TNF-α-Induced p38MAPK Activation Regulates TRPA1 and TRPV4 Activity in Odontoblast-Like Cells

The transient receptor potential (TRP) channels are unique cellular sensors that are widely expressed in many neuronal and nonneuronal cells. Among the TRP family members, TRPA1 and TRPV4 are emerging as candidate mechanosensitive channels that play a pivotal rote in inflammatory pain and mechanical hyperalgesia. Odontobtasts are nonneuronal cells that possess many of the features of mechanosensitive cells and mediate important defense and sensory functions. However, the effect of inflammation on the activity of the odontoblasts mechanosensitive channels remains unknown. By using immunohistochemistry and calcium microfluorimetry, we showed that odontoblast-like cells express TRPA1 and TRPV4 and that these channels were activated by hypotonicity-induced membrane stretch. Short treatment of odontoblastlike cells with tumor necrosis factor (TNF)-alpha enhanced TRPA1 and TRPV4 responses to their chemical agonists and membrane stretch. This enhanced channel activity was accompanied by phospho-p38 mitogenactivated protein kinase (MAPK) expression. Treatment of cells with the p38 inhibitor SB202190 reduced TNF-alpha effects, suggesting modulation of channel activity via p38 MAPK. In addition, TNF-alpha treatment also resulted in an up-regulation of TRPA1 expression but down-regulation of TRPV4. Unlike TRPV4, enhanced TRPA1 expression was also evident in dental pulp of carious compared with noncarious teeth. 513202190 treatment significantly reduced TNF-alpha-induced TRPA1 expression, suggesting a role for p38 MAPK signaling in modulating both the transcriptional and non-transcriptional regulation of TRP channels in odontoblasts.