IL-37 alleviates alveolar bone resorption and inflammatory response through the NF-κB/NLRP3 signaling pathway in male mice with periodontitis

IL-37 possesses both anti-inflammatory and antiviral effects against Middle East respiratory syndrome coronavirus infection

BACKGROUND

The aim was to elucidate the function of IL-37 in middle east respiratory syndrome coronavirus (MERS-CoV) infection, thereby providing a novel therapeutic strategy for managing the clinical treatment of inflammatory response caused by respiratory virus infection.

METHODS

We investigated the development of MERS by infecting hDPP4 mice with hCoV-EMC (107 TCID50 [50% tissue culture infectious dose]) intranasally. We infected A549 cells with MERS-CoV, which concurrently interfered with IL-37, detecting the viral titer, viral load, and cytokine expression at certain points postinfection. Meanwhile, we administered IL-37 (12.5 μg/kg) intravenously to hDPP4 mice 2 h after MERS-CoV-2 infection and collected the serum and lungs 5 days after infection to investigate the efficacy of IL-37 in MERS-CoV infection.

RESULTS

The viral titer of MERS-CoV-infected A549 cells interfering with IL-37 was significantly reduced by 4.7-fold, and the viral load of MERS-CoV-infected hDPP4 mice was decreased by 59-fold in lung tissue. Furthermore, the administration of IL-37 suppressed inflammatory cytokine and chemokine (monocyte chemoattractant protein 1, interferon-γ, and IL-17A) expression and ameliorated the infiltration of inflammatory cells in hDPP4 mice.

CONCLUSION

IL-37 exhibits protective properties in severe pneumonia induced by MERS-CoV infection. This effect is achieved through attenuation of lung viral load, suppression of inflammatory cytokine secretion, reduction in inflammatory cell infiltration, and mitigation of pulmonary injury.

Cathepsin K inhibition alleviates periodontal bone resorption by promoting type H vessel formation through PDGF-BB/PDGFR-β axis

OBJECTIVES

To explore the effects of cathepsin K (CTSK) inhibition on type H vessel formation and alveolar bone resorption within periodontitis.

METHODS

Conditioned media derived from preosteoclasts pretreated with the CTSK inhibitor odanacatib (ODN), ODN supplemented small interfering RNA targeting PDGF-BB (si-PDGF-BB), or PBS were prepared, to assess their proangiogenic effects on endothelial cells (HUVECs). A series of angiogenic-related assays were conducted to evaluate HUVEC proliferation, migration, and tube formation abilities in vitro. In addition, qRT-PCR and Western blot assays were employed to examine the expression levels of genes/proteins related to PDGF-BB/PDGFR-β axis components. A mouse periodontitis model was established to evaluate the effects of CTSK inhibition on type H vessel formation.

RESULTS

CTSK inhibition promoted PDGF-BB secretion from preosteoclasts and proliferation, migration, and tube formation activities of HUVECs in vitro. However, the conditioned medium from preosteoclasts pretreated by si-PDGF-BB impaired the angiogenic activities of HUVECs. This promoted angiogenesis function by CTSK inhibition may be mediated by the PDGF-BB/PDGFR-β axis. Functionally, in vivo studies demonstrated that CTSK inhibition significantly accelerated type H vessel formation and alleviated bone loss within periodontitis.

CONCLUSION

CTSK inhibition promotes type H vessel formation and attenuates alveolar bone resorption within periodontitis via PDGF-BB/PDGFR-β axis.

[Research Progress in the Molecular Regulatory Mechanisms of Alveolar Bone Restoration]

Alveolar bone, the protruding portion of the maxilla and the mandible that surrounds the roots of teeth, plays an important role in tooth development, eruption, and masticatory performance. In oral inflammatory diseases, including apical periodontitis, periodontitis, and peri-implantitis, alveolar bone defects cause the loosening or loss of teeth, impair the masticatory function, and endanger the physical and mental health of patients. However, alveolar bone restoration is confronted with great clinical challenges due to the the complicated effect of the biological, mechanical, and chemical factors in the oral microenvironment. An in-depth understanding of the underlying molecular regulatory mechanisms will contribute to the exploration of new targets for alveolar bone restoration. Recent studies have shown that Notch, Wnt, Toll-like receptor (TLR), and nuclear factor-κB (NF-κB) signaling pathways regulate the proliferation, differentiation, apoptosis, and autophagy of osteoclasts, osteoblasts, osteocytes, periodontal ligament cells, macrophages, and adaptive immune cells, modulate the expression of inflammatory mediators, affect the balance of the receptor activator for nuclear factor-κB ligand/receptor activator for nuclear factor-κB/osteoprotegerin (RANKL/RANK/OPG) system, and ultimately participate in alveolar bone restoration. Additionally, alveolar bone restoration involves AMP-activated protein kinase (AMPK), phosphatidyl inositol 3-kinase/protein kinase B (PI3K/AKT), Hippo/YAP, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and transforming growth factor β (TGF-β) signaling pathways. However, current studies have failed to construct mature molecular regulatory networks for alveolar bone restoration. There is an urgent need for further research on the molecular regulatory mechanisms of alveolar bone restoration by using new technologies such as single-cell transcriptome sequencing and spatial transcriptome sequencing.

IL-37 counteracts inflammatory injury in the temporomandibular joint via the intracellular pathway

Background: The temporomandibular joint is often afflicted by osteoarthritis (TMJOA), causing pain and dysfunction, which is particularly prevalent in the elderly population. IL-37 is effective in avoiding excessive inflammatory damage to the organism. This article investigates the role and mechanism of intracellular IL-37 in TMJOA. Methods: Enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, Western blotting, Senescence-associated β-galactosidase staining, immunofluorescence, and lentivirus were performed to elucidate the underlying mechanism. Results: The results confirmed that IL-37 in synovial cells decreased with aging. Inflammatory stimulus elevated intracellular IL-37 in synoviocytes, while lentiviral knockdown of IL-37 resulted in more inflammatory factor production. Dynamic changes of IL-37 were observed in the nucleus and supernatant. In addition, Caspease-1 inhibitor hindered intracellular IL-37 maturation, and Smad3 inhibitor caused the loss of nuclear translocation of mature IL-37. Transfection of synovial cells with IL-37-expressing lentivirus resulted in relief not only of synovitis but also of the cartilage damage and inflammation caused by synovitis. Conclusion: This study provides new insights into the intracellular anti-inflammatory mechanism of IL-37. It also confirms that IL-37 decreases with cellular senescence and that increasing intracellular IL-37 can effectively treat synovitis and synovitis-induced inflammatory damage to cartilage.

The Development of Naringin for Use against Bone and Cartilage Disorders

Bone and cartilage disorders are the leading causes of musculoskeletal disability. There is no absolute cure for all bone and cartilage disorders. The exploration of natural compounds for the potential therapeutic use against bone and cartilage disorders is proving promising. Among these natural chemicals, naringin, a flavanone glycoside, is a potential candidate due to its multifaceted pharmacological activities in bone and cartilage tissues. Emerging studies indicate that naringin may promote osteogenic differentiation, inhibit osteoclast formation, and exhibit protective effects against osteoporosis in vivo and in vitro. Many signaling pathways, such as BMP-2, Wnt/β-catenin, and VEGF/VEGFR, participate in the biological actions of naringin in mediating the pathological development of osteoporosis. In addition, the anti-inflammatory, anti-oxidative stress, and anti-apoptosis abilities of naringin also demonstrate its beneficial effects against bone and cartilage disorders, including intervertebral disc degeneration, osteoarthritis, rheumatoid arthritis, bone and cartilage tumors, and tibial dyschondroplasia. Naringin exhibits protective effects against bone and cartilage disorders. However, more efforts are still needed due to, at least in part, the uncertainty of drug targets. Further biological and pharmacological evaluations of naringin and its applications in bone tissue engineering, particularly its therapeutic effects against osteoporosis, might result in developing potential drug candidates.