Check out our New Publishers' Select for Free Articles

Biochemical Pharmacology (v.77, #6)

Editorial Advisory Board (pp. iii).

Dietary n−6 and n−3 polyunsaturated fatty acids: From biochemistry to clinical implications in cardiovascular prevention by Gian Luigi Russo (pp. 937-946).

Linoleic acid (LA) and alpha linolenic acid (ALA) belong to the n−6 (omega-6) and n−3 (omega-3) series of polyunsaturated fatty acids (PUFA), respectively. They are defined “essential” fatty acids since they are not synthesized in the human body and are mostly obtained from the diet. Food sources of ALA and LA are most vegetable oils, cereals and walnuts. This review critically revises the most significant epidemiological and interventional studies on the cardioprotective activity of PUFAs, linking their biological functions to biochemistry and metabolism. In fact, a complex series of desaturation and elongation reactions acting in concert transform LA and ALA to their higher unsaturated derivatives: arachidonic acid (AA) from LA, eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) from ALA. EPA and DHA are abundantly present in fish and fish oil. AA and EPA are precursors of different classes of pro-inflammatory or anti-inflammatory eicosanoids, respectively, whose biological activities have been evoked to justify risks and benefits of PUFA consumption. The controversial origin and clinical role of the n−6/ n−3 ratio as a potential risk factor in cardiovascular diseases is also examined. This review highlights the important cardioprotective effect of n−3 in the secondary prevention of sudden cardiac death due to arrhythmias, but suggests caution to recommend dietary supplementation of PUFAs to the general population, without considering, at the individual level, the intake of total energy and fats.

Keywords: Abbreviations; AA; arachidonic acid (20:4; n; −; 6); AI; adequate intake; ALA; alpha-linolenic acid (18:3; n; −; 3, omega-3); CHD; coronary heart disease; COX; cyclooxygenase; CVD; cardiovascular diseases; d-6-d and d-5-d; delta-6- and delta-5- desaturases; DHA; docosahexaenoic acid (22:6; n; −; 3); EFA; essential fatty acids; OA; oleic acid (18:1; n; −; 9); EPA; eicosapentaenoic acid (20:5; n; −; 3); FADS2; delta-6 fatty acid desaturase; LA; linoleic acid (18:2; n; −; 6, omega-6); LDL; low-density lipoprotein; LOX; lipoxygenase; LXR; liver X receptors; MI; myocardium infarction; PPAR; peroxisome proliferator-activated receptor; PUFA and MUFA; polyunsaturated and monounsaturated fatty acids respectively; SREBP-1c; sterol regulatory element-binding protein 1c; TCR; T-cell receptor; VLDL; very low-density lipoproteins; UL; upper intake limitLinoleic acid; Alpha-linolenic acid; n; −; 6 (omega-6) fatty acids; n; −; 3 (omega-3) fatty acids docosahexaenoic acid; Eicosapentaenoic acid; Arachidonic acid; Polyunsaturated fatty acids; Essential fatty acids; Cardiovascular disease

Timing is everything: Consequences of transient and sustained AhR activity by Kristen A. Mitchell; Cornelis J. Elferink (pp. 947-956).

The aryl hydrocarbon receptor (AhR) was implicated as a mediator of xenobiotic toxicity over three decades ago. Although a complete picture continues to elude us, investigations by many laboratories during the ensuing period have revealed much about AhR biology in normal physiological processes, as well as the toxicities induced by the dioxins and related polychlorinated aromatic hydrocarbons. The findings are captured in numerous excellent reviews. This commentary attempts to inject a new perspective on some new as well as frequently overlooked observations in the context of established receptor properties. Specifically, we examine the impact of transient versus sustained receptor activation on AhR biology, and explore the potential role for cytochrome P450 expression in regulating AhR activity amongst various tissues. The growing recognition that AhR action functions through multiple mechanisms serves to further highlight the importance of limiting prolonged receptor activation.

Keywords: Abbreviations; 1-PP; 1-(1-propynyl)pyrene; AhR; aryl hydrocarbon receptor; AhRR; Ah receptor repressor protein; ARNT; Ah receptor nuclear translocator; bHLH; basic helix-loop-helix; CA-AhR; constitutively active Ah receptor; CDK; cyclin-dependent kinase; CYP; cytochrome P450; DEN; N-nitrosodiethylamine; EGFR; epidermal growth factor receptor; FICZ; 6-formylindolo[3,2-b]carbazole; HAH; halogenated aromatic hydrocarbons; PAH; polyaromatic hydrocarbons; PAS; Per-ARNT-Sim; PH; partial hepatectomy; pRB; retinoblastoma protein; TCDD; 2,3,7,8-tetrachlorodibenzo-; p; -dioxin; XRE; xenobiotic response elementAh receptor; Endogenous; Cytochrome P450

The alkyl chain length of 3-alkyl-3′,4′,5,7-tetrahydroxyflavones modulates effective inhibition of oxidative damage in biological systems: Illustration with LDL, red blood cells and human skin keratinocytes by Paulo Filipe; Artur M.S. Silva; Raquel S.G.R. Seixas; Diana C.G.A. Pinto; Alvaro Santos; Larry K. Patterson; João N. Silva; José A.S. Cavaleiro; João P. Freitas; Jean-Claude Mazière; René Santus; Patrice Morlière (pp. 957-964).

It is shown that the relationship between the alkyl chain length of 3-alkyl-3′,4′,5,7 tetrahydroxyflavones (FnH) bearing alkyl chains of n=1, 4, 6, 10 carbons and their capacity to counter oxidative damage varies markedly with the nature of the biological system. In Cu²⁺-induced lipid peroxidation of low-density lipoprotein (LDL), the less hydrophobic short-chain F1H and F4H are probably located in the outer layer of LDL and parallel the reference flavonoid antioxidant, quercetin (Q) as effective inhibitors of lipid peroxidation. A marked inhibition of haemolysis induced in red blood cells (RBC) suspensions by the membrane-permeant oxidant, tert-butylhydroperoxide (t-BuOOH), is observed with F4H and F6H present at concentration in the micromolar range. However, F10H the most hydrophobic FnH is even more effective than Q against both haemolysis and lipid peroxidation as measured by malondialdehyde (MDA) equivalents. In oxidation of RBC by H₂O_2, at least 50 times more F6H and F10H than by t-BuOOH are required to only partly inhibit haemolysis and MDA production. The F1H, F4H and Q are found rather inactive under these conditions. At concentrations in the micromolar range, a marked protection against the cytotoxic effects of the t-BuOOH-induced oxidative stress in human skin NCTC 2544 keratinocytes is also exhibited by the four FnH antioxidants and is comparable to that of Q. Thus, the four FnH species under study may be considered as potent antioxidants which manifest complementary anti-oxidative actions in biological systems of markedly different complexity.

Keywords: Lipid peroxidation; Hydrogen peroxide; tert; -Butylhydroperoxide; Flavonoid; Quercetin; Cytotoxicity

SJ23B, a jatrophane diterpene activates classical PKCs and displays strong activity against HIV in vitro by Luis M. Bedoya; Nieves Márquez; Natalia Martínez; Silvia Gutiérrez-Eisman; Amparo Álvarez; Marco A. Calzado; José M. Rojas; Giovanni Appendino; Eduardo Muñoz; José Alcamí (pp. 965-978).

Existence of virus reservoirs makes the eradication of HIV infection extremely difficult. Current drug therapies neither eliminate these viral reservoirs nor prevent their formation. Consequently, new strategies are needed to target these reservoirs with the aim of decreasing their size. We analysed a series of jatrophane diterpenes isolated from Euphorbia hyberna and we found that one of them, SJ23B, induces the internalization of the HIV-1 receptors CD4, CXCR4 and CCR5 and prevents R5 and X4 viral infection in human primary T cells at the nanomolar range. Moreover, SJ23B is a potent antagonist of HIV-1 latency. Using Jurkat-LAT-GFP cells, a model for HIV-1 latency, we found that prostratin and SJ23B activate HIV-1 gene expression, with SJ23B being at least 10-fold more potent than prostratin. SJ23B did not elicit transforming foci activity in NIH 3T3 cells but is a potent activator of PKCα and δ as measured by in vitro kinase assays and by cellular translocation experiments. By using isoform-specific PKC inhibitors we found that cPKCs are critical for SJ23B-induced HIV-1 reactivation. We also showed that both SJ23B-induced IκBα degradation and NF-κB activation were inhibited by the classical PKC inhibitor, Gö6976. Accordingly, SJ23B synergizes with ionomycin to translocate PKCα to the plasma membrane and to activate the NF-κB pathway. Moreover, SJ23B activates both NF-κB and Sp1-dependent transcriptional activities in primary T cells. We have shown that diterpene jatrophanes represent a new member of anti-AIDS agents that could be developed for mitigating HIV reactivation.

Keywords: Abbreviations; PKC; protein kinase C; HIV-1; human immunodeficiency virus-1; PMA; phorbol myristate acetate; HAART; highly active antiretroviral therapy; DAG; 2-diacyl-; sn; -glycerolHIV-1 and latency reactivation; SJ23B; Prostratin and phorbol esters; Receptors down-regulation; NF-κB and PKC pathways

Functions of epidermal growth factor receptor in cisplatin response of thyroid cells by Antonella Muscella; Loredana Urso; Nadia Calabriso; Carla Vetrugno; Francesco Paolo Fanizzi; Carlo Storelli; Santo Marsigliante (pp. 979-992).

Epidermal growth factor receptor (EGFR) signal transduction pathway has been reported to play a vital role in the biologic progression of several tumours and as targets for therapeutic intervention. We have investigated the role of EGFR in the thyroid PC Cl3 cells response to the chemo-therapeutic agent cisplatin. It was found that cisplatin provoked (1) the activation (phosphorylation) and internalization of EGFR, (2) the phosphorylation of mitogen-activated protein kinase (MAPK)/p38, (3) the activation of PKC-ɛ, (4) the enhancement of matrix metalloproteinase-2 (MMP-2) expression and activity, (5) the generation of reactive oxygen species (ROS) and (6) the activation of the apoptotic intrinsic pathway. Inhibition or down regulation of EGFR reduced (1) the phosphorylation of MAPK/p38, (2) the cisplatin-provoked activation of PKC-ɛ, and (3) the activation of caspase-7 and PARP cleavage and the overall cells sensitivity to cisplatin. PKC-ɛ inhibition achieved by siRNA blocked MAPK/p38 activation and significantly increased the cell resistance to cisplatin. Finally, when the cisplatin-induced ROS generation was blocked by using NAD(P)H oxidase inhibitors, a decrease in cisplatin-induced MMP-2 enhancement, MAPK/p38 and EGFR activation, and caspase-7 proteolysis occurred.In conclusion, these findings supported a model in which cisplatin provokes an oxidant-induced MMP-2-dependent EGFR transactivation responsible for the induction of cell apoptosis, a process ascribable to the intracellular signalling of PKC-ɛ and MAPK/p38.

Keywords: Abbreviations; DAPI; 4,6-diammine-2-phenylindol; ECL; enhanced chemiluminescence; EGFR; epidermal growth factor receptor; ERK; extracellular signal-regulated kinase; MAPK; mitogen-activated protein kinase; MEK; MAPK/ERK kinase; MTT; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide; PARP; poly(ADP-ribose) polymerase; PBS; phosphate-buffered saline; PVDF; polyvinylidene difluoride membrane; SDS; sodium dodecyl sulphate; siRNA; small interfering RNA; SRB; sulforhodamine BEGFR; p38/MAPK; PKC-ɛ; MMP-2; ROS; Cisplatin; Thyroid; PC Cl3

Cepharanthine is a potent reversal agent for MRP7(ABCC10)-mediated multidrug resistance by Ying Zhou; Elizabeth Hopper-Borge; Tong Shen; Xiao-Cong Huang; Zhi Shi; Ye-Hong Kuang; Tatsuhiko Furukawa; Shin-ichi Akiyama; Xing-Xiang Peng; Charles R. Ashby Jr.; Xiang Chen; Gary D. Kruh; Zhe-Sheng Chen (pp. 993-1001).

Multidrug resistance protein 7 (MRP7; ABCC10) is an ABC transporter that confers resistance to anticancer agents such as the taxanes. We previously reported that several inhibitors of P-gp and MRP1 were able to inhibit the in vitro transport of E₂17βG by MRP7 in membrane vesicles transport assays. However, compounds that are able to reverse MRP7-mediated cellular resistance have not been identified. In this study, we examined the effects of cepharanthine (6′,12′-dimethoxy-2,2′-dimethyl-6,7-[methylenebis(oxy)]oxyacanthan), an herbal extract isolated from Stephania cepharantha Hayata, to reverse paclitaxel resistance in MRP7-transfected HEK293 cells. Cepharanthine, at 2μM, completely reversed paclitaxel resistance in MRP7-transfected cells. In contrast, the effect of cepharanthine on the parental transfected cells was significantly less than that on the MRP7-transfected cells. In addition, cepharanthine significantly increased the accumulation of paclitaxel in MRP7-transfected cells almost to the level of control cells in the absence of cepharanthine. The efflux of paclitaxel from MRP7-transfected cells was also significantly inhibited by cepharanthine. The ability of cepharanthine to inhibit MRP7 was analyzed in membrane vesicle assays using E₂17βG, an established substrate of MRP7, as a probe. E₂17βG transport was competitively inhibited by cepharanthine with a K_i value of 4.86μM. These findings indicate that cepharanthine reverses MRP7-mediated resistance to paclitaxel in a competitive manner.

Keywords: Abbreviations; MDR; multidrug resistance; ABC; ATP-binding cassette; BCRP/ABCG2/MXR; breast cancer resistance protein; P-gp/MDR1/ABCB1; P-glycoprotein; MRP7/ABCC10; multidrug resistance protein 7; cepharanthine; 6′,12′-dimethoxy-2,2′-dimethyl-6,7-[methylenebis(oxy)oxyacan-than]; E; ₂; 17βG; 17-β-estradiol-(17-beta-; d; -glucuronide); VCR; vincristine; VBL; vinblastine; MTT; (3-(4,5-dimethylthiazol-2-yl)-3, 5-diphenylformazanMRP7; MDR; Cepharanthine; Paclitaxel; E; ₂; 17βG transport

A newly synthetic chromium complex—Chromium (d-phenylalanine)₃ activates AMP-activated protein kinase and stimulates glucose transport by Peng Zhao; Jingying Wang; Heng Ma; Yao Xiao; Leilei He; Chao Tong; Zhenhua Wang; Qiusheng Zheng; E. Kurt Dolence; Sreejayan Nair; Jun Ren; Ji Li (pp. 1002-1010).

We synthesized the chromium (phenylalanine)₃ [Cr(d-phe)₃] by chelating chromium(III) withd-phenylalanine ligand in aqueous solution to improve the bioavailability of chromium, and reported that Cr(d-phe)₃ improved insulin sensitivity. AMP-activated protein kinase (AMPK) is a key mediator for glucose uptake and insulin sensitivity. To address the molecular mechanisms by which Cr(d-phe)₃ increases insulin sensitivity, we investigated whether Cr(d-phe)₃ stimulates glucose uptake via activation of AMPK signaling pathway. H9c2 myoblasts and isolated cardiomyocytes were treated with Cr(d-phe)₃ (25μM). Western blotting was used for signaling determination. The glucose uptake was determined by 2-deoxy-d-glucose-³H accumulation. HPLC measured concentrations of AMP. The mitochondrial membrane potential (Δ ψ) was detected by JC-1 fluorescence assay. Cr(d-phe)₃ stimulated the phosphorylation of α catalytic subunit of AMPK at Thr¹⁷², as well the downstream targets of AMPK, acetyl-CoA carboxylase (ACC, Ser²¹²) and eNOS (Ser¹¹⁷⁷). Moreover, Cr(d-phe)₃ significantly stimulated glucose uptake in both H9c2 cells and cardiomyocytes. AMPK inhibitor compound C (10μM) dramatically inhibited the glucose uptake stimulated by Cr(d-phe)₃, while it did not affect insulin stimulation of glucose uptake. Furthermore, in vivo studies showed that Cr(d-phe)₃ also activated cardiac AMPK signaling pathway. The increase of cardiac AMP concentration and the decrease of mitochondrial membrane potential (Δ ψ) may contribute to the activation of AMPK induced by Cr(d-phe)₃. Cr(d-phe)₃ is a novel compound that activates AMPK signaling pathway, which contributes to the regulation of glucose transport during stress conditions that may be associated the role of AMPK in increasing insulin sensitivity.

Keywords: Chromium; AMP-activated protein kinase; Glucose transport; Insulin resistance

Involvement of sphingosine-1-phosphate and S1P₁ in angiogenesis: Analyses using a new S1P₁ antagonist of non-sphingosine-1-phosphate analog by Kiyoaki Yonesu; Yumi Kawase; Tatsuya Inoue; Nana Takagi; Jun Tsuchida; Yoh Takuwa; Seiichiro Kumakura; Futoshi Nara (pp. 1011-1020).

Chemical lead 2 (CL2) is the first non-sphingosine-1-phosphate (Sph-1-P) analog type antagonist of endothelial differentiation gene-1 (Edg-1/S1P₁), which is a member of the Sph-1-P receptor family. CL2 inhibits [³H]Sph-1-P/S1P₁ binding and shows concentration-dependent inhibition activity against both intracellular cAMP concentration decrease and cell invasion induced by the Sph-1-P/S1P₁ pathway. It also inhibits normal tube formation in an angiogenesis culture model, indicating that CL2 has anti-angiogenesis activity. This compound improved the disease conditions in two angiogenic models in vivo. It significantly inhibited angiogenesis induced by vascular endothelial growth factor in a rabbit cornea model as well as the swelling of mouse feet in an anti-type II collagen antibody-induced arthritis model. These results indicate that the Sph-1-P/S1P₁ pathway would have an important role in disease-related angiogenesis, especially in the processes of migration/invasion and tube formation. In addition, CL2 would be a powerful tool for the pharmacological study of the mechanisms of the Sph-1-P/S1P₁ pathway in rheumatoid arthritis, diabetes retinopathy, and solid tumor growth processes.

Keywords: Abbreviations; bFGF; basic fibroblast growth factor; CHO; Chinese hamster ovary; CL2; chemical lead 2; dhfr; dihydrofolate reductase; Edg-1/S1P; ₁; endothelial differentiation gene-1; FBS; fetal bovine serum; FLIPR; fluorometric imaging plate reader; HEK293; human embryonic kidney 293; homo KO; homozygous knockout; HUVEC; human umbilical vein endothelial cells; IBMX; 3-isobutyl-1-methylxanthine; LPS; lipopolysaccharide; MTX; methotrexate; NZW; New Zealand white; Sph-1-P; sphingosine-1-phosphate; VEGF; vascular endothelial growth factorAngiogenesis inhibitor; Sphingosine-1-phosphate (Sph-1-P); Endothelial differentiation gene-1 (Edg-1/S1P; ₁; ); Tube formation; Anti-arthritis

Growth inhibitory and differentiation effects of chloroquine and its analogue on human leukemic cells potentiate fetal hemoglobin production by targeting the polyamine pathway by Efemwonkiekie Iyamu; Harrison Perdew; Gerald Woods (pp. 1021-1028).

Elevated arginase activity has been implicated in several pathological conditions in sickle cell disease (SCD) and other inflammatory disorders. Recently, we showed that chloroquine (CQ), an anti-malarial and anti-rheumatoid drug, displays a competitive mode of inhibition on sickle erythrocyte arginase. However, the effects of CQ and its analogue, hydroxychloroquine (HCQ) on erythroid differentiation leading to induced fetal hemoglobin (Hb F) production is unknown. In the present study, we obtained evidence of the anti-proliferative and differentiation effects of CQ and HCQ at pharmacologically attainable concentrations. This differentiation effect was linked to a dose-dependent inhibition of arginase activity and induced hemoglobinization, as Hb F synthesis was increased by 3.4- and 3.2-fold for CQ or HCQ, respectively. Treatment of K562 cells with lipopolysaccharide (LPS) or 8-bromo-cAMP (Br-cAMP) failed to reverse the inhibitory effects of CQ or HCQ on arginase activity. Indeed, the combination of Br-cAMP with CQ in LPS-treated cells resulted in a significant enhancement of Hb F and total hemoglobin production. Further, we showed that CQ or HCQ maximally stimulated intracellular cGMP levels by 6.6- and 3.0-fold at 6 and 3h, respectively, as demonstrated by immunosorbent assay. However, co-treatment of K562 cells with CQ or HCQ in the presence of inhibitors of sGC-PKG-pathways reduced Hb F stimulation, suggesting the possible involvement of the sGC-PKG pathway. This is the first evidence demonstrating the capacity of anti-rheumatoid drugs to modulate the arginine-pathway and result in the enhancement of Hb F production, and thus may provide a paradigm for targeted therapy of hemoglobinopathies and other inflammation-related disorders.

Keywords: Fetal hemoglobin; Inflammation; Erythroid differentiation; Chloroquine; Hydroxychloroquine; Arginase

Aspirin and indomethacin reduce lung inflammation of mice exposed to cigarette smoke by Paulo Castro; Helena Nasser; Agessandro Abrahão; Larissa Cardilo dos Reis; Ingred Riça; Samuel S. Valença; Daniele C. Rezende; Luis E.M. Quintas; Moisés C. Marinho Cavalcante; Luis Cristóvão Porto; Vera Lucia G. Koatz (pp. 1029-1039).

Neutrophil accumulation response to cigarette smoke (CS) in humans and animal models is believed to play an important role in pathogenesis of many tobacco-related lung diseases. Here we evaluated the lung anti-inflammatory effect of aspirin and indomethacin in mice exposed to CS.C57BL/6 mice were exposed to four cigarettes per day during 4 days and were treated i.p. with aspirin or indomethacin, administered each day 1h before CS exposure. Twenty four hours after the last exposure, cells and inflammatory mediators were assessed in bronchoalveolar lavage (BAL) fluid and the lungs used for evaluation of lipid peroxidation, p38 mitogen-activated protein kinase (MAPK) phosphorylation and nuclear transcription factor κB (NF-κB) activation.Exposure to CS resulted in a marked lung neutrophilia. Moreover, the levels of oxidative stress-related lipid peroxidation, prostaglandin E₂ (PGE₂), interleukin 1β (IL-1β), monocyte chemotactic protein 1 (MCP-1), and activated NF-κB and p38 MAPK were greatly increased in CS group. Aspirin or indomethacin treatment led to a significant reduction of neutrophil influx, but only aspirin resulted in dramatic decrease of inflammatory mediators. Moreover, both drugs reduced lung p38 MAPK and NF-κB activation induced by CS.These results demonstrate that short-term CS exposure has profound airway inflammatory effects counteracted by the anti-inflammatory agents aspirin and indomethacin, probably through COX-dependent and -independent mechanisms.

Keywords: Cigarette smoke; Aspirin; Indomethacin; Lung inflammation; NF-κB; p38 MAP kinase

The insulinotropic effect of fluoroquinolones by Hany Ghaly; Christine Kriete; Seher Sahin; Anja Pflöger; Ulrike Holzgrabe; Bernd Joachim Zünkler; Ingo Rustenbeck (pp. 1040-1052).

Antimicrobial fluoroquinolones induce, with strongly varying frequency, life-threatening hypoglycemias, which is explained by their ability to block K_ATP channels in pancreatic B-cells and thus to initiate insulin secretion. In apparent contradiction to this, we observed that none of the fluoroquinolones in this study (gatifloxacin, moxifloxacin, ciprofloxacin, and a number of fluorophenyl-substituted compounds) initiated insulin secretion of perifused mouse islets when the glucose concentration was basal (5mM). Only when the glucose concentration was stimulatory by itself (10mM), the fluoroquinolones enhanced secretion. The fluoroquinolones were ineffective on SUR1 Ko islets, which do not have functional K_ATP channels. All of these fluoroquinolones depolarized the membrane potential of mouse B-cells (patch-clamping in the whole-cell mode). Using metabolically intact B-cells (perforated-patch mode) however, 100μM of gatifloxacin, ciprofloxacin or moxifloxacin were unable to depolarize when the glucose concentration was 5mM, whereas other K_ATP channel blockers (tolbutamide and efaroxan) remained effective. Only at a very high concentration (500μM) gatifloxacin and moxifloxacin, but not ciprofloxacin induced repetitive depolarizations which could be antagonized by diazoxide. In the presence of 10mM glucose all fluoroquinolones which enhanced secretion markedly elevated cytosolic calcium concentration ([Ca²⁺]_i). In the presence of 5mM glucose gatifloxacin and moxifloxacin at 500μM but not at 100μM elevated [Ca²⁺]_i. It is concluded that fluoroquinolones in the clinically relevant concentration range are not initiators, but rather enhancers of glucose-induced insulin secretion. The block of K_ATP channels appears necessary but not sufficient to explain the hypoglycemic effect of fluoroquinolones.

Keywords: Abbreviations; [Ca; ²⁺; ]; _i; cytosolic free calcium concentration; K; _ATP; channel ATP-sensitive K; ⁺; channel; SUR; sulfonylurea receptorFluoroquinolones; Gatifloxacin; K; _ATP; channel; Plasma membrane potential; Cytosolic calcium concentration; Insulin secretion

Long-term resveratrol administration reduces metabolic disturbances and lowers blood pressure in obese Zucker rats by Leonor Rivera; Rocío Morón; Antonio Zarzuelo; Milagros Galisteo (pp. 1053-1063).

Resveratrol is a natural polyphenolic stilbene derivative found in several human diet components that possess important and wide-ranging effects in biological systems including anticancer, anti-inflammatory, antioxidant, cardio-protective, and anti-ageing actions and beneficial properties against metabolic diseases. This study addresses the effects of long-term administration of resveratrol on several functional alterations arising from the metabolic syndrome experimental model of obese Zucker rats, and the possible mechanisms involved. The high plasma concentrations of triglycerides, total cholesterol, free fatty acids, insulin and leptin found in obese Zucker rats were reduced in obese rats that received resveratrol. Furthermore, the elevated hepatic lipid content was significantly lower in obese rats treated with resveratrol, an effect which was related to the increased phosphorylation of 5′-AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in the liver of these animals. Resveratrol treatment also improved the inflammatory status peculiar to this model, as it increased the concentration of adiponectin and lowered tumor necrosis factor-α production in the visceral adipose tissue (VAT) of obese Zucker rats. Moreover, chronic intake of resveratrol enhanced VAT eNOS expression among obese Zucker rats. These effects parallel the activation of AMPK and inhibition by phosphorylation of ACC in this tissue. The raised systolic blood pressure and reduced aortic eNOS expression found in obese Zucker rats were significantly improved in the resveratrol-treated obese rats. In conclusion, resveratrol improved dyslipidemia, hyperinsulinemia, hyperleptinemia and hypertension in obese Zucker rats, and produced anti-inflammatory effects in VAT, effects that seem to be mediated by AMPK activation.

Keywords: Abbreviations; ACC; acetyl-CoA carboxylase; AMPK; 5′-AMP-activated protein kinase; eNOS; endothelial nitric oxide synthase; FFA; free fatty acids; LC; lean control rats group; LR; lean rats treated with resveratrol group; NO; nitric oxide; NOx; nitrates plus nitrites; OC; obese control rats group; OR; obese rats treated with resveratrol group; p-ACC; phospho-ACC; p-AMPK; phospho-AMPK (Thr172); SBP; systolic blood pressure; TNF-α; tumor necrosis factor-αMetabolic syndrome; Obese Zucker rats; Resveratrol; Inflammatory status; AMPK activation

Nitric oxide inhibits insulin-degrading enzyme activity and function through S-nitrosylation by Crystal M. Cordes; Robert G. Bennett; Gerri L. Siford; Frederick G. Hamel (pp. 1064-1073).

Insulin-degrading enzyme (IDE) is responsible for the degradation of a number of hormones and peptides, including insulin and amyloid β (Aβ). Genetic studies have linked IDE to both type 2 diabetes and Alzheimer's disease. Despite its potential importance in these diseases, relatively little is known about the factors that regulate the activity and function of IDE. Protein S-nitrosylation is now recognized as a redox-dependent, cGMP-independent signaling component that mediates a variety of actions of nitric oxide (NO). Here we describe a mechanism of inactivation of IDE by NO. NO donors decreased both insulin and Aβ degrading activities of IDE. Insulin-degrading activity appeared more sensitive to NO inhibition than Aβ degrading activity. IDE-mediated regulation of proteasome activity was affected similarly to insulin-degrading activity. We found IDE to be nitrosylated in the presence of NO donors compared to that of untreated enzyme and the control compound. S-nitrosylation of IDE enzyme did not affect the insulin degradation products produced by the enzyme, nor did NO affect insulin binding to IDE as determined by cross-linking studies. Kinetic analysis of NO inhibition of IDE confirmed that the inhibition was noncompetitive. These data suggest a possible reversible mechanism by which inhibition of IDE under conditions of nitrosative stress could contribute to pathological disease conditions such as Alzheimer's disease and type 2 diabetes.

Keywords: Abbreviations; Aβ; amyloid-beta; DSS; disuccinimydyl suberate; IDE; insulin-degrading enzyme; iNOS; inducible nitric oxide synthase; KFC; potassium ferricyanide; LLVY; succinyl-leu-leu-val-tyr-7-amido-4-methyl coumarin; LSTR; boc-leu-ser-thr-arg-7-amido-4-methyl coumarin; MMTS; methyl methanethiolsulfonate; NAP; N; -acetylpenicillamine; NEM; N; -ethylmalemide; NO; nitric oxide; PAPA-NONOate; (; Z; )-1-[; N; -3-aminopropyl]-; N; -(; n; -propyl)amino]diazen-1-ium-1,2-dolate; SNAP; S; -nitroso-; N; -acetylpenicillamine; SNP; sodium nitroprusside; sulfo-NONOate; disodium (; E; )-1-sulfonatodiazen-1-ium-1,2-diolate; TCA; trichloroacetic acidInsulysin; Proteasome; Amyloid-β; Type 2 diabetes mellitus; Alzheimer's disease

Regression of prostate cancer xenografts by RLIP76 depletion by Sharad S. Singhal; Cherice Roth; Kathryn Leake; Jyotsana Singhal; Sushma Yadav; Sanjay Awasthi (pp. 1074-1083).

RLIP76 plays a central role in radiation and chemotherapy resistance through its activity as a multi-specific ATP-dependent transporter which is over-expressed in a number of types of cancers. RLIP76 appears to be necessary for cancer cell survival because both in vitro cell culture and in vivo animal tumor studies show that depletion or inhibition of RLIP76 causes selective toxicity in malignant cells. RLIP76 induces apoptosis in cancer cells through the accumulation of endogenously formed GS-E. The results of our in vivo studies demonstrate that administration of RLIP76 antibodies, siRNA or anti-sense to mice bearing xenografts of PC-3 prostate cancer cells leads to near complete regression of established subcutaneous xenografts with no apparent toxic effects. Since anti-RLIP76 IgG (which inhibit RLIP76-mediated transport), siRNA and antisense (which deplete RLIP76) showed similar tumor regressing activities, our results indicate that the inhibition of RLIP76 transport activity at the cell surface is sufficient for observed anti-tumor activity. These studies indicate that RLIP76 serves a key effector function for the survival of prostate cancer cells and that it is a valid target for cancer therapy.

Keywords: Abbreviations; RLIP76 (RalBP1); Ral-interacting protein; GSH; glutathione; GS-E; glutathione-electrophile-conjugates; DNP-SG; dinitrophenyl S-glutathione; DOX; doxorubicin; 4HNE; 4-hydroxy-t-nonenal; IOVs; in-side out vesicles; MDR; multi-drug-resistance; Pgp; P-glycoprotein; MRP1; multi-drug-resistance associated protein; SCLC; small cell lung cancer; NSCLC; non- small cell lung cancer; POB1; partner of RalBP1; TUNEL; TdT-mediated dUTP nick end labeling assayRLIP76; Cancer; Drug-resistance; Xenografts; Glutathione-conjugate transport

C75 is converted to C75-CoA in the hypothalamus, where it inhibits carnitine palmitoyltransferase 1 and decreases food intake and body weight by Paula Mera; Assia Bentebibel; Eduardo López-Viñas; Antonio G. Cordente; Chandrashekaran Gurunathan; David Sebastián; Irene Vázquez; Laura Herrero; Xavier Ariza; Paulino Gómez-Puertas; Guillermina Asins; Dolors Serra; Jordi García; Fausto G. Hegardt (pp. 1084-1095).

Central nervous system administration of C75 produces hypophagia and weight loss in rodents identifying C75 as a potential drug against obesity and type 2 diabetes. However, the mechanism underlying this effect is unknown. Here we show that C75-CoA is generated chemically, in vitro and in vivo from C75 and that it is a potent inhibitor of carnitine palmitoyltranferase 1 (CPT1), the rate-limiting step of fatty-acid oxidation. Three-D docking and kinetic analysis support the inhibitory effect of C75-CoA on CPT1. Central nervous system administration of C75 in rats led to C75-CoA production, inhibition of CPT1 and lower body weight and food intake. Our results suggest that inhibition of CPT1, and thus increased availability of fatty acids in the hypothalamus, contribute to the pharmacological mechanism of C75 to decrease food intake.

Keywords: Abbreviations; ARC; arcuate nucleus; CPT; carnitine palmitoyltransferase; CrAT; carnitine acetyltransferase; FAS; fatty-acid synthase; wt; wild-typeFatty-acid metabolism; Anti-obesity drugs; C75; CPT1 carnitine palmitoyltransferase; FAS fatty-acid synthase

Metabolism of protocatechuic acid influences fatty acid oxidation in rat heart: New anti-angina mechanism implication by Yan-guang Cao; Lin Zhang; Chen Ma; Bo-bo Chang; Yuan-Cheng Chen; Yi-qun Tang; Xiao-dong Liu; Xiao-quan Liu (pp. 1096-1104).

Protocatechuic acid (PA), a structurally typical phenolic acid in danshen, shows anti-angina efficacy. But until now, besides scavenging of oxygen free radicals, the understanding of its anti-angina mechanism has been limited. In our study, based on a novel metabolic route of PA identified in rat heart and its influence on fatty acid oxidation (FAO), we proposed a new mechanism for its anti-angina. In detail, three metabolites, catechol methylated metabolite, acyl-coenzyme (CoA) thioester and glycine conjugation, were identified in rat heart. A novel metabolic pathway was confirmed based on several metabolic systems incubated with heart mitochondria, cytosol, microsomes and homogenate. Results indicated that PA was firstly methylated in microsomes and cytosol, which was regarded as the prerequisite step for further metabolism and could be inhibited by tolcapone, and then the resulting methylated metabolite (vanillic acid) diffused into mitochondria where it was converted into acyl-CoA thioester, in similar with FAO. In addition, part of the acyl-CoA thioester was transformed into glycine conjugation, a step also localized within mitochondria. Furthermore, based on isolated rat heart perfusion, it was found that PA markedly decreased FAO, which was shown by higher residual fatty acid level in perfusate ( p<0.05) and lower acy-CoA/CoA ratio in heart ( p<0.05). The FAO inhibiting effect of PA could be largely reversed by its methylation inhibitor tolcapone, indicating the effect was closely related with the identified metabolic pathway of PA in heart. The decrease of FAO may switch heart energy substrate preference from fatty acid to glucose, which is beneficial for ischemia heart.

Keywords: Protocatechuic acid; Metabolism; Fatty acid oxidation; Anti-angina

Epithelial cell survival by activating transcription factor 3 (ATF3) in response to chemical ribosome-inactivating stress by Hyun Yang; Seong Hwan Park; Hye Jin Choi; Yuseok Moon (pp. 1105-1115).

Ribotoxic stress responses lead to the expression of genes important for cellular homeostasis by modulating cell survival, proliferation and differentiation. ATF3 was investigated for its modulation of the epithelial cellular integrity in response to mucosal ribotoxic stress. ATF3 expression was up-regulated by chemical agents causing ribotoxic stress such as deoxynivalenol and anisomycin in different types of intestinal epithelial cells. Moreover, reduction of ATF3 gene expression promoted ribotoxic stress-triggered programmed cell death, implicating a protective role of ATF3 in epithelial cell survival. Mechanistically, stabilization of ATF3 messenger RNA and protein played a critical role in maintaining enhanced levels of ATF3 production in response to the ribotoxic chemical agent. For ATF3 mRNA stability, p38 specific inhibitor SB203580 was the most efficient agent for suppression, suggesting the involvement of the p38 MAP kinase in ATF3 mRNA stabilization. In addition, the p38 MAP kinase as well as its downstream mediator glycogen synthase kinase 3β (GSK3β) was involved in ATF3 protein stabilization caused by chemical ribotoxic stress in human epithelial cells. As another separate signaling cascade, double-stranded RNA (dsRNA)-activated protein kinase (PKR) was demonstrated to translationally modulate ATF3 expression and contribute to the epithelial cell survival. PKR interference caused cells to be more susceptible to cell death caused by the chemical ribotoxic stress. The results of this study showed that enhanced ATF3 production was associated with cellular defenses by maintaining the epithelial survival after ribotoxic mucosal insults.

Keywords: Ribotoxic stress; Activating transcription factor 3 (ATF3); Epithelial cell survival; p38 MAP kinase; Double-stranded RNA (dsRNA)-activated protein kinase (PKR)

Sections

Personal tools

Biochemical Pharmacology (v.77, #6)

Sections

Personal tools

Local resources

Biochemical Pharmacology (v.77, #6)