Hepatotoxicity of titanium dioxide nanoparticles.

The food additive E171 (titanium dioxide, TiO2), is widely used in foods, pharmaceuticals and cosmetics. It is a fine white powder, with at least one third of its particles sized in the nanoparticulate (˂100 nm range, TiO2 NPs). The use of E171 is controversial as its relevant risk assessment has never been satisfactorily accomplished. In vitro and in vivo studies have shown dose-dependent toxicity in various organs including the liver. TiO2 NPs have been shown to induce inflammation, cell death and structural and functional changes within the liver. The toxicity of TiO2 NPs in experimental models varies between organs and according to their physiochemical characteristics and parameters such as dosage and route of administration. Among these factors, ingestion is the most significant exposure route, and the liver is a key target organ. The aim of this review is to highlight the reported adverse effects of orally administered TiO2 NPs on the liver and to discuss the controversial state of its toxicity.

A review of monoamine oxidase (MAO) inhibitors in tobacco or tobacco smoke.

Tobacco smoking is reputed to be the most difficult addiction of all to give up, and nicotine has been noted as the major addictive agent in tobacco smoke. However, research shows that nicotine addiction is due to more than nicotine alone. One hypothesis is that monoamine oxidase (MAO) inhibition from non-nicotinic components in, or derived from, tobacco smoke contributes to nicotine addiction. Harman and norharman, have been recognised as major and potent MAO inhibitors in tobacco smoke, but these two inhibitors together comprise perhaps less than 10% of the total MAO A inhibitory activity in cigarette smoke suggesting other unidentified components may make significant contributions to total inhibitory activity. Therefore, we reviewed an index of the chemical components of tobacco and tobacco smoke and identified those known to be MAO inhibitors. Amongst these inhibitors, phenols and phenolic acids with MAO inhibitory activity are commonly reversible and selective MAO A inhibitors, whereas trans,trans-farnesol, 2-methyl-1,4-naphthoquinone (menadione), 1,4-naphthoquinone, scopoletin, and diosmetin with MAO inhibitory activity are reversible and selective MAO B inhibitors. The compound, 1,4-benzoquinone is an irreversible MAO A inhibitor and to the best of our knowledge, this is the first irreversible MAO A inhibitor to be reported in tobacco smoke. MAO inhibitors have been used clinically to treat depression, anxiety, and Parkinson's disease. The MAO inhibitors identified from tobacco and tobacco smoke and summarized in this review, are potential pharmacological candidates to be investigated further. This review will enhance our knowledge of the way tobacco smoke affects MAO activity in smokers and will also be important in helping to understand nicotine addiction.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health.

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson's Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Acute toxicity of dihydroanatoxin-a from Microcoleus autumnalis in comparison to anatoxin-a.

The cyanobacterium Microcoleus autumnalis grows as thick benthic mats in rivers and is becoming increasingly prevalent around the world. M. autumnalis can produce high concentrations of anatoxins and ingestion of benthic mats has led to multiple dog deaths over the past two decades. M. autumnalis produces a suite of different anatoxin congeners including anatoxin-a (ATX), dihydroanatoxin-a, (dhATX), homoanatoxin-a and dihydrohomoanatoxin-a. Benthic mat samples often contain high levels of dhATX, but there is little toxicology information on this congener. In the present study, natural versions of dhATX and ATX were purified from cyanobacteria to determine the acute toxicity by different routes of administration using mice. Nuclear magnetic resonance spectroscopy was used to confirm the putative structure of dhATX. By intraperitoneal (ip) injection, the median lethal dose (LD50) for dhATX was 0.73 mg/kg, indicating a reduced toxicity compared to ATX (LD50 of 0.23 mg/kg). However, by oral administration (both gavage and feeding), dhATX was more toxic than ATX (gavage LD50 of 2.5 mg/kg for dhATX and 10.6 mg/kg for ATX; feeding LD50 of 8 mg/kg for dhATX and 25 mg/kg for ATX). The relative nicotinic acetylcholine receptor-binding affinities of ATX and dhATX were determined using the Torpedo electroplaque assay which showed consistency with the relative toxicity determined by ip injection. This work highlights that toxicity studies based solely on ip injection may not yield LD50 values that are relevant to those derived via oral administration, and hence, do not provide a good estimate of the risk posed to human and animal health in situations where oral ingestion is the likely route of exposure. The high acute oral toxicity of dhATX, and its abundance in M. autumnalis proliferations, demonstrates that it is an important environmental contaminant that warrants further investigation.

Monoamine oxidase inhibitory activity of flavoured e-cigarette liquids.

BACKGROUND AND AIMS: Monoamine oxidase inhibitors have been hypothesised to be important in tobacco dependence, reinforcing the brain's response to nicotine by delaying the degradation of neurotransmitters by monoamine oxidases. The development of electronic cigarettes has provided an alternative nicotine delivery system, which is widely viewed as less toxic than tobacco smoke. However, significant data gaps remain. This paper reports the results of measurements of monoamine oxidase inhibitory activity in a small sample of commercially available, flavoured e-liquids. METHODS: Twelve e-liquids were tested for monoamine oxidase inhibitory activity, using the kynuramine assay and monoamine oxidase enzymes (human, recombinant). Control samples of carrier liquids, propylene glycol and glycerol, and nicotine were also tested. RESULTS: Four e-liquids contained high levels of inhibitory activity, four more were moderately inhibitory. The remaining four e-liquids were mildly inhibitory, while the carrier liquids, and nicotine were inactive at relevant concentrations. The active compounds in the e-liquids were subsequently identified as vanillin and ethyl vanillin. Under some conditions of use, the sampled e-liquids with the highest concentrations of monoamine oxidase inhibitory activity have the potential to expose consumers to physiologically significant levels of MAO inhibitory activity. CONCLUSIONS: While only a small sample of e-liquids was tested, the findings suggest that some flavours have pharmacological actions, with potential to enhance the response to nicotine or to other drugs. The public health implications of these preliminary findings on addiction and smoking cessation warrant exploration and further research.

Government and public health responses to e-cigarettes in New Zealand: vapers' perspectives.

BACKGROUND: The New Zealand (NZ) government is to lift the ban on the sale of nicotine for use in electronic cigarettes (e-cigarettes). METHODS: Using a naturalistic approach, we sought to understand how the current law was experienced by e-cigarette users (vapers). Twenty-nine vapers were interviewed by telephone, between May and September 2016, using a semi-structured interview schedule. Open-ended questions covered: initiating vaping, the experience of stopping smoking, technical problems encountered, reasons for vaping, acceptability of vaping, addiction to vaping and advice given to smokers about vaping. The audio recordings were transcribed and then independently coded using a general inductive thematic analysis. RESULTS: This paper presents the main theme which was that vapers employed a range of reactionary strategies to the ban on the sale of nicotine e-liquid in NZ. These included lobbying government, spreading the word, establishing vaper support groups, helping people stop smoking by switching to vaping and advocating for e-cigarettes to be incorporated into smoking cessation practice. CONCLUSIONS: Vapers' experience and observations form a popular or lay epidemiology--one that identified that e-cigarettes were helping people stop smoking and could thus deliver public health benefits. Public health researchers and workers, and government fears about vaping, and proposals to strengthen restrictions contributed to the growth of the vaper community who reacted by forming self-help groups and providing alternative cessation support to smokers. For a significant switch from smoking to vaping to occur, the health sector needs to have a change of attitude towards vaping that is positive, and the public needs evidence-based information on vaping. A first step could be for the health sector to collaborate with the vaping community to reorient current tobacco control and cessation practice to encourage smokers to switch to less harmful smoke-free alternatives to smoking.

Acceptability of electronic cigarettes as an option to replace tobacco smoking for alcoholics admitted to hospital for detoxification.

AIM: A feasibility/acceptability trial was undertaken at Ward 5, Kenepuru Hospital, Porirua, to ascertain whether electronic cigarettes (e-cigarettes) were a useful option to replace or reduce smoking in the detoxification ward. METHODS: Two groups of patients were studied. Tobacco use and dependency data were collected for each. The first group was surveyed on the usefulness of standard nicotine replacement therapy (NRT). The second group were offered e-cigarettes with the option of standard NRT as well. All were asked to record their use of cigarettes, e-cigarettes and NRT during their stay on the ward, and to comment on their experiences. Outcomes monitored were self-reported use of NRT and of tobacco. Informal impressions of the nursing staff were also collected, where offered. For the e-cigarette group, a blood sample was taken on day 3 or 4 of their stay in hospital for nicotine/cotinine analysis, to confirm nicotine intake status. RESULTS: E-cigarettes were well tolerated as a form of nicotine replacement, eliciting positive comments, though they were not effective for all. The average reduction in median cigarettes per day was very similar between the group given standard NRT and the e-cigarette group, at 80% and 86% respectively. There were no adverse effects reported. CONCLUSION: The study showed that e-cigarettes were an acceptable form of nicotine replacement for these alcohol-dependent patients during their time in the ward. For heavily tobacco-dependent smokers, e-cigarettes may provide a useful aid to patient management within a hospital setting.

An Online Survey of New Zealand Vapers.

Using electronic cigarettes (vaping) is controversial, but is increasingly widespread. This paper reports the results of an electronic survey of vapers in New Zealand, a country where the sale and supply of e-liquids containing nicotine is illegal, although vapers can legally access e-liquids from overseas. An on-line survey was conducted, using vaper and smoking cessation networks for recruitment, with follow up surveys conducted 1 and 2 months after the initial survey. 218 participants were recruited. Almost all had been smokers, but three quarters no longer smoked, with the remainder having significantly reduced their tobacco use. Three participants were non-smokers before starting to vape, but none had gone on to become smokers. The overriding motivation to begin and continue vaping was to stop or to reduce smoking. The results were consistent with a progression from initially both vaping and smoking using less effective electronic cigarette types, then moving to more powerful devices, experimentation with flavors and nicotine strengths-all resulting in reducing or stopping tobacco use. Lack of access to nicotine and lack of support for their chosen cessation method were the main problems reported. Vaping had resulted in effective smoking cessation for the majority of participants.

Monoamine oxidase inhibitory activity in tobacco particulate matter: Are harman and norharman the only physiologically relevant inhibitors?

Monoamine oxidase inhibition is significant in smokers, but it is still unclear how the inhibition that is seen in the brains and bodies of smokers is brought about. Our aim was to test the contribution of the harman and norharman in tobacco smoke to MAO-A inhibition from tobacco smoke preparations, as part of a re-examination of harman and norharman as the cause of the inhibition of MAO-A inhibition in the brain. Tobacco smoke particulate matter and cigarette smoke particulate matter were prepared and the amounts of harman and norharman measured. The results were compared with the total monoamine oxidase-A inhibitory activity. At a nicotine concentration of 0.6µM (a "physiological" concentration in blood) the total monoamine oxidase-A inhibitory activity measured in these samples was sufficient to inhibit the enzyme by approximately 10%. Of this inhibitory activity, only a small proportion of the total was found to be due to harman and norharman. These results show that harman and norharman provide only a moderate contribution to the total monoamine oxidase-A inhibitory activity of tobacco smoke, perhaps under 10%. This suggests that other inhibitors (either known or unknown) may be more significant contributors to total inhibitory activity than has yet been established, and deserve closer examination.

Tobacco particulate matter self-administration in rats: differential effects of tobacco type.

Nicotine self-administration in rats is the most widely used animal model of tobacco dependence. There is increasing evidence, however, that non-nicotinic constituents in smoke contribute to addiction and that different tobacco products contain varying levels of these constituents. The present study firstly sought to compare self-administration of pure nicotine to tobacco particulate matter (TPM) to determine if there were differences in reward-efficacy attributable to the non-nicotine constituents. Secondly, cigarette and roll-your-own (RYO) TPM groups were included and compared to determine whether different formulations of non-nicotinic constituents could impact reward. Briefly, male Sprague Dawley rats were implanted with indwelling jugular catheters for self-administration (n = 76). The reinforcing efficacy of infusions of nicotine (0.0 or 30.0 µg/kg/infusion) versus cigarette/RYO TPM (with matched nicotine content) was determined using spontaneous acquisition of self-administration on a fixed ratio schedule. The progressive ratio schedule was then employed to determine the motivation to receive each drug and within-subject dose-response curves were also produced (7.5, 15.0, 30.0 and 60.0 µg/kg/infusion nicotine). The main finding was that the RYO TPM was more reinforcing and produced a different profile of reward-related behaviour compared with both the nicotine and the cigarette TPM groups. The conclusions were that non-nicotinic components have a role in tobacco dependence and that some tobacco products could have higher abuse liability, irrespective of nicotine levels.

Whole tobacco smoke extracts to model tobacco dependence in animals.

Smoking tobacco is highly addictive and a leading preventable cause of death. The main addictive constituent is nicotine; consequently it has been administered to laboratory animals to model tobacco dependence. Despite extensive use, this model might not best reflect the powerful nature of tobacco dependence because nicotine is a weak reinforcer, the pharmacology of smoke is complex and non-pharmacological factors have a critical role. These limitations have led researchers to expose animals to smoke via the inhalative route, or to administer aqueous smoke extracts to produce more representative models. The aim was to review the findings from molecular/behavioural studies comparing the effects of nicotine to tobacco/smoke extracts to determine whether the extracts produce a distinct model. Indeed, nicotine and tobacco extracts yielded differential effects, supporting the initiative to use extracts as a complement to nicotine. Of the behavioural tests, intravenous self-administration experiments most clearly revealed behavioural differences between nicotine and extracts. Thus, future applications for use of this behavioural model were proposed that could offer new insights into tobacco dependence.

The effects of nicotine and tobacco particulate matter on dopamine uptake in the rat brain.

Cigarette smoking is the leading cause of preventable death worldwide. Recently, tobacco extracts have been shown to have a different pharmacological profile to nicotine alone and there is increasing evidence of a role for non-nicotinic components of cigarette smoke in smoking addiction. Nicotine is known to affect the uptake of dopamine in the brain of laboratory animals, but studies in the literature are often contradictory and little is known of the effects on non-nicotinic tobacco components on dopamine uptake. This study has examined the acute and chronic effects of nicotine and a tobacco extract (TPM) on dopamine uptake by the dopamine and norepinephrine transporters (DAT and NET) ex vivo using rotating disk electrode voltammetry, and quantified DAT and NET protein and mRNA expression in key brain regions. Nicotine (0.35 mg/kg) significantly decreased DAT function in the nucleus accumbens (NAc) at 30 min with no change in protein expression. This effect was sensitive to mecamylamine and DHßE but not MLA, indicating that it is dependent on α4 subunit containing nicotinic receptors. Furthermore, TPM, but not nicotine, increased DAT function in the dorsal striatum at 1 h in a nicotinic receptor independent manner with no change in DAT protein expression. At 1 h DAT mRNA in the ventral tegmental area was decreased by both acute and chronic TPM treatments.

Nicotine-, tobacco particulate matter- and methamphetamine-produced locomotor sensitisation in rats.

RATIONALE: Repeated nicotine exposure produces a weak and transient sensitised locomotor response in rats. Since tobacco smoke contains thousands of non-nicotine chemical constituents, these could alter the sensitised response. OBJECTIVES: This study aims to compare the magnitude, persistence and spatial distribution of locomotor sensitisation produced by repeated doses of nicotine, aqueous tobacco particulate matter (TPM) and a positive methamphetamine control. METHODS: Male Sprague-Dawley rats received five nicotine (0.0, 0.2 or 0.4 mg/kg), TPM (containing 0.2 or 0.4 mg/kg nicotine) or methamphetamine (0.5 mg/kg) injections every second day, followed by a 4-day withdrawal before the first challenge (Challenge 1, C1). The animals were re-challenged again at 15 days post C1 to test for the persistence of sensitisation (Challenge 2, C2). RESULTS: There were no major differences in sensitisation profile between nicotine and TPM. At the lowest 0.2 mg/kg nicotine/TPM dose, however, small differences emerged on select test days. CONCLUSIONS: The results indicated that the non-nicotinic agents in TPM did not greatly impact the nicotine-produced locomotor-sensitised response. These findings might suggest that the differential pharmacological properties of TPM do not have major clinical significance. Alternatively, the locomotor model might not expose effects of non-nicotinic constituents, and furthermore, might not closely relate to human tobacco dependence. Different reward-related behavioural models should also be utilised to assess potential effects of non-nicotinic constituents before a role in dependence is discounted.

Proteins isolated with TRIzol are compatible with two-dimensional electrophoresis and mass spectrometry analyses.

TRIzol is used for RNA isolation but also permits protein recovery. We investigated whether proteins prepared with TRIzol were suitable for two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization mass spectrometry. Proteins from TRIzol-treated SH-SY5Y cells produced 2-DE spot patterns similar to those from an equivalent untreated sample. Subsequent identification of TRIzol-treated proteins using peptide mass fingerprinting was successful. TRIzol exposure altered neither the mass of myoglobin extracted from sodium dodecyl sulfate (SDS) gels nor the masses of myoglobin peptides produced by in-gel trypsin digestion. These findings suggest that proteins isolated with TRIzol remain amenable to proteomic analyses.

Monoamine oxidase inhibitory activity in tobacco smoke varies with tobacco type.

BACKGROUND: It has been suggested that inhibition of monoamine oxidase (MAO) activity by components of cigarette smoke may impact on smoking addiction, but it is unclear to what extent the known MAO inhibitors in tobacco smoke cause this inhibition. METHODS: MAO inhibitory activity was measured in a series of tobacco particulate matter preparations from different brands of cigarette and loose-leaf tobacco commonly available in New Zealand. RESULTS: When tobacco extracts were diluted to contain a physiologically relevant nicotine concentration of 0.2 µM, all samples tested inhibited MAO-A and MAO-B by between 4% and 12% in a standard assay. Per mg of nicotine, samples from factory-made cigarettes contained significantly less MAO inhibitory activity than did samples from loose-leaf tobacco. When inhibitory activity was calculated on a per mg of tar basis, there was no significant difference between loose-leaf tobaccos and factory-made cigarettes. CONCLUSIONS: The present study shows that the ratio of nicotine to MAO inhibitory activity varies depending on the type of tobacco product used. The roll-your-own tobaccos tested delivered more tar and more MAO inhibitory activity per mg of nicotine than the factory-made cigarettes. These findings suggest that smokers of roll-your-own tobacco may experience greater difficulty in stopping smoking.

The effects of nicotine and cigarette smoke on the monoamine transporters.

Cigarette smoking is the leading cause of preventable illness worldwide; however, smoking addiction remains poorly understood and cessation therapies based on nicotine replacement have limited success. The monoamine transporters are the primary mechanism for regulating the levels of dopamine, serotonin and norepinephrine in the synapse, and have been implicated in addiction and associated behaviors. Furthermore, the non-nicotinic smoking cessation therapy bupropion acts at least in part by blocking the dopamine and norepinephrine transporters. Despite this, little work has been conducted into the effects of nicotine and cigarette smoke on the monoamine transporters. This review will outline research that has been conducted to date on cigarette smoke, nicotine and the monoamine transporters. This will include monoamine transporter regulation by nicotine and cigarette smoke, genetic associations of the transporters with smoking behavior, and the potential for monoamine transporters to be targets in the development of smoking cessation pharmacotherapies.

The algal metabolite yessotoxin affects heterogeneous nuclear ribonucleoproteins in HepG2 cells.

The dinoflagellate metabolite yessotoxin (YTX) is produced by several species of algae and accumulates in marine food chains, leading to concerns about possible affects on aquaculture industries and human health. In mice used for toxicity testing, YTX is lethal by the intraperitoneal route, but is considerably less toxic when orally administered. The mode of action of YTX and its potential effect on humans is unclear and we therefore conducted the first proteomic analysis of the effects of this compound. We used 2-DE to examine protein changes in HepG2 cell cultures exposed to 1.4 microM YTX for 3, 12.5, 18 and 24 h. After selecting proteins that changed more than three-fold after YTX exposure, 55 spots were deemed significantly affected by the toxin (p<0.05). Major groups of affected proteins include members from the heterogeneous nuclear ribonucleoprotein (hnRNP), lamin, cathepsin and heat shock protein families that often are associated with apoptosis. We therefore confirmed apoptosis using Annexin-V-FLUOS staining of phosphatidylserine exposed at the surface of apoptotic cells. Ingenuity pathways analysis also indicated effects on pathways involved in protein processing, cell cycling and cell death.

Tobacco particulate matter is more potent than nicotine at upregulating nicotinic receptors on SH-SY5Y cells.

The effect of total particulate matter (TPM) from cigarette smoke on the expression and binding properties of nicotinic acetylcholine receptors (nAChRs) was investigated using a human neuroblastoma cell line (SH-SY5Y). TPM but not nicotine on its own inhibited cell growth at nicotine concentrations above 5 microM. To examine effects on nAChR expression, intact cells were incubated with 3H-epibatidine, and a Bmax of 13 fmoles/10(5) cells (7.8 x 10(4) binding sites/cell) was measured in unexposed cells as well as in cells treated with 2 microM nicotine alone or with TPM containing 2 microM nicotine. Using Scatchard analysis, we measured a Kd of 0.3 nM for 3H-epibatidine binding to nAChRs. This Kd was increased to 1.3 nM by addition of nicotine or TPM extract, both at 2 microM nicotine. Bmax, however, was unaffected, suggesting competitive binding of nicotine to its receptor. Short-term and prolonged 3-day exposures of SH-SY5Y cells to either TPM or nicotine at nicotine concentrations ranging from 0.2 microM to 20 microM increased specific binding, suggesting upregulation of nAChR expression. Most significant, binding was consistently greater in cells pretreated with TPM than in cells pretreated with nicotine. We conclude that TPM contains compounds that are toxic to cells at high concentrations (cell growth inhibition) but that do not compete with nicotine for binding to nAChRs (Scatchard analysis). These non-nicotinic compounds are capable of increasing the expression of one or more of the nAChR subunits. Furthermore, our cell culture assay provides a useful in vitro model for assessing the relative addictiveness of different tobacco products, including that of non-nicotine components.