Exposure-disease continuum for 2-chloro-2'-deoxyadenosine, a prototype ocular teratogen. 1. Dose-response analysis

Risks and risk management in modern multiple sclerosis immunotherapeutic treatment

In recent years, there has been a paradigm shift in the treatment of multiple sclerosis (MS) owing to the approval of a number of new drugs with very distinct mechanisms of action. All approved disease-modifying drugs primarily work directly on the immune system. However, the identification of an ‘optimal choice’ for individual patients with regard to treatment efficacy, treatment adherence and side-effect profile has become increasingly complex including conceptual as well as practical considerations. Similarly, there are peculiarities and specific requirements with regard to treatment monitoring, especially in relation to immunosuppression, the development of secondary immune-related complications, as well as the existence of drug-specific on- and off-target effects. Both classical immunosuppression and selective immune interventions generate a spectrum of potential therapy-related complications. This article provides a comprehensive overview of available immunotherapeutics for MS and their risks, detailing individual mechanisms of action and side-effect profiles. Furthermore, practical recommendations for patients treated with modern MS immunotherapeutics are provided.

Hydroxyurea embryotoxicity is enhanced in P53-deficient mice

Hydroxyurea, a ribonucleotide reductase inhibitor, is a potent teratogen in mice, causing severe limb and skeletal defects. The exposure of gestation day nine murine embryos to hydroxyurea elicits an early embryonic stress response that involves activation of the P53 transcription factor. The impact of this P53 activation on the embryotoxicity of hydroxyurea- is not known. The goal of this study was to test the hypothesis that P53 acts to suppress hydroxyurea embryotoxicity. Trp53^+/- timed pregnant mice were treated with saline or hydroxyurea (200 or 400 mg/kg) on gestation day nine; fetuses were examined for viability and external and skeletal malformations on gestation day eighteen. Neither the deletion of Trp53 nor hydroxyurea treatment significantly affected fetal growth although a trend towards a decrease in fetal weights was observed in Trp53^-/- fetuses. However, hydroxyurea induced a significantly higher incidence of malformations and resorptions in Trp53^-/- fetuses compared to their wildtype littermates. Thus, fetal P53 genotype is an important determinant of the effects of hydroxyurea on organogenesis-stage embryos.

How much progress has there been in the second-line treatment of multiple sclerosis: A 2017 update

In 1993, the US Food and Drug Administration (FDA) approved the first drug specifically for treating multiple sclerosis (MS). More than two decades later, a dozen such treatments are now available. Of these, four are considered second-line treatments for use in escalation strategies and two new drugs are currently undergoing accreditation procedures. Soon, they will provide clinicians with a range of six effective disease-modifying treatments (DMTs) to thwart the inflammatory processes in MS patients with active disease. However, while such a large number of DMTs for MS can help to control early inflammation, any decisions to be made by clinicians have also been made substantially more complex. This complexity is increased by the lack of head-to-head studies comparing these second-line therapies and the benefit-risk profiles for each of these drugs, which are likely to vary among patients. Ultimately, good awareness of the benefits and, more important, the risks of each MS DMT is crucial for the effective management of inflammation in MS.

Intrinsic apoptosis pathway in fallopian tube epithelial cells induced by cladribine

Cladribine is a purine nucleoside analog which initiates the apoptotic mechanism within cells. Moreover, the available data confirms that cladribine, with the participation of the p53 protein, as well as the proapoptotic proteins from the Bcl-2 family, also induces the activation of the intrinsic apoptosis pathway. However, while there has been a lot of research devoted to the effect of cladribine on lymphatic system cells, little is known about the impact of cladribine on the reproductive system. The aim of our study was to evaluate apoptosis in oviduct epithelial cells sourced from 15 different female rats. In so doing, the sections were stained with caspases 3, 9, and 8. Results suggest that cladribine also induces apoptosis in the oviduct epithelial cells by way of the intrinsic pathway. Indeed, the discontinuing of the administration of cladribine leads to a reduction in the amount of apoptotic cells in the oviduct epithelium.

Immunohistochemical evaluation of cell proliferation and apoptosis markers in ovarian surface epithelial cells of cladribine-treated rats

Cladribine has been used in the treatment of hairy cell leukemia for about 30 years. In addition, the number of indications for the application of 2-CdA is constantly increasing. The treatment with cladribine, of younger persons and even children, appears to be a major factor stimulating the more exact recognition of its activities. However, till now, little has been known about the impact of cladribine on the reproductive system. The aim of the study was to evaluate the immunohistochemical expression of cell proliferation and apoptosis markers in ovarian surface epithelial (OSE) cells. In our study, ten rats were placed into two equal groups. The study group received daily subcutaneous injections of cladribine in a dose of 0.10 mg/kg of weight/day for one cycle lasting 7 days. The control group received only saline injections. The rats were sacrificed 24 h after the last injection, and their ovaries were extracted. The sections were immunohistochemically stained with cell proliferation marker Ki-67 and the apoptosis marker caspase 3. The expressions of the markers were evaluated using a light microscope. An analysis was made using an image analysis system and the CellAD software. The results were then statistically explored by way of the Mann-Whitney U test. The proliferative index (Ki-67) of ovarian surface epithelial cells was significantly lower in the study group than in the control group (p < 0.05). These results suggest that cladribine treatment has a potential to inhibit the OSE cell proliferation in rats. The apoptosis marker demonstrated a significant increase after the cladribine treatment. These suggest that cladribine induces apoptosis in OSE cells.

Effect of maternal immunopotentiation on apoptosis-associated molecules expression in teratogen-treated embryos

PROBLEM

Potentiation of the maternal immune system was shown by us to affect the embryonic response to teratogenic insults. In order to understand better the mechanisms underlying that phenomenon, we explored the effect of maternal immunopotentiation by rat splenocytes on the early stages of the embryonic response to cyclophosphamide (CP).

METHOD OF STUDY

Immunopotentiated CP-treated embryos were analysed for cell cycle changes by flow cytometry, while cell proliferation and apoptosis were assessed by 5'-bromo-2'-deoxyuridine (BrdU) incorporation and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) respectively. The expression of the p65 subunit of NF-kappaB, IkappaBalpha, Bax, bcl-2 and p53 was assessed by flow cytometry.

RESULTS

Exposure to CP resulted in significant growth retardation and in the appearance of cellular damage, a reduction in cell proliferation and the appearance of apoptotic cells, which were all found to be delayed in immunopotentiated embryos. In parallel, CP-treated embryos demonstrated a reduction in the percentage of p65- or IkappaBalpha-positive cells, while the percentage of bcl-2- or p53-positive cells increased initially and decreased later. Those changes were normalized by maternal immunopotentiation when tested at 24 hrs after exposure to the teratogen.

CONCLUSION

Our data implicate maternal immunopotentiation to protect the embryo against teratogenic insults, possibly through its effect on the expression of p65, bcl-2 or p53.

Reprogramming of genetic networks during initiation of the Fetal Alcohol Syndrome

Fetal Alcohol Spectrum Disorders (FASD) are birth defects that result from maternal alcohol use. We used a non a priori approach to prioritize candidate pathways during alcohol-induced teratogenicity in early mouse embryos. Two C57BL/6 substrains (B6J, B6N) served as the basis for study. Dosing pregnant dams with alcohol (2x 2.9 g/kg ethanol spaced 4 hr on day 8) induced FASD in B6J at a higher incidence than B6N embryos. Counter-exposure to PK11195 (4 mg/kg) significantly protected B6J embryos but slightly promoted FASD in B6N embryos. Microarray transcript profiling was performed on the embryonic headfold 3 hr after the first maternal alcohol injection (GEO data series accession GSE1074). This analysis revealed metabolic and cellular reprogramming that was substrain-specific and/or PK11195-dependent. Mapping ethanol-responsive KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways revealed down-regulation of ribosomal proteins and proteasome, and up-regulation of glycolysis and pentose phosphate pathway in B6N embryos; and significant up-regulation of tight junction, focal adhesion, adherens junction, and regulation of the actin cytoskeleton (and near-significant up-regulation of Wnt signaling and apoptosis) pathways in both substrains. Expression networks constructed computationally from these altered genes identified entry points for EtOH at several hubs (MAPK1, ALDH3A2, CD14, PFKM, TNFRSF1A, RPS6, IGF1, EGFR, PTEN) and for PK11195 at AKT1. Our findings are consistent with the growing view that developmental exposure to alcohol alters common signaling pathways linking receptor activation to cytoskeletal reorganization. The programmatic shift in cell motility and metabolic capacity further implies cell signals and responses that are integrated by the mitochondrial recognition site for PK11195.

Teratogen-induced apoptotic cell death: Does the apoptotic machinery act as a protector of embryos exposed to teratogens?

Considerable evidence has been collected demonstrating that many teratogens induce apoptotic cell death in embryonic structures that turn out to be malformed in fetuses and newborns. Apoptosis is a genetically regulated process that is realized by the activation of death and pro-survival signaling cascades, and the interplay between these cascades determines whether the cell exposed to apoptotic stimuli dies or survives. Therefore, there is intense interest in understanding how the apoptotic machinery functions in embryos exposed to teratogens. However, the interpretation of the results obtained remains problematic. The main problem is that excessive embryonic cell death, regardless of its nature, if uncompensated for, ultimately leads to maldevelopment or embryonic death. Therefore, we can easily interpret results when the intensity of teratogen-induced cell death and the severity or incidence of teratogen-induced anomalies directly correlate with each other. However, when teratogen-induced cell death is not followed by the formation of anomalies, a usual explanation is that teratogen-induced apoptotic cell death contributes to the renewal of teratogen-targeted cell populations by promoting the removal of injured cells. It is clear that such an explanation leaves vague the role of the anti-apoptotic signaling mechanism (and, hence, the apoptotic machinery as a whole) with respect to protecting the embryo against teratogenic stress. In this review, we summarize the data from studies addressing the function of the apoptotic machinery in embryos exposed to teratogens, and then we discuss approaches to interpreting the results of these studies. We hypothesize that activation of a proapoptotic signaling in teratogen-targeted cell populations is a necessary condition for an anti-apoptotic signaling that counteracts the process of maldevelopment to be activated. If such a scenario is true, we need to modify our approaches to choosing molecular targets for studies addressing this topic.

Searching for biomarkers of developmental toxicity with microarrays: normal eye morphogenesis in rodent embryos

Gene expression arrays reveal the potential linkage of altered gene expression with specific adverse effects leading to disease phenotypes. But how closely do microarray data reflect early physiological or pharmacological measures that predict toxic event(s)? To explore this issue, we have undertaken experiments in early mouse embryos exposed to various teratogens during neurulation stages with the aim of correlating large-scale changes in gene expression across the critical period during exposure. This study reports some of the large-scale changes in gene expression that can be detected in the optic rudiment of the developing mouse and rat embryo across the window of development during which the eye is exceedingly sensitive to teratogen-induced micro-/anophthalmia. Microarray analysis was performed on RNA from the headfold or ocular region at the optic vesicle and optic cup stages when the ocular primordium is enriched for Pax-6, a master control gene for eye morphogenesis. Statistical selection of differentially regulated genes and various clustering techniques identified groups of genes in upward or downward trajectories in the normal optic primordium during early eye development in mouse and rat species. We identified 165 genes with significant differential expression during eye development, and a smaller subset of 58 genes that showed a tight correlation between mouse-rat development. Significantly over-represented functional categories included fatty acid metabolism (up-regulated) and glycolysis (down-regulated). From studies such as these that benchmark large-scale gene expression during normal embryonic development, we may be able to identify the panel of biomarkers that best correlate with species differences and the risks for developmental toxicity.

Response characteristics of the mitochondrial DNA genome in developmental health and disease

This review focuses on mitochondrial biology in mammalian development; specifically, the dynamics of information transfer from nucleus to mitochondrion in the regulation of mitochondrial DNA genomic expression, and the reverse signaling of mitochondrion to nucleus as an adaptive response to the environment. Data from recent studies suggest that the capacity of embryonic cells to react to oxygenation involves a tradeoff between factors that influence prenatal growth/development and postnatal growth/function. For example, mitochondrial DNA replication and metabolic set points in nematodes may be determined by mitochondrial activity early in life. The mitochondrial drug PK11195, a ligand of the peripheral benzodiazepine receptor, has antiteratogenic and antidisease action in several developmental contexts in mice. Protein malnutrition during early life in rats can program mitochondrial DNA levels in adult tissues and, in humans, epidemiological data suggest an association between impaired fetal growth and insulin resistance. Taken together, these findings raise the provocative hypothesis that environmental programming of mitochondrial status during early life may be linked with diseases that manifest during adulthood. Genetic defects that affect mitochondrial function may involve the mitochondrial DNA genome directly (maternal inheritance) or indirectly (Mendelian inheritance) through nuclear-coded mitochondrial proteins. In a growing number of cases, the depletion of, or deletion in, mitochondrial DNA is seen to be secondary to mutation of key nuclear-coded mitochondrial proteins that affect mitochondrial DNA replication, expression, or stability. These defects of intergenomic regulation may disrupt the normal cross-talk or structural compartmentation of signals that ultimately regulate mitochondrial DNA integrity and copy number, leading to depletion of mitochondrial DNA.

Exposure-disease continuum for 2-chloro-2'-deoxyadenosine, a prototype ocular teratogen. 3. Intervention with PK11195

BACKGROUND

Treatment of pregnant mice with 2-chloro-2'-deoxyadenosine (2CdA) on Day 8 of gestation induces microphthalmia through a mechanism linked to the p53 tumor suppressor pathway. The present study defines the response of Day 8 mouse embryos through time with respect to pharmacologic intervention with PK11195, a ligand of the mitochondrial peripheral benzodiazepine receptor (Bzrp).

METHODS

Pregnant CD-1 mice dosed with 2CdA with or without PK11195 on gestation Day 8 provided fetuses for teratologic evaluation on Day 14 and Day 17; HPLC measured pyridine nucleotides (NADH/NAD+) at 1.5 hr, RT-PCR measured mitochondrial 16S rRNA abundance at 3.0 hr, and p53 protein induction was assessed with immunostaining at 4.5 hr postexposure.

RESULTS

The mean incidences of malformed fetuses were significantly higher in the 7.5 mg/kg 2CdA treatment group (50.2% malformed) vs. the 2CdA + 4.0 mg/kg PK11195 co-treatment group (4.4% malformed). Malformed fetuses displayed a range of ocular defects that included microphthalmia and keratolenticular dysgenesis (Peters anomaly). No malformations were observed in the control or PK11195 alone groups. PK11195 also protected litters from increased resorption rates and fetal weight reduction. It did not rescue early effects on NADH balance (1.5 hr) or 16S rRNA expression (3.0 hr); however, the p53 response (4.5 hr) was downgraded in 2CdA + PK11195 embryos vs. 2CdA alone. By delaying the administration of PK11195 in 1.5 hr intervals it was determined that the window for protection closed between 4.5 to 6.0 hr after 2CdA.

CONCLUSIONS

The capacity of PK11195 to suppress the pathogenesis of microphthalmia implies a critical role for mitochondrial peripheral benzodiazepine receptors in the p53-dependent mode of action of 2CdA on ocular development.