Involvement of the visfatin/toll-like receptor 4 signaling axis in human dental pulp cell senescence: Protection via toll-like receptor 4 blockade

Chang Youp Ok; Sera Park; Hye-Ock Jang; Moon-Kyoung Bae; Soo-Kyung Bae

doi:10.1016/j.jds.2022.10.008

Involvement of the visfatin/toll-like receptor 4 signaling axis in human dental pulp cell senescence: Protection via toll-like receptor 4 blockade

J Dent Sci. 2023 Jul;18(3):1177-1188. doi: 10.1016/j.jds.2022.10.008. Epub 2022 Oct 21.

Authors

Chang Youp Ok^{1

2}, Sera Park¹, Hye-Ock Jang¹, Moon-Kyoung Bae^{2

3}, Soo-Kyung Bae^{1

4}

Affiliations

¹ Department of Dental Pharmacology, BK21 PLUS Project, Education and Research Team for Life Science on Dentistry, School of Dentistry, Pusan National University, Yangsan, South Korea.
² Periodontal Disease Signaling Network Research Center (MRC), Pusan National University, Yangsan, South Korea.
³ Department of Oral Physiology, School of Dentistry, Pusan National University, Yangsan, South Korea.
⁴ Dental and Life Science Institute, Pusan National University, Yangsan, South Korea.

Abstract

Background: /purpose: Dental pulp plays an important role in the maintenance of tooth homeostasis and repair. The aging of dental pulp affects the functional life of the tooth owing to the senescence of dental pulp cells. Toll-like receptor 4 (TLR4) is involved in regulating cellular senescence in dental pulp. We have recently demonstrated that visfatin induces the senescence of human dental pulp cells (hDPCs). Here, we explored the association of TLR4 with visfatin signaling in cellular senescence in hDPCs.

Materials and methods: mRNA levels were determined using reverse transcription polymerase chain reaction (PCR) and quantitative real time-PCR. Protein levels were determined using immunofluorescence staining and Western blot analysis. Gene silencing was performed using small interfering RNA. The degree of cellular senescence was measured by senescence-associated-β-galactosidase (SA-β-gal) staining. Oxidative stress was determined by measurement of NADP/NADPH levels and intracellular reactive oxygen species (ROS) levels.

Results: Neutralizing anti-TLR4 antibodies or TLR4 inhibitor markedly blocked visfatin-induced hDPCs senescence, as revealed by an increase in the number of SA-β-gal-positive hDPCs and upregulation of p21 and p53 proteins. Moreover, visfatin-induced senescence was associated with excessive ROS production; NADPH consumption; telomere DNA damage induction; interleukin (IL)-1β, IL-6, IL-8, cyclooxygenase-2, and tumor necrosis factor-α upregulation; and nuclear factor-κB and mitogen-activated protein kinase activation. All of these alterations were attenuated by TLR4 blockade.

Conclusion: Our findings indicate that TLR4 plays an important role in visfatin-induced senescence of hDPCs and suggest that the visfatin/TLR4 signaling axis can be a novel therapeutic target for the treatment of inflammaging-related diseases, including pulpitis.

Keywords: Human dental pulp cells; Inflammaging; Senescence; TLR4; Visfatin.