Guoyi Ma

Colon Cancer Chemopreventive Activities of Pomegranate Ellagitannins and Urolithins

Pomegranate juice derived ellagitannins and their intestinal bacterial metabolites, urolithins, inhibited TCDD-induced CYP1-mediated EROD activity in vitro with IC(50) values ranging from 56.7 microM for urolithin A to 74.8 microM for urolithin C. These compounds exhibited dose- and time-dependent decreases in cell proliferation and clonogenic efficiency of HT-29 cells. Inhibition of cell proliferation was mediated through cell cycle arrest in the G(0)/G(1) and G(2)/M stages of the cell cycle followed by induction of apoptosis. These results indicate that the ellagitannins and urolithins released in the colon upon consumption of pomegranate juice in considerable amounts could potentially curtail the risk of colon cancer development, by inhibiting cell proliferation and inducing apoptosis.

Antimicrobial and Antileishmanial Activities of Hypocrellins A and B

ABSTRACT Hypocrellins A and B were evaluated for in vitro antimicrobial and antileishmanial activities. Hypocrellin A exhibited promising activity against Candida albicans and moderate activity against Staphylococcus aureus, methicillin-resistant S. aureus, Pseudomonas aeruginosa, and Mycobacterium intracellulare. Hypocrellin B showed weak antimicrobial activities. Hypocrellin A exhibited potent antileishmanial activity, while hypocrellin B was only moderately active. These results of promising antifungal and antileishmanial activity of hypocrellin A may be useful for further structure-activity relationship and in vivo studies.

Pharmacological Effects of Ephedrine Alkaloids on Human α1- and α2-Adrenergic Receptor Subtypes

Ephedra species of plants have both beneficial and adverse effects primarily associated with the presence of ephedrine alkaloids. Few reports have appeared that examine the direct actions of ephedrine alkaloids on human subtypes of adrenergic receptors (ARs). In the present study, ephedrine alkaloids were evaluated for their binding affinities on human α1A-, α1B-, α1D-, α2A-, α2B-, and α2C-AR subtypes expressed in HEK and Chinese hamster ovary cells. Cell-based reporter gene assays were used to establish functional activity of ephedrine alkaloids at α1A-, α2A-, and α2C-ARs. The data showed that ephedrine alkaloids did not activate α1- and α2-ARs and that they antagonized the agonist-mediated effects of phenylephrine and medetomidine on α1- and α2-ARs, respectively. As in the binding studies, 1R,2R- and 1R,2S-ephedrine showed greater functional antagonist activity than the 1S,2R- and 1S,2S-isomers. The rank order of affinity for the isomers was 1R,2R > 1R,2S > 1S,2R > 1S,2S. The rank order of potencies of alkaloids containing a 1R,2S-configuration was norephedrine ≥ ephedrine ≫ N-methylephedrine. These studies have demonstrated that orientation of the β-hydroxyl group on the ethylamino side chain and the state of N-methyl substitution are important for α-AR binding and functional activity of the ephedrine alkaloids. In conclusion, the ephedrine isomers and analogs studied did not exhibit any direct agonist activity and were found to possess moderate antagonist activities on cloned human α-ARs. The blockade of presynaptic α2A- and α2C-ARs may have a pharmacological role in the direct actions of Ephedra alkaloids.

Inhibition of NF-κB-mediated transcription and induction of apoptosis by melampolides and repandolides

PurposeNuclear factor-κB (NF-κB) plays a crucial role in the regulation of inflammatory processes, cell proliferation, and apoptosis. Blocking NF-κB signaling may represent a therapeutic strategy in cancer and inflammation therapy. The aim of this study was to investigate the effects of sesquiterpenes isolated from Asteraceae, namely melampolides (enhydrin, tetraludin A) and repandolides (repandins A, B, D and E) on the activation of NF-κB, cell growth of cancer cells, cell cycle progression and apoptosis. In addition, their effects on the activity of cyclooxygenase-2 (COX-2) enzyme were also evaluated.MethodsCell-based reporter gene assay was conducted in SW1353 cells. COX-2 enzyme activity and cell growth inhibition was determined by enzyme immunoassay and MTT assay respectively. Cell cycle analysis was carried out by flow cytometry and apoptosis was observed by DAPI staining assay.ResultsIn SW1353 cells, transcription mediated by NF-κB was inhibited by enhydrin, tetraludin A and repandins A, B, D and E, while Sp-1 mediated transcription was not affected. COX-2 enzyme activity was inhibited by enhydrin, repandin A and E, but not by tetraludin A, repandin B and D. These compounds were effective in inhibiting the growth of a panel of human tumor cell lines in a concentration-dependent manner. Cell cycle analysis and DAPI staining indicated cell cycle arrest in G2/M phase and induction of apoptosis.ConclusionsEnhydrin, tetraludin A and repandins A, B, D and E inhibited tumor cell growth and induced cell cycle arrest and apoptosis. These effects may be related to inhibition of NF-B activation.

Design, synthesis, biological evaluation and docking studies of pterostilbene analogs inside PPARα

Pterostilbene, a naturally occurring analog of resveratrol, has previously shown PPARalpha activation in H4IIEC3 cells and was found to decrease cholesterol levels in animals. In this study, analogs of pterostilbene were synthesized and their ability to activate PPARalpha was investigated. Among analogs that was synthesized (E)-4-(3,5-dimethoxystyryl)phenyl dihydrogen phosphate showed activity higher than pterostilbene and control drug ciprofibrate. Docking of the stilbenes inside PPARalpha showed the presence of important hydrogen bond interactions for PPARalpha activation.

Effects of Synephrine and β-Phenethylamine on Human α-Adrenoceptor Subtypes

Synephrine and beta-phenethylamine, two naturally occurring compounds, are structurally related to ephedrine. In this study, the effects of synephrine and beta-phenethylamine on alpha-adrenergic receptor (alpha-AR) subtypes are investigated in human embryonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-norephedrine. The rank order of binding affinities was found to be the same for the subtypes tested (alpha(1A)-, alpha(2A)-, and alpha(2C)-AR) viz, 1R,2S-norephedrine > beta-phenethylamine > synephrine. Functional studies on the alpha(1A)-AR subtype showed that synephrine was a partial agonist giving a maximal response at 100 microM that was equal to 55.3 % of the L-phenylephrine maximum. In contrast, neither 1R,2S-norephedrine nor beta-phenethylamine exhibited agonist activity at the highest concentration tested (300 microM). beta-Phenethylamine was more potent as an antagonist than 1R,2S-norephedrine and synephrine on the alpha(1A)-AR subtype. Functional studies on the alpha(2A)- and alpha(2C)-AR subtypes indicated that synephrine and beta-phenethylamine did not act as agonists. Similar to 1R,2S-norephedrine, both of these analogs reversed the effect of medetomidine against forskolin-induced cAMP elevations at 300 microM, and the rank order of antagonist potency was: 1R,2S-norephedrine = beta-phenethylamine > synephrine; and beta-phenethylamine > 1R,2S-norephedrine > synephrine, respectively. These differences suggest that the presence of a 4-hydroxy group, as in synephrine, reduced the potency in these subtypes. In conclusion, at the alpha(1A)-AR, synephrine acted as a partial agonist, while beta-phenethylamine did not exhibit any direct agonist activity. Both, synephrine and beta-phenethylamine, may act as antagonists of pre-synaptic alpha(2A/2C)-ARs present in nerve terminals.

Selective inhibition of human leukemia cell growth and induction of cell cycle arrest and apoptosis by pseudolaric acid B

PurposeThe leukemias account for the largest number of cases of childhood cancer and remain the primary cause of cancer-related mortality among children in the United States. There is a need for novel antileukemia agents due to toxicity and resistant to existing chemotherapeutic agents. In this study, the effects of pseudolaric acid B (PAB) on three human leukemia cell lines, acute promyelocytic leukemia HL-60 cells, acute lymphoblastic leukemia CCRF-CEM cells, and human chronic myeloid leukemia blast-phase K562 cells were investigated in vitro, compared to normal human peripheral blood mononuclear cells (PBMC).MethodsCell viability was determined using CellTiter-Glo luminescent reagent. Colony formation was assessed by Microtitration cloning assay. Cell cycle analysis was carried out by flow cytometry. Tubulin polymerization was measured by recording the increase in absorbance. Inhibition of topoisomerase I (topo I) and topoisomerase II (topo II) enzyme activities was measured by DNA relaxation assay using topo I and II drug screening kit. Apoptosis was observed by DAPI staining assay and Caspase3/7 activities was measured using Caspase-Glo® 3/7 assay kit.ResultsPseudolaric acid B selectively inhibited the growth of human leukemia HL-60, CCRF-CEM and K562 cells, but not normal PBMC. PAB suppressed colony formation in HL-60 cells. Cell cycle analysis showed that PAB blocked the cell cycle at G2/M phase in HL-60 cells, suggesting that it suppresses mitosis. DNA topo I and topo II were not inhibited, but tubulin polymerization was inhibited. PAB-induced apoptosis and activated caspase-3/7 activity.ConclusionsThis study indicates that PAB has a potential for use against leukemia and its effects might be mediated by inhibiting tubulin polymerization, preventing cell division and activating caspase-3, which leads to apoptosis.

Effects of synephrine and beta-phenethylamine on human alpha-adrenoceptor subtypes.

Synephrine and beta-phenethylamine, two naturally occurring compounds, are structurally related to ephedrine. In this study, the effects of synephrine and beta-phenethylamine on alpha-adrenergic receptor (alpha-AR) subtypes are investigated in human embryonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-norephedrine. The rank order of binding affinities was found to be the same for the subtypes tested (alpha(1A)-, alpha(2A)-, and alpha(2C)-AR) viz, 1R,2S-norephedrine > beta-phenethylamine > synephrine. Functional studies on the alpha(1A)-AR subtype showed that synephrine was a partial agonist giving a maximal response at 100 microM that was equal to 55.3 % of the L-phenylephrine maximum. In contrast, neither 1R,2S-norephedrine nor beta-phenethylamine exhibited agonist activity at the highest concentration tested (300 microM). beta-Phenethylamine was more potent as an antagonist than 1R,2S-norephedrine and synephrine on the alpha(1A)-AR subtype. Functional studies on the alpha(2A)- and alpha(2C)-AR subtypes indicated that synephrine and beta-phenethylamine did not act as agonists. Similar to 1R,2S-norephedrine, both of these analogs reversed the effect of medetomidine against forskolin-induced cAMP elevations at 300 microM, and the rank order of antagonist potency was: 1R,2S-norephedrine = beta-phenethylamine > synephrine; and beta-phenethylamine > 1R,2S-norephedrine > synephrine, respectively. These differences suggest that the presence of a 4-hydroxy group, as in synephrine, reduced the potency in these subtypes. In conclusion, at the alpha(1A)-AR, synephrine acted as a partial agonist, while beta-phenethylamine did not exhibit any direct agonist activity. Both, synephrine and beta-phenethylamine, may act as antagonists of pre-synaptic alpha(2A/2C)-ARs present in nerve terminals.

Inhibition of NF-κB-mediated transcription and induction of apoptosis in human breast cancer cells by epoxypseudoisoeugenol-2-methyl butyrate

PurposeBreast cancer is one of the most prevalent woman cancers. Genomic instability, accumulative mutations, and subsequent changes in intracellular signaling cascades play key roles in the development of human breast cancers. Activation of nuclear factor-κB (NF-κB) has been implicated in oncogenesis of breast cancers and is known to be associated with resistance to anticancer agents and apoptosis. Blocking NF-κB signaling may represent a therapeutic strategy in breast cancer therapy. The objective of this study is to investigate the in vitro effects of epoxypseudoisoeugenol-2-methyl butyrate (EPB), a phenylpropranoid isolated from Pimpinella corymbosa, on the activation of NF-κB, cell growth, cell cycle progression and apoptosis in MCF-7 (estrogen-dependent) and BT-549 (estrogen-independent) breast cancer cells.MethodsTranscriptional activity of NF-κB was measured by cell based reporter gene assay. Cell proliferation was determined by MTT assay. Cell cycle analysis was carried out by flow cytometry and apoptosis was observed by DAPI staining assy.ResultsEPB inhibited the NF-κB-mediated transcription activity induced by tumor necrosis factor-α (TNF-α) and phorbol myristate acetate (PMA) in MCF-7 cells. EPB also inhibited constitutive NF-κB transcriptional activity in BT-549 cells. EPB inhibited the proliferation of both MCF-7 and BT-549 cells in a concentration- and time-dependent manner. EPB induced cell cycle arrest in G1/G0 phase and apoptosis in both MCF-7 and BT 549 cells.ConclusionsThese in vitro results indicated that EPB has a potential for use against both hormone-dependent and hormone-independent breast cancers and its effects seem to be mediated by inhibiting the NF-κB activity.

Effects of Synephrine andβ-Phenethylamine on Humanα-Adrenoceptor Subtypes

Synephrine and beta-phenethylamine, two naturally occurring compounds, are structurally related to ephedrine. In this study, the effects of synephrine and beta-phenethylamine on alpha-adrenergic receptor (alpha-AR) subtypes are investigated in human embryonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-norephedrine. The rank order of binding affinities was found to be the same for the subtypes tested (alpha(1A)-, alpha(2A)-, and alpha(2C)-AR) viz, 1R,2S-norephedrine > beta-phenethylamine > synephrine. Functional studies on the alpha(1A)-AR subtype showed that synephrine was a partial agonist giving a maximal response at 100 microM that was equal to 55.3 % of the L-phenylephrine maximum. In contrast, neither 1R,2S-norephedrine nor beta-phenethylamine exhibited agonist activity at the highest concentration tested (300 microM). beta-Phenethylamine was more potent as an antagonist than 1R,2S-norephedrine and synephrine on the alpha(1A)-AR subtype. Functional studies on the alpha(2A)- and alpha(2C)-AR subtypes indicated that synephrine and beta-phenethylamine did not act as agonists. Similar to 1R,2S-norephedrine, both of these analogs reversed the effect of medetomidine against forskolin-induced cAMP elevations at 300 microM, and the rank order of antagonist potency was: 1R,2S-norephedrine = beta-phenethylamine > synephrine; and beta-phenethylamine > 1R,2S-norephedrine > synephrine, respectively. These differences suggest that the presence of a 4-hydroxy group, as in synephrine, reduced the potency in these subtypes. In conclusion, at the alpha(1A)-AR, synephrine acted as a partial agonist, while beta-phenethylamine did not exhibit any direct agonist activity. Both, synephrine and beta-phenethylamine, may act as antagonists of pre-synaptic alpha(2A/2C)-ARs present in nerve terminals.