Abstract
BackgroundOur recent results show that all-trans retinoic acid (ATRA), an active metabolite of vitamin A, induces COX-dependent hyperalgesia and allodynia in rats. This effect was mediated by retinoic acid receptors (RARs) and was associated with increased COX-2 expression in the spinal cord. Since ATRA also up-regulated COX-2 expression in SH-SY5Y human neuroblastoma cells, the current study was undertaken to analyze in these cells the mechanism through which ATRA increases COX activity.MethodsCultured SH-SY5Y neuroblastoma cells were treated with ATRA. COX expression and kinase activity were analyzed by western blot. Transcriptional mechanisms were analyzed by RT-PCR and promoter assays. Pharmacological inhibitors of kinase activity and pan-antagonists of RAR or RXR were used to assess the relevance of these signaling pathways. Production of prostaglandin E2 (PGE2) was quantified by enzyme immunoabsorbent assay. Statistical significance between individual groups was tested using the non-parametric unpaired Mann-Whitney U test.ResultsATRA induced a significant increase of COX-2 expression in a dose- and time-dependent manner in SH-SY5Y human neuroblastoma cells, while COX-1 expression remained unchanged. Morphological features of differentiation were not observed in ATRA-treated cells. Up-regulation of COX-2 protein expression was followed by increased production of PGE2. ATRA also up-regulated COX-2 mRNA expression and increased the activity of a human COX-2 promoter construct. We next explored the participation of RARs and mitogen-activated peptide kinases (MAPK). Pre-incubation of SH-SY5Y human neuroblastoma cells with either RAR-pan-antagonist LE540 or MAP kinase kinase 1 (MEK-1) inhibitor PD98059 resulted in the abolition of ATRA-induced COX-2 promoter activity, COX-2 protein expression and PGE2 production whereas the retinoid X receptor pan-antagonist HX531, the p38 MAPK inhibitor SB203580 or the c-Jun kinase inhibitor SP600125 did not have any effect. The increase in RAR-β expression and extracellular-regulated kinase 1/2(ERK1/2) phosphorylation in ATRA-incubated cells suggested that RARs and ERK1/2 were in fact activated by ATRA in SH-SY5Y human neuroblastoma cells.ConclusionThese results highlight the importance of RAR-dependent and kinase-dependent mechanisms for ATRA-induced COX-2 expression and activity.
Highlights
Our recent results show that all-trans retinoic acid (ATRA), an active metabolite of vitamin A, induces COX-dependent hyperalgesia and allodynia in rats
ATRA-induced COX-2 protein expression and prostaglandin E2 (PGE2) production are inhibited by retinoic acid receptors (RARs) pan-antagonist LE540 or MAP kinase kinase 1 (MEK-1) inhibitor PD98059 To confirm the relevance of the findings described above, we studied the effect of LE540 and PD98059 on ATRAinduced COX-2 protein expression and PGE2 production
The transcriptional effects of ATRA are most commonly mediated by binding to nuclear receptors RARs, which normally act as ligand-inducible transcription factors by binding, as heterodimers with the retinoid X receptors (RXRs), to DNA response elements known as retinoic acid response elements [25]
Summary
Our recent results show that all-trans retinoic acid (ATRA), an active metabolite of vitamin A, induces COX-dependent hyperalgesia and allodynia in rats. This effect was mediated by retinoic acid receptors (RARs) and was associated with increased COX-2 expression in the spinal cord. The expression of cyclooxygenase-2 (COX-2), for example, is enhanced rapidly in the spinal cord during sensitization, along with the production of prostaglandins like prostaglandin E2 (PGE2) [1]. The mechanism of action involved an over-expression of COX-2, but not COX-1, in the lumbar spinal cord [19]. When ATRA was administered intrathecally, the sensitization-like effect was inhibited by a RARpan-antagonist and associated with a modulation of COX-2 and IL-1 activities [20]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
