p53 regulates cyclophosphamide teratogenesis by controlling caspases 3, 8, 9 activation and NF-kappaB DNA binding

Loss of tumor protein 53 protects against alcohol-induced facial malformations in mice and zebrafish

BACKGROUND

Alcohol exposure during the gastrulation stage of development causes the craniofacial and brain malformations that define fetal alcohol syndrome. These malformations, such as a deficient philtrum, are exemplified by a loss of midline tissue and correspond, at least in part, to regionally selective cell death in the embryo. The tumor suppressor protein Tp53 is an important mechanism for cell death, but the role of Tp53 in the consequences of alcohol exposure during the gastrulation stage has yet to be examined. The current studies used mice and zebrafish to test whether genetic loss of Tp53 is a conserved mechanism to protect against the effects of early developmental stage alcohol exposure.

METHODS

Female mice, heterozygous for a mutation in the Tp53 gene, were mated with Tp53 heterozygous males, and the resulting embryos were exposed during gastrulation on gestational day 7 (GD 7) to alcohol (two maternal injections of 2.9 g/kg, i.p., 4 h apart) or a vehicle control. Zebrafish mutants or heterozygotes for the tp53^zdf1  M214K mutation and their wild-type controls were exposed to alcohol (1.5% or 2%) beginning 6 h postfertilization (hpf), the onset of gastrulation.

RESULTS

Examination of GD 17 mice revealed that eye defects were the most common phenotype among alcohol-exposed fetuses, occurring in nearly 75% of the alcohol-exposed wild-type fetuses. Tp53 gene deletion reduced the incidence of eye defects in both the heterozygous and mutant fetuses (to about 35% and 20% of fetuses, respectively) and completely protected against alcohol-induced facial malformations. Zebrafish (4 days postfertilization) also demonstrated alcohol-induced reductions of eye size and trabeculae length that were less common and less severe in tp53 mutants, indicating a protective effect of tp53 deletion.

CONCLUSIONS

These results identify an evolutionarily conserved role of Tp53 as a pathogenic mechanism for alcohol-induced teratogenesis.

The effects of magnesium sulfate on cyclophosphamide-induced ovarian damage: Folliculogenesis

Cyclophosphamide (CYP) is one of the alkylating chemotherapeutic agents and its adverse effects on folliculogenesis in the ovary are well-known due to the previous scientific research on this topic. Magnesium has various effects in organisms, including catalytic functions on the activation and inhibition of many enzymes, and regulatory functions on cell proliferation, cell cycle, and differentiation. In this study, the effects of magnesium sulfate (MgSO₄) on CYP induced ovarian damage were investigated. Immature Wistar-Albino female rats of 28-days were treated with pregnant mare serum gonadotrophin (PMSG) to develop the first generation of preovulatory follicles. Rats of the experimental groups were then treated with either CYP (100 mg/kg, i.p) and MgSO₄ (270 mg/kg loading dose; 27 mg/kg maintenance doseX12, i.p) solely or in combination. Following in-vivo 5-bromo-2-deoxyuridine (BrdU) labeling, animals were sacrificed and ovaries were embedded in paraffin and Epon. In the ovaries, added to the evaluation of general morphology and follicle count; BrdU and TUNEL-labeling, cleaved caspase-3 and p27 (cyclin-dependent kinase inhibitor) staining was also performed immunohistochemically and an ultrastructural evaluation was performed by transmission electron microscopy (TEM). The number of primordial follicles were decreased and multilaminar primary and atretic follicles were increased in CYP group. After MgSO₄ treatment, while primordial follicle pool were elevated, the number of atretic follicles were decreased. Additionally, decreased BrdU-labeling, increased cleaved caspase 3 immunoreactivity and increased TUNEL labeling were observed in CYP group. In CYP treated animals, observations showed that while MgSO₄ administration caused no alterations in BrdU proliferation index and caspase-3 immunoreactivity, it significantly reduced the TUNEL labeling. It was also observed that, while p27 immunoreactivity significantly increased in the nuclei of granulosa and theca cells in the CYP group; MgSO₄ treatment significantly reduced these immunoreactivities. The ultrastructural observations showed frequent apoptotic profiles in granulosa and theca cells in both early and advanced stages of follicles in the CYP group and the MgSO₄ treatment before the CYP application led to ultrastructural alleviation of the apoptotic process. In conclusion, our data suggest that MgSO₄ may provide an option of pharmacologic treatment for fertility preservation owing to the beneficial effects of on chemotherapy-induced accelerated follicular apoptotic process, and the protection of the primordial follicle pool.

The Roles of P53 and Its Family Proteins, P63 and P73, in the DNA Damage Stress Response in Organogenesis-Stage Mouse Embryos

Members of the P53 transcription factor family, P53, P63, and P73, play important roles in normal development and in regulating the expression of genes that control apoptosis and cell cycle progression in response to genotoxic stress. P53 is involved in the DNA damage response pathway that is activated by hydroxyurea in organogenesis-stage murine embryos. The extent to which P63 and P73 contribute to this stress response is not known. To address this question, we examined the roles of P53, P63, and P73 in mediating the response of Trp53-positive and Trp53-deficient murine embryos to a single dose of hydroxyurea (400 mg/kg) on gestational day 9. Hydroxyurea treatment downregulated the expression of Trp63 and upregulated Trp73 in the absence of effects on the levels of Trp53 transcripts; Trp73 upregulation was P53-dependent. At the protein level, hydroxyurea treatment increased the levels and phosphorylation of P53 in the absence of effects on P63 and P73. Upregulation of the expression of genes that regulate cell cycle arrest and apoptosis, Cdkn1a, Rb1, Fas, Trp53inp1, and Pmaip1, was P53-dependent in hydroxyurea-treated embryos. The increase in cleaved caspase-3 and cleaved mammalian sterile-20-like-1 kinase levels induced by hydroxyurea was also P53-dependent; in contrast, the increase in phosphorylated H2AX, a marker of DNA double-strand breaks, in response to hydroxyurea treatment was only partially P53-dependent. Together, our data show that P53 is the principal P53 family member that is activated in the embryonic DNA damage response.

Fetal Toxicity of Immunosuppressive Drugs in Pregnancy

Women affected by autoimmune diseases, organ transplantation, or neoplasia need to continue immunosuppressive treatment during pregnancy. In this setting, not only a careful planning of pregnancy, but also the choice of drugs is critical to preventing maternal complications and minimizing the fetal risks. Some immunosuppressive drugs are teratogenic and should be replaced even before the pregnancy, while other drugs need to be managed with caution to prevent fetal risks, including miscarriage, intrauterine growth restriction, prematurity, and low birth weight. In particular, the increasing use of biologic agents raises the question of their compatibility with reproduction. In this review we present data on the indication and safety in pregnancy of the most frequently used immunosuppressive drugs.

Editor's Highlight: Hydroxyurea Exposure Activates the P53 Signaling Pathway in Murine Organogenesis-Stage Embryos

Hydroxyurea, an anticancer agent and potent teratogen, induces oxidative stress and activates a DNA damage response pathway in the gestation day (GD) 9 mouse embryo. To delineate the stress response pathways activated by this drug, we investigated the effect of hydroxyurea exposure on the transcriptome of GD 9 embryos. Timed pregnant CD-1 mice were treated with saline or hydroxyurea (400 mg/kg or 600 mg/kg) on GD 9; embryonic gene and protein expression were examined 3 h later. Microarray analysis revealed that the expression of 1346 probe sets changed significantly in embryos exposed to hydroxyurea compared with controls; the P53 signaling pathway was highly affected. In addition, P53 related family members, P63 and P73, were predicted to be activated and had common and unique downstream targets. Western blot analysis revealed that active phospho-P53 was significantly increased in drug-exposed embryos; confocal microscopy showed that the translocation of phospho-P53 to the nucleus was widespread in the embryo. Furthermore, qRT-PCR showed that the expression of P53-regulated genes (Cdkn1A, Fas, and Trp53inp1) was significantly upregulated in hydroxyurea-exposed embryos; the concentration of the redox sensitive P53INP1 protein was also increased in a hydroxyurea dose-dependent fashion. Thus, hydroxyurea elicits a significant effect on the transcriptome of the organogenesis stage murine embryo, activating several key developmental signaling pathways related to DNA damage and oxidative stress. We propose that the P53 pathway plays a central role in the embryonic stress response and the developmental outcome after teratogen exposure.

Curcumin and epithelial-mesenchymal transition in breast cancer cells transformed by low doses of radiation and estrogen

Breast cancer is a major cause of global mortality in women. Curcumin exerts anti-proliferative, anti-migratory and apoptotic effects. The aim of this study was to evaluate gene expression involved in epithelial-mesenchymal transition (EMT). An in vitro model was developed with the MCF-10F immortalized breast epithelial cell line exposed to low radiation doses of high LET (linear energy transfer) α-particles (150 keV/µm) and cultured in the presence of 17β-estradiol (estrogen). The following cell lines were used: i) MCF-10F, normal; ii) Alpha5, pre-tumorigenic, and iii) Tumor2 derived from Alpha5 injected into the nude mice. Our previous results have shown that Alpha5 and Tumor2 increased cell proliferation, anchorage independency, invasive capabilities and tumor formation in nude mice in comparison to control. Results indicated that curcumin decreased expression of EMT-related genes in Tumor2 cell line when compared to its counterpart as E-cadherin, N-cadherin, ZEB2, Twist1, Slug, Axl, vimentin, STAT-3, fibronectin; and genes p53 and caveolin-1, as well as apoptotic genes caspase-3, caspase-8, and others such as cyclin D1 and NFκB. All these changes induced a decrease in migratory and invasive capabilities of such a cell line. Thus, it seems that curcumin may impinge upon apoptosis and metastatic properties of the malignant cells exerting antitumor activity in breast cancer cells transformed by low doses of α-particles and estrogen in vitro.

Thalidomide (5HPP-33) suppresses microtubule dynamics and depolymerizes the microtubule network by binding at the vinblastine binding site on tubulin

Thalidomides were initially thought to be broad-range drugs specifically for curing insomnia and relieving morning sickness in pregnant women. However, its use was discontinued because of a major drawback of causing teratogenicity. In this study, we found that a thalidomide derivative, 5-hydroxy-2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione (5HPP-33), inhibited the proliferation of MCF-7 with a half-maximal inhibitory concentration of 4.5 ± 0.4 μM. 5HPP-33 depolymerized microtubules and inhibited the reassembly of cold-depolymerized microtubules in MCF-7 cells. Using time-lapse imaging, the effect of 5HPP-33 on the dynamics of individual microtubules in live MCF-7 cells was analyzed. 5HPP-33 (5 μM) decreased the rates of growth and shortening excursions by 34 and 33%, respectively, and increased the time microtubules spent in the pause state by 92% as compared to that of the vehicle-treated MCF-7 cells. 5HPP-33 (5 μM) reduced the dynamicity of microtubules by 62% compared to the control. 5HPP-33 treatment reduced the distance between the two poles of a bipolar spindle, induced multipolarity in some of the treated cells, and blocked cells at mitosis. In vitro, 5HPP-33 bound to tubulin with a weak affinity. Vinblastine inhibited the binding of 5HPP-33 to tubulin, and 5HPP-33 inhibited the binding of BODIPY FL-vinblastine to tubulin. Further, a molecular docking analysis suggested that 5HPP-33 shares its binding site on tubulin with vinblastine. The results provided significant insight into the antimitotic mechanism of action of 5HPP-33 and also suggest a possible mechanism for the teratogenicity of thalidomides.

Oxidative stress, unfolded protein response, and apoptosis in developmental toxicity

Physiological development requires precise spatiotemporal regulation of cellular and molecular processes. Disruption of these key events can generate developmental toxicity in the form of teratogenesis or mortality. The mechanism behind many developmental toxicants remains unknown. While recent work has focused on the unfolded protein response (UPR), oxidative stress, and apoptosis in the pathogenesis of disease, few studies have addressed their relationship in developmental toxicity. Redox regulation, UPR, and apoptosis are essential for physiological development and can be disturbed by a variety of endogenous and exogenous toxicants to generate lethality and diverse malformations. This review examines the current knowledge of the role of oxidative stress, UPR, and apoptosis in physiological development as well as in developmental toxicity, focusing on studies and advances in vertebrates model systems.

MicroRNA-34a is dispensable for p53 function as teratogenesis inducer

The tumor suppressor protein p53 is a powerful regulator of the embryo's susceptibility to diverse teratogenic stimuli, functioning both as a teratogenesis inducer and suppressor. However, the targets that p53 engages to fulfill its functions remain largely undefined. We asked whether the microRNA (miRNA) miR-34 family, identified as one of the main targets of p53, mediates its function as a teratogenesis inducer. For this, pregnant ICR-, p53- and miR-34a-deficient mice, as well as rats, were exposed to 5-aza-2'-deoxycytidine (5-aza), a teratogen inducing limb reduction anomalies (LRA) of the hindlimbs in mice and either the hindlimbs or forelimbs in rats. Using hind- and forelimb buds of 5-aza-exposed embryos, we identified that the miR-34 family members are the most upregulated miRNAs in mouse and rat limb buds, with their increase level being significantly higher in limb buds destined for LRA. We showed that p53 mediates the 5-aza-induced miR-34 transcription followed by met proto-oncogene and growth-arrest-specific 1 target suppression in embryonic limb buds. We demonstrated that p53 regulates the teratogenic response to 5-aza acting as a teratogenesis inducer albeit miR-34a deletion does not affect the susceptibility of mice to 5-aza. Overall, our study thoroughly characterizes the expression and regulation of miR-34 family in teratogen-resistant and teratogen-sensitive embryonic structures and discusses the involvement of epigenetic miRNA-mediated pathway(s) in induced teratogenesis.

Methanolic Extract of Nigella sativa Seed Inhibits SiHa Human Cervical Cancer Cell Proliferation Through Apoptosis

Nigella sativa (NS), also known as black cumin, has long been used in traditional medicine for treating various cancer conditions. In this study, we sought to investigate the potential anti-cancer effects of NS extract using SiHa human cervical cancer cells. NS showed an 88.3% inhibition of proliferation of SiHa human cervical cancer cells at a concentration of 125 μL/mL methanolic extract at 24 h, and an IC50 value 93.2 pL/mL. NS exposure increased the expression of caspase-3, -8 and -9 several-fold. The analysis of apoptosis by DeadEnd terminaltransferase-mediated dUTP-digoxigeninend labeling (TUNEL) assay was used to further confirm that NS induced apoptosis. Thus, NS was concluded to induce apoptosis in SiHa cell through bothp53 and caspases activation. NS could potentially be an alternative source of medicine for cervical cancer therapy.

Catechin hydrate inhibits proliferation and mediates apoptosis of SiHa human cervical cancer cells

Catechin hydrate (CH), one of the chemical compounds in green tea, has been shown to inhibit tumor growth. Green tea possesses anticancer potential and is one of the most commonly used herbal medicines worldwide. In this study, we sought to characterize the DNA damage and downstream genes targeted by CH extracts using SiHa human cervical cancer cells. The efficacy of CH in killing cervical cancer cells in vitro was investigated in this study to determine whether CH possesses anticancer potential and could be developed as a therapeutic agent for cervical cancer upon further investigation. To scientifically validate the anticancer activities of CH on cervical cancer, CH was tested for its cytotoxic and growth-inhibition properties, specifically the induction of apoptosis in SiHa cervical cancer cells. CH showed a 50% inhibition of SiHa human cervical cancer cells at a concentration of 196.07 μg/mL at 24h. CH induced the several folds increase of caspase-3, -8, and -9 after 24h and 48 h; the increase of these genes may be involved in the induction of apoptosis. The analysis of apoptosis by DeadEnd terminal transferase-mediated dUTP-digoxigenin-end labeling (TUNEL) assay was used to further confirm that CH induced apoptosis. The results suggested that CH has the potential to benefit cervical cancer prevention. This is the first report that shows the possible mechanism of the anti-proliferative effects of CH in the prevention of cervical cancer in cell culture models. CH, either in its original form or in combination with other anticancer drugs, could potentially be an alternative medicine for cervical cancer. Further study may increase our understanding of the mechanism by which CH has an effect on cervical cancer therapy.

Catechin hydrate suppresses MCF-7 proliferation through TP53/Caspase-mediated apoptosis

Catechin hydrate (CH), a strong antioxidant that scavenges radicals, is a phenolic compound that is extracted from plants and is present in natural food and drinks, such as green tea and red wine. CH possesses anticancer potential. The mechanism of action of many anticancer drugs is based on their ability to induce apoptosis. In this study, I sought to characterize the downstream apoptotic genes targeted by CH in MCF-7 human breast cancer cells. CH effectively kills MCF-7 cells through induction of apoptosis. Apoptosis was confirmed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and real-time PCR assays. Cells were exposed to 150 μg/ml CH and 300 μg/mL CH for 24 hours, which resulted in 40.7% and 41.16% apoptotic cells, respectively. Moreover, a 48-hour exposure to 150 μg/ml CH and 300 μg/ml CH resulted in 43.73% and 52.95% apoptotic cells, respectively. Interestingly, after 72 hours of exposure to both concentrations of CH, almost 100% of cells lost their integrity. These results were further confirmed by the increased expression of caspase-3,-8, and -9 and TP53 in a time-dependent and dose-dependent manner, as determined by real-time quantitative PCR. In summary, the induction of apoptosis by CH is affected by its ability to increase the expression of pro-apoptotic genes such as caspase-3, -8, and -9 and TP53.

Mechanisms of the embryo's response to embryopathic stressors: a focus on p53

Whether the embryo develops normally or not depends not only on the mechanisms regulating embryonic development, but also on the mechanisms acting to resist and repair injures in the embryo due to harmful maternal stimuli or exposure to developmental toxicants. The key role of p53 in the regulation of the embryo's response to embryopathic stress inducing DNA damage is beyond doubt. Yet, the question why p53 in some cases acts as a suppressor of teratogenesis, whereas in other cases it induces teratogenesis, remains unanswered. In this minireview we analyze studies in which organogenesis-stage embryos were exposed to various developmental toxicants and suggest a model unifying the teratogenesis-suppressing and teratogenesis-promoting role of p53. This model predicts that p53 protects embryos from developmental toxicant inducing oxidative stress and promotes the process of maldevelopment induced by developmental toxicants activating apoptotic machinery. Certainly, many questions must be answered before concluding the extent to which this model is correct. Yet, it does allow us to explain some discrepancies obtained in studies performed to date. Also, the model might be useful in choosing molecular targets for further studies addressing p53-controlled and p53-independent mechanisms, which determine the embryo's resistance to embryopathic stress.

Teratogen-induced alterations in microRNA-34, microRNA-125b and microRNA-155 expression: correlation with embryonic p53 genotype and limb phenotype

Background

In a large number of studies, members of the microRNA (miRNA)-34 family such as miRNA-34a, miRNA-34b, miRNA-34c, as well as miRNA-125b and miRNA-155, have been shown to be regulators of apoptosis. The ability of these miRNAs to perform this function is mainly attributed to their ability to interact with the p53 tumor suppressor, which is a powerful regulator of the teratologic susceptibility of embryos. We chose to explore whether miRNA-34a/b/c, miRNA-125b and miRNA-155 may play a role in teratogenesis by using p53^+/- pregnant mice treated with cyclophosphamide (CP) as a model. We evaluated how CP-induced alterations in the expression of these miRNAs in the embryonic limbs correlate with embryonic p53 genotype and CP-induced limb phenotypes.

Results

The limbs of p53 positive embryos were more sensitive to CP-induced teratogenic insult than the limbs of p53 negative embryos. The hindlimbs were more severely affected than the forelimbs. Robust miRNA-34a expression was observed in the fore- and hindlimbs of p53^+/+ embryos exposed to 12.5 mg/kg CP. The dose of 20 mg/kg CP induced almost a two-fold increase in the level of miRNA-34a expression as compared to that exhibited by p53^+/+ embryos exposed to a lower dose. Increased miRNA-34b and miRNA-34c expression was also observed. Of note, this dose activated miRNA-34a and miRNA-34c in the forelimbs of p53^-/- embryos. When embryos were exposed to 40 mg/kg CP, the expression pattern of the miRNA-34a/b/c was identical to that registered in the limbs of embryos exposed to 20 mg/kg CP. However, this dose suppressed miRNA-125b and miRNA-155 expression in the fore- and hindlimbs of p53^+/+ embryos.

Conclusion

This study demonstrates that teratogen-induced limb dysmorphogenesis may be associated with alterations in miRNA-34, miRNA-125b and miRNA-155 expression. It also suggests for the first time that p53-independent mechanisms exist contributing to teratogen-induced activation of miRNA-34a and miRNA-34c. At the same time, teratogen-induced suppression of miRNA-125b and miRNA-155 expression may be p53 dependent. The analysis of correlations between the expression pattern of the tested miRNAs and CP induced limb phenotypes implies that miRNAs regulating apoptosis may differ from each other with respect to their functional role in teratogenesis: some miRNAs act to protect embryos, whereas other miRNAs boost a teratogen-induced process of maldevelopment to induce embryonic death.

Hyperglycemia alters renal cell responsiveness to pressure in a model of malignant hypertension

OBJECTIVE

Poor glycemic control contributes to development of diabetic nephropathy. However, for a majority of clinical situations, the mechanisms responsible for high glucose-induced aggravation of renal tissue injury are not fully elucidated. We investigated responsiveness to pressure of various renal cell subsets subjected to hyperglycemic environment in an in-vitro model of malignant hypertension.

METHODS

Rat renal mesangium, epithelium and endothelium were exposed to high glucose-containing medium for 10 days and then subjected to high hydrostatic pressure for 1 h to simulate the incidence of malignant hypertension. In some cultures, renin-angiotensin system was experimentally suppressed prior to pressure application. Proliferation, apoptosis, intrarenal p53, H2O2 and angiotensin-II synthesis were subsequently assessed.

RESULTS

By contrast to cultures not exposed to high glucose, in all hyperglycemic cells p53 expression, angiotensin-II synthesis and apoptosis were increased, whereas proliferation depressed, irrespective of pressure enforcement. H2O2 release was enhanced by high pressure per se, and increased further following exposure to high glucose. In all diabetic cultures, inhibition of p53 by a specific inhibitor pifithrin concomitantly significantly decreased apoptosis.

CONCLUSION

Hyperglycemic environment alters responsiveness of renal cells to in-vitro simulation of malignant hypertension. The main consequence of either malignant hypertension or hyperglycemia is exaggerated apoptosis. However, the operating mechanisms differ: Malignant hypertension stimulates renal cell apoptosis via increased angiotensin-II, whereas hyperglycemia elicits apoptosis via augmented p53. By contrast to pressure-induced excessive proliferation of normoglycemic cells, hyperglycemia prohibits elevated proliferation in response to pressure. Angiotensin-II production is maximally augmented by hyperglycemic environment and is not stimulated further by pressure application.

TNFalpha in the pathogenesis of diabetes-induced embryopathies: functions and targets

Hyperglycemia-induced increase in the production of reactive oxygen species (ROS) is proposed to be an initial step in the pathogenesis of diabetes-induced spontaneous abortions and structural inborn anomalies. However, the subsequent steps in this process are incompletely understood. One of the key molecules involved is tumor necrosis factor-alpha (TNFalpha): its expression is regulated by ROS and it regulates ROS production in turn. This cytokine has been the focus of many studies addressing the mechanisms of different forms of diabetes-induced embryopathies, such as early pregnancy loss, inborn anomalies, fetal growth retardation as well as some pathologies appearing during adult life. In this review, we analyze the results of these studies and discuss how TNFalpha may regulate the response of pre- and post-implantation stage embryos to diabetes-induced detrimental stimuli. The data presented in this review suggest that TNFalpha may play a dual role in the pathogenesis of diabetes-induced embryopathies. It may act both as a mediator of diabetes-induced embryotoxic stimuli leading to the death of peri-implantation stage embryos and, possibly, as a suppressor of diabetes-induced apoptosis in post-implantation stage embryos. It also appears that TNFalpha fulfills these functions via interaction with leukemia inhibitory factor (LIF) and the transcription factor NF-kappaB. These molecules are presently considered as attractive targets for the treatment of diabetes-induced complications. Therefore, further studies addressing their role in the mechanisms underlying diabetes-induced embryopathies are needed to evaluate the safety of such therapies for diabetic women of childbearing age.