Abstract 12818: KPNA4 Mediates Vitamin D-Dependent Inhibition of NF-kB Activity in Swine Epicardial Preadipocytes
Inflammatory phenotype of epicardial adipose tissue (EAT) could determine the pathophysiology of coronary heart disease. However, what triggers the in ammatory response in adipose tissue remains unknown. We found that vitamin D-deficient swine administered with hypercholesterolemic diet displayed increased expression of NF-κβ target genes, including MCP-1, TNF-α and IL-6, and inflammation in EAT, suggesting that vitamin D signaling negatively regulates NF-κβ activation. To identify the molecular mechanisms underlying vitamin D-dependent inhibition of NF-κβ in EAT, we isolated and cultured primary preadipocytes from swine EAT. We found 1,25-dihydroxyvitamin D3 (VD3) inhibited mRNA expression of karyopherin-α4 (KPNA4), a shuttling protein critical for NF-κβ nuclear translocation. The maximum inhibitory effect of VD3 was ~70%. The reduction in the mRNA transcripts was accompanied with decreased KPNA4 protein levels. To determine the anti-inflammatory effect of VD3 in EAT, preadipocytes were incubated with VD3 for 24 hrs and treated with 10ng/ml TNF-α for 20 min. TNF-α markedly increased nuclear p65 and p50 levels compared with controls. Pretreatment with VD3 resulted in a 60-65% reduction of TNF-α-induced p65 and p50 nuclear translocation. To determine a mechanistic link between vitamin D-dependent reduction of KPNA4 and suppression of NF-κβ activation, we transfected cells with KPNA4 expression vector with NF-κβ -luciferase/renilla-luciferase treated with VD3 in the presence of TNF-α. Treatment with TNF-α led to a 5-fold increase in NF-κβ luciferase activity normalized to renilla-luciferase activity, which was reduced by about 60% with VD3 treatment. Co-transfection with KPNA4 expression vector, which rescued the reduced KPNA4 shuttle number, significantly decreased VD3-dependent inhibition of TNF-α-induced NF-κβ activation, suggesting that KPNA4 is a target responsible for vitamin D-mediated suppression of NF-κβ activation in preadipocytes. These findings provide novel insights into the anti-inflammatory role of vitamin D signaling in EAT and help to explore the potential utility of vitamin D supplementation for prevention and treatment of cardiovascular diseases.
Author Disclosures: S. Chen: None. C. Boosani: None. D.K. Agrawal: None.
- © 2014 by American Heart Association, Inc.