CiteULike: jyuh's Miyata

Kidney-specific enhancement of ANG II stimulates endogenous intrarenal angiotensinogen in gene-targeted mice.

H Kobori — 2008-06-06T04:27:23-00:00

American journal of physiology. Renal physiology, Vol. 293, No. 3. (September 2007)

This study was performed in transgenic mice to test the hypothesis that the selective intrarenal overproduction of ANG II increases intrarenal mouse (m) angiotensinogen (AGT) expression. We used the following three groups: 1) single transgenic mice (group A, n = 14) expressing human (h) AGT only in the kidney, 2) double-transgenic mice (group D, n = 13) expressing human renin systemically in addition to hAGT only in the kidney, and 3) wild-type (group W, n = 12) mice. Exogenous hAGT protein is inactive in group A because endogenous mouse renin cannot cleave hAGT to ANG I because of a high species specificity. All mice were monitored from 12 to 18 wk of age. Systolic blood pressure progressively increased from 116 +/- 5 mmHg (12 wk) to 140 +/- 7 (18 wk) in group D. This increase was not observed in groups A or W. Intrarenal hAGT levels were similar in groups A and D; however, hAGT was not detectable in kidneys of group W. Kidney ANG II levels were increased in group D (216 +/- 43 fmol/g) compared with groups A (117 +/- 16) and W (118 +/- 17). However, plasma ANG II concentrations were similar among the three groups. Endogenous renal mAGT mRNA was increased significantly in group D (1.46 +/- 0.19, ratio) compared with groups A (0.97 +/- 0.12) and W (1.00 +/- 0.08). Endogenous renal mAGT protein was also significantly increased in group D compared with groups A and W. Interstitial collagen-positive area, interstitial macrophage/monocyte infiltration, and afferent arteriolar wall thickness were increased significantly in group D compared with groups A and W. These data indicate for the first time that the selective stimulation of intrarenal production of ANG II from hAGT augments endogenous intrarenal mAGT mRNA and protein expression.

High-density association study and nomination of susceptibility genes for hypertension in the Japanese National Project.

N Kato — 2008-05-23T03:12:59-00:00

Human molecular genetics, Vol. 17, No. 4. (15 February 2008), pp. 617-627.

Essential hypertension is one of the most common, complex diseases, of which considerable efforts have been made to unravel the pathophysiological mechanisms. Over the last decade, multiple genome-wide linkage analyses have been conducted using 300-900 microsatellite markers but no single study has yielded definitive evidence for 'principal' hypertension susceptibility gene(s). Here, we performed a three-tiered, high-density association study of hypertension, which has been recently made possible. For tier 1, we genotyped 80 795 SNPs distributed throughout the genome in 188 male hypertensive subjects and two general population control groups (752 subjects per group). For tier 2 (752 hypertensive and 752 normotensive subjects), we genotyped a panel of 2676 SNPs selected (odds ratio >or= 1.4 and P <or= 0.015 in tier 1) and identified 75 SNPs that showed similar tendency of association in tier 1 and tier 2 samples (P <or= 0.05 for allele frequency and P <or= 0.01 for genotype distribution tests). For tier 3 (619 hypertensive and 1406 normotensive subjects), we genotyped the 75 SNPs and found nine SNPs from seven genomic loci to be associated with hypertension (P <or= 0.05). In three of these loci, the lowest P-values were observed for rs3755351 (P = 1.7 x 10(-5)) in ADD2, rs3794260 (P = 0.0001) in KIAA0789 and rs1805762 (P = 0.0003) in M6PR when case-control comparison was made in the combined data. An SNP (rs3755351) within ADD2 had the lowest P-value and its experiment-wide significance level is 0.13. Thus, these results have nominated several susceptibility genes for hypertension, and independent replication will clarify their etiological relevance.

Hematopoietic origin of hepatic stellate cells in the adult liver.

E Miyata — 2008-05-14T15:38:57-00:00

Blood, Vol. 111, No. 4. (15 February 2008), pp. 2427-2435.

Hepatic stellate cells are believed to play a key role in the development of liver fibrosis. Several studies have reported that bone marrow cells can give rise to hepatic stellate cells. We hypothesized that hepatic stellate cells are derived from hematopoietic stem cells. To test this hypothesis, we generated chimeric mice by transplantation of clonal populations of cells derived from single enhanced green fluorescent protein (EGFP)-marked Lin(-)Sca-1(+)c-kit(+)CD34(-) cells and examined the histology of liver tissues obtained from the chimeric mice with carbon tetrachloride (CCl(4))-induced injury. After 12 weeks of CCl(4) treatment, we detected EGFP(+) cells in the liver, and some cells contained intracytoplasmic lipid droplets. Immunofluorescence analysis demonstrated that 50% to 60% of the EGFP(+) cells were negative for CD45 and positive for vimentin, glial fibrillary acidic protein, ADAMTS13, and alpha-smooth muscle actin. Moreover, EGFP(+) cells isolated from the liver synthesized collagen I in culture. These phenotypes were consistent with those of hepatic stellate cells. The hematopoietic stem cell-derived hepatic stellate cells seen in male-to-male transplants revealed only one Y chromosome. Our findings suggest that hematopoietic stem cells contribute to the generation of hepatic stellate cells after liver injury and that the process does not involve cell fusion.

Visualizing Spatiotemporal Dynamics of Multicellular Cell-Cycle Progression

Asako Sakaue-Sawano — 2008-02-08T16:32:00-00:00

Cell, Vol. 132, No. 3. (8 February 2008), pp. 487-498.

Summary The cell-cycle transition from G1 to S phase has been difficult to visualize. We have harnessed antiphase oscillating proteins that mark cell-cycle transitions in order to develop genetically encoded fluorescent probes for this purpose. These probes effectively label individual G1 phase nuclei red and those in S/G2/M phases green. We were able to generate cultured cells and transgenic mice constitutively expressing the cell-cycle probes, in which every cell nucleus exhibits either red or green fluorescence. We performed time-lapse imaging to explore the spatiotemporal patterns of cell-cycle dynamics during the epithelial-mesenchymal transition of cultured cells, the migration and differentiation of neural progenitors in brain slices, and the development of tumors across blood vessels in live mice. These mice and cell lines will serve as model systems permitting unprecedented spatial and temporal resolution to help us better understand how the cell cycle is coordinated with various biological events.

Establishment of a sandwich ELISA for human megsin, a kidney-specific serine protease inhibitor

Reiko Inagi — 2008-05-05T01:59:06-00:00

Nephrol. Dial. Transplant., Vol. 22, No. 11. (1 November 2007), pp. 3311-3317.

Background. We previously identified a novel serine protease inhibitor (serpin), megsin, which is predominantly expressed in the kidney. Megsin expression is up-regulated in human and experimental renal diseases associated with mesangial proliferation and expansion, suggesting that urinary megsin may be a novel diagnostic marker for some renal diseases. Methods. We established a specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) for megsin and measured urinary megsin of patients with various renal diseases. Results. Megsin ELISA specifically detected megsin but not other serpins. The detection limit was 0.04 ng/ml, which allowed detection of urinary megsin in 3.6% of healthy individuals. The antigenic epitope in the urine detected by the ELISA was confirmed as megsin protein by time-of-flight mass spectrometry. Among patients with rapidly progressive glomerulonephritis (n = 18), 55.6% were urinary megsin-positive, while 24.1% in IgA nephropathy (n = 112) and 15.1% in chronic non-IgA glomerulonephritis (n = 245) were urinary megsin-positive, respectively. Among patients with chronic renal failure due to unknown causes (n = 74), 18.9% were positive for urinary megsin. In diabetic patients with or without nephropathy (n = 1073), 12.3% were urinary megsin-positive, while positivity of urinary megsin in patients with non-renal diseases (n = 768) was equivalent (3.3%) to that of healthy individuals. Of note, when urinary megsin-positive patients with diabetic nephropathy (n = 71) were classified into four stages by their proteinuria and estimated glomerular filtration rate, urinary megsin excretion increased as the stage progressed up to stage 3A, suggesting correlation of that with mesangial expansion level. Urinary megsin decreased in the advanced stage, probably reflecting development of glomerulosclerosis. Conclusion. We established a high-sensitive megsin ELISA, which detects urinary megsin in some patients with renal diseases and in only a few healthy subjects. Megsin ELISA may be a novel diagnostic tool for renal diseases. 10.1093/ndt/gfm391

Determination of plasma and urinary angiotensinogen levels in rodents by newly developed ELISA

Hiroyuki Kobori — 2008-05-02T10:12:41-00:00

Am J Physiol Renal Physiol, Vol. 294, No. 5. (1 May 2008), pp. F1257-1263.

We recently reported that urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-dependent hypertensive rats. Angiotensinogen concentrations in mouse plasma are thought to be much lower than those in rat plasma; however, detailed information is deficient due to lack of direct quantitative measurements of rodent angiotensinogen. To elucidate this issue, we have developed a quantitative method for measurement of rodent angiotensinogen using a sandwich-type ELISA. The standard curve for mouse and rat angiotensinogen exhibited a high linearity at 0.16-10 and 0.08-5 ng/ml, respectively, with correlation coefficients >0.99. While plasma angiotensinogen concentrations of male high serum IgA (HIGA) mice (IgA nephritis model animals, 1,308 +/- 47 ng/ml; n = 10) were lower than those of control BALB/c mice (1,620 +/- 384; n = 12), urinary angiotensinogen concentrations of HIGA mice (14.6 +/- 1.5 ng/ml; n = 34) were higher than those of BALB/c mice (4.6 +/- 0.1; n = 2). In a similar manner, while plasma angiotensinogen concentrations of Zucker diabetic fatty (ZDF) obese rats (type 2 diabetic model animals, 1,789 +/- 50 ng/ml; n = 5) were lower than those of control ZDF lean rats (2,296 +/- 47; n = 5), urinary angiotensinogen concentrations of ZDF obese rats (88.2 +/- 11.4 ng/ml; n = 15) were higher than those of ZDF lean rats (31.3 +/- 1.9; n = 15). These data indicate that plasma and urinary angiotensinogen concentrations are less in mice than rats. However, these data suggest that urinary angiotensinogen levels are different from plasma angiotensinogen levels in rodents. The development of rodent angiotensinogen ELISA allows quantitative comparisons in mouse and rat angiotensinogen levels in models of hypertension and cardiovascular and kidney diseases. 10.1152/ajprenal.00588.2007

Inhibition of Advanced Glycation End Products. An Implicit Goal in Clinical Medicine for the Treatment of Diabetic Nephropathy?

Toshio Miyata — 2008-04-24T08:38:42-00:00

Annals of the New York Academy of Sciences, Vol. 1126, No. 1. (2008), pp. 141-146.

Several factors have been incriminated in the genesis of diabetic nephropathy. To elucidate their interplay, we have used a hypertensive, obese, diabetic rat model with nephropathy (SHR/NDmcr-cp) that mimics human type 2 diabetes. This model is characterized by hypertension, obesity with the metabolic syndrome, diabetes with insulin resistance, and intrarenal advanced glycation end product (AGE) accumulation. In order to achieve renoprotection, which was evaluated by histology and albuminuria, various therapeutic approaches were used: caloric restriction, antihypertensive agents (angiotensin II receptor blocker [ARB] and calcium channel blocker), lipid- (bezafibrate) or glucose-lowering (insulin and pioglitazone) agents, and cobalt chloride (a hypoxia-inducible factor activator). Altogether, renoprotection is not necessarily associated with blood pressure or glycemic control. By contrast, it is almost always associated with decreased AGE formation, with the exception of insulin, which induces hyperinsulinemia, eventually leading to an overproduction of transforming growth factor-beta. AGE formation is reduced directly by in vitro active compounds (e.g., ARBs) or indirectly by in vitro inactive compounds (e.g., pioglitazone and cobalt). In the latter cases, AGE reduction may reflect a decreased oxidative stress as it is concomitant with a marked reduction of oxidative stress markers. It remains to be seen whether the renoprotection offered by these various approaches may be additive.

An alternative fast and convenient genotyping method for the screening of angiotensin converting enzyme gene polymorphisms.

C Tanaka — 2008-03-30T14:49:51-00:00

Hypertens Res, Vol. 26, No. 4. (April 2003), pp. 301-306.

Insertion/deletion (I/D) polymorphisms in intron 16 of the angiotensin converting enzyme gene (ACE) are associated with the plasma angiotensin converting enzyme (ACE) levels, and individuals with the DD allele have been reported to be more susceptible to cardiovascular disease than those without. The conventional genotyping method for the screening of I/D polymorphisms, which involves polymerase chain reaction (PCR)-gel electrophoresis, is laborious and time-consuming. In this study, we assessed the use of TaqMan-PCR genotyping for the screening of I/D polymorphisms as a replacement for the conventional method. We genotyped seven single nucleotide polymorphisms (SNPs) in linkage disequilibrium (LD) with the I/D polymorphisms, and calculated the LD coefficients of the I/D polymorphisms. We found that three polymorphisms, rs4331, rs4334 and rs4341, exhibited the highest LD coefficients (D' = 1.000; r2 = 0.967) and that the genotyping of rs4341 by the TaqMan-PCR method yielded the best discrimination among the different genotypes. Genotyping of 511 samples took only 2 h and the amount of DNA required for each test was only 6 ng by the TaqMan-PCR method using rs4341. In the course of this study, we identified a novel additional polymorphism (a deletion of six amino acids) in exon 13, near rs4316. The deletion allele encoded the testicular ACE, but not the plasma ACE. We concluded that genotyping of the rs4341 ACE polymorphism by the TaqMan-PCR method is a fast and convenient alternative method for direct I/D genotyping. We also concluded that testicular ACE may manifest a deletion of six amino acids that may result in deleterious function of this enzyme.

A severe diabetic nephropathy model with early development of nodule-like lesions induced by megsin overexpression in RAGE/iNOS transgenic mice.

R Inagi — 2008-03-22T01:10:06-00:00

Diabetes, Vol. 55, No. 2. (February 2006), pp. 356-366.

Many factors are involved in the pathogenesis of diabetic nephropathy. A single gene abnormality may be prerequisite but insufficient to the disease to manifest. It is therefore only when a second or sometimes a third damage is associated that the consequences of pathogenic phenotypes become evident. We generated the triple transgenic mice overexpressing megsin (a novel glomerular-specific serpin), a receptor for advanced glycation end products (RAGE), and inducible nitric oxide synthase (iNOS). Compared with the single- or two-gene transgenic mice, the triple transgenic mice developed, at an early age (16 weeks), severe albuminuria and renal damage with all of the characteristics of human diabetic nephropathy (i.e., glomerular hypertrophy, diffuse mesangial expansion, inflammatory cell infiltration, and interstitial fibrosis). Interestingly, 30-40% of glomeruli exhibit nodule-like lesions. Oxidative and carbonyl stress makers (pentosidine, N(epsilon)-carboxymethyllysine, and 8-hydroxy-deoxyguanosine) were significantly higher in the triple transgenic mice. The iNOS transgenic mice have a diabetes phenotype, the renal consequences of which are moot, and the superimposition of RAGE leads to more conspicuous manifestations. By additional overexpression of megsin, a gene known to be involved in mesangial proliferation and expansion, these local consequences become dramatically manifest and approximate those observed in human pathology. This multiple hit approach is of interest in consideration of the sequential events during development of diabetic nephropathy.

Erythropoietin induces heme oxygenase-1 expression and attenuates oxidative stress.

P Katavetin — 2008-03-12T06:53:29-00:00

Biochem Biophys Res Commun, Vol. 359, No. 4. (10 August 2007), pp. 928-934.

Recent studies have established that erythropoietin (EPO) is a pleiotropic cytokine. In this study we investigated whether pleiotropic effects of EPO may involve regulation of heme oxygenase (HO)-1, an anti-oxidative stress protein. A stimulatory effect of EPO on HO-1 expression was demonstrated in cultured renal endothelial cells, in which EPO decreased intracellular oxidative stress and provided cytoprotection against H(2)O(2). These beneficial effects were partially reversed by a HO-1 inhibitor. We then evaluated whether EPO induces HO-1 and ameliorates renal injury in vivo. Administration of EPO to Dahl salt-sensitive (DS) rats with low salt diet, a model of chronic tubulointerstitial injury, reduced proteinuria, and renal injury including peritubular capillaries rarefaction as compared to vehicle-treated DS rats. This renoprotection was associated with up-regulation of HO-1 in the kidney. In conclusion, EPO-induced HO-1 expression is likely to provide cytoprotection against oxidative stress.

A novel class of advanced glycation inhibitors ameliorates renal and cardiovascular damage in experimental rat models

Yuko Izuhara — 2008-02-11T09:36:21-00:00

Nephrol. Dial. Transplant., Vol. 23, No. 2. (1 February 2008), pp. 497-509.

Background. The reno- and cardiovascular-protective effects of angiotensin II receptor blockers (ARBs), have been ascribed, at least in part, to their ability to inhibit the formation of advanced glycation end products (AGEs), independently of their effect on blood pressure. They act through decreased oxidative stress, unlike previously reported AGE inhibitors which entrap reactive carbonyl (RCOs) precursors of AGEs. The hypotensive effects of ARBs', however, may limit their use. In the present study, we report the synthesis of a new AGE inhibitor, TM2002, and its effects in vitro and in vivo. Methods. We screened a large chemical library ([~]1300 compounds) including edaravone, a drug used to treat cerebral infarction, for in vitro AGE inhibitory activity. Based upon the structure-function analysis of edaravone derivatives, we synthesized a novel AGE inhibitor, 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-6-methyl-1,3-dihydro-furo[3,4-c]pyridine-7-ol (TM2002). We delineate in vitro the biological characteristics of TM22002, evaluate in vivo its toxico-pharmacokinetics and document in animal models of rat, their renal and cardiovascular protective effectiveness. Results. Screening of a large chemical library disclosed that edaravone inhibits in vitro AGE formation efficiently. Unfortunately, like most AGE inhibitors, it also traps pyridoxal, limiting its clinical usefulness. We therefore synthesized a novel AGE inhibitor, TM2002, that does not trap pyridoxal. In vitro, TM2002 shows powerful AGE inhibitory activity. Markers of oxidation, i.e. o-tyrosine formation and transition metal chelation, are efficiently inhibited by TM2002-like ARBs. TM2002 does not bind to the angiotensin II type 1 receptor. It is readily bioavailable and non-toxic. In vivo, TM2002, given acutely or for 8 weeks, has no adverse effects. In four different rat models of renal injury (anti-Thy1 and ischaemia-reperfusion) and cardiovascular injury (carotid artery balloon injury and angiotensin II-induced cardiac fibrosis), TM2002 improves renal and cardiovascular lesions without modification of blood pressure. Conclusions. TM2002 is a novel, non-toxic AGE inhibitor acting through ARB-like mechanisms, able to prevent renal and cardiovascular diseases independently of blood pressure lowering. 10.1093/ndt/gfm601

Aldosterone stimulates collagen gene expression and synthesis via activation of ERK1/2 in rat renal fibroblasts.

Y Nagai — 2008-01-28T12:10:53-00:00

Hypertension, Vol. 46, No. 4. (October 2005), pp. 1039-1045.

Recently, we demonstrated that in rats treated chronically with aldosterone and salt, severe tubulointerstitial fibrosis is associated with the activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERK1/2). Here, we investigated whether aldosterone stimulates collagen synthesis via ERK1/2-dependent pathways in cultured rat renal fibroblasts. Gene expression of mineralocorticoid receptor (MR) and types I, II, III, and IV collagen was measured by real-time polymerase chain reaction (PCR). MR protein expression and ERK1/2 activity were evaluated by Western blotting analysis with anti-MR and anti-phospho-ERK1/2 antibodies, respectively. Collagen synthesis was determined by [3H]-proline incorporation. Significant levels of MR mRNA and protein expression were observed in rat renal fibroblasts. Treatment with aldosterone (0.1 to 10 nmol/L) increased ERK1/2 phosphorylation in a concentration-dependent manner with a peak at 5 minutes. Aldosterone (10 nmol/L) also increased the mRNA levels of types I, III, and IV collagen at 36 hours but had no effect on the type II collagen mRNA level. [3H]-proline incorporation was significantly increased by aldosterone in both the medium and cell layer at 48 hours. Aldosterone-induced ERK1/2 phosphorylation was markedly attenuated by pretreatment with eplerenone (10 micromol/L), a selective MR antagonist, or PD98059 (10 micromol/L), a specific inhibitor of MAPK kinase/ERK kinase, which is the upstream activator of ERK1/2. In addition, both eplerenone and PD98059 prevented the aldosterone-induced increases in types I, III, and IV collagen mRNA and [3H]-proline incorporation. These results suggest that aldosterone stimulates collagen gene expression and synthesis via MR-mediated ERK1/2 activation in renal fibroblasts, which may contribute to the progression of aldosterone-induced tubulointerstitial fibrosis.

Transdifferentiation of cultured tubular cells induced by hypoxia.

K Manotham — 2008-01-23T01:59:52-00:00

Kidney Int, Vol. 65, No. 3. (March 2004), pp. 871-880.

BACKGROUND: Tubulointerstitial fibrosis leads to progressive kidney disease and, ultimately, may result in end-stage renal disease (ESRD). Myofibroblasts, which express alpha-smooth muscle actin (alpha-SMA) in their cytoplasm, regulate renal fibrogenesis. Recent studies suggest that certain interstitial myofibroblasts derive from renal tubular cells that have undergone epithelial-mesenchymal transformation (EMT) (transdifferentiation). However, the role(s) of hypoxia, which is involved in progressive kidney disease, on tubular EMT remains unclear. METHODS: Immortalized rat proximal tubular cells (IRPTC) were cultured in normobaric hypoxia (1% O2) for 3, 6, or 15 days, with match control in normoxic conditions. alpha-SMA, vimentin, and desmin chosen as markers of EMT were measured by immunocytochemistry and immunoblots collagen I production and cell motility were chosen as functional assays. Various concentrations of cobaltous chloride (CoCl2) were used as hypoxic mimickers. In vivo studies were carried out in a chronic ischemic kidney model. RESULTS: Immunohistochemical studies revealed increased expression of alpha-SMA. Striking morphologic changes were detected after 6 days of hypoxia for alpha-SMA-positive fibroblast-like cells (SMA + fib) and after 15 days for alpha-SMA-positive myofibroblast-like cells (SMA + myo). Immunoblots confirmed these findings. Collagen I production increased in a time-dependent manner parallel to alpha-SMA expression. Cell motility assays demonstrated that transformed cells had higher migratory capacity than normal tubular cells. Cobaltous salt also induced alpha-SMA and collagen I synthesis. Chronic ischemic kidney revealed in vivo tubular EMT at day 7. CONCLUSION: Hypoxia can induce tubular EMT. This process may play an important role in progression of kidney disease.

Hypoxia in Renal Disease with Proteinuria and/or Glomerular Hypertension

Tetsuhiro Tanaka — 2008-01-15T04:57:52-00:00

Am J Pathol, Vol. 165, No. 6. (1 December 2004), pp. 1979-1992.

Despite the increasing need to identify and quantify tissue oxygenation at the cellular level, relatively few methods have been available. In this study, we developed a new hypoxia-responsive reporter vector using a hypoxia-responsive element of the 5' vascular endothelial growth factor untranslated region and generated a novel hypoxia-sensing transgenic rat. We then applied this animal model to the detection of tubulointerstitial hypoxia in the diseased kidney. With this model, we were able to identify diffuse cortical hypoxia in the puromycin aminonucleoside-induced nephrotic syndrome and focal and segmental hypoxia in the remnant kidney model. Expression of the hypoxia-responsive transgene increased throughout the observation period, reaching 2.2-fold at 2 weeks in the puromycin aminonucleoside model and 2.6-fold at 4 weeks in the remnant kidney model, whereas that of vascular endothelial growth factor showed a mild decrease, reflecting distinct behaviors of the two genes. The degree of hypoxia showed a positive correlation with microscopic tubulointerstitial injury in both models. Finally, we identified the localization of proliferating cell nuclear antigen-positive, ED-1-positive, and terminal dUTP nick-end labeled-positive cells in the hypoxic cortical area in the remnant kidney model. We propose here a possible pathological tie between chronic tubulointerstitial hypoxia and progressive glomerular diseases.

Thiazolidinediones provide better renoprotection than insulin in an obese, hypertensive type II diabetic rat model.

S Ohtomo — 2007-11-20T01:42:14-00:00

Kidney Int (26 September 2007)

Hyperinsulinemia has been implicated in the development of diabetic nephropathy. In the present study we compared the renoprotective effects of the thiazolidinedione, pioglitazone (PGZ), to that of insulin in a hypertensive, obese, type II diabetic rat model. PGZ aggravated obesity and gave less glycemic control than insulin. However, renoprotection was markedly better with PZG compared to insulin as shown by lower proteinuria, improved renal function, and less histological evidence of diabetic glomerular and tubulointerstitial lesions. PZG and insulin both reduced renal accumulation of pentosidine and oxidative stress to a similar extent. In contrast, PGZ but not insulin suppressed enhanced transforming growth factor-beta (TGF-beta) expression. We further confirmed in cultured rat proximal tubular cells that insulin enhanced TGF-beta mRNA expression and protein production. Our results identify hyperinsulinemia and the attendant increase of TGF-beta expression as potential therapeutic targets in diabetes independent of glycemic control. This confirms prior clinical evidence that PZG provides renoprotection in obese, diabetic patients with nephropathy.Kidney International advance online publication, 26 September 2007; doi:10.1038/sj.ki.5002570.

Cobalt Ameliorates Renal Injury in an Obese, Hypertensive Type 2 Diabetes Rat Model

Shuichi Ohtomo — 2007-11-01T09:30:07-00:00

Nephrol. Dial. Transplant. (28 October 2007), gfm715.

Background. Chronic renal hypoxia is suspected to play a pathogenic role in the genesis of diabetic nephropathy (DN). Cobalt enhances the activity of the hypoxia-inducible factor (HIF), a key factor in the defence against hypoxia. Its long-term effect on DN is evaluated. Methods. Cobalt chloride was given to hypertensive, type 2 diabetic rats with nephropathy (SHR/NDmcr-cp). Treatment was initiated at the age of 13 weeks and continued for 26 weeks. Results. Cobalt did not correct hypertension and metabolic abnormalities (obesity, hyperglycaemia and hyperlipidaemia) but reduced proteinuria as well as histological kidney injury. Cobalt upregulated renal HIF-1alpha and HIF-2alpha expression and increased the expression of HIF-regulated genes, including erythropoietin, vascular endothelial growth factor and heme oxygenase-1. The renal expression of transforming growth factor (TGF)-beta and connective tissue growth factor (CTGF) was significantly reduced by cobalt. The renal expression of NADPH oxidase, a marker of oxidative stress, and the renal content of pentosidine, a marker of advanced glycation, were also significantly reduced by cobalt. Conclusions. Cobalt achieved renal protection independently of metabolic status and blood pressure. Its effect was attributed to the upregulation of HIF and HIF-regulated genes and to a mitigated advanced glycation and oxidative stress. 10.1093/ndt/gfm715

In a type 2 diabetic nephropathy rat model, the improvement of obesity by a low calorie diet reduces oxidative/carbonyl stress and prevents diabetic nephropathy.

M Nangaku — 2007-10-23T09:11:32-00:00

Nephrol Dial Transplant, Vol. 20, No. 12. (December 2005), pp. 2661-2669.

BACKGROUND: The present study has been undertaken to unravel the critical factors involved in the progression of diabetic nephropathy (DN). METHODS: A unique type 2 diabetic rat model with a wide range of metabolic derangements and hypertension has been utilized, the spontaneously hypertensive/NIH-corpulent rat SHR/NDmcr-cp(cp/cp). It develops histologically evident glomerular injury and tubulointerstitial damage, including mesangial activation, podocyte injury, and inflammatory cell infiltration in the tubulointerstitium. RESULTS: A low calorie diet for 22 weeks significantly improves obesity, proteinuria and renal morphological alterations. The correction of renal injury is independent of blood pressure control. Obesity correction, although partial, normalizes the renal content of pentosidine taken as a marker of oxidative stress and advanced glycation end products (AGEs). This occurs despite the fact that, in this model, improvement of glucose control and hyperlipidaemia is limited. Proteinuria and body weight are highly correlated with renal pentosidine content, while proteinuria and body weight are also correlated with each other. Diabetic renal injury is thus inhibited by a low calorie diet with an attendant reduction of oxidative stress and AGE formation, despite sustained hypertension. CONCLUSION: The present findings suggest a direct role of obesity in the generation of a localized oxidative stress and AGE formation, directly responsible for DN.

Anti-hypertensive agents inhibit in vivo the formation of advanced glycation end products and improve renal damage in a type 2 diabetic nephropathy rat model.

M Nangaku — 2007-10-23T09:11:03-00:00

J Am Soc Nephrol, Vol. 14, No. 5. (May 2003), pp. 1212-1222.

Prevention or retardation of diabetic nephropathy (DN) includes anti-hypertensive treatment with angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II type 1 receptor blockers (ARB) on the premises that these drugs have an added protective effect beyond their influence on BP. The present study used a strain of spontaneously hypertensive/NIH-corpulent rats [SHR/NDmc-cp (fat/fat)] as a model of type II DN to unravel the renoprotective effects of anti-hypertensive drugs. Olmesartan (1 or 5 mg/kg per d), an ARB, and hydralazine (5mg/kg per d), an anti-hypertensive drug without effect on the renin-angiotensin system (RAS), were given for 20 wk. BP, renal function, glucose and insulin levels, and proteinuria were monitored. Glomerular lesions and kidney pentosidine content were assessed at the end of the study. Olmesartan (1 and 5 mg) significantly reduced BP and kidney pentosidine content and improved histologic renal damage and proteinuria. The changes were dose-dependent. The effect of hydralazine (5 mg) was similar to that of olmesartan (1 mg) but reached statistical significance only for kidney pentosidine content. The similarity of both drugs' effects on kidney damage and proteinuria suggest that renoprotection does not hinge on manipulation of RAS in these rats. By contrast, the inhibition of renal pentosidine formation assessed both by immunohistochemistry and HPLC suggests a critical role of advanced glycation end product (AGE) formation together with hypertension in the genesis of diabetic nephropathy. This view is supported by the correlation found between renal pentosidine content and proteinuria. The unsuspected AGE-lowering effect of hydralazine was further confirmed in vitro and elucidated; it is due to both reactive carbonyl compounds trapping and modifications of the oxidative metabolism. It is concluded that AGE inhibition should be included in the therapeutic strategy of DN.

Methylglyoxal induces apoptosis through activation of p38 mitogen-activated protein kinase in rat mesangial cells.

BF Liu — 2007-09-13T09:08:16-00:00

Kidney Int, Vol. 63, No. 3. (March 2003), pp. 947-957.

BACKGROUND: The formation of methylglyoxal (MG), a highly reactive dicarbonyl compound, is accelerated through several pathways, including the glycation reaction under diabetic conditions, presumably contributing to tissue injury in diabetes. On the other hand, apoptotic cell death of glomerular cells has been suggested to play a role in the development of glomerulosclerosis in various types of glomerular injuries. We therefore examined whether MG was capable of inducing apoptosis in rat mesangial cells to address the possible mechanism by which hyperglycemia-related products accelerated pathologic changes in diabetic glomerulosclerosis. METHODS: Rat mesangial cells were incubated with 0 to 400 micromol/L MG, followed by the detection of apoptosis by both TUNEL method and electrophoretic analysis for DNA fragmentation. In addition, we investigated intracellular mechanisms mediating MG-induced apoptosis, focusing especially on the p38 mitogen-activated protein kinase (MAPK) pathway. RESULTS: MG induced apoptosis in rat mesangial cells in a dose-dependent manner and was accompanied by the activation of p38alpha isoform. Aminoguanidine and N-acetyl-l-cysteine inhibited the MG-induced p38 MAPK activation, as well as apoptosis in rat mesangial cells, suggesting the involvement of oxidative stress in these phenomena. SB203580, a specific inhibitor of p38 MAPK also suppressed the MG-induced apoptosis in rat mesangial cells. CONCLUSIONS: These results suggest a potential role for MG in glomerular injury through p38 MAPK activation under diabetic conditions and may serve as a novel insight into the therapeutic strategies for diabetic nephropathy.

Overexpression of thioredoxin1 in transgenic mice suppresses development of diabetic nephropathy.

Y Hamada — 2007-07-05T01:48:57-00:00

Nephrol Dial Transplant, Vol. 22, No. 6. (June 2007), pp. 1547-1557.

BACKGROUND: Oxidative stress has been suggested to play an important role in the pathogenesis of diabetic nephropathy. In the present study, the effects of thioredoxin1 (TRX1) overexpression, a small protein with antioxidant property, on the development of diabetic nephropathy in streptozotocin-induced diabetic animals were investigated using TRX1 transgenic mice (TRX1-Tg). METHODS: Eight-week-old male TRX1-Tg and wild-type mice littermates (WT) mice were treated either with streptozotocin (200 mg/kg) or vehicle alone. After 24 weeks of treatment, diabetic nephropathy and oxidative stress were assessed in these four groups of mice, by biochemical analyses of blood and urine, as well as by histological analyses of the kidneys. RESULTS: Haemoglobin A1c (HbA1c) levels of diabetic TRX1-Tg were not significantly different from those of the diabetic WT. Nevertheless, an augmented urinary albumin excretion observed in diabetic WT was significantly diminished in diabetic TRX1-Tg. Histological study revealed that pathological changes such as mesangial matrix expansion and tubular injury were significantly prevented in diabetic TRX1-Tg accompanied by a reduced tendency of expression of transforming growth factor-beta as compared with diabetic WT. In parallel, urinary excretion of 8-hydroxy-2'-deoxyguanosine and acrolein adduct and the immunostaining intensities of these markers in the kidney were significantly higher in diabetic WT compared with non-diabetic mice. The markers were significantly suppressed in diabetic TRX1-Tg, an indication of systemic and renal oxidative stress attenuation by TRX1 overexpression. CONCLUSION: These findings indicated the significant role of oxidative stress in the development of diabetic nephropathy and a potential inhibition of progression of nephropathy by TRX1.