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In 2019, a nationwide questionnaire survey on the management of chronic kidney disease (CKD) was circulated to general practitioners (GPs) throughout Japan by The Japan Physicians Association. The aim was to assess the current state of CKD medical care in the country and evaluate the utilization of CKD-specific guidelines in the treatment by GPs. The voluntary survey targeted all members of Japan Physicians Association, a nationwide organization consisting primarily of 15,000 GPs in clinics throughout the country. GPs were divided into groups: 171 GPs using and 414 GPs not using the guidelines. Comparisons between the groups' responses were made using propensity score matching and component cluster analysis. Overall responses revealed that the estimated glomerular filtration rate's utilization rate was high (95.1%). However, evidence-practice gaps in urine protein quantification and anemia remedy were prominent. There were significantly favorable answers in terms of CKD management in the user group compared with those in the non-user group, except for the questions about a urine check at the first visit, stopping the use of renin-angiotensin system inhibitors, and the target blood pressure for elderly CKD patients. The differences suggest that utilization of the CKD guidelines has improved CKD management practices by GPs. Further promotion of CKD guidelines utilization (28% in this survey) is considered valid for CKD medical education.

Background Pleuroperitoneal communication is a potential complication of peritoneal dialysis (PD). Of the various treatment strategies for pleuroperitoneal communication, successful treatment with pleurodesis using autologous blood has rarely been reported. Case presentation A 58-year-old man with end-stage kidney disease secondary to diabetic nephropathy and severe heart failure was placed on PD. He developed right-sided hydrothorax after the commencement of PD. Technetium-99m macro-aggregated human serum albumin peritoneal scintigraphy revealed pleuroperitoneal communication. PD was temporarily discontinued and substituted with hemodialysis. Subsequently, the levels of pleural fluid decreased. However, the resumption of PD exacerbated the hydrothorax. After thoracentesis, 50 mL of autologous blood was instilled into the right pleural cavity. There were no complications related to the procedure. PD was reinitiated 5 days after pleurodesis. Repeated chest X-rays did not depict any evidence of recurrent hydrothorax over the subsequent 10 months. Conclusions Pleurodesis using autologous blood was effective for pleuroperitoneal communication and was evidently safe in our patient. It should be considered in patients with severe heart failure since it is minimally invasive.

Objective: Peroxisome proliferator–activated receptor (PPAR)-γ ligand, pioglitazone (PIO), is reported to induce edema especially in postmenopausal women. The aim of this study was to elucidate the mechanism for PIO-induced sodium retention and to discover the therapeutic strategy for the PIO-induced changes in renal sodium handling. Methods and Procedures: Zucker obese rats were ovariectomized and were given PIO for 8 weeks. Renal sodium excretion and renal expressions of several enzymes that generate natriuretic substances were examined. Results: Sodium excretion was decreased in ovariectomized (OVX) rats that were given PIO when compared with OVX rats that were not. Urinary nitrites/nitrates excretion was decreased in OVX rats, but was restored by PIO. The expressions of nitric oxide synthases (NOSs) and cyclooxygenases-1/2 (COX-1/2) were unaltered. Similarly, the expression of epithelial sodium channels (ENaC), identified as a PPAR-γ-regulated gene product, was unaffected. In contrast, the expression of cytochrome P450 4A (CYP4A) was increased in OVX rats, and was downregulated by PIO. Co-treatment of OVX rats with PIO and PPAR-α ligand, fenofibrate, a putative inducer of CYP4A, restored not only the impaired sodium excretion but also the downregulated CYP4A expression. Discussion: PIO-induced sodium retention is specific in female OVX rats. Ovariectomy decreases renal NO production, but upregulates renal CYP4A expression to compensate for renal sodium balance. In this setting, PIO downregulates CYP4A, leading to sodium retention. Furthermore, PPAR-α ligands can provide a novel strategy for preventing the PIO-induced sodium retention.

Cardiovascular events are accelerated in chronic kidney disease (CKD). Although deranged nitric oxide (NO) pathways and asymmetric dimethylarginine (ADMA) cause endothelial dysfunction, no direct evidence for coronary artery endothelial dysfunction in CKD has been documented. CKD was induced in male dogs by heminephrectomy (1/2Nx) or five-sixths nephrectomy (5/6Nx). After 4 wk, renal ablation reduced GFR (control 76 [54 to 85]; 1/2Nx 38 [29 to 47]; 5/6Nx 15 [12 to 46] ml/min) and elevated plasma ADMA (control 1.88 [1.68 to 2.54]; 1/2Nx 2.51 [2.11 to 3.55]; 5/6Nx 3.84 [2.16 to 3.95] micromol/L). Coronary circulatory responses to acetylcholine revealed marked increases in coronary blood flow in control group (83 +/- 17% increment) but blunted responses in 1/2Nx (34 +/- 8% increment) and 5/6Nx (20 +/- 4% increment). The acetylcholine-induced changes in epicardial arteriolar diameter, using needle-lens probe charge-coupled device videomicroscopy, showed similar results. The responsiveness to sodium nitroprusside did not differ among three groups. Plasma nitrite/nitrate levels decreased in 1/2Nx and 5/6Nx, and the mRNA expressions of dimethylarginine dimethylaminohydrolase-II (DDAH-II), ADMA-degrading enzyme, and endothelial NO synthase (eNOS) in coronary arteries were downregulated in 1/2Nx and 5/6Nx. Finally, 4-wk treatment with all-trans retinoic acid restored the impaired endothelium-dependent vasodilation and reversed the expression of eNOS but not DDAH-II. Coronary endothelial function is impaired in the early stage of CKD. The dysfunction is attributed to the downregulation of eNOS and/or DDAH-II in coronary arteries. Furthermore, the manipulation of NO pathways may constitute a therapeutic strategy for the prevention of coronary dysfunction in CKD.

Objectives— Dimethylarginie dimethylaminohydrolase (DDAH) is a degrading enzyme for asymmetrical dimethylarginine, an endogenous NO synthase inhibitor. The molecular mechanism for DDAH-induced vascular endothelial growth factor (VEGF) expression was examined. Methods and Results— Although the transfection of expression vectors for 2 isoforms of DDAH, DDAH1, or DDAH2 increased DDAH activity in bovine aortic endothelial cells and human umbilical vein endothelial cells, expression and secretion of VEGF were increased only in DDAH2-transfected cells. Knocking down the DDAH2 gene reduced VEGF production, and DDAH2 overexpression enhanced both proliferation and migration of endothelial cells. The VEGF promoter activity was increased by DDAH2 transfection, which was not blocked by an NO synthase (NOS) inhibitor but required the Sp1 sites. DDAH2 overexpression increased nuclear protein levels bound to Sp1 oligonucleotides in endothelial cells. Sp1 small interfering RNA blocked DDAH2-induced upregulation of VEGF. DDAH2 transfection increased nuclear and threonine-phosphorylation levels of Sp1 in a protein kinase A (PKA)–dependent manner. Protein–protein interaction between DDAH2 and PKA was enhanced in DDAH2-transfected cells. Conclusions— DDAH2 upregulated the expression of VEGF through Sp1-dependent and NO/NOS system-independent promoter activation. DDAH2-increased Sp1 DNA binding activity was PKA dependent. These mechanisms may provide a novel therapeutic strategy for VEGF-related vasculopathies such as atherosclerosis.

Background and aims We previously demonstrated that acetylcholine elicited nitric oxide-dependent sustained and endothelium-derived hyperpolarizing factor (EDHF)-dependent transient dilation of afferent arterioles. The present study examined whether free radicals interacted with nitric oxide-dependent and EDHF-dependent vasodilator mechanisms in renal microvessels of salt-sensitive hypertension, using the isolated perfused hydronephrotic kidney. Methods and results Following the pretreatment with indomethacin (100 micromol/L) with or without nitro- l-arginine methylester (100 micromol/L), the effect of acetylcholine on noradrenaline (0.3 micromol/L)-induced constriction was evaluated in kidneys from Dahl salt-sensitive and salt-resistant rats. Although acetylcholine (0.01-10 micromol/L) caused dose-dependent and sustained vasodilation of afferent arterioles, attenuated dilation was observed in Dahl salt-sensitive rats, compared with that in salt-resistant rats (58 +/- 4 vs 101 +/- 11% reversal at 10 micromol/L acetylcholine). In the presence of nitro- l-arginine methylester, acetylcholine elicited only transient dilation, with vasodilator response blunted in Dahl salt-sensitive rats (64 +/- 4 vs 100 +/- 9% reversal at 10 micromol/L acetylcholine). Furthermore, chronic (8-10 weeks) treatment with tempol caused partial restoration of acetylcholine (10 micromol/L)-induced sustained arteriolar dilation (71 +/- 3% reversal), but complete reversal of transient dilation (92 +/- 4% reversal). Finally, acute treatment with tempol not only improved the sustained component of the acetylcholine-induced dilation but also restored the impaired responsiveness of transient dilation in Dahl salt-sensitive rats. Conclusion Both sustained (nitric oxide-mediated) and transient (EDHF-mediated) components of acetylcholine-induced afferent arteriolar dilation were attenuated in Dahl salt-sensitive rats, which was attributed, in part, to enhanced free radical activity. A reversal of the sustained and transient vasodilation by the acute tempol treatment suggests possible interaction between free radicals and EDHF as well as increased bioavailability of nitric oxide.

Although multiple antihypertensive agents are required to control blood pressure (BP) in chronic renal disease, it remains undetermined whether the combination therapy with angiotensin receptor blockers (ARB) plus calcium antagonists or angiotensin-converting enzyme inhibitors (ACEI) confers more preferable action on renal disease than the ARB monotherapy. In the present study, we compared the effect of the combination therapy with ARB plus calcium antagonists/ACEI on proteinuria with that of the ARB monotherapy in chronic nondiabetic renal disease. At 1 month of the drug treatment, the candesartan monotherapy (n=19) reduced BP from 154+/-3/93+/-2 to 146+/-3/88+/-2 mmHg (P0.05), and a similar magnitude of BP reductions was observed with the combination therapy with candesartan plus ACEI/amlodipine (from 153+/-2/95+/-2 to 144+/-2/88+/-2 mmHg, P0.05, n=39). The depressor action of these therapies was sustained throughout the 12-month treatment. In contrast, the reduction in proteinuria was greater with the combination therapy (-52+/-3% at 12 months, n=39) than with the candesartan monotherapy (-25+/-3%, n=19), although the baseline values of proteinuria were nearly the same in the candesartan monotherapy group (1.74+/-0.22 g/day) and the combination therapy group (2.10+/-0.19 g/day, P0.2). Of note, the proteinuria-sparing effect did not differ between the candesartan+ACEI group and the candesartan+amlodipine group. In conclusion, the present study suggests more beneficial action of the combination therapy with ARB plus ACEI/amlodipine than the ARB monotherapy in nondiabetic renal disease. Since the reduction in BP was achieved to the same level, the distinct proteinuria-sparing action of these therapies is attributed to BP-independent mechanisms, which should vary depending on the agents used.

Although the angiotensin-converting enzyme (ACE) inhibitor-induced bradykinin enhances nitric oxide (NO) release, bradykinin may also stimulate the production of an additional vasodilator, endothelium-derived hyperpolarizing factor (EDHF). This study examined the role of EDHF in mediating the NO-independent action of ACE inhibitors in canine renal microcirculation in vivo. We used intravital CCD camera videomicroscopy that allowed direct visualization of renal microcirculation in superficial and juxtamedullary nephrons in an in vivo, in situ, and relatively intact setting. In the presence of E4177 (an angiotensin receptor blocker), cilazaprilat (30 μg/kg) had no effect on diameter of superficial afferent arterioles (Aff), but it increased renal contents of bradykinin and nitrate plus nitrite, and it elicited dilation of juxtamedullary Aff (from 24.0±0.2 to 28.2±0.8 μm), juxtamedullary efferent arterioles (Eff) (from 24.2±0.2 to 28.0±0.8 μm), and superficial Eff (from 18.2±0.2 to 19.7±0.2 μm). These changes in diameters were prevented by N α -adamantaneacetyl- d -Arg-[Hyp 3 ,Thi 5,8 ,D-Phe 7 ]bradykinin, a bradykinin receptor antagonist. The pretreatment with nitro- l -arginine methylester ( l -NAME) plus E4177 eliminated the dilator response of juxtamedullary/superficial Eff and the increase in renal nitrate plus nitrite levels induced by cilazaprilat. In contrast, in the presence of E4177+ l- NAME, cilazaprilat still caused 8%±3% dilation of juxtamedullary Aff, which was completely eliminated by proadifen, a cytochrome-P450 and K Ca channel blocker. Collectively, the ACE inhibitor exerts multiple vasodilator mechanisms, including the inhibition of angiotensin II formation; blockade of angiotensin II activity appears to be a dominant mechanism in superficial Aff, whereas the bradykinin-induced NO acts on superficial Eff and juxtamedullary Aff/Eff. Furthermore, a putative EDHF is an additional mechanism for the ACE inhibitor-induced vasodilation of juxtamedullary Aff in vivo.

We examined the role of free radicals in renal microvascular tone induced by various vasoactive stimuli. Isolated perfused rat hydronephrotic kidneys were used for direct visualization of renal microcirculation. The effect of tempol on angiotensin II-, norepinephrine-, KCl-, and pressure-induced afferent arteriolar constriction was evaluated. Under angiotensin II-induced constriction, tempol (3 mmol/L) caused 57 +/- 8% dilation of afferent arterioles. In contrast, tempol elicited only 38 +/- 8% and 26 +/- 9% dilation of norepinephrine- and KCl-induced constriction. Similarly, myogenic response induced by elevating renal arterial pressure from 80 to 180 mmHg was resistant to the vasodilator action of tempol (22 +/- 7% inhibition). Furthermore, tempol failed to reverse nitro-L-arginine methylester-induced afferent constriction, nor had vasodilator effect on the angiotensin II-induced constriction in the presence of nitro-L-arginine methylester. In contrast, nitroprusside elicited marked vasodilation of angiotensin II- (97 +/- 5% reversal) and norepinephrine-induced afferent constriction (89 +/- 6% reversal), but had less effect on KCl- (46 +/- 8% reversal) and pressure-induced constriction (26 +/- 9% reversal). These different actions were also observed when polyethylene-glycolated superoxide dismutase was used as an antioxidant. In conclusion, the role of free radicals in afferent arteriolar tone varies, depending on the underlying vasoconstrictor stimuli, with greater contribution of free radicals to angiotensin II-induced constriction. The heterogeneity in the responsiveness to free radical scavengers is attributed to both magnitude of free radicals produced and sensitivity of the underlying vasoconstrictors to nitric oxide.

Although nifedipine and other conventional calcium antagonists elicit preferential vasodilation of renal afferent arterioles, we demonstrate that mibefradil and nickel, T-type calcium channel blockers, reverse the angiotensin II-induced constriction of both afferent and efferent arterioles. Since the angiotensin II-induced vasoconstriction involves inositol trisphosphate (IP3)-induced calcium release from the sarcoplasmic reticulum in the afferent arteriole, and both IP3- and protein kinase C (PKC)-mediated pathways in the efferent arteriole, we investigated the cellular mechanism for the mibefradil-induced dilation of angiotensin II-constricted renal arterioles, using the isolated perfused hydronephrotic rat kidney. Mibefradil caused a dose-dependent dilation of angiotensin II-constricted afferent and efferent arterioles, with 88 ± 9% and 74 ± 10% reversal observed at 1 μmol/L, respectively. The blockade of PKC by staurosporine did not alter the mibefradil-induced vasodilator responses of either arterioles (P > 0.5). In contrast, the pretreatment with thapsigargin, which predominantly blocked the IP3-mediated intracellular calcium release, prevented the afferent arteriolar constrictor response to angiotensin II, but caused a significant constriction of efferent arterioles. The subsequent addition of mibefradil had no effect on the efferent arteriolar diameter. Furthermore, the efferent arteriolar constriction induced by direct PKC activation by phorbol myristate acetate was refractory to mibefradil, but completely reversed by LOE908, a nonselective cation channel blocker. In summary, mibefradil markedly dilates the angiotensin II-induced renal arteriolar constriction; the action of mibefradil is most likely mediated by the inhibition of the IP3-mediated pathway, but the inhibitory action on the PKC pathway appears modest.

It has becoming clear that angiotensin receptor blockers (ARBs) show varying levels of angiotensin II type 1 (AT1) receptor blocking activity. Although the duration of activity and the efficacy on blood pressure of ARB are reported to vary, depending on the agents used, it has not been examined whether the effects on proteinuria and urinary nitrite/nitrate (NOx) excretion differ in hypertensive patients with chronic renal disease. In the present study, patients with hypertension (140 and/or 90 mmHg) and chronic renal disease (proteinuria0.5g/day; serum creatinine265 micromol/l or creatinine clearance30 ml/min/1.72 m2) were randomly assigned to perindopril- (n = 15), trandolapril- (n = 15), candesartan- (n = 17), and losartan-treated groups (n = 15), and were followed up for 96 weeks. All agents decreased blood pressure to the same level, and none of them had any effect on creatinine clearance. Candesartan, perindopril, and trandolapril reduced proteinuria markedly (from 3.0 +/- 0.6 to 1.8 +/- 0.5 g/day, 2.7 +/- 0.5 to 1.6 +/- 0.4 g/day, and 2.7 +/- 0.5 to 1.7 +/- 0.4 g/day, respectively) at 12 weeks, and the beneficial effect persisted throughout the study. The effect of losartan, however, diminished over the study period. Whereas perindopril, trandolapril, and candesartan markedly increased urinary NOx excretion (from 257 +/- 23 to 1,011 +/- 150 micromol/day, 265 +/- 70 to 986 +/- 130 micromol/day, and 260 +/- 62 to 967 +/- 67 micromol/day at 12 weeks, respectively), a relatively blunted increase was observed with losartan (from 309 +/- 42 to 596 +/- 64 micromol/day). In conclusion, renal action of ARB varies, with relatively less proteinuria-sparing, as well as NOx-enhancing, effects observed with candesartan showing the greatest reduction of proteinuria and greatest enhancement of NOx. Furthermore, renal nitric oxide may contribute to the renal protective action of these agents when administered to patients with chronic renal disease.

Renal afferent arterioles (AFF) regulate glomerular capillary pressure through two main mechanisms: the myogenic response (MYO) and tubuloglomerular feedback (TGF). Because Rho-kinase and nitric oxide synthase (NOS) are established factors that modulate vascular tone, we examined the role of these factors in pressure-induced AFF tone in Wistar-Kyoto rats and in spontaneously hypertensive rats (SHR) using an intravital CCD camera. Elevated renal perfusion pressure elicited marked AFF constriction that was partially inhibited by gadolinium, furosemide and fasudil, which inhibit MYO, TGF and Rho-kinase, respectively; however, this AFF constriction was completely blocked by combined treatment with fasudil+gadolinium or fasudil+furosemide. S-methyl-L-thiocitrulline (SMTC) partially reversed the fasudil-induced inhibition of TGF-mediated, but not that of MYO-mediated, AFF constriction. In SHR, the pressure-induced AFF response was enhanced, and MYO- and TGF-induced constriction were exaggerated. In the presence of gadolinium, SMTC partially mitigated the fasudil-induced inhibition of TGF-mediated AFF constriction. Immunoblot analyses demonstrated that both Rho-kinase activity and neuronal NOS were augmented in SHR kidneys. In conclusion, Rho-kinase contributes to MYO- and TGF-mediated AFF responses, and these responses are enhanced in SHR. Furthermore, neuronal NOS-induced nitric oxide modulates the TGF mechanism. This mechanism constitutes a target for Rho-kinase in TGF-mediated AFF constriction.

Rho-kinase plays an important role in hypertension and is reported to interfere with insulin signaling through serine phosphorylation of insulin receptor substrate-1 (IRS-1) in cultured vascular smooth muscle cells. We therefore examined the role of Rho-kinase in the development of insulin resistance in Zucker obese rats. In skeletal muscles and aortic tissues of Zucker obese rats, activation of RhoA/Rho-kinase was observed. Long-term Rho-kinase inhibition by 4 wk treatment with fasudil (a Rho-kinase inhibitor) not only reduced blood pressure but corrected glucose and lipid metabolism, with improvement in serine phosphorylation of IRS-1 and insulin signaling in skeletal muscles. Direct visualization of skeletal muscle arterioles with an intravital CCD videomicroscope demonstrated that both acetylcholine- and sodium nitroprusside-induced vasodilations were blunted, which were restored by the fasudil treatment. Furthermore, both fasudil and Y-27632 prevented the serine phosphorylation of IRS-1 induced by insulin and/or tumor necrosis factor-alpha in skeletal muscle cells. Collectively, Rho-kinase is responsible for the impairment of insulin signaling and may constitute a critical mediator linking between metabolic and hemodynamic abnormalities in insulin resistance.

The development of obesity involves multiple mechanisms. Here, we identify adipocyte signaling through the guanosine triphosphatase Rho and its effector Rho-kinase as one such mechanism. Mice fed a high-fat diet (HFD) showed increased Rho-kinase activity in adipose tissue compared to mice fed a low-fat diet. Treatment with the Rho-kinase inhibitor fasudil attenuated weight gain and insulin resistance in mice on a HFD. Transgenic mice overexpressing an adipocyte-specific, dominant-negative form of RhoA (DN-RhoA TG mice) showed decreased Rho-kinase activity in adipocytes, decreased HFD-induced weight gain, and improved glucose metabolism compared to wild-type littermates. Furthermore, compared to HFD-fed wild-type littermates, DN-RhoA TG mice on a HFD showed decreased adipocyte hypertrophy, reduced macrophage recruitment to adipose tissue, and lower expression of mRNAs encoding various adipocytokines. Lipid accumulation in cultured adipocytes was associated with increased Rho-kinase activity and increased abundance of adipocytokine transcripts, which was reversed by a Rho-kinase inhibitor. Direct application of mechanical stretch to mature adipocytes increased Rho-kinase activity and stress fiber formation. Stress fiber formation, which was also observed in adipocytes from HFD-fed mice, was prevented by Rho-kinase inhibition and in DN-RhoA TG mice. Our findings indicate that lipid accumulation in adipocytes activates Rho to Rho-kinase (Rho-Rho-kinase) signaling at least in part through mechanical stretch and implicate Rho-Rho-kinase signaling in inflammatory changes in adipose tissue in obesity. Thus, inhibition of Rho-Rho-kinase signaling may provide a therapeutic strategy for disrupting a vicious cycle of adipocyte stretch, Rho-Rho-kinase signaling, and inflammation of adipose tissue that contributes to and aggravates obesity.

Sirt1, a NAD-dependent protein deacetylase, is reported to regulate intracellular metabolism and attenuate reactive oxidative species (ROS)-induced apoptosis leading to longevity and acute stress resistance. We created transgenic (TG) mice with kidney-specific overexpression of Sirt1 using the promoter sodium-phosphate cotransporter IIa (Npt2) driven specifically in proximal tubules and investigated the kidney-specific role of Sirt1 in the protection against acute kidney injury (AKI). We also elucidated the role of number or function of peroxisome and mitochondria in mediating the mechanisms for renal protective effects of Sirt1 in AKI. Cisplatin-induced AKI decreased the number and function of peroxisomes as well as mitochondria and led to increased local levels of ROS production and renal tubular apoptotic cells. TG mice treated with cisplatin mitigated AKI, local ROS, and renal tubular apoptotic tubular cells. Consistent with these results, TG mice treated with cisplatin also exhibited recovery of peroxisome number and function, as well as rescued mitochondrial function; however, mitochondrial number was not recovered. Immunoelectron microscopic findings consistently demonstrated that the decrease in peroxisome number by cisplatin in wild type mice was restored in transgenic mice. In HK-2 cells, a cultured proximal tubule cell line, overexpression of Sirt1 rescued the cisplatin-induced cell apoptosis through the restoration of peroxisome number, although the mitochondria number was not restored. These results indicate that Sirt1 overexpression in proximal tubules rescues cisplatin-induced AKI by maintaining peroxisomes number and function, concomitant up-regulation of catalase, and elimination of renal ROS levels. Renal Sirt1 can be a potential therapeutic target for the treatment of AKI.

NAD(+)-dependent protein deacetylase Sirt1 regulates cellular apoptosis. We examined the role of Sirt1 in renal tubular cell apoptosis by using HK-2 cells, proximal tubular cell lines with or without reactive oxygen species (ROS), H(2)O(2). Without any ROS, Sirt1 inhibitors enhanced apoptosis and the expression of ROS scavenger, catalase, and Sirt1 overexpression downregulated catalase. When apoptosis was induced with H(2)O(2), Sirt1 was upregulated with the concomitant increase in catalase expression. Sirt1 overexpression rescued H(2)O(2)-induced apoptosis through the upregulation of catalase. H(2)O(2) induced the nuclear accumulation of forkhead transcription factor, FoxO3a and the gene silencing of FoxO3a enhanced H(2)O(2)-induced apoptosis. In conclusion, endogenous Sirt1 maintains cell survival by regulating catalase expression and by preventing the depletion of ROS required for cell survival. In contrast, excess ROS upregulates Sirt1, which activates FoxO3a and catalase leading to rescuing apoptosis. Thus, Sirt1 constitutes a determinant of renal tubular cell apoptosis by regulating cellular ROS levels.

Dimethylarginie dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, and comprises 2 isoforms, DDAH1 and DDAH2. To investigate the in vivo role of DDAH2, we generated trangenic mice overexpressing DDAH2. The transgenic mice manifested reductions in plasma ADMA and elevations in cardiac NO levels but no changes in systemic blood pressure (SBP), compared with the wild-type mice. When infused into wild-type mice for 4 weeks, ADMA elevated SBP and caused marked medial thickening and perivascular fibrosis in coronary microvessels, which were accompanied by ACE protein upregulation and cardiac oxidative stress. The treatment with amlodipine reduced SBP but failed to ameliorate the ADMA-induced histological changes. In contrast, these changes were abolished in transgenic mice, with a reduction in plasma ADMA. In coronary artery endothelial cells, ADMA activated p38 MAP kinase and the ADMA-induced ACE upregulation was suppressed by p38 MAP kinase inhibition by SB203580. In wild-type mice, long-term treatment with angiotensin II increased plasma ADMA and cardiac oxidative stress and caused similar vascular injury. In transgenic mice, these changes were attenuated. The present study suggests that DDAH2/ADMA regulates cardiac NO levels but has modest effect on SBP in normal conditions. Under the circumstances where plasma ADMA are elevated, including angiotensin II–activated conditions, ADMA serves to contribute to the development of vascular injury and increased cardiac oxidative stress, and the overexpression of DDAH2 attenuates these abnormalities. Collectively, the DDAH2/ADMA pathway can be a novel therapeutic target for vasculopathy in the ADMA or angiotensin II–induced pathophysiological conditions.

Peroxisome proliferator activated receptor-gamma (PPARgamma) ligands increase nitric oxide (NO) production and reduce systemic blood pressure. Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase (NOS) inhibitor degraded by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which has two isoforms, DDAH-I and -II. In order to elucidate the mechanism whereby PPARgamma ligands affect NO metabolism, their effects on the DDAH-ADMA pathway were investigated. Six-week-old male Wister-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were maintained with or without pioglitazone (PIO), a PPARgamma ligand. After 4 weeks, serum ADMA levels and urinary daily NO excretion were analyzed. Tissue DDAH expression was examined by real-time polymerase chain reaction (PCR), immunoblotting, and immunohistochemistry. The results showed that PIO decreased serum ADMA and increased urinary NO excretion in both WKY and SHR. Also in both strains, the expression level of DDAH-II in the kidney was increased at transcriptional levels, although the DDAH-I level was unaffected. PIO lowered blood pressure in SHR, but not in WKY. We also demonstrated that PIO induced DDAH-II protein expression in Marbin-Dubin Canine Kidney (MDCK) cells, a renal tubular cell line. In conclusion, a PPARgamma ligand was here found to increase NO production partly by upregulating tissue DDAH-II expression and decreasing systemic ADMA levels. This mechanism constitutes a direct action on renal tubular cells, but is less likely to be responsible for the blood pressure-lowering effects of PPARgamma ligands. Since ADMA is one of the risk factors for cardiovascular events, this study provides compelling evidence that PPARgamma ligands have the potential for reducing cardiovascular risks.

The present study examined the role of L-/T-type Ca channels and the interaction between these channels and protein kinase C (PKC) in hypertension. The isolated perfused hydronephrotic rat kidney model was used to visualize directly the renal microvascular effects of L-/T-type Ca channel blockers (nifedipine and mibefradil, respectively). Nifedipine reversed the angiotensin II-induced constriction of afferent, but not efferent, arterioles in kidneys from Wistar-Kyoto rats (WKY), and similar magnitude in dilation was observed in spontaneously hypertensive rats (SHR). Although mibefradil elicited dilation of both arterioles, the afferent arteriolar dilation was less in SHR than in WKY (57+/-5% vs. 80+/-4% reversal at 1 micrommol/L). The pretreatment with staurosporine did not alter the angiotensin II-induced afferent arteriolar constriction in WKY, but attenuated this response in SHR. Furthermore, staurosporine enhanced the nifedipine-induced afferent arteriolar dilation (62+/-3% vs. 50+/-3% reversal at 10 nmol/L), and restored the attenuated afferent arteriolar response to mibefradil in SHR. The pretreatment with thapsigargin (a blocker of IP3-mediated intracellular calcium release) prevented the angiotensin II-induced afferent arteriolar constriction in WKY, but caused a significant constriction of afferent arterioles in SHR and efferent arterioles in WKY and SHR; in this setting, mibefradil did not alter efferent arteriolar tone. In conclusion, although both L-type (nifedipine) and T-type Ca channel blockers (mibefradil) exerted potent vasodilation of rat renal microvessels, these actions were modified by PKC, which determined the afferent arteriolar sensitivity to these blockers in SHR. Furthermore, the enhancement in nifedipine-induced afferent arteriolar dilation by staurosporine in SHR suggests that L-type Ca channel activity is augmented in hypertensive animals.

Angiotensin II enhances the development of atherosclerotic lesion in which cellular proliferation and/or migration are critical steps. Although cyclin-dependent kinase inhibitor, p27, and Rho/Rho-kinase pathway have recently been implicated as factors regulating these events cooperatively, their role in vivo has not been fully elucidated. We evaluated the contribution of p27 and Rho-kinase to angiotensin II-induced vascular injury using p27-deficient mice. Two-week angiotensin II (1500 ng/kg per minute SC) infusion elicited similar degrees of elevation in systolic blood pressure in wild-type mice (159±5 mm Hg) and p27-deficient mice (157±5 mm Hg; P >0.05). Angiotensin II infusion to wild-type mice resulted in increases in the medial thickness of aorta, proliferating cell number, and monocyte/macrophage infiltration within the vasculature. In p27-deficient mice, however, these changes were more prominent than those in wild-type mice. Treatment of wild-type mice with fasudil, a selective Rho-kinase inhibitor, did not alter blood pressure but significantly upregulated p27 expression, decreased medial thickness of aorta, reduced proliferating cell number, and prevented monocyte/macrophage infiltration. These protective effects of fasudil were attenuated in p27-deficient mice. In conclusion, p27 constitutes an important modulator of angiotensin II–induced monocyte/macrophage infiltration and vascular remodeling, which is mediated in part by Rho-kinase stimulation. Inhibition of Rho-kinase activity improves angiotensin II–induced vascular injury through p27-dependent and p27-independent mechanisms.

Although peroxisome proliferator-activated receptor γ (PPARγ) ligands have an antihypertensive effect in vivo, the precise mechanism has not been fully elucidated. We examined their effects on Rho/Rho kinase pathway, a key regulator of vascular tone. In cultured rat aortic smooth muscle cells (RASMC), Rho kinase stimulated by angiotensin II was suppressed by the pretreatment with pioglitazone and troglitazone, and these effects were explained by the inhibition of the Rho translocation to the cell membrane. We evaluated the role of Vav, a GTP/GDP exchange factor upregulating Rho kinase activity, and Src homology region 2–containing protein tyrosine phosphatase-2 (SHP-2), a protein tyrosine phosphatase that dephosphorylated Vav and subsequently inactivated Rho kinase. Both pioglitazone and troglitazone upregulated SHP-2, particularly in the cytosolic fraction, and the SHP-2-bound Vav, and reduced the phosphorylation of Vav. Furthermore, 4-week treatment with pioglitazone lowered systolic blood pressure in spontaneously hypertensive rats (SHR) and suppressed the Rho/Rho kinase activity in aortic tissues isolated from SHR. Consistently, the expression of SHP-2 was upregulated in vascular tissues from pioglitazone-treated SHR. The phosphorylated Vav was increased in SHR, compared with that in normotensive Wistar–Kyoto rats (WKY), which was mitigated by pioglitazone. Finally, both basal and angiotensin II–stimulated levels of Rho kinase activity were greater in RASMC from SHR than those from WKY, and the enhanced Rho kinase activity was blocked by pioglitazone or troglitazone in both strains. Collectively, PPARγ ligands inhibit the Rho/Rho kinase pathway through upregulation of cytosolic SHP-2 expression and inactivation of Vav, and may contribute to the hemodynamic, in addition to metabolic, action in hypertensive metabolic syndrome. The full text of this article is available online at http://circres.ahajournals.org.

Although available evidence demonstrates that obesity manifests insulin resistance and causes glomerular sclerosis, it has not been determined whether insulin resistance alters the renal microvascular reactivity. This study examined whether insulin- and acetylcholine (ACH)-induced vasodilation was impaired in Zucker obese rats, and attempted to clarify the change in myogenic afferent arteriolar constriction, a determinant of glomerular pressure. Isolated perfused hydronephrotic rat kidneys were used to visualize the renal microcirculation. In Zucker lean rats, insulin (10 to 300 [mu ]U/mL) inhibited norepinephrine (NE)-induced afferent and efferent arteriolar constriction in a dose-dependent manner, with 112 % [plusmn] 8% and 98% [plusmn] 8% reversal at 300 [mu ]U/mL Similarly, ACH elicited dose-dependent dilation of these vessels. In Zucker obese rats, by contrast, afferent and efferent arterioles failed to dilate in response to insulin, and manifested diminished vasodilator responses to acetylcholine In the presence of nitro- L -arginine methylester (LNAME; 100 [mu ]mol/L), ACH (10 [mu ]mol/L) induced transient afferent arteriolar dilation (121% [plusmn] 9% reversal) in Zucker lean rats, whereas this response was blunted in obese rats (72% [plusmn] 8% reversal) Furthermore, myogenic afferent arteriolar constriction by elevating renal arterial pressure to 180 mm Hg was diminished in Zucker obese rats ([minus ]14% [plusmn] 3% decrement in diameter), compared with that in lean rats ([minus ]23% [plusmn] 2% decrement) Finally, the impairment in these vasodilator and vasoconstrictor responses was partially prevented by troglitazone, an insulin-sensitizing agent. Collectively, in insulin resistance, renal microvessels are refractory to the vasodilator action of insulin. Furthermore, [ldquo ]renal insulin resistance[rdquo ] is associated with the impaired vasodilator responses to ACH-induced nitric oxide (NO) and the diminished vasoconstrictor responses to pressure. The blunted myogenic afferent arteriolar constriction would allow glomerular hypertension, and in concert with the impaired endothelium-dependent vasodilation, could be responsible for the development of glomerular injury in obesity.

The present study was undertaken to clarify the role of intrarenal angiotensin (Ang) II and its generating pathways in clipped and nonclipped kidneys of 4-week unilateral renal artery stenosis in anesthetized dogs. After 4 weeks, renal plasma flow (RPF) decreased in clipped and nonclipped kidneys (baseline, 59±3; clipped, 16±1; nonclipped, 44±2 mL/min; P P P 11 - d -Ala 12 ]Ang I (an inactive precursor that yields Ang II by chymase but not by ACE; 1 to 50 nmol/kg) markedly elevated intrarenal Ang II in clipped, but not in nonclipped, kidneys. In conclusion, renal Ang II contents were elevated in both clipped and nonclipped kidneys, which contributed to the altered renal hemodynamics and microvascular tone. Furthermore, the mechanisms for intrarenal Ang II generation differ, and chymase activity is enhanced in clipped kidneys, whereas ACE-mediated Ang II generation is possibly responsible for elevated Ang II contents in nonclipped kidneys.

Haemorrhagic diathesis develops in chronic renal failure, in which calcium antagonists are used widely as antihypertensive agents. Although calcium antagonists are reported to impair platelet function, it has not been examined whether calcium antagonists alter bleeding time. The present study was conducted to clarify whether calcium antagonists affect bleeding time in chronic renal failure. Patients with chronic renal failure without and with calcium antagonists were enrolled (n = 156), and bleeding time (Ivy's method) as well as blood parameters (BUN, creatinine, platelet counts, and haemoglobin) were compared in patients with normal and prolonged bleeding time. Among patients not taking calcium antagonists (n = 34), three cases manifested prolonged bleeding time, whereas abnormal bleeding time was observed in 31 patients out of 122. Positive correlations were observed between bleeding time and BUN in both calcium antagonist-untreated (r = 0.46) and -treated groups (r = 0.25). The odds ratio for prolongation of bleeding time in patients taking calcium antagonists was 3.52 (95% CI, 1.01-12.33). In 12 calcium antagonist-treated patients with prolonged bleeding time, the withdrawal of calcium antagonists markedly shortened bleeding time (from 11.3 +/- 0.8 to 5.4 +/- 0.8 min, P < 0.05, n = 12). In contrast, in the additional group (n = 9), the continued treatment with calcium antagonists had no effect on bleeding time (from 11.7 +/- 0.9 to 10.0 +/- 1.0 min). Despite the inhibitory effect of calcium antagonists on bleeding time, no clinically serious events associated with haemorrhagic diathesis developed. In conclusion, calcium antagonists prolong bleeding time in patients with chronic renal failure. The subclinical (laboratory) effect of calcium antagonists however is not necessarily associated with haemorrhagic events of clinical significance.