[Show abstract][Hide abstract] ABSTRACT: Excess mesangial extracellular matrix (ECM) and mesangial cell proliferation is the major pathologic feature of diabetic nephropathy (DN). Fenofibrate, a PPARα agonist, has been shown to attenuate extracellular matrix formation in diabetic nephropathy. However, the mechanisms underlying this effect remain to be elucidated. In this study, the effect of fenofibrate on high-glucose induced cell proliferation and extracellular matrix exertion and its mechanisms were investigated in cultured rat mesangial cells by the methylthiazoletetrazolium (MTT) assay, flow cytometry and western blot. The results showed that treatment of mesangial cells (MCs) with fenofibrate repressed high-glucose induced up-regulation of extracellular matrix Collagen-IV, and inhibited entry of cell cycle into the S phase. This G1 arrest and ECM inhibition was caused by the reduction of phosphorylation and activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT. On the contrary, PPARα siRNA accelerated high glucose-induced cell cycle progression by ERK1/2 and AKT activation. Taken together, fenofibrate ameliorated glucose-induced mesangial cell proliferation and matrix production via its inhibition of PI3K/AKT and ERK1/2 signaling pathways. Such mechanisms may contribute to the favorable effects of treatment using fenofibrate in diabetic nephropathy.
PLoS ONE 01/2013; 8(10):e76836. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The safety of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) used in hemodialysis (HD) patients was evaluated. Medline, Embase, the Cochrane Library, some databases of clinical trial registries, grey literatures, other reference lists of eligible articles and review articles for the randomized clinical trials (RCTs) on comparison of ACEIs/ARBs or placebo in HD patients were retrieved. RCTs reporting the risk of hyperkalemia by using ACEIs/ARBs in HD patients were selected. Eight articles met the eligibility criteria and were subjected to meta-analysis by using the Cochrane Collaboration's RevMan 4.2 software package. The results showed that there was no significant difference in hyperkalemia in HD patients between ACEIs or ARBs group and control group (ACEIs vs. control: RD=0.03, 95% CI=-0.13-0.18, Z=0.34, P=0.73; ARBs vs. control: RD=-0.02, 95% CI=-0.07-0.03, Z=0.75, P=0.45). However, there was no significant difference in the serum potassium between ACEIs or ARBs group and control group in HD patients (ACEIs vs. control: WMD=0.10, 95% CI=0.06-0.15, Z=4.64, P<0.00001; ARBs vs. control: WMD=-0.24, 95% CI=-0.37-0.11, Z=3.58, P=0.0003). The use of ACEIs or ARBs could not cause an increased risk of hyperkalemia in HD patients, however the serum potassium could be increased with use of ACEIs in HD patients. Therefore the serum potassium concentration should still be closely monitored when ACEIs are taken during the maintenance HD.
Journal of Huazhong University of Science and Technology 10/2012; 32(5):785-92. · 0.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVES: This study aims to analyze the relationship between nutcracker syndrome (NCS) and nutcracker phenomenon (NCP) in glomerular nephritis (GN) of patients with symptom of isolated hematuria. Our observations reveal that patients with combined GN and NCP/NCS have dysmorphic urine red blood cells or mixed-morphological urine red blood cells while patients with NCS only (without GN) contain isomorphic urine red blood cells. PATIENTS AND METHODS: Clinical and pathological data of 32 patients with NCP and complicating GN were analyzed. A different group of 17 patients with NCS served as the control. All patients underwent color Doppler ultrasonography. Routine urine examination, red blood cell counts, and phase observations of urinary sediments were performed both before and after exercise. twenty four hour urinary protein and albumin quantities were determined. Twenty-nine patients underwent renal needle biopsy. RESULTS: All 32 patients were diagnosed with NCP. Results of urinary sediment examination of patients were either normal or showed isomorphic hematuria before exercise. Most patients exhibited mixed-morphological or dysmorphic hematuria at different degrees after exercise. Renal pathological findings in 29 patients included multiple types and showed no relevance to urinary examination results. All patients diagnosed with GN complicated by NCP were identified through clinical and laboratory examinations and renal biopsy. CONCLUSIONS: NCP may coexist with a glomerular disease. NCS patients with urine red blood cells of mixed morphology or showing dysmorphism after exercise should be noted, with or without the coexistence of GN. Renal needle biopsy must be performed when necessary to avoid adverse effects on the patient's condition.
International Urology and Nephrology 09/2012; · 1.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Oxidative stress is associated with vascular remodeling and increased preglomerular resistance that are both implicated in the pathogenesis of renal and cardiovascular disease. Angiotensin II induces superoxide production, which is metabolized by superoxide dismutase (SOD) or scavenged by NO. We investigated the hypothesis that SOD1 regulates renal microvascular remodeling, blood pressure, and arteriolar responsiveness and sensitivity to angiotensin II using SOD1-transgenic (SOD1-tg) and SOD1-knockout (SOD1-ko) mice. Blood pressure, measured telemetrically, rose more abruptly during prolonged angiotensin II infusion in SOD1-ko mice. The afferent arteriole media:lumen ratios were reduced in SOD1-tg and increased in SOD1-ko mice. Afferent arterioles from nontreated wild types had graded contraction to angiotensin II (sensitivity: 10(-9) mol/L; responsiveness: 40%). Angiotensin II contractions were less sensitive (10(-8) mol/L) and responsive (14%) in SOD1-tg but more sensitive (10(-13) mol/L) and responsive (89%) in SOD1-ko mice. Arterioles from SOD1-ko had 4-fold increased superoxide formation with angiotensin II at 10(-9) mol/L. N(G)-nitro-l-arginine methyl ester reduced arteriole diameter of SOD1-tg and enhanced angiotensin II sensitivity and responsiveness of wild-type and SOD1-tg mice to the level of SOD1-ko mice. SOD mimetic treatment with Tempol increased arteriole diameter and normalized the enhanced sensitivity and responsiveness to angiotensin II of SOD1-ko mice but did not affect wild-type or SOD1-tg mice. Neither SOD1 deficiency nor overexpression was associated with changes in nitrate/nitrite excretion or renal mRNA expression of NO synthase, NADPH oxidase, or SOD2/SOD3 isoforms and angiotensin II receptors. In conclusion, SOD1 limits afferent arteriole remodeling and reduces sensitivity and responsiveness to angiotensin II by reducing superoxide and maintaining NO bioavailability. This may prevent an early and exaggerated blood pressure response to angiotensin II.
[Show abstract][Hide abstract] ABSTRACT: Many agents constrict isolated afferent arterioles only at concentrations higher than their physiological levels. Here we determined if norepinephrine, as released by sympathetic nerve activity, could influence the angiotensin II responsiveness of isolated mouse afferent arterioles. Pretreatment of the arterioles for short periods with norepinephrine significantly increased the ability of 10 picomolar angiotensin II to constrict the vessels, an effect inhibited by the alpha receptor blockers prazosin (alpha-1) or yohimbine (alpha-2). Although the intracellular calcium transients induced by angiotensin were not different, phosphorylation of the 20 kDa myosin light chain was significantly increased in the presence of norepinephrine. Phosphorylation of the p38 mitogen-activated protein kinase was not changed. Phosphorylation of the myosin phosphatase targeting subunit at Thr696, but not at Thr850, was significantly enhanced by, norepinephrine pretreatment, thus increasing the calcium sensitivity of the arteriolar smooth muscle. Our results show that norepinephrine increases afferent arteriolar sensitivity to angiotensin II by means of alpha receptor activation, causing increased calcium sensitivity through phosphorylation of the myosin phosphatase targeting subunit.
Kidney International 08/2009; 76(9):953-9. · 8.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: NADPH oxidases (NOX) are the major source of reactive oxygen species (ROS) in the vasculature and contribute to the control of renal perfusion. The role of NOX2 in the regulation of blood pressure and afferent arteriole responsiveness was investigated in NOX2(-/-) and wild-type mice. Arteriole constrictions to ANG II (10(-14)-10(-6) mol/l) were weaker in NOX2(-/-) compared with wild types. N(omega)-nitro-l-arginine methyl ester (l-NAME; 10(-4) mol/l) treatment reduced basal diameters significantly more in NOX2(-/-) (-18%) than in wild types (-6%) and augmented ANG II responses. Adenosine (10(-11)-10(-4) mol/l) constricted arterioles of wild types but not of NOX2(-/-). However, simultaneous inhibition of adenosine type-2 receptors induced vasoconstriction, which was stronger in NOX2(-/-). Adenosine (10(-8) mol/l) enhanced the ANG II response in wild type, but not in NOX2(-/-). This sensitizing effect by adenosine was abolished by apocynin. Chronic ANG II pretreatment (14 days) did not change the ANG II responses in NOX2(-/-), but strengthened the response in wild types. ANG II pretreatment augmented the l-NAME response in NOX2(-/-) (-33%), but not in wild types. Simultaneous application of l-NAME and ANG II caused a stronger constriction in the NOX2(-/-) (-64%) than in wild types (-46%). Basal blood pressures were similar in both genotypes, however, chronic ANG II infusion elevated blood pressure to a greater extent in wild-type (15 +/- 1%) than in NOX2(-/-) (8 +/- 1%) mice. In conclusion, NOX2 plays an important role in the control of afferent arteriole tone and is involved in the contractile responses to ANG II and/or adenosine. NOX2 can be activated by elevated ANG II and may play an important role in ANG II-induced hypertension. NOX2-derived ROS scavenges nitric oxide, causing subsequent nitric oxide-deficiency.
[Show abstract][Hide abstract] ABSTRACT: Afferent arterioles were used to investigate the role of adenosine, angiotensin II, NO, and reactive oxygen species in the pathogenesis of increased tubuloglomerular feedback response in hydronephrosis. Hydronephrosis was induced in wild-type mice, superoxide dismutase-1 overexpressed mice (superoxide-dismutase-1 transgenic), and deficient mice (superoxide dismutase-1 knockout). Isotonic contractions in isolated perfused arterioles and mRNA expression of NO synthase isoforms, adenosine, and angiotensin II receptors were measured. In wild-type mice, N(G)-nitro-L-arginine methyl ester (L-NAME) did not change the basal arteriolar diameter of hydronephrotic kidneys (-6%) but reduced it in control (-12%) and contralateral arterioles (-43%). Angiotensin II mediated a weaker maximum contraction of hydronephrotic arterioles (-18%) than in control (-42%) and contralateral arterioles (-49%). The maximum adenosine-induced constriction was stronger in hydronephrotic (-19%) compared with control (-8%) and contralateral kidneys (+/-0%). The response to angiotensin II became stronger in the presence of adenosine in hydronephrotic kidneys and attenuated in contralateral arterioles. L-NAME increased angiotensin II responses of all of the groups but less in hydronephrotic kidneys. The mRNA expression of endothelial NO synthase and inducible NO synthase was upregulated in the hydronephrotic arterioles. No differences were found for adenosine or angiotensin II receptors. In superoxide dismutase-1 transgenic mice, strong but similar L-NAME response (-40%) was observed for all of the groups. This response was totally abolished in arterioles of hydronephrotic superoxide dismutase-1 knockout mice. In conclusion, hydronephrosis is associated with changes in the arteriolar reactivity of both hydronephrotic and contralateral kidneys. Increased oxidative stress, reduced NO availability, and stronger reactivity to adenosine of the hydronephrotic kidney may contribute to the enhanced tubuloglomerular feedback responsiveness in hydronephrosis and be involved in the development of hypertension.
[Show abstract][Hide abstract] ABSTRACT: Adenosine triphosphate (ATP) and norepinephrine (NE) interact in the control of blood flow in the kidney. A combined effect of NE and ATP has not been previously investigated at the level of the afferent arteriole (Af). We studied the effects of ATP on the contractile response of the Af to NE. Vascular reactivity to ATP, NE, and their combination was investigated in isolated perfused Af from mice. The roles of alpha-adrenoceptors and P2-ATP-receptors were investigated by use of specific agonists and antagonists. Cytosolic calcium was measured using the fluorescent calcium dye fura-2. ATP in concentrations from 10(-12) to 10(-4) mol/l induced transient contractions. NE constricted the Af in a dose-dependent manner and induced significant contractions at > 10(-7) mol/l. Treatment with ATP (10(-8) and 10(-6) mol/l) increased the NE response. Diameters were reduced by 20% already at 10(-11) mol/l NE during ATP treatment of 10(-6) mol/l. ATP increased the calcium response to NE significantly at 10(-8) and 10(-7)mol/l NE. The P2-type ATP receptor blocker pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) (10(-5) mol/l) abolished the sensitization of the NE response by ATP. The alpha(1)-blocker prazosin (10(-7) mol/l) inhibited the ATP effect, as did the alpha 2-blocker yohimbine (10(-7) mol/l). Neither the phenylephrine- nor clonidine-induced concentration response curves was affected by ATP in the bath solution. Costimulation with ATP enhances the response of the Af to NE. This effect is mediated by increased cytosolic calcium. The enhancing effect involves P2-type ATP receptors and both alpha (1)- and alpha 2-adrenoceptors.