Ayse Tarbin Jannuzzi

Investigation on the toxic potential of Tribulus terrestris in vitro

Abstract Context: Tribulus terrestris L. (Zygophyllaceae) has been commonly used to energize, vitalize, and improve sexual function and physical performance in men. Objective: This study investigates the potential cytotoxic and genotoxic, and endocrine disrupting activities of T. terrestris in vitro. Materials and methods: The whole T. terrestris plant was extracted with water, methanol, and chloroform. The genotoxic potential of T. terrestris extracts at 3–2400 µg/mL was assessed by Comet assay in a rat kidney cell line (NRK-52E) and by Ames assay in Salmonella typhimurium TA98 and TA100 strains. Endocrine disrupting effects of the extracts at concentrations of 0.22–25 000 µg/mL were assessed by YES/YAS assay in Saccharomyces cerevisiae. Cytotoxic activity of the extracts was determined by the MTT test in NRK-52E cells. The different exposure times were used for four tests (3–48 h). Results: The methanol extract of T. terrestris IC50 value was 160 µg/mL. The other extracts did not show cytotoxic effects. In the Comet and Ames genotoxicity assays, none of the extracts possessed genotoxic activities at concentrations of 0–2400 µg/mL. Only the water extract of T. terrestris induced frame shift mutations after metabolic activation. The water extract also showed estrogenic activity by YES/YAS assay in S. cerevisiae at concentrations ≥27 µg/mL (≥2.6-fold), while the other T. terrestris extracts had anti-estrogenic properties. Conclusion: Tribulus terrestris had estrogenic and genotoxic activities. The study was useful in determining its toxicological effects and the precautions regarding consumption.

VEGF gene polymorphisms and susceptibility to colorectal cancer.

AIMS Colorectal cancer (CRC) is the third most common cancer in the world and its etiology involves the interaction of genetic and environmental factors. New blood vessels form through a process called angiogenesis and have an essential role in tumor growth, progression, and metastasis of malignant tumors. The vascular endothelial growth factor (VEGF), one of the most important angiogenic factors, is a specific mitogen for vascular endothelial cells. In the present case-control study, we carried out the study to evaluate whether the VEGF single-nucleotide polymorphisms play a role in modulating susceptibility to CRC. METHODS We evaluated the VEGF -2578A>C, +936C>T, and -460C>T genotypes obtained from 103 patients with CRC and 129 healthy controls by using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Also, haplotype analysis was determined. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated. RESULTS -2578A>C was significantly associated with CRC risk (OR 1.81; 95% CI 0.94-3.47; p=0.0495), while distribution of +936C>T and -460C>T genotypes in cases and controls did not significantly differ. The VEGF A2578-T936-T460 haplotype might be associated with the development of CRC (OR 8.77; 95% CI 1.05-73.36; p=0.0434). There was significant haplotype effect for all eight haplotypes (p=0.02). CONCLUSIONS These results suggest that the VEGF polymorphisms might play a role in the development of CRC. Therefore, the VEGF polymorphisms might be further investigated to use in the determination of risk factors for CRC and to have a predictive value for anti-VEGF-targeted cancer therapies.

Telomerase Reverse Transcriptase (TERT) Gene Variations and Susceptibility of Colorectal Cancer

AIM Colorectal cancer is the third most common cause of cancer-related mortality. Previous studies demonstrated increased telomerase activity in colorectal cancer tissue and suggested a prognostic value for patients with colorectal carcinoma. Telomerase reverse transcriptase (TERT), one of the main functional subunits of the telomerase, is an important factor in modulating telomerase activity, telomere length, and genomic stability. However, there are few studies that have addressed the association between genetic variation at TERT and the risk of colorectal cancer. METHOD We evaluated the influence of three common single-nucleotide polymorphisms (SNPs) of the TERT gene (rs2853669, rs2736100, rs2736098) on susceptibility to colorectal cancer in 104 patients and 135 controls in a Turkish population. RESULTS We observed that rs2736098 was significantly associated with increased risk of colorectal cancer (OR = 2.53; 95% CI = 1.26-5.10; p = 0.008). On the other hand, rs2736100 and rs2853669 showed no association with colorectal cancer (p ≥ 0.128). CONCLUSION These findings are the first results of TERT allele distributions in the Turkish population and also provide increased understanding with respect to colorectal cancer etiology.

Evaluation of DNA damage and DNA repair capacity in occupationally lead-exposed workers

Occupational lead (Pb) exposure remains a significant concern for workers in Turkey. Health hazards of Pb exposure have been investigated in various test systems, but results regarding its potential genotoxic effects on exposed populations are contradictory. In this study, a control group and an exposed group were studied, each consisting of 25 male subjects. Blood lead levels (BLLs) were estimated by graphite furnace atomic absorption spectrometry. Genotoxic effects of Pb exposure were studied in leukocytes by comet and challenge assays. The effect of Pb exposure to DNA repair capacity was evaluated following in vitro hydrogen peroxide exposure. Pb-exposed workers had significantly higher BLLs than the control group (p < 0.01). DNA damage in exposed workers had a significantly higher percentage of DNA in tail than the control group (p < 0.05). In the challenge assay, it was found that the mean DNA% repair capacity was significantly decreased in Pb-exposed workers (p < 0.01). The results indicated that occupational Pb exposure is associated with DNA damage and causes decrease in DNA% repair capacity, indicating a potential health concern for occupationally Pb-exposed populations.

Celastrol ameliorates acetaminophen-induced oxidative stress and cytotoxicity in HepG2 cells

Acetaminophen (APAP) is the most commonly used analgesic and antipyretic drug in the world. However, hepatotoxicity caused by APAP overdose is the most frequent cause of acute liver failure worldwide and oxidative stress involved in the pathogenesis of APAP hepatotoxicity. Celastrol is a natural triterpenoid derived from Tripterygium wilfordii Hook F. that exhibits antioxidant, anti-inflammatory, and antitumor activities. In this study, we aimed to investigate the potential ameliorative effects of celastrol against APAP-induced cytotoxicity and oxidative stress. Human hepatocellular carcinoma cells (HepG2) were incubated with 20 mM of APAP for 24 h and posttreated with 50 nM, 100 nM, or 200 nM of celastrol for a further 24 h. The methylthiazolyldiphenyl-tetrazolium bromide, lactate dehydrogenase, and neutral red uptake assays showed celastrol posttreatments recovered cell viability and cell membrane integrity in a concentration-dependent manner. Celastrol posttreatments exerted a significant increase in the glutathione content and a decrease in the malondialdehyde and protein carbonylation levels. Also, celastrol posttreatments attenuated the APAP-induced oxidative stress by raising glutathione peroxidase, glutathione reductase, and catalase activities. However, superoxide dismutase activity did not change. In conclusion, celastrol treatment may improve cell viability and increase cellular antioxidant defense in HepG2 cells. These results suggest that celastrol may have the potential to ameliorate the APAP-induced oxidative stress and cytotoxicity.