Major histocompatibility complex class II transactivator inhibits cysteine-rich 61 expression in osteoblastic cells and its implication in the pathogenesis of periapical lesions.
ABSTRACT Osteoblastic expression of cysteine-rich 61 (Cyr61) correlates with the severity of periapical lesion-associated bone loss, but the regulatory mechanism of Cyr61 expression was not known.
In the study we examined the effect of major histocompatibility complex class II transactivator (CIITA) on tumor necrosis factor (TNF)-alpha-induced Cyr61 synthesis in U2OS human osteoblastic cells by Western blot analysis. In a rat model of bacteria-induced apical periodontitis, we assessed the relation between osteoblastic expressions of CIITA/Cyr61 and disease progression by radiographic and immunohistochemistry studies.
We found that forced expression of CIITA suppressed Cyr61 synthesis in U2OS cells. In rat periapical lesions, osteoblastic CIITA decreased as the disease progressed, and expression of CIITA is negatively related to Cyr61 synthesis in osteoblasts.
Our data showed that CIITA is a repressor of Cyr61 synthesis in osteoblasts, and it might play a protective role in the pathogenesis of bone resorption in apical periodontitis, possibly through down-regulating the expression of Cyr61 in osteoblasts.
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ABSTRACT: Human dental apical papilla cells (APCs) have mineralization potential, which plays a key role in the root development of young permanent teeth. Limited literature is available about APC mineralization in the presence of inflammatory cytokines. The purpose of this study was to investigate the effects of tumor necrosis factor-α (TNF-α) on APC mineralization. APC cultures were established with the enzymatic dissociation method in vitro. The viability of APCs treated with TNF-α was investigated using methyl-thiazol-tetrazolium assays. Cells were then cultured in osteo-/dentinogenic medium with TNF-α, and mineralization was assessed by alizarin red S staining. Bone sialoprotein (BSP) and dentin sialoprotein (DSP) were analyzed using immunocytochemistry. Mineralization genes such as BSP, dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and dentin matrix acidicphosphoprotein-1 (DMP1) were determined with real-time polymerase chain reaction analyses. The viability of cultured cells was higher with TNF-α concentrations of 10 ng/mL and 50 ng/mL than with 5 ng/mL or in the control group. Alizarin red S staining showed that APCs had a higher mineralization activity when the osteo-/dentinogenic culture medium contained 10 ng/mL TNF-α. Immunocytochemical detection showed that the expression of BSP and DSP was positive in APCs after they were induced in osteo-/dentinogenic medium. The expression of mineralization genes differed when treated with 10 ng/mL TNF-α (ie, the expression of DSPP mRNA increased on days 7 and 14, whereas the expression of DSPP mRNA decreased on day 21). TNF-α may promote APC mineralization in short-term cultures and inhibit the mineralization in long-term cultures.Journal of endodontics 07/2012; 38(7):960-4. DOI:10.1016/j.joen.2012.04.005 · 2.95 Impact Factor
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ABSTRACT: In this study, the role of transcription factor Forkhead/winged helix box protein O3a (FoxO3a) in Cyr61 expression and its modulation by simvastatin were investigated in cultured murine osteoblasts and a rat model of induced apical periodontitis. We also examined the effects of simvastatin on the synthesis of chemokine CCL2 and chemotaxis of macrophages in vitro. We assessed tumor necrosis factor (TNF)-α-stimulated expression of Cyr61 and phosphorylated inactive FoxO3a (p-FoxO3a) in MC3T3-E1 murine osteoblasts by Western analysis. Forced expression of FoxO3a by lentiviral-based gene transduction was performed, and its effect on Cyr61 expression was evaluated. The modulation of CCL2 secretion and macrophage chemotaxis by simvastatin were examined by enzyme-linked immunosorbent assay and transwell migration assay, respectively. In a rat model of induced apical periodontitis, the relation between disease progression and osteoblastic expression of Cyr61, p-FoxO3a, and CCL2 and macrophage recruitment were studied by radiographic and immunohistochemistry analyses. Western blot analysis showed enhanced expression of Cyr61 and p-FoxO3a after TNF-α treatment in a time-dependent manner. Simvastatin significantly counteracted the actions of TNF-α. Forced expression of FoxO3a reduced TNF-α-stimulated Cyr61 synthesis. Simvastatin and FoxO3a diminished TNF-α-induced CCL2 secretion and macrophage recruitment, whereas Cyr61 partially restored the stimulating action. In rat periapical lesions, simvastatin significantly attenuated bone resorption, reduced osteoblastic expressions of Cyr61, p-FoxO3a, and CCL2, and suppressed macrophage recruitment. Simvastatin may alleviate periapical lesions by enhancing FoxO3a activity to suppress the synthesis of Cyr61 in osteoblasts. Moreover, the downstream effector mechanism of Cyr61 may involve CCL2 production and macrophage recruitment.Journal of endodontics 05/2013; 39(5):619-25. DOI:10.1016/j.joen.2012.12.014 · 2.95 Impact Factor
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ABSTRACT: Protective and destructive immunoreactions take place simultaneously in apical periodontitis. However, the same reactions defending the periapical area from infection-derived damage may also result in host tissue injury. The inflammatory reaction of the periapical tissues is self-limited. Regeneration of the injured tooth-supporting structures may follow elimination of the causative microbial irritation. Recent experimental and clinical observations have identified important interplay between positive and negative regulatory pathways. A network of stimulatory and inhibitory feedback loops may influence the intensity of the defense and inflammatory responses and the balance between bone resorption and regeneration, resulting in lesion expansion or healing of apical periodontitis. We critically discuss research data on regulatory mechanisms that control the activity of host effector cells and signaling molecules during interactions with pathogenic microbes.Journal of endodontics 02/2014; 40(2):155-63. DOI:10.1016/j.joen.2013.10.036 · 2.95 Impact Factor