Nicotinic cholinergic and dopaminergic receptor mRNA expression in male and female rats with high or low preference for nicotine

The inflammation and oxidative status of rat lung tissue following smoke/vapor exposure via E-cigarette, cigarette, and waterpipe

BACKGROUND

Tobacco smoking is a major worldwide health issue that contributes to millions of deaths annually. Electronic cigarettes (E-cigarettes) are also harmful. Smoke/vapor from E-cigarettes and tobacco products consists of free radicals and other toxic substances. Tissue damage in smokers, such as lungs, is highly observed and is linked to oxidative damage and inflammation.

METHODS

The inflammation and oxidative status of rat lung tissues was examined following whole-body smoke/vapor exposure via E-cigarette, cigarette, and waterpipe for 2 h daily, 5 days per week for 8 weeks.

RESULTS

Lung tissue damage was higher in cigarettes and waterpipe groups compared to the E-cigarette group. Collectively, there was a significant increase (p < 0.05) in the mRNA expression of pro-inflammatory mediators (TNF-α, NF-κB, IL-1β) with the exception of IL-1β in the E-cigarettes group. As for the anti-inflammatory mediators (Nrf2 and IL-10), a significant reduction (p < 0.05) of mRNA expression was observed with the exception of Nrf2 in the E-cigarette group. As for IL-6, there was a significant increase in its mRNA expression (p < 0.05) in the cigarette and waterpipe groups. There was also a significant decrease (p < 0.05) in the antioxidant activity of all antioxidants tested (GPx, SOD, and CAT) in all groups with the exception of SOD in the cigarette group.

CONCLUSION

Smoke/vapor administered via E-cigarette, cigarette, and waterpipe elicits inflammation and oxidative stress in rat lungs that is accompanied by histopathological changes.

Molecular imaging of excitability difference between alkaloids/salts (nicotine, nicotinic benzoate, caffeine and arecoline hydrobromide)

Comparison of the excitability of four different alkaloids/salts, including nicotine, nicotinic benzoate, caffeine and arecoline hydrobromide. Based on positron emission tomography (PET) imaging and 18F-Fallypride, a novel technique for measuring alkaloid/salt excitability in SD rats was developed. Different doses and types of alkaloids/salts were administered to the SD rats in a single nebulised inhalation. The results showed that: (1) PET imaging technology can detect the excitability intensity of SD rats after single inhalation of alkaloids/salts in non-invasive real time and the optimal PET scanning time of four different alkaloids/salts (nicotine, nicotinic benzoate, caffeine and arecoline hydrobromide) were slightly different. (2) The excitatory saturation effect of four alkaloids/salts was observed in SD rats after single inhalation and the saturation effect doses of nicotine, nicotine benzoate, caffeine and arecine hydrobromide were 0.063 mg/kg, 0.075 mg/kg, 0.33 mg/kg and 0.075 mg/kg, respectively. (3) In the case of single inhalation of the same dose of four alkaloids/salts, male SD rats inhaled arecoline hydrobromide with the strongest excitability, while female SD rats inhaled nicotinic benzoate. A PET method for noninvasive real-time detection of alkaloid/salt excitability in SD rats was established. The finding of an excitatory saturation effect for four alkaloids/salts (nicotine, nicotinic benzoate, caffeine and arecoline hydrobromide) and the presence of excitatory intensity and gender differences at the same dose of inhalation of four alkaloids/salts, which provide a new theoretical basis for determiningthe content of alkaloids/salts.

Hypersensitivity of the nicotinic acetylcholine receptor subunit (CHRNA2L9'S/L9'S) in female adolescent mice produces deficits in nicotine-induced facilitation of hippocampal-dependent learning and memory

Adolescence is characterized by a critical period of maturation and growth, during which regions of the brain are vulnerable to long-lasting cognitive disturbances. Adolescent exposure to nicotine can lead to deleterious neurological and psychological outcomes. Moreover, the nicotinic acetylcholine receptor (nAChR) has been shown to play a functionally distinct role in the development of the adolescent brain. CHRNA2 encodes for the α2 subunit of nicotinic acetylcholine receptors associated with CA1 oriens lacunosum moleculare GABAergic interneurons and is associated with learning and memory. Previously, we found that adolescent male hypersensitive CHRNA2L9'S/L9' mice had impairments in learning and memory during a pre-exposure-dependent contextual fear conditioning task that could be rescued by low-dose nicotine exposure. In this study, we assessed learning and memory in female adolescent hypersensitive CHRNA2L9'S/L9' mice exposed to saline or a subthreshold dose of nicotine using a hippocampus-dependent task of pre-exposure-dependent contextual fear conditioning. We found that nicotine-treated wild-type female mice had significantly greater improvements in learning and memory than both saline-treated wild-type mice and nicotine-treated CHRNA2L9'S/L9' female mice. Thus, hyperexcitability of CHRNA2 in female adolescent mice ablated the nicotine-mediated potentiation of learning and memory seen in wild-types. Our results indicate that nicotine exposure during adolescence mediates sexually dimorphic patterns of learning and memory, with wild-type female adolescents being more susceptible to the effects of sub-threshold nicotine exposure. To understand the mechanism underlying sexually dimorphic behavior between hyperexcitable CHRNA2 mice, it is critical that further research be conducted.

Targeting α7-nAChR by galantamine mitigates reserpine-induced fibromyalgia-like symptoms in rats: Involvement of cAMP/PKA, PI3K/AKT, and M1/M2 microglia polarization

Fibromyalgia (FM) is a pain disorder marked by generalized musculoskeletal pain accompanied by depression, fatigue, and sleep disturbances. Galantamine (Gal) is a positive allosteric modulator of neuronal nicotinic acetylcholine receptors (nAChRs) and a reversible inhibitor of cholinesterase. The current study aimed to explore the therapeutic potential of Gal against reserpine (Res)-induced FM-like condition along with investigating the α7-nAChR's role in Gal-mediated effects. Rats were injected with Res (1 mg/kg/day; sc) for 3 successive days then Gal (5 mg/kg/day; ip) was given alone and with the α7-nAChR blocker methyllycaconitine (3 mg/kg/day; ip), for the subsequent 5 days. Galantamine alleviated Res-induced histopathological changes and monoamines depletion in rats' spinal cord. It also exerted analgesic effect along with ameliorating Res-induced depression and motor-incoordination as confirmed by behavioral tests. Moreover, Gal produced anti-inflammatory effect through modulating AKT1/AKT2 and shifting M1/M2 macrophage polarization. The neuroprotective effects of Gal were mediated through activating cAMP/PKA and PI3K/AKT pathways in α7-nAChR-dependent manner. Thus, Gal can ameliorate Res-induced FM-like symptoms and mitigate the associated monoamines depletion, neuroinflammation, oxidative stress, apoptosis, and neurodegeneration through α7-nAChR stimulation, with the involvement of cAMP/PKA, PI3K/AKT, and M1/M2 macrophage polarization.

Expression, correlation, and prognostic significance of different nicotinic acetylcholine receptors, programed death ligand 1, and dopamine receptor D2 in lung adenocarcinoma

Objective

The objective of this study is to evaluate the expression of different nicotinic acetylcholine receptors (nAChRs), programmed death ligand-1 (PD-L1), and dopamine receptor D2 (DRD2) as prognostic factors in lung cancer and any correlation among them. Since all of the above genes are typically upregulated in response to smoking, we hypothesized that a correlation might exist between DRD2, PD-L1, and nAChR expression in NSCLC patients with a smoking history and a prediction model may be developed to assess the clinical outcome.

Methods

We retrospectively analyzed samples from 46 patients with primary lung adenocarcinoma who underwent surgical resection at Mayo Clinic Rochester from June 2000 to October 2008. The expression of PD-L1, DRD2, CHRNA5, CHRNA7, and CHRNA9 were analyzed by quantitative PCR and correlated amongst themselves and with age, stage and grade, smoking status, overall survival (OS), and relapse-free survival (RFS).

Results

Only PD-L1 showed a statistically significant increase in expression in patients older than 65. All the above genes showed higher expression in stage IIIB than IIIA, but none reached statistical significance. Interestingly, we did not observe significant differences among never, former, and current smokers, but patients with pack years greater than 30 showed significantly higher expression of CHRNA9. We observed a strong positive correlation between PD-L1/DRD2, PD-L1/CHRNA5, and CHRNA5/CHRNA7 and a weak positive correlation between DRD2/CHRNA5 and DRD2/CHRNA7. Older age was independently associated with poor OS, whereas lower CHRNA7 expression was independently associated with better OS.

Conclusions

We observed strong positive correlations among PD-L1, DRD2, and some of the nAChRs. We investigated their prognostic significance in lung cancer patients and found CHRNA7 to be an independent prognostic factor. Overall, the results obtained from this preliminary study warrant a large cohort-based analysis that may ultimately lead to potential patient-specific stratification biomarkers predicting cancer-treatment outcomes.

Increased Risky Choice and Reduced CHRNB2 Expression in Adult Male Rats Exposed to Nicotine Vapor

While the cognitive enhancing effects of nicotine use have been well documented, it has also been shown to impair decision making. The goal of this study was to determine if exposure to nicotine vapor increases risky decision making. The study also aims to investigate possible long-term effects of nicotine vapor exposure on the expression of genes coding for cholinergic and dopaminergic receptors in brain. Thirty-two adult male Sprague Dawley rats were exposed to 24 mg/mL nicotine vapor or vehicle control, immediately followed by testing in the probability discounting task for 10 consecutive days. Fifty-four days after the 10-day vapor exposure, animals were sacrificed and expression of genes coding for the α4 and β2 cholinergic receptor subunits, and dopamine D1 and D2 receptors, were analyzed using RT-PCR. Exposure to nicotine vapor caused an immediate and transient increase in risky choice. Analyses of gene expression identified significant reductions in CHRNB2 and DRD1 in the nucleus accumbens core and CHRNB2 and DRD2 in the medial prefrontal cortex of rats previously exposed to nicotine vapor, relative to vehicle controls. Results provide data on the negative cognitive effects of nicotine vapor exposure and identify cholinergic and dopaminergic mechanisms that may affected with repeated use.

Sex Differences in the Nicotinic Acetylcholine Receptor System of Rodents: Impacts on Nicotine and Alcohol Reward Behaviors

Alcohol and nicotine are the two most widely used and misused drugs around the world, and co-consumption of both substances is highly prevalent. Multiple lines of evidence show a profound effect of sex in many aspects of alcohol and nicotine reward, with women having more difficulty quitting smoking and showing a faster progression toward developing alcohol use disorder compared with men. Both alcohol and nicotine require neuronal nicotinic acetylcholine receptors (nAChRs) to elicit rewarding effects within the mesolimbic system, representing a shared molecular pathway that likely contributes to the frequent comorbidity of alcohol and nicotine dependence. However, the majority of preclinical studies on the mechanisms of alcohol and nicotine reward behaviors utilize only male rodents, and thus our understanding of alcohol and nicotine neuropharmacology relies heavily on male data. As preclinical research informs the development and refinement of therapies to help patients reduce drug consumption, it is critical to understand the way biological sex and sex hormones influence the rewarding properties of alcohol and nicotine. In this review, we summarize what is known about sex differences in rodent models of alcohol and nicotine reward behaviors with a focus on neuronal nAChRs, highlighting exciting areas for future research. Additionally, we discuss the way circulating sex hormones may interact with neuronal nAChRs to influence reward-related behavior.

Sex Differences in Dopamine Receptors and Relevance to Neuropsychiatric Disorders

Dopamine is an important neurotransmitter that plays a key role in neuropsychiatric illness. Sex differences in dopaminergic signaling have been acknowledged for decades and have been linked to sex-specific heterogeneity in both dopamine-related behaviours as well as in various neuropsychiatric disorders. However, the overall number of studies that have evaluated sex differences in dopamine signaling, both in health and in these disorders, is low. This review will bring together what is known regarding sex differences in innate dopamine receptor expression and function, as well as highlight the known sex-specific roles of dopamine in addiction, depression, anxiety, schizophrenia, and attention deficit hyperactivity disorder. Due to differences in prognosis, diagnosis, and symptomatology between male and female subjects in disorders that involve dopamine signaling, or in responses that utilize pharmacological interventions that target dopamine receptors, understanding the fundamental sex differences in dopamine receptors is of vital importance for the personalization of therapeutic treatment strategies.

Neuroimmune Mechanisms as Novel Treatment Targets for Substance Use Disorders and Associated Comorbidities

Recent studies examining the neurobiology of substance abuse have revealed a significant role of neuroimmune signaling as a mechanism through which drugs of abuse induce aberrant changes in synaptic plasticity and contribute to substance abuse-related behaviors. Immune signaling within the brain and the periphery critically regulates homeostasis of the nervous system. Perturbations in immune signaling can induce neuroinflammation or immunosuppression, which dysregulate nervous system function including neural processes associated with substance use disorders (SUDs). In this review, we discuss the literature that demonstrates a role of neuroimmune signaling in regulating learning, memory, and synaptic plasticity, emphasizing specific cytokine signaling within the central nervous system. We then highlight recent preclinical studies, within the last 5 years when possible, that have identified immune mechanisms within the brain and the periphery associated with addiction-related behaviors. Findings thus far underscore the need for future investigations into the clinical potential of immunopharmacology as a novel approach toward treating SUDs. Considering the high prevalence rate of comorbidities among those with SUDs, we also discuss neuroimmune mechanisms of common comorbidities associated with SUDs and highlight potentially novel treatment targets for these comorbid conditions. We argue that immunopharmacology represents a novel frontier in the development of new pharmacotherapies that promote long-term abstinence from drug use and minimize the detrimental impact of SUD comorbidities on patient health and treatment outcomes.

Genetics of OCD and Related Disorders; Searching for Shared Factors

Obsessive compulsive disorder (OCD) and several other obsessive-compulsive related disorders (OCRDs) including hoarding disorder, body dysmorphic disorder (BDD), skin picking disorder, trichotillomania and the newly arising public health conditions of online gaming and gambling disorders, under the umbrella of Problematic Usage of the Internet (PUI), not only share some common phenotypes, but there is evidence to suggest share some genetic risk factors. The simple fact that these disorders segregate within families points to this notion. However, the current data are still scarce. This chapter focuses on identifying the shared genetic factors. To address this question, a systematic review of the literature investigating genetic findings in OCD and OCRDs including PUI was conducted, with a focus on their genetic similarities. Greater knowledge of the specific genetic risks shared among OCRDs would be expected to open new avenues in the understanding of the biological mechanisms causing the development of these phenotypes, as well as provide opportunities to develop new animal and cellular models testing new therapy avenues.

Impact of Menthol on Oral Nicotine Consumption in Female and Male Sprague Dawley Rats

INTRODUCTION

One of the preferable flavors in oral nicotine delivery systems is menthol which masks the harshness of tobacco. However, possible interactions between oral menthol and nicotine on intake and preference remain unclear. Therefore, we aimed to determine the impact of menthol on oral nicotine consumption.

METHODS

Adult Sprague Dawley female and male rats (n = 8 per group) were given a choice of water or drug solution by using two-bottle free choice paradigm for 2 weeks: vehicle (5% ethanol), nicotine (20 mg/L), menthol (1 g/L) and mentholated nicotine groups. At the end of the study, plasma nicotine levels were determined.

RESULTS

When rats were given a choice of nicotine or water, nicotine intake was similar between female and male rats. Menthol addition to nicotine solution significantly increased nicotine intake and preference in male but not female rats without a considerable effect on total fluid intake and body weight change in either sex. The average nicotine intake in male rats was 0.5 ± 0.05 and 1.4 ± 0.12 mg/kg/day for nicotine and menthol-nicotine combination (p < .05), respectively. The average nicotine intake in female rats was 0.6 ± 0.05 and 0.6 ± 0.03 mg/kg/day for nicotine and menthol-nicotine combination (p > .05), respectively. Plasma nicotine levels were not significantly different between the groups in either male (nicotine group: 20.8 ± 4.9, mentholated nicotine group: 31.9 ± 3.2 ng/mL) or female (nicotine group: 24.0 ± 3.3, mentholated nicotine group: 17.8 ± 2.9 ng/mL) rats (p > .05).

CONCLUSIONS

Menthol increases oral nicotine consumption in male, but not female, rats.

IMPLICATIONS

This study may provide data on the co-use of menthol and nicotine in smokeless tobacco, particularly oral dissolvable tobacco products.

Increased alcohol preference and intake in nicotine-preferring rats

BACKGROUND

Alcohol and tobacco are among the leading substances that are misused together and shared genetic vulnerability is likely. Increased susceptibility to nicotine self-administration has been shown in alcohol-preferring rat-lines. However, a nicotine-preferring (nP) rat-line has not been studied for alcohol preference.

OBJECTIVES

To evaluate alcohol preference and intake in male and female nP rats. We hypothesized that nP rats and females would drink more ethanol than control rats and males, respectively.

METHODS

nP rats are being selectively outbred for high oral nicotine intake at Ege University. Seventeen nP (18^th generation) and 20 naïve female and male SD rats, not previously exposed to alcohol or nicotine, were used. Twelve-week-old rats were given intermittent access to 20% ethanol in a 2-bottle-choice-procedure for six weeks. After one week withdrawal, six weeks of oral nicotine self-administration was applied.

RESULTS

nP rats drank significantly more ethanol than controls and their preference for ethanol over water was higher. Female rats' ethanol intake was higher than males'. The nP rats' nicotine preference and intake were higher than controls, and they gained less weight.

CONCLUSION

We have shown for the first time that nP rats also have high alcohol intake. Our results support the hypothesis that shared genetic factors may underlie concurrent addiction to nicotine and alcohol and have translational value in understanding their misuse. Considering the increased vulnerability for alcohol use disorder in smokers and sex differences observed, early preventive measures in families with a history of tobacco addiction, specifically targeting female members, could have public health benefits.

The effect of genetic variations in the choline acetyltransferase gene (ChAT) on waterpipe tobacco smoking dependence

INTRODUCTION

Waterpipe tobacco smoking (WS) is a popular form of tobacco use, globally. While the impact of genetic variations on smoking behavior has been well-investigated, few studies have examined this issue with regard to WS. In the current study, associations between choline acetyltransferase gene (ChAT) rs1917810 and rs7094248 polymorphisms and WS dependence were examined.

METHODS

Genotyping of rs1917810 and rs7094248 in 266 Jordanian waterpipe smokers was performed using RFLP-PCR. Dependence on WS was measured using the LWDS-10J scale.

RESULTS

The frequency of rs1917810 G allele was 38.5% and that of the rs7094248 G allele was 40.8%. The rs1917810 was significantly associated with the WS dependence level (p<0.05). Carriers of the AA genotype of rs1917810 were more dependent on WS than those with GG genotype (p<0.05). However, no association between rs7094248 single-nucleotide polymorphism (SNP) and dependence on WS was observed (p>0.05).

CONCLUSIONS

The rs1917810 in the ChAT gene might be associated with dependence on WS.

Ganglionic and ovarian action of acetylcholine during diestrous II in rats. Neuroendocrine control of the luteal regression

Our aim was to investigate if acetylcholine (Ach), added to the celiac ganglion-superior ovarian nerve-ovary system (CG-SON-ovary) or in ovary incubations, modifies the release of progesterone (P₄), androstenedione (A₂), dopamine (DA), norepinephrine (NE), gonadotropin-releasing hormone (GnRH), and alters the expression of 3β-hydroxysteroid dehydrogenase (3β-HSD), 20α-hydroxysteroid dehydrogenase (20α-HSD), and apoptotic genes in ovarian tissue during the diestrous II (DII) in rats. The CG-SON-ovary system or the ovary alone were removed and placed into separate cuvettes both containing Krebs-Ringer solution (control groups). In experimental groups, 10^-6 M Ach was added into the ganglion compartment or into the ovary compartment. P₄, A₂ and GnRH were measured by RIA, mRNA expression by RT-PCR, and catecholamines by HPLC. In addition, a routine histological technique was applied. In ex-vivo system, 10^-6 M Ach into the ganglion compartment decreased P₄ and NE release, altered 3β-HSD and 20α-HSD expression, and decreased bax/bcl-2 ratio, while increasing the release of A₂ and DA, and bcl-2 expression. In ovary incubations, 10^-6 M Ach decreased P₄ and GnRH release, decreased 3β-HSD and bcl-2 expression, increased A₂ release, increased 20α-HSD and bax expression, and the bax/bcl-2 ratio, and induced disorganization of the corpus luteum structure. The peripheral nervous system protected the ovary from the apoptotic mechanisms while in the ovary incubation the effect was reversed. Our results indicate that Ach in DII regulates steroidogenesis and apoptosis in the ovary, by modulating the concentration of neurotransmitters. In vivo, an alteration in the extrinsic cholinergic innervation of the ovary could disrupt the endocrine control of the reproductive function.