No abstract

This work demonstrates for the first time that TNF-alpha may act as a protector of embryos exposed to teratogenic stress. One possible mechanism may be restoration of NF-kappaB activity in embryonic cells surviving the teratogenic insult.

It is known that programmed cell death (apoptosis) is an important physiological determinant of embryonic development. In parallel, it may be one of the major events involved in induced teratogenesis. The present study was designated to evaluate to what extent is apoptosis involved in the formation of some final abnormalities induced by cyclophosphamide (CP) in ICR mice. The level of apoptosis in limbs, tail, liver, and whole embryo was assessed 24 h after administration of various doses of CP (day 12 of pregnancy) by flow cytometric analysis and by DNA fragmentation assay. In parallel, the rate of limb and tail malformations, resorptions, and growth retardation induced by various doses of CP was evaluated in animals sacrificed on day 19 of pregnancy using routine teratological methods. A striking correlation between the rate of CP-induced apoptosis in limb and tail cells and the severity of limb and tail anomalies was found after administration of CP ranging from 10 to 40 mg/kg. Thus, the percent of apoptotic cells collected from limbs and tails increased from 18 to 78%. In parallel, the severity of limb and tail anomalies increased from digit anomalies to amely and from crooked to short or absent tail. CP-induced embryolethality and fetal growth retardation also correlated with the level of apoptosis in cells collected from whole embryos but to a lesser extent. These results claim that CP-induced apoptosis is one of the inevitable events in the pathway leading to the formation of CP-induced abnormalities and also suggest that the extent of the involvement of apoptosis in the formation of different types of final abnormalities, may be different.

Programmed cell death or apoptosis is a widespread biological phenomenon. Apoptosis is characterized by typical cell features such as membrane blebbing, chromatin condensation, and DNA fragmentation. It involves a number of membrane receptors (e.g., Fas, TNFR) and a cascade of signal transduction steps resulting in the activation of a number of cysteine proteases known as caspases. Disordered apoptosis may lead to carcinogenesis and participates in the pathogenesis of Alzheimer disease, Parkinson disease, or AIDS. Programmed cell death plays an important role in the processes of gamete maturation as well as in embryo development, contributing to the appropriate formation of various organs and structures. Apoptosis is one of the mechanisms of action of various cytotoxic agents and teratogens. Teratogen-induced excessive death of embryonic cells is undoubtedly one of the most important events preceding the occurrence of structural abnormalities, regardless of their nature. Therefore understanding the mechanisms involved in physiological as well as in disturbed or dysregulated apoptosis may lead to the development of new methods of preventive treatment of various developmental abnormalities. The present review summarizes data on the mechanisms of programmed cell death and concentrates on apoptosis involved in normal or disturbed gametogenesis and in normal and abnormal embryonic development.

Our results suggest a possible role for the apoptotic process in mechanisms mediating pregnancy loss and indicate an involvement of p53 and bcl-2 in its regulation.

Data presented in this review suggest that NF-kappaB may act as a protector of embryos exposed to embryopathic stresses, possibly, because of the ability of NF-kappaB to prevent the induction of programmed cell death as well as to activate cell proliferation.

The present work was aimed to assess the possible effect of stimulation of the maternal immune system on the teratogenic potential of diabetes mellitus. ICR female mice were immunized with splenocytes of male rats 3 weeks before the beginning of mating and were injected with 240 mg/kg streptozocin (STZ) 10 days after immunization. Females with blood glucose levels over 27.8 mmol/l and HbA1c levels over 6 standard deviations (SD) above the mean of intact animals were used for teratological studies. The rate of malformed fetuses, resorptions and fetal weights were evaluated for animals killed on day 19 of pregnancy using routine teratological methods. Also, phenotyping of spleen cells of these females was performed by fluorescein activated cell sorter analysis. Two main effects possibly due to immunostimulation of ICR females were observed: 1) immunostimulated females had significantly fewer litters with malformed fetuses than non-immunized females: only 4 litters out of 22 (18%) compared to 10 out of 16 (63%). Correspondingly, the incidence of malformed fetuses was also decreased: 2.1 compared to 8.9%; 2) a significant increase in the pregnancy rate in immunized diabetic ICR mice: 69% as compared to 44% in non-immunized diabetic females. Also, immunostimulation resulted in a visible increase in spleen cellularity and a certain increase in the number of cells with mature T-cell and macrophage surface markers. These results strongly suggest that immunostimulation increases the tolerance of ICR females to the teratogenic effect of STZ-induced diabetes.

TNF-alpha will boost death signaling to kill the embryo if initial events (damages) triggered by detrimental stimuli may culminate in structural anomalies, and stimulate protective mechanisms if the repair of these damages may prevent maldevelopment.