tretinoin and pyrazolanthrone

Mechanisms regulating CYP4F genes remain under investigation, although characterization of CYP4F regulatory modalities would facilitate the discovery of new drug targets. This present study shows that all-trans- and 9-cis-retinoic acids can inhibit CYP4F11 expression in human keratinocyte-derived HaCaT cells. Transrepression of many genes by retinoic acids is mediated by interactions between retinoid receptors and the activator protein 1 (AP-1) complex. Proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta, which can activate the AP-1 complex, induce CYP4F11 transcription in HaCaT cells. The c-Jun N-terminal kinase (JNK)-specific inhibitor 1,9-pyrazoloanthrone (SP600125) blocked the induction of CYP4F11 by both cytokines, indicating involvement of the JNK pathway. Furthermore, TNF-alpha failed to induce CYP4F11 transcription when HaCaT cells were preincubated with retinoic acids. Retinoic acids are ligands for the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). The RXR agonist 6-(1(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)cyclopropyl) nicotinic acid (LG268) greatly induced CYP4F11 transcription, whereas the RAR agonist 4-(2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl)benzoic acid (TTNPB) markedly inhibited CYP4F11 transcription, indicating that down-regulation of CYP4F11 transcription by retinoic acid is mediated by RARs and may also be related to ligand competition for RXRs. Thus, the CYP4F11 gene is positively regulated by multiple signaling pathways in HaCaT keratinocytes, including RXR and JNK signaling pathways.

Topics: Alitretinoin; Anthracenes; Benzoates; Cell Line; Cytochrome P-450 Enzyme System; Cytochrome P450 Family 4; Gene Expression; Gene Expression Regulation; Humans; Interleukin-1alpha; JNK Mitogen-Activated Protein Kinases; Keratinocytes; Nicotinic Acids; Phosphorylation; Protein Kinase Inhibitors; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoic Acid Receptor gamma; Retinoid X Receptor alpha; Retinoid X Receptor beta; Retinoids; Signal Transduction; Tetrahydronaphthalenes; Tretinoin; Tumor Necrosis Factor-alpha

This study aims to investigate the effects and mechanisms of all-trans retinoic acid (t-RA) on interleukin(IL)-1-induced production of several inflammatory mediators in human chondrocytes. The cartilage from OA patients receiving total knee or total hip replacement was obtained and chondrocytes were prepared. Chemokine concentrations were measured by ELISA. The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was determined by Western blotting and/or RT/PCR. Nitrite levels were measured by Griess assays. The DNA-binding activity and transcriptional activity of activator protein-1 (AP-1) were measured by electrophoresis mobility shift assay and luciferase assay. We showed that t-RA suppressed IL-1-induced release of chemokines, including regulated upon activation, normal T cell expressed and secreted (RANTES), monocyte chemoattractant protein 2 (MCP-2), macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta. Four different retinoid derivatives all preserved inhibitory effects albeit the potency was different. t-RA potently suppressed IL-1-induced expression of iNOS and COX-2 and production of nitric oxide and prostaglandin E(2). In consistent with the results in primary chondrocytes, t-RA down-regulated IL-1-induced AP-1 DNA binding activity and transcriptional activity in a human fibroblast-like (commercially labeled as chondrocyte) cell line. By examining the effect of a c-jun N-terminal kinase (JNK) specific inhibitor, we showed that the suppression of JNK-AP-1 signaling was enough to inhibit IL-1-induced production of chemokines and activation of iNOS and COX-2 pathways. Collectively, our results raise a therapeutic option that intra-articular administration of retinoid derivatives at 10-1000 nanomolar concentrations may be effective to suppress the progression of inflammatory OA.

Topics: Anthracenes; Cell Line; Chemokines; Chondrocytes; Cyclooxygenase 2; Dinoprostone; Humans; Interleukin-1; MAP Kinase Kinase 4; Nitric Oxide Synthase Type II; Transcription Factor AP-1; Tretinoin

Recent studies indicate that activation of stress-activated protein kinases may be implicated in a broad range of biological activities including differentiation. To directly examine whether stress-activated protein kinases are involved in neuronal differentiation, we utilized retinoic acid-induced and spontaneous models of neurite outgrowth in dopaminergic neurons. Here, we show that retinoic acid-induced neurite outgrowth in MN9D dopaminergic neuronal cells was accompanied by activation of c-Jun N-terminal kinase but not p38. Consequently, cotreatment with a specific inhibitor of c-Jun N-terminal kinase or overexpression of c-Jun N-terminal kinase-binding domain of c-Jun N-terminal kinase-interacting protein-1 blocked retinoic acid-induced neurite outgrowth. In primary cultures of dopaminergic neurons, the extent of neurite outgrowth increased spontaneously in a time-dependent manner. When these cultures were treated with a specific inhibitor of c-Jun N-terminal kinase, the total extent of neurites, the primary neurite length and the number of neurites per cell were suppressed significantly. Thus, our data indicate that the c-Jun N-terminal kinase signal seems to play an important role during morphological differentiation in cultured dopaminergic neurons.

Topics: Analysis of Variance; Animals; Anthracenes; Blotting, Western; Cells, Cultured; Dopamine; Dose-Response Relationship, Drug; Drug Interactions; Embryo, Mammalian; Enzyme Activation; Enzyme Inhibitors; Hybridomas; Immunohistochemistry; JNK Mitogen-Activated Protein Kinases; Mesencephalon; Mice; Mitogen-Activated Protein Kinases; Neurites; Neurons; Rats; Time Factors; Transfection; Tretinoin; Tyrosine 3-Monooxygenase