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Biochemical Pharmacology (v.72, #5)

Editorial Advisory Board (pp. iii).

TGF-β in cancer and as a therapeutic target by Jan Pinkas; Beverly A. Teicher (pp. 523-529).

Cancer develops through a series of genetic changes leading to malignant transformation. Numerous gene and pathways involved in stages of progression to frank malignancy have been elucidated. These genetic changes result in aberrations in fundamental cellular processes controlling proliferation, apoptosis, differentiation and genomic stability. Metastasis is the hallmark of malignancy. The process of metastasis is extremely complex and involves steps including dissemination of tumor cells from the primary tumor through the vascular and lymphatic system and growth selectively in distant tissues and organs. Transforming growth factor-β which is a growth suppressive cytokine in many normal situations becomes an active and important participant in malignant disease including angiogenesis, extracellular matrix deposition, immuno-suppression and metastasis growth promotion. Transforming growth factor-β and its receptors are targets for antibody therapeutics and small molecule kinase inhibitors.

Keywords: Transforming growth factor-beta; TGF-β; Breast cancer; Prostate cancer

Differential anti-proliferative actions of peroxisome proliferator-activated receptor-γ agonists in MCF-7 breast cancer cells by Ki Young Kim; Sung Soo Kim; Hyae Gyeong Cheon (pp. 530-540).

Peroxisome proliferator-activated receptor-γ (PPARγ) activation has been a new approach to cancer therapy. In the present study, we investigated the effects of two structurally different PPARγ agonists, rosiglitazone and KR-62980 on MCF-7 breast cancer cells. Both agonists inhibited the cell proliferation and colony formation via apoptosis. PTEN expression was increased with decreased Akt phosphorylation by the agonists, whereas agonists actions were abolished in PTEN knockdown cells, indicating the critical role of PTEN in the anti-proliferative effects of PPARγ activation. Rosiglitazone induced the MCF-7 cell differentiation but KR-62980 did not alter the differentiation pattern with little effects on the lipid accumulation and the expression of lipogenesis markers. These results suggest that PPARγ activation may result in the inhibition of cell proliferation and/or induction of cell differentiation depending on the type of PPARγ agonists, and that KR-62980 may be useful in breast cancer therapy by inducing apoptosis.

Keywords: KR-62980; Rosiglitazone; Apoptosis; Differentiation; PPARγ; PTEN; Breast cancer

8-Chloro-adenosine inhibits growth at least partly by interfering with actin polymerization in cultured human lung cancer cells by Yan-Yan Gu; Hong-Yu Zhang; Hai-Jun Zhang; Shu-Yan Li; Ju-Hua Ni; Hong-Ti Jia (pp. 541-550).

A key feature of actin is its ability to bind and hydrolyze ATP. 8-Chloro-adenosine (8-Cl-Ado), which can be phosphorylated to the moiety of 8-Cl-ATP in living cells, inhibits tumor cell proliferation. Therefore we tested the hypothesis that 8-Cl-Ado can interfere with the dynamic state of actin polymerization. We found that 8-Cl-Ado inhibited the growth of human lung cancer cell line A549 and H1299 in culture, and arrested the target cells in G2/M phase evidenced by fluorescence-activated cell sorting (FACS). Immunocytochemistry showed that the normal organization of microfilaments was disrupted in 8-Cl-Ado-exposed cells, which is accompanied by the decrease of cell size and the alteration of cell shape, and by aberrant mitosis and apoptosis in targeted cells. Furthermore, in vitro light scattering assays revealed that 8-Cl-ATP could directly inhibit the transition of G-actin to F-actin. DNase I inhibition assays showed that the G/F-actin ratio, a surrogate marker of actin polymerization status in living cells, was significantly increased in 8-Cl-Ado-exposed A549 and H1299 cells, compared to the G/F-actin ratio in unexposed cells. Taken together, these results indicate that 8-Cl-Ado exposure can alter the dynamic properties of actin polymerization, disrupt the dynamic instability or the rearrangement ability of actin filaments. Therefore, our data suggest that 8-Cl-Ado may exert its cytotoxicity at least partly by interfering with the dynamic instability of microfilaments, which may correlate with its inhibitory effects on cell proliferation and cell death.

Keywords: 8-Chloro-adenosine; G/F-actin ratio; Actin polymerization; G2/M arrest; Human lung cancer cell

Identification and characterization of triosephosphate isomerase that specifically interacts with the integrin αIIb cytoplasmic domain by Qiang-Yuan Liu; Martha Corjay; Giora Z. Feuerstein; Ponnal Nambi (pp. 551-557).

Integrin αIIb/β3 (IIb/IIIa), a platelet fibrinogen receptor, has been shown to play a critical role in thrombosis and hemostasis. However, the mechanisms by which ligands interact with the αIIb/β3 receptor is not very clear at this time. The interaction between the ligand, the receptor and the transmission of extracellular signals may involve the cytoplasmic domains of these integrins. The objective of this investigation was to identify novel proteins that interact with the cytoplasmic tail of αIIb. Using αIIb cytoplasmic tail as the bait and a yeast two-hybrid system, we have identified three separate clones containing inserts that encoded the same protein with different truncated N-terminals. Sequence analysis showed that the inserts of the three clones encoded a previously identified enzyme: triose phosphate isomerase (TPI). In addition, we demonstrated that TPI failed to interact with the integrin α2 tail, β3 tail and lamin, but showed a weak binding to the αV tail which shares the highest homology with αIIb tail among the integrin α family. Site-directed mutagenesis studies around the homology region indicated that the critical peptide sequence necessary for the interaction between TPI and αIIb tail is GFFKRNRPPLEE. Using RT-PCR, we have demonstrated the presence of TPI mRNA in platelets. In addition, experiments were also performed to demonstrate specific binding of TPI to αIIb using an ELISA and fusion protein. Taken together, these data suggest that TPI specifically interacts with αIIb and may play a critical role in αIIb/β3-mediated platelet function.

Keywords: Abbreviations; TPI; triose phosphate isomerase; GST; glutathione S-transferase; ELISA; enzyme-linked immunosorbent assayIntegrins; Triosephosphase isomerase; Platelet; Adhesion molecules GPllb

Crocetin improves endothelium-dependent relaxation of thoracic aorta in hypercholesterolemic rabbit by increasing eNOS activity by F.T. Tang; Z.Y. Qian; P.Q. Liu; S.G. Zheng; S.Y. He; L.P. Bao; H.Q. Huang (pp. 558-565).

Our previous studies have proven that crocetin (CCT), extracted from Gardenia jasminoides Ellis, possesses the anti-atherosclerotic effect. Because endothelial dysfunction strongly contributes to the initiation and progression of atherosclerosis, the present study aims to investigate whether CCT is capable of improving this dysfunction and to explore the possible mechanisms. Endothelial dysfunction was induced by in vivo feeding high cholesterol diet (HCD) to rabbit and by in vitro treating bovine aortic endothelial cells (BAECs) with oxidized LDL (oxLDL). Endothelium-dependent relaxation (EDR) evoked by acetylcholine (Ach) and endothelium-independent relaxation (RIDR) mediated by sodium nitroprusside (SNP) of thoracic aorta isolated from rabbit were measured. The results indicated that the EDR in HCD alone treated rabbits was seriously impaired and the maximal relaxation induced by Ach (10^−5.5M) was only 54% that in control rabbit fed with regular diet. Oral complementation with CCT (15, 30mg/kg) dose-dependently improved this impairment and restored the maximal relaxation to 68% and 80% that in control group, respectively. However, the EIDR maintained comparable in all groups. Complementation with CCT (15, 30mg/kg) simultaneously increased serum level of nitric oxide (NO), upregulated vessel activity and mRNA expression of endothelial NO synthase (eNOS) as well as vessel cyclic GMP (cGMP) content compared with those in rabbit treated with HCD alone. Inducible NOS (iNOS) activity remained unchangeable in all groups. In BAECs, oxLDL treatment decreased NO production, downregulated both activity and mRNA expression of eNOS. While those decrease or downregulation were inhibited by co-treatment with CCT (0.1, 1, 10μM) in a dose-dependent manner. These findings suggested that CCT significantly restored the EDR of thoracic aorta in hypercholesterolemic rabbit, which might be explained by its action to increase the vessel eNOS activity, leading to elevation of NO production.

Keywords: Vascular relaxation function; Nitric oxide; Endothelial nitric oxide synthase; Bovine aortic endothelial cells; Oxidized low density lipoprotein; Crocetin

Down-regulation of estrogen receptor-α in MCF-7 human breast cancer cells after proteasome inhibition by Kannan V. Balan; Yongbao Wang; Siming W. Chen; Panayotis Pantazis; James H. Wyche; Zhiyong Han (pp. 566-572).

The eukaryotic proteasome is a 26S ATP-dependent proteolytic complex, which possesses chymotrypsin-like, trypsin-like and peptidyl glutamyl peptide hydrolase (PGPH) activities, which enable the proteasome to degrade all short-lived and many long-lived proteins, and consequently regulate a myriad of activities in cells. In this study, we observed that inhibition of the proteasome, and more specifically, inhibition of the chymotrypsin-like activity of the proteasome, in MCF-7 human breast cancer cells resulted in selective down-regulation of the nuclear estrogen receptor-α (ERα). Our data indicated that estrogen had no effect, whereas the ERα antagonist, tamoxifen, reduced the amount of ERα that could be subjected to down-regulation after proteasome inhibition. Furthermore, our data demonstrated that protein synthesis was required for the down-regulation of ERα to occur. Collectively, these data indicate the existence of a proteasome-dependent mechanism that is utilized by MCF-7 cells to maintain a steady-state level of ERα.

Keywords: Proteasome; Inhibitor; Estrogen receptor-α down-regulation; Estrogen

Proteasome-independent down-regulation of estrogen receptor-α (ERα) in breast cancer cells treated with 4,4′-dihydroxy- trans-stilbene by Kannan V. Balan; Yongbao Wang; Siming W. Chen; Jin-Chun Chen; Li-Fang Zheng; Li Yang; Zhong-Li Liu; Panayotis Pantazis; James H. Wyche; Zhiyong Han (pp. 573-581).

Treatment of cells with estrogens and several pure ERα antagonists rapidly induces down-regulation of the α-type estrogen receptor (ERα) in the nucleus by mechanisms that are sensitive to the proteasome inhibitors, MG132 and clasto-lactacystin-β-lactone. Hence, it is believed that these ER ligands induce down-regulation of ERα by proteasome-dependent mechanisms, which serve to control both the amount of transcriptional activity and the level of ligand-bound ERα in cells. In this study, we observed that treatment of cultured MCF-7 and T47D human breast cancer cells with the low affinity ER ligand, 4,4′-dihydroxy- trans-stilbene (4,4′-DHS), inhibited the transcriptional activity of ERα and induced slow and gradual decrease in the amount of ERα protein (henceforth referred to as down-regulation of ERα). The 4,4′-DHS-induced down-regulation of ERα in MCF-7 cells involved a mechanism that was insensitive to the two most specific proteasome inhibitors, clasto-lactacystin-β-lactone and epoxomycin, but sensitive to MG132 at concentrations exceeding that required for maximal inhibition of the proteasome in MCF-7 cells. Therefore, 4,4′-DHS appears to induce down-regulation of ERα by a proteasome-independent mechanism. Here, we present data to show that both 4-OH and 4′-OH are critical for the ability of 4,4′-DHS to induce down-regulation of ERα and suggest that 4,4′-DHS provides a useful scaffold for development of novel ERα antagonists.

Keywords: Proteasome; Estrogen receptor-α; Down-regulation; Protease; trans; -Stilbene

Sodium tanshinone IIA sulfonate derived from Slavia miltiorrhiza Bunge up-regulate the expression of prolactin releasing peptide (PrRP) in the medulla oblongata in ovariectomized rats by Yao Xiaoa; Wang Xiao Qing; Ma Shu Lan; Chen Bo Ying (pp. 582-587).

Sodium tanshinone IIA sulfonate (STS), a derivative of tanshinone IIA, is isolated from the root of Salvia miltiorrhiza known as “Danshen�?. Although injection of S. miltiorrhiza extract and STS is used successfully in clinics in China for treating postmenopausal syndrome, the exact mechanism for its therapeutic basis is poorly understood. The present study was undertaken to characterize the effect of STS on the expression of prolactin releasing peptide (PrRP) in the medulla oblongata in ovariectomized rats. In addition, estrogen (E2) levels were detected in OVX rats treated with STS. The results showed that STS might significantly increase the blood level of E2 and PrRP cell number in the medulla oblongata of ovariectomized rats. The number of PrRP immunoreactivity (ir) neurons was higher in the group ovariectomized with STS than that in the ovariectomized group. The numbers of PrRP-ir neurons in Sham and Sham+STS were not significantly different between the two groups. These results suggest that the mechanism that STS improved postmenopausal symptoms induced by ovariectomy in rats might be related to the modulation of the blood E2 level and the expression of PrRP in medulla oblongata of ovariectomized rats.

Keywords: Slavia miltiorrhiza; Sodium tanshinone IIA sulfonate; Prolactin releasing peptide (PrRP); Medulla oblongata; Ovariectomy; Rat

Characterization of the molecular pharmacology of AMD3100: A specific antagonist of the G-protein coupled chemokine receptor, CXCR4 by Simon P. Fricker; Virginia Anastassov; Jennifer Cox; Marilyn C. Darkes; Ognjen Grujic; Stefan R. Idzan; Jean Labrecque; Gloria Lau; Renee M. Mosi; Kim L. Nelson; Ling Qin; Zeffy Santucci; Rebecca S.Y. Wong (pp. 588-596).

The chemokine receptor CXCR4 is widely expressed on different cell types, is involved in leukocyte chemotaxis, and is a co-receptor for HIV. AMD3100 has been shown to be a CXCR4 receptor antagonist, and to block HIV infection of T-tropic, X4-using, virus in vitro and in vivo. AMD3100 is an effective mobilizer of hematopoietic stem cells and is being investigated in clinical trials in multiple myeloma and non-Hodgkins lymphoma patients. Using the CCRF–CEM T-cell line that constitutively expresses CXCR4 we confirmed that AMD3100 was an antagonist of SDF-1/CXCL12 ligand binding (IC₅₀=651±37nM). We have also shown that AMD3100 inhibits SDF-1 mediated GTP-binding (IC₅₀=27±2.2nM), SDF-1 mediated calcium flux (IC₅₀=572±190nM), and SDF-1 stimulated chemotaxis (IC₅₀=51±17nM). AMD3100 did not inhibit calcium flux against cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7 when stimulated with their cognate ligands, nor did it inhibit receptor binding of LTB₄. AMD3100 did not, on its own, induce a calcium flux in the CCRF–CEM cells, which express multiple GPCRs including CXCR4, CCR4 and CCR7. Furthermore, AMD3100 neither stimulated GTP-binding, an assay for GPCR activation, in CEM cell membranes; nor chemotaxis of CCRF–CEM cells. These data therefore demonstrate that AMD3100 is a specific antagonist of CXCR4, is not cross-reactive with other chemokine receptors, and is not an agonist of CXCR4.

Keywords: AMD3100; Chemokine; CXCR4; Stromal cell-derived factor; G-protein coupled receptor; Antagonist

Crystal structures of acetylcholinesterase in complex with HI-6, Ortho-7 and obidoxime: Structural basis for differences in the ability to reactivate tabun conjugates by Fredrik Ekström; Yuan-Ping Pang; Malin Boman; Elisabet Artursson; Christine Akfur; Susanne Börjegren (pp. 597-607).

Inhibition of acetylcholinesterase (AChE) by organophosphorus compounds (OPs) such as pesticides and nerve agents causes acute toxicity or death of the intoxicated individual. The inhibited AChE may be reactivated by certain oximes as antidotes for clinical treatment of OP-intoxications. Crystal structures of the oximes HI-6, Ortho-7 and obidoxime in complex with Mus musculus acetylcholinesterase (mAChE) reveal different roles of the peripheral anionic site (PAS) in the binding of the oximes. A limited structural change of the side chains of Trp286 and Asp74 facilitates the intercalation of the 4-carboxylamide pyridinium ring of HI-6 between the side chains of Tyr124 and Trp286. The 2-carboxyimino pyridinium ring of HI-6 is accommodated at the entrance of the catalytic site with the oximate forming a hydrogen bond to the main-chain nitrogen atom of Phe295. In contrast to HI-6, the coordination of Ortho-7 and obidoxime within the PAS is facilitated by an extended structural change of Trp286 that allows one of the carboxyimino pyridinium rings to form a cation-π interaction with the aromatic groups of Tyr72 and Trp286. The central chain of Ortho-7 and obidoxime is loosely coordinated in the active-site gorge, whereas the second carboxyimino pyridinium ring is accommodated in the vicinity of the phenol ring of Tyr337. The structural data clearly show analogous coordination of Ortho-7 and obidoxime within the active-site gorge of AChE. Different ability to reactivate AChE inhibited by tabun is shown in end-point reactivation experiments where HI-6, Ortho-7 and obidoxime showed an efficiency of 1, 45 and 38%, respectively. The low efficiency of HI-6 and the significantly higher efficiency of Ortho-7 and obidoxime may be explained by the differential binding of the oximes in the PAS and active-site gorge of AChE.

Keywords: Acetylcholinesterase; HI-6; Ortho-7; Obidoxime; X-ray crystallography; Structural changeAbbreviations; ACh; acetylcholine; AChE; acetylcholinesterase; eAChE; Electrophorus electricus; acetylcholinesterase; DTNB; 5,5′-dithiobis(2-nitrobenzoic acid); DFP; diisopropyl phosphorofluoridate; Echothiophate; O; ,; O; ′-diethyl; S; -2-trimethylaminoethyl phosphorothiolate iodide; HI-6; 1-(2-hydroxy-iminomethylpyridinium)-1-(4-carboxyamino)-pyridinium dimethylether dichloride; hAChE; Homo sapiens; acetylcholinesterase; HLö-7; 1-[[[4-(aminocarbonyl)pyridinio]methoxy]metyl]-2,4-bis[(hydroxyimino)methyl] pyridinium dimethanedisulfonate; mAChE; Mus musculus; acetylcholinesterase; MEPQ; 7-(; O; -ethyl methylphosphinyloxy)-1-methylquinolinium iodide; Obidoxime; 1,1′-(oxydimethylene)bis(4-formylpyridinium) dioxime; OP; organophosphorus compound; Sarin; methylethyl methylphosphonofluoridate; Ortho-7; 1,7-heptylene-bis-; N; ,; N; ′-2-pyridiniumaldoxime dichloride; Paraoxon; diethyl; p; -nitrophenyl phosphate; Soman; 1,2,2-trimethylpropyl methylphosphonofluoridate; PAS; peripheral anionic site; Tabun; ethyl; N; ,; N; -dimethylphosphoramidocyanidate; TMB-4; 1,1′-trimethylenebis(4-formylpyridinium bromide) dioxime; TcAChE; Torpedo californica; acetylcholinesterase; TMTFA; m; -(; N; ,; N; ,; N; -trimethylammonio)-2,2,2-trifluoroacetophenone; VX; O; -ethyl S-2-isopropylaminoethyl methylphosphonothiolate; 2-PAM; 2-pyridine aldoxime

Protein S-glutathionylation and platelet anti-aggregating activity of disulfiram by Ranieri Rossi; Daniela Giustarini; Isabella Dalle-Donne; Aldo Milzani (pp. 608-615).

Blood platelets are central to haemostasis, and reactions in platelets involving sulfhydryl groups play important roles in platelet function. Reduced glutathione (GSH) plays an important role in platelet aggregation and glutathione-depleting chemicals inhibit platelet aggregation. The lipophilic drug disulfiram, because of its affinity for sulfhydryl groups, is a highly thiol-reacting agent. As a consequence, GSH and sulfhydryl groups of protein cysteines in human platelets, in analogy to other components of human blood, are a potential target of disulfiram. In the present study, we have shown that exposure of human platelets to disulfiram causes the depletion of platelet GSH and augmentation of mixed disulfides between GSH and protein sulfhydryl groups to form protein-glutathione mixed disulfides ( S-glutathionylated proteins). The depletion of platelet GSH and the increase in S-glutathionylated proteins occurred at concentrations of disulfiram that inhibited platelet aggregation, suggesting that protein S-glutathionylation is involved in the inhibition of platelet aggregation caused by disulfiram.

Keywords: Abbreviations; ALDH; aldehyde dehydrogenase; DTT; dithiothreitol; GSH; reduced glutathione; GSSG; glutathione disulfide; mBrB; monobromobimane; MeDTC-SO; S; -methyl-; N; ,; N; -diethylthiocarbamoyl sulfoxide; NEM; N; -ethylmaleimide; PKC; protein kinase C; PPP; platelet-poor plasma; PRP; platelet-rich plasma; PSSG; protein-GSH mixed disulfides (; S; -glutathionylated proteins); SH group; thiol group; TCA; trichloroacetic acid; tGSH; total glutathioneDisulfiram; Human platelets; ADP-induced platelet aggregation; Protein thiols; S; -Glutathionylated proteins

Adiponectin protects human neuroblastoma SH-SY5Y cells against acetaldehyde-induced cytotoxicity by Tae Woo Jung; Ji Young Lee; Wan Sub Shim; Eun Seok Kang; Jong Sun Kim; Chul Woo Ahn; Hyun Chul Lee; Bong Soo Cha (pp. 616-623).

Acetaldehyde, an inhibitor of mitochondrial function, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with elevation of the intracellular reactive oxygen species (ROS) level and apoptosis. Adiponectin, secreted from adipose tissue, mediates systemic insulin sensitivity with liver and muscle as target organs. In this study, we investigated the protective effects of adiponectin on acetaldehyde-induced apoptosis in human neuroblastoma SH-SY5Y cells and attempted to examine its mechanism. Acetaldehyde-induced apoptosis was moderately reversed by adiponectin treatment. Our results suggest that the protective effects of adiponectin on acetaldehyde-induced apoptosis may be ascribed to ability to induce the expression of anti-oxidant enzymes and to regulate Bcl-2 and Bax expression. These data indicate that adiponectin may provide a useful therapeutic strategy for the prevention of progressive neurodegenerative disease such as Parkinson's disease.

Keywords: Acetaldehyde; Parkinson's disease; Adiponectin; ROS; Apoptosis; SH-SY5Y

Metabolism of the soyabean isoflavone daidzein by CYP1A2 and the extra-hepatic CYPs 1A1 and 1B1 affects biological activity by Kathryn M. Atherton; Elaine Mutch; Dianne Ford (pp. 624-631).

Metabolism of the isoflavones daidzein and genistein, which may protect against some cancers, was studied using human liver microsomes and recombinant CYP isoforms. The detection of three, more polar metabolites of each isoflavone by RP-HPLC required NADPH, consistent with CYP-mediated metabolism. For different liver preparations, metabolite generation from daidzein showed a significant linear correlation with metabolite generation from genistein, indicating metabolism by the same CYP(s). The lowest rate of metabolism of both isoflavones was by the preparation with the lowest CYP1A2 activity. Metabolite peak areas were substantially and significantly reduced by the CYP1A2 inhibitor furafylline and to a lesser extent by the CYP2E1 inhibitor 4-methylpyrazole. Recombinant CYP1A2, but not CYP2E1, generated the metabolites of daidzein and genistein and recombinant CYP1A1 and CYP1B1, expressed at sites including the breast and prostate, were also active. The effects of two CYP-derived metabolites of daidzein, 6,7,4′-trihydroxyisoflavone and 7,3′,4′-trihydroxyisoflavone, were studied in the MCF-7 human breast cancer cell line at a concentration (50μM) at which daidzein induces an antiproliferative response. 7,3′,4′-Trihydroxyisoflavone reduced total cell numbers to a greater extent than 6,7,4′-trihydroxyisoflavone or daidzein and increased cell death. Together, these data demonstrate proof of principle that CYP-mediated metabolism of daidzein can be an activation pathway. We conclude that CYP1A2 makes the major contribution to the hepatic metabolism of both daidzein and genistein and along with metabolism at sites of hormone-dependent tumours may enhance a cancer-protective effect of daidzein if sufficiently high concentrations are reached in target tissues.

Keywords: Phytoestrogen; Isoflavone; Genistein; Daidzein; Cytochrome P450; MCF-7 cells

Effect of human serum albumin on transplacental transfer of glyburide by Tatiana N. Nanovskaya; Ilona Nekhayeva; Gary D.V. Hankins; Mahmoud S. Ahmed (pp. 632-639).

Glyburide is a second-generation sulfonylurea hypoglycemic drug used for the treatment of select women with pregestational and gestational diabetes mellitus (GDM). In vitro and in vivo investigations demonstrated its very low transplacental transfer to the fetal circulation. However, the factors influencing its low transfer across the human placenta remain unclear. Therefore, the goal of the current investigation was to determine the effect of human serum albumin (HSA) on the transfer and distribution of glyburide across the human placenta. To achieve this goal, the technique of dual perfusion of the placental lobule was utilized. The effect of HSA on the transfer of glyburide was determined at the range of glyburide to HSA molar ratios of 1:2–1:100. The transfer rate of free/unbound glyburide to the fetal circuit was 73±10% of the freely diffusible marker compound antipyrine (AP). Data obtained indicates the dependence of glyburide transfer and its retention by the placental tissue on the concentration of HSA.

Keywords: Dual perfusion; Gestational diabetes; Glyburide; Human placenta; Human serum albumin; Transplacental transfer

Green tea flavonols inhibit glucosidase II by Alessandra Gamberucci; Laura Konta; Angela Colucci; Roberta Giunti; Judit É. Magyar; József Mandl; Gábor Bánhegyi; Angelo Benedetti; Miklós Csala (pp. 640-646).

Green tea is getting into the focus of scientific interest due to its beneficial health effects, most of which are attributed to its catechin content. Polyphenolic tea catechins have antioxidant, antiproliferative, antiangiogenic and proapoptotic effects, which makes them promising anticancer compounds. Other poly-hydroxy molecules have similar antitumor potentials through the inhibition of glucosidase II, which affects the glycoprotein maturation and quality control in the endoplasmic reticulum. We investigated the effect of tea catechins on glucosidase II activity in rat liver microsomes using 4-methylumbelliferyl glucoside and 4-nitrophenyl glucoside as substrates. A concentration-dependent inhibition with non-competitive kinetics was found. The IC₅₀ and K_i values for certain tea catechins were comparable with those of N-butyldeoxynojirimycin, the widely used glucosidase inhibitor. The possible interference of tea catechins with the glycoprotein processing in the endoplasmic reticulum should be considered as a potential mechanism of their dietary or pharmacological effects.

Keywords: Abbreviations; EGC; epigallocatechin; EGCG; epigallocatechin gallate; NBDJ; N; -butyldeoxynojirimycin; MUG; 4-methylumbelliferyl α-; d; -glucopyranoside; NPG; 4; -; nitrophenyl α-; d; -glucopyranoside; GC; gallocatechin; GCG; gallocatechin gallate; ECG; epicatechin gallate; PG; propyl gallate; MOPS; 4-morpholinepropanesulfonic acid; TFA; trifluoroacetic acid; MUGase; methylumbelliferyl glucosidase; NPGase; 4-nitrophenyl glucosidaseGreen tea; Endoplasmic reticulum; Glucosidase II; Kinetics; Inhibition; Rat liver

List of Reviewers 2005 (pp. 647-660).

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Biochemical Pharmacology (v.72, #5)