Enhancement by caffeine of the growth inhibitory effects of antimetabolites in lymphoma L5178Y cells

Enhancement of methotrexate-induced growth inhibition, cell killing and DNA lesions in cultured L5178Y cells by the reduction of DNA repair efficiency

Acute treatment of L5178Y cells by methotrexate (MTX) caused concentration-dependent post-treatment growth inhibition and cell killing. The effects were potentiated in the presence of caffeine (CAF). At the same experimental conditions the CAF-dependent increase in mature and newly formed DNA lesions was found. The results suggest that even short MTX treatment can cause DNA lesions which are normally, at least partially, repaired. By the reduction of DNA repair efficiency with CAF, these lesions can be expressed what finds its reflection in the enhancement of MTX cytotoxicity.

Potentiative interactions between caffeine and various teratogenic agents

Acetazolamide and inhibitors of DNA synthesis (hydroxyurea, 5-fluoro-2'-deoxyuridine), RNA synthesis (actinomycin D), and protein synthesis (cycloheximide, emetine) were each administered to pregnant rats together with caffeine at doses where each agent alone caused minimal embryotoxicity. Caffeine co-administered with any of the other agents induced a powerful potentiative response. It is not clear from the present experiments whether much lower caffeine dosage, as normally encountered in humans, would potentiate embryotoxicity due to other agents.

Induction of sister chromatic exchanges and inhibition of cellular proliferation in vitro. I. Caffeine

Cytogenetic assay systems based on the detection of sister chromatid exchanges (SCE) are widely advocated as a sensitive screening method for assessing genotoxic potential. While many agents have been examined for their ability to induce SCE's, complete dose-response information has often been lacking. We have reexamined the ability of one such compound-caffeine-to induce SCEs and also to inhibit cellular proliferation in human peripheral lymphocytes in vitro. An acute exposure to caffeine prior to the DNA synthetic period did not affect either SCE frequency or the rate of cellular proliferation. Chronic exposure to caffeine throughout the culture period lead to both a dose-dependent increase in SCEs (SCEd or doubling dose = 2.4 mM; SCE10 or the dose capable of inducing 10 SCE = 1.4 mM) and a dose-dependent inhibition of cellular proliferation (IC50 or the 50% inhibition concentration = 2.6 mM). The relative proportion of first generation metaphase cels, an assessment of proliferative inhibition, increased linearly with increasing caffeine concentrations. However, SCE frequency increased nonlinearly over the same range of caffeine concentrations. Examination of the ratio of nonsymmetrical to symmetrical SCEs in third generation metaphase cells indicated that caffeine induced SCEs in equal frequency in each of three successive generations. The dependency of SCE induction and cellular proliferative inhibition on caffeine's presence during the DNa synthetic period suggests that caffeine may act as an antimetabolite in normal human cells. The significance of these results in regard to both caffeine's genotoxic potential and to the reliability of the SCE assay system are discussed.