Maternal aripiprazole exposure interacts with 7-dehydrocholesterol reductase mutations and alters embryonic neurodevelopment

Effect of aripiprazole on neural tube development in early chick embryos

INTRODUCTION

Aripiprazole (ARI) is a recently developed antipsychotic medication that belongs to the second generation of antipsychotics. The literature has contradictory information regarding ARI, which has been classified as pregnant use category C by the FDA.

METHODS

125 pathogen-free fertilized eggs were incubated for 28 h and divided into five groups of 25 eggs each (including the control group), and 18 eggs with intact integrity were selected from each group. After the experimental groups were divided, ARI was administered subblastodermally with a Hamilton micro-injector at 4 different doses (1 mg/kg, 5 mg/kg, 10 mg/kg, 20 mg/kg). At the 48th hour of incubation, all eggs were hatched and embryos were removed from the embryonic membranes. And then morphologic (position of the neural tube (open or closed), crown-rump length, number of somites, embryological development status), histopathologic (apoptosis (caspase 3), cell proliferation (PCNA), in situ recognition of DNA breaks (tunnel)), genetic (BRE gene expression) analyzes were performed.

RESULTS

According to the results of the morphological analysis, when the frequency of neural tube patency was evaluated among the experimental groups, a statistically significant difference was determined between the control group and all groups (p < 0.001). In addition, the mean crown-rump length and somite number of the embryos decreased in a dose-dependent manner compared to the control group. It was determined that mRNA levels of the BRE gene decreased in embryos exposed to ARI compared to the control group (p < 0.001).

CONCLUSION

Morphologically, histopathologically, and genetically, aripiprazole exposure delayed neurogenesis and development in early chick embryos. These findings suggest its use in pregnant women may be teratogenic. We note that these results are preliminary for pregnant women, but they should be expanded and studied with additional and other samples.

Prenatal aripiprazole induces alterations of rat placenta: a histological, immunohistochemical and ultrastructural study

Antipsychotic drugs (APDs) are used to treat many psychiatric illnesses as schizophrenia. Typical antipsychotic drugs (TAPDs) are being used; however, they have many side effects. Atypical antipsychotic drugs (AAPDs) are newer medications with known fewer side effects. Aripiprazole (ARI) is an AAPD, recommended by healthcare providers, even during pregnancy. It can cross the placental barrier and enter fetal circulation, so it might be possible that ARI can adversely impair normal placental development and growth, if it is given prenatally. ARI was applied orally to pregnant female rats in two doses (3& 6 mg/kg body weight). On gestation day 20, the mothers were sacrificed, and the placentas were removed and processed for general histological and electron microscopic evaluations. Immunohistochemistry was done using anti-PCNA (proliferating cell nuclear antigen), anti-Bax (for apoptosis) and anti-vascular endothelial growth factor alpha (VEGFA). Morphological evaluation revealed degenerative changes in the placenta as dark nuclei, vacuolization, and cyst formation. Ultra-structurally, there was degeneration of cellular components including organelles and nuclei. These changes were found in different cells of the basal and labyrinth zones and were dose dependent. Immunohistochemistry revealed upregulation of Bax and VEGFA and downregulation of PCNA. Prenatal administration of the AAPD, ARI to pregnant female rats resulted in histological changes in the placenta. Additionally, there was a decrease in cellular proliferation and increase in apoptosis, and vascular impairment. This indicates placental atrophy and dysgenesis and might suggest possible teratogenic effects to ARI, which needs further evaluation.

Chronic Aripiprazole and Trazodone Polypharmacy Effects on Systemic and Brain Cholesterol Biosynthesis

The concurrent use of several medications is a common practice in the treatment of complex psychiatric conditions. One such commonly used combination is aripiprazole (ARI), an antipsychotic, and trazodone (TRZ), an antidepressant. In addition to their effects on dopamine and serotonin systems, both of these compounds are inhibitors of the 7-dehydrocholesterol reductase (DHCR7) enzyme. To evaluate the systemic and nervous system distribution of ARI and TRZ and their effects on cholesterol biosynthesis, adult mice were treated with both ARI and TRZ for 21 days. The parent drugs, their metabolites, and sterols were analyzed in the brain and various organs of mice using LC-MS/MS. The analyses revealed that ARI, TRZ, and their metabolites were readily detectable in the brain and organs, leading to changes in the sterol profile. The levels of medications, their metabolites, and sterols differed across tissues with notable sex differences. Female mice showed higher turnover of ARI and more cholesterol clearance in the brain, with several post-lanosterol intermediates significantly altered. In addition to interfering with sterol biosynthesis, ARI and TRZ exposure led to decreased ionized calcium-binding adaptor molecule 1 (IBA1) and increased DHCR7 protein expression in the cortex. Changes in sterol profile have been also identified in the spleen, liver, and serum, underscoring the systemic effect of ARI and TRZ on sterol biosynthesis. Long-term use of concurrent ARI and TRZ warrants further studies to fully evaluate the lasting consequences of altered sterol biosynthesis on the whole body.

Gestational Exposure to Haloperidol Changes Cdkn1a and Apaf1 mRNA Expressions in Mouse Hippocampus

BACKGROUND

The onset of schizophrenia is associated with both genetic and environmental risks during brain development. Environmental factors during pregnancy can represent risk factors for schizophrenia, and we have previously reported that several microRNA and mRNA expression changes in fetal brains exposed to haloperidol during pregnancy may be related to the onset of this disease. This study aimed to replicate that research and focused on apoptotic-related gene expression changes.

METHODS

Haloperidol (1mg/kg) or aripiprazole (1mg/kg) was injected into pregnant mice. Using RNA sequencing for the hippocampus of each offspring born from pregnant mice exposed to haloperidol, we analyzed genes identified as changed in our previous report and validated two apoptosis-related genes (Cdkn1a and Apaf1) using quantitative polymerase chain reaction (qPCR) methods. Furthermore, we attempted to elucidate the direct effects of haloperidol and aripiprazole on those mRNA expressions in in vitro experiments.

RESULTS

RNA sequencing successfully replicated 16 up-regulated and 5 down-regulated genes in this study. Of those, up-regulations of Cdkn1a and Apaf1 mRNA expression were successfully validated by direct quantification. Moreover, haloperidol and aripiprazole dose-dependent upregulation of both mRNA expressions were confirmed in a Neuro2a cell line.

CONCLUSIONS

In the hippocampus of offspring, intraperitoneal injection of haloperidol to pregnant mice induced up-regulation of apoptotic genes that representing the phenotypic change without apoptosis. These findings will be useful for understanding the molecular biological mechanisms underlying the effects of antipsychotics on the fetal brain.

Integrated multi-dimensional analysis highlights DHCR7 mutations involving in cholesterol biosynthesis and contributing therapy of gastric cancer

BACKGROUND

Genetic background plays an important role in the occurrence and development of gastric cancer (GC). With the application of genome-wide association study (GWAS), an increasing number of tumor susceptibility genes in gastric cancer have been discovered. While little of them can be further applicated in clinical diagnosis and treatment due to the lack of in-depth analysis.

METHODS

A GWAS of peripheral blood leukocytes from GC patients was performed to identify and obtain genetic background data. In combination with a clinical investigation, key SNP mutations and mutated genes were screened. Via in vitro and in vivo experiments, the function of the mutated gene was verified in GC. Via a combination of molecular function studies and amino acid network analysis, co-mutations were discovered and further identified as potential therapeutic targets.

RESULTS

At the genetic level, the G allele of rs104886038 in DHCR7 was a protective factor identified by the GWAS. Clinical investigation showed that patients with the rs104886038 A/G genotype, age ≥ 60, smoking ≥ 10 cigarettes/day, heavy drinking and H. pylori infection were independent risk factors for GC, with odds ratios of 12.33 (95% CI, 2.10 ~ 72.54), 20.42 (95% CI, 2.46 ~ 169.83), and 11.39 (95% CI, 1.82 ~ 71.21), respectively. Then molecular function studies indicated that DHCR7 regulated cell proliferation, migration, and invasion as well as apoptosis resistance via cellular cholesterol biosynthesis pathway. Further amino acid network analysis based on the predicted structure of DHCR7 and experimental verification indicated that rs104886035 and rs104886038 co-mutation reduced the stability of DHCR7 and induced its degradation. DHCR7 mutation suppressed the malignant behaviour of GC cells and induced apoptosis via inhibition on cell cholesterol biosynthesis.

CONCLUSION

In this work, we provided a comprehensive multi-dimensional analysis strategy which can be applied to in-depth exploration of GWAS data. DHCR7 and its mutation sites identified by this strategy are potential theratic targets of GC via inhibition of cholesterol biosynthesis.

Effects of Psychotropic Medication on Somatic Sterol Biosynthesis of Adult Mice

Polypharmacy is commonly used to treat psychiatric disorders. These combinations often include drugs with sterol biosynthesis inhibiting side effects, including the antipsychotic aripiprazole (ARI), and antidepressant trazodone (TRZ). As the effects of psychotropic medications are poorly understood across the various tissue types to date, we investigated the effects of ARI, TRZ, and ARI + TRZ polypharmacy on the post-lanosterol biosynthesis in three cell lines (Neuro2a, HepG2, and human dermal fibroblasts) and seven peripheral tissues of an adult mouse model. We found that both ARI and TRZ strongly interfere with the function of 7-dehydrocholesterol reductase enzyme (DHCR7) and lead to robust elevation in 7-dehydrocholesterol levels (7-DHC) and reduction in desmosterol (DES) across all cell lines and somatic tissues. ARI + TRZ co-administration resulted in summative or synergistic effects across the utilized in vitro and in vivo models. These findings suggest that at least some of the side effects of ARI and TRZ are not receptor mediated but arise from inhibiting DHCR7 enzyme activity. We propose that interference with sterol biosynthesis, particularly in the case of simultaneous utilization of medications with such side effects, can potentially interfere with functioning or development of multiple organ systems, warranting further investigation.

Metoprolol Inhibits Developmental Brain Sterol Biosynthesis in Mice

De novo sterol synthesis is a critical homeostatic mechanism in the brain that begins during early embryonic development and continues throughout life. Multiple medications have sterol-biosynthesis-inhibiting side effects, with potentially detrimental effects on brain health. Using LC-MS/MS, we investigated the effects of six commonly used beta-blockers on brain sterol biosynthesis in vitro using cell lines. Two beta-blockers, metoprolol (MTP) and nebivolol, showed extreme elevations of the highly oxidizable cholesterol precursor 7-dehydrocholesterol (7-DHC) in vitro across multiple cell lines. We followed up on the MTP findings using a maternal exposure model in mice. We found that 7-DHC was significantly elevated in all maternal brain regions analyzed as well as in the heart, liver and brain of the maternally exposed offspring. Since DHCR7-inhibiting/7-DHC elevating compounds can be considered teratogens, these findings suggest that MTP utilization during pregnancy might be detrimental for the development of offspring, and alternative beta-blockers should be considered.

Individual and simultaneous treatment with antipsychotic aripiprazole and antidepressant trazodone inhibit sterol biosynthesis in the adult brain

Polypharmacy, or the simultaneous use of multiple drugs to treat a single patient, is a common practice in psychiatry. Unfortunately, data on the health effects of commonly used combinations of medications are very limited. In this study, we therefore investigated the effects and interactions between two commonly prescribed psychotropic medications with sterol inhibiting side effects, trazodone (TRZ), an antidepressant, and aripiprazole (ARI), an antipsychotic. In vitro cell culture experiments revealed that both medications alone disrupted neuronal and astroglial sterol biosynthesis in dose-dependent manners. Furthermore, when ARI and TRZ were combined, exposure resulted in an additive 7-dehydrocholesterol (7-DHC) increase, as well as desmosterol (DES) and cholesterol decreases in both cell types. In adult mice, at baseline, we found that the three investigated sterols showed significant differences in distribution across the eight assessed brain regions. Furthermore, experimental mice treated with ARI or TRZ, or a combination of both medications for 8 days, showed strong sterol disruption across all brain regions. We show ARI or TRZ alone elevated 7-DHC and decreased DES levels in all brain regions, but with regional differences. However, the combined utilization of these two medications for 8 days did not lead to additive changes in sterol disturbances. Based on the complex roles of 7-DHC derived oxysterols, we conclude that individual and potentially simultaneous use of medications with sterol biosynthesis-inhibiting properties might have undesired side effects on the adult brain, with as yet unknown long-term consequences on mental or physical health.

Plasma oxysterols in drug-free patients with schizophrenia

Evidence from clinical, genetic, and medical studies has shown the neuronal developmental disorder aspect of schizophrenia (SZ). Whereas oxysterols are vital factors in neurodevelopment, it is still unknown whether they are involved in the pathophysiology of SZ. The current study aims to explore the profile of oxysterols in plasma, ratio to total cholesterol (Tchol) and the association with clinical factors in patients with SZ. Forty men diagnosed with SZ and forty healthy controls matched for age and sex were included in the study. The ratios of cholestane-3β,5α,6β-triol, 27-hydroxycholesterol (27-OHC) and Cholestanol to Tchol increased in the schizophrenic group compared to controls. However, levels of 24S-hydroxycholesterol (24-OHC) were not significantly different between patients and controls. For the SZ patients, the plasma 24-OHC levels were positively correlated with the positive and negative syndrome total scores (PANSS) but negatively correlated with the Montreal Cognitive Assessment scores (MOCA). Moreover, the ratio Cholestanol to Tchol was negatively correlated with MOCA scores and positively correlated with PANSS general. The binary logistic regression analysis revealed that the ratio Cholestane-3β,5α,6β-triol/TChol could be considered as an independent risk factor for SZ. On the other hand, the receiver's operating characteristics analysis corresponding to potential biomarkers on SZ showed Areas Under the Curve (AUCs) of 82.1%; 69.7% and 77.6% for the ratio of Cholestane-3β,5α,6β-triol/TChol, 27-OHC/TChol and Cholestanol/TChol respectively. The relevance of Cholestane-3β,5α,6β-triol, 27-OHC and Cholestanol assays as biomarkers of this disease deserves further investigation.

Desmosterol and 7-dehydrocholesterol concentrations in post mortem brains of depressed people: The role of trazodone

Major depressive disorder (MDD) is a common, disabling, and heterogeneous condition that responds unpredictably to current treatments. We previously showed an association between depressive symptoms and plasma concentrations of two cholesterol precursors, desmosterol and 7-dehydrocholesterol (7DHC). Here, we measured total cholesterol and sterol concentrations with mass spectrometry in postmortem brain samples from depressed and control subjects. Mean (±SEM) desmosterol concentration was 8.9 ± 0.97 ng/mg in the depressed versus 10.7 ± 0.72 ng/mg in the control group. The mean of the posterior probability distribution for the difference in desmosterol concentration between the two groups was 2.36 (95% highest density interval [HDI] 0.59-4.17). Mean 7DHC concentrations, 12.5 ± 4.1 ng/mg in the depressed versus 5.4 ± 0.74 ng/mg in the control group, were unlikely to be different (95% HDI, [-1.37-0.34]). We found that presence of trazodone in the peri-mortem toxicology screen accounted for the observed difference in desmosterol concentrations. We also observed extremely high 7DHC levels in all 4 subjects who had taken trazodone. Trazodone has been recently found to inhibit 7-dehydrocholesterol reductase and alter sterol concentrations in rodents, cell culture, human fibroblasts, and blood. In this study, we demonstrate for the first time that trazodone alters human brain sterol composition. Given congenital deficiency of 7-dehydrocholesterol reductase results in Smith-Lemli-Opitz syndrome, our findings support the hypothesis that this commonly used medication may have previously unappreciated risks.

Medication effects on developmental sterol biosynthesis

Cholesterol is essential for normal brain function and development. Genetic disruptions of sterol biosynthesis result in intellectual and developmental disabilities. Developing neurons synthesize their own cholesterol, and disruption of this process can occur by both genetic and chemical mechanisms. Many commonly prescribed medications interfere with sterol biosynthesis, including haloperidol, aripiprazole, cariprazine, fluoxetine, trazodone and amiodarone. When used during pregnancy, these compounds might have detrimental effects on the developing brain of the offspring. In particular, inhibition of dehydrocholesterol-reductase 7 (DHCR7), the last enzyme in the biosynthesis pathway, results in accumulation of the immediate cholesterol precursor, 7-dehydrocholesterol (7-DHC). 7-DHC is highly unstable, giving rise to toxic oxysterols; this is particularly pronounced in a mouse model when both the mother and the offspring carry the Dhcr7^+/- genotype. Studies of human dermal fibroblasts from individuals who carry DCHR7^+/- single allele mutations suggest that the same gene*medication interaction also occurs in humans. The public health relevance of these findings is high, as DHCR7-inhibitors can be considered teratogens, and are commonly used by pregnant women. In addition, sterol biosynthesis inhibiting medications should be used with caution in individuals with mutations in sterol biosynthesis genes. In an age of precision medicine, further research in this area could open opportunities to improve patient and fetal/infant safety by tailoring medication prescriptions according to patient genotype and life stage.

Identifying Molecular Fragments That Drive 7-Dehydrocholesterol Elevation

Medications having the unwanted side effect of inhibiting 7-dehydrocholesterol reductase (DHCR7), one of the last enzymes in the cholesterol biosynthesis pathway, account for about 300 million yearly prescriptions in the United States. Many of these drugs are currently prescribed to pregnant women. Many DHCR7-inhibiting medications share chemical similarities, which can be the active substructure responsible for the medication affinity to the enzyme. This work highlights a computational strategy to identify enriched fragments in a set of DHCR7-inhibiting medications. The computational approach used here involves systematic fragmentation of molecules using the molBLOCKS tool, followed by enrichment analysis. The results of this approach highlight putative pharmacophores that might be responsible for the DHCR7-inhibiting activity of some of these medications. The identification of DHCR7-inhibiting substructures is an important step toward knowledge-based drug development and can improve the neurodevelopmental safety of medications.

Metabolic Control of Sensory Neuron Survival by the p75 Neurotrophin Receptor in Schwann Cells

We report that the neurotrophin receptor p75 contributes to sensory neuron survival through the regulation of cholesterol metabolism in Schwann cells. Selective deletion of p75 in mouse Schwann cells of either sex resulted in a 30% loss of dorsal root ganglia (DRG) neurons and diminished thermal sensitivity. P75 regulates Schwann cell cholesterol biosynthesis in response to BDNF, forming a co-receptor complex with ErbB2 and activating ErbB2-mediated stimulation of sterol regulatory element binding protein 2 (SREBP2), a master regulator of cholesterol synthesis. Schwann cells lacking p75 exhibited decreased activation of SREBP2 and a reduction in 7-dehydrocholesterol (7-DHC) reductase (DHCR7) expression, resulting in accumulation of the neurotoxic intermediate, 7-dehyrocholesterol in the sciatic nerve. Restoration of DHCR7 in p75 null Schwann cells in mice significantly attenuated DRG neuron loss. Together, these results reveal a mechanism by which the disruption of lipid metabolism in glial cells negatively influences sensory neuron survival, which has implications for a wide range of peripheral neuropathies.SIGNIFICANCE STATEMENT Although expressed in Schwann cells, the role of p75 in myelination has remained unresolved in part because of its dual expression in sensory neurons that Schwann cells myelinate. When p75 was deleted selectively among Schwann cells, myelination was minimally affected, while sensory neuron survival was reduced by 30%. The phenotype is mainly due to dysregulation of cholesterol biosynthesis in p75-deficient Schwann cells, leading to an accumulation of neurotoxic cholesterol precursor, 7-dehydrocholesterol (7-DHC). Mechanism-wise, we discovered that in response to BDNF, p75 recruits and activates ErbB2 independently of ErbB3, thereby stimulating the master regulator, sterol regulatory element binding protein 2 (SREBP2). These results together highlight a novel role of p75 in Schwann cells in regulating DRG neuron survival by orchestrating proper cholesterol metabolism.

Carrier frequency and incidence estimation of Smith-Lemli-Opitz syndrome in East Asian populations by Genome Aggregation Database (gnomAD) based analysis

Background

Smith–Lemli–Opitz syndrome (SLOS) is an autosomal, recessively inherited congenital malformation syndrome characterized by multiple congenital anomalies such as microcephaly with mental defects, distinctive facial features, genital abnormalities, and 2–3 syndactyly of the toes. SLOS is caused by defective 7-dehydrocholesterol reductase, which is encoded by the DHCR7 gene. This study aimed to analyze the carrier frequency and expected incidence of SLOS in East Asians and Koreans using exome data from the Genome Aggregation Database (gnomAD) through the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology guideline (2015 ACMG-AMP guideline).

Methods

We analyzed 9197 exomes for East Asian populations from gnomAD, comprising 1909 Korean, 76 Japanese, and 7212 other East Asian populations. All identified variants were classified according to the 2015 ACMG-AMP guideline.

Results

According to the 2015 ACMG-AMP guideline, 15 pathogenic variant/likely pathogenic variant (PV/LPV) cases were identified in 33 East Asian individuals (33/9191 = 0.4%). Among them, four PVs/LPVs were identified in 19 Korean individuals (19/1909 = 1.0%). The predicted incidence, based upon the carrier rates of PV/LPV of DHCR7 alleles, is 1 in 310,688 in East Asians and l in 40,380 in Koreans.

Conclusions

This study is the first to identify carrier frequencies in East Asians and Koreans using gnomAD. It was confirmed that East Asians (0.4%) had a lower carrier frequency than did other ethnicities (1–3%) and Koreans (1.0%) had similar or lower carrier frequencies than other ethnicities. The variant spectrums of DHCR7 in East Asian and Korean populations differed greatly from those of other ethnic groups.

Sterol Biosynthesis Inhibition in Pregnant Women Taking Prescription Medications

Sterol biosynthesis is a critical homeostatic mechanism of the body. Sterol biosynthesis begins during early embryonic life and continues throughout life. Many commonly used medications, prescribed >200 million times in the United States annually, have a sterol biosynthesis inhibition side effect. Using our high-throughput LC-MS/MS method, we assessed the levels of post-lanosterol sterol intermediates (lanosterol, desmosterol, and 7-dehydrocholesterol (7-DHC)) and cholesterol in 1312 deidentified serum samples from pregnant women. 302 samples showing elevated 7-DHC were analyzed for the presence of 14 medications known to inhibit the 7-dehydrocholesterol reductase enzyme (DHCR7) and increase 7-DHC. Of the 302 samples showing 7-DHC elevation, 43 had detectable levels of prescription medications with a DHCR7-inhibiting side effect. Taking more than one 7-DHC-elevating medication in specific combinations (polypharmacy) might exacerbate the effect on 7-DHC levels in pregnant women, suggesting a potentially additive or synergistic effect. As 7-DHC and 7-DHC-derived oxysterols are toxic, and as DHCR7-inhibiting medications are considered teratogens, our findings raise potential concerns regarding the use of prescription medication with a DHCR7-inhibiting side effect during pregnancy. The use of prescription medications during pregnancy is sometimes unavoidable, but choosing a medication without a DHCR7-inhibiting side effect might lead to a heathier pregnancy and prevent putatively adverse outcomes for the developing offspring.

Altered Cholesterol Biosynthesis Affects Drug Metabolism

The last step of cholesterol biosynthesis is the conversion of 7-dehydrocholesterol (7-DHC) into cholesterol, a reaction catalyzed by dehydrocholesterol reductase 7 (DHCR7). Investigation of the effect of Dhcr7 single-allele mutations on the metabolism of aripiprazole (ARI) and cariprazine (CAR) in maternally exposed transgenic pups revealed that ARI, CAR, and their active metabolites were decreased in the liver and brain of Dhcr7 ^+/- . This difference in the drug and metabolite levels resulted in an increased turnover of ARI and CAR in tissues from Dhcr7 ^+/- animals, indicating an enhanced metabolism, which was at least partially due to increased levels of Cyp2d6 in the liver of Dhcr7 ^+/- mice. Finally, experiments with both WT and DHCR7 ^+/- human fibroblasts revealed lower drug levels in DHCR7 ^+/- heterozygous cells. Our findings have potential clinical implications, as DHCR7 heterozygosity is present in 1-3% in the human population, and these individuals might have reduced therapeutic levels of Cyp2d6-metabolized medications and are putatively more susceptible to unwanted side effects.

Prescription Medications Alter Neuronal and Glial Cholesterol Synthesis

Mouse brain contains over 100 million neuronal, glial, and other support cells. Developing neurons and astrocytes synthesize their own cholesterol, and disruption of this process can occur by both genetic and chemical mechanisms. In this study we have exposed cultured murine neurons and astrocytes to six different prescription medications that cross the placenta and blood-brain barriers and analyzed the effects of these drugs on cholesterol biosynthesis by an LC-MS/MS protocol that assays 14 sterols and 7 oxysterols in a single run. Three antipsychotics (haloperidol, cariprazine, aripiprazole), two antidepressants (trazodone and sertraline), and an antiarhythmic (amiodarone) inhibited one or more sterol synthesis enzymes. The result of the exposures was a dose-dependent increase in levels of various sterol intermediates and a decreased level of cholesterol in the cultured cells. Four prescription medications (haloperidol, aripiprazole, cariprazine, and trazodone) acted primarily on the DHCR7 enzyme. The result of this exposure was an increase in 7-dehydrocholesterol in neurons and astrocytes to levels that were comparable to those found in cultured neurons and astrocytes from transgenic mice that carried a Dhcr7 pathogenic mutation modeling the neurodevelopmental disorder Smith-Lemli-Opitz syndrome.

Trazodone effects on developing brain

Trazodone (TRZ) is a commonly prescribed antidepressant with significant off-label use for insomnia. A recent drug screening revealed that TRZ interferes with sterol biosynthesis, causing elevated levels of sterol precursor 7-dehydrocholesterol (7-DHC). Recognizing the well-documented, disruptive effect of 7-DHC on brain development, we designed a study to analyze TRZ effects during pregnancy. Utilizing an in vivo model and human biomaterial, our studies were designed to also account for drug interactions with maternal or offspring Dhcr7 genotype. In a maternal exposure model, we found that TRZ treatment increased 7-DHC and decreased desmosterol levels in brain tissue in newborn pups. We also observed interactions between Dhcr7 mutations and maternal TRZ exposure, giving rise to the most elevated toxic oxysterols in brains of Dhcr7^+/- pups with maternal TRZ exposure, independently of the maternal Dhcr7 genotype. Therefore, TRZ use during pregnancy might be a risk factor for in utero development of a neurodevelopmental disorder, especially when the unborn child is of DHCR7^+/- genotype. The effects of TRZ on 7-DHC was corroborated in human serum samples. We analyzed sterols and TRZ levels in individuals with TRZ prescriptions and found that circulating TRZ levels correlated highly with 7-DHC. The abundance of off-label use and high prescription rates of TRZ might represent a risk for the development of DHCR7 heterozygous fetuses. Thus, TRZ use during pregnancy is potentially a serious public health concern.

Brain-Specific Oxysterols and Risk of Schizophrenia in Clinical High-Risk Subjects and Patients With Schizophrenia

Accumulating evidence from clinical, genetic, and epidemiologic studies suggest that schizophrenia might be a neuronal development disorder. While oxysterols are important factors in neurodevelopment, it is unknown whether oxysterols might be involved in development of schizophrenia. The present study investigated the relationship between tissue-specifically originated oxysterols and risk of schizophrenia. A total of 216 individuals were recruited in this study, including 76 schizophrenia patients, 39 clinical high-risk (CHR) subjects, and 101 healthy controls (HC). We investigated the circulating levels of brain-specific oxysterol 24(S)-hydroxycholesterol (24OHC) and peripheral oxysterol 27-hydroxycholesterol (27OHC) in all participants and analyzed the potential links between the oxysterols and specific clinical symptoms in schizophrenic patients and CHR. Our data showed an elevation of 24OHC in both schizophrenia patients and CHR than that in HC, while a lower level of 27OHC in the schizophrenia group only. The ratio of 24OHC to 27OHC was only increased in the schizophrenic group compared with CHR and HC. For the schizophrenic patients, the circulating 24OHC levels are significantly associated with disease duration, positively correlated with the positive and negative syndrome total scores, while the 27OHC levels were inversely correlated with the positive symptom scores. Together, our data demonstrated the disruption of tissue-specifically originated cholesterol metabolism in schizophrenia and CHR, suggesting the circulating 24OHC or 24OHC/27OHC ratio might not only be a potential indicator for risk for schizophrenia but also be biomarkers for functional abnormalities in neuropathology of schizophrenia.

Impact of Sex and Age on the Mevalonate Pathway in the Brain: A Focus on Effects Induced by Maternal Exposure to Exogenous Compounds

The mevalonate pathway produces cholesterol and other compounds crucial for numerous cellular processes. It is well known that age and sex modulate this pathway in the liver. Recently, similar effects were also noted in different brain areas, suggesting that alterations of the mevalonate pathway are at the root of marked sex-specific disparities in some neurodevelopmental disorders related to disturbed cholesterol homeostasis. Here, we show how the mevalonate pathway is modulated in a sex-, age- and region-specific manner, and how maternal exposure to exogenous compounds can disturb the regulation of this pathway in the brain, possibly inducing functional alterations.

Screening ToxCast™ for Chemicals That Affect Cholesterol Biosynthesis: Studies in Cell Culture and Human Induced Pluripotent Stem Cell-Derived Neuroprogenitors

BACKGROUND

Changes in cholesterol metabolism are common hallmarks of neurodevelopmental pathologies. A diverse array of genetic disorders of cholesterol metabolism support this claim as do multiple lines of research that demonstrate chemical inhibition of cholesterol biosynthesis compromises neurodevelopment. Recent work has revealed that a number of commonly used pharmaceuticals induce changes in cholesterol metabolism that are similar to changes induced by genetic disorders with devastating neurodevelopmental deficiencies.

OBJECTIVES

We tested the hypothesis that common environmental toxicants may also impair cholesterol metabolism and thereby possibly contribute to neurodevelopmental toxicity.

METHODS

Using high-throughput screening with a targeted lipidomic analysis and the mouse neuroblastoma cell line, Neuro-2a, the ToxCast™ chemical library was screened for compounds that impact sterol metabolism. Validation of chemical effects was conducted by assessing cholesterol biosynthesis in human induced pluripotent stem cell (hiPSC)-derived neuroprogenitors using an isotopically labeled cholesterol precursor and by monitoring product formation with UPLC-MS/MS.

RESULTS

Twenty-nine compounds were identified as validated lead-hits, and four were prioritized for further study (endosulfan sulfate, tributyltin chloride, fenpropimorph, and spiroxamine). All four compounds were validated to cause hypocholesterolemia in Neuro-2a cells. The morpholine-like fungicides, fenpropimorph and spiroxamine, mirrored their Neuro-2a activity in four immortalized human cell lines and in a human neuroprogenitor model derived from hiPSCs, but endosulfan sulfate and tributyltin chloride did not.

CONCLUSIONS

These data reveal the existence of environmental compounds that interrupt cholesterol biosynthesis and that methodologically hiPSC neuroprogenitor cells provide a particularly sensitive system to monitor the effect of small molecules on de novo cholesterol formation. https://doi.org/10.1289/EHP5053.

Maternal cariprazine exposure inhibits embryonic and postnatal brain cholesterol biosynthesis

Cariprazine (CAR) is a strong inhibitor of the Dhcr7 enzyme, the last enzyme in the cholesterol biosynthesis pathway. We assessed the effects of CAR on maternally exposed Dhcr7^+/- and wild-type mouse offspring, and tested the biochemical effects of CAR in human serum samples. Dhcr7^+/- and wild-type time-pregnant mice were exposed to vehicle or 0.2 mg/kg CAR from E12 to E19. Levels of CAR, CAR metabolites, sterols, and oxysterols were measured in the brain of maternally exposed offspring at various time points using LC-MS/MS. Embryonic exposure to CAR significantly increased levels of 7-DHC in all organs of exposed embryos, with a particularly strong effect in the brain. Detectable levels of CAR and elevated 7-DHC were observed in the brain of newborn pups 14 days after drug exposure. In addition, CAR altered sterol metabolism in all animals analyzed, with the strongest effect on the brain of Dhcr7^+/- pups born to Dhcr7^+/- dams. Furthermore, CAR elevated toxic oxysterols in the brain of maternally exposed Dhcr7^+/- offspring to levels approaching those seen in a mouse model of Smith-Lemli-Opitz syndrome. Finally, we observed that patients taking CAR have elevated 7-DHC in their serum. In summary, maternal DHCR7 heterozygosity, combined with offspring DHCR7 heterozygosity might represent a vulnerability factor to medications that interfere with sterol biosynthesis. Due to the conserved sterol biosynthesis between mice and humans, we suggest that the 1-3% of patient population with single-allele DHCR7 mutations might not be ideal candidates for CAR use, especially if they are nursing, pregnant or plan to become pregnant.