Prevention of tilorone developmental toxicity with progesterone

Counteraction of the Embryolethal Effects, But Not the Maternal Toxicity, of Bropirimine and Tilorone by Coadministration of Indomethacin

Bropirimine and tilorone are immunomodulators with experimental antiviral and antitumor activities. In earlier studies, treatment with bropirimine resulted in either death of the entire litter, if given once on specific days during or prior to the period of organogenesis, or litter survival comparable with that of controls. For example, bropirimine and tilorone were both found to be embryolethal when administered orally at 400 mg/kg to Upj:TUC(SD)spf rats on day 10 of gestation. Previous studies also have shown that coadministration of progesterone with either of these immunomodulators could prevent the embryolethality but not the pronounced maternal toxicity seen concurrently. Thus, bropirimine and tilorone appear to affect maternal support of the pregnancy rather than having a direct effect on the embryos. Since administration of bropirimine or tilorone appears to mimic the luteolytic effects of prostaglandin F2a, it was hypothesized that coadministration of the prostaglandin synthesis inhibitor indomethacin might prevent such embryolethality. Thus, indomethacin was administered s.c. in combination with bropirimine or tilorone (400 mg/kg orally on day 10 of gestation), at 0.4 or 0.8 mg/rat on days 9-11 (bropirimine experiment) or days 9-12 of gestation; the dams were killed on day 13, at which time the status of each conceptus was ascertained. Although unable to prevent maternal toxicity, which was found 24 h after administration of either immunomodulator, coadministration of indomethacin resulted in a decrease in the embryolethality associated with administration of either immunomodulator on day 10 of gestation. No live embryos were found on day 13 of gestation in five of six pregnant dams given bropirimine only, whereas in the drug-combination groups six of seven (indomethacin at 0.4 mg/day) and six of eight (indomethacin at 0.8 mg/day) pregnant dams had litters containing live embryos. In the tilorone experiment, six of eight litters were completely lost in utero in the group receiving the immunomodulator only. However, only one of four surviving dams had no live embryos in the drug-combination group that received indomethacin at 0.4 mg/day, with all eight surviving dams having live embryos in the group that received 0.8 mg/day of this drug. The results of this study and of earlier combination experiments with progesterone support the following hypothesis: bropirimine or tilorone administration to Upj:TUC-(SD)spf rats on day 10 of gestation inhibits progesterone production by the corpora lutea by a mechanism involving prostaglandin synthesis, resulting in a disruption in maternal support to the pregnant uterus and subsequent embryolethality.

Chloroquine effects on intrauterine and postnatal dendritic maturation of hippocampal neurons and on lipid composition of the developing rat brain

The aim of the study was to analyse the intrauterine effects of Chloroquine on the dendritic maturation in the hippocampal region under considering of the lipid composition in brain tissue. 131 brains of rat pups from day 22 of pregnancy and 49 brains from offsprings from day 7 of life were investigated. The findings indicate changes in the geometric dendritic architecture of the CA3 neurons on the 7th day of life. The length of apical shaft, apical dendrites and basilar dendrites of the CA3 neurons showed a significant elongation (p < 0.05) under low doses of Chloroquine. Furthermore a early considerable formation of dendritic spines during the intrauterine period could be observed for CA1 spines at the day 22 p.c. A significant increase of the fatty acids, a reduced amount of sphingomyelines, cephalines and gangliosides was found. These results underline the fact of a mild toxic effect under a low dosis of Chloroquine in our model.

Abnormal dendritic maturation of neurons under the influence of a Tilorone analogue (R 10.874)

Tilorone analogue (R 10.874) has a close affinity to the lysosomal compartment of cells and forms a non degradable carbohydrate-lipid-drug complex accumulated within digesting organelles. Resembling biochemical and structural changes are seen in hereditary mucopolysaccharidoses accompanied with abnormal dendritogenesis. On the other hand, developmental toxicity (TERRY et al. 1992), antiproliferative effects (ALGARRA et al. 1993) and interactions with DNA (GELLER et al. 1985) are generated by tilorone. Therefore it should be interesting to know whether the amphiphilic cationic compound is able to produce an abnormal dendritogenesis as in storage diseases or an impaired arborisation of dendrites and what could be the reason for the misdevelopment. We demonstrate that there was a fetal retardation in the development of dendritic network, even under influence of low dosis of the analogue R 10.874. The dendritic dismaturation was concomitant with an increased amount of fatty acids and a slightly disarranged metabolic pathway of gangliosides. The dendritic arborisation closed the gap of retarded development between intrauterine treated and untreated rats after 7 days of postnatal drug elimination. We suppose that a fetotoxic effect and not the lysosomopathy is responsible for the reduced dendritic network.

Prevention of human recombinant interleukin-1 beta (rhIL-1 beta) embryolethality with progesterone or indomethacin

PROBLEM

Bropirimine and tilorone were found in earlier studies to be embryolethal when administered to Crl:TUC(SD)spf (TUC) rats on gestation day 10. Progesterone or indomethacin could, at least partially, prevent this effect. The immunomodulators appeared to mimic the luteolytic effects of PGF2 alpha, resulting in a shutdown in progesterone release by the corpora lutea, followed by a disruption in maternal support to the pregnant uterus and embryolethality. Since bropirimine has been shown to induce interleukin-1, and since this cytokine has been found to increase PGF2 alpha levels in human decidual cells, the decision was made to investigate whether human interleukin-1 beta might act in an analogous manner to bropirimine and tilorone.

METHOD

Bropirimine (400 mg/kg, p.o.) or rhIL-1 beta (20, 30, or 40 micrograms/kg, s.c.) was administered on gestation day 10 to Crl:CD[BR] (CD) or TUC rats, alone and in combination with progesterone (2 mg/kg/day, s.c.) or indomethacin (0.6 mg/day, s.c., days 9-11). On gestation day 14 the dams were killed and their uterine contents examined.

RESULTS

rhIL-1 beta (30-40 micrograms/kg) was embryolethal when administered to CD or TUC rats on gestation day 10. Progesterone or indomethacin coadministration prevented, at least partially, the embryolethality seen when rhIL-1 beta was administered (30 micrograms/kg) to TUC rats.

CONCLUSION

Evidence was obtained in support of the hypothesis that interleukin-1 is involved in the embryolethal actions of the immunomodulators bropirimine and tilorone.

Role of maternal toxicity in assessing developmental toxicity in animals: a discussion

The belief that any drug or chemical, when administered at a high enough dose, can be expected to produce fetal malformations is not consistent with the facts. However, the stress associated with maternally toxic doses can be expected to result in associated, often transient, fetal abnormalities that may not be the result of deviant organogenesis. Sometimes the toxicity toward the pregnant animal, including her embryos/fetuses since they are hardly in a sanctuary, is severe enough to result in resorption of the embryo or abortion of the fetus. Thus, it is possible that the embryolethality and other indications of developmental toxicity, produced by some drugs and chemicals, may be the result of a mechanism(s) other than selective toxicity toward the embryo. Also, some test materials have been shown to affect maternal homeostasis, thereby disrupting support to the embryo, without causing significant overt toxicity to the embryo or dam; e.g., the endocrine system of the dam is altered. Routine testing has thus far revealed a relatively limited number of true teratogens, although a large number of drugs and chemicals have resulted in fetal effects such as developmental variations when administered at doses that approach lethal levels. Such effects on the fetus should be expected when the maternal animals are stressed by the high dosages usually employed. A better understanding of the etiology and biological relevance of the embryo/fetal deviations often seen in developmental toxicology studies might help to avoid the sometimes unjustified withholding of potentially useful drugs and chemicals from the marketplace.