Cyclooxygenase-2 inhibits T helper cell type 9 differentiation during allergic lung inflammation via down-regulation of IL-17RB.

RATIONALE: Helper CD4(+) T cell subsets, including IL-9- and IL-10-producing T helper cell type 9 (Th9) cells, exist under certain inflammatory conditions. Cyclooxygenase (COX)-1 and COX-2 play important roles in allergic lung inflammation and asthma. It is unknown whether COX-derived eicosanoids regulate Th9 cells during allergic lung inflammation. OBJECTIVES: To determine the role of COX metabolites in regulating Th9 cell differentiation and function during allergic lung inflammation. METHODS: COX-1(-/-), COX-2(-/-), and wild-type (WT) mice were studied in an in vivo model of ovalbumin-induced allergic inflammation and an in vitro model of Th9 differentiation using flow cytometry, cytokine assays, confocal microscopy, real-time PCR, and immunoblotting. In addition, the role of specific eicosanoids and their receptors was examined using synthetic prostaglandins (PGs), selective inhibitors, and siRNA knockdown. MEASUREMENTS AND MAIN RESULTS: Experimental endpoints were not different between COX-1(-/-) and WT mice; however, the percentage of IL-9(+) CD4(+) T cells was increased in lung, bronchoalveolar lavage fluid, lymph nodes, and blood of allergic COX-2(-/-) mice relative to WT. Bronchoalveolar lavage fluid IL-9 and IL-10, serum IL-9, and lung IL-17RB levels were significantly increased in allergic COX-2(-/-) mice or in WT mice treated with COX-2 inhibitors. IL-9, IL-10, and IL-17RB expression in vivo was inhibited by PGD2 and PGE2, which also reduced Th9 cell differentiation of murine and human naive CD4(+) T cells in vitro. Inhibition of protein kinase A significantly increased Th9 cell differentiation of naive CD4(+) T cells isolated from WT mice in vitro. CONCLUSIONS: COX-2-derived PGD2 and PGE2 regulate Th9 cell differentiation by suppressing IL-17RB expression via a protein kinase A-dependent mechanism.

Cyclooxygenase-2 regulates Th17 cell differentiation during allergic lung inflammation.

RATIONALE: Th17 cells comprise a distinct lineage of proinflammatory T helper cells that are major contributors to allergic responses. It is unknown whether cyclooxygenase (COX)-derived eicosanoids regulate Th17 cells during allergic lung inflammation. OBJECTIVES: To determine the role of COX metabolites in regulating Th17 cell differentiation and function during allergic lung inflammation. METHODS: COX-1(-/-), COX-2(-/-), and wild-type mice were studied in an in vivo model of ovalbumin-induced allergic inflammation and an in vitro model of Th17 differentiation using flow cytometry, cytokine assays, confocal microscopy, real-time polymerase chain reaction, and immunoblotting. In addition, the role of specific eicosanoids and their receptors was examined using synthetic prostaglandins (PGs), selective inhibitors, and siRNA knockdown. MEASUREMENTS AND MAIN RESULTS: Th17 cell differentiation in lung, lymph nodes, and bronchoalveolar lavage fluid was significantly lower in COX-2(-/-) mice after ovalbumin sensitization and exposure in vivo. In vitro studies revealed significantly impaired Th17 cell differentiation of COX-2(-/-) naive CD4(+) T cells with decreased Stat3 phosphorylation and RORγt expression. Synthetic PGF(2α) and PGI(2) enhanced Th17 cell differentiation of COX-2(-/-) CD4(+) T cells in vitro. The selective COX-2 inhibitor, NS-398, and PGF(2α) receptor and PGI(2) receptor siRNA knockdown significantly decreased Th17 cell differentiation in vitro. Administration of synthetic PGs restored accumulation of Th17 cells in lungs of allergic COX-2(-/-) mice in vivo. CONCLUSIONS: COX-2 is a critical regulator of Th17 cell differentiation during allergic lung inflammation via autocrine signaling of PGI(2) and PGF(2α) through their respective cell surface receptors.