Abstract 465: Lipid-lowering Agent Gemcabene Down-regulates Acute Phase C-reactiveProtein via /EBP-δ-mediated Transcriptional Mechanism and Attenuates Inflammation and Osteoarthritis in Animal Models

Abstract

Background: Inflammation plays a key role in setting the stage as well as causing the progression of atherosclerosis. High sensitivity c-reactive protein (hsCRP), an acute phase reactant released during inflammatory processes, has been recognized as a predictor of cardiovascular risk. Experiments & Results: Since gemcabene reduced hsCRP in humans, we investigated the mechanism of hsCRP reduction and efficacy of anti-inflammatory activity in animal models of arthritis and pain. In human hepatoma cell line, PLC/PRF/5, gemcabene showed dose-dependent inhibition of IL-6+ IL-1β-induced CRP production by -70% inhibition at 2 mM. In TNF-α-stimulated primary human coronary artery endothelial cells, both CRP and IL-6 productions were inhibited by gemcabene in a dose-dependent manner (-70% at 2mM). Transfection studies with human CRP regulatory sequences in luciferase/ β-gal system showed a 25-fold increase in IL-6- as well as IL-6+ IL-1β -stimulated CRP transcription, which was reduced by gemcabene (-50% at 2 mM), suggesting transcriptional down-regulation of CRP. Site-directed mutation of C/EBP, NF-κB, and STAT sites of the human CRP promoter suggested that the overlapping downstream C/EBP and NF-κB binding sites are important for gemcabene-mediated down-regulation of CRP promoter. STAT3 response element, while needed for IL-6-induced expression of CRP, is not required for gemcabene-mediated inhibition. Identification of the protein, in a gel-shift assay, that interacts with C/EBP binding sites revealed it to be C/EBPδ. Anti-inflammatory efficacy of gemcabene was evaluated in a rat model of monosodium iodoacetate (MIA)-induced osteoarthritis (OA) and carrageenan-induced thermal hyperalgesia (CITH). Gemcabene improved joint comfort (-50% at 30 mg/kg/d for 2 wk) in MIA and attenuated paw withdrawal latency (60% at 30 mg/kg/d and 97% at 100 mg/kg/d, compared to untreated control) in the CITH model. These findings were further confirmed by an IL-6/IL-6sR knee injection model showing 63 and 71% reduction in hind paw weight distribution at 10 and 30 mg/kg/d doses, respectively. Conclusions: Gemcabene decreases CRP by C/EBPδ and NF-κB mediated transcriptional mechanism, and attenuates inflammation-induced OA and hyperalgesia.