Opioid growth factor and organ development in rat and human embryos

Prenatal Opioid Exposure and Immune-Related Conditions in Children

Importance

Prenatal opioid exposure (POE) may alter with fetal development of the immune system, which may influence long-term health and susceptibility to immune-related conditions.

Objective

To compare the risk of hospitalization and emergency department presentation for immune-related conditions in children with and without POE.

Design, Setting, and Participants

This retrospective, population-based cohort study used linked administrative health records of all children born in Western Australia between January 1, 2003, and December 31, 2018 (N = 401 462).

Exposure

Prenatal exposure to prescription opioids (overall and by trimester), neonatal abstinence syndrome diagnosis, and opioid indication (pain or opioid use disorder [OUD]).

Main Outcomes and Measures

The main outcome was hospital admissions and emergency department presentations during which a child was diagnosed with an immune-related condition, including infections, conditions associated with an overactive immune system (eg, asthma, eczema, and allergy and anaphylaxis), and autoimmune diseases diagnosed before age 5 years or June 30, 2020. Data were analyzed between August 30, 2022, and February 27, 2023.

Results

Neonates with POE (1656 [0.4%]; mean [SD] gestational age, 37.7 [2.1] weeks; 836 females [50.5%]; 820 males [49.5%]) were more likely to be born preterm, have low birth weight for gestational age, and be coexposed to cigarette smoke compared with nonexposed neonates. Perinatal opioid exposure was associated with an increased risk of perinatal infection (adjusted odds ratio [AOR], 1.62; 95% CI, 1.38-1.90) and eczema and dermatitis (AOR, 11.91; 95% CI, 9.84-14.41) compared with nonexposure. Neonatal abstinence syndrome was also associated with both conditions (AOR, 2.91 [95% CI, 2.36-3.57] and 31.11 [95% CI, 24.64-39.28], respectively). Prenatal opioid exposure was also associated with an increased risk of childhood asthma (adjusted hazard ratio [AHR], 1.44; 95% CI, 1.16-1.79), but not allergies and anaphylaxis. It was also associated with an increased risk of childhood eczema and dermatitis, but only in children with POE from opioids used to treat OUD (AHR, 1.47; 95% CI, 1.08-1.99) rather than pain. In contrast, POE from opioids used for pain was associated with an increased risk of infection (AHR, 1.44; 95% CI, 1.32-1.58), but POE to opioids used to treat OUD was not. Autoimmune conditions were rare and were not observed to be associated with POE.

Conclusions and Relevance

In this cohort study, POE was associated with an increased risk of infection, eczema and dermatitis, and asthma, but not allergies and anaphylaxis or autoimmune conditions. These findings highlight the importance of further study of opioid-induced immune changes during pregnancy, the potential impact on long-term health in exposed children, and the mechanisms of opioid-induced immune dysregulation.

The Opioid Growth Factor in Growth Regulation and Immune Responses in Cancer

It has become apparent that endogenous opioids act not only as neurotransmitters and neuromodulators, but have multiple functions in the body. Activation of the opioid system by opiate drugs is associated with a risk of cancer development through direct stimulation of tumor cell proliferation and through immunosuppression. In contrast, the endogenous peptide opioid [Met5]-enkephalin, now commonly referred to as Opioid Growth Factor (OGF), negatively regulates cell proliferation in a wide number of cells during development, homeostasis, and neoplasia. This action is mediated through the opioid growth factor receptor, originally designated the zeta (ζ) opioid receptor. Further, contrary to the traditional notion of opiates as immunosuppressive, endogenous OGF has been shown to possess a number of positive immunomodulatory properties and may provide a beneficial effect in cancer by augmenting the activity of cells involved in both innate and acquired immunity. Taken together, the evidence supports consideration of opioid peptides such as OGF as new strategies for cancer therapy.

Prenatal exposure to morphine enhances excitability in locus coeruleus neurons

Opioid abuse during pregnancy may have noteworthy effects on the child's behavioral, emotional and cognitive progression. In this study, we assessed the effect of prenatal exposure to morphine on electrophysiological features of locus coeruleus (LC) noradrenergic neurons which is involved in modulating cognitive performance. Pregnant dams were randomly divided into two groups, that is a prenatal saline treated and prenatal morphine-treated group. To this end, on gestational days 11-18, either morphine or saline (twice daily, s.c.) was administered to pregnant dams. Whole-cell patch-clamp recordings were conducted on LC neurons of male offspring. The evoked firing rate, instantaneous frequency and action potentials half-width, and also input resistance of LC neurons significantly increased in the prenatal morphine group compared to the saline group. Moreover, action potentials decay slope, after hyperpolarization amplitude, rheobase current, and first spike latency were diminished in LC neurons following prenatal exposure to morphine. In addition, resting membrane potential, rise slope, and amplitude of action potentials were not changed by prenatal morphine exposure. Together, the current findings show a significant enhancement in excitability of the LC neurons following prenatal morphine exposure, which may affect the release of norepinephrine to other brain regions and/or cognitive performances of the offspring.

Opioid exposure during pregnancy and the risk of congenital malformation: a meta-analysis of cohort studies

BACKGROUND

Opioid exposure during pregnancy has increased alarmingly in recent decades. However, the association between prenatal opioid exposure and congenital malformation risk has still been controversial. We aim to assess the association between opioid exposure during pregnancy and the risk of congenital malformations.

METHOD

PubMed, Embase, and Cochrane library of clinical trials were systematically searched to September 13th, 2021. Cohort studies reporting risk of congenital malformation after opioid exposure compared with non-exposure during pregnancy were included. Risk of studies was appraised with the ROBINS-I tool. Meta-analysis was conducted using the random-effects model. Subgroup analyses were conducted for the primary outcome based on indication, exposed period, whether adjusted data was used, and risk of bias assessment. Meta-regression was performed to evaluate the relation of publication year.

MAIN RESULTS

Eighteen cohort studies with 7,077,709 patients were included. The results showed a significant increase in the risk of overall congenital malformation (RR = 1.30, 95%CI: 1.11-1.53), major malformation (RR = 1.57, 95%CI:1.11-2.22), central nervous system malformation (RR = 1.36, 95% CI:1.19-1.55), and limb malformation (RR = 2.27, 95%CI:1.29-4.02) with opioid exposure during pregnancy. However, the predictive interval conveyed a different result on overall congenital malformation (95%PI: 0.82-2.09) and major malformation (95%PI: 0.82-2.09). No association between opioid exposure and overall congenital malformation in the first trimester (RR = 1.12, 95%CI:0.97-1.31) and prescribed for analgesic or antitussive treatment (RR = 1.03, 95%CI:0.94-1.13) were observed. In subgroups that study provided data adjusted for confounders (RR = 1.06, 95%CI:0.93-1.20) or identified moderate or serious risk of bias (RR = 1.00, 95%Cl: 0.85-1.16; RR = 1.21, 95%Cl: 1.60-2.68), no association was found.

CONCLUSION

Opioid exposed in the first trimester or prescribed for analgesic or antitussive treatment did not increase the risk of overall congenital malformation. The findings should be discussed in caution considering the situation of individual patients and weigh out its potential risk of congenital malformation.

TRIAL REGISTRATION

Registration number: CRD42021279445 .

Genetic vulnerability of exposures to antenatal maternal treatments in 1- to 2-month-old infants

The growth and maturation of the nervous system are vulnerable during pregnancy. The impact of antenatal exposures to maternal treatments, in the context of genetic vulnerability of the fetus, on sensorimotor functioning in early infancy remains unexplored. Statistical features of head movements obtained from resting-state sleep fMRI scans are examined in 1- to 2-month-old infants, both those at high risk (HR) for autism spectrum disorder (ASD) due to a biological sibling with ASD and at low risk (LR) (N = 56). In utero exposures include maternal prescription medications (psychotropic Rx: N = 3_HR ; N = 5_LR vs. non-psychotropic Rx: N = 11_HR ; N = 9_LR vs. none: N = 11_HR ; N = 16_LR ), psychiatric diagnoses (two or more Dx₂ : N = 5_HR ; N = 1_LR ; one Dx₁ : N = 4_HR ; N = 5_LR ; no Dx: N = 12_HR ; N = 19_LR ), infections requiring antibiotics (infection: N = 5_HR ; N = 8_LR ; no infection: N = 20_HR ; N = 22_LR ), or high fever (fever: N = 2_HR ; N = 2_LR ; no fever: N = 23_HR ; N = 27_LR ). Movements with significantly higher variability are detected in infants exposed to psychotropics (e.g., opioid analgesics) and those whose mothers had fever, and this effect is significantly worse for infants at HR for ASD. Movements are significantly less variable in HR infants with non-psychotropic exposures (e.g., antibiotics). Heightened number of psychiatric or mental health conditions is associated with noisier movements in both risk groups. Genetic vulnerability due to in utero exposure to maternal treatments is an important future approach to be advanced in the field of early mind and brain development.

Association of Gestational Opioid Exposure and Risk of Major and Minor Congenital Malformations

IMPORTANCE

The rapid increase of opioid-related overdoses and deaths has become a public health concern in the US. Use of prescription opioids in pregnant women has increased; results from teratogenicity studies remain controversial.

OBJECTIVE

To evaluate the association between maternal prescription opioid use (excluding opioid use disorders) during pregnancy and the incidence of congenital malformations.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective population-based cohort study evaluated linked Rhode Island Medicaid claims and vital statistics data of live births from January 1, 2008, to December 31, 2016. Data analysis was conducted from May 1, 2019, to May 31, 2020. Women who had a live birth during the study period, but no cancer or opioid use disorder, were followed up from 3 months before pregnancy to the end of pregnancy.

EXPOSURES

Data on the mother's prescription opioid exposure were obtained through pharmacy claims and exposure was defined as dispensing of at least 1 prescription opioid during the first, second, or third trimester.

MAIN OUTCOMES AND MEASURES

The primary outcome was overall major or minor congenital malformations, defined as 1 or more major or minor congenital malformation. Secondary outcomes were defined as 10 specific categories of congenital malformations classified by organ systems using International Classification of Diseases diagnosis codes.

RESULTS

Of 12 424 included pregnancies, 891 mothers (7.2%) received prescription opioids during pregnancy and 3153 infants (25.4%) were diagnosed with major or minor congenital malformations. Comparing prescription opioid exposure vs nonexposure, no excess risk was observed for major birth defects in infants with opioid exposure in trimester 1 (adjusted relative risk [aRR], 1.40; 95% CI, 0.84-2.34), and higher risks were found for overall minor birth defects in trimester 3 (aRR, 1.26; 95% CI, 1.04-1.53) and minor birth defects in the musculoskeletal system in trimester 2 (aRR, 1.50; 95% CI, 1.10-2.03) and trimester 3 (aRR, 1.65; 95% CI, 1.23-2.22). Significant dose responses in selected minor malformations and effects of specific opioids were also identified. Hydrocodone in trimester 2 (aRR, 3.01; 95% CI, 1.80-5.03) and oxycodone in trimester 3 (aRR, 2.43; 95% CI, 1.37-4.02) were associated with plagiocephaly, polydactyly, and other specified congenital deformities of the hip.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest a higher risk of minor congenital malformations associated with use of prenatal prescription opioids in trimester 3, which seems to be dose-dependent. Further investigation is needed to establish causality and explore the physiologic plausibility of the association.

Association of first trimester prescription opioid use with congenital malformations in the offspring: population based cohort study

OBJECTIVE

To evaluate the risk of first trimester exposure to prescription opioids for major congenital malformations, previously reported to be associated with such exposure.

DESIGN

Population based cohort study.

SETTING

Nationwide sample of publicly and commercially insured pregnant women linked to their liveborn infants, nested in the Medicaid Analytic eXtract (MAX, 2000-14) and the MarketScan Research Database (MarketScan, 2003-15).

PARTICIPANTS

1 602 580 publicly insured (MAX) and 1 177 676 commercially insured (MarketScan) pregnant women with eligibility from at least three months before pregnancy to one month after delivery; infants with eligibility for at least three months after birth.

INTERVENTIONS

Use of prescription opioids was ascertained by requiring two or more dispensations of any opioid during the first trimester.

MAIN OUTCOMES MEASURES

Major malformations overall, cardiac malformations overall, ventricular septal defect, secundum atrial septal defect/patent foramen ovale, neural tube defect, clubfoot, and oral cleft, defined based on validated algorithms. Propensity score stratification was used to adjust for potential confounders and/or proxies for confounders. Estimates from each database were combined using meta-analysis.

RESULTS

70 447 (4.4%) of 1 602 580 publicly insured and 12 454 (1.1%) of 1 177 676 commercially insured pregnant women had two or more dispensations of an opioid during the first trimester. Absolute risk of malformations overall was 41.0 (95% confidence interval 39.5 to 42.5) per 1000 pregnancies exposed to opioids versus 32.0 (31.7 to 32.3) per 1000 unexposed pregnancies in the MAX cohort, and 42.6 (39.0 to 46.1) and 37.3 (37.0 to 37.7) per 1000, respectively, in the MarketScan cohort. Pooled unadjusted relative risk estimates were raised for all outcomes but shifted substantially toward the null after adjustment; for malformations overall (relative risk 1.06, 95% confidence interval 1.02 to 1.10), cardiovascular malformations (1.09, 1.00 to 1.18), ventricular septal defect (1.07, 0.95 to 1.21), atrial septal defect/patent foramen ovale (1.04, 0.88 to 1.24), neural tube defect (0.82, 0.53 to 1.27), and clubfoot (1.06, 0.88 to 1.28). The relative risk for oral clefts remained raised after adjustment (1.21, 0.98 to 1.50), with a higher risk of cleft palate (1.62, 1.23 to 2.14).

CONCLUSIONS

Prescription opioids used in early pregnancy are not associated with a substantial increase in risk for most of the malformation types considered, although a small increase in the risk of oral clefts associated with their use is possible.

Methionine Enkephalin Suppresses Osteocyte Apoptosis Induced by Compressive Force through Regulation of Nuclear Translocation of NFATc1

Mechanical stress stimulates bone remodeling, which occurs through bone formation and resorption, resulting in bone adaptation in response to the mechanical stress. Osteocytes perceive mechanical stress loaded to bones and promote bone remodeling through various cellular processes. Osteocyte apoptosis is considered a cellular process to induce bone resorption during mechanical stress-induced bone remodeling, but the underlying molecular mechanisms are not fully understood. Recent studies have demonstrated that neuropeptides play crucial roles in bone metabolism. The neuropeptide, methionine enkephalin (MENK) regulates apoptosis positively and negatively depending on cell type, but the role of MENK in osteocyte apoptosis, followed by bone resorption, in response to mechanical stress is still unknown. Here, we examined the roles and mechanisms of MENK in osteocyte apoptosis induced by compressive force. We loaded compressive force to mouse parietal bones, resulting in a reduction of MENK expression in osteocytes. A neutralizing connective tissue growth factor (CTGF) antibody inhibited the compressive force-induced reduction of MENK. An increase in osteocyte apoptosis in the compressive force-loaded parietal bones was inhibited by MENK administration. Nuclear translocation of NFATc1 in osteocytes in the parietal bones was enhanced by compressive force. INCA-6, which inhibits NFAT translocation into nuclei, suppressed the increase in osteocyte apoptosis in the compressive force-loaded parietal bones. NFATc1-overexpressing MLO-Y4 cells showed increased expression of apoptosis-related genes. MENK administration reduced the nuclear translocation of NFATc1 in osteocytes in the compressive force-loaded parietal bones. Moreover, MENK suppressed Ca²⁺ influx and calcineurin and calmodulin expression, which are known to induce the nuclear translocation of NFAT in MLO-Y4 cells. In summary, this study shows that osteocytes expressed MENK, whereas the MENK expression was suppressed by compressive force via CTGF signaling. MENK downregulated nuclear translocation of NFATc1 probably by suppressing Ca²⁺ signaling in osteocytes and consequently inhibiting compressive force-induced osteocyte apoptosis, followed by bone resorption. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Pregnancy outcome following opioid exposure: A cohort study

INTRODUCTION

Opioids constitute a cornerstone of pain relief treatment. However, opioid safety during pregnancy has not been well established. Recent studies reported an association between in utero opioid exposure and spina bifida.

METHODS

In order to further evaluate the association of opioids exposure during pregnancy with adverse pregnancy outcomes, we conducted a large historical cohort by linking four databases: medications dispensations, births, pregnancy terminations for medical reasons and infant hospitalizations during the years of 1999-2009. Confounders that were controlled for included maternal age, ethnicity, maternal diabetes, smoking status, parity, obesity, year and folic acid intake. A secondary analysis for total major malformations and for spina bifida was performed using propensity score matching for first trimester exposure.

RESULTS

Of the 101,586 women included in the study, 3003 were dispensed opioids during the first trimester. Intrauterine exposure to opioids was not associated with overall major malformations (adjusted odds ratio (aOR) 0.97, 95% CI 0.83-1.13), cardiovascular malformations (aOR = 0.89, 95% CI 0.70-1.13) other malformations by systems or spina bifida in particular. However, the risk for spina bifida among newborns and abortuses who were exposed to codeine was four times higher than that of the unexposed (aOR = 4.42, 95% CI 1.60-12.23). This association remained significant in a secondary analysis using propensity score matching. Third trimester exposure to opioids was not associated with low birth weight (aOR = 1.08, 95% CI 0.77-1.52), perinatal death (aOR = 1.38, 95% CI 0.64-2.99) and other adverse pregnancy outcomes.

CONCLUSIONS

These findings suggest that opioids exposure (as a homogenous group) is not a significant risk factor for overall major malformations. Exposure to codeine during the first trimester was found to be associated with increased risk of spina bifida. However, this finding was based on a small number of cases and need to be verified in future work.

Genome-wide association analysis for body weight identifies candidate genes related to development and metabolism in rainbow trout (Oncorhynchus mykiss)

Growth is one of the most important traits from both a physiological and economic perspective in aquaculture species. Thus, identifying the genomic regions and genes underpinning genetic variation for this trait is of particular interest in several fish species, including rainbow trout. In this work, we perform a genome-wide association study (GWAS) to identify the genomic regions associated with body weight at tagging (BWT) and at 18 months (BW18M) using a dense SNP panel (57 k) and 4596 genotyped rainbow trout from 105 full-sib families belonging to a Chilean breeding population. Analysis was performed by means of single-step GBLUP approach. Genetic variance explained by 20 adjacent SNP windows across the whole genome is reported. To further explore candidate genes, we focused on windows that explained the highest proportion of genetic variance in the top 10 chromosomes for each trait. The main window from the top 10 chromosomes was explored by BLAST using the first and last SNP position of each window to determine the target nucleotide sequence. As expected, the percentage of genetic variance explained by windows was relatively low, due to the polygenic nature of body weight. The most important genomic region for BWT and BW18M were located on chromosomes 15 and 24 and they explained 2.14% and 3.02% of the genetic variance for each trait, respectively. Candidate genes including several growth factors, genes involved in development of skeletal muscle and bone tissue and nutrient metabolism were identified within the associated regions for both traits BWT and BW18M. These results indicate that body weight is polygenic in nature in rainbow trout, with the most important loci explaining as much as 3% of the genetic variance for the trait. The genes identified here represent good candidates for further functional validation to uncover biological mechanisms underlying variation for growth in rainbow trout.

Modeling prenatal opioid exposure in animals: Current findings and future directions

The past decade has seen a drastic rise in the number of infants exposed to opioids in utero. It is unclear what lasting effect this exposure may have on these children. Animal models of prenatal opioid exposure may provide insight into potential areas of vulnerability. The present review summarizes the findings across animal models of prenatal opioid exposure, including exposure to morphine, methadone, buprenorphine, and oxycodone. Details regarding the drug, doses, and duration of treatment, as well as key findings, are summarized in tables with associated references. Finally, significant gaps in the current preclinical literature and future directions are discussed.

Opioid Drug Use and Acute Cardiac Events Among Pregnant Women in the United States

BACKGROUND

Cardiovascular disease remains a leading cause of pregnancy-associated deaths in the United States. The extent to which increasing opioid use among pregnant women contributes to fatal cardiovascular events is unknown. We examined trends in opioid use among pregnant women over the previous decade and the association between changes in temporal trends in opioid drug use and the incidence of acute cardiac events among mothers.

METHODS

In this retrospective analysis of the Healthcare and Cost Utilization Project, we used a 2-stage stratified cluster sampling of all inpatient hospital discharges from nonfederal hospitals from January 1, 2002 through December 31, 2014. The study population comprised pregnant women aged 13-49 years and related hospitalizations, including delivery. The primary exposure of interest was opioid use during pregnancy. The primary outcome was the occurrence of acute myocardial infarction or cardiac arrest during pregnancy or childbirth.

RESULTS

Among the estimated 57.4 million pregnancy-related inpatient hospitalizations, 511,469 (approximately 1%) had documented use of opioids, cocaine, and/or amphetamines. There was a 300% increase in the use of opioids during pregnancy over the study period, whereas cocaine consumption significantly decreased and that of amphetamine remained stable. Over the 13-year period, the rise in opioid use paralleled a 50% increase in the incidence of acute cardiac events among mothers.

CONCLUSION

Over the previous decade opioid use during pregnancy increased significantly, in parallel with the rise in the incidence of acute cardiac events in pregnancy and childbirth. An effective national policy is needed to address this emerging public health challenge.

Morphine Suppresses Lung Cancer Cell Proliferation Through the Interaction with Opioid Growth Factor Receptor: An In Vitro and Human Lung Tissue Study

BACKGROUND

There have been inconsistent reports on whether opioids promote or inhibit lung cancer growth. In this study, we suggest that opioid growth factor receptor (OGFR), a negative regulator of cell proliferation, is a binding site of morphine and is involved in subsequent morphine-induced lung cancer growth suppression.

METHODS

The expression and distribution of OGFR in human lung cancer tissues and cell lines were assessed with immunohistochemistry and real-time reverse transcription polymerase chain reaction. The human lung cancer cell line, H1975 (adenocarcinoma), which overexpressed OGFR but not μ-opioid receptors, was selected for further analysis to verify the interaction between morphine and OGFR and the impact of morphine on cancer cell growth.

RESULTS

OGFR was expressed in lung cancer tissues and all cancer cell lines tested. Adenocarcinoma showed a higher OGFR expression than squamous cell carcinoma (reverse transcription polymerase chain reaction relative quantitation value: median [interquartile range], 13.1 [9.3-20.0] vs 4.3 [2.2-6.6]; P = 0.003). OGFR expression showed an inverse correlation with cell proliferation (r = -0.92, P = 0.0001). Morphine treatment reduced the median H1975 cell number by approximately 23% (P = 0.03). Growth suppression by morphine was attenuated when OGFR was knocked down. A confocal experiment demonstrated binding of morphine to OGFR. Growth suppression by morphine occurred in the S phase of the cell cycle.

CONCLUSIONS

Lung cancer tissues and cell lines express OGFR. Morphine interacts with OGFR and may suppress lung cancer progression.

Tracing the dynamics of gene transcripts after organismal death

In life, genetic and epigenetic networks precisely coordinate the expression of genes-but in death, it is not known if gene expression diminishes gradually or abruptly stops or if specific genes and pathways are involved. We studied this by identifying mRNA transcripts that apparently increase in relative abundance after death, assessing their functions, and comparing their abundance profiles through postmortem time in two species, mouse and zebrafish. We found mRNA transcript profiles of 1063 genes became significantly more abundant after death of healthy adult animals in a time series spanning up to 96 h postmortem. Ordination plots revealed non-random patterns in the profiles by time. While most of these transcript levels increased within 0.5 h postmortem, some increased only at 24 and 48 h postmortem. Functional characterization of the most abundant transcripts revealed the following categories: stress, immunity, inflammation, apoptosis, transport, development, epigenetic regulation and cancer. The data suggest a step-wise shutdown occurs in organismal death that is manifested by the apparent increase of certain transcripts with various abundance maxima and durations.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.

Opioids, Neutral Endopeptidase, its Inhibitors and Cancer: Is There a Relationship among them?

The role of endogenous animal opioids in the biology of cancer is widely recognized but poorly understood. This is, among others, because of the short half-life of these peptides, which are quickly inactivated by endopeptidases, e.g., neutral endopeptidase (NEP, CD10). It has been established that NEP is engaged in the modulation of the tumor microenvironment, among others that of colon cancer, by exerting influence on cell growth factors, the extracellular matrix and other biologically active substances. Although there are some discrepancies among the findings on the role of both opioids and NEP in cancer development, authors agree that their role seems to depend on the origin, stage and grade of tumor, and even on the method of examination. Moreover, recently, natural inhibitors of NEP, such as sialorphin, opiorphin and spinorphin have been detected. Their analgesic activity has been established. It is interesting to ask whether there is a relationship among opioid peptides, tumor-associated NEP and its inhibitors.

Birth-date dependent arrangement of spinal enkephalinergic neurons: evidence from the preproenkephalin-green fluorescent protein transgenic mice

Enkephalin (ENK) has been postulated to play important roles in modulating nociceptive transmission, and it has been proved that ENKergic neurons acted as a critical component of sensory circuit in the adult spinal cord. Revealing the developmental characteristics of spinal ENKergic neurons will be helpful for understanding the formation and alteration of the sensory circuit under pain status. However, the relationship between the embryonic birth date and the adult distribution of ENKergic neurons has remained largely unknown due to the difficulties in visualizing the ENKergic neurons clearly. Taking advantage of the preproenkephalin-green fluorescent protein (PPE-GFP) transgenic mice in identifying ENKergic neurons, we performed the current birth-dating study and examined the spinal ENKergic neurogenesis. The ENKergic neurons born on different developmental stages and their final location during adulthood were investigated by combining bromodeoxyuridine (BrdU) incorporation and GFP labeling. The spinal ENKergic neurogenesis was restricted at E9.5 to E14.5, and fitted in the same pattern of spinal neurogenesis. Further comparative analysis revealed that spinal ENKergic neurons underwent heterogeneous characteristics. Our study also indicated that the laminar arrangement of ENKergic neurons in the superficial spinal dorsal horn depended on the neurogenesis stages. Taken together, the present study suggested that the birth date of ENKergic neurons is one determinant for their arrangement and function.

Periconceptional use of opioids and the risk of neural tube defects

OBJECTIVE

Opioid medications are among the most effective analgesics. However, the consequences of opioid exposure to the developing human offspring are not known. We assessed whether maternal opioid use in the periconceptional period was associated with the risk of neural tube defects in the offspring.

METHODS

We used data from 1998 to 2010 from the Slone Epidemiology Center Birth Defects Study, an ongoing case-control study. Mothers were interviewed by telephone within 6 months of delivery about sociodemographic factors and exposures during pregnancy including detailed questions on type and timing of medication use. Mothers of 305 offsprings with neural tube defect were compared with mothers of 7,125 offsprings in the nonmalformed control group and 13,405 offsprings in the malformed control group. Periconceptional opioid use was defined as any reported use in the 2 months after the last menstrual period. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for study center.

RESULTS

A higher percentage of mothers of offsprings with neural tube defects (3.9%) reported using an opioid medication than mothers of offsprings in the nonmalformed control group (1.6%) and offsprings in the malformed control group (2.0%) with adjusted ORs of 2.2 (95% CI 1.2 -4.2) and 1.9 (95% CI 1.0 -3.4), respectively. When offsprings were restricted to those with spina bifida, the adjusted ORs were 2.5 (95% CI 1.3-5.0) and 2.2 (95% CI 1.1-4.1), respectively.

CONCLUSION

A 2.2-fold increase in risk would translate to a neural tube defect prevalence of 5.9 per 10,000 live births among women who use opioids. Overall, opioid use in the periconceptional period appeared to be associated with a modest increased risk of neural tube defects.

LEVEL OF EVIDENCE

: II.

Increasing pregnancy-related use of prescribed opioid analgesics

PURPOSE

To quantify the prevalence of prescribed opioid analgesics among pregnant women enrolled in Tennessee Medicaid from 1995 to 2009.

METHODS

Retrospective cohort study of 277,555 pregnancies identified from birth and fetal death certificates, and linked to previously validated, computerized pharmacy records. Poisson regression was used to estimate trends over time, rate ratios, and 95% confidence intervals (CI).

RESULTS

During the study period, 29% of pregnant women filled a prescription for an opioid analgesic. From 1995 to 2009, any pregnancy-related use increased 1.90-fold (95% CI, 1.83-1.98), first trimester use increased 2.27-fold (95% CI, 2.14-2.41), and second or third trimester use increased 2.02-fold (95% CI, 1.93-2.12), after adjusting for maternal characteristics. Any pregnancy-related, first trimester, and second or third trimester use were each more likely among mothers who were at least 21 years old, white, non-Hispanic, prima gravid, resided in nonurban areas, enrolled in Medicaid owing to disability, and who had less than a high school education.

CONCLUSIONS

Opioid analgesic use by Tennessee Medicaid-insured pregnant women increased nearly 2-fold from 1995 to 2009. Additional study is warranted to understand the implications of this increased use.

An opioid growth factor receptor (OGFR) for [Met5]-enkephalin in Chlamys farreri

Opioid growth factor receptor (OGFR) is a receptor for [Met(5)]-enkephalin and plays important roles in the regulation of cell growth and embryonic development. In the present study, a cDNA of 2381 bp for the scallop Chlamys farreri OGFR (designated as CfOGFR) was identified by rapid amplification of cDNA ends (RACE) approach and expression sequence tag (EST) analysis. The complete cDNA sequence of CfOGFR contained an open reading frame (ORF) of 1200 bp, which encoded a protein of 399 amino acids. The amino acid sequence of CfOGFR shared 33-64% similarity with other OGFRs. There was a low complexity domain and a conserved OGFR_N domain at the N-terminal of CfOGFR. The mRNA transcripts of CfOGFR were constitutively expressed in the tested tissues with the highest expression level in hepatopancreas. During the early embryonic development, the mRNA transcripts of CfOGFR could be detected in different development stages, where the expression level presented a downward trend as a whole. The stimulations of LPS, Glu and poly (I:C) significantly induced the expression of CfOGFR mRNA in hemocytes (P < 0.05), while PGN stimulation exerted no influence. Co-IP and western blot results revealed that the CfOGFR in hemocytes displayed high affinity and specificity to [Met(5)]-enkephalin. Exogenous [Met(5)]-enkephalin was observed to inhibit the proliferation of HEK293T cells transfected with pcDNA3.1(+)-CfOGFR in a time and dosage dependent manner. These results collectively indicated that CfOGFR, as a homolog of OGFRs in C. farreri, played an important role in cells proliferation, and might be involved in the immune response of scallops.

Multigenerational effects of adolescent morphine exposure on dopamine D2 receptor function

RATIONALE

The use and misuse of prescription opiates in adolescent populations, and in particular, adolescent female populations, has increased dramatically in the past two decades. Given the significant role that opioids play in neuroendocrine function, exposure to opiates during this critical developmental period could have significant consequences for the female, as well as her offspring.

OBJECTIVES

In the current set of studies, we utilized the female rat to model the transgenerational impact of adolescent opiate exposure.

METHODS

We examined locomotor sensitization in response to the dopamine D2/D3 receptor agonist quinpirole in the adult male progeny (F1 and F2 generations) of females exposed to morphine during adolescence. All females were drug-free for at least 3 weeks prior to conception, eliminating the possibility of direct fetal exposure to morphine.

RESULTS

Both F1 and F2 progeny of morphine-exposed females demonstrated attenuated locomotor sensitization following repeated quinpirole administration. These behavioral effects were coupled with increased quinpirole-induced corticosterone secretion and upregulated kappa opioid receptor and dopamine D2 receptor (D2R) gene expression within the nucleus accumbens.

CONCLUSIONS

These results suggest significant modifications in response to repeated D2R activation in the progeny of females exposed to opiates during adolescence. Given the significant role that the D2R plays in psychopathology, adolescent opiate exposure could shift the vulnerability of future offspring to psychological disorders, including addiction. Moreover, that effects are also observed in the F2 generation suggests that adolescent opiate exposure can trigger transgenerational epigenetic modifications impacting systems critical for motivated behavior.

Maternally administered sustained-release naltrexone in rats affects offspring neurochemistry and behaviour in adulthood

Naltrexone is not recommended during pregnancy. However, sustained-release naltrexone implant use in humans has resulted in cases of inadvertent foetal exposure. Here, we used clinically relevant dosing to examine the effects of maternally administered sustained-release naltrexone on the rat brain by examining offspring at birth and in adulthood. Maternal treatment (naltrexone or placebo implant) started before conception and ceased during gestation, birth or weaning. Morphometry was assessed in offspring at birth and adulthood. Adult offspring were evaluated for differences in locomotor behaviour (basal and morphine-induced, 10 mg/kg, s.c.) and opioid neurochemistry, propensity to self-administer morphine and cue-induced drug-seeking after abstinence. Blood analysis confirmed offspring exposure to naltrexone during gestation, birth and weaning. Naltrexone exposure increased litter size and reduced offspring birth-weight but did not alter brain morphometry. Compared to placebo, basal motor activity of naltrexone-exposed adult offspring was lower, yet they showed enhanced development of psychomotor sensitization to morphine. Developmental naltrexone exposure was associated with resistance to morphine-induced down-regulation of striatal preproenkephalin mRNA expression in adulthood. Adult offspring also exhibited greater operant responding for morphine and, in addition, cue-induced drug-seeking was enhanced. Collectively, these data show pronounced effects of developmental naltrexone exposure, some of which persist into adulthood, highlighting the need for follow up of humans that were exposed to naltrexone in utero.

Gene expression analysis of the embryonic subplate

The subplate layer of the cerebral cortex is comprised of a heterogeneous population of cells and contains some of the earliest-generated neurons. In the embryonic brain, subplate cells contribute to the guidance and areal targeting of thalamocortical axons. At later developmental stages, they are predominantly involved in the maturation and plasticity of the cortical circuitry and the establishment of functional modules. We aimed to further characterize the embryonic murine subplate population by establishing a gene expression profile at embryonic day (E) 15.5 using laser capture microdissection and microarrays. The microarray identified over 300 transcripts with higher expression in the subplate compared with the cortical plate at this stage. Using quantitative reverse transcription-polymerase chain reaction, in situ hybridization (ISH), and immunohistochemistry (IHC), we have confirmed specific expression in the E15.5 subplate for 13 selected genes, which have not been previously associated with this compartment (Abca8a, Cdh10, Cdh18, Csmd3, Gabra5, Kcnt2, Ogfrl1, Pls3, Rcan2, Sv2b, Slc8a2, Unc5c, and Zdhhc2). In the reeler mutant, the expression of the majority of these genes (9 of 13) was shifted in accordance with the altered position of subplate. These genes belong to several functional groups and likely contribute to synapse formation and axonal growth and guidance in subplate cells.

Case-control studies for identifying novel teratogens

The case-control study design offers an operationally efficient approach to measuring an association between an exposure and an outcome, especially when the outcome is rare, as is true for specific birth defects. For example, instead of following 50,000 pregnant women to have sufficient statistical power to identify a doubling in risk of oral clefts associated with a common exposure (e.g., cigarette smoking), 75 cases and 3 controls per case could be studied with equal statistical power. Examples of case sources include hospital or clinical series, or birth defect registries. For validity, control subjects should represent the population base of the cases, which can be difficult to identify for non-population-based case groups. Case-control studies typically rely on retrospective exposure measurement, which presents a major challenge and sets up the possibility of recall bias. Approaches are discussed to keep sources of bias to a minimum, including recall, non-differential information, and selection biases. Case-control studies can play an important role in this process for both hypothesis-generation and hypothesis-testing of potential teratogens. Examples of case-control studies and their contributions to the field are presented. © 2011 Wiley-Liss, Inc.

Maternal treatment with opioid analgesics and risk for birth defects

OBJECTIVE

We examined whether maternal opioid treatment between 1 month before pregnancy and the first trimester was associated with birth defects.

STUDY DESIGN

The National Birth Defects Prevention Study (1997 through 2005) is an ongoing population-based case-control study. We estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIS) for birth defects categories with at least 200 case infants or at least 4 exposed case infants.

RESULTS

Therapeutic opioid use was reported by 2.6% of 17,449 case mothers and 2.0% of 6701 control mothers. Treatment was statistically significantly associated with conoventricular septal defects (OR, 2.7; 95% CI, 1.1-6.3), atrioventricular septal defects (OR, 2.0; 95% CI, 1.2-3.6), hypoplastic left heart syndrome (OR, 2.4; 95% CI, 1.4-4.1), spina bifida (OR, 2.0; 95% CI, 1.3-3.2), or gastroschisis (OR, 1.8; 95% CI, 1.1-2.9) in infants.

CONCLUSION

Consistent with some previous investigations, our study shows an association between early pregnancy maternal opioid analgesic treatment and certain birth defects. This information should be considered by women and their physicians who are making treatment decisions during pregnancy.

Adolescent opiate exposure in the female rat induces subtle alterations in maternal care and transgenerational effects on play behavior

The non-medical use of prescription opiates, such as Vicodin(®) and MSContin(®), has increased dramatically over the past decade. Of particular concern is the rising popularity of these drugs in adolescent female populations. Use during this critical developmental period could have significant long-term consequences for both the female user as well as potential effects on her future offspring. To address this issue, we have begun modeling adolescent opiate exposure in female rats and have observed significant transgenerational effects despite the fact that all drugs are withdrawn several weeks prior to pregnancy. The purpose of the current set of studies was to determine whether adolescent morphine exposure modifies postpartum care. In addition, we also examined juvenile play behavior in both male and female offspring. The choice of the social play paradigm was based on previous findings demonstrating effects of both postpartum care and opioid activity on play behavior. The findings revealed subtle modifications in the maternal behavior of adolescent morphine-exposed females, primarily related to the amount of time females' spend nursing and in non-nursing contact with their young. In addition, male offspring of adolescent morphine-exposed mothers (MOR-F1) demonstrate decreased rough and tumble play behaviors, with no significant differences in general social behaviors (i.e., social grooming and social exploration). Moreover, there was a tendency toward increased rough and tumble play in MOR-F1 females, demonstrating the sex-specific nature of these effects. Given the importance of the postpartum environment on neurodevelopment, it is possible that modifications in maternal-offspring interactions, related to a history of adolescent opiate exposure, plays a role in the observed transgenerational effects. Overall, these studies indicate that the long-term consequences of adolescent opiate exposure can impact both the female and her future offspring.

Expression of opioid growth factor (OGF)-OGF receptor (OGFr) axis in human nonmedullary thyroid cancer

BACKGROUND

Although thyroid cancers are readily treatable with surgery and radioactive iodine, there are problems in managing recurring, as well as locally advanced, thyroid cancer. The opioid growth factor (OGF) and its receptor, OGF receptor (OGFr), form a tonically active, autocrine-paracrine loop that serves to inhibit cell proliferation in a wide variety of normal and abnormal cells and tissues. In the present study we examined the presence and distribution of OGF and OGFr in nonmedullary thyroid cancer, including papillary, follicular, and anaplastic, as well as thyroid tissue from patients with nonmalignant disease.

METHODS

Patient samples of thyroid cancers and goiter were collected at the time of resection and processed for immunohistochemistry of OGF and OGFr, as well as pharmacological binding assays for OGFr.

RESULTS

Both peptide and receptor were detected in the cytoplasm and nucleus of all nonmedullary thyroid cancers, as well as in goiter. Specific and saturable binding of OGFr was found in all thyroid samples.

CONCLUSIONS

The finding that a potent negative growth regulator and its receptor are present in nonmedullary thyroid cancers and thyroid tissues from patients with nonmalignant disease lead us to suggest that the OGF-OGFr axis serves as a regulator of cell proliferation in these tissues. Moreover, modulation of this biological system may be used to treat progression of nonmedullary thyroid neoplasias.

Amyloid precursor protein 96-110 and beta-amyloid 1-42 elicit developmental anomalies in sea urchin embryos and larvae that are alleviated by neurotransmitter analogs for acetylcholine, serotonin and cannabinoids

Amyloid precursor protein (APP) is overexpressed in the developing brain and portions of its extracellular domain, especially amino acid residues 96-110, play an important role in neurite outgrowth and neural cell differentiation. In the current study, we evaluated the developmental abnormalities caused by administration of exogenous APP(96-110) in sea urchin embryos and larvae, which, like the developing mammalian brain, utilize acetylcholine and other neurotransmitters as morphogens; effects were compared to those of beta-amyloid 1-42 (Abeta42), the neurotoxic APP fragment contained within neurodegenerative plaques in Alzheimer's Disease. Although both peptides elicited dysmorphogenesis, Abeta42 was far more potent; in addition, whereas Abeta42 produced abnormalities at developmental stages ranging from early cleavage divisions to the late pluteus, APP(96-110) effects were restricted to the intermediate, mid-blastula stage. For both agents, anomalies were prevented or reduced by addition of lipid-permeable analogs of acetylcholine, serotonin or cannabinoids; physostigmine, a carbamate-derived cholinesterase inhibitor, was also effective. In contrast, agents that act on NMDA receptors (memantine) or alpha-adrenergic receptors (nicergoline), and that are therapeutic in Alzheimer's Disease, were themselves embryotoxic, as was tacrine, a cholinesterase inhibitor from a different chemical class than physostigmine. Protection was also provided by agents acting downstream from receptor-mediated events: increasing cyclic AMP with caffeine or isobutylmethylxanthine, or administering the antioxidant, a-tocopherol, were all partially effective. Our findings reinforce a role for APP in development and point to specific interactions with neurotransmitter systems that act as morphogens in developing sea urchins as well as in the mammalian brain.

The OGF-OGFr axis utilizes the p16INK4a and p21WAF1/CIP1 pathways to restrict normal cell proliferation

Opioid growth factor (OGF) is an endogenous opioid peptide ([Met(5)]enkephalin) that interacts with the OGF receptor (OGFr) and serves as a tonically active negative growth factor in cell proliferation of normal cells. To clarify the mechanism by which OGF inhibits cell replication in normal cells, we investigated the effect of the OGF-OGFr axis on cell cycle activity in human umbilical vein endothelial cells (HUVECs) and human epidermal keratinocytes (NHEKs). OGF markedly depressed cell proliferation of both cell lines by up to 40% of sterile water controls. Peptide treatment induced cyclin-dependent kinase inhibitor (CKI) p16(INK4a) protein expression and p21(WAF1/CIP1) protein expression in HUVECs and NHEKs, but had no effect on p15, p18, p19, or p27 protein expression in either cell type. Inhibition of either p16(INK4a) or p21(WAF1/CIP1) activation by specific siRNAs blocked OGF inhibitory action. Human dermal fibroblasts and mesenchymal stem cells also showed a similar dependence of OGF action on p16(INK4a) and p21(WAF1/CIP1). Collectively, these results indicate that both p16(INK4a) and p21(WAF1/CIP1) are required for the OGF-OGFr axis to inhibit cell proliferation in normal cells.

Endogenous cardiac opioids: enkephalins in adaptation and protection of the heart

Opiates have been used for thousands of years in the form of opium for relief of pain or fever and to induce sleep. However, it was only in the 1970s that the endogenous ligands for the opiate receptors were identified and termed opioid peptides. Opioid peptides activate G protein-coupled receptors in the central and autonomic nervous system, with marked effects on the regulation of pain perception, body temperature, respiration, heart rate and blood pressure. Cardiovascular regulatory effects of endogenous opioids were initially considered to originate from neural centres in the central nervous system, facilitating a regulatory role in neuro-transmission, as demonstrated by the presynaptic co-release from sympathetic neurones of norepinephrine with enkephalin or acetylcholine with enkephalin. However, opioid peptides of myocardial origin have also recently been shown to play a key role in local regulation of the heart. This brief review highlights the key features of the enkephalin opioids in the heart and the current understanding of their role in development, ageing, cardioprotection, hypertension, hypertrophy, and heart failure.

The effects of maternally administered methadone, buprenorphine and naltrexone on offspring: review of human and animal data

Most women using heroin are of reproductive age with major risks for their infants. We review clinical and experimental data on fetal, neonatal and postnatal complications associated with methadone, the current "gold standard", and compare these with more recent, but limited, data on developmental effects of buprenorphine, and naltrexone. Methadone is a micro-opioid receptor agonist and is commonly recommended for treatment of opioid dependence during pregnancy. However, it has undesired outcomes including neonatal abstinence syndrome (NAS). Animal studies also indicate detrimental effects on growth, behaviour, neuroanatomy and biochemistry, and increased perinatal mortality. Buprenorphine is a partial micro-opioid receptor agonist and a kappa-opioid receptor antagonist. Clinical observations suggest that buprenorphine during pregnancy is similar to methadone on developmental measures but is potentially superior in reducing the incidence and prognosis of NAS. However, small animal studies demonstrate that low doses of buprenorphine during pregnancy and lactation lead to changes in offspring behaviour, neuroanatomy and biochemistry. Naltrexone is a non-selective opioid receptor antagonist. Although data are limited, humans treated with oral or sustained-release implantable naltrexone suggest outcomes potentially superior to those with methadone or buprenorphine. However, animal studies using oral or injectable naltrexone have shown developmental changes following exposure during pregnancy and lactation, raising concerns about its use in humans. Animal studies using chronic exposure, equivalent to clinical depot formulations, are required to evaluate safety. While each treatment is likely to have maternal advantages and disadvantages, studies are urgently required to determine which is optimal for offspring in the short and long term.

Opioids and migration, chemotaxis, invasion, and adhesion of human cancer cells

This study was designed to examine the role of opioids on cell migration, chemotaxis, invasion, and adhesion, with an emphasis on whether the opioid growth factor (OGF, [Met(5)]-enkephalin) or the opioid antagonist naltrexone (NTX) impacts any or all of these processes. Drug concentrations of OGF and NTX known to depress or stimulate, respectively, cell proliferation and growth were analyzed. Three different human cancers (pancreatic, colon, and squamous cell carcinoma of the head and neck), represented by seven different cancer cell lines (PANC-1, MIA PaCa-2, BxPC-3, CAL-27, SCC-1, HCT-116, and HT-29), were evaluated. In addition, the influence of a variety of other natural and synthetic opioids on cell motility, invasion, and adhesion was assessed. Positive and negative controls were included for comparison. OGF and NTX at concentrations of 10(-4) to 10(-6)M, and dynorphin A1-8, beta-endorphin, endomorphin-1, endomorphin-2, leucine enkephalin, [D-Pen(2,5)]-enkephalin (DPDPE), [D-Ala(2), MePhe(4), Glycol(5)]-enkephalin (DAMGO), morphine, and U69,593 at concentrations of 10(-6)M, did not alter cell migration, chemotaxis, or invasion of any cancer cell line. OGF and NTX at a concentration of 10(-6)M, and incubation for 24 or 72h, did not change adhesion of these cancer cells to collagen I, collagen IV, fibronectin, laminin, or vitronectin. Moreover, all other opioids tested at 10(-6)M concentrations and for 24h had no effect on adhesion. These results indicate that the inhibitory or stimulatory actions of OGF and NTX, respectively, on cell replication and growth are independent of cell migration, chemotaxis, invasion, and adhesive properties. Moreover, a variety of other exogenous and endogenous opioids, many specific for the micro, delta, or kappa opioid receptors, also did not alter these biological processes, consonant with previous observations of a lack of effects of these compounds and their receptors on the biology of cancer cells.

Proenkephalin-A mRNA Is Widely Expressed in Tissues of the Human Gastrointestinal Tract

BACKGROUND

It has been shown that the non-opioid effects of Met-enkephalin, which is derived from proenkephalin-A, are mediated through a specific opioid growth factor (OGF) receptor which is assumed to be involved in the control of cell growth. The expression and tissue location of proenkephalin-A mRNA in the gastrointestinal tract remains largely unknown.

METHODS

In this study we have analyzed the expression of proenkephalin-A mRNA in the human esophagus, gastrointestinal tract and surrounding organs by means of reverse-transcriptase PCR (RT-PCR).

RESULTS

The present study demonstrates proenkephalin-A mRNA expression in the human esophagus, gastrointestinal tract, pancreas, and gallbladder.

CONCLUSION

The present study demonstrates proenkephalin-A mRNA expression in regions of the human esophagus, gastrointestinal tract, pancreas, and gallbladder tissues which provides information for the future mapping of proenkephalin-A mRNA and protein expression/co-expression at the cellular level.

Effect of naloxone hydrochloride on osteogenesis in chick embryos

Naloxone hydrochloride, an opioid receptors blocker, was administered to chick embryos. Morphological analysis of femoral bones of embryos showed an appreciable increase in the thickness of the perichondral bone cuff in the tubular bone diaphyses and increased mitotic activity in the zone of proliferating young cartilage of the epiphyseal plate.

Opioids and differentiation in human cancer cells

This study was designed to examine the role of opioids on cell differentiation, with an emphasis on the mechanism of opioid growth factor (OGF, [Met5]-enkephalin)-dependent growth inhibition. Three human cancer cell lines (SK-N-SH neuroblastoma and SCC-1 and CAL-27 squamous cell carcinoma of the head and neck), along with OGF and the opioid antagonist naltrexone (NTX) at a dosage (10(-6) M) known to repress or increase, respectively, cell replication, were utilized. The effects on differentiation (neurite formation, process lengths, betaIII-tubulin, involucrin) were investigated in cells exposed to OGF or NTX for up to 6 days. In addition, the influence of a variety of other natural and synthetic opioids on differentiation was examined. OGF, NTX, naloxone, [D-Pen2,5]-enkephalin, dynorphin A1-8, beta-endorphin, endomorphin-1 and -2, [D-Ala2, MePhe4, Glycol5]-enkephalin (DAMGO), morphine, and U69,593 at concentrations of 10(-6) M did not alter cell differentiation of any cancer cell line. In NTX-treated SK-N-SH cells, cellular area was increased 23%, and nuclear area was decreased 17%, from control levels; no changes in cell or nuclear area were recorded in OGF-exposed cells. F-actin concentration was increased 40% from control values in SK-N-SH cells subjected to NTX, whereas alpha-tubulin was decreased 53% in OGF-treated cells. These results indicate that the inhibitory or stimulatory actions of OGF and NTX, respectively, on cell growth in tissue culture are not due to alterations in differentiation pathways. However, exposure to OGF and NTX modified some aspects of cell structure, but this was independent of differentiation. The absence of effects on cancer cell differentiation by a variety of other opioids supports the previously reported lack of growth effects of these compounds.

The delta opioid receptor 1 is expressed by proliferating bile ductules in rats with cholestasis: implications for the study of liver regeneration and malignant transformation of biliary epithelium

In sharp contrast with the normal adult liver, the fetal human and rat livers and the liver of rats with cholestasis secondary to bile duct resection express the preproenkephalin mRNA, which codes for the endogenous opioid peptide Met-enkephalin. Furthermore, Met-enkephalin immunoreactivity is detected in hepatocytes and in proliferating bile ductules in the cholestatic rat liver. These data suggest that in cholestasis endogenous opioids may have a local effect in the cholestatic liver. As endogenous opioids exert their effect by binding to opioid receptors, the presence of opioid receptors in the cholestatic livers would support the hypothesis that Met-enkephalin plays a role in situ. Preliminary data presented in this manuscript reveals the expression of the delta opioid receptor in the liver of rats with cholestasis. This finding suggests that there is a scenario in which Met-enkephalin can bind to opioid receptors in the liver in cholestasis to exert a local effect. In vivo studies in this model of cholestasis with the use of opioid agonist and antagonist will shed light on the possible role of opioidergic regulation of liver regeneration. Studies on the effect of opiate antagonists on the evolution of cholestasis in this animal model may provide insight into the mechanisms of liver regeneration. In addition, as some conditions associated with cholestasis and bile ductular proliferation can be complicated by malignancy, the expression of the delta opioid receptor in malignant tumors of the biliary tree merits research.

Opioid growth factor enhances tumor growth inhibition and increases the survival of paclitaxel-treated mice with squamous cell carcinoma of the head and neck

Paclitaxel is used as a single agent, and in combination with other drugs, as a standard of care in the treatment of squamous cell carcinoma of the head and neck (SCCHN). However, the use of paclitaxel for therapy of SCCHN may be accompanied by serious side effects. Paclitaxel is a known cytotoxic inhibitor of cell proliferation that acts by stabilizing microtubules and inducing apoptosis. Opioid growth factor (OGF), [Met(5)]-enkephalin, is an endogenous peptide that has tonically active inhibitory effects on the growth of SCCHN in vitro and in vivo. OGF action is rapid, reversible, mediated by the nuclear-associated OGF receptor (OGFr), and is not cytotoxic (nor apoptotic related). The present study was designed to examine whether a combination of chemotherapy with paclitaxel and biotherapy with OGF is more effective than either agent alone in inhibiting tumor growth. Moreover, focus was placed on whether there are changes in the side effects known to occur with paclitaxel alone, following this combined therapy. Human SCC-1 cells, derived from a well differentiated SCCHN, were transplanted into athymic mice. The mice were randomized to receive intraperitoneal (i.p.) injections of sterile saline (controls), OGF (10 mg/kg, daily), paclitaxel (8 mg/kg, every other day), or both paclitaxel (8 mg/kg, every other day) and OGF (10 mg/kg, daily) beginning on the day of tumor inoculation. OGF, but not paclitaxel, delayed measurable and visible tumor appearance of mice with SCCHN. Treatment with paclitaxel, but not with other agents, had a marked effect on the body weights. Survival only was reduced in the paclitaxel group, with an average life span of 34.3+/-3.1 days recorded, in comparison to the 50-day survival (date of termination) for all other groups. Beginning after week 4 of tumor inoculation and drug treatment, the tumor weight of the paclitaxel/OGF group was significantly reduced from the control, OGF, and paclitaxel-exposed mice. The OGFr number of the SCCHN tumors was 2.1-fold greater in the animals exposed to OGF or paclitaxel, and elevated 38% in the paclitaxel/OGF group; significant differences from the control group were found for the OGF and paclitaxel groups. These data suggest that combined chemotherapy (i.e., paclitaxel) and biotherapy (OGF) provides a valuable alternative to the standard of care for SCCHN patients.

Gene expression of OGFr in the developing and adult rat brain and cerebellum

The native opioid peptide, [Met5]-enkephalin (termed opioid growth factor (OGF)), is a tonically active negative growth factor targeted to cell proliferation in the developing nervous system. OGF action is mediated by the OGF receptor (OGFr). The present study investigates gene expression of OGFr in the developing and adult brain and cerebellum of the rat using Northern blot analysis and normalization to GAPDH. OGFr was detected in whole brain at embryonic day 20 and birth, and was at least twofold greater than neonatal levels during the first week of life. From postnatal day 15 onwards to adulthood, levels of OGFr mRNA in the whole brain were detectable but less than those at birth. OGFr mRNA in cerebellum was found on embryonic day 20, and remained relatively constant until postnatal day 12 when a sharp increase was recorded. In the third week of life and continuing into adulthood, cerebellar OGFr mRNA was detected at levels comparable to those in postnatal week 1. These results show that message for OGFr is developmentally regulated prior to and after birth, is ubiquitously expressed during development, and is present in the adult brain and cerebellum even though OGF receptor binding is not recorded.

The expression and function of the OGF-OGFr axis - a tonically active negative regulator of growth - in COS cells

This study was designed to examine the presence and role of the opioid growth factor (OGF, [Met(5)]-enkephalin) and the OGF receptor (OGFr) in COS-7 cells; these cells lack classical opioid receptors. Preproenkephalin mRNA, which encodes OGF, was detected by Northern blot analysis, and OGFr mRNA was recorded by RT-PCR. Receptor binding analysis showed specific and saturable binding (K(d)=3.5nm, B(max)=44fmol/mg protein) for OGFr in the nuclear fraction. Both OGF and OGFr were recorded in COS-7 cells by immunocytochemistry. Addition of OGF to log-phase COS-7 cultures depressed growth by 41.6% from control levels, whereas opioid-receptor blockade by the opioid antagonist, naltrexone, increased the number of cells by 29.8% from control values. The effect of OGF was receptor mediated. Exposure to a wide variety of synthetic and natural opioid peptides, including those selective for micro, delta, and kappa opioid receptors, showed that only OGF had an effect. Treatment with antisense OGFr oligonucleotides increased the number of cells by over 2-fold compared to wild-type cultures of COS-7 cells and preparations receiving scrambled oligonucleotides. These results indicate that the OGF-OGFr axis is present and functions in COS-7 cells, and in the absence of classical opioid receptors.

Ontogeny, regional and cellular distribution of the novel metalloprotease neprilysin 2 in the rat: a comparison with neprilysin and endothelin-converting enzyme-1

The localisation of the gene transcripts of a recently discovered peptidase, neprilysin 2 (NEP2), was established by in situ hybridisation in rat tissues during development and adulthood. It was compared with those of neprilysin (NEP), a closely related enzyme in terms of sequence homology or substrate specificity, and of endothelin-converting enzyme 1 (ECE-1) which, like the other two, belongs to the M-13 sub-family of zinc-dependent metallopeptidases. The ontogeny of the three enzymes differed markedly, the expression of NEP2 being restricted to developing and differentiating fields of the CNS, whereas NEP and ECE-1 genes were broadly expressed early on in the CNS and periphery. In contrast to the wide expression of NEP and ECE-1 in peripheral adult tissues and in CNS, NEP2 was almost exclusively expressed in selected neuronal populations of the brain and spinal cord. The only exceptions were the intermediate and anterior lobes of the pituitary as well as the choroid plexuses, where NEP2 was also strongly expressed. These localisations as well as those in the hypothalamic nuclei, together with the previously established pattern of cleaved peptides, suggest the involvement of NEP2 in the metabolism of neurohormones of the hypothalamo-pituitary axis.Complementary distributions of NEP and NEP2 mRNAs were observed in a large number of brain areas with, for instance the former being highly expressed in the striatum in which NEP2 transcripts were almost undetectable. In contrast, NEP2 was highly expressed in numerous thalamic, hypothalamic and brainstem nuclei from which NEP was absent. Since both peptidases are able to cleave the same neuropeptides, this pattern may suggest a complementary role in their peptide inactivation functions in the CNS. Finally, ECE-1 mRNAs were generally observed in neuronal populations known to express the pre-proendothelin-1 gene, confirming the function of the metallopeptidase in endothelin-1 generation.

Postnatal development of mu-opioid receptors in the rat caudate-putamen nucleus parallels asymmetric synapse formation

The mu-opioid receptor (MOR) in the caudate-putamen nucleus (CPN) appears early during prenatal development, and shows a patch-like distribution throughout the postnatal period and adulthood. In the adult rat CPN, neurons in patch compartments receive glutamatergic excitatory input mainly from the cortex through synapses onto spines, many of which express MORs. Thus, MOR expression in spines may be related to corticostriatal synaptogenesis. We used electron microscopic immunocytochemistry to determine potential age-dependent changes in the distribution pattern of MOR during postnatal synaptogenesis in the rat CPN. Immunogold-silver labeling revealed that the dendritic plasmalemmal density of MOR at postnatal day (P) 0 was significantly lower than, but after P10 was similar to, that of adult. In contrast, such age-dependent changes were not observed in axon terminals. Stereological analysis of immunoperoxidase labeling for MOR showed a good correlation in the developmental numerical densities of synapses with MOR-labeled spines and those of total asymmetric axospinous synapses, linear correlation coefficient r=0.99. Synapses with MOR-labeled dendrites, however, had a low correlation with axodendritic synapses (r=0.61), and synapses with MOR-labeled terminals showed no correlation with axospinous and axodendritic synapses (r=0.19). These results provide ultrastructural evidence that the targeting of MOR on the plasma membrane of dendrites and spines parallels the peak period of synaptogenesis during the third postnatal week in the rat CPN. Thus, the postnatal spatiotemporal expression pattern of MOR appears to match the functional maturation of corticostriatal glutamate transmission.

Presence of opioid growth factor and its receptor in the normal dog, cat and horse cornea

OBJECTIVE

To determine if opioid growth factor (OGF, [Met5]enkephalin) and its specific receptor (OGFr) are present in normal cat, dog and horse cornea.

ANIMALS STUDIED

Normal dog, cat and horse.

PROCEDURE

Corneas were obtained from animals euthanized for reasons unrelated to this project. One cornea from each of three normal cats, dogs and horses was evaluated. The right or left cornea from each animal was chosen randomly. Corneas were harvested and placed in corneal storage media for transport to The M.S. Hershey Medical Center of The Pennsylvania State University where immunocytochemistry techniques were used to demonstrate the presence and location of OGF and OGFr. Tissues were rinsed in Sorenson's phosphate buffer, immersed in 20% sucrose in buffer and then snap frozen in isopentane. Corneas were then embedded in OCT medium and 15 micro m cryostat sections were created. Presence of OGF was determined by using a polyclonal antibody to [Met5]enkephalin and assessing immunoreactivity. OGFr presence was determined by using a previously characterized rabbit polyclonal antibody to the receptor.

RESULTS

OGF and OGFr were identified in large quantities in the corneal epithelium of all three species.

CONCLUSION

Opioid growth factor and its specific receptor are present in the corneal epithelium of normal cats, dogs and horses. OGF is present in the cornea of many species and its presence is theorized to inhibit healing of injured tissue.

Defects in the opioid growth factor receptor in human squamous cell carcinoma of the head and neck

BACKGROUND

The endogenous opioid peptide, [Met(5)]-enkephalin, termed opioid growth factor (OGF), interacts with its receptor (OGFr) to play a role as a constitutively expressed inhibitory growth factor in the proliferation of epithelial cells. This study compared protein and gene expression of OGFr in surgical specimens of human squamous cell carcinoma of the head and neck (SCCHN) with normal epithelium.

METHODS

Tissues from 64 patients with SCCHN and from 49 patients undergoing uvulapalatoplasty or tonsillectomy were utilized. Binding affinity and capacity were assessed by receptor binding assays and the levels of OGFr protein were determined by quantitative Western blot analysis. Immunohistochemistry assessed the presence and distribution of OGFr. Levels of OGFr mRNA were quantitated by Northern blot analysis. Protein and gene expressions of OGFr also were evaluated in the margins of SCCHN.

RESULTS

Binding analyses indicated nearly ninefold fewer OGFr binding sites in tumor tissue in comparison with normal samples. The OGFr protein levels were reduced fivefold in tumor tissues relative to normal epithelium. Values of OGFr mRNA were comparable in tumors and normal epithelium. Tumor margins had intermediate levels of protein and binding, but OGFr mRNA values were similar to those of normal specimens.

CONCLUSIONS

These data demonstrate that OGFr is defective in SCCHN and that translation/posttranslation of OGFr protein, but not transcriptional levels of the OGFr gene, is involved. In addition, the attenuated levels of OGFr binding capacity may serve as a marker for SCCHN. These subnormal levels of OGFr may be responsible in part for tumor progression, diminishing the interaction of OGF with OGFr that aids in stabilizing cell replication by an inhibitory mechanism. Gene therapy to reinstate OGFr and/or function could provide a useful treatment for inhibiting tumor progression.

Opioids and the apoptotic pathway in human cancer cells

This study was designed to examine the role of opioids in cell survival, with an emphasis on the mechanism of opioid growth factor (OGF, [Met(5)]-enkephalin)-dependent growth inhibition. Using three human cancer cell lines: MIA PaCa-2 pancreatic adenocarcinoma, HT-29 colon adenocarcinoma, and CAL-27 squamous cell carcinoma of the head and neck, and OGF and the opioid antagonist naltrexone (NTX) at a dosage (10(-6)M) selected because it is known to repress or increase, respectively, cell replication, the effects on apoptosis (TUNEL, Annexin V) and necrosis (trypan blue) were investigated on days 2, 5, and 7 of exposure. In addition, the influence of a variety of other natural and synthetic opioids on apoptosis and necrosis was examined at a dosage of 10(-6)M. OGF, NTX, naloxone, [D-Pen(2,5)]-enkephalin, [Leu(5)]-enkephalin, dynorphin A1-8, beta-endorphin, endomorphin-1 and -2, and methadone at concentrations of 10(-6)M did not alter cell viability of any cancer cell line. Exposure of cultures to [D-Ala(2),MePhe(4),Glycol(5)]-enkephalin (DAMGO), morphine, or etorphine at 10(-6)M significantly increased the number of adherent cells positively stained for TUNEL and Annexin V, as well as the number of necrotic cells in the supernatant, from control levels at all time points studied. The effects of DAMGO, morphine, and etorphine on apoptosis/necrosis were not fully blocked by concomitant administration of naloxone. Despite the increase in cell death in some opioid-treated groups, the number of apoptotic and necrotic adherent cells, and the number of necrotic cells in the supernatant, was no more than 1-2% of the total cell population. These results indicate that the inhibitory (OGF) or stimulatory (NTX) action on cell growth in tissue culture is not due to alterations in apoptotic or necrotic pathways. Moreover, although some opioids increased cell death, and dose-effect relationships need to be established, this activity was not of great magnitude and supports the previously reported lack of growth inhibition of many of these compounds.

Expression of neuropeptide FF, prolactin-releasing peptide, and the receptor UHR1/GPR10 genes during embryogenesis in the rat

Recently, several RF-amide peptides have been identified in mammals. These peptides have a similar C-terminal RF-motif and share some G-protein coupled receptors. Neuropeptide FF (NPFF) and prolactin-releasing peptide (PrRP) are expressed in the same brain areas in the adult rat and act both in prolactin release and cardiovascular regulation. Here, we characterized the embryonal expression from embryonal day 14 to postnatal day 0 of both peptide mRNAs and the mRNA distribution of UHR1/GPR10-like receptor by using in situ hybridization (ISH) and quantitative reverse transcriptase-polymerase chain reaction. NPFF mRNA was found in the spinal cord, caudal solitary tract nucleus, and surprisingly, in the medullary reticular formation. The only peripheral organs displaying NPFF mRNA expression were the lungs and the spleen. PrRP gene expression was seen in the caudal solitary tract nucleus, medullary reticular formation, pontine isthmus and liver, kidney, and testis. The receptor UHR1/GPR10 gene was expressed consistently in the medullary reticular formation and the adrenal gland but also transiently in several locations. All three genes showed weak but even ISH signal in the pituitary. These findings suggest different roles for the peptides during development and indicate that UHR1/GPR10-like receptor could also bind other ligands in addition to PrRP.

Aberrant methylation of CpG islands in intraductal papillary mucinous neoplasms of the pancreas

BACKGROUND & AIMS

The functional abrogation of several tumor suppressor genes, including p16, DPC4, and p53, is a major mechanism underlying pancreatic ductal carcinogenesis. However, mutational inactivation of these genes is relatively uncommon in intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. We hypothesized that an alternative mechanism for gene inactivation (notably, transcriptional silencing by promoter methylation) could be important in the pathogenesis of IPMNs.

METHODS

Using methylation-specific polymerase chain reaction, we analyzed the methylation status of 7 CpG islands previously identified as aberrantly methylated in pancreatic adenocarcinoma (including preproenkephalin [ppENK], p16, and thrombospondin 1) in 51 IPMNs of different histologic grades. The relationship between methylation status and expression was evaluated using reverse-transcription polymerase chain reaction for ppENK and immunohistochemistry for p16.

RESULTS

We found that more than 80% of the IPMNs exhibited hypermethylation of at least one of these CpG islands. Hypermethylation of ppENK and p16 was detected at a significant higher frequency in high-grade (in situ carcinoma) IPMNs than in low-grade (adenoma/borderline) IPMNs (ppENK, 82% vs. 28%, P = 0.0002; p16, 21% vs. 0%, P = 0.04). Furthermore, the average number of methylated loci was significantly higher in high-grade IPMNs than in low-grade IPMNs (2.4 vs. 0.9; P = 0.0008). Aberrant methylation of ppENK and p16 was associated with loss of expression.

CONCLUSIONS

These results suggest that de novo methylation of multiple CpG islands is one of the critical pathways that contributes to the malignant progression of IPMNs.

Delta opioid receptor localization in the rat cerebellum

Opioid receptors have been localized to a number of brain regions in rats as well as in other species. In situ hybridization has demonstrated the presence of mRNA for the delta receptor subtype in adult rat cerebellar cortex and in several deep nuclei, but there are no reports on localization of the delta receptor protein in cerebellar regions. In the present study, both quantitative immunohistochemistry and Western blots reveal the presence of delta receptors in the adult rat cerebellum, using a specific affinity-purified antibody. Purkinje cells and processes, as well as cells in the granule cell layer, were positively stained with the antibody. Quantitation of confocal microscopy images illustrated a lower relative level of delta receptor immunoreactivity in cerebellar cortical neurons as compared to neurons in hippocampal regions, striatum and cerebral cortex. Stimulation of delta receptors with a selective agonist, DPDPE, in frozen sections of rat brain, induced a significant increase in binding of [35S]-GTPgammaS in the cerebellar cortex as compared to basal binding levels, thereby demonstrating coupling of the receptor subtype to G-protein. Functional implications for the delta receptor in the cerebellum are discussed, particularly in light of evidence for the presence of a cerebellar opioid receptor for the endogenous opioid methionine enkephalin during early postnatal life.

Chronic exposure to the opioid growth factor, [Met5]-enkephalin, during pregnancy: maternal and preweaning effects

The opioid peptide, [Met(5)]-enkephalin (termed opioid growth factor, OGF), is an autocrine growth factor that serves as a constitutively active inhibitory agent. OGF crosses the placenta and depresses DNA synthesis in the fetus. The role of OGF in pregnancy and parturition, and the influence exerted on prenatal and neonatal features of the offspring, were studied in rats. Females received daily injections of 10 mg/kg OGF throughout gestation; all offspring were cross-fostered to lactating noninjected dams at birth. No effects on the length of gestation, course of pregnancy, behavior of the pregnant dam, maternal weight gain, or food and water intake throughout gestation were recorded in OGF-treated mothers. Moreover, nociceptive response in these females was not altered by chronic OGF exposure, and no signs of physical dependence or withdrawal could be observed following a challenge by the opioid antagonist naloxone. Litter size and the number of live births per litter of OGF-treated mothers were reduced by 25% from control subjects and a fourfold increase in stillborns was noted for mothers receiving OGF compared to control levels. Histopathologic analysis confirmed the stillborns to have died in utero. OGF-exposed neonates were normal in body weight and crown-to-rump length, but these pups were observed to be lethargic and cyanotic, and had subnormal weights of many organs. Body weights of 10-, 15-, and 21-day-old OGF-exposed rats were reduced 11-27% from control levels. Wet and dry organ weights of the rats maternally subjected to OGF were decreased from control values in six of the eight organs evaluated at 10 days. At weaning, some organs were subnormal in weight. These data lead us to hypothesize that a native opioid peptide-OGF-is integral to certain aspects of maternal, neonatal, and postnatal well-being, and that disruptions in this opioid peptide have serious repercussions on the course of pregnancy and fetal outcome.