Search

We identified the inv gene that encodes left and right asymmetry and regulates kidney development based on the information of the inv mutant mouse. However, functional properties and the modulator of gene expression of inv have been unclear. We used the tissue injury model for assessing the functional roles of inv in ischemia reperfusion injury (IRI). The kidney tissue taken from rats with IRI showed reciprocal changes in mRNA expression of inv: a 0.25-fold decrease at 6 hours and then a gradual increase to a maximum 1.8-fold rise at 10 days of reperfusion. Next, oxidative stress was induced by exposing mouse inner medullary collecting duct (mIMCD-3) cells to hydrogen peroxide(H2O2) in the medium. Real-time PCR showed that mRNA expression of inv decreased 0.52-fold at 3 hours with 0.2 mM H2O2 in the medium, and then increased 3.1-fold at 24 hours with 0.1 mM H2O2 in the medium. RNA interference (RNAi) is a powerful tool to inhibit gene expression in experimental model systems. We knocked down inv gene expression in mIMCD-3 cells using RNAi to investigate the function of the inv gene. We designed a small interfering RNA (siRNA) to target the coding region of inv (inv-siRNA) and random-sequence scrambled siRNA(control siRNA). mIMCD-3 cells transfected with either the inv-siRNA or control siRNA were observed by microscopy. The cells transfected with inv-siRNA progressively lost cell-to-cell contact and the cell population significantly diminished approximately 48 hours post-transfection. The changes in gene expression profile were observed at time points (36 hours) using real-time PCR-based gene screening with categorized primer sets. Several genes related to structural protein of the matrix were downregulated. In contrast, repairing related genes were upregulated. In conclusion, gene expression of inv was modulated under oxidative stress and the inv gene may play a role in repairing and regenerating renal epithelial cells.

Background: In diabetic nephropathy, tubulointerstitial fibrosis is an important component of renal injury. Transforming growth factor (TGF)-beta is a key cytokine that is involved in the pathogenesis of tubulointerstitial fibrosis. However, signal transduction cascades of TGF-beta under high-glucose conditions remain to be clarified. We undertook this study to elucidate whether mitogen-activated protein (MAP) kinase and Smad proteins were involved in TGF-beta-induced fibronectin (FN) production under high glucose in NRK fibroblasts., Methods: After serum restriction, NRK cells were exposed to either normal glucose (5.5 mM d-glucose), high glucose (30 mM d-glucose), or 30 mM l-glucose in the presence or absence of TGF-beta for 24 h. MAP kinase inhibitors (SB 203580 and PD 98059) were added to the cultured NRK fibroblasts 2 h before TGF-beta1, and the incubations continued for 8 h. The phosphorylation of p38 MAP kinase, extracellular signal-regulated kinase (ERK)1/ERK2, and c-Jun N-amino terminal kinase (JNK) was assessed by immunoblotting. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were performed to determine FN mRNA and protein expression, respectively., Results: High glucose significantly increased the expression of FN mRNA, by 2.4 +/- 1.4-fold. In the presence of either SB 203580 or PD 98059, the high glucose-induced FN mRNA increase was completely inhibited. Incubation of NRK fibroblasts for 48 h in 30 mM d-glucose did not alter p38 MAP kinase, ERK1/ERK2, or JNK phosphorylation. The addition of exogenous TGF-beta1 (1 ng/ml) for 8 h increased FN mRNA by 2.7 +/- 1.1-fold. Both the TGF-beta1- and high glucose-induced FN mRNA increases were inhibited by SB 203580 and PD 98059. Dominant-negative Smad4 did not affect the FN mRNA increase induced by TGF-beta1 and high glucose. Exogenous TGF-beta1 under both normal and high glucose, enhanced the phosphorylation of both p38 MAP kinase and ERK1/ERK2, but not that of JNK., Conclusions: NRK fibroblasts exposed to high glucose demonstrated increased TGF-beta1-induced p38 MAP kinase activation. The FN synthesis induced by high glucose and TGF-beta1 was not affected by the Smads pathway and was not due to increased osmolarity. The enhanced activation of p38 MAP kinase may contribute to the altered fibroblast phenotype that leads to progressive diabetic nephropathy.

Background: Recent studies have shown that steroid therapy is effective for IgA nephropathy (IgAN) in patients with moderate proteinuria and active histological findings. However, the effectiveness of steroid therapy has not been determined yet in patients with advanced IgAN and impaired renal function., Methods: Sixty IgAN patients whose creatinine clearance was under 70 ml/min at the time of renal biopsy were studied retrospectively. The patients were divided into two groups according to treatment: a steroid group ( n = 20) and a nonsteroid group ( n = 40). The mean age was 39.6 +/- 14.9 years in the steroid group and 40.6 +/- 10.9 years in the nonsteroid group. The mean follow-up period was 4.5 +/- 2.2 years in the steroid group and 4.6 +/- 2.4 years in the nonsteroid group. Patients with high proteinuria and high histological activity were treated with prednisolone. Clinical and histological findings before treatment and the outcome after treatment were analyzed., Results: In the retrospective analysis, the amount of urinary protein excretion before treatment tended to be higher in the steroid group than in the nonsteroid group, but was not significantly different (2.33 +/- 1.54 vs 1.39 +/- 1.87 g/day). Histologically, the percentage of patients with crescent formation, especially that of cellular or fibrocellular crescents, was significantly higher in the steroid group than in the nonsteroid group (17.2 +/- 15.9% vs 2.3 +/- 4.5%; P < 0.0001). The grades of mesangial cell proliferation (1.65 +/- 0.55 vs 1.21 +/- 0.47; P = 0.002) and mesangial matrix increase (1.88 +/- 0.64 and 1.41 +/- 0.67; P = 0.01) were higher in the steroid group than in the nonsteroid group. In the evaluation of the outcome after treatment, the amount of urinary protein excretion at 1 year after treatment had significantly decreased in the steroid group (before treatment, 2.33 +/- 1.54 g/day; at 1 year, 1.02 +/- 0.98 g/day; P = 0.003), but the amount remained unchanged in the nonsteroid group (before treatment, 1.39 +/- 1.87 g/day; at 1 year, 1.28 +/- 2.19 g/day). The levels of serum creatinine before treatment and at 1 year after treatment were not changed in either of the groups, however, in the nonsteroid group, the level at the final observation was significantly higher than the level before treatment (2.51 +/- 3.43 vs 1.27 +/- 0.33 mg/dl; P = 0.0219)., Conclusions: In the present study, in advanced IgAN patients whose creatinine clearance was under 70 ml/min, steroid therapy effectively reduced the amount of proteinuria and maintained the serum creatinine level, if the treatment was selectively applied to patients with a moderate amount of proteinuria and active glomerular lesions such as cellular and fibrocellular crescents, and mesangial cell proliferation.

Progression to chronic renal failure is influenced by the extent of irreversible interstitial fibrosis. For a quantitative evaluation of interstitial fibrosis, we attempted color extraction of the interstitial area treated with Masson-Trichrome stain using an image analyzer. The subjects were 20 cases of IgA nephropathy with a mean age of 33.4 +/- 12.3 years. The interstitial lesions were graded simultaneously by renal pathologists without clinical information. In addition, immunohistochemical studies using specific antibodies against type III collagen, alpha-smooth muscle actin and CD34 were performed to further characterize the interstitial lesions. The percentage of interstitium in the renal cortex evaluated by an image analyzer was significantly correlated with the pathological grade of fibrous interstitial damage(sigma = 0.861, p < 0.0002), the type III collagen-positive area(sigma = 0.954, p < 0.0001) and alpha-smooth muscle actin-positive area(sigma = 0.686, p = 0.0005). Moreover, the percentage of interstitium was negatively correlated with 24-hr creatinine clearance(r = -0.744, p < 0.0001) and the numbers of peritubular capillaries detected by CD34(r = -0.649, p < 0.0014). These findings suggest that color extraction of the interstitial area stained with Masson-Trichrome using image analysis is useful for a quantitative evaluation of the interstitial fibrous lesions in IgA nephropathy.

The major metabolic change that characterizes nephrotic syndrome (NS) is hypoalbuminemia. Edema, which is a well-recognized clinical feature, often results in disorder of peripheral circulation and congestive heart failure. We previously reported that the albumin content of kidney lysosomal proteins was increased more than ten-fold in nephrotic rats compared to control rats, suggesting that kidney lysosomes play an important role in protein degradation in NS. The present study was carried out to elucidate the role of catabolism of BNP, which is one of the functional protein-natriuretic peptides. We injected puromysin aminonucleoside(PAN) to induce the nephrotic rat state and isolated kidney lysosomes from normal and nephrotic rat kidney cortex by our methods. Immunoblot analysis of tricine-SDS polyacrylamide gel electrophoresis of rat kidney lysosomal proteins revealed the presence of an immuno-reactive peptide band, corresponding to the endogenous BNP. In addition, this was reduced as compared with the normal control. These result suggest that kidney lysosomes play an important role in BNP metabolism to maintain body fluid homeostasis and regulate blood pressure levels.

The ets-1 proto-oncogene is a member of the transcriptional factor family and was identified by homology to the v-ets oncogene. It was recently demonstrated that Ets-1 protein interacts with the promoter region of the genes coding for proteinases, including matrix metalloproteinase-1 (MMP-1), MMP-3, and urokinase-type plasminogen activator, suggesting that it may play an important role in the regulation of MMP expression. The role of the ets-1 proto-oncogene in advanced glomerular diseases, where extracellular matrix accumulation is observed, remains undefined. In this study, the expression of ets-1 mRNA and protein during the progression of rat crescentic glomerulonephritis was examined using immunohistochemical analysis, reverse transcription-PCR, and in situ hybridization. Passive accelerated anti-glomerular basement membrane-induced nephritis was induced in rats by intravenous injection of nephrotoxic serum. Rats were euthanized on day 7, 14, 21, 28, or 42. Immunohistochemical analysis demonstrated significant upregulation of Ets-1 protein expression in glomeruli and the interstitium in anti-glomerular basement membrane-induced nephritis. The numbers of Ets-1-positive cells were increased 8.8-fold on day 21 in glomeruli (1.2+/-0.1 cells/glomerular cross-section, P<0.001) and sixfold on day 28 in the interstitium (21+/-1.3 cells/mm(2), P<0.001), compared with control samples. Ets-1 protein was predominantly localized in glomerular epithelial cells, endothelial cells, and interstitial cells. A small number of vascular endothelial cells, macrophages, and T cells also expressed Ets-1 protein. MMP-3 deposition was upregulated and positive cells in the interstitium often coexpressed Ets-1, whereas only a few glomerular cells were positive for both MMP-3 and Ets-1 protein. The expression of ets-1 mRNA was also markedly increased in diseased kidneys. The distribution of ets-1 mRNA was similar to that of the protein. These results indicate that overexpression of the ets-1 proto-oncogene by phenotypically altered renal cells might be associated with the pathogenesis of rat crescentic glomerulonephritis.

Under normal conditions, kidney expresses Smad6 and Smad7 most abundantly among the organs of the body. To understand the physiological roles of these Smad expressions in the kidney, we first identified the sites of Smad6 and Smad7 expression in the rat kidney by in situ hybridization. The expression of Smad7 in the rat kidney was only observed in the glomeruli, while Smad6 was expressed in both the glomeruli and thick ascending limb of Henle's loop. In order to investigate whether Smad6 and 7 are also involved in the negative feedback loop of TGF-beta signaling in vivo, we examined the changes of mRNA levels of these Smads in the glomeruli of rat anti-Thy1 (1-22-3) nephritis, a model where the expression of TGF-beta in the glomeruli has been shown to be most up-regulated from day 4 to 14 after the antibody injection. Unexpectedly, 7 days after injection, the levels of Smad6 and Smad7 did not increase but rather decreased to approximately 70% of the levels on day 0. During that period, Smad7 immunostaining was observed in the glomerular endothelial cells (GEN) where Smad3 immunostaining was also observed. This suggested that Smad7 expression was not augmented by the TGF-beta signal in GEN in vivo in anti-Thy-1 nephritis. The absence of up-regulation of these inhibitory Smads may be involved in the pathogenesis of anti-Thy-1 nephritis., (Copyright 2000 Academic Press.)

In vitro data support that extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), members of mitogen-activated protein (MAP) kinases, mediate the signal transduction pathways responsible for the cell proliferation. However, in vivo role of these MAP kinases is poorly understood. Intramuscular injection of 50% glycerol solution induces acute renal failure in rats. This injury is known as a model of rhabdomyolysis in human. To investigate the molecular mechanism of the signaling pathway in this injury, we examined the role of ERK and JNK. After the glycerol injection JNK was rapidly and transiently activated at about 4 h, while the activation of ERK was gradually increased and the levels were sustained at least to 24 h. Next, we examined the expression of cell-cycle related proteins after the glycerol injection using Western blot analysis. The levels of proliferating cell nuclear antigen (PCNA) protein as a marker for cell proliferation were induced at 2 h and significantly increased to 24 h after the injection. In addition, cyclins D1, D2, and D3 as markers for G1 phase also increased with similar time courses. To examine whether activation of ERK and/or JNK are involved in the renal regeneration after the glycerol injection, we examined the effect of genistein, which is an inhibitor of tyrosine kinase, on the activation of ERK and JNK. Administration of genistein to rats with this injury decreased the activation of ERK, but not JNK. The induction of PCNA and cyclin D1 was also prevented by this treatment. In this condition, renal function was further worsened as compared to control rats. These results provide the first evidence that ERK may be involved in the repair process of renal tubules damaged by this injury., (Copyright 1999 Academic Press.)

In hypertension, impairment of hyperpolarization by K+ efflux through ATP-sensitive K+ (K(ATP)) channels may contribute to the elevated renal vascular resistance. To elucidate such a role for K(ATP) channels in the renal vasculature, we used micropuncture techniques to examine the effect of K(ATP) channel opener, pinacidil (0.15 mg/h per kg body wt i.v.), on renal and glomerular haemodynamics in spontaneously hypertensive rats (SHR) and in normotensive controls (Wistar Kyoto, WKY). Since pinacidil reduced blood pressure significantly in both groups, the abdominal aorta was clamped before pinacidil administration to yield a renal perfusion pressure equivalent to that during pinacidil infusion. Pinacidil significantly decreased renal vascular resistance in both groups, but the relative change from baseline value was greater in WKY than in SHR. These effects of pinacidil were abolished by pretreatment with glibenclamide (3 mg/kg body wt i.v.). Proximal tubular stop-flow pressure (Psf), an index of glomerular capillary pressure, was significantly elevated by pinacidil infusion in WKY, a response abolished by pretreatment with glibenclamide, but not in SHR. The tubuloglomerular feedback response of Psf was not affected by pinacidil in either group. These data suggest that the activity of K(ATP) channels in SHR may be attenuated in the renal microvasculature. This may contribute to the elevated vascular tone in the renal preglomerular vasculature in SHR.

Most vertebrate internal organs show a distinctive left/right asymmetry. The inv (inversion of embryonic turning) mutation in mice was created previously by random insertional mutagenesis; it produces both a constant reversal of left/right polarity (situs inversus) and cyst formation in the kidneys. Asymmetric expression patterns of the genes nodal and lefty are reversed in the inv mutant, indicating that inv may act early in left/right determination. Here we identify a new gene located at the inv locus. The encoded protein contains 15 consecutive repeats of an Ank/Swi6 motif at its amino terminus. Expression of the gene is the highest in the kidneys and liver among adult tissues, and is seen in presomite-stage embryos. Analysis of the transgenic genome and the structure of the candidate gene indicate that the candidate gene is the only gene that is disrupted in inv mutants. Transgenic introduction of a minigene encoding the candidate protein restores normal left/right asymmetry and kidney development in the inv mutant, confirming the identity of the candidate gene.

The present study was undertaken to clarify the mechanism of the regulation of nitric oxide synthase (NOS)-I in the macula densa of the kidney. We determined the changes in NOS-I immunoreactivity of the macula densa relevant to the changes in systemic blood pressure (BP) and the renin-angiotensin system. Rats received four different types of treatment, and kidney sections were immunohistochemically stained for renin, NOS-I, and NOS-III. Plasma renin activity (PRA) and angiotensin II (Ang II) concentration were determined by radioimmunoassay. In the low-salt group, PRA, plasma Ang II, and the number of renin and NOS-I positively stained areas in the juxtaglomerular apparatus (JGA) were all increased, while BP and NOS-III in the glomerular capillaries did not change. In the desoxycorticosterone acetate (DOCA)-salt group, in contrast to the elevation of BP, PRA, plasma Ang II, and all immunohistochemical parameters were decreased. In the Ang II infusion group, BP, plasma Ang II, and the number of NOS-I positive glomeruli were increased, while PRA and renin staining were decreased. Administration of Ang II type 1 receptor (AT-1) antagonist TCV-116 significantly increased PRA, plasma Ang II, and the number of renin-positive glomeruli. However, BP, and NOS-I and NOS-III staining did not show any difference. These results clearly suggest that NOS-I in the macula densa changes in parallel with plasma Ang II, but not renin or systemic BP.

Intramuscular injection of hypertonic glycerol solution to rats results in acute renal injury. In this model, the proximal tubules are characteristically damaged. After glycerol injection renal glutathione (GSH) levels drastically decreased. On the other hand, stress protein heme oxygenase-1 (HO-1) was induced. When N-acetyl cysteine was administered to rats before 1 h glycerol injection, renal function was obviously improved. In this condition, the renal GSH content were sustained in the normal levels and HO-1 protein levels were decreased compared with those of glycerol-treated rats. Induction of HO-1 was accompanied by reduced renal GSH content. In addition, to investigate whether the location of HO-1 protein induced by glycerol injection is restricted to injured region or not in the kidney, we determined the localization of HO-1 protein using immunohistochemical staining. HO-1 protein was identified in the epithelia of the distal tubules, Henle's loop and collecting ducts, but not in the injured proximal tubules.

Rat p38 mitogen-activated protein (MAP) kinase cDNA was isolated from rat kidney cDNA library using a PCR cloning strategy. The deduced amino acid sequence consists of 360 amino acids and shares 95.3% similarity with human p38 MAP kinase. The message for rat p38 MAP kinase was about 3.4 kilobases and was highly expressed in the kidney. In water-deprived rat kidneys, the steady-state levels of p38 MAP kinase mRNA increased about 2.7-fold as compared with those of control rats. This result suggests that p38 MAP kinase may play an important role in the osmoregulation in the kidney.

These experiments were performed in an attempt to determine whether chronic stimulation of glomerular endothelial cells with recombinant human erythropoietin would alter mesangial cell proliferation. Glomerular endothelial cells in culture incubated with various concentrations of erythropoietin for up to 4 days exhibited dose-dependent endothelin-1 production. Moreover, the conditioned medium from erythropoietin-stimulated glomerular endothelial cells enhanced [3H]thymidine incorporation into mesangial cells. This enhancement was significantly attenuated in the presence of a endothelin A receptor antagonist, BQ-123. These results suggest that endothelin-1 mediates erythropoietin-stimulated glomerular endothelial cell-dependent mesangial cell proliferation, resulting in the progression of glomerulonephritis.

The effects of 2 hours of renal artery occlusion were studied in previously uninephrectomized rabbits. Oliguric renal failure by arterial clamping was produced. Renal blood flow was maintained during observation periods, except for an early decrease in outer cortical blood flow without change elsewhere. During the oliguric stage medullary osmolality was markedly diminished, concomitantly with reduced (U/P)osm. Cin, EPAH and sodium reabsorption were decreased, accompanied by tubular necrosis and intratubular casts. During the early diuretic stage Cin, medullary osmolality and (U/P)osm were still reduced. Intratubular casts disappeared while regenerated tubular cells were focally observed. Two weeks after the occlusion, improved Cin, EPAH, sodium reabsorption, medullary osmolality and (U/P)osm, and regenerated tubular epithelium were found. In 7 weeks Cin and EPAH had returned to the preclamping values whereas medullary osmolality remained decreased with the appearance of medullary fibrosis. (U/P)osm was not completely restored. The findings indicate that during the oliguric stage of acute renal failure of rabbits renal blood flow is maintained, except for a decrease in outer cortical flow, and urine concentrating ability is restored more slowly than other measured functions.