Sphingosine kinase 1 regulates mucin production via ERK phosphorylation

Abstract

Our previous report showed that inhibition of sphingosine kinase (SphK) ameliorates eosinophilic inflammation and mucin production in a mouse asthmatic model. To clarify the role of SphK in airway mucin production, we utilized the mouse asthmatic model and found that both SphK and MUC5AC expression were increased and co-localized in airway epithelium. Next we cultured normal human bronchial epithelial cells in an air-liquid interface and treated with IL-13 to induce their differentiation into goblet cells. We found that SphK1 and MUC5AC expression was increased by IL-13 treatment at both protein and mRNA levels, whereas SphK2 expression was not changed. N,N-dimethylsphingosine (DMS), a potent SphK inhibitor, decreased MUC5AC expression up-regulated by IL-13 treatment. Furthermore, DMS inhibited IL-13-induced ERK1/2 phosphorylation but neither p38 MAPK nor STAT6 phosphorylation. These results suggest that SphK1 is involved in MUC5AC production induced by IL-13 upstream of ERK1/2 phosphorylation, and independent of STAT6 phosphorylation.

Interleukin-13 Induces Mucin 5AC Production Involving STAT6/SPDEF in Human Airway Epithelial Cells

“…Furthermore, STAT6 siRNA did not decrease IL-13-increased MUC5AC mRNA expression and protein production to baseline levels. These results are consistent with a previous study that indicated that sphingosine kinase 1 regulates IL-13-induced MUC5AC production via extracellular signal-regulated kinase (ERK) phosphorylation, and independent of STAT6 phosphorylation (Kono et al 2010).…”

“…These data indicate that in addition to SPDEF, other pathways may be involved in IL-13-mediated MUC5AC expression. These results were consistent with reports demonstrating that IL-13 induced mucus hypersecretion through mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling pathways (Atherton et al 2003;Kono et al 2010).…”

IL-13–induced airway mucus production is attenuated by MAPK13 inhibition

“…We observed that doxycycline treatment of NCI-H292-rtTA-CLCA1 cells caused time-dependent activation of 12 MAPKs ( Figure 3A and data not shown). The largest doxycycline-induced increase in MAPK phosphorylation (doxycycline treatment compared with no treatment) was found for MAPK14 ( Figure 3A), consistent with MAPK14 inhibitor blockade of cytok- ine-induced MUC5AC gene expression in airway epithelial cells (12,13,21,26). However, blockade was only achieved at relatively high (10-20 μM) concentrations of inhibitor that may no longer be specific for MAPK14 (27).…”

“…The lack of identifiable STAT6-binding sites in the MUC5AC mucin gene promoter indicates that intermediate steps are required to convert the IL-13 signal to mucin gene expression (10,11). In that regard, other studies of cultured human airway epithelial cells have suggested that activation of MEK1/2, PI3K, SPhk1, and MAPK14 (p38α-MAPK) are necessary for IL-13-induced mucus production (12,13). However, these conclusions were typically based on the effects of chemical inhibitors at relatively high concentrations without target validation using genetic tools.…”

Ongoing activation of sphingosine 1-phosphate receptors mediates maturation of exosomal multivesicular endosomes

“…For RNA interference, we used the oligonucleotides (Japan Bio Services, Saitama, Japan) as described previously 30,63 and listed in Supplementary Table S2.…”