Hematopoietic prostaglandin D synthase-derived prostaglandin D₂ ameliorates adjuvant-induced joint inflammation in mice.

Although prostaglandins (PGs) are known to be involved in the progression of arthritis, the role of PGD₂ remains unclear. In this study, we evaluated the role of PGD₂ in joint inflammation using genetically modified mice. Injection of complete Freund's adjuvant (CFA) increased the production of PGD₂ and induced paw swelling and cartilage erosion in wild-type (WT) mice. These phenomena were accompanied with an increase in the mRNA levels of TNF-α, IL-6, IL-1β, and matrix-degrading metalloproteinase-9. Knockdown of hematopoietic PGD synthase (H-PGDS) abolished the PGD₂ production and exacerbated all of the arthritic manifestations in the inflamed paw. Immunostaining revealed that infiltrating macrophages strongly expressed H-PGDS in the CFA-injected paw. Morphologic studies revealed vascular hyperpermeability and angiogenesis in the inflamed WT paw. H-PGDS deficiency was accelerated, whereas daily administration of a PGD₂ receptor D prostanoid (DP) agonist attenuated the CFA-induced hyperpermeability and angiogenesis. We further confirmed that DP deficiency exacerbated, whereas the administration of the DP agonist improved, the CFA-induced arthritic manifestations. The findings demonstrate that H-PGDS-derived PGD₂ ameliorates joint inflammation by attenuating vascular permeability and subsequent angiogenesis and indicates the therapeutic potential of a DP agonist for arthritis.-Tsubosaka, Y., Maehara, T., Imai, D., Nakamura, T., Kobayashi, K., Nagata, N., Fujii, W., Murata, T. Hematopoietic prostaglandin D synthase-derived prostaglandin D₂ ameliorates adjuvant-induced joint inflammation in mice.

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