151. Evaluation of [3-(1-methyl-1H-indol-3-yl-methylene)-2-oxo-2, 3-dihydro-1H-indole-5-sulfonamide] (OXSI-2), as a Syk-selective inhibitor in platelets.
- Author
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Bhavaraju K, Kim S, Daniel JL, and Kunapuli SP
- Subjects
- Adaptor Proteins, Signal Transducing metabolism, Blood Platelets enzymology, Blotting, Western, Crotalid Venoms pharmacology, Cytoplasmic Granules drug effects, Cytoplasmic Granules enzymology, Cytoplasmic Granules metabolism, Dose-Response Relationship, Drug, Enzyme Inhibitors chemistry, Extracellular Signal-Regulated MAP Kinases metabolism, Humans, Indoles chemistry, Intracellular Signaling Peptides and Proteins metabolism, Lectins, C-Type, Maleimides pharmacology, Membrane Proteins metabolism, Oligopeptides pharmacology, Phospholipase C gamma antagonists & inhibitors, Phospholipase C gamma metabolism, Phosphorylation drug effects, Platelet Function Tests, Protein Kinases pharmacology, Protein-Tyrosine Kinases metabolism, Signal Transduction physiology, Stilbenes pharmacology, Sulfonamides chemistry, Syk Kinase, Thromboxanes metabolism, Tyrosine metabolism, src-Family Kinases antagonists & inhibitors, src-Family Kinases metabolism, Blood Platelets drug effects, Enzyme Inhibitors pharmacology, Indoles pharmacology, Intracellular Signaling Peptides and Proteins antagonists & inhibitors, Protein-Tyrosine Kinases antagonists & inhibitors, Sulfonamides pharmacology
- Abstract
In the present study, we characterized OXSI-2 [3-(1-Methyl-1H-indol-3-yl-methylene)-2-oxo-2, 3-dihydro-1H-indole-5-sulfonamide], a putative inhibitor of Syk, and determined its specificity and selectivity in platelets. We found that OXSI-2 completely abolished convulxin-induced platelet functional responses. In order to determine whether OXSI-2 inhibited Src family kinase-mediated platelet responses, we evaluated its effect on Src family kinase (SFK)-mediated signaling events in platelets, viz. Lyn-mediated phosphorylation of Y352 on Syk, LAT-Y191 phosphorylation by Syk, and protease-activated receptor (PAR)-mediated phosphorylation of ERK. In the present work, we report that convulxin mediated Syk tyrosine 352 phosphorylation is not inhibited by OXSI-2, whereas piceatannol and PP2 abolished it. Syk-mediated Y191 LAT phosphorylation is abolished by all the three inhibitors. AYPGKF-induced phosphorylation of ERK was marginally inhibited by OXSI-2, whereas treatment with PP2 and piceatannol completely abolished it. However, PAR-mediated thromboxane generation (an event mediated by ERK) was potentiated by OXSI-2 whereas PP2 and piceatannol brought thromboxane to basal levels. Protein kinase C (PKC) inhibitors are known to potentiate PAR-mediated thromboxane generation in platelets. In contrast, OXSI-2, unlike PKC inhibitors, did not inhibit secretion. Therefore, we conclude that OXSI-2 is not a Syk-selective inhibitor in platelets because of its unexplained non-specific effects.
- Published
- 2008
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