Pilot trial of nicotine patches as an alternative to corticosteroids in ulcerative colitis

Transdermal nicotine in non-smokers: A systematic review to design COVID-19 clinical trials

Recent data show an interaction between COVID-19 and nicotine and indicate the need for an assessment of transdermal nicotine use in non-smokers. Assessments have been conducted into the short-term cognitive effects of nicotine and into diseases such as Parkinson's, Tourette syndrome, ADHD or ulcerative colitis.

METHODS

Analyses of nicotine administration protocols and safety were conducted after reviewing Medline and Science Direct databases performing a search using the words [transdermal nicotine] AND [non-smoker] AND selected diseases.

RESULTS

Among 298 articles identified, there were 35 reviewed publications reporting on 33 studies of non-smokers receiving transdermal nicotine for >48hours. In the 16 randomized trials, 7 crossover, 1 case/control and 9 open studies patients received an initial nicotine dose of between 2.5mg and 15mg/day. In 22 studies, daily doses increased by 2 to 7 steps in 3 to 96 days until the dose was between 5mg and 105mg/day. The target nicotine dose was 19.06±20.89mg/day. The 987 non-smokers (534 never-smokers, 326 ex-smokers and 127 classified as "non-smokers") received or did not receive nicotine. The most common side-effects were nausea and skin itching. Forty-three (7.1%) non-smokers stopped treatment because of an adverse event of nicotine. No hospitalization related to nicotine side-effects were reported.

CONCLUSION

Despite a relatively safe tolerance profile, transdermal nicotine therapy in non-smokers can only be used in clinical trials. There is a lack of formal assessment of the potential risk of developing a tobacco addiction. This review offers baseline data to set a transdermal nicotine protocol for non-smokers with a new purpose.

Transdermal Nicotine as a Treatment Option for Ulcerative Colitis: A Review

Ulcerative colitis (UC) is primarily a disease of non-smokers or ex-smokers. Since there have been previous claims of the beneficial effects of transdermal nicotine, researchers studied its efficacy to include it in the treatment regimen: to prevent remissions and as maintenance therapy. This review aims to evaluate the efficacy of transdermal nicotine as a treatment option for mild to moderately active ulcerative colitis. We shortlisted 22 articles after a careful analysis and elimination process. These articles were reviewed and analyzed, and it was found that transdermal nicotine in combination with conventional therapy was more beneficial than individual treatment with either. Further controlled studies evaluating the appropriate dosage for remission and maintenance treatment needs to be done.

Ulcerative colitis in smokers, non-smokers and ex-smokers

Smoking is a major environmental factor that interferes in the establishment and clinical course of ulcerative colitis (UC). Firstly, the risk of smoking status impact in the development of UC is reviewed, showing that current smoking has a protective association with UC. Similarly, being a former smoker is associated with an increased risk of UC. The concept that smoking could have a role in determining the inflammatory bowel disease phenotype is also discussed. Gender may also be considered, as current smoking delays disease onset in men but not in women. No clear conclusions can be driven from the studies trying to clarify whether childhood passive smoking or prenatal smoke exposure have an influence on the development of UC, mainly due to methodology flaws. The influence of smoking on disease course is the second aspect analysed. Some studies show a disease course more benign in smokers that in non-smokers, with lower hospitalizations rates, less flare-ups, lower use of oral steroids and even less risk of proximal extension. This is not verified by some other studies. Similarly, the rate of colectomy does not seem to be determined by the smoking status of the patient. The third issue reviewed is the use of nicotine as a therapeutic agent. The place of nicotine in the treatment of UC is unclear, although it could be useful in selected cases, particularly in recent ex-smokers with moderate but refractory attacks of UC. Finally, the effect of smoking cessation in UC patients is summarised. Given that smoking represents a major worldwide cause of death, for inpatients with UC the risks of smoking far outweigh any possible benefit. Thus, physicians should advise, encourage and assist UC patients who smoke to quit.

Cholinergic agonists regulate JAK2/STAT3 signaling to suppress endothelial cell activation

The cholinergic anti-inflammatory pathway is a physiological mechanism that inhibits cytokine production and minimizes tissue injury during inflammation. Previous investigations revealed that cholinergic stimulation (via cholinergic agonists and vagus nerve stimulation) suppresses endothelial cell activation and leukocyte recruitment. The purpose of this study was to investigate the mechanisms by which cholinergic agonists (e.g., nicotine and GTS-21) regulate endothelial cell activation. Specifically, we examined the effects of cholinergic agonists on IL-6-mediated endothelial cell activation through the JAK2/STAT3 signaling pathway. Treatment of macrovascular human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells (MVECs) with the cholinergic agonists nicotine and GTS-21 significantly reduced IL-6-mediated monocyte chemoattractant protein-1 (MCP-1) production and ICAM-1 expression which are regulated through the JAK2/STAT3 pathway. We found that treatment of endothelial cells with cholinergic agonists significantly reduced STAT3 activation by phosphorylation and DNA binding. The inhibition of STAT3 phosphorylation was reversed by sodium orthovanadate, an inhibitor of tyrosine phosphatases, as well as by NSC-87877 suggesting a SHP1/2-dependent mechanism. Further investigations showed that cholinergic agonists reduced the phosphorylation of JAK2, an upstream component of the JAK2/STAT3 pathway. Finally, we observed that nicotine and GTS-21 treatment decreased levels of SOCS3 (suppressor of cytokine signaling; a regulator of the inflammatory activity of IL-6) in activated endothelial cells. These data demonstrate that cholinergic agonists suppress IL-6-mediated endothelial cell activation through the JAK2/STAT3 pathway. Our results have significant implications for better understanding the therapeutic potential of cholinergic agonists for treating IL-6 mediated inflammatory conditions.

Hypothesis about mechanisms through which nicotine might exert its effect on the interdependence of inflammation and gut barrier function in ulcerative colitis

Ulcerative colitis (UC) is characterized by impairment of the epithelial barrier and the formation of ulcer-type lesions, which result in local leaks and generalized alterations of mucosal tight junctions. Ultimately, this results in increased basal permeability. Although disruption of the epithelial barrier in the gut is a hallmark of inflammatory bowel disease and intestinal infections, it remains unclear whether barrier breakdown is an initiating event of UC or rather a consequence of an underlying inflammation, evidenced by increased production of proinflammatory cytokines. UC is less common in smokers, suggesting that the nicotine in cigarettes may ameliorate disease severity. The mechanism behind this therapeutic effect is still not fully understood, and indeed it remains unclear if nicotine is the true protective agent in cigarettes. Nicotine is metabolized in the body into a variety of metabolites and can also be degraded to form various breakdown products. It is possible these metabolites or degradation products may be the true protective or curative agents. A greater understanding of the pharmacodynamics and kinetics of nicotine in relation to the immune system and enhanced knowledge of gut permeability defects in UC are required to establish the exact protective nature of nicotine and its metabolites in UC. This review suggests possible hypotheses for the protective mechanism of nicotine in UC, highlighting the relationship between gut permeability and inflammation, and indicates where in the pathogenesis of the disease nicotine may mediate its effect.

Cholinergic stimulation blocks endothelial cell activation and leukocyte recruitment during inflammation

Endothelial cell activation plays a critical role in regulating leukocyte recruitment during inflammation and infection. Based on recent studies showing that acetylcholine and other cholinergic mediators suppress the production of proinflammatory cytokines via the α7 nicotinic acetylcholine receptor (α7 nAChR) expressed by macrophages and our observations that human microvascular endothelial cells express the α7 nAChR, we examined the effect of cholinergic stimulation on endothelial cell activation in vitro and in vivo. Using the Shwartzman reaction, we observed that nicotine (2 mg/kg) and the novel cholinergic agent CAP55 (12 mg/kg) inhibit endothelial cell adhesion molecule expression. Using endothelial cell cultures, we observed the direct inhibitory effects of acetylcholine and cholinergic agents on tumor necrosis factor (TNF)-induced endothelial cell activation. Mecamylamine, an nAChR antagonist, reversed the inhibition of endothelial cell activation by both cholinergic agonists, confirming the antiinflammatory role of the nAChR cholinergic pathway. In vitro mechanistic studies revealed that nicotine blocked TNF-induced nuclear factor–κB nuclear entry in an inhibitor κB (IκB)α- and IκBɛ-dependent manner. Finally, with the carrageenan air pouch model, both vagus nerve stimulation and cholinergic agonists significantly blocked leukocyte migration in vivo. These findings identify the endothelium, a key regulator of leukocyte trafficking during inflammation, as a target of anti-inflammatory cholinergic mediators.

Neuronal nicotinic receptors: from structure to pathology

Neuronal nicotinic receptors (NAChRs) form a heterogeneous family of ion channels that are differently expressed in many regions of the central nervous system (CNS) and peripheral nervous system. These different receptor subtypes, which have characteristic pharmacological and biophysical properties, have a pentameric structure consisting of the homomeric or heteromeric combination of 12 different subunits (alpha2-alpha10, beta2-beta4). By responding to the endogenous neurotransmitter acetylcholine, NAChRs contribute to a wide range of brain activities and influence a number of physiological functions. Furthermore, it is becoming evident that the perturbation of cholinergic nicotinic neurotransmission can lead to various diseases involving nAChR dysfunction during development, adulthood and ageing. In recent years, it has been discovered that NAChRs are present in a number of non-neuronal cells where they play a significant functional role and are the pathogenetic targets in several diseases. NAChRs are also the target of natural ligands and toxins including nicotine (Nic), the most widespread drug of abuse. This review will attempt to survey the major achievements reached in the study of the structure and function of NAChRs by examining their regional and cellular localisation and the molecular basis of their functional diversity mainly in pharmacological and biochemical terms. The recent availability of mice with the genetic ablation of single or double nicotinic subunits or point mutations have shed light on the role of nAChRs in major physiological functions, and we will here discuss recent data relating to their behavioural phenotypes. Finally, the role of NAChRs in disease will be considered in some details.

Drug delivery across the skin

Since the introduction of the first through the skin (TTS) therapeutic in 1980, a total of 34 TTS products have been marketed and numerous drugs have been tested by more than 50 commercial organisations for their suitability for TTS delivery. Most of the agents which have been tested have had low molecular weights, due to the impermeability of the skin barrier. This barrier resides in the outermost skin layer, the stratum corneum. It is mechanical, anatomical, as well as chemical in nature; laterally overlapping cell multi-layers are sealed by tightly packed, intercellular, lipid multi-lamellae. Chemical skin permeation enhancers increase the transport across the barrier by partly solubilising or extracting the skin lipids and by creating hydrophobic pores. This is often irritating and not always well-tolerated. The TTS approach allows drugs (< 400 kDa in size) to permeate through the resulting pores in the skin, with a short lag-time and subsequent steady-state period. Drug bioavailability for TTS delivery is typically below 50%, avoiding the first pass effect. Wider, hydrophilic channels can be generated by skin poration, with the aid of a small electrical current (> 0.4 mA/cm2) across the skin (iontophoresis) or therapeutic ultrasound (few W/cm2; sonoporation). High-voltage (> 150 V, electroporation) widens the pores even more and often irreversibly. These standard poration methods require experience and equipment and are therefore, not practical; at best, charged/small molecules (< or = 4000 kDa in size) can be delivered efficiently across the skin. In spite of the potential harm of gadget-driven skin poration, this method is used to deliver molecules which conventional TTS patches are unable to deliver, especially polypeptides. Lipid-based drug carriers (liposomes, niosomes, nanoparticle microemulsions, etc.) were proposed as alternative, low-risk delivery vehicles. Such suspensions provide an improved drug reservoir on the skin, but the aggregates remain confined to the surface. Conventional carrier suspensions increase skin hydration and/or behave as skin permeation enhancers. The recently developed carriers; Transferomes, comprise pharmaceutically-acceptable, established compounds and are thought to penetrate the skin barrier along the naturally occurring transcutaneous moisture gradient. Transfersomes are believed to penetrate the hydrophilic (virtual) channels in the skin and widen the former after non-occlusive administration. Both small and large hydrophobic and hydrophilic molecules are deliverable across the stratum after conjugation with Transfersomes. Drug distribution after transdermal delivery probably proceeds via the lymph. This results in quasi-zero order kinetics with significant systemic drug levels reached after a lag-time of up to a few hours. The relative efficiency of TTS drug delivery with Transfersomes is typically above 50 %; with the added possibility of regional drug targeting.

Metabolism and biochemical effects of nicotine for primary care providers

Nicotine is a colorless and volatile liquid alkaloid naturally occurring in the leaves and stems of Nicotiana tabacum and Nicotiana rustica. Nicotine, the primary component of tobacco, is responsible for both tobacco product addiction (with chronic exposure) and the odor associated with tobacco. In addition to cigarettes, nicotine is found in chewing gum, transdermal patches, nasal spray, and sublingual tablets. Following its inhalation and absorption, nicotine and its metabolic products exert diverse physiologic and pharmacologic effects. This article covers the absorption and metabolism of nicotine, nicotine toxicity, pharmacologic effects of nicotine, nicotine-drug interactions, and the use of nicotine for the treatment of disease.

Inflammatory bowel disease and smoking: a review of epidemiology, pathophysiology, and therapeutic implications

The relationship between smoking behavior and inflammatory bowel disease (IBD) is complex. While Crohn's disease (CD) is associated with smoking and smoking has detrimental effects on the clinical course of the disease, ulcerative colitis (UC) is largely a disease of nonsmokers and former smokers. Furthermore, cigarette smoking may even result in a beneficial influence on the course of ulcerative colitis. The potential mechanisms involved in this dual relationship include changes in humoral and cellular immunity, cytokine and eicosanoid levels, gut motility, permeability, and blood flow, colonic mucus, and oxygen free radicals. Nicotine is assumed to be the active moiety. The differential therapeutic consequences comprise the cessation of smoking in CD and, so far, clinical trials using nicotine in different forms of application for UC. In this article, we review the relationship between cigarette smoking and IBD, considering epidemiological, pathogenetic, and clinical aspects.

Role of smoking in inflammatory bowel disease: implications for therapy

The relationship between smoking and inflammatory bowel disease is now firmly established but remains a source of confusion among both patients and doctors. It is negatively associated with ulcerative colitis but positively associated with Crohn's disease. In addition, it has opposite influences on the clinical course of the two conditions with benefit in ulcerative colitis but a detrimental effect in Crohn's disease. These differences have been the subject of much interest and scrutiny with the hope that they may offer some insight into the pathogenesis of the two conditions and possibly lead to alternative therapeutic options. Nicotine is probably the principal active ingredient in smoking responsible for the association; trials have shown it to be of some benefit in ulcerative colitis, but further research is required to establish its therapeutic role, and the relevant mechanisms responsible for its action. In this article, we review the role of smoking in inflammatory bowel disease and its implication for therapy.

Nicotine therapy for ulcerative colitis: a review of rationale, mechanisms, pharmacology, and clinical results

Smoking is protective against developing ulcerative colitis. Nicotine may be the cause of this protective effect. Controlled trials have demonstrated efficacy of transdermal nicotine for active ulcerative colitis. Side effects observed with transdermal nicotine include contact dermatitis, nausea, and lightheadedness. Topical administration of nicotine to the colon reduces nicotine blood concentrations and side effects, and may be of clinical benefit.

Inflammatory bowel disease and smoking--a review

The relationship between smoking and inflammatory bowel disease is a curious but well-established one. It is negatively associated with ulcerative colitis but positively associated with Crohn's disease. It also has opposite influences on the clinical course of the two conditions with possible beneficial effect in ulcerative colitis and detrimental effect in Crohn's disease. The diametrically "opposite" relationship of smoking status with the two conditions has been the subject of much interest in the hope that it may reveal pathogenic mechanisms responsible for the two conditions and possibly offer the key to alternative therapeutic options. Nicotine may be the principal agent in smoking responsible for the association; trials have shown it to be of some benefit in ulcerative colitis, but further research is required to establish its therapeutic role and possible mechanisms of action. In this article, we review the historical, clinical, and therapeutic aspects of the association between smoking and inflammatory bowel disease.

Nicotinic acetylcholine receptors in health and disease

Nicotinic acetylcholine receptors (AChRs) are a family of acetylcholine-gated cation channels that form the predominant excitatory neurotransmitter receptors on muscles and nerves in the peripheral nervous system. AChRs are also expressed on neurons in lower amounts throughout the central nervous system. AChRs are even being reported on unexpected cell types such as keratinocytes. Structures of these AChRs are being determined with increasing precision, but functions of some orphan subunits are just beginning to be established. Functional roles for postsynaptic AChRs in muscle are well known, but in neurons the post-, peri-, extra-, and presynaptic roles of AChRs are just being revealed. Pathogenic roles of AChRs are being discovered in many diseases involving mechanisms ranging from mutations, to autoimmune responses, to the unknown; involving cell types ranging from muscles, to neurons, to keratinocytes; and involving signs and symptoms ranging from muscle weakness to epilepsy, to neurodegenerative disease, to psychiatric disease, to nicotine addiction. Awareness of AChR involvement in some of these diseases has provoked new interests in development of therapeutic agonists for specific AChR subtypes and the use of expressed cloned AChR subunits as possible immunotherapeutic agents. Highlights of recent developments in these areas will be briefly reviewed.