The adenomatous polyposis coli gene ( APC ) is mutated in familial adenomatous polyposis and in sporadic colorectal tumors. Here the APC gene product is shown to bind through its armadillo repeat domain to a Rac-specific guanine nucleotide exchange factor (GEF), termed Asef. Endogenous APC colocalized with Asef in mouse colon epithelial cells and neuronal cells. Furthermore, APC enhanced the GEF activity of Asef and stimulated Asef-mediated cell flattening, membrane ruffling, and lamellipodia formation in MDCK cells. These results suggest that the APC-Asef complex may regulate the actin cytoskeletal network, cell morphology and migration, and neuronal function.

Nitric oxide (NO) is produced in almost all tissues and organs, exerting a variety of biological actions under physiological and pathological conditions. NO is synthesized by three different isoforms of NO synthase (NOS), including neuronal, inducible, and endothelial NOSs. Because there are substantial compensatory interactions among the NOS isoforms, the ultimate roles of endogenous NO in our body still remain to be fully elucidated. Here, we have successfully developed mice in which all three NOS genes are completely deleted by crossbreeding singly NOS ؊/؊ mice. NOS expression and activities were totally absent in the triply NOS ؊/؊ mice before and after treatment with lipopolysaccharide. Although the triply NOS ؊/؊ mice were viable and appeared normal, their survival and fertility rates were markedly reduced as compared with the wild-type mice. Furthermore, these mice exhibited marked hypotonic polyuria, polydipsia, and renal unresponsiveness to an antidiuretic hormone, vasopressin, all of which are characteristics consistent with nephrogenic diabetes insipidus. In the kidney of the triply NOS ؊/؊ mice, vasopressin-induced cAMP production and membranous aquaporin-2 water channel expression were reduced associated with tubuloglomerular lesion formation. These results provide evidence that the NOS system plays a critical role in maintaining homeostasis, especially in the kidney.

Objective-Asymmetric dimethylarginine (ADMA) is widely believed to be an endogenous nitric oxide synthase (eNOS) inhibitor. However, in this study, we examined our hypothesis that the long-term vascular effects of ADMA are not mediated by inhibition of endothelial NO synthesis. Methods and Results-ADMA was infused in wild-type and eNOS-knockout (KO) mice by osmotic minipump for 4 weeks. In wild-type mice, long-term treatment with ADMA caused significant coronary microvascular lesions. Importantly, in eNOS-KO mice, treatment with ADMA also caused an extent of coronary microvascular lesions that was comparable to that in wild-type mice. These vascular effects of ADMA were not prevented by supplementation of L-arginine, and vascular NO production was not reduced by ADMA treatment. Treatment with ADMA caused upregulation of angiotensin-converting enzyme (ACE) and an increase in superoxide production that were comparable in both strains and that were abolished by simultaneous treatment with temocapril (ACE inhibitor) or olmesartan (AT 1 receptor antagonist), which simultaneously suppressed vascular lesion formation. Key Words: asymmetric dimethylarginine Ⅲ arteriosclerosis Ⅲ nitric oxide Ⅲ endothelial nitric oxide synthase Ⅲ mice E ndothelium-derived nitric oxide (NO), synthesized from L-arginine by endothelial NO synthase (eNOS), has several important antiatherogenic actions. 1-5 Indeed, reduction of endothelial NO synthesis (endothelial dysfunction) predisposes the blood vessel to arteriosclerosis, 1-5 and the eNOS-deficient (eNOS-KO) mice exhibit accelerated vascular lesion formation. 6,7 As pharmacological tools to inhibit endothelial NO synthesis, synthetic L-arginine analogues have been used in vitro and in vivo. Among them, N -nitro-L-arginine methyl ester (L-NAME) is the most frequently used agent. [1][2][3][4][5] Long-term treatment with L-NAME is known to cause arteriosclerotic coronary lesions, especially at microvascular levels, in experimental animals. 8,9 This model with L-NAME is regarded as a useful animal model for examining the protective roles of endothelium-derived NO in the pathogenesis of arteriosclerosis. 8,9 See cover However, it is controversial whether these vascular effects of L-NAME are caused primarily by the inhibition of endothelial NO synthesis for the following reasons: first, the importance of endothelium-derived NO decreases as the vessel size becomes smaller, 10 whereas L-NAME-induced vascular lesions are prominent at microvascular levels; 8 second, long-term treatment with L-NAME does not reduce eNOS activity; 11 third, multiple actions of L-NAME other than simple inhibition of NO synthesis have been reported. 12,13 The most appropriate way to address this issue is to use mice that are deficient in the eNOS gene and to examine whether long-term treatment with L-NAME causes coronary vascular lesions in those mice. We have recently shown that treatment with L-NAME causes a comparable extent of Conclusions-These

Background-The roles of nitric oxide (NO) in the cardiovascular system have been investigated extensively in pharmacological studies with NO synthase (NOS) inhibitors and in studies with NOS isoform-deficient mice. However, because of the nonspecificity of the NOS inhibitors and the compensatory interactions among NOS isoforms (nNOS, iNOS, and eNOS), the ultimate roles of endogenous NO derived from the entire NOS system are still poorly understood. In this study, we examined this point in mice deficient in all 3 NOS isoforms (triply n/i/eNOS Ϫ/Ϫ mice) that we have recently developed. Methods and Results-The triply n/i/eNOSϪ/Ϫ mice, but not singly eNOS Ϫ/Ϫ mice, exhibited markedly reduced survival, possibly due to spontaneous myocardial infarction accompanied by severe coronary arteriosclerotic lesions. Furthermore, the triply n/i/eNOS Ϫ/Ϫ mice manifested phenotypes that resembled metabolic syndrome in humans, including visceral obesity, hypertension, hypertriglyceridemia, and impaired glucose tolerance. Importantly, activation of the renin-angiotensin system was noted in the triply n/i/eNOS Ϫ/Ϫ mice, and long-term oral treatment with an angiotensin II type 1 receptor blocker significantly suppressed coronary arteriosclerotic lesion formation and the occurrence of spontaneous myocardial infarction and improved the prognosis of those mice, along with ameliorating the metabolic abnormalities. Conclusions-These results provide the first direct evidence that genetic disruption of the whole NOS system causes spontaneous myocardial infarction associated with multiple cardiovascular risk factors of metabolic origin in mice in vivo through the angiotensin II type 1 receptor pathway, demonstrating the critical role of the endogenous NOS system in maintaining cardiovascular and metabolic homeostasis.

A novel approach to the treatment of bone tumors using tissue-engineered implants is reported in this study. The number of mesenchymal stem cells (MSCs) obtained from each patient's bone marrow cells was first increased, and the MSCs were forced to differentiate into osteoblasts followed by bone matrix formation on hydroxyapatite (HA) ceramics. The strong osteogenic ability of the implants, as evidenced by high osteoblastic activity, was confirmed. Consequently, the HA surface was covered with the patient's derived cultured osteoblast/bone matrix. The tissue-engineered HA was used to fill the patient's bone cavity after tumor curettage. Immediate healing potential was found by serial plain radiographs and computed tomograhy images, and no adverse reactions were noted in these patients. The results indicate that tissue-engineered osteogenic ceramics might be an alternative to autologous bone grafts.

Nitric oxide (NO) has multiple important actions that contribute to the maintenance of vascular homeostasis. NO is synthesized by three different isoforms of NO synthase (NOS), all of which have been reported to be expressed in human atherosclerotic vascular lesions. Although the regulatory roles of endothelial NOS (eNOS) and inducible NOS (iNOS) on the development of atherosclerosis have been described, little is known about the role of neuronal NOS (nNOS). Here, we show that nNOS also exerts important vasculoprotective effects in vivo. In a carotid artery ligation model, nNOS gene-deficient (nNOS-KO) mice exhibited accelerated neointimal formation and constrictive vascular remodeling caused by blood flow disruption. In a rat balloon injury model, the selective inhibition of nNOS activity potently enhanced vasoconstrictor responses to a variety of calcium-mobilizing stimuli, suppressed tissue cGMP concentrations, a marker of vascular NO production, and exacerbated neointimal formation. In both models, nNOS was absent before injury and was up-regulated only after the injury, and was predominantly expressed in the neointima and medial smooth muscle cells. These results provide the first direct evidence that nNOS plays important roles in suppressing arteriosclerotic vascular lesion formation in vivo.

Background-N-nitro-L-arginine methyl ester (L-NAME) is widely used to inhibit endothelial synthesis of NO in vivo. However, it is controversial whether the long-term vascular effects of L-NAME are mediated primarily by inhibition of endothelial NO synthesis. We addressed this point in mice that are deficient in the endothelial NO synthase gene (eNOS-KO mice). Methods and Results-Wild-type and eNOS-KO mice received L-NAME in drinking water for 8 weeks. In wild-type mice, long-term treatment with L-NAME caused significant medial thickening and perivascular fibrosis in coronary microvessels but not in large coronary arteries. Importantly, in eNOS-KO mice, treatment with L-NAME also caused an extent of medial thickening and perivascular fibrosis in coronary microvessels that was comparable to that in wild-type mice and that was not prevented by supplementation of L-arginine. Vascular NO and cGMP levels were not significantly reduced by L-NAME treatment, and no expression of inducible or neuronal NO synthase was noted in microvessels of eNOS-KO mice, suggesting an involvement of NO-independent mechanisms. Treatment with L-NAME caused an upregulation of vascular ACE and an increase in cardiac lucigenin chemiluminescence that were comparable in both strains and that were abolished by simultaneous treatment with temocapril (ACE inhibitor) or CS866 (angiotensin II type 1 receptor antagonist) along with the suppression of vascular lesion formation. Conclusions-These results provide the first direct evidence that the long-term vascular effects of L-NAME are not mediated by simple inhibition of endothelial NO synthesis. Direct upregulation of local ACE and increased oxidative stress appear to be involved in the long-term vascular effects of

Abstract. Nitric oxide (NO) is produced in almost all tissues and organs, exerting multiple biological actions under both physiological and pathological conditions. NO is synthesized by three different isoforms of NO synthase (NOS): neuronal, inducible, and endothelial NOSs. Due to the substantial compensatory interactions among the NOS isoforms, the ultimate roles of endogenous NO in our body still remain to be fully elucidated. To address this point, we have successfully developed mice in which all three NOS genes are completely disrupted. NOS expression and activities were totally absent in the triply n / i / eNOS −/ − mice before and after treatment with lipopolysaccharide. While the triply n / i / eNOS −/ − mice were viable, their survival and fertility rates were markedly reduced as compared with wild-type mice. The phenotypes of those mice that we first noticed were polyuria, polydipsia, and renal unresponsiveness to vasopressin, characteristics consistent with nephrogenic diabetes insipidus. We subsequently observed that in those mice, arteriosclerosis is spontaneously developed with a clustering of cardiovascular risk factors. These results provide the first evidence that the systemic deletion of all three NOSs causes a variety of cardiovascular diseases in mice, demonstrating a critical role of the endogenous NOSs system in maintaining cardiovascular homeostasis.