Abstract 58: Signal Transducer and Activation of Transcription (STAT) 4 Deficiency Reduces Adipose Tissue Inflammation and Atherosclerosis

Abstract

Adipose tissue (AT) inflammation is key for the development of insulin resistance (IR) and contributes to progression of atherosclerosis. Previous work from our group showed that STAT4 deficiency is protective for IR in obesity and reduces atherosclerosis. However, the mechanisms are not completely understood. In this study we examined the effect of STAT4 deficiency on peri-vascular and visceral AT inflammation in atherosclerosis. To this purpose we: i) generated STAT4-deficient apo E-deficient ( Stat-4 -/- Apoe -/- ) mice and, ii) used a novel small molecule inhibitor of the IL12/STAT4 pathway (Cpd9) in Apoe -/- mice. Compared to Apoe -/- controls, Stat-4 -/- Apoe -/- female mice fed Western diet (WD) for 12 weeks showed a ~40% reduction in the thoracic aorta lesion area. Peri-aortic AT immune cells analyzed by flow cytometry showed a significant (p<0.001) and prominent decrease in CD45+CD3+ (3-fold), CD3+CD8+ (10-fold) and Nk46+ (9-fold) cells in Stat-4 -/- Apoe -/- vs. Apoe -/- mice. Also, the percentage of CD206+/F4/80+ macrophages was increased by ~8.5-fold, while the CD45+/F4/80+ cells were reduced by ~5-fold in the Stat-4 -/- Apoe -/- mice (p<0.01). In addition gene expression of TNFα and IL12p40 were both reduced by 3.5 and 6-fold, respectively in Stat-4 -/- Apoe -/- , while PPARγ expression was increased by 2-fold (p<0.05). Peri-gonadal adipose tissue showed similar reduction in CD8+ and NK cell infiltration in STAT4 deficient mice but no differences were found in macrophage numbers or phenotype. The short-term effects of IL12/STAT4 inhibition on AT inflammation were examined in Apoe -/- mice on 7 days WD alone or with oral Cpd9 treatment (0.3mmol/kg). Gene array analysis showed between 2.5- and 6-fold reduction of several cytokines and chemokines such as Ccl2, Ccl12, Cxcl13. Also, adiponectin as well and Bmp2, 4 and 7 were 4- to 15-fold reduced, suggesting reduced inflammation and possibly adipogenesis. Vegfa expression was one of the 4 up-regulated genes by 2.5-fold in Cpd9 treated mice. Collectively, data show that STAT4 reduction has early beneficial effects on AT inflammation and that peri-aortic AT inflammation is dramatically reduced. Thus targeting STAT4 may be a novel approach to treat atherosclerosis by reducing peri-vascular AT inflammation.