Assessment of toxicity, clastogenicity, mutagenicity and transforming activity of pentoxifylline in mammalian cells cultured in vitro

Toxicity, Clastogenicity and Genotoxicity of Theophylline and Pentoxifylline in Mammalian Cells Cultured In Vitro

— As part of a developmental study on theophylline and pentoxifylline, these drugs were tested for possible cytotoxic, mutagenic and clastogenic effects on V79 hamster cells and human lymphocytes cultured in vitro. After the short-term treatment of V79 cells with theophylline and pentoxifylline, the cells were relatively resistant to the toxic effects of these methylxanthines. Generally, only high concentrations of theophylline or pentoxifylline had toxic effects on exposed V79 cells. Short-term treatment of V79 cells with theophylline or pentoxifylline did not induce 6-thioguanine resistant mutations in either the presence or absence of S9 fractions. However, in the absence of an S9 fraction, elevated levels of single-strand breaks in DNA were induced. Both methylxanthines caused clastogenic effects in human lymphocytes and hamster V79 cells after long-term exposure. We suggest that theophylline and pentoxifylline are clastogenic but not genotoxic, and that the molecular mechanism for the induction of single-strand breaks in DNA and the induction of chromosomal aberrations in cells treated with theophylline and pentoxifylline is not the induction of lesions in the DNA but the inhibition of DNA chain elongation.

Pharmacodynamics of pentoxifylline and/or praziquantel in murine schistosomiasis mansoni

Pentoxifylline (PTX) was proved to exert both anti-inflammatory and anti-fibrotic effects, and was used therapeutically in this experimental model to investigate its role alone or with praziquantel (PZQ) in Schistosoma mansoni-infected mice, and to explore its impact on the tissue expression of transforming growth factor-beta1 (TGF-beta1). S. mansoni-infected mice were divided into seven groups: Control untreated (I), treated with curative dose of PZQ, 500 mg/kg/day for 2 consecutive days (II), or subcurative dose, 100 mg/kg/day for 2 consecutive days (III), treated with PTX (10 mg/kg/day for 5 days/wk) alone for 4 weeks (IV) or in addition to subcurative dose of PZQ (V), and treated with PTX alone for 8 weeks (VI) or in addition to subcurative dose of PZQ (VII). All animals were killed 10 weeks post infection. Parasitological assessment of worm burden, tissue egg load and oogram pattern was carried out. The degree of granulomatous fibrosis and eosinophilic cell population was quantified in Sirius-red-stained sections and tissue transforming growth factor beta-1 expression was estimated immunohistochemically. Serum ALAT and GGT, as well as hepatic content of reduced GSH, were measured. The results revealed the highest percent of worm reduction and dead ova in groups (II) and (VII) accompanied by significant diminution in granulomatous parameters, collagen content and TGF-beta1 tissue expression. Moreover, treatments with PTX and/or PZQ ameliorated the liver functions. In conclusion, prolonged treatment with PTX has a potent anti-fibrogenic role especially when used in the early stages of infection, with limited toxic effects on schistosome worms and eggs. Thus, PTX can be used as an adjuvant therapeutic tool with anti-helminthic drugs in the treatment of human schistosomiasis.

Mutagenicity evaluation of Schistosoma spp. extracts by the umu-test and V79/HGPRT gene mutation assay

Schistosomiasis has been suspected of being a risk factor for various types of cancers for sometime, e.g., bladder cancer, colorectal cancer and hepatic cancer. Among them, the etiological relationship between urinary schistosomiasis and bladder cancer is now widely accepted. However, mechanisms of the carcinogenesis are still unclear. Here, we tested the mutagenicity of the parasite extracts by the umu-test and hypoxanthine guanine phosphoribosyltransferase (HGPRT) gene mutation assay, which both overcome disadvantages of the Ames plate assay. Adult worm extracts and egg extracts of Schistosoma haematobium and Schistosoma mansoni were tested. Under our experimental conditions, neither worm nor egg extracts were shown to have any mutagenicity in both tests even in the presence of S9 mix. Our results suggest that there is very little possibility of immediate gene mutation due to the parasite-derived substances in schistosomiasis-related carcinogenesis.

Chromosomal aberrations, sister chromatid exchanges and micronuclei induced by pentoxifylline in in vitro cultivated Chinese hamster cells (V79) and human blood lymphocytes

Pentoxifylline (PTX) is a methylxanthine widely used in clinical practice. The mechanism of PTX effects on cellular and molecular level have not been fully explained yet. The present study was carried out to investigate the cytogenetic effect of this drug using cultured Chinese hamster V79 cells and human blood lymphocytes in vitro. The occurrence of chromosomal aberrations (CA), sister chromatid exchanges (SCE) and micronuclei (MN) was observed after the treatment of cells by different concentrations (0.002-2.0mg/ml) of PTX. In exposed V79 cells and lymphocytes as well, the dose-dependent increases of the above mentioned cytogenetic endpoints were found. The statistically significant increase has appeared at lower PTX concentrations in human lymphocytes than in V79 cells in all the investigated parameters. Our results show that, the applied concentrations of PTX has the clastogenic effect on in vitro cultured V79 cells and human lymphocytes. These findings are notable because of the frequent use of this drug and may serve as preliminary data to the further detailed examination of PTX action on molecular level.