Exposure to tobacco smoke during the early postnatal period modifies receptors and enzymes of the endocannabinoid system in the brainstem and striatum in mice

Nicotine exposure through breastfeeding affects BDNF and synaptic proteins levels in the brain of stressed adult female mice

Nicotine has been used during pregnancy and lactation as a tobacco harm reduction strategy. However, it is unclear whether nicotine exposure during a critical development period negatively impacts stress responses in adulthood. This study investigated how nicotine, administered via breastfeeding, affects the brain-derived neurotrophic factor (BDNF), synaptic proteins levels, and anxiety-like behavior in adult female mice subjected to stress. Female Swiss mice were exposed to saline or nicotine (8 mg/kg/day) through breastfeeding between their fourth and 17th postnatal days (P) via implanted osmotic mini pumps. The unpredictable chronic mild stress (UCMS) protocol was performed during their adulthood (P65) for 10 consecutive days, followed by the elevated plus maze (EPM) test one day after the protocol. Animals were euthanized and their blood, collected for plasma corticosterone measurements and their brain structures, dissected for BDNF and synaptic proteins analyses. We found no significant differences in corticosterone levels between groups (Saline/Non-stress, Nicotine/Non-stress, Saline/Stress, and Nicotine/Stress). The UCMS protocol hindered weight gain. Mice exposed to nicotine through breastfeeding with or without the UCMS protocol in adulthood showed higher grooming and head dipping frequency; decreased BDNF levels in cerebellum and striatum; increased postsynaptic density protein 95 (PSD-95), synapsin I, and synaptophysin levels in cerebellum; and decreased PSD-95 and synapsin I levels in brainstem. Our results indicate that nicotine exposure through breastfeeding leads to long-lasting behavioral effects and synaptic protein changes, most of which were independent of the UCMS protocol, even after a long nicotine-free period, highlighting the importance of further studies on nicotine exposure during development.

Biomarkers of the Endocannabinoid System in Substance Use Disorders

Despite substance use disorders (SUD) being one of the leading causes of disability and mortality globally, available therapeutic approaches remain ineffective. The difficulty in accurately characterizing the neurobiological mechanisms involved with a purely qualitative diagnosis is an obstacle to improving the classification and treatment of SUD. In this regard, identifying central and peripheral biomarkers is essential to diagnosing the severity of drug dependence, monitoring therapeutic efficacy, predicting treatment response, and enhancing the development of safer and more effective pharmacological tools. In recent years, the crucial role that the endocannabinoid system (ECS) plays in regulating the reinforcing and motivational properties of drugs of abuse has been described. This has led to studies characterizing ECS alterations after exposure to various substances to identify biomarkers with potential diagnostic, prognostic, or therapeutic utility. This review aims to compile the primary evidence available from rodent and clinical studies on how the ECS components are modified in the context of different substance-related disorders, gathering data from genetic, molecular, functional, and neuroimaging experimental approaches. Finally, this report concludes that additional translational research is needed to further characterize the modifications of the ECS in the context of SUD, and their potential usefulness in the necessary search for biomarkers.

Spelta LE, Duro SDO, Barreto dos Santos N, Paranhos BAPB, Zanluqui NG, Yonamine M, Pierre Schatzmann Peron J, Munhoz CD, Marcourakis T. In Utero Exposure to Environmental Tobacco Smoke Increases Neuroinflammation in Offspring

The embryonic stage is the most vulnerable period for congenital abnormalities. Due to its prolonged developmental course, the central nervous system (CNS) is susceptible to numerous genetic, epigenetic, and environmental influences. During embryo implantation, the CNS is more vulnerable to external influences such as environmental tobacco smoke (ETS), increasing the risk for delayed fetal growth, sudden infant death syndrome, and immune system abnormalities. This study aimed to evaluate the effects of in utero exposure to ETS on neuroinflammation in the offspring of pregnant mice challenged or not with lipopolysaccharide (LPS). After the confirmation of mating by the presence of the vaginal plug until offspring birth, pregnant C57BL/6 mice were exposed to either 3R4F cigarettes smoke (Kentucky University) or compressed air, twice a day (1h each), for 21 days. Enhanced glial cell and mixed cell cultures were prepared from 3-day-old mouse pups. After cell maturation, both cells were stimulated with LPS or saline. To inhibit microglia activation, minocycline was added to the mixed cell culture media 24 h before LPS challenge. To verify the influence of in utero exposure to ETS on the development of neuroinflammatory events in adulthood, a different set of 8-week-old animals was submitted to the Autoimmune Experimental Encephalomyelitis (EAE) model. The results indicate that cells from LPS-challenged pups exposed to ETS in utero presented high levels of proinflammatory cytokines such as interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNFα) and decreased cell viability. Such a proinflammatory environment could modulate fetal programming by an increase in microglia and astrocytes miRNA155. This scenario may lead to the more severe EAE observed in pups exposed to ETS in utero.

Ayahuasca, a psychedelic beverage, modulates neuroplasticity induced by ethanol in mice

Alcohol use disorder needs more effective treatments because relapse rates remain high. Psychedelics, such as ayahuasca, have been used to treat substance use disorders. Our study aimed to evaluate the effects of ayahuasca on ethanol-induced behavioral sensitization (EIBS). Swiss mice received 2.2 g/kg ethanol or saline IP injections every other day across nine days (D1, D3, D5, D7, and D9), and locomotor activity was evaluated 10 min after each injection. Then, animals were treated daily with ayahuasca (corresponding to 1.76 mg/kg of N,N-dimethyltryptamine, DMT) or water by oral gavage for eight consecutive days. On the seventh day, mice were evaluated in the elevated plus maze. Then, mice were challenged with a single dose of ethanol to measure their locomotor activity. Dopamine receptors, serotonin receptors, dynorphin, and prodynorphin levels were quantified in the striatum and hippocampus by blot analysis. Repeated ethanol administration resulted in EIBS. However, those animals treated with ayahuasca had an attenuated EIBS. Moreover, ayahuasca reduced the anxiogenic response to ethanol withdrawal and prevented the ethanol-induced changes on 5-HT1a receptor and prodynorphin levels in the hippocampus and reduced ethanol effects in the dynorphin/prodynorphin ratio levels in the striatum. These results suggest a potential application of ayahuasca to modulate the neuroplastic changes induced by ethanol.

Anhydroecgonine methyl ester, a cocaine pyrolysis product, contributes to cocaine-induced rat primary hippocampal neuronal death in a synergistic and time-dependent manner

Crack cocaine users are simultaneously exposed to volatilized cocaine and to its main pyrolysis product, anhydroecgonine methyl ester (AEME). Although the neurotoxic effects of cocaine have been extensively studied, little is known about AEME or its combination. We investigated cell death processes using rat primary hippocampal cells exposed to cocaine (2 mM), AEME (1 mM) and their combination (C + A), after 1, 3, 6 and 12 h. Cocaine increased LC3 I after 6 h and LC3 II after 12 h, but reduced the percentage of cells with acid vesicles, suggesting failure in the autophagic flux, which activated the extrinsic apoptotic pathway after 12 h. AEME neurotoxicity did not involve the autophagic process; rather, it activated caspase-9 after 6 h and caspase-8 after 12 h leading to a high percentage of cells in early apoptosis. C + A progressively reduced the percentage of undamaged cells, starting after 3 h; it activated both apoptotic pathways after 6 h, and was more neurotoxic than cocaine and AEME alone. Also, C + A increased the phosphorylation of p62 after 12 h, but there was little difference in LC3 I or II, and a small percentage of cells with acid vesicles at all time points investigated. In summary, the present study provides new evidence for the neurotoxic mechanism and timing response of each substance alone and in combination, indicating that AEME is more than just a biological marker for crack cocaine consumption, as it may intensify and hasten cocaine neurotoxicity.

Endocannabinoid-Like Lipid Neuromodulators in the Regulation of Dopamine Signaling: Relevance for Drug Addiction

The family of lipid neuromodulators has been rapidly growing, as the use of different -omics techniques led to the discovery of a large number of naturally occurring N-acylethanolamines (NAEs) and N-acyl amino acids belonging to the complex lipid signaling system termed endocannabinoidome. These molecules exert a variety of biological activities in the central nervous system, as they modulate physiological processes in neurons and glial cells and are involved in the pathophysiology of neurological and psychiatric disorders. Their effects on dopamine cells have attracted attention, as dysfunctions of dopamine systems characterize a range of psychiatric disorders, i.e., schizophrenia and substance use disorders (SUD). While canonical endocannabinoids are known to regulate excitatory and inhibitory synaptic inputs impinging on dopamine cells and modulate several dopamine-mediated behaviors, such as reward and addiction, the effects of other lipid neuromodulators are far less clear. Here, we review the emerging role of endocannabinoid-like neuromodulators in dopamine signaling, with a focus on non-cannabinoid N-acylethanolamines and their receptors. Mounting evidence suggests that these neuromodulators contribute to modulate synaptic transmission in dopamine regions and might represent a target for novel medications in alcohol and nicotine use disorder.

Early postnatal tobacco smoke exposure aggravates experimental autoimmune encephalomyelitis in adult rats

Although substantial evidence supports smoking as a risk factor for the development of multiple sclerosis (MS) in adulthood, it remains controversial whether early-life exposure to environmental tobacco smoke (ETS) increases the risk of MS later in life. Here, using experimental autoimmune encephalomyelitis (EAE) as an animal model for MS, we show that exposing neonatal rats during the first week (ETS1-EAE), but not the second week (ETS2-EAE) and the third week (ETS3-EAE) after birth, increased the severity of EAE in adulthood in comparison to pups exposed to filtered compressed air (AIR-EAE). The ETS1-EAE rats showed a worse neurological deficit score and a significant increase in CD4⁺ cell infiltration, demyelination, and axonal injury in the spinal cord compared to AIR-EAE, ETS2-EAE, and ETS3-EAE groups. Flow cytometry analysis showed that the ETS1 group had decreased numbers of regulatory T (Treg) cells and increased effector T (Teff) cells in the brain and spinal cord. The expressions of Treg upstream regulator Foxp3 and downstream cytokines such as IL-10 were also altered accordingly. Together, these findings demonstrate that neonatal ETS exposure suppresses Treg functions and aggravates the severity of EAE, confirming early-life exposure to ETS as a potential risk factor for multiple sclerosis in adulthood.

Environmental Tobacco Smoke During the Early Postnatal Period of Mice Interferes With Brain 18 F-FDG Uptake From Infancy to Early Adulthood - A Longitudinal Study

Exposure to environmental tobacco smoke (ETS) is associated with high morbidity and mortality, mainly in childhood. Our aim was to evaluate the effects of postnatal ETS exposure in the brain 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (¹⁸F-FDG) uptake of mice by positron emission tomography (PET) neuroimaging in a longitudinal study. C57BL/6J mice were exposed to ETS that was generated from 3R4F cigarettes from postnatal day 3 (P3) to P14. PET analyses were performed in male and female mice during infancy (P15), adolescence (P35), and adulthood (P65). We observed that ETS exposure decreased ¹⁸F-FDG uptake in the whole brain, both left and right hemispheres, and frontal cortex in both male and female infant mice, while female infant mice exposed to ETS showed decreased ¹⁸F-FDG uptake in the cerebellum. In addition, all mice showed reduced ¹⁸F-FDG uptake in infancy, compared to adulthood in all analyzed VOIs. In adulthood, ETS exposure during the early postnatal period decreased brain ¹⁸F-FDG uptake in adult male mice in the cortex, striatum, hippocampus, cingulate cortex, and thalamus when compared to control group. ETS induced an increase in ¹⁸F-FDG uptake in adult female mice when compared to control group in the brainstem and cingulate cortex. Moreover, male ETS-exposed animals showed decreased ¹⁸F-FDG uptake when compared to female ETS-exposed in the whole brain, brainstem, cortex, left amygdala, striatum, hippocampus, cingulate cortex, basal forebrain and septum, thalamus, hypothalamus, and midbrain. The present study shows that several brain regions are vulnerable to ETS exposure during the early postnatal period and these effects on ¹⁸F-FDG uptake are observed even a long time after the last exposure. This study corroborates our previous findings, strengthening the idea that exposure to tobacco smoke in a critical period interferes with brain development of mice from late infancy to early adulthood.

Bedsharing and Breastfeeding: The Academy of Breastfeeding Medicine Protocol #6, Revision 2019

A central goal of the Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

Cigarette smoke during lactation in rat female progeny: Late effects on endocannabinoid and dopaminergic systems

AIMS

Maternal smoking is considered a risk factor for childhood obesity. In a rat model of tobacco exposure during breastfeeding, we previously reported hyperphagia, overweight, increased visceral fat and hyperleptinemia in adult female offspring. Obesity and eating disorders are associated with impairment in the endocannabinoid (EC) and dopaminergic (DA) systems. Considering that women are prone to eating disorders, we hypothesize that adult female Wistar rats that were exposed to cigarette smoke (CS) during the suckling period would develop EC and DA systems deregulation, possibly explaining the eating disorder in this model.

MATERIAL AND METHODS

To mimic maternal smoking, from postnatal day 3 to 21, dams and offspring were exposed to a smoking machine, 4×/day/1 h (CS group). Control animals were exposed to ambient air. Offspring were evaluated at 26 weeks of age.

KEY FINDINGS

Concerning the EC system, the CS group had increased expression of diacylglycerol lipase (DAGL) in the lateral hypothalamus (LH) and decreased in the liver. In the visceral adipose tissue, the EC receptor (CB1r) was decreased. Regarding the DA system, the CS group showed higher dopamine transporter (DAT) protein expression in the prefrontal cortex (PFC) and lower DA receptor (D2r) in the arcuate nucleus (ARC). We also assessed the hypothalamic leptin signaling, which was shown to be unchanged. CS offspring showed decreased plasma 17β-estradiol.

SIGNIFICANCE

Neonatal CS exposure induces changes in some biomarkers of the EC and DA systems, which can partially explain the hyperphagia observed in female rats.