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Biomedical subjects

A Otani

Publications and source records attributed to A Otani.

At least 19 recordsLinked to original sources
PubMed2001

Angiotensin II induces expression of the Tie2 receptor ligand, angiopoietin-2, in bovine retinal endothelial cells.

Recent studies have shown that angiopoietins (Angs) and their receptor, Tie2, play a role in vascular integrity and neovascularization. The renin-angiotensin system has been hypothesized to contribute to the development of diabetic retinopathy. In this study, we investigated the effect of angiotensin II (AII) on Ang1 and Ang2 expression in cultured bovine retinal endothelial cells (BRECs). AII stimulated Ang2 but not Ang1 mRNA expression in a dose- and time-dependent manner. This response was inhibited completely by angiotensin type 1 receptor (AT1) antagonist. AII increased the transcription of Ang2 mRNA, but did not change the half-life. Protein kinase C (PKC) inhibitor completely inhibited AII-induced Ang2 expression, and the mitogen-activated protein kinase (MAPK) inhibitor also inhibited it by 69.4+/-15.6%. In addition, we confirmed the upregulation of Ang2 in an AII-induced in vivo rat corneal neovascularization model. These data suggest that AII stimulates Ang2 expression through AT1 receptor-mediated PKC and MAPK pathways in BREC, and AII may play a novel role in retinal neovascularization.

Angiopoietin-1↗
PubMed2000

Angiotensin II-stimulated vascular endothelial growth factor expression in bovine retinal pericytes.

PURPOSE: Angiotensin II (AII) has been shown to play a role in many vascular diseases. In the study described, the effect of AII on vascular endothelial growth factor (VEGF) expression and related intracellular signaling mechanism was investigated in bovine retinal microcapillary pericytes. METHODS: Cultured bovine retinal microvascular endothelial cells and pericytes were prepared. VEGF expression was determined by Northern blot analysis and immunoprecipitation assay. Cell proliferation was assessed by DNA content growth assay. Reporter gene studies were performed to identify the AII responsible transcription-activating region of VEGF gene. RESULTS: Angiotensin II induced a significant increase in VEGF mRNA in a time- and dose-dependent manner. Angiotensin II type I receptor antagonist inhibited this effect. Angiotensin II activates the transcription of VEGF gene without changing the mRNA half-life, and the AII responsible region was found in the 5'-flanking region of the VEGF gene. Angiotensin II also increased the expression of c-fos and c-jun mRNA, and antisense oligonucleotides against c-Fos blocked the AII-induced VEGF mRNA expression. The conditioned media of AII-stimulated pericyte cultures had a growth-promoting effect on endothelial cells, and this effect was inhibited almost completely by VEGF neutralizing antibody. CONCLUSIONS: These findings suggest that AII might induce angiogenic activity through a paracrine function of VEGF in retinal microvascular cells.

Angiotensin II↗
PubMed1999

Hypoxia and vascular endothelial growth factor selectively up-regulate angiopoietin-2 in bovine microvascular endothelial cells.

Recent studies have shown that the angiopoietin-Tie2 system is a predominant regulator of vascular integrity. In this study, we investigated the effect of two known angiogenic stimuli, hypoxia and vascular endothelial growth factor (VEGF), on these molecules. VEGF induced both a time- and concentration-dependent increase in angiopoietin-2 (Ang2) mRNA expression in bovine microvascular endothelial cells. This up-regulation was derived primarily from an increased transcription rate as evidenced by nuclear run-on assay and mRNA decay study. The increased Ang2 expression upon VEGF treatment was almost totally abolished by inhibition of tyrosine kinase or mitogen-activated protein kinase and partially by suppression of protein kinase C. Hypoxia also directly increased Ang2 mRNA expression. In contrast, Ang1 and Tie2 responded to neither of these stimuli. The enhanced Ang2 expression following VEGF stimulation and hypoxia was accompanied by de novo protein synthesis as detected by immunoprecipitation. In a mouse model of ischemia-induced retinal neovascularization, Ang2 mRNA was up-regulated in the ischemic inner retinal layer, and remarkable expression was observed in neovascular vessels. These data suggest that both hypoxia- and VEGF-induced neovascularization might be facilitated by selective induction of Ang2, which deteriorates the integrity of preexisting vasculature.

Angiopoietin-2↗
PubMed1999

Expression of thrombospondin-1 in ischemia-induced retinal neovascularization.

Thrombospondin-1 is an extracellular matrix protein that inhibits endothelial cell proliferation, migration, and angiogenesis. This study was performed to investigate the role of thrombospondin-1 in ischemic retinal neovascularization. In a murine model of retinal neovascularization, thrombospondin-1 mRNA was increased from postnatal day 13 (P13), with a threefold peak response observed on P15, corresponding to the time of development of retinal neovascularization. Prominent expression of thrombospondin-1 was observed in neovascular cells, specifically, cells adjacent to the area of nonperfusion. It has been suggested that vascular endothelial growth factor (VEGF) plays a major role in ischemia-induced retinal neovascularization of this model, so we studied the effects of VEGF on thrombospondin-1 expression. In bovine retinal microcapillary endothelial cells, VEGF induced a biphasic response of thrombospondin-1 expression; VEGF decreased thrombospondin-1 mRNA 0.41-fold after 4 hours, whereas it increased, with a threefold peak response, after 24 hours. VEGF-induced endothelial cell proliferation was completely inhibited by exogenous thrombospondin-1 and increased by 37.5% with anti-thrombospondin-1 antibody. The present findings suggest that, in the ischemic retina, retinal neovascular cells increase thrombospondin-1 expression, and VEGF may stimulate endogenous thrombospondin-1 induction, which inhibits endothelial cell growth. VEGF-mediated thrombospondin-1 induction in ischemia-induced angiogenesis may be a negative feedback mechanism.

Animals↗
PubMed1999

New surgical approach for removing massive foveal hard exudates in diabetic macular edema.

OBJECTIVE: To examine the efficacy of surgical removal of foveal hard exudates in diabetic macular edema and to determine the expression of vascular endothelial growth factor (VEGF) in the excised specimens. DESIGN: Cohort study. PARTICIPANTS: Seven eyes of six patients with massive subfoveal hard exudate due to diabetic macular edema were examined. The average age of the patient was 56 years (range, 46-60 years). INTERVENTION: Pars plana vitrectomy for removal of massive foveal exudates was performed. MAIN OUTCOME MEASURES: Preoperative and postoperative visual acuity and complications were recorded; immunohistochemical staining for VEGF and other cell markers for macrophage and pigment epithelial cells in excised specimens was performed. RESULTS: Postoperative best-corrected visual acuity improved by two or more lines of Snellen equivalent in five eyes (71%) (P = 0.0061). VEGF, identified by anticytokeratin and CD68 antibodies, was expressed in pigment epithelial cells and macrophages invading the hard exudates. CONCLUSION: Surgical removal of foveal hard exudates might be effective in low-vision patients with diabetic maculopathy. VEGF might play a role in the formation and persistence of foveal hard exudates in diabetic macular edema.

Cohort Studies↗
PubMed1999

Tranilast inhibits protein kinase C-dependent signalling pathway linked to angiogenic activities and gene expression of retinal microcapillary endothelial cells.

1. Tranilast, first developed as an anti-allergic drug, has been reported to inhibit vascular endothelial growth factor (VEGF)-induced angiogenesis and vasopermeability. To further clarify the inhibitory mechanism, we investigated the effects of tranilast on VEGF binding and subsequent intracellular signalling pathway linked to angiogenic activities and gene expression of bovine retinal microcapillary endothelial cells. 2. Tranilast significantly (P<0.01) inhibited VEGF, basic fibroblast growth factor (bFGF), and hypoxia conditioned media-induced BREC proliferation in a dose dependent manner with IC50's of 22, 82 and 10 microM, respectively. 3. VEGF-induced migration was also inhibited by tranilast in a dose dependent manner, with IC50 of 18 microM, and complete inhibition was observed at 300 microM (P<0.01). Tranilast suppressed VEGF-induced tube formation in a dose dependent manner with maximum (46%) inhibition observed at 300 microM (P<0.05). 4. Tranilast inhibited phorbol myristate acetate (PMA)-dependent stimulation of [3H]-thymidine incorporation and VEGF- and PMA-induced gene expression of integrin alpha v and c-fos in BREC. 5. Tranilast suppressed VEGF- and PMA-stimulated PKC activity in BREC. 6. Tranilast did not affect VEGF binding or VEGF-induced phosphorylation of tyrosine residues of VEGF receptor- and phospholipase Cgamma and their associated proteins. 7. These data suggest that tranilast might prove an effective inhibitor to prevent retinal neovascularization in ischaemic retinal diseases, and that its inhibitory effect might be through suppression of PKC-dependent signal transduction in BREC.

Animals↗
PubMed1999

The potential angiogenic role of macrophages in the formation of choroidal neovascular membranes.

PURPOSE: To investigate the distribution of inflammatory mediators such as interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha and angiogenic cytokines such as vascular endothelial growth factor (VEGF) and to identify their cellular source in surgically excised choroidal neovascular membranes (CNVMs) of various origins. METHODS: Immunoperoxidase staining was performed on paraffin-embedded sections of 11 surgically excised CNVMs to identify cellular distribution and localization of cytokines. Immunofluorescent double staining was performed to detect the cellular source of cytokines. RESULTS: Cytokeratin-positive cells were detected in the RPE layer, in stromal cells, and around neovascular vessels. Macrophages identified by their cellular marker CD68 showed almost the same distribution as cytokeratin-positive cells, although they were most prominent in the stroma. A substantial number of neovascular vessels were also immunoreactive to IL-1beta and TNF-alpha. Immunofluorescent double staining revealed that the RPE layers immunopositive for cytokeratin were also immunopositive for all cytokines, whereas stromal cells immunostained for CD68 were positive for IL-1beta and TNF-alpha, but not for VEGF. CONCLUSIONS: These results indicate that IL-1beta and TNF-alpha secreted by macrophages may promote, at least in part, angiogenesis in CNVMs by stimulating VEGF production in RPE cells.

Adult↗
PubMed1999

Expressions of angiopoietins and Tie2 in human choroidal neovascular membranes.

PURPOSE: To elucidate the potential role of angiopoietins and the Tie2 system in choroidal neovascularization. METHODS: Surgically excised choroidal neovascular membranes (CNVMs) were obtained at vitrectomy from five eyes with age-related macular degeneration, three eyes with idiopathic neovascular maculopathy, and two eyes had degenerative myopia and two eyes had angioid streaks. Light microscopic immunohistochemistry was performed to detect cytokines such as vascular endothelial growth factor (VEGF), Ang1, and Ang2 and cellular components such as retinal pigment epithelial (RPE) cells, macrophages, and endothelial cells. Immunofluorescent double staining using confocal microscopy was performed to identify the cell types that secrete specific cytokines. RESULTS: Ang1 and Ang2 were positive in all surgically excised CNVMs, regardless of the primary disease. Double staining revealed that many of the cytokeratin, CD68 and factor VIII positive cells also had Ang1 and Ang2 immunoreactivities. In contrast to Ang1, Ang2 immunoreactivity tends to be higher in the highly vascularized regions of many CNVMs, and the localization was very similar to that of VEGF staining. Almost all vascular structures had prominent immunoreactivity for Tie2, which was confirmed by double staining for Tie2 and factor VIII. Tie2 immunoreactivity was also observed in the RPE monolayer and in pigmented, polygonal, and fibroblast-like cells in the stroma. CONCLUSIONS: Present findings that Ang2 and VEGF are co-upregulated and that Tie2 is expressed in a variety of cell types in CNVMs further support a crucial role of the interaction between VEGF and Ang2 in pathologic angiogenesis of CNVM formation.

Adult↗
PubMed1999

17 Beta-estradiol increases VEGF receptor-2 and promotes DNA synthesis in retinal microvascular endothelial cells.

PURPOSE: Estrogen is known to promote angiogenesis in gonads. The presence of estrogen receptors in the vascular endothelium of organs other than gonads has been reported. The goal of this study was to determine whether estrogen promotes the proliferation of retinal microvascular endothelial cells and to explore the mechanism of it. METHODS: DNA was quantitated using primary cultures of bovine retinal endothelial cells that were incubated with different doses of 17 beta-estradiol (E2), VEGF, or both. The changes in expression level of VEGF and VEGF receptor-2 (VEGFR2) were measured using northern blot analysis after treatment with E2. The presence of estrogen receptors in the endothelial cells was studied by immunohistochemistry and western blot analysis. RESULTS: 17 Beta-estradiol (E2) increased the DNA level in bovine retinal capillary endothelial cells (BRECs) by 177% at 1 nM (P < 0.05) and 150% at 10 nM (P < 0.05) by comparison with unstimulated BREC. One hundred nanomole tamoxifen completely blocked the E2-induced DNA synthesis in BRECs. Ten nanomole E2 augmented vascular endothelial growth factor (VEGF)-induced DNA synthesis in BRECs significantly (160%, P < 0.01). Ten nanomole E2 also increased VEGF mRNA expression, which peaked after 24 hours (6.7 times, P < 0.05), and VEGF receptor-2 (VEGFR2) mRNA expression, which peaked after 9 hours (2.4 times, P < 0.05). The mRNA expression level of VEGFR2 peaked with 10 nM E2 (P < 0.05) and that of VEGF reached maximum with 1 nM E2 (15 times, P < 0.001). VEGFR2 and VEGF proteins increased in parallel with their mRNA levels. Immunocytochemistry showed estrogen receptor expression in BRECs, and western blot analysis indicated the presence of a 67-kDa protein that was compatible with the estrogen receptor. CONCLUSIONS: These findings suggest that E2 may stimulate BREC growth by the receptor-mediated pathway and that E2 may augment the VEGF-dependent angiogenesis partly through the upregulation of VEGFR2.

Animals↗
PubMed1998

Angiotensin II potentiates vascular endothelial growth factor-induced angiogenic activity in retinal microcapillary endothelial cells.

Angiotensin II (Ang II) plays a role in the development of many vascular diseases. In the present study, we have investigated the effect of Ang II on vascular endothelial growth factor (VEGF) receptor expression and VEGF-induced angiogenic activity in bovine retinal microcapillary endothelial cells (BRECs). Ang II induced a significant increase of kinase domain-containing receptor/total liver kinase (KDR/Flk-1) mRNA in a time- and dose-dependent manner, with a maximal 4.3+/-0.8-fold increase after a 4-hour stimulation. Ang II increased the rate of KDR gene transcription by 5.4-fold, whereas the half-life of KDR mRNA was not increased significantly. The increase depended partially on new protein synthesis. The Ang II-induced KDR mRNA increase was inhibited by either [Sar1,Ile8]angiotensin or angiotensin type 1 receptor antagonists but was not significantly altered by angiotensin type 2 receptor antagonists. The PKC inhibitor reduced Ang II-induced KDR mRNA expression by 70+/-15%. The tyrosine kinase inhibitor reduced the Ang II- and phorbol 12-myristate 13-acetate-induced KDR mRNA increases by 35+/-8% and 44+/-26%, respectively. Ang II increased by 3.1-fold the 35S-labeled KDR/Flk-1 immunoprecipitated by a specific antibody to KDR/Flk-1. Scatchard analysis demonstrated that Ang II induced a significant increase of binding sites without changing binding affinity. Ang II enhanced VEGF-induced cell growth and tube formation. Ang II itself had no effect on cell growth, tube formation, or mRNA levels of VEGF and tms-like tyrosine kinase (Flt-1) in BRECs. These findings suggest that Ang II might potentiate VEGF-induced angiogenic activity through an increase of the VEGF receptor KDR/Flk-1.

Angiotensin II↗
PubMed1998

Increased expression of KDR/Flk-1 (VEGFR-2) in murine model of ischemia-induced retinal neovascularization.

Although the vascular endothelial growth factor (VEGF)/VEGF receptor system plays a critical role in the pathogenesis of ischemic retinal neovascular diseases such as diabetic retinopathy, regulation of VEGF receptor expression in ischemic retina has not been fully investigated in vivo. Accordingly, we studied the regulation of Flt-1 (VEGFR-1) and KDR/Flk-1 (VEGFR-2) expression in a mouse model of ischemia-induced retinal neovascularization. Immunohistochemistry for Flt-1 and KDR/Flk-1 revealed that, in hypoxic retina, the immunoreactivity of KDR/Flk-1 was increased in both intensity and extent of involvement in the vessels near the avascular area, particularly at the neovascular tufts, but that the pattern of Flt-1 expression in hypoxic retina was almost the same as that of control animals. The number of KDR/Flk-1-positive vessels was significantly increased in hypoxic retina (P < 0.01). In addition, expression of both Flt-1 and KDR/Flk-1 was observed in nonvascular cells of the neural retina. Northern blot analysis demonstrated that the mRNA levels of KDR/Flk-1 were greater in the neovascular retina of hypoxic animals than in control animals. We suggest that the increased expression of KDR/Flk-1 in vascular cells might potentiate the VEGF-mediated angiogenesis that accompanies many ischemic retinal diseases.

Animals↗
PubMed1998

Hypoxia and vascular endothelial growth factor stimulate angiogenic integrin expression in bovine retinal microvascular endothelial cells.

PURPOSE: Integrins alphavbeta3 and alphavbeta5 are cell-to-matrix adhesion molecules that have been reported to mediate vascular cell proliferation and migration. The authors investigated the regulation of expression of these angiogenic integrins by hypoxia and vascular endothelial growth factor (VEGF) in retinal microvascular endothelial cells in culture. METHODS: Cultured bovine retinal capillary endothelial cells were exposed to human recombinant VEGF under normoxic (95% air, 5% CO2) conditions to assess the effects of VEGF. Hypoxia studies were performed under lower oxygen concentration (0.5%-1.5% O2) induced by nitrogen replacement in constant 5% CO2 conditions. Integrin family mRNA and protein expression were assessed by northern blot analysis and immunoprecipitation. RESULTS: VEGF (25 ng/ml) increased integrin alphav, beta3, and 35 mRNA after 24 hours 6.1+/-0.8-fold (P < 0.001), 5.9+/-1.1-fold (P < 0.001), and 1.9+/-0.2-fold (P < 0.01), respectively. Similarly, hypoxia stimulated gene expression of integrin alphav and beta3 after 24 hours by 5.1+/-1.7-fold (P < 0.01) and 3.0+/-0.5-fold (P < 0.01), respectively, and integrin beta5 after 9 hours 1.4+/-0.2-fold (P < 0.05). This hypoxia-induced, integrin alphav mRNA elevation was inhibited significantly by anti-VEGF neutralizing antibody. Also, a conditioned medium from confluent endothelial cells maintained under hypoxic conditions for 24 hours produced a 7.1+/-1.1-fold increase (P < 0.001) in integrin alphav mRNA expression after 24 hours, which was reversed by anti-VEGF neutralizing antibody. Induction of integrin alphav by VEGF and hypoxia was confirmed in the protein level. CONCLUSIONS: These data suggest that hypoxia stimulates expression of vascular integrins alphavbeta3 and alphavbeta5 in retinal microvascular endothelial cells partially through autocrine-paracrine action of VEGF induced by the hypoxic state.

Animals↗
PubMed1995

[Long-term prognosis of intraocular lens implantation in diabetic patients].

We retrospectively studied 255 eyes of 190 diabetic patients who underwent cataract extraction with posterior chamber intraocular lens (IOL) implantation. One hundred forty-six eyes (57.3%) achieved the best visual acuity of 20/30 or better and 221 eyes (86.7%) achieved the acuity of 20/100 or better. Among 161 eyes that were followed up over 6 months, 26 eyes (16%) showed a progression of the retinopathy. Eight eyes developed proliferative retinopathy from non-proliferative retinopathy. The level of glycosylated hemoglobin of the progression group at the time of surgery was significantly higher than that of the non-progression group (8.0 +/- 2.4% vs 6.8 +/- 1.6%, p < 0.05). Sixty-five patients received IOL implantation in one eye. Of these patients, 10 eyes (15%) showed progression of the retinopathy. Seventy percent of the fellow eyes also showed the progression, where as 95% of the non-progression group did not show progression in the fellow eyes. The results suggested that the progression of diabetic retinopathy after IOL implantation was correlated with diabetic control at the time of surgery. Additionally, patients who developed the progression of the retinopathy in pseudophakic eyes frequently showed the progression in the fellow unoperated eyes.

Adult↗
PubMed1994

The superficial neurovasculature of the head and neck.

The majority of dermatologic procedures are performed in the sun-damaged regions of the head and neck. These regions have special cosmetic and functional importance, and dermatologists should become familiar with the underlying structures. Even though all the major nerves and vessels arborize below the superficial fascia, cutaneous atrophy and fibrosis from previous surgeries can make these neurovascular structures susceptible to damage from superficial procedures. Hence, it is advisable to utilize blunt dissection whenever possible, and to identify vital structures when working in their vicinity.

Arteries↗
PubMed1993

Cross validation of the Hypnotic Induction Profile factor structure: simultaneous confirmatory factor analysis of two published samples.

This study cross-validated factor structure and psychometric characteristics of the Hypnotic Induction Profile (HIP). Earlier studies identified two constructs of the HIP, but their methodology did not allow empirical confirmation of the number of factors. I have used a new methodology, confirmatory factor analysis, and submitted the data from the previous studies to a simultaneous, multisample, factor analysis. The results showed that the HIP indeed consists of two factors. Although the HIP two-factor model is statistically adequate, 7 of the 10 scales have very low item reliability. Issues of measurement error and clinical implications of the study are also discussed in relation to the current findings.

Factor Analysis, Statistical↗