Therapeutic Applications of Nicotinic Stimulation: Successes, Failures, and Future Prospects

Challenges in legitimizing further measures against smoking in jurisdictions with robust infrastructure for tobacco control: how far can the authorities allow themselves to go?

BACKGROUND

According to a recently published study, approximately half of those who currently smoke in Norway have little or no desire to quit despite a hostile regulatory and socio-cultural climate for smoking. On this background, we discuss some challenges that regulators will face in a further tightening of structural measures to curb smoking.

MAIN BODY

Central to our discussion is the research literature concerned with the concept of state-paternalism in tobacco control-the line between an ethically justified interference with the freedom of those who smoke and an exaggerated infringement disproportionate to the same people's right to live as they choose. In countries with an already advanced infrastructure for tobacco control, this dilemma might become quite intrusive for regulators. We ask that if people, who smoke are aware of and have accepted the risks, are willing to pay the price, smoke exclusively in designated areas, and make decisions uninfluenced by persuasive messages from manufacturers-is a further tightening of anti-smoking measures still legitimate? Strengthening of the infrastructure for tobacco control can be seen as a "help" to people who-due to some sort of "decision failure"-continue to smoke against their own will. However, for those who want to continue smoking for reasons that for them appear rational, such measures may appear unwanted, punitive, and coercive. Is it within the rights of regulators to ignore peoples' self-determination for the sake of their own good? We problematize the "help" argument and discuss the authorities' right to elevate the zero-vision of smoking as universally applicable while at the same time setting up barriers to switching to alternative nicotine products with reduced risk.

CONCLUSION

We recommend that a further intensification of smoking control in countries that already have a well-developed policy in this area requires that regulators start to exploit the opportunity that lies in the ongoing diversification of the recreational nicotine market.

Nicotine-mediated effects in neuronal and mouse models of synucleinopathy

Introduction

Alpha-synuclein (α-Syn) aggregation, transmission, and contribution to neurotoxicity represent central mechanisms underlying Parkinson's disease. The plant alkaloid "nicotine" was reported to attenuate α-Syn aggregation in different models, but its precise mode of action remains unclear.

Methods

In this study, we investigated the effect of 2-week chronic nicotine treatment on α-Syn aggregation, neuroinflammation, neurodegeneration, and motor deficits in D-line α-Syn transgenic mice. We also established a novel humanized neuronal model of α-Syn aggregation and toxicity based on treatment of dopaminergic neurons derived from human induced pluripotent stem cells (iPSC) with α-Syn preformed fibrils (PFF) and applied this model to investigate the effects of nicotine and other compounds and their modes of action.

Results and discussion

Overall, our results showed that nicotine attenuated α-Syn-provoked neuropathology in both models. Moreover, when investigating the role of nicotinic acetylcholine receptor (nAChR) signaling in nicotine's neuroprotective effects in iPSC-derived dopaminergic neurons, we observed that while α4-specific antagonists reduced the nicotine-induced calcium response, α4 agonists (e.g., AZD1446 and anatabine) mediated similar neuroprotective responses against α-Syn PFF-provoked neurodegeneration. Our results show that nicotine attenuates α-Syn-provoked neuropathology in vivo and in a humanized neuronal model of synucleinopathy and that activation of α4β2 nicotinic receptors might mediate these neuroprotective effects.

Lynx1 and the family of endogenous mammalian neurotoxin-like proteins and their roles in modulating nAChR function

The promise of nicotinic receptors as a therapeutic target has yet to be fully realized, despite solid data supporting their involvement in neurological and neuropsychiatric diseases. The reasons for this are likely complex and manifold, having to do with the widespread action of the cholinergic system and the biophysical mechanism of action of nicotinic receptors leading to fast desensitization and down-regulation. Conventional drug development strategies tend to focus on receptor subtype-specific action of candidate therapeutics, although the broad agonist, nicotine, is being explored in the clinic. The potential negative effects of nicotine make the search for alternate strategies warranted. Prototoxins are a promising yet little-explored avenue of nicotinic receptor drug development. Nicotinic receptors in the brain belong to a complex of proteins, including those that bind to the extracellular face of the receptor, as well as chaperones that bind the intracellular domain, etc. Lynx prototoxins have allosteric modularity effects on receptor function and number and have been implicated in complex in vivo processes such as neuroplasticity, learning, and memory. Their mechanism of action and binding specificity on sets of nAChR subtypes present intriguing possibilities for more efficacious and nuanced therapeutic targeting than nicotinic receptor subtypes alone. An allosteric drug may restrict its actions to physiologically relevant time points, which tend to be correlated with salient events which would be encoded into long-term memory storage. Rather than blanketing the brain with a steady and prolonged elevation of agonist, an allosteric nAChR compound could avoid side effects and loss of efficacy over time. This review details the potential strengths and challenges of prototoxin proteins as therapeutic targets, and some of the utility of such therapeutics based on the emerging understanding of cholinergic signaling in a growing number of complex neural processes.

The Basal Forebrain Cholinergic Nuclei and Their Relevance to Schizophrenia and Other Psychotic Disorders

The basal forebrain cholinergic nuclei (BFCN) provide the main cholinergic input to prefrontal cortices, the hippocampi, and amygdala. These structures are highly relevant for the regulation and maintenance of many cognitive functions, such as attention and memory. In vivo neuroimaging studies reported alterations of the cholinergic system in psychotic disorders. Particularly, a downregulation of nicotinic and muscarinic acetylcholine receptors has been found. Crucially, such alterations in neurotransmission have been associated with cognitive impairments and positive and negative symptoms. Recent pharmacological studies support these findings, as they demonstrated an association between the manipulation of cholinergic transmission and an attenuation in symptom severity. Targeting acetylcholine receptors has therefore become a focus for the development of novel psychopharmacological drugs. However, many open questions remain. For instance, it remains elusive what causes such alterations in neurotransmission. While evidence supports the idea that BFCN structural integrity is altered in schizophrenia, it remains to be determined whether this is also present in other psychotic disorders. Furthermore, it is unclear when throughout the course of the disorder these alterations make their appearance and whether they reflect changes in the BFCN alone or rather aberrant interactions between the BFCN and other brain areas. In this review, the specific role of the BFCN and their projections are discussed from a neuroimaging perspective and with a focus on psychotic disorders alongside future directions. These directions set the stage for the development of new treatment targets for psychotic disorders.

Perceptions of nicotine in current and former users of tobacco and tobacco harm reduction products from seven countries

Purpose

Nicotine is widely known as a tobacco constituent and for its use as a tobacco cessation aid. The development of new devices for nicotine delivery in recent years has led to uncertainty among consumers regarding the health risks of nicotine relative to tobacco. The purpose of this study was to discover if current and former consumers of tobacco and tobacco harm reduction (THR) products could distinguish between “nicotine” and “cigarettes” and examined the preceding media dialogue to determine if conflicting messages by the media influence public perceptions.

Design/methodology/approach

A quantitative survey was administered online in Norway (NO), Japan (JP), the United Kingdom (UK) and the United States (US), while face-to-face computer-aided interviews were conducted with randomly selected samples in India (IN), Greece (GR) and South Africa (SA). Participants were between 18 and 69 years of age and either current users of tobacco and THR products or previous users who quit within the past five years. Questions assessed beliefs about harmfulness of nicotine. Nicotine and other products and substances were also independently rated for harmfulness on a scale of 1–10 and subsequently compared. In addition, the authors examined the media dialogue of top media outlets in four countries to assess the potential influence on people’s beliefs.

Findings

A total of 54,267 participants (NO: 1,700, JP: 2,227, UK: 2,250, USA: 2,309, IN: 41,633, GR: 1,801, SA: 2,359) were sampled with the percentage of women participants ranging from 14.8% (IN) to 53.8% (UK). Between 68.3% (men, IN) and 88.7% (men, USA) of current consumers believed nicotine is harmful. Current consumers who agreed with the statement that nicotine is the primary cause of tobacco-related cancer ranged from 43.7% (men, UK) to 78.0% (men, SA). In six countries nicotine was rated nearly as harmful as cigarettes and alcohol, while other substances such as sugar, salt or caffeine, were usually rated as less harmful.

Research limitations/implications

A large proportion of consumers across all surveyed countries view nicotine and cigarettes similarly. Clearer communication on the harmful properties of both by the media is needed to help consumers make informed decisions about products across the continuum of risk. Messaging to consumers, especially via the media, propagates misinformation about the relative harms of tobacco and nicotine through reporting that is often incomplete and biased toward more negative aspects.

Originality/value

This study specifically assessed public perceptions of nicotine as opposed to products containing nicotine, which is the focus of previous studies. Apart from showing that consumers often incorrectly perceive nicotine and cigarettes as similar in terms of harmfulness, the authors highlight the need for more accurate and complete reporting by the media to clarify widespread misunderstandings and mitigate public uncertainty.

Healthy Subjects With Extreme Patterns of Performance Differ in Functional Network Topology and Benefits From Nicotine

Do subjects with atypical patterns in attentional and executive behaviour show different brain network topology and react differently towards nicotine administration? The efficacy of pro-cognitive drugs like nicotine considerably varies between subjects and previous theoretical and empirical evidence suggest stronger behavioural nicotine effects in subjects with low performance. One problem is, however, how to best define low performance, especially if several cognitive functions are assessed for subject characterisation. We here present a method that used a multivariate, robust outlier detection algorithm to identify subjects with suspicious patterns of performance in attentional and executive functioning. In contrast to univariate approaches, this method is sensitive towards extreme positions within the multidimensional space that do not have to be extreme values in the individual behavioural distributions. The method was applied to a dataset of healthy, non-smoking subjects (n = 34) who were behaviorally characterised by an attention and executive function test on which N = 12 volunteers were classified as outliers. All subjects then underwent a resting-state functional magnetic resonance imaging (fMRI) scan to characterise brain network topology and an experimental behavioural paradigm under placebo and nicotine (7 mg patch) that gauged aspects of attention and executive function. Our results indicate that subjects with an atypical multivariate pattern in attention and executive functioning showed significant differences in nodal brain network integration in visual association and pre-motor brain regions during resting state. These differences in brain network topology significantly predicted larger individual nicotine effects on attentional processing. In summary, the current approach successfully identified a subgroup of healthy volunteers with low behavioural performance who differ in brain network topology and attentional benefit from nicotine.

Bio-oils from vacuum ablative pyrolysis of torrefied tobacco residues

Thermochemical conversion of tobacco residues to value-added bio-fuels and chemicals via fast pyrolysis, in combination with torrefaction pretreatment, in a rotating blade ablative reactor under vacuum conditions.