Fig. 1.

N⁶-cyclopentyladenosine (N⁶-CPA) increases protein phosphatase 2A (PP2A) activity and decreases endotoxin-induced chemokine production in MH-S cells. A: MH-S cells were treated with increasing concentrations (1–100 μM) of N⁶-CPA for 30 min. B: MH-S cells were exposed to 10 μM N⁶-CPA for between 15 and 120 min. Specific PP2A activity was calculated from a standard curve of purified PP2A protein. C: cultured primary alveolar epithelial cells were treated with 10 μM N⁶-CPA for 1 h. D: MH-S cells were pretreated with 10 μM N⁶-CPA for 1 h before 6 h LPS (100 ng/ml) stimulation. CXCL1 production in cell supernatants was determined via ELISA. E: MH-S cells were pretreated with 10 μM FTY-720 for 1 h before 6 h LPS stimulation. CXCL1 production or CXCL2 production (F) in cell supernatants was determined via ELISA. Statistical analysis is summarized inset as *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001; statistical significance is compared with vehicle control in A and B using one-way ANOVA with Bonferroni's correction and as shown in C using a two-tailed student's t-test.