TRPA1 Channels Mediate Human Gingival Fibroblast Response to Phenytoin

Abstract

Drug-induced gingival enlargement (GE) is a frequent adverse effect observed in patients treated with anticonvulsant, immunosuppressant, and some antihypertensive medications-the antiepileptic phenytoin being the main drug associated with GE due to its high incidence (around 50%). The molecular mechanisms behind drug-induced gingival overgrowth are still unknown. By reverse transcription polymerase chain reaction, we demonstrate that the calcium-permeable ion channels TRPA1, TRPV1, and its capsaicin-insensitive isoform TRPV1b are expressed in human gingival fibroblasts (HGFs), the most abundant cellular type in periodontal tissue. Cultured HGFs responded with intracellular calcium elevations to phenytoin and to the canonical TRPA1 agonist allyl isothiocyanate. Application of phenytoin activated a nonselective cationic current in HGFs with a typical signature for TRPA1 channels. Moreover, this activation was blocked by HC030031, a specific TRPA1 blocker. Similarly, the use of shRNAs against hTRPA1 in HGFs reduced TRPA1 expression and activation by phenytoin. In addition, we show that phenytoin increased intracellular calcium levels in cells transfected with mouse or human TRPA1 channels. Responses to phenytoin were not observed in untransfected cells or cells expressing TRPM8 or TRPV1. The activation of HGFs by phenytoin was markedly reduced in the presence of antioxidant vitamins: ascorbic acid, folic acid, and α-tocopherol. By performing cell proliferation assays, we found that phenytoin did not augment the proliferation rate of HGFs. In contrast, alcian blue and picrosirius red staining of long-term HGFs cultures indicated that phenytoin induces extracellular matrix accumulation of collagen. Collectively, these findings support an important role of TRPA1 channels in phenytoin-induced GE, provide insight into the pathophysiologic mechanism, and offer novel therapeutic opportunities for its treatment.

Activated KCNQ1 channel promotes fibrogenic response in hereditary gingival fibromatosis via clustering and activation of Ras

“…Gingival fibroblasts, the most abundant cellular type in periodontal tissue, play crucial role in GO 1,26 . In the present study, we showed that enhanced expression of KCNQ1 as well as increased outward K + currents was presented in gingival tissues derived from HGF patients.…”

“…While extensive studies focused on intracellular Ca 2+ metabolism in DIGO, 26,27 our study firstly proposed that intracellular K + changes may be the cause of GO. Indeed, gain‐of‐function mutations in five potassium channel genes, KCNQ1 , KCNH1 , KCNJ8 , ABCC9 , and KCNK4 , were all strongly positively correlated with a GO phenotype in different syndromic diseases 7,8,10‐12 .…”

Alkaline extracellular conditions promote the proliferation and mineralization of a human cementoblast cell line

“…), and the activation of TRPA1 by phenytoin has been shown to increase the proliferation of human gingival fibroblasts (Lopez‐Gonzalez et al . ). Therefore, it was hypothesized that an alkaline pH stimulates channels and activates extracellular‐regulated kinase (ERK; phospho‐p44/42) in HCEM.…”

A new target to ameliorate the damage of periodontal disease: The role of transient receptor potential vanilloid type‐1 in contrast to that of specific cannabinoid receptors in rats

“…Endogenously, TRPV1 is opened mainly by high temperatures (>43°C), acidity, N ‐arachidonoyl dopamine, N ‐oleoyldopamine, and AEA . TRPV1 consists of a protein with six transmembrane domains and is found mainly in the nociceptive neurons of the peripheral nervous system, but has also been described in many other tissues, including gingival fibroblasts and periodontal ligament cells . TRPV1 is involved in the transmission and modulation of pain, is mainly permeable to Ca 2+ , and has been demonstrated to regulate vasodilatation, inflammatory response, and osteogenesis .…”

“…15,16 TRPV1 consists of a protein with six transmembrane domains and is found mainly in the nociceptive neurons of the peripheral nervous system, but has also been described in many other tissues, including gingival fibroblasts and periodontal ligament cells. 17,18 TRPV1 is involved in the transmission and modulation of pain, is mainly permeable to Ca 2+ , and has been demonstrated to regulate vasodilatation, inflammatory response, and osteogenesis. 19,20 Moreover, both TRPV1 and TLR4 have been associated to distinct types of periodontal disease in a study of human tissue samples.…”