Cellular and molecular mechanisms of cigarette smoke-induced lung damage and prevention by vitamin C

The effects of vitamin C on respiratory, allergic and immunological diseases: an experimental and clinical-based review

Vitamin C is used in modern medicine supplements for treatment of various disorders associated with oxidative stress, inflammation and immune dysregulation. In this review article, experimental and clinical results regarding the effects of vitamin C on respiratory immunologic, and allergic diseases are reviewed. Various databases and appropriate keywords are used to search the effect of vitamin C on respiratory diseases until the end of May 2022. Books, theses and articles were included. These studies assessed the effects of vitamin C on respiratory disorders including asthma, chronic obstructive pulmonary disease (COPD), lung infection and lung cancer. Vitamin C showed relaxant effect on tracheal smooth muscle via various mechanisms. The preventive effects of vitamin C were mediated by antioxidant, immunomodulatory and anti-inflammatory mechanisms in the experimental animal models of different respiratory diseases. Some clinical studies also indicated the effect of vitamin C on lung cancer and lung infections. Therefore, vitamin C could be used a preventive and/or relieving therapy in respiratory diseases.

Activation of PTP1B/EGFR signaling and cytotoxicity during combined exposure to ambient electrophiles in A431 cells

Chemical modification of the thiol group on protein tyrosine phosphatase (PTP) 1B triggers an activation of epidermal growth factor receptor (EGFR) signaling that is mimicked by environmental electrophiles through S-modification of PTP1B. While activation of PTP1B/EGFR by a single exposure to an electrophile has been established, the effects of combined exposure to electrophiles are unknown. Here, we examined the activation of EGFR signaling by combined exposure to ambient electrophiles in human epithelial carcinoma A431 cells. Simultaneous exposure to 1,2- and 1,4-naphthoquinone (NQ) augmented the S-modification of endogenous and recombinant human PTP1B (hPTP1B). Combined exposure of hPTP1B or A431 cells to 1,2- and 1,4-NQ escalated the inactivation of PTP compared with individual exposure. Phosphorylation of EGFR and its downstream kinase extracellular signal-regulated kinase (ERK) 1/2 by 1,2-NQ exposure was facilitated by simultaneous exposure to 1,2-NQ with 10 µM 1,4-NQ. An EGFR inhibitor diminished the phosphorylation of ERK1/2, indicating that ERK was phosphorylated following EGFR activation by the NQ cocktail. The combined exposure to NQs also accelerated cell death in A431 cells compared with each NQ alone. While no EGFR/ERK activation was seen following 1,4-benzoquinone (BQ) treatment, exposure to 1,4-NQ in the presence of 1,4-BQ increased 1,4-NQ-mediated activation of EGFR. This suggests that the enhancement of 1,4-NQ-dependent EGFR activation by 1,4-BQ is caused by a different mechanism than 1,2-NQ with 1,4-NQ. These results suggest that combined exposure to ambient electrophiles, even at low concentrations, can induce stronger activation of redox signaling than individual exposure. Our findings indicate that combining different electrophiles may produce unexpected effects.

Preoperative Cumulative Smoking Dose on Lung Cancer Surgery in a Japanese Nationwide Database

BACKGROUND

Smoking is a known risk factor for postoperative mortality and morbidity. However, the significance of cumulative smoking dose in preoperative risk assessment has not been established. We examined the influence of preoperative cumulative smoking dose on surgical outcomes after lobectomy for primary lung cancer.

METHODS

A total of 80,989 patients with primary lung cancer undergoing lobectomy from 2014 to 2016 were enrolled. Preoperative cumulative smoking dose was categorized by pack-years (PY): nonsmokers, PY = 0; light smokers, 0 < PY < 10; moderate smokers, 10 ≤ PY < 30; and heavy smokers, 30 ≤ PY. The risk of short-term outcomes was assessed according to PY by multivariable analysis adjusted for other covariates.

RESULTS

Postoperative 30-day mortality, as well as pulmonary, cardiovascular, and infectious complications, increased with preoperative PY. Multivariable analysis revealed that the odds ratios (ORs) for postoperative mortality compared with nonsmokers were 1.76 for light smokers (P = .044), 1.60 for moderate smokers (P = .026), and 1.73 for heavy smokers (P = .003). The ORs for pulmonary complications compared with nonsmokers were 1.20 for light smokers (P = .022), 1.40 for moderate smokers (P < .001), and 1.72 for heavy smokers (P < .001). Heavy smokers had a significantly increased risk of postoperative cardiovascular (OR, 1.26; P = .002) and infectious (OR, 1.39; P = .007) complications compared with nonsmokers.

CONCLUSIONS

The risk of mortality and morbidity after lung resection could be predicted according to preoperative cumulative smoking dose. These findings contribute to the development of strategies in perioperative management of lung resection patients.

The Association of Cigarette Smoke Exposure with Lung Cellular Toxicity and Oxidative Stress: the Protective Role of Crocin

Cigarette smoke (CS) contains many free radicals and toxic chemicals. Nuclear erythroid-related factor-2 (Nrf2) is a transcriptional regulator of several phase II antioxidant genes, including glutamate-cysteine ligase (GCL). In this study, it was hypothesized that Crocin may mediate antioxidant signaling pathway to protect human lung epithelial cells against CS-mediated toxicity and oxidative stress via inducing glutathione (GSH) biosynthesis and activation of Nrf2 pathway. Alveolar epithelial cells (A549) were exposed to 1, 2.5 and 5% cigarette smoke extracts (CSE) with or without Crocin (500 μM). After 48 h exposure, the cytotoxicity, oxidant/antioxidant parameters and the Nrf2 pathway modification were assayed. Treatment of A549 cells with all concentrations of CSE dose dependently decreased cell viability, antioxidant levels, GCL and Nrf2 gene expression, which was associated with increased production of reactive oxygen species. Crocin not only restored CSE-depleted GSH levels by enhancing GCL expression via activation of Nrf2 but also quenched the CSE-generation and release of reactive oxygen species. Crocin attenuated CSE-mediated Nrf2 modifications, thereby inducing its nuclear accumulation associated with GCL gene transcription leading to enhanced GSH levels. By inducing GSH synthesis, Crocin attenuates CSE-mediated GSH depletion and protects cells against CSE-induced oxidative stress via Nrf2 pathway. These results may have implications in dietary modulation of natural antioxidants in treatment of pulmonary diseases.

MRE11A Polymorphisms Are Associated With Subclinical Atherosclerosis and Cardiovascular Risk Factors. A Case-Control Study of the GEA Mexican Project

DNA damage and subsequent repair pathways have been involved in the initiation and progression of atherosclerosis. Meiotic recombination 11 homolog A (MRE11A) gene polymorphisms have been associated with the presence of myocardial infarction. We analyzed five MRE11A gene polymorphisms in 386 individuals with subclinical atherosclerosis and 1093 healthy controls. Under different models, the rs13447720 (Odds ratio = 0.646, P_additive = 0.009; Odds ratio = 0.636, P_dominant = 0.012; Odds ratio = 0.664, P_{over–dominant} = 0.025; Odds ratio = 0.655, P_codominant1 = 0.021) and rs499952 (Odds ratio = 0.807, P_additive = 0.032; Odds ratio = 0.643, P_codominant2 = 0.034) polymorphisms were associated with a lower risk of subclinical atherosclerosis. On the other hand, the rs2155209 polymorphism was associated with a reduced risk of having a coronary artery calcification score ≥ 100 Agatston units. The rs13447720, rs499952, and rs2155209 polymorphisms, as well as the haplotypes that included the five studied polymorphisms were associated with some clinical and metabolic parameters in both subclinical atherosclerosis and healthy individuals. Our results suggest that the rs13447720 and rs499952 polymorphisms are associated with a decreased risk of developing subclinical atherosclerosis, whereas the rs2155209 is associated with a lower subclinical atherosclerosis severity (coronary artery calcification < 100 Agatston units). MRE11A polymorphisms and haplotypes were associated with clinical and metabolic parameters.

Pathobiology of cigarette smoke-induced invasive cancer of the renal pelvis and its prevention by vitamin C

Urothelial cancer of the renal pelvis (CRP) is predominantly associated with cigarette smoking. However, the molecular pathogenesis of initiation and progression of cigarette smoke (CS)-induced CRP is unknown. Majority of CRP is high grade and high stage at presentation and has a high recurrence rate even after surgery. Earlier we reported that prolonged treatment (24 weeks) of a guinea pig model with p-benzoquinone (p-BQ), a product of CS in vivo, produced carcinoma in situ in the renal pelvis, a noninvasive cancer. Since CS is known to induce invasive cancer, we investigated the effect of CS exposure to the guinea pigs. We observed that CS exposure for a short period (18 weeks) produced invasive tumor (pT1). pT1 was confirmed by immunohistochemistry showing increased immunoexpression of nuclear p53 indicating p53 mutation, aberrant CK20, increased Ki-67 and uniformly negative labeling of CD44. As observed earlier with p-BQ treatment, the initial events of CS exposure were oxidative damage and apoptosis that was followed by persistent signaling through EGFR and MAP kinase pathway. CS exposure also caused hyperphosphorylation of pRb, activation of cyclin E and cell cycle deregulation leading to infiltration of epithelial cells in lamina propria of the renal pelvis resulting in pT1 tumor. Oral supplementation of vitamin C (30 mg/kg guinea pig/day) inhibited oxidative damage and apoptosis and holistically prevented the tumor formation. We consider that our preclinical findings on the intake of adequate vitamin C, along with intense advice for cessation of smoking, will be helpful for the prevention of CS-induced CRP in smokers.

Conjugation of para-benzoquinone of Cigarette Smoke with Human Hemoglobin Leads to Unstable Tetramer and Reduced Cooperative Oxygen Binding

Besides multiple life-threatening diseases like lung cancer and cardiovascular disease, cigarette smoking is known to produce hypoxia, a state of inadequate oxygen supply to tissues. Hypoxia plays a pivotal role in the development of chronic obstructive pulmonary disease. Smoking during pregnancy imposes risk for the unborn child. In addition to carbon monoxide, conjugation of para-benzoquinone (pBQ), derived from cigarette smoke, with human hemoglobin (HbA) was also reported to contribute in hypoxia. In fact, conjugation of pBQ is more alarming than carbon monoxide as it is an irreversible covalent modification. In the present study, the functional assay of Hb-pBQ, performed through oxygen equilibrium curve, showed a significant decrease in both P₅₀ and cooperativity. However, the structural changes associated with the observed functional perturbation of the hemoglobin conjugate (Hb-pBQ) are unknown to date. Enhanced sensitivity and high resolution of nano-ESI mass spectrometry platform have enabled to investigate the native structure of oligomers of hemoglobin in a single scan. The structural integrity of Hb-pBQ measured through the dissociation equilibrium constants (K_d) indicated that compared to HbA, K_d of tetramer-dimer and dimer-monomer equilibria were increased by 4.98- and 64.3-folds, respectively. Using isotope exchange mass spectrometry, we observed perturbations in the inter-subunit interactions of deoxy and oxy states of Hb-pBQ. However, the three-dimensional architecture of Hb-pBQ, monitored through collision cross-sectional area, did not show any change. We propose that the significant destabilization of the functionally active structure of hemoglobin upon conjugation with pBQ results in tighter oxygen binding that leads to hypoxia. Graphical Abstract ᅟ.

p-Benzoquinone-induced aggregation and perturbation of structure and chaperone function of α-crystallin is a causative factor of cigarette smoke-related cataractogenesis

Cigarette smoking is a significant risk factor for cataract. However, the mechanism by which cigarette smoke (CS) causes cataract remains poorly understood. We had earlier shown that in CS-exposed guinea pig, p-benzoquinone (p-BQ) derived from CS in the lungs is carried by the circulatory system to distant organs and induces various smoke-related pathogeneses. Here, we observed that CS exposure caused accumulation of the p-BQ-protein adduct in the eye lens of guinea pigs. We also observed accumulation of the p-BQ-protein adduct in resected lens from human smokers with cataract. No such accumulation was observed in the lens of never smokers. p-BQ is a strong arylating agent that forms Michael adducts with serum albumin and haemoglobin resulting in alterations of structure and function. A major protein in the mammalian eye lens is αA-crystallin, which is a potent molecular chaperone. αA-crystallin plays a key role in maintaining the integrity and transparency of the lens. SDS-PAGE indicated that p-BQ induced aggregation of αA-crystallin. Various biophysical techniques including UV-vis spectroscopy, fluorescence spectroscopy, FT-IR, bis-ANS titration suggested a perturbation of structure and chaperone function of αA-crystallin upon p-BQ modification. Our results indicate that p-BQ is a causative agent involved in the modification of αA-crystallin and pathogenesis of CS-induced cataract. Our findings would educate public about the impacts of smoking on eye health and help to discourage them from smoking. The study might also help scientists to develop new drugs for the intervention of CS-induced cataract at an early stage.

Anti-p-benzoquinone antibody level as a prospective biomarker to identify smokers at risk for COPD

Background and objective

Identification of smokers having predisposition to COPD is important for early intervention to reduce the huge global burden of the disease. Using a guinea pig model, we have shown that p-benzoquinone (p-BQ) derived from cigarette smoke (CS) in the lung is a causative factor for CS-induced emphysema. p-BQ is also derived from CS in smokers and it elicits the production of anti-p-BQ antibody in humans. We therefore hypothesized that anti-p-BQ antibody might have a protective role against COPD and could be used as a predictive biomarker for COPD in smokers. The objective of this study was to compare the serum anti-p-BQ antibody level between smokers with and without COPD for the evaluation of the hypothesis.

Methods

Serum anti-p-BQ antibody concentrations of current male smokers with (n=227) or without (n=308) COPD were measured by an indirect enzyme-linked immunoabsorbent assay (ELISA) developed in our laboratory. COPD was diagnosed by spirometry according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines.

Results and discussion

A significant difference was observed in the serum anti-p-BQ antibody level between smokers with and without COPD (Mann–Whitney U-test =4,632.5, P=0.000). Receiver operating characteristic (ROC) curve analysis indicated that the ELISA had significant precision (area under the curve [AUC] =0.934, 95% confidence interval [CI]: 0.913–0.935) for identifying smokers with COPD from their low antibody level. The antibody cutoff value of 29.4 mg/dL was constructed from the ROC coordinates to estimate the risk for COPD in smokers. While 90.3% of smokers with COPD had a low antibody value (≤29.4 mg/dL), the majority (86.4%) of smokers without COPD had a high antibody value (≤29.4 mg/dL); 13.6% of current smokers without COPD having an antibody level below this cutoff value (odds ratio [OR] =59.3, 95% CI: 34.15–101.99) were considered to be at risk for COPD.

Conclusion and future directions

Our results indicate that serum anti-p-BQ antibody level may be used as a biomarker to identify asymptomatic smokers at risk for COPD for early intervention of the disease.

p-Benzoquinone initiates non-invasive urothelial cancer through aberrant tyrosine phosphorylation of EGFR, MAP kinase activation and cell cycle deregulation: Prevention by vitamin C

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p-Benzoquinone induces non-invasive urothelial carcinoma in a guinea pig model.

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The mechanisms involved are persistent growth signaling and cell cycle deregulation.

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Vitamin C prevents p-benzoquinone-induced non-invasive urothelial carcinoma.

According to WHO classification system, non-invasive urothelial carcinoma represents urothelial carcinoma in situ (CIS) and dysplasia. Dysplastic urothelium often progresses to CIS that further advances to urothelial carcinoma (UC). The strongest risk factor for UC is cigarette smoking. However, the pathogenesis of cigarette smoke (CS)-induced UC is poorly understood. Earlier we had shown that p-benzoquinone (p-BQ), a major toxic quinone derived from p-benzosemiquinone of CS in vivo, is a causative factor for various CS-induced diseases. Here, using a guinea pig model we showed that prolonged treatment with p-BQ led to non-invasive UC, specifically carcinoma in situ (CIS) of the renal pelvis and dysplasia in the ureter and bladder. The mechanisms of carcinogenesis were p-BQ-induced oxidative damage and apoptosis that were later suppressed and followed by activation of epidermal growth factor receptor, aberrant phosphorylation of intracellular tyrosine residues, activation of MAP kinase pathway and persistent growth signaling. This was accompanied by deregulation of cell cycle as shown by marked decrease in the expression of p21^waf1/cip1 and cyclin D1 proteins as well as hyperphosphorylation of pRb. UC has been characterised by histopathology and immunohistochemistry showing aberrant CK20, increased Ki-67, and marked p53 nuclear immunopositivity with uniformly negative labelling of CD44. Oral supplementation of vitamin C (30 mg/kg body weight/day) prevented CIS of the renal pelvis and dysplasia in the ureter and bladder. Since majority of non-invasive UC progresses to invasive cancer with increased risk of mortality, our preclinical study might help to devise effective strategies for early intervention of the disease.

Protein Carbonylation in Human Smokers and Mammalian Models of Exposure to Cigarette Smoke: Focus on Redox Proteomic Studies

SIGNIFICANCE

Oxidative stress is one mechanism whereby tobacco smoking affects human health, as reflected by increased levels of several biomarkers of oxidative stress/damage isolated from tissues and biological fluids of active and passive smokers. Many investigations of cigarette smoke (CS)-induced oxidative stress/damage have been carried out in mammalian animal and cellular models of exposure to CS. Animal models allow the investigation of many parameters that are similar to those measured in human smokers. In vitro cell models may provide new information on molecular and functional differences between cells of smokers and nonsmokers. Recent Advances: Over the past decade or so, a growing number of researches highlighted that CS induces protein carbonylation in different tissues and body fluids of smokers as well as in in vivo and in vitro models of exposure to CS.

CRITICAL ISSUES

We review recent findings on protein carbonylation in smokers and models thereof, focusing on redox proteomic studies. We also discuss the relevance and limitations of these models of exposure to CS and critically assess the congruence between the smoker's condition and laboratory models.

FUTURE DIRECTIONS

The identification of protein targets is crucial for understanding the mechanism(s) by which carbonylated proteins accumulate and potentially affect cellular functions. Recent progress in redox proteomics allows the enrichment, identification, and characterization of specific oxidative protein modifications, including carbonylation. Therefore, redox proteomics can be a powerful tool to gain new insights into the onset and/or progression of CS-related diseases and to develop strategies to prevent and/or treat them. Antioxid. Redox Signal. 26, 406-426.

Interaction of p-benzoquinone with hemoglobin in smoker's blood causes alteration of structure and loss of oxygen binding capacity

Cigarette smoke (CS) is an important source of morbidity and early mortality worldwide. Besides causing various life-threatening diseases, CS is also known to cause hypoxia. Chronic hypoxia would induce early aging and premature death. Continuation of smoking during pregnancy is a known risk for the unborn child. Although carbon monoxide (CO) is considered to be a cause of hypoxia, the effect of other component(s) of CS on hypoxia is not known. Here we show by immunoblots and mass spectra analyses that in smoker's blood p-benzoquinone (p-BQ) derived from CS forms covalent adducts with cysteine 93 residues in both the β chains of hemoglobin (Hb) producing Hb-p-BQ adducts. UV-vis spectra and CD spectra analyses show that upon complexation with p-BQ the structure of Hb is altered. Compared to nonsmoker's Hb, the content of α-helix decreased significantly in smoker's Hb (p = 0.0224). p-BQ also induces aggregation of smoker's Hb as demonstrated by SDS-PAGE, dynamic light scattering and atomic force microscopy. Alteration of Hb structure in smoker's blood is accompanied by reduced oxygen binding capacity. Our results provide the first proof that p-BQ is a cause of hypoxia in smokers. We also show that although both p-BQ and CO are responsible for causing hypoxia in smokers, exposure to CO further affects the function over and above that produced by Hb-p-BQ adduct.

Crosstalk Between Co-cultured A549 Cells and THP1 Cells Exposed to Cigarette Smoke

Cigarette smoke (CS) is considered as a major etiological factor in the pathogenesis of chronic obstructive pulmonary disease. In this study we used A549 cells and THP-1 cells grown for 24 h in monoculture or in co-culture in CS-conditioned media and changes in their proliferation, viability, acetylated histone H3 levels and expression of extracellular antigens CD14, HLA-DR, CD11a, and CD11b were assessed. CS was highly toxic to A549 cells but not to THP1 cells. In A549 cells, oxidative stress reached the highest values after 1 h of CS exposure and then decreased. In THP1 cells oxidative stress was lower and increased progressively with time. CS decreased proliferation of A549 and THP1 cells by about 80% and 21%, respectively. CS did not alter acetylated histone H3 levels in A549 cells, while in THP1 cells the levels were reduced by about 35%. CS significantly increased expression of CD14, HLA-DR, CD11a, and CD11b in THP1 cells. In co-culture, naïve or CS-pretreated THP1 cells significantly protected A549 cells against CS toxicity but had higher death rates. These results show that epithelial cells are more fragile to CS than monocytes and that CS-activated monocytes may protect epithelial cells against CS-induced cytotoxicity.

Molecular Links between Alcohol and Tobacco Induced DNA Damage, Gene Polymorphisms and Patho-physiological Consequences: A Systematic Review of Hepatic Carcinogenesis

Chronic alcohol and tobacco abuse plays a crucial role in the development of different liver associated disorders. Intake promotes the generation of reactive oxygen species within hepatic cells exposing their DNA to continuous oxidative stress which finally leads to DNA damage. However in response to such damage an entangled protective repair machinery comprising different repair proteins like ATM, ATR, H2AX, MRN complex becomes activated. Under abnormal conditions the excessive reactive oxygen species generation results in genetic predisposition of various genes (as ADH, ALDH, CYP2E1, GSTT1, GSTP1 and GSTM1) involved in xenobiotic metabolic pathways, associated with susceptibility to different liver related diseases such as fibrosis, cirrhosis and hepatocellular carcinoma. There is increasing evidence that the inflammatory process is inherently associated with many different cancer types, including hepatocellular carcinomas. The generated reactive oxygen species can also activate or repress epigenetic elements such as chromatin remodeling, non-coding RNAs (micro-RNAs), DNA (de) methylation and histone modification that affect gene expression, hence leading to various disorders. The present review provides comprehensive knowledge of different molecular mechanisms involved in gene polymorphism and their possible association with alcohol and tobacco consumption. The article also showcases the necessity of identifying novel diagnostic biomarkers for early cancer risk assessment among alcohol and tobacco users.

Leucine and its transporter provide protection against cigarette smoke-induced cell death: A potential therapy for emphysema

Cigarette smoke (CS) is a major risk factor for emphysematous changes in the lungs and the underlying mechanism involves CS-induced cell death. In the present study we investigated the ability of nutrients to rescue CS-induced cell death. We observed that pre-treatment with excess leucine can partially rescue CS extract-induced cell death in Saccharomyces cerevisiae and alveolar epithelial A549 cells. Excess dietary leucine was also effective in alleviating effects of CS in guinea pig lungs. Further investigation to understand the underlying mechanism showed that CS exposure causes downregulation of leucine transporter that results in inactivation of mTOR, which is a positive regulator of protein synthesis and cell proliferation. Notably, leucine supplemented diet ameliorated even existing CS-induced emphysematous changes in guinea pig lung, a condition hitherto thought to be irreversible. Thus the current study documents a new mechanism by which CS affects cellular physiology wherein leucine transporter is a key target.

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

Dual effects of cigarette smoke extract on proliferation of endothelial progenitor cells and the protective effect of 5-aza-2'-deoxycytidine on EPCs against the damage caused by CSE

Cigarette smoke is a major public health problem associated with multitude of diseases, including pulmonary and vascular diseases. Endothelial progenitor cells (EPCs) contribute to neovascularization and play an important role in the development of these diseases. The effect of CSE on EPCs is seldom studied. The aim of the current study is to observe the effect of CSE on biological behavior of EPCs and, further, to search for potential candidate agent in protection of proliferation of EPCs against the damage caused by CSE exposure in vitro. Methods. The proliferations of EPCs isolated from bone marrow of C57BL/6J mice were assessed by MTT after incubating the EPCs with a series of concentrations of CSE (1.0%, 2.5%, 5.0%, and 10.0%) for different times (3, 6, and 24 hours) as well as with 1.0% CSE in presence of 5-AZA-CdR for 24 hours. Results. The proliferations of EPCs were significantly enhanced after 3 hours of exposure to concentrations of 1.0% and 2.5% CSE but depressed when exposed to concentrations of 5.0% and 10.0% CSE. Furthermore, the 5-AZA-CdR in concentrations of 2.0 μmol/L and 5.0 μmol/L partly protected against the depression of proliferation of EPCs caused by CSE exposure. Conclusions. The CSE showed dual effects on proliferation of EPCs isolated from mice. The 5-AZA-CdR partly protected the proliferation of EPCs against the damage caused by CSE exposure in vitro, suggesting that DNA methylation may be involved in the dysfunction of EPCs induced by CSE.

P21-PARP-1 pathway is involved in cigarette smoke-induced lung DNA damage and cellular senescence

Persistent DNA damage triggers cellular senescence, which may play an important role in the pathogenesis of cigarette smoke (CS)-induced lung diseases. Both p21^CDKN1A (p21) and poly(ADP-ribose) polymerase-1 (PARP-1) are involved in DNA damage and repair. However, the role of p21-PARP-1 axis in regulating CS-induced lung DNA damage and cellular senescence remains unknown. We hypothesized that CS causes DNA damage and cellular senescence through a p21-PARP-1 axis. To test this hypothesis, we determined the levels of γH2AX (a marker for DNA double-strand breaks) as well as non-homologous end joining proteins (Ku70 and Ku80) in lungs of mice exposed to CS. We found that the level of γH2AX was increased, whereas the level of Ku70 was reduced in lungs of CS-exposed mice. Furthermore, p21 deletion reduced the level of γH2AX, but augmented the levels of Ku70, Ku80, and PAR in lungs by CS. Administration of PARP-1 inhibitor 3-aminobenzamide increased CS-induced DNA damage, but lowered the levels of Ku70 and Ku80, in lungs of p21 knockout mice. Moreover, 3-aminobenzamide increased senescence-associated β-galactosidase activity, but decreased the expression of proliferating cell nuclear antigen in mouse lungs in response to CS. Interestingly, 3-aminobenzamide treatment had no effect on neutrophil influx into bronchoalveolar lavage fluid by CS. These results demonstrate that the p21-PARP-1 pathway is involved in CS-induced DNA damage and cellular senescence.

(-)-Epigallocatechin-gallate (EGCG) stabilize the mitochondrial enzymes and inhibits the apoptosis in cigarette smoke-induced myocardial dysfunction in rats

The present study brings out the preventive role of (-)-epigallocatechin-gallate (EGCG) on cardiac mitochondrial metabolism and apoptosis in cigarette smoke (CS)-exposed rats. The CS-exposed rats showed significantly decreased activities of TCA cycle enzymes and mitochondrial enzymatic antioxidants, on the other hand, mitochondrial lipid peroxidation was increased and GSH level was decreased. Further, CS exposure was found to induce cardiac apoptosis through release of cytochrome c into the cytosol, cleavage of pro-caspase-3 to active caspase-3, up-regulation of pro-apoptotic (Bax) and down-regulation of antiapoptotic (Bcl-2) molecules. The CS-induced apoptosis was further confirmed by mitochondrial and nuclear ultra structural apoptotic features as evaluated by electron microscopic studies. EGCG supplementation shelters the activities of TCA cycle enzymes and antioxidant enzymes, with concomitant decrease in lipid peroxidation and increase in GSH level. EGCG administration inhibited apoptosis through the inhibition of cytochrome c release into cytosol, activation of pro-caspase-3, down regulation of Bax and significant up regulation of Bcl-2. EGCG reversed the ultra structural apoptotic alterations of mitochondria and nucleus. The present study has provided experimental evidences that the EGCG treatment enduring to cardio protection at mitochondrial level.

Recent applications of engineered animal antioxidant deficiency models in human nutrition and chronic disease

Dietary antioxidants are essential nutrients that inhibit the oxidation of biologically important molecules and suppress the toxicity of reactive oxygen or nitrogen species. When the total antioxidant capacity is insufficient to quench these reactive species, oxidative damage occurs and contributes to the onset and progression of chronic diseases, such as neurodegenerative diseases, cardiovascular diseases, and cancer. However, epidemiological studies that examine the relationship between antioxidants and disease outcome can only identify correlative associations. Additionally, many antioxidants also have prooxidant effects. Thus, clinically relevant animal models of antioxidant function are essential for improving our understanding of the role of antioxidants in the pathogenesis of complex diseases as well as evaluating the therapeutic potential and risks of their supplementation. Recent progress in gene knockout mice and virus-based gene expression has potentiated these areas of study. Here, we review the current genetically modified animal models of dietary antioxidant function and their clinical relevance in chronic diseases. This review focuses on the 3 major antioxidants in the human body: vitamin C, vitamin E, and uric acid. We examine genetic models of vitamin C synthesis (guinea pig, Osteogenic Disorder Shionogi rat, Gulo(-/-) and SMP30(-/-) mouse mutants) and transport (Slc23a1(-/-) and Slc23a2(-/-) mouse mutants), vitamin E transport (Ttpa(-/-) mouse mutant), and uric acid synthesis (Uox(-/-) mouse mutant). The application of these models to current research goals is also discussed.

Cyto-genotoxic effects of smoke from commercial filter and non-filter cigarettes on human bronchial and pulmonary cells

Cigarette smoke is a complex mixture of chemicals, some of which are known as carcinogens. The cyto-genotoxic effects of cigarette-smoke extract (CSE) from commercial cigarettes without (A and B) and with filter (C and D) were evaluated at different CSE concentrations on A549 and BEAS-2B cells. The particle content of the cigarette smoke and the metal composition of the CSE were also analyzed. The cells were exposed to 1-10% of the CSE from one cigarette per experiment. Cytotoxicity was evaluated by use of the MTT assay after 24h, and the lactate dehydrogenase (LDH) assay after 30min and 24h. The Fpg-modified comet assay was used to evaluate direct-oxidative DNA damage on cells exposed for 30min. As expected, unfiltered cigarette smoke (particularly from the B cigarette) contained a higher number of particles than filtered smoke. With smoke extract from the B cigarette we found a decrease in cell viability only in BEAS-2B cells. The results of the LDH test showed membrane damage for B-cigarette smoke extract, particularly in BEAS-2B cells. Extracts from unfiltered cigarette smoke induced significant direct DNA damage, to a larger extent in A549 cells. Filtered cigarette-smoke extract induced a significant direct DNA damage at 5-10%. A significant induction of oxidative DNA damage was found at the highest CSE concentration in both cell types (by smoke extracts from B and C cigarettes in A549 cells, and from A and D cigarettes in BEAS-2B cells). Smoke extracts from filter cigarettes induced less direct DNA damage than those from unfiltered cigarettes in A549 cells, probably due to a protective effect of filter. In BEAS-2B cells the smoke extract from the B-cigarette showed the highest genotoxic effect, with a concentration-dependent trend. These findings show a higher cyto-genotoxicity for smoke extracts from the B-cigarette and oxidative effects for those from the A and D cigarettes, particularly in BEAS-2B cells. Moreover, there was a higher responsiveness of A549 cells to genotoxic insult of CSE, and a cigarette-dependent genotoxicity in BEAS-2B cells. Our experimental model demonstrated to be suitable to sensitively detect early genotoxic response of different lung-cell types to non-cytotoxic concentrations of complex inhalable mixtures.

Molecular and cellular mechanisms of cigarette smoke-induced myocardial injury: prevention by vitamin C

BACKGROUND

Cardiovascular disease (CVD) remains one of the major killers in modern society. One strong risk factor of CVD is cigarette smoking that causes myocardial injury and leads to the genesis of pathological cardiovascular events. However, the exact toxic component(s) of cigarette smoke (CS) and its molecular and cellular mechanisms for causing myocardial injury leading to heart damage and its prevention are largely unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Using a guinea pig model, here we show that chronic exposure to CS produces myocardial injury that is prevented by vitamin C. Male guinea pigs were fed either vitamin C-deficient (0.5 mg/day) or vitamin C-sufficient (15 mg/day) diet and subjected to CS exposure from 5 Kentucky Research cigarettes (3R4F)/day (6 days/week) in a smoke chamber up to 8 weeks. Pair-fed sham controls were subjected to air exposure instead of CS exposure under similar conditions. Myocardial injury was produced in CS-exposed marginal vitamin C-deficient guinea pigs as evidenced by release of cardiac Troponin-T and I in the serum, oxidative stress, inflammation, apoptosis, thrombosis and collagen deposition in the myocardium. Treatment of rat cardiomyocyte cells (H9c2) in vitro and guinea pigs in vivo with p-benzoquinone (p-BQ) in amounts derived from CS revealed that p-BQ was a major factor responsible for CS-induced myocardial damage. A moderately large dose of vitamin C (15 mg/day) prevented CS/p-BQ-induced myocardial injury. Population based studies indicated that plasma vitamin C levels of smokers without disease were significantly lower (p = 0,0000) than that of non-smokers. Vitamin C levels of CS-related cardiovascular patients were further lower (p = 0.0000) than that of smokers without disease.

CONCLUSIONS/SIGNIFICANCE

The results indicate that dietary supplementation of vitamin C may be a novel and simple therapy for the prevention of pathological cardiovascular events in habitual smokers.

Cigarette Smoke Extract-induced Reduction in Migration and Contraction in Normal Human Bronchial Smooth Muscle Cells

The proliferation, migration, cytokine release, and contraction of airway smooth muscle cells are key events in the airway remodeling process that occur in lung disease such as asthma, chronic obstruction pulmonary disease, and cancer. These events can be modulated by a number of factors, including cigarette smoke extract (CSE). CSE-induced alterations in the viability, migration, and contractile abilities of normal human airway cells remain unclear. This study investigated the effect of CSE on cell viability, migration, tumor necrosis factor (TNF)-α secretion, and contraction in normal human bronchial smooth muscle cells (HBSMCs). Treatment of HBSMCs with 10% CSE induced cell death, and the death was accompanied by the generation of reactive oxygen species (ROS). CSE-induced cell death was reduced by N-acetyl-l-cysteine (NAC), an ROS scavenger. In addition, CSE reduced the migration ability of HBSMCs by 75%. The combination of NAC with CSE blocked the CSE-induced reduction of cell migration. However, CSE had no effect on TNF-α secretion and NF-κB activation. CSE induced an increase in intracellular Ca²⁺ concentration in 64% of HBSMCs. CSE reduced the contractile ability of HBSMCs, and the ability was enhanced by NAC treatment. These results demonstrate that CSE treatment induces cell death and reduces migration and contraction by increasing ROS generation in normal HBSMCs. These results suggest that CSE may induce airway change through cell death and reduction in migration and contraction of normal HBSMCs.

The effect of black coral extraction on acute lung inflammation induced by cigarette smoke in mice

Short-term exposure to cigarette smoke (CS) introduces an abundance of free radicals into the lungs, causing oxidative stress and inflammation. CS is an important risk factor related to the pathogenesis of several pulmonary diseases, especially chronic obstructive pulmonary disease. Black coral (BC) is a marine biomaterial commonly used for cigarette holders in southeast China. The purpose of the present study was to evaluate the in vivo bioactivity of BC extract (BCE). Groups of mice (male Kunming) were subjected to ultrasonic atomizing inhalation of BCE (0.3, 1.5, and 3 mg/mL) before being exposed to CS (10 cigarettes per day for 4 days). The control group and the CS group were administered normal saline rather than BCE prior to CS exposure. Superoxide dismutase (SOD), malondialdehyde (MDA), and myeloperoxidase (MPO) levels were measured in lung homogenates. Histologic and morphologic studies of the right upper lung were performed. SOD activity increased 1.32 times in the CS+BCE (3 mg/mL) group (P < .001) compared with the CS group. The MDA content increased 4% (P < .001) in the CS+BCE (3 mg/mL) group compared with the control group. MPO was reduced 40% in the CS+BCE (3 mg/mL) group compared with the CS group (P < .001). Histologic analysis revealed decreased inflammation in the BCE group compared with the CS group. These results suggest that BCE has antioxidant and anti-inflammatory activity in vivo. BCE may protect against lung injury in smokers.

Molecular mechanisms of cigarette smoke-induced proliferation of lung cells and prevention by vitamin C

Lung cancer is the leading cause of cancer dearth. Cigarette smoking is the strongest risk factor for developing lung cancer, which is conceivably initiated by proliferation. Here, we show that low concentration of aqueous extract of cigarette smoke (AECS) causes excessive proliferation of human lung epithelial cells (A549) without any apoptotic cell death. The causative factor responsible for AECS-induced proliferation has been identified as p-benzoquinone (p-BQ). Coimmunoprecipitation and immunoblot experiments indicate that p-BQ binds with epidermal growth factor receptor (EGFR). However, in contrast to EGF, it causes aberrant phosphorylation of EGFR that lacks c-Cbl-mediated ubiquitination and degradation resulting in persistent activation of EGFR. This is followed by activation of Hras + Kras and the downstream survival and proliferative signaling molecules Akt and ERK1/2, as well as the nuclear transcription factors c-Myc and c-Fos. Vitamin C and/or antibody to p-BQ prevents AECS/p-BQ-induced proliferation of lung cells apparently by inactivating p-BQ and thereby preventing activation of EGFR and the downstream signaling molecules. The results suggest that vitamin C and/or antibody to p-BQ may provide a novel intervention for preventing initiation of lung cancer in smokers.

NAD(P)H: quinone oxidoreductase 1 deficiency conjoint with marginal vitamin C deficiency causes cigarette smoke induced myelodysplastic syndromes

Background

The etiology of myelodysplastic syndromes (MDS) is largely unknown. Exposure to cigarette smoke (CS) is reported to be associated with MDS risk. There is inconsistent evidence that deficiency of NAD(P)H-quinone: oxidoreductase 1 (NQO1) increases the risk of MDS. Earlier we had shown that CS induces toxicity only in marginal vitamin C-deficient guinea pigs but not in vitamin C-sufficient ones. We therefore considered that NQO1 deficiency along with marginal vitamin C deficiency might produce MDS in CS-exposed guinea pigs.

Methodology and Principal Findings

Here we show that CS exposure for 21 days produces MDS in guinea pigs having deficiency of NQO1 (fed 3 mg dicoumarol/day) conjoint with marginal vitamin C deficiency (fed 0.5 mg vitamin C/day). As evidenced by morphology, histology and cytogenetics, MDS produced in the guinea pigs falls in the category of refractory cytopenia with unilineage dysplasia (RCUD): refractory anemia; refractory thrombocytopenia that is associated with ring sideroblasts, micromegakaryocytes, myeloid hyperplasia and aneuploidy. MDS is accompanied by increased CD34(+) cells and oxidative stress as shown by the formation of protein carbonyls and 8-oxodeoxyguanosine. Apoptosis precedes MDS but disappears later with marked decrease in the p53 protein. MDS produced in the guinea pigs are irreversible. MDS and all the aforesaid pathophysiological events do not occur in vitamin C-sufficient guinea pigs. However, after the onset of MDS vitamin C becomes ineffective.

Conclusions and Significance

CS exposure causes MDS in guinea pigs having deficiency of NQO1 conjoint with marginal vitamin C deficiency. The syndromes are not produced in singular deficiency of NQO1 or marginal vitamin C deficiency. Our results suggest that human smokers having NQO1 deficiency combined with marginal vitamin C deficiency are likely to be at high risk for developing MDS and that intake of a moderately large dose of vitamin C would prevent MDS.

Volatile constituents, inorganic elements and primary screening of bioactivity of black coral cigarette holders

Black corals (BC) have been used for a long time in Chinese medicine, and may have some pharmaceutical functions when used as material for cigarette holders in southeast China. This study is aimed to investigate the bioactivities of volatile constituents in BC and to explore the folklore behind the use of BC cigarette holders (BCCHs). We extracted the volatile constituents of BC by supercritical fluid extraction (SFE) with carbon dioxide (CO₂-SFE), then identified and analyzed the constituents by gas chromatography-mass spectrometry (GC-MS). In total, 15 components were reliably identified in BC and found to be biologically active. These included triethyl phosphate, butylated hydroxytoluene, cedrol, n-hexadecanoic acid, squalene, and cholesterol. Meanwhile 13 inorganic elements (P, Ca, Mg, S, B, Si, Fe, Cu, Zn, Ba, etc.) were determined by inductively coupled plasma spectrometer (ICPS). In the bioactivity tests, the BC extract (BCE) showed a scavenging activity of 2,2-diphenyl-1-picrylhydrazyl free radicals and hydroxyl radicals by phenanthroline-Fe (II) oxidation and moderate inhibition of Gram-positive microorganisms. The antioxidant and antimicrobial activities of BC, which are related to the active chemical composition, may explain the perceived benefit for cigarette smokers who use BCCHs.

Aged red garlic extract reduces cigarette smoke extract-induced cell death in human bronchial smooth muscle cells by increasing intracellular glutathione levels

Increasing antioxidant capacity has been proposed as a promising strategy to prevent cigarette smoke-induced lung diseases. This study tested whether garlic extracts prevented cigarette smoke extract (CSE)-induced cell death in human bronchial smooth muscle cells (HBSMCs). Garlic extracts were prepared from fresh raw garlic (FRG), aged black garlic (ABG) and aged red garlic (ARG). Treatment of HBSMCs with 10% CSE induced cell death accompanied by activation of caspase. Of the garlic extracts, treatment with ARG extract reduced CSE-induced cell death. The combination of ARG extract with CSE attenuated the CSE-induced reduction in glutathione (GSH) content, generation of reactive oxygen species (ROS) and induction of heme oxygenase-1 expression compared with CSE treatment without ARG extract. Furthermore, the combination of L-BSO, a GSH synthesis inhibitor, with ARG and CSE extracts failed to increase the intracellular GSH content and cell viability. Taken together, these results demonstrate that ARG extract reduces CSE-induced cell death by increasing GSH content and reducing ROS generation in HBSMCs.

A short overview of vitamin C and selected cells of the immune system

Vitamin C (ascorbic acid) is an essential water-soluble nutrient that primarily exerts its effect on a host defense mechanisms and immune homeostasis and is the most important physiological antioxidant. Stable intake of vitamin C is essential for life in humans because the body does not synthesize it. Even the numerous studies have demonstrated that vitamin C supplementation stimulates the immune system, prevents DNA damage and significantly decreases the risk of a wide range of pathologies; the potential protective mechanisms are still largely unknown. This review summarizes the recently known facts about the role of vitamin C on the selected cells of the immune system and potential molecular mechanisms involved. Further, in this review, many new data about the positive effects of vitamin C on the immune system, potential toxicological effects, vitamin C supplementation in disease development, as well as some proposed mechanisms of vitamin C activity, are discussed.

Addition of açaí (Euterpe oleracea) to cigarettes has a protective effect against emphysema in mice

Chronic inhalation of cigarette smoke (CS) induces emphysema by the damage contributed by oxidative stress during inhalation of CS. Ingestion of açai fruits (Euterpe oleracea) in animals has both antioxidant and anti-inflammatory effects. This study compared lung damage in mice induced by chronic (60-day) inhalation of regular CS and smoke from cigarettes containing 100mg of hydroalcoholic extract of açai berry stone (CS + A). Sham smoke-exposed mice served as the control group. Mice were sacrificed on day 60, bronchoalveolar lavage was performed, and the lungs were removed for histological and biochemical analyses. Histopathological investigation showed enlargement of alveolar space in CS mice compared to CS + A and control mice. The increase in leukocytes in the CS group was higher than the increase observed in the CS + A group. Oxidative stress, as evaluated by antioxidant enzyme activities, mieloperoxidase, glutathione, and 4-hydroxynonenal, was reduced in mice exposed to CS+A versus CS. Macrophage and neutrophil elastase levels were reduced in mice exposed to CS + A versus CS. Thus, the presence of açai extract in cigarettes had a protective effect against emphysema in mice, probably by reducing oxidative and inflammatory reactions. These results raise the possibility that addition of açaí extract to normal cigarettes could reduce their harmful effects.

Activated charcoal filter effectively reduces p-benzosemiquinone from the mainstream cigarette smoke and prevents emphysema

In this paper, we have made a comparative evaluation of the cytotoxicity and pathophysiological effects of mainstream smoke from cellulose acetate (CA)-filtered cigarettes with that of charcoal-filtered cigarettes developed in our laboratory. Previously, we had demonstrated that the mainstream smoke from an Indian CA-filtered commercial cigarette contains p-benzosemiquinone (p-BSQ), a major, highly toxic, long-lived water-soluble radical. Here, we have examined 16 brands of different CA-filtered cigarettes including Kentucky research cigarettes, and observed that mainstream smoke from all the cigarettes contains substantial amounts of p-BSQ (100-200 μg/cigarette). We also show that when the CA filter is replaced by a charcoal filter, the amount of p-BSQ in the mainstream smoke is reduced by 73-80%, which is accompanied by a reduction of carbonyl formation in bovine serum albumin to the extent of 70- 90%. The charcoal filter also prevented cytotoxicity in A549 cells as evidenced by MTT assay, apoptosis as evidenced by FACS analysis, TUNEL assay, overexpression of Bax, activation of p53 and caspase 3, as well as emphysematous lung damage in a guinea pig model as seen by histology and morphometric analysis. The results indicate that the charcoal filter developed in our laboratory may protect smokers from cigarette smoke-induced cytotoxity, protein modification, apoptosis and emphysema.

Antioxidant intervention of smoking-induced lung tumor in mice by vitamin E and quercetin

Background

Epidemiological and in vitro studies suggest that antioxidants such as quercetin and vitamin E (VE) can prevent lung tumor caused by smoking; however, there is limited evidence from animal studies.

Methods

In the present study, Swiss mouse was used to examine the potential of quercetin and VE for prevention lung tumor induced by smoking.

Results

Our results suggest that the incidence of lung tumor and tumor multiplicity were 43.5% and 1.00 ± 0.29 in smoking group; Quercetin has limited effects on lung tumor prevention in this in vivo model, as measured by assays for free radical scavenging, reduction of smoke-induced DNA damage and inhibition of apoptosis. On the other hand, vitamin E drastically decreased the incidence of lung tumor and tumor multiplicity which were 17.0% and 0.32 ± 0.16, respectively (p < 0.05); and demonstrated prominent antioxidant effects, reduction of DNA damage and decreased cell apoptosis (p < 0.05). Combined treatment with quercetin and VE in this animal model did not demonstrate any effect greater than that due to vitamin E alone. In addition, gender differences in the occurrence of smoke induced-lung tumor and antioxidant intervention were also observed.

Conclusion

We conclude that VE might prevent lung tumor induced by smoking in Swiss mice.