IL-37 inhibits M1-like macrophage activation to ameliorate temporomandibular joint inflammation through the NLRP3 pathway.

IL-37 has been identified as an important anti-inflammatory and immunosuppressive factor. This study was undertaken to explore how IL-37 affects M1/M2-like macrophage polarization and thus contributes to anti-inflammatory processes in the temporomandibular joint. Western blotting, quantitative real-time PCR (qRT-PCR) and immunofluorescence were used to verify the IL-37-induced polarization shift from the M1 phenotype to the M2 phenotype, and the related key pathways were analysed by western blotting. Human chondrocytes were stimulated with M1-conditioned medium (CM) or IL-37-pretreated M1-CM, and inflammatory cytokines were detected. siRNA-IL-1R8 and MCC-950 were used to investigate the mechanism underlying the anti-inflammatory effects of IL-37. Complete Freund's adjuvant-induced and disc perforation-induced inflammation models were used for in vivo studies. Haematoxylin and eosin, immunohistochemical and safranin-O staining protocols were used to analyse histological changes in the synovium and condyle. Western blotting, qRT-PCR and immunofluorescence showed that IL-37 inhibited M1 marker expression and upregulated M2 marker expression. Western blotting and qRT-PCR showed that pretreatment with IL-37 suppressed inflammatory cytokine expression in chondrocytes. IL-37 inhibited the expression of NLRP3 and upregulated the expression of IL-1R8. Si-IL-1R8 and MCC-950 further confirmed that the anti-inflammatory properties of IL-37 were dependent on the presence of IL-1R8 and NLRP3. In vivo, IL-37 reduced synovial M1 marker expression and cartilage degeneration and increased M2 marker expression. IL-37 shifting of the polarization of macrophages from the pro-inflammatory M1 phenotype to the beneficial anti-inflammatory M2 phenotype seems to be a promising therapeutic strategy for treating temporomandibular joint inflammation.

Luo P ，Peng S ，Yan Y ，Ji P ，Xu J ... -  《-》

Berberine inhibits NLRP3 inflammasome activation and proinflammatory macrophage M1 polarization to accelerate peripheral nerve regeneration.

Berberine (BBR) has demonstrated potent anti-inflammatory effects by modulating macrophage polarization. Nevertheless, the precise mechanisms through which berberine regulates post-injury inflammation within the peripheral nerve system remain elusive. This study seeks to elucidate the role of BBR and its underlying mechanisms in inflammation following peripheral nerve injury (PNI). Adult male C57BL/6J mice subjected to PNI were administered daily doses of berberine (0, 60, 120, 180, 240 ​mg/kg) via gavage from day 1 through day 28. Evaluation of the sciatic function index (SFI) and paw withdrawal threshold revealed that BBR dose-dependently enhanced both motor and sensory functions. Immunofluorescent staining for anti-myelin basic protein (anti-MBP) and anti-neurofilament-200 (anti-NF-200), along with histological staining comprising hematoxylin-eosin (HE), luxol fast blue (LFB), and Masson staining, demonstrated that BBR dose-dependently promoted structural regeneration. Molecular analyses including qRT-PCR, Western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence confirmed that inactivation of the NLRP3 inflammasome by MCC950 shifted macrophages from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, while also impeding macrophage infiltration. Furthermore, BBR significantly downregulated the expression of the NLRP3 inflammasome and its associated molecules in macrophages, thereby mitigating NLRP3 inflammasome activation-induced macrophage M1 polarization and inflammation. In summary, BBR's neuroprotective effects were concomitant with the suppression of inflammation after PNI, achieved through the inhibition of NLRP3 inflammasome activation-induced macrophage M1 polarization.

Sun J ，Zeng Q ，Wu Z ，Huang L ，Sun T ，Ling C ，Zhang B ，Chen C ，Wang H ... -  《-》

IL-37b alleviates inflammation in the temporomandibular joint cartilage via IL-1R8 pathway.

Interleukin (IL)-37 is a natural suppressor of innate inflammation. This study was conducted to explore the anti-inflammatory effects of IL-37 in temporomandibular joint (TMJ) inflammation. The expression of IL-37 in the TMJ was measured using ELISA and IHC. Human TMJ chondrocytes were treated with IL-37b and IL-1β, and inflammation-related factors were detected. siRNA-IL-1R8 was transfected into chondrocytes, and the affected pathways were detected. IL-37b was used in disc-perforation-induced TMJ inflammation in SD rats. Micro-CT, IHC, real-time PCR and histological staining were used to quantify the therapeutic effect of IL-37b. IL-37 was expressed in the synovium and the disc of patients with osteoarthritis (OA) and in the articular cartilage of condylar fracture patients. IL-37 was highly expressed in synovial fluid of patients with synovitis than in those with OA and disc displacement and was closely related to visual analogue scale (VAS) score. In vitro, IL-37b suppressed the expression of pro-inflammatory factors. In addition, IL-37b exerted anti-inflammatory effects via IL-1R8 by inhibiting the p38, ERK, JNK and NF-κB activation, while silencing IL-1R8 led to inflammation and upregulation of these signals. In disc-perforation-induced TMJ inflammation in SD rats, IL-37b suppressed inflammation and inhibited osteoclast formation to protect against TMJ. IL-37b may be a novel therapeutic agent for TMJ inflammation.

Luo P ，Feng C ，Jiang C ，Ren X ，Gou L ，Ji P ，Xu J ... -  《-》

IL-38-mediated NLRP3/caspase-1 inhibition is a disease-modifying treatment for TMJ inflammation.

Recently, interleukin-38 (IL-38) was identified as an important anti-inflammatory and immunosuppressive factor, but its functional role in temporomandibular joint (TMJ) inflammation remains unknown. This study aimed to elucidate how IL-38 affects chondrocytes and the underlying mechanism that contributes to anti-inflammatory processes in the TMJ. Western blotting, quantitative real-time PCR, enzyme-linked immunosorbent assay, and immunofluorescence analysis were used to verify that IL-38 has anti-inflammatory effects on chondrocytes, and the related key pathways were analyzed by western blotting. SiRNA-IL-38, siRNA-NLRP3, and MCC950 were used to investigate the mechanism underlying the anti-inflammatory effects of IL-38. Inflammation models were induced by injection of complete Freund's adjuvant in TMJ with mouse recombinant IL-38 in in vivo studies. Histological and immunohistochemical analyses were used to investigate histological changes in the cartilage. The results showed that IL-38 inhibited the expression of inflammatory cytokines and MMPs. IL-38 limited inflammation by inhibiting the expression of MAPKs/NF-κB and the NLRP3/caspase-1 pathway. In vivo, IL-38 reduced chondrocyte inflammation and limited cartilage degeneration. This study shows for the first time that IL-38 plays a protective role in TMJ cartilage. IL-38 exerts anti-inflammatory effects through the NLRP3/caspase-1 pathway and may be a promising agent for treating TMJ inflammation.

Luo P ，Zhao T ，He H 《-》

Interleukin-37 ameliorates periodontitis development by inhibiting NLRP3 inflammasome activation and modulating M1/M2 macrophage polarization.

Our study was designed to explore the role of IL-37 in M1/M2 macrophage polarization imbalance in the pathogenesis of periodontitis. Periodontitis is a chronic progressive inflammatory disease featured by gingival inflammation and alveolar bone resorption. Recent research has revealed that regulating macrophage polarization is a viable method to ameliorate periodontal inflammation. IL-37 is an anti-inflammatory cytokine, which has been reported to inhibit innate and adaptive immunity. For in vitro experiment, mouse macrophage RAW264.7 cells were pretreated with 0.1 ng/mL recombinant human IL-37. M1 and M2 polarizations of RAW264.7 cells were induced by 100 ng/mL LPS and 20 ng/mL IL-4, respectively. The expression of M1 (iNOS, TNF-α, and IL-6) and M2 (CD206, Arg1, and IL-10) phenotype markers in RAW264.7 cells was detected by RT-qPCR, western blotting, and immunofluorescence staining. For in vivo experiment, experimental periodontitis mouse models were established by sterile silk ligation (5-0) around the bilateral maxillary second molar of mice for 1 week. H&E staining of the maxillary alveolar bone was used to show the resorption of root cementum and dentin. Alveolar bone loss in mouse models was evaluated through micro-CT analysis. The expression of iNOS and CD206 in gingival tissues was assessed by immunohistochemistry staining. NLRP3 inflammasome activation was confirmed by western blotting. IL-37 pretreatment reduced iNOS, TNF-α, and IL-6 expression in LPS-treated RAW264.7 cells but increased CD206, Arg1, and IL-10 in IL-4-treated RAW264.7 cells. LPS-induced upregulation in NLRP3, GSDMD, cleaved-IL-1β, and cleaved-caspase-1 expression was antagonized by IL-37 treatment. In addition, IL-37 administration ameliorated the resorption of root cementum and dentin in periodontitis mouse models. IL-37 prominently decreased iNOS+ cell population but increased CD206+ cell population in gingival tissues of periodontitis mice. The enhancement in NLRP3, GSDMD, cleaved-IL-1β, and cleaved-caspase-1 expression in the gingival tissues of periodontitis mice was offset by IL-37 administration. IL-37 prevents the progression of periodontitis by suppressing NLRP3 inflammasome activation and mediating M1/M2 macrophage polarization.

Yang L ，Tao W ，Xie C ，Chen Q ，Zhao Y ，Zhang L ，Xiao X ，Wang S ，Zheng X ... -  《-》