Molecular pharmacology
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Molecular pharmacology · Feb 2004
Comparative StudyPeroxisome proliferator-activated receptor-gamma-independent repression of collagenase gene expression by 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid and prostaglandin 15-deoxy-delta(12,14) J2: a role for Smad signaling.
Matrix metalloproteinases (MMPs) degrade extracellular matrix components, and overexpression of these enzymes contributes to tissue destruction in arthritis. Of particular importance are the collagenases, MMP-1 and MMP-13, which have high activity against the interstitial collagens in cartilage. In this study, we address the mechanisms of two inhibitors of collagenase gene expression, the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and 15-deoxy-delta(12,14)-prostaglandin J2 (15-dPGJ2). ⋯ We found that CDDO requires Smads (transcription factors activated by TGF-beta) for the repression of MMP-1. Specifically, MMP-1 is inhibited neither by CDDO in the absence of TGF-beta receptor-activated Smad3 nor when a negative regulator, Smad7, attenuates TGF-beta signaling. We conclude that CDDO represses MMP gene expression through a novel PPAR-gamma-independent mechanism that requires Smad signaling.
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Molecular pharmacology · Feb 2004
Proteasome inhibitors induce inhibitory kappa B (I kappa B) kinase activation, I kappa B alpha degradation, and nuclear factor kappa B activation in HT-29 cells.
The transcription factor nuclear factor kappaB (NF-kappaB) is activated and seems to promote oncogenesis in certain cancers. A major mechanism of NF-kappaB activation in cells involves cytoplasm-to-nucleus translocation of this transcription factor after hydrolysis of the cytoplasmic inhibitor inhibitory kappaB (IkappaB) by the 26S proteasome. Because selective proteasome inhibitors have been shown to block IkappaB degradation; consequently, NF-kappaB activation in a variety of cellular systems, proteasome inhibitors were proposed as potential therapeutic agents for the treatment of cancer. ⋯ Furthermore, proteasome inhibitors induced the expression of NF-kappaB target genes. In summary, these results demonstrate a unique effect of proteasome inhibitors on the IkappaB-NF-kappaB systems in HT-29 cells, in which proteasome inhibitors activate rather than deactivate the NF-kappaB system. We conclude that the use of proteasome inhibitors to block NF-kappaB activation in cancer cells may not always be a viable approach.
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Molecular pharmacology · Feb 2004
Two-pore-domain K+ channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane.
Nitrous oxide, xenon, and cyclopropane are anesthetic gases that have a distinct pharmacological profile. Whereas the molecular basis for their anesthetic actions remains unclear, they behave very differently to most other general anesthetics in that they have little or no effect on GABAA receptors, yet strongly inhibit the N-methyl-d-aspartate subtype of glutamate receptors. Here we show that certain members of the two-pore-domain K+ channel superfamily may represent an important new target for these gaseous anesthetics. ⋯ In contrast, TASK-3, a member of this family that is very sensitive to volatile anesthetics, such as halothane, is insensitive to the anesthetic gases. We demonstrate that the C-terminal cytoplasmic domain is not an absolute requirement for the actions of the gases, although it clearly plays an important modulatory role. Finally, we show that Glu306, an amino acid that has previously been found to be important in the modulation of TREK-1 by arachidonic acid, membrane stretch and internal pH, is critical for the activating effects of the anesthetic gases.
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Molecular pharmacology · Jan 2004
Hydroxy metabolites of the Alzheimer's drug candidate 3-[(2,4-dimethoxy)benzylidene]-anabaseine dihydrochloride (GTS-21): their molecular properties, interactions with brain nicotinic receptors, and brain penetration.
3-[(2,4-dimethoxy)benzylidene]-anabaseine dihydrochloride (DMXBA; GTS-21), an Alzheimer's drug candidate, selectively stimulates alpha7 nicotinic acetylcholine receptors. It rapidly enters the brain after oral administration and enhances cognitive behavior. Less than 1% of orally administered DMXBA is recovered in the urine. ⋯ The hydroxy metabolites were much more polar than DMXBA, derived from their experimentally estimated octanol/water partition coefficients, and they entered the brain much less readily than DMXBA. Their contributions to the behavioral effects of orally administered DMXBA, if any, would probably be very small during short-term administration. Benzylidene anabaseines pharmacologically similar to the hydroxy metabolites, but which enter the brain more readily, may provide greater stimulation of alpha7 receptors in the whole organism.
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Molecular pharmacology · Jan 2004
Defining the propofol binding site location on the GABAA receptor.
The GABAA receptor is a target of many general anesthetics. The low affinity of general anesthetics has complicated the search for the location of anesthetic binding sites. Attention has focused on two pairs of residues near the extracellular ends of the M2 and M3 membrane-spanning segments, alpha1Ser270/beta2Asn265 (15' M2) and alpha1Ala291/beta2Met286 (M3). ⋯ Propofol protected, in a concentration-dependent manner, the cysteine substituted for beta2Met286 from reaction with pCMBS-. Propofol did not protect the cysteine substituted for the aligned alpha1 subunit position or the 15' M2 segment Cys mutants in either subunit. We infer that propofol may bind near the extracellular end of the betasubunit M3 segment.