Blockade of PD-L1/PD-1 signaling promotes osteo-/odontogenic differentiation through Ras activation

Overexpression of programmed cell death ligand 1 reduces LPS-induced inflammatory cytokine upregulation and enhances osteo/odontogenic-differentiation of human dental pulp stem cells via upregulation of CCCTC-binding factor

OBJECTIVE

The aim of this study was to explore the effect and mechanism of programmed cell death ligand 1 (PD-L1) in promoting the proliferation and osteo/odontogenic-differentiation of human dental pulp stem cells (hDPSCs) by mediating CCCTC-binding factor (CTCF) expression.

DESIGN

The interaction between PD-L1 and CTCF was verified through co-immunoprecipitation. hDPSCs transfected with PD-L1 overexpression and CTCF knockdown vectors were treated with lipopolysaccharide or an osteogenic-inducing medium. Inflammatory cytokines and osteo/odontogenic-differentiation related genes were measured. Osteo/odontogenic-differentiation of hDPSCs was assessed using alkaline phosphatase (ALP) and alizarin red S staining.

RESULTS

Overexpression of PD-L1 inhibited LPS-induced pro-inflammatory cytokine upregulation, cell proliferation, ALP activity, and calcium deposition in hDPSCs and elevated the expression of osteo/odontogenic-differentiation related genes; however, such expression patterns could be reversed by CTCF knockdown. Co-immunoprecipitation results confirmed the binding of PD-L1 to CTCF, indicating that PD-L1 overexpression in hDPSCs increases CTCF expression, thus inhibiting the inflammatory response and increasing osteo/odontogenic-differentiation of hDPSCs.

CONCLUSION

PD-L1 overexpression in hDPSCs enhances the proliferation and osteo/odontogenic-differentiation of hDPSCs and inhibit the inflammatory response by upregulating CTCF expression.

Apoptosis Regulation in Dental Pulp Cells and PD-1/PD-L1 Expression Dynamics Under Ozone Exposure - A Pilot Approach

This study aimed to determine the effect of ozone on the expression of Bax and Bcl-2 genes in dental pulp cells. Additionally, the programmed cell death protein 1, programmed death-ligand 1, and CD200 antigens were determined in lymphocytes to assess their surface expression. Dental pulp cells were cultured from extracted healthy third molars and characterized as dental pulp stromal cells. Gene expression of Bcl-2 and Bax was analyzed at 0 s, 6 s, and 12 s of ozone exposure using real-time PCR. Lymphocytes from dental pulp were subjected to ozone exposure for 12 s and PD-1, PD-L1, and CD200/CD200R expression was analyzed by flow cytometry. Upon exposure to ozone for 6 s, the Bcl-2 expression decreased significantly to -0.09, and at 12 s, it increased significantly to 0.3. Bax gene expression level increased significantly to 0.188 after 6 s exposure, and at 12 s, to 0.16. Lymphocytes exposed to ozone for 12 s showed minimal changes in PD-1, PD-L1, and CD200/CD200R expression levels, indicating that oxidative stress does not impact the signaling pathways regulating these molecules. The significant upregulation of Bcl-2 at 12 s highlights the cells' effort to protect themselves from prolonged oxidative stress, possibly tipping the balance toward cell survival and tissue repair. However, the absence of changes in PD-1 and PD-L1 expression on lymphocytes under oxidative stress suggests that these molecules are not sensitive to oxidative stress in this context.

BACH1 regulates the proliferation and odontoblastic differentiation of human dental pulp stem cells

Background

The preservation of biological and physiological vitality as well as the formation of dentin are among the main tasks of human dental pulp for a life time. Odontoblastic differentiation of human dental pulp stem cells (hDPSCs) exhibits the capacity of dental pulp regeneration and dentin complex rebuilding. Exploration of the mechanisms regulating differentiation and proliferation of hDPSCs may help to investigate potential clinical applications. BTB and CNC homology 1 (BACH1) is a transcription repressor engaged in the regulation of multiple cellular functions. This study aimed to investigate the effects of BACH1 on the proliferation and odontoblastic differentiation of hDPSCs in vitro.

Methods

hDPSCs and pulpal tissues were obtained from extracted human premolars or third molars. The distribution of BACH1 was detected by immunohistochemistry. The mRNA and protein expression of BACH1 were examined by qRT-PCR and Western blot analysis. BACH1 expression was regulated by stable lentivirus-mediated transfection. Cell proliferation and cell cycle were assessed by cell counting kit-8 assay, 5-Ethynyl-2'-deoxyuridine assay and flow cytometry. The expression of mineralization markers, alkaline phosphatase (ALP) activity and alizarin red S staining were conducted to assess the odontoblastic differentiation ability.

Results

BACH1 expression was stronger in the odontoblast layer than in the cell rich zone. The total and nuclear protein level of BACH1 during odontoblastic differentiation was downregulated initially and then upregulated gradually. Knockdown of BACH1 greatly inhibited cell proliferation, arrested cell cycle, upregulated the heme oxygenase-1 (HO-1) expression and attenuated ALP activity, decreased calcium deposits and downregulated the expression of mineralization markers. Treatment of Tin-protoporphyrin IX, an HO-1 inhibitor, failed to rescue the impaired odonto/osteogenic differentiation capacity. Overexpression of BACH1 increased cell proliferation, ALP activity and the expression of mineralization markers.

Conclusions

Our findings suggest that BACH1 is an important regulator of the proliferation and odontoblastic differentiation of hDPSCs in vitro. Manipulation of BACH1 expression may provide an opportunity to promote the regenerative capacity of hDPSCs.

Phosphofructokinase 1 platelet isoform induces PD-L1 expression to promote glioblastoma immune evasion

BACKGROUND

Overexpression of PD-L1 is observed in many types of human cancer, including glioblastoma (GBM) and contributes to tumor immune evasion. In addition, GBM shows highly-activated aerobic glycolysis due to overexpression of phosphofructokinase 1 platelet isoform (PFKP), which the key enzyme in the glycolysis. However, it remains unclear whether the metabolic enzyme PFKP plays a role in the regulation of PD-L1 expression and GBM immune evasion.

OBJECTIVE

We aimed to investigate the non-metabolic role of PFKP in PD-L1 expression-induced GBM immune evasion.

METHODS

The mechanisms of PFKP-induced PD-L1 expression were studied by several experiments, including real-time PCR, immunoblot analysis, and ATP production. The coculture experiments using GBM cell and T cells were performed to evaluate the effect of PFKP on T cell activation. The clinical relationship between PFKP and PD-L1 was analyzed in The Cancer Genome Atlas (TCGA) database and in human GBM specimens.

RESULTS

We showed that PFKP promotes EGFR activation-induced PD-L1 expression in human GBM cells. Importantly, we demonstrated that EGFR-phosphorylated PFKP Y64 plays an important role in AKT-mediated β-catenin transactivation and subsequent PD-L1 transcriptional expression, thereby enhancing the GBM immune evasion. In addition, based on our findings, the levels of PFKP Y64 phosphorylation are positively correlated with PD-L1 expression in human GBM specimens, highlighting the clinical significance of PFKP Y64 phosphorylation in the GBM immune evasion.

CONCLUSION

These findings provide new mechanistic insight into the regulation of PD-L1 expression by a non-metabolic function of PFKP on tumor cells.