Novel biomarkers to assess in utero effects of maternal opioid use: First steps toward understanding short- and long-term neurodevelopmental sequelae

Prenatal Opioid and Alcohol Exposures: Association with Altered Placental Serotonin Transporter Structure and/or Expression

Fetal exposures to many drugs of abuse, e.g., opioids and alcohol (EtOH), are associated with adverse neurodevelopmental problems in early childhood, including abnormalities in activity of the serotonin (5HT) transporter (SERT), which transports 5HT across the placenta. Little is known about the effects of these drugs on SERT expression. Pregnant women who used EtOH or opioids were compared to gestational age-matched controls using a structured questionnaire to determine prenatal substance exposure. Following elective pregnancy termination, placental membranous vesicles and exosomes were prepared from first and second trimester human placentas. Changes in EtOH- or opioid-exposed placental SERT expression and modifications were assessed by quantitative western blot. Novel SERT isoforms were sequenced and analyzed. Opioid-exposed but not EtOH-exposed maternal placentas showed SERT cleavage and formation of new SERT fragments (isoforms). Alcohol-exposed cases showed reduced SERT levels. Antibodies to the N-terminal SERT region did not recognize either of the two cleavage products, while antibodies to the central and C-terminal regions recognized both bands. The secondary band seen in the opioid group may represent a hypophosphorylated SERT fragment. These changes in SERT modifications and expression may result in altered fetal brain serotonergic neurotransmission, which could have neurodevelopmental implications.

Biomarkers of Affective Dysregulation Associated with In Utero Exposure to EtOH

INTRODUCTION

Children with fetal alcohol spectrum disorders (FASD) exhibit behavioral and affective dysregulation, including hyperactivity and depression. The mechanisms are not known, but they could conceivably be due to postnatal social or environmental factors. However, we postulate that, more likely, the affective dysregulation is associated with the effects of EtOH exposure on the development of fetal serotonergic (5-HT) and/or dopaminergic (DA) pathways, i.e., pathways that in postnatal life are believed to regulate mood. Many women who use alcohol (ethanol, EtOH) during pregnancy suffer from depression and take selective serotonin reuptake inhibitors (SSRIs), which might influence these monoaminergic pathways in the fetus. Alternatively, monoaminergic pathway abnormalities might reflect a direct effect of EtOH on the fetal brain. To distinguish between these possibilities, we measured their expressions in fetal brains and in fetal brain-derived exosomes (FB-Es) isolated from the mothers' blood. We hypothesized that maternal use of EtOH and/or SSRIs during pregnancy would be associated with impaired fetal neural development, detectable as abnormal levels of monoaminergic and apoptotic biomarkers in FB-Es.

METHODS

Fetal brain tissues and maternal blood were collected at 9-23 weeks of pregnancy. EtOH groups were compared with unexposed controls matched for gestational age (GA). The expression of 84 genes associated with the DA and 5-HT pathways was analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) on microarrays. FB-Es also were assayed for serotonin transporter protein (SERT) and brain-derived neurotrophic factor (BDNF) by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Six EtOH-exposed human fetal brain samples were compared to SSRI- or polydrug-exposed samples and to unexposed controls. EtOH exposure was associated with significant upregulation of DA receptor D3 and 5-HT receptor HTR2C, while HTR3A was downregulated. Monoamine oxidase A (MAOA), MAOB, the serine/threonine kinase AKT3, and caspase-3 were upregulated, while mitogen-activated protein kinase 1 (MAPK1) and AKT2 were downregulated. ETOH was associated with significant upregulation of the DA transporter gene, while SERT was downregulated. There were significant correlations between EtOH exposure and (a) caspase-3 activation, (b) reduced SERT protein levels, and (c) reduced BDNF levels. SSRI exposure independently increased caspase-3 activity and downregulated SERT and BDNF. Early exposure to EtOH and SSRI together was associated synergistically with a significant upregulation of caspase-3 and a significant downregulation of SERT and BDNF. Reduced SERT and BDNF levels were strongly correlated with a reduction in eye diameter, a somatic manifestation of FASD.

CONCLUSIONS

Maternal use of EtOH and SSRI during pregnancy each was associated with changes in fetal brain monoamine pathways, consistent with potential mechanisms for the affective dysregulation associated with FASD.

Effects of In Utero EtOH Exposure on 18S Ribosomal RNA Processing: Contribution to Fetal Alcohol Spectrum Disorder

Fetal alcohol spectrum disorders (FASD) are leading causes of neurodevelopmental disability. The mechanisms by which alcohol (EtOH) disrupts fetal brain development are incompletely understood, as are the genetic factors that modify individual vulnerability. Because the phenotype abnormalities of FASD are so varied and widespread, we investigated whether fetal exposure to EtOH disrupts ribosome biogenesis and the processing of pre-ribosomal RNAs and ribosome assembly, by determining the effect of exposure to EtOH on the developmental expression of 18S rRNA and its cleaved forms, members of a novel class of short non-coding RNAs (srRNAs). In vitro neuronal cultures and fetal brains (11-22 weeks) were collected according to an IRB-approved protocol. Twenty EtOH-exposed brains from the first and second trimester were compared with ten unexposed controls matched for gestational age and fetal gender. Twenty fetal-brain-derived exosomes (FB-Es) were isolated from matching maternal blood. RNA was isolated using Qiagen RNA isolation kits. Fetal brain srRNA expression was quantified by ddPCR. srRNAs were expressed in the human brain and FB-Es during fetal development. EtOH exposure slightly decreased srRNA expression (1.1-fold; p = 0.03). Addition of srRNAs to in vitro neuronal cultures inhibited EtOH-induced caspase-3 activation (1.6-fold, p = 0.002) and increased cell survival (4.7%, p = 0.034). The addition of exogenous srRNAs reversed the EtOH-mediated downregulation of srRNAs (2-fold, p = 0.002). EtOH exposure suppressed expression of srRNAs in the developing brain, increased activity of caspase-3, and inhibited neuronal survival. Exogenous srRNAs reversed this effect, possibly by stabilizing endogenous srRNAs, or by increasing the association of cellular proteins with srRNAs, modifying gene transcription. Finally, the reduction in 18S rRNA levels correlated closely with the reduction in fetal eye diameter, an anatomical hallmark of FASD. The findings suggest a potential mechanism for EtOH-mediated neurotoxicity via alterations in 18S rRNA processing and the use of FB-Es for early diagnosis of FASD. Ribosome biogenesis may be a novel target to ameliorate FASD in utero or after birth. These findings are consistent with observations that gene-environment interactions contribute to FASD vulnerability.

In utero ethanol exposure induces mitochondrial DNA damage and inhibits mtDNA repair in developing brain

Introduction

Mitochondrial dysfunction is postulated to be a central event in fetal alcohol spectrum disorders (FASD). People with the most severe form of FASD, fetal alcohol syndrome (FAS) are estimated to live only 34 years (95% confidence interval, 31 to 37 years), and adults who were born with any form of FASD often develop early aging. Mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage, hallmarks of aging, are postulated central events in FASD. Ethanol (EtOH) can cause mtDNA damage, consequent increased oxidative stress, and changes in the mtDNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1). Studies of molecular mechanisms are limited by the absence of suitable human models and non-invasive tools.

Methods

We compared human and rat EtOH-exposed fetal brain tissues and neuronal cultures, and fetal brain-derived exosomes (FB-Es) from maternal blood. Rat FASD was induced by administering a 6.7% alcohol liquid diet to pregnant dams. Human fetal (11-21 weeks) brain tissue was collected and characterized by maternal self-reported EtOH use. mtDNA was amplified by qPCR. OGG1 and Insulin-like growth factor 1 (IGF-1) mRNAs were assayed by qRT-PCR. Exosomal OGG1 was measured by ddPCR.

Results

Maternal EtOH exposure increased mtDNA damage in fetal brain tissue and FB-Es. The damaged mtDNA in FB-Es correlated highly with small eye diameter, an anatomical hallmark of FASD. OGG1-mediated mtDNA repair was inhibited in EtOH-exposed fetal brain tissues. IGF-1 rescued neurons from EtOH-mediated mtDNA damage and OGG1 inhibition.

Conclusion

The correlation between mtDNA damage and small eye size suggests that the amount of damaged mtDNA in FB-E may serve as a marker to predict which at risk fetuses will be born with FASD. Moreover, IGF-1 might reduce EtOH-caused mtDNA damage and neuronal apoptosis.

Prenatal Morphine Exposure Increases Cardiovascular Disease Risk and Programs Neurogenic Hypertension in the Adult Offspring

BACKGROUND

The opioid overdose and opioid use disorder epidemics are concomitant with increased metabolic and CVD risk. Although opioid use disorder causes adverse pregnancy outcomes, the offspring's cardiovascular health is understudied. We hypothesized that offspring exposed to in utero morphine exposure (IUME) would show increased CVD risk factors and endogenous opioid system dysregulation.

METHODS

Sprague Dawley dams were treated with saline (vehicle, n=10) or escalating doses of morphine (5-20 mg/kg per day, SC, n=10) during gestation. Cardiovascular and metabolic parameters were assessed in adult offspring.

RESULTS

Litter size and pups' birth weight were not different in response to IUME. Female and male IUME offspring showed reduced body length at birth (P<0.05) and body weight from weeks 1 to 3 of life (P<0.05), followed by a catch-up growth effect. By week 16, female and male IUME rats showed reduced tibia length (P<0.05) and fat mass. IUME increases the mean arterial pressure and the depressor response to mecamylamine (5 mg/kg per day, IP) induced by IUME were abolished by a chronic treatment with an alpha-adrenergic receptor blocker (prazosin; 1 mg/kg per day, IP). Although circulating levels of angiotensin peptides were similar between groups, IUME exacerbated maximal ex vivo Ang (angiotensin) II-induced vasoconstriction (P<0.05) and induced endothelial dysfunction in a sex-specific manner (P<0.05). Proenkephalin, an endogenous opioid peptide that lowers blood pressure and sympathetic-mediated vasoconstriction, showed reduced mRNA expression in the heart, aorta, and kidneys from morphine versus vehicle group (P<0.05).

CONCLUSIONS

Among the effects of IUME, neurogenic hypertension, vascular dysfunction, and metabolic dysfunction could be associated with the dysregulation of the endogenous opioid system.

Exosomal Lipid Biomarkers of Oligodendrocyte Pathology to Predict Scoliosis in Children with Cerebral Palsy

Introduction

Cerebral Palsy (CP), the most common cause of disability in children, is phenotypically heterogeneous. Approximately 20% of cases develop severe scoliosis. A pathological hallmark of CP is periventricular leukomalacia (PVL), which is due to dysmyelination, suggesting the possibility of a lipidomic abnormality. Risk factors for CP include perinatal hypoxia, prematurity, multiple gestation, ischemia, infection, and maternal alcohol consumption. There is evidence for low serum levels of omega-3 (ω-3) fatty acids in CP patients, and separately in idiopathic scoliosis. Many effects of free fatty acids (FFAs) are mediated via specific G protein-coupled free fatty acid receptors (FFARs), which play essential roles as nutritional and signaling molecules. FFAs, including ω-3, and their receptors are involved in the development and metabolism of oligodendrocytes (OLs), and are critical to myelination. Thus, the cases of CP that will develop severe scoliosis might be those in which there is a deficiency of ω-3, FFARs, or other lipidomic abnormality that is detectable early in the plasma. If so, we might be able to predict scoliosis and prevent it with dietary supplementation.

Methods

Blood samples were collected from four groups of patients at the Philadelphia Shriners Children's Hospital (SCH-P): 1) patients with CP; 2) severe scoliosis (>40o); 3) CP plus scoliosis; and 4) non-impaired controls stratified by age (2-18 yrs), gender, and race/ethnicity, under an IRB-approved protocol. Serum proteins and RNA were purified, and OL-derived exosomes (OL-Es) isolated, using myelin basic protein (MBP) as a late OL marker. Protein was used for the detection of MBP and FFAR by enzyme-linked immunosorbent assays (ELISAs), and by flow cytometry. RNA was assayed by digital droplet polymerase chain reaction (ddPCR) for OL markers and FFAR expression.

Results

FFAR and MBP proteins were downregulated in each of the three patient groups compared to controls, and this difference was greatest in both patients with CP plus scoliosis.

Conclusion

Altogether, MBP and FFAR levels were reduced in OL-Es from both children with CP plus scoliosis. The lipid abnormalities specific to CP with scoliosis were concentrated in OLs. Our data might i) suggest therapeutic targets to reduce dysmyelination and scoliosis in CP, ii) predict which children are at risk for developing scoliosis, iii) lead to therapeutic trials of fatty acids for CP and other dysmyelinating neurological disorders.

Maternal Blood Lipid Biomarkers of Oligodendrocyte Pathology to Predict Fetal Alcohol Spectrum Disorders

Introduction

Up to 9.9% of children have fetal alcohol spectrum disorders (FASD), the most frequent cause of intellectual disability in the US. FASD may involve abnormal brain development, including dysmyelination, suggesting abnormal development of oligodendrocytes (OLs), which make myelin and are rich in lipids. Indeed, low serum levels of omega-3 fatty acids (ω-3) have been reported in FASD. Free fatty acids bind to specific receptors (FFARs). We have isolated cell type-specific fetal brain-derived exosomes (FB-E) from maternal blood and sampled their contents to search for lipid-related biomarkers that predict FASD.

Methods

Blood samples were collected from two groups of pregnant women: 1) those who consumed EtOH during pregnancy, and 2) non-EtOH using controls, under an IRB-approved protocol. Serum and OL-derived exosomes (OL-Es) were used to assay myelin basic protein (MBP) and FFAR by ELISA and droplet digital PCR (ddPCR), respectively.

Results

FFAR and MBP proteins were downregulated in the EtOH group compared to controls, and this difference was greatest in OL-Es from maternal blood compared maternal serum.

Conclusion

MBP and FFAR levels were reduced in OL-Es from EtOH-consuming pregnant women. The data suggest potential therapeutic targets to predict which children are at risk for developing FASD and reduce dysmyelination in developing.

PET imaging of kappa opioid receptors and receptor expression quantified in neuron-derived extracellular vesicles in socially housed female and male cynomolgus macaques

Recent positron emission tomography (PET) studies of kappa opioid receptors (KOR) in humans reported significant relationships between KOR availability and social status, as well as cocaine choice. In monkey models, social status influences physiology, receptor pharmacology and behavior; these variables have been associated vulnerability to cocaine abuse. The present study utilized PET imaging to examine KOR availability in socially housed, cocaine-naïve female and male monkeys, and peripheral measures of KORs with neuron-derived extracellular vesicles (NDE). KOR availability was assessed in dominant and subordinate female and male cynomolgus macaques (N = 4/rank/sex), using PET imaging with the KOR selective agonist [11C]EKAP. In addition, NDE from the plasma of socially housed monkeys (N = 13/sex; N = 6-7/rank) were isolated by immunocapture method and analyzed for OPRK1 protein expression by ELISA. We found significant interactions between sex and social rank in KOR availability across 12 of 15 brain regions. This was driven by female data, in which KOR availability was significantly higher in subordinate monkeys compared with dominant monkeys; the opposite relationship was observed among males, but not statistically significant. No sex or rank differences were observed for NDE OPRK1 concentrations. In summary, the relationship between brain KOR availability and social rank was different in female and male monkeys. This was particularly true in female monkeys. We hypothesize that lower [11C]EKAP binding potentials were due to higher concentrations of circulating dynorphin, which is consistent with greater vulnerability in dominant compared with subordinate females. These findings suggest that the KOR is an important target for understanding the neurobiology associated with vulnerability to abused drugs and sex differences, and detectable in peripheral circulation.

Molecular Markers in Maternal Blood Exosomes Allow Early Detection of Fetal Alcohol Spectrum Disorders

Prenatal alcohol exposure can cause developmental abnormalities (fetal alcohol spectrum disorders; FASD), including small eyes, face and brain, and neurobehavioral deficits. These cannot be detected early in pregnancy with available imaging techniques. Early diagnosis could facilitate development of therapeutic interventions. Banked human fetal brains and eyes at 9−22 weeks’ gestation were paired with maternal blood samples, analyzed for morphometry, protein, and RNA expression, and apoptotic signaling. Alcohol (EtOH)-exposed (maternal self-report) fetuses were compared with unexposed controls matched for fetal age, sex, and maternal race. Fetal brain-derived exosomes (FB-E) were isolated from maternal blood and analyzed for protein, RNA, and apoptotic markers. EtOH use by mothers, assessed by self-report, was associated with reduced fetal eye diameter, brain size, and markers of synaptogenesis. Brain caspase-3 activity was increased. The reduction in eye and brain sizes were highly correlated with amount of EtOH intake and caspase-3 activity. Levels of several biomarkers in FB-E, most strikingly myelin basic protein (MBP; r > 0.9), correlated highly with morphological abnormalities. Reduction in FB-E MBP levels was highly correlated with EtOH exposure (p < 1.0 × 10−10). Although the morphological features of FAS appear long before they can be detected by live imaging, FB-E in the mother’s blood may contain markers, particularly MBP, that predict FASD.

Ethanol-mediated alterations in oligodendrocyte differentiation in the developing brain

INTRODUCTION

Alterations of white matter integrity and subsequent white matter structural deficits are consistent findings in Fetal Alcohol Syndrome (FAS), but knowledge regarding the molecular mechanisms underlying these abnormalities is incomplete. Experimental rodent models of FAS have shown dysregulation of cytokine expression leading to apoptosis of oligodendrocyte precursor cells (OPCs) and altered oligodendrocyte (OL) differentiation, but whether this is representative of human FAS pathogenesis has not been determined.

METHODS

Fetal brain tissue (12.2-21.4 weeks gestation) from subjects undergoing elective termination of pregnancy was collected according to an IRB-approved protocol. Ethanol (EtOH) exposure status was classified based on a detailed face-to-face questionnaire adapted from the National Institute on Alcohol Abuse and Alcoholism Prenatal Alcohol and Sudden Infant Death Syndrome and Stillbirth (PASS) study. Twenty EtOH-exposed fetuses were compared with 20 gestational age matched controls. Cytokine and OPC marker mRNA expression was quantified by Real-Time Polymerase chain reaction (qRT-PCR). Patterns of protein expression of OPC markers and active Capase-3 were studied by Fluorescence Activated Cell Sorting (FACS).

RESULTS

EtOH exposure was associated with reduced markers of cell viability, OPC differentiation, and OL maturation, while early OL differentiation markers were unchanged or increased. Expression of mRNAs for proteins specific to more mature forms of OL lineage (platelet-derived growth factor α (PDGFRα) and myelin basic protein (MBP) was lower in the EtOH group than in controls. Expression of the multifunctional growth and differentiation-promoting growth factor IGF-1, which is essential for normal development, also was reduced. Reductions were not observed for markers of early stages of OL differentiation, including Nuclear transcription factor NK-2 homeobox locus 2 (Nkx2.2). Expression of mRNAs for the proinflammatory cytokine, tumor necrosis factor-α (TNFα), and several proinflammatory chemokines was higher in the EtOH group compared to controls, including: Growth regulated protein alpha/chemokine (C-X-C motif) ligand 1 (GRO-α/CXCL1), Interleukin 8/chemokine (C-X-C motif) ligand 8 (IL8/CXCL8), Chemokine (C-X-C motif) ligand 6/Granulocyte chemotactic protein 2 (CXCL16/GCP2), epithelial-derived neutrophil-activating protein 78/chemokine (C-X-C motif) ligand 5 (ENA-78/CXCL5), monocyte chemoattractant protein-1 (MCP-1). EtOH exposure also was associated with an increase in the proportion of cells expressing markers of early stage OPCs, such as A2B5 and NG2. Finally, apoptosis (measured by caspase-3 activation) was increased substantially in the EtOH group compared to controls.

CONCLUSION

Prenatal EtOH exposure is associated with excessive OL apoptosis and/or delayed OL maturation in human fetal brain. This is accompanied by markedly dysregulated expression of several chemokines and cytokines, in a pattern predictive of increased OL cytotoxicity and reduced OL differentiation. These findings are consistent with findings in animal models of FAS.

Role of Extracellular Vesicles in Substance Abuse and HIV-Related Neurological Pathologies

Extracellular vesicles (EVs) are a broad, heterogeneous class of membranous lipid-bilayer vesicles that facilitate intercellular communication throughout the body. As important carriers of various types of cargo, including proteins, lipids, DNA fragments, and a variety of small noncoding RNAs, including miRNAs, mRNAs, and siRNAs, EVs may play an important role in the development of addiction and other neurological pathologies, particularly those related to HIV. In this review, we summarize the findings of EV studies in the context of methamphetamine (METH), cocaine, nicotine, opioid, and alcohol use disorders, highlighting important EV cargoes that may contribute to addiction. Additionally, as HIV and substance abuse are often comorbid, we discuss the potential role of EVs in the intersection of substance abuse and HIV. Taken together, the studies presented in this comprehensive review shed light on the potential role of EVs in the exacerbation of substance use and HIV. As a subject of growing interest, EVs may continue to provide information about mechanisms and pathogenesis in substance use disorders and CNS pathologies, perhaps allowing for exploration into potential therapeutic options.

Developmental opioid exposures: Neurobiological underpinnings, behavioral impacts, and policy implications

The devastating impact of opioid abuse and dependence on the individual, family, and society are well known but extremely difficult to combat. During pregnancy, opioid drugs and withdrawal also affect fetal brain development and newborn neural functions, in addition to maternal effects. Neonatal Abstinence Syndrome/Neonatal Opioid Withdrawal Syndrome (NAS/NOWS) rates have drastically increased in the US in the past decade. Solutions to this complex problem must be multi-faceted, which would be greatly enhanced by a translational, multidisciplinary understanding. Therefore, this mini-review incorporates biomedical, clinical, and policy aspects of opioid use during pregnancy. We review the known roles for endogenous opioids in mediating circuit formation and function in the developing brain, discuss how exogenous opioid drug use and addiction impact these processes in animal models and humans, and discuss the implications of these data on public policy. We suggest that some current policy initiatives produce unintended harm on both mothers and their children and delineate recommendations for how legislation could better contribute to addiction recovery and increase neural resilience in affected children.

Impact statement

Opioid abuse is a critical epidemic affecting individuals, families, and communities. This mini-review summarizes current literature on the impact of opioid drugs—including prescription pain relievers and illicit opioids—on neurobiological and neurobehavioral development. Using concepts related to the medical model of addiction as a brain disease, we review the public policy implications of these data and identify needs for future investigations.