Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P05109 (S100A8)
 1,212 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inverse agonists are ligands that are capable of repressing basal receptor activity in the absence of an agonist. We have designed a series of C-1-substituted acetylenic retinoids that exhibit potent antagonism of retinoic acid receptor (RAR)-mediated transactivation. Comparison of these related retinoid antagonists for their ability to repress basal RAR transcriptional activity demonstrates that the identity of the C-1 substituent differentiates these ligands into two groups: RAR inverse agonists and neutral antagonists. We show that treatment of cultured human keratinocytes with a RAR inverse agonist, but not a RAR neutral antagonist, leads to the repression of the serum-induced differentiation marker MRP-8. While RAR-selective agonists also repress expression of MRP-8, cotreatment with a RAR inverse agonist and a RAR agonist results in a mutual repression of their individual inhibitory activities, indicating the distinct modes of action of these two disparate retinoids in modulating MRP-8 expression. Our data indicate that RARs, like beta2-adrenoreceptors, are sensitive to inverse agonists and that this new class of retinoids will provide insight into the molecular mechanisms of RAR function in skin and other responsive tissues.
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PMID:Identification and functional separation of retinoic acid receptor neutral antagonists and inverse agonists. 879 42

Retinoids down-regulate the expression of metalloproteinases, cytokines, and other genes involved in cell proliferation and inflammation. Tazarotene (AGN 190168), a retinoic acid receptor (RAR)-specific retinoid, is effective in the treatment of psoriasis, a hyperproliferative and inflammatory skin disease. Because negative regulation of genes appears to be important in the antiproliferative and antiinflammatory action of retinoids, we studied the down-regulation of genes in skin raft cultures by this antipsoriatic retinoid. By subtraction hybridization, we found that migration inhibitory factor-related protein (MRP-8) and skin-derived anti-leukoproteinase (SKALP) are down-regulated by AGN 190168. MRP-8 and SKALP are overexpressed in psoriatic lesions as compared to the normal epidermis, and they are markers of hyperproliferative keratinocyte differentiation. We also show that MRP-8 expression is retinoid inhibitable in cultured keratinocytes induced to differentiate with 10% serum or IFN-gamma, and that MRP-8 is inhibited by RAR but not by retinoid X receptor-specific retinoids in a dose-dependent manner. Finally, MRP-8, SKALP, and the previously characterized differentiation marker, transglutaminase I, are all down-regulated in vivo in psoriatic lesions after treatment with AGN 190168 in comparison to placebo. Taken together, these data suggest that these markers may be down-regulated by tazarotene in psoriasis through direct action on keratinocyte gene expression rather than by an overall tazarotene effect on lesional therapeutic status.
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PMID:Negative regulation of two hyperproliferative keratinocyte differentiation markers by a retinoic acid receptor-specific retinoid: insight into the mechanism of retinoid action in psoriasis. 895 47

Retinoids are important regulators of epithelial differentiation. AGN 193109 is a high-affinity antagonist and inverse agonist for the nuclear retinoic acid receptors (RARs). Paradoxically, both AGN 193109 and retinoid agonists inhibit the expression of the differentiation marker MRP-8 in normal human keratinocytes (NHKs). TTNPB, an RAR agonist, and AGN 193109 mutually antagonize MRP-8 inhibition at both mRNA and protein levels. We find that this antagonism, which is greatest at an AGN 193109:TTNPB ratio of about 10:1, is absent when either compound is in significant excess. The potent RARalpha-specific agonist, AGN 193836, has no effect on MRP-8 regulation. These data indicate that inverse agonists and agonists suppress MRP-8 in NHKs through RARgamma using distinct and mutually inhibitory mechanisms. The activity of AGN 193109 on MRP-8 is cell type specific. In differentiating ECE16-1 cervical cells, TTNPB inhibits while AGN 193109 induces MRP-8 mRNA levels. The effect of AGN 193109 on genes inhibited by retinoid agonists in NHKs is also selective; expression of the differentiation markers transglutaminase 1 and keratin 6 is not down-regulated by AGN 193109 whereas stromelysin-1 expression is suppressed. These results show a complex gene and cell context-specific interplay between agonist and inverse agonist for the regulation of gene expression.
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PMID:Cell type and gene-specific activity of the retinoid inverse agonist AGN 193109: divergent effects from agonist at retinoic acid receptor gamma in human keratinocytes. 1031 95

Damage-associated molecular patterns (DAMPs) trigger sterile inflammation after tissue injury, but the mechanisms underlying the resolution of inflammation remain unclear. In this study, we demonstrate that common DAMPs, such as high-mobility-group box 1 (HMGB1), peroxiredoxins (PRXs), and S100A8 and S100A9, were internalized through the class A scavenger receptors MSR1 and MARCO in vitro. In ischemic murine brain, DAMP internalization was largely mediated by MSR1. An elevation of MSR1 levels in infiltrating myeloid cells observed 3 d after experimental stroke was dependent on the transcription factor Mafb. Combined deficiency for Msr1 and Marco, or for Mafb alone, in infiltrating myeloid cells caused impaired clearance of DAMPs, more severe inflammation, and exacerbated neuronal injury in a murine model of ischemic stroke. The retinoic acid receptor (RAR) agonist Am80 increased the expression of Mafb, thereby enhancing MSR1 expression. Am80 exhibited therapeutic efficacy when administered, even at 24 h after the onset of experimental stroke. Our findings uncover cellular mechanisms contributing to DAMP clearance in resolution of the sterile inflammation triggered by tissue injury.
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PMID:MAFB prevents excess inflammation after ischemic stroke by accelerating clearance of damage signals through MSR1. 2852 22