FIGURE 6.

PGD₂-induced HA synthesis is through the DP1-cAMP signal pathway. A, DP1 activation by PGD₂ or BW245C increases intracellular cAMP level. Orbital fibroblasts were treated with PGD₂ or BW245C for up to 60 min, and intracellular cAMP was detected as described under ”Experimental Procedures.“ There was a significant increase in cAMP within 15 min of treatment with PGD₂ compared with vehicle control (*, p < 0.05). cAMP further increased by 30 and 60 min (***, p < 0.001). B, cultures of confluent orbital fibroblasts were treated with 5 μm forskolin or 200 μm IBMX, with or without 5 μm PGD₂ or 2 μm PGJ₂, for 18 h, and the cell culture supernatant was collected for HA ELISA. There was a significant increase in HA when cells were treated with forskolin, PGD₂, or PGJ₂ compared with vehicle-treated (open bar) (*, p < 0.05; **, p < 0.01). Augmenting cAMP (via IBMX) in conjunction with PGD₂ or PGJ₂ significantly increased HA when compared with PGD₂ and PGJ₂ alone (#, p < 0.05). Results are expressed as the mean ± S.D. (error bars).