Masahiro Muraguchi

Plasma Concentrations of a Novel, Adipose-Specific Protein, Adiponectin, in Type 2 Diabetic Patients

Adiponectin is a novel, adipose-specific protein abundantly present in the circulation, and it has antiatherogenic properties. We analyzed the plasma adiponectin concentrations in age- and body mass index (BMI)-matched nondiabetic and type 2 diabetic subjects with and without coronary artery disease (CAD). Plasma levels of adiponectin in the diabetic subjects without CAD were lower than those in nondiabetic subjects (6.6+/-0.4 versus 7.9+/-0.5 microg/mL in men, 7.6+/-0.7 versus 11.7+/-1.0 microg/mL in women; P<0.001). The plasma adiponectin concentrations of diabetic patients with CAD were lower than those of diabetic patients without CAD (4.0+/-0.4 versus 6.6+/-0.4 microg/mL, P<0.001 in men; 6.3+/-0.8 versus 7.6+/-0. 7 microg/mL in women). In contrast, plasma levels of leptin did not differ between diabetic patients with and without CAD. The presence of microangiopathy did not affect the plasma adiponectin levels in diabetic patients. Significant, univariate, inverse correlations were observed between adiponectin levels and fasting plasma insulin (r=-0.18, P<0.01) and glucose (r=-0.26, P<0.001) levels. In multivariate analysis, plasma insulin did not independently affect the plasma adiponectin levels. BMI, serum triglyceride concentration, and the presence of diabetes or CAD remained significantly related to plasma adiponectin concentrations. Weight reduction significantly elevated plasma adiponectin levels in the diabetic subjects as well as the nondiabetic subjects. These results suggest that the decreased plasma adiponectin concentrations in diabetes may be an indicator of macroangiopathy.

Adiponectin, an Adipocyte-Derived Plasma Protein, Inhibits Endothelial NF-κB Signaling Through a cAMP-Dependent Pathway

BackgroundAmong the many adipocyte-derived endocrine factors, we found an adipocyte-derived plasma protein, adiponectin, that was decreased in obesity. We recently demonstrated that adiponectin inhibited tumor necrosis factor-&agr; (TNF-&agr;)–induced expression of endothelial adhesion molecules and that plasma adiponectin level was reduced in patients with coronary artery disease (Circulation. 1999;100:2473–2476). However, the intracellular signal by which adiponectin suppressed adhesion molecule expression was not elucidated. The present study investigated the mechanism of modulation for endothelial function by adiponectin. Methods and ResultsThe interaction between adiponectin and human aortic endothelial cells (HAECs) was estimated by cell ELISA using biotinylated adiponectin. HAECs were preincubated for 18 hours with 50 &mgr;g/mL of adiponectin, then exposed to TNF-&agr; (10 U/mL) or vehicle for the times indicated. NF-&kgr;B–DNA binding activity was determined by electrophoretic mobility shift assays. TNF-&agr;–inducible phosphorylation signals were detected by immunoblotting. Adiponectin specifically bound to HAECs in a saturable manner and inhibited TNF-&agr;–induced mRNA expression of monocyte adhesion molecules without affecting the interaction between TNF-&agr; and its receptors. Adiponectin suppressed TNF-&agr;–induced I&kgr;B-&agr; phosphorylation and subsequent NF-&kgr;B activation without affecting other TNF-&agr;–mediated phosphorylation signals, including Jun N-terminal kinase, p38 kinase, and Akt kinase. This inhibitory effect of adiponectin is accompanied by cAMP accumulation and is blocked by either adenylate cyclase inhibitor or protein kinase A (PKA) inhibitor. ConclusionsThese observations raise the possibility that adiponectin, which is naturally present in the blood stream, modulates the inflammatory response of endothelial cells through cross talk between cAMP-PKA and NF-&kgr;B signaling pathways.

Adipocyte-Derived Plasma Protein, Adiponectin, Suppresses Lipid Accumulation and Class A Scavenger Receptor Expression in Human Monocyte-Derived Macrophages

Background —Excessive lipid accumulation in macrophages plays an important role in the development of atherosclerosis. Recently, we discovered an adipocyte-specific plasma protein, adiponectin, that is decreased in patients with coronary artery disease. We previously demonstrated that adiponectin acts as a modulator for proinflammatory stimuli and inhibits monocyte adhesion to endothelial cells. The present study investigated the effects of adiponectin on lipid accumulation in human monocyte-derived macrophages. Methods and Results —Human monocytes were differentiated into macrophages by incubation in human type AB serum for 7 days, and the effects of adiponectin were investigated at different time intervals. Treatment with physiological concentrations of adiponectin reduced intracellular cholesteryl ester content, as determined using the enzymatic, fluorometric method. The adiponectin-treated macrophages contained fewer lipid droplets stained by oil red O. Adiponectin suppressed the expression of the class A macrophage scavenger receptor (MSR) at both mRNA and protein levels by Northern and immunoblot analyses, respectively, without affecting the expression of CD36, which was quantified by flow cytometry. Adiponectin reduced the class A MSR promoter activity, as measured by luciferase reporter assay. Adiponectin treatment dose-dependently decreased class A MSR ligand binding and uptake activities. The mRNA level of lipoprotein lipase as a marker of macrophage differentiation was decreased by adiponectin treatment, but that of apolipoprotein E was not altered. Adiponectin was detected around macrophages in the human injured aorta by immunohistochemistry. Conclusions —The adipocyte-derived plasma protein adiponectin suppressed macrophage-to-foam cell transformation, suggesting that adiponectin may act as a modulator for macrophage-to-foam cell transformation.

Adipocyte-Derived Plasma Protein Adiponectin Acts as a Platelet-Derived Growth Factor-BB–Binding Protein and Regulates Growth Factor–Induced Common Postreceptor Signal in Vascular Smooth Muscle Cell

Background—Vascular smooth muscle cell proliferation plays an important role in the development of atherosclerosis. We previously reported that adiponectin, an adipocyte-specific plasma protein, accumulated in the human injured artery and suppressed endothelial inflammatory response as well as macrophage-to-foam cell transformation. The present study investigated the effects of adiponectin on proliferation and migration of human aortic smooth muscle cells (HASMCs). Methods and Results—HASMC proliferation was estimated by [3H] thymidine uptake and cell number. Cell migration assay was performed using a Boyden chamber. Physiological concentrations of adiponectin significantly suppressed both proliferation and migration of HASMCs stimulated with platelet-derived growth factor (PDGF)-BB. Adiponectin specifically bound to 125I-PDGF-BB and significantly inhibited the association of 125I-PDGF-BB with HASMCs, but no effects were observed on the binding of 125I-PDGF-AA or 125I-heparin–binding epidermal growth factor (EGF)–like growth factor (HB-EGF) to HASMCs. Adiponectin strongly and dose-dependently suppressed PDGF-BB–induced p42/44 extracellular signal–related kinase (ERK) phosphorylation and PDGF &bgr;-receptor autophosphorylation analyzed by immunoblot. Adiponectin also reduced PDGF-AA–stimulated or HB-EGF–stimulated ERK phosphorylation in a dose-dependent manner without affecting autophosphorylation of PDGF &agr;-receptor or EGF receptor. Conclusions—The adipocyte-derived plasma protein adiponectin strongly suppressed HASMC proliferation and migration through direct binding with PDGF-BB and generally inhibited growth factor–stimulated ERK signal in HASMCs, suggesting that adiponectin acts as a modulator for vascular remodeling.

A neutrophil elastase inhibitor (ONO-5046) reduces neurologic damage after spinal cord injury in rats

In view of a cytoprotective effect of elastase inhibitor on chemokine‐mediated tissue injury, we examined the neuroprotective effect of ONO‐5046, a specific inhibitor of neutrophil elastase, in rats with spinal cord injury. Standardized spinal cord compression markedly increased cytokine‐induced neutrophil chemo‐attractant (CINC)‐1 mRNA and protein. Their increases correlated with neurologic severity of injured rats. Immunohistochemically, CINC‐1 protein was detected sequentially in vascular endothelial cells at 4 h, in perivascular neutrophils at 8 h, and in neutrophils infiltrating into cord substance at 12 h. Pretreatment with ONO‐5046 (50 mg/kg) markedly ameliorated motor disturbance in injured rats, and reduced CINC‐1 protein and mRNA expression. ONO‐5046 also significantly reduced the increase of neutrophil accumulation or infiltration estimated by myeloperoxidase activity, and the extent of vascular permeability by Evans blue extravasation in the injured cord segment in comparison to control animals receiving vehicle. These results suggest that CINC‐1 contributed to inflammation in rat spinal cord injury and ONO‐5046 attenuated neurologic damage partly by blocking CINC‐1 production of the chemoattractant, preventing neutrophil activation and vascular endothelial cell injury.

Possible Involvement of Interleukin‐1 in Cyclooxygenase‐2Induction After Spinal Cord Injury in Rats

Abstract : A standardized compression injury of rat spinal cord brought about a time‐dependent biphasic production of thromboxane A2 (detected as thromboxane B2) and prostaglandin I2 (detected as 6‐ketoprostaglandin F1α. Thromboxane B2 was predominant during the first 1 h, whereas the 6‐ketoprostaglandin F1α level exceeded that of thromboxane B2 at 8 h postinjury. As examined by inhibitor experiments and northern blotting, cyclooxygenase‐1 was responsible for the first phase, and cyclooxygenase‐2 was involved in the second phase. On compression injury the levels of interleukin‐1α and ‐1β detected as mRNA and protein increased and peaked at 2‐4 h. Injection of exogenous interleukin‐1 α into the spinal cord resulted in an increase of cyclooxygenase‐2 mRNA content and a predominant production of 6‐ketoprostaglandin F1α resembling the second phase of eicosanoid production. Concomitantly, extravascular migration of polymorphonuclear leukocytes was enhanced after the interleukin‐1α injection. These cells together with vascular endothelial cells and glial cells were stained positively with an anti‐cyclooxygenase‐2 antibody. The results suggest that the immediate eicosanoid synthesis after spinal cord injury was due to the constitutive cyclooxygenase‐1 and the delayed synthesis of eicosanoids was attributable to the induction of cyclooxygenase‐2 mediated by interleukin‐1 α.

Chemically Modified DNA Aptamers Bind Interleukin-6 with High Affinity and Inhibit Signaling by Blocking Its Interaction with Interleukin-6 Receptor

Background: IL-6 signaling is a key component of inflammatory diseases. Results: Modified DNA aptamers that inhibit IL-6 signaling were discovered and optimized. Conclusion: Modified aptamers are stable in serum and block the interaction of IL-6 with its receptor IL-6Rα. Significance: Modified aptamers are a new class of antagonist with properties potentially suitable for clinical treatment of inflammation. Interleukin-6 (IL-6) is a pleiotropic cytokine that regulates immune and inflammatory responses, and its overproduction is a hallmark of inflammatory diseases. Inhibition of IL-6 signaling with the anti-IL-6 receptor antibody tocilizumab has provided some clinical benefit to patients; however, direct cytokine inhibition may be a more effective option. We used the systematic evolution of ligands by exponential enrichment (SELEX) process to discover slow off-rate modified aptamers (SOMAmers) with hydrophobic base modifications that inhibit IL-6 signaling in vitro. Two classes of IL-6 SOMAmers were isolated from modified DNA libraries containing 40 random positions and either 5-(N-benzylcarboxamide)-2′-deoxyuridine (Bn-dU) or 5-[N-(1-naphthylmethyl)carboxamide]-2′-deoxyuridine (Nap-dU) replacing dT. These modifications facilitate the high affinity binding interaction with IL-6 and provide resistance against degradation by serum endonucleases. Post-SELEX optimization of one Bn-dU and one Nap-dU SOMAmer led to improvements in IL-6 binding (10-fold) and inhibition activity (greater than 20-fold), resulting in lead SOMAmers with sub-nanomolar affinity (Kd = 0.2 nm) and potency (IC50 = 0.2 nm). Although similar in inhibition properties, the two SOMAmers have unique sequences and different ortholog specificities. Furthermore, these SOMAmers were stable in human serum in vitro for more than 48 h. Both SOMAmers prevented IL-6 signaling by blocking the interaction of IL-6 with its receptor and inhibited the proliferation of tumor cells in vitro as effectively as tocilizumab. This new class of IL-6 inhibitor may be an effective therapeutic alternative for patients suffering from inflammatory diseases.

Up-regulation of vascular endothelial growth factor in response to glucose deprivation

Vascular endothelial growth factor (VEGF), also known as a vascular permeability factor (VPF), is an endothelial specific mitogen and is a potent inducer of angiogenesis. Recently it has been reported that hypoxia induces VEGF mRNA expression in various cells. Since both oxygen and glucose are required for efficient production of energy, we examined the effect of glucose deprivation on VEGF mRNA expression and VEGF protein production in U‐937 (a human monocytic cell line) cells. Both the mRNA expression and secretion of VEGF increased after exposure to low glucose. Addition of L‐glucose, the L‐stereoisomer of D‐glucose, did not prevent the up‐regulation of VEGF expression. The conditioned medium from glucose‐deprived cells, followed by supplementation with glucose, did not up‐regulate VEGF mRNA expression in U‐937 cells. The low glucose‐induced VEGF mRNA expression returned to the control level after supplementation with D‐glucose. Furthermore, oligomycin, a mitochondrial ATP synthase inhibitor, increased VEGF protein production. The results suggest that the up‐regulation of VEGF mRNA in U‐937 cells in response to glucose deprivation is not mediated by autocrine factors from the cells nor is the osmotic change of the medium mediated by the deficiency of glucose metabolism in the cells. Our results also suggest that the intracellular ATP depletion due to glucose deprivation may be one of the causes for increased VEGF mRNA expression. We speculate that local hypoglycemia may act as an essential trigger for angiogenesis through the VEGF gene expression.

Successful immunogene therapy using colon cancer cells (colon 26) transfected with plasmid vector containing mature interleukin-18 cDNA and the Igκ leader sequence

IL-18 is a novel cytokine that induces interferon (IFN)-γ secretion and plays an important role in antitumor immunity. In the present study, we constructed plasmid vectors encoding the murine mature IL-18 cDNA linked with the Igκ leader sequence and the pro-IL-18 cDNA to estimate the efficacy of the mature IL-18 vector and to evaluate IL-18–producing tumor cells as a tumor vaccine. Colon 26 cells were transfected with the abovementioned vectors or with vector alone (mock). Reverse transcription-polymerase chain reaction analysis showed increased expression of murine IL-18 cDNA in both mature IL-18 and pro-IL-18 transfectants in comparison to that in mock transfected cells. The ability of the culture supernatants of mature IL-18 transfectants to induce IFN-γ secretion was extremely high (40–140 pg/106 cells) in comparison to that of pro-IL-18 transfectants (4–18 pg/106 cells). When injected into syngeneic BALB/c mice, the growth of mature IL-18 transfectants, but not pro-IL-18 transfectants, was significantly less than that in mock transfected cells (P<.01, by ANOVA and analysis of covariance). In addition, injection of colon 26 or Meth-A cells into mice immunized with a mature IL-18 transfectant revealed acquired immunity. Depletion of natural killer cells did not affect the growth of transfectants. However, the growth inhibitory effects were partially abrogated following treatment with anti-CD4+ and anti-CD8+ antibodies. These data suggest that the rejection of mature IL-18/colon 26 cells was mediated through T-cell activation. Gene therapy using mature IL-18 transfectants containing a plasmid vector and the Igκ leader sequence may be a useful tumor vaccine. Cancer Gene Therapy (2001) 8, 9–16

Identification of aquaporin-5 and lipid rafts in human resting saliva and their release into cevimeline-stimulated saliva

BACKGROUND It is unknown whether AQP5 and lipid rafts are released into human unstimulated (resting) saliva and saliva in response to secretagogues. METHODS In order to quantitate the salivary concentration of AQP5, we produced a polyclonal antibody for human AQP5 and developed an enzyme-like immunosorbent assay (ELISA). RESULTS AQP5 and lipid rafts were identified in human resting saliva. The amount of AQP5 in resting saliva showed a diurnal variation with high levels during waking hours, and an age-related decrease in AQP5 was coincident with the volume of resting saliva. Cevimeline, a muscarinic acetylcholine receptor (mAChR) agonist, induced the release of AQP5 with lipid rafts, amylase, mucin, and lysozyme. Changes in saliva AQP5 levels after cevimeline administration occurred simultaneously with changes in saliva flow rates. Confocal microscopy revealed that AQP5 was located in the apical plasma membrane and showed a diffuse pattern in parotid glands under resting conditions. Following cevimeline administration, AQP5 was predominantly associated with the APM and was localized in the lumen. GENERAL SIGNIFICANCE AQP5 and lipid rafts were released with salivary proteins from human salivary glands by the stimulation of M3 mAChRs, and that changes in saliva AQP5 levels can be used as an indicator of salivary flow rate and also as a useful index of M3 mAChR agonists action on human salivary glands.