Accumulating evidence shows that PD-L1 expression on dendritic cells (DC) is critical for cancer immunotherapy and that Porphyromonas gingivalis (Pg) colonization aggravates the progression of upper gastrointestinal cancers. However, the effects of Pg infection on PD-L1 expression on DCs and related immune consequences in the infection milieu of oral cancer remain unexplored. Here, we found that Pg infection robustly enhanced PD-L1 expression on DCs in a gingipain-dependent manner in cultured cell and systemic infection assays. Pg infection suppressed antigen-specific CD8+ T cells through upregulation of PD-L1 expression on ovalbumin (OVA)-pulsed DCs. This suppression was manifested by decreased IFNγ, perforin, granzyme B, and CD107a. Further analysis showed that Pg drastically reduced CD8+ T cells’ ability to lyse OVA-pulsed target cells. Additionally, Pg infection increased the phosphorylation of Akt and STAT3, leading to a significant increase in PD-L1 expression. This was substantiated by using siRNA, overexpression plasmids, and pharmacologic inhibitors. Consistent with the in vitro observations, in a syngeneic mouse oral cancer model, Pg infection significantly enhanced PD-L1 expression on DCs from intratumoral tissues and cervical lymph nodes and exacerbated oral cancer progression, whereas a Pg lysine-specific, gingipain-defective mutant failed to do so. These influences of Pg were largely diminished when tumor cells were pretreated with antibiotics or a STAT3 inhibitor. Therefore, we demonstrated that Pg infection upregulates PD-L1 expression on DCs through Akt-STAT3 signaling, suppresses CD8+ T-cell cytotoxicity, and aggravates oral cancer growth, suggesting targeting Pg, and/or its mediated signaling, could be a therapeutic strategy to improve the efficacy of checkpoint blockade immunotherapy.

Expression and activity of serum- and glucocorticoid-inducible kinase 1 (SGK1) are associated with many metabolic and inflammatory diseases. In this study, we report that SGK1 promotes alternative macrophage polarization and restrains inflammation in the infectious milieu of the gingiva. Inhibition of SGK1 expression or activity enhances characteristics of classically activated (M1) macrophages by directly activating the transcription of genes encoding iNOS, IL-12P40, TNF-α, and IL-6 and repressing IL-10 at message and protein levels. Moreover, SGK1 inhibition robustly reduces the expression of alternatively activated (M2) macrophage molecular markers, including arginase-1, Ym-1, Fizz1, and Mgl-1. These results were confirmed by multiple gain- and loss-of-function approaches, including small interfering RNA, a plasmid encoding SGK1, and LysM-Cre–mediated sgk1 gene knockout. Further mechanistic analysis showed that SGK1 deficiency decreases STAT3 but increases FoxO1 expression in macrophages under M2 or M1 macrophage–priming conditions, respectively. Combined with decreased FoxO1 phosphorylation and the subsequent suppressed cytoplasmic translocation observed, SGK1 deficiency robustly enhances FoxO1 activity and drives macrophage to preferential M1 phenotypes. Furthermore, FoxO1 inhibition abrogates M1 phenotypes, and STAT3 overexpression results in a significant increase of M2 phenotypes, indicating that both FoxO1 and STAT3 are involved in SGK1-mediated macrophage polarization. Additionally, SGK1 differentially regulates the expression of M1 and M2 molecular markers, including CD68 and F4/F80 and CD163 and CD206, respectively, and protects against Porphyromonas gingivalis–induced alveolar bone loss in a mouse model. Taken together, these results have demonstrated that SGK1 is critical for macrophage polarization and periodontal bone loss, and for the first time, to our knowledge, we elucidated a bifurcated signaling circuit by which SGK1 promotes alternative, while suppressing inflammatory, macrophage polarization.

Objective: To compare the biomechanical stability and compatibility of two iliosacral screws (ISS), a tension band plate (TBP), and a minimally invasive adjustable plate (MIAP) for treating Tile C pelvic fractures.Methods: Three groups of finite element models of the intact pelvis, including the main ligament and the proximal one‐third of both femurs, were developed to simulate vertical sacral fractures and treated with the three abovementioned internal fixation techniques. A 500 N vertical load, a 500 N vertical load plus a 10 Nm moment of forward sagittal direction, and 500 N vertical load plus a 10 Nm moment of right lateral direction were applied to the sacrum to simulate standing status, bending status, and flexion status, respectively. The maximum displacement value, the stress value, and the stress value of the fracture interface were compared among the three internal fixation techniques.Results: The results showed that all three internal fixation techniques effectively restored the biomechanical transmission of the injured pelvis. The stress on the implants in the TBP model was 167.47% and 53.41% higher than that in the ISS model and the MIAP model, respectively, and the stress shielding phenomenon of the TBP model was more obvious than in the other two models. Meanwhile, the stress between the fracture interfaces in the TBP fixation models was apparently higher than that in the other two models. However, the vertical displacement of the MIAP model was not significantly different from that in the ISS and TBP model; therefore, strong fixation could be obtained in all three models.Conclusion: Based on our results, we believe that the stability of Tile C pelvic fracture fixed with MIAP was similar to that of fractures fixed with ISS and TBP, but the stress shielding phenomenon and safety of implants in the TBP models were inferior to those in the MIAP and ISS fixation models. Meanwhile, MIAP and ISS fixation were more helpful to the healing processing than was TBP fixation, especially at the fracture interface of the second and third vertebral body levels.

Microbial dysbiosis in the upper digestive tract is linked to an increased risk of esophageal squamous cell carcinoma (ESCC). Overabundance of Porphyromonas gingivalis is associated with shorter survival of ESCC patients. We investigated the molecular mechanisms driving aggressive progression of ESCC by P. gingivalis. Intracellular invasion of P. gingivalis potentiated proliferation, migration, invasion, and metastasis abilities of ESCC cells via transforming growth factor-β (TGFβ)-dependent Drosophila mothers against decapentaplegic homologs (Smads)/Yes-associated protein (YAP)/Transcriptional coactivator with PDZ-binding motif (TAZ) activation. Smads/YAP/TAZ/TEA domain transcription factor1 (TEAD1) complex formation was essential to initiate downstream target gene expression, inducing an epithelial–mesenchymal transition (EMT) and stemness features. Furthermore, P. gingivalis augmented secretion and bioactivity of TGFβ through glycoprotein A repetitions predominant (GARP) up-regulation. Accordingly, disruption of either the GARP/TGFβ axis or its activated Smads/YAP/TAZ complex abrogated the tumor-promoting role of P. gingivalis. P. gingivalis signature genes based on its activated effector molecules can efficiently distinguish ESCC patients into low- and high-risk groups. Targeting P. gingivalis or its activated effectors may provide novel insights into clinical management of ESCC.

Serum- and glucocorticoid-regulated kinase 1 (SGK1) is a serine/threonine kinase that plays important roles in the cellular stress response. While SGK1 has been reported to restrain inflammatory immune responses, the molecular mechanisms involved remain elusive, especially in oral bacteria-induced inflammatory milieu. Here, we found that SGK1 curtails Porphyromonas gingivalis–induced inflammatory responses through maintaining levels of tumor necrosis factor receptor-associated factor (TRAF) 3, thereby suppressing NF-κB signaling. Specifically, SGK1 inhibition significantly enhances production of proinflammatory cytokines, including tumor necrosis factor α, interleukin (IL)-6, IL-1β, and IL-8 in P. gingivalis–stimulated innate immune cells. The results were confirmed with siRNA and LysM-Cre–mediated SGK1 KO mice. Moreover, SGK1 deletion robustly increased NF-κB activity and c-Jun expression but failed to alter the activation of mitogen-activated protein kinase signaling pathways. Further mechanistic data revealed that SGK1 deletion elevates TRAF2 phosphorylation, leading to TRAF3 degradation in a proteasome-dependent manner. Importantly, siRNA-mediated traf3 silencing or c-Jun overexpression mimics the effect of SGK1 inhibition on P. gingivalis–induced inflammatory cytokines and NF-κB activation. In addition, using a P. gingivalis infection–induced periodontal bone loss model, we found that SGK1 inhibition modulates TRAF3 and c-Jun expression, aggravates inflammatory responses in gingival tissues, and exacerbates alveolar bone loss. Altogether, we demonstrated for the first time that SGK1 acts as a rheostat to limit P. gingivalis–induced inflammatory immune responses and mapped out a novel SGK1–TRAF2/3–c-Jun–NF-κB signaling axis. These findings provide novel insights into the anti-inflammatory molecular mechanisms of SGK1 and suggest novel interventional targets to inflammatory diseases relevant beyond the oral cavity.