Cucurbitacin B induces apoptosis in colorectal cells through reactive oxygen species generation and endoplasmic reticulum stress pathways

Cucurbitacin B (CuB) is a member of the cucurbitacin family, which has shown potent anticancer pharmacological activity. Prolonged or severe endoplasmic reticulum stress (ERS) induces apoptosis; therefore, the present study investigated whether CuB may activate the ERS pathway to induce apoptosis. HT-29 and SW620 colorectal cancer (CRC) cells were treated with a range of concentrations of CuB for 48 h, and the viability and proliferation of cells were determined using Cell Counting Kit 8 (CCK8) and colony formation assays. Subsequently, the appropriate CuB concentration (5 µM) was selected for treatment of CRC cells for 48 h. Western blot analysis was used to measure the expression levels of ERS-related proteins, flow cytometry was used to evaluate apoptosis, the dichlorodihydrofluorescein diacetate fluorescent probe was used to detect reactive oxygen species (ROS) production, and the relationship between ROS and ERS was determined by western blot analysis. Furthermore, flow cytometry was used to evaluate apoptosis after treatment with the ERS inhibitor 4-phenylbutyric acid, the ROS inhibitor N-acetylcysteine and following knockdown of CHOP expression. In addition, western blot analysis was performed to measure Bax and Bcl2 protein expression levels, and a CCK8 assay was performed to evaluate the viability of cells following knockdown of CHOP. Notably, CuB treatment increased apoptosis and inhibited cell proliferation in CRC cell lines, and these effects were mediated by ROS and ROS-regulated activation of the PERK and XBP1 ERS pathways. In conclusion, CuB may induce apoptosis in HT-29 and SW620 CRC cells via ROS and ERS.

LPCAT1 enhances the invasion and migration in gastric cancer: Based on computational biology methods and in vitro experiments

BACKGROUND AND AIM

The biological functions and clinical implications of lysophosphatidylcholine acyltransferase 1 (LPCAT1) remain unclarified in gastric cancer (GC). The aim of the current study was to explore the possible clinicopathological significance of LPCAT1 and its perspective mechanism in GC tissues.

MATERIALS AND METHODS

The protein expression and mRNA levels of LPCAT1 were detected from in-house immunohistochemistry and public high-throughput RNA arrays and RNA sequencing. To have a comprehensive understanding of the clinical value of LPCAT1 in GC, all enrolled data were integrated to calculate the expression difference and standard mean difference (SMD). The biological mechanism of LPCAT1 in GC was confirmed by computational biology and in vitro experiments. Migration and invasion assays were also conducted to confirm the effect of LPCAT1 in GC.

RESULTS

Both protein and mRNA expression levels of LPCAT1 in GC were remarkably higher than those in noncancerous controls. Comprehensively, the SMD of LPCAT1 mRNA was 1.11 (95% CI = 0.86-1.36) in GC, and the summarized AUC was 0.85 based on 15 datasets containing 1727 cases of GC and 940 cases of non-GC controls. Moreover, LPCAT1 could accelerate the invasion and migration of GC by boosting the neutrophil degranulation pathway and disturbing the immune microenvironment.

CONCLUSION

An increased level of LPCAT1 may promote the progression of GC.

Ambra1 regulates apoptosis and chemosensitivity in breast cancer cells through the Akt-FoxO1-Bim pathway

The sensitivity of cells to chemotherapeutic agents has a major effect on disease outcome in breast cancer patients. Unfortunately, there are numerous factors involved in the regulation of chemosensitivity, and the mechanisms need to be further investigated. Autophagy/Beclin 1 regulator 1 (Ambra1) is a key protein in the crosstalk between autophagy and apoptosis. It controls the switch between these two processes, which determines whether cells survive or die. Induction of apoptosis is the primary mechanism by which most chemotherapeutic drugs eliminate cancer cells. Recently, Ambra1 has been shown to modulate paclitaxel-induced apoptosis in breast cancer cells via the Bim/mitochondrial pathway, thereby modifying the sensitivity of cells to paclitaxel. However, how Ambra1 regulates Bim expression remains unclear. Here, we further confirmed that Bim plays an indispensable role in Ambra1's regulation of apoptosis and chemosensitivity in breast cancer cells. Furthermore, Ambra1 was found to regulate Bim expression at the transcriptional level through the Akt-FoxO1 pathway. Therefore, we propose a novel pathway, Ambra1-Akt-FoxO1-Bim, which regulates apoptosis and chemosensitivity in breast cancer cells. Thus, Ambra1 may represent a potential target for breast cancer treatment.

Ambra1 inhibits paclitaxel-induced apoptosis in breast cancer cells by modulating the Bim/mitochondrial pathway

Cancer cells often evade apoptosis induced by anti-cancer drugs, which reduces the efficacy of the drugs. Autophagy/Beclin 1 regulator 1 (Ambra1) is a crucial proautophagic protein. It also plays an important role in the execution of apoptosis. However, the mechanism by which Ambra1 regulates apoptosis has not been fully clarified. Moreover, whether Ambra1 participates in the regulation of paclitaxel-induced apoptosis in breast cancer cells is not clear. Here, we show that Ambra1 inhibits paclitaxel-induced apoptosis in breast cancer cells. Moreover, Bim and mitochondria are key effectors of Ambra1 in this process. Thus, Ambra1 is a protein that makes breast cancer cells resistant to apoptosis by modulating the Bim/mitochondrial pathway. Therefore, Ambra1 may be a potential target for the treatment of breast cancer.

[The analysis of serum allergen spectrum in 0－12 years old children with allergic diseases in Liaoning Province]

Objective:To explore the distribution and characteristics of allergens in children aged 0－12 years old in liaoning province. Method:46 620 children with suspected allergic diseases were grouped according to age, sex and detection time. Then allergen detections were conducted. The distribution of allergen in different groups was analyzed. Result:Most children were sensitized to single allergen, followed by a double positive. 98.08% children showed sensitivities to up to five kinds of allergen. The allergen spectrum of patients in different age groups was slightly different. With the increase of age, the rate, degree and number of allergen positive are generally on the rise. The positive rate and degree of each allergen were statistically significant in different age groups, seasons and genders, but not the trend and degree of variation. The onset time in this region is relatively concentrated in July to September, and the incidence of allergen in summer and autumn is higher than that in winter and spring. Conclusion:In Liaoning Province, household dust mites, animal dander, egg white, milk are the main allergens in patients with allergic disease, and the onset time is relatively concentrated in summer and autumn. Clear the main allergens, the region characteristic and changing trend is conducive to the treatment of allergic disease take effective and preventive measures.

Ambra1 modulates the sensitivity of breast cancer cells to epirubicin by regulating autophagy via ATG12

The sensitivity of breast cancer cells to epirubicin (EPI) is closely related to the efficacy of the drug and the prognosis of patients. A growing body of research has suggested that autophagy is involved in the treatment of a variety of cancers, including breast cancer, and modifies the sensitivity of anticancer drugs. However, the mechanism by which autophagy participates in cancer therapy and modulates drug sensitivity has not been fully elucidated. In this study, we showed that the expression of Autophagy/Beclin 1 regulator 1 (Ambra1), a key protein of autophagy, was negatively correlated with EPI sensitivity in breast cancer cells. In addition, it altered the sensitivity of breast cancer cells to EPI by regulating EPI-induced autophagy. As a potential mechanism, we demonstrated that autophagy-related protein 12 (ATG12) was a downstream protein that Ambra1-regulated EPI-induced autophagy. Therefore, Ambra1 plays an important role in regulating the sensitivity of breast cancer cells to EPI. And the regulatory effect of Ambra1 on EPI sensitivity is achieved through the regulation of autophagy by targeting ATG12. Overall, we propose a novel mechanism by which autophagy modulates the sensitivity of breast cancer cells to EPI. ATG12 is a novel targeting protein of Ambra1 in regulating EPI-induced autophagy. In addition, the important role of Ambra1 in modulating the sensitivity of breast cancer cells to EPI is confirmed in vivo. This finding indicates that Ambra1 might be a target for developing breast cancer treatments.

Characterization of a novel psychrophilic and halophilic β-1, 3-xylanase from deep-sea bacterium, Flammeovirga pacifica strain WPAGA1

β-1, 3-Xylanase is one of the most important hydrolytic enzymes to prepare oligosaccharides as functional foods in seaweed industry. However, less than five β-1, 3-xylanases have been experimentally expressed and characterized; moreover, none of them is psychrophilic and salt tolerant. Here, we mined a novel β-1, 3-xylanase (Xyl512) from the genome of the deep-sea bacterium Flammeovirga pacifica strain WPAGA1 and biochemically characterized it in detail. The Xyl512 did not contain any carbohydrate-binding module; the catalytic domain of it belonged to the glycoside hydrolase family 26. The optimum temperature and pH of the purified β-1, 3-xylanase was 20 °C and pH 7.0 in the condition of no NaCl. However, they shifted to 30 °C and 7.5 with 1.5 mol/L NaCl, respectively. In this condition (1.5 mol/L NaCl), the overall activity was 2-fold as high as that without NaCl. Based on the residue interactions and the electrostatic surfaces, we addressed the possible mechanism of its adaption to low temperature and relative high NaCl concentration. The Xyl512 showed significantly reduced numbers of hydrogen bonds leading to a more flexible structure, which is likely to be responsible for its cold adaptation. While the negatively charged surface may contribute to its salt tolerance. The β-1, 3-xylanase we identified here was the first reported psychrophilic and halophilic one with functionally characterized. It could make new contributions to exploring and studying the β-1, 3-xylanase for further associated investigations.

Clinical value of miR-182-5p in lung squamous cell carcinoma: a study combining data from TCGA, GEO, and RT-qPCR validation

BACKGROUND

MiR-182-5p, as a member of miRNA family, can be detected in lung cancer and plays an important role in lung cancer. To explore the clinical value of miR-182-5p in lung squamous cell carcinoma (LUSC) and to unveil the molecular mechanism of LUSC.

METHODS

The clinical value of miR-182-5p in LUSC was investigated by collecting and calculating data from The Cancer Genome Atlas (TCGA) database, the Gene Expression Omnibus (GEO) database, and real-time quantitative polymerase chain reaction (RT-qPCR). Twelve prediction platforms were used to predict the target genes of miR-182-5p. Protein-protein interaction (PPI) networks and gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to explore the molecular mechanism of LUSC.

RESULTS

The expression of miR-182-5p was significantly over-expressed in LUSC than in non-cancerous tissues, as evidenced by various approaches, including the TCGA database, GEO microarrays, RT-qPCR, and a comprehensive meta-analysis of 501 LUSC cases and 148 non-cancerous cases. Furthermore, a total of 81 potential target genes were chosen from the union of predicted genes and the TCGA database. GO and KEGG analyses demonstrated that the target genes are involved in pathways related to biological processes. PPIs revealed the relationships between these genes, with EPAS1, PRKCE, NR3C1, and RHOB being located in the center of the PPI network.

CONCLUSIONS

MiR-182-5p upregulation greatly contributes to LUSC and may serve as a biomarker in LUSC.

Autophagy facilitates multidrug resistance development through inhibition of apoptosis in breast cancer cells

Acquired multidrug resistance (MDR) is the main mechanism of chemotherapeutic drugs resistance. Nevertheless, the mechanisms of MDR are complex and still not very clear. Recently, including our previous study, several studies have revealed that macroautophagy (here referred to as autophagy) induced by anti-cancer drugs in breast cancer cells may facilitate the development of resistance to epirubicin (EPI), paclitaxel (PTX), tamoxifen or herceptin. Whereas there are a few studies on the relationship between autophagy and MDR, especially the studies designed directly employing induced resistant breast cancer cells. Based on previous study, we explored the relationship between autophagy and MDR. The results showed that induced EPI-resistant MCF-7er and SK-BR-3er cells were simultaneously resistant to PTX and vinorelbine (NVB), which demonstrated that the cells obtained MDR phenotype. Furthermore, PTX and NVB could also induce autophagy in MCF-7er and SK-BR-3er cells, and the induced autophagy protected the cells from apoptosis, which facilitated the development of resistance to PTX and NVB. Thus, autophagy promoted the development of MDR in breast cancer cells through inhibition of apoptosis. In addition, we found that P-glycoprotein (Pgp) was overexpressed in MCF-7er and SK-Br-3er cells. And we preliminarily investigated the relationship between autophagy and P-glycoprotein (Pgp). The results showed that the expression of the protein did not obviously change despite the inhibition of autophagy. Therefore, the role of Pgp in the development of MDR might be independent of autophahy. Also this finding implies that autophagy might be a target to overcome MDR in breast cancer cells, and clinical use autophagy inhibitors might be one of the important strategies for overcoming MDR in breast cancer therapy.

KEYWORDS

Autophagy, apoptosis, multidrug resistance, breast cancer, chemotherapy.

Rapid and specific determination of DNA adducts for clinical diagnosis of poisoning and disease associated with aristolochic acid

1. A liquid chromatography-mass spectrometry method was developed to detect and characterise aristocholic acid-DNA adducts in biological samples. 2. The detection of DNA adducts in plasma, urine or the cells found in urine may be useful to support the diagnosis and monitoring of aristocholic acid-associated poisoning and disease. 3. Efforts should be made to improve the sensitivity and specificity of this approach for the detection and characterisation of exposure to other mutagens/carcinogens.

Assessment of risk of PCDD/Fs and dioxin-like PCBs in marine and freshwater fish in Pearl River Delta, China

Fish consumption is known to be beneficial to human health. However since the age of industrialization, the released/disposed chemical pollutants into water systems make fish a source of various environmental toxicants to humans. In oceanic cities with heavy industrial activities, fish products contribute the greatest proportion of exposure to pollutants. In this study, risks and potential effects of dioxins to health of coastal populations in the Pearl River Delta were assessed. Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) were measured in common fish species purchased at local markets. Concentrations of total dioxins in fish ranged from 0.481 to 9.05 pg TEQ/g wet weight were similar to the lesser concentrations reported for fish from other countries. The greatest concentrations of dioxins were measured in mandarin fish, a carnivorous freshwater fish. Exposure of murine primary leydig and ovarian cells to 2,3,7,8-tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) reduced the synthesis of progesterone, testosterone and/or estrogen. The reductions were probably via inhibitory effects on the expression of the steroidogenic enzymes, steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage enzyme (P450scc). Based on these reproductive parameters, the concentrations of dioxins and dioxin-like residues represent a moderate health risk due to consumption of fish.

Gene profiling after knocking-down expression of nucleostemin in Hela cells using oligonucleotide DNA microarray

Nucleostemin (NS) is preferentially and exclusively expressed in the stem cells and cancer cells, but not in differentiated adult tissues and cells. NS is likely to take part in controlling the proliferation and differentiation switch in stem cells and progenitor cells. Its deregulation in cancer also contributes to the elevated proliferation and undifferentiation of cancer cells. However, the mechanisms by which NS helps to maintain both cancer and stem cells in undifferentiated state remain unclear. In this study, we carried out gene profilings using oligonucleotide DNA microarray after knocking down the expression of NS in Hela cells. Of the 21,329 genes, 200 genes were found differentially expressed in NS silenced Hela cells with > 2 fold ratio (either > 2 or < 0.5). Category analysis indicated these differential genes were mainly related with cancer pathogenesis, cell death, cell growth and proliferation. NS related gene pathway analysis suggested NS was mostly involved in the networks of cell cycle and differentiation controls. p53 may not be the only partner of NS in its regulated pathways. c-Myc may directly or indirectly interact with it to control the proliferation and differentiation switch in cancer cells. Our study provides a general view of the NS-target genes, and indicates the possible pathways in which NS plays its role in proliferation control.

The effect of vascular endothelial growth factor on the healing of ischaemic skin wounds

The effect of exogenous vascular endothelium growth factor (VEGF) on wound healing in an ischaemic skin flap model was evaluated in this study. Seventy-two Sprague-Dawley rats were used. Normal incisional wound and H-shaped double flaps were used as the wound models. The study was divided into two parts. In Part I, VEGF protein levels were determined from the incisional and H-shaped ischaemic wounds at 12 and 24 h, postoperatively. In Part II, tensile strength and immunohistochemical stains were examined to determine the level of microvessel density (MVD) at 1 and 2 weeks, postoperatively in simple incisional wounds, ischaemic wounds, and ischaemic wounds following 1 ml (1 microg/ml) exogenous VEGF injections into the subcutaneous tissue. The results showed a significantly higher level of VEGF protein in the ischaemic wounds than the incisional wounds. Tensile strength was statistically higher in the incisional wound group and in the ischaemic flap wounds with VEGF treatment compared to the ischaemic flaps with no treatment at 1 week, postoperatively (p>0.05). MVD data indicated that ischaemic wound repair with VEGF treatment had significantly higher MVD than the normal incisional wounds and ischaemic wounds without treatment. We conclude that exogenous application of VEGF can increase early angiogenesis and tensile strength in the ischaemic wound.

The effect of glucose during ischemia on brain ATP, lactate, and glutamate in piglets

Glucose worsens hypoxic-ischemic brain injury in 0- to 3-day-old piglets. Piglets were randomly assigned to have blood glucose increased with glucose infusion (n = 12), or decreased with insulin (n = 13), or a sham group (n = 10). In the insulin and glucose groups at time 0, both carotid arteries were clamped, and blood was withdrawn to reduce the blood pressure one third. At time 15 min FiO2 was reduced to 6%. At time 30 min cerebrospinal fluid (CSF) was taken for glutamate, and the brains were frozen. The shams had CSF removed and brains frozen without hypoxia or ischemia. Brain ATP was 1.7 +/- 0.09 mumol/g wet weight in the shams, 0.98 +/- 0.09 in the glucose group (p < 0.01 vs. sham), and 0.52 +/- 0.10 in the insulin group (p < 0.01 vs. glucose). Brain lactate levels were 4.3 +/- 1.0 mumol/g wet weight in the shams, 18.3 +/- 1.9 in the insulin group (p < 0.01 vs. sham), and 29.4 +/- 2.6 in the glucose group (p < 0.01 vs. insulin). CSF glutamate was 9.3 +/- 3.6 microM in the glucose group, 9.6 +/- 3.5 in the insulin group, and 2.2 +/- 0.9 in the shams (p < 0.05, glucose and insulin > sham). The Bmax for MK-801 binding was 2.3 +/- 0.2 pmol/mg protein in the glucose group, 2.6 +/- 0.1 in the insulin group (p < 0.05 vs. sham), and 2.0 +/- 0.2 in the shams, and the Kd was the same in the three groups (p = nonsignificant). Brain Na+,K(+)-ATPase was the same in the three groups (p = nonsignificant). Providing additional glucose preserves ATP during hypoxic-ischemic brain injury in the piglet but does not change CSF glutamate or brain-801 binding and probably worsens outcome by elevating brain lactate levels above the threshold for cellular injury.

Ultrastructural, protein, and lipid changes in liver associated with chlordecone treatment of mice

Pretreatment of mice with chlordecone (CD) reduced hepatic accumulation of a subsequent dose of [14C]CD without significantly changing [14C]CD biotransformation. To determine if CD-induced changes in hepatic [14C]CD accumulation were coincident with altered cell composition, we examined the effects of CD on hepatic protein and lipid content, on fatty acid profiles of liver and kidney, and on the ultrastructure of hepatocytes. SDS-polyacrylamide gel electrophoresis detected an apparent CD dose-related increase in a microsomal protein with a molecular weight of about 23 kDa. Total liver or kidney lipid contents were not altered by CD but relative amounts of several hepatic fatty acids were changed. CD caused marked hepatic mitochondrial swelling, increased amounts of endoplasmic reticulum, apparently increased numbers of peroxisome-like structures, and decreased numbers of lipid droplets in cytoplasm of hepatocytes. Numbers of lipid droplets were not decreased in perisinusoidal fat storage cells. In addition, the numbers of cytoplasmic lipoprotein vesicles were apparently increased in some hepatocytes. Overall these changes indicated an increased hepatocyte secretory activity and suggested that CD changed hepatocellular lipid transport, storage, and metabolism pathways.

Benzothiazepine binding domain of purified L-type calcium channels: direct labeling using a novel fluorescent diltiazem analogue

We have synthesized a series of N-propylamino-substituted benzazepinones (NPSBs) as specific probes for the benzothiazepinone (BTZ) binding domain of muscle L-type calcium channels (LTCCs). NPSBs were identified which possess high affinity for the channel after purification. We synthesized a fluorescent NPSB, DMBODIPY-BAZ, as the first benz(othi)azepinone derivative known to reversibly label partially purified LTCCs. DMBODIPY-BAZ binds to the partially purified channel with high affinity (Kd = 25 nM, Bmax = 580 pmol/mg of protein). Fluorescence resonance energy transfer (FRET) occurred between tryptophan residues of the channel protein and the DMBODIPY fluorophore upon specific drug binding. FRET was exploited to allow highly time-resolved detection of specific drug binding kinetics. We found that the dissociation half-life (t1/2) of DMBODIPY-BAZ decreased with the concentration of an unlabeled competitor, which indicates ligand-induced accelerated dissociation. In contrast, t1/2 was concentration-dependently increased by the dihydropyridine (DHP) (+)-isradipine. These kinetic properties of DMBODIPY-BAZ indicate that a high-affinity BTZ binding domain also exists on purified LTCCs. NPSBs represent novel tools to provide further insight into the molecular pharmacology of the BTZ binding domain on LTCCs.

Tumorigenic activity of fluoranthene, 2-methylfluoranthene and 3-methylfluoranthene in newborn CD-1 mice

Fluoranthene (FA) is frequently among the more abundant components detected in environmental mixtures of polycyclic aromatic hydrocarbons. Several methylated fluoranthenes, although less prevalent than FA, have also been detected as environmental pollutants. While FA is inactive as a tumorigenic agent on mouse skin, it does induce lung and liver tumors in newborn mice. Among the five isomers of methylfluoranthene, only 2-methylfluoranthene (2-MeFA) and 3-methylfluoranthene (3-MeFA) are active as tumor initiators on mouse skin. A comparative bioassay was performed to determine the relative tumorigenic activity of FA, 2-MeFA and 3-MeFA in newborn CD-1 mice. All three compounds were assayed at doses of 3.46 and 17.3 mumol. The bioassay was terminated when mice were 1 year old. At a dose of 17.3 mumol, FA and 2-MeFA induced a similar incidence of lung tumors (65-96%) in both male and female mice. However, tumor multiplicity in the lung was different between FA and 2-MeFA. At a dose of 17.3 mumol, the multiplicity of lung tumors observed for mice administered 2-MeFA ranged from 3.04 to 3.94 tumors per mouse. In contrast, animals treated with FA developed only an average of 1.12-2.45 tumors per mouse. 3-MeFA did not induce a statistically significant incidence of lung tumors in either male or female mice. All three compounds when administered to newborn mice did induce a significant incidence of liver tumors among male mice. The relative tumorigenic potency observed was FA > or = 2-MeFa >> 3-MeFA. Only 2-MeFA at a dose of 17.3 mumol was tumorigenic in the liver of female mice. These bioassay results are contrasted with prior studies on the in vitro genotoxic activity and metabolic activation pathways of FA, 2-MeFA and 3-MeFA.

Evaluation of the tumor-initiating activity of 4-, 5-, 6-, and 7-fluorobenzo[b]fluoranthene in mouse skin

Benzo[b]fluoranthene and 4-, 5-, 6-, and 7-fluorobenzo[b]fluoranthene were evaluated for tumor-initiating activity in mouse skin. These fluorinated benzo[b]fluoranthene derivatives were assayed at doses of 400, 120, 40, and 10 nmol per mouse. Similar tumorigenic activity was observed for benzo[b]fluoranthene and 5-fluorobenzo[b]fluoranthene. While 4-fluorobenzo[b]fluoranthene did produce a significant tumorigenic response at each dose assayed, substantially fewer tumors per mouse were observed compared to benzo[b]fluoranthene at initiator doses at or above 120 nmol. Only moderate tumorigenic activity was observed for 6- and 7-fluorobenzo[b]fluoranthene. Both of these fluorinated derivatives were significantly less tumorigenic (P < 0.05) than 4-fluorobenzo[b]fluoranthene when administered at initiator doses at or below 120 nmol. These results were unanticipated in view of data which indicate that metabolism of trans-9,10-dihydro-9,10-dihydroxybenzo[b]-fluoranthene to trans-9,10-dihydro-5,9,10-trihydroxybenzo[b]fluoranthene represents a principal activation mechanism of benzo[b]fluoranthene in mouse skin. The potential of fluorine substitution not only to inhibit metabolism, but also to alter the genotoxic activity of those metabolites which do form could explain the tumorigenic activity observed with these fluorinated derivatives of benzo[b]fluoranthene. These data suggest caution in the interpretation of results based exclusively upon the assumption that the only influence of fluorine substitution is inhibition of the formation of specific metabolites.

Detection of the major DNA adducts of benzo[b]fluoranthene in mouse skin: role of phenolic dihydrodiols

The primary mechanism of activation of benzo[b]fluoranthene (B[b]F) to a genotoxic agent does not involve the bay region dihydrodiol epoxide trans-9,10-dihydroxy-anti- 11,12-epoxy-9,10,11,12-tetrahydrobenzo[b]fluoranthene (B[b]F-9,10-DE). Previous results have suggested that the major DNA adduct(s) formed in vivo with B[b]F are more polar than those formed from B[b]F-9,10-DE. Employing newly-developed synthetic methods for the formation of B[b]F derivatives, trans-9,10-dihydro-5,9,10-trihydroxybenzo[b]fluoranthene (5-OH-B[b]F-9,10-diol) and trans-9,10-dihydro-6,9,10-trihydroxybenzo[b]fluoranthene (6-OH-B[b]F-9,10-diol) were synthesized and evaluated for tumor-initiating activity at initiation doses of 0.04, 0.12, and 0.4 mumol per mouse. In contrast to previous bioassay results, both of these phenolic dihydrodiols exhibited tumor-initiating activity. 5-OH-B[b]F-9,10-diol was the more potent tumor initiator, inducing a 90% incidence of tumor-bearing mice with an average of 7.50 tumors per mouse at a total initiator dose of 0.4 mumol. 6-OH-B[b]F-9,10-diol was significantly less active as a tumor initiator in this bioassay, inducing a 50% incidence of tumor-bearing mice with an average of 0.60 tumor per mouse at a total dose of 0.4 mumol. 32P-Postlabeling analysis was employed to evaluate the DNA adducts formed in vivo in mouse skin from both 5- and 6-OH-B[b]F-9,10-diol. HPLC analysis of B[b]F-DNA adducts formed in mouse skin demonstrated the presence of a single major adduct together with four additional minor adducts. The DNA adducts formed with 5-OH-B[b]F-9,10-diol had identical HPLC retention to the major and one of the minor adducts observed for B[b]F. These two DNA adducts account for 58% of the modified nucleotides detected in mouse skin following the topical application of B[b]F. Methods for the preparation of trans-9,10-dihydroxy-anti-11,12-epoxy-5-hydroxy-9,10,11,12- tetrahydrobenzo[b]fluoranthene (5-OH-B[b]F-9,10-DE) were developed. The DNA adducts formed with 5-OH-B[b]F-9,10-DE were similar to the adducts formed with 5-OH-B[b]F-9,10-diol. The results of the DNA binding studies along with the tumor-initiating data indicate that 5-OH-B[b]F-9,10-diol is the major proximate tumorigenic metabolite of B[b]F on mouse skin. Studies performed with deoxyguanosine 3'-phosphate suggest that the principal adducts formed with anti-5-OH-B[b]F-9,10-DE are the result of the interaction with deoxyguanosine.

Protection from CCl4 toxicity by prestimulation of hepatocellular regeneration in partially hepatectomized gerbils

The present investigation was undertaken to test our hypothesis that the slow responses of hepatocellular regeneration and tissue repair after CCl4-induced liver injury are responsible for the high sensitivity of gerbils to the hepatotoxic and lethal effects of CCl4. These studies were conducted in normal and actively regenerating livers using male gerbils 5 or 15 days after partial (2/3) hepatectomy (PH5 and PH15, respectively), or those undergoing sham operation (SH). An LD50 dose of CCl4 (80 microL/kg, i.p.) resulted in a mortality (21%) significantly (P less than 0.05) less than 50% in PH5 gerbils 48 hr after CCl4 administration, whereas the mortality observed in PH15 or SH gerbils was not significantly different from 50%. The elevations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly (P less than 0.05) less in PH5 gerbils than in PH15 or SH groups after the administration of either the LD50 dose or a low dose (15 microL/kg) of CCl4. Histopathological and histomorphometric examinations also indicated that CCl4-induced liver injury was less severe in PH5 gerbils than in the PH15 and SH groups. The hepatic microsomal cytochrome P450 content measured before CCl4 administration in the PH5 gerbils was decreased (26%) significantly (P less than 0.05) as compared with the SH group, but was not significantly different from that of PH15 gerbils. In vivo metabolism of 14CCl4 and lipid peroxidation in liver tissue were not significantly different among the various groups. Therefore, the protection against CCl4 toxicity observed in PH5 gerbils is unlikely to be due to decreased bioactivation of CCl4 or lipid peroxidation in that group. [3H]Thymidine incorporation into hepatocellular nuclear DNA was 4- to 5-fold higher in PH5 gerbils than in the PH15 and SH groups, indicating active hepatocellular proliferation in PH5 gerbils. [3H]Thymidine incorporation was further increased significantly (P less than 0.05) 24 hr after challenge with a low dose of CCl4 in PH5 gerbils, whereas it remained low until 48 hr after the CCl4 injection in the PH15 or SH group. The protection against CCl4 toxicity afforded by partial hepatectomy was closely associated with active hepatocellular regeneration. The overall results confirm the concept that the high sensitivity of gerbils to CCl4 is due to very sluggish hepatocellular regeneration and tissue repair response to the CCl4-induced liver injury.

Lethal effects of CCl4 and its metabolism by Mongolian gerbils pretreated with chlordecone, phenobarbital, or mirex

Gerbils are much more sensitive to the hepatotoxic and lethal effects of CCl4 than rats as indicated by 48-hr LD50 values (0.08 vs 2.8 ml/kg). On the other hand, gerbils are refractory to chlordecone (CD) potentiation of CCl4 toxicity. To investigate the possible mechanism underlying the high sensitivity of gerbils to CCl4 lethality, the metabolism of CCl4 was studied in gerbils pretreated with dietary CD, phenobarbital (PB), or mirex (M) at 10, 225, and 10 ppm, respectively. The hepatic content of 14CCl4, the expiration of 14CCl4 and 14CCl4-derived 14CO2, and lipid peroxidation were measured and the results were compared with the previous data for rats. After the 15-day dietary pretreatment, male gerbils (60-80 g) received 14CCl4 (0.08 ml/kg; sp act 0.04 mCi/mmol) ip in corn oil and the radioactivity present in the expired air was collected for 6 hr. More than 80% of the parent compound as represented by the 14C-label in the toluene trap was expired in 6 hr regardless of the pretreatments. Expiration of 14CO2 measured during the 6 hr after 14CCl4 administration in control gerbils was 3.5-fold more than that in rats and was significantly increased in pretreated groups (M greater than PB greater than CD). PB and M pretreatments resulted in a significant increase of 14C-label bound to the nonlipid fraction of the liver as compared with CD-treated or control gerbils. The radiolabel present in the livers of control gerbils was 5-fold higher than that of rats. In vivo lipid peroxidation measured as diene conjugation in lipid extracts from the livers was lower in gerbils than in rats, and none of the pretreatments significantly affected lipid peroxidation. The serum alanine aminotransferase and aspartate aminotransferase were significantly elevated at 6 hr after CCl4 injection in all groups of gerbils. These data indicate that the more extensive metabolism of CCl4, as represented by 14CO2 formation and 14C-label bound to hepatic tissue, in gerbils as compared with rats, may partially explain the high sensitivity of gerbils to CCl4 toxicity. However, the enhanced metabolism of CCl4 found in CD-, PB-, or M-pretreated gerbils did not lead to amplified hepatotoxic and lethal effects of CCl4. The reason gerbils may be refractory to CD amplification of CCl4 injury might be associated with other factors yet to be investigated.