Mahito Sato

Hypoxia Induces Transcription of the Plasminogen Activator Inhibitor-1 Gene Through Genistein-Sensitive Tyrosine Kinase Pathways in Vascular Endothelial Cells

A decline in oxygen concentration perturbs endothelial function, which promotes local thrombosis. In this study, we determined whether hypoxia in the range of that observed in pathophysiological hypoxic states stimulates plasminogen activator inhibitor-1 (PAI-1) production in bovine aortic endothelial cells. PAI-1 production, measured by ELISA, was increased by 4.7-fold (P<0.05 versus normoxic control, n=4) at 12 hours after hypoxic stimulation. Northern blot analysis showed the progressive time-dependent increase in the steady-state level of PAI-1 mRNA expression by hypoxia, which reached a 7.5-fold increase (P<0.05 versus control, n=4) at 12 hours. Deferoxamine, which has been known to bind heme protein and to reproduce the hypoxic response, induced PAI-1 production at both the mRNA and protein levels. The half-life of PAI-1 mRNA, as determined by a standard decay assay, was not affected by hypoxia, suggesting that induction of PAI-1 mRNA was regulated mainly at the transcriptional level. Transient transfection assays of the human PAI-1 promoter-luciferase construct indicates that a hypoxia-responsive region lies between -414 and -107 relative to the transcription start site, where no putative hypoxia response element is found. The hypoxia-mediated increase in PAI-1 mRNA levels was attenuated by the tyrosine kinase inhibitors genistein (50 micromol/L) and herbimycin A (1 micromol/L), whereas PD98059 (50 micromol/L, MEK1 inhibitor), SB203580 (10 micromol/L, p38 mitogen-activated protein kinase inhibitor), and calphostin C (1 micromol/L, protein kinase C inhibitor) had no effect on the induction of PAI-1 expression by hypoxia and deferoxamine. Genistein but not daidzein blocked the production of hypoxia- and deferoxamine-induced PAI-1 protein. Thus, we conclude that hypoxia stimulates PAI-1 gene transcription and protein production through a signaling pathway involving genistein-sensitive tyrosine kinases in vascular endothelial cells.

Basic Fibroblast Growth Factor Antagonizes Transforming Growth Factor-β1–Induced Smooth Muscle Gene Expression Through Extracellular Signal–Regulated Kinase 1/2 Signaling Pathway Activation

Objective—Transforming growth factor-β1 (TGFβ1) and fibroblast growth factor (FGF) families play a pivotal role during vascular development and in the pathogenesis of vascular disease. However, the interaction of intracellular signaling evoked by each of these growth factors is not well understood. The present study was undertaken to examine the molecular mechanisms that mediate the effects of TGFβ1 and basic FGF (bFGF) on smooth muscle cell (SMC) gene expression. Methods and Results—TGFβ1 induction of SMC gene expression, including smooth muscle protein 22-&agr; (SM22&agr;) and smooth muscle &agr;-actin, was examined in the pluripotent 10T1/2 cells. Marked increase in these mRNA levels by TGFβ1 was inhibited by c-Src-tyrosine kinase inhibitors and protein synthesis inhibitor cycloheximide. Functional studies with deletion and site-directed mutation analysis of the SM22&agr; promoter demonstrated that TGFβ1 activated the SM22&agr; promoter through a CC(A/T-rich)6GG (CArG) box, which serves as a serum response factor (SRF)–binding site. TGFβ1 increased SRF expression through an increase in transcription of the SRF gene. In the presence of bFGF, TGFβ1 induction of SMC marker gene expression was significantly attenuated. Transient transfection assays showed that bFGF significantly suppressed induction of the SM22&agr; promoter–driven luciferase activity by TGFβ1, whereas bFGF had no effects on the TGFβ1-mediated increase in SRF expression and SRF:DNA binding activity. Mitogen-activated protein kinase kinase-1 (MEK1) inhibitor PD98059 abrogated the bFGF-mediated suppression of TGFβ1-induced SMC gene expression. Conclusion—Our data suggest that bFGF-induced MEK/extracellular signal-regulated kinase signaling plays an antagonistic role in TGFβ1-induced SMC gene expression through suppression of the SRF function. These data indicate that opposing effects of bFGF and TGFβ1 on SMC gene expression control the phenotypic plasticity of SMCs.

Fibroblast growth factor-2 induces osteogenic differentiation through a Runx2 activation in vascular smooth muscle cells

Expression of bone-associated proteins and osteoblastic transcription factor Runx2 in arterial cells has been implicated in the development of vascular calcification. However, the signaling upstream of the Runx2-mediated activation of osteoblastic program in vascular smooth muscle cells (VSMC) is poorly understood. We examined the effects of fibroblast growth factor-2 (FGF-2), an important regulator of bone formation, on osteoblastic differentiation of VSMC. Stimulation of cultured rat aortic SMC (RASMC) with FGF-2 induced the expression of the osteoblastic markers osteopontin (OPN) and osteocalcin. Luciferase assays showed that FGF-2 induced osteocyte-specific element (OSE)-dependent transcription. Downregulation of Runx2 by siRNA repressed the basal and FGF-2-stimulated expression of the OPN gene in RASMC. FGF-2 produced hydrogen peroxide in RASMC, as evaluated by fluorescent probe. Induction of OPN expression by FGF-2 was inhibited not only by PD98059 (MEK1 inhibitor) and PP1 (c-Src inhibitor), but also by an antioxidant, N-acetyl cysteine. Nuclear extracts from FGF-2-treated RASMC exhibited increased DNA-binding of Runx2 to its target sequence. Immunohistochemistry of human coronary atherectomy specimens and calcified aortic tissues showed that expression of FGF receptor-1 and Runx2 was colocalized. In conclusion, these results suggest that FGF-2 plays a role in inducing osteoblastic differentiation of VSMC by activating Runx2 through mitogen-activated protein kinase (MAPK)-dependent- and oxidative stress-sensitive-signaling pathways.

c-Src and Hydrogen Peroxide Mediate Transforming Growth Factor-β1–Induced Smooth Muscle Cell–Gene Expression in 10T1/2 Cells

Objective— Transforming growth factor-β1 (TGF-β1) controls the expression of numerous genes, including smooth muscle cell (SMC)–specific genes and extracellular matrix protein genes. Here we investigated whether c-Src plays a role in TGF-β1 signaling in mouse embryonic fibroblast C3H10T1/2 cells. Methods and Results— TGF-β1 induction of the SMC contractile protein SM22α gene expression was inhibited by PP1 (an inhibitor of Src family kinases) or by C-terminal Src kinase (a negative regulator of c-Src). Induction of SM22α by TGF-β1 was markedly attenuated in SYF cells (c-Src−, Yes−, and Fyn−) compared with Src++ cells (c-Src++, Yes−, and Fyn−). PP1 also inhibited the TGF-β1–induced expression of serum response factor (SRF), a transcription factor regulating the SMC marker gene expression. Confocal immunofluorescence analysis showed that TGF-β1 stimulates production of hydrogen peroxide. Antioxidants such as catalase or NAD(P)H oxidase inhibitors such as apocynin inhibited the TGF-β1–induced expression of SM22α. Furthermore, we demonstrate that TGF-β1 induction of the plasminogen activator inhibitor-1 (PAI-1) gene, which is known to be dependent on Smad but not on SRF, is inhibited by PP1 and apocynin. Conclusion— Our results suggest that TGF-β1 activates c-Src and generates hydrogen peroxide through NAD(P)H oxidase, and these signaling pathways lead to the activation of specific sets of genes, including SM22α and PAI-1.

The role of VAMP7/TI-VAMP in cell polarity and lysosomal exocytosis in vivo

VAMP7 or tetanus neurotoxin‐insensitive vesicle‐ associated membrane protein (TI‐VAMP) has been proposed to regulate apical transport in polarized epithelial cells, axonal transport in neurons and lysosomal exocytosis. To investigate the function of VAMP7 in vivo, we generated VAMP7 knockout mice. Here, we show that VAMP7 knockout mice are indistinguishable from control mice and display a similar localization of apical proteins in the kidney and small intestine and a similar localization of axonal proteins in the nervous system. Neurite outgrowth of cultured mutant hippocampal neurons was reduced in mutant neurons. However, lysosomal exocytosis was not affected in mutant fibroblasts. Our results show that VAMP7 is required in neurons to extend axons to the full extent. However, VAMP7 does not seem to be required for epithelial cell polarity and lysosomal exocytosis.

14-3-3 proteins and protein phosphatases are not reduced in tau-deficient mice.

Tau is an axonal microtubule-associated protein, whose dysfunction causes neurodegenerative diseases such as Alzheimers disease and other tauopathies. Earlier studies have shown the interactions of tau with glycogen synthase kinase-3&bgr;, 14-3-3ζ, protein phosphatase 1 and protein phosphatase 2A. In this study, we compared the amounts of these tau-interacting proteins in brain microtubule-enriched fractions from wild-type and tau-deficient mice. Contrary to our expectation, we detected no difference in the amount of these proteins between wild-type and tau-deficient mice. Our findings indicate that only a small portion of tau-interacting proteins are bound to tau in vivo, and suggest the existence of other scaffolding proteins. We propose that tau-deficient mice are an ideal system for confirming the function of tau-interacting proteins.

Visceral fat obesity contributes to the tortuosity of the thoracic aorta on chest radiograph in poststroke Japanese patients.

Tortuosity of the thoracic aorta on chest radiographs is characteristic of atherosclerotic disease. Aging and hypertension are associated with the tortuosity, but little is known about the influence of other atherosclerotic risk factors on this abnormality. The purpose of this study was to examine which atherosclerotic risk factors are determinants for tortuosity of the thoracic aorta. Forty-five poststroke Japanese patients (31 men and 14 women, age range 41-78 years and mean 60.5 ±8.6) were studied. The distance factor, ie, the ratio of meandering vessel length to the straight-line distance between its end points, was used to measure arterial tortuosity. The hospital records were reviewed for clinical and biochemical variables. Tortuosity of the thoracic aorta had a significant positive relationship with body mass index (BMI) (r =0.397, p<0.01), waist circumference (r =0.360, p<0.05), and the cardiothoracic ratio (CTR) (r =0.526, p<0.001), and a significant negative relationship with ankle-brachial pressure index (ABPI) (r =-0.360, p<0.05). Stepwise regression analysis showed that waist circumference and CTR were independently correlated with increased tortuosity, whereas ABPI was negatively correlated with it. These results suggest that visceral fat obesity is a novel contributor to tortuosity of the thoracic aorta, which may be as a shortening of the distance between aortic tethering points due to elevation of the diaphragm by excessive intraabdominal fat and as a consequence of aortic elongation due to arteriosclerosis caused by obesity-related metabolic disorders.

Smooth Muscle Cell Outgrowth from Coronary Atherectomy Specimens in vitro Is Associated with Less Time to Restenosis and Expression of a Key Transcription Factor KLF5/BTEB2

Atherectomy specimens offer an opportunity to study the biology of coronary artery lesions. We cultured smooth muscle cells (SMCs) from specimens obtained from 24 patients with coronary restenosis after angioplasty to study the relationship between activity of SMCs (in vitro outgrowth) and the time course of restenosis. We also examined expression of a Kruppel-like zinc-finger transcription factor 5 (KLF; also known as BTEB2 and IKLF), which is markedly induced in activated SMCs, in the same specimens. SMC outgrowth was observed in 9 of 24 specimens (37.5%). Restenosis occurred sooner (p < 0.01) in patients whose specimens showed outgrowth compared to those whose specimens showed no outgrowth. Immunostaining for KLF5 was more common in specimens with outgrowth (89 vs. 20%, p < 0.01). These data suggest that the number of activated SMCs in lesions may determine in vitro outgrowth and also affect the time to restenosis.

Indomethacin induced bulky lymphadenopathy and eosinophilic pneumonia.

Abstract: Indomethacin is one of the most popular non‐steroidal anti‐inflammatory drugs (NSAID). Although NSAID occasionally provoke bronchospasm and hypersensitivity pneumonia, they seldom cause lymphadenopathy. This is the first report in which NSAID induced both eosinophilic pneumonia and bulky intrathoracic lymphadenopathy simultaneously. A 76‐year‐old Japanese man experienced high fever and dyspnoea after using an indomethacin suppository. Computed tomography scan of his chest revealed massive mediastinal and hilar lymphadenopathy along with diffuse infiltration in both lungs. He was diagnosed to have eosinophilic pneumonia because of eosinophilia in his peripheral blood and bronchoalveolar lavage fluid (BALF). Without using glucocorticoids, the pulmonary infiltration and lymphadenopathy subsided spontaneously. As the blastoid transformation test using the lymphocytes in his BALF was positive to indomethacin, we judged that both his eosinophilic pneumonia and mediastinal lymphadenopathy were due to a hypersensitivity reaction to indomethacin. An allergic reaction to NSAID should be considered as a rare cause of mediastinal lymphadenopathy.

VAMP2 is expressed in myogenic cells during rat development

Vesicle‐associated membrane protein 2 (VAMP2) is a member of the SNARE family of proteins that regulate the intracellular vesicle fusion process. This study investigated the developmental expression of VAMP2 in the rat embryo. In the trunk, VAMP2 was primarily found in the heart on embryonic day (E) 10. On E12.5, VAMP2 expression was found in nerve fibers, somites, and heart. In somites, epithelial cells in the dorsomedial lip, and elongated myoblasts in myotome were positive for VAMP2. On E16.5, VAMP2 was expressed in the heart, nerve fibers, and skeletal muscles. In skeletal muscles, multinuclear myotubes were positive for VAMP2. In the head, where muscles are derived both from somitic and non‐somitic origin, VAMP2 was found in myotubes of the extrinsic ocular muscles and masseter muscle on E16.5. These findings suggest the involvement of VAMP2 in the development of skeletal muscles of somitic and non‐somitic origins. Developmental Dynamics 237:1886–1892, 2008.