Transcriptional regulation of CD38 expression by tumor necrosis factor‐α in human airway smooth muscle cells: role of NF‐κB and sensitivity to glucocorticoids

The transmembrane glycoprotein CD38 catalyzes the synthesis of the calcium mobilizing molecule cyclic ADP-ribose from NAD. In human airway smooth muscle (HASM) cells, the expression and function of CD38 are augmented by the inflammatory cytokine tumor necrosis factor-alpha (TNF- alpha ), leading to increased intracellular calcium response to agonists. A glucocorticoid response element in the CD38 gene has been computationally described, providing evidence for transcriptional regulation of its expression. In the present study, we investigated the effects of dexamethasone, a glucocorticoid, on CD38 expression and ADP-ribosyl cyclase activity in HASM cells stimulated with TNF- alpha . In HASM cells, TNF- alpha augmented CD38 expression and ADP-ribosyl cyclase activity, which were attenuated by dexamethasone. TNF- alpha increased NF- Kappa B expression and its activation, and dexamethasone partially reversed these effects. TNF- alpha increased the expression of I Kappa B alpha , and dexamethasone increased it further. An inhibitor of NF- Kappa B activation or transfection of cells with I Kappa B mutants decreased TNF- alpha -induced CD38 expression. The results indicate that TNF- alpha -induced CD38 expression involves NF- Kappa B expression and its activation and dexamethasone inhibits CD38 expression through NF- Kappa B-dependent and -independent mechanisms.