Effects of tobacco smoke constituents, anabasine and anatabine, on memory and attention in female rats

Protective effect of compatible herbs in Jin-Gu-Lian formula against Alangium chinense-induced neurotoxicity via oxidative stress, neurotransmitter metabolisms, and pharmacokinetics

Background: A. chinense frequently used in Miao medicine to treat rheumatic diseases. However, as a famous toxic herb, Alangium chinense and its representative components exhibit ineluctable neurotoxicity, thus creating significant challenges for clinical application. The combined application with compatible herbs in Jin-Gu-Lian formula attenuates such neurotoxicity according to the compatible principle of traditional Chinese medicines. Purpose: We aimed to investigate the detoxification of the compatible herbs in Jin-Gu-Lian formula on A. chinense-induced neurotoxicity and investigate its mechanism. Methods: Neurobehavioral and pathohistological analysis were used to determine the neurotoxicity in rats administered with A. chinense extract (AC), extract of compatible herbs in Jin-Gu-Lian formula (CH) and combination of AC with CH for 14 days. The mechanism underlying the reduction of toxicity by combination with CH was assessed by enzyme-linked immunosorbent assays, spectrophotometric assays, liquid chromatography tandem-mass spectrometry and real-time reverse transcription-quantitative polymerase chain reaction. Results: Compatible herbs attenuated the AC-induced neurotoxicity as evidenced by increased locomotor activity, enhanced grip strength, the decreased frequency of AC-induced morphological damage in neurons, as well as a reduction of neuron-specific enolase (NSE) and neurofilament light chain (NEFL) levels. The combination of AC and CH ameliorated AC-induced oxidative damage by modulating the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC). AC treatment significantly reduced the levels of monoamine and acetylcholine neurotransmitters in the brains of rats, including acetylcholine (Ach), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), and serotonin (5-HT). Combined AC and CH treatment regulated the abnormal concentrations and metabolisms of neurotransmitters. Pharmacokinetic studies showed that the co-administration of AC and CH significantly decreased plasma exposure levels of two main components of AC, as evidenced by the reduction of maximum plasma concentration (C_max), area under the plasma concentration-time curve (AUC) compared to AC. In addition, the AC-induced downregulation in mRNA expression of cytochrome P450 enzymes was significantly reduced in response to combined AC and CH treatment. Conclusion: Compatible herbs in Jin-Gu-Lian formula alleviated the neurotoxicity induced by A. chinense by ameliorating oxidative damage, preventing abnormality of neurotransmitters and modulating pharmacokinetics.

Differentiating the Neuropharmacological Properties of Nicotinic Acetylcholine Receptor-Activating Alkaloids

Alkaloids that target nicotinic acetylcholine receptors (nAChR) are of great interest because of the critical role they play in mood and anxiety. However, understanding of the neuropharmacological effects of nicotinic alkaloids, such as cotinine and anatabine, is very limited. In this study, we investigated the neuropharmacological effects of three naturally occurring alkaloids-nicotine, cotinine, and anatabine-in vitro and in vivo. A single injection of nicotine induced anxiolytic-like behavioral features in mice by using the SmartCube® behavioral profiling system, while cotinine and anatabine had no detectable effect. The results were corroborated by using the zebrafish novel tank test (NTT), which showed a profound anxiolytic-like effect induced by multiple doses of nicotine after a single 20-min treatment. When the regulation of dopamine and norepinephrine release-the neurotransmitter systems relevant for anxiety-were examined in vitro, we found that nicotine stimulated the release of both norepinephrine and dopamine, while cotinine and anatabine mainly stimulated the dopamine release. The molecular targets of nicotine were confirmed to be nAChRs with its most potent activities against α4β2 and α6/3β2β3 subtypes in vitro. Anatabine was a weaker agonist for these receptors than nicotine. Cotinine was the least potent nAChR compound, only being able to activate α4β2 and α6/3β2β3 subtypes at high doses and no detectable activities against α3β4 and α7 subtypes at the concentrations tested. The observed effects were unlikely due to the off-target effect, because these alkaloids did not bind or regulate >160 other molecular targets in vitro. Thus, the present results suggest that natural nicotinic alkaloids can induce an anxiolytic-like behavior in nonclinical animal models, potency of which may depend on the activation of various nAChRs and regulation of various neurotransmitter systems. Further investigations would help understand their effects on humans, because non-clinical studies should not be taken as a direct indication for human behavior and nicotine is not risk free.

Anatabine, Nornicotine, and Anabasine Reduce Weight Gain and Body Fat through Decreases in Food Intake and Increases in Physical Activity

Obesity is a leading cause of preventable death in the United States. Currently approved pharmacotherapies for the treatment of obesity are associated with rebound weight gain, negative side effects, and the potential for abuse. There is a need for new treatments with fewer side effects. Minor tobacco alkaloids (MTAs) are potential candidates for novel obesity pharmacotherapies. These alkaloids are structurally related to nicotine, which can help reduce body weight, but without the same addictive potential. The purpose of the current study was to examine the effects of three MTAs (nornicotine, anatabine, and anabasine) and nicotine on weight gain, body composition, chow intake, and physical activity. We hypothesized that the MTAs and nicotine would reduce weight gain through reductions in chow intake and increases in physical activity. To test this, male Sprague Dawley rats were housed in metabolic phenotyping chambers. Following acclimation to these chambers and to (subcutaneous (sc)) injections of saline, animals received daily injections (sc) of nornicotine, anabasine, anatabine, or nicotine for one week. Compared to saline-injected animals that gained body weight and body fat during the treatment phase, injections of nornicotine and anatabine prevented additional weight gain, alongside reductions in body fat. Rats receiving anabasine and nicotine gained body weight at a slower rate relative to rats receiving saline injections, and body fat remained unchanged. All compounds reduced the intake of chow pellets. Nornicotine and nicotine produced consistent increases in physical activity 6 h post-injection, whereas anabasine’s and anatabine’s effects on physical activity were more transient. These results show that short-term, daily administration of nornicotine, anabasine, and anatabine has positive effects on weight loss, through reductions in body fat and food intake and increases in physical activity. Together, these findings suggest that MTAs are worthy of further investigations as anti-obesity pharmacotherapies.

Self-administration by female rats of low doses of nicotine alone vs. nicotine in tobacco smoke extract

BACKGROUND

Nicotine has reinforcing effects, but there are thousands of other compounds in tobacco, some of which might interact with nicotine reinforcement.

AIMS

This rat study was conducted to determine if nicotine self-administration is altered by co-administration of the complex mixture of compounds in tobacco smoke extract (TSE).

METHODS

Female Sprague-Dawley rats were tested for self-administration of low doses of nicotine (3 or 10 µg/kg/infusion) at three different rates of reinforcement (FR1, FR3 and FR5) over three weeks either alone or together with the complex mixture of tobacco smoke extract (TSE).

RESULTS

Rats self-administering 3 µg/kg/infusion of nicotine alone showed a rapid initiation on an FR1 schedule, but declined with FR5. Rats self-administering nicotine in TSE acquired self-administration more slowly, but increased responding over the course of the study. With 10 µg/kg/infusion rats self-administered significantly more nicotine alone than rats self-administering the same nicotine dose in TSE. Rats self-administering nicotine alone took significantly more infusions with the 10 than the 3 µg/kg/infusion dose, whereas rats self-administering nicotine in TSE did not. Nicotine in TSE led to a significantly greater locomotor hyperactivity at a dose of 0.1 mg/kg compared to rats that received nicotine alone. Rats self-administering nicotine alone had significantly more responding on the active vs. inactive lever, but rats self-administering the same nicotine doses in TSE did not.

CONCLUSIONS

Self-administration of nicotine in a purer form appears to be more clearly discriminated and dose-related than nicotine self-administered in the complex mixture of TSE.

Effects of nicotinic acetylcholine receptor-activating alkaloids on anxiety-like behavior in zebrafish

Alkaloids are a structurally complex group of natural products that have a diverse range of biological activities and significant therapeutic applications. In this study, we examined the acute, anxiolytic-like effects of nicotinic acetylcholine receptor (nAChR)-activating alkaloids with reported neuropharmacological effects but whose effects on anxiety are less well understood. Because α4β2 nAChRs can regulate anxiety, we first demonstrated the functional activities of alkaloids on these receptors in vitro. Their effects on anxiety-like behavior in zebrafish were then examined using the zebrafish novel tank test (NTT). The NTT is a relatively high-throughput behavioral paradigm that takes advantage of the natural tendency of fish to dive down when stressed or anxious. We report for the first time that cotinine, anatabine, and methylanatabine may suppress this anxiety-driven zebrafish behavior after a single 20-min treatment. Effective concentrations of these alkaloids were well above the concentrations naturally found in plants and the concentrations needed to induce anxiolytic-like effect by nicotine. These alkaloids showed good receptor interactions at the α4β2 nAChR agonist site as demonstrated by in vitro binding and in silico docking model, although somewhat weaker than that for nicotine. Minimal or no significant effect of other compounds may have been due to low bioavailability of these compounds in the brain, which is supported by the in silico prediction of blood-brain barrier permeability. Taken together, our findings indicate that nicotine, although not risk-free, is the most potent anxiolytic-like alkaloid tested in this study, and other natural alkaloids may regulate anxiety as well.

Nicotine-like discriminative and aversive effects of two α4β2-selective nicotine agonists, ispronicline and metanicotine

An attempt to determine the receptor selective nature of some of nicotine's behavioral effects was undertaken through the evaluation of the ability of two nicotinic α4β2*-selective receptor agonists to produce nicotine-like effects and modify rates of responding in a discrimination assay and in an aversive stimulus assay. A group of eight rats was trained to discriminate the presence of 1 mg/kg nicotine base. Another group of 4-6 rats was trained to report the aversive effects of nicotine by selecting a lever that produced one food pellet over a second lever that produced two food pellets and an intravenous injection of nicotine. Ispronicline and metanicotine, two α4β2*-selective receptor agonists, increased selection of the nicotine-appropriate lever in a dose-related manner, up to a maximum of approximately 75%. The α4β2*-selective receptor antagonist, dihydro-beta-erythroidine blocked both the discriminative stimulus effects and the rate-suppressing effects of ispronicline, metanicotine, and small, but not large doses of nicotine. The nonselective antagonist, mecamylamine, antagonized the discriminative stimulus effects of each of the three nicotine agonists as well as the rate-decreasing effects of nicotine and metanicotine. Mecamylamine did not modify the rate-decreasing effects of ispronicline. Both ispronicline and metanicotine as well as nicotine were avoided in the drug + food vs. food choice situation. The receptor-selective nature of ispronicline and metanicotine was hereby confirmed in a behavioral assay, as were earlier reports that the discriminative stimulus effects of relatively small doses of nicotine are likely mediated by activity at the α4β2* nicotine receptor.

Differential effects of alkaloids on memory in rodents

Nicotinic acetylcholine receptors (nAChRs) play a critical role in the neuropharmacology of learning and memory. As such, naturally occurring alkaloids that regulate nAChR activity have gained interest for understanding and potentially improving memory function. In this study, we tested the acute effects of three known nicotinic alkaloids, nicotine, cotinine, and anatabine, in suppressing scopolamine-induced memory deficit in rodents by using two classic memory paradigms, Y-maze and novel object recognition (NOR) in mice and rats, respectively. We found that all compounds were able to suppress scopolamine-induced spatial memory deficit in the Y-maze spontaneous alternation paradigm. However, only nicotine was able to suppress the short-term object memory deficit in NOR, despite the higher doses of cotinine and anatabine used to account for their potential differences in nAChR activity. These results indicate that cotinine and anatabine can uniquely regulate short-term spatial memory, while nicotine seems to have more robust and general role in memory regulation in rodents. Thus, nAChR-activating alkaloids may possess distinct procognitive properties in rodents, depending on the memory types examined.

In Vivo Profiling of a Natural Alkaloid, Anatabine, in Rodents: Pharmacokinetics and Anti-Inflammatory Efficacy

Natural alkaloids, a large class of plant-derived substances, have attracted considerable interest because of their pharmacological activities. In this study, the in vivo pharmacokinetics and anti-inflammatory profile of anatabine, a naturally occurring alkaloid, were characterized in rodents. Anatabine was found to be bioavailable and brain-penetrant following systemic administration. Following intraperitoneal (i.p.) administration (1, 2, and 5 mg/kg), anatabine caused a dose-dependent reduction in carrageenan-induced paw edema in rats; in mice, it inhibited the production of pro-inflammatory cytokines and simultaneously elevated the levels of an anti-inflammatory cytokine in a dose-dependent manner 2 h after lipopolysaccharide challenge. Furthermore, anatabine (∼10 and ∼20 mg/kg/day for 4 weeks; inhalation exposure) had effects in a murine model of multiple sclerosis, reducing neurological deficits and bodyweight loss. Comparative studies of the pharmacokinetics and anti-inflammatory activity of anatabine demonstrated its bioequivalence in rats following i.p. administration and inhalation exposure. This study not only provides the first detailed profile of anatabine pharmacokinetics in rodents but also comprehensively characterizes the anti-inflammatory activities of anatabine in acute and chronic inflammatory models. These findings provide a basis for further characterizing and optimizing the anti-inflammatory properties of anatabine.

A 3-month-delayed treatment with anatabine improves chronic outcomes in two different models of repetitive mild traumatic brain injury in hTau mice

To date, an overwhelming number of preclinical studies have addressed acute treatment in mild TBI (mTBI) and repetitive mTBI (r-mTBI), whereas, in humans, there often exists a significant time gap between the injury and the first medical intervention. Our study focused on a delayed treatment with anatabine, an anti-inflammatory compound, in hTau mice using two different models of r-mTBI. The rationale for using two models of the same impact but different frequencies (5 hit mTBI over 9 days and 24 hit mTBI over 90 days) was chosen to address the heterogeneity of r-mTBI in clinical population. Following the last injury in each model, three months elapsed before the initiation of treatment. Anatabine was administered in drinking water for 3 months thereafter. Our data demonstrated that a 3-month delayed treatment with anatabine mitigated astrogliosis in both TBI paradigms but improved cognitive functions only in more-frequently-injured mice (24 hit mTBI). We also found that anatabine decreased the phosphorylation of tau protein and NFκB, which were increased after r-mTBI in both models. The ability of anatabine to suppress these mechanisms suggests that delayed treatment can be effective for clinical population of r-mTBI. The discrepancy between the two models with regard to changes in cognitive performance suggests that r-mTBI heterogeneity may influence treatment efficiency and should be considered in therapeutic development.

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.

Interactions of Aβ1-42 Peptide and Its Three Fragments (Aβ8-12, Aβ8-13, and Aβ5-16) with Selected Nonsteroidal Drugs and Compounds of Natural Origin

In the following paper, we present the results of our studies on the interactions of the Aβ1-42 peptide and its three short fragments, namely Aβ5-16 (RHDSGYEVHHQK; HZ1), Aβ8-13 (SGYEVH; HZ2), and Aβ8-12 (SGYEV; HZ3) with selected painkillers (ibuprofen and aspirin) and compounds of natural origin (anabasine and epinephrine). Steady-state fluorescence spectroscopy was used to study the binding properties of the selected systems. Additionally, based on molecular dynamics (MD) calculations supported by NMR-derived restrains, we have proposed the most likely area of the interactions of Aβ1-42 and Aβ5-16 peptides with the investigated compounds. The influence of symmetrically oriented side chains of amino acid residues present in the first part of the Aβ1-42 sequence on the stability of the resulting complexes has been discussed. Finally, the changes in the peptide structures on account of complex formation were analyzed.

The effects of acute nicotine administration on cognitive and early sensory processes in schizophrenia: a systematic review

Nicotine use, which is mostly done through smoking tobacco, is among the most burdensome comorbidities of schizophrenia. However, the ways in which nicotine affects the cognitive and early sensory alterations found in this illness are still debated. After conducting a systematic literature search, 29 studies were selected. These studies involve individuals with schizophrenia who underwent cognitive and/or early sensory function assessments after acute nicotine administration and include 560 schizophrenia subjects and 346 non-schizophrenia controls. The findings highlight that a single dose of nicotine can improve a range of cognitive functions in schizophrenia subjects, such as attention, working memory, and executive functions, with attention being the most responsive domain. In addition, nicotine can modulate early detection of changes in the sensory environment at both the auditory and visual levels. Nevertheless, effects vary strongly depending on the type of neuropsychological assessment and nicotine intake conditions used in each study. The current findings suggest the need to consider a potential decrease of cognitive and early sensory performance when patients with schizophrenia quit smoking.

A Pharmacological Comparison of Two Isomeric Nicotinic Receptor Agonists: The Marine Toxin Isoanatabine and the Tobacco Alkaloid Anatabine

Many organisms possess "secondary" compounds to avoid consumption or to immobilize prey. While the most abundant or active compounds are initially investigated, more extensive analyses reveal other "minor" compounds with distinctive properties that may also be of biomedical and pharmaceutical significance. Here, we present an initial in vitro investigation of the actions of two isomeric tetrahydropyridyl ring-containing anabasine analogs: isoanatabine, an alkaloid isolated from a marine worm, and anatabine, a relatively abundant minor alkaloid in commercial tobacco plants. Both compounds have a double bond that is distal to the piperidine ring nitrogen of anabasine. Racemic isoanatabine and anatabine were synthesized and their S- and R-enantiomers were isolated by chiral high pressure liquid chromatography (HPLC). Both isoanatabines displayed higher efficacies at α4β2 nicotinic acetylcholine receptors (nAChRs) relative to the anatabines; R-isoanatabine was most potent. Radioligand binding experiments revealed similar α4β2 nAChR binding affinities for the isoanatabines, but R-anatabine affinity was twice that of S-anatabine. While the two anatabines and S-isoanatabine were highly efficacious agonists at α7 nAChRs, R-isoanatabine was only a weak partial agonist. The four compounds share an ability to stimulate both α4β2 and α7 nAChRs, a property that may be useful in developing more efficacious drugs to treat neurodegenerative and other medical disorders.

The D2-family receptor agonist bromocriptine but, not nicotine, reverses NMDA receptor antagonist-induced working memory deficits in the radial arm maze in mice

Hypofunction of the NMDA receptor (NMDAr) may underlie cognitive deficits associated with schizophrenia and other psychiatric conditions including working memory (WM) impairments. Given that these deficits link closely to functional outcome, treatments remediating such deficits require identification. NMDAr hypofunction can be modeled via treatment with the antagonist MK-801. Hence, the present study determined whether cholinergic or dopaminergic agonists attenuate MK-801-induced WM deficits in mice. WM was assessed in male C57BL/6 mice trained on an automated 12-arm radial arm maze (RAM) paradigm, wherein rewards were delivered after the first but, not after subsequent entries into WM arms (8/12) and never delivered for entries into reference memory (RM) arms (4/12). Mice were then treated with MK-801 (vehicle or 0.3 mg/kg) and nicotine (vehicle, 0.03 or 0.30 mg/kg) in a cross-over design. After a 2-week washout, mice were then retested with MK-801 and the dopamine D₂-family receptor agonist bromocriptine (vehicle, 3 or 10 mg/kg). In both experiments, MK-801 reduced WM span and increased RM and WM error rates. Nicotine did not attenuate these deficits. In contrast, a bromocriptine/MK-801 interaction was observed on WM error rate, where bromocriptine attenuated MK-801 induced deficits without affecting MK-801-induced RM errors. Additionally, bromocriptine produced the main effect of slowing latency to collect rewards. Hence, while NMDAr hypofunction-induced deficits in WM was unaffected by nicotine, it was remediated by treatment with the dopamine D₂-family agonist bromocriptine. Future studies should determine whether selective activation of dopamine D₂, D₃, or D₄ receptors remediate this NMDAr hypofunction-induced WM deficit.

Neurobehavioral effects of selected tobacco constituents in rodents following subchronic administration

Bidirectional correlations between cigarette smoking and affective disorders, such as depression, anxiety, and schizophrenia, are well documented. These findings have led to substantial investigations into the effects of the major tobacco alkaloid, nicotine, and to a lesser extent, of other tobacco constituents, on the central nervous system (CNS). However, systematic profiling of the neuropharmacological effects of tobacco constituents is limited. To elucidate the effects of selected tobacco constituents on the CNS, we used the SmartCube® system, which captures and classifies behavioral features of compound-treated mice, to profile the psychiatric drugs-like properties of previously reported neuroactive tobacco compounds in mice. Daily intraperitoneal injection of nicotine (0.5 and 1 mg/kg/day) and anatabine (5 mg/kg/day) for 7 days produced antidepressant-like behavioral SmartCube® signatures in mice, and these results were supported by the improved active coping responses in the forced swim tests. Conversely, ferulic acid did not show any identifiable class signatures in the SmartCube® tests, but rather displayed subclass signatures associated with acetylcholinesterase inhibitors. In novel object recognition memory test in rats, ferulic acid improved memory after 7 days of subcutaneous injection at 0.3 or 3 mg/kg/day. These results support previous findings showing the antidepressant drug-like effects of nicotine and the nootropic effects of ferulic acid. This is also the first report on the antidepressant drug-like effects of anatabine in rodents. This study provides a systemic behavioral evaluation of tobacco alkaloids and further insights into the association between affective disorders and smoking incidence.

Vortioxetine Differentially Modulates MK-801-Induced Changes in Visual Signal Detection Task Performance and Locomotor Activity

Attention impairment is a common feature of Major Depressive Disorder (MDD), and MDD-associated cognitive dysfunction may play an important role in determining functional status among this patient population. Vortioxetine is a multimodal antidepressant that may improve some aspects of cognitive function in MDD patients, and may indirectly increase glutamate neurotransmission in brain regions classically associated with attention function. Previous non-clinical research suggests that vortioxetine has limited effects on attention. This laboratory previously found that vortioxetine did not improve attention function in animals impaired by acute scopolamine administration, using the visual signal detection task (VSDT). However, vortioxetine has limited effects on acetylcholinergic neurotransmission, and thus it is possible that attention impaired by other mechanisms would be attenuated by vortioxetine. This study sought to investigate whether acute vortioxetine administration can attenuate VSDT impairments and hyperlocomotion induced by the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801. We found that acute vortioxetine administration had no effect on VSDT performance on its own, but potentiated MK-801-induced VSDT impairments. Furthermore, vortioxetine had no effect on locomotor activity on its own, and did not alter MK-801-induced hyperlocomotion. We further investigated whether vortioxetine's effect on MK-801 could be driven by a kinetic interaction, but found that plasma and brain exposure for vortioxetine and MK-801 were similar whether administered alone or in combination. Thus, it appears that vortioxetine selectively potentiates MK-801-induced impairments in attention without altering its effects on locomotion, and further that this interaction must be pharmacodynamic in nature. A theoretical mechanism for this interaction is discussed.

Cognitive and Behavioral Impairments Evoked by Low-Level Exposure to Tobacco Smoke Components: Comparison with Nicotine Alone

Active maternal smoking has adverse effects on neurobehavioral development of the offspring, with nicotine (Nic) providing much of the underlying causative mechanism. To determine whether the lower exposures caused by second-hand smoke are deleterious, we administered tobacco smoke extract (TSE) to pregnant rats starting preconception and continued through the second postnatal week, corresponding to all 3 trimesters of fetal brain development. Dosing was adjusted to produce maternal plasma Nic concentrations encountered with second-hand smoke, an order of magnitude below those seen in active smokers. We then compared TSE effects to those of an equivalent dose of Nic alone, and to a 10-fold higher Nic dose. Gestational exposure to TSE and Nic significantly disrupted cognitive and behavioral function in behavioral tests given during adolescence and adulthood (postnatal weeks 4-40), producing hyperactivity, working memory deficits, and impairments in emotional processing, even at the low exposure levels corresponding to second-hand smoke. Although TSE effects were highly correlated with those of Nic, the effects of TSE were much larger than could be attributed to just the Nic in the mixture. Indeed, TSE effects more closely resembled those of the 10-fold higher Nic levels, but still exceeded their magnitude. In combination with our earlier findings, this study thus completes the chain of causation to prove that second-hand smoke exposure causes neurodevelopmental deficits, originating in disruption of neurodifferentiation, leading to miswiring of neuronal circuits, and as shown here, culminating in behavioral dysfunction. As low level exposure to Nic alone produced neurobehavioral teratology, 'harm reduction' Nic products do not abolish the potential for neurodevelopmental damage.

Nicotine mediates expression of genes related to antioxidant capacity and oxidative stress response in HIV-1 transgenic rat brain

Oxidative stress plays an important role in the progression of HIV-1 infection. Nicotine can either protect neurons from neurodegeneration or induce oxidative stress, depending on its dose and degree of oxidative stress impairment. However, the relationship between nicotine and oxidative stress in the HIV-1-infected individuals remains largely unknown. The purpose of this study was to determine the effect of nicotine on expression of genes related to the glutathione (GSH)-centered antioxidant system and oxidative stress in the nucleus accumbens (NAc) and ventral tegmental area (VTA) of HIV-1 transgenic (HIV-1Tg) and F344 control rats. Adult HIV-1Tg and F344 rats received nicotine (0.4 mg/kg, base, s.c.) or saline injections once per day for 27 days. At the end of treatment, various brain regions including the NAc and VTA were collected from each rat. Following total RNA extraction and complementary DNA (cDNA) synthesis of each sample, quantitative reverse transcription PCR (RT-PCR) analysis was performed for 43 oxidative-stress-related genes. Compared with F344 control rats, HIV-1Tg rats showed a significant downregulation of genes involved in ATPase and cyctochrome oxidase at the messenger RNA (mRNA) level in both regions. Further, we found a significant downregulation of Gstm5 in the NAc and upregulation of Cox1, Cox3, and Gsta6 in the VTA of HIV-1Tg rats. HIV-1Tg rats showed brain-region-specific responses to chronic nicotine treatment. This response resulted in a change in the expression of genes involved in antioxidant mechanisms including the downregulation of genes such as Atp5h, Calml1, Gpx7, Gstm5, Gsr, and Gsta6 and upregulation of Sod1 in the NAc, as well as downregulation of genes like Cox5a, Gpx4, Gpx6, Gpx7, Gstm5, and Sod1 in the VTA of HIV-1Tg rats. Together, we conclude that chronic nicotine treatment has a dual effect on the antioxidant defense system and oxidative-stress-induced apoptosis signaling in HIV-1Tg rats. These findings suggest that nicotine has a negative effect on response to oxidative stress and antioxidant processes in HIV-1 Tg rat brain, especially in the VTA.

Chronic Anatabine Treatment Reduces Alzheimer's Disease (AD)-Like Pathology and Improves Socio-Behavioral Deficits in a Transgenic Mouse Model of AD

Anatabine is a minor tobacco alkaloid, which is also found in plants of the Solanaceae family and displays a chemical structure similarity with nicotine. We have shown previously that anatabine displays some anti-inflammatory properties and reduces microgliosis and tau phosphorylation in a pure mouse model of tauopathy. We therefore investigated the effects of a chronic oral treatment with anatabine in a transgenic mouse model (Tg PS1/APPswe) of Alzheimer's disease (AD) which displays pathological Aβ deposits, neuroinflammation and behavioral deficits. In the elevated plus maze, Tg PS1/APPswe mice exhibited hyperactivity and disinhibition compared to wild-type mice. Six and a half months of chronic oral anatabine treatment, suppressed hyperactivity and disinhibition in Tg PS1/APPswe mice compared to Tg PS1/APPswe receiving regular drinking water. Tg PS1/APPswe mice also elicited profound social interaction and social memory deficits, which were both alleviated by the anatabine treatment. We found that anatabine reduces the activation of STAT3 and NFκB in the vicinity of Aβ deposits in Tg PS1/APPswe mice resulting in a reduction of the expression of some of their target genes including Bace1, iNOS and Cox-2. In addition, a significant reduction in microgliosis and pathological deposition of Aβ was observed in the brain of Tg PS1/APPswe mice treated with anatabine. This is the first study to investigate the impact of chronic anatabine treatment on AD-like pathology and behavior in a transgenic mouse model of AD. Overall, our data show that anatabine reduces β-amyloidosis, neuroinflammation and alleviates some behavioral deficits in Tg PS1/APPswe, supporting further exploration of anatabine as a possible disease modifying agent for the treatment of AD.

Cadmium increases the sensitivity of adolescent female mice to nicotine-related behavioral deficits

This study investigates spatial and nonspatial working memory, anxiety related behavior, and motor activities in cadmium and/or nicotine exposed female adolescent mice. P28 female adolescent mice (albino strain) were divided into four groups of five (n = 5) mice each. A set of mice (Nic) received subcutaneous nicotine (2.0 mg/kg) while a separate set (Cd) was treated with 2.0 mg/kg cadmium (subcutaneous). For the combined treatments of cadmium and nicotine, we administered 2.0 mg/kg Nicotine and 2.0 mg/kg of Cd. Subsequently, a separate group of animals (n = 5; control) received normal saline. The total duration of treatment for all groups was 28 days (P28–P56). At P56, the treatment was discontinued, after which the animals were examined in behavioural tests. Nicotine and cadmium increased the metabolism and food intake in the female adolescent mice. This also corresponded to an increase in weight when compared with the control. However, a combined nicotine-cadmium treatment induced a decline in weight of the animals versus the control. Also, nicotine administration increased the motor function, while cadmium and nicotine-cadmium treatment caused a decline in motor activity. Both nicotine and cadmium induced a reduction in memory index; however, nicotine-cadmium treatment induced the most significant decrease in nonspatial working memory.