Genotoxic effects of myosmine in a human esophageal adenocarcinoma cell line

Degradation of myosmine by a novel bacterial strain Sphingopyxis sp. J-6 and its degradation pathways

This study isolated a myosmine-degrading bacterial strain J-6 from tobacco-growing soil. The identification of this strain revealed it to be a new species within the genus Sphingopyxis. Analysis of the myosmine degradation products by HPLC, preparative HPLC, and UHPLC-MS/MS identified 8 metabolites, among which 3-pyridylacetic acid (3-PAA), 5-(3-pyridyl)tetrahydrofuranone-2 (PTHF), and 4-hydroxy-4-(3-pyridyl)butanoic acid (HPBA) were three novel metabolites that were not previously found in microbial degradation of tobacco alkaloids. Interestingly, these metabolites have been observed in the nicotine metabolic pathways of humans and animals. In addition, 3-PAA, which is believed to be the major end product of nicotine metabolism in humans, is also found to be an end product of myosmine degradation in strain J-6. Based on the identified metabolites and genomic analysis, a previously unreported bacterial degradation pathway for tobacco alkaloids was proposed. The downstream part of this pathway for converting SP to 3-PAA resembles the pathway for mammalian metabolism of SP to 3-PAA. Overall, the findings in this study offer novel insights into the degradation pathways and mechanisms of myosmine, which will deepen our understanding on the fate of myosmine both in the environment and within the human body.

Global Metabolomics Reveals That Vibrio natriegens Enhances the Growth and Paramylon Synthesis of Euglena gracilis

The microalga Euglena gracilis is utilized in the food, medicinal, and supplement industries. However, its mass production is currently limited by its low production efficiency and high risk of microbial contamination. In this study, physiological and biochemical parameters of E. gracilis co-cultivated with the bacteria Vibrio natriegens were investigated. A previous study reports the benefits of E. gracilis and V. natriegens co-cultivation; however, no bacterium growth and molecular mechanisms were further investigated. Our results show that this co-cultivation positively increased total chlorophyll, microalgal growth, dry weight, and storage sugar paramylon content of E. gracilis compared to the pure culture without V. natriegens. This analysis represents the first comprehensive metabolomic study of microalgae-bacterial co-cultivation, with 339 metabolites identified. This co-cultivation system was shown to have synergistic metabolic interactions between microalgal and bacterial cells, with a significant increase in methyl carbamate, ectoine, choline, methyl N-methylanthranilate, gentiatibetine, 4R-aminopentanoic acid, and glu-val compared to the cultivation of E. gracilis alone. Taken together, these results fill significant gaps in the current understanding of microalgae-bacteria co-cultivation systems and provide novel insights into potential improvements for mass production and industrial applications of E. gracilis.

Analysis of the clinicopathological features and prognostic factors in 734 cases of Chinese Hui and Han patients with adenocarcinoma of the esophagogastric junction

OBJECTIVE

To explore the clinicopathological features and prognostic factors of 734 cases of Chinese Hui and Han patients with adenocarcinoma of the esophagogastric junction (AEG).

METHODS

In total, 734 patients were confirmed to have AEG by gastroscopy and pathology at the General Hospital of Ningxia Medical University between January 2002 and December 2012. Univariate and multivariate analyses of demographic, clinicopathological, and prognostic data were performed.

RESULTS

In total, 734 AEG patients underwent surgical intervention, including 169 Hui patients and 565 Han patients. The male to female ratio was 9.5:1 in Hui patients and 6.4:1 in Han patients, and the average age in both groups was approximately 61 years. The Han patients were more likely to have a cigarette smoking history and an alcohol consumption history than the Hui patients (58.8% vs. 29.4%, p = 0.000; 45.8% vs. 14.6%, p = 0.000). The 5-year survival rate in the Hui and Han patients was 54.3% and 39.9%, respectively (p = 0.024). Age (p = 0.005), sex (p = 0.015), pathologic T stage (p = 0.056), pathologic N stage (p = 0.000), pathologic M stage (p = 0.001), number of resected lymph nodes (p = 0.001) and adjuvant chemoradiotherapy (p = 0.002) were significant independent prognostic factors.

CONCLUSION

The AEG patients were primarily male and elderly in both Hui and Han groups with the prognosis of Hui patients better than Han patients. Age, sex, pathologic T3-4 stage, pathologic N stage, pathologic M stage, number of resected lymph nodes, and adjuvant chemoradiotherapy were significant independent factors predictive of the prognosis of AEG in both groups.

Isolation of Nicotinic Acid (Vitamin B3) and N-Propylamine after Myosmine Peroxidation

The alkaloid myosmine (3-(1-pyrroline-2-yl)pyridine) is widespread in biological matrixes including foodstuffs and tobacco products. Some in vitro tests in cellular systems showed mutagenic activity for myosmine. Myosmine activation including peroxidation mechanism employs unstable oxazirane intermediates. The formation of minor metabolite 3-hydroxymethyl-pyridine in rat metabolism experiments as well as in in vitro peroxidation assays suggests its further oxidation to nicotinic acid and possible concomitant formation of n-propylamine. A sensitive high-performance liquid chromatography-ultraviolet (HPLC-UV) method was developed for the direct analysis of n-propylamine in the peroxidation assay solution of myosmine employing derivatization with 3,5-dinitrobenzoyl chloride. Additionally, during peroxidation procedures, formation of 3-pyridylmethanol to nicotinic acid, the essential vitamin B3, was observed and characterized using HPLC-UV and gas chromatography/mass spectrometry. This new reaction pathway may present further contribution to our knowledge of myosmine's significance in human food including its activation in human organism, foodstuffs, and biological systems.

Plant alkaloids that cause developmental defects through the disruption of cholinergic neurotransmission

The exposure of a developing embryo or fetus to alkaloids from plants, plant products, or plant extracts has the potential to cause developmental defects in humans and animals. These defects may have multiple causes, but those induced by piperidine and quinolizidine alkaloids arise from the inhibition of fetal movement and are generally referred to as multiple congenital contracture-type deformities. These skeletal deformities include arthrogyrposis, kyposis, lordosis, scoliosis, and torticollis, associated secondary defects, and cleft palate. Structure-function studies have shown that plant alkaloids with a piperidine ring and a minimum of a three-carbon side-chain α to the piperidine nitrogen are teratogenic. Further studies determined that an unsaturation in the piperidine ring, as occurs in gamma coniceine, or anabaseine, enhances the toxic and teratogenic activity, whereas the N-methyl derivatives are less potent. Enantiomers of the piperidine teratogens, coniine, ammodendrine, and anabasine, also exhibit differences in biological activity, as shown in cell culture studies, suggesting variability in the activity due to the optical rotation at the chiral center of these stereoisomers. In this article, we review the molecular mechanism at the nicotinic pharmacophore and biological activities, as it is currently understood, of a group of piperidine and quinolizidine alkaloid teratogens that impart a series of flexure-type skeletal defects and cleft palate in animals.

The role of tobacco, alcohol, and obesity in neoplastic progression to esophageal adenocarcinoma: a prospective study of Barrett's esophagus

BACKGROUND

Esophageal adenocarcinoma (EA) incidence in many developed countries has increased dramatically over four decades, while survival remains poor. Persons with Barrett's esophagus (BE), who experience substantially elevated EA risk, are typically followed in surveillance involving periodic endoscopy with biopsies, although few progress to EA. No medical, surgical or lifestyle interventions have been proven to safely lower EA risk.

DESIGN

We investigated whether smoking, obesity or alcohol could predict progression to EA in a prospective cohort of 411 BE patients. Data were collected during personal interview. Adjusted hazard ratios (HR) were estimated using Cox regression.

RESULTS

39% had body mass index (BMI) over 30 and 64% had smoked cigarettes. Main analyses focused on those with at least 5 months of follow-up (33,635 person-months), in whom 45 developed EA. Risk increased by 3% per year of age (trend p-value 0.02), with approximate doubling of risk among males. EA risk increased with smoking pack-years (trend p-value 0.04) and duration (p-value 0.05). Compared to never-smokers, the HR for those in the highest pack-year tertile was 2.29 (95%CI 1.04-5.07). No association was found with alcohol or BMI, whereas a suggestion of increased risk was observed in those with higher waist-hip ratio, especially among males.

CONCLUSION

EA risk significantly increased with increasing age and cigarette exposure. Abdominal obesity, but not BMI, was associated with a modest increased risk. Continued follow-up of this and other cohorts is needed to precisely define these relationships so as to inform risk stratification and preventive interventions.

Effects of Myosmine on Antioxidative Defence in Rat Liver

Myosmine [3-(1-pyrrolin-2-yl) pyridine] is an alkaloid structurally similar to nicotine, which is known to induce oxidative stress. In this study we investigated the effects of myosmine on enzymatic and non-enzymatic antioxidative defence in rat liver. Wistar rats received a single i.p. injection of 19 mg kg-1 of myosmine and an oral dose of 190 mg kg-1 by gavage. Nicotine was used as a positive control. Through either route of administration, myosmine altered the hepatic function by decreasing the levels of reduced glutathione, superoxide dismutase, and glutathione peroxidase activities on one hand and by increasing malondialdehyde, catalase, and glutathione reductase activity on the other. Compared to control, both routes caused significant lipid peroxidation in the liver and altered hepatic enzymatic and non-enzymatic antioxidative defences. The pro-oxidant effects of myosmine were comparable with those of nicotine.

Analysis of myosmine, cotinine and nicotine in human toenail, plasma and saliva

Myosmine is a minor tobacco alkaloid with widespread occurrence in the human diet. Myosmine is genotoxic in human cells and is readily nitrosated and peroxidated yielding reactive intermediates with carcinogenic potential. For biomonitoring of short-term and long-term exposure, analytical methods were established for determination of myosmine together with nicotine and cotinine in plasma, saliva and toenail by gas chromatography-mass spectrometry (GC/MS). Validation of the method with samples of 14 smokers and 10 non-smokers showed smoking-dependent differences of myosmine in toenails (66 +/- 56 vs 21 +/- 15 ng g(-1), p <0.01) as well as saliva (2.54 +/- 2.68 vs 0.73 +/- 0.65 ng ml(-1), p <0.01). However, these differences were much smaller than those with nicotine (1971 +/- 818 vs 132 +/- 82 ng g(-1), p <0.0001) and cotinine (1237 +/- 818 vs <35 ng g(-1)) in toenail and those of cotinine (97.43 +/- 84.54 vs 1.85 +/- 4.50 ng ml(-1), p <0.0001) in saliva. These results were confirmed in plasma samples from 84 patients undergoing gastro-oesophageal endoscopy. Differences between 25 smokers and 59 non-smokers are again much lower for myosmine (0.30 +/- 0.35 vs 0.16 +/- 0.18 ng ml(-1), p <0.05) than for cotinine (54.67 +/- 29.63 vs 0.61 +/- 1.82 ng ml(-1), p <0.0001). In conclusion, sources other than tobacco contribute considerably to the human body burden of myosmine.

Investigation of the reaction of myosmine with sodium nitrite in vitro and in rats

Previous studies have shown that the minor tobacco alkaloid myosmine (5) reacts with NaNO2 in the presence of acid to yield 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB, 8) via 4-(3-pyridyl)-4-oxobutanediazohydroxide (7). Intermediate 7 is also formed in the metabolism of the tobacco-specific nitrosamines N'-nitrosonornicotine (NNN, 1) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 2), resulting in pyridyloxobutylation of DNA and Hb. These pyridyloxobutyl adducts can be quantified by analyzing HPB released upon acid treatment of DNA or base treatment of Hb. Quantitation of HPB-releasing DNA and Hb adducts has been used to assess the metabolic activation of NNN and NNK in smokers and smokeless tobacco users. Because myosmine is found in the diet as well as in tobacco products, it has been suggested that nitrosation of myosmine could lead to the formation of HPB-releasing adducts in people not exposed to tobacco products. We investigated the nitrosation of myosmine in vitro and in vivo in rats. The reaction of myosmine with NaNO2 under acidic conditions produced HPB, as previously reported. A new product was identified as 3'-oximinomyosmine (11) based on its spectral properties. NNN was not detected. Groups of rats were treated with NNN, NNK, myosmine, NaNO2, or combinations of myosmine and NaNO2. HPB-releasing Hb and DNA adducts were clearly detected in the rats treated with NNN or NNK, but we found no evidence for production of these adducts from the combination of myosmine plus NaNO2. The results of this study do not support the hypothesis that exposure to dietary myosmine could lead to HPB-releasing DNA or Hb adducts in humans.

Tissue distribution and excretion of myosmine after i.v. administration to Long–Evans rats using quantitative whole-body autoradiography

Occurrence of the tobacco alkaloid myosmine has been proven in various staple foods, vegetables and fruits. Myosmine can be easily activated by nitrosation yielding 4-hydroxy-1-(3-pyridyl)-butanone (HPB) and the esophageal carcinogen N'-nitrosonornicotine. Most of the reaction products after myosmine peroxidation were also identified as urinary metabolites after oral administration to rats. Whole-body autoradiography with freeze dried or multiple solvent extracted tissue sections was used to trace [2'-(14)C]myosmine (0.1 mCi/kg bw) 0.1, 0.25, 1, 4 and 24 h after i.v. injection in Long-Evans rats. In addition, in vitro binding of radioactivity to esophageal and eye tissue was determined and excretion of radioactivity via urine and feces was quantified. Radioactivity is rapidly eliminated by renal excretion. Approximately 30% of the administered radioactivity was recovered in urine within the first 4 h and excretion with urine (72%) and feces (15%) was nearly complete after 24 h. A rapid concentration of radioactivity can be seen in the stomach and in the salivary and lachrymal glands. Rats killed 1 and 4 h after treatment showed by far the highest labeling in the accessory genital gland. High levels of nonextractable radioactivity were present in esophageal tissue and melanin. The half lives for the disappearance of radioactivity from various tissues are in the order of about 1 h. Eye and esophagus sections both showed nonextractable labeling after in vitro incubation with (14)C-myosmine. In conclusion, the toxicological significance of myosmine accumulation in esophagus and accessory genital gland requires further investigations. Hair analysis might be applicable for myosmine biomonitoring, because of possible enrichment in melanin containing tissues.