Determination of nicotine in mushrooms by various GC/MS- and LC/MS-based methods

The role of α7-nAChR-mediated PI3K/AKT pathway in lung cancer induced by nicotine

Nicotine enters the environment mainly through human activity, as well as natural sources. This review article examines the increasing evidence implicating nicotine in the initiation and progression of lung cancer. Moreover, it primarily focuses on elucidating the activation mechanism of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, also known as AKT) signaling pathway, regulated by α7 subtype nicotinic acetylcholine receptor (α7-nAChR), in relation to the proliferation, invasion, and metastasis of lung cancer cells induced by nicotine, as well as nicotine-mediated anti-apoptotic effects. This process involves PI3K/AKT phosphorylated-B-cell lymphoma-2 (Bcl-2) family proteins, PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/nuclear factor-κB (NF-κB), hepatocyte growth factor (HGF)/cellular-mesenchymal epithelial transition factor (c-Met)-induced PI3K/AKT and PI3K/AKT activated-hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathways. In addition, we also deliberated on the related challenges and upcoming prospects within this field. These lay the foundation for further study on nicotine, lung tumorigenesis, and PI3K/AKT related molecular mechanisms. This work has the potential to significantly contribute to the treatment and prognosis of gastric cancer in smokers. Besides, the crucial significance of PI3K/AKT signaling pathway in multiple molecular pathways also suggests that its target antagonists may inhibit the development and progression of lung cancer, providing a possible new perspective for solving the problem of nicotine-promoted lung cancer. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the environmental assessment of tobacco and other nicotine-containing products.

Development of a solid phase microextraction method for the determination of nicotine in dried mushrooms

Official control of EU market foodstuffs repeatedly reports high nicotine levels in dried wild mushrooms without any clear scientific consensus about their origin. The advised constant monitoring calls for improvements to existing methods. For this purpose, our aim was to develop a headspace solid phase microextraction (HS-SPME) method coupled to gas chromatography with mass spectrometric detection (GC-MS) that would eliminate the need for extensive sample pre-treatment. The type of fiber coating, amount of sample, extraction temperature and time, desorption time and salt addition were investigated and optimized as parameters affecting the SPME procedure. The optimized conditions were used to validate a quantitative method for nicotine analysis by matrix-matched calibration and isotopically labelled internal standard correction. The method provided good linearity (r2 = 0.9994) over the tested concentration range (0.025-1 mg kg-1), low detection limit (0.005 mg kg-1) and low quantification limit (0.017 mg kg-1) for nicotine, being below the EU foodstuff regulations. For both of the tested concentration levels (0.050 and 0.200 mg kg-1), precision expressed as relative standard deviation was below 10% (4.5% and 8.5%, respectively), while accuracy was 98.2% and 100.3%. The optimized method was then used to determine nicotine levels in 18 samples of dried Boletus mushrooms from southeastern European countries entering the EU market. We demonstrated our HS-SPME procedure to be fast, simple, sensitive, solvent-free, cost-effective and thus suitable for controlling consumer safety regarding nicotine level in dried mushrooms.

Nicotine in the button mushroom Agaricus bisporus, endogenous biosynthesis?

In early 2009 nicotine was unexpectedly detected in dried mushroom samples. As its origin has not yet been elucidated, this study addressed possible endogenous synthesis of nicotine. Therefore, Agaricus bisporus fruiting bodies were grown in a representative and controlled (nicotine-free) setup. Fruiting bodies (fresh versus stored, intact versus processed (sliced/cooked)) from different harvest days and flushes were analysed with a validated, sensitive dilute-and-shoot UHPLC-MS/MS methodology for nicotine and its precursors putrescine and nicotinic acid. Neither storage nor processing initiated any endogenous nicotine biosynthesis (detection limit 1.6 ng g^-1 fresh weight). In contrast, putrescine and nicotinic acid were detected in all samples, with increasing amounts in the different treatments. In silico analysis of the fully sequenced genome of A. bisporus confirmed its inability to produce nicotine. The data obtained do not provide evidence for natural, endogenous presence of nicotine in mushrooms, indicating an exogenous contamination source (e.g. contamination during hand-picking, sample preparation/analysis).

High-resolution metabolomics-based biomarker discovery using exhaled breath condensate from patients with lung cancer

Early diagnosis and treatment are critical for improving the survival of patients with lung cancer, which is the leading cause of cancer-related deaths worldwide. In this study, we investigated whether the metabolomics analysis of exhaled breath condensate (EBC) from patients with lung cancer can provide biomarkers that can be used for noninvasive screening for lung cancer diagnosis. EBC samples obtained from patients with lung cancer (n = 20) and healthy individuals (n = 5) were subjected to high-resolution metabolomics (HRM) using liquid chromatography–mass spectrometry (LC–MS). Univariate analysis, with a false discovery rate (FDR), q = 0.05, and hierarchical clustering analysis were performed to discover significantly different metabolites between the healthy controls and patients with lung cancer. This was followed by the identification of the metabolites using the METLIN database. Pathway analysis based on the identified metabolites revealed that arachidonic acid (AA) metabolism was the most significantly affected pathway. Finally, 5-hydroxyicosatetraenoic acid (HETE) (m/z 343.2233, [M + Na]+), a metabolite involved in AA metabolism, was found to be significantly higher in patients with lung cancer than in healthy counterparts. Our finding suggested that the HRM of EBC samples is a useful approach for identifying biomarkers for noninvasive screening for lung cancer diagnosis.

Validation and measurement uncertainty of GC-MS quantification method for nicotine in dried mushrooms using QuEChERS extraction

Nicotine is an alkaloid and a secondary plant metabolite that has been used as an insecticide. Despite their widespread application, the EU banned the use of nicotine-containing pesticides in December 2008. However, studies in Europe have found nicotine in mushrooms. Nicotine has also been detected in wild mushrooms, so there are other causes of contamination as well as pesticide. This study reports the development of GC-MS method for quantitatively analysing nicotine in mushrooms. This method provides recoveries of 89.5-92.5%, intra-day precisions of 0.32-0.85%, and inter-day precisions of 0.73-2.36%, with limits of detection and quantification of 0.38 and 1.15 μg kg-1, respectively. The relative expanded uncertainty result of 2.8-4.0% complies with CODEX requirements. The method was successfully applied to eleven mushroom samples in which nicotine was detected at levels of 0.033-1.713 mg kg-1. Therefore, this method is suitable for the quantification of nicotine in dried mushrooms to ensure pre-emptive food safety.

Determination of 4(5)-methylimidazole in foods and beverages by modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry analysis

The determination of carcinogenic 4(5)-methylimidazole (4-MeI) in complex matrices at trace levels is a challenge because of its higher polarity and weaker column retention capability. Here, we proposed a novel method for the quantification of 4-MeI in various foods and beverages using modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The evaluated QuEChERS extraction with LC-MS/MS method showed excellent linearity (1-200 μg/L, with correlation coefficient (R²) > 0.999), trueness (91-113%), and precision (relative standard deviation (RSD) ≤ 12.3%), but low matrix effect (92-108%) for cola, tea, beer, coffee beverage, bread, biscuit and instant coffee. The expanded measurement uncertainty was less than 34.4% at 95% confidence level. The proposed method can be successfully applied to determine 4-MeI in 28 commercial foods and beverages purchased from local market. Therefore, we believe this method is likely to provide a potential for 4-MeI determination in practical application.

High-Temperature Induced Changes of Extracellular Metabolites in Pleurotus ostreatus and Their Positive Effects on the Growth of Trichoderma asperellum

Pleurotus ostreatus is a widely cultivated edible fungus in China. Green mold disease of P. ostreatus which can seriously affect yield is a common disease during cultivation. It occurs mostly after P. ostreatus mycelia have been subjected to high temperatures. However, little information is available on the relationship between high temperature and green mold disease. The aim of this study is to prove that extracellular metabolites of P. ostreatus affected by high temperature can promote the growth of Trichoderma asperellum. After P. ostreatus mycelia was subjected to high temperature, the extracellular fluid of P. ostreatus showed a higher promoting effect on mycelial growth and conidial germination of T. asperellum. The thiobarbituric acid reactive substance (TBARS) content reached the maximum after 48 h at 36°C. A comprehensive metabolite profiling strategy involving gas chromatography-mass spectrometry (GC/MS) combined with liquid chromatography-mass spectrometry (LC/MS) was used to analyze the changes of extracellular metabolites in response to high temperature. A total of 141 differential metabolites were identified, including 84.4% up-regulated and 15.6% down-regulated. Exogenous metabolites whose concentrations were increased after high temperature were randomly selected, and nearly all of them were able to promote the mycelial growth and conidial germination of T. asperellum. The combination of all selected exogenous metabolites also has the promotion effects on the mycelial growth and conidial germination of T. asperellum in a given concentration range in vitro. Overall, these results provide a first view that high temperature affects the extracellular metabolites of P. ostreatus, and the extensive change in metabolites promotes T. asperellum growth.

Investigation of the Hepatoprotective Effect of Prunus mume Sieb. et Zucc Extract in a Mouse Model of Alcoholic Liver Injury Through High-Resolution Metabolomics

This study aimed to identify the changes in the metabolomics profile of liver damage caused by alcohol consumption and verify the beneficial effect of Prunus mume Sieb. et Zucc extract (PME) in protection of alcohol-induced injury by attenuating the level of identified metabolites. Mice were treated with PME and saline or untreated once daily for 5 days, followed by alcohol injection. The plasma samples were analyzed using liquid chromatography-mass spectrometry-based high-resolution metabolomics followed by a multivariate statistical analysis using MetaboAnalyst 3.0 to obtain significantly expressed metabolites, using a false discovery rate threshold of q = 0.05. Metabolites were annotated using Metlin database and mapped through Kyoto Encyclopedia of Genes and Genomes (KEGG). Among 4999 total features, 101 features were significant among alcohol- and PME-treated mice groups. All the samples cluster showed a clear separation in the heat map, and the scores plot of orthogonal partial least squares-discriminant analysis (OPLS-DA) model discriminated the three groups. Phosphatidylcholine, Saikosaponin BK1, Ganoderiol I, and N-2-[4-(3,3-dimethylallyloxy) phenyl] ethylcinnamide were among the significant compounds with a low intensity in alcohol group compared to PME group, suggesting that these compounds have a relation in the development of PME's protective effect. The study confirms the hepatoprotective, antioxidant, and anti-inflammatory effects of PME against alcohol-induced liver steatosis, inflammation, and apoptosis.

A metabolomic study on high-risk stroke patients determines low levels of serum lysine metabolites: a retrospective cohort study

Metabolic alteration at early neurological deterioration during cerebral ischemia.

High resolution metabolomics to discriminate compounds in serum of male lung cancer patients in South Korea

BACKGROUND

The cancer death rate escalated during 20th century. In South Korea, lung cancer is expected to contribute 12,736 deaths in men, the highest amount among all cancers. Several risk factors may increase the chance to acquiring lung cancer, with mostly related to exogenous compounds found in cigarette smoke and synthetic manufacturing materials. As the mortality rate of lung cancer increases, deeper understanding is necessary to explore risk factors that may lead to this malignancy. In this regard, this study aims to apply high resolution metabolomics (HRM) using LC-MS to detect significant compounds that might contribute in inducing lung cancer and find the correlation of these compounds to the subjects' smoking habit.

METHODS

The comparison was made between healthy control and lung cancer groups for metabolic differences. Further analyses to determine if these differences are related to tobacco-induced lung cancer (past-smoker control vs. past-smoker lung cancer patients (LCPs) and non-smoker control vs. current-smoker LCPs) were selected. The univariate analysis was performed, including a false discovery rate (FDR) of q = 0.05, to determine the significant metabolites between the analyses. Hierarchical clustering analysis (HCA) was done to discriminate metabolites between the control and case subjects. Selected compounds based on significant m/z features of human serum then experienced MS/MS examination, showing that for many m/z, the patterns of ion dissociation matched with standards. Then, the significant metabolites were identified using Metlin database and features were mapped on the human metabolic pathway mapping tool of the Kyoto Encyclopedia of Genes and Genomes (KEGG).

RESULTS

Using metabolomics-wide association studies, metabolic changes were observed among control group and lung cancer patients. Bisphenol A (211.11, [M + H-H2O](+)), retinol (287.23, [M + H](+)) and L-proline (116.07, [M + H](+)) were among the significant compounds found to have contributed in the discrimination between these groups, suggesting that these compounds might be related in the development of lung cancer. Retinol has been seen to have a correlation with smoking while both bisphenol A and L-proline were found to be unrelated.

CONCLUSIONS

Two potential biomarkers, retinol and L-proline, were identified and these findings may create opportunities for the development of new lung cancer diagnostic tools.