Baicalein induced in vitro apoptosis undergo caspases activity in human promyelocytic leukemia HL-60 cells.

In this study, we evaluated the potential apoptosis effects of baicalein on human promyelocytic leukemia HL-60 cells in vitro. Apoptosis induction, cell viability, morphology and caspase-3 activity were then performed to determine by flow cytometric assay, DNA gel electrophoresis, anti-ADP-ribose stain and determination of caspase-3 activity. There is a significant difference in cell death of HL-60 cells that was detected between baicalein-treated and untreated groups. Furthermore, there was a further significant increase in apoptosis induction when cells were treated with baicalein compared to without baicalein treated groups. Flow cytometric assays and DNA fragmentation gel electrophoresis also confirmed baicalein induced apoptosis in HL-60 cells. Baicalein also promoted caspase-3 activity then leading to cleavage of poly-ADP-ribose polymerase finally leading to DNA fragmentation occurrence. Furthermore, the baicalein-induced apoptosis was markedly blocked by the broad-spectrum caspase inhibitor, z-VAD-fmk. Taken together, these results suggest that treatment of human leukemia HL-60 cells with baicalein induced apoptosis through activation of caspase-3 activity.

Quercetin glucuronides inhibited 2-aminofluorene acetylation in human acute myeloid HL-60 leukemia cells.

Our earlier study has demonstrated that following the exposure of rat to the arylamine carcinogen 2-aminofluorene, DNA-2-aminofluorene adducts were found in the target tissues liver, bladder, colon, lung and also in circulating leukocytes (lymphocytes and monocytes). The result also demonstrated that orally treated antioxidants decreased N-acetylation of 2-aminofluorene in target tissues and leukocytes. Therefore, this study investigated whether quercetin glucuronides could affect N-acetylation of 2-aminofluorene in human acute myeloid leukemia HL-60 cells. Evidence is presented here that human leukemia cells are capable of acetylating 2-aminofluorene. Quercetin glucuronides did inhibit 2-aminofluorene acetylation in intact cells. The results also indicated that quercetin glucuronides induced cytotoxicity in dose-dependent manner in the examined human acute myeloid leukemia HL-60 cells.

Inhibitory actions of luteolin on the growth and arylamine N-acetyltransferase activity in strains of Helicobacter pylori from ulcer patients.

Helicobacter pylori is now recognized as an important cause of type B gastritis, which is strongly associated with gastric and duodenal ulcer disease. H. pylori may be a causative factor in patients with gastric cancer. The growth inhibition and N-acetylation of 2-Aminofluorene (AF) or P-aminobenzoic acid (PABA) by arylamine N-acetyltransferase (NAT) in H. pylori were inhibited by luteolin, a component in herbal medicine. The growth inhibition was based on the changes of optical density (OD) by using a spectrophotometer. The N-acetylation of AF or PABA by NAT from H. pylori were assayed by the amounts of acetylated and non-acetylated AF or PABA in cytosols and intact bacteria of H. pylori by using HPLC. An inhibition of growth on H. pylori demonstrated that luteolin elicited a dose-dependent growth inhibition in the H. pylori cultures. Cytosols and suspensions of H. pylori with or without specific concentrations of luteolin co-treatment showed different percentages of AF or PABA acetylation. The data indicated that there was decreased NAT activity associated with increased levels of luteolin in H. pylori cytosols and suspensions. Using standard steady-state kinetic analysis, it was demonstrated that luteolin was a possible uncompetitive inhibitor to NAT enzyme in H. pylori. This report is the first demonstration to show that luteolin can inhibit H. pylori growth and NAT activity.

Evidence for arylamine N-acetyltransferase in Hymenolepis nana.

N-acetyltransferase activities with p-aminobenzoic acid and 2-aminofluorene were determined in Hymenolepis nana, a cestode found in the intestine of the Sprague-Dawley rats. The N-acetyltransferase activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. The N-acetyltransferase activities from a number of Hymenolepis nana whole tissue homogenizations were found to be 2.83 +/- 0.31 nmole/min/mg for 2-aminofluorene and 2.07 +/- 0.24 nmole/min/mg for p-aminobenzoic acid. The apparent Km and Vmax were 1.06 +/- 0.38 mM and 8.92 +/- 1.46 nmol/min/mg for 2-aminofluorene, and 2.16 +/- 0.19 mM and 12.68 +/- 2.26 nmol/min/mg for p-aminobenzoic acid. The optimal pH value for the enzyme activity was pH 8.0 for both substrates tested. The optimal temperature for enzyme activity was 37 degrees C for both substrates. The N-acetyltransferase activity was inhibited by iodacetamide. At 0.25 mM iodacetamide the activity was reduced 50% and 1.0 mM iodacetamide inhibited activity more than 90%. Among a series of divalent cations and salts, Fe2+, Ca2+ and Zn2+ were demonstrated to be the most potent inhibi-tors. Among the protease inhibitors, only ethylenediaminetetraacetic acid significantly protected N-acetyltransferase. Iodoacetate, in contrast to other agents, markedly inhibited N-acetyltransferase activity. This is the first demonstration of acetyl CoA:arylamine N-acetyltransferase activity in a cestode and extends the number of phyla in which this activity has been found.

Evidence for arylamine N-acetyltransferase in the nematode Anisakis simplex.

N-Acetyltransferase activities with p-aminobenzoic acid and 2-aminofluorene were determined in Anisakis simplex, a nematode found in the intestine of the salt water fish Trichiurus lepturus. The N-acetyltransferase activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. The N-acetyltransferase activity from a number of Anisakis simplex whole tissue homogenizations was found to be 2.89 +/- 0.52 nmol/min per mg for 2-aminofluorene and 2.54 +/- 0.45 nmol/min per mg for p-aminobenzoic acid. The K(m) and Vmax values obtained were 1.06 +/- 0.69 mM and 9.34 +/- 1.94 nmol/min per mg for 2-aminofluorene, and 2.25 +/- 0.10 mM and 14.44 +/- 0.7 nmol/min per mg for p-aminobenzoic acid. The optimal pH value for the enzyme activity was pH 8.0 for both substrates tested. The optimal temperature for enzyme activity was 37 degrees C for both substrates. The N-acetyltransferase activity was inhibited by iodoacetamide: at 0.25 mM iodoacetamide, activity was reduced 50% and 1.0 mM iodoacetamide inhibits activity more than 90%. Among a series of divalent cations and salts, Cu2+ and Zn2+ were demonstrated to be the most potent inhibitors. This is the first demonstration of acetyl CoA/arylamine N-acetyltransferase activity in a nematode and extends the number of phyla in which this activity has been found.