Neonatal Nicotine Exposure Research Articles

Neonatal nicotine exposure affects adult rat hepatic pathways involved in endoplasmic reticulum stress and macroautophagy in a sex-dependent manner.

Nonalcoholic fatty liver disease (NAFLD) involves changes in hepatic pathways, as lipogenesis, oxidative stress, endoplasmic reticulum (ER) stress, and macroautophagy. Maternal nicotine exposure exclusively during lactation leads to fatty liver (steatosis) only in the adult male offspring, not in females. Therefore, our hypothesis is that neonatal exposure to nicotine sex-dependently affects the signaling pathways involved in hepatic homeostasis of the offspring, explaining the hepatic lipid accumulation phenotype only in males. For this, between postnatal days 2 and 16, Wistar rat dams were implanted with osmotic minipumps, which released nicotine (NIC; 6 mg/Kg/day) or vehicle. The livers of offspring were evaluated at postnatal day 180. Only the male offspring that had been exposed to nicotine neonatally showed increased protein expression of markers of unfolded protein response (UPR), highlighting the presence of ER stress, as well as disruption of the activation of the macroautophagy repair pathway. These animals also had increased expression of diacylglycerol O-acyltransferase 1 and 4-hydroxynonenal, suggesting increased triglyceride esterification and oxidative stress. These parameters were not altered in the female offspring that had been neonatally exposed to nicotine, however they exhibited increased phospho adenosine monophosphate-activated protein kinase pAMPK expression, possibly as a protective mechanism. Thus, the disturbance in the hepatic homeostasis by UPR, macroautophagy, and oxidative stress modifications seem to be the molecular mechanisms underlying the liver steatosis in the adult male offspring of the nicotine-programming model. This highlights the importance of maternal smoking cessation during breastfeeding to decrease the risk of NAFLD development, especially in males.

Neurological repercussions of neonatal nicotine exposure: A review.

Smoking during pregnancy is hazardous to both the mother and the foetus, according to a substantial amount of recorded data. Exposure to nicotine and other compounds in cigarette smoke increases the risk of sudden infant death syndrome (SIDS) by two to five times during pregnancy. Serotonergic abnormalities have been discovered in SIDS infants in the zone of the medulla oblongata, which is known to control cardio-respiratory function. SIDS establishes a connection between depression, learning difficulties and behavioural disorders. Prenatal nicotine intake during the second trimester affects the dopaminergic neurological system, making the foetal brain more susceptible to nicotine and developing ADHD symptoms not just in a foetus but in adolescents also. Prenatal nicotine exposure alters the neurological route of neurotransmitters, acetylcholine and dopamine. Nicotine enhances neuronal activity in adults but desensitizes these processes in babies and young children exposed prenatally. The impact of a neurotoxin like nicotine is determined by the amount and duration of exposure. Continued exposure throughout pregnancy will influence a wide range of activities in the neurodevelopment, whereas exposure confined to a single stage of pregnancy may only affect the processes that are forming at that stage. To decrease the effect of nicotine on neonates due to maternal smoking strategies like nicotine replacement therapy (NRT), folic acid treatment and other behavioural treatments have been studied. Hence, this review focuses on the impact of exposure to nicotine on neonates, which results in various neurological consequences and smoking cessation therapies.

Neonatal nicotine exposure changes insulin status in fat depots: sex-related differences.

Nicotine is the main psychoactive substance present in cigarette smoke that is transferred to the baby by breast milk. In rats, maternal nicotine exposure during breastfeeding induces obesogenesis and hormone dysfunctions in adult male offspring. As glucocorticoid (GC), insulin, and vitamin D change both adipogenesis and lipogenesis processes, we assessed parameters related to metabolism and action of these hormones in visceral and subcutaneous adipose tissues (VAT and SAT) of adult male and female rats in a model of neonatal nicotine exposure. At postnatal (PN) day 2, dams were kept with six pups (three per sex) and divided into nicotine and control groups for implantation of osmotic minipumps that released 6mg/kg nicotine or saline, respectively. At PN180, fat mass, hormone levels, and protein contents of biomarkers of the GC activation and receptor (11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor alpha), insulin signaling pathway [insulin receptor beta (IRβ), phosphorylated insulin receptor substrate 1, insulin receptor substrate 1 (IRS1), phosphorylated serine/threonine kinase (pAKT), serine/threonine kinase, glucose transporter type 4 (GLUT4)], and vitamin D activation and receptor (1α-hydroxylase and vitamin D receptor) were evaluated. While nicotine-exposed males showed increased fat mass, hypercorticosteronemia, hyperinsulinemia, and higher 25-hydroxyvitamin D, these alterations were not observed in nicotine-exposed females. Nicotine-exposed males only showed lower IRS1 in VAT, while the females had hyperglycemia, higher pAKT in VAT, while lower IRβ, IRS1, and GLUT4 in SAT. Parameters related to metabolism and action of GC and vitamin D were unaltered in both sexes. We evidence that exposure exclusively to nicotine during breastfeeding affects the hormone status and fat depots of the adult progeny in a sex-dependent manner.

Nicotine exposure during lactation causes disruption of hedonic eating behavior and alters dopaminergic system in adult female rats

Tobacco smoke during gestation is associated with increased consumption of palatable foods by the offspring in humans and rats. Postpartum relapse is observed in lactating women who quit smoking during pregnancy, putting their children at risk of adverse health outcomes caused by secondhand smoke. Nicotine is transferred through milk and alters the dopaminergic reward system of adult male rats, reducing dopamine action in the nucleus accumbens (NAc) and hypothalamic arcuate nucleus. Here, we evaluated the long-term effects of nicotine-only exposure during lactation on eating behavior, anxiety, locomotion, dopaminergic system, hypothalamic leptin signaling and nicotinic receptor in the adult female rat progeny. Two days after birth (PN2), Wistar rat dams were separated into control and nicotine (Nic) groups for implantation of osmotic minipumps that released respectively saline or 6 mg/kg nicotine. Lactating dams were kept with 6 pups. After weaning (PN21; nicotine withdrawal), only the female offspring were studied. Euthanasia occurred at PN180. Nic females showed hyperphagia, preference for a high-sucrose diet, increased anxiety-like behavior, lower tyrosine hydroxylase (TH), lower dopamine transporter and higher dopamine receptor (Drd2) in NAc; lower Drd1 in prefrontal cortex and lower TH in dorsal striatum (DS). These animals showed changes that can explain their hyperphagia, such as: lower leptin signaling pathway (Leprb, pJAK2, pSTAT3) and Chrna7 expression in hypothalamus. Neonatal nicotine exposure affects the brain reward system of the female progeny differently from males, mainly decreasing dopamine production in NAc and DS. Therefore, Nic females are more susceptible to develop food addiction and obesity.

Early Life Exposure to Nicotine: Postnatal Metabolic, Neurobehavioral andRespiratory Outcomes and the Development of Childhood Cancers.

Cigarette smoking during pregnancy is associated with numerous obstetrical, fetal, and developmental complications, as well as an increased risk of adverse health consequences in the adult offspring. Nicotine replacement therapy and electronic nicotine delivery systems (e-cigarettes) have been developed as a pharmacotherapy for smoking cessation and are considered safer alternatives for women to smoke during pregnancy. The safety of nicotine replacement therapy use during pregnancy has been evaluated in a limited number of short-term human trials, but there is currently no information on the long-term effects of developmental nicotine exposure in humans. However, animal studies suggest that nicotine alone may be a key chemical responsible for many of the long-term effects associated with maternal cigarette smoking on the offspring and increases the risk of adverse neurobehavioral outcomes, dysmetabolism, respiratory illness, and cancer. This review will examine the long-term effects of fetal and neonatal nicotine exposure on postnatal health.

Nicotine exposure during breastfeeding reduces sympathetic activity in brown adipose tissue and increases in white adipose tissue in adult rats: Sex-related differences

Nicotine transfer via breast milk induces obesity in the adult offspring. We hypothesize that sympathetic nervous system (SNS) activity, brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) lipogenesis/adipogenesis are altered in adult rats that were exposed to nicotine exclusively during the breastfeeding period. Lactating Wistar rats were separated into two groups: nicotine (NIC), dams implanted with osmotic minipumps containing 6 mg/kg of nicotine at postnatal day (PN) 2; control, dams were implanted with saline-containing minipumps. Euthanasia occurred at PN120 or PN180. NIC offspring had lower BAT SNS activity and higher BAT lipid content. NIC males showed lower UCP1, β3-AR and CPT1a, while NIC females showed lower UCP1, TRα1, CPT1a, suggesting lower thermogenesis. NIC males showed higher WAT SNS activity, WAT β3-AR, adrenal catecholamine, FAS, PPARγ and adipocytes area, while NIC females showed higher ACC, FAS, CEBPβ and PPARγ. These findings indicate increased lipogenesis/adipogenesis in both sexes, with a possible compensatory sympathetic activated-lipolysis in males. NIC males had higher hypothalamic pAMPK/AMPK, explaining the lower BAT sympathetic activity. Neonatal nicotine exposure reduces BAT SNS activity and thermogenesis, and, only in males, increases WAT adipogenesis/lipogenesis, despite higher WAT SNS activity. These alterations can be associated with obesogenesis in this programming model.

Neonatal Nicotine Exposure Primes Midbrain Neurons to a Dopaminergic Phenotype and Increases Adult Drug Consumption

BackgroundNicotine intake induces addiction through neuroplasticity of the reward circuitry, altering the activity of dopaminergic neurons of the ventral tegmental area. Prior work demonstrated that altered circuit activity can change neurotransmitter expression in the developing and adult brain. Here we investigated the effects of neonatal nicotine exposure on the dopaminergic system and nicotine consumption in adulthood. MethodsMale and female mice were used for two-bottle-choice test, progressive ratio breakpoint test, immunohistochemistry, RNAscope, quantitative polymerase chain reaction, calcium imaging, and DREADD (designer receptor exclusively activated by designer drugs)-mediated chemogenic activation/inhibition experiments. ResultsNeonatal nicotine exposure potentiates drug preference in adult mice, induces alterations in calcium spike activity of midbrain neurons, and increases the number of dopamine-expressing neurons in the ventral tegmental area. Specifically, glutamatergic neurons are first primed to express transcription factor Nurr1, then acquire the dopaminergic phenotype following nicotine re-exposure in adulthood. Enhanced neuronal activity combined with Nurr1 expression is both necessary and sufficient for the nicotine-mediated neurotransmitter plasticity to occur. ConclusionsOur findings illuminate a new mechanism of neuroplasticity by which early nicotine exposure primes the reward system to display increased susceptibility to drug consumption in adulthood.

Epigenetic down-regulation of BKCa channel by miR-181a contributes to the fetal and neonatal nicotine-mediated exaggerated coronary vascular tone in adult life

BackgroundFetal origin of adult cardiovascular disease is one of the most pressing public concerns and economic problem in modern life. Maternal cigarette smoking/nicotine abuse increases the risk of cardiovascular disease in offspring. However, the underlying mechanisms and theranostics remain unclear. We hypothesized that fetal and neonatal nicotine exposure enhances microRNA-181a (miR-181a) which targets large-conductance Ca2+-activated K+ (BKCa) channels, resulting in increased coronary vascular tone in adult offspring. MethodsNicotine or saline was administered to pregnant rats via subcutaneous osmotic minipumps from gestational day 4 until postnatal day 10. Experiments were conducted in adult (~6 month old) male offspring. ResultsNicotine enhanced pressure-induced coronary vascular tone, which was abrogated by BKCa channel blocker. Nicotine selectively attenuated coronary BKCa β1 but not α subunit expression. Functionally, nicotine suppressed BKCa current density and inhibited BKCa activator NS1619-induced coronary relaxations. Furthermore, activation of BKCa increased coronary flow and improved heart ischemia/reperfusion-induced infarction. Nicotine selectively enhanced miR-181a expression. MiR-181a mimic inhibited BKCa β1 expression/channel current and decreased NS1619-induced coronary relaxation. Antioxidant eliminated the difference of BKCa current density between the saline and nicotine-treated groups and partially restored NS1619-induced relaxation in nicotine group. MiR-181a antisense decreased vascular tone and eliminated the differences between nicotine exposed and control groups. ConclusionFetal and neonatal nicotine exposure-mediated miR-181a overexpression plays an important role in nicotine-enhanced coronary vascular tone via epigenetic down-regulation of BKca channel mechanism, which provides a potentially novel therapeutic molecular target of miR-181a/BKca channels for the treatment of coronary heart ischemic disease.

Activation of immediate early genes by nicotine after chronic neonatal nicotine exposure in brain areas involved in stress and anxiety responses

Maternal smoking has negative long-term consequences on affective behaviors, and in rodents, chronic neonatal nicotine exposure (CNN) results in increased anxiety. In rat pups, acute nicotine stimulation activates brain regions associated with stress and anxiety, but chronic nicotine exposure could desensitize of nicotinic acetylcholine receptors, the molecular target of nicotine. Here, we determined whether CNN affected neuronal activation by an acute nicotine challenge. Using in situ hybridization, we analyzed mRNA expression of the immediate-early genes (IEGs) c-Fos, Arc, Egr-1 and Npas4, which are markers for neuronal activation and implicated in synaptic plasticity. Following CNN (6 mg/kg/day) or control treatment from postnatal day (P)1 to P7, an acute i.p. nicotine (0.7 mg/kg) or saline injection (control) was administered on P8, and brains collected after 30 min. In drug-naive pups, acute nicotine stimulated IEGs expression specifically in brain areas associated with innate anxiety including the paraventricular hypothalamic nucleus, central nucleus of the amygdala (CeA), and locus coeruleus (LC). Following CNN, acute nicotine stimulated IEG expression in all three areas, but activation was significantly reduced in the LC (c-Fos, Egr-1, Npas4), and CeA (c-Fos). Notably, nicotine-induced Npas4 expression was greatly diminished in the LC, which may affect inhibitory synapse formation in noradrenergic neurons. Thus, after CNN, neurons located in areas associated with anxiety brain circuitry maintained responsiveness to nicotine, but tolerance differentially developed to nicotine. In the developing brain, repeated activation by nicotine of areas related to limbic pathways could alter circuit connectivity and increase responsiveness to stress and anxiety later in life.

Maternal nicotine exposure leads to decreased cardiac protein disulfide isomerase and impaired mitochondrial function in male rat offspring.

Smoking throughout pregnancy can lead to complications during gestation, parturition and neonatal development. Thus, nicotine replacement therapies are a popular alternative thought to be safer than cigarettes. However, recent studies in rodents suggest that fetal and neonatal nicotine exposure alone results in cardiac dysfunction and high blood pressure. While it is well known that perinatal nicotine exposure causes increased congenital abnormalities, the mechanisms underlying longer-term deficits in cardiac function are not completely understood. Recently, our laboratory demonstrated that nicotine impairs placental protein disulfide isomerase (PDI) triggering an increase in endoplasmic reticulum stress, leading us to hypothesize that this may also occur in the heart. At 3months of age, nicotine-exposed offspring had 45% decreased PDI levels in the absence of endoplasmic reticulum stress. Given the association of PDI and superoxide dismutase enzymes, we further observed that antioxidant superoxide dismutase-2 levels were reduced by 32% in these offspring concomitant with a 26-49% decrease in mitochondrial complex proteins (I, II, IV and V) and tissue inhibitor of metalloproteinase-4, a critical matrix metalloprotease for cardiac contractility and health. Collectively, this study suggests that perinatal nicotine exposure decreases PDI, which can promote oxidative damage and mitochondrial damage, associated with a premature decline in cardiac function.

Effects of cigarette smoke exposure during suckling on food intake, fat mass, hormones, and biochemical profile of young and adult female rats.

Children from smoking mothers have a higher risk of developing obesity and associated comorbidities later in life. Different experimental models have been used to assess the mechanisms involved with this increased risk. Using a rat model of neonatal nicotine exposure via implantation of osmotic minipumps in lactating dams, we have previously shown marked sexual dimorphisms regarding metabolic and endocrine outcomes in the adult progeny. Considering that more than four thousand substances are found in tobacco smoke besides nicotine, we then studied a rat model of neonatal tobacco smoke exposure: adult male offspring had hyperphagia, obesity, hyperglycemia, hypertriglyceridemia, secondary hyperthyroidism and lower adrenal hormones. Since litters were culled to include only males and since sexual dimorphisms had already been identified in the nicotine exposure model, here we also evaluated the effects of tobacco smoke exposure during lactation on females. Wistar rat dams and their pups were separated into two groups of 8 litters each: SMOKE (4 cigarettes per day, from postnatal day 3 to 21) and CONTROL (filtered air). Offspring of both sexes were euthanized at PN21 and PN180. Changes in male offspring corroborated previous data. At weaning, females showed lower body mass gain and serum triglycerides, but no alterations in visceral fat and hormones. At adulthood, females had higher body mass, hyperphagia, central obesity, hyperleptinemia, hypercholesterolemia, hypercorticosteronemia, but no change in serum TSH and T3, and adrenal catecholamine CONCLUSIONS: Sexual dimorphisms were observed in several parameters, thus indicating that metabolic and hormonal changes due to smoke exposure during development are sex-dependent.

Neonatal Nicotine Exposure Leads to Hypothalamic Gliosis in Adult Overweight Rats.

Astrocytes and microglia, the immune competent cells of central nercous system, can be activated in response to metabolic signals such as obesity and hyperleptinaemia. In rats, maternal exposure to nicotine during lactation leads to central obesity, hyperleptinaemia, leptin resistance and alterations in hypothalamic neuropeptides in the offspring during adulthood. In the present study, we studied the activation of astrocytes and microglia, as well as the pattern of inflammatory mediators, in adult offspring of this experimental model. On postnatal day 2 (P2), osmotic minipumps releasing nicotine (NIC) (-6mg/kg/day) or saline for 14days were s.c. implanted in dams. Male offspring were killed on P180 and hypothalamic immunohistochemistry, retroperitoneal white adipose tissue (WAT) polymerase chain reaction analysis and multiplex analysis for plasma inflammatory mediators were carried out. At P180, NIC astrocyte cell number was higher in the arcuate nucleus (ARC) (medial: +82%; lateral: +110%), in the paraventricular nucleus (PVN) (+144%) and in the lateral hypothalamus (+121%). NIC glial fibrillary acidic protein fibre density was higher in the lateral ARC (+178%) and in the PVN (+183%). Interleukin-6 was not affected in the hypothalamus. NIC monocyte chemotactic protein1 was only higher in the periventricular nucleus (+287%). NIC microglia (iba-1-positive) cell number was higher (+68%) only in the PVN, as was the chemokine (C-X3-C motif) receptor 1 density (+93%). NIC interleukin-10 was lower in the WAT (-58%) and plasma (-50%). Thus, offspring of mothers exposed to nicotine during lactation present hypothalamic astrogliosis at adulthood and microgliosis in the PVN.

Neonatal nicotine exposure increases excitatory synaptic transmission and attenuates nicotine-stimulated GABA release in the adult rat hippocampus

Developmental exposure to nicotine has been linked to long-lasting changes in synaptic transmission which may contribute to behavioral abnormalities seen in offspring of women who smoke during pregnancy. Here, we examined the long-lasting effects of developmental nicotine exposure on glutamatergic and GABAergic neurotransmission, and on acute nicotine-induced glutamate and GABA release in the adult hippocampus, a structure important in cognitive and emotional behaviors. We utilized a chronic neonatal nicotine treatment model to administer nicotine (6 mg/kg/day) to rat pups from postnatal day (P) 1–7, a period that falls developmentally into the third human trimester. Using whole-cell voltage clamp recordings from CA1 pyramidal neurons in hippocampal slices, we measured excitatory and inhibitory postsynaptic currents in neonatally control- and nicotine-treated young adult males. Neonatal nicotine exposure significantly increased AMPA receptor-mediated spontaneous and evoked excitatory signaling, with no change in glutamate release probability in adults. Conversely, there was no increase in spontaneous GABAergic neurotransmission in nicotine-males. Chronic neonatal nicotine treatment had no effect on acute nicotine-stimulated glutamate release in adults, but acute nicotine-stimulated GABA release was significantly attenuated. Thus, neonatal nicotine exposure results in a persistent net increase in excitation and a concurrent loss of nicotinic acetylcholine receptor (nAChR)-mediated regulation of presynaptic GABA but not glutamate release, which would exacerbate excitation following endogenous or exogenous nAChR activation. Our data underscore an important role for nAChRs in hippocampal excitatory synapse development, and suggest selective long-term changes at specific presynaptic nAChRs which together could explain some of the behavioral abnormalities associated with maternal smoking.This article is part of the Special Issue entitled ‘GABAergic Signaling in Health and Disease’.

Effects of sex and chronic neonatal nicotine treatment on Na2+/K+/Cl− co-transporter 1, K+/Cl− co-transporter 2, brain-derived neurotrophic factor, NMDA receptor subunit 2A and NMDA receptor subunit 2B mRNA expression in the postnatal rat hippocampus

Chronic exposure to nicotine during the first postnatal week in rats, a developmental period that corresponds to the third trimester of human gestation, results in sexually dimorphic long-term functional defects in the adult hippocampus. One potential cause could be the sex-specific differences in the maturation of GABAA receptor-mediated responses from excitatory to inhibitory, which depends on the expression of the Na2+/K+/Cl− co-transporter 1 (NKCC1) and the K+/Cl− co-transporter 2 (KCC2). In the rat hippocampus, this switch occurs during the first and second postnatal week in females and males, respectively, and is regulated by nicotinic receptor activation. Excitatory GABAergic signaling can increase brain-derived neurotrophic factor (BDNF) expression, which might exacerbate sex differences by impacting synaptogenesis. We hypothesized that chronic neonatal nicotine (CNN) exposure differentially regulates the expression of these co-transporters and BDNF in males and females. We use quantitative isotopic in situ hybridization to examine the expression of mRNAs for NKCC1, KCC2, BDNF, and NMDA receptor subunit 2A (NR2A) and NMDA receptor subunit 2B (NR2B) in the postnatal day (P) 5 and 8 rat hippocampi in both sexes that were either control-treated or with 6mg/kg/day nicotine in milk formula (CNN) via gastric intubation starting at P1. In line with prolonged GABAergic excitation, we found that at P5 males had significantly higher mRNA expression of NKCC1 and BDNF than females. CNN treatment resulted in a significant increase in KCC2 and BDNF mRNA expression in male but not female hippocampus (p<0.05). Males also had higher expression of NR2A and lower expression of NR2B at P5 compared to females (p<0.05). At P8, there were neither sex nor treatment effects on mRNA expression, indicating the end of a critical period for sensitivity to nicotine. These results suggest that differential maturation of GABAAR-mediated responses result in sex-specific sensitivity to nicotine during early postnatal development, potentially explaining the differential long-term effects of CNN on hippocampal function.

Maternal antioxidants prevent β‐cell apoptosis and promote formation of dual hormone‐expressing endocrine cells in male offspring following fetal and neonatal nicotine exposure

Fetal and neonatal nicotine exposure causes β-cell oxidative stress and apoptosis in neonates, leading to adult-onset dysglycemia. The aim of the present study was to determine whether an antioxidant intervention could prevent nicotine-induced β-cell loss. Nulliparous female Wistar rats received daily subcutaneous injections of either saline or nicotine bitartrate (1.0 mg/kg per day) for 2 weeks prior to mating until weaning. Nicotine-exposed dams received either normal chow or diet containing antioxidants (1000 IU/kg vitamin E, 0.25% w/w coenzyme Q10, and 0.1% w/w α-lipoic acid) during mating, pregnancy, and lactation; saline-exposed dams received normal chow. Pancreatic tissue was collected from male offspring at 3 weeks of age to measure β-cell fraction, apoptosis, proliferation, and the presence of cells coexpressing insulin and glucagon. The birth weight of offspring born to nicotine-exposed dams was significantly reduced in those receiving dietary antioxidants compared with those fed normal chow. Most interestingly, the antioxidant intervention to nicotine-exposed dams prevented the β-cell loss and apoptosis observed in nicotine-exposed male offspring whose mothers did not receive antioxidants. Male pups born to nicotine-treated mothers receiving antioxidants also had a tendency for increased β-cell proliferation and a significant increase in islets containing insulin/glucagon bihormonal cells compared with the other two treatment groups. The present study demonstrates that exposure to maternal antioxidants protects developing β-cells from the damaging effects of nicotine, thus preserving β-cell mass.

Chronic neonatal nicotine exposure increases excitation in the young adult rat hippocampus in a sex-dependent manner

Smoking during pregnancy exposes the fetus to nicotine, resulting in nicotine-stimulated neurotransmitter release. Recent evidence suggests that the hippocampus develops differently in males and females with delayed maturation in males. We show that chronic nicotine exposure during the first postnatal week has sex-specific long-term effects. Neonatal rat pups were chronically treated with nicotine (6mg/kg/day) (CNN) from postnatal day 1 to 7 or milk only (Controls), and hippocampal slices were prepared from Control- and CNN-treated young adults. Field excitatory postsynaptic potentials (fEPSPs) or population spikes (PSs) were recorded from the CA1 hippocampus following CA1 s. radiatum stimulation. Input/Output curves constructed from fEPSP data indicated that CNN-males, but not females, had significantly increased excitatory responses compared to Controls (p<0.05, n=10 Con, n=11 CNN). Long-term potentiation (LTP) was not significantly changed by CNN. In the presence of bicuculline, which blocks inhibitory GABAA receptors, an epileptiform burst consisting of a series of PSs was evoked. The amplitude of the first PS was significantly larger in CNN-males and females compared to Controls (males: p<0.01, n=8 Con, n=8 CNN; females: p<0.05, n=9 Con, n=7 CNN). Only CNN-males also had significantly larger second PSs (p<0.05, n=8 con, n=8 CNN). Epileptiform activity evoked by zero Mg2+ incubation did not differ in amplitude or duration of bursts in CNN-males or females compared to Controls. These data indicate that neonatal nicotine exposure has long lasting effects and results in increased excitation within the CA1 hippocampus in adulthood, with males showing increased sensitivity to nicotine's effects.

Calcium supplementation reverts central adiposity, leptin, and insulin resistance in adult offspring programed by neonatal nicotine exposure

Obesity is a worldwide epidemic. Calcium influences energy metabolism regulation, causing body weight loss. Because maternal nicotine exposure during lactation programs for obesity, hyperleptinemia, insulin resistance (IR), and hypothyroidism, we decided to evaluate the possible effect of dietary calcium supplementation on these endocrine dysfunctions in this experimental model. Osmotic minipumps containing nicotine solution (N: 6 mg/kg per day for 14 days) or saline (C) were s.c. implanted in lactating rats 2 days after giving birth (P2). At P120, N and C offspring were subdivided into four groups: 1) C - standard diet; 2) C with calcium supplementation (CCa, 10 g calcium carbonate/kg rat chow); 3) N - standard diet; and 4) N with calcium supplementation (NCa). Rats were killed at P180. As expected, N offspring showed higher visceral and total body fat, hyperleptinemia, lower hypothalamus leptin receptor (OB-R) content, hyperinsulinemia, and higher IR index. Also, higher tyrosine hydroxylase (TH) expression (+51%), catecholamine content (+37%), and serum 25-hydroxyvitamin D(3) (+76%) were observed in N offspring. Dietary calcium supplementation reversed adiposity, hyperleptinemia, OB-R underexpression, IR, TH overexpression, and vitamin D. However, this supplementation did not reverse hypothyroidism. In NCa offspring, Sirt1 mRNA was lower in visceral fat (-37%) and higher in liver (+42%). In conclusion, dietary calcium supplementation seems to revert most of the metabolic syndrome parameters observed in adult offspring programed by maternal nicotine exposure during lactation. It is conceivable that the reduction in fat mass per se, induced by calcium therapy, is the main mechanism that leads to the increment of insulin action.

Effects of Pre- and Neonatal Nicotine Exposure in Rodents: Inconsistent Evidence

This review presents an analysis of the literature on behavioral effects of developmental exposure to nicotine, as assessed in rodent models that mimic the consequences for human offspring of maternal cigarette smoking. Despite the frequency of reports of low birth weight, hyperactivity, cognitive deficits, and psychiatric problems, inconsistencies exist in both the clinical and experimental literature. Confounding socioeconomic and other demographic variables may account for discrepancies in clinical reports, and the choice of developmental exposure period and the method of nicotine administration may explain differences in experimental outcomes. Analysis of a number of variables (e.g., physical, behavioral, and cognitive) shows that fetal exposure to nicotine does not consistently cause growth retardation or decreased birth weight, nor reliably affect motor activity. But combined pre- and neonatal exposure is likely to result in delayed reflex development, global impairments in learning and memory, and an increased incidence of symptoms that model psychiatric illness. There is also support for increased self-administration of nicotine and other drugs of abuse in animals exposed developmentally to nicotine, as well as potent effects on offspring responses to drug challenges. Unlike reports in the clinical literature, sexually dimorphic effects were not evident in most animal models. Possible neuroanatomical and cholinergic mechanisms responsible for behavioral changes are briefly discussed. Statistical and design considerations are provided to increase the translational value of this research and, most importantly, enhance the replicability of reported findings.

Neonatal nicotine exposure alters leptin signaling in the hypothalamus–pituitary–thyroid axis in the late postnatal period and adulthood in rats

Aims Postnatal nicotine exposure causes precocious primary hypothyroidism and programs for overweight, hyperleptinemia and secondary hypothyroidism in adulthood. As leptin and thyroid hormones share the ability to increase energy expenditure, we studied the effects of maternal nicotine exposure during lactation on the leptin signaling in the hypothalamus–pituitary–thyroid axis of suckling and adult offspring. Main methods Two days after delivery, osmotic minipumps were implanted in lactating rats, and nicotine (NIC, 6 mg/kg/day s.c.) or saline (C) was administered for 14 days. Offspring were killed at 15 and 180 days-old. Proteins belonging to leptin signaling were analyzed by Western blot. Significant differences had p < 0.05. Key findings In the hypothalamus, NIC offspring showed higher OB-R and pSTAT-3 content (+ 58%,+1.34x) at 15 days, and lower OB-R, JAK-2 and pSTAT-3 (−61%, −42%, −56%) at 180 days. In the pituitary gland, NIC offspring showed lower JAK-2 content (−52%) at 15 days, but no differences in adulthood. In the thyroid gland, the NIC group presented lower OB-R, JAK-2 and STAT-3 (−44%, −50%, −47%) and higher pSTAT-3 expression (+ 80%) at 15 days. At 180 days-old, NIC offspring presented higher thyroid OB-R (+ 1.54x) and lower pSTAT-3 content (−34%). Significance Neonatal primary hypothyroidism induced by maternal nicotine exposure during lactation may be partially explained by decreased leptin signaling in the thyroid, though the early stimulation of the central leptin pathway did not prevent the thyroid dysfunction. Long-term effects of postnatal nicotine exposure on leptin signaling in the hypothalamus and thyroid appear to involve central and peripheral leptin resistance in adulthood.

Neonatal nicotine exposure causes insulin and leptin resistance and inhibits hypothalamic leptin signaling in adult rat offspring

Maternal nicotine (NIC) exposure during lactation leads to overweight, hyperleptinemia, and hypothyroidism in adult rat offspring. In this model, we analyzed adipocyte morphology, glucose homeostasis (serum insulin and adiponectin; liver and muscle glycogen), serum lipid, and the leptin signaling pathway. After birth, osmotic minipumps were implanted in lactating rats, which were divided into the groups NIC (6 mg/kg per day s.c. for 14 days) and control (C, saline). NIC and C offspring were killed at the age of 180 days. Adult NIC rats showed higher total body fat (+10%, P<0.05), visceral fat mass (+12%, P<0.05), and cross-sectional area of adipocytes (epididymal: +12% and inguinal: +43%, P<0.05). Serum lipid profile showed no alteration except for apolipoprotein AI, which was lower. We detected a lower adiponectin:fat mass ratio (-24%, P<0.05) and higher insulinemia (+56%, P<0.05), insulin resistance index (+43%, P<0.05), leptinemia (+113%, P<0.05), and leptin:adiponectin ratio (+98%, P<0.05) in the adult NIC group. These rats presented lower hypothalamic contents of the proteins of the leptin signaling pathway (leptin receptor (OB-R): -61%, janus tyrosine kinase 2: -41%, and p-signal transducer and activator of transcription 3: -56%, P<0.05), but higher suppressor of cytokine signaling 3 (+81%, P<0.05). Therefore, NIC exposure only during lactation programs rats for adipocyte hypertrophy in adult life, as well as for leptin and insulin resistance. Through the effects of NIC, perinatal maternal cigarette smoking may be responsible for the future development of some components of the metabolic syndrome in the offspring.