The PPAR target gene CD36 is a rate limiting factor for the sensing of gram positive S-aureus in vascular smooth muscle cells but not in macrophages

Bacteria activate macrophages and vascular smooth muscle cells (VSMCs) resulting in induction of nitric oxide synthase (NOS)II activity. Here we show that the PPARc agonist rosiglitazone (rosi) increases the sensing of Gram positive bacteria by VSMCs but not macrophages via a CD36 dependent pathway. NOSII activity was increased in rat VSMCs by Gram positive S. aureus (3 · 108CFU/ml) or Gram negative E. coli (108 CFU/mL). Pre-treatment of cells with rosi increased NOSII activity in cells treated with S. aureus, but not E. Coli (Fig 1A), an effect prevented by the PPARc antagonist GW9962 (10-5 M; 91 ± 9% control) or a specific binding antibody to CD36 (99 ± 14%). CD36 levels in VSMCs were increased by rosi (by 8.7 ± 0.2 fold, n = 4). By contrast, rosi inhibited NOSII activity induced by bacteria in macrophages from wild type mice and CD36-/- mice (Fig 1B). S. aureus induced similarly hyporeactivity (mediated by NOSII) in vessels from wild type (not shown) or CD36-/- mice (Fig 1C).
These data reveal a mechanism by which PPARc agonists may propagate vascular
inflammation.