Inhibitory effects of PPARβ agonists on NOSII activity induced by bacteria in murine macrophages

Lucy Bailey, Laura Moreno, Mark Paul-Clark, Jane Mitchell. Imperial College, London, United Kingdom

The peroxisome proliferator-activated receptors (PPARs) are cytosolic receptors which regulate inflammatory responses via genomic and non-genomic pathways (Moraes et al., 2006). There are three PPAR isoforms: α, β and γ, of which PPARβ is the least studied. In the current study we have investigated the effects of two PPARβ agonists, GW0742 and L165041, on nitric oxide synthase (NOS) II activity induced by Gram-positive or Gram-negative bacteria in murine macrophages.

Murine macrophages (J774) were cultured using standard techniques (Paul-Clark et al., 2006) and plated into 96-well plates for treatment. Cells were treated with a range of concentrations of GW0742 or L165041 and stimulated with whole heat-killed E. coli or lipopolysaccaride (LPS), a component of Gram-negative bacteria, for 24 hours or with S. aureus for 48 hours. After the incubation period, NOSII activity was assessed by measuring the accumulation of nitrite in cell supernatants using the Griess reaction.

 
Figure 1. Effect of the PPARβ agonists GW0742 and L165041 on NOSII activity induced by whole heat-killed E. coli (3x107 CFU/ml)(A) or S. aureus (1x108 CFU/ml)(C) or by LPS (1 μg/ml) (B). Agonists were added 4 hours prior to bacteria or LPS. Data is mean ± S.E.M of n=3-9. # denotes significant difference between agonists (determined by two way ANOVA) and *(GW0742) or +(L165041) denotes results significantly different to control (determined by one-sample t-test) at P<0.05.

The data shows that, in murine macrophages, PPARβ agonists inhibit NOSII activity induced by either Gram-negative (Figure 1A and B) or Gram-positive (Figure 1C) bacteria. GW0742 was more potent than L165041 as an inhibitor of NOSII activity.

PPARβ agonists are currently in clinical trials for the treatment of human disease. Our findings that PPARβ agonists inhibit the sensing of bacteria by macrophages suggest that immunosuppresion may emerge as a possible side effect associated with the use of these drugs.

Moraes, L.A. et al. (2006) Pharmacology & Therapeutics 110(3), 371-385