A systematic review of possible serious adverse health effects of nicotine replacement therapy.

We conducted a systematic literature review to identify and critically evaluate studies of serious adverse health effects (SAHEs) in humans using nicotine replacement therapy (NRT) products. Serious adverse health effects refer to adverse events, leading to substantial disruption of the ability to conduct normal life functions. Strength of evidence evaluations and conclusions were also determined for the identified SAHEs. We evaluated 34 epidemiological studies and clinical trials, relating NRT use to cancer, reproduction/development, CVD, stroke and/or other SAHEs in patients, and four meta-analyses on effects in healthy populations. The overall evidence suffers from many limitations, the most significant being the short-term exposure (≤12 weeks) and follow-up to NRT product use in most of the studies, the common failure to account for changes in smoking behaviour following NRT use, and the sparse information on SAHEs by type of NRT product used. The only SAHE from NRT exposure we identified was an increase in respiratory congenital abnormalities reported in one study. Limited evidence indicated a lack of effect between NRT exposure and SAHEs for CVD and various reproduction/developmental endpoints. For cancer, stroke and other SAHEs, the evidence was inadequate to demonstrate any association with NRT use. Our conclusions agree with recent statements from authoritative bodies.

Comprehensive review of epidemiological and animal studies on the potential carcinogenic effects of nicotine per se.

The effects of long-term use of nicotine per se on cancer risk, in the absence of tobacco extract or smoke, are not clearly understood. This review evaluates the strength of published scientific evidence, in both epidemiological and animal studies, for the potential carcinogenic effects of nicotine per se; that is to act as a complete carcinogen or as a modulator of carcinogenesis. For human studies, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a carcinogenic effect due to the limited information available. In animal studies, limited evidence suggests an association between long-term nicotine exposure and a lack of a complete carcinogenic effect. Conclusive studies using current bioassay guidelines, however, are missing. In studies using chemical/physical carcinogens or transgenic models, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a modulating (stimulating) effect on carcinogenesis. This is primarily due to the large number of conflicting studies. In contrast, a majority of studies provides sufficient evidence for an association between nicotine exposure and enhanced carcinogenesis of cancer cells inoculated in mice. This modulating effect was especially prominent in immunocompromized mice. Overall, taking the human and animal studies into consideration, there appears to be inadequate evidence to conclude that nicotine per se does or does not cause or modulate carcinogenesis in humans. This conclusion is in agreement with the recent US Surgeon General's 2014 report on the health consequences of nicotine exposure.

Chemical, physical, and in vitro characterization of research cigarettes containing denicotinized tobacco.

The use of very low nicotine tobacco cigarettes is currently being investigated as a possible harm reduction strategy. Here, we report the smoke chemistry, toxicity, and physical characteristics of very low nicotine cigarettes that were made using blended tobacco processed through a supercritical CO2 fluid extraction, which resulted in elimination of 96% of nicotine content (denicotinized (denic) tobacco). Three types of test cigarettes (TCs) were manufactured with tobacco filler containing 100% denic tobacco (TC100), 50% denic tobacco and 50% unextracted tobacco (TC50/50), and 100% unextracted tobacco (TC0). Mainstream smoke (MS) was generated for measurement of 46 analytes and cytotoxicity and mutagenicity determination. Analysis of physical characteristics of TCs demonstrated they were well made with <5% variability among cigarettes for most parameters measured. We observed significant changes in the levels of smoke constituents, including decreases in formaldehyde, nitrosamines, and phenol, and increases in aliphatic hydrocarbons, aliphatic nitrogen compounds, aromatic amines, halogen compounds, and metals. Use of denic tobacco resulted in changes in the chemical composition of MS, but these changes did not modify biological activity as measured in the mutagenicity and cytotoxicity assays.

Emerging mechanistic targets in lung injury induced by combustion-generated particles.

The mechanism for biological effect following exposure to combustion-generated particles is incompletely defined. The identification of pathways regulating the acute toxicological effects of these particles provides specific targets for therapeutic manipulation in an attempt to impact disease following exposures. Transient receptor potential (TRP) cation channels were identified as "particle sensors" in that their activation was coupled with the initiation of protective responses limiting airway deposition and inflammatory responses, which promote degradation and clearance of the particles. TRPA1, V1, V4, and M8 have a capacity to mediate adverse effects after exposure to combustion-generated particulate matter (PM); relative contributions of each depend upon particle composition, dose, and deposition. Exposure of human bronchial epithelial cells to an organic extract of diesel exhaust particle was followed by TRPV4 mediating Ca(++) influx, increased RAS expression, mitogen-activated protein kinase signaling, and matrix metalloproteinase-1 activation. These novel pathways of biological effect can be targeted by compounds that specifically inhibit critical signaling reactions. In addition to TRPs and calcium biochemistry, humic-like substances (HLS) and cell/tissue iron equilibrium were identified as potential mechanistic targets in lung injury after particle exposure. In respiratory epithelial cells, iron sequestration by HLS in wood smoke particle (WSP) was associated with oxidant generation, cell signaling, transcription factor activation, and release of inflammatory mediators. Similar to WSP, cytotoxic insoluble nanosized spherical particles composed of HLS were isolated from cigarette smoke condensate. Therapies that promote bioelimination of HLS and prevent the disruption of iron homeostasis could function to reduce the harmful effects of combustion-generated PM exposure.

Reference moist smokeless tobacco-induced apoptosis in human monocytes/macrophages cell line MM6.

Moist smokeless tobacco use is associated with various types of oral injury, including leukoplakia and dipper's pouch, although the mechanism by which the injury is caused still remains unclear. One possible mechanism is that moist smokeless tobacco affects the inflammatory response. For example, a study by Johnson et al. demonstrated a reduction in the volume density of macrophages and increased inflammation and redness at the smokeless tobacco placement site when compared to non-placement site. The current study investigated the direct effect of reference moist smokeless tobacco extract (STE) exposure on the viability of MM6 monocyte/macrophage cell line. The exposure of MM6 cells to various concentrations of STE, led to a significant and dose-related decrease in cell viability. Furthermore, STE exposure resulted in an increase in Annexin V/PI positive cells, an increase in TUNEL-positive cells, and cleaved PARP staining all of which were inhibited by pre-incubation with a pan-caspase inhibitor, suggesting that the observed STE toxicity was due to the induction of apoptosis. Next, the role of various moist smokeless tobacco-derived components in STE-induced apoptosis of MM6 cells was investigated. Our findings suggest that STE-induced osmotic stress, but not exposure to nicotine, plays an important role in STE-induced apoptosis of MM6 cells. Together, these data show for the first time that STE exposure leads to the induction of apoptosis in human monocyte/macrophage cells, which appears to be induced in part, by reference STE-mediated osmotic stress.

Role of plasma membrane disruption in reference moist smokeless tobacco-induced cell death.

An oral injury is thought to presage the development of mucosal lesions that are common in moist smokeless tobacco (MST) users. The abrasion or mechanical stress caused by direct contact of MST with the oral mucosa may contribute to this injury by causing transient disruptions in the cell membrane. In order to test this hypothesis, we developed an in vitro exposure system that directly exposes cells to reference MST on a rocking platform to simulate the abrasion that might be experienced in the oral cavity when using MST. Using this treatment paradigm, we monitored plasma membrane disruption as a measure of cell wounding caused by direct interaction of the tobacco material itself with monolayer cultures of Het-1A immortalized human esophageal cells as a potential contributor to the injury process. We found that a washed reference MST preparation, in which MST-associated chemicals were removed but the tobacco material retained, causes cell wounding as indicated by the uptake through plasma membrane disruptions of a fluorescent marker normally impermeable to the cell. Having established that non-chemical properties of MST cause cell wounding, subsequent experiments revealed that cell wounding during simultaneous exposure to an aqueous MST-extract result in greater than additive cell death when compared to treatment with washed MST or MST-extract alone. Furthermore, we found that the high levels of free calcium found in MST-extract appear to be playing an important role. Taken together, these results indicate that MST-induced oral injury may result from a combined interaction of physical disruption of the plasma membrane by the tobacco material itself and the adverse effects of MST chemical constituents, notably high levels of calcium, that gain entry to the cell by way of MST-induced cell wounding.

Role of oxidative stress and MAPK signaling in reference moist smokeless tobacco-induced HOK-16B cell death.

The use of smokeless tobacco products is often associated with an oral injury at the site of repeated use. To further our understanding of this injury process, the effect of reference moist smokeless tobacco extract (STE) on cell death, oxidative stress, and MAPK signaling in a human oral keratinocyte cell line, HOK-16B, was investigated. STE caused dose-dependent cell death and reactive oxygen species (ROS) production within 30 min to 3h of exposure. This same insult enhanced the activity of ERK1/2, JNK1/2, p38 MAPK and ASK1, an upstream activator of JNK1/2 and p38 MAPK. Inhibition of JNK1/2 and to a lesser extent p38 MAPK, but not ERK1/2, suppressed STE-induced cell death. Pretreatment with antioxidants and an iron chelator, deferoxamine suppressed ROS production, ASK1, JNK1/2 and p38 MAPK activation, and reduced cell death after STE exposure. Interestingly, extracellular free iron levels in STE (29.4+/-0.5 microM) were significantly elevated as compared with cell culture medium (4.9+/-0.6 microM) and the addition of extracellular free iron (14, 30 or 70 microM) to HOK-16B cultures (without STE) caused dose-dependent cell death after 3h. Thus, acute exposure to STE leads to HOK-16B cell death in part through oxidative stress via activation of ASK1 and the JNK1/2 and p38 MAPK pathways.

Direct high-performance liquid chromatographic analysis of D-tocopheryl acid succinate and derivatives.

A method of analysis of a Vitamin E derivative D-tocopheryl acid succinate (TS) in biological fluids and commercially available products is necessary to study the kinetics of in vitro and in vivo metabolism, tissue distribution, and content uniformity. A simple and inexpensive high-performance liquid chromatographic method was developed for the direct determination of D-tocopheryl acid succinate in commercially available products, rat serum, and rat tissues. This method can also be applied to the determination of 15 Vitamin E derivatives. Rat serum (0.1 ml) was extracted with sodium dodecyl sulfate, ethanol, hexane, and then dried under nitrogen gas after addition of the internal standard, DL-alpha-tocopherol acetate. Separation was achieved on a C18 column with UV detection at 205 nm. The calibration curve for D-tocopheryl acid succinate was linear ranging from 0.025 to 100 microg/ml. The mean extraction efficiency was >92%. Precision of the assay was <5% (CV), and was within 5% at the limit of quantitation (0.025 microg/ml). Bias of the assay was lower than 5%, and was within 5% at the limit of quantitation. The assay was applied successfully to the serum and tissue distribution of D-tocopheryl acid succinate in rats, various Vitamin E derivatives, and content uniformity in commercially available products containing D-tocopheryl acid succinate.

Angiotensin II protects cultured midbrain dopaminergic neurons against rotenone-induced cell death.

In this study, we demonstrate that angiotensin II (Ang II) protects dopamine (DA) neurons from rotenone toxicity in vitro. Primary ventral mesencephalic (VM) cultures from E15 rats were grown for 5 days and then cultured in the presence of the mitochondrial complex I inhibitor, rotenone. Acute exposure (20 h) to 20 nM rotenone reduced the number of tyrosine hydroxylase-positive (TH+) neurons by 50 +/- 6% when compared to untreated cultures. Pre-treatment of VM cultures with 100 nM Ang II decreased TH+ neuronal loss to 25 +/- 10% at the 20-nM rotenone concentration. Ang II in the presence of the angiotensin type 1 receptor (AT1R) antagonist, losartan, was even more effective in protecting DA neurons showing a loss of only 13 +/- 4% at 20 nM rotenone. Conversely, the AT2R antagonist, PD123319, abolished the protective effects of Ang II. Furthermore, both the NMDA receptor antagonist, MK801, and the antioxidant, alpha-tocopheryl succinate (vitamin E analogue), prevented rotenone-induced toxicity. Here, we show that acute exposure of VM cultures to the pesticide rotenone leads to dopaminergic neuronal cell death and that angiotensin acting through the AT2 receptor protects dopamine neurons from rotenone toxicity.

Pharmacokinetics and tissue distribution of d-alpha-tocopheryl succinate formulations following intravenous administration in the rat.

Unlike d-alpha tocopherol (T), d-alpha tocopheryl succinate (TS) has the unique ability to selectively kill tumor cells while protecting normal tissue from toxic oxidative stress. The pharmacokinetics of TS and the serum and tissue disposition of TS were studied in male Sprague-Dawley rats to delineate formulation dependent disposition between TS administered as the Tris salt (TS-T) (a liposomal formulation) or as the free acid (TS-FA) dissolved in polyethylene glycol (PEG) 400. The pharmacokinetics of TS was studied after single intravenous (i.v.) equimolar doses of 124 mg/kg TS-T and 100 mg/kg of TS-FA. Serial blood samples were collected via a catheter inserted into the right jugular vein and serum samples were analysed for TS and T levels using a reverse phase HPLC method. Terminal tissue samples were also collected at 24 and 48 h. After an acute i.v. dose of TS-T, serum AUC, t(1/2), Cl and V(d) of TS were 2601.0 +/- 351.7 microg h/ml, 9.98 +/- 1.02 h, 0.049 +/- 0. 0073 l/h/kg and 0.7 +/- 0.14 l/kg (mean +/- SD), respectively. The acute i.v. administration of TS-FA (PEG formulation) yielded results similar to those observed for TS-T, with a serum AUC, t(1/2), Cl and V(d) of 2553.3 +/- 166.4 microg h/ml, 9.83 +/- 0.86 h, 0.039 +/- 0.0027 l/h/kg and 0.56 +/- 0.09 l/kg (mean +/- SD), respectively. Distribution into tissues and a low Cl was apparent, with the highest concentrations of TS in the liver and lung, regardless of formulation. As expected, baseline endogenous concentrations of T were present in both groups, with a net increase in T levels, occurring as TS was hydrolysed to T, which slowly peaked in serum between 7-8 h post-dose. Intravenous TS administration, regardless of formulation, also resulted in significant T accumulation in all tissues examined, which was especially abundant in the liver and lung. Likewise, there was a lack of significant effect of formulation on the pharmacokinetics and tissue distribution of TS. The only significant formulation difference was a small but significant increase in serum T and liver T levels in the TS in PEG formulation group. These results indicate that TS may be especially useful for the targeted delivery of T and TS to the lung and liver for anti-oxidant and anti-cancer activity.

Role of mitochondria in toxic oxidative stress.

Oxidative stress and mitochondrial oxidative damage have been implicated in the etiology of numerous common diseases. The critical mitochondrial events responsible for oxidative stress-mediated cell death (toxic oxidative stress), however, have yet to be defined. Several oxidative events implicated in toxic oxidative stress include alterations in mitochondrial lipids (e.g., cardiolipin), mitochondrial DNA, and mitochondrial proteins (eg. aconitase and uncoupling protein 2). Furthermore, recent findings indicate the enrichment of mitochondrial membranes with vitamin E protects cells against the toxic effects of oxidative stress. This review briefly summarizes the role of these mitochondrial events in toxic oxidative stress, including: 1) the protective role of mitochondrial vitamin E in toxic oxidative stress, 2) the role of mitochondrial DNA in toxic oxidative stress, 3) the interaction between cardiolipin and cytochrome c in mitochondrial regulation of apoptosis, 4) the role of mitochondrial aconitase in oxidative neurodegeneration, and 5) the role of mitochondrial uncoupling protein 2 in the pathogenesis of type 2 diabetes.

Chemopreventive effect of dietary d-alpha-tocopheryl succinate supplementation on precancer colon aberrant crypt formation and vitamin E analogue levels in young and old rats.

This study examined the effects of dietary d-alpha-tocopheryl succinate (TS) in female rats, 20 mo (OLD) or 2 mo (YNG) of age, on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) and tissue distribution of d-alpha-tocopherol (alphaT), d-gamma-tocopherol (gammaT), and alphaTS. Rats were fed a commercial rodent chow supplemented with or without 1 (YNG) or 2 (OLD) g alphaTS/kg diet for 1 week prior to ip administration of AOM to induce colon ACF. The animals were sacrificed after 49 days of exposure. The results showed that OLD rats had significantly fewer ACF than YNG animals, and the percent body fat and serum triglycerides were significantly higher in the OLD group compared with the YNG. However, only OLD animals receiving alphaTS had significantly reduced numbers of larger ACF and significantly higher levels of colonic alphaT, gammaT, and alphaTS. These data support previous studies demonstrating that dietary alphaTS administration is protective against intestinal cancer. Also, this is the first study to show that alphaTS accumulates in most tissues following dietary exposure. We hypothesize that increased colon accumulation of fat-soluble vitamin E compounds and subsequent chemoprevention may be related to greater percent body fat and serum triglycerides in OLD animals receiving dietary TS.

Vitamin E analogues: a new class of inducers of apoptosis with selective anti-cancer effects.

In spite of unrelenting effort, the net incidence of neoplastic diseases appears not to have been curbed. While some types of cancer have been suppressed significantly, others are either stagnating or on the increase. Therefore, the need for a cure is imperative, in particularly a drug or combination of drugs that would be selective for malignant cells, i.e. with as low secondary toxicity as possible. Recent data strongly suggest that analogues of vitamin E, epitomised by the most studied alpha-tocopheryl succinate (alpha-TOS), may meet the need for the coveted drugs with a selective anti-neoplastic effect. The reasons for this optimism are reviewed in this article.

Fluorescence microplate reader measurement of tissue susceptibility to lipid peroxidation.

This unit describes a method for the measurement of cellular membrane antioxidant capacity or susceptibility of tissue samples to lipid peroxidation using a fluorescence microplate reader. The assay is simple and has the advantage of monitoring susceptibility to lipid peroxidation in a large number of samples in real time.

Role of lipid peroxidation as a mechanism of liver injury after acetaminophen overdose in mice.

Mitochondrial oxidant stress and peroxynitrite formation have been implicated in the pathophysiology of acetaminophen-induced (AAP-induced) liver injury. Therefore, we tested the hypothesis that lipid peroxidation (LPO) might be involved in the injury mechanism. Male C3Heb/FeJ mice fed a diet high in vitamin E (1 g d-alpha-tocopheryl acetate/kg diet) for 1 week had 6.7-fold higher hepatic tocopherol levels than animals on the control diet (8.2 +/- 0.1 nmol/g liver). Treatment of fasted mice with 300 mg/kg AAP caused centrilobular necrosis with high plasma alanine aminotransferase (ALT) activities at 6 h (3280 +/- 570 U/l) but no evidence of LPO (hepatic malondialdehyde, 4-hydroxynonenal). Animals on the vitamin E diet had similar injury and LPO as mice on the control diet. To verify a potential effect of the vitamin E diet on drug-induced liver injury, animals were pretreated with a combination of phorone, FeSO4, and allyl alcohol. We observed, 2 h after allyl alcohol, massive LPO and liver cell injury in the livers of animals on the control diet, as indicated by a 32-fold increase in malondialdehyde levels, extensive staining for 4-hydroxynonenal, and ALT activities of 2310 +/- 340 U/l. Animals on the vitamin E diet had 40% lower hepatic malondialdehyde levels and 85% lower ALT values. Similar results were obtained when animals were treated for 3 days with alpha- or gamma-tocopherol (0.19 mmol/kg, ip). Both treatments reduced LPO and injury after allyl alcohol but had no effect on AAP hepatotoxicity. Thus, despite the previously shown mitochondrial oxidant stress and peroxynitrite formation, LPO does not appear to be a critical event in AAP-induced hepatotoxicity.

Vitamin E therapy in Parkinson's disease.

Though the etiology is not well understood, late-onset Parkinson's disease (PD) appears to result from several key factors including exposure to unknown environmental toxicants, toxic endogenous compounds and genetic alterations. A plethora of scientific evidence suggest that these environmental and endogenous factors cause PD by producing mitochondrial (mito) oxidative stress and damage in the substantia nigra, leading to cell death. Thus assuming a critical role for mito oxidative stress in PD, therapies to treat or prevent PD must target these mito and protect them against oxidative damage. The focus of this article is to briefly review the experimental and clinical evidence for the role of environmental toxicants and mito oxidative stress/damage in PD as well as discuss the potential protective role of mito d-alpha-tocopherol (T) enrichment and vitamin E therapy in PD. New experimental data are presented that supports the enrichment of mito with T as a critical event in cytoprotection against toxic mito-derived oxidative stress. We propose that chronic, high dose vitamin E dietary supplementation or parenteral vitamin E administration (e.g. vitamin E succinate) may serve as a successful therapeutic strategy for the prevention or treatment of PD (by enriching substantia nigra mito with protective levels of T).

Chemotherapy induced gastrointestinal toxicity in rats: involvement of mitochondrial DNA, gastrointestinal permeability and cyclooxygenase -2.

PURPOSE: The gastrointestinal damage induced by xenobiotics is occurring more frequently and with greater toxicological significance than previously thought. Although there are some preliminary clinical studies and reports, there does not appear to be an extensive examination of gastrointestinal toxicity of various chemotherapeutic agents in the rat. This study was undertaken to examine the suitability of a rat model to detect the gastrointestinal damage after administration of various anti-neoplastic agents including etoposide, teniposide, melphalan, 5-fluorouracil, methotrexate and cisplatin. METHODS: Acute toxic doses of indomethacin and chemotherapeutic agents were administered to rats. The urinary excretion of orally administered sucrose and 51(Cr)-EDTA were measured as markers of gastroduodenal and intestinal permeability, respectively. Cyclooxygenase-2 messenger RNA and mitochondrial DNA damage were measured as toxicological endpoints. RESULTS: Each anti-neoplastic agent examined induced appreciable and significant dose-dependent increase in gastrointestinal permeability that correlated with gross toxicological and pathological changes to the gastrointestinal tract including ulceration and bleeding. COX-2 mRNA was upregulated > 2 fold in intestinal mucosa with enteropathy and dose-dependent mitochondrial oxidative damage was apparent in gastric and intestinal mucosa. After administration of each drug, the rats presented with histological evidence of drug-induced gastroenteropathy, ulceration and increased cecal hemoglobin. CONCLUSIONS: The rat appears to be a suitable model to study gastrointestinal toxicity of chemotherapeutic agents and non-steroidal anti-inflammatory drugs. Damage to mitochondrial DNA occurs in both the gastric and intestinal epithelium after the administration of these agents and may be an important factor in the pathogenesis and resolution of gastrointestinal toxicity.

Thenoyltrifluoroacetone, a potent inhibitor of carboxylesterase activity.

Thenoyltrifluoroacetone (TTFA), a conventional mitochondrial complex II inhibitor, was found to inhibit purified porcine liver carboxylesterase non-competitively with a K(i) of 0.61x10(-6)M and an IC(50) of 0.54x10(-6)M. Both rat plasma and liver mitochondrial esterases were inhibited in a concentration-dependent fashion. Results indicate that TTFA is a potent inhibitor of carboxylesterase activity, in addition to its ability to inhibit mitochondrial complex II activity. Therefore, caution is warranted in using TTFA as a mitochondrial complex inhibitor in combination with esterase substrates, such as fluorescence probes or vitamin E esters.

Vitamin E succinate is a potent novel antineoplastic agent with high selectivity and cooperativity with tumor necrosis factor-related apoptosis-inducing ligand (Apo2 ligand) in vivo.

Alpha-tocopheryl succinate (alpha-TOS), a redox-inactive analogue of vitamin E, is a strong inducer of apoptosis, whereas alpha-tocopherol (alpha-TOH) lacks apoptogenic activity (J. Neuzil et al., FASEB J., 15: 403-415, 2001). Here we investigated the possible antineoplastic activities of alpha-TOH and alpha-TOS and further explored the potential of alpha-TOS as an antitumor agent. Using nude mice with colon cancer xenografts, we found that alpha-TOH exerted modest antitumor activity and acted by inhibiting tumor cell proliferation. In contrast, alpha-TOS showed a more profound antitumor effect, at both the level of inhibition of proliferation and induction of tumor cell apoptosis. alpha-TOS was nontoxic to normal cells and tissues, triggered apoptosis in p53(-/-) and p21(Waf1/Cip1(-/-)) cancer cells, and exerted a cooperative proapoptotic activity with tumor necrosis factor-related apoptosis-inducing ligand (Apo2 ligand) due to differences in proapoptotic signaling. Finally, alpha-TOS cooperated with tumor necrosis factor-related apoptosis-inducing ligand in suppression of tumor growth in vivo. Vitamin E succinate is thus a potent and highly specific anticancer agent and/or adjuvant of considerable therapeutic potential.