A chemical approach to searching for bioactive ingredients in cigarette smoke

Detoxification Mechanism of α,β-Unsaturated Carbonyl Compounds in Cigarette Smoke Observed in Sheep Erythrocytes

Highly reactive α,β-unsaturated carbonyl compounds, such as acrolein (ACR), crotonaldehyde (CA) and methyl vinyl ketone (MVK), are environmental pollutants present in high concentrations in cigarette smoke. We have previously found that these carbonyl compounds in cigarette smoke extract (CSE) react with intracellular glutathione (GSH) to produce the corresponding GSH-ACR, GSH-CA and GSH-MVK adducts via Michael addition reaction. These adducts are then further reduced to the corresponding alcohol forms by intracellular aldo-keto reductases in highly metastatic mouse melanoma (B16-BL6) cells and then excreted into the extracellular fluid. This time, we conducted a similar study using sheep erythrocytes and found analogous changes in the sheep erythrocytes after exposure to CSE as those with B16-BL6 cells. This indicates similarity of the detoxification pathways of the α,β-unsaturated carbonyl compounds in sheep blood cells and B16-BL6 cells. Also, we found that the GSH-MVK adduct was reduced by aldose reductase in a cell-free solution to generate its alcohol form, and its reduction reaction was completely suppressed by pretreatment with epalrestat, an aldose reductase inhibitor, a member of the aldo-keto reductase family. In the presence of sheep blood cells, however, reduction of the GSH-MVK adduct was partially inhibited by epalrestat. This revealed that some member of the aldo-keto reductase superfamily other than aldose reductase is involved in reduction of the GSH-MVK adduct in sheep blood. These results suggest that blood cells, mainly erythrocytes are involved in reducing the inhalation toxicity of cigarette smoke via an aldo-keto reductase pathway other than that of aldose reductase.

Cigarette Smoke Extract Disrupts Transcriptional Activities Mediated by Thyroid Hormones and Its Receptors

Cigarette smoke contains over 4800 compounds, including at least 200 toxicants or endocrine disruptors. Currently, effects of cigarette smoke on thyroid hormone (TH) levels remains to be clarified. Here, we demonstrate that cigarette smoke extract (CSE) possesses thyroid hormone properties and acts synergistically as a partial agonist for thyroid hormone receptors (TRs) in the presence of TH. In transient gene expression experiments, CSE stimulated transcriptional activity with TH in a dose-dependent manner. Stimulatory effects were observed with physiological TH concentrations, although CSE did not activate TRs without TH. CSE (5%) dissolved in phosphate-buffered saline (PBS) supplemented with 1 nM TH was approximately comparable to 3.2±0.1 and 2.3±0.2 nM of TRα1 and TRβ1, respectively. To illustrate probable mechanisms of the CSE agonistic activity, effects on TR mediated transcriptional functions with cofactors were investigated. With a mammalian two-hybrid assay, CSE recruited the nuclear coactivators glucocorticoid receptor interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC1) to the TR. Unsaturated carbonyl compounds, acrolein, crotonaldehyde, and methyl vinyl ketone, representative constituents of CSE, retained such agonistic properties and possibly contributed to stimulatory effects. The results suggest that CSE recruits a transcriptional activator and may reinforce TH binding to the TR additively, resulting in gene expression. CSE partially agonizes TH action and may disturb the function of various nuclear hormone receptor types and their cofactors to disrupt the physiological processes.

Mass Spectrometric Approaches to the Identification of Potential Ingredients in Cigarette Smoke Causing Cytotoxicity

Cigarette smoke contains many harmful chemicals that contribute to the pathogenesis of smoking-related diseases such as chronic obstructive pulmonary disease, cancer, and cardiovascular disease. Many studies have been done to identify cytotoxic chemicals in cigarette smoke and elucidate the onset of the above-mentioned diseases caused by smoking. However, definitive mechanisms for cigarette smoke toxicity remain unknown. As candidates for cytotoxic chemicals, we have recently found methyl vinyl ketone (MVK) and acetic anhydride in nicotine/tar-free cigarette smoke extract (CSE) using L-tyrosine (Tyr), an amino acid with highly reactive hydroxyl group. The presence of MVK and acetic anhydride in CSE was confirmed by gas chromatography-mass spectrometry (GC/MS). We also found new reaction products formed in B16-BL6 mouse melanoma (B16-BL6) cells treated with CSE using LC/MS. These were identified as glutathione (GSH) conjugates of α,β-unsaturated carbonyl compounds, MVK, crotonaldehyde (CA), and acrolein (ACR), by the mass value and product ion spectra of these new products. ACR and MVK are type-2 alkenes, which are well known as electron acceptors and form Michael-type adducts to nucleophilic side chain of amino acids on peptides. These α,β-unsaturated carbonyl compounds may have a key role in CSE-induced cell death.

Advances in Behavioral Laboratory Methods that Inform Tobacco Regulatory Science: A TCORS Working Group Special Issue

Objective

The 2009 Family Smoking Prevention and Tobacco Control Act (TCA) created unprecented enabling conditions for establishing national regulatory policy that reduces the burden of public health and societal problems associated with tobacco product use. The Center for Tobacco Products (CTP), created by the FDA to implement the TCA, developed a first-of-its-kind FDA/National Institutes of Health (NIH) collaborative program to fund Tobacco Centers of Regulatory Science (TCORS).

Methods

To assist the TCORS with addressing research priorites, working groups (WGs) comprised of FDA-CTP liasions and TCORS investigators were formed. Under the direction of the Center for Evaluation and Coordination of Trainin and Research (CECTR), the TCORS WGs seek to develop tangible work products in their respective areas of focus.

Results

The focus of the behavioral pharmacology WG evolved from publishing a narrow paper on behavioral methods in electronic cigarette research to a collection of papers on advances in behavioral laboratory methods that may inform tobacco regulatory science.

Conclusion

This Special Issue contains articles that address all of the CTP research priorities and demonstrates how advances in behavioral laboratory methods made by TCORS investigators can inform FDA efforst to regulate tobacco products.

Thalidomide prevents cigarette smoke extract-induced lung damage in mice

Chronic obstructive pulmonary disease (COPD) is characterized by a progressive airway obstruction that is not completely reversible and is mainly caused by smoking tobacco. COPD is a major cause of morbidity and mortality worldwide and there are currently no proven effective treatments. The pathogenesis of COPD involves several factors such as chronic inflammation, oxidative stress, and apoptosis. Cytokines play important roles in chronic inflammation. Thalidomide (Thal) has been used to treat multiple myeloma due to its inhibitory effects on IL-6-induced cell growth. We recently demonstrated that thalidomide (Thal) played important roles in cytokine-induced lung damage in a bleomycin-induced pulmonary fibrosis model in mice. We herein examined the preventative effects of Thal on cigarette smoke extract (CSE)-induced emphysematous changes in mice. We performed histological examinations and quantitative measurements of the expression of IL-1β and IL-6 mRNA, as well as apoptosis in CSE-induced mouse lung tissues treated with or without Thal. The results of the histological examination showed that Thal ameliorated CSE-induced emphysema in mice. It also inhibited the expression of IL-1β and IL-6 mRNA in mouse lung tissues. Thal decreased apoptosis in the mouse lung. In vitro studies revealed that Thal decreased 1) the expression of IL-1β and IL-6 in human lung epithelial cells, and 2) CSE-induced apoptosis and the inhibition of cell growth, which may be the underlying mechanisms for the preventative effects of Thal on emphysema. These results provide a rationale for exploring the clinical use of Thal for COPD.

Cigarette smoke-induced iBALT mediates macrophage activation in a B cell-dependent manner in COPD

Chronic obstructive pulmonary disease (COPD) is characterized by a progressive decline in lung function, caused by exposure to exogenous particles, mainly cigarette smoke (CS). COPD is initiated and perpetuated by an abnormal CS-induced inflammatory response of the lungs, involving both innate and adaptive immunity. Specifically, B cells organized in iBALT structures and macrophages accumulate in the lungs and contribute to CS-induced emphysema, but the mechanisms thereof remain unclear. Here, we demonstrate that B cell-deficient mice are significantly protected against CS-induced emphysema. Chronic CS exposure led to an increased size and number of iBALT structures, and increased lung compliance and mean linear chord length in wild-type (WT) but not in B cell-deficient mice. The increased accumulation of lung resident macrophages around iBALT and in emphysematous alveolar areas in CS-exposed WT mice coincided with upregulated MMP12 expression. In vitro coculture experiments using B cells and macrophages demonstrated that B cell-derived IL-10 drives macrophage activation and MMP12 upregulation, which could be inhibited by an anti-IL-10 antibody. In summary, B cell function in iBALT formation seems necessary for macrophage activation and tissue destruction in CS-induced emphysema and possibly provides a new target for therapeutic intervention in COPD.

The composition of cigarette smoke determines inflammatory cell recruitment to the lung in COPD mouse models

COPD (chronic obstructive pulmonary disease) is caused by exposure to toxic gases and particles, most often CS (cigarette smoke), leading to emphysema, chronic bronchitis, mucus production and a subsequent decline in lung function. The disease pathogenesis is related to an abnormal CS-induced inflammatory response of the lungs. Similar to active (mainstream) smoking, second hand (sidestream) smoke exposure severely affects respiratory health. These processes can be studied in vivo in models of CS exposure of mice. We compared the acute inflammatory response of female C57BL/6 mice exposed to two concentrations [250 and 500 mg/m³ TPM (total particulate matter)] of sidestream and mainstream CS for 3 days and interpreted the biological effects based on physico-chemical differences in the gas and particulate phase composition of CS. BAL (bronchoalveolar lavage fluid) was obtained to perform differential cell counts and to measure cytokine release. Lung tissue was used to determine mRNA and protein expression of proinflammatory genes and to assess tissue inflammation. A strong acute inflammatory response characterized by neutrophilic influx, increased cytokine secretion [KC (keratinocyte chemoattractant), TNF-α (tumour necrosis factor α), MIP-2 (macrophage inflammatory protein 2), MIP-1α and MCP-1 (monocyte chemoattractant protein-1)], pro-inflammatory gene expression [KC, MIP-2 and MMP12 (matrix metalloproteinase 12)] and up-regulated GM-CSF (granulocyte macrophage colony-stimulating factor) production was observed in the mainstream model. After sidestream exposure there was a dampened inflammatory reaction consisting only of macrophages and diminished GM-CSF levels, most likely caused by elevated CO concentrations. These results demonstrate that the composition of CS determines the dynamics of inflammatory cell recruitment in COPD mouse models. Different initial inflammatory processes might contribute to COPD pathogenesis in significantly varying ways, thereby determining the outcome of the studies.