A comparative study of zero-shot inference with large language models and supervised modeling in breast cancer pathology classification

Although supervised machine learning is popular for information extraction from clinical notes, creating large, annotated datasets requires extensive domain expertise and is time-consuming. Meanwhile, large language models (LLMs) have demonstrated promising transfer learning capability. In this study, we explored whether recent LLMs can reduce the need for large-scale data annotations. We curated a manually labeled dataset of 769 breast cancer pathology reports, labeled with 13 categories, to compare zero-shot classification capability of the GPT-4 model and the GPT-3.5 model with supervised classification performance of three model architectures: random forests classifier, long short-term memory networks with attention (LSTM-Att), and the UCSF-BERT model. Across all 13 tasks, the GPT-4 model performed either significantly better than or as well as the best supervised model, the LSTM-Att model (average macro F1 score of 0.83 vs. 0.75). On tasks with a high imbalance between labels, the differences were more prominent. Frequent sources of GPT-4 errors included inferences from multiple samples and complex task design. On complex tasks where large annotated datasets cannot be easily collected, LLMs can reduce the burden of large-scale data labeling. However, if the use of LLMs is prohibitive, the use of simpler supervised models with large annotated datasets can provide comparable results. LLMs demonstrated the potential to speed up the execution of clinical NLP studies by reducing the need for curating large annotated datasets. This may increase the utilization of NLP-based variables and outcomes in observational clinical studies.

[Mechanism of podocyte pyroptosis aggravated by up-regulation of phospholipase A2 receptor by hepatitis B virus X protein]

Objective: To explore the effect and underlying mechanism of increased expression of M-type phospholipase A₂ receptor (PLA₂R) on podocyte membrane induced by hepatitis B virus X protein (HBx) on podocyte pyroptosis in hepatitis B virus-associated glomerulonephritis (HBV-GN). Methods: Transfection of the HBx gene into human kidney podocytes was used to mimic the HBV-GN pathogenesis process. Subsequently, podocytes were divided into the following eight groups: normal control plus secretory phospholipase A₂-ⅠB (sPLA₂-ⅠB) group, empty plasmid plus sPLA₂-ⅠB group, HBx group, HBx plus sPLA₂-ⅠB group, HBx plus sPLA₂-ⅠB plus PLA₂R control siRNA group, HBx plus sPLA₂-ⅠB plus PLA₂R-siRNA group, HBx plus sPLA₂-ⅠB plus ROS control siRNA group, and HBx plus sPLA₂-ⅠB plus ROS-siRNA group. Podocyte morphology was observed under a transmission electron microscope, and PLA₂R expression was detected under a fluorescence microscope. Podocyte pyroptosis and reactive oxygen species (ROS) expression were analyzed by flow cytometry, and the mRNA and protein expression of PLA₂R, nucleotide-binding oligomerization domain-like receptor 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, interleukin (IL)-1β and IL-18 were determined by real-time fluorescence quantitative PCR and Western blot. Results: Compared with the control group, the expression of PLA₂R on podocyte membrane significantly increased after transfection with HBx plasmid in vitro (4.07±0.41 vs 1.01±0.17, P<0.001). Transmission electron microscope and fluorochrome-labeled inhibitor of caspases/propidium iodide (FLICA/PI) double staining suggested that overexpressed PLA₂R combined with sPLA₂-ⅠB caused aggravated podocyte injury and increased pyroptosis (20.22%±0.36% vs 7.86%±0.28%, P<0.001). Moreover, the expression levels of ROS (4 324 515±222 764 vs 12 920±46, P<0.001), NLRP3 (48.30±2.73 vs 1.00±0.11, P<0.001), ASC (4.02±0.84 vs 1.01±0.15, P<0.001), caspase-1 (3.99±0.42 vs 1.00±0.11, P<0.001), IL-1β (9.08±0.75 vs 1.00±0.09, P<0.001) and IL-18 (19.20±0.70 vs 1.00±0.02, P<0.001) increased when PLA₂R was overexpressed. In contrast, with the addition of PLA₂R-siRNA or ROS-siRNA to knockdown the expression of related substances, podocyte injury was alleviated and the degree of pyroptosis decreased, and the expressions of genes related to the downstream signaling pathway (NLRP3, ASC, caspase-1, IL-1β and IL-18) decreased (all P<0.01). Conclusion: HBx may promote podocyte pyroptosis in HBV-GN by targeting the ROS-NLRP3 signaling pathway via the upregulation of PLA₂R.

Cinchona Alkaloid-Inspired Urea-Containing Autophagy Inhibitor Shows Single-Agent Anticancer Efficacy

Autophagy is upregulated in response to metabolic stress, a hypoxic tumor microenvironment, and therapeutic stress in various cancers and mediates tumor progression and resistance to cancer therapy. Herein, we identified a cinchona alkaloid derivative containing urea (C1), which exhibited potential cytotoxicity and inhibited autophagy in hepatocellular carcinoma (HCC) cells. We showed that C1 not only induced apoptosis but also blocked autophagy in HCC cells, as indicated by the increased expression of LC3-II and p62, inhibition of autophagosome-lysosome fusion, and suppression of the Akt/mTOR/S6k pathway in the HCC cells. Finally, to improve its solubility and efficacy, we encapsulated C1 into PEGylated lipid-poly(lactic-co-glycolic acid) (PLGA) nanoscale drug carriers. Systemic administration of nanoscale C1 significantly suppressed primary tumor growth and prevented distant metastasis while maintaining a desirable safety profile. Our findings demonstrate that C1 combines autophagy modulation and apoptosis induction in a single molecule, making it a promising therapeutic option for HCC.

Modulation of rumen fermentation and microbial community through increasing dietary cation-anion difference in Chinese Holstein dairy cows under heat stress conditions

AIMS

The effect of increasing dietary cation-anion difference (DCAD) on rumen fermentation and ruminal microbial community in dairy cows under heat stress (HS) conditions were evaluated.

METHODS AND RESULTS

This study was performed as a two-period cross-over design during the summer season, with eight lactating dairy cows randomly distributed to either a control DCAD diet (CON: 33·5 mEq/100 g DM) or high DCAD diet (HDCAD: 50·8 mEq/100 g DM). Throughout the present study, the temperature and humidity index (THI; 80·2 ± 4·29) was generally elevated above the threshold (THI = 72) that is reported to cause HS in lactating dairy cows. Rumen liquid samples were collected on 15 and 21 d during each 21 d-period. The absolute concentration of ruminal total volatile fatty acid (TVFA) in HDCAD treatment was significantly (P < 0·05) higher than those in the control, whilst the ruminal pH, NH₃ -N, and VFA molar percentages were unaffected through increasing DCAD. Furthermore, the copy numbers of the cellulolytic bacteria Ruminococcus albus and Ruminococcus flavefaciens in rumen fluid significantly (P < 0·05) rose along with the increment of DCAD. Although the Alpha diversity indexes and the bacterial microbiota structure were unaffected, increasing DCAD significantly (P < 0·05) enriched the phylum Fibrobacteres and genus Fibrobacter in the microflora of rumen fluid, whilst the genera Flexilinea and Dubosiella were the most differentially abundant taxa in the control.

CONCLUSIONS

Increasing DCAD under HS conditions resulted in a greater concentration of total VFA without affecting rumen bacteria diversity or structure, although the enrichment of some cellulolytic/hemicellulolytic bacteria was observed.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study provides information on the modulation of rumen fermentation and microbial community through the increment of DCAD in Holstein dairy cows under HS conditions.

[Change and relationship between Gli1 and β-catenin on rats' bone formation with chronic fluorosis]

Objective: To investigate the change and association of glioma-associated oncogene homolog 1 (Gli1) and β-catenin on bone formation in rats with chronic fluorosis which were inhibited by cyclopamine (Cycl). Methods: Forty-eight Sprague-Dawley rats were evenly divided to four groups, including control, F, F+Cycl and F+DMSO groups. The control group were fed with tap water (NaF<1 ppm). The F, F+Cycl and F+DMSO groups were exposed to NaF (50 ppm) in drinking water as the chronic fluorosis model. Then the rats in F+Cycl or F+DMSO groups were injected by Cycl or DMSO after 6 months, respectively. Urine fluoride concentration was detected using fluorine ion selective electrode. The enzyme-linked immunosorbent assay (ELISA) was used to detect bone alkaline phosphatase (BALP). Bone tissues were stained with hematoxylin-eosin. The mRNA and protein expression of Gli1 and β-catenin in bone tissue were detected using real-time PCR, immunohistochemistry and Western blot. Results: Compared with the controls, the urine fluoride concentration and the width and volume of bone trabeculae were increased in the F, F+Cycl and F+DMSO groups, but no statistical difference among the 3 fluorosis groups. The concentration of BALP was increased in the F group and decreased in F+Cycl group (P<0.05). The expression of Gli1 and β-catenin mRNA and protein was higher in the F and F+Cycl groups than controls, but lower in the F+Cycl group than in the F group. There was positive correlation between the expression of Gli1 and β-catenin (r=0.476, P<0.05). The expression of Gli1 and β-catenin was also associated with BALP concentration and volume of bone trabeculae, respectively (r(1)=0.457, r(2)=0.466, r(3)=0.581, r(4)=0.554, respectively, P<0.05 for all). Conclusions: The expression of Gli1 can be inhibited by Cycl. It may be involved in the bone formation of rats with chronic fluorosis. It may also affect the expression of β-catenin, which is an osteogenesis factor.

[Effect of GSK-3β inhibitor on the expression of RANK-RANKL in rats kidney tissue with diabetic nephropathy]

Objective: To investigate the effect and significance of GSK-3β inhibitor(LiCl)and RANK-RANKL on the renal tissue of diabetic nephropathy(DN) rats. Methods: SD rats were divided into normal control group (NC), DN model group (DN) and GSK-3β inhibitor intervention group (LiCl). Twenty-four hour urine protein of rats were determined by Coomassie brilliant blue. Kidney tissue sections were stained by HE. The expression of GSK-3β, RANK and RANKL protein were determined by immunohistochemistry staining. The mRNA of GSK-3β, RANK, RANKL was detected by RT-qPCR. Results: Compared with NC group[(14.72±3.37)g], the level of 24-hour urinary protein[(154.17±20.65)g] increased significantly in DN group; compared with DN Group, the level of 24-hour urinary protein [(107.22±31.15)g]decreased in LiCl group(P<0.05). Compared with NC group(2.10±0.60, 1.10±0.20, 1.21±0.20; 19.52±3.20, 1.80±1.10, 1.81±0.50), the pathological changes of renal tissues of DN group aggravated, the mRNA and expression of protein of GSK-3β, RANK and RANKL increased(9.10±2.15, 8.95±2.40, 9.90±2.60; 32.70±7.20, 19.20±4.32, 20.92±5.90); compared with DN group, the pathological changes of renal tissues of LiCl group alleviated, mRNA and the expression of protein of factors above declined(2.70±0.80, 2.32±0.65, 3.58±1.10; 22.35±3.25, 4.20±2.42, 5.90±2.36; P<0.05). Conclusion: RANK and RANKL play an important role in the development of DN, LiCl influence Wnt and NF-κB signal pathway down-regulating RANK and RANKL to suspend development of diabetic nephropathy.

Quantitative Identification of Compound-Dependent On-Modules and Differential Allosteric Modules From Homologous Ischemic Networks

Module‐based methods have made much progress in deconstructing biological networks. However, it is a great challenge to quantitatively compare the topological structural variations of modules (allosteric modules [AMs]) under different situations. A total of 23, 42, and 15 coexpression modules were identified in baicalin (BA), jasminoidin (JA), and ursodeoxycholic acid (UA) in a global anti‐ischemic mice network, respectively. Then, we integrated the methods of module‐based consensus ratio (MCR) and modified Z_summary module statistic to validate 12 BA, 22 JA, and 8 UA on‐modules based on comparing with vehicle. The MCRs for pairwise comparisons were 1.55% (BA vs. JA), 1.45% (BA vs. UA), and 1.27% (JA vs. UA), respectively. Five conserved allosteric modules (CAMs) and 17 unique allosteric modules (UAMs) were identified among these groups. In conclusion, module‐centric analysis may provide us a unique approach to understand multiple pharmacological mechanisms associated with differential phenotypes in the era of modular pharmacology.

Concentration dependent stereoselectivity of propafenone N-depropylation metabolism with human hepatic recombinant CYP1A2

Concentration dependency of stereoselective N-depropylation metabolism of propafenone was studied by using transgenic cell line expressing human CYP1A2. Enantiomers of propafenone and N-depropylpropafenone were separated and assayed simultaneously by RP-HPLC with precolumn GITC chiral derivatization. The experimental results showed that CYP1A2 was involved in enantioselective N-depropylation of propafenone and that the metabolic stereoselectivity depends on substrate concentration. For racemic propafenone, stereoselectivity was observed at low substrate concentration and was not seen at high substrate concentration. For individual isomers, S-(+)-propafenone was metabolized faster than its antipode at higher enantiomer concentrations and R-(-)-propafenone was eliminated faster than its antipode at lower enantiomer concentrations. There is interaction between S- and R-propafenone. R-(-)-propafenone inhibited the metabolism of S-(+)-propafenone with IC50 0.225 mmol/L for human CYP1A2.

Difference in Protein Expression in Vero Cells after Antisense-blocking Genes Involved in the Suppression of Non-targeted Mutagenesis

A cDNA fragment (fragment 9) has been isolated by mRNA differential display and antisense technology in this lab, and its relevant gene (fragment 9 related gene, FNR gene) might be involved in the inhibition of non-targeted mutagenesis induced by N -methyl- N ' -nitro-N-nitrosoguanidine(MNNG) in mammalian cells. In order to elucidate the functional mechanism of the FNR gene, the protein expression was compared between MNNG-exposed Vero cells transfected with antisense RNA expression plasmid (Vero-pM-amp(-)-9(-)) and those with vector DNA (Vero-pM-amp(-)), by using two-dimensional gel electrophoresis followed by 2D image software analysis. Our analysis indicated that 12 proteins were specifically expressed only in Vero-pM-amp(-)-9(-), and 2 proteins in Vero-pM-amp(-). In addition,there were 24 proteins expressed in higher level in Vero-pM-amp(-)-9(-) as compared with Vero-pM-amp(-)( P <0.05), among them the expression of 7 proteins were enhanced by greater than 5 folds. These results suggest that antisense blocking the FNR gene expression triggered a series of alteration of other gene expression and the FNR gene might be a regulatory factor. This study will also facilitate the identification and characterization of these proteins and corresponding genes involved in the non-targeted mutagenesis.

Cloning of UGT1A9 cDNA from liver tissues and its expression in CHL cells

AIM: To clone the cDNA of UGT1A9 from a Chinese human liver and establish the Chinese hamster lung (CHL) cell line expressing human UGT1A9.

METHODS: cDNA of UGT1A9 was transcripted from mRNA by reverse transcriptase-ploymerase chain reaction, and was cloned into the pGEM-T vector which was amplified in the host bacteric E. coli DH5α. The inserted fragment, verified by DNA sequencing, was subcloned into the Hind III/Not I site of a mammalian expression vector pREP9 to construct the plasmid termed pREP9-UGT1A9. CHL cells were transfected with the resultant recombinants, pREP9-UGT1A9, and selected by G418 (400 mg•L¯¹) for one month. The surviving clone (CHL-UGT1A9) was harvested as a pool and sub-cultured in medium containing G418 to obtain samples for UGT1A9 assays. The enzyme activity of CHL-UGT1A9 towards propranolol in S9 protein of the cell was determined by HPL C.

RESULTS: The sequence of the cDNA segment cloned, which was 1666 bp in length, was id entical to that released by GeneBank (GenBank accession number: AF056188) in co ding region. The recombinant constructed, pREP9-UGT1A9, contains the entire coding region, along with 18 bp of the 5’ and 55 bp of the 3’ untranslated region of the UGT1A9 cDNA, respectively. The cell lines established expressed the protein of UGT1A9, and the enzyme activity towards propranolol in S9 protein was found to be 101 ± 24 pmol•min^-1•mg^-1 protein (n = 3), but was not detectable in parental CHL cells.

CONCLUSION: The cDNA of UGT1A9 was successfully cloned from a Chinese human liver and transfected into CHL cells. The CHL-UGT1A9 cell lines established efficiently expressed the protein of UGT1A9 for the further enzyme study of drug glucuronidation.

Stereoselective metabolism of propafenone by human liver CYP3A4 expressed in transgenic Chinese hamster CHL cells lines

AIM

To investigate the stereoselective metabolism of propafenone (PPF) by human liver CYP3A4.

METHODS

A chiral and an achiral HPLC were combined to determine the enantiomer of PPF in S9 incubates prepared from transgenic Chinese hamster CHL cells lines expressing CYP3A4. The time-dependent study was performed using individual enantiomer or racemate at low or high substrate concentration. Kinetic parameters were determined employing individual enantiomers as substrates. Enantiomeric inhibition experiments were performed by using R(-)-PPF as an inhibitor and S(+)-PPF as a substrate.

RESULTS

Stereoselectivity was found in metabolism of racemic PPF at low substrate concentration (10 mg/L) (S < R), and lost at high substrate concentration (400 mg/L) When an individual enantiomer of high concentration (200 mg/L) was used as a substrate, S(+)-PPF was eliminated faster than its isomer (S < R). However, the opposite situation was observed at low concentration (5 mg/L) (S < R). The Vmax of S(+)-PPF was significantly greater than that of R(-)-PPF [(2.66 +/- 0.32) vs (1.71 +/- 0.19) micromol . mg-1 . min-1]. The Km of R(-)-PPF was significantly lower than that of S(+)-PPF [(73 +/- 11) vs (185 +/- 17) micromol/L]. R(-)-PPF inhibited S(+)-isomer with an IC50 value of 125 micromol . L-1.

CONCLUSION

It is concluded that stereoselectivity in metabolism of propafenone via CYP3A4 depend on substrate concentration. Enantiomer/enantiomer interaction of PPF occurred at high concentration of substrate, and resulted in the loss of stereoselectivity. There maybe no enantiomer/enantiomer interaction at low concentration thus keeping the superiority of R(-)-PPF in metabolism.

[Reversed-phase high performance liquid chromatography used for determination of amino acids of parasites]

The compositions and contents of amino acids of parasites in different areas of China have been determined by precolumn derivatization, reversed-phase high performance liquid chromatography (HPLC) separation and ultra-violet absorption quantitation in order to prevent diseases caused from parasites. The results show that there were some differences in contents of amino acids in B. malayi from seven different areas in China. The contents of amino acids gradually increased from the southern to the northern areas in China. The method is simple and accurate, and the results have important values to investigate the life activities of parasites.

[Purification and characterization of recombinant human interleukin 11 which expressed by Pichia pastoris]

This study first time report a method to purify the rhIL-11 which expressed by Pichia pastoris. rhIL-11 was secreted into the supernatant and collected by centrifugation. The purity of rhIL-11 reached 97% through the steps of ultrafiltration, SP Sepharose FF, Phenyl Sepharose HP and Sephadex G25. Analysis of SDS-PAGE, Western-blotting, IEF, RP-HPLC, Mass spectrometer, N and C terminus amino acid sequence and bioactivity was conducted. All the analysis results proved that the rhIL-11 expressed by Pichia pastoris was the same as Neumeg which was expressed in E. coli with fusion expression system. So it is possibly a cheaper and easier method to produce rhIL-11 for clinical use.

[Novel affinity membrane used for bilirubin removal]

Bilirubin is a toxic substance. In order to effectively remove it from the hepatic patients' blood, two novel affinity membranes were prepared. These were prepared by chemically grafting on cellulose and immobilized with different ligands. One kind of ligand was poly-D-lysine, the other one was quaternary ammonium salt. Both affinity membranes were used for removal bilirubin from phosphate buffer and HSA solutions, and the effects of temperature, HSA concentration, adsorption time in static state experiment and flow rate in dynamic state experiment have been investigated. The results indicated that the membranes could remove over 70% bilirubin from phosphate buffer and at least 50% from low concentration HSA solutions. The results also indicated that the removal efficiency was better at higher temperature. In the static state experiment, four hours can be selected as adsorption time. In the dynamic state experiment, the flow rate can be properly increased.

[Mismatch repair in MNNG-induced genetically unstable monkey kidney vero cell]

Gel retardation analysis and in vitro DNA mismatch repair system were used to examine whether there were mismatch repair deficiency in MNNG-induced genetically unstable vero cell, which was manifested by a delayed and highly increased rate of non-targeted mutation. A mismatch binding protein which could selectively bind to G.T mispair in DNA was identified in its whole-cell extracts. It was also identified that G.T mispair could be specifically and effectively corrected into G.C pair in its nuclear extracts. Compared with normal vero cell, there were no functional deficiency of the above mismatch repair mechanisms. So it could be excluded the possibility that the functional deficiency of mismatch binding protein or G.T mismatch repair pathway participated in the induction of genetic instability in vero cell by MNNG.

Specific peptide-activated proteolytic cleavage of Escherichia coli elongation factor Tu

Phage exclusion is a form of programmed cell death in prokaryotes in which death is triggered by infection with phage, a seemingly altruistic response that limits multiplication of the phage and its spread through the population. One of the best-characterized examples of phage exclusion is the exclusion of T-even phages such as T4 by the e14-encoded Lit protein in many Escherichia coli K-12 strains. In this exclusion system, transcription and translation of a short region of the major head coat protein gene late in phage infection activates proteolysis of translation elongation factor Tu (EF-Tu), blocking translation and multiplication of the phage. The cleavage occurs between Gly-59 and Ile-60 in the nucleotide-binding domain. In the present work, we show that a 29-residue synthetic peptide spanning the activating region of the major head coat protein can activate the cleavage of GDP-bound EF-Tu in a purified system containing only purified EF-Tu and purified Lit protein. Lit behaves as a bona fide enzyme in this system, cleaving EF-Tu to completion when present at substoichiometric amounts. Two mutant peptides with amino acid changes that reduce the activation of cleavage of EF-Tu in vivo were also greatly reduced in their ability to activate EF-Tu cleavage in vitro but were still able to activate cleavage at a high concentration. Elongation factor G, which has the same sequence at the cleavage site and a nucleotide-binding domain similar to EF-Tu, was not cleaved by this system, and neither was heat-inactivated EF-Tu, suggesting that the structural context of the cleavage site may be important for specificity. This system apparently represents an activation mechanism for proteolysis that targets one of nature's most evolutionarily conserved proteins for site-specific cleavage.

[Effect of aging on the syndrome of essential debility and evil reality--an exploration on mechanism of senility by traditional Chinese medicine]

Effect of aging on essential debility and evil reality was explored by an epidemiological investigation of clinical syndrome with TCM in 878 cases of middle and old-aged patients, inquiring into their relation of senility with visceral weakness and stagnation of Qi, blood stasis, and phlegm turbid. The results indicated that (1) several viscera, feeble and damaged, were the basis of senility, and the feeble kidney was the stress; (2) the syndrome of stagnation of Qi, blood stasis and phlegm turbid speeded up process of senility. The mechanism of feeble phenomena appeared in the middle-old aged patients is that with the rise of age in the patients observed there was interaction between the feeble visceral function and the syndrome of stagnation of Qi, blood stasis and phlegm turbid, that is, there was interaction between essential debility and evil reality. Essential debility may lead to evil reality and the latter will worsen essential debility. Thus, on repeating themselves in alternate cycles, a systemic hypofunction will be formed up to exhaustion. Therefore, "to nourish essential debility first and to purge evil reality second" should be considered as an essential direction of preparing anti-aging drugs in TCM.

Study of SOS-inducing kinetics and inhibitory effect on induction of Escherichia coli

It was found that modified pulse induction could produce SOS responses of the sfi gene in 15 minutes. The responses peaked at 30-60 minutes and were twice as strong as those by persistent induction. The modified pulse induction could therefore more truly reflect the inducing effect. However, the SOS-inducing kinetics of MMC and 4NQO was not identical suggesting distinct kinetic patterns of induction by different mutagens. A suppressive effect on 4NQO-induced SOS response by cinnamic aldehyde and diallyl trisulfate was also observed. The effect might be due to an interference with the metabolic activation of 4NQO or breakdown of 4NQO by the bacteria.

Experimental studies on the late effects of female sex hormones

Inj. Hydroxyprogesterone Co. (EP) was injected i.m. into female Wistar rats, different strains of mice of both sex and Syrian golden hamsters with doses of 5-100 times the human contraceptive dose once or twice a month for 10-32 times. In some experiments EP was combined with whole-body 3 Gy gamma ray radiation once or twice. Results show that EP has obvious carcinogenicity and can enhance the gamma ray carcinogenicity, thereby increasing the tumor incidence or the ratio of malignant to benign tumours. Carcinogenic mechanisms of EP have also been studied.

Antimutagenic effect of garlic (Allium sativum L.) on 4NQO-induced mutagenesis in Escherichia coli WP2

Aqueous extract prepared from garlic bulbs markedly suppressed the mutagenesis in both E. coli WP2 trp- and E. coli WP2 trp- uvrA- induced by 4-nitroquinoline 1-oxide (4NQO), but not that induced by UV. Cellular toxicity, inhibition of the expression of the Trp+ phenotype and delay of the first cell division after 4NQO treatment were not observed in the presence of the extract. Since the extract showed identical antimutagenic effects against 4NQO in both test strains but no effect on the mutagenesis of UV, it seems that the extract might act by inactivating the electrophilic group(s) of 4NQO or inhibiting its metabolic activation.

Induction of cytochrome P450 isozymes in human amnion FL cells

The human epithelial FL cell line contains low levels of constitutive ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase and aminopyrine N-demethylase activities, of which ethoxyresorufin O-deethylase could be induced by norepinephrine, beta-naphthoflavone and 3-methylcholanthrene, but ethoxy-couarin O-deethylase and aminopyrine N-demethylase activities could be induced by norepinephrine, beta-naphthoflavone and 3-methylcholanthrene as well as phenobarbital. Inducibility of ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase and aminopyrine N-demethylase activities was 3.1-6.7-, 1.8-3.1- and 1.4-2.0-fold respectively. Co-treatment with 3-methylcholanthrene and norepinephrine resulted in higher ethoxyresorufin O-deethylase and aminopyrine N-demethylase activities than treatment with 3-methylcholanthrene alone. The induced ethoxyresorufin O-deethylase and ethoxycoumarin O-deethylase activities remained at a high level for 24-36 h after removal of the inducer from the medium. The metabolizing ability of induced FL cells is stronger than that of non-induced ones in a given time following induction. The results further confirm that it is feasible to use the cytochrome P450 isozyme-induced FL cell as a biological indicator in short-term tests for screening promutagens/procarcinogens.

[Is hypomethylation of cellular DNA a step required in the initiation process of chemical carcinogenesis?]

There seems to be a current view that the inhibition of DNA methylation may be a mechanism of initiation of carcinogenesis or one of the steps required in the carcinogenic process. However, because of the deficiencies in research works on cellular level, there is a long way to make such a general relationship between carcinogen and the inhibition of cellular DNA methylation. In this paper the effects of some chemical carcinogens on methylation of newly replicated DNA in human FL cells was analyzed by comparing the weight average length (Lw) of the DNA digests after complete digestion by restriction endonuclease Hpa II. It was observed that two non-genotoxic carcinogens (5-azacytidine and L-ethionine) and two genotoxic carcinogens (MNNG and aflatoxin B1) used in this study all caused obvious cytotoxicity on FL cells at the test concentration. Five days after the termination of 5-azacytidine treatment (2 x 10(-6) M, 24 hours), Lw (kb) of the Hpa II digests of cellular DNA was smaller than that of control (8.0 +/- 0.1 vs 10.9 +/- 1.0, P less than 0.01), the Lw change rate was -27%. When DNA was analyzed from FL cells after 9 days continuous treatment of L-ethionine (2 x 10 M), the digestibility of Hpa II was also increased as compared with that of the control, the Lw values (kb) showed a decrease of about 8% (9.8 +/- 0.3 vs 10.6 +/- 0.3, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The cell-cycle dependent and the DNA-damaging agent-induced changes of cellular NAD content and their significance

NAD is the substrate of a novel chromatin-associated enzyme-ADP-ribosyl transferase (ADPRT). In this study, the cell-cycle dependent change in cellular NAD content was observed in a line of human amnion FL cells. It was found that the cellular NAD content of FL cells was highest in G1 and lowest in S/G2-G2. 3AB, a potent ADPRT inhibitor, can inhibit the cell cycle dependent change in cellular NAD content and also inhibit DNA synthesis in the S phase and extend the S phase. The results indicate that ADP-ribosylation may be involved in DNA replication and cell cycle progression. It was also found that the DNA-damaging agents, MNNG, MMS and 4NQO could lower cellular NAD content in a dose-dependent way. This DNA-damage-induced NAD lowering could be partially or completely prevented by the ADPRT inhibitors, 3AB or nicotinamide, which were shown to exert no influence on either the cellular NAD content of normal quiescent FL cells or the metabolic blocking agent, 2,4-DNP-induced cellular NAD lowering. The possibility of establishing a simple and specific method to detect DNA-damaging agents by measuring cellular NAD content in the presence or absence of ADPRT inhibitor is explored.

A test using cultured cells with induced mixed-function oxygenase in the unscheduled DNA synthesis assay for detecting promutagens/procarcinogens

The human FL cell line contains very low levels of constitutive AHH activity, but it could be greatly induced by NE, beta-NF and 3-MC, and induced slightly by PB. When two different types of inducer, for example, 3-MC and PB or 3-MC and NE were given in combination, an additive inductive effect was not observed. Both the constitutive and induced AHH in FL cells have characteristics of MFO, namely, NADPH-dependence and CO-sensitivity. The fact that the constitutive and induced AHH in FL cells could be inhibited by a known hydroxylase inhibitor 7,8-BF indicated that the AHH in FL cells belongs to the cytochrome P-448 dependent MFO type. After removal of inducer from the medium, the induced AHH activity remained at a high level for at least 24-36 h. By using AHH-induced FL cells in the UDS assay system for the detection of promutagens/procarcinogens, we found that AFB1 and 3-MC did not induce a UDS reaction in uninduced FL cells, while in beta-NF induced cells, 10(-6)-10(-4) M AFB1 and 10(-7)-10(-6) M 3-MC elicited a very significant UDS reaction, which was concordant with the results obtained in the UDS assay system using HeLa cells or FL cells supplemented with liver microsomes or using primary cultured hepatocytes as indicator cells. B(a)P elicited the UDS reaction at concentrations of 10(-6)-10(-3) M in beta-NF induced cells, whereas 10(-4)-10(-3) M was required in uninduced cells. The results above indicate that this new design is feasible, but further study is needed to assure its accuracy.

Cell cycle effects on the basal and DNA-damaging-agent-stimulated ADPRT activity in cultured mammalian cells

ADP-ribosyl transferase (ADPRT) is a DNA-dependent chromatin-associated enzyme which covalently attaches ADP-ribose moieties derived from NAD+ to protein acceptors to form poly(ADP-ribose). ADPRT activity is strongly stimulated by breaks in DNA, and it is suggested that its activity is required for efficient DNA excision repair. In this paper, a cell-cycle-dependent fluctuation of basal ADPRT activity was demonstrated by measuring it in permeabilized FL cells. The cell used was subjected to arginine starvation for 48 h before being released from the block by replacement of deficient medium with complete medium and cells in different proliferating stages were traced by [3H]TdR pulse labelling and obtained at different intervals after block release. The peak basal ADPRT activity appeared 4-6 h after the appearance of the peak of DNA synthesis. After treating the cells with MNNG (10(-4) M), MMS (10(-3)-10(-4) M) and 4NQO (10(-5) M) for 90 min just after release of the block, the ADPRT activity was markedly stimulated. It was further demonstrated that the effects of MNNG/4NQO and cell cycle influence on the level of poly(ADP-ribose) synthesis appear to be additive. While concerning MMS, quite a different pattern of ADPRT stimulation in the cell cycle was demonstrated, i.e., the activity of ADPRT stimulation of 10(-3) M MMS was found to be completely dependent on the basal ADPRT activity. In the cells with the highest basal ADPRT activity 12 h after block release, the MMS-induced ADPRT stimulation could not be observed. It was suggested that more than one pathway might be present in ADPRT stimulation induced by DNA-damaging chemicals, and the cells synchronized in late G1 stage might be the most suitable for demonstrating poly(ADP-ribose) synthesis after DNA damage.

Genotoxic activity of caramel on Salmonella and cultured mammalian cells

The genetic activity of 2 commercial caramel preparations, manufactured either by heating the malt sugar solution directly (non-ammoniated caramel) or by heating it with ammonia (ammoniated caramel) was studied in the Salmonella mutagenicity test and UDS assay in cultured mammalian cells. The non-ammoniated caramel was found to be mutagenic to S. typhimurium TA100, while the ammoniated one was genetically active in all the tester strains used, namely TA100, TA97 and TA98. It was also demonstrated that non-ammoniated caramel was capable of inducing UDS in cultured human amnion FL cells, but for the ammoniated one, no such activity was observed. Furthermore, based on the results obtained in the DNA synthesis inhibition assay, it was suggested that the DNA synthesis inhibition seen in our experiments with the ammoniated caramel was probably not of DNA damage in origin. These data indicate that the mutagenic fractions formed during ammoniated and non-ammoniated caramelization were quite different.

A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.