Abstract
The atopic asthmatic response is very complex and involves various mediators, second messengers and cell types whose roles in the inflammatory response are being elucidated at the present time. Suplatast tosilate (IPD), a novel anti-allergic drug, plays an important role in the inflammatory process by reducing serum IgE levels and eosinophilia. The exact intracellular signaling mechanisms used by IPD have not been identified and this research was designed to identify the pathways and second messengers, utilized by IPD, to facilitate its mode of action. Since IPD has been reported to inhibit cytokine production from T cells, suppress blood and tissue eosinophilia, inhibit IgE production, and prevent goblet cell metaplasia, it was my hypothesis that IPD inhibits a pro-inflammatory pathway in human blood eosinophils and airway epithelial cells involving G-proteins and decrease in intracellular free calcium.|The effect of IPD on G-proteins, activated nuclear factor kB (NF-kB), P (I) 3-kinase and Akt was evaluated using Western blotting on cellular lysates of HBECs and eosinophils treated with IPD. Calcium mobilization assays were performed on HBECs and eosinophils treated with or without IPD and cytokines.|At 24 hour treatment of the cells with PAF, an increase of both Giccl and Gia2 proteins in eosinophils was evident. IPD in the presence of PAF enhanced Gsa protein and decreased both Gia1 and Gia2 proteins in human blood eosinophils. IPD inhibited the expression of P (I) 3-kinase and NF-kB in human blood eosinophils.|In HBECs treated for 24 hours, IPD had no effect on Gsa protein expression. PAF significantly decreased Gia protein in HBECs. Both IL-4 and PAF increased the expression of P (I) 3-kinase, Akt, and NF-kB, which was significantly decreased by IPD in HBECs.|Intracellular free Ca2+ concentration was measured to examine the activation of the HBECs and eosinophils treated with PAF and/or IPD. PAF significantly increased intracellular free Ca2+ concentration in both eosinophils and HBECs. IPD significantly inhibited PAF-induced increase of intracellular free Ca2+ concentration in both cells.|These results suggest that the anti-inflammatory and anti-asthmatic effect of IPD could be due to the inhibition of pro-constrictory, pro-inflammatory and secretory pathways that involve G-proteins, PI-3 kinase, Akt, and NF-kB.|iv