Fetus Exposure to Drugs and Chemicals: A Holistic Overview on the Assessment of Their Transport and Metabolism across the Human Placental Barrier

© 2024 The Author(s). Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Background: The placenta exerts a crucial role in fetus growth and development during gestation, protecting the fetus from maternal drugs and chemical exposure. However, diverse drugs and chemicals (xenobiotics) can penetrate the maternal placental barrier, leading to deleterious, adverse effects concerning fetus health. Moreover, placental enzymes can metabolize drugs and chemicals into more toxic compounds for the fetus. Thus, evaluating the molecular mechanisms through which drugs and chemicals transfer and undergo metabolism across the placental barrier is of vital importance. In this aspect, this comprehensive literature review aims to provide a holistic approach by critically summarizing and scrutinizing the potential molecular processes and mechanisms governing drugs and chemical transfer and metabolism across the placental barrier, which may lead to fetotoxicity effects, as well as analyzing the currently available experimental methodologies used to assess xenobiotics placental transfer and metabolism. Methods: A comprehensive and in-depth literature review was conducted in the most accurate scientific databases such as PubMed, Scopus, and Web of Science by using relevant and effective keywords related to xenobiotic placental transfer and metabolism, retrieving 8830 published articles until 5 February 2024. After applying several strict exclusion and inclusion criteria, a final number of 148 relevant published articles were included. Results: During pregnancy, several drugs and chemicals can be transferred from the mother to the fetus across the placental barrier by either passive diffusion or through placental transporters, resulting in fetus exposure and potential fetotoxicity effects. Some drugs and chemicals also appear to be metabolized across the placental barrier, leading to more toxic products for both the mother and the fetus. At present, there is increasing research development of diverse experimental methodologies to determine the potential molecular processes and mechanisms of drug and chemical placental transfer and metabolism. All the currently available methodologies have specific strengths and limitations, highlighting the strong demand to utilize an efficient combination of them to obtain reliable evidence concerning drug and chemical transfer and metabolism across the placental barrier. To derive the most consistent and safe evidence, in vitro studies, ex vivo perfusion methods, and in vivo animal and human studies can be applied together with the final aim to minimize potential fetotoxicity effects. Conclusions: Research is being increasingly carried out to obtain an accurate and safe evaluation of drug and chemical transport and metabolism across the placental barrier, applying a combination of advanced techniques to avoid potential fetotoxic effects. The improvement of the currently available techniques and the development of novel experimental protocols and methodologies are of major importance to protect both the mother and the fetus from xenobiotic exposure, as well as to minimize potential fetotoxicity effects.Peer reviewe

pq-COBRA-FISH and premature chromosome condensation; a novel combination in molecular cytogenetics

Human chromosomes have been studied for over a century, but it took until the 1950s that the correct human chromosome number was determined. The development of chromosome pretreatment procedures and modification of DNA staining techniques some 20 years later, allowed more precise chromosome identification based on banding patterns. This landmarkadvance in human cytogenetics allowed researchers to address specific clinical and research questions and make rapid progress in understanding the chromosomal basis of many genetic diseases and cancer. Although banding methodologies allow the distinction of individual chromosome pairs and the detection of gross karyotype aberrations, the analysis is heavily dependent on the accumulated experience and sometimes subjective interpretation of cytogeneticists. The low mitotic index, poor growth rate and sub-optimal chromosome morphology, which are hallmarks of tumour metaphase chromosome preparations, make cancer cytogenetics a particularly difficult discipline. Introduction of fluorescent in situ hybridisation (FISH) in combination with recombinant DNA technology opened a new chapter in detection and investigation of chromosomal basis of human genetic diseases in the 1990s. The success of this new discipline, molecular cytogenetics, in gene mapping and precise characterisation of chromosomal abnormalities, hinged on development of nucleic acids modification to incorporate fluorescent reporter molecules into nucleic acid hybridization probes. This thesis contributes to further advancement of molecular cytogenetics. The pq-COBRAFISH method presented in Chapter 2, employs a combination of binary and ratio-labelling to discriminate in one experiment all human chromosome arms, thus enhancing and objectifying the detection of chromosomal abnormalities. In Chapter 3, it has been used to detect chromosomal rearrangements in individuals with abnormal phenotype and normal G-banding patterns. It also aided in identification of a novel cancerous gene alteration by discovering BCL11B, as a new candidate gene in acute myelocytic leukaemia. pq-COBRA-FISH readily resolves complex karyotypes, characteristic of solid tumours. As such it was instrumental to discovery of a novel function of the chromatin remodelling complex, hSNF5, in maintenance of chromosome stability and ploidy (Chapter 4). Although molecular cytogenetics with its sophisticated multicolour FISH technology has allowed significant advancement in cancer and has become an intricate part of diagnosis and research there are still analytical and methodological problems in cancer cytogenetics. Full karyotyping, for example, is still restricted to mitotic cells. Chapter 5 of this thesis presents studies where a potent phosphatase inhibitor, calyculin A, was employed to prematurely condense the chromosomes of non-mitotic cells. This premature chromosome condensation technique or PCC increases the number of analysable chromosome structures compared to classical mitotic arrest, with minimum culture. This greatly improves the capacity of researchers to cytogenetically study solid tumours, where the success of comprehensive karyotyping of biopsy material has always been problematic. The specific morphological characteristics of PCC chromosomes furthermore allow distinction of the G1 and G2 phases of the cell cycle. The possibility to assess (differences in) chromosomal abnormalities of cells in the various cell cycle phases can offer valuable insight into the mechanisms underlying the tumorigenesis processes, including the much debated chromosome instability.Kreatech Diagnostics (Amsterdam, The Netherlands) Stichting Leids Universitair Fonds (LUF)Microscopische beeldvorming en technologi

The muntjac spindle staining assay: An investigation of the ability of this assay to detect potential aneuploidy inducing agents

This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.An assay using muntjac fibroblasts in conjunction with a differential spindle and chromosome stain was developed and evaluated for its ability to detect aneuploidy inducing agents. The effects of the spindle poison colcemid and the human carcinogen diethylstilboestrol were compared with those obtained after treatment of the cells with a number of compounds each believed to impair mitotic spindle function via a different mechanism. Vinblastine and nocodazole were both shown to have colcemid like effects suggesting a common mode of action and potential aneugenic activity. p-Fluorophenylalanine affected the spindle morphology resulting in an accumulation of atypical metaphases but without significant chomosome loss. Hydroquinone induced metaphase arrest and significant spindle damage but at doses very close to the toxic limits for this compound. Lastly, acenaphthene appeared to have no significant effect on mitosis at doses up to toxic levels. The ability of the muntjac fibroblasts to express aneuploid elements in recovery cell populations following treatment with colcemid and p-fluorophenylalanine was also examined. The results were inconclusive although an induction of endoreduplication was - indicated. Although both the spindle staining assay and recovery protocol require further refinement and validation, it was concluded that the assay was able to detect aneugenic agents especially those which act via the spindle

Studies in human genetics and cytogenetics

This thesis consists of 85 publications, of which 21 have been submitted for other degrees and are only included for completeness, leaving 64 assessable works. These fall into four broad categories, population cytogenetics, clinical genetics and cytogenetics, studies on amniotic fluid and prenatal diagnosis, and studies of heritable fragile sites on human chromosomes.The section on population cytogenetics includes most of the Australian studies on XYY males, epidemiological studies on Down syndrome in Australia and studies on the cytogenetics of paediatric necropsies. The clinical cytogenetics section mainly contains clinical case reports, which include a description of one of the first recognised insertional translocations in man, an important paper on trisomy 9 and one of the first discussions of genetic counselling of pericentric inversion carriers. This section also includes papers on gene mapping, alpha-1- antitrypsin phenotypes in chromosome abnormalities with descriptions of a new alpha-1-antitrypsin allele and studies on sister chromatid exchange in various groups of individuals with the documentation of an increase in this phenomenon in patients with multiple sclerosis.The section on prenatal diagnosis includes studies of the enzymology of amniotic fluid and cultured amniotic fluid cells, the discovery of rapidly adhering cells in amniotic fluid and documentation of their increased numbers in amniotic fluid surrounding fetuses with neural tube defects, and studies of chromosomal mosaicism in cultured amniotic fluid cells.The most important section of this thesis is the final one on studies of heritable fragile sites on human chromosomes. This section documents the discovery of the tissue culture requirements for the expression of fragile sites in lymphocyte culture, the finding of several new folate sensitive fragile sites and the co-discovery of the BrdU requiring fragile site at 10q25. Contributions to establishing fragile X-linked mental retardation as the second commonest genetic cause of mental retardation after Down syndrome, and population cytogenetic data for fragile sites are presented. Genetic linkage studies with fragile sites have established that a fragile site is coded for at the locus of the fragile site. Micronucleus studies have suggested that the folate sensitive fragile sites might be special examples of chromosome damage due to deprivation of DNA precursors

Meiosis

Meiosis, the process of forming gametes in preparation for sexual reproduction, has long been a focus of intense study. Meiosis has been studied at the cytological, genetic, molecular and cellular levels. Studies in model systems have revealed common underlying mechanisms while in parallel, studies in diverse organisms have revealed the incredible variation in meiotic mechanisms. This book brings together many of the diverse strands of investigation into this fascinating and challenging field of biology

Multidisciplinary graduate research conference program and abstracts : first annual GSA conference

50 p.The Proceedings of the Multidisciplinary Graduate Student Research Conference, organized by the University of Lethbridge Graduate Students Association (U of L GSA), is the outcome of the research and organizational contributions of a large number of enthusiastic graduate students and faculty members from the University of Lethbridge. The Conference was held July 28, 2006, during the Summer semester, and was the first of its kind at the U of L. It brought together representatives of a diverse array of disciplines and interests, from Biology to Sociology and from gender issues to neuroscience. These Conference Proceedings thus showcase the diversity of research conducted at U of L. The Proceedings have four major subsections: peer reviewed abstracts of the talks and of the posters presented at the Conference; peer-reviewed graduate student articles (12); and invited articles from faculty members from several different disciplines. Initially, the editors insisted on having all references formatted according to either APA or MLA style guidelines. However, due to differences in preferred citation styles among widely divergent fields, the editors have decided to allow multiple formats within this single document, to better showcase the beauty of different stylistic patterns used within modern academia. The contributors and their coauthors hail from a variety of institutes and universities within Canada and internationally. We are very happy to have them united under our GSA banner. It has been a great pleasure and privilege for the GSA editorial board members to work with an extremely capable group of reviewers from across Canada and abroad. They were of great help in making these Proceedings a reality, and in improving the quality of the articles submitted. The GSA editorial board highly appreciates and thanks all of them for their encouragement, support and prompt responses throughout the process. The editorial board would also like to extend their gratitude to all contributors from the U of L and other institutions for their kind cooperation, patience and support; and to the executive council members of GSA, the offices of the President and Vice Presidents, and the School of Graduate Studies at the U of L for their continued encouragement and financial support for this initiative. The Proceedings will be available in both hardcopy and electronic versions. We hope that this inaugural Conference will provide the model for many excellent gatherings to come.Ye

IVF based approaches towards the treatment and prevention of mitochondrial disease

PhD ThesisMitochondria are strictly maternally inherited, with all paternal mitochondria being destroyed following fertilisation. Women known to be carriers of pathogenic mtDNA mutations are therefore at increased risk of conceiving affected children. These women are currently offered the following options to aid in genetic counselling: oocyte donation, prenatal genetic diagnosis (PND) or preimplantation genetic diagnosis (PGD). One of the aims of this thesis, was to examine the feasibility of PGD for mtDNA inherited disorders, with specific emphasis on answering the following questions: how accurately does the mutation load observed in the biopsied blastomeres reflect the mutation load in the remaining embryo, are those mutation loads initially observed in the biopsied blastomeres maintained throughout preimplantation embryonic development and do mutation loads observed in the inner cell mass reflect those mutation loads observed in the extra-embryonic trophectoderm cells? In my thesis, I have now been able to provide data towards answering each of these questions through the examination of mutation loads in oocytes, embryos and blastocysts obtained from mitochondrial patients undergoing fertility treatment. Techniques, which have been developed in my current laboratory, have facilitated the characterisation of a nuclear transfer technique known as pronuclear transfer (PNT). This is a method to prevent the transmission of mitochondrial DNA disease from mother to child (Craven et al, 2010). As part of the work for my thesis, I have examined the reproducibility of the PNT technique by assessing whether the procedure could be performed by different operators, whilst maintaining levels of efficiency, survival and developmental outcome. Experiments are now being performed to examine the feasibility of PNT in normally fertilised human zygotes, created from donated oocytes. As it is unlikely that egg collection will be possible from two independent donors on the same day, the final purpose of this study was to examine the potential and feasibility of vitrification of eggs or fertilised embryos at both the pronuclear (PN) and Metaphase II (MII) stage for the purpose of the PNT technique. In summary, my studies has examined the reliability of current methods to reduce the likelihood of having a child affected by a mitochondrial DNA disorder and new techniques currently being developed to prevent the transmission of defective mitochondrial DNA, altogether. I hope this will provide fresh hope for patients with mitochondrial DNA disease

Investigating the consequences of chromosome abnormalities arising during pre-implantation development of the mouse

The majority of human pre-implantation embryos created through in vitro fertilization (IVF) are mosaic as they are constituted of a mixture of diploid and aneuploid cells. Chromosome abnormalities are widely believed to contribute towards the relatively low success rates of IVF treatment. Consequently major efforts have been undertaken to develop effective tools to aid the selection of embryos with minimal abnormalities with the aim of improving clinical outcomes. However, the ultimate fate of mosaic embryos is not known. Human embryo research is limited by practical and ethical constraints, and directly relevant animal studies are sparse. To circumvent many of these limitations, a mouse model for pre-implantation chromosome mosaicism was developed. Acute chromosome segregation errors were induced in cleavage stage mouse blastomeres by bypassing the spindle assembly checkpoint (SAC). This model was used to investigate the fate of abnormal cells within the developing pre-implantation embryo, and the ultimate developmental outcome of mosaic embryos. Time-lapse imaging of pre-implantation development revealed that cells with chromosome abnormalities were progressively depleted during blastocyst maturation; inner cell mass (ICM) cells exhibited higher rates of apoptosis, while in the trophectoderm (TE) lineage effects on the cell-cycle predominated. Depletion continued throughout post-implantation development. Significantly, the presence of a critical number of control blastomeres within the embryo could rescue the early post-implantation lethality that occurred in embryos containing high rates of abnormalities. Thus it was demonstrated that mosaic embryos can achieve full developmental potential and that abnormal cells are progressively depleted as development proceeds. Finally, the mechanisms responsible for eliminating the abnormal cells from the embryo were investigated, revealing that embryos containing chromosome abnormalities may have increased metabolic requirements which could contribute to their clonal depletion; a feature previously characterised in aneuploid cells in the context of cancer research.This work was sponsored by a Wellcome Trust Clinical PhD Fellowshi