Research advances in the degradation of aflatoxin by lactic acid bacteria.

Aflatoxins are toxic secondary metabolites that often contaminate food and animal feed, causing huge economic losses and serious health hazards. Aflatoxin contamination has become a major concern worldwide. Biological methods have been used to reduce aflatoxins in food and feed by inhibiting toxin production and detoxification. Among biological methods, lactic acid bacteria are of significant interest because of their safety, efficiency, and environmental friendliness. This study aimed to review the mechanisms by which lactic acid bacteria degrade aflatoxins and the factors that influence their degradation efficiency, including the action of the lactic acid bacteria themselves (cell wall adsorption) and the antifungal metabolites produced by the lactic acid bacteria. The current applications of lactic acid bacteria to food and feed were also reviewed. This comprehensive analysis provided insight into the binding mechanisms between lactic acid bacteria and aflatoxins, facilitating the practical applications of lactic acid bacteria to food and agriculture.

3, 3'-diindolylmethane, a natural aryl hydrocarbon receptor agonist, alleviates ulcerative colitis by enhancing "glycolysis-lactate-STAT3″ and TIP60 signals-mediated Treg differentiation.

BACKGROUND: Aryl hydrocarbon receptor (AhR) plays an important role in the occurrence and development of ulcerative colitis (UC). In this study, the effect and mechanism of 3, 3'-diindolylmethane (DIM), the classical AhR agonist, on UC was investigated from the angle of recovering the balance of Th17/Treg. METHODS: The in vivo colitis model was established in mice by using dextran sulfate sodium, and CD4+ T cells were used to simulate the in vitro differentiation of Treg and Th17 cells. The proportions and related factors of Th17 and Treg cells were measured using flow cytometry, Q-PCR and western blotting. The glycolysis was evaluated by examining the glucose uptake, glucose consumption and lactate production using kits or immunofluorescence. The activation of AhR was detected by western blotting and the XRE-luciferase reporter gene. The co-immunoprecipitation, transfection or other methods were selected to investigate and identify the signaling molecular pathway. RESULTS: DIM significantly attenuated symptoms of colitis mice by rebuilding the balance of Th17/Treg in anoxic colons. In hypoxia, a more potent promotion of Treg differentiation was showed by DIM relative to normoxia, and siFoxp3 prevented DIM-suppressed Th17 differentiation. DIM repressed the excessive glycolysis in hypoxia evidenced by down-regulated glucose uptake, lactate production, Glut1 and HK2 levels. Interestingly, IL-10, the function-related factor of Treg cells, showed the feedback effect of DIM-suppressed glycolysis. Besides, 2-deoxy-D-glucose, HK2 plasmid and IL-10 antibody prevented increase of DIM on the expression of Foxp3 at the transcriptional level and subsequent Treg differentiation through the lactate-STAT3 pathway, and reasons for the direct improvement of DIM on Foxp3 protein was attributed to promoting the formation of HIF-1α/TIP60 complexes as well as subsequent acetylation and protein stability. Finally, AhR dependence and mechanisms for DIM-improved Treg differentiation in vitro and in vivo were well confirmed by using plasmids or inhibitors. CONCLUSIONS: DIM enhances activation of AhR and subsequent "glycolysis-lactate-STAT3″ and TIP60 signals-mediated Treg differentiation.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane.

N-doped mesoporous carbon spheres (NHMC@mSiO2 ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H2 , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

Therapeutic effect and mechanism of combination therapy with ursolic acid and insulin on diabetic nephropathy in a type I diabetic rat model.

This work aims to investigate the therapeutic effect of ursolic acid (UA) plus insulin (In) on diabetic nephropathy (DN) in streptozotocin (STZ)-induced T1DM rats. The experimental groups and operational details are as follows: A total of thirty-two SD rats were divided into four groups: the DN model group (DN, n = 8), DN + In treatment group (DN + In, n = 8), DN + In + UA administration group (DN + In + UA, n = 8), and negative control group (control, n = 8). After 8 weeks, changes in renal function indices and pathological damage were assessed. Additionally, oxidative stress-, apoptosis-, and fibrosis-related proteins in kidney tissue were measured. Compared with the control group, the vehicle group showed higher levels of creatine, blood urea nitrogen, urinary protein, apoptosis, and lipid peroxidation; lower superoxide dismutase levels; more severe levels of pathological kidney damage and renal fibrosis; and a deepened degree of EMT and EndMT. Better outcomes were achieved with the combined treatment than with insulin-only treatment. The improvement of TGF-ß1, phosphorylated p38 MAPK, FGFR1, SIRT3 and DPP-4 expression levels in renal tissues after combination therapy was greater than that after insulin-only treatment. This study shows that the combination of insulin and UA significantly improved the pathological changes in the renal tissue of T1DM rats, and the underlying mechanism may be related to improving apoptosis and oxidative stress by regulating p38 MAPK, SIRT3, DPP-4 and FGFR1 levels, thereby blocking TGF-ß signaling pathway activation and inhibiting EMT and EndMT processes.

A flavonoid derivative of icariside II (YS-10) improves erectile dysfunction in radiation-injured rats via oxidative stress pathway.

Background: We explored the preventive effect and mechanism of YS-10, a novel synthesized flavonoid derivative based on the structure of icariside II (ICA II), on a rat model of radiation-induced erectile-dysfunction (Ri-ED). Methods: Eighteen 10-week-old male Sprague-Dawley (SD) rats were randomly divided into 3 groups. Six rats were used as the control group (Control), and the remaining 12 were given a single X-ray irradiation of 20 Gy in the prostate and then randomly divided into the radiation injury group (Ri-ED group) and YS-10 treatment group (Ri-ED+YS-10, 2.5 mg/kg/day). After 4 weeks of drug administration and a 2-week drug washout period in the YS-10 treatment group, the erectile function of the animals was evaluated, and the tissues were collected for histopathological analysis and detection of oxidative stress indicators. Results: After radiation injury, the ratio of maximum intracavernosal pressure (ICP) to mean arterial pressure (MAP), the number of neuronal nitric oxide synthase (n-NOS) positive nerve fibers in the penis cavernosa, endothelial cell content, and n-NOS and endothelial nitric oxide synthase (e-NOS) proteins in the Ri-ED group were significantly lower than those in control group. Compared with the control group, the Ri-ED group had lower superoxide dismutase (SOD) levels and higher malondialdehyde (MDA) levels. Compared with the Ri-ED group, the YS-10 group had a significant increase in the ratio of ICP/MAP in the corpus cavernosum (0.59±0.06 vs. 0.43±0.06, P<0.01), the number of n-NOS positive nerve fibers, and the content of endothelial cells. The protein content of n-NOS and e-NOS in the corpus cavernosum increased and could significantly reduce the level of MDA (2.67±0.27 vs. 3.25±0.21, P<0.05). Conclusions: As a novel ICA II derivative, YS-10 could significantly improve the erectile dysfunction and pathological damage in rats caused by radiation injury, and its mechanism may be related to the improvement of radiation-induced oxidative stress.

[Preventive and therapeutic effects of Icariside â ¡ on radiation injury-induced erectile dysfunction in rats].

OBJECTIVE: To explore the preventive and therapeutic effects of Icariside Ⅱ (ICAⅡ) on radiation injury-induced ED (Ri-ED) in rats. METHODS: Twenty-four 10-week-old male SD rats received exposure of the prostate to single X-ray irradiation of 20 Gy, and were randomly equally divided into an Ri-ED group (6 survived and 6 died) and a treatment group treated with ICAⅡ at 4.5 mg/kg/d (9 survived and 3 died). Another 6 SD rats were taken as negative controls. After 4 weeks of continuous intragastric administration and 2 weeks of drug elution, the erectile function of the rats was evaluated by measurement of the maximum intracavernous pressure / mean arterial pressure (ICPmax/MAP), and the penile tissues were subjected to immunofluorescence staining, immunohistochemistry, Masson's trichrome staining, Western blot and detection of oxidative stress indicators. RESULTS: Compared with the negative controls, the rats in the Ri-ED group showed significant decreases in ICPmax/MAP (0.76 ± 0.09 vs 0.42 ± 0.06, P < 0.01), the number of nNOS-positive nerve fibers in the corpus cavernosum (10.17 ± 2.64 vs 3.17 ± 1.72, P < 0.01), the content of endothelial cells (1.39 ± 0.30 vs 0.35 ± 0.12, P < 0.01), the expressions of nNOS (0.42 ± 0.08 vs 0.08 ± 0.01, P < 0.01) and eNOS (0.99 ± 0.24 vs 0.12 ± 0.08, P < 0.01) and the activity of superoxide dismutase (SOD) (ï¼»343.73 ± 58.57ï¼½ vs ï¼»153.50 ± 34.06ï¼½ U/mg prot, P < 0.01), but an increase in the malondialdehyde (MDA) level (ï¼»1.80 ± 0.31ï¼½ vs ï¼»3.25 ± 0.21ï¼½ nmol/mg prot, P < 0.01). In comparison with the Ri-ED group, the animals treated with ICAⅡ exhibited remarkably increased ICP/MAP (0.42 ± 0.06 vs 0.66 ± 0.07, P < 0.01), number of nNOS-positive nerve fibers (3.17 ± 1.72 vs 7.33 ± 1.75, P < 0.05), content of endothelial cells (0.35 ± 0.12 vs 1.07 ± 0.36, P < 0.01), and expressions of nNOS (0.08 ± 0.01 vs 0.16 ± 0.05, P < 0.05) and eNOS (0.12 ± 0.08 vs 0.86 ± 0.30, P < 0.01) in the corpus cavernosum, but a decreased level of MDA (ï¼»3.25 ± 0.21ï¼½ vs ï¼»2.17 ± 0.55ï¼½ nmol/mg prot, P < 0.05). In addition, ICAⅡ effectively reduced radiation injury-induced mortality of the rats. CONCLUSION: IcarisideⅡ can significantly improve ED and pathological changes and reduce mortality caused by radiation injury in rats, which may be related to its ability of improving radiation-induced oxidative stress.

Activation of ATM/Chk2 by Zanthoxylum armatum DC extract induces DNA damage and G1/S phase arrest in BRL 3A cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Zanthoxylum armatum DC is a traditional medicinal plant. It is widely used in clinical treatment and disease prevention in China, India and other regions. Modern studies have reported the phytotoxicity, cytotoxicity and the animal toxicity of Zanthoxylum armatum DC, and the damage of genetic material has been observed in plants, but the detailed mechanism has not been explored. Besides, the toxicity of normal mammalian cells has not been evaluated. AIM OF THE STUDY: To evaluate the effects and underlying mechanism of genetic material damage in BRL 3A cells induced by Zanthoxylum armatum DC. MATERIALS AND METHODS: Ultra-High Performance Liquid Chromatography and Orbitrap High-Resolution Mass Spectrometry was used for identification of compounds in methanol extract of Zanthoxylum armatum DC. BRL 3A cells were incubated with different concentrations of methanol extract of Zanthoxylum armatum DC (24 h). The cytotoxicity of extract was assessed with cell viability, LDH release rate, and ROS production. The damage of genetic material was assessed with OTM value of comet cells, cell cycle and the expression levels of p-ATM, p- Chk2, Cdc25A, and CDK2. RESULTS: Ultra-High Performance Liquid Chromatography and Orbitrap High-Resolution Mass Spectrometry investigation revealed the presence of compounds belonging to flavonoid, fatty acid and alkaloid groups. The viability of BRL 3A cells was reduced in a time-dose dependent manner treated by methanol extract of Zanthoxylum armatum DC. It increased LDH release rate and ROS production, activated the DNA double strand damage marker of γH2AX and produced comet cells. In addition, methanol extract of Zanthoxylum armatum DC caused ATM-mediated DNA damage, further phosphorylated Chk2, inhibited cell cycle related proteins, and arrested the G1/S cycle. CONCLUSIONS: Methanol extract of Zanthoxylum armatum DC induces DNA damage and further leads G1/S cell cycle arrest by triggering oxidative stress in the BRL 3A cells. This study provides some useful evidences for its development as an antitumor drug via activation of ATM/Chk2.

[Low-intensity pulsed ultrasound versus low-energy shock wave in the treatment of neurogenic penile erectile dysfunction].

OBJECTIVE: To investigate the effect and safety of low-intensity pulsed ultrasound (LIPUS) versus low-energy shock wave (LESW) in the treatment of neurogenic penile ED in male SD rats. METHODS: Twenty-four 12-week-old male SD rats were randomly divided into four groups of an equal number: sham operation, bilateral cavernous nerves injury (BCNI), LIPUS (300 mW /cm2, 3 times a week for 2 weeks), and LESW (300 strokes once, 3 times a week for 2 weeks). At 28 days after intervention, the erectile function of the rats was assessed by comparing the ratio of maximum intracavernous pressure to mean arterial pressure (ICPmax/MAP), and the histopathological changes in the corpus cavernosum of the penis were observed by immunohistochemistry, immunofluorescence staining, and Masson trichromatic staining. RESULTS: After treatment, the LIPUS and LESW groups, compared with the BCNI group, showed significantly increased ICPmax/MAP ratio (0.56 ± 0.13 and 0.55 ± 0.10 versus 0.35 ± 0.14, P = 0.017 and P = 0.013), improved smooth muscle/collagen value (0.08 ± 0.01 and 0.08 ± 0.02 versus 0.06 ± 0.02, P = 0.017 and P = 0.019), and elevated proportion of smooth muscle to cavernosum (0.20 ± 0.05 and 0.21 ± 0.03 versus 0.15 ± 0.02, P = 0.046 and P = 0.020), with no statistically significant difference between the LIPUS and LESW groups. No obvious adverse reactions were observed in the LIPUS or LESW group. CONCLUSIONS: Both LIPUS and LESW can effectively improve penile erectile function and repair histopathological injury in the animal model of neurogenic ED.

Periodicity and multi-periodicity generated by impulses control in delayed Cohen-Grossberg-type neural networks with discontinuous activations.

This paper discusses the periodicity and multi-periodicity in delayed Cohen-Grossberg-type neural networks (CGNNs) possessing impulsive effects, whose activation functions possess discontinuities and are allowed to be unbounded or nonmonotonic. Based on differential inclusion and cone expansion-compression fixed-point theory of set-valued mapping, several improved criteria are given to derive the positive solution with ω-periodicity and ω-multi-periodicity for delayed CGNNs under impulsive control. These ω-periodicity/ω-multi-periodicity orbits are produced by impulses control. The analytical method and theoretical results presented in this paper are of certain significance to the design of neural network models or circuits possessing discontinuous neuron activation and impulsive effects in periodic environment.

Novel liquid fermentation medium of Cordyceps militaris and optimization of hydrothermal reflux extraction of cordycepin.

In this study, we developed a novel liquid fermentation medium of Cordyceps militaris using pupa powder and wheat bran as nitrogen resources instead of the traditionally used peptone. This process not only reduced the cost by approximately 50%, but increased production by over 30%. Then, we explored a method to extract and purify cordycepin by combining hydrothermal reflux extraction with macroporous resin adsorption, which is inexpensive and suitable for the industrial production. The optimum conditions for hydrothermal reflux were extracting three times at 95 °C with 1:10 sample-to-water ratio, and the cordycepin purity with macroporous resin HPD-100 reached 95.23%.[Formula: see text].

Urological complications after radical hysterectomy with postoperative radiotherapy and radiotherapy alone for cervical cancer.

Radiotherapy is a reliable method to cure cervical cancer patients, but it could cause serious urological complications after the treatment due to the anatomical location of the cervix. The main purpose of this retrospective analysis is to study the incidence, latency, and therapeutic efficacy of urological complications caused by radical hysterectomy with postoperative radiotherapy or radiotherapy alone in patients with cervical cancer.A retrospective analysis was conducted on patients with cervical cancer who received radical hysterectomy with postoperative radiotherapy or radiotherapy alone at the First Hospital of Jilin University between January 2010 and May 2016. The urological complications were confirmed by clinical manifestation, ultrasound, computed tomography (CT), nuclear scintigraphy, and assessment of renal function. All the patients with urological complications received conventional treatment, including conservative, electrosurgery, ureteral stents, nephrectomy, and neoplasty. The onset time of radiation injury symptoms was confirmed according to the medical history and follow-up. The surveillance for the therapeutic effects for these complications was accomplished by cystoscopy, imaging, and laboratory assessment.The overall rate of urological complications after treatment was 3.26%, comprising 2.12% ureteral obstruction, 0.98% radiocystitis, and 0.16% vesicovaginal fistula. The incidence of ureteral obstruction in patients treated with radical hysterectomy with postoperative radiotherapy and radiotherapy alone was not statistically significant (2.18% vs 1.59%, P > .05). The median onset time of radiocystitis and ureteral obstruction was 10 months (0-75 months) and 12 months (2-66.3 months), respectively. The onset time of vesicovaginal fistula was 3.5 months. After the appropriate treatment, the majority of the complications were under control.The incidence of urological complications is acceptable. There was no statistical difference in the risk between patients treated with radical hysterectomy with postoperative radiotherapy and radiotherapy alone. The latency period between radiotherapy and the manifestation of urological complications may be relatively long. So it is crucial to underline long-term follow-up after radiotherapy. The majority of urological complications were alleviated after symptomatic treatment and the patients with cervical cancer achieved long-term remissions or cures.

Rare adrenal gland incidentaloma: an unusual Ewing's sarcoma family of tumor presentation and literature review.

BACKGROUND: Members of the Ewing's sarcoma family of tumor (ESFT) are malignant neoplasms and rarely observed in the adrenal gland. CASE PRESENTATION: We report an extremely exceptional case of ESFT rising from the adrenal gland in a 57-year-old Chinese man. The patient was hospitalized with abdominal swelling for 2 months. Computed tomography (CT) scan revealed a nearly-circular mass measuring about 8.1 × 10.6 cm in the right adrenal region. The patient underwent right adrenal resection. Histopathologic examination found the tumor was composed of small round blue cells forming typical Homer-Wright rosettes in focal area. The immunohistochemical analysis confirmed the case to be ESFT, which was positive for membranous CD99 and nuclear FLI-1. The patient was scheduled for four courses of large doses of chemotherapy and died for cancer metastasis one year later after surgery. CONCLUSIONS: Histopathological evidence of Homer-Wright rosettes and immunohistochemical markers positivity, such as CD99 and FLI-1, are valuable factors for ESFT diagnosis, although cytogenetic analysis is considered as the gold standard. Complete surgery is the treatment of choice for ESFT and adjuvant radiotherapy and combination chemotherapy can significantly improve the survival rate of postoperative patients.

Retroperitoneoscopic ureteroplasty for retrocaval ureter: report of nine cases and literature review.

OBJECTIVE: The aim of this study was to report the experience of retroperitoneal laparoscopic ureteroplasty for nine cases of retrocaval ureter. MATERIAL AND METHODS: Six males and three females were referred with a diagnosis of retrocaval ureter. A retroperitoneal laparoscopic approach was taken in all patients, who were diagnosed by intravenous pyelography (IVP), computed tomography urography and retrograde pyelography. After the dilated proximal ureter was mobilized, the ureter was transected just above the retrocaval segment, which was repositioned to the anterior of the vena cava. The retrocaval segment was observed and evaluated to enable a decision as to whether or not to reserve. Then, tension-free, water-tight anastomosis was performed with absorbable sutures using intracorporeal suturing techniques over a double-J stent, which was laparoscopically inserted in an antegrade manner. The stent was removed 4-6 weeks postoperatively. RESULTS: The ureteroplasty was accomplished in all cases. The retrocaval segment of the ureter was reserved with a grossly normal appearance in six cases; the abnormal retrocaval segment was excised in the three other cases. The mean operative duration was 103 min (range 89-110 min) and the mean hospital stay was 7 days (range 6-9 days). No serious complications occurred. Follow-up by ultrasonography and IVP, lasting 6 months to 4 years, revealed considerable improvement in hydronephrosis and upper ureteral dilatation. No ureteral stenosis was found at the anastomotic site. CONCLUSION: Retroperitoneoscopic ureteroplasty should be recommended as the first line treatment for retrocaval ureter because of its advantages of minimal invasion and shorter hospital stay than open surgery. Skilled laparoscopic anastomosis with a retroperitoneal approach can shorten the operative duration.

[Construction and expression of the eukaryotic expression vector containing AIF gene].

OBJECTIVE: To construct the eukaryotic express vector containing apoptosis-inducing factor (AIF) gene and to study its expression in A549 cells. METHODS: According to the GenBank AIF mRNA sequence, specific primers to amplify AIF gene from lung carcinoma cell line A549 by RT-PCR was designed. The amplified AIF gene fragment was cloned into plasmid pUC-T by TA cloning, then double enzyme digestion and DNA sequencing were used to identifying the positive recombinant AIF-pUC-T. The target fragment was retrieved and cloned into the eukaryotic express vector pcDNA3.1(+). The positive recombinant AIF-pcDNA3.1(+) was transfected into A549 cells, and expression of AIF gene was verified by RT-PCR and Western blot. RESULTS: AIF target gene was successfully amplified and cloned into the pUC-T. The target fragment was retrieved and cloned into the eukaryotic express vector pcDNA3.1(+), and it was completely coincided with the AIF sequence in GenBank suggested by cells transfected with AIF-pcDNA3. 1(+) was much higher than that of control cells which was not transfected with AIF-pcDNA3.1(+). CONCLUSION: The AIF eukaryotic expression vector AIF-pcDNA3.1(+) is successfully constructed in A549 cells and it could be experimental foundations for further study of AIF gene.

[Effect of PARP-1 inhibitor 4-amino-1 ,8-naphthalimide on the on the sensitivity of adriamycin].

OBJECTIVE: To explore the effect of inhibition of poly (ADP-ribose) polymerase-1 (PARP-1) on the sensitivity of cells to adriamycin (ADM). METHODS: Mouse embryonic fibroblasts (MEFs) were divided into two groups according to whether they were treated with 4-amino-1,8-naphthalimide (4-AN) or not. And then the differences of cell viability and genotoxicity between the 4-AN treatment group and the non-treated group were compared after exposure to ADM. RESULTS: The half-inhibitory concentrations of ADM (IC50) in the 4-AN treatment group was significantly lower than the non-treated group (P < 0.05). At 0.025-0.2 microg/ml concentration of ADM, the cell viability of the treatment group was significantly lower than that of the non-treated group (P < 0.05). Moreover, the population doubling time and the colony formation rate were significant longer or higher (P < 0.05) at 0.05-0.2 microg/ml concentration of ADM. Results from the comet assay and micronucleus assay showed that the doses of ADM increased, the comet rate, tail length, Olive tail moment, frequency of micronucleated cells and frequency of micronucleus formation of the both groups increased. At 0.02-1 microg/ml concentration of ADM, the comet rate, tail length, Olive tail moment of the treatment group were significant higher than those of controls (P < 0.05), and at 0.01-0.2 microg/ml concentration of ADM, both the frequency of micronucleated cells and the frequency of micronucleus formation were significantly increased (P < 0.05). CONCLUSION: Inhibition of PARP-1 can significantly increase the sensitivity of cells to adriamycin, and DNA damage and repair may be a potential mechanism for this effect.

Deregulated expression of DNA polymerase ß is involved in the progression of genomic instability.

Deregulated expression of DNA polymerase beta (pol ß) has been implicated in genomic instability that leads to tumorigenesis, yet the mechanisms underlying the pol ß-mediated genetic instability remain elusive. In this study, we investigated the roles of deregulated expression of pol ß in spontaneous and xenobiotic-induced genetic instability using mouse embryonic fibroblasts (MEFs) that express distinct pol ß levels (wild-type, null, and overexpression) as a model system. Three genetic instability endpoints, DNA strand breaks, chromosome breakage, and gene mutation, were examined under various expression levels of pol ß by comet assay, micronuclei test, and hprt mutation assay. Our results demonstrate that neither pol ß deficiency nor pol ß overexpression is sufficient for accumulation of spontaneous DNA damage that promotes a hyperproliferation phenotype. However, pol ß null cells exhibit increased sensitivity to exogenous DNA damaging agents with increased genomic instability compared with pol ß wild-type and overexpression cells. This finding suggests that a pol ß deficiency may underlie genomic instability induced by exogenous DNA damaging agents. Interestingly, pol ß overexpression cells exhibit less chromosomal or DNA damage, but display a higher hprt mutation frequency upon methyl methanesulfonate exposure compared with the other two cell types. Our results therefore indicate that an excessive amount of pol ß may promote genomic instability, presumably through an error-prone repair response, although it enhances overall BER capacity for induced DNA damage.

Links between DNA polymerase beta expression and sensitivity to bleomycin.

Bleomycin (BLM), an important anti-tumor antibiotic, enables cell death through oxidative DNA damage mediated by reactive oxygen species (ROS). However, increasing cellular resistance has become a serious limitation to its clinical application. Base excision repair (BER), the major pathway for repairing oxidative bases, is involved in resistance of DNA-damaging anticancer drugs. DNA polymerase beta (pol ß), a critical BER enzyme, has been reported to play a crucial role in combating BLM-induced oxidative DNA damage, as a result, pol ß inhibition may increase the sensitivity to BLM. To test this hypothesis, we evaluated the sensitivity to BLM using mouse embryo fibroblasts (MEFs) with distinct pol ß expression levels (wild-type, pol ß deficiency) and explored the underlying mechanisms. The results showed that cell viability of pol ß-deficient MEFs was significantly lower than that of isogenic wild type when treated with the same BLM dosage. In addition, increased ROS level, DNA single strand breaks, and chromosomal breakage were observed in pol ß deficient cells, indicating impaired DNA repair and enhanced oxidative DNA damage under pol ß deficiency. In agreement with the findings, an enhanced hprt gene mutation frequency was also detected in pol ß null cells. In summary, this study demonstrated that BLM-induced DNA damage could be repaired through BER pathway and absence of pol ß allows oxidative DNA/chromosome damage and gene mutation, which contributes to BLM hypersensitivity.

[Effects of pol beta on biological characteristics and DNA damage in mouse embryonic fibroblast].

OBJECTIVE: To explore the effect of DNA polymerase beta (pol beta) expression level on biological characteristics of mouse embryonic fibroblast (MEF) and the cellular response to DNA damage induced by potassium dichromate. METHODS: pol beta wild-type cells (pol beta +/+), pol beta null cells (pol beta -/-) and pol beta overexpressed cells (pol beta oe) were applied as a model system. The growth curve of cells was plotted by MTT assay; the doubling time of cells was detected by double time experiment; the spontaneous mutation frequency was determined by HGPRT gene mutation method and single cell gel electrophoresis assay (SCGE) was employed to observe the DNA damage either happened spontaneously or induced by potassium dichromate. RESULTS: Growth characteristic and doubling time of the three kinds of cells were similar and no obvious differences were found on spontaneous DNA damage and mutations frequency among them (P > 0.05). Potassium dichromate increased comet rate and tail length in the three kinds of cells in a concentration dependent way. DNA damage of pol beta -/- cells at the same dosage were more serious than the other cells both in comet rate and tail length (P < 0.05). pol beta oe cells demonstrated more resistant to DNA damage obviously than the others. CONCLUSION: The expression level of pol beta has no significant effect on the biological characteristic and spontaneous mutation frequency of MEF. pol beta knock out cells is more sensitive to DNA damage induced by potassium dichromate, whereas, pol beta over expression can help cells response to DNA damage and protect cells from death in a certain degree.

Involvement of DNA polymerase beta in repairing oxidative damages induced by antitumor drug adriamycin.

Adriamycin (ADM) is a widely used antineoplastic drug. However, the increasing cellular resistance has become a serious limitation to ADM clinical application. The most important mechanism related to ADM-induced cell death is oxidative DNA damage mediated by reactive oxygen species (ROS). Base excision repair (BER) is a major pathway in the repair of DNA single strand break (SSB) and oxidized base. In this study, we firstly applied the murine embryo fibroblasts wild-type (pol ß +/+) and homozygous pol ß null cell (pol ß -/-) as a model to investigate ADM DNA-damaging effects and the molecular basis underlying these effects. Here, cellular sensitivity to ADM was examined using colorimetric assay and colony forming assay. ADM-induced cellular ROS level and the alteration of superoxide dismutase (SOD) activity were measured by commercial kits. Further, DNA strand break, chromosomal damage and gene mutation were assessed by comet assay, micronucleus test and hprt gene mutation assay, respectively. The results showed that pol ß -/- cells were more sensitive to ADM compared with pol ß +/+ cells and more severe SSB and chromosomal damage as well as higher hprt gene mutation frequency were observed in pol ß -/- cells. ROS level in pol ß -/- cells increased along with decreased activity of SOD. These results demonstrated that pol ß deficiency could enable ROS accumulation with SOD activity decrease, further elevate oxidative DNA damage, and subsequently result in SSB, chromosome cleavage as well as gene mutation, which may be partly responsible for the cytotoxicity of ADM and the hypersensitivity of pol ß -/- cells to ADM. These findings suggested that pol ß is vital for repairing oxidative damage induced by ADM.

[Cigarette smoke-induced oxidative damage to human bronchial epithelial cells].

OBJECTIVE: To determine the oxidative damage of mainstream smoke (MS) on Human bronchial epithelial cells (HBE) and its role in lung cancer. METHODS: MTT assay was used to test the cytotoxicity of MS on HBE. The HBE cells were treated with different concentrations of MS for 12 h. The chromatosome damage and DNA strand breaks were measured by micronucleus test and alkaline comet assay respectively. The contents of ROS in the HBE cells were determined using fluorescence method. RESULTS: With the increase of MS, the viability of HBE cells decreased. The IC50 decreased with the increasing exposure time to MS, showing significant dose-effect and time-effect relationships. The MS induced DNA strand break in the HBE cells. The comet, L Tail, Tail DNA and OTM increased with the increase of MS concentrations. Cigarette smoke also induced chromosome damage. The micronucleus rate of the HBE cells exposed to more than one cigarette/L of MS was significantly greater than the controls (P<0.05). The ROS increased with the concentration of MS. CONCLUSION: MS induces ROS in HBE cells, resulting in increased cytotoxicity, chromosome damage and DNA strand breaks, which suggests that oxidative damage is an important mechanism of lung cancer caused by MS.