Caffeine (1,3,7-trimethylxanthine), a temperature promoter of DMBA-induced rat mammary gland carcinogenesis

The administration of caffeine to the drinking water (250 mg/l and 500 mg/l) of female Sprague-Dawley rats after treatment with 7,12-dimethylbenzanthracene (DMBA) (5 mg i.g.) resulted in an increase in mammary carcinoma incidence. The confidence levels of statistical significance for the groups of rats receiving the 250-mg and 500-mg doses of caffeine were greater than 0.70 and greater than 0.99, respectively. This increase in mammary carcinoma incidence was observed when caffeine treatment was initiated commencing 3 days after DMBA treatment and continued for 21 weeks. This effect was also observed when caffeine treatment was initiated commencing 20 weeks after DMBA treatment and continued for 6 weeks in rats relatively refractory to carcinogen treatment (mammary tumor-free at onset of treatment) and in rats relatively sensitive to the carcinogen (mammary tumor bearing at onset of caffeine treatment). Caffeine treatment of rats prior to and during carcinogen treatment did not significantly affect mammary carcinoma incidence. Thus caffeine consumption has been shown to significantly enhance the promoting phase but is without effect on the initiating phase of this carcinogenic process.

Potentiating effects of methylxanthines on teratogenicity of mitomycin C in mice

A previous study demonstrated that caffeine strongly potentiated the teratogenic action of mitomycin C in mice. In the present study the effect of methylxanthines including caffeine, theophylline, theobromine (theobromine sodium salicylate), paraxanthine, and 1-methylxanthine was compared in order to analyze the structure-activity relationship. Jcl:ICR mice were injected IP with 3 mg/kg of mitomycin C, immediately followed by SC injection of each methylxanthine on day 11 of gestation. The doses of methylxanthines were calculated so that the mice received 50 mg/kg of caffeine or the equimolecular amount of the other methylxanthines. Fetuses were examined for external malformations on day 18 of gestation. Mitomycin C at 3 mg/kg and the methylxanthines at the doses used were not teratogenic. Combined administration of caffeine or theophylline with mitomycin C produced more than 80% of malformed fetuses. Although less effective than caffeine or theophylline, paraxanthine also significantly increased the incidence of malformed fetuses. Theobromine and 1-methylxanthine were virtually ineffective. From these findings, it is suggested that the methyl group at N-1 position of the xanthines is important for the enhancement but the N-1 methylation alone is ineffective unless accompanied with the substitution of the methyl moiety at the other position(s).

External malformations in chick embryos following concomitant administration of methylxanthines and beta-adrenomimetic agents: 1. Gross pathologic features

The objectives of this report are to document external malformations observed in chick embryos following concomitant administration of methylxanthines (caffeine, theophylline) and beta-adrenomimetic agents (isoproterenol, epinephrine) and to suggest reasonable explanations for the anomalies. Administration of caffeine or theophylline alone (2.5-5.0 mg/egg) retarded growth in a dose-dependent fashion. Doses of 5.0 mg caffeine and theophylline produced beak malformations in 4.9% and 57.1% of embryos, respectively. Limb malformations, seen in low frequency (3.6% in 56 embryos) after administration of 1 microgram isoproterenol, were not seen in 224 methylxanthine-treated embryos. Structural defects following coadministration of methylxanthines and beta-adrenomimetics were frequently observed in limbs (primarily lower limbs with predilection for left-sided oligodactyly) and beak. Other findings included limb hematomas, hygromas in the nuchal region, and prominent generalized edema. The most dramatic effects observed in this study were those induced by concomitant administration of 2.5 mg caffeine and 1 microgram isoproterenol. This combination produced at least one of the embryopathies listed above in 87.9% of treated embryos and frequently induced beak (24.2%) and lower limb defects (75.8%) in addition to nuchal hygromas (9.1%). Similar severe malformations were observed following administration of 3.8 mg theophylline with 1 microgram epinephrine. Embryos that died within 12-48 hours following drug insult demonstrated marked cardiac dilation, apparently due to congestive heart failure. The results of this study suggest that methylxanthines and beta-adrenomimetic agents are synergistic in their action in the developing chick. Doses of alpha-adrenomimetic agents that were used in this study were not synergistic with methylxanthines. Increased intracellular cyclic adenosine monophosphate (AMP) is offered as an explanation for digital anomalies due to inhibition of proximodistal development of limbs. Increased intracellular cyclic AMP may also explain limb hypoplasia and loss of intermediate limb structures as a result of inhibited mitosis and/or necrosis of embryonic tissue.

[Combined action of caffeine and sydnocarb]

Combined application of two stimulants caffeine and sydnocarb (a sydnonimine derivative) was studied in rabbits, rats and mice using the method of summation of impulses in the central nervous system, the method of conditioned avoidance response, forced swimming and hexobarbital sleep in order to find out the changes in their main and side effects. It was established that the main stimulant effect of the drug combination given in optimal doses appeared to be additive, while side effects on the ECG and blood pressure remained unchanged.

Potentiating effects of caffeine on teratogenicity of alkylating agents in mice

Teratogenic to subteratogenic doses of x-ray, mitomycin C, MNNG, thio-TEPA, cyclophosphamide, and chlorambucil were administered to pregnant ICR mice together with caffeine at doses of 12.5, 25, or 50 mg/kg on day 11 of gestation. Fetuses were examined for gross malformations on day 18 of gestation. The teratogenicity of mitomycin C was significantly potentiated by caffeine at a dose as low as 12.5 mg/kg. The teratogenicity of chlorambucil was also significantly potentiated by caffeine at 50 mg/kg, but similar potentiation was not observed for x-ray, MNNG, thio-TEPA, and cyclophosphamide.

In vitro and in vivo cytotoxicity of possible uracil metabolites of methylxanthines

The present study was designed to elucidate the cytotoxic potential of 8 possible substituted uracilic metabolites of methylxanthines. 5-Fluorouracil (5-FU) was used as a reference uracil analogue with cytotoxic activity. Substituted uracil derivatives examined in this study did not affect the proliferative capacity of PHA-stimulated rat lymphocytes, murine L1210 leukaemia and rat chondrocytes. Caffeine had some growth inhibitory activity of extremely high concentrations (greater than 100 micrograms/ml). In vivo administration of 6-amino-5[N-methyl-formylamino]1,3-dimethyluracil (1,3,7-TAU) and 6-amino-5[N-acetylamino]3-methyluracil (7-A3-MAU) caused a transient short-lived reduction of L1210 tumour cell numbers. These observations do not appear to support the hypothesis that substituted uracils are involved in the toxicity of high doses of caffeine in rats.

Enhancement by methylxanthines of sister-chromatid exchange frequency induced by cytostatics in normal and leukemic human lymphocytes

The effect of theobromine (TB) and diphylline (DP) or (1,2-dihydroxy-3-propyl)theophylline on SCE rates induced in vitro by mitomycin C (MMC), and the effect of caffeine on SCE rates induced in vitro by cytosine arabinoside (Ara-C) was studied. The combined treatments with MMC plus TB or DP showed the potentiating ability of the latter drugs. Caffeine also enhanced SCEs induced by Ara-C in cultured human lymphocytes. Caffeine and adriamycin (ADR) did not act synergistically on induction of SCEs. In a combined study, in vivo and in vitro, lymphocytes taken from 2 leukemic patients who had been given chlorambucil (CBC) or Ara-C by injection 3 h before, and then treated with caffeine in vitro, were found to have synergistically increased exchange frequencies.

Induction at high frequency of a unique phenotypic class of Bacillus subtilis mutants by methylxanthines

Caffeine and theophylline are mutagenic at high concentration in the B. subtilis multigene sporulation test for mutagens; caffeine is a stronger mutagen than theophylline in this test. An unusually high fraction of the mutant colonies appear to be phenotypically identical, as judged by colonial morphology and microscopic appearance of the vegetative cells. These mutants do not bring about the pH increase normally associated with sporulation of B. subtilis; such behavior is frequently associated with lack of a functional tricarboxylic acid (TCA) cycle, essential for normal sporulation of this species. Similar mutants have not been noted in the course of screening a variety of well-known mutagens, including acriflavine. Caffeine is maximally effective in inducing these mutants about 10 min after germination commences. Adenosine greatly reduces the ability of caffeine to induce these mutants.

Enhanced killing effects of caffein post-treatment in ultraviolet-light irradiated mouse lymphoma cells: is cAMP a mediator of the effects?

Effects of post-treatment with caffein, cyclic adenosine 3':5'-monophosphate (cAMP) and N6, O2-dibutyryl cAMP (dbcAMP) were investigated in ultraviolet light (UV)-irradiated mouse lymphoma L5178Y cells. Under conditions where UV or each chemical alone caused only slight cytotoxic effects, caffein post-treatment showed clear synergistic effects in cell killing but not for cAMP or dbcAMP. Subsequently, a mutant clone resistant to cAMP was isolated. This mutant was supposed to be deficient in cAMP-mediated cellular functions. Using the mutant cells, it was found that these cells were also sensitive to caffein post-treatment as wild cells after UV-irradiation. The results imply that the enhanced killing effects by caffein post-treatment in UV irradiated cells is not mediated by cAMP.

Caffeine: effects on the behaviors of juvenile rats

Caffeine, a central nervous system stimulant, was found to alter the expression of 3 behaviors in the juvenile rat. After caffeine administration, locomotor activity was increased in rats of all ages studied (24-84 days old). Pinning, a behavior characteristic of the juvenile period and used as an index of play-fighting, was suppressed following caffeine exposure, but only in rats 24-54 days old. Social investigation was not affected by caffeine in 24- and 34-day-old rats. However, in animals 44-84 days of age caffeine increased both the frequency and duration of investigation of a novel juvenile. Although caffeine influenced all the behaviors we observed, the developmental time course of caffeine's effects was different for each behavior.

Adverse effect of maternal caffeine ingestion on fetal cerebrum in rat

This study was undertaken to determine whether maternal caffeine ingestion is or is not a risk factor in fetal cerebral development using experimental rat models. Pregnant rats of the Wistar strain were given 0.04% caffeine in drinking water before and/or during pregnancy for various numbers of days. Control rats received water for the same periods. There was no reduction of maternal body weight, fetal body weight or fetal total brain weight. Low fetal cerebral weight and placental weight were observed when dams were given caffeine before mating for long times and/or throughout pregnancy. DNA, RNA and protein contents per cerebrum were also reduced in fetuses from dams given caffeine throughout pregnancy or for the last 6 gestational days. Cerebral DNA and protein contents as expressed per wet weight were higher and significantly lower respectively in the fetuses from dams given caffeine throughout pregnancy when compared to controls. Activity of thymidine kinase was not significantly decreased in caffeine-treated fetuses. There was a positive correlation between maternal serum and fetal cerebral caffeine levels. Additionally a negative correlation between maternal caffeine levels and fetal survival rates which decreased in litters from dams given caffeine throughout pregnancy was demonstrated. Our rat model indicates maternal caffeine ingestion during pregnancy is associated with reduction of fetal cerebral weight and protein content without reduction of body weight.

Effects of a combination of X-rays and caffeine on preimplantation mouse embryos in vitro

The influence of a combination of caffeine (0.1 mM, 1 mM, or 2 mM) and X-rays (0.24 Gy, 0.94 Gy, or 1.88 Gy) on preimplantation mouse embryos in vitro was studied under different conditions. The agents were applied either singly or in combination. The embryos were irradiated in the G2-phase of the two-cell stage (28 h p. c. or 32 h p. c.) either 1 h after or immediately before application of caffeine. Caffeine was present during the whole incubation period (until 144 h p. c.). The effects on the microscopic visible development (formation of blastocysts 96 h p. c., hatching of blastocysts 144 h p. c.) and on the cell numbers of embryos at different times (48 h p. c., 56 h p. c., 96 h p. c., 144 h p. c.) were determined. We found conditions under which caffeine markedly enhanced radiation risk, i.e., under which the combination effect exceeded the sum of the single effects. This is true, in particular, for the embryonal development, for which the risk may almost be doubled, whereas the enhancement of risk is not so great for the proliferation of cells. In some cases the combination results lie even outside the envelope of additivity in the range of supra-additivity. The amount of caffeine necessary for such marked effects, however, is so high (at least 1 mM caffeine for rather long times), that it is almost impossible to reach them in vivo by consumption of caffeine-containing beverages.

Caffeine and social investigation in the adult male rat

In three experiments with adult rats, caffeine (0, 10, 20, 40 mg/kg) was found to increase the social investigation of a novel juvenile conspecific. Activity was elevated only after caffeine injections, whereas the duration of social investigation was raised after both the injection of caffeine and the administration of caffeine via the drinking water, suggesting the mechanisms of action of caffeine on these two behaviors may be independent. Duration and frequency of investigation were each increased following caffeine exposure, but the amount of investigation/episode was not influenced by this substance. Finally, the acute response to caffeine was not altered by prior exposure to the methylxanthine in the subject's drinking water.

Growth and death of HeLa cells in the presence of caffeine

Proliferation and death were measured in synchronously growing cultures of HeLa S3 cells during treatment with up to 30 mM caffeine. Changes in the number of colony-forming cells were determined by single-cell plating, while changes in the total number of cells were measured both by electronic counting and by monitoring cell division and physiological death cinemicrographically. At concentrations between 2 and 5 mM, cell killing occurs over several days during which the cells traverse the generation cycle once or a few times before losing colony-forming ability, with consequent proliferation of non-colony-forming cells. This indicates that lethal damage is accumulated with time. Death occurs more rapidly at higher concentrations, without proliferation, the kinetics of inactivation being strongly dependent on the phase of the cycle (cell age) at which treatment is initiated. G1 cells are killed more slowly in 10 mM caffeine than are S cells, but G1 cells respond rapidly to 20 mM caffeine, suggesting the inception of an additional mode of killing. The incidence of sister-cell fusion increases with increasing caffeine concentration above 1 mM. On addition of 10 mM caffeine to a culture prepared from collected mitotic cells, the cells undergo a transient rounding and then respread after several hours; with 20 mM, they never respread. The generation cycle is prolonged in a concentration-dependent fashion, as is the duration of G1; the generation time is doubled in 5-6 mM caffeine. G2 and M are also prolonged at concentrations above 3 mM, but S is not prolonged even by 10 mM caffeine.

Blood levels of caffeine and results of fetal examination after oral administration of caffeine to pregnant rats

Pregnant FDA-strain Osborne-Mendel rats were administered repeated doses of caffeine by oral intubation (gavage) and by administration in the drinking water (ad libitum sipping). When [1-methyl-14C]caffeine was administered at a dosage of 80 mg per kg per day by ad libitum sipping on days 12 to 15 of gestation, the amounts of radioactivity in blood were variable; the highest level on day 12 was 0.2% of the dose per ml of blood. The highest blood level of caffeine observed during a 24-h sampling period averaged 5.7 micrograms ml-1. When [14C]caffeine was administered by gavage at a dosage of 80 mg kg-1 on day 12, the blood level of radioactivity reached a peak of 0.4% of the dose per ml of blood and declined rapidly thereafter. The highest amount of caffeine observed in blood averaged 63.1 micrograms ml-1, 1 h after gavage. The overall blood elimination half-life of radioactivity in pregnant rats treated by gavage was 2.6 h, and the half-life of caffeine in blood was 1.7 h. The levels of radioactivity in the fetus and maternal muscle per unit weight were comparable after each method of administration. A comparison of autopsy results from both groups indicated that resorptions were increased when compared with rats that did not receive caffeine; this effect was more marked in the gavage group than in the ad libitum sipping group. Ectrodactyly was observed only in offspring of the gavage group. The incidences of ectrodactyly or resorptions did not appear to be directly related to nutrition or fluid intake.

Reduction in caffeine toxicity by acetaminophen

A patient who allegedly consumed 100 tablets of an over-the-counter analgesic containing sodium acetylsalicylate, caffeine, and acetaminophen displayed no significant CNS stimulation despite the presence of 175 micrograms of caffeine per mL of serum. Because salicylates have been reported to augment the stimulatory effects of caffeine on the CNS, attention was focused on the possibility that the presence of acetaminophen (52 micrograms/mL) reduced the CNS toxicity of caffeine. Studies in DBA/2J mice showed that: 1) pretreatment with acetaminophen (100 mg/kg) increased the interval between the administration of caffeine (300 to 450 mg/kg IP) and the onset of fatal convulsions by a factor of about two; and 2) pretreatment with acetaminophen (75 mg/kg) reduced the incidence of audiogenic seizures produced in the presence of caffeine (12.5 to 75 mg/kg IP). The frequency of sound-induced seizures after 12.5 or 25 mg/kg caffeine was reduced from 50 to 5% by acetaminophen. In the absence of caffeine, acetaminophen (up to 300 mg/kg) did not modify the seizures induced by maximal electroshock and did not alter the convulsant dose of pentylenetetrezol in mice (tests performed by the Anticonvulsant Screening Project of NINCDS). Acetaminophen (up to 150 micrograms/mL) did not retard the incorporation of radioactive adenosine into ATP in slices of rat cerebral cortex. Thus the mechanism by which acetaminophen antagonizes the actions of caffeine in the CNS remains unknown.

Long-term study on the effect of caffeine in Wistar rats

Wistar rats of both sexes were given synthetic caffeine in their drinking water for 78 weeks. Three hundred Wistar rats were divided into three groups of 50 males and 50 females each. Group 1 was given normal tap water without caffeine as a control. Group 2 was given 0.1% caffeine solution and group 3 was given 0.2% caffeine solution for 78 weeks. All the animals were killed after 104 experimental weeks. Various tumors were found in both experimental and control groups, but their incidences were not higher in the experimental groups. Thus, there was no evidence that caffeine was carcinogenic to Wistar rats when given continuously in the drinking water for 78 weeks.

Coffee consumption during pregnancy: subsequent behavioral abnormalities of the offspring

Offspring of rats fed coffee during pregnancy had reduced body, liver, and brain weight at birth. By 30 days postnatally these animals had recovered in size but exhibited increased locomotion, decreased grooming time, and decreased time spent with a novel object. Offspring of dams fed decaffeinated coffee demonstrated reduced liver weight at birth and similar behavioral characteristics at 30 days of age.

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.

Toxic and teratologic effects of caffeine on explanted early chick embryos

The toxic and teratologic effects of caffeine on chick embryos explanted at stages 4-7 and cultured for 19-22 hours were investigated. Caffeine, at 200-300 micrograms/ml, significantly increased the incidence of neural tube defects regardless of the developmental stage at treatment. Concentrations of 500 micrograms/ml or higher inhibited morphogenesis of nearly all organ primordia. In general, the effects of caffeine were concentration dependent and younger embryos were more susceptible to treatment than their older counterparts. Microscopic studies confirmed that the developing neuroepithelium was most sensitive to treatment. Caffeine, at concentrations sufficient to inhibit neural tube closure, caused no apparent alteration in the ultrastructure of cellular components except that apical microfilament bundles were thinner and less conspicuous than usual. Furthermore, caffeine (400 micrograms/ml) selectively inhibited uplifting of neural folds (and hence, closure of the neural tube) in embryos explanted at stage 8 and cultured for 4-6 and 16 hours. Affected neuroepithelial cells lacked the typical bottle-shaped characteristic and folded apical surfaces. Overall results of this study suggest that caffeine causes neural tube defects, at least in part, through its inhibitory action on the contractile activity of apical microfilament bundles in developing neuroepithelial cells.

In vitro and in vivo cytotoxicity of 6 amino-5-formyl-methylamino-1,3-dimethyl uracil, a uracilic metabolite of caffeine

The in vitro cytotoxicity of 6 amino-5 formylmethylamino-1,3 dimethyluracil (ADMU) a major metabolite of caffeine in rats was studied by cell counts or [3H]thymidine incorporation in the murine Lewis lung carcinoma (3LL) and L929 fibroblast cells and in the human E cell line derived from an ovarian carcinoma. Unlike 5-fluorouracil (5FU) which was markedly cytotoxic, ADMU concentrations up to 60 micrograms/ml were devoid appreciable cytocidal action. Similarly, 1-10 micrograms 5FU markedly inhibited the blastogenic response of rat lymphocytes to PHA, whereas lymphoproliferation was not affected at ADMU concentrations up to 100 micrograms/ml. In vivo administration of ADMU (40 mg/kg, twice a day on day 1 to 3) to L1210 leukaemia-bearing mice caused a transient short-lasting reduction of tumour cell numbers only on day 6 after leukaemia inoculation.U

The toxicology of cocoa and methylxanthines: a review of the literature

The critical review of the literature cited on pharmacology, toxicology, metabolism, and safety assessment clearly demonstrates that cocoa per se has not attracted a great deal of scientific interest because of its long-term usage with no reported adverse effects that would be injurious to man. On the other hand, a great deal of research has been directed towards understanding the pharmacological properties of the methylxanthines--caffeine, theobromine, and theophylline. Much of the emphasis on metabolism, toxicology, teratogenic potential, and safety assessment has been on the evaluation of caffeine. In light of the serious health concerns ascribed to the effects of caffeine and the lack of basic information on theobromine and theophylline, it is imperative that a major research program be undertaken to evaluate these methylxanthines and, of course, cocoa, coffee, and tea. It only will be through elucidating their mechanism of action that we will be in a position to assess their safety. Before committing research efforts to evaluating the long-term effects of these methylxanthines and their respective foodstuffs, which serve as our primary source of exposure, it is critical to initiate more basic research on the metabolism of caffeine, theophylline, and theobromine in several animal species and man. While published reports do appear in this area, it is essential to understand fully the similarities and differences between various animals and man. The influence of dietary factors and drug interactions must also be determined. Before establishing dosage levels for a chronic toxicity study, the pharmacokinetics of the dose must be determined in the species that will be used in long-term studies. This is necessary if there is a dose-dependency in the animal above which saturation may occur and the plasma half-life kinetics change, or shifts occur either in the metabolic pathways of degradation and/or in the route of excretion from the body. The area of teratology must also be thoroughly evaluated. Studies undertaken should include identification and quantitation of the metabolites of caffeine, theophylline, and theobromine in the pregnant animal, the respective pharmacokinetics of each compound, dose-dependency (if this is the case), and their potential teratogenicity. In addition, the influence of other drugs or dietary variables must be included. In addition to teratology, a great deal of research is needed to assess and quantitate fetal and neonatal metabolism of these compounds.(ABSTRACT TRUNCATED AT 400 WORDS)