Molecular pharmacology
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Molecular pharmacology · Oct 2009
Resveratrol protects mitochondria against oxidative stress through AMP-activated protein kinase-mediated glycogen synthase kinase-3beta inhibition downstream of poly(ADP-ribose)polymerase-LKB1 pathway.
Arachidonic acid (AA, a proinflammatory fatty acid) in combination with iron promotes excess reactive oxygen species (ROS) production and exerts a deleterious effect on mitochondria. We have shown previously that activation of AMP-activated protein kinase (AMPK) protects hepatocytes from AA + iron-induced apoptosis. Resveratrol, a polyphenol in grapes, has beneficial effects mediated through SIRT1, LKB1, and AMPK. ⋯ Furthermore, this LKB1-dependent mitochondrial protection resulted from resveratrol's poly(ADP-ribose)polymerase activation, but not SIRT1 activation, as supported by the experiment using 3-aminobenzamide, a poly(ADP-ribose)polymerase inhibitor. Other polyphenols, such as apigenin, genistein, and daidzein, did not activate AMPK or protect mitochondria against AA + iron. Thus, resveratrol protects cells from AA + iron-induced ROS production and mitochondrial dysfunction through AMPK-mediated inhibitory phosphorylation of GSK3beta downstream of poly(ADP-ribose)polymerase-LKB1 pathway.
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Molecular pharmacology · Aug 2009
Activation of mGlu2/3 metabotropic glutamate receptors negatively regulates the stimulation of inositol phospholipid hydrolysis mediated by 5-hydroxytryptamine2A serotonin receptors in the frontal cortex of living mice.
The interaction between 5-hydroxytryptamine(2A) (5-HT(2A)) serotonin receptors and metabotropic glutamate (mGlu) 2/3 receptors underlies the antipsychotic activity of mGlu2/3 receptor agonists in experimental animals and humans. The molecular nature of this interaction is only partially known. We here report for the first time that pharmacological activation of mGlu2/3 receptors attenuates the stimulation of polyphosphoinositide (PI) hydrolysis mediated by 5-HT(2A) receptors in the frontal cortex of living mice. ⋯ Surprisingly, contrasting results were obtained in cortical slice preparations, where LY379268 amplified both DOI- and 3,5-dihydroxyphenylglycine-stimulated PI hydrolysis. Amplification was abrogated by the mGlu5 receptor antagonist 2-methyl-6-(phenylethynyl)pyridine, suggesting that experiments in brain slices are biased by an additional component of receptor-stimulated PI hydrolysis. This highlights the importance of in vivo models for the study of the interaction between 5-HT(2A) and mGlu2/3 receptors.
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Molecular pharmacology · Aug 2009
Augmentation of fear extinction by infusion of glycine transporter blockers into the amygdala.
It is known that fear extinction is blocked by the N-methyl D-aspartate (NMDA) receptor antagonist. In this study, we investigate whether extinction could be facilitated by the enhancement of NMDA response, achieved by the blocking of glycine transporters. In amygdala slices, NMDA at a concentration that normally does not have a long-term effect was found to reduce the cellular levels of postsynaptic density protein 95 and synapse-associated protein 97, in addition to the surface expression of GluR1/2, in the presence of a glycine transporter blocker, N[3-(4-fluorophenil)-3-(4'-phenilphenoxy)] propylsarcosine (NFPS). ⋯ In parallel, NFPS treatment in conjunction with extinction reversed the conditioning-induced alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/NMDA ratio. In behavioral tests, Tat-GluR2(3Y), a synthetic peptide that has been shown to block AMPA receptor endocytosis, inhibited only the additional reduction caused by NFPS treatment, rather than returning the fear potentiation levels to those of fear-conditioned animals that did not undergo extinction. These results suggest that NFPS in combination with extinction training reverses GluR1/2 surface expression and thus augments the extinction of conditioned fear.
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Molecular pharmacology · Jul 2009
Heme-oxygenase-1 induction and carbon monoxide-releasing molecule inhibit lipopolysaccharide (LPS)-induced high-mobility group box 1 release in vitro and improve survival of mice in LPS- and cecal ligation and puncture-induced sepsis model in vivo.
We examined our hypothesis that heme-oxygenase-1 (HO-1)-derived carbon monoxide (CO) inhibits the release of high-mobility group box 1 (HMGB1) in RAW264.7 cells activated with lipopolysaccharide (LPS) in vitro and in LPS- or cecal ligation and puncture (CLP)-induced septic mice in vivo, so that HO-1 induction or CO improves survival of sepsis in rodents. We found that pretreatment with HO-1 inducers (hemin, cobalt protoporphyrin IX) or transfection of HO-1 significantly inhibited HMGB1 release, which was blocked by HO-1 small interfering RNA, in cells activated by LPS. Carbon monoxide-releasing molecule 2 (CORM-2) but not bilirubin or deferoxamine inhibited HMGB1 release in LPS-activated macrophages. ⋯ Plasma levels of HMGB1 in mice challenged with LPS or CLP were significantly reduced by the administration of HO-1 inducers or CORM-2, which was accompanied by either reduction (pretreatment) or no change (delayed administration) of serum TNF-alpha and IL-1beta levels. Regardless of pretreatment or delayed administration, CORM-2 and hemin rescued mice from lethal endotoxemia and sepsis induced by LPS or CLP. Taken together, we concluded that HO-1-derived CO reduces HMGB1 release in LPS-activated cells and LPS- or CLP-induced animal model of sepsis.
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Molecular pharmacology · Jun 2009
Enhancement of doxorubicin cytotoxicity on human esophageal squamous cell carcinoma cells by indomethacin and 4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide (SC236) via inhibiting P-glycoprotein activity.
Doxorubicin is a chemotherapeutic drug widely used for the treatment of advanced esophageal squamous cell carcinoma. However, its efficacy is usually limited by the development of multidrug resistance (MDR), which has been linked to the up-regulation of P-glycoprotein (P-gp) in cancer cells. Conventional nonsteroidal anti-inflammatory drugs and cyclooxygenase 2 (COX-2)-selective inhibitors have been demonstrated to overcome MDR in some cancer cells. ⋯ To this end, we observed that indomethacin and SC236 directly functioned as noncompetitive inhibitors of P-gp, which were manifested as a reduction of P-gp ATPase activity. Collectively, these findings suggest that the direct inhibitory effects of indomethacin and SC236 on P-gp may contribute to their ability to increase the intracellular retention of doxorubicin and thus enhance its cytotoxicity. The combination of indomethacin or SC236 with doxorubicin may have significant potential clinical application, especially in the circumvention of P-gp-mediated MDR in cancer cells.