TNF-α Regulation of CD38 expression in human airway smooth muscle: Role of MAP kinases and NF-κB

The pleiotropic cytokine TNF-α has been implicated in airway inflammation and airway hyperresponsiveness (AHR), hallmark features of asthma. Polymorphisms in the TNF gene cluster are associated with increased TNF-α production and risk of asthma. Our laboratory has demonstrated that in human airway smooth muscle (HASM) cells, TNF-α augments the expression of CD38, a type II transmembrane glycoprotein which synthesizes the calcium-mobilizing molecule cyclic ADP-ribose. Mice challenged intranasally with TNF-α develop AHR to inhaled methacholine. However, mice that are deficient in CD38 fail to develop AHR, indicating that CD38 expressed in the airways is required for cytokine-induced AHR. In HASM cells, TNF-α-induced CD38 expression is decreased in the presence of inhibitors of p38, JNK, and ERK mitogen-activated protein kinases (MAPKs). The decreased CD38 expression by p38 and JNK MAPK inhibitors is associated with decreased activation of NF-κB, whereas the decrease by the ERK MAPK inhibitor is due to decreased stability of CD38 transcripts. TNF-α induced a twofold activation of a 3 kb cd38 promoter following its transfection in HASM cells. However, there was no activation of the promoter lacking the NF-κB site. These results demonstrate that TNF-α regulation of CD38 expression in HASM cells is mediated transcriptionally through p38 and JNK MAPKs and NF-κB and post-transcriptionally through the ERK MAPK. These findings support a role for CD38/cADPR signaling in TNF-α-induced AHR.