TGF-β1 Sensitizes TRPV1 through Cdk5 Signaling in Odontoblast-Like Cells

Abstract

BackgroundOdontoblasts are specialized cells that form dentin and they are believed to be sensors for tooth pain. Transforming growth factor-β1 (TGF-β1), a pro-inflammatory cytokine expressed early in odontoblasts, plays an important role in the immune response during tooth inflammation and infection. TGF-β1 is also known to participate in pain signaling by regulating cyclin-dependent kinase 5 (Cdk5) in nociceptive neurons of the trigeminal and dorsal root ganglia. However, the precise role of TGF-β1 in tooth pain signaling is not well characterized. The aim of our present study was to determine whether or not in odontoblasts Cdk5 is functionally active, if it is regulated by TGF-β1, and if it affects the downstream pain receptor, transient receptor potential vanilloid-1 (TRPV1).ResultsWe first determined that Cdk5 and p35 are indeed expressed in an odontoblast-enriched primary preparation from murine teeth. For the subsequent analysis, we used an odontoblast-like cell line (MDPC-23) and found that Cdk5 is functionally active in these cells and its kinase activity is upregulated during cell differentiation. We found that TGF-β1 treatment potentiated Cdk5 kinase activity in undifferentiated MDPC-23 cells. SB431542, a specific inhibitor of TGF-β1 receptor 1 (Tgfbr1), when co-administered with TGF-β1, blocked the induction of Cdk5 activity. TGF-β1 treatment also activated the ERK1/2 signaling pathway, causing an increase in early growth response-1 (Egr-1), a transcription factor that induces p35 expression. In MDPC-23 cells transfected with TRPV1, Cdk5-mediated phosphorylation of TRPV1 at threonine-407 was significantly increased after TGF-β1 treatment. In contrast, SB431542 co-treatment blocked TRPV1 phosphorylation. Moreover, TGF-β1 treatment enhanced both proton- and capsaicin-induced Ca2+ influx in TRPV1-expressing MDPC-23 cells, while co-treatment with either SB431542 or roscovitine blocked this effect.ConclusionsCdk5 and p35 are expressed in a murine odontoblast-enriched primary preparation of cells from teeth. Cdk5 is also functionally active in odontoblast-like MDPC-23 cells. TGF-β1 sensitizes TRPV1 through Cdk5 signaling in MDPC-23 cells, suggesting the direct involvement of odontoblasts and Cdk5 in dental nociceptive pain transduction.

Acute Effects of Transforming Growth Factor-β1 on Neuronal Excitability and Involvement in the Pain of Rats with Chronic Pancreatitis

“…signaling sensitizes TRPV1 in primary sensory neurons. [14][15][16] ] i increase. Thus, another possibility mediating the acute effects of TGF-β1 is that calcium released from intracellular calcium pools as a second message opens one or more non-selective cation channels in direct or indirect ways, thus resulting in robust depolarization and discharges.…”

“…[8][9][10] However, the role of TGF-β1 in pain processing is controversial. Evidence suggests that TGF-β1 has protective effects against neuropathic pain in the central nervous system, 11,12 while in peripheral nervous system, TGF-β1 is recently reported as an algogenic substance that contributes to peripheral sensitization by downregulation of the KCNA4 gene, 13 or activation of cyclin-dependent kinase-transient receptor potential vanilloid type 1 (Cdk5-TRPV1) signaling 14,15 and transforming growth factor β activated kinase 1 (TAK1)/protein kinase C (PKC)-TRPV1 signaling. 16 As mentioned in those studies, [13][14][15][16] TGF-β1 is a complex modulator of sensory neuronal function, and its signaling pathway in the induction and development of pancreatic pain in rats with chronic pancreatitis was not fully understood.…”

Cyclin-dependent kinase 5 modulates the P2X2a receptor channel gating through phosphorylation of C-terminal threonine 372

“…We reported earlier that Cdk5 regulates pain signaling in nociceptive neurons of the dorsal root ganglion (DRG) and trigeminal ganglion (TG) [41; 46; 47; 52]. Cdk5 activity increases during peripheral inflammation, by the action of cytokines such as TNF-α [47; 53; 57] and TGF-β1 [54; 56]. Moreover, we found that Cdk5 phosphorylates the transient receptor potential vanilloid 1 (TRPV1) in Thr407, a key ion channel implicated in pain, increasing its function [25; 33; 40; 47; 54; 56].…”

“…Cdk5 activity increases during peripheral inflammation, by the action of cytokines such as TNF-α [47; 53; 57] and TGF-β1 [54; 56]. Moreover, we found that Cdk5 phosphorylates the transient receptor potential vanilloid 1 (TRPV1) in Thr407, a key ion channel implicated in pain, increasing its function [25; 33; 40; 47; 54; 56]. Remarkably, TRPV1 is phosphorylated in Ser116 and Thr370 by PKA [35], and its dephosphorylation is important for the desensitization process [36].…”

Sigma-1 receptor regulates Tau phosphorylation and axon extension by shaping p35 turnover via myristic acid

“…Cdk5 activity is largely dependent on the availability of its activators, p35 and p39 (8,(15)(16)(17). Transcription of p35 is under the control of early growth response protein 1 (EGR-1) (18)(19)(20). p35 is degraded by two main pathways: the ubiquitin-proteasome pathway is the predominant form of degradation in fetal neurons, whereas, in adult neurons, p35 is preferentially cleaved to p25 by the calciumdependent protease calpain (21-23).…”