Forskolin stimulates SS but not AA RBC adhesion to laminin.
(A) SS RBCs (n = 7, solid lines) and AA RBCs (n = 2, dashed lines) were pretreated with 200 μM IBMX for 2 hours to inhibit phosphodiesterase activity. The RBCs were subsequently treated with 36 nM 14-22 amide PKA inhibitor (PKAI) for 1 hour, 80 μM forskolin (Fsk) for 15 minutes, or a combination of Fsk and PKAI as indicated. Adhesion to laminin was measured in the flow adhesion assay (“Materials and methods”). Basal adhesion was normalized to 1. (B-C), SS RBCs patient samples were separated into a low-density (reticulocyte-enriched) and a high-density (reticulocyte-depleted) population using an arabinogalactan density gradient (“Materials and methods”). (B) cAMP levels were measured in 1 × 108low-density (solid lines) or high-density (dotted lines) SS RBCs/condition from 5 separate patients during baseline and forskolin-treated conditions (80 μM for 15 minutes) as indicated. (C) Fold change in adhesion of low-density (LD, ▪) and high-density (HD, ■) SS RBCs to laminin was measured in the flow adhesion assay (“Materials and methods”) in response to forskolin (80 μM for 15 minutes) in SS RBCs from 3 separate patients. Basal adhesion is normalized to 1.
