The role of nuclear receptor 4A1 (NR4A1) in drug‐induced gingival overgrowth

Abstract

Drug‐induced gingival overgrowth (DIGO) is a side effect of cyclosporine A (CsA), nifedipine (NIF), and phenytoin (PHT). Nuclear receptor 4A1 (NR4A1) plays a role in fibrosis in multiple organs. However, the relationship between NR4A1 and DIGO remains unclear. We herein investigated the involvement of NR4A1 in DIGO. In the DIGO mouse model, CsA inhibited the up‐regulation of Nr4a1 expression induced by periodontal disease (PD) in gingival tissue, but not that of Col1a1 and Pai1. We detected gingival overgrowth (GO) in Nr4a1 knock out (KO) mice with PD. A NR4A1 agonist inhibited the development of GO in DIGO model mice. TGF‐β increased Col1a1 and Pai1 expression levels in KO mouse gingival fibroblasts (mGF) than in wild‐type mice, while the overexpression of NR4A1 in KO mGF suppressed the levels. NR4A1 expression levels in gingival tissue were significantly lower in DIGO patients than in PD patients. We also investigated the relationship between nuclear factor of activated T cells (NFAT) and NR4A1. NFATc3 siRNA suppressed the TGF‐β‐induced up‐regulation of NR4A1 mRNA expression in human gingival fibroblasts (hGF). CsA suppressed the TGF‐β‐induced translocation of NFATc3 into the nuclei of hGF. Furthermore, NIF and PHT also decreased NR4A1 mRNA expression levels and suppressed the translocation of NFATc3 in hGF. We confirmed that CsA, NIF, and PHT reduced cytosolic calcium levels increased by TGF‐β, while CaCl2 enhanced the TGF‐β‐up‐regulated NR4A1 expression. We propose that the suppression of the calcium‐NFATc3‐NR4A1 cascade by these three drugs plays a role in the development of DIGO.

Epithelial-to-mesenchymal transition, inflammation, subsequent collagen production, and reduced proteinase expression cooperatively contribute to cyclosporin-A-induced gingival overgrowth development

“…We previously reported that Spock1 -Tg mice exhibit gingival overgrowth in the absence of periodontal inflammation due to the promotion of epithelial-to-mesenchymal transition by SPOCK-1 overexpression ( Alshargabi et al, 2020 ). Generally, gingival or periodontal inflammation promotes gingival thickening in patients with DIGO ( Sousa et al, 2011 ; Okanobu et al, 2017 ; Hatano et al, 2021 ). To confirm whether periodontal inflammation enhanced gingival overgrowth related to SPOCK-1 overexpression, Spock1 -Tg and WT mice were subjected to experimental periodontitis via placement of a silk ligature ( Figure 1A ).…”

“…Plaque control is recommended for the treatment of DIGO. Most importantly, CsA, which is reported to induce frequent DIGO in human and mouse models ( Okanobu et al, 2017 ; Hatano et al, 2021 ), is known to inhibit CN/NF-AT signals. Therefore, we hypothesized that other factors that promote EMT cooperatively contributed to the development of DIGO and focused on the involvement of inflammation and NF-AT signaling.…”

“…Thus, we aimed to further elucidate the pathogenesis of DIGO by including periodontal inflammation and administering causative drugs to Spock1 -Tg mice to understand the involvement of these factors in DIGO pathology. Most previous reports have used CsA to implement an experimental DIGO model since CsA is known to induce some degree of DIGO in mice ( Hallmon and Rossmann, 1999 ; Okanobu et al, 2017 ; Hatano et al, 2021 ); however, the resulting enlarged gingiva may not cover the entire crown of the tooth. Thus, the reproducibility of this drug in an animal model of DIGO in mice is known.…”

“…In addition, previous studies also demonstrated that placing a silk ligature around the molars could successfully induce experimental periodontitis, leading to alveolar bone resorption, similar to human chronic inflammatory periodontal disease ( Marchesan et al, 2018 ). Furthermore, in vivo and in vitro studies have demonstrated that the combination of CsA with ligature-induced experimental periodontitis effectively elicits DIGO, with the tooth crown being almost completely covered by enlarged gingiva via collagen accumulation due to the downregulation of the CN/NF-AT axis in mice ( Okanobu et al, 2017 ; Hatano et al, 2021 ).…”