Immunorthodontics: Role of HIF-1α in the Regulation of (Peptidoglycan-Induced) PD-L1 Expression in Cementoblasts under Compressive Force

Abstract

Patients with periodontitis undergoing orthodontic therapy may suffer from undesired dental root resorption. The purpose of this in vitro study was to investigate the molecular mechanisms resulting in PD-L1 expression of cementoblasts in response to infection with Porphyromonas gingivalis (P. gingivalis) peptidoglycan (PGN) and compressive force (CF), and its interaction with hypoxia-inducible factor (HIF)-1α molecule.: The cementoblast (OCCM-30) cells were kinetically infected with various concentrations of P. gingivalis PGN in the presence and absence of CF. Western blotting and RT-qPCR were performed to examine the protein expression of PD-L1 and HIF-1α as well as their gene expression. Immunofluorescence was applied to visualize the localization of these proteins within cells. An HIF-1α inhibitor was added for further investigation of necroptosis by flow cytometry analysis. Releases of soluble GAS-6 were measured by ELISA. P. gingivalis PGN dose dependently stimulated PD-L1 upregulation in cementoblasts at protein and mRNA levels. CF combined with P. gingivalis PGN had synergistic effects on the induction of PD-L1. Blockade of HIF-1α inhibited the P. gingivalis PGN-inducible PD-L1 protein expression under compression, indicating an HIF-1α dependent regulation of PD-L1 induction. Concomitantly, an HIF-1α inhibitor decreased the GAS-6 release in the presence of CF and P. gingivalis PGN co-stimulation. The data suggest that PGN of P. gingivalis participates in PD-L1 up-regulation in cementoblasts. Additionally, the influence of compressive force on P. gingivalis PGN-induced PD-L1 expression occurs in HIF-1α dependently. In this regard, HIF-1α may play roles in the immune response of cementoblasts via immune-inhibitory PD-L1. Our results underline the importance of molecular mechanisms involved in bacteria-induced periodontics and root resorption.

Ciliary Neurotrophic Factor (CNTF) and Its Receptors Signal Regulate Cementoblasts Apoptosis through a Mechanism of ERK1/2 and Caspases Signaling

“…An immortalized murine cementoblast (OCCM-30) cell line [ 31 , 32 ] was kindly provided by Prof. M. Somerman (Laboratory of Oral Connective Tissue Biology, NIH, Bethesda, MD, USA). OCCM-30 cells were cultured in α-minimal essential medium (α-MEM) (11095-080, Gibco, Gaithersburg, MA, USA), supplemented with 10% ( v / v ) fetal bovine serum (FBS) (10270-106, Gibco) and 1% Penicillin/Streptomycin (P/S) (15140-122, Gibco) in 6-wells cell culture plates (657160, Greiner bio-one, Frickenhausen, Germany) at 37 °C humidified atmosphere with 5% CO 2 .…”

Ciliary Neurotrophic Factor (CNTF) Inhibits In Vitro Cementoblast Mineralization and Induces Autophagy, in Part by STAT3/ERK Commitment

“…The immortalized murine cementoblast cell line (OCCM-30) [ 28 , 29 ] (generously provided by Prof. J. Deschner and Dr. M. Nokhbehsaim, Department of Periodontology, University of Bonn, Germany) was plated with a seeding density of 1 × 10 6 cell/well and maintained at 37 °C in a humidified atmosphere with 5% CO 2 in air. OCCM-30 cells were cultured in the regular growth medium α-MEM (Gibco, Gaithersburg, MA, USA), supplemented with 10% ( v / v ) heat-inactivated fetal bovine serum (FBS) (Gibco) and 1% penicillin/streptomycin (Gibco) in 6-well plates (Greiner bio-one, Frickenhausen, Germany).…”

PD-L1, a Potential Immunomodulator Linking Immunology and Orthodontically Induced Inflammatory Root Resorption (OIIRR): Friend or Foe?

“…It has been demonstrated to be up-regulated upon immune activation conditions, such as inflammations [ 83 ]. In recent studies, we identified for the first time that PD-L1 is induced and constantly expressed on murine cementoblasts in response to compression and hypoxia, simulating orthodontic-force-induced microenvironmental changes [ 84 , 85 ]. In detail, the recent data revealed that the application of a compressive force at a magnitude of 2.4 gf/cm 2 enhances the PD-L1 expression in cementoblasts.…”

“…When cementoblasts were subjected to a modified compression, they expressed stable PD-L1, which in turn may facilitate their antigenic escape from immune surveillance. In addition, it was revealed that HIF-1α plays an pivotal role in the PD-L1 modulation [ 84 ]. Another very recent study conducted by our group showed that long-term exposure to hypoxic conditions augmented PD-L1 expression on cementoblasts [ 85 ].…”