Targeting NLRP3 Inflammasome Alleviates Synovitis by Reducing Pyroptosis in Rats with Experimental Temporomandibular Joint Osteoarthritis.

The mechanism of temporomandibular joint osteoarthritis (TMJOA), which leads to the final erosion of cartilage and subchondral bone, has been widely demonstrated, but still not clearly elucidated. Many studies have pointed that NLRP3-mediated inflammation played a vital role in degenerative diseases. However, its interaction with synovitis of TMJOA has remained poorly investigated. In our study, we explored the role of NLRP3 inflammasome in TMJOA synovitis and the therapeutic potential of caspase-1 and NLRP3 inhibitors. By establishing a rat TMJOA model, we found that NLRP3 was upregulated in synovial tissue of TMJOA. It was involved in the progress of a programmed cell death called pyroptosis, which was caspase-1 dependent and ultimately triggered inflammatory mediator interleukin IL-1ß release. Treatment with Ac-YVAD-cmk and MCC950, inhibitors targeting caspase-1 and NLRP3, respectively, significantly suppressed pyroptosis in TMJOA synovial tissue. Then, a macrophage- and fibroblast-like synoviocyte (FLS) cocultured model further verified the above results. Macrophage somehow promoted FLS pyroptosis in this study. Our results suggested that the NLRP3 inflammasome-mediated pyroptosis participated in synovial inflammation of TMJOA. Interfering with the progress could be a potential option for controlling TMJOA development.

Up-regulation of PKMζ expression in the anterior cingulate cortex following experimental tooth movement in rats.

OBJECTIVE: To explore the involvement of synaptic plasticity in pain induced by experimental tooth movement, we evaluated the expression of protein kinase M zeta (PKMζ), an enzyme necessary for maintaining long-term potentiation (LTP) in the anterior cingulate cortex (ACC). METHODS: Male Sprague-Dawley rats weighing 250-300g were used. The change of the expression of PKMζ in the ACC was measured by western blot, and the mRNA of PKMζ was detected by quantitative real-time PCR 1, 3, 7 days after experimental tooth movement. The average time spent on mouth-wiping behaviour of rats involved in pain perception was detected. After that a selective PKMζ inhibitor, called myristoylated ζ-pseudosubstrate inhibitory peptide (ZIP) was injected into ACC, and the effects of ZIP were evaluated. RESULTS: The mouth-wiping behaviour of rats was significantly increased 1, 3, and 7 days after experimental tooth movement. Changes in PKMζ levels were not detected on day 1 but were found to be increased 3 days following the tooth movement, and then declined to the baseline 7 days after tooth movement in the ACC. PKMζ mRNA levels were not significantly different between the experimental and sham-treated groups at the three time points. Time spent on mouth-wiping behaviour was reduced after ZIP was injected into ACC 3 days after tooth movement, and the analgesic effect last for at least 24h. CONCLUSION: PKMζ in the ACC acts to maintain the pain induced by experimental tooth movement. Increased expression of PKMζ protein is attributed to persistent translation of PKMζ mRNA. Synaptic plasticity may be involved in the development of tooth movement pain.

[Changes of protein kinases Mζ expression in the anterior cingulate cortex after applying three different magnitude of orthodontic force].

OBJECTIVE: To investigate the regulatory effect of central synaptic plasticity on pain induced by experimental tooth movement and to analyzethe expression of protein kinases Mζ (PKMζ) in the anterior cingulate cortex (ACC) after applying different magnitude of orthodontic force. METHODS: One hundred and thirty-six male Sprague-Dawley (SD) rats (200-250 g) were used in this study. Orthodontic tooth movement devices were placed on the teeth in the experimental group, and different orthodontic forces (0.39, 0.78, 1.17 N) were applied to move the maxillary first molars, respectively. The same mechanical devices were placed on the teeth in sham-treated group and no orthodontic force was applied. No orthodontic procedure was applied in blank control group. The average time spent on mouth- wiping behavior in each group was recorded after experimental tooth movement. Brain tissue of the anterior cingulate cortex was isolated on day 3 after experiment, and the expression level of PKMζ was analyzed with the method of immunohistochemistry and enzyme-linked immune sorbent assay. ζ-pseudosubstrate inhibitory peptide (ZIP), a selective inhibitor for PKMζ, was injected into ACC on day 3 after experimental tooth movement, and the effects of ZIP on mouth-wiping behavior were evaluated. RESULTS: No statistical difference was found between the blank control group and the sham- treated group in the average time spent on mouth-wiping, value of A and expression level of PKMζ (P > 0.05). Compared with the sham-treated group and blank control group, the average time of mouth-wiping behavior [(58.6±6.9), (66.3±7.8), (78.9±8.7) s], value of A (4 569±454, 6 850±365, 8 294±558) and expression level of PKMζ [(0.32±0.02), (0.34±0.02), (0.36±0.02) mg/L] in 0.39, 0.78, 1.17 N force group were found to be up-regulated with the increase of orthodontic force (P < 0.05). LSD test in three experimental sub-group showed statistical difference (P < 0.05). After microinjection of ZIP, the average time spent on mouth-wiping behavior significantly decreased (P < 0.01), while microinjecting saline did not change rats' mouth-wiping behavior (P > 0.05). CONCLUSIONS: More pain caused by increased orthodontic force maybe due to the up-regulation of PKMζ in the anterior cingulate cortex.