COX-2 regulation by 1alpha,25(OH)2D3-VDR ligand in endothelial cells expressing vGPCR

Abstract

The Kaposi's Sarcoma-associated Herpes virus G Protein-Coupled Receptor (vGPCR) is a key molecule in the pathogenesis of Kaposi Sarcoma. 1α,25(OH)2D3 anti-proliferative impact in vGPCR cells occur in part by NF-κB pathway negative modulation, family of conserved transcription factors critical during the inflammatory response. In this work, we studied if COX-2 modulation by 1alpha,25(OH)2D3 in vGPCR cells contributes to the anti-inflammatory action. As we have previously reported vGPCR cell proliferation is inhibited by 1alpha,25(OH)2D3 (10 nM, 48 h) due to a reduction on cell number. The blockage of arachidonic acid release by ATK (cPLA2 inhibitor) or the COX-2 inhibition (Celecoxib) decreased vGPCR cell number in a dose dependent manner (10-20 µM), similarly to 1alpha,25(OH)2D3. These changes were accompanied by morphological modifications observed at the microscope. qRT-PCR analysis of COX-2 gene expression revealed a mRNA increase within 20 min of 1alpha,25(OH)2D3 treatment and remains increased at least for 72 h. Moreover, ATK (20 µM) could not counteract COX-2 mRNA induced by 1alpha,25(OH)2D3 (10 nM, 24 h). Finally, COX-2 VDR dependence was evaluated using the stable VDR knock-down cell line vGPCR-shVDR where COX-2 mRNA rise by 1alpha,25(OH)2D3 was found impaired. Significant differences of the data between control (vehicle) and treated conditions were analyzed by one way-ANOVA followed by Bonferroni test (p< 0.05) or t-test (*p< 0.05, **p<0.01). All together, these results suggest that 1alpha,25(OH)2D3 enhances endothelial inflammation initiation through COX-2 upregulation and contributes to its timely resolution through the antineoplastic action. This shows a possible dual effect as both a promoter and attenuator of inflammation.