Evidence for the role of nitric oxide in antiapoptotic and genotoxic effect of nicotine on human gingival fibroblasts

Areca nut and smokeless tobacco exposure induces micronucleus, other nuclear abnormalities and cytotoxicity in early chick embryo

Areca nut (AN) and smokeless tobacco (SLT) are indiscriminately consumed among the populations of Southeast and South Asian countries, even by women during the gestational period. This study aimed to investigate the genotoxic and cytotoxic potentials of AN and Sadagura (SG), a unique homemade SLT preparation, alone and in combination in early chick embryos. Fertile white leghorn chicken eggs were randomly divided into five treatment groups: vehicle control, positive control (Mitomycin C, 20 μg/egg), AN, SG, and AN+SG. AN, SG, and AN+SG were given at dosages of 0.125, 0.25, and 0.5 mg/egg. The hen's egg test for micronucleus induction (HET-MN) was performed in chick embryos to evaluate the genotoxic potential of the test agents. Furthermore, the cytotoxic potential was assessed by studying erythroblast cell populations and the polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs) ratio. Our results indicated a significant increase (p < .001) in MN frequency and other nuclear abnormalities, suggesting the potential of AN and SG to cause genotoxicity. Also, AN and SG exposure alone and in combination considerably altered the erythroblast cell population (%) and the PCE to NCE ratio in all the treatment periods. Our findings established the genotoxic and cytotoxic potential of both AN and SG alone and in combination during early embryonic development in the chick embryo.

Scrutinizing pathways of Nicotine effect on renal Alpha-7 Nicotinic Acetylcholine receptor and Mitogen-activated protein kinase (MAPK) expression in Ehrlich ascites carcinoma-bearing Mice: role of Chlorella vulgaris

Nicotine is one of several physiologically stable and active chemicals found in tobacco. The mechanism through which nicotine causes kidney damage is still obscure. As a result, the goal of this research was to investigate how oral nicotine intake can lead to kidney damage. Naturaly occurring superfood green algae are immense supplements help us using extra chemicals during cancer prevalence if the patient is exposed to nicotine. Hence, the mitigating role of Chlorella vulgaris extract (CVE) against nicotine-nephrotoxic impact in Ehrlich ascites carcinoma (EAC)-bearing mice was studied. For this purpose, four groups of Swiss female mice were assigned, nicotine group (NIC) (100 µg/ml/kg), CVE group (100 mg/kg), CVE+Nicotine, and a control group. Renal dysfunction was evaluated by estimating serum biomarkers ofrenal damage. The expression pattern of Nf-_KB, MAPK, P53, and α7-nAchR, lipid peroxidation biomarker, and antioxidant enzyme activities were evaluated in kidney tissue. Also, micro-morphometric examination and apoptosis immunohistochemical reactivity of kidney tissue were applied. The obtained results indicated up-regulation of all estimated genes and oxidative stress. Moreover, a significant (P<0.05) increment in the apoptotic marker Caspase-3 and declined BCL-2 proteins were recorded. In serum, a significant (P<0.05) elevation of urea, creatinine, TNF-α, IL-1β, and Kim-1 were evident. Histological investigation reinforced the aforementioned data, revealing structural changes involving the tubules, glomeruli, and interstitium of mice kidneys. CVE may be a strong contender for protecting renal tissue damage since it reduces renal tissue injury and oxidative stress. Cancer patients who regularly use nicotine through direct smoking or second-hand exposure can benefit from CVE usage as a dietary supplement.

An approach for the extract generation and toxicological assessment of tobacco-free 'modern' oral nicotine pouches

Tobacco-free 'modern' oral nicotine pouches (MOPs), are similar in appearance and use to Swedish-style snus, but without tobacco. There are few identified methods to create test samples for toxicologically assessment of MOPs in vitro. In this study we present a simple method for the extraction of pouch material in cell culture media, providing consistent nicotine concentration and easy in vitro assessment. A series of contemporary in vitro screening assays (viability, cell health markers, oxidative stress and genotoxicity) using human oral fibroblasts (HGF) and human lung epithelial cells (H292) were employed. Extracts were generated from LYFT and compared to snus (CRP1.1) and cigarette (1R6F) reference products. MOP and CRP1.1 extracts were generated by incubating one pouch in 20 ml of cell culture media, while 1R6F AqE was prepared by smoking 1 cigarette into 20 ml of cell culture media. 1R6F demonstrated toxicological responses in most assays; CRP1.1 had minimal to moderate effects while MOP demonstrated little or no response in all assays. This study demonstrated the generation of MOPs extracts and their toxicological evaluation using in vitro screening approaches. Future product usage, pharmacokinetics and clinical studies will further substantiate the reduced risk potential of MOPs.

A comparative study of electronic cigarette vapor extracts on airway-related cell lines in vitro

The use of electronic cigarettes (ECs) is rapidly increasing worldwide; however, scientific evidence regarding EC cytotoxicity is limited. The aim of this study was to evaluate the acute cytotoxicity of EC vapor extract (ECE) on airway-related cells in vitro. Cigarette smoke extract (CSE), vapor extract of fifteen brands/flavors of ECs and the extract from the E-vehicle (propylene glycol and glycerin) was collected. Extracts, in concentrations of 100-12.5%, were added to human bronchial epithelial (BEAS-2B, IB3-1 and C38), fibroblast (Wi-38) and macrophage (J774 and THP-1) cell lines. Viability was assessed after 24 h using a standard XTT assay. Viability of <70% of control (no extract) was considered cytotoxic according to UNI EN ISO 10993-5 standards. CSE displayed a concentration-dependent influence on cell viability across all four cell lines with 100% producing the most toxic effect, therefore validating the model and indicating higher cytotoxicity than in ECEs. ECEs did reduce viability although this was not correlated with nicotine content or the E-vehicle. However, several flavors proved cytotoxic, with variation between different brands and cell lines. These data indicate that not all ECs are the same and that use of a particular flavor or brand may have differing effects. The cell line used is also an important factor. More research is crucial to ascertain the health effects of different ECs before they can be accepted as a safe alternative to tobacco cigarettes.

Expression Changes of Apoptotic Genes in Tissues from Mice Exposed to Nicotine

Objective:

Smoking is the leading preventable cause of various diseases such as lung cancer, chronic obstructive pulmonary disease and cardiovascular disease. Nicotine, one of the major toxic components of tobacco, contributes to the pathogenesis of different diseases.

Methods:

Given the controversy about nicotine toxicity, the present study was conducted to determine apoptotic effects of nicotine on the heart, kidney, lung and liver of male mice. Real-time PCR was performed to identify mRNA expression changes in apoptotic-related genes between nicotine treated and control mice.

Result:

In the heart and lung, nicotine caused significant decrease in P53, Bax and Caspase-3 mRNA expression levels compared to the control group. However, in the kidney and liver, the result was significant increase in Bax, Caspase-2, Caspase-3 and a significant decrease in P53 mRNA expression (p<0.01). DNA fragmentation assays indicated no fragmentation in the heart and lung, but in the kidney and liver of nicotine treated mice, isolated DNA was fragmented.

Conclusion:

Our study provided insight into the molecular mechanisms of nicotine anti-apoptotic effects on the heart and lung as well as pro-apoptotic effects on kidney and liver via a P53-independent pathway.

The effect of nicotine and cotinine on human gingival fibroblasts attachment to root surfaces

BACKGROUND

Different compounds of smoking (e.g., nicotine and cotinine) are risk factors for various diseases such as oral cancer and periodontal diseases. Some studies reported the negative effects of nicotine on cell proliferation and differentiation. The present in vitro study assessed the effects of nicotine and cotinine (long-acting metabolite of nicotine) on the attachment and viability of human gingival fibroblast (HGF) cells to tooth root surfaces.

METHODS

A total of 70 teeth specimens were placed into 48-well culture plates and covered with HGF cell suspension, in complete Dulbecco's modified Eagle's medium culture medium containing 1 nM, 1 μm, 1 mM, and 5 mM of nicotine and cotinine concentrations. Cellular attachment and viability measured using an MTT assay and a scanning electron microscope were used for cell morphological evaluation.

RESULTS

After 24 h, low (nanomolar and micromolar) and high concentrations (millimolar) of nicotine and cotinine caused a significant reduction in the initial cell adhesion in comparison with the control group, but no significant difference was observed between the nicotine and the cotinine groups (p<0.05). Dentally attached cells with low concentrations of nicotine and cotinine proliferated 48 h after exposure, the same as the control group. However, dentally attached cells with high concentrations of nicotine and cotinine (especially 5 mM) did not proliferate 24 h after exposure (p<0.05).

CONCLUSIONS

Low concentrations of nicotine and cotinine caused a reduction in the initial cell adhesion. However, no significant adverse effects on the proliferation of attached cells were seen in the longer period. High concentrations of nicotine and cotinine have adverse effects on the cell adhesion and proliferation of HGF cells.

Oxidative Stress, Cytotoxicity, and Genotoxicity Induced by Methyl Parathion in Human Gingival Fibroblasts: Protective Role of Epigallocatechin-3-Gallate

Organophosphorous (OP) compounds are pesticides frequently released into the environment because of extensive use in agriculture. Among these, methyl parathion (mPT) recently received attention as a consequence of illegal use. The predominant route of human exposure to mPT is via inhalation, but inadvertent consumption of contaminated foods and water may also occur. The goal of this study was to investigate the in vitro effects of mPT on cells in the oral cavity and evaluate the potential protective role of epigallocathechin-3-gallate (EGCG) on these effects. Human gingival fibroblasts (HGF) were exposed to 10, 50, or 100 μ g/ml mPT for 24 h and assessed for oxidative stress, as evidenced by reactive generation of oxygen species (ROS), induction of apoptotic cell death, DNA damage (comet assay and cytochinesis-block micronucleus test), and nitric oxide (NO) production. The results showed that mPT produced significant oxidative stress, cytotoxicity, and genotoxicity and increased NO levels through stimulation of inducible NO synthase expression. Finally, data demonstrated that EGCG (10, 25, or 50 μ M) was able to inhibit the pesticide-induced effects on all parameters studied. Data indicate that cytotoxic and genotoxic effects may be associated with oxidative stress induced by mPT observed in HGF cultures and that EGCG plays a protective role via antioxidant activities.

Nicotine stimulation increases proliferation and matrix metalloproteinases-2 and -28 expression in human dental pulp cells

AIMS

Dental pulp is the specialized tissue responsible for maintaining tooth viability. When tooth mineralized matrix is damaged, pulp is exposed to a plethora of environmental stimuli. In particular, in smokers, pulp become exposed to very high concentrations of nicotine. The aim of this study was to investigate the effect of direct nicotine stimulation on human dental pulp cell proliferation. Moreover, as it is known that nicotine could upregulate the expression of matrix metalloproteinases (MMPs), enzymes involved in pulpal inflammation, the effects of nicotine stimulation on MMP-2 and MMP-28 gene expression have also been investigated.

MAIN METHODS

Human dental pulp cells were extracted from impacted third molars obtained from healthy patients undergoing routine orthodontic treatments. Such cells were treated with growing concentrations of nicotine in the presence or absence of a nicotine antagonist (hexamethonium chloride) or of a MEK signaling inhibitor (PD98059). Cell proliferation was evaluated by cell counting, while nicotine effects on MMP expression were evaluated by PCR.

KEY FINDINGS

The data obtained indicate that nicotine is able to increase human dental pulp cell proliferation by acting through nicotinic cholinergic receptors and downstream MAPK signaling pathway. Moreover, it is also able to increase both MMP-2 and MMP-28 gene expression.

SIGNIFICANCE

In summary these results highlight that direct exposure of human dental pulp cells to nicotine results in an inflammatory response, that could have a role in pulpal inflammation onset, a pathological condition that, when ignored, could eventually spread to the surrounding alveolar bone and progress to pulp necrosis.

Nicotine causes genotoxic damage but is not metabolized during long-term exposure of human nasal miniorgan cultures

Human nasal miniorgan cultures (MOC) are a useful tool in ecogenotoxicology. Repetitive exposure to nicotine showed reversible DNA damage, and stable CYP2A6 expression was demonstrated in nasal MOC in previous investigations. The aim of the present study was to evaluate the genotoxic effect of nicotine in nasal MOC after chronic nicotine exposure, and to monitor possible metabolism capacities. MOC were dissected from human nasal mucosa and cultured under standard cell culture conditions. MOC were exposed to nicotine for 3 weeks at concentrations of 1 μM and 1 mM. The concentrations were chosen based on nicotine plasma levels in heavy smokers, and possible concentrations used in topical application of nicotine nasal spray. DNA damage was assessed by the comet assay at days 7, 14 and 21. Concentrations of nicotine and cotinine were analyzed in cell culture medium by gas chromatography/mass spectrometry to determine a possible metabolism of nicotine by MOC. Distinct DNA damage in MOC could be demonstrated after 1 week of exposure to 1 μM and 1 mM nicotine. This effect decreased after 2 and 3 weeks with no statistically relevant DNA migration. No nicotine metabolism could be detected by changes in nicotine and cotinine concentrations in the supernatants. This is the first time genotoxic effects have been evaluated in nasal MOC after chronic nicotine exposure for up to 3 weeks. Genotoxic effects were present after 1 week of culture with a decrease over time. Down-regulation of nicotinic acetylcholine receptors, which are expressed in nasal mucosa, may be a possible explanation. The lack of nicotine metabolism in this model could be explained by the functional loss of CYP2A6 during chronic nicotine exposure. Further investigations are necessary to provide a more detailed description of the underlying mechanisms involved in DNA damage by nicotine.

Nicotine affects cutaneous wound healing in stressed mice

Stress is an important condition of modern life. Nicotine addiction can modulate the physiological response to stress. Cutaneous healing is a complex process resulting in scar formation, which can be delayed by stress. Therefore, the aim of this study was to investigate the effects of nicotine administration on cutaneous wound healing in chronically stressed mice. Male mice were submitted to rotational stress, whereas control animals were not subjected to stress. These stressed and control animals were treated with a transdermal nicotine patch that was changed every day. A full-thickness excisional lesion was also generated, and 14 days later, lesions had recovered. However, the Stress + Nicotine group presented a delay in wound contraction. These wounds showed a decrease in inflammatory cell infiltration and lower expression of transforming growth factor-β (TGF-β), whereas there was an increase in angiogenesis and tumor necrosis factor-α (TNF-α) expression. In vitro fibroblast migration was also impaired by the nicotine treatment of stressed-stimulated cells. In conclusion, nicotine administration potentiates the delay in wound closure observed in mice submitted to stress.

Cytotoxicity evaluation of electronic cigarette vapor extract on cultured mammalian fibroblasts (ClearStream-LIFE): comparison with tobacco cigarette smoke extract

CONTEXT

Electronic cigarettes (ECs) are used as alternatives to smoking; however, data on their cytotoxic potential are scarce.

OBJECTIVE

To evaluate the cytotoxic potential of 21 EC liquids compared to the effects of cigarette smoke (CS).

METHODS

Cytotoxicity was evaluated according to UNI EN ISO 10993-5 standard. By activating an EC device, 200 mg of liquid was evaporated and was extracted in 20 ml of culture medium. CS extract from one cigarette was also produced. The extracts, undiluted (100%) and in five dilutions (50%, 25%, 12.5%, 6.25% and 3.125%), were applied to cultured murine fibroblasts (3T3), and viability was measured after 24-hour incubation by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Viability of less than 70% was considered cytotoxic.

RESULTS

CS extract showed cytotoxic effects at extract concentrations above 12.5% (viability: 89.1 ± 3.5% at 3.125%, 77.8 ± 1.8% at 6.25%, 72.8 ± 9.7% at 12.5%, 5.9 ± 0.9% at 25%, 9.4 ± 5.3% at 50% and 5.7 ± 0.7% at 100% extract concentration). Range of fibroblast viability for EC vapor extracts was 88.5-117.8% at 3.125%, 86.4-115.3% at 6.25%, 85.8-111.7% at 12.5%, 78.1-106.2% at 25%, 79.0-103.7% at 50% and 51.0-102.2% at 100% extract concentration. One vapor extract was cytotoxic at 100% extract concentration only (viability: 51.0 ± 2.6%). However, even for that liquid, viability was 795% higher relative to CS extract.

CONCLUSIONS

This study indicates that EC vapor is significantly less cytotoxic compared tobacco CS. These results should be validated by clinical studies.

Assessment of nicotine-induced DNA damage in a genotoxicological test battery

The role of the tobacco-alkaloid nicotine in tumour biology is widely discussed in the literature. Due to a strong capacity to induce angiogenesis, a pro-mutagenic potential in non-tumour and cancer cells, and a pro- and anti-apoptotic influence, nicotine seems to promote the growth of established tumours. However, results indicating DNA damage and genetic instability associated with nicotine have been contradictory thus far. A variety of markers and endpoints of genotoxicity are required to characterize the genotoxic potential of nicotine. Induction of DNA single- and double-strand breaks, the formation of micronuclei, and the induction of sister chromatid exchange and chromosome aberrations represent possible genotoxicological endpoints at different cellular levels. Human lymphocytes were exposed to nicotine concentrations between 1μM and 1mM for 24h in vitro. The comet assay, the cytokinesis-block micronucleus test, the chromosome aberration (CA) test, and the sister chromatid exchange (SCE) test were then applied. Viability and apoptosis were measured by flow cytometry in combination with the annexin V-propidium iodide staining test. In this test setting, no enhanced DNA migration was measured by the comet assay. An increase in the micronucleus frequency was detected at a concentration of 100μM nicotine without affecting the frequency of apoptotic cells. A distinct genotoxic effect was determined by the CA test and the SCE test, with a significant increase in CA and SCE at a concentration of 1μM. In the annexin V test, nicotine did not influence the proportion of apoptotic or necrotic cells. The current data indicating the induction of CA by nicotine underscore the necessity of ongoing investigations on the potential of nicotine to initiate mutagenesis and tumour promotion. Taking into account the physiological nicotine plasma levels in smokers or in nicotine-replacement therapy, particularly the long-term use of nicotine should be critically discussed.

Effects of cigarette smoke and nicotine on cell viability, migration and myofibroblastic differentiation

BACKGROUND AND OBJECTIVE

Several studies have analysed the role of nicotine as a prominent agent affecting wound repair in smokers. However, tobacco smoke contains several components that may alter gingival wound healing. The present study aimed to analyse the roles of cigarette smoke condensate (CSC) and nicotine on cell viability, cell migration/invasion and myofibroblastic differentiation using primary cultures of human gingival fibroblasts.

MATERIAL AND METHODS

To compare the effects of CSC and nicotine, gingival fibroblasts were stimulated with CSC (0.4–500 lg/mL) and the corresponding nicotine concentrations (0.025–32 lg/mL) present in research cigarettes (1R3F). Cell viability was evaluated through the MTS assay. Cell migration and invasion were assessed through scratch wound assays, collagen nested matrices and trans well migration. a-Smooth muscle actin production was evaluated by western blotting.

RESULTS

Cigarette smoke condensate at 50 lg/mL induced a moderate increase in cell viability, whereas the corresponding nicotine concentration (3.2 lg/mL) did not produce this response. Cigarette smoke condensate at 250 lg/mL, but not nicotine at 16 lg/mL (the corresponding nicotine concentration), induced cell death. Both nicotine and CSC stimulated cell migration (50 lg/mL CSC; 3.2 lg/mL nicotine). At 150 lg/mL, CSC inhibited cell migration; however, the corresponding concentration of nicotine (9.6 lg/mL), did not have this effect. Although both nicotine and CSC inhibited a-smooth muscle actin production, only the latter induced a statistically significant effect on this response.

CONCLUSION

Cigarette smoke condensate may stimulate cell survival and migration at low concentrations and inhibit these cell responses at higher levels of exposure. Moreover, CSC may interfere in myofibroblastic differentiation.These results show that cigarette smoke, but not nicotine, may significantly alter cell viability, cell migration and myofibroblastic differentiation in gingival mesenchymal cells.

Nicotine: specific role in angiogenesis, proliferation and apoptosis

Nowadays, tobacco smoking is the cause of ~5-6 million deaths per year, counting 31% and 6% of all cancer deaths (affecting 18 different organs) in middle-aged men and women, respectively. Nicotine is the addictive component of tobacco acting on neuronal nicotinic receptors (nAChR). Functional nAChR, are also present on endothelial, haematological and epithelial cells. Although nicotine itself is regularly not referred to as a carcinogen, there is an ongoing debate whether nicotine functions as a 'tumour promoter'. Nicotine, with its specific binding to nAChR, deregulates essential biological processes like regulation of cell proliferation, apoptosis, migration, invasion, angiogenesis, inflammation and cell-mediated immunity in a wide variety of cells including foetal (regulation of development), embryonic and adult stem cells, adult tissues as well as cancer cells. Nicotine seems involved in fundamental aspects of the biology of malignant diseases, as well as of neurodegeneration. Investigating the biological effects of nicotine may provide new tools for therapeutic interventions and for the understanding of neurodegenerative diseases and tumour biology.

Analysis of nicotine-induced DNA damage in cells of the human respiratory tract

Epithelium of the upper and lower airways is a common origin of tobacco-related cancer. The main tobacco alkaloid nicotine may be associated with tumor progression. The potential of nicotine in inducing DNA mutations as a step towards cancer initiation is still controversially discussed. Different subtypes of nicotinic acetylcholine receptors (nAChR) are expressed in human nasal mucosa and a human bronchial cell line representing respiratory mucosa as a possible target for receptor-mediated pathways. In the present study, both cell systems were investigated with respect to DNA damage induced by nicotine and its mechanisms. Specimens of human nasal mucosa were harvested during surgery of the nasal air passage. After enzymatic digestion over night, single cells were exposed to an increasing nicotine concentration between 0.001 mM and 4.0mM. In a second step co-incubation was performed using the antioxidant N-acetylcysteine (NAC) and the nAChR antagonist mecamylamine. DNA damage was assessed using the alkali version of the comet assay. Dose finding experiments for mecamylamine to evaluate the maximal inhibitory effect were performed in the human bronchial cell line BEAS-2B with an increasing mecamylamine concentration and a constant nicotine concentration. The influence of nicotine in the apoptotic pathway was evaluated in BEAS-2B cells with the TUNEL assay combined with flow cytometry. After 1h of nicotine exposure with 0.001, 0.01, 0.1, 1.0 and 4.0mM, significant DNA damage was determined at 1.0mM. Further co-incubation experiments with mecamylamine and NAC were performed using 1.0mM of nicotine. The strongest inhibitory effect was measured at 1.0mM mecamylamine and this concentration was used for co-incubation. Both, the antioxidant NAC at a concentration of 1.0mM, based on the literature, as well as the receptor antagonist were capable of complete inhibition of the nicotine-induced DNA migration in the comet assay. A nicotine-induced increase or decrease in apoptosis as assessed by the TUNEL assay in BEAS-2B could not be detected. These results support the hypothesis that oxidative stress is responsible for nicotine-induced DNA damage. Similar results exist for other antioxidants in different cell systems. The decrease in DNA damage after co-incubation with a nAChR antagonist indicates a receptor-dependent pathway of induction for oxidative stress. Further investigations concerning pathways of receptor-mediated DNA damage via nAChR, the role of reactive oxygen species and apoptosis in this cell system will elucidate underlying mechanisms.

Cardiac-specific overexpression of metallothionein rescues nicotine-induced cardiac contractile dysfunction and interstitial fibrosis

Cigarette smoking is a devastating risk factor for cardiovascular diseases and nicotine is believed the main toxin component responsible for the toxic myocardial effects of smoking. Nonetheless, neither the precise mechanism of nicotine-induced cardiac dysfunction nor effective treatment is elucidated. The aim of this study was to evaluate the impact of cardiac-specific overexpression of heavy metal scavenger metallothionein on myocardial geometry and mechanical function following nicotine exposure. Adult male friend virus B (FVB) wild-type and metallothionein mice were injected with nicotine (2 mg/kg/d) intraperitoneally for 10 days. Mechanical and intracellular Ca²+ properties were examined. Myocardial histology (cross-sectional area and fibrosis) was evaluated by hematoxylin and eosin (H&E) and Masson trichrome staining, respectively. Oxidative stress and apoptosis were measured by fluoroprobe 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H₂DCFDA) fluorescence and caspase-3 activity, respectively. Nicotine exposure failed to affect the protein abundance of metallothionein. Our data revealed reduced echocardiographic contractile capacity (fractional shortening), altered cardiomyocyte contractile and intracellular Ca²+ properties including depressed peak shortening amplitude, maximal velocity of shortening/relengthening, resting and electrically-stimulated rise in intracellular Ca²+, as well as prolonged duration of relengthening and intracellular Ca²+ clearance in hearts from nicotine-treated FVB mice, the effect of which was ameliorated by metallothionein. Biochemical and histological findings depicted overt accumulation of reactive oxygen species (ROS), apoptosis and myocardial fibrosis without any change in myocardial cross-sectional area following nicotine treatment, which was mitigated by metallothionein. Taken together, our findings suggest the antioxidant metallothionein may reconcile short-term nicotine exposure-induced myocardial contractile dysfunction and fibrosis possibly through inhibition of ROS accumulation and apoptosis.

Nicotine and apoptosis

Cigarette smoking is associated with a plethora of different diseases. Nicotine is the addictive component of cigarette but also acts onto cells of the non-neuronal system, including immune effector cells. Although nicotine itself is usually not referred to as a carcinogen, there is ongoing debate whether nicotine functions as a 'tumor enhancer.' By binding to nicotinic acetylcholine receptors, nicotine deregulates essential biological processes like angiogenesis, apoptosis, and cell-mediated immunity. Apoptosis plays critical roles in a wide variety of physiologic processes during fetal development and in adult tissue and is also a fundamental aspect of the biology of malignant diseases. This review provides an overlook how nicotine influences apoptotic processes and is thus directly involved in the etiology of pathological conditions like cancer and obstructive diseases.