This article may require copy editing for grammar, style, cohesion, tone, or spelling.(May 2024) |
Names | |
---|---|
Preferred IUPAC name Methyl[4-oxo-4-(pyridin-3-yl)butyl]nitrous amide | |
Other names N-Nitrosonornicotine ketone; 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone | |
Identifiers | |
3D model (JSmol) | |
3548355 | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.164.147 |
KEGG | |
PubChem CID | |
UNII | |
UN number | 2811 |
CompTox Dashboard (EPA) | |
| |
| |
Properties | |
C10H13N3O2 | |
Molar mass | 207.233 g·mol−1 |
Hazards | |
GHS labelling: | |
Danger | |
H301, H302, H317, H351 | |
P201, P202, P261, P264, P270, P272, P280, P281, P301+P310, P301+P312, P302+P352, P308+P313, P321, P330, P333+P313, P363, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Nicotine-derived nitrosamine ketone (NNK) is one of the key tobacco-specific nitrosamines derived from nicotine. It plays an important role in carcinogenesis. [1] The conversion of nicotine to NNK entails opening of the pyrrolidine ring.
NNK can be produced by standard methods of organic synthesis. [2]
NNK is both found in cured tobacco and is produced during its burning (pyrolysis). [3] The amount of NNK delivered in cigarette smoke ranged from 30 to 280 ng/cigarette in one study [4] and 12 to 110 ng/cigarette in another. [5]
Sun-cured tobaccos (a.k.a. "Oriental") contain very little NNK and other TSNAs due to low-nitrate soil, lack of nitrate fertilizer, and sun-curing. Flue-cured tobacco (a.k.a. "Virginia" tobacco [6] ), especially when using an open flame, contains most of the NNK in American blended tobaccos [7] although Marlboro's "virginia blend" had the lowest levels of NNK per nicotine out of many tested with the exception of Natural American Spirit. [8]
e-Cigarette do not convert nicotine to NNK due to their lower operating temperatures. [9] The amount of NNK delivered by e-cigarettes reaches 2.8 ng per 15 puffs (approximately 1 cigarette). [5] NNK was found in 89% of Korean e-cigarette liquids. Concentrations range from 0.22 to 9.84 μg/L. [10] For the product that had the highest amount, if 1 ml is equivalent to 20 cigarettes, [11] there would be 9.84/20 = 0.5 ng NNK per e-cig cigarette dose. Cigarettes with 1 gram of tobacco average about 350 ng. [7]
NNK is initially a procarcinogen that needs activation to exert its effects. The activation of NNK is done by enzymes of the cytochrome pigment (CYP) multigene family. These enzymes catalyze hydroxylation reactions. Beside the CYP family NNK can also be activated by metabolic genes, like myeloperoxidase (MPO) and epoxide hydrolase (EPHX1).[ citation needed ] NNK can be activated by two different routes, the oxidative path and the reductive path. In the oxidative metabolism NNK undergoes an α-hydroxylation catalyzed by cytochrome P450. This reaction can be done by two pathways namely by α-methylhydroxylation or by α-methylenehydroxylation. Both pathways produce the carcinogenic metabolized isoform of NNK, NNAL.[ citation needed ]
In the reductive metabolism NNK undergoes either a carbonyl reduction or a pyridine N-oxidation, both producing NNAL.[ citation needed ]
NNAL can be detoxified by glucuronidation producing a non-carcinogenic compounds known as NNAL-Glucs. The glucuronidation can take place on the oxygen next to the ring (NNAL-O-Gluc), or it takes place on the nitrogen inside the ring(NNAL-N-Gluc). The NNAL-Glucs are then excreted by the kidneys into the urine. [12]
Once NNK is activated, it initiates a cascade of signaling pathways (for example ERK1/2, NF-κB, PI3K/Akt, MAPK, FasL, K-Ras), resulting in uncontrolled cellular proliferation and tumorigenesis. [1]
NNK activates μ en m-calpain kinase which induces lung metastasis via the ERK1/2 pathway. This pathway upregulates cellular myelocytomatosis (c-Myc) and B cell leukemia/lymphoma 2 (Bcl-2) in which the two oncoproteins are involved in cellular proliferation, transformation and apoptosis. Also NNK promotes cell survival via phosphorylation with cooperation of c-Myc and Bcl-2 causing cellular migration, invasion and uncontrolled proliferation. [13]
The ERK1/2 pathway also phosphorylates NF-κB causing an upregulation of cyclin D1, a G1 phase regulator protein. When NNK is present it directly involves cellular survival dependent on NF-κB. Further studies are needed to better understand NNK cellular pathways of NF-κB. [14] [15]
The phosphoinositide 3-kinase (PI3K/Akt) pathway is also an important contributor to NNK-induced cellular transformations and metastasis. This process ensures the proliferation and survival of tumorigenic cells. [16] The ERK1/2 and Akt pathways show consequential changes in levels of protein expression as a result of NNK-activation in the cells, but further research is needed to fully understand the mechanism of NNK-activated pathways.[ citation needed ]
NNK is known as a mutagen, which means it causes polymorphisms in the human genome. Studies showed that NNK induced gene polymorphisms in cells that involve in cell growth, proliferation and differentiation. There are multiple NNK dependent routes that involve cell proliferation. One example is the cell route that coordinates the downregulation of retinoic acid receptor beta (RAR-β). Studies showed that with a 100 mg/kg dose of NNK, several point mutations were formed in the RAR-β gene, inducing tumorigenesis in the lungs.[ citation needed ]
Other genes affected by NNK include sulfotransferase 1A1 (SULT1A1), transforming growth factor beta (TGF-β), and angiotensin II (AT2).[ citation needed ]
NNK plays a very important role in gene silencing, modification, and functional disruption which induce carcinogenesis. [1]
Chemical compounds derived from cruciferous vegetables and EGCG inhibit lung tumorigenesis by NNK in animal models. [17] Whether these effects have any relevance to human health is unknown and is a subject of ongoing research.[ citation needed ]
A carcinogen is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruses and bacteria. Most carcinogens act by creating mutations in DNA that disrupt a cell's normal processes for regulating growth, leading to uncontrolled cellular proliferation. This occurs when the cell's DNA repair processes fail to identify DNA damage allowing the defect to be passed down to daughter cells. The damage accumulates over time. This is typically a multi-step process during which the regulatory mechanisms within the cell are gradually dismantled allowing for unchecked cellular division.
Nicotine is a naturally produced alkaloid in the nightshade family of plants and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits where it acts as a receptor antagonist.
Toxication, toxification or toxicity exaltation is the conversion of a chemical compound into a more toxic form in living organisms or in substrates such as soil or water. The conversion can be caused by enzymatic metabolism in the organisms, as well as by abiotic chemical reactions. While the parent drug are usually less active, both the parent drug and its metabolite can be chemically active and cause toxicity, leading to mutagenesis, teratogenesis, and carcinogenesis. Different classes of enzymes, such as P450 monooxygenases, epoxide hydrolase, or acetyltransferases can catalyze the process in the cell, mostly in the liver.
Tar is the name for the resinous, combusted particulate matter made by the burning of tobacco and other plant material in the act of smoking. Tar is toxic and damages the smoker's lungs over time through various biochemical and mechanical processes. Tar also damages the mouth by rotting and blackening teeth, damaging gums, and desensitizing taste buds. Tar includes the majority of mutagenic and carcinogenic agents in tobacco smoke. Polycyclic aromatic hydrocarbons (PAH), for example, are genotoxic and epoxidative.
Smokeless tobacco is a tobacco product that is used by means other than smoking. Their use involves chewing, sniffing, or placing the product between gum and the cheek or lip. Smokeless tobacco products are produced in various forms, such as chewing tobacco, snuff, snus, and dissolvable tobacco products. Smokeless tobacco is widely used in South Asia and this accounts for about 80% of global consumption. All smokeless tobacco products contain nicotine and are therefore highly addictive. Quitting smokeless tobacco use is as challenging as smoking cessation.
In molecular biology, extracellular signal-regulated kinases (ERKs) or classical MAP kinases are widely expressed protein kinase intracellular signalling molecules that are involved in functions including the regulation of meiosis, mitosis, and postmitotic functions in differentiated cells. Many different stimuli, including growth factors, cytokines, virus infection, ligands for heterotrimeric G protein-coupled receptors, transforming agents, and carcinogens, activate the ERK pathway.
The chemokine ligand 1 (CXCL1) is a small peptide belonging to the CXC chemokine family that acts as a chemoattractant for several immune cells, especially neutrophils or other non-hematopoietic cells to the site of injury or infection and plays an important role in regulation of immune and inflammatory responses. It was previously called GRO1 oncogene, GROα, neutrophil-activating protein 3 (NAP-3) and melanoma growth stimulating activity, alpha (MGSA-α). CXCL1 was first cloned from a cDNA library of genes induced by platelet-derived growth factor (PDGF) stimulation of BALB/c-3T3 murine embryonic fibroblasts and named "KC" for its location in the nitrocellulose colony hybridization assay. This designation is sometimes erroneously believed to be an acronym and defined as "keratinocytes-derived chemokine". Rat CXCL1 was first reported when NRK-52E cells were stimulated with interleukin-1β (IL-1β) and lipopolysaccharide (LPS) to generate a cytokine that was chemotactic for rat neutrophils, cytokine-induced neutrophil chemoattractant (CINC). In humans, this protein is encoded by the gene CXCL1 and is located on human chromosome 4 among genes for other CXC chemokines.
In molecular genetics, a DNA adduct is a segment of DNA bound to a cancer-causing chemical. This process could lead to the development of cancerous cells, or carcinogenesis. DNA adducts in scientific experiments are used as biomarkers of exposure. They are especially useful in quantifying an organism's exposure to a carcinogen. The presence of such an adduct indicates prior exposure to a potential carcinogen, but it does not necessarily indicate the presence of cancer in the subject animal.
Third-hand smoke is contamination by tobacco smoke that lingers following the extinguishing of a cigarette, cigar, or other combustible tobacco product. First-hand smoke refers to what is inhaled into the smoker's own lungs, while second-hand smoke is a mixture of exhaled smoke and other substances leaving the smoldering end of the cigarette that enters the atmosphere and can be inhaled by others. Third-hand smoke or "THS" is a neologism coined by a research team from the Dana–Farber/Harvard Cancer Center, where "third-hand" is a reference to the smoking residue on surfaces after "second-hand smoke" has cleared out.
Mitogen-activated protein kinase 1, also known as ERK2, is an enzyme that in humans is encoded by the MAPK1 gene.
Swietenia macrophylla, commonly known as mahogany, Honduran mahogany, Honduras mahogany, or big-leaf mahogany is a species of plant in the Meliaceae family. It is one of three species that yields genuine mahogany timber (Swietenia), the others being Swietenia mahagoni and Swietenia humilis. It is native to South America, Mexico and Central America, but naturalized in the Philippines, Singapore, Malaysia and Hawaii, and cultivated in plantations and wind-breaks elsewhere.
Lymphotoxin-alpha (LT-α) formerly known as tumor necrosis factor-beta (TNF-β) is a protein that in humans is encoded by the LTA gene. Belonging to the hematopoietic cell line, LT-α exhibits anti-proliferative activity and causes the cellular destruction of tumor cell lines. As a cytotoxic protein, LT-α performs a variety of important roles in immune regulation depending on the form that it is secreted as. Unlike other members of the TNF superfamily, LT-α is only found as a soluble homotrimer, when found at the cell surface it is found only as a heterotrimer with LTβ.
B-cell lymphoma 3-encoded protein is a protein that in humans is encoded by the BCL3 gene.
Cytochrome P450 2A13 is a protein that in humans is encoded by the CYP2A13 gene.
UDP-glucuronosyltransferase 2B17 is an enzyme that in humans is encoded by the UGT2B17 gene.
Copine-1 is a protein that in humans is encoded by the CPNE1 gene.
Tobacco-specific nitrosamines (TSNAs) comprise one of the most important groups of carcinogens in tobacco products, particularly cigarettes and fermented dipping snuff.
The PI3K/AKT/mTOR pathway is an intracellular signaling pathway important in regulating the cell cycle. Therefore, it is directly related to cellular quiescence, proliferation, cancer, and longevity. PI3K activation phosphorylates and activates AKT, localizing it in the plasma membrane. AKT can have a number of downstream effects such as activating CREB, inhibiting p27, localizing FOXO in the cytoplasm, activating PtdIns-3ps, and activating mTOR which can affect transcription of p70 or 4EBP1. There are many known factors that enhance the PI3K/AKT pathway including EGF, shh, IGF-1, insulin, and CaM. Both leptin and insulin recruit PI3K signalling for metabolic regulation. The pathway is antagonized by various factors including PTEN, GSK3B, and HB9.
The use of electronic cigarettes (vaping) carries health risks. The risk depends on the fluid and varies according to design and user behavior. In the United Kingdom, vaping is considered by some to be around 95% less harmful than tobacco after a controversial landmark review by Public Health England.
Smoker's macrophages are alveolar macrophages whose characteristics, including appearance, cellularity, phenotypes, immune response, and other functions, have been affected upon the exposure to cigarettes. These altered immune cells are derived from several signaling pathways and are able to induce numerous respiratory diseases. They are involved in asthma, chronic obstructive pulmonary diseases (COPD), pulmonary fibrosis, and lung cancer. Smoker’s macrophages are observed in both firsthand and secondhand smokers, so anyone exposed to cigarette contents, or cigarette smoke extract (CSE), would be susceptible to these macrophages, thus in turns leading to future complications.