Developmental neurotoxicity role of cyclophosphamide on post‐neural tube closure of rodents in vitro and in vivo

Efficacy of coenzyme Q10 and curcumin on antioxidant enzyme activity and hippocampal alteration following exposure to cyclophosphamide in male rat

Coenzyme Q10 (KQ10) and curcumin (KUR) supplements are extensively used for their potential antioxidant, anticancer, and antiapoptotic properties. The present study investigated the neuroprotective potential of KQ10 and KUR against the side effect of cyclophosphamide (SF) (150 mg/kg) on the hippocampus of male Wistar albino rats. Forty-nine 10-12 weeks old rats were randomly divided into seven groups: control, olive oil (OL), SF, KQ10, KUR, SF+KQ10, and SF+KUR. Our biochemical finding showed a significant decrease in superoxide dismutase (SOD) level in the SF group compared to the control group (p < 0.05). There was also a significant reduction in the total number of the hippocampal pyramidal neurons in the CA1, CA2, and CA1-3 regions in the SF group compared to the control group (p < 0.05). In the SF+KQ10 group, we found a significant increase in serum SOD level and the total number of the hippocampal pyramidal neurons in the CA1, CA2, and CA1-3 regions compared to the SF group (p < 0.05). Immunohistochemical and histopathological examination exhibited noteworthy findings in the hippocampus tissues. Our findings showed that KQ10 administration significantly mitigated the hippocampal alteration caused by SF through enhancing antioxidant enzyme activity and reducing apoptosis. However, we found no protective activity of KUR on the hippocampus tissue, which may be due to its weak antioxidative activity.

Neural Tube Defects and Folate Deficiency: Is DNA Repair Defective?

Neural tube defects (NTDs) are complex congenital malformations resulting from failure of neural tube closure during embryogenesis, which is affected by the interaction of genetic and environmental factors. It is well known that folate deficiency increases the incidence of NTDs; however, the underlying mechanism remains unclear. Folate deficiency not only causes DNA hypomethylation, but also blocks the synthesis of 2'-deoxythymidine-5'-monophosphate (dTMP) and increases uracil misincorporation, resulting in genomic instabilities such as base mismatch, DNA breakage, and even chromosome aberration. DNA repair pathways are essential for ensuring normal DNA synthesis, genomic stability and integrity during embryonic neural development. Genomic instability or lack of DNA repair has been implicated in risk of development of NTDs. Here, we reviewed the relationship between folate deficiency, DNA repair pathways and NTDs so as to reveal the role and significance of DNA repair system in the pathogenesis of NTDs and better understand the pathogenesis of NTDs.

Chemotherapy and the pediatric brain

Survival rates of children with cancer are steadily increasing. This urges our attention to neurocognitive and psychiatric outcomes, as these can markedly influence the quality of life of these children. Neurobehavioral morbidity in childhood cancer survivors affects diverse aspects of cognitive function, which can include attention, memory, processing speed, intellect, academic achievement, and emotional health. Reasons for neurobehavioral morbidity are multiple with one major contributor being chemotherapy-induced central nervous system (CNS) toxicity. Clinical studies investigating the effects of chemotherapy on the CNS in children with cancer have reported causative associations with the development of leukoencephalopathies as well as smaller regional grey and white matter volumes, which have been found to correlate with neurocognitive deficits.Preclinical work has provided compelling evidence that chemotherapy drugs are potent neuro- and gliotoxins in vitro and in vivo and can cause brain injury via excitotoxic and apoptotic mechanisms. Furthermore, chemotherapy triggers DNA (deoxyribonucleic acid) damage directly or through increased oxidative stress. It can shorten telomeres and accelerate cell aging, cause cytokine deregulation, inhibit hippocampal neurogenesis, and reduce brain vascularization and blood flow. These mechanisms, when allowed to operate on the developing brain of a child, have high potential to not only cause brain injury, but also alter crucial developmental events, such as myelination, synaptogenesis, neurogenesis, cortical thinning, and formation of neuronal networks.This short review summarizes key publications describing neurotoxicity of chemotherapy in pediatric cancers and potential underlying pathomechanisms.

The effect of inhibiting glycinamide ribonucleotide formyl transferase on the development of neural tube in mice

Background

Folate deficiency is closely related to the development of neural tube defects (NTDs). However, the exact mechanism is not completely understood. This study aims to induce murine NTDs by inhibiting one of the folate metabolic pathways, de novo purine synthesis and preliminarily investigate the potential mechanisms. The key enzyme, glycinamide ribonucleotide formyl transferase (GARFT) was inhibited by a specific inhibitor, lometrexol (DDATHF) in the pregnant mice.

Methods

Pregnant mice were intraperitoneally injected with various doses of DDATHF on gestational day 7.5 and embryos were examined for the presence of NTDs on gestational day 11.5. GARFT activity and levels of ATP, GTP, dATP and dGTP were detected in embryonic brain tissue. Proliferation and apoptosis was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR), immunohistochemical assay and western blotting.

Results

40 mg kg⁻¹ body weight (b/w) of DDATHF caused the highest incidence of NTDs (30.8 %) and therefore was selected as the optimal dose to establish murine NTDs. The GARFT activity and levels of ATP, GTP, dATP and dGTP in embryonic brain tissue were significantly decreased after DDATHF treatment. Furthermore, Levels of proliferation-related genes (Pcna, Foxg1 and Ptch1) were downregulated and apoptosis-related genes (Bax, Casp8 and Casp9) were upregulated. Expression of phosphohistone H3 was significantly decreased while expression of cleaved caspase-3 was greatly increased.

Conclusions

Results indicate that DDATHF induced murine NTDs by disturbing purine metabolism and further led to abnormal proliferation and apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0114-x) contains supplementary material, which is available to authorized users.

Chemotherapy-induced neurotoxicity in pediatric solid non-CNS tumor patients: An update on current state of research and recommended future directions

Neurocognitive sequelae are known to be induced by cranial radiotherapy and central-nervous-system-directed chemotherapy in childhood Acute Lymphoblastic Leukemia (ALL) and brain tumor patients. However, less evidence exists for solid non-CNS-tumor patients. To get a better understanding of the potential neurotoxic mechanisms of non-CNS-directed chemotherapy during childhood, we performed a comprehensive literature review of this topic. Here, we provide an overview of preclinical and clinical studies investigating neurotoxicity associated with chemotherapy in the treatment of pediatric solid non-CNS tumors. Research to date suggests that chemotherapy has deleterious biological and psychological effects, with animal studies demonstrating histological evidence for neurotoxic effects of specific agents and human studies demonstrating acute neurotoxicity. Although the existing literature suggests potential neurotoxicity throughout neurodevelopment, research into the long-term neurocognitive sequelae in survivors of non-CNS cancers remains limited. Therefore, we stress the critical need for neurodevelopmental focused research in children who are treated for solid non-CNS tumors, since they are at risk for potential neurocognitive impairment.

Expanding the test set: Chemicals with potential to disrupt mammalian brain development

High-throughput test methods including molecular, cellular, and alternative species-based assays that examine critical events of normal brain development are being developed for detection of developmental neurotoxicants. As new assays are developed, a "training set" of chemicals is used to evaluate the relevance of individual assays for specific endpoints. Different training sets are necessary for each assay that would comprise a developmental neurotoxicity test battery. In contrast, evaluation of the predictive ability of a comprehensive test battery requires a set of chemicals that have been shown to alter brain development after in vivo exposure ("test set"). Because only a small number of substances have been well documented to alter human neurodevelopment, we have proposed an expanded test set that includes chemicals demonstrated to adversely affect neurodevelopment in animals. To compile a list of potential developmental neurotoxicants, a literature review of compounds that have been examined for effects on the developing nervous system was conducted. The search was limited to mammalian studies published in the peer-reviewed literature and regulatory studies submitted to the U.S. EPA. The definition of developmental neurotoxicity encompassed changes in behavior, brain morphology, and neurochemistry after gestational or lactational exposure. Reports that indicated developmental neurotoxicity was observed only at doses that resulted in significant maternal toxicity or were lethal to the fetus or offspring were not considered. As a basic indication of reproducibility, we only included a chemical if data on its developmental neurotoxicity were available from more than one laboratory (defined as studies originating from laboratories with a different senior investigator). Evidence from human studies was included when available. Approximately 100 developmental neurotoxicity test set chemicals were identified, with 22% having evidence in humans.

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.

[Nervous system side effects of disease modifying treatments of rheumatoid arthritis]

Antirheumatic medication is of crucial importance within the treatment concept of chronic inflammatory disorders. Side effects may affect various organ systems, among which are neurologic manifestations. If patients have comorbidities involving the nervous system this should be taken into consideration before choosing an individual immunosuppressant or immunomodulatory compound, as any worsening of the underlying neurologic disease should be avoided. In this article, relevant neurologic disorders will be described with respect to the clinical manifestations, differential diagnosis and treatment. In the second part, pharmaceuticals and biologicals which are frequently used as part of an antirheumatic regimen are discussed with respect to the potential to induce side effects specifically related to the nervous system.

Towards a more representative in vitro method for fish ecotoxicology: morphological and biochemical characterisation of three-dimensional spheroidal hepatocytes

The use of fish primary cells and cell lines offer an in vitro alternative for assessment of chemical toxicity and the evaluation of environmental samples in ecotoxicology. However, their uses are not without limitations such as short culture periods and loss of functionality, particularly with primary tissue. While three-dimensional (spheroid) technology is now established for in vitro mammalian toxicity studies, to date it has not been considered for environmental applications in a model aquatic species. In this study we report development of a reproducible six-well plate, gyratory-mediated method for rainbow trout (Oncorhynchus mykiss) hepatocyte spheroid culture and compare their functional and biochemical status with two-dimensional (2D) monolayer hepatocytes. Primary liver spheroid formation was divided into two stages, immature (1-5 days) and mature (≥6 days) according to size, shape and changes in functional and biochemical parameters (protein, glucose, albumin and lactate dehydrogenase). Mature spheroids retained the morphological characteristics (smooth outer surface, tight cell-cell contacts) previously described for mammalian spheroids as demonstrated by light and scanning electron microscopy. Glucose production and albumin synthesis were significantly higher in mature spheroids when compared to conventional 2D monolayer cultures (P < 0.01) and increased as spheroids matured (P < 0.01). Basal lactate dehydrogenase (LDH) leakage significantly decreased during spheroid formation and was significantly lower than 2D cultures (P < 0.01). It is therefore suggested that mature spheroids can maintain a high degree of functional, biochemical and morphological status over-time in culture that is superior to conventional 2D models and can provide realistic organotypic responses in vitro. Trout spheroids that take ~6-8 days to reach maturity would be suitable for use in acute toxicological tests and since it is possible to culture individual spheroids for over a month, there is potential for this work to lead towards in vitro bioaccumulation alternatives and to conduct high throughput screens of chronic exposure. This is an important step forward for developing alternative in vitro tools in future fish ecotoxicological studies.

Mechanisms of neurotoxicity induced in the developing brain of mice and rats by DNA-damaging chemicals

It is not widely known how the developing brain responds to extrinsic damage, although the developing brain is considered to be sensitive to diverse environmental factors including DNA-damaging agents. This paper reviews the mechanisms of neurotoxicity induced in the developing brain of mice and rats by six chemicals (ethylnitrosourea, hydroxyurea, 5-azacytidine, cytosine arabinoside, 6-mercaptopurine and etoposide), which cause DNA damage in different ways, especially from the viewpoints of apoptosis and cell cycle arrest in neural progenitor cells. In addition, this paper also reviews the repair process following damage in the developing brain.

Neuroprotective effects of genistein and folic acid on apoptosis of rat cultured cortical neurons induced by β-amyloid 31-35

Genistein and folic acid have been reported respectively to protect against the development of cognitive dysfunction; however, the underlying mechanism(s) for this protection remain unknown. In this report, the mechanism(s) contributing to the neuroprotective effects of genistein and folic acid were explored using rat cortical neuron cultures. We found that genistein and folic acid, both separately and collaboratively, increased cell viability and mitochondrial membrane potential in β-amyloid (Aβ) 31-35-treated neurons. Furthermore, reduced percentage of comet cells and shortened tail length were observed in the neurons treated with genistein or folic acid. A more significant reduction in tail length of the comet neurons was observed in the co-administered neurons. RT-PCR analysis of the cultured cortical neurons showed down-regulated expression of p53, bax and caspase-3, but up-regulated expression of bcl-2 in the three neuroprotective treatment groups compared with neurons from the Aβ31-35 solo-treated group. In a nuclear dyeing experiment using Hoechst 33342, we found that both genistein and folic acid prevent neuronal apoptosis. Collectively, these findings suggest that the mechanism underlying the neuroprotection of genistein and folic acid singly or in combination observed in cultured cortical neuron studies might be related to their anti-apoptotic properties.