Objective: To establish a method for the determination of eight N-nitrosamines (N-nitrosodimethylamine, N-nitrosodimethylamine, N-nitrosomethylmethylamine, N-nitrosodibutylamine, N-nitrosopropylamine, N-nitrosomorpholine, N-nitrosodianiline and N-nitrosopiperidine) in the air of workplace by gas chromatography-tandem mass spectrometry (GC-MS/MS) . Methods: From January to August 2023, eight N-nitrosamines in the air of workplace were collected by ThermoSorb/N column, eluted with 4 ml methanol-dichloromethane (1∶1 volume ratio), separated by VF-624 ms capillary column, detected by multiple reaction monitoring mode and quantified by external standard method. The detection limit and precision of the method were also analyzed. Results: The linear range of the method for the determination of eight N-nitrosamines was 1.0-20.0 μg/L, the correlation coefficient was 0.9993-0.9999, the detection limit was 0.051-0.132 μg/L, and the minimum quantitative concentration was 0.030-0.078 μg/m(3) (calculated by collecting 22.5 L of air sample and eluting with 4.0 ml stripping liquid). The within-run precisions were 2.05%-6.89% and the between-run precisions were 2.41%-8.26%. The desorption rates were 67.20%-102.60%. The sample can be kept at least 7 days at 4 ℃. Conclusion: GC-MS/MS method for the determination of eight N-nitrosamines in workplace air has high sensitivity and good precision, and can accurately determine the content of eight N-nitrosamines in workplace air.
目的： 建立工作场所空气中N-亚硝基二甲胺、N-亚硝基二乙胺、N-亚硝基甲基乙胺、N-亚硝基二丁胺、N-亚硝基正丙胺、N-亚硝基吗啉、N-亚硝基二苯胺和N-亚硝基吡咯烷8种N-亚硝胺化合物的气相色谱-串联质谱（GC-MS/MS）检测方法。 方法： 于2023年1至8月，以ThermoSorb/N柱采集工作场所中空气中8种N-亚硝胺，用4 ml甲醇-二氯甲烷（体积比1∶1）溶液解吸，VF-624 ms毛细管色谱柱分离，多反应监测模式检测，外标法定量，并对方法的检出限和精密度等指标进行分析。 结果： 8种N-亚硝胺测定方法的线性范围为1.0~20.0 μg/L，相关系数0.999 3~0.999 9，方法检出限0.051~0.132 μg/L，最低定量浓度0.030~0.078 μg/m(3)（以空气体积22.5 L，解吸液体积4.0 ml计），批内精密度2.05%~6.89%，批间精密度2.41%~8.26%，解吸效率67.20%~102.60%；样品在4 ℃条件下至少可保存7 d。 结论： GC-MS/MS测定工作场所空气中8种N-亚硝胺方法的灵敏度高、精密度好，可准确测定工作场所空气中8种N-亚硝胺含量。.

Food processing unavoidably introduces various risky ingredients that threaten food safety. N-Nitrosamines (NAs) constitute a class of food contaminants, which are considered carcinogenic to humans. According to the compiled information, pretreatment methods based on solid-phase extraction (SPE) were widely used before the determination of volatile NAs in foods. The innovation of adsorbents and hybridization of other methods have been confirmed as the future trends of SPE-based pretreatment methods. Moreover, technologies based on liquid chromatography and gas chromatography were popularly applied for the detection of NAs. Recently, sensor-based methods have garnered increasing attention due to their efficiency and flexibility. More portable sensor-based technologies are recommended for on-site monitoring of NAs in the future. The application of artificial intelligence can facilitate data processing during high-throughput detection of NAs. Natural bioactive compounds have been confirmed to be effective in mitigating NAs in foods through antioxidation, scavenging precursors, and regulating microbial activities. Meanwhile, they exhibit strong protective activities against hepatic damage, pancreatic cancer, and other NA injuries. Further supplementation of data on the bioavailability of bioactives can be achieved through encapsulation and clinical trials. The utilization of bioinformatics tools rooted in various omics technologies is suggested for investigating novel mechanisms and finally broadening their applications in targeted therapies.

N-Nitrosamine disinfection by-products (NAs-DBPs) have been well proven for its role in esophageal carcinogenesis. However, the role of intratumoral microorganisms in esophageal squamous cell carcinoma (ESCC) has not yet been well explored in the context of exposure to NAs-DBPs. Here, the multi-omics integration reveals F. periodonticum (Fp) as \"facilitators\" is highly enriched in cancer tissues and promotes the epithelial mesenchymal transition (EMT)-like subtype formation of ESCC. We demonstrate that Fp potently drives de novo synthesis of fatty acids, migration, invasion and EMT phenotype through its unique FadAL adhesin. However, N-nitrosomethylbenzylamine upregulates the transcription level of FadAL. Mechanistically, co-immunoprecipitation coupled to mass spectrometry shows that FadAL interacts with FLOT1. Furthermore, FLOT1 activates PI3K-AKT/FASN signaling pathway, leading to triglyceride and palmitic acid (PA) accumulation. Innovatively, the results from the acyl-biotin exchange demonstrate that FadAL-mediated PA accumulation enhances Wnt3A palmitoylation on a conserved cysteine residue, Cys-77, and promotes Wnt3A membrane localization and the translocation of β-catenin into the nucleus, further activating Wnt3A/β-catenin axis and inducing EMT phenotype. We therefore propose a \"microbiota-cancer cell subpopulation\" interaction model in the highly heterogeneous tumor microenvironment. This study unveils a mechanism by which Fp can drive ESCC and identifies FadAL as a potential diagnostic and therapeutic target for ESCC.

Quaternary ammonium compounds (QACs) are widely detected in the aquatic environment due to their extensive use in a wide array of antibacterial products during the pandemic. In the current study, UV/monochloramine (UV/NH2Cl) was used to degrade three typical QACs, namely benzalkonium compounds (BACs), dialkyl dimethyl ammonium compounds (DADMACs), and alkyl trimethyl ammonium compounds (ATMACs). This process achieved high efficiency in removing BACs from water samples. The transformation products of QACs treated with UV/NH2Cl were identified and characterized using a high-resolution mass spectrometer, and transformation pathways were proposed. The formation of N-nitroso-N-methyl-N-alkylamines (NMAs) and N-nitrosodimethylamine (NDMA) were observed during QAC degradation. The molar formation yield of NDMA from C12-BAC was 0.04 %, while yields of NMAs reached 1.05 %. The ecotoxicity of NMAs derived from QACs was predicted using ECOSAR software. The increased toxicity could be attributed to the formation of NMAs with longer alkyl chains; these NMAs, exhibited a one order of magnitude increase in toxicity compared to their parent QACs. This study provides evidence that QACs are the specific and significant precursors of NMAs. Greater attention should be given to NMA formation and its potential threat to the ecosystem, including humans.

Lung cancer remains the leading cause of cancer-related deaths, with cigarette smoking being the most critical factor, linked to nearly 90% of lung cancer cases. NNK, a highly carcinogenic nitrosamine found in tobacco, is implicated in the lung cancer-causing effects of cigarette smoke. Although NNK is known to mutate or activate certain oncogenes, its potential interaction with p27 in modulating these carcinogenic effects is currently unexplored. Recent studies have identified specific downregulation of p27 in human squamous cell carcinoma, in contrast to adenocarcinoma. Additionally, exposure to NNK significantly suppresses p27 expression in human bronchial epithelial cells. Subsequent studies indicates that the downregulation of p27 is pivotal in NNK-induced cell transformation. Mechanistic investigations have shown that reduced p27 expression leads to increased level of ITCH, which facilitates the degradation of Jun B protein. This degradation in turn, augments miR-494 expression and its direct regulation of JAK1 mRNA stability and protein expression, ultimately activating STAT3 and driving cell transformation. In summary, our findings reveal that: (1) the downregulation of p27 increases Jun B expression by upregulating Jun B E3 ligase ITCH, which then boosts miR-494 transcription; (2) Elevated miR-494 directly binds to 3\'-UTR of JAK1 mRNA, enhancing its stability and protein expression; and (3) The JAK1/STAT3 pathway is a downstream effector of p27, mediating the oncogenic effect of NNK in lung cancer. These findings provide significant insight into understanding the participation of mechanisms underlying p27 inhibition of NNK induced lung squamous cell carcinogenic effect.

N-nitrosamines are a type of nitrogen-containing organic pollutant with high carcinogenicity and mutagenicity. In the main drinking water sources of small and medium-sized towns in China, the contamination levels of N-nitrosamines remain unclear. In addition, there is still lack of research on the concentration of N-nitrosamines and their precursors in tributary rivers. In this study, eight N-nitrosamines and their formation potentials （FPs） were investigated in the Qingjiang River, which is a primary tributary of the Yangtze River. The sewage discharge sites were also monitored, and the environmental influencing factors, carcinogenic and ecological risks caused by N-nitrosamines, and their precursors were evaluated. The results showed that six N-nitrosamines were detected in water samples of the Qingjiang River, among which NDMA [（10 ±15） ng·L-1], NDEA [（9.3 ±9.3） ng·L-1], and NDBA [（14 ±7.8） ng·L-1] were the dominant N-nitrosamines, whereas seven N-nitrosamines were detected in chloraminated water samples, among which NDMA-FP [（46 ±21） ng·L-1], NDEA-FP [（26 ±8.3） ng·L-1], and NDBA-FP [（22 ±13） ng·L-1] were the dominant N-nitrosamine FPs. The concentrations of N-nitrosamines in the middle reaches of the Qingjiang River were higher than those in the upper and lower reaches. Furthermore, the concentrations of N-nitrosamines in the sample sites of sewage discharge and tributaries were significantly higher than those in other sampling sites. The monitoring results at the direct sewage discharge points indicated that the main source of N-nitrosamines in river water was the sewage carrying N-nitrosamines and their precursors. In addition, the concentrations of the three dominant N-nitrosamines including NDMA, NDBA, and NDEA were positively correlated with each other, mainly because of their similar sewage sources. The average carcinogenic risk to residents due to N-nitrosamine in drinking water sources was 2.4×10-5, indicating a potential carcinogenic risk. Moreover, due to the high concentrations of N-nitrosamine formation potentials in the Qingjiang River, the carcinogenic risk of drinking water may be even higher. The ecological risk assessment showed that the ecological risk quotient values of N-nitrosamines in the Qingjiang River watershed were lower than 0.002, which was negligible.

The Food and Drug Administration (FDA) recently reported a new nitrosamine impurity in sitagliptin that was named nitroso-STG-19 (NTTP), whose acceptable intake limit was extremely low at 37 ng per day. In addition, NTTP was found to be a degradation impurity in sitagliptin tablets, which was formed by the reaction of 3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine hydrochloride and nitrite salts introduced via excipients. Consequently, the NTTP content in tablets was larger than that in active pharmaceutical ingredients (APIs). To control the impurity, an ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) procedure for the detection of NTTP in sitagliptin phosphate tablets and APIs was developed and validated. Furthermore, a derivatization method for the detection of nitrite salts at lower concentration was developed to select applicable excipients to decelerate the generation of NTTP. During validation of the analytical procedure for NTTP, the quantitation limit (LOQ) of NTTP was 56 ppb (0.056 ng mL-1), the linear correlation coefficient was 0.9998, and recoveries of NTTP in spiked samples ranged from 95.5% to 105.2%, indicating that the method is rapid, sensitive and accurate for an NTTP test. In the nitrite salt detection method, the LOQ was 0.21 ng mL-1, and recoveries of NTTP in spiked samples ranged from 87.6% to 107.8%, indicating a sensitive and accurate method, suitable for screening appropriate pharmaceutical excipients.

Exposure to environmental carcinogens is a significant contributor to cancer development, with genetic and epigenetic alterations playing pivotal roles in the carcinogenic process. However, the interplay between epigenetic regulation and genetic changes in carcinogenesis has yet to receive comprehensive attention. This study investigates the impact of continuous exposure to the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on bronchial epithelial cells, leading to malignant transformation. Our findings reveal the down-regulation of the tumor suppressor-like circular RNA circNIPBL during oncogenic processes concomitant with the accumulation of the TP53-H179R, a single nucleotide variant. Diminished circNIPBL expression enhances the proliferative, distant metastatic, and tumor-forming capabilities of NNK-induced cancerous cells and lung cancer cell lines (A549, H1299), while also promoting the accumulation of TP53-H179R during NNK-induced carcinogenesis. Mechanistic investigations demonstrate that circNIPBL interacts with HSP90α to regulate the translocation of AHR into the nucleus, which may be a potential regulatory mechanism for NNK-induced carcinogenesis and TP53-H179R accumulation. This study introduces a novel perspective on the interplay between genetic alterations and epigenetic regulation in chemical carcinogenesis, which provides novel insight into the etiology of cancer.

The discharge of electroplating wastewater, containing high concentrations of N-nitrosamines, poses significant risks to human health and aquatic ecosystems. Karst aquatic environment is easily impacted by N-nitrosamines due to the fragile surface ecosystem. However, it\'s still unclear in understanding N-nitrosamine transformation in karst water systems. To explore the response and transport of nine N-nitrosamines in electroplating effluent within both karst surface water and groundwater, different river and groundwater samples were collected from both the upper and lower reaches of the effluent discharge areas in a typical karst industrial catchment in Southwest China. Results showed that the total average concentrations of N-nitrosamines (∑NAs) in electroplating effluent (1800 ng/L) was significantly higher than that in the receiving river water (130 ng/L) and groundwater (70 ng/L). The dynamic nature of karst aquifers resulted in comparable average concentrations of ∑NAs in groundwater (70 ng/L) and river water (79 ng/L) at this catchment. Based on the principal component analysis and multiple linear regression analysis, the electroplating effluent contributed 89% and 53% of N-nitrosamines to the river water and groundwater, respectively. The results based on the species sensitivity distribution model revealed N-nitrosodibutylamine as a particularly toxic compound to aquatic organisms. Furthermore, the average N-nitrosamine carcinogenic risk was significantly higher in lower groundwater reaches compared to upper reaches. This study represents a pioneering effort in considering specific N-nitrosamine properties in evaluating their toxicity and constructing species sensitivity curves. It underscores the significance of electroplating effluent as a primary N-nitrosamine source in aquatic environments, emphasizing their swift dissemination and significant accumulation in karst groundwater.

Reducing nitrites tends to increase the accumulation of hazardous biogenic amines (BAs) in Chinese fermented sausages (CFSs). Gallic acid (GA) has emerged as a potential alternative to reduce nitrite usage and control BAs. This study explored how GA inhibits BAs and nitrosamines accumulation in reduced-nitrite CFSs. Results demonstrated that combining 0.05% (w/w) GA with reduced nitrite effectively curbed BAs and N-nitrosodimethylamine, decreasing total BA from 271.48 to 125.46 mg/kg. Fifty-one metabolites associated with the metabolism of BAs and N-nitrosodimethylamine were identified. GA boosted Lactococcus while reducing spoilage bacteria and Macrococcus. This dual regulation suppressed BAs and dimethylamine accumulation by regulating amino acids and trimethylamine pathways. Consequently, GA achieved an 89.86% reduction in N-nitrosodimethylamine by decreasing the key precursors like putrescine, dimethylamine, and nitrite. These findings offer new insights into utilizing GA and similar plant polyphenols to manage BAs and nitrosamines in meat products with reduced nitrite usage.