Different modes of inhibition of mouse Cyp2a5 and rat CYP2A3 by the food-derived 8-methoxypsoralen.

CYP2A enzymes are responsible for nicotine metabolism and for activating tobacco-related carcinogens. Inhibition of CYP2A is a promising approach in chemoprevention, which could lead to a decrease in cigarette consumption and to a reduction in tobacco-related cancer risk. 8-Methoxypsoralen (8-MOP) is a mechanism-based inhibitor of human CYP2A6 and CYP2A13. 8-MOP is also an inhibitor of Cyp2a5, but the mode of this inhibition is unknown. There is no published data on the inhibition of CYP2A3 by 8-MOP. The objective of this work was to investigate the characteristics of 8-MOP inhibition on mouse hepatic Cyp2a5 and rat nasal CYP2A3, in order to determine the best experimental model for chemoprevention studies using 8-MOP. The results show that 8-MOP inhibits CYP2a5 through three different mechanisms: competitive, non-competitive (K(iu)=1.7 microM), and mechanism-based (K(inactivation) of 0.17 min(-1)). By contrast, 8-MOP was able to inhibit CYP2A3-mediated coumarin 7-hydroxylase only in a non-competitive way (K(iu)=0.22 microM). In conclusion, we showed that 8-MOP inhibits Cyp2a5 and CYP2A3 through different mechanisms.     

黄曲霉毒素及其产毒菌株的实验室去毒法研究

目的 研究黄曲霉毒素及其产毒菌株的实验室去毒方法。方法 根据黄曲霉毒素及其产毒菌株的特点，采用强碱氢氧化钠和氧化剂次氯酸钠对其进行去毒处理。结果 采用4％～5％的次氯酸钠处理5min或2．0mol／L的氢氧化钠处理20min，均能达到破坏黄曲霉毒素的效果。结论 次氯酸钠和氢氧化钠均为黄曲霉毒素的良好去毒剂。     

Maternal aflatoxin exposure during pregnancy and adverse birth outcomes in Uganda

Aflatoxins are toxic metabolites of Aspergillus moulds and are widespread in the food supply, particularly in low‐ and middle‐income countries. Both in utero and infant exposure to aflatoxin B₁ (AFB₁) have been linked to poor child growth and development. The objective of this prospective cohort study was to investigate the association between maternal aflatoxin exposure during pregnancy and adverse birth outcomes, primarily lower birth weight, in a sample of 220 mother–infant pairs in Mukono district, Uganda. Maternal aflatoxin exposure was assessed by measuring the serum concentration of AFB₁‐lysine (AFB‐Lys) adduct at 17.8 ± 3.5 (mean ± SD)‐week gestation using high‐performance liquid chromatography. Anthropometry and birth outcome characteristics were obtained within 48 hr of delivery. Associations between maternal aflatoxin exposure and birth outcomes were assessed using multivariable linear regression models adjusted for confounding factors. Median maternal AFB‐Lys level was 5.83 pg/mg albumin (range: 0.71–95.60 pg/mg albumin, interquartile range: 3.53–9.62 pg/mg albumin). In adjusted linear regression models, elevations in maternal AFB‐Lys levels were significantly associated with lower weight (adj‐β: 0.07; 95% CI: ?0.13, ?0.003; p = 0.040), lower weight‐for‐age z‐score (adj‐β: ?0.16; 95% CI: ?0.30, ?0.01; p = 0.037), smaller head circumference (adj‐β: ?0.26; 95% CI: ?0.49, ?0.02; p = 0.035), and lower head circumference‐for‐age z‐score (adj‐β: ?0.23; 95% CI: ?0.43, ?0.03; p = 0.023) in infants at birth. Overall, our data suggest an association between maternal aflatoxin exposure during pregnancy and adverse birth outcomes, particularly lower birth weight and smaller head circumference, but further research is warranted.     

Associated Factors in Modulating Aflatoxin B1–Albumin Adduct Level in Three Chinese Populations

To elucidate the potential factors modulating exposure to aflatoxin B₁ (AFB₁) in three Chinese populations, an epidemiologic study was conducted in Fusui County and Nanning City of Guangxi Province and Chengdu City of Sichuan Province. The incidence rates of hepatocelluar carcinoma (HCC) for males in these three regions were 92–97 per 100,000, 32–47 per 100,000, and 21 per 100,000, respectively. Eighty-nine residents from Fusui, 196 residents from Nanning, and 118 residents from Chengdu were screened for AFB₁–albumin adduct (AAA) levels and hepatitis virus (HBV, HCV, HDV, HEV, and HGV) infections, as well as liver biochemistry (alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [ALP], -glutamyl transpeptidase [GGT], 5-nucleotidase, globulin [GLO], direct bilirubin, indirect bilirubin, and bile acid levels). At least one marker of hepatitis virus (HV) infection was present in 47.2% (42/89) of subjects from Fusui, while in Nanning and Chengdu the values were 15.8% (31/196) and 22.0% (26/118), respectively. In contrast to females, a higher level of AAA was observed in males; the difference was statistically significant in both the Nanning (P = 0.023) and the Chengdu (P = 0.026) subjects. In the Chengdu group, there was a significantly higher level of AAA in cases with HV infection (P = 0.041). There was a close association between AAA level and BMI in the adults without HV infection (r = 0.148, P = 0.044). Also, AAA was closely associated with DBIL and GGT in non-HV-infected minors (P < 0.05), closely associated with ALB, GLO, and GGT in HV-infected minors (P < 0.05), and closely associated with IBIL, GLO, TBA, and AST in non-HV-infected adults (P < 0.01). The co-effect of HV infection and AFB₁ exposure may be responsible for the high risk of HCC in the Fusui region, whereas age, gender, BMI, and HV infection may modify individual aflatoxin levels. The relationship between AAA level and liver biochemistry indicates injury induced by aflatoxin to both hepatic parenchyma and biliary tract. But the associations vary with age and HV infection status.     

Genome-wide miRNA-profiling of aflatoxin B1-induced hepatic injury using deep sequencing

Aflatoxin B1 is a potent carcinogen which can induce** hepatocellular carcinoma (HCC) in mammals. Though microRNAs are known to play important roles in tumorigenesis, the functional complexity of microRNAs in AFB1-induced hepatocellular tumorigenesis has not yet been elucidated. Here, we applied Illumina deep sequencing technology for high-throughput profiling of microRNA in rat liver tissue before and after treatment with aflatoxin B1. Analysis of mature miRNAs from different arms of pre-miRNAs allowed us to identify the predominant form of miRNA. We studied the differential expression profile of miRNAs in two libraries, identifying several cancer-related microRNAs which exhibit abnormal expression. KEGG analysis indicated that predicted target genes of differentially expressed miRNAs are involved in cancer-related pathways. Bioinformatic analysis predicted 16 potential novel miRNAs. Our work provides new insights at the miRNA level into AFB1-induced hepatic injury which may lead to HCC.     

LC-MS / MS 检测莲子中黄曲霉毒素 B1、B2、G1、G2的方法探讨简

目的 建立LC-MS/MS检测莲子中的黄曲霉毒素B1、B2、G1、G2的方法.方法 收集5批莲子,采用高效液相色谱-串联四极杆质谱联用技术,多反应监测（MRM）模式进行定量检测.结果 1批发霉的莲子中检出黄曲霉毒素B1、B2、G1、G2.结论 该方法专属性强、灵敏度高,可用于莲子中的黄曲霉毒素B1、B2、G1、G2的同时测定.     

Screening a Strain of Aspergillus niger and Optimization of Fermentation Conditions for Degradation of Aflatoxin B1

Aflatoxin B₁, a type of highly toxic mycotoxin produced by some species belonging to the Aspergillus genus, such as Aspergillus flavus and Aspergillus parasiticus, is widely distributed in feed matrices. Here, coumarin was used as the sole carbon source to screen microorganism strains that were isolated from types of feed ingredients. Only one isolate (ND-1) was able to degrade aflatoxin B₁ after screening. ND-1 isolate, identified as a strain of Aspergillus niger using phylogenetic analysis on the basis of 18S rDNA, could remove 26.3% of aflatoxin B₁ after 48 h of fermentation in nutrient broth (NB). Optimization of fermentation conditions for aflatoxin B₁ degradation by selected Aspergillus niger was also performed. These results showed that 58.2% of aflatoxin B₁ was degraded after 24 h of culture under the optimal fermentation conditions. The aflatoxin B₁ degradation activity of Aspergillus niger supernatant was significantly stronger than cells and cell extracts. Furthermore, effects of temperature, heat treatment, pH, and metal ions on aflatoxin B₁ degradation by the supernatant were examined. Results indicated that aflatoxin B₁ degradation of Aspergillus niger is enzymatic and this process occurs in the extracellular environment.     

Protective effect of Kalpaamruthaa in combating the oxidative stress posed by aflatoxin B1‐induced hepatocellular carcinoma with special reference to flavonoid structure–activity relationship

Aims/Background: Aflatoxin B₁ (AFB₁) is a potent hepatotoxic and hepatocarcinogenic mycotoxin. It has been postulated to play a major role in the aetiology of primary human liver cancer. Lipid peroxidation (LPO) is one of the main manifestations of oxidative damage and has been found to play an important role in the toxicity and carcinogenesis of many carcinogens. The present investigation aimed at assessing the effect of Kalpaamruthaa (KA), a modified Siddha preparation, on AFB₁‐mediated hepatocellular carcinoma (HCC). Methods: The drug was administered orally (300 mg/kg body weight/day) for 28 days to HCC‐bearing rats. The level of lipid peroxides, antioxidant enzymes, glutathione and glutathione‐metabolizing enzyme activity were determined in the plasma, haemolysate and liver homogenate of control and experimental rats. Results: Rats subjected to AFB₁ showed a decline in the thiol capacity of the cell, accompanied by high malondialdehyde levels along with lowered activities of enzymic and non‐enzymic antioxidant and glutathione‐metabolizing enzyme levels. KA treatment restored the deranged LPO and enzyme activities almost to control levels, thereby suggesting hepatoprotection. Conclusion: This study highlighted the beneficial effect of KA in reversing the damage posed by AFB₁ and thereby bringing about an improvement in the antioxidant status to combat the oxidative stress.     

Synergistic interaction between aflatoxin B1 and hepatitis B virus in hepatocarcinogenesis

Abstract: Chronic hepatitis B virus (HBV) infection and dietary exposure to aflatoxin B₁ (AFB₁), two of the major risk factors in the multifactorial aetiology of hepatocellular carcinoma (HCC), co‐exist in those countries with the highest incidences of and the youngest patients with this tumour, raising the possibility of a synergistic carcinogenic interaction between the two agents. Experimental studies in HBV‐transgenic mice and woodchucks infected with woodchuck hepatitis virus were the first to show a synergistic hepatocarcinogenic effect between hepadnaviral infection and AFB₁ exposure. With the availability of urinary and serum biomarkers that more accurately reflect dietary exposure to AFB₁ than did the initially used food sampling and dietary questionnaires, cohort studies of patients with HCC in China and Taiwan have provided compelling evidence for a multiplicative or sub‐multiplicative interaction between HBV and AFB₁ in the genesis of human HCC. A number of possible mechanisms for the interaction have been suggested. Chronic HBV infection may induce the cytochrome P450s that metabolise inactive AFB₁ to the mutagenic AFB₁‐8,9‐epoxide. Hepatocyte necrosis and regeneration and the generation of oxygen and nitrogen reactive species resulting from chronic HBV infection increase the likelihood of the AFB₁‐induced p53 249^ser and other mutations and the subsequent clonal expansion of cells containing these mutations. Nuclear excision repair, which is normally responsible for removing AFB₁–DNA adducts, is inhibited by HBV×protein, favouring the persistence of existing mutations. This protein also increases the overall frequency of DNA mutations, including the p53 249^ser mutation, and may contribute to uncontrolled cell cycling when p53 is non‐functional.