Co-oxidation-mediated xenobiotic activation and cytotoxicity by 12-lipoxygenase in intact platelets

5-Lipoxygenase Contributes to Benzo[a]pyrene-Induced Cytotoxicity and DNA Damage in Human Bronchial Epithelial Cells

Metabolic activation of indirect-acting carcinogens in target organs is a recognized mechanism of carcinogenesis. This study aimed to determine the role of benzo[a]pyrene (BaP) metabolism enzymes lipoxygenase (LOX), cytochrome P4501A1 (CYP1A1), and prostaglandin synthetase (PGS) in the cytotoxicity and DNA damage induced by BaP in the human tracheobronchial epithelial cells (HBECs) using RNA interference strategy and metabolic enzyme inhibitors. Our results showed that in three epithelial cell lines (HBE, HTR-8/SVneo, and HaCat), BaP significantly upregulated 5-LOX protein expression. 15-LOX-2 expression also increased with increasing BaP concentration, but the change was less pronounced than that of 5-LOX. BaP caused significant cytotoxicity, DNA strand breaks, and 8-hydroxy-2'-deoxyguanosine formation in HBE, which was inhibited by 5-LOXshRNA, a specific inhibitor of 5-LOX (AA861), the CYP1A1 inhibitor α-naphthoflavone, and the PGS inhibitor naproxen. The protective effects of 5-LOXshRNA were stronger than AA861, naproxen and α-naphthoflavone. We conclude that BaP may be activated more by 5-LOX than by CYP1A1 and PGS to produce cytotoxicity and DNA damage in HBE.

Phenolic Compounds of Rumex roseus L. Extracts and Their Effect as Antioxidant and Cytotoxic Activities

Rumex roseus L. (R. roseus) is acknowledged as an aromatic plant. For its excellent biological properties, it was used as a traditional medicine. The aim of the present study is to evaluate the chemical components and their effect as the biological activities of Tunisian extracts of R. roseus. Consecutive extractions by cold maceration of the aerial part with solvents of increasing polarity (cyclohexane (CYH), dichloromethane (DCM), and methanol (MeOH)) were performed, and the different chemical groups (phenolics, flavonoids, tannins, anthocyanins, etc.) were identified. In addition, the volatile compounds of the obtained extracts were identified before and after derivatization. Moreover, their antioxidant and anticancer activities were evaluated. The analysis of HPLC-DAD revealed the identification of 18 components from organic extracts, among them are, for example, chlorogenic acid and shikonin, while GC-MS analysis allowed the detection of 34 volatile compounds. Some of those compounds were identified for the first time in plant extracts such as pyrazolo[3,4-d] pyrimidine-3,4(2H,5H)-dione (1); L-proline (16); 2-amino-3-hydroxybutanoic acid (19); L-(-)-arabitol (23); D-(-)-fructopyranose (25); and D-(+)-talopyranose (27). DPPH tests revealed that the most important antioxidant activity was found in the methanolic extract with 75.2% inhibition at 50 mg/L and that the highest cytotoxic activity against HCT-116 and MCF-7 was recorded in the dichloromethane extract with 62.1 and 80.0% inhibition at 50 mg/L, respectively. The biological activities were fully correlated with the chemical composition of the different extracts. So, we can suggest that R. roseus is a source of bioactive molecules that could be considered potential alternatives for use in dietary supplements for the prevention or treatment of diseases.

In silico prediction of mitochondrial toxicity of chemicals using machine learning methods

Mitochondria are important organelles in human cells, providing more than 95% of the energy. However, some drugs and environmental chemicals could induce mitochondrial dysfunction, which might cause complex diseases and even worsen the condition of patients with mitochondrial damage. Some drugs have been withdrawn from the market due to their severe mitochondrial toxicity, such as troglitazone. Therefore, there is an urgent need to develop models that could accurately predict the mitochondrial toxicity of chemicals. In this paper, suitable data were obtained from literature and databases first. Then nine types of fingerprints were used to characterize these compounds. Finally, different algorithms were used to build models. Meanwhile, the applicability domain of the prediction models was defined. We have also explored the structural alerts of mitochondrial toxicity, which would be helpful for medicinal chemists to better predict mitochondrial toxicity and further optimize lead compounds.

RNA Interference Protects Against 5-Lipoxygenase-Induced Cocarcinogen, Benzidine, Oxidation and Cytotoxicity in Human Tracheobronchial Epithelial Cells

Lipoxygenase (LOX)-catalyzed cooxidation of the human carcinogen benzidine (BZD) has been shown in in vitro enzyme systems. This study aimed to determine whether BZD could be activated by arachidonate 5-lipoxygenase (ALOX5) in the human tracheobronchial epithelial cells (HBECs) using RNA interference strategy and a 5-LOX-specific inhibitor, AA861. We show that the soybean LOX catalyzed the cooxidation of BZD, generating BZD diimine. Benzidine induced expression of ALOX5 messenger RNA and 5-LOX protein in HBECs, and significantly decreased cell proliferation, but enhanced DNA damage and apoptosis in HBECs which were significantly inhibited by lentiviral-mediated small hairpin RNA-knockdown of ALOX5 and by AA861. Thus, BZD could upregulate the expression of ALOX5 in HBECs, while inhibition of the protein or gene expression or enzyme activity could prevent BZD-induced cytotoxicity and DNA damage in HBECs, which might be caused by the 5-LOX-catalyzed oxidative activation of BZD.

In vitro oxidative metabolism of xenobiotics in the lancet fluke (Dicrocoelium dendriticum) and the effects of albendazole and albendazole sulphoxide ex vivo

Dicrocoeliosis, a parasitic infection caused by Dicrocoelium dendriticum (lancet fluke), is often treated by the anthelmintic drug albendazole (ABZ). In the lancet fluke, ABZ metabolism via enzymatic sulphoxidation was found, but no information about ABZ oxidases has been available. The aim of our project was to find out which enzyme of the lancet fluke is responsible for ABZ sulphoxidation, as well as to assay the activities of oxidation enzymes. We also studied whether ex vivo 24-h exposures of flukes to ABZ or its sulphoxide (ABZ.SO) would alter ABZ sulphoxidation rate and the activities of tested enzymes. In subcellular fractions from flukes, marked activities of peroxidase (Px), glutathione Px (GPx), catalase (CAT), superoxide dismutase, and thioredoxin glutathione reductase were found. Using specific inhibitors, the participation of flavine monooxygenases in ABZ-oxidation was found. The ex vivo exposition of flukes to ABZ or ABZ.SO did not change the rate of ABZ sulphoxidation in vitro, but the ex vivo exposure of flukes to anthelmintics increased Px, CAT, and GPx activity. The modulation of these enzyme activities after ABZ or ABZ.SO exposition may be characteristic of the parasite’s protective mechanism against oxidative stress caused by drug treatment.