Hideki Sekiya

αvβ3 Integrin ligands enhance volume-sensitive calcium influx in mechanically stretched osteocytes

We propose that specific osteocyte–matrix interactions regulate the volume-sensitive calcium influx pathway, which we have shown is mediated by stretch-activated cation channels (SA-Cat) and is essential for the stretch-activated anabolic response in bone. The current study measured the hypotonic swelling-induced increase in cytosolic calcium concentration, [Ca2+]i, in rat osteocytes, and found that cells adherent to different matrices behave differently. Osteopontin and vitronectin, matrix molecules that bind the αVβ3 integrin, induced larger responses to the hypotonic swelling than other matrix molecules that bind other integrins. Addition of echistatin, which is a soluble αVβ3 ligand, significantly enhanced the hypotonic [Ca2+]i increase in addition to inducing an immediate increase in [Ca2+]i by itself. These results strongly support the contention that αVβ3 integrin signaling in osteocytes interacts with that in mechanotransduction, which is downstream of SA-Cat.

CCR7 ligands up-regulate IL-23 through PI3-kinase and NF-κB pathway in dendritic cells

We reported previously that the production of IL‐23 is impaired in DCs from mice that lack expression of the chemokines CCL19 and CCL21, which share the receptor CCR7, suggesting that these chemokines are required for IL‐23 expression. However, the molecular mechanism of CCR7‐mediated IL‐23 production in DCs is unknown. We found that CCL19 and CCL21 stimulated DCs through CCR7 and induced transcription of IL‐23p19 mRNA and IL‐23 production in splenic and BMDC. Stimulation of DCs with CCR7 ligands induced phosphorylation of MAPK family members and of Akt, but only a specific PI3K inhibitor, LY294002, not inhibitors of ERK, JNK, or p38, decreased IL‐23p19 transcription and IL‐23 production. In DCs stimulated with CCL19 or CCL21, IκBα was degraded, and NF‐κB was translocated into the nucleus. Prevention of NF‐κB activation blocked chemokine‐mediated IL‐23p19 transcription. A PI3K inhibitor abolished NF‐κB activation and IL‐23 production. Based on these findings, we concluded that PI3K and NF‐κB signaling pathways play a critical role in CCR7‐mediated IL‐23 production in murine DCs. As IL‐23 contributes to Th17 cell generation, and Th17 cells are pathogenic in autoimmune diseases, precise elucidation of these mechanisms would contribute to the development of strategies to control autoimmune diseases.

Severity of arthroscopically observed pathology and levels of inflammatory cytokines in the synovial fluid before and after visually guided temporomandibular joint irrigation correlated with the clinical outcome in patients with chronic closed lock

OBJECTIVEnThis study aimed to investigate the severity of arthroscopically observed pathologies and the levels of a set of inflammatory cytokines in aspirated synovial fluid (A-SF) in patients with chronic closed lock (CCL) of the temporomandibular joint (TMJ) before and after visually guided TMJ irrigation (VGIR). Furthermore, the findings were correlated with the clinical outcome after VGIR.nnnSTUDY DESIGNnVGIR was performed in 56 consecutive patients with unilateral CCL. Forty-nine of them, who underwent a second VGIR either as a follow-up arthroscopy or as a repeated therapeutic irrigation, were analyzed. They were assigned to either the successful (s-) group (n = 31) or unsuccessful (u-) group (n = 18), according to the clinical success criteria. The severity of arthroscopic findings of osteoarthritis (OA), synovitis, and fibrous adhesion (FA) were evaluated as arthroscopic scores. The levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-8, IL-12, and IL-10 in the A-SF were measured. At the first and second VGIR, the arthroscopic scores and the levels of each investigated cytokine were compared between the s- and u-groups. In each group, same parameters were compared between the first and second VGIR.nnnRESULTSnAt the first and second VGIR, there are no differences in the arthroscopic scores between the s- and u-groups. After the first VGIR, the severity of synovitis significantly improved, that of OA was unchanged, and that of FA became worse in the s- and u-groups. At the first VGIR, the levels of IL-6 and IL-8 were significantly higher in the u-group, and the IL-10 level was significantly higher in the s-group. At the second VGIR, however, there were no differences in the levels of each investigated cytokine between the s- and u-groups. The levels of each cytokine did not significantly change between the first and second VGIR, regardless of the clinical outcome.nnnCONCLUSIONSnVGIR may contribute to the remission of synovitis in patients with TMJ CCL. However, the severity of arthroscopically observed pathologies and the levels of each investigated cytokine do not seem to be reflected by the clinical state. Moreover even if the intra-articular inflammation is asymptomatic, an exacerbation may not be ruled out even after a successful VGIR.