A distinct TthMutY bifunctional glycosylase that hydrolyzes not only adenine but also thymine opposite 8-oxoguanine in the hyperthermophilic bacterium, Thermus thermophilus.

Oxidative damage represents a major threat to genomic stability because the major product of DNA oxidation, 8-oxoguanine (GO), frequently mispairs with adenine during replication. We were interested in finding out how hyperthermophilic bacteria under goes the process of excising mispaired adenine from A/GO to deal with genomic oxidative damage. Herein we report the properties of an Escherichia coli MutY (EcMutY) homolog, TthMutY, derived from a hyperthermophile Thermus thermophilus. TthMutY preferentially excises on A/GO and G/GO mispairs and has additional activities on T/GO and A/G mismatches. TthMutY has significant sequence homology to the A/G and T/G mismatch recognition motifs, respectively, of MutY and Mig.MthI. A substitution from Tyr112 to Ser or Ala (Y112S and Y112A) in the putative thymine-binding site of TthMutY showed significant decrease in DNA glycosylase activity. A mutant form of TthMutY, R134K, could form a Schiff base with DNA and fully retained its DNA glycosylase activity against A/GO and A/G mispair. Interestingly, although TthMutY cannot form a trapped complex with substrate in the presence of NaBH(4), it expressed AP lyase activity, suggesting Tyr112 in TthMutY may be the key residue for AP lyase activity. These results suggest that TthMutY may be an example of a novel class of bifunctional A/GO mismatch DNA glycosylase that can also remove thymine from T/GO mispair.

Acacetin-induced apoptosis of human breast cancer MCF-7 cells involves caspase cascade, mitochondria-mediated death signaling and SAPK/JNK1/2-c-Jun activation.

The mechanism of acacetin-induced apoptosis of human breast cancer MCF-7 cells was investigated. Acacetin caused 50% growth inhibition (IC50) of MCF-7 cells at 26.4% 0.7% M over 24 h in the MTT assay. Apoptosis was characterized by DNA fragmentation and an increase of sub-G1 cells and involved activation of caspase-7 and PARP (poly-ADP-ribose polymerase). Maximum caspase 7 activity was observed with 100 microM acacetin for 24 h. Caspase 8 and 9 activation cascades mediated the activation of caspase 7. Acacetin caused a reduction of Bcl-2 expression leading to an increase of the Bax:Bcl-2 ratio. It also caused a loss of mitochondrial membrane potential that induced release of cytochrome c and apoptosis inducing factor (AIF) into the cytoplasm, enhancing ROS generation and subsequently resulting in apoptosis. Pretreatment of cells with N-acetylcysteine (NAC) reduced ROS generation and cell growth inhibition, and pretreatment with NAC or a caspase 8 inhibitor (Z-IETD-FMK) inhibited the acacetin-induced loss of mitochondrial membrane potential and release of cytochrome c and AIF. Stress-activated protein kinase/c-Jun NH4-terminal kinase 1/2 (SAPK/ JNK1/2) and c-Jun were activated by acacetin but extracellular-regulated kinase 1/2 (Erk1/2) nor p38 mitogen-activated protein kinase (MAPK) were not. Our results show that acacetin-induced apoptosis of MCF-7 cells is mediated by caspase activation cascades, ROS generation, mitochondria-mediated cell death signaling and the SAPK/JNK1/2-c-Jun signaling pathway, activated by acacetin-induced ROS generation.

Alzheimer's disease drug discovery from herbs: neuroprotectivity from beta-amyloid (1-42) insult.

OBJECTIVE: To comparatively evaluate selected herbs for their ability to protect neuronal cells from direct betaA(1-42) insult. DESIGN: Twenty-seven (27) herbs were selected, extracted with aqueous methanol (90%) and chloroform, and the extracts were evaluated for their ability to protect PC12 rat pheochromocytoma and primary neuronal cells from betaA(1-42) insult using both 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction assay and lactate dehydrogenase efflux assay. RESULTS: Curcuma aromatia (ul-keum) and Zingiber officinale (ginger) extracts effectively protected cells from betaA(1-42) insult, followed by Ginkgo biloba (ginkgo), Polygonatum sp. (King Solomon's seal), Cinnamum cassia (Chinese cinnamon), Rheum coreanum (Korean rhubarb), Gastrodia elata (gastrodia), and Scutellaria baicalensis (skullcap). Several extracts showed cytotoxicity at high concentration (approximately 150 microg/mL), whereas other extracts did not at all protect cells from betaA(1-42) insult. CONCLUSION: Selective herbs may be potentially important resources to discover drug candidates against the onset of Alzheimer's disease.

Curcuminoids in neurodegenerative diseases.

Neurodegeneration is a term used to describe progressive deterioration of structure and/or function of neurons that affects different parts of the central nervous system and leads to eventual death. Neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and Down's syndrome (DS), multiple sclerosis (MS), glaucoma, age-related macular degeneration (AMD), and diabetic encephalopathy (DE). Although the initial events that trigger these disorders may be different from each other, they share similar biochemical reactions that lead to neurodegeneration. Curcuminoids, polyphenol compounds from turmeric (Curcuma longa), possess diverse biological properties that modulate debilitating biochemical processes involved in AD that include attenuation of mitochondrial dysfunction-induced oxidative stress and inflammatory responses to inflammatory cytokines, COX-2, and iNOS. Curcuminoids also bind to ß-amyloid (Aß) plaques to inhibit amyloid accumulation and aggregation in the brain, in addition to inhibiting the toxic Aß oligomer formation and oligomer-dependent Aß toxicity. These properties can be further elaborated to DS, glaucoma and AMD. Curcuminoids also prevent α-synuclein aggregation in PD; attenuate ROS-induced COX-2 expression in ALS; ameliorate the symptoms of MS, DE and traumatic brain injury, in addition to neurodamages caused by heavy metal poisoning. These results demonstrate curcuminoids may be potentially effective therapeutic means to treat neurodegenerative diseases. A bulk of patents discloses methods to improve bioavailability of curcuminoids for therapeutic development. This review provides a comprehensive description on the current progress on curcuminoids against neurodegenerative diseases.

Genistein-induced apoptosis of human breast cancer MCF-7 cells involves calpain-caspase and apoptosis signaling kinase 1-p38 mitogen-activated protein kinase activation cascades.

The molecular mechanisms of genistein-induced apoptosis of human breast cancer MCF-7 cells were investigated. Genistein showed 50% cell growth inhibition at IC50=27.5+/-0.8 micromol/l in 24 h incubation under 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay conditions. Genistein is known to express both cell growth activity at nanomolar concentrations and anti-cell growth activity at micromolar concentrations. It was found that genistein at 100 micromol/l concentration effectively induced apoptosis of MCF-7 cells in 24 h. Genistein-induced apoptosis involved activation of calpain, caspase 7 and poly(ADP ribose) polymerase. Dantrolene, an inhibitor of Ca release from the endoplasmic reticulum, inhibited genistein-induced activation of calpain and caspase 7, in addition to effectively negating genistein-induced apoptosis. MCF-7 cells treated with genistein also showed increased phosphorylation of p38 mitogen-activated protein kinase, whereas no effect was observed for extracellular signal-regulating kinase 1/2. Phosphorylation of apoptosis signaling kinase 1, an upstream regulator of p38 mitogen-activated protein kinase, was also increased by genistein treatment. Genistein-induced phosphorylation of apoptosis signaling kinase 1 and p38 mitogen-activated protein kinase was diminished by the presence of dantrolene. These results suggest that genistein-induced apoptosis in MCF-7 cells is mediated through calpain-caspase 7 and apoptosis signaling kinase 1-p38 mitogen-activated protein kinase activation cascades that involve Ca release from the endoplasmic reticulum.

Side-chain length is important for shogaols in protecting neuronal cells from beta-amyloid insult.

Ten shogaols were synthesized to evaluate the importance of the side-chain length in protecting cells from betaA(1-42) insult using PC12 rat pheochromocytoma and IMR-32 human neuroblastoma cells. The compounds cell protectivity against betaA insult was demonstrated using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay. The efficacy of cell protection from betaA insult by these shogaols was shown to improve as the length of the side chain increase.

Discovery of natural products from Curcuma longa that protect cells from beta-amyloid insult: a drug discovery effort against Alzheimer's disease.

From Curcuma longa, two novel compounds, 4' '-(3' "-methoxy-4' "-hydroxyphenyl)-2' '-oxo-3' '-enebutanyl 3-(3'-methoxy-4'hydroxyphenyl)propenoate (calebin-A, 1) and 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,4,6-heptatrien-3-one (2), and seven known compounds, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin, 3), 1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (demethoxycurcumin, 4), 1,7-bis(4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (bisdemethoxycurcumin, 5), 1-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-6-heptene-3,5-dione (6), 1,7-bis(4-hydroxyphenyl)-1-heptene-3,5-dione (7), 1,7-bis(4-hydroxyphenyl)-1,4,6-heptatrien-3-one (8), and 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadien-3-one (9), were isolated following a bioassay-guided fractionation scheme utilizing an assay to detect protection of PC12 cells from beta-amyloid insult. Compounds 1, 3-5, and 7 were found to more effectively protect PC12 cells from betaA insult (ED(50) = 0.5-10 microg/mL) than Congo red (10) (ED(50) = 37-39 microg/mL).

New triterpenoids from the leaves of Abrus precatorius.

Three new (1-3) triterpenoids and one known (4) triterpenoid were isolated from an acid hydrolyzed methanol-soluble extract of the leaves of Abrus precatorius. Their structures were identified as (20S,22S)-3beta,22-dihydroxycucurbita-5(10),24-diene-26,29-dioic acid delta-lactone (1), 3-O-[6'-methyl-beta-D-glucuronopyranosyl]-3beta,22beta-dihydroxyolean-12-en-29-oic acid methyl ester (2), 3-O-beta-D-glucuronopyranosylsophoradiol methyl ester (3), and sophoradiol (4) by spectroscopic techniques including 2D NMR.

Shogaols from Zingiber officinale protect IMR32 human neuroblastoma and normal human umbilical vein endothelial cells from beta-amyloid(25-35) insult.

From the rhizome of Zingiber officinale L. (Zingiberaceae), four shogaols that protect IMR32 human neuroblastoma and normal human umbilical vein endothelial cells from beta-amyloid(25 - 35) insult at EC50 = 4.5 - 81 microM were isolated. The efficacy of cell protection from beta-amyloid(25 - 35) insult by these shogaols was shown to improve as the length of the side chain increases.