Effects of ciprofloxacin on eucaryotic pyrimidine nucleotide biosynthesis and cell growth

Abstract

Several of the new 4-quinolones significantly increase the incorporation of [3HJthymidine into the DNA of mitogen-stimulated human lymphocytes. This study suggests that ciprofloxacin inhibits de novo pyrimidine biosynthesis, thereby resulting in a compensatory increase in the uptake of pyrimidine precursors through salvage pathways, and that additional effects may affect eucaryotic cell growth. Incorporation of deoxyuridine, uridine, and orotic acid as well as thymidine was increased in the presence of ciprofloxacin, one of the antibacterially most active of the new 4-quinolones. In contrast, the uptake was decreased in very high concentrations of the drug. Culture in HAT (hypoxanthine, aminopterine, thymidine) medium, which blocks de novo thymidylate synthesis, abrogated the increase in [3H]thymidine incorporation induced by ciprofloxacin.Ciprofloxacin also failed to increase the uptake of [14C]hypoxanthine or leucine, indicating a selective effect on pyrimidine and not on purine nucleotide biosynthesis. N-(Phosphonacetyl)-L-aspartate, an inhibitor of pyrimidine nucleotide biosynthesis, also increased [3H]thymidine incorporation in phytohemagglutininstimulated lymphocytes in a fashion similar to ciprofloxacin. The growth of several cell lines was partially inhibited by ciprofloxacin at 20 ,ig/ml and completely inhibited at 80 to 160 jug/mi. Growth inhibition by ciprofloxacin could not be restored by the addition of uridine to the medium. Chromosome breaks, gene amplification, or other genetic alterations could not be detected in human lymphocytes incubated with up to 25 jig of ciprofloxacin per ml.Many of the new 4-quinolones have a broader spectrum and are more potent than their structurally related predecessors (7,12). The antibacterial activity of nalidixic acid is caused by inhibition of DNA synthesis, resulting from inhibition of DNA gyrase (23,28). Although the new 4-quinolones have not been studied as extensively as nalidixic acid, they have been shown to inhibit gyrase function (2,10,21,22), possibly through DNA binding (19). However, a recent study demonstrated a lack of correlation between antibacterial activity and inhibition of gyrase activity, thereby suggesting that other factors are responsible for the potency of these drugs (29).We have found that in eucaryotic cells, many of the new quinolones cause a significant (11 to 231%) increase in the uptake of [3H]thymidine into trichloroacetic acid (TCA)-precipitable material in mitogen-stimulated human lymphocytes at drug concentrations of 1.6 to 50 ,ug/ml (8; A. Forsgren, S. F. Schlossman, and T. F. Tedder, submitted for publication). However, cell growth and progression through the cell cycle were inhibited by 20 jig or more of ciprofloxacin per ml. In addition, ciprofloxacin at a clinically achievable concentration of 5 ,ug/ml caused a 50% decrease in immunogloblin production by mitogen-stimulated lymphocytes in vitro.In this study, we investigated the reasons for the increased [3H]thymidine uptake and the decreased function of lymphocytes cultured...

Inhibitory effects of quinolone antibacterial agents on eucaryotic topoisomerases and related test systems

“…Ciprofloxacin at 20 jig/ml was shown to inhibit the progression of mitogen-stimulated lymphocytes through the S and G2/M stages of the cell cycle and to decrease the secretion of immunoglobulins G and M in pokeweed mitogen-stimulated B cells (21). The (6,20,21 (30) and the unscheduled DNA synthesis (UDS) test, the latter of which is run with quinolones incubated in rat hepatocyte cell cultures and also with rat hepatocytes removed from animals dosed with the test quinolone and analyzed directly (38). A number of quinolones are inhibitory in some of these in vitro genotoxicity tests, although positive in vivo tests are rare (Table 1).…”

Inhibitory effects of quinolones on pro- and eucaryotic DNA topoisomerases I and II

“…This irreversible formation of DNA strand breakage induces a sequence of events that leads ultimately to cell death. Recently published data (18,19,24,27,34) …”

“…This irreversible formation of DNA strand breakage induces a sequence of events that leads ultimately to cell death. Recently published data (18,19,24,27,34) show that quinolones may affect some eucaryotic enzymes, especially those involved in DNA synthesis. However, as pointed out by Gootz et al (22), there are relatively few reports on this topic, and none assaying the four pro-and eucaryotic topoisomerases together.…”

No cytogenetic effects of quinolone treatment in humans

“…The new 4-quinolones bind to DNA (9) and significantly increase the incorporation of [3H]thymidine into the DNA of mitogenstimulated human lymphocytes (1)(2)(3), indicating a stimulation of DNA synthesis in vitro. It has also been suggested that the quinolones may affect de novo pyrimidine biosynthesis and at high concentrations inhibit cell growth in vitro (2) No significant differences were found in the mean yield of any aberration type or of the total number of aberrations between before and after 1 week of treatment with either ciprofloxacin or ofloxacin (Table 1). There were no differences in cytogenetic effects between the two treatment groups for any of the individual parameters or for the total number of aberrations.…”