Biomedical subjects

K Ohura

Publications and source records attributed to K Ohura.

At least 19 recordsLinked to original sources

PubMed2003

Apoptosis in human oral squamous cell carcinomas is induced by 15-deoxy-delta 12,14-prostaglandin J2 but not by troglitazone.

15-deoxy-Delta(12,14)-prostaglandin J(2) (15-d-PGJ(2)) and troglitazone have been shown to induce apoptosis in several carcinoma cell lines. However, apoptotic signaling pathways of these agents are poorly understood. We tested the hypothesis that peroxisome proliferator-activated receptor-gamma ligands such as these two agents will induce caspase-mediated apoptosis in human oral squamous cell carcinomas (SCC). Treatment of these cell lines with 15-d-PGJ(2) or troglitazone decreased cell viability in a time- and dose-dependent manner. 15-d-PGJ(2), but not troglitazone, induced apoptosis, and this effect was time-dependent. Exposure of cells to 20 micro M of 15-d-PGJ(2) initiated early cytochrome c release, followed by late caspase activation. Furthermore, co-treatment with caspase inhibitors such as Z-VAD-FMK or Z-DEVD-FMK of oral SCC cells that had been treated with 20 micro M of 15-d-PGJ(2) blocked apoptosis. Our study demonstrates that treatment with 15-d-PGJ(2), but not troglitazone, induces apoptosis in human SCC cell lines, and 15-d-PGJ(2) appears to work through cytochrome c release and caspase activation.

Amino Acid Chloromethyl Ketones↗

PubMed2002

Relationship between vitamin D receptor gene polymorphism and periodontitis.

UNLABELLED: Recent studies have shown that vitamin D receptor (VDR) gene polymorphism had regulatory effects on bone mineral density (BMD) and bone turnover. The VDR gene has also been indicated as a candidate gene for the susceptibility of osteoporosis. However, it is unclear whether VDR genotypes could be associated with alveolar bone loss of patients with periodontitis, or whether vitamin D receptor gene could be a candidate gene for susceptibility to periodontitis. The purpose of this study was to answer these two questions. METHODS: Twenty-four cases of adult periodontitis (AP), 37 cases of early onset periodontitis (EOP) and 39 healthy controls were recruited for the study. Individual samples of venous blood and DNA were obtained from each subject. Genotypes of the TaqI VDR gene were determined by PCR and TaqI restriction endonuclease digestion. RESULTS: One out of 24 AP patients, nine out of 37 EOP patients and two out of 39 healthy controls were detected with Tt genotype, while the rest had the TT genotype. The detected frequency of Tt genotype was significantly higher in EOP patients (24.3%) than in AP patients (4.2%) and healthy controls (5.1%). The frequency of t allele was also significantly higher in EOP patients. There was no statistical difference in the distribution of TaqI VDR genotypes between AP patients and healthy controls. The study suggests that Tt genotype might be a risk indicator for the susceptibility to EOP. Carriage of the allele (t) of the TaqI VDR gene may increase the risk of developing EOP.

Adolescent↗

PubMed2002

Endomorphins 1 and 2 inhibit IL-10 and IL-12 production and innate immune functions, and potentiate NF-kappaB DNA binding in THP-1 differentiated to macrophage-like cells.

We evaluated immunological effects of opioid peptides endomorphins 1 and 2 on the production of interleukin-10 (IL-10) and IL-12 cytokines, functions related to innate immunity and NF-kappaB DNA binding in human cell line THP-1. Endomorphins 1 and 2 inhibited lipopolysaccharide (LPS)-stimulated IL-10 and IL-12 production in THP-1 differentiated to macrophage-like cells by phorbol 12-myristate 13-acetate (PMA). Similarly, they suppressed LPS-stimulated IL-10 and IL-12 production in THP-1 matured to monocytes by 1alpha,25-dihydroxyvitamin D3. In addition, endomorphins 1 and 2 led to marked potentiation of NF-kappaB binding in THP-1 differentiated to macrophage-like cells. Furthermore, these endomorphins further potentiated LPS-induced NF-kappaB binding. Moreover, they inhibited chemotaxis, phagocytosis of Escherichia coli and PMA-stimulated production of hydrogen peroxide in THP-1 differentiated to macrophage-like cells. These results suggest that endomorphins 1 and 2 may inhibit THP-1 functions, such as cytokine production and functions related to innate immune, and potentiate NF-kappaB DNA binding in THP-1.

Cell Differentiation↗

PubMed2002

Porphyromonas gingivalis lipopolysaccharide signaling in gingival fibroblasts-CD14 and Toll-like receptors.

Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection of oral bacteria. Porphyromonas gingivalis (P. gingivalis) is one of the suspected periodontopathic bacteria and is frequently isolated from the periodontal pockets of patients with chronic periodontal disease. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Gingival fibroblasts, which are the major constituents of gingival connective tissue, may directly interact with bacteria and bacterial products, including LPS, in periodontitis lesions. It is suggested that gingival fibroblasts play an important role in the host responses to LPS in periodontal disease. P. gingivalis LPS enhances the production of inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) in gingival fibroblasts. However, the receptor that binds with P. gingivalis LPS on gingival fibroblasts remained unknown for many years. Recently, it was demonstrated that P. gingivalis LPS binds to gingival fibroblasts. It was also found that gingival fibroblasts express CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS treatment of gingival fibroblasts activates several intracellular proteins, including protein tyrosine kinases, and up-regulates the expression of monocyte chemoattractant protein-1 (MCP-1), extracellular signal-regulated kinase 1 (ERK1), and signal-regulated kinase 2 (ERK2), IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1). These results suggest that the binding of P. gingivalis LPS to CD14 and TLR4 on gingival fibroblasts activates various second-messenger systems. In this article, we review recent findings on the signaling pathways induced by the binding of P. gingivalis LPS to CD14 and Toll-like receptors (TLRs) in gingival fibroblasts.

Animals↗

PubMed2001

Heterogeneous expression of Toll-like receptor 4 and downregulation of Toll-like receptor 4 expression on human gingival fibroblasts by Porphyromonas gingivalis lipopolysaccharide.

Porphyromonas gingivalis (P. gingivalis) is implicated in the initiation and progression of periodontitis. Human gingival fibroblasts (HGFs) are the major constituent of gingival connective tissue. P. gingivalis or its components such as lipopolysaccharide (LPS) upregulate the production of various inflammatory cytokines including interleukin (IL)-1 and IL-6 in HGFs. Recently, we demonstrated that the binding of P. gingivalis LPS to Toll-like receptor 4 (TLR4) on HGFs activates various second messenger systems (Biochem. Biophys. Res. Commun. 273, 1161-1167, 2000). In the present study, we examined the level of TLR4 expression on HGFs by flow cytometric analysis (FACS), and studied the levels of IL-1 and IL-6 in the culture medium upon LPS stimulation of HGFs by enzyme-linked immunosorbent assay (ELISA). Upon stimulation by P. gingivalis LPS for 24 h, HGFs that expressed a high level of TLR4 secreted significantly higher levels of IL-1 and IL-6 than HGFs that expressed a low level of TLR4. On the other hand, after stimulation with P. gingivalis LPS for 24 h, the level of TLR4 on the surface of HGFs decreased. These results suggest that the level of TLR4 expression on HGFs reflects the extent of inflammation in the gingival tissue, and that P. gingivalis LPS downregulates TLR4 expression on HGFs. These findings may be used to control inflammatory and immune responses in periodontal disease.

Antibodies, Monoclonal↗

PubMed2001

Endomorphins 1 and 2 modulate chemotaxis, phagocytosis and superoxide anion production by microglia.

We evaluate the role of endomorphins 1 and 2 on microglial functions. Endomorphins 1 and 2 blocked phagocytosis of Escherichia coli. In addition, both markedly inhibited chemotaxis toward zymosan-activated serum. In contrast, when microglia was preincubated with these endomorphins, followed by incubation with LPS before stimulation with phorbol 12-myristate 13-acetate (PMA) at 200 nM, they potentiated superoxide anion production. Furthermore, when microglia was preincubated with these endomorphins together with PMA at 20 nM, followed by stimulation with PMA at 200 nM, superoxide anion production was potentiated. These results suggest that endomorphins 1 and 2 modulate phagocytosis, chemotaxis and superoxide anion production by microglia.

Animals↗

PubMed2001

Hyperglycemia in diabetic rats reduces the glutathione content in the aortic tissue.

The glutathione redox cycle plays a major role in scavenging hydrogen peroxide (H2O2) under physiological conditions. Recently, we demonstrated that a high glucose concentration in the culture medium reduced the level of H2O2 scavenging activity of human vascular smooth muscle cells (hVSMCs). We also showed that a high glucose concentration reduced the intracellular glutathione (GSH) content and the rate of uptake of cystine, which itself is a rate-limiting factor that maintains the GSH level (FEBS Lett.421: 19-22,1998). In the present study, we investigated whether the hyperglycemic condition in diabetic rats impairs the glutathione content in the aortic tissue in vivo. Wistar rats were divided into the following three groups: streptozotocin-induced diabetic rats (STZ-D, n=7), insulin-treated STZ-D rats (I-STZ-D, n=8), and non-diabetic controls (C, n=7). Fourteen days after streptozotocin injection, the aortic tissue was extracted and the GSH content in the aortic tissue was measured. Furthermore, the relationship between the GSH content in the aortic tissue and blood glucose level in Otsuka Long-Evans Tokushima Fatty (OLETF) rats aged 30 weeks, which developed diabetes spontaneously, was investigated. The GSH content in the aortic tissue of the STZ-D group (0.99+/-0.14 nmol/mg protein) was significantly lower than that of the control group (1.68+/-0.15 nmol/mg protein). Insulin treatment to the diabetic rats restored the GSH content in the aortic tissue (I-STZ-D group; 1.45+/-0.11 nmol/mg protein). Among the 22 Wistar rats, the GSH content in the aortic tissue was negatively correlated with the blood glucose level (r=-0.69, p<0.01, n=22). Among the OLETF rats, a similar negative correlation between the GSH content in the aortic tissue and blood glucose level was seen (r=-0.64, p<0.05, n=10). We demonstrated in vivo that the hyperglycemic condition in STZ-induced diabetic Wistar rats and OLETF rats reduced the GSH content in aortic tissue. This suggested reduced glutathione redox cycle function of aorta.

Animals↗

PubMed2001

Differentiation by in vitro treatment of lidocaine-epinephrine and prilocaine-felypressine in neutrophils.

Neutrophils are often the first cells of the immune system to encounter an invader, such as bacteria and fungi. Lidocaine-epinephrine induced transient potentiation of the production of superoxide anion, while prilocaine-felypressine induced persistent inhibition of the production in neutrophils. Moreover, lidocaine-epinephrine inhibited the production of hydrogen peroxide in spite that it potentiated the production of superoxide anion, while prilocaine-felypressine inhibited the production of hydrogen peroxide as well as superoxide anion. By contrast, lidocaine-epinephrine and prilocaine-felypressine are both effective in significantly inhibiting adhesion and phagocytosis. Using flow cytometric analysis, both local anesthetics were found to be effective in inhibiting the expression of Mac-1 (CD11b/CD18) in neutrophils. These results suggest that lidocaine-epinephrine and prilocaine-felypressine differentially modulate the production of superoxide anion, and could similarly inhibit adhesion, phagocytosis, and the production of hydrogen peroxide by neutrophils.

Anesthetics, Local↗

PubMed2001

15-Deoxy-delta(12,14)-prostaglandin J(2) inhibits IL-10 and IL-12 production by macrophages.

15-Deoxy-Delta(12,14)-prostaglandin J(2) (dPGJ(2)) is a metabolite of prostaglandin D(2), that binds to peroxisome proliferator-activated receptor gamma (PPARgamma). PPARgamma and prostaglandin D(2) synthase, which is required for dPGJ(2) synthesis, are predominantly expressed in macrophages. In contrast, IL-10 and IL-12 produced by macrophages stimulate Th1 and Th2 immune response, respectively. This study investigated the effect of dPGJ(2) on IL-10 and IL-12 production by macrophages in response to lipopolysaccharide (LPS). Our data clearly demonstrated that dPGJ(2) inhibits LPS-induced IL-10 and IL-12 production by macrophages. A different agonist of PPARgamma, 13-hydroxyoctadecadienoic acid, similarly inhibited the production of IL-10 and IL-12 in response to LPS. Further, dPGJ(2) did not appear to act through the PGD(2) receptor. These results suggest that dPGJ(2) may inhibit LPS-induced IL-10 and IL-12 production by macrophages through PPARgamma.

Animals↗

PubMed2001

Streptococcus mutans lipoteichoic acid-induced apoptosis in cultured dental pulp cells from human deciduous teeth.

Herein, we suggest that Streptococcus mutans lipoteichoic acid-induced death of dental pulp cells on human deciduous teeth is caused by apoptosis. We provide evidence for the causal role of apoptosis in this process by demonstrating an increase in the proportion of fragmented DNA in such dental pulp cells, which results in a ladder pattern of DNA fragmentation. Additionally, Streptococcus mutans lipoteichoic acid-induced apoptotic cell death is suppressed by caspase inhibitor. Collectively, these findings suggest that Streptococcus mutans lipoteichoic acids may cause apoptosis in human dental pulp cells, and serve as an important factor in pulpitis.

Apoptosis↗

PubMed2001

Quinolones alter defense reactions mediated by macrophages.

The innate host defense system is regulated in part by the number and activation of the function of neutrophils and macrophages. The immunological effects of a variety of quinolones on host defense functions of macrophage are reported. Ofloxacin (OFLX), lomefloxacin (LFLX), tosufloxacin (TFLX), fleroxacin (FLRX), sparfloxacin (SPFX) and levofloxacin (LVFX) significantly inhibited phagocytosis of Escherichica coli by macrophages. Moreover, TFLX markedly potentiated the expression of the adhesion molecule Mac-1 by macrophages. No significant alteration was detected in the adherence and the expression of adhesion molecule Mac-1 in macrophages treated with the other quinolones. In contrast, OFLX, LFLX, TFLX, and LVFX were effective in significantly increasing the production of hydrogen peroxide, while the other agents did not. These results suggest that the quinolones at a therapeutic concentration differentially affect phagocytosis, adhesion, and the production of hydrogen peroxide by macrophages.

Animals↗

PubMed2001

Comparison of the effect of lidocaine-epinephrine and prilocaine-felypressine to alter macrophage functions.

In vitro treatment of macrophages with lidocaine-epinephrine or prilocaine-felypressine resulted in inhibition of their adhesion, chemotaxis and phagocytosis. However, prilocaine-felypressine was a much more potent inhibitor of adhesion and phagocytosis than lidocaine-epinephrine. On the other hand, lidocaine-epinephrine induced transient potentiation of superoxide anion production by macrophages, while prilocaine-felypressine consistently inhibited this. Moreover, lidocaine-epinephrine and prilocaine-felypressine both inhibited the production of hydrogen peroxide. In contrast, epinephrine strongly potentiated superoxide anion production, while markedly inhibiting hydrogen peroxide production. This potentiation by epinephrine was not prevented by adrenergic antagonists. In addition, superoxide dismutase potentiated the production of hydrogen peroxide, which was in part prevented by epinephrine. These results suggest that lidocaine-epinephrine and prilocaine-felypressine inhibit adhesion, chemotaxis, phagocytosis, and the production of hydrogen peroxide by macrophages. In addition, lidocaine-epinephrine evidently differs from prilocaine-felypressine regarding the molecular mechanisms underlying the modulation of superoxide anion production by macrophages.

Adrenergic Agonists↗

PubMed2001

Histamine inhibits chemotaxis, phagocytosis, superoxide anion production, and the production of TNFalpha and IL-12 by macrophages via H2-receptors.

Histamine is released from stimulated basophils and mast cells, and plays an important role in the pathogenesis of allergic inflammatory processes. In vitro treatment of macrophages with histamine resulted in inhibition of chemotaxis. Moreover, histamine at l0(-5) M markedly inhibited the production of superoxide anions by both opsonized zymosan-A and phorbol 12-myristate 13-acetate (PMA) stimulated macrophages and histamine at a concentration range of 10(-7) to 10(-5) M significantly inhibited phagocytosis of Escherichia coli by macrophages. In addition, H2-selective receptor agonist dimaprit resulted in inhibition of macrophage chemotaxis and markedly inhibited the production of superoxide anion by PMA-stimulated macrophages and phagocytosis of E. coli by macrophages. On the other hand, histamine and dimaprit both resulted in a concentration-dependent inhibition of lipopolysaccharide-induced production of TNFalpha and IL-12 by macrophages. These results suggest that histamine and dimaprit may inhibit chemotaxis, phagocytosis, superoxide anion production, and the production of TNFalpha and IL-12 by macrophages via H2-histamine receptors. reserved.

Animals↗

PubMed2001

15-Deoxy-delta(12,14)-prostaglandin J2 is a negative regulator of macrophage functions.

15-Deoxy-delta(12,14)-prostaglandin J2 (dPGJ2) is a bioactive metabolite of the J2 series that has been identified as a ligand for peroxisome proliferator-activated receptor gamma (PPARgamma). Because PPARgamma is highly expressed in macrophages obtained from stimulant-elicited peritonitis, but not in resident peritoneal macrophages, the effect of dPGJ2 was tested on innate functions of macrophages. dPGJ2 inhibited adhesion and phagocytosis of Escherichia coli. Inhibition of these functions by dPGJ2 was not mediated via the adhesion molecule Mac-1. In addition, dPGJ2 inhibited chemotaxis toward zymosan-activated serum and it also inhibited the production of superoxide anion when macrophages were stimulated with phorbol 12-myristate 13-acetate (PMA) or opsonized zymosan (OPZ), but not lipopolysaccharide. Similarly, dPGJ2 inhibited the production of hydrogen peroxide when macrophages were stimulated with either PMA or OPZ. These studies suggest that dPGJ2 may be a negative regulator of macrophage functions.

Animals↗

PubMed2001

Association of vitamin D receptor gene polymorphism with periodontal diseases in Japanese and Chinese.

We examined whether polymorphisms in the vitamin D receptor (VDR) gene are associated with the incidence of adult periodontitis (AP) and early-onset periodontitis (EOP) in case-controlled studies of Japanese and Chinese subjects. Restriction fragment length polymorphisms in the VDR gene detected by digestion with Taq I were found to be significantly associated with the occurrence of AP or EOP, suggesting that the VDR genotype a risk factor for periodontitis.

Adult↗

PubMed2001

Effect of Actinobacillus actinomycetemcomitans protease on the proliferation of gingival epithelial cells.

OBJECTIVE: Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) has been implicated as an important pathogen in periodontal disease. The aim of this report is to examine the effect of in vitro application of A. actinomycetemcomitans protease on the cell growth, DNA synthesis, and fibronectin level of human gingival epithelial cells. MATERIALS AND METHODS: A. actinomycetemcomitans protease was isolated from the culture supernatant of A. actinomycetemcomitans. Human gingival epithelial cells were incubated in the presence or absence of A. actinomycetemcomitans protease (0.01, 0.1, or I U) for 48 h. The proliferation of cells were tested with the MTT assay and the BrdU assay. The fibronectin level was examined by flow cytometric analysis. RESULTS: The cell growth rate, DNA synthesis rate, and fibronectin level of the gingival epithelial cells that had been incubated with protease, were lower than the respective values in the untreated gingival epithelial cells; as the dose of A. actinomycetemcomitans protease increased, the cell growth rate, DNA synthesis rate, and fibronectin level of the gingival epithelial cells decreased. A. actinomycetemcomitans protease may inhibit the proliferation of human gingival epithelial cells. CONCLUSIONS: This protease may play a key role as a major virulence factor in the development of periodontal disease.

Aggregatibacter actinomycetemcomitans↗

PubMed2000

Effect of vitamin E on the degradation of hydrogen peroxide in cultured human umbilical vein endothelial cells.

Vitamin E reacts with radicals such as lipid peroxyl radical (LOO*) and singlet oxygen ((1)O2), and plays a role in inhibiting lipid peroxidation in cell membranes and preventing the oxidation of low-density lipoproteins (LDL). However, only a few studies have investigated the effect of vitamin E on the degradation of hydrogen peroxide (H2O2). Therefore, we examined the effect of vitamin E on glutathione redox cycle-dependent H2O2 degradation activity in human umbilical vein endothelial cells (HUVEC). Confluent HUVEC were cultured for seven days in media containing various concentrations of vitamin E (alpha-tocopherol). The level of glutathione redox cycle-dependent H2O2 degradation activity and the intracellular glutathione level were determined. HUVEC that had been cultured in the presence of higher concentrations of vitamin E had a higher level of H2O2 degradation activity and a higher intracellular content of the reduced form of glutathione (GSH). Therefore, it is suggested that the vitamin E-induced increase in H2O2 degradation activity in HUVEC results from an increase in intracellular GSH level.

Cells, Cultured↗

PubMed2000

Immunomodulation of the neutrophil respiratory burst by endomorphins 1 and 2.

Opioid peptides were found to be released from cells of the immune system during inflammation and stress, and were associated with altered immune responses. Production of superoxide anions by PMA-stimulated neutrophils was markedly inhibited in a concentration-dependent manner by preincubation for 15 min with 10(-18) - 10(-6) M of the endogenous opioid peptides endomorphin 1 or 2. Inhibition was prevented by prior treatment with the micro-opioid receptor-selective antagonist beta-funaltrexamine at 10(-12) - 10(-8) M, but not the delta-opioid receptor-selective antagonist naltrindole. In contrast, endomorphins 1 and 2 caused significant potentiation of superoxide anion production in unstimulated neutrophils. These results suggest that the endogenous opioid peptides endomorphins 1 and 2 may modulate the production of superoxide anions in neutrophils via mu-opioid receptors.

Animals↗