Biomedical subjects

Nobuyo Maeda

Publications and source records attributed to Nobuyo Maeda.

At least 37 records · Page 2Linked to original sources

PubMed2006

Abnormal spermatogenesis in mice unable to synthesize ascorbic acid.

Although exposure to environmental toxicants, including endocrine-disrupting chemicals, is thought to be a possible cause of male infertility, the pathogenesis of male reproductive disorders remains unclear. In the present study, we used Gulo-/- mutant mice, which are unable to synthesize ascorbic acid, to study the importance of dietary vitamin C (VC) on spermatogenesis. Regular chow containing approximately 110 mg/kg VC is unable to support the growth of these mutant mice, but a VC supplement in their drinking water (330 mg/L) is able to ameliorate the VC deficiency. Testes of Gulo-/- mutants born from heterozygous mothers without VC supplement (VC-deficient mice) and those born from mothers given a VC supplement (VC-sufficient mice) were examined by morphological and biochemical analyses. Morphological analysis revealed that apoptosis of spermatocytes occurred frequently in VC-deficient mice at 20 days of age. Two-dimensional electrophoresis analysis revealed the specific disappearance of heat-shock protein (Hsp) 70 in the testes of 20-day-old VC-deficient mice. In the present study, the relationship between the apoptosis of spermatocytes and Hsp70 in VC-deficient mice is discussed.

Animals↗

PubMed2006

Tissue inhibitor of metalloproteinase-3 plays important roles in the kidney following unilateral ureteral obstruction.

Tissue inhibitor of metalloproteinase-3 (Timp-3), an inhibitor of matrix-degrading enzymes, is an important molecule for maintenance of the extracellular matrix. In this study, we generated Timp-3-deficient mice and used them to examine the effect of Timp-3-deficiency on blood pressure and to investigate the role of Timp-3 in the kidney following unilateral ureteral obstruction. The blood pressure and heart rate of Timp-3-deficient mice were not significantly different from those of wild-type mice. On the other hand, the obstructed kidneys of Timp-3-deficient mice developed more severe hydronephrosis than those of wild-type animals. Matrix metalloproteinase activities assessed by in situ zymography and transforming growth factor-beta expression were elevated in Timp-3-deficient mice. The renal tissues were thinner and the ratio of renal medulla to cortex was significantly lower in the obstructed Timp-3-deficient kidneys. These findings indicate that Timp-3-deficiency does not substantially affect the blood pressure in mice, and that Timp-3 plays an important role in the maintenance of renal macrostructure after unilateral ureteral obstruction.

Animals↗

PubMed2006

alpha-Lipoic acid prevents the increase in atherosclerosis induced by diabetes in apolipoprotein E-deficient mice fed high-fat/low-cholesterol diet.

Considerable evidence indicates that hyperglycemia increases oxidative stress and contributes to the increased incidence of atherosclerosis and cardiovascular complications in diabetic patients. To examine the effect of alpha-lipoic acid, a potent natural antioxidant, on atherosclerosis in diabetic mice, 3-month-old apolipoprotein (apo) E-deficient (apoE(-/-)) mice were made diabetic by administering streptozotocin (STZ). At 4 weeks after starting the STZ administration, a high-fat diet with or without alpha-lipoic acid (1.65 g/kg) was given to the mice and to nondiabetic apoE(-/-) controls. At 20 weeks, markers of oxidative stress were significantly lower in both the diabetic apoE(-/-) mice and their nondiabetic apoE(-/-) controls with alpha-lipoic acid supplement than in those without it. Remarkably, alpha-lipoic acid completely prevented the increase in plasma total cholesterol, atherosclerotic lesions, and the general deterioration of health caused by diabetes. These protective effects of alpha-lipoic acid were accompanied by a reduction of plasma glucose and an accelerated recovery of insulin-producing cells in the pancreas, suggesting that part of its effects are attributable to protecting pancreatic beta-cells from damage. Our results suggest that dietary alpha-lipoic acid is a promising protective agent for reducing cardiovascular complications of diabetes.

Animals↗

PubMed2006

Inducible nitric oxide synthase mediates prostaglandin h2 synthase nitration and suppresses eicosanoid production.

Nitric oxide (NO) modulates the biological levels of arachidonate-derived cell signaling molecules by either enhancing or suppressing the activity of prostaglandin H(2) isoforms (PGHS-1 and PGHS-2). Whether NO activates or suppresses PGHS activity is determined by alternative protein modifications mediated by NO and NO-derived species. Here, we show that inducible NO synthase (iNOS) and PGHS-1 co-localize in atherosclerotic lesions of ApoE(-/-) mouse aortae. Immunoblotting and immunohistochemistry revealed Tyr nitration in PGHS-1 in aortic lesions but markedly less in adjacent nonlesion tissue. PGHS-2 was also found in lesions, but 3-nitrotyrosine incorporation was not detected. 3-Nitrotyrosine formation in proteins is considered a hallmark reaction of peroxynitrite, which can form via NO-superoxide reactions in an inflammatory setting. That iNOS-derived NO is essential for 3-nitrotyrosine modification of PGHS-1 was confirmed by the absence of 3-nitrotyrosine in lesions from ApoE(-/-)iNOS(-/-) mice. Mass spectrometric studies specifically identified the active site residue Tyr385 as a 3-nitrotyrosine modification site in purified PGHS-1 exposed to peroxynitrite. PGHS-mediated eicosanoid (PGE(2)) synthesis was more than fivefold accelerated in cultured iNOS(-/-) versus iNOS-expressing mouse aortic smooth muscle cells, suggesting that iNOS-derived NO markedly suppresses PGHS activity in vascular cells. These results further suggest a regulatory role of iNOS in eicosanoid biosynthesis in human atherosclerotic lesions.

Animals↗

PubMed2005

Early diet-induced non-alcoholic steatohepatitis in APOE2 knock-in mice and its prevention by fibrates.

BACKGROUND/AIMS: The molecular mechanisms leading to Non-Alcoholic Steatohepatitis (NASH) are not fully understood. In mice, NASH can be inhibited by fenofibrate, a synthetic agonist for the nuclear receptor peroxisome proliferator activated receptor alpha, which regulates hepatic triglyceride metabolism. This study aimed to elucidate the relation between steatosis and inflammation in NASH in a human-like hyperlipidemic mouse model. METHODS: Liver phenotype and gene expression were assessed in APOE2 knock-in mice that were fed a western-type high fat diet with or without co-administration of fenofibrate. RESULTS: In response to a western diet, APOE2 knock-in mice developed NASH characterized by steatosis and inflammation. Strikingly, macrophage accumulation in the liver preceded the steatosis during progression of the disease. This phenotype was in line with gene expression patterns, which showed regulation of two major groups of genes, i.e. inflammatory and lipid genes. Fenofibrate treatment decreased hepatic macrophage accumulation and abolished steatosis. Moreover, a marked reduction in the expression of inflammatory genes occurred immediately after fenofibrate treatment. CONCLUSIONS: These data indicate that inflammation might play an instrumental role during the development of NASH in this mouse model. Inhibition of NASH by fenofibrate may be due, at least in part, to its inhibitory effect on pro-inflammatory genes.

ATP-Binding Cassette Transporters↗

PubMed2005

Ascorbic acid-independent synthesis of collagen in mice.

The mouse has become the most important model organism for the study of human physiology and disease. However, until the recent generation of mice lacking the enzyme gulanolactone oxidase (Gulo), the final enzyme in the ascorbic acid biosynthesis pathway, examination of the role of ascorbic acid in various biochemical processes using this model organism has not been possible. In the mouse, similar to most mammals but unlike humans who carry a mutant copy of this gene, Gulo produces ascorbic acid from glucose. We report here that, although ascorbic acid is essential for survival, its absence does not lead to measurable changes in proline hydroxylation. Vitamin C deficiency had no significant effect on the hydroxylation of proline and collagen production during tumor growth or in angiogenesis associated with tumor or mammary gland growth. This suggests that factors other than ascorbic acid can support proline hydroxylation and collagen synthesis in vivo. Furthermore, the failure of Gulo-/- mice to thrive on a vitamin C-deficient diet therefore suggests that ascorbic acid plays a critical role in survival other than the maintenance of the vasculature.

Animals↗

PubMed2005

The role of natriuretic peptides in cardioprotection.

Atrial natriuretic peptide (ANP) and brain (B-type) natriuretic peptide (BNP) are circulating hormones of cardiac origin that play an important role in the regulation of intravascular blood volume and vascular tone. The plasma concentrations of ANP and BNP are elevated in heart failure, and they are considered to compensate for heart failure because of their diuretic, natriuretic, and vasodilating actions and inhibitory effects on renin and aldosterone secretion. Evidence is also accumulating from recent work that ANP and BNP exert their cardioprotective functions not only as circulating hormones but also as local autocrine and/or paracrine factors. In studies using cultured neonatal myocytes and fibroblasts, exogenous administration of both ANP and ANP antagonists demonstrated that ANP has antihypertrophic and antifibrotic functions. Corroborating these in vitro results, mice lacking natriuretic receptor-A (NPR-A), the receptor for ANP and BNP, develop cardiac hypertrophy and fibrosis independent of their blood pressure. Recent studies also suggest that the intracardiac natriuretic peptides/cGMP system plays a counter-regulatory role against the intracardiac renin-angiotensin-aldosterone system and TGF-beta mediated pathway. In a clinical setting, human recombinant ANP and BNP may be used for a therapy of heart failure; however, further evaluation is required in the future.

Animals↗

PubMed2005

Dietary cholesterol suppresses the ability of olive oil to delay the development of atherosclerotic lesions in apolipoprotein E knockout mice.

To test the hypothesis that cholesterol might suppress the beneficial effect of olive oil in atherosclerosis, we fed apoE KO mice diets containing extra virgin olive oil, either with or without cholesterol, for 10 weeks and assessed the development of atherosclerosis. Within each sex, mice were assigned randomly to one of the following four experimental groups: (1) a standard chow diet, (2) a chow diet supplemented with 0.1% cholesterol (w/w) cholesterol, (3) a chow diet enriched with 20% (w/w) extra virgin olive oil and (4) a chow diet containing 0.1% cholesterol and 20% extra virgin olive oil. On the standard chow diet, average plasma cholesterol levels were higher in males than in females. Olive oil- and cholesterol-enriched diets, separately or in combination, induced hypercholesterolemia in both sexes, and abolished the difference between the sexes in plasma cholesterol levels. The addition of cholesterol to chow or olive oil diets decreased apolipoprotein A-I significantly in females and serum paraoxonase activities in males. The latter activity was higher in females than in males. In both sexes, the size of aortic atherosclerotic lesions was similar in olive oil- and chow-fed animals and smaller than in cholesterol-supplemented groups. Size of aortic lesions were positively correlated with circulating paraoxonase activity, particularly in males, and the relationship remained after adjusting for apolipoprotein A-I and HDL cholesterol levels. Our results demonstrate that the nutritional regulation of paraoxonase is an important determinant of atherosclerotic lesions dependent on sex. They also suggest that the mere inclusion of olive oil in Western diets is insufficient and the adoption of Mediterranean diet would be more effective in retarding the development of atherosclerotic lesions.

Animals↗

PubMed2005

Targeted inactivation of hepatic Abca1 causes profound hypoalphalipoproteinemia and kidney hypercatabolism of apoA-I.

Patients with Tangier disease exhibit extremely low plasma HDL concentrations resulting from mutations in the ATP-binding cassette, sub-family A, member 1 (ABCA1) protein. ABCA1 controls the rate-limiting step in HDL particle assembly by mediating efflux of cholesterol and phospholipid from cells to lipid-free apoA-I, which forms nascent HDL particles. ABCA1 is widely expressed; however, the specific tissues involved in HDL biogenesis are unknown. To determine the role of the liver in HDL biogenesis, we generated mice with targeted deletion of the second nucleotide-binding domain of Abca1 in liver only (Abca1(-L/-L)). Abca1(-L/-L) mice had total plasma and HDL cholesterol concentrations that were 19% and 17% those of wild-type littermates, respectively. In vivo catabolism of HDL apoA-I from wild-type mice or human lipid-free apoA-I was 2-fold higher in Abca1(-L/-L) mice compared with controls due to a 2-fold increase in the catabolism of apoA-I by the kidney, with no change in liver catabolism. We conclude that in chow-fed mice, the liver is the single most important source of plasma HDL. Furthermore, hepatic, but not extrahepatic, Abca1 is critical in maintaining the circulation of mature HDL particles by direct lipidation of hepatic lipid-poor apoA-I, slowing its catabolism by the kidney and prolonging its plasma residence time.

ATP Binding Cassette Transporter 1↗

PubMed2005

Complex control of mouse apolipoprotein B gene expression revealed by targeted duplication.

An elevated plasma level of apolipoprotein B-containing lipoproteins is a risk factor for atherosclerotic cardiovascular disease. Subtle genetic abnormalities in gene expression including an increased expression of the APOB gene may play an important role in determining overall risk. In an attempt to increase mouse Apob expression, we used gene targeting and duplicated approximately 65 kb of genomic DNA containing the Apob locus in its natural genomic position in mice. While we successfully generated mice carrying the Apob gene duplication, the amount of the total Apob mRNA was not increased in their liver. In the intestine, total Apob mRNA was reduced to half of the wild-type mice. Plasma lipids in the Apob duplication mice were not altered. Expression analyses showed that the proximal Apob gene in the duplicated locus was preferentially expressed in both tissues suggesting a limitation of tissue-specific enhancer function. The previously characterized distant intestinal control element was not duplicated, explaining the unequal ratio of intestinal Apob expression. While the existence of an additional liver-specific enhancer element is unknown, our findings suggest the presence of an additional enhancer outside the duplicated region, and that Apob gene expression is more complicated than previously thought.

Animals↗

PubMed2005

Repopulation of apolipoprotein E knockout mice with CCR2-deficient bone marrow progenitor cells does not inhibit ongoing atherosclerotic lesion development.

OBJECTIVE: Using bone marrow transplantation, we have previously demonstrated the critical role that hematopoietic CCR2 plays in early atherogenesis. Reconstitution of irradiated apolipoprotein (apo) E3-Leiden mice with CCR2-deficient bone marrow progenitor cells resulted in 86% reduction on overall atherosclerotic lesion development. However, no data on CCR2 in the cause of established atherosclerosis have been reported so far. METHODS AND RESULTS: To study the role of CCR2 in established atherosclerotic lesions, bone marrow progenitor cells harvested from apoE-/- and apoE-/-/CCR2-/- mice were transplanted into lethally irradiated 16-week-old apoE-/- mice with established atherosclerotic lesions. No significant differences were found in serum total cholesterol and triglycerides levels at different time points after transplantation. At age 16 weeks, lesion size in control apoE-/- mice was 3.28+/-1.06x10(5) microm2. At 9 weeks after transplantation, apoE-/---> apoE-/- and apoE-/-/CCR2-/---> apoE-/- mice had developed significantly larger atherosclerotic lesions (4.49+/-0.92x10(5) microm2, P<0.02 and 4.15+/-0.62x10(5) microm2, P<0.04 compared with controls, respectively). However, no significant effect of disruption of hematopoietic CCR2 was observed on the progression of lesions. Furthermore, the macrophage positive area (78+/-4% versus 72+/-9%) and collagen content (11+/-6% versus 15+/-3%) of the lesions were similar as well. CONCLUSIONS: In contrast to the critical role of CCR2 in the initiation of atherogenesis, bone marrow progenitor cell-derived CCR2 does not influence the progression of established atherosclerotic lesions, pointing to additional mechanisms for recruitment of monocytes at later stages of lesion development.

Animals↗

PubMed2005

Increased susceptibility to heart failure in response to volume overload in mice lacking natriuretic peptide receptor-A gene.

OBJECT: Contribution of the natriuretic peptide system to the development of heart failure (HF) in vivo was examined using mice lacking or having decreased natriuretic peptide receptor-A (NPRA), a guanylyl cyclase-linked receptor. METHODS: Volume-overloaded HF was produced by aortocaval fistula in mice with wild-type (+/+), heterozygous (+/-), and homozygous null mutants (-/-) of the NPRA gene. Severity of HF was assessed 4 weeks after operation on the basis of organ weight, hemodynamics, echocardiographic indices, urinary variables, neurohumoral factors, and myocardial gene expression. RESULTS: There were no significant differences in lung weight, kidney weight, left ventricular end-diastolic pressure (LVEDP), left ventricular systolic function, or urinary variables among the three sham-operated groups; however, sham-operated (-/-) mice had higher blood pressure and individual cardiac chamber weights than did (+/+) mice. In contrast, (-/-) mice with aortocaval fistula had higher LVEDP, left and right ventricular weights, lung weight, and left ventricular dimension, as well as lower fractional shortening and urinary sodium and cyclic guanosine monophosphate (cGMP) excretion than did (+/+) mice with aortocaval fistula. In addition, ventricular mRNA expression of natriuretic peptides and beta-myosin heavy chain increased markedly only in (-/-) mice. Plasma atrial natriuretic peptide, renin, and aldosterone, but not cGMP, showed greater responses to aortocaval fistula in (-/-) mice than in (+/+) mice. Both sham-operated and aortocaval fistula NPRA (+/-) mice almost consistently showed a phenotype intermediate between those of NPRA (-/-) and NPRA (+/+) mice. CONCLUSION: These results provide genetic evidence that NPRA signaling protects against HF induced by volume overload in mice.

Aldosterone↗

PubMed2005

Human apoE4-targeted replacement mice display synaptic deficits in the absence of neuropathology.

The human APOE*4 allele is associated with an early age of onset and increased risk of Alzheimer's disease (AD). Long before the onset of AD, cognitive deficits can be identified in APOE*4 carriers. We examined neurons in the lateral amygdala of young apolipoprotein (apo) E3 and apoE4 targeted replacement (TR) mice for changes in synaptic integrity. ApoE4 mice displayed significantly reduced excitatory synaptic transmission and dendritic arborization. Despite these changes there were no signs of gliosis, amyloid deposition or neurofibrillary tangles in these mice. To our knowledge, this is the first study to suggest that cognitive deficits in APOE*4 carriers are due to inherent defects in synaptic function that appear prior to any age-dependent markers of neuropathology.

Affective Symptoms↗

PubMed2005

PPARgamma: a critical determinant of body fat distribution in humans and mice.

Evidence emerging from studies of humans and mice has indicated peroxisome proliferator-activated receptor gamma (PPARgamma) to be not only a key factor for adipogenesis but also a critical determinant of body fat distribution. Whereas genetically reduced PPARgamma activity in adipose tissue leads to reduction of total fat mass in humans and in mice, mutations in the ligand-binding domain of PPARgamma cause abnormal body fat distributions. It is less clear from mutation analysis how PPARgamma is involved in metabolic disturbances such as insulin resistance and its cardiovascular complications. Nevertheless, similarities and differences in the phenotypes associated with PPARgamma mutations in humans and in mouse models provide opportunities to dissect relationships between body fat distribution and its metabolic complications.

Animals↗

PubMed2005

The role of neutrophils in the induction of glomerulonephritis by anti-myeloperoxidase antibodies.

In humans, circulating anti-neutrophil cytoplasm autoantibodies (ANCAs) with specificity for myeloperoxidase (MPO) are strongly associated with the development of pauci-immune necrotizing and crescentic glomerulonephritis (NCGN). In mice, we have demonstrated that intravenous injection of mouse antibodies specific for mouse MPO induces NCGN that closely mimics the human disease. We now report that the development of NCGN in this experimental model is accompanied by glomerular accumulation of neutrophils and macrophages. Neutrophil infiltration was most conspicuous at sites of glomerular necrosis and crescent formation, with macrophages also most numerous in crescents. Lymphocytes, however, were sparse in acute lesions. Importantly, mice that were depleted of circulating neutrophils with NIMP-R14 rat monoclonal antibodies were completely protected from anti-MPO IgG-induced NCGN. These findings provide direct evidence that neutrophils play a major role in the pathogenesis of anti-MPO-induced NCGN in this animal model and implicate neutrophils in the induction of human ANCA disease. This raises the possibility that therapeutic strategies to reduce circulating neutrophils could be beneficial to patients with ANCA-induced NCGN.

Animals↗

PubMed2005

Endogenous production of lipoic acid is essential for mouse development.

alpha-Lipoic acid (LA) is a cofactor for mitochondrial alpha-ketoacid dehydrogenase complexes and is one of the most potent, natural antioxidants. Reduction of oxidative stress by LA supplementation has been demonstrated in patients with diabetic neuropathy and in animal models. To determine how normal development or pathological conditions are affected by genetic alterations in the ability of mammalian cells to synthesize LA and whether dietary LA can circumvent its endogenous absence, we have generated mice deficient in lipoic acid synthase (Lias). Mice heterozygous for disruption of the Lias gene develop normally, and their plasma levels of thiobarbituric acid-reactive substances do not differ from those of wild-type mice. However, the heterozygotes have significantly reduced erythrocyte glutathione levels, indicating that their endogenous antioxidant capacity is lower than those of wild-type mice. Homozygous embryos lacking Lias appear healthy at the blastocyst stage, but their development is retarded globally by 7.5 days postcoitum (dpc), and all the null embryos die before 9.5 dpc. Supplementing the diet of heterozygous mothers with LA (1.65 g/kg of body weight) during pregnancy fails to prevent the prenatal deaths of homozygous embryos. Thus, endogenous LA synthesis is essential for developmental survival and cannot be replaced by LA in maternal tissues and blood.

Animals↗

PubMed2005

An improved technique for tail-cuff blood pressure measurements with dark-tailed mice.

Study of the genetics of hypertension has been facilitated greatly by the use of mice with modified genes that affect blood pressure. A current successful method for measuring blood pressure in mice relies on detection of light passing through the tail to determine the pressure in a tail-cuff necessary to stop pulsed flow. Success in obtaining reliable blood pressure measurements in light-tailed strains of mice (e.g., C57BL/6J) has been excellent. However, in our and others' experience, mice having highly pigmented tails (e.g., 129S6/SvEvTac) have yielded less consistent measurements. We report here that simple modifications to the channel containing the pulse detection sensor can greatly improve the pulse detection of dark-tailed mice. The first modification--lining the sensor channel with four layers of clear plastic wrap--increased the frequency of successful blood pressure measurements of 129S6/SvEvTac mice twofold and reduced variability by one-third. The second modification--lining the sides of the channel with reflective foil--also improved the success rate with dark-tailed mice. Mean blood pressures were unaffected by these modifications, which enhance detection of the pulse wave and likely will be helpful in diverse applications in which blood pressure is measured in rodent strains with pigmented tails.

Animals↗

PubMed2004

Role of CYP27A in cholesterol and bile acid metabolism.

The CYP27A gene encodes a mitochondrial cytochrome P450 enzyme, sterol 27-hydroxylase, that is expressed in many different tissues and plays an important role in cholesterol and bile acid metabolism. In humans, CYP27A deficiency leads to cerebrotendinous xanthomatosis. To gain insight into the roles of CYP27A in the regulation of cholesterol and bile acid metabolism, cyp27A gene knockout heterozygous, homozygous, and wild-type littermate mice were studied. In contrast to homozygotes, heterozygotes had increased body weight and were mildly hypercholesterolemic, with increased numbers of lipoprotein particles in the low density lipoprotein size range. Cyp7A expression was not increased in heterozygotes but was in homozygotes, suggesting that parts of the homozygous phenotype are secondary to increased cyp7A expression and activity. Homozygotes exhibited pronounced hepatomegaly and dysregulation in hepatic cholesterol, bile acid, and fatty acid metabolism. Hepatic cholesterol synthesis and synthesis of bile acid intermediates were increased; however, side chain cleavage was impaired, leading to decreased bile salt concentrations in gallbladder bile. Expression of Na-taurocholate cotransporting polypeptide, the major sinusoidal bile salt transporter, was increased, and that of bile salt export pump, the major canalicular bile salt transporter, was decreased. Gender played a modifying role in the homozygous response to cyp27A deficiency, with females being generally more severely affected. Thus, both cyp27A genotype and gender affected the regulation of hepatic bile acid, cholesterol, and fatty acid metabolism.

Animals↗