Daisuke Yorimitsu

Renal denervation reduces glomerular injury by suppressing NAD(P)H oxidase activity in Dahl salt-sensitive rats

BACKGROUND Renal sympathetic nerve activity has important effects on renal function in chronic kidney disease. Recent studies indicated that beta agonists directly stimulate NAD(P)H oxidase in endothelial cells. Therefore, we investigated whether renal denervation protects renal function through an anti-oxidative effect. METHODS The right kidney was removed from Dahl salt-sensitive hypertensive rats. Two weeks later, the rats underwent either left renal denervation (Nx-RDNx; n = 10) or a sham operation (Nx-Sham; n = 10). After a further 6 weeks, kidney function and renal tissue were assessed. In this ex vivo study, using isolated glomeruli from Sprague-Dawley rats, the direct effects of catecholamine on NAD(P)H oxidase activity were assessed. RESULTS After the Nx-RDNx or Nx-Sham surgery, urinary albumin excretion and the histologic glomerular sclerosis index were lower in the Nx-RDNx group than in the Nx-Sham group. Fluorescence staining for reactive oxygen species in isolated glomeruli was significantly weaker in the Nx-RDNx group. A lucigenin assay of NAD(P)H oxidase activity in isolated glomeruli indicated that renal denervation may have caused the reduction in reactive oxygen species through suppression of the activity of NAD(P)H oxidase. The levels of mRNA for NAD(P)H oxidase components and the levels of rac1 were higher in glomeruli from the Nx-Sham group than from the Nx-RDNx group. In this ex vivo study, although the NAD(P)H oxidase activity did not change with administration of either the alpha- or beta2-agonist, it increased with the beta1-agonist. CONCLUSIONS Renal sympathetic denervation helps to protect against glomerular sclerosis, possibly by suppressing NAD(P)H oxidase activity, thereby decreasing glomerular reactive oxygen species.

Tacrolimus induces glomerular injury via endothelial dysfunction caused by reactive oxygen species and inflammatory change.

Background/Aims: The immunosuppressive drug tacrolimus (FK506) is used clinically to reduce the rejection rate in patients with kidney transplantation; however, the resultant nephrotoxicity remains a serious problem. In the present study we attempted to elucidate the mechanisms of glomerular injury induced by FK506 and the renoprotective effects of the angiotensin II receptor blocker telmisartan. Methods: Seven-week-old male Wistar rats were divided into three groups: vehicle group, FK506 group, and FK506 + telmisartan group. After 8 weeks, we assessed kidney function and renal morphological changes including oxidative stress. We also assessed the effect of FK506 in human glomerular endothelial cells (hGECs) with regard to reactive oxygen species (ROS). Results: FK506 induced ROS production via activation of NAD(P)H oxidase in the glomeruli. Expression of ICAM mRNA was increased in glomeruli from the FK506 group. These effects resulted in macrophage infiltration into the glomeruli. FK506 directly promoted NAD(P)H oxidase activity and accelerated production of ROS in hGECs. Conversely, cotreatment with telmisartan inhibited both NAD(P)H oxidase activity and production of ROS. Conclusion: These findings suggest that glomerular injury resulting from FK506 is caused by oxidative stress mediated by activation of NAD(P)H oxidase and that telmisartan exerts a renoprotective effect via antioxidative activity.

Overexpression of klotho protein modulates uninephrectomy-induced compensatory renal hypertrophy by suppressing IGF-I signals

The klotho gene is highly expressed in the distal convoluted tubule of the kidney, while its encoded protein has many physiological and pathophysiological renal roles. We investigated the effect of klotho protein on physiological compensatory renal hypertrophy after nephrectomy in klotho transgenic (KLTG) mice. Renal hypertrophy was suppressed in KLTG mice compared with wild-type mice, and this was associated with suppression of insulin growth factor-1 (IGF-1) signaling by klotho protein. In vitro, IGF-1 signaling was suppressed in human proximal tubular cells transfected with the klotho plasmid. Our data suggest that klotho modulates compensatory renal hypertrophy after nephrectomy via suppression of the IGF-1 signaling pathway, indicating a novel physiological role for klotho protein in the kidney.

Comparison of Combination Therapy of Olmesartan plus Azelnidipine or Hydrochlorothiazide on Renal and Vascular Damage in SHR/NDmcr-cp Rats

Background: Although the recommended target blood pressure for patients with chronic kidney disease is <130/80 mm Hg, this is difficult to achieve by treatment with an angiotensin receptor blocker alone. Addition of either a calcium channel blocker or a diuretic is suggested as second-line medication; however, which combination is most beneficial for target-organ protection remains unknown. Methods: SHR/NDmcr-cp rats were administered no medications (control) or low-dose olmesartan for 2 weeks and then either olmesartan at an increased dose, azelnidipine, or the hydrochlorothiazide for 3 weeks. We assessed oxidative stress in the kidney and aorta, and endothelial function. Results: Urinary protein excretion was lower in all treated rats than in control rats. Oxidative stress caused by activation of NAD(P)H oxidase was observed in the glomeruli and aorta of control rats and was significantly suppressed in the olmesartan/azelnidipine (Olm/Azl) groups. Combination therapy with olmesartan and hydrochlorothiazide (Olm/HCTZ) however failed to suppress oxidative stress. The Olm/Azl groups maintained the endothelial surface layer in the glomeruli and protected endothelial function in the aorta. Conclusion: In an animal model of metabolic syndrome, a combination of Olm/Azl is superior to a combination of Olm/HCTZ in terms of prevention of glomerular and vascular injuries.

Relationship between vascular function indexes, renal arteriolosclerosis, and renal clinical outcomes in chronic kidney disease

Hypertension contributes critically to the development of renal arteriolosclerosis in chronic kidney disease (CKD), but the impact of vascular function indexes including central blood pressure on renal arteriolosclerosis has not been investigated. We determined whether vascular function indexes were related to renal arteriolosclerosis and renal clinical outcomes in CKD.

Co-occurrence of poststreptococcal reactive arthritis and acute glomerulonephritis

We report a 16-year-old patient who developed concurrent poststreptococcal reactive arthritis and acute glomerulonephritis. A high titer of antistreptolysin O antibody confirmed the preceding streptococcal infection. The patient presented with symmetric persistent tenosynovitis of hands and feet. Renal biopsy showed typical findings of acute glomerulonephritis with crescent formation. Physicians who treat patients with arthritis of acute onset, especially after throat infection, should be aware of possible urinary abnormalities or renal dysfunction.

Establishment of a Blood Purification System for Renal Failure Rats Using Small‐Size Dialyzer Membranes

Hemodialysis techniques for small animals have not been established because no small dialysis apparatus has been available. We recently developed a small‐size dialyzer and established an appropriate blood purification system for small animals. To confirm the appropriate dialysate flow rate, bovine blood was dialyzed for 60 min at a fixed blood flow rate of 1.0 mL/min and variable dialysate flow rates. Blood urea nitrogen and creatinine levels decreased significantly at a dialysate flow rate of 5 mL/min (from 13.7 ± 0.2 to 10.3 ± 1.2 mg/dL and 1.07 ± 0.15 to 0.61 ± 0.12 mg/dL, respectively, P < 0.05). To determine the appropriate in vivo conditions, extracorporeal circulation was performed in anesthetized male Sprague‐Dawley rats at a dialysate flow rate of 0.0 mL/min, for 240 min, and at variable blood flow rates. Extracorporeal circulation was successful at a blood flow rate of 1.0 mL/min, but not 1.5 mL/min. To establish in vivo hemodialysis conditions, we used the animal model of end stage renal failure. Sprague‐Dawley rats were fed a 0.75% adenine‐containing diet for 3 weeks, after which they received hemodialysis for 120 min at a dialysate and blood flow rate of 5.0 and 1.0 mL/min, respectively. There were no significant changes in systolic blood pressure or heart rate during dialysis. Thus, this blood purification system can be safely used for small animals at a dialysate flow rate of 5.0 mL/min and a blood flow rate of 1.0 mL/min. This system provides a basis for further research on hemodialysis therapy.

High dietary protein intake induces endothelial dysfunction in uninephrectomized rats

High dietary protein (HP) intake is a risk factor for chronic kidney disease (CKD). HP intake is associated with the development of albuminuria and glomerulosclerosis in uninephrectomized rats. In such rats, we investigated whether HP intake induces endothelial dysfunction. Male Wistar rats were divided into sham-operated rats fed a standard-protein diet, sham-operated rats fed a high-protein diet, uninephrectomized rats fed a standard-protein diet (NxSP) and uninephrectomized rats fed a high-protein diet (NxHP) (n=8 each). One week after treatment, endothelial function and urinary albumin excretion (UAE) were measured. Protein expression, phosphorylation at serine residue 1177 and uncoupling of endothelial nitric oxide synthase (eNOS), and mRNA expression of NADPH oxidase components were assessed in the aorta. NxHP rats showed hypertriglyceridemia and modest hyperhomocysteinemia. Endothelial function was significantly lower, and UAE was significantly higher in NxHP rats compared with the other groups (P<0.01 each), although there was no difference in creatinine clearance between NxSP and NxHP rats. Expression levels, phosphorylation and the dimer/monomer ratio of eNOS did not differ among the four groups. HP intake did not modify p22phox and p47phox expression levels in uninephrectomized rats. In conclusion, HP intake induced endothelial dysfunction and enhanced albuminuria in uninephrectomized rats, inde-pendent of renal function, suggesting that HP intake may cause the development of cardiovascular disease associated with CKD.

Proteinuria in neuronal intranuclear inclusion disease

Recently, clinical features of adult‐onset neuronal intranuclear inclusion disease have gradually become characterized by premortem diagnoses based on eosinophilic, ubiquitin‐positive intranuclear inclusions demonstrated using skin biopsy specimens. A 65‐year‐old healthy woman with proteinuria was admitted because of cognitive impairment and walking instability. She had frontal lobe dysfunction and sensory ataxia with high‐signal‐intensity lesions in the corticomedullary junction on performing diffusion‐weighted brain magnetic resonance imaging. She was incidentally diagnosed with adult‐onset sporadic neuronal intranuclear inclusion disease based on the presence of intranuclear inclusions in renal biopsy specimens. Proteinuria might be a non‐neuronal symptom of neuronal intranuclear inclusion disease because no other causes for proteinuria were found on renal testing.

PS 14-36 EFFECT OF SINGLE PILL-BASED COMBINATION THERAPY OF OLMESARTAN AND AZELNIDIPINE ON VARIABILITY OF HOME BLOOD PRESSURE IN HYPERTENSIVE OUTPATIENTS

Objective: Recent studies have shown the association between blood pressure (BP) variability and cardiovascular events. The present study was designed to investigate the effects of the single pill-based combination therapy of olmesartan and azelnidipine on achievement of the target BP and day-by-day home BP variability in outpatients with hypertension. Design and Method: We enrolled hypertensive outpatients if they could not achieve the BP goal (home systolic BP ≥ 135 mmHg and diastolic BP ≥ 85 mmHg) by treatment with olmesartan or azelnidipine monotherapy for over 4 weeks. After the run-in period, eligible patients were given a single pill of olmesartan/azelnidipine tablet (olmesartan medoxomil /azelnidipine; 20/16 mg) in the morning for 16 weeks. Home BP was taken in triplicate in the morning for 5 consecutive days before each visit. Visits occurred at 4-week intervals. Home BP variability was defined as within-individual standard deviation (SD), coefficient of variation (CV), and maxi- mum minus minimum difference (MMD) of the 5-day home BP. Results: The combination therapy with of olmesartan and azelnidipine for 16 weeks significantly decreased both clinic and home BP, and achievement of target BP control was attained in an average of 43% after the combination therapy in spite of the presence of no achievement at baseline. In addition, the combination therapy significantly decreased the SD and MMD, but not CV. Especially, addition of azelnidipine significantly decreased the SD and MMD. Conclusions: Single pill-based combination therapy of olmesartan and azelnidipine is effective to home BP reduction for hypertensive outpatients whose BP is not controlled by each monotherapy. Home BP variability is partially decreased by combination therapy.