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Qiu P.,Ocean University of China | Qiu P.,University of Massachusetts Amherst | Dong P.,University of Massachusetts Amherst | Guan H.,Ocean University of China | And 5 more authors.
Molecular Nutrition and Food Research | Year: 2010

Hydroxylated polymethoxyflavones (PMFs) are a class of novel flavonoid compounds mainly found in citrus plants. We studied the effects of three major 5-hydroxy PMFs, namely: 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone, 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone, and 5-hydroxy-6,7,8,4′-tetramethoxyflavone, on human colon cancer HCT116 and HT29 cells. Their effects were compared with those produced by their permethoxylated counterparts, namely: nobiletin, 3,5,6,7,8,3′,4′-heptamethoxylflavone, and tangeretin. 5-Hydroxy PMFs showed much stronger inhibitory effects on the growth of the colon cancer cells in comparison with their permethoxylated counterparts, suggesting the pivotal role of hydroxyl group at 5-position in the enhanced inhibitory activity by 5-hydroxy PMFs. Flow cytometry analysis demonstrated that three 5-hydroxy PMFs produced different effects on the cell cycle and apoptosis, which may suggest that three 5-hydroxy PMFs act through different mechanisms. For example, 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone caused cell cycle arrest at G2/M phase in HT29 cells, while 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone led to significant G0/G1 phase arrest. In contrast, 5-hydroxy-6,7,8,4′-tetramethoxyflavone increased sub-G0/G1 cell population, which has been confirmed to be due to enhanced apoptosis. Our results further demonstrated that the inhibitory effects of 5-hydroxy PMFs were associated with their ability in modulating key signaling proteins related to cell proliferation and apoptosis, such as p21 Cip1/Waf1, CDK-2, CDK-4, phosphor-Rb, Mcl-1, caspases 3 and 8, and poly ADP ribose polymerase (PARP). Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Qiu P.,Ocean University of China | Qiu P.,University of Massachusetts Amherst | Guan H.,Ocean University of China | Dong P.,University of Massachusetts Amherst | And 5 more authors.
Molecular Nutrition and Food Research | Year: 2011

Scope: Previously, we reported that 5-hydroxy polymethoxyflavones (5OH-PMFs) isolated from orange, namely 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone, 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone (5HHMF) and 5-hydroxy-6,7,8,4'-tetramethoxyflavone (5HTMF), potently induced apoptosis and cell-cycle arrest in multiple human colon cancer cells. Herein, using isogenic variants of HCT116 human colon cancer cells, we investigated the effects of p53, Bax and p21 on the apoptosis and cell-cycle arrest induced by different 5OH-PMFs. Methods and results: Annexin V/PI co-staining assay demonstrated that 5HHMF and 5HTMF significantly induced apoptosis in HCT116 (p53+/+) cells but not in HCT116 (p53-/-) cells. Furthermore, 5HHMF and 5HTMF significantly induced apoptosis in HCT116 (Bax+/-) cells, whereas their pro-apoptotic effects on HCT116 (Bax-/-) cells were marginal. All three 5OH-PMFs increased G0/G1 cell population of HCT116 (p53+/+) cells, and these effects were abolished in HCT116 (p53-/-) and HCT116 (p21-/-) cells. Immunoblotting analysis showed that 5HHMF and 5HTMF increased the levels of cleaved caspase-3, cleaved PARP in both HCT116 (p53+/+) and HCT116 (Bax+/-) cells and these effects were much weaker in HCT116 (p53-/-) and HCT116 (Bax-/-) cells. Conclusion: Our results demonstrated that 5OH-PMFs, especially 5HHMF and 5HTMF, induce apoptosis and cell-cycle arrest by p53-, Bax- and p21-dependent mechanism. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bryant B.,Monell Chemical Senses Center | Xu J.,Monell Chemical Senses Center | Audige V.,University of Pennsylvania | Lischka F.W.,Monell Chemical Senses Center | Rawson N.E.,Wellgen Inc.
ACS Chemical Neuroscience | Year: 2010

Smokers regulate their smoking behavior on the basis of sensory stimuli independently of the pharmacological effects of nicotine (Rose, J. E., et al. (1993) Pharmacol., Biochem. Behav. 44 (4), 891 -900). A better understanding of sensory mechanisms underlying smoking behavior may help to develop more effective smoking alternatives. Olfactory stimulation by nicotine makes up a considerable part of the flavor of tobacco smoke, yet our understanding of the cellular mechanisms responsible for olfactory detection of nicotine remains incomplete. We used biophysical methods to characterize the nicotine sensitivity and response mechanisms of neurons from olfactory epithelium. In view of substantial differences in the olfactory receptor repertoire between rodent and human (Mombaerts, P. (1999) Annu. Rev. Neurosci. 22, 487-509), we studied biopsied human olfactory sensory neurons (OSNs), cultured human olfactory cells (Gomez, G., et al. (2000) J. Neurosci. Res. 62 (5), 737-749), and rat olfactory neurons. Rat and human OSNs responded to S(-)-nicotine with a concentration dependent influx of calcium and activation of adenylate cyclase. Some rat OSNs displayed some stereoselectivity, with neurons responding to either enantiomer alone or to both. Freshly biopsied and primary cultured human olfactory neurons were less stereoselective. Nicotinic cholinergic antagonists had no effect on the responses of rat or human OSNs to nicotine. Patch clamp recording of rat OSNs revealed a nicotine-activated, calcium-sensitive nonspecific cation channel. These results indicate that nicotine activates a canonical olfactory receptor pathway rather than nicotinic cholinergic receptors on OSNs. Further, because the nicotine-sensitive mechanisms of rodents appear generally similar to those of humans, this animal model is an appropriate one for studies of nicotine sensation. © 2010 American Chemical Society. Source

Yee K.K.,Monell Chemical Senses Center | Pribitkin E.A.,Monell Chemical Senses Center | Pribitkin E.A.,Thomas Jefferson University | Cowart B.J.,Monell Chemical Senses Center | And 8 more authors.
American Journal of Rhinology and Allergy | Year: 2010

Background: Chronic rhinosinusitis (CRS) is a complex heterogeneous inflammatory disease that affects the nasal cavity, but the pathological examination of the olfactory mucosa (OM) in this disease has been limited. Methods: Nasal biopsy specimens were obtained from 20 control subjects and 50 CRS patients in conjunction with clinical assessments. Histopathology of these nasal biopsy specimens was performed and immunohistochemistry was used to characterize nonneuronal, neuronal, and inflammatory cells in the OM. These OM characteristics were then evaluated to determine the degree to which pathological features may be related to smell loss in CRS. Results: Histopathological examination of control and CRS OM revealed changes in the normal pseudostratified olfactory epithelium (OE): intermixing of goblet cells, metaplasia to squamous-like cells, and erosion of the OE. Lower percentages of normal epithelium and olfactory sensory neurons were found in CRS OE compared with controls. Relative to other CRS patients, those with anosmia had the greatest amount of OE erosion, the highest density of eosinophils infiltrating the OE, and exhibited the most extensive abnormalities on CT and endoscopic examination, including being significantly more likely to exhibit nasal polyposis. Conclusion: Our results suggest that OM pathology observed in nasal biopsy specimens can assist in understanding the degree of epithelial change and sensorineural damage in CRS and the potential for olfactory loss. Copyright © 2010, OceanSide Publications, Inc. Source

Dong P.,University of Massachusetts Amherst | Qiu P.,University of Massachusetts Amherst | Qiu P.,Ocean University of China | Zhu Y.,University of Massachusetts Amherst | And 5 more authors.
Journal of Chromatography A | Year: 2010

Accumulating evidence has suggested the potential health-promoting effects of 5-hydroxy polymethoxyflavones (5-OH-PMFs) naturally existing in citrus genus. However, research efforts are hampered by the lack of reliable and sensitive methods for their determination in plant materials and biological samples. Using reversed-phase high performance liquid chromatography (HPLC) equipped with electrochemical (EC) detection, we have developed a fast and highly sensitive method for quantification of four 5-OH-PMFs, namely 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone, 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone, 5-hydroxy-6,7,4′-trimethoxyflavone, and 5-hydroxy-6,7,8,4′-tetramethoxyflavone. The method was fully validated in terms of linearity, accuracy and precision. The limit of detection (LOD) was determined as being between 0.65 and 1.8 ng/mL (ppb), demonstrating an over 160 times higher sensitivity in comparison with the previously reported method using UV detection. The recovery rate of the method was between 96.17% and 110.82%, and the precision for the retention times and peak areas was all below 13%. The method was successfully used to quantify 5-OH-PMFs with a wide range of abundance in the citrus products and preparations, such as orange juice, citrus peel, and dried tangerine peel. The quantification method for 5-OH-PMFs developed herein could be useful for the nutritional and pharmacological studies of these compounds in future. © 2009 Elsevier B.V. All rights reserved. Source

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