永井 良三

マルチプルリスクファクター症候群では,動脈硬化性疾患の合併率が高く,死亡率も高い,最近,その基盤として,インスリン抵抗性の存在が注目されている.インスリンは血管内皮細胞においてNOを産生遊離し,血管内皮依存性の血管弛緩反応をもたらすが,インスリン抵抗性では内皮機能が障害されるため,内皮型NO合成酵素(eNOS)活性が低下し,内皮依存性弛緩反応が障害される.これはインスリン抵抗性の増悪,血管壁における炎症の惹起,血栓形成性の亢進をもたらし,結果として動脈硬化を進展させるため重要である.近年,インスリン抵抗性における血管内皮機能障害の分子メカニズムとして,酸化ストレスの亢進が提唱されている

最新テクノロジーであるITの発達に伴い,米国を中心にヒトゲノム解析の研究が急速に進められ,様々な疾患とゲノムとの関連が明らかになってきた.しかし,大部分の現場医療において,ゲノム研究の解析結果に対して実際有効に活用されている面は乏しい.ゲノム解析の推進にも欠かせない技術としてITは貢献してきたが,こうしたゲノム研究を最大限に活用するためにも,臨床情報とゲノム情報の円滑な融合が現在の課題である.こうした研究の応用により実際の医療が行われた場合,各個人の遺伝子に応じた医療(テーラーメード医療)が実現する

We analyzed the main disaccharide units of glycosaminoglycans synthesized by cardiac myxoma cells in vivo and in cell culture using high-performance liquid chromatography after 1-phenyl-3-methyl-5-pyrasolone labeling. Cardiac myxoma tissues contained large amounts of chondroitin-6-sulfate (46%) and hyaluronic acid (32%), along with some chondroitin-4-sulfate (13%), chondroitin (6%), and much less dermatan sulfate (3%). Cultured cardiac myxoma cells synthesized mainly chondroitin-6-sulfate. The abundant glycosaminoglycans in myxoma tissues may make up the characteristic friable gelatinous matrix which is favorable for embolism and tumor cell growth.

Recently, variants in ATP-binding cassette transporter A1 (ABCA1) were demonstrated to be associated with increased level of high density lipoprotein cholesterol (HDL-C) and decreased risk of coronary artery disease (CAD) in Caucasians. However, this is not universally applicable due to the ethnic or environmental differences. In this context, to clarify the effect of ABCA1 in Japanese, we evaluated the phenotypic effects of I/M 823 and R/K 219 variants on the plasma level of HDL-C in 410 patients recruited in our hospital. Subjects with M 823 allele had significantly higher level of HDL-C than those without M823 allele (49.0+/-15.1 vs. 44.9+/-11.5 mg/dl, respectively, P<0.05). This statistical significance did not change even after multiple regression analysis. In contrast, there was no difference in HDL-C level among the genotypes in R/K 219 polymorphism. Further, in our study population an inverse relationship was shown to exist between HDL-C level and incidence of CAD. However, no positive association was observed between those variants and susceptibility to CAD. In this study, we provide evidence that I/M 823 variant, not R/K 219 variant, in ABCA1 is one of the determinants of HDL-C level, suggesting the importance of this gene on lipid metabolism in Japanese.

BACKGROUND: Insulin resistance is associated with atherosclerosis, but its mechanism is unknown. It has been reported that insulin receptor substrate (IRS)-1 deficient (IRS-1-/-) mice showed insulin resistance without type 2 diabetes, whereas the IRS-2 deficient (IRS-2-/-) mice showed insulin resistance with type 2 diabetes. METHODS AND RESULTS: We investigated neointima formation in the IRS-1-/- and IRS-2-/- mice at 8 and 20 weeks. The IRS-2-/- mice showed much greater neointima formation than the IRS-1-/- and wild-type mice at 8 weeks. At 20 weeks, the IRS-2-/- mice had greater neointima formation than the IRS-1-/- mice, which showed more enhanced neointima formation than the wild-type mice. The IRS-1-/- and IRS-2-/- mice had dyslipidemia, hypertension, and insulin resistance. The IRS-2-/- mice had more metabolic abnormalities than the IRS-1-/- mice at 8 and 20 weeks. IRS-2 expression was detected, but IRS-1 expression was not detected in the vessels. CONCLUSIONS: The neointima formation in the IRS-1-/- and IRS-2-/- mice appears to be related to abnormalities induced by the altered metabolic milieu in insulin-resistant states. Moreover, because neointima formation was much greater in the IRS-2-/- mice than in the IRS-1-/- mice at 8 and 20 weeks, it is suggested that a lack of IRS-2 renders the vasculature more susceptible to injury in the abnormal metabolic milieu, and IRS-2 may have a protective effect on neointima formation. We conclude that IRS-2 is protective and retards the development of neointima formation in insulin-resistant states.

Expression of adrenomedullin, discovered as a vasodilatory peptide, is markedly up-regulated under pathological conditions such as tissue ischemia and inflammation, which are associated with neovascularization. Here, we tested the hypothesis that overly expressed adrenomedullin may augment collateral flow to ischemic tissues. We induced hindlimb ischemia in wild-type mice and injected a naked plasmid expressing human adrenomedullin or an empty vector into the ischemic muscle, followed by in vivo electroporation. Adrenomedullin markedly enhanced blood flow recovery as determined by Laser Doppler imaging. The mice treated with an empty vector suffered frequent autoamputation of the ischemic toe, which was completely prevented by adrenomedullin. Anti-CD31 immunostaining revealed that adrenomedullin significantly increased capillary density. The angiogenic effect of adrenomedullin was abrogated in endothelial nitric oxide synthase (eNOS)-deficient mice. These results indicate that adrenomedullin may promote collateral growth in response to ischemia through activation of eNOS.

Cardiomyocyte hypertrophy is observed in various cardiovascular diseases and causes heart failure. We here examined the role of small GTP-binding proteins of Rho family in phenylephrine (PE)-or leukocyte inhibitory factor (LIF)-induced hypertrophic morphogenesis of cultured neonatal rat cardiomyocytes. Both LIF and PE increased cell size of cardiomyocytes. LIF induced an increase in the length/width ratio of cardiomyocytes, while PE did not change the ratio. Adenoviral gene transfer of constitutively active mutants of Cdc42 increased the length/width ratio of cardiomyocytes and dominant negative mutants of Cdc42 conversely inhibited LIF-induced cell-elongation, while mutants of RhoA and Rac1 did not affect the length/width ratio of cardiomyocytes. These results suggest that Cdc42, but not RhoA and Rac1, is involved in LIF-induced sarcomere assembly in series in cardiomyocytes.

To examine the physiological role of the histamine H(2) receptor, histamine H(2) receptor-null mice were generated by homologous recombination. Histamine H(2) receptor-null mice, which developed normally and were fertile and healthy into adulthood, exhibited markedly enlarged stomachs and marked hypergastrinemia. The former was due to hyperplasia of gastric gland cells (small-sized parietal cells, enterochromaffin-like cells and mucous neck cells which were rich in mucin), but not of gastric surface mucous cells, which were not increased in number as compared with those in wild-type mice despite the marked hypergastrinemia. Basal gastric pH was slightly but significantly higher in histamine H(2) receptor-null mice. Although carbachol but not gastrin induced in vivo gastric acid production in histamine H(2) receptor-null mice, gastric pH was elevated by both muscarinic M(3) and gastrin antagonists. Thus, both gastrin and muscarinic receptors appear to be directly involved in maintaining gastric pH in histamine H(2) receptor-null mice. Interestingly, gastric glands from wild-type mice treated with an extremely high dose of subcutaneous lansoprazole (10 mg/kg body weight) for 3 months were very similar to those from histamine H(2) receptor-null mice. Except for hyperplasia of gastric surface mucous cells, the findings for gastric glands from lansoprazole-treated wild-type mice were almost identical to those from gastric glands from histamine H(2) receptor-null mice. Therefore, it is possible that the abnormal gastric glands in histamine H(2) receptor-null mice are secondary to the severe impairment of gastric acid production, induced by the histamine H(2) receptor disruption causing marked hypergastrinemia. Analyses of the central nervous system (CNS) of histamine H(2) receptor-null mice revealed these mice to be different from wild-type mice in terms of spontaneous locomotor activity and higher thresholds for electrically induced convulsions. Taken together, these results suggest that (1) gastrin receptors are functional in parietal cells in histamine H(2) receptor-null mice, (2) abnormal gastric glands in histamine H(2) receptor-null mice may be secondary to severe impairment of gastric acid production and secretion and (3) histamine H(2) receptors are functional in the central nervous system.

Deficiency of protein S causes potential problems of thrombosis. Cases of familial venous thrombosis due to deficiency of protein S were presented. First, an 85-year-old woman had pulmonary thromboembolism due to left deep femoral venous thrombosis, which might be triggered by leg fracture and the long-term treatment with a plaster cast. Next, her 29-year-old granddaughter had episodes of recurrent venous thrombosis in her legs and arms, which might be triggered by the treatment with a plaster cast and abortion. In the latter part, the aspects of risks for thromboembolism, potential problems in gestational period, and an advisability of thromboprophylaxis in patients with deficiency of protein S are described.

BACKGROUND & AIMS: Peroxisome proliferator-activated receptor gamma (PPAR gamma) is one of the nuclear receptors that plays a central role in adipocyte differentiation and insulin sensitivity. PPAR gamma has also recently been recognized as an endogenous regulator of intestinal inflammation. However, its levels are decreased during chronic inflammation in human and mice, thus limiting PPAR gamma ligand therapy during established disease. We sought to determine whether this decrease in PPAR gamma could be counteracted by a gene therapy approach. METHODS: We characterized PPAR gamma levels in experimental colitis associated with dextran sodium sulfate administration to mice. In this model, the therapeutic benefits of PPAR gamma gene therapy using a replication-deficient adenovirus vector expressing PPAR gamma (Ad-PPAR gamma) was assessed. RESULTS: PPAR gamma protein levels were decreased in whole colonic tissue, lamina propria lymphocytes, and peritoneal exudate cells during the course of colitis. PPAR gamma gene delivery using Ad-PPAR gamma restored responsiveness to a PPAR gamma ligand, resulting in marked amelioration of tissue inflammation associated with the colitis, which included attenuation of intercellular adhesion molecule-1, cyclooxygenase-2 and tumor necrosis factor-alpha expression. CONCLUSIONS: Our results suggest that gene delivery of PPAR gamma can be used to restore and/or enhance endogenous anti-inflammatory processes that are normally operative in mammalian tissues such as in the colon.

Differentiated smooth muscle cells (SMCs) remain highly plastic, enabling them to alter their phenotype in response to environmental and pathologic stimuli. SMCs in vascular pathologies such as atherosclerosis exhibit phenotypes clearly different from those of the mature cells in normal blood vessels. These phenotypically modulated SMCs play an integral role in the development of vascular diseases. This review addresses recent progress in our understanding of the mechanisms that control SMC phenotype during vascular development and in vascular disease. A particular focus is on the transcriptional control programs of the differentiated state of SMCs.

Advanced glycation end products (AGEs) are nonenzymatically glycosylated proteins, which accumulate in vascular tissues in aging and diabetes. Receptors for AGEs include scavenger receptors, which recognize acetylated low density lipoproteins (Ac-LDL) such as scavenger receptor class AI/AII (SR-A), cell surface glycoprotein CD36, scavenger receptor class B type I (SRBI), and lectin-like oxidized low density lipoprotein receptor-1. The broad ligand repertoire of these receptors as well as the diversity of the receptors for AGEs have prompted us to examine whether AGEs are also recognized by the novel scavenger receptors, which we have recently isolated from a cDNA library prepared from human umbilical vein endothelial cells, such as the scavenger receptor expressed by endothelial cells-I (SREC-I); the fasciclin EGF-like, laminin-type EGF-like, and link domain-containing scavenger receptor-1 (FEEL-1); and its paralogous protein, FEEL-2. At 4 degreesC, I-125-AGE-bovine serum albumin (BSA) exhibited high affinity specific binding to Chinese hamster ovary (CHO) cells overexpressing FEEL-1 (CHO-FEEL-1) and FEEL-2 (CHO-FEEL-2) with K-d of 2.55 and 1.68 mug/ml, respectively, but not to CHO cells expressing SREC (CHO-SREC) and parent CHO cells. At 37 degreesC, I-125-AGE-BSA was taken up and degraded by CHO-FEEL-1 and CHO-FEEL-2 cells but not by CHO-SREC and parent CHO cells. Thus, the ability to bind Ac-LDL is not necessarily a prerequisite to bind AGEs. The I-125-AGE-BSA binding to CHO-FEEL-1 and CHO-FEEL-2 cells was effectively inhibited by Ac-LDL and polyanionic SR-A inhibitors such as fucoidan, polyinosinic acids, and dextran sulfate but not by native LDL, oxidized LDL, or HDL. FEEL-1, which is expressed by the liver and vascular tissues, may recognize AGEs, thereby contributing to the development of diabetic vascular complications and atherosclerosis.

The expression of inducible nitric oxide synthase (iNOS) and the resultant increased nitric oxide production are associated with endotoxemia and atherosclerotic lesions observed in transplant hearts or balloon-injured artery. Ursodeoxycholic acid has been shown to have cardiovascular protective effects, such as inhibition of the development of transplant arteriosclerosis, but its mechanism remains unclear. Here, we investigated the effects of ursodeoxycholic acid on nitric oxide production and the expression of iNOS in vascular smooth muscle cells isolated from adult rat aorta and rabbit coronary artery. Nitrite released from cells in the culture medium was measured with the Griess reaction. iNOS mRNA and protein were measured by Northern and Western blot analyses. Treatment with ursodeoxycholic acid (30-1000 microM) significantly inhibited lipopolysaccharide plus interferon-gamma-induced nitric oxide production in a concentration-dependent manner, but ursodeoxycholic acid showed only small inhibitory effects on nitric oxide production that had already been induced by lipopolysaccharide plus interferon-gamma. Ursodeoxycholic acid by itself did not affect basal nitric oxide production. Ursodeoxycholic acid also suppressed lipopolysaccharide plus interferon-gamma-induced expression of iNOS mRNA and protein. Ursodeoxycholic acid had the most potent inhibitory effect among various kinds of bile acids examined, i.e. chenodeoxycholic acid, deoxycholic acid, cholic acid and conjugated bile acids such as tauroursodeoxycholic acid. These results suggest that ursodeoxycholic acid inhibits the induction of iNOS and then nitric oxide production in aortic and coronary artery smooth muscle cells, suggesting a possible mechanism for the cardiovascular protective effect of ursodeoxycholic acid under various pathophysiological conditions such as endotoxemia and atherosclerosis.