18 kV and at 20 degrees C. The calibration curves were linear over the 125-625 ng/mL concentration range. The mean recoveries for praziquantel and trans-4-hydroxypraziquantel were up to 96 and 71%, respectively, with good precision. All four enantiomers were quantified at two concentration levels (200 and 600 ng/mL) with precision and accuracy below 15%. The quantitation limit was 50 ng/mL for (-)-(R)- and (+)-(S)-praziquantel and 62.5 ng/mL for (-)-(R)- and (+)-(S)-trans-4-hydroxypraziquantel, using 1 mL of human plasma.

Neurocysticercosis and oncogenesis

Recent studies suggest that neurocysticercosis may be a risk factor for human cancer. Pathogenetic mechanisms explaining possible oncogenic effects of cysticerci include the following: (a) parasite-induced modulation of the host immune response that may be associated with loss of regulatory mechanisms implicated in the immunological surveillance against cancer; (b) transfer of genetic material from the parasite to the host, causing DNA damage and malignant transformation of host cells, and (c) chronic inflammation with liberation of nitric oxide and inhibition of tumor suppressor genes. Further research is needed to confirm the potential role of cysticercosis in the development of cancer. These studies should determine the presence of cysticercotic factors responsible for the transfer of genetic material and potential mutations in the tumor suppressor genes in proliferating astrocytes surrounding cysticercotic lesions. Additionally, the complex interaction between the immune state of the host with variable cytokine release and the presence of inflammatory cells releasing nitric oxide that cause DNA damage and impair tumor suppressive mechanisms needs to be investigated.

Genotoxic activity of praziquantel

Praziquantel is a synthetic drug with a remarkable activity against parasites, particularly treamatodes and cestodes. Initial genotoxicity tests used a spectrum of endpoints including tests in bacteria, yeasts, mammalian cells and Drosophila and each one gave negative results. Effects on reproductive cells of mice were negative as well. However, host mediated studies in mice and humans were contradictory and a comutagenic effect with several mutagens and carcinogens was found. Later studies, including monitoring in humans and pigs have shown that Praziquantel induces a greater frequency of hyperploid lymphocytes as well as structural chromosomal aberrations, but not in all the individuals treated. In vitro studies have demonstrated that Praziquantel can induce micronuclei in syrian hamster embryonic (SHE) cells and in lymphocytes of some individuals. The same was found about structural chromosomal aberrations. Fetal death and fetal resorption were found when Praziquantel was administered in high doses to pregnant rats between the 6th and 10th day of gestation. Due to its efficiency as a parasiticide, Praziquantel is in use in Latin-American, Asiatic, African and East-European countries where infections by trematodes and cestodes are frequent. However, the extensive use of Praziquantel in multiple reinfections, in non-infected and non-diagnosed individuals for prevention, in higher doses or repeated doses for cysticercosis treatment and in individuals exposed to environmental mutagens, in conjunction with new findings about its metabolism and genotoxic properties, make it necessary to further evaluate the potential of this drug not only to be mutagenic per se, but to contribute in the development of neoplasm.

Induction of micronuclei in Syrian hamster embryo cells: comparison to results in the SHE cell transformation assay for National Toxicology Program test chemicals

Sixteen chemicals currently being tested in National Toxicology Program (NTP) carcinogenicity studies were evaluated in the Syrian hamster embryo (SHE) cell in vitro micronucleus assay. Results from these studies were compared to the results from the SHE cell transformation assay for the same chemicals The overall concordance between induction of micronuclei and transformation of SHE cells was 56%, which is far lower that the 93% concordance between these two tests reported previously by Fritzenschaf et al. (1993; Mutation Res. 319, 47-53). The difference between our results appears to be due to differences in the types of chemicals in the two studies. Overall, there is good agreement between the SHE cell micronucleus and transformation assays for mutagenic chemicals, but, as our study highlights, the SHE cell transformation assay has the added utility of detecting nonmutagenic carcinogens. The utility of a multi-endpoint assessment in SHE cells for carcinogen screening is discussed.

Antischistosomal drugs: past, present ... and future?

The major antischistosomal drugs that have been or still are in use against infections with schistosomes are considered here together with some compounds that have not been in clinical use, but show interesting characteristics. Each individual compound presents aspects that may be enlightening about parasite biochemistry, parasite biology, and host-parasite relationships. Special attention is given to the mechanisms of action, an understanding of which is seen here as a major factor of progress in chemotherapy. Three compounds are currently in use, i.e., metrifonate, oxamniquine, and praziquantel, and all three are included in the World Health Organization list of essential drugs. They are analyzed in some detail, as each one presents advantages and disadvantages in antischistosomal therapy. The reported occurrence of drug-resistant schistosomes after treatment with oxamniquine and praziquantel suggests strict monitoring of such phenomena and encourages renewed efforts toward the development of multiple drugs against this human parasite.

Mutation at the HPRT locus in patients with neurocysticercosis treated with praziquantel

Praziquantel (PZQ) is the drug of choice in the treatment of neurocysticercosis (NC), a parasitic disease caused by Taenia solium larvae. Variant frequencies at the hprt locus were analyzed in a group of NC patients before and after treatment with PZQ as well as in two control groups: healthy donors and non-parasitic neurological patients. Data show that PZQ does not induce hprt mutations, but that cysticerci by themselves or together with palliative treatment administered to NC patients could induce mutations in some patients.