PPAR gamma Controls Dectin-1 Expression Required for Host Antifungal Defense against Candida albicans

We recently showed that IL-13 or peroxisome proliferator activated receptor gamma (PPAR gamma) ligands attenuate Candida albicans colonization of the gastrointestinal tract. Here, using a macrophage-specific Dectin-1 deficient mice model, we demonstrate that Dectin-1 is essential to control fungal gastrointestinal infection by PPAR gamma ligands. We also show that the phagocytosis of yeast and the release of reactive oxygen intermediates in response to Candida albicans challenge are impaired in macrophages from Dectin-1 deficient mice treated with PPAR gamma ligands or IL-13. Although the Mannose Receptor is not sufficient to trigger antifungal functions during the alternative activation of macrophages, our data establish the involvement of the Mannose Receptor in the initial recognition of non-opsonized Candida albicans by macrophages. We also demonstrate for the first time that the modulation of Dectin-1 expression by IL-13 involves the PPAR gamma signaling pathway. These findings are consistent with a crucial role for PPAR gamma in the alternative activation of macrophages by Th2 cytokines. Altogether these data suggest that PPAR gamma ligands may be of therapeutic value in esophageal and gastrointestinal candidiasis in patients severely immunocompromised or with metabolic diseases in whom the prevalence of candidiasis is considerable.