Effects of glycyrrhetinic acid on aminonucleoside nephrosis in rats

The effects of glycyrrhetinic acid (GA), an aglycon of glycyrrhizin extracted from the roots of Glycyrrhizae radix, on puromycin aminonucleoside (PA) nephrosis were studied in rats. Urine protein excretion in female rats (130g–150g) receiving PA (50 mg/kg) alone was significantly elevated on the 2nd day after injection of PA and reached a peak on the 14th day. Urinary protein on the 14th day was reduced to 74% in animals treated with GA (20 mg/kg) starting on the 2nd day after injection of PA. The increase in serum cholesterol and the decrease in serum protein were also suppressed by GA. Observation by electron microscopy revealed that the degree of abnormality in glomerular epithelial cells, i.e. loss or fusion of foot processes, was lower in the rats treated with GA after PA injection than in the rat treated with PA alone. Moreover, pretreatment with GA did not suppress urinary protein excretion but when it was given at the same time as PA and after PA a significant decrease in urinary protein excretion was observed. Correspondence to: H. Abe at the above address     

Podocalyxin在大鼠嘌呤霉素肾病模型中的表达及其意义

目的:研究大鼠嘌呤霉素肾病(PAN)模型中podocalyxin的表达,探讨其在蛋白尿发生中的意义.方法:建立PAN模型,应用光镜、电镜观察肾脏病理改变,免疫荧光法检测podocalyxin在肾脏的表达与分布.结果:①PAN 4 d组大鼠24 h尿蛋白量较对照组升高(P＜o.01),PAN 7 d组达高峰(P＜0.001),于28 d逐渐下降至正常.②透射电镜显示PAN 4 d组大鼠足突部分融合,PAN 7 d组大鼠足突广泛融合,PAN 28 d组大鼠足突形态有所恢复.③免疫荧光显示podocalyxin在肾小球表达,PAN 4 d组podocalyxin的表达较对照组降低(P＜0.05).PAN 7 d组表达明显低于对照组(P＜0.01).PAN 28 d组podocalyxin的表达明显高于PAN 7 d组(P＜0.01),与蛋白尿产生明显相关.结论:大鼠PAN模型中,podocalyxin的表达减少可引起足突融合,并与蛋白尿产生密切相关.     

Changes of Atrial Natriuretic Peptide System in Rats with Puromycin Aminonucleoside-Induced Nephrotic Syndrome

Sodium retention is a hallmark of nephrotic syndrome. We investigated whether sodium retention is associated with changes of natriuretic peptide system at different stages (i.e., a sodium retaining stage and a compensatory stage) of nephrotic syndrome. At day 7 after PAN (puromycin aminonucleoside) injection, the urinary excretion of sodium was decreased, along with the development of ascites and positive sodium balance. The plasma and urinary ANP (atrial natriuretic peptide) immunoreactivities were increased. ANP mRNA expression was increased in the heart and kidney, whereas that of NPR (natriuretic peptide receptor)-A and NPR-C mRNA was decreased in the kidney. The expression of NEP was decreased in the kidney. At day 14, urinary excretion of sodium did not differ from the control. The plasma ANP level and heart ANP mRNA expression returned to their control values. The expression of ANP mRNA in the kidney was increased in association with increased urinary ANP immunoreactivities. The expression of NPR-A in the kidney became normal, whereas that of NPR-C kept decreased. The expression of NEP (neutral endopeptidase) remained decreased. These findings suggest that the increased renal ANP synthesis in association with decreased metabolism via NEP and NPR-C may play a compensatory role against the development of sodium retention in nephrotic syndrome. The decreased of NPR-A expression in the kidney may contribute to the ANP resistance at day 7. The subsequent recovery of NPR-A expression may play a role in promoting sodium excretion in later stage (at day 14).     

Alteration of Connexin43 expression in a rat model of obesity-related glomerulopathy

It is accepted that alteration of connexin43 (Cx43) expression in glomeruli is a common pathological response in several forms of kidney diseases. To date, however the change of the Cx43 expression in obesity-related glomerulopathy (ORG) has not been reported. In this study, the alteration of Cx43 expression in the glomeruli of rat with ORG was defined. Five-week-old rats were fed with high-fat diet for 18 weeks to establish the ORG model, then the histological change of glomeruli, the foot process effacement of podocyte, the markers for podocyte injury (nephrin,podocin and WT1) and Cx43 expression in glomeruli were examined respectively. The results demonstrated metabolic disorder, hyperinsulinemia, systemic inflammation and microalbuminuria in ORG rats. There was significant hypertrophy, glomerular expansion and inflammatory cell infiltration in the kidney of ORG rats compared to the control group. Significant foot process effacement of the podocyte in the glomeruli, nephrin loss and density reduction were shown in the ORG rats, and Cx43 expression was significant upregulated in glomeruli of ORG rats compared to the control group. The results indicate the correlation of overexpressed Cx43 with the obesity related renal inflammation and suggest that Cx43 might be a potential target in the development of obesity related glomerulopathy.     

Fluvastatin attenuates the down?regulation of β1 integrin expression in PAN?treated podocytes by inhibiting ROS

Objective To investigate the effect of fluvastatin（FLV）on the expression of β1 integrin in puromycin aminonucleoside (PAN)?treated podocytes and its mechanism. Methods Cultured human podocytes were divided into PAN, different concentrations of fluvastatin（1×10-8 to 1×10-5 mol/L）,SOD, H2O2 groups respectively. Expressions of β1 integrin and reactive oxygen species (ROS) in podocytes were detected by Western blotting and DCFHDA (2’7’?Dichlorofluoresecein 3’6’?diacetate) respectively. The viability of podocyte was determined by MTT colorimetry. Results PAN and H2O2 significantly decreased the expression of β1 integrin and increased the synthesis of ROS in podocytes (P<0.05 respectively). Lower concentration fluvastatin or SOD treatment up?regulated β1 integrin and down?regulated ROS of podocytes induced by PAN (P<0.05 respectively). MTT revealed that lower podocyte viability was found in higher concentration fluvastatin, PAN and H2O2 groups. Lower concentration fluvastatin and SOD could protect podocytes against PAN. Conclusion Fluvastatin attenuates the injury of podocyte induced by PAN and increases the expression of β1 integrin, whose mechanism may be associated with the inhibition of the ROS activity.     

Role of Protein Synthesis on Ethanol Regulation of Adenylyl Cyclase Activity in Wild-Type S49 Murine Lymphoma Cells

Adenylyl cyclase activity was determined in membranes from wild-type S49 murine lymphoma cells that had been exposed to ethanol for 4 hr. Mn-, NaF-, and forskolin-stimulated adenylyl cyclase activities of cells—pretreated with cycloheximide, puromycin, or serum deprivation—were significantly decreased by treatment with 50 mM of ethanol. As demonstrated for Mn-stimulated activity, the decrease was dose-dependent on ethanol and was temporal; a normal activity recovered after 16–24 hr treatment, even in the presence of cycloheximide and ethanol. Studies with a cell-free membrane system of S49 cells revealed a similar activity decrease after treatment of the membranes with ethanol. In contrast, cells treated with 50 mM of ethanol in a regular culture condition showed no decrease in adenylyl cyclase activity over 24 hr. These results indicate that ethanol regulation of adenylyl cyclase activity in S49 cells depends on reduced or impaired protein synthesis.     

低蛋白血症大鼠模型的建立

目的：探讨大鼠尾静脉注射阿霉素（Adriamycin，ADR）建立低蛋白血症模型的可行性。方法：SD大鼠尾静脉一次性注射阿霉素5mg／kg、7．5mg／kg及10mg／kg。观察给药后大鼠一般情况及尿量，检测尿蛋白、血清总蛋白、白蛋白、胆固醇、甘油三酯等指标，观察肾组织病理学变化，以嘌呤霉素为阳性对照。结果：阿霉素的三个剂量中，7．5mg/kg及10mg／kg组第4天开始出现尿蛋白，第15天血清总蛋白及白蛋白明显下降。两组大鼠均出现蛋白尿，血清白蛋白及总蛋白明显下降，血清胆固醇及甘油三酯升高，肾脏病理学结果符合低蛋白血症变化，但10mg／kg组大鼠死亡率高。嘌呤霉素组亦出现类似变化。结论：大鼠尾静脉注射阿霉素7．5mg／kg，15d后可建立低蛋白血症动物模型。     

Increased glomerular and urinary malondialdehyde in puromycin aminonucleoside-induced proteinuria in rats

Puromycin aminonucleoside (PAN)-induced proteinuria in rats may be mediated by reactive oxygen metabolites (ROM), which are injurious to several cell components including membrane lipids. Increased malondialdehyde (MDA) production is indicative of lipid peroxidation. We examined if MDA content of glomeruli and its urinary excretion were increased in rats administered PAN. Of three groups of 8 Sprague-Dawley rats each, group 1 served a control, group 2 animals received a single intravenous injection of PAN (5 mg/100 g body weight) and group 3 animals PAN with intraperitoneal injections of dimethylthiourea (DMTU), a free radical scavenger of oxidants such as hydroxyl radicals, for 4 days. The rats were sacrificed on day 8 after PAN injection. Increasing proteinuria, starting on day 4, developed in animals in group 2 but not in the others. The glomerular MDA (nmol/mg protein) in group 2 animals was 2.93±1.91, significantly higher than 0.87±0.63 and 1.26±0.76 in groups 1 and 3, respectively. urinary levels of MDA markedly increased in group 2 rats on day 3 and remained high thereafter, but no such increase occurred in the control animals and those administered PAN with DMTU; the latter was thus protective against PAN toxicity. Our observations support the view that ROM are involved in PAN-induced glomerular injury and that increased urinary MDA excretion can be a marker of ROM-mediated lipid peroxidation.     

The renal functional and structural consequences of corticosteroid and angiotensin-converting enzyme inhibitor therapy in chronic puromycin aminonucleoside nephropathy

Glomerular diseases are characterized by increased urinary protein excretion. Treatment of this abnormality frequently involves administration of corticosteroids and angiotensin-converting enzyme inhibitors. There has been much recent interest in the potential impact of these drugs on progressive renal dysfunction, since they have opposing effects on intraglomerular hemodynamics. Therefore, we investigated the effect of methylprednisolone or captopril treatment on animals with chronic puromycin aminonucleoside nephropathy. In rats given a single injection of puromycin aminonucleoside, 15 mg/100 g body weight, both methylprednisolone and captopril significantly reduced proteinuria at 6 months [83±14 untreated (n=7), 34±6 with methylprednisolone (n=8), and 6±1 mg/24h with captopril (n=5),P<0.001]. Segmental glomerulosclerosis occurred with equal frequency in the untreated (7.8±2.3%) and methylprednisolone-treated rats (5.0±1.11%), but was significantly reduced by the administration of captopril (1.0±0.5%,P<0.001). We conclude that in chronic puromycin aminonucleoside nephropathy, treatment with corticosteroids reduces proteinuria without increasing the incidence of segmental glomerulosclerosis. Therapy with an angiotensin-converting enzyme inhibitor substantially decreases proteinuria and lessens the severity of glomerular scarring.     

Effect of antibiotics on retention of visual discrimination training and on protein synthesis in the pigeon

Forty-three pigeons were trained for one day on a visual discrimination (horizontal vs. vertical stripes) and then immediately injected with either puromycin (PM), cycloheximide (CXM), control saline, or combined PM and CXM solution. PM produced a marked amnesic effect, CXM a weaker effect. PM injected animals (but not CXM's) also took significantly more than 1 day longer than controls to reach criterion levels, indicating an effect on continued acquisition of the discrimination beyond the amnesia for Day 1. Combination with CXM did not attenuate the PM effects. Protein inhibition profiles showed maximum PM activity of 90% inhibition, whereas CXM's maximum was 98% and was distributed more widely throughout different brain regions. In a second experiment, PM (N = 8), CXM (N = 8) or saline (N = 8) were again injected immediately after training, but the S+ was reversed on all postinjection training trials. In this case, PM animals were superior in percentage of S+ pecks on Day 2 to controls and CXM's. Further, the continued acquisition deficit was absent in the PM group, indicating that this effect is highly specific to those behavioral circuits active at the time of injection.