Toxic Effect of Cigarette Smoke on Brainstem Nicotinic Receptor Expression: Primary Cause of Sudden Unexplained Perinatal Death

New Step in Understanding the Pathogenetic Mechanism of Sudden Infant Death Syndrome: Involvement of the Pontine Reticular Gigantocellular Nucleus

This study aimed to investigate, for the first time, the potential role of the gigantocellular nucleus, a component of the reticular formation, in the pathogenetic mechanism of Sudden Infant Death Syndrome (SIDS), an event frequently ascribed to failure to arouse from sleep. This research was motivated by previous experimental studies demonstrating the gigantocellular nucleus involvement in regulating the sleep-wake cycle. We analyzed the brains of 48 infants who died suddenly within the first 7 months of life, including 28 SIDS cases and 20 controls. All brains underwent a thorough histological and immunohistochemical examination, focusing specifically on the gigantocellular nucleus. This examination aimed to characterize its developmental cytoarchitecture and tyrosine hydroxylase expression, with particular attention to potential associations with SIDS risk factors. In 68% of SIDS cases, but never in controls, we observed hypoplasia of the pontine portion of the gigantocellular nucleus. Alterations in the catecholaminergic system were present in 61% of SIDS cases but only in 10% of controls. A strong correlation was observed between these findings and maternal smoking in SIDS cases when compared with controls. In conclusion we believe that this study sheds new light on the pathogenetic processes underlying SIDS, particularly in cases associated with maternal smoking during pregnancy.

Sudden Unexpected Postnatal Collapse: Review and Management

Sudden unexpected postnatal collapse (SUPC) of healthy newborns is a catastrophic event caused by cardiorespiratory collapse in a healthy newborn. The most common cause of SUPC is poor positioning of the newborn during skin-to-skin contact or breastfeeding when the newborn is not being observed by a health professional, attentive parent, or caretaker. Maternal/newborn health care professionals need to know about the essential information, definitions, incidence, risk factors, clinical presentation, outcomes, and prevention and management strategies to minimize the occurrence and impact of SUPC. A sample SUPC hospital policy is included in the manuscript.

Environmental Exposure Science and Human Health

Human health and environmental exposure form an inseparable binomial [...].

The roles of familial transmission and smoking during pregnancy on executive function skills: A sibling-comparison study

This research examines maternal smoking during pregnancy and risk for poorer executive function in siblings discordant for exposure. Data (N = 173 families) were drawn from the Missouri Mothers and Their Children study, a sample, identified using birth records (years 1998-2005), in which mothers changed smoking behavior between two pregnancies (Child 1 [older sibling]: M age = 12.99; Child 2 [younger sibling]: M age = 10.19). A sibling comparison approach was used, providing a robust test for the association between maternal smoking during pregnancy and different aspects of executive function in early-mid adolescence. Results suggested within-family (i.e., potentially causal) associations between maternal smoking during pregnancy and one working memory task (visual working memory) and one response inhibition task (color-word interference), with increased exposure associated with decreased performance. Maternal smoking during pregnancy was not associated with stop-signal reaction time, cognitive flexibility/set-shifting, or auditory working memory. Initial within-family associations between maternal smoking during pregnancy and visual working memory as well as color-word interference were fully attenuated in a model including child and familial covariates. These findings indicate that exposure to maternal smoking during pregnancy may be associated with poorer performance on some, but not all skills assessed; however, familial transmission of risk for low executive function appears more important.

Harmful Effect of Intrauterine Smoke Exposure on Neuronal Control of "Fetal Breathing System" in Stillbirths

This article is aimed to contribute to the current knowledge on the role of toxic substances such as nicotine on sudden intrauterine unexplained deaths’ (SIUDS’) pathogenetic mechanisms. The in-depth histopathological examination of the autonomic nervous system in wide groups of victims of SIUDS (47 cases) and controls (20 cases), with both smoking and no-smoking mothers, highlighted the frequent presence of the hypodevelopment of brainstem structures checking the vital functions. In particular, the hypoplasia of the pontine parafacial nucleus together with hypoplastic lungs for gestational age were observed in SIUDS cases with mothers who smoked cigarettes, including electronic ones. The results allow us to assume that the products of cigarette smoke during pregnancy can easily cross the placental barrier, thus entering the fetal circulation and damaging the most sensitive organs, such as lungs and brain. In a non-negligible percentage of SIUDS, the mothers did not smoke. Furthermore, based on previous and ongoing studies conducted through analytical procedures and the use of scanning electron microscopy, the authors envisage the involvement of toxic nanoparticles (such as agricultural pesticides and nanomaterials increasingly used in biomedicine, bioscience and biotechnology) in the death pathogenesis, with similar mechanisms to those of nicotine.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

Prenatal Exposure to Tobacco and Alcohol Alters Development of the Neonatal Auditory System

Prenatal exposures to alcohol (PAE) and tobacco (PTE) are known to produce adverse neonatal and childhood outcomes including damage to the developing auditory system. Knowledge of the timing, extent, and combinations of these exposures on effects on the developing system is limited. As part of the physiological measurements from the Safe Passage Study, Auditory Brainstem Responses (ABRs) and Transient Otoacoustic Emissions (TEOAEs) were acquired on infants at birth and one-month of age. Research sites were in South Africa and the Northern Plains of the U.S. Prenatal information on alcohol and tobacco exposure was gathered prospectively on mother/infant dyads. Cluster analysis was used to characterize three levels of PAE and three levels of PTE. Repeated-measures ANOVAs were conducted for newborn and one-month-old infants for ABR peak latencies and amplitudes and TEOAE levels and signal-to-noise ratios. Analyses controlled for hours of life at test, gestational age at birth, sex, site, and other exposure. Significant main effects of PTE included reduced newborn ABR latencies from both ears. PTE also resulted in a significant reduction of ABR peak amplitudes elicited in infants at 1-month of age. PAE led to a reduction of TEOAE amplitude for 1-month-old infants but only in the left ear. Results indicate that PAE and PTE lead to early disruption of peripheral, brainstem, and cortical development and neuronal pathways of the auditory system, including the olivocochlear pathway.

Nicotinic Receptors in the Brainstem Ascending Arousal System in SIDS With Analysis of Pre-natal Exposures to Maternal Smoking and Alcohol in High-Risk Populations of the Safe Passage Study

Pre-natal exposures to nicotine and alcohol are known risk factors for sudden infant death syndrome (SIDS), the leading cause of post-neonatal infant mortality. Here, we present data on nicotinic receptor binding, as determined by 125I-epibatidine receptor autoradiography, in the brainstems of infants dying of SIDS and of other known causes of death collected from the Safe Passage Study, a prospective, multicenter study with clinical sites in Cape Town, South Africa and 5 United States sites, including 2 American Indian Reservations. We examined 15 pons and medulla regions related to cardiovascular control and arousal in infants dying of SIDS (n = 12) and infants dying from known causes (n = 20, 10 pre-discharge from time of birth, 10 post-discharge). Overall, there was a developmental decrease in 125I-epibatidine binding with increasing postconceptional age in 5 medullary sites [raphe obscurus, gigantocellularis, paragigantocellularis, centralis, and dorsal accessory olive (p = 0.0002-0.03)], three of which are nuclei containing serotonin cells. Comparing SIDS with post-discharge known cause of death (post-KCOD) controls, we found significant decreased binding in SIDS in the nucleus pontis oralis (p = 0.02), a critical component of the cholinergic ascending arousal system of the rostral pons (post-KCOD, 12.1 ± 0.9 fmol/mg and SIDS, 9.1 ± 0.78 fmol/mg). In addition, we found an effect of maternal smoking in SIDS (n = 11) combined with post-KCOD controls (n = 8) on the raphe obscurus (p = 0.01), gigantocellularis (p = 0.02), and the paragigantocellularis (p = 0.002), three medullary sites found in this study to have decreased binding with age and found in previous studies to have abnormal indices of serotonin neurotransmission in SIDS infants. At these sites, 125I-epibatidine binding increased with increasing cigarettes per week. We found no effect of maternal drinking on 125I-epibatidine binding at any site measured. Taken together, these data support changes in nicotinic receptor binding related to development, cause of death, and exposure to maternal cigarette smoking. These data present new evidence in a prospective study supporting the roles of developmental factors, as well as adverse exposure on nicotinic receptors, in serotonergic nuclei of the rostral medulla-a finding that highlights the interwoven and complex relationship between acetylcholine (via nicotinic receptors) and serotonergic neurotransmission in the medulla.

Impact of nicotine and maternal BMI on fetal birth weight

BACKGROUND

According to the World Health Organization, smoking is the most important risk factor for adverse pregnancy outcomes in industrialized nations. As the individual factors (body mass index - BMI (kg/m2) - and cigarette consumption) have been extensively investigated in pregnancy, we aimed to establish how maternal BMI and nicotine interact with regard to perinatal outcomes and birth weight.

METHODS

Data from 110.047 singleton pregnancies, achieved from the German Perinatal Survey in Schleswig-Holstein and registered between 2010 and 2017 were analyzed in August 2018 concerning maternal BMI and smoking. The BMI was taken from the maternity log. Information concerning the smoking status were self-reported and further subdivided into the following four categories: a) non-smokers; b) 1-7 cigarettes/day; c) 8-14 cigarettes/ day; and d) ≥ 15 cigarettes/ day. Furthermore, we classified women by their BMI into underweight, normal weight, overweight and obese. Comparisons between non-smokers and the respective smoking group, and their relationship with maternal BMI were performed by the t-test (birth weight). A P-value ≤0.05 was considered to indicate statistical significance.

RESULTS

A number of 97.092 women (88.2%) were non-smokers and 12.955 (11.8%) were smokers. Furthermore 10.3% of women of normal weight smoked during pregnancy, but both high and low BMI were associated with a high prevalence of smoking. The proportion of smokers was highest (18.1%) among underweight women (BMI ≤ 18.5 kg/m2). A large number of smokers (15.5%) were registered in the obesity group (BMI ≥ 30 kg/m2). Mean birth weight (≥ 37 + 0 gestational age) increased with increasing maternal BMI, and was reduced by smoking for every BMI category. The differences between smokers and non-smokers were always highly significant (p < 0.001). Mean birth weight varied between 2995 g in underweight frequent smokers and 3607 g in obese non-smokers.

CONCLUSION

Both maternal BMI and smoking during pregnancy influences the birth weight and therefore pregnancy outcome. Smoking during pregnancy was significantly associated with low birth weight. Pregnant women should be advised to cease or at least reduce smoking in order to improve the birth weight of the newborn and to minimize child morbidities.

Immunohistochemical Expression of the Alpha Nicotinic Acetylcholine Receptor 7 in the Human Normal, Diabetic, and Preeclamptic Placenta and Products of Conception

Preeclampsia (PE) and gestational diabetes (GD) are complications in advanced pregnancy while miscarriage for early pregnancy. However, the etiological factors are not well understood. Smoking has been associated with these complications as well as the sudden intrauterine deaths, sudden infant death, miscarriages, and still births. However, the immunolocalization of alpha 7 nicotine acetylcholine receptor (α7-nAChR) is not studied. Materials and Methods: α7-nAChR subunit expression was evaluated in 10 paraffin-embedded placental tissues after delivery and 10 tissue samples of products of conception during first trimester by immunohistochemistry. Among the placental tissues, two samples were normal placental tissue, four from PE mother, and four from GD mother. The expression of α7-nAChR was compared between the two groups in general and within the subgroups of placenta as well. Protein expression was evaluated using the nuclear labeling index (%) of villi with positive cells stained, positive cells in the decidua, and intensity of staining in the outer villous trophoblast layer. Results: The expression of α7-nAChR protein was high in all the cases of placenta and products of conception (POCs). α7-nAChR expression showed no notable differences among different cases of miscarriages irrespective of the mother's age and gestational age at which the event occurred. However, there were some changes among the normal, PE, and GD placental groups in the linings of the blood vessels. Changes were restricted to the villi (as opposed to the decidua) lining cells, both cytotrophoblast and syncytiotrophoblast, and were specific to the α7 subunit. PE blood vessel lining was thicker and showed more expression of this receptor in endothelial cells and myofibroblasts in PE and GD groups. In POCs, the strong expression was observed in the decidua myocytes of maternal blood vessels and in syncytiotrophoblast and cytotrophoblast of chronic villi. Conclusion: Nicotine acetyl choline receptors are found to be expressed highly in the placental tissues and in products of conception. They may be associated with the sudden perinatal deaths and miscarriages or complications of pregnancy.

The Role of Maternal Smoking in Sudden Fetal and Infant Death Pathogenesis

Maternal smoking is a risk factor for both sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death syndrome (SIUDS). Both SIDS and SIUDS are more frequently observed in infants of smoking mothers. The global prevalence of smoking during pregnancy is 1.7% and up to 8.1% of women in Europe smoke during pregnancy and worldwide 250 million women smoke during pregnancy. Infants born to mothers who smoke have an abnormal response to hypoxia and hypercarbia and they also have reduced arousal responses. The harmful effects of tobacco smoke are mainly mediated by release of carbon monoxide and nicotine. Nicotine can enter the fetal circulation and affect multiple developing organs including the lungs, adrenal glands and the brain. Abnormalities in brainstem nuclei crucial to respiratory control, the cerebral cortex and the autonomic nervous system have been demonstrated. In addition, hypodevelopment of the intermediolateral nucleus in the spinal cord has been reported. It initiates episodic respiratory movements that facilitate lung development. Furthermore, abnormal maturation and transmitter levels in the carotid bodies have been described which would make infants more vulnerable to hypoxic challenges. Unfortunately, smoking cessation programs do not appear to have significantly reduced the number of pregnant women who smoke.

Substantia Nigra Abnormalities Provide New Insight on the Neural Mechanisms Underlying the Sleep-Arousal Phase Dysfunctions in Sudden Infant Death Syndrome

The purpose of this study was to research possible developmental alterations of the substantia nigra (SN) in sudden infant death syndrome (SIDS), a syndrome frequently attributed to arousal failure from sleep. Brain stems of 46 victims of sudden infant death, aged from 1 to about 7 months (4 to 30 postnatal weeks), were investigated. Twenty-six of these cases were diagnosed as SIDS, due to the lack of any pathological finding, while the remaining 20 cases in which the cause of death was determined at autopsy served as controls. Maternal smoking was reported in 77% of SIDS and 10% of controls. Histopathological examination of the SN was done on 5-µm-thick sections of caudal midbrain stained with both hematoxylin-eosin and Klüver-Barrera. Densitometry, immunohistochemistry and histochemistry were applied to highlight the neuronal concentration, the tyrosine hydroxylase (TH) expression, and the presence of neuromelanin (NM) in this structure. Hypoplasia of the pars compacta portion of the SN was observed in 69% of SIDS but never in controls; TH expression was significantly higher in controls than in SIDS; and NM was observed only in 4 infants of the control group but not in SIDS. A significant correlation was found between SIDS, hypoplasia/low neuronal density, low TH expression in the pars compacta, and maternal smoking. Because the SN pars compacta, being the major dopamine brain center, controls many functions, including the sleep-arousal phase, its alterations, especially concurrently with smoking exposure, may contribute to explain the pathogenesis of SIDS that occur in the great part of cases at awakening from sleep.

Neurochemistry of the Kölliker-Fuse nucleus from a respiratory perspective

The Kölliker-Fuse nucleus (KF) is a functionally distinct component of the parabrachial complex, located in the dorsolateral pons of mammals. The KF has a major role in respiration and upper airway control. A comprehensive understanding of the KF and its contributions to respiratory function and dysfunction requires an appreciation for its neurochemical characteristics. The goal of this review is to summarize the diverse neurochemical composition of the KF, focusing on the neurotransmitters, neuromodulators, and neuropeptides present. We also include a description of the receptors expressed on KF neurons and transporters involved in each system, as well as their putative roles in respiratory physiology. Finally, we provide a short section reviewing the literature regarding neurochemical changes in the KF in the context of respiratory dysfunction observed in SIDS and Rett syndrome. By over-viewing the current literature on the neurochemical composition of the KF, this review will serve to aid a wide range of topics in the future research into the neural control of respiration in health and disease.