Biomedical subjects
Kazuo Takeda
Publications and source records attributed to Kazuo Takeda.
[WHO/ISH 2003].
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Severe hyperparathyroidism with bone abnormalities and metastatic calcification in rats with adenine-induced uraemia.
BACKGROUND: Marked parathyroid hyperplasia with bone diseases and vascular calcification are unsolved issues in dialysis patients. In this study, we made azotemic model rats by adenine feeding and analyzed the development and progression of the abnormalities. METHODS: Renal failure was induced in 8-week-old male Wistar rats by feeding 0.75% adenine-containing diet for 6 weeks. Serum parameters, parathyroid hyperplasia, bone changes and metastatic calcification were examined at 2, 4 and 6 weeks. RESULTS: Progressive increase of serum creatinine and inorganic phosphate, and decreased levels of serum calcium and 1,25(OH)2D3 were confirmed. Markedly enlarged parathyroid glands and extremely high PTH levels were observed in all adenine-fed rats compared with the control (PTH: 199.3+/-58.0 vs 10.5+/-3.0 pmol/l, P<0.01, respectively, at 6 weeks). In cortical bone of the femur, the morphometric parameters showed increased bone resorption with increased fibrosis, whereas in the trabecular bone, bone resorption decreased and bone volume increased with a larger amount of osteoid compared with the control. Metastatic calcification in aorta, coronary artery and other soft tissues were also found in adenine-fed rats. CONCLUSIONS: Uraemic rats made by adenine diet developed severe abnormalities of calcium metabolism in a relatively short period and therefore they may serve as a useful model for the analysis of parathyroid hyperplasia and vascular calcification in chronic renal failure.
Involvement in K+ access of Leu318 at the extracellular domain flanking M3 and M4 of the Na+,K+-ATPase alpha-subunit.
The effect of point mutation in the sequence 316TWLE319, which occurs in the extracellular loop flanking the third (M3) and the fourth (M4) transmembrane segment (L3/4) of the Na+,K+-ATPase alpha-subunit, was examined. Mutation of Glu319 to Asp yielded an enzyme with full activity, whereas substituting Glu319 to Ala resulted in a severe loss of activity. A negative charge was introduced along the sequence, one residue at a time, from Thr316 to Leu318 (by E-scanning) in the mutant construct with Glu319 already mutated to Gln. The activity that had been reduced to 60% by the mutation of Glu319 to Gln was restored upon the introduction of a negative charge by E-scanning. When Leu318 was replaced by Glu in a series of scanning experiments, the K+ sensitivity of the ATPase activity was lowered. The lowering of K+ sensitivity was further demonstrated when a mutation of Leu318 to Glu was introduced into the wild-type enzyme. Furthermore, mutants with Leu318 to Gln, Arg, and Phe displayed lower K+ sensitivity similar to that of Leu318 to Glu mutant. Leu318 may be in access path for K+, and any substitution at this position may interfere with access of K+ from outside the cell.
Sarcoid granulomatous interstitial nephritis and sarcoid abdominal aortic aneurysms.
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Subunit composition and role of Na+,K+-ATPases in adrenal chromaffin cells.
Adrenal medullary (AM) cells are exposed to high concentrations of cortical hormones, one of which is a ouabain-like substance. Thus, the effects of ouabain on catecholamine secretion and distribution of Na+,K+-ATPase alpha and beta subunits in rat and guinea-pig AM cells were examined using amperometry and immunological techniques. While exposure to 1 microm ouabain did not have a marked effect on resting secretion, it induced an increase in secretion due to mobilization of Ca2+ ions that were stored during a 4 min interval between muscarine applications. Immunocytochemistry revealed that Na+,K+-ATPase alpha1 subunit-like and beta3 subunit-like immunoreactive (IR) materials were distributed ubiquitously at the cell periphery, whereas alpha2- and beta2-like IR materials were present in restricted parts of the cell periphery. The alpha1 and alpha2 subunits were mainly immunoprecipitated from AM preparations by anti-beta3 and anti-beta2 antisera, respectively. Peripheral BODIPY-FL-InsP3 binding sites were localized below membrane domains with alpha2- and beta2-like IR materials. The results indicate that in AM cells, alpha1beta3 isozymes of Na+,K+-ATPase were present ubiquitously in the plasma membrane, while alpha2beta2 isozymes were in the membrane domain closely associated with peripheral Ca2+ store sites. This close association of the alpha2beta2 isozyme with peripheral Ca2+ store sites may account for the facilitation of mobilization-dependent secretion in the presence of 1 microm ouabain.
Fe(II)/Cu(I)-dependent P-type ATPase activity in the liver of Long-Evans cinnamon rats.
This study examined Fe(II)-dependent ATPase activity in OTG (octylthioglucoside) -treated microsomes isolated from Wistar and LEC rats. The ATPase activity of the liver OTG-microsomes from Wistar rats increased sharply in the 5-150 microM range of Fe(II) with a K0.5 value of 23.9+/-3.6 microM, while the activity of LEC rat liver microsomes increased with increasing Fe(II) up to 500 microM with a K0.5 value of 64.4+/-8.1 microM. The K0.5 values for Fe(II)-dependent ATPase activity of spleen OTG-microsomes were nearly identical at 59.3 microM in the Wistar rat and 63.7 microM in the LEC rats with a similar level of activity at each Fe(II) concentration in both strains of animals. These results indicated that there are two types of Fe(II)-dependent ATPase with different Fe(II) sensitivity, a high sensitive (H) and a low sensitive (L) type, and that the H-type activity was specific to the liver. The H-type activity was, however, deficient in the liver of LEC rats that accumulate copper and iron in hepatocytes as a result of mutations in the Wilson's disease protein (WNDP). On the basis of these results, together with the similarity in optimal conditions required for full activity of the enzyme, we conclude that the Fe(II)-dependent ATPase (H-type) and WNDP may be identical.
Low frequency regular exercise improves flow-mediated dilatation of subjects with mild hypertension.
Although exercise is recommended for the primary prevention of hypertension, and although it is generally known to have a beneficial effect on endothelial function, working individuals often find it difficult to maintain a consistent exercise regimen. In the present study, therefore, we examined the effects of infrequently performed exercise on flow-mediated dilatation (FMD), which is an index of endothelial function, in 15 subjects with hypertension (mild hypertensives) and 10 normotensive subjects (normotensives). All subjects performed mild bicycle exercise twice a week for 12 weeks. To assess the FMD, the diameter of the brachial artery was measured using ultrasound at baseline, during reactive hyperemia, and following sublingual administration of nitroglycerin. Measurement of these parameters was performed twice, at the beginning and the end of the exercise program. At the baseline, FMD was significantly lower in the mild hypertensives than in the normotensives. Nitroglycerin-mediated dilatation (NTG-D) was similar in the two groups. The exercise decreased blood pressure in the mild hypertensives, and increased high-density lipoprotein (HDL) cholesterol in both groups. The exercise improved FMD without altering NTG-D in the mild hypertensives, but did not result in any change in the normotensives. Multiple regression analysis revealed that the elevation in FMD was positively associated with changes in HDL cholesterol, and negatively associated with changes in plasma norepinephrine and systolic blood pressure. These findings suggest that regular exercise at a low frequency improves FMD, and thereby endothelial function, and lowers blood pressure in mild hypertensives.
Augmentation of pulse wave velocity precedes vascular structural changes of the aorta in rats treated with N(omega)-nitro-L-arginine methyl ester.
We examined the relationship between structural changes of the aorta and pulse wave velocity (PWV), and the effects of antihypertensive treatments on PWV in N(omega)-nitro-L-arginine methyl ester (L-NAME)-treated rats. Twelve-week-old Wistar-Kyoto (WKY) rats were divided into the following groups, all of which received drug treatment in their drinking water: an untreated control group (n = 36), an L-NAME-treated group (0.7 mg/ml) (n = 32), an L-NAME and angiotensin converting enzyme (ACE) inhibitor (ACEI)-treated group (imidapril: 0.4 mg/ml) (n = 8), and an L-NAME and hydralazine-treated group (0.2 mg/ml) (n = 10). PWV was measured at the same blood pressure (BP) level as in the control group and the wall-to-lumen ratio of the thoracic aorta was evaluated in all groups. In the L-NAME group, PWV increased compared with the value in the control group, at the same time that BP was increasing. After the third day of treatment, PWV was higher in the L-NAME group than in the control group after adjusting BP to the control level, while the wall-to-lumen ratios were equal between the two groups. After the first week of treatment, not only the adjusted PWV, but also the wall-to-lumen ratios were greater in the L-NAME group than in the control group. With administration of antihypertensive agents, both PWV and the thickening of the aortic wall were reduced, but there was no significant difference between the ACEI and hydralazine-treated groups. In conclusion, in a rat model of nitric oxide (NO) synthesis inhibition, the increase in PWV preceded the vascular structural changes, while antihypertensive treatment reduced both changes. There was no significant difference between treatments with ACEI and hydralazine in this model.
HMG-CoA reductase inhibitors up-regulate anti-aging klotho mRNA via RhoA inactivation in IMCD3 cells.
OBJECTIVE: Klotho is thought to play a critical role in the development of age-related disorders including arteriosclerosis. Statins may exert vascular protective effects, independent of the lowering of plasma cholesterol levels. We investigated the impact of statins on mRNA expression of the age-suppressor gene, klotho in mIMCD3 cells. METHODS AND RESULTS: Klotho mRNA levels were evaluated with real-time RT-PCR. Atorvastatin and pitavastatin increased the expression of klotho mRNA in a dose-dependent manner. This stimulatory effect was abolished by the addition of mevalonate, GGPP and FPP, essential molecules for isoprenylation of the small GTPase Rho. As was the case with the statin treatment, inhibition of Rho-kinase by Y27632 up-regulated klotho mRNA. In contrast to the statin treatment, stimulation with angiotensin II down-regulated klotho mRNA expression without obvious morphological changes. Furthermore, pretreatment with atorvastatin blunted the angiotensin II-induced response and ameliorated the decrease in klotho mRNA expression towards basal levels. RhoA activity was further evaluated by detection of its translocation. Angiotensin II activated RhoA, whereas statins potently inactivated RhoA and blocked RhoA activation by angiotensin II. CONCLUSION: Statins inactivate the RhoA pathway, resulting in over-expression of klotho mRNA, which may contribute to the novel pleiotropic effects of statins towards vascular protection.
Effects of angiotensin II type 1 receptor antagonist on pressor responses to pulsatile compression of the rostral ventrolateral medulla in rats.
The rostral ventrolateral medulla (RVLM) is known to be a major center regulating sympathetic and cardiovascular activities. A possible association between neurovascular compression of the RVLM and essential hypertension has been indicated. The present study was performed to determine the role of angiotensin II (AngII) in the pressor and sympathetic responses to pulsatile compression of the RVLM. To determine the role of glutamate and AngII in the RVLM, L-glutamate (Glu) 2 nmol or AngII 100 pmol was injected into the RVLM with or without RVLM pretreatment of kynurenate (Glu receptor antagonist) 3nmol, candesartan (AngII type 1 (AT1) receptor antagonist) 2 nmol, or PD123319 (AngII type 2 (AT2) receptor antagonist) 1 nmol in anesthetized Wistar rats. In addition, to determine the role of glutamate and AngII in the pressor and sympathetic effects to the RVLM compression, kynurenate, candesartan, or PD123319 was locally injected before pulsatile compression of the RVLM. Finally, to determine the effects of peripherally administered AngII antagonists in these pressor and sympathetic excitatory responses, candesartan 0.25 micromol or PD123319 0.05 micromol was intravenously injected before pulsatile compression of the RVLM. Glu injected into the RVLM significantly increased mean arterial pressure (MAP) and splanchnic sympathetic nerve activity (SNA), and these effects were reduced by RVLM pretreatment with kynurenate, but were unaffected by candesartan or PD123319. AngII injected into the RVLM and pulsatile compression of the RVLM also increased MAP and SNA. However, in contrast with Glu injections, these effects were reduced by RVLM pretreatment with candesartan or kynurenate, but were unaffected by PD123319. Pressor and sympathetic excitatory responses to RVLM compression were reduced by intravenous pretreatment with candesartan but not with PD123319. These results indicate that, upon pulsatile compression of the RVLM, AngII may activate RVLM neurons via AT1 receptors and stimulate Glu release to thereby elicit sympathetic activation and pressor effects. Candesartan may exert its hypotensive effect at least in part by affecting the RVLM neurons to reduce sympathetic outflow induced by pulsatile compression of the RVLM.
[Pulse wave velocity(PWV)].
Brachial-ankle pulse wave velocity(baPWV) is a noninvasive and simple method of measuring arterial stiffness and an independent predictor of cardiovascular mortality in some lifestyle-related diseases. We evaluated that baPWV is well correlated with many atherosclerotic risk factors including abdominal visceral obesity and HOMA, and that the accumulation of these risk factors increases baPWV. The promotion of exercise and nutrition education for metabolic syndrome patients improves not only each risk factor but also baPWV. Multiple linear regression analysis demonstrated that baPWV is improved by decreases in SBP and BMI through several lifestyle modifications. Reversibility of baPWV suggests that vessel damage is not so serious and may be only endothelial dysfunction. Therefore baPWV should be monitored and ameliorated in treating metabolic syndrome.
[Case of non-Hodgkin lymphoma with acute renal failure successfully treated with chemotherapy].
We report a case of non-Hodgkin lymphoma (NHL) with acute renal failure. A 62-year-old man was admitted to our hospital on March 8, 2002 with leg edema and dyspnea on effort. About 3 weeks before admission, he was found to have slightly high serum creatinine (Cr) and high lactate dehydrogenase (LDH) levels by another home doctor. Physical examination revealed anemic conjunctivae and leg edema, but the urinary volume was preserved. Blood examination showed high BUN (64 mg/dl) and Cr levels (3.91 mg/dl). Urinary analysis showed proteinuria (1.05 g/day) and high BMG (14,434/microg/day) and NAG (4.55 U/day) levels, suggesting severe tubulointerstitial injury. On ultrasonography of the kidney, the bilateral kidneys showed marked swelling without hydronephrosis. To investigate the genesis of renal failure, we performed a renal biopsy. The specimen showed normal glomeruli, but a large number of cells infiltrated in the tubulointerstitial area with normal tubulointerstitial structure. The cells stained positively with anti-leukocyte antigen and L26 (B cell marker), and negatively with cytokeratin and UCHL-1 (T cell marker). These findings indicate that the interstitial cells were non-Hodgkin lymphoma with B cell diffuse large cells. Chemotherapy was performed with VAD (vincristine sulfate, doxorubicin hydrochloride, dexamethasone) considering his renal dysfunction. To avoid tumor lysis syndrome after chemotherapy, hemodialysis was performed on days 1-4 after the initiation of chemotherapy. After a series of chemotherapy, the urinary volume increased and serum Cr levels decreased to 2 mg/dl. After additional therapy with 4 courses of CHOP, he improved and was discharged on day 180 after admission.
Functional role of the N-terminus of Na(+),K(+)-ATPase alpha-subunit as an inactivation gate of palytoxin-induced pump channel.
The N-terminus of the Na(+),K(+)-ATPase alpha-subunit shows some homology to that of Shaker-B K(+) channels; the latter has been shown to mediate the N-type channel inactivation in a ball-and-chain mechanism. When the Torpedo Na(+),K(+)-ATPase is expressed in Xenopus oocytes and the pump is transformed into an ion channel with palytoxin (PTX), the channel exhibits a time-dependent inactivation gating at positive potentials. The inactivation gating is eliminated when the N-terminus is truncated by deleting the first 35 amino acids after the initial methionine. The inactivation gating is restored when a synthetic N-terminal peptide is applied to the truncated pumps at the intracellular surface. Truncated pumps generate no electrogenic current and exhibit an altered stoichiometry for active transport. Thus, the N-terminus of the alpha-subunit appears to act like an inactivation gate and performs a critical step in the Na(+),K(+)-ATPase pumping function.
HMG-CoA reductase inhibitor enhances inducible nitric oxide synthase expression in rat vascular smooth muscle cells; involvement of the Rho/Rho kinase pathway.
Little is known about the mechanism by which HMG-CoA reductase inhibitors affect inducible nitric oxide synthase (iNOS) expression. We investigated the effect of HMG-CoA reductase inhibitor cerivastatin on iNOS expression in cultured rat vascular smooth muscle cells (VSMCs). Quiescent VSMCs were incubated with or without various concentrations of drugs as follows: cerivastatin, C3 exoenzyme or Y-27632. Then, pretreated VSMCs were stimulated by a vehicle or interleukin (IL)-1beta (10 ng/ml). Treatment of VSMCs with cerivastatin (10(-7)-10(-5) mol/l), which inhibits isoprenylation of Rho and other small G proteins, significantly increased nitrite/nitrate (NOx) production and upregulated the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. This effect of cerivastatin was abolished by cotreatment with mevalonate (2x10(-4) mol/l) or geranylgeranyl-pyrophosphate (GGPP) (10(-5) mol/l), but not by farnesyl-pyrophosphate (10(-5) mol/l). Furthermore, C3 exoenzyme (50 microg/ml), an inactivator of Rho protein, and Rho kinase inhibitor Y-27632 (10(-5) mol/l) also enhanced NOx production and the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. Immunocytochemical study revealed that cerivastatin, C3 exoenzyme and Y-27632 did not affect the nuclear translocation of nuclear factor-kappaB in IL-1beta-stimulated VSMCs. Our study suggests that cerivastatin stimulates iNOS expression in IL-1beta treated VSMCs by its inhibitory effect on Rho/Rho kinase pathway. In addition, this effect of cerivastatin, by enhancing iNOS expression, may contribute to the prevention of restenosis after percutaneous coronary intervention and protect against atherothrombosis.
Candesartan Antihypertensive Survival Evaluation in Japan (CASE-J) trial of cardiovascular events in high-risk hypertensive patients: rationale, design, and methods.
Hypertension continues to be a major public health issue in the world. To combat this problem, many anti-hypertensive drugs have been developed and proven effective at controlling blood pressure in the last half century. In recent decades, antihypertensive drugs have been shown to have cardiovascular benefits beyond the reduction of blood pressure, and the focus has shifted to clarification of these effects. Angiotensin II receptor antagonists and calcium channel blockers are the most widely used antihypertensive drugs in Japan. However, these two classes of drugs have not yet been compared with respect to their efficacy for treating cardiovascular events. The Candesartan Antihypertensive Survival Evaluation in Japan (CASE-J) trial described herein is a prospective, multicenter, randomized, open-label, active-controlled, 2-arm parallel group comparison with a response-dependent dose titration and blinded assessment of endpoints in high-risk hypertensive patients treated with either an angiotensin II receptor antagonist (candesartan cilexetil) or a third-generation calcium channel blocker (amlodipine besilate). The eligibility criteria in this study were 1) age between 20 and 85 years; 2) systolic blood pressure (SBP) > or = 140 mmHg in those below 70 years of age or > or = 160 mmHg in those above 70 years of age or diastolic blood pressure (DBP) > or = 90 mmHg on two consecutive measurements at clinic; and 3) at least one of the following high risk factors for cardiovascular events: a) SBP > or = 2180 mmHg or DBP > or = 110 mmHg on two consecutive visits, b) type 2 diabetes mellitus (fasting blood glucose > or = 126 mg/dl, casual blood glucose > or = 200 mg/dl, HbA1c > or = 6.5%, 2 h blood glucose on 75 g oral glucose tolerance test (OGTT) > or = 200 mg/dl, or current treatment with hypoglycemic therapy), c) history of cerebral hemorrhage, cerebral infarction, or transient ischemic attack until 6 months prior to the screening, d) left ventricular hypertrophy on either echocardiography or ECG, angina pectoris, or history of myocardial infarction until 6 months prior to screening, e) proteinuria or serum creatinine > or = 1.3 mg/dl, and f) symptoms of arteriosclerotic artery obstruction. The therapeutic goals of blood pressure control were set as follows: SBP < 130 mmHg and DBP < 85 mmHg for patients below 60 years of age, SBP < 140 mmHg and DBP < 90 mmHg for those in their 60s, SBP < 150 mmHg and DBP < 90 mmHg for those in their 70s, and SBP < 160 mmHg and DBP < 90 mmHg for those in their 80s. A total of 3,200 patients, equally allocated to each of the two treatment arms, were required based on a two-sided alpha level 0.05 and 90% power. The CASE-J is also the first study to employ the newly developed Automatic Bar Code Data-Capturing/Allocation, Booking & Trial Coding, Data Management (ABCD) system for data collection and management. Enrollment of patients started in September 2001 and ended in December 2002. Follow-up data will be collected every 6 months until December 2005. The CASE-J trial will provide important evidence on the comparative effectiveness of candesartan cilexetil and amlodipine besilate on cardiovascular morbidity and mortality among Japanese. In addition, the use of the ABCD system is expected to contribute to the development of more efficient data management systems for large-scale clinical trials.
[Intravascular ultrasound imaging of the renal artery in patients with renovascular hypertension caused by neurofibromatosis 1].
A 26-year-old woman with neurofibromatosis 1 was admitted to our hospital for investigation of prolonged hypertension after toxemia of pregnancy. Plasma renin activity was elevated. From the renogram, stenosis of right renal artery was suspected and we performed renal arteriography, which revealed proximal right renal artery stenosis. The intravascular ultrasound (IVUS) image showed concentric stenosis with intimal and medial hypertrophy, which was iso-echoic and partly high echoic. Percutaneous transluminal renal angioplasty was performed and the lesion was well dilated. After angioplasty, blood pressure normalized in a week. From the clinical course and the IVUS image, we suspected that renal artery stenosis was due to neurofibromatosis 1.
Monomeric sarcoplasmic reticulum Ca(2+)-ATPase is functionally active.
cRNAs for wild type and a functionless mutant of sarcoplasmic reticulum (SR) Ca(2+)-ATPase were co-injected into Xenopus oocytes in various molar ratios. SR Ca(2+)-ATPase activity of the microsomal fraction prepared from the injected oocytes increased linearly with increasing amounts of wild type cRNA. This result suggests that monomers are functional units of membrane-bound SR Ca(2+)-ATPase.