Aspirin inhibits glucose­6­phosphate dehydrogenase activity in HCT 116 cells through acetylation: Identification of aspirin-acetylated sites.

Glucose-6-phosphate dehydrogenase (G6PD) catalyzes the first reaction in the pentose phosphate pathway, and generates ribose sugars, which are required for nucleic acid synthesis, and nicotinamide adenine dinucleotide phosphate (NADPH), which is important for neutralization of oxidative stress. The expression of G6PD is elevated in several types of tumor, including colon, breast and lung cancer, and has been implicated in cancer cell growth. Our previous study demonstrated that exposure of HCT 116 human colorectal cancer cells to aspirin caused acetylation of G6PD, and this was associated with a decrease in its enzyme activity. In the present study, this observation was expanded to HT­29 colorectal cancer cells, in order to compare aspirin­mediated acetylation of G6PD and its activity between HCT 116 and HT­29 cells. In addition, the present study aimed to determine the acetylation targets of aspirin on recombinant G6PD to provide an insight into the mechanisms of inhibition. The results demonstrated that the extent of G6PD acetylation was significantly higher in HCT 116 cells compared with in HT­29 cells; accordingly, a greater reduction in G6PD enzyme activity was observed in the HCT 116 cells. Mass spectrometry analysis of aspirin­acetylated G6PD (isoform a) revealed that aspirin acetylated a total of 14 lysine residues, which were dispersed throughout the length of the G6PD protein. One of the important amino acid targets of aspirin included lysine 235 (K235, in isoform a) and this corresponds to K205 in isoform b, which has previously been identified as being important for catalysis. Acetylation of G6PD at several sites, including K235 (K205 in isoform b), may mediate inhibition of G6PD activity, which may contribute to the ability of aspirin to exert anticancer effects through decreased synthesis of ribose sugars and NADPH.

Aspirin acetylates wild type and mutant p53 in colon cancer cells: identification of aspirin acetylated sites on recombinant p53.

Aspirin's ability to inhibit cell proliferation and induce apoptosis in cancer cell lines is considered to be an important mechanism for its anti-cancer effects. We previously demonstrated that aspirin acetylated the tumor suppressor protein p53 at lysine 382 in MDA-MB-231 human breast cancer cells. Here, we extended these observations to human colon cancer cells, HCT 116 harboring wild type p53, and HT-29 containing mutant p53. We demonstrate that aspirin induced acetylation of p53 in both cell lines in a concentration-dependent manner. Aspirin-acetylated p53 was localized to the nucleus. In both cell lines, aspirin induced p21(CIP1). Aspirin also acetylated recombinant p53 (rp53) in vitro suggesting that it occurs through a non-enzymatic chemical reaction. Mass spectrometry analysis and immunoblotting identified 10 acetylated lysines on rp53, and molecular modeling showed that all lysines targeted by aspirin are surface exposed. Five of these lysines are localized to the DNA-binding domain, four to the nuclear localization signal domain, and one to the C-terminal regulatory domain. Our results suggest that aspirin's anti-cancer effect may involve acetylation and activation of wild type and mutant p53 and induction of target gene expression. This is the first report attempting to characterize p53 acetylation sites targeted by aspirin.

Phytochemical screening studies on Melia orientalis by GC-MS analysis.

BACKGROUND: Melia orientalis (MO) is an important Ayurvedic medicinal plants. The plant part such as leaves and roots are traditionally used for the treatment of diabetes, edema, traumatic swelling, skin diseases, oligospermia and bleeding disorders. OBJECTIVE: To investigate the phytochemical identification of ethanol leaf extract of MO. MATERIALS AND METHODS: The fresh leaves of MO (1000g) were collected and shade dried at room temperature for 30 days and the dried leaves were made into a fine powder. The ethanol leaf extract obtained was dried and used for phytochemical identification by GC-MS analysis. RESULTS: The phytochemical screening studies have been carried out and identified ten chemical constituents present in the leaf extract of MO. CONCLUSION: Thus, our results show that MO possess important phytocomponents such as phytol, squalene and stigmasterol.

Phytochemical investigation and radical scavenging activities of Melia azedarach and its DNA protective effect in cultured lymphocytes.

CONTEXT: Melia azedarach Linn (Meliaceae) is an Ayurvedic medicinal plant which is native to India. It is traditionally used for the treatment of leprosy, inflammation, scrofula, anthelmintic, antilithic, diuretic, deobstruent and cardiac disorders. OBJECTIVE: To evaluate the phytochemical constituents and antioxidant activities of the ethanol leaf extract of Melia azedarach (MA) and its protective effect against H2O2-induced cellular damage in cultured lymphocytes. MATERIALS AND METHODS: The dose-dependent study of MA (20, 40, 60, 80, 100 µg/ml) was used to study in vitro radical scavenging assays. The effective dose of MA (60 µg/ml) was further used to study the H2O2-induced DNA damage (comet assay and DNA fragmentation assay) in cultured lymphocytes. RESULTS: The ethanol extract of MA (20, 40, 60, 80, 100 µg/ml) exhibited a significant dose-dependent inhibition of in vitro radical scavenging assays and their corresponding IC50 values as follows: hydroxyl radical (26.50 ± 0.26 µg/ml), superoxide anion (30.00 ± 0.32 µg/ml), nitric oxide radical (48.00 ± 0.48 µg/ml), DPPH radical (30.55 ± 0.32 µg/ml) and reducing power (22.00 ± 0.22 µg/ml). The increase in the severity of DNA damage and TBARS was increased significantly (p<0.05) at 500 µM H2O2-treated cultured lymphocytes and RBC cellular membranes. The phytochemical screening studies identified 13 chemical constituents present in the leaf extract of MA. DISCUSSION AND CONCLUSION: The results of this study demonstrate that MA offers protection against H2O2-induced cellular damage and it can be developed as an effective antioxidant during oxidative stress.

Protective role of ferulic acid on carbon tetrachloride-induced hyperlipidemia and histological alterations in experimental rats.

BACKGROUND: The present study aimed to evaluate the antihyperlipidemic effect of ferulic acid (FA) on carbon tetrachloride (CCl4)-treated rats. METHODS: Female albino rats of the Wistar strain were used in the present study. The rats were divided into four groups: groups 1 and 4 received physiological saline (3 mL/kg body weight/week) by subcutaneous injection, whereas groups 2 and 3 received a subcutaneous injection of CCl4 (3 mL/kg body weight/week) for a total period of 12 weeks. In addition, groups 3 and 4 were administered FA (20 mL/kg body weight) every day for the last 90 days. RESULTS: The results showed significantly (p≤0.05) elevated levels of cholesterol, triglycerides (TG), and free fatty acids (FFA) in the liver and kidney of CCl4-treated rats as compared with those of the controls. In addition, the levels of cholesterol, FFA, phospholipids (PL), and TG were elevated significantly in the circulation. Administration of FA effectively reduced these levels of lipids in the plasma, liver, and kidney of CCl4-treated rats. The PL level was significantly decreased in the liver and kidney of CCl4-treated rats and was positively modulated by FA treatment. Our histopathological observations were also in correlation with the biochemical parameters. CONCLUSIONS: From the results obtained, we could conclude that FA effectively protects the system against hyperlipidemia and may be an effective therapeutic agent for the treatment of this disorder.

Aspirin acetylates multiple cellular proteins in HCT-116 colon cancer cells: Identification of novel targets.

Epidemiological and clinical observations provide consistent evidence that regular intake of aspirin may effectively inhibit the occurrence of epithelial tumors; however, the molecular mechanisms are not completely understood. In the present study, we determined the ability of aspirin to acetylate and post-translationally modify cellular proteins in HCT-116 human colon cancer cells to understand the potential mechanisms by which it may exerts anti-cancer effects. Using anti-acetyl lysine antibodies, here we demonstrate that aspirin causes the acetylation of multiple proteins whose molecular weight ranged from 20 to 200 kDa. The identity of these proteins was determined, using immuno-affinity purification, mass spectrometry and immuno-blotting. A total of 33 cellular proteins were potential targets of aspirin-mediated acetylation, while 16 were identified as common to both the control and aspirin-treated samples. These include enzymes of glycolytic pathway, cytoskeleton proteins, histones, ribosomal and mitochondrial proteins. The glycolytic enzymes which were identified include aldolase, glyceraldehyde-3-phosphate dehydrogenase, enolase, pyruvate kinase M2, and lactate dehydrogenase A and B chains. Immunoblotting experiment showed that aspirin also acetylated glucose-6-phosphate dehydrogenase and transketolase, both enzymes of pentose phosphate pathway involved in ribonucleotide biosynthesis. In vitro assays of these enzymes revealed that aspirin did not affect pyruvate kinase and lactate dehydrogenase activity; however, it decreased glucose 6 phosphate dehydrogenase activity. Similar results were also observed in HT-29 human colon cancer cells. Selective inhibition of glucose-6-phosphate dehydrogenase may represent an important mechanism by which aspirin may exert its anti-cancer effects through inhibition of ribonucleotide synthesis.

Ferulic Acid modulates altered lipid profiles and prooxidant/antioxidant status in circulation during nicotine-induced toxicity: a dose-dependent study.

Nicotine, an active ingredient of tobacco smoke, is known to induce hyperlipidemia and disturb the prooxidant-antioxidant status. In our study, ferulic acid, a naturally occurring nutritional compound, was tested for its antioxidant and antihyperlipidemic property in a dose-dependent manner against nicotine-induced toxicity in female Wistar rats. We tested three different doses of ferulic acid-10 mg, 20 mg, and 40 mg/kg body weight-for their protective effects. The activities of biochemical marker enzymes lactate dehydrogenase and alkaline phosphatase, levels of peroxidative indices (thiobarbituric acid reactive substances and hydroperoxides), nitric oxide, and circulatory lipids (cholesterol, triglycerides, free fatty acids, and phospholipids) were increased significantly in the nicotine-treated group when compared to normal, which were brought down in ferulic acid-treated groups. The antioxidant status (superoxide dismutase, catalase, glutathione peroxidase, vitamin E, and reduced glutathione) was found to be decreased in the nicotine-treated group, and was significantly increased in ferulic acid-administered groups. Further, ferulic acid also positively modulated the nicotine-induced changes in the micronutrients (zinc and copper) level. The dose 20 mg/kg body weight was found to be more effective than the other two doses. Our data suggest that FA exerts its preventive effects by modulating the degree of lipid peroxidation, antioxidant status, lipid profiles, and trace element levels during nicotine-induced toxicity.