PPARγin Bacterial Infections: A Friend or Foe?

Abstract

Peroxisome proliferator-activated receptorγ(PPARγ) is now recognized as an important modulator of leukocyte inflammatory responses and function. Its immunoregulatory function has been studied in a variety of contexts, including bacterial infections of the lungs and central nervous system, sepsis, and conditions such as chronic granulomatous disease. Although it is generally believed that PPARγactivation is beneficial for the host during bacterial infections via its anti-inflammatory and antibacterial properties, PPARγagonists have also been shown to dampen the host immune response and in some cases exacerbate infection by promoting leukocyte apoptosis and interfering with leukocyte migration and infiltration. In this review we discuss the role of PPARγand its activation during bacterial infections, with focus on the potential of PPARγagonists and perhaps antagonists as novel therapeutic modalities. We conclude that adjustment in the dosage and timing of PPARγagonist administration, based on the competence of host antimicrobial defenses and the extent of inflammatory response and tissue injury, is critical for achieving the essential balance between pro- and anti-inflammatory effects on the immune system.