Fig. 7.

Mean tumor necrosis factor-α (TNF-α) levels increase in clonal and primary synovial cell cultures after treatment with glutamate receptor agonists measured by immunoassay. A: dose response for increasing doses of PMA with a fixed dose of 5 μM NMDA and 5 μM ACPD (N+A). Coincubation of SW982 human synoviocytes with PMA and N+A resulted in a significant increase in mean TNF-α concentrations compared with cell cultures incubated with PMA alone, demonstrating an enhancement of PMA activation by glutamate receptor agonists. *P < 0.05, PMA alone vs. PMA and N+A. ^P < 0.05, 100 nM PMA vs. 25 nM PMA. Each condition represents the mean of 9 samples. B: coincubation of primary synovial cell cultures derived from the synovial fluid of a patient with active psoriatic arthritis with 25 nM PMA, 5 μM NMDA, and 5 μM ACPD resulted in a significant increase (4.3-fold) in mean TNF-α concentrations compared with cell cultures incubated with PMA alone. *P < 0.05, PMA alone vs. PMA and N+A. Untreated cells and cells treated with 5 μM NMDA and 5 μM ACPD did not demonstrate increases in TNF-α levels in the culture supernatant. C: coincubation of SW892 human synoviocytes with 25 nM PMA, 5 μM NMDA, and 5 μM ACPD resulted in a significant increase in mean TNF-α concentrations compared with cell cultures incubated with PMA alone (*P < 0.05 compared with PMA alone). Preincubation of the cells with NRS did not diminish the enhancement seen with PMA, NMDA, and ACPD incubations (**P < 0.01 compared with PMA alone). However, preincubation with specific NMDA NR1 antibody blocked the increase in mean TNF-α levels seen with coincubation of SW892 synoviocytes with PMA and NMDA and ACPD (^P < 0.05 comparing cells preincubated with NRS to cells preincubated with NMDA NR1 antibody).