Masanori Jotoku

Osteopontin deficiency protects against aldosterone-induced inflammation, oxidative stress, and interstitial fibrosis in the kidney

Osteopontin (OPN) has been implicated in the pathology of several renal conditions. Recently, we demonstrated in vitro that aldosterone has important roles in collagen synthesis by inducing OPN (Irita J, Okura T, Kurata M, Miyoshi K, Fukuoka T, Higaki J. Hypertension 51: 507-513, 2008). The aim of the present study was to clarify the roles of OPN in aldosterone-mediated renal fibrosis by infusing aldosterone into either wild-type (WT) or OPN knockout mice (OPN(-/-)). We used uninephrectomized mice treated with aldosterone and high salt to exacerbate renal fibrosis. After 4 wk of treatment with aldosterone, we showed similar increases in systolic blood pressure in both strains of mice. Urine albumin excretion was greater in aldosterone-infused WT mice than in aldosterone-infused OPN(-/-) mice. Immunohistochemical analysis showed high levels of OPN expression in aldosterone-infused WT mice. Interstitial fibrosis and inflammatory infiltrations were increased in aldosterone-infused WT mice compared with either vehicle-infused WT or aldosterone-infused OPN(-/-) mice. These changes were ameliorated markedly by eplerenone treatment in aldosterone-infused WT mice. Aldosterone-infused WT mice also had increased expression of NADPH oxidase subunits compared with aldosterone-infused OPN(-/-) mice. We observed a marked increase in oxidative stress markers in aldosterone-infused WT mice compared with aldosterone-infused OPN(-/-) mice. These results indicate that OPN is a promoter of aldosterone-induced inflammation, oxidative stress, and interstitial fibrosis in the kidney and suggest that inhibition of OPN may be a potential therapeutic target for prevention of renal injury.

Undercarboxylated osteocalcin is a biomarker of carotid calcification in patients with essential hypertension.

The development of vascular calcification is an active, highly regulated process with similarities to bone formation. Osteocalcin (OC), a vitamin K-dependent protein expressed by osteoblasts, contains 3 γ-carboxyglutamic acid residues derived from the vitamin K-dependent posttranslational modification of glutamic acid residues. Circulating undercarboxylated OC (ucOC) is increased in vitamin K deficiency and serum ucOC is reported to be a clinical marker of vitamin K status. Vitamin K deficiency is associated with vascular calcification as well as osteoporosis. We evaluated the relationship between ucOC and carotid artery calcification in 92 patients with essential hypertension. Ultrasound of the common carotid artery was performed to identify vascular calcification and subjects were divided into 2 groups: a calcification (+) group and a calcification (–) group. Serum creatinine and ucOC levels were higher in the calcification (+) group than in the calcification (–) group and serum ucOC correlated with serum creatinine. To identify the independent determinant factor for carotid artery calcification, we applied both ucOC and estimated glomerular filtration rate as independent factors in logistic regression analysis. Serum ucOC was an independent determinant of carotid calcification, suggesting that circulating ucOC may be an important biomarker of carotid artery calcification.

The Relationship Between Osteopontin and Adiponectin in Patients with Essential Hypertension

The renin angiotensin aldosterone system (RAAS) induces inflammation and accelerates atherosclerosis, contributes to both pro- and anti-inflammatory cytokines. Osteopontin (OPN) is known as a pro-inflammatory cytokine and adiponectin is known as an anti-inflammatory cytokine. C-reactive protein (CRP) not only reflects an inflammatory state but also leads to inflammation. Previous studies clarified that OPN and adiponectin were regulated by RAAS. In this study, we hypothesized that plasma OPN level relates to serum adiponectin level in patients with essential hypertension (EHT). Sixty-two patients (32 females) with EHT were enrolled in this study. They were evaluated for conventional risk factors for atherosclerosis, further plasma aldosterone, plasma OPN, serum adiponectin, and CRP levels were assayed. There were significant gender differences in creatinine, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-denisty lipoprotein(LDL) cholesterol, log transformed (ln) adiponectin and ln CRP. Osteopontin was correlated positively with aldosterone and ln CRP (r = 0.277, p = 0.029, r = 0.278, p = 0.029, respectively), negatively with adiponectin (r = −0.346, p = 0.006). Ln adiponectin was correlated positively with HDL cholesterol (r = 0.373, p = 0.003) and negatively with gender (male as 1), creatinine, triglyceride, aldosterone, and ln CRP (r = −0.55, p < 0.001, r = −0.279, p = 0.028, r = −0.406, p = 0.001, r = −0.307, p < 0.015, r = −0.289, p = 0.023, respectively). Stepwise regression analysis showed that adiponectin was an independent predictor of OPN β= −0.0339, p = 0.004). Our results suggest that OPN and adiponectin are related to each other underlying the mechanisms of RAAS and inflammation.

Osteopontin plays a critical role in interstitial fibrosis but not glomerular sclerosis in diabetic nephropathy.

Background/Aims: Osteopontin (OPN) has been implicated in the pathology of several renal conditions. The aim of this study was to clarify the roles of OPN in diabetic nephropathy. Methods: Diabetes mellitus (DM) was induced in wild-type (WT) and OPN knockout (KO) mice by injecting streptozotocin. The mice were killed 20 weeks after induction of DM and their kidneys removed. Results: Renal mRNA expression of OPN was increased in WT-DM mice compared to WT-sham mice. Immunohistochemistry showed high levels of OPN expression in the proximal tubules of WT-DM mice. Kidney weight and urinary albumin excretion increased to similar levels in the WT-DM and KO-DM mice. Interstitial fibrosis was increased in WT-DM mice compared to KO-DM mice. However, there were no differences in the degree of mesangial expansion or glomerular hypertrophy between the two groups. F4/80-positive cells (macrophages) and FSP-1-positive cells (fibroblasts) showed significantly higher infiltration in WT-DM mice than in KO-DM mice. Renal mRNA expression of NADPH oxidase subunits and urinary 8-isoprostane excretion were also increased in WT-DM mice. Conclusions: These results indicated that OPN is a key molecule that induces interstitial fibrosis in the diabetic kidney, but does not induce glomerular sclerosis.

Comparison of the Effect of Combination Therapy with an Angiotensin II Receptor Blocker and Either a Low-Dose Diuretic or Calcium Channel Blocker on Cardiac Hypertrophy in Patients with Hypertension

Left ventricular hypertrophy (LVH) regression is an important issue in hypertensive patients. Patients with LVH who had received the angiotensin receptor blocker (ARB) treatment for 8 weeks and had not reached the target blood pressure level were enrolled in the study. Patients were assigned to either losartan (50 mg)/hydrochlorothiazide (HCTZ, 12.5 mg) group or ARB + CCB group (usual dose of ARB and calcium channel blocker, CCB). After 48 weeks, LV mass index was found to be reduced significantly in the losartan/HCTZ group but not in the ARB + CCB group. These results suggest that combination therapy of an ARB and diuretic has greater potential to cause regression compared with an ARB and CCB.

Case of membranoproliferative glomerulonephritis due to essential cryoglobulinemia without hepatitis C virus infection

An 81‐year‐old man was admitted to our hospital because of leg edema. Serological studies for anti‐neutrophil cytoplasmic antibody (ANCA), anti‐double stranded DNA antibodies, and antibodies to hepatitis C and B were negative. Severe hypocomplementemia was present and a cryoglobulin was detected with serum immunoelectrophoresis being positive for the immunoglobulin (Ig)M κ type. The cryoglobulin was characterized by immunoelectrophoresis which showed that the protein was composed of polyclonal IgG and κ‐type monoclonal IgM. A diagnosis of essential type II cryoglobulinemia was made and the patient underwent a renal biopsy. The renal biopsy revealed endocapillary and mesangial cell proliferation with increased matrix. The resultant lobular appearance of the glomerulus and double contours of the basement membrane were indicative of membranoproliferative glomerulonephritis (MPGN). Immunofluorescence studies demonstrated granular staining in the capillary wall for IgG, IgA, IgM and C4 with little C3 deposition but no C1q. He was finally diagnosed with MPGN due to mixed cryoglobulinemia type II. MPGN with essential cryoglobulinemia type II without evidence of hepatitis C virus infection, like that found in the present case, is very rare.

Relationship between renal hemodynamics and urinary type IV collagen in patients with essential hypertension.

Urinary type IV collagen excretion (uT4C) in diabetic patients is higher than in normal subjects. In this study, we investigated the relationship between uT4C and renal hemodynamics in 42 patients with essential hypertension. The renal resistive index (RI) is calculated from blood flow velocities measured using pulsed-wave in interlobar arteries. There was a significant correlation between uT4C to creatinine ratio (uT4C/uCr) and age, hemoglobin A1c (HbA1c), and RI. A stepwise regression analysis showed that RI was independently associated with uT4C/uCr. These results indicated that uT4C may be a marker of renovascular stiffness due to glomerulosclerosis in patients with essential hypertension.

HbA1c is an Independent Determinant of Renal Vascular Resistance Estimated by Doppler Sonography in Non-Diabetic Hypertensive Patients

Background Diabetic nephropathy is a progressive disease that leads to renal failure and end stage renal disease. A frequent and early manifestation of diabetic nephropathy is hyaline arteriolosclerosis. The noninvasive method for estimating the severity of arteriolosclerosis is measurement of the renal resistive index (RI). In this study, we determined whether or not normal blood glucose control, classified as an HbA1c < 5.8%, was a sufficiently low level to prevent arteriolosclerosis in patients with essential hypertension. Methods The study subjects were 93 patients with essential hypertension with HbA1c levels <5.8%. Patients with a history of medication for diabetes mellitus were excluded. Blood flow velocity of the renal interlobar arteries was assessed by a Doppler ultrasonography and the RI calculated. Results RI correlated positively with age, body mass index, pulse pressure, pulse rate and HbA1c, and negatively with diastolic blood pressure. A multivariate analysis identified age, pulse pressure and HbA1c as significant independent determinants of RI. Our data show that RI correlates with HbA1c independent of other variables, even in normoglycemic patients with HbA1c levels <5.8%. Conclusions The results of this cross-sectional study suggest that blood glucose levels should be kept as low as possible in order to prevent arteriolosclerosis in the kidney in hypertensive patients.

Carotid hemodynamics is associated with monocyte count determined by serum homocysteine level in patients with essential hypertension

Abstract To examine the association between pulsatility index (PI) in the common carotid artery (CCA) as a marker of vascular resistance and cardiovascular risk factors, including serum homocysteine and inflammation, 67 hypertensive patients were enrolled. PI correlated with homocysteine and interleukin-6, monocyte count, gender, age and BMI, with monocyte count and age being independent determinants for PI. In turn, monocyte count correlated with homocysteine, tumor necrosis factor-alpha, and HDL-cholesterol, BMI, and gender, with HDL-cholesterol and homocysteine being independent determinants for monocyte count. These results indicated monocyte count determined by homocysteine is associated with arterial stiffness in hypertensive patients.