Peroxisome proliferator–activated receptor γ is expressed in airways and inhibits features of airway remodeling in a mouse asthma model☆

Toluene diisocyanate (TDI) is a leading cause of occupational asthma. Although considerable controversy remains regarding its pathogenesis, TDI-induced asthma is an inflammatory disease of the airways characterized by airway remodeling. Peroxisome proliferator-activated receptor γ (PPARγ) has been shown to play a critical role in the control of airway inflammatory responses. However, no data are available on the role of PPARγ in TDI-induced asthma. We have used a mouse model for TDI-induced asthma to determine the effect of PPARγ agonist, rosiglitazone, or pioglitazone, and PPARγ on TDI-induced bronchial inflammation and airway remodeling. This study with the TDI-induced model of asthma revealed the following typical pathophysiological features: increased numbers of inflammatory cells of the airways, airway hyperresponsiveness, increased levels of Th2 cytokines (IL-4, IL-5, and IL-13), adhesion molecules (ICAM-1 and VCAM-1), chemokines (RANTES and eotaxin), TGF-β1, and NF-κB in nuclear protein extracts. In addition, the mice exposed to TDI developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer, subepithelial collagen deposition, and increased airway mucus production. Administration of PPARγ agonists or adenovirus carrying PPARγ2 cDNA reduced the pathophysiological symptoms of asthma and decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, TGF-β1, and NF-κB in nuclear protein extracts after TDI inhalation. In addition, inhibition of NF-κB activation decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, and TGF-β1 after TDI inhalation. These findings demonstrate a protective role of PPARγ in the pathogenesis of the TDI-induced asthma phenotype.

Section: Discussionsupporting

confidence: 92%

Modulation of Airway Remodeling and Airway Inflammation by Peroxisome Proliferator-Activated Receptor γ in a Murine Model of Toluene Diisocyanate-Induced Asthma

Lee¹,

Park²,

Kim³

et al. 2006

“…PPAR-g is a key regulator of carbohydrate and lipid metabolism (45), but growing evidence indicates that PPAR-g also plays an important role in controlling immune and inflammatory responses, including allergic airway inflammation. Indeed, the PPAR-g agonists ciglitazone, rosiglitazone, and GI 262570 display beneficial effects in various animal models of allergic asthma at least in part due to the capacity of PPAR-g to reduce maturation, migration, and immunogenicity of DCs (56)(57)(58)(59)(60). Thus, given that most of the effects of sirtuin inhibitors were demonstrated on highly purified DCs and were similar to the effects observed in mice conditionally deficient for Sirt1 in their DCs, it is evident that Sirt1 acts in a cell-autonomous manner to control DC function.…”

Section: Discussionmentioning

confidence: 99%

Sirtuin 1 Promotes Th2 Responses and Airway Allergy by Repressing Peroxisome Proliferator-Activated Receptor-γ Activity in Dendritic Cells

Legutko

Marichal

Fiévez

et al. 2011

Sirtuins are a unique class of NAD+-dependent deacetylases that regulate diverse biological functions such as aging, metabolism, and stress resistance. Recently, it has been shown that sirtuins may have anti-inflammatory activities by inhibiting proinflammatory transcription factors such as NF-κB. In contrast, we report in this study that pharmacological inhibition of sirtuins dampens adaptive Th2 responses and subsequent allergic inflammation by interfering with lung dendritic cell (DC) function in a mouse model of airway allergy. Using genetic engineering, we demonstrate that sirtuin 1 represses the activity of the nuclear receptor peroxisome proliferator-activated receptor-γ in DCs, thereby favoring their maturation toward a pro-Th2 phenotype. This study reveals a previously unappreciated function of sirtuin 1 in the regulation of DC function and Th2 responses, thus shedding new light on our current knowledge on the regulation of inflammatory processes by sirtuins.

“…12/15-LOX is known to interfere with T cell proliferation by generating lipid metabolites, including 12(S)-HETE, that can function as ligands for PPAR␥ (28 -30). Notably, treatment of mice with the endogenous PPAR␥ ligand 15-deoxy-⌬12,14-PGJ 2 or with synthetic ligand significantly reduces lung inflammation, mucus production, and remodeling following induction of allergic airways disease (31,32). Although further studies are required, the levels of 12(S)-HETE produced in the allergic lung would make it a more likely endogenous ligand of PPAR␥ than 15-deoxy-⌬12,14-PGJ 2 , which some have suggested is produced at too low a level to be considered a physiological ligand for PPAR␥ (33).…”

Section: Discussionmentioning

confidence: 99%

Ym1/2 Promotes Th2 Cytokine Expression by Inhibiting 12/15(S)-Lipoxygenase: Identification of a Novel Pathway for Regulating Allergic Inflammation

Cai

Kumar

Zhou

et al. 2009

The Ym1/2 lectin is expressed abundantly in the allergic mouse lung in an IL-13-dependent manner. However, the role of Ym1/2 in the development of allergic airways disease is largely unknown. In this investigation, we show that treatment of mice with anti-Ym1/2 Ab during induction of allergic airways disease attenuated mediastinal lymph node production of IL-5 and IL-13. Ym1/2 was found to be expressed by dendritic cells (DCs) in an IL-13-dependent manner and supplementation of DC/CD4+ T cell cocultures with Ym1/2 enhanced the ability of IL-13−/− DCs to stimulate the secretion of IL-5 and IL-13. Affinity chromatography identified 12/15(S)-lipoxygenase (12/15-LOX) as a Ym1/2-interacting protein and functional studies suggested that Ym1/2 promoted the ability of DCs to stimulate cytokine production by inhibiting 12/15-LOX-mediated catalysis of 12-hydroxyeicosatetraenoic acid (12(S)-HETE). Treatment of DC/CD4+ T cell cultures with the 12/15-LOX inhibitor baicalein enhanced, whereas 12(S)-HETE inhibited the production of Th2 cytokines. Notably, delivery of 12(S)-HETE to the airways of mice significantly attenuated the development of allergic airways inflammation and the production of IL-5 and IL-13. In summary, our results suggest that production of Ym1/2 in response to IL-13 promotes Th2 cytokine production and allergic airways inflammation by inhibiting the production of 12(S)-HETE by 12/15-LOX.