Naohiko Kobayashi

Cardioprotective Mechanism of Telmisartan via PPAR-γ-eNOS Pathway in Dahl Salt-Sensitive Hypertensive Rats

BACKGROUNDnRecently, some investigators have shown that telmisartan, an angiotensin II (Ang II)-receptor blocker (ARB), is a partial agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). We investigate whether telmisartan improves cardiovascular remodeling associated with the production of endothelial nitric oxide synthase (eNOS) through PPAR-gamma, inhibits the Rho-kinase pathway, and suppresses oxidative stress in Dahl salt-sensitive (DS) hypertensive rats.nnnMETHODSnTelmisartan (1 mg/kg per day) or telmisartan plus PPAR-gamma inhibitor, GW9662 (1 mg/kg per day) was administered from the age of 6-11 weeks. Age-matched male Dahl salt-resistant (DR) rats served as a control group.nnnRESULTSnThe levels of eNOS and PPAR-gamma expression, and eNOS phosphorylation were significantly lower in DS rats than in DR rats. Chronic telmisartan treatment in DS rats significantly increased these parameters, but not telmisartan plus GW9662. Telmisartan effectively inhibited the vascular lesion formation such as medial thickness and perivascular fibrosis, but not telmisartan plus GW9662. Moreover, upregulated RhoA protein, Rho-kinase mRNA, and myosin light-chain phosphorylation in DS rats was decreased by telmisartan to a similar degree as observed after treatment with Y-27632, a selective Rho-kinase inhibitor. In addition, NAD(P)H oxidase p22phox, p47phox, gp91phox expression, and mitogen-activated protein kinase and its downstream effector p70 S6 kinase phosphorylation in DS rats was also inhibited by telmisartan.nnnCONCLUSIONSnThese results suggest that the cardioprotective mechanism of telmisartan may be partly due to improvement of endothelial function associated with PPAR-gamma-eNOS, oxidative stress, and Rho-kinase pathway.

Complement 3 activates the renal renin-angiotensin system by induction of epithelial-to-mesenchymal transition of the nephrotubulus in mice

We have demonstrated that mesenchymal cells from spontaneously hypertensive rats genetically express complement 3 (C3). Mature tubular epithelial cells can undergo epithelial-to-mesenchymal transition (EMT) that is linked to the pathogenesis of renal fibrosis and injury. In this study, we investigated the contribution of C3 in EMT and in the renal renin-angiotensin (RA) systems associated with hypertension. C3a induced EMT in mouse TCMK-1 epithelial cells, which displayed increased expression of renin and Krüppel-like factor 5 (KLF5) and nuclear localization of liver X receptor α (LXRα). C3 and renin were strongly stained in the degenerated nephrotubulus and colocalized with LXRα and prorenin receptor in unilateral ureteral obstruction (UUO) kidneys from wild-type mice. In C3-deficient mice, hydronephrus and EMT were suppressed, with no expression of renin and C3. After UUO, systolic blood pressure was increased in wild-type but not C3-deficient mice. In wild-type mice, intrarenal angiotensin II (ANG II) levels were markedly higher in UUO kidneys than normal kidneys and decreased with aliskiren. There were no increases in intrarenal ANG II levels after UUO in C3-deficient mice. Thus C3 induces EMT and dedifferentiation of epithelial cells, which produce renin through induction of LXRα. These data indicate for the first time that C3 may be a primary factor to activate the renal RA systems to induce hypertension.

Cardioprotective Effects of Pitavastatin on Cardiac Performance and Remodeling in Failing Rat Hearts

BACKGROUNDnActivation of phosphatidylinositol 3-kinase (PI3K)-Akt signaling by statins increases the activity of endothelial nitric oxide synthase (eNOS). We investigate whether statins (pitavastatin) improve cardiac function and remodeling via eNOS production associated with the PI3K-Akt signaling pathway, Rho-kinase (ROCK) pathway, and the development of oxidative stress in Dahl salt-sensitive (DS) hypertensive rats with heart failure (DSHF).nnnMETHODSnPitavastatin (3 mg/kg per day), or pitavastatin plus specific PI3K inhibitor, wortmannin (1 mg/kg per day), or wortmannin alone were administered from the age of 11-18 weeks. Age-matched male Dahl salt-resistant (DR) rats served as a control group.nnnRESULTSnDecreased end-systolic elastance (Ees) and percent fractional shortening (%FS) in failing rats was significantly ameliorated by pitavastatin, but not pitavastatin plus wortmannin or wortmannin alone. Upregulation of eNOS and Akt phosphorylation by pitavastatin was suppressed by pitavastatin plus wortmannin or wortmannin alone. Pitavastatin effectively inhibited the vascular lesion formation such as medial thickness and perivascular fibrosis, but not pitavastatin plus wortmannin or wortmannin alone. Activated RhoA and myosin light chain phosphorylation and RhoA, ROCK expression was inhibited by pitavastatin or a specific ROCK inhibitor, Y-27632, and downregulated eNOS expression and Akt phosphorylation was ameliorated by Y-27632. Increased expression of NAD(P)H oxidase subunits and activated p65 nuclear factor (NF)-kappaB, p44/p42 extracellular signal-regulated kinases and its downstream effector p90 ribosomal S6 kinase phosphorylation in failing rat hearts was inhibited by pitavastatin.nnnCONCLUSIONSnThese findings suggest that pitavastatin may improve cardiac function and remodeling via eNOS production associated with the PI3K-Akt signaling pathway, the ROCK pathway and oxidative stress.

Effect of Eplerenone on Endothelial Progenitor Cells and Oxidative Stress in Ischemic Hindlimb

BACKGROUNDnWe have demonstrated that angiotensin II receptor blocker (ARB) improved endothelial progenitor cells (EPCs) dysfunction through the antioxidative mechanism. Therefore, we investigate whether the selective mineralocorticoid receptor (MR) antagonist eplerenone improves EPCs function in rat hindlimb ischemia.nnnMETHODSnUnilateral hindlimb ischemia was surgically induced in Wistar rats. After induced ischemia, rats received eplerenone (30 mg/kg/day), valsartan (3 mg/kg/day), or vehicle for 3 weeks. Peripheral blood mononuclear cells were isolated, subjected to flow cytometric analysis to determine the number of circulating EPCs, cultured to assay EPC colony formation, and subjected to a migration chamber assay to evaluate EPCs migration.nnnRESULTSnBlood perfusion by laser Doppler image was significantly higher in eplerenone than in vehicle. Capillary density by isolectin B4 stained of ischemic muscle was significantly increased in eplerenone compared with vehicle. Eplerenone significantly increased the number, colony formation, and migration of EPCs. Levels of endothelial nitric oxide synthase (eNOS) and angiogenic factor such as vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), and angiopoietin-2 (Ang-2) protein expression by western blot were significantly higher in eplerenone than in vehicle. Eplerenone significantly decreased the NAD(P)H oxidase p22(phox), p47(phox), gp91(phox) and MR expression and expression of aldosterone effector kinase serum and glucocorticoid-induced protein kinase 1 (Sgk1). These effects of eplerenone are similar extent as valsartan.nnnCONCLUSIONSnThis study showed that eplerenone improves the proliferation and function of EPCs in rat hindlimb ischemia, suggesting that eplerenone may provide a novel and effective therapeutic strategy for the repair of cardiovascular diseases.

Renoprotective mechanisms of telmisartan on renal injury and inflammation in SHRSP.Z-Leprfa/IzmDmcr rats.

BackgroundSHRSP.Z-Leprfa/IzmDmcr (SHRSP fatty) rats create a new animal model of metabolic syndrome. However, the renoprotective effect of telmisartan therapy and its underlying mechanisms in SHRSP fatty rats remain unknown. We evaluate the effects of long-term telmisartan therapy on renal dysfunction, podocyte injury, inflammation, and transforming growth factor-β1 (TGF-β1)/Smad, epithelial-mesenchymal transition (EMT), mitogen-activated protein kinase (MAPK), Rho-kinase, and cell-cycle progression pathway in the renal cortex of SHRSP fatty rats.MethodsSeven-week-old male SHRSP fatty rats were treated with vehicle, telmisartan, and hydralazine for 8xa0weeks. Age-matched male Wistar-Kyoto/Izumo rats served as a control group.ResultsVehicle-treated SHRSP fatty rats developed proteinuria and renal dysfunction, which in the telmisartan group was less than the vehicle and hydralazine group without changing blood pressure. Glomerulosclerosis and interstitial fibrosis were impaired in SHRSP fatty rats, and the renal damage in the telmisartan group was less than the vehicle and hydralazine groups. Decreased expression of nephrin and podocin and increased desmin-positive area in SHRSP fatty rats were restored by telmisartan but not hydralazine. TGF-β1/Smad, EMT marker, MAPK, Rho-kinase, and cell-cycle progression pathways were upregulated in SHRSP fatty rats, and these increased proteins in the telmisartan group were less than the vehicle and hydralazine group. Telmisartan administration resulted in significant suppression in tumor necrosis factor-α expression and nuclear factor-κB phosphorylation.ConclusionLong-term telmisartan therapy may improve renal dysfunction, glomerulosclerosis, podocyte injury, and inflammation associated with EMT, TGF-β/Smad, MAPK, Rho-kinase pathway in SHRSP fatty rats. Thus, telmisartan may have significant therapeutic potential for metabolic syndrome.

Assessment on Antihypertensive Effect and Safety of Nifedipine Controlled-Release Tablet Administered at 80 mg/day in Practical Clinic

In this study, the effect of nifedipine controlled-release tablets at a dose of 80 mg/day (NCR80) on blood pressure (BP) and safety was investigated. In essential hypertension (n = 50, >140/90 mm Hg) despite a combined therapy with antihypertensive agents, NCR80 was administered instead of the previous antihypertensive agents and changes in BP and pulse rate (PR), side effects, and changes in laboratory test values were examined for 24 months. Thirty-three patients switched to NCR80 as the initial dose from the previous antihypertensive agents (Initial), while 17 patients started treatment at NCR40 and increased to NCR80 after 1–3 months (Up-titration). In the Initial group, BP decreased significantly and this significant reduction continued for 24 months, but not in the case of PR. In the Up-titration group, BP decreased significantly during the treatment with NCR40, and further reduced in 1–2 month(s) after NCR80. This significant reduction continued for 12 months, but not in the case of PR. The mean change in BP after increasing NCR40 to NCR80 was −16/–6 mm Hg at 6 months. When patients who received NCR80 were stratified into three grades according to the baseline systolic blood pressure level (SBP) (≥180, 160–179, and 140–159 mm Hg), the mean change in BP at 1 month was −55, −27, and −16 mm Hg, respectively. None of the 50 patients treated with NCR80 experienced any side effects and no abnormal change was observed in their laboratory test values. These findings suggested that NCR80 demonstrated the ability to control BP appropriately depending on the severity with favorable safety.

Role of complement 3a in the growth of mesangial cells from stroke-prone spontaneously hypertensive rats

Abstract Vascular smooth muscle cells (VSMCs) derived from spontaneously hypertensive rats (SHR) show exaggerated growth with a synthetic phenotype and angiotensin II (Ang II) production associated with increased production of complement (C3). We hypothesized that C3 is involved in the growth of mesangial cells (MCs) from hypertensive rats. We examined the effects of a C3a receptor inhibitor on proliferation, phenotype and Ang II generation in MCs from stroke prone-spontaneously hypertensive rats (SHR)-SP, SHR and Wistar-Kyoto (WKY) rats. Expression of C3 and C3a receptor were evaluated by immunohistochemical staining of the renal cortex. We examined the effects of the C3a inhibitor, SB290157, on proliferation, the expression of phenotype-marker mRNAs and Ang II production in cells from SHR-SP, SHR and WKY rats. Immunostaining of C3 was stronger in SHR and SHRSP glomeruli. MCs from SHR-SP and SHR abundantly express pre-pro C3 mRNA. SB290157 significantly inhibited basal DNA synthesis and proliferation of MCs from SHR-SP and SHR. Expression of osteopontin mRNA in MCs from SHR-SP and SHR was decreased with SB290157 treatment, whereas MC basal expression of α-SMA mRNA was decreased. SB290157 significantly decreased the production of Ang II in MCs from SHR-SP and SHR. Endogenous C3a promotes exaggerated growth with a synthetic phenotype and the production of Ang II in MCs from SHR-SP and SHR. The C3 and C3a receptor system may primarily be involved in the pathogenesis of renal remodeling in hypertensive rats.