Osamu Takeichi

Cytokine regulation on the synthesis of nitric oxide in vivo by chronically infected human polymorphonuclear leucocytes

To determine if nitric oxide (NO) is produced by chronically infected human polymorphonuclear leucocytes (PMNs) in vivo, inflamed exudates (periapical exudates: PE) collected from periapical periodontitis patients were examined. Cell‐free supernatants and cells were separated by centrifugation. Significant levels of nitrite concentrations were observed in the supernatants. The production of inducible NO synthase (iNOS) in highly purified PMNs derived from PEs was then immunocytochemically determined using rabbit anti‐human iNOS antiserum. In vitro, human peripheral blood PMNs (PB‐PMNs) isolated from patients were cultured with a combination of Esherichia coli–lipopolysaccharide (LPS), recombinant human interferon‐γ (rhIFN‐γ) and/or interleukin‐1β (rhIL‐1β). The stimulated PB‐PMNs showed steady‐state levels of nitrite. The stimulation of LPS, rhIFN‐γ and rhIL‐1β showed more NO induction than that of LPS with either IFN‐γ or IL‐1β, suggesting the synergistic effects of cytokines. Cryostat sections of surgically removed periapical tissues were also immunohistochemically examined for iNOS, IFN‐γ and IL‐1β. Two‐colour immunohistochemistry revealed the interaction of iNOS‐producing PMNs and IFN‐γ‐ or IL‐1β‐producing mononuclear cells. On the basis of these data, we concluded that with the stimulation of inflammatory cytokines derived from mononuclear cells, PMNs can spontaneously produce NO at the site of chronic infection. The present studies are consistent with a hypothesis suggesting that PMNs could be regulated and delicately balanced to produce NO by mononuclear cell‐derived cytokines in vivo. NO‐producing cells may play a pivotal role in chronic inflammation.

Expression of inflammatory cytokine genes in vivo by human alveolar bone-derived polymorphonuclear leukocytes isolated from chronically inflamed sites of bone resorption.

Alveolar bone-derived polymorphonuclear leukocytes (PMNs) were characterized for their ability to produce inflammatory cytokines such as interleukin-1α (IL-1α), IL-1β, tumor necrosis factor α(TNFα), and IL-6in vivo. Periapical exudates (PE) were collected from periapical lesions with chronic periapical periodontitis through root canals. Cells and noncellular supernatants were then isolated by centrifugation. The concentration of cytokines present in the noncellular supernatants were determined by ELISA. High concentrations of IL-1α, IL-1β, and IL-6 were detected in PE, however, TNFα was not. PE contains predominantly PMNs (>95% of residing cells) with a few percent of lymphocytes and/or macrophages. These alveolar bone-derived PMNs were purified by the Ficoll-Hypaque gradient method and were analyzed for cytokine mRNA expression using the cytokine-specific reverse-transcription polymerase chain reaction. Highly purified PMNs (>99.5%) isolated from PE expressed significant levels of mRNA for IL-α, IL-1β, and TNFα. IL-6 mRNA was not detected, although a high concentration of IL-6 was detected in supernatants of PE by ELISA. The IL-6 secretion in PE could be derived from macrophages, T lymphocytes, osteoblasts, or fibroblasts around periapical lesions. These data strongly suggest that human PMNs derived from alveolar bone can spontaneously produce IL-1α, IL-1β, and TNFα at sites of inflammation, and probably initiate inflammation and regulate augmentation of bone resorptionin vivo.

Predictability of Painful Stimulation Modulates Subjective and Physiological Responses

UNLABELLED Clinical observations suggest that the perceived intensity of a painful event increases as the unpredictability of its occurrence increases. We examined the effect of varying stimulus predictability on the Somatosensory Evoked Potential (SEP), Pupil Diameter Response (PDR), Pain Report (PR), and Fear Report (FR) in 25 healthy female volunteers experiencing repeated noxious fingertip shocks. Each volunteer underwent high- and low-stimulus intensities in 4 stimulus patterns defined by stimulus sequence (SEQ) and interstimulus interval (ISI) as follows: A) serial stimulus intensity SEQ with fixed ISI; B) serial stimulus intensity SEQ with varied ISI; C) random stimulus intensity SEQ with fixed ISI; and D) random stimulus intensity SEQ with varied ISI. Results revealed that: (1) lower stimulus predictability led to higher PR and FR, greater PDR magnitude, and greater SEP amplitude; and (2) the 4 dependent measures showed the same response pattern across levels of stimulus predictability. These findings support the hypothesis that lower stimulus predictability is associated with higher reported pain and fear as well as greater physiological arousal. PERSPECTIVE Patients undergoing painful procedures experience more distress when the occurrence of a painful event is unpredictable. Poor predictability increases pain, fear, and associated physiological arousal. Maximizing the predictability of painful events may improve the quality of patient care by minimizing associated levels of pain and fear.

Production of Human-Inducible Nitric Oxide Synthase in Radicular Cysts

To examine if nitric oxide (NO) is produced in radicular cysts, NO synthase (NOS) production was analyzed. Periapical tissues were removed from patients at the time of endodontic surgery. Frozen tissue sections were histologically evaluated with hematoxylin-eosin staining. Production of human-inducible NOS (iNOS) in apical cysts was then immunohistochemically examined. Immunoreactive human iNOS was widely distributed in epithelial cells, endothelial cells, fibroblasts, macrophages, or polymorphonuclear leukocytes. Remarkably, iNOS-positive cells were significantly present around blood vessels, and cells residing apart from the blood vessels showed weak or no iNOS production, suggesting that only cells around blood vessels could be stimulated for iNOS synthesis. These data demonstrated the possibility that several, but not all, cells could be stimulated to synthesize iNOS in inflamed tissues. In the presence of iNOS, NO can be produced spontaneously in periapical lesions and may play a crucial role in the regulation of chronic infection.

IL-6 and soluble IL-6 receptor stimulate the production of MMPs and their inhibitors via JAK-STAT and ERK-MAPK signalling in human chondrocytes

Elevated concentrations of IL‐6 (interleukin‐6) and sIL‐6r (soluble IL‐6 receptor) in the synovial fluid and serum of patients with arthritis have been implicated in joint cartilage destruction. This study examined the effects of IL‐6 and sIL‐6r on the expression of MMPs (matrix metalloproteinases), TIMPs (tissue inhibitor of metalloproteinases), the plasminogen activation system including tPA (tissue‐type PA), uPA (urokinase‐type PA) and PAI‐1 (PA inhibitor type 1) using chondrocytes derived from normal human femur cartilage. The cells were cultured with or without 50 ng/ml IL‐6 and/or 30 ng/ml sIL‐6r in the presence or absence of the JAK3 (Janus kinase 3) inhibitor WHI‐P131 or the MEK [MAPK (mitogen‐activated protein kinase)/ERK (extracellular signal protein kinase) kinase] inhibitor PD98059 for up to 28 days. The expression of MMPs, TIMPs, uPA, tPA and PAI‐1 was investigated at the mRNA and protein levels. MMP protein expression and pSTAT3 (phosphorylation of signal transducer and activator of transcription 3) and pERK (phosphorylation of ERK) were also measured. Treatment with both IL‐6 and sIL‐6r markedly increased the expression of MMP‐1, MMP‐13, TIMP‐1 and PAI‐1, while significantly decreasing the expression of tPA and uPA and stimulating pSTAT3 and pERK. Adding WHI‐P131 or PD98059 decreased IL‐6 and sIL‐6r enhancement of MMP‐1, −3 and −13. The results suggest that IL‐6 and sIL‐6r stimulate the production of MMPs and their inhibitor via JAK—STAT and ERK—MAPK signalling in chondrocytes.

Confocal immunolocalization of VE-cadherin- and CXC chemokine-expressing endothelial cells in periapical granulomas.

AIM To determine whether endothelial cells (ECs) in periapical granulomas can express vascular endothelial (VE)-cadherin, CXCL8 and CXCL10 by examining with two-colour confocal laser scanning microscope. METHODOLOGY Periapical lesions were surgically removed from patients with chronic periapical periodontitis (n = 20), and the paraffin-embedded sections were prepared after being fixed with cold acetone. The 7-mum-thick sections were stained with haematoxylin-eosin and then examined pathologically using a light microscope. The lesions diagnosed as periapical granulomas (17 specimens) were analysed further using immunofluorescence and antibodies specific for human VE-cadherin, CXCL8, and CXCL10. The slides were carefully examined using a confocal laser scanning microscope. The numbers of positive ECs were counted, and the comparison between VE-cadherin-positive ECs and CXCL8 or CXCL10 was assessed statistically using one-way ANOVA followed by a Student-Newman-Keuls test. RESULTS The expression of CXCL8 and CXCL10 by ECs was detected in 60.4 +/- 13.4 and 67.2 +/- 13.9%, respectively. However, the percentage of VE-cadherin-expressing ECs was 40.4 +/- 10.5%, which was significantly lower (P < 0.01) than CXCL8 and CXCL10-expressing ECs. Two-colour immunofluorescence staining revealed that ECs co-expressed VE-cadherin and CXCL8 (37.4 +/- 14.1%) or CXCL10 (39.1 +/- 13.8%). CONCLUSIONS VE-cadherin expression in ECs was lower than CXCL8 and CXCL10, suggesting that inflamed ECs in periapical granulomas could increase vascular permeability and that leukocyte chemotaxis mediated by ECs might occur. These findings may suggest the possibility that ECs could play a pivotal role in cell recruitment in periapical granulomas.

Nitric oxide attenuates vascular endothelial cadherin-mediated vascular integrity in human chronic inflammation

In this study, we examined the role of nitric oxide (NO) in controlling vascular integrity mediated by vascular endothelial (VE)‐cadherin in chronic inflammation. Periapical granulomas were analysed for the expression of inducible NO synthase (iNOS) and VE‐cadherin, and more iNOS expression than VE‐cadherin was shown. Human umbilical vein endothelial cells (HUVECs) were stimulated with proinflammatory cytokines and lipopolysaccharide extracted from Porphyromonas gingivalis and it induced iNOS expression, whereas it reduced VE‐cadherin expression, compared with negative controls. On the other hand, pre‐incubation with 1400W, an iNOS‐specific inhibitor, markedly reduced iNOS expression in stimulated HUVECs and restored VE‐cadherin expression to its control level, suggesting that vascular integrity was modulated in conjunction with the reduction of NO. Immunocytochemistry confirmed the functional role of NO in cultured HUVEC monolayers with or without 1400W. These data are consistent with a hypothesis suggesting that NO could attenuate VE‐cadherin‐mediated vascular integrity in human chronic inflammation.

Epstein-Barr Virus Infection in Chronically Inflamed Periapical Granulomas

Periapical granulomas are lesions around the apex of a tooth caused by a polymicrobial infection. Treatment with antibacterial agents is normally performed to eliminate bacteria from root canals; however, loss of the supporting alveolar bone is typically observed, and tooth extraction is often selected if root canal treatment does not work well. Therefore, bacteria and other microorganisms could be involved in this disease. To understand the pathogenesis of periapical granulomas more precisely, we focused on the association with Epstein-Barr virus (EBV) using surgically removed periapical granulomas (n = 32). EBV DNA was detected in 25 of 32 periapical granulomas (78.1%) by real-time PCR, and the median number of EBV DNA copies was approximately 8,688.01/μg total DNA. In contrast, EBV DNA was not detected in healthy gingival tissues (n = 10); the difference was statistically significant according to the Mann-Whitney U test (p = 0.0001). Paraffin sections were also analyzed by in situ hybridization to detect EBV-encoded small RNA (EBER)-expressing cells. EBER was detected in the cytoplasm and nuclei of B cells and plasma cells in six of nine periapical granulomas, but not in healthy gingival tissues. In addition, immunohistochemical analysis for latent membrane protein 1 (LMP-1) of EBV using serial tissue sections showed that LMP-1-expressing cells were localized to the same areas as EBER-expressing cells. These data suggest that B cells and plasma cells in inflamed granulomas are a major source of EBV infection, and that EBV could play a pivotal role in controlling immune cell responses in periapical granulomas.

Midkine Expression in Human Periapical Granulomas

INTRODUCTION The expression of midkine (MK), a heparin-binding growth factor, is increased in various human tumors, making it a promising tumor marker and target for tumor therapy. MK is also related to the regulation of the development and etiology of chronic or autoimmune diseases; however, the involvement of MK in apical periodontitis has never been examined. This study compared the localization of MK-expressing cells and MK messenger RNA expression in periapical granulomas with healthy gingival tissues. METHODS Periapical lesions were removed surgically from chronic apical periodontitis patients, and serial tissue sections were stained with hematoxylin-eosin. The lesions diagnosed as periapical granulomas pathologically were examined by immunohistochemistry using human MK monoclonal antibodies. MK messenger RNA expression was also detected using real-time polymerase chain reaction analysis. Healthy gingival tissues were analyzed in the same manner. RESULTS MK was expressed by inflammatory cells, such as macrophages, lymphocytes, and neutrophils, as well as by endothelial cells in periapical granulomas but not in healthy gingival tissues. The MK-expressing inflammatory cells were seen adjacent to blood vessels, which contained MK-expressing endothelial cells, suggesting the interaction of MK among these cells during the process of inflammatory cell infiltration. Quantitative analysis of MK messenger RNA expression revealed that periapical granulomas expressed significantly more MK than healthy gingival tissues. CONCLUSIONS These findings suggest that MK is involved in the pathogenesis of periapical granulomas.

Receptor for advanced glycation end products (RAGE)-expressing endothelial cells co-express AGE and S100 in human periapical granulomas

OBJECTIVE The engagement of the receptor for advanced glycation end products (RAGE) by AGE or S100 perturbs homeostatic mechanisms and provides a basis for cellular dysfunction in pathological situations. To assess the mechanism of vascular immune reactions in chronic periapical periodontitis, we analysed co-expression of RAGE and AGE or S100 in periapical granulomas. METHODS Surgically removed periapical lesions, which had been diagnosed as chronic periodontitis, were inspected histologically using paraffin-embedded sections stained with haematoxylin and eosin. Cryostat sections of the tissues, which were identified histologically as periapical granulomas, were then examined by double immunohistochemistry using polyclonal antibodies raised against human CD34 and monoclonal antibodies specific for human RAGE, AGE or S100. Dual-colour immunofluorescence image analysis was also performed to assess the co-expression of RAGE and AGE or RAGE and S100 by endothelial cells. RESULTS Marked expression of RAGE, AGE, and S100 by CD34(+) endothelial cells was noted. Dual-colour immunofluorescence image analysis revealed that the RAGE-expressing endothelial cells co-expressed AGE and S100; however, the number of RAGE-AGE-expressing endothelial cells was significantly higher than that of RAGE-S100-expressing endothelial cells. CONCLUSIONS Co-expression of RAGE and AGE by endothelial cells in periapical granulomas is more relevant than that of RAGE and S100. The possible engagement of RAGE and AGE may trigger cellular activation and mediate tissue injury.