Protective effect of statin therapy on connective tissue growth factor induction by diabetes in vivo and high glucose in vitro

Transcriptional activity of connective tissue growth factor (CTGF) promoter in transfected HEK293 cells was determined by luciferase assays. Secreted CTGF in cultured human mesangial cells was measured by enzyme-linked immunosorbent assay (ELISA). CTGF in urine and plasma was also measured in 405 subjects with/without type 2 diabetes. Our results showed that high glucose significantly increased transcription of the promoter in the transfected cells by more than 2.5-folds (p < 0.0005). CTGF secretion was induced by high glucose in the cells (p < 0.0005). These increases were inhibited by simvastatin. Urine CTGF was positively associated with plasma CTGF in both type 2 diabetes (p = 0.0005) and controls (p = 0.01). Urine CTGF levels in patients with macroalbuminuria were significantly higher than patients without macroalbuminuria (p < 0.05). In conclusion, our in vitro study suggests that statin may have a renal-protective effect through the inhibition of CTGF expression. Urine CTGF may be a good marker for the prediction of diabetic nephropathy.

Increased class A scavenger receptor and glomerular lipid precede mesangial matrix expansion in the bGH mouse model

OBJECTIVE

Elevated neutral lipid content and mRNA expression of class A scavenger receptor (SRA) have been found in the renal cortex of the bovine growth hormone (bGH) mouse model of progressive glomerulosclerosis (GS). We hypothesize that the increased expression of SRA precedes glomerular scarring in this model.

DESIGN

Real time RT-PCR and immunofluorescence were employed to measure SRA and collagen types I and IV in the bGH transgenic and control mice at 5 and 12 weeks (wk) of age to determine the chronology of change in SRA expression in relation to glomerular scarring. Alternative mechanisms for increasing glomerular lipid were assessed by measuring mRNA expression levels of low-density lipoprotein receptor (LDL-r), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and ATP-binding cassette transporter A1 (ABCA1). In addition, the involvement of macrophages in early GS was assessed by CD68 mRNA expression in kidney cortex.

RESULTS

Both mRNA and protein levels of SRA were significantly increased in 5-wk bGH compared with control mice, whereas the expression of collagen I and IV was unaltered. Unchanged levels of LDL-r and HMGR mRNA indicate that neither regulated cholesterol uptake via LDL-r nor the cholesterol synthetic pathway played a role in the early lipid increase. The finding of increased ABCA1 expression was an indicator of excess intracellular lipid in the renal cortex of bGH mice at 5 wk. CD68 expression in bGH did not differ significantly from that of controls at 5 wk suggesting that cortical macrophage infiltration was not increased in bGH mice at this time point.

CONCLUSION

An early increase in SRA mRNA and protein expression in the bGH kidney precedes glomerular scarring and is independent of macrophage influx.

[Glomerular deposition disease, regarding a case of fibrillary glomerulonephritis]

In routine diagnosis for renal biopsy, glomerular diseases are encountered that, viewed by electron microscopy, reveal deposits with a fibrillary structure in the extracellular matrix of the glomeruli. Amyloidosis is the most common glomerulopathy that shows deposits with an ultrastructural fibrillary structure. However, other glomerulopathies have deposits with an ultrastructural fibrillary structure and which are negative for Congo-red stain, but positive for immunoglobulins. Fibrillary glomerulonephritis is a well-characterized disease, and clearly identified in approximately 0.5% to 1% of biopsies of native kidneys. These cases usually manifest themselves as severe renal insufficiencies with nephrotic-range proteinuria. No treatment regimes have been clearly established and the prognosis is poor. Herein, the clinical and histological characteristics are described for the first case of idiopathic fibrillary glomerulonephritis reported in Colombia.

A pediatric occurrence of crescentic glomerulonephritis associated with antineutrophil cytoplasmic antibodies and mesangial IgA deposits

Antineutrophil cytoplasmic antibody-(ANCA) associated glomerulonephritis usually shows histopathologic features of pauciimmune crescentic glomerulonephritis and occurs late in life. We report a 14-year-old Japanese girl presenting with proteinuria, hematuria and mildly elevated serum creatinine. A renal biopsy specimen demonstrated crescentic glomerulonephritis, immunofluorescence showed mesangial IgA staining. Electron microscopic examination disclosed paramesangial deposits. Serum ANCA against myeloperoxidase (MPO) were detected at high titers. Myeloperoxidase-ANCA-related nephritis accompanied by IgA nephropathy is considered rare in childhood and teen years. Yet, if ANCA assays and detailed electron microscopic examination of renal specimens were performed routinely in patients with rapidly progressive glomerulonephritis, the diagnosis might be more frequent in young patients.

Plasma exchange combined with immunosuppressive treatment in a child with rapidly progressive IgA nephropathy

Although diffuse crescentic formation in immunoglobulin A (IgA) nephropathy, histologically characterized by extensive extracapillary proliferation, is assumed to have a poor prognosis, there has still been no established treatment because of the low prevalence of the condition, especially in pediatric patients. This paper reports on a 5-year-old boy with rapidly progressive IgA nephropathy requiring dialysis for 1 month. He had been treated with plasma exchange (PE) combined with immunosuppressive treatment, including steroids and mizoribine, because renal function deteriorated rapidly despite initial treatment with intravenous methylprednisolone pulse. The histological findings at that time revealed IgA nephropathy, with large circumferential cellular crescent formation in approximately 80% of the glomeruli. Three weeks after PE initiation, serum levels of creatinine and IgA-containing immune complexes returned to normal, and urinary protein excretion gradually decreased. The second renal biopsy taken 7 months later demonstrated mild IgA nephropathy with small fibrocellular crescents. This case report indicates that PE combined with immunosuppressive treatment may benefit children with rapidly progressive IgA nephropathy, even when extensive crescent formations are present.

Mesangial immune complex glomerulonephritis due to complement factor D deficiency

Complement factor D is a serine protease essential for the activation of the alternative pathway and is expressed in the kidney, adipocytes, and macrophages. Factor D is found at relatively high levels in glomeruli suggesting that this component of the complement cascade could influence renal pathophysiology. In this study, we utilize mice with a targeted deletion of the activating complement factor D gene and compare these results to mice with targeted deletion of the inhibitory complement factor H gene. Eight-month-old mice with a deleted factor D gene spontaneously develop albuminuria and have reduced creatinine clearance due to mesangial immune complex glomerulonephritis. These mesangial deposits contain C3 and IgM. In contrast to the mesangial location of the immune deposits in the factor D-deficient mice, age-matched factor H-deficient mice develop immune deposits along the glomerular capillary wall. Our observations suggest that complement factor D or alternative pathway activation is needed to prevent spontaneous accumulation of C3 and IgM deposits within the mesangium. Our studies show that the complement factor D gene knockout mice are a novel model of spontaneous mesangial immune complex glomerulonephritis.

Is there a role for rituximab in the treatment of idiopathic childhood nephrotic syndrome?

We each have nephrotic patients who become steroid dependent and in whom multiple immunosuppressive agents are employed. There is a need to balance possible therapeutic benefits with drug toxicity. This case report describes such a patient, who has suffered from nephrotic syndrome for over 11 years and had become resistant to the usual therapies. He was therefore given a single dose of the anti-CD20 drug rituximab, to which he showed a prompt response, leaving him free of proteinuria for the past 10 months.

Renal mitochondrial dysfunction in spontaneously hypertensive rats is attenuated by losartan but not by amlodipine

Mitochondrial dysfunction is associated with cardiovascular damage; however, data on a possible association with kidney damage are scarce. Here, we aimed at investigating whether 1) kidney impairment is related to mitochondrial dysfunction; and 2) ANG II blockade, compared with Ca2+ channel blockade, can reverse potential mitochondrial changes in hypertension. Eight-week-old male spontaneously hypertensive rats (SHR) received water containing losartan (40 mg·kg−1·day−1, SHR+Los), amlodipine (3 mg·kg−1·day−1, SHR+Amlo), or no additions (SHR) for 6 mo. Wistar-Kyoto rats (WKY) were normotensive controls. Glomerular and tubulointerstitial damage, systolic blood pressure, and proteinuria were higher, and creatinine clearance was lower in SHR vs. SHR+Los and WKY. In SHR+Amlo, blood pressure was similar to WKY, kidney function was similar to SHR, and renal lesions were lower than in SHR, but higher than in SHR+Los. In kidney mitochondria from SHR and SHR+Amlo, membrane potential, nitric oxide synthase, manganese-superoxide dismutase and cytochrome oxidase activities, and uncoupling protein-2 content were lower than in SHR+Los and WKY. In SHR and SHR+Amlo, mitochondrial H2O2 production was higher than in SHR+Los and WKY. Renal glutathione content was lower in SHR+Amlo relative to SHR, SHR+Los, and WKY. In SHR and SHR+Amlo, glutathione was relatively more oxidized than in SHR+Los and WKY. Tubulointerstitial α-smooth muscle actin labeling was inversely related to manganese-superoxide dismutase activity and uncoupling protein-2 content. These findings suggest that oxidant stress is associated with renal mitochondrial dysfunction in SHR. The mitochondrial-antioxidant actions of losartan may be an additional or alternative way to explain some of the beneficial effects of AT1-receptor antagonists.

Lipoxin A4 modifies platelet-derived growth factor-induced pro-fibrotic gene expression in human renal mesangial cells

Lipoxins (LXs), endogenously produced eicosanoids, possess potent anti-inflammatory, pro-resolution bioactivities. We investigated the potential of LXA(4) (1 to 10 nmol/L) to modify the effects of platelet-derived growth factor (PDGF)-induced gene expression in human renal mesangial cells (hMCs). Using oligonucleotide microarray analysis we profiled pro-fibrotic cytokines and matrix-associated genes induced in response to PDGF. LXA(4) modulated the expression of many PDGF-induced genes, including transforming growth factor-beta1, fibronectin, thrombospondin, matrix metalloproteinase 1, and several collagens. Analysis of both transcript and protein levels confirmed these findings. Because the activated glomerulus is frequently a source of injurious mediators that contribute to tubulointerstitial damage, we investigated the effect of hMC-secreted products on the integrity of renal proximal tubular epithelial cells using an in vitro model of progressive renal disease. Cell supernatant from PDGF-stimulated hMCs caused morphological and genetic changes in proximal tubular epithelial cells, consistent with a pro-fibrotic phenotype. Interestingly, supernatant from cells pre-exposed to LXA(4) and PDGF did not induce these effects. These results suggest a novel role for LXA(4) as a potent modulator of matrix accumulation and pro-fibrotic change and suggest a potential protective role in progressive renal disease.

Expanding the pathologic spectrum of light chain deposition disease: a rare variant with clinical follow-up of 7 years

We report an unusual histologic manifestation of light chain deposition disease in a 69-year-old female patient, who presented with nephrotic syndrome and an increased serum creatinine. The renal biopsy findings by light and electron microscopy suggested a glomerulonephritis with massive immune-complex deposition, such as lupus nephritis. However, the overall clinical scenario was inconsistent with lupus. Subsequent tests revealed multiple myeloma confirmed by bone marrow biopsy and identification of a monoclonal kappa light chain immunoglobulin by serum and urine immunoelectrophoresis and immunofixation. Additional immunohistochemistry of the first biopsy also demonstrated strong kappa light chain staining of the glomerular capillary walls and mesangium but not lambda light chain or IgG staining. The patient responded well to therapy and was asymptomatic until nearly 7 years later. A repeat biopsy revealed similar findings to the first biopsy with the addition of immunofluorescence microscopy, which confirmed the prominent kappa light chain staining of the glomeruli, tubular basement membranes, and interstitium with corresponding electron-dense deposits visualized by electron microscopy. This case represents an unusual histologic variant of light chain deposition disease, which to our knowledge has not been previously described and further expands the wide clinicopathologic spectrum within the diagnostic entity of light chain deposition disease.

A case of renal sarcoidosis with complement activation via the lectin pathway

A 57-year-old woman with pulmonary sarcoidosis was admitted to the hospital because of an elevation of serum creatinine and blood urea nitrogen. On admission, the laboratory data suggested interstitial nephritis without proteinuria and hematuria, whereas a renal biopsy showed granulomatous interstitial nephritis and mild mesangial proliferative glomerulonephritis. Immunoglobulin and C1q deposits were negative, but mannose-binding lectin, C3, C4d, and C5b-9 deposits were marked in the glomerular mesangial areas. The lectin pathway of complement activation may have contributed to the development of glomerular injury in this patient. DNA of Propionibacterium acnes , which is now strongly suspected as the pathogen of sarcoidosis, was detected in the patient's glomerular mesangial cells; tubular epithelial cells, which were involved in granulomatous inflammation; and mononuclear cells in epithelioid granulomas by in situ hybridization. These findings may add new insights to the pathogenesis of renal sarcoidosis, including its relation to infection, because mannose-binding lectin plays a crucial role in the host defense against various pathogens. From this case of renal sarcoidosis, it is hypothesized that P acnes may be involved in pathogenesis of granulomatous interstitial nephritis and that it plays a role in glomerular complement activation via the lectin pathway.

Co-operative interactions between NFAT (nuclear factor of activated T cells) c1 and the zinc finger transcription factors Sp1/Sp3 and Egr-1 regulate MT1-MMP (membrane type 1 matrix metalloproteinase) transcription by glomerular mesangial cells

The transition of normally quiescent glomerular MCs (mesangial cells) to a highly proliferative phenotype with characteristics of myofibroblasts is a process commonly observed in inflammatory diseases affecting the renal glomerulus, the ultimate result of which is glomerulosclerosis. Generation of proteolytically active MMP (matrix metalloproteinase)-2 by the membrane-associated membrane type 1 (MT1)-MMP is responsible for the transition of mesangial cells to the myofibroblast phenotype [Turck, Pollock, Lee, Marti and Lovett (1996) J. Biol. Chem. 271, 15074-15083]. In the present study, we show that the expression of MT1-MMP within the context of MCs is mediated by three discrete cis -acting elements: a proximal non-canonical Sp1 site that preferentially binds Sp1; an overlapping Sp1/Egr-1-binding site that preferentially binds Egr-1; and a more distal binding site for the NFAT (nuclear factor of activated T cells) that binds the NFAT c1 isoform present in MC nuclear extracts. Transfection with an NFAT c1 expression plasmid, or activation of calcineurin with a calcium ionophore, yielded major increases in NFAT c1 nuclear DNA-binding activity, MT1-MMP transcription and protein synthesis, which were additive with the lower levels of transactivation provided by the proximal Sp1 and the overlapping Sp1/Egr-1 sites. Specific binding of NFAT c1 to the MT1-MMP promoter was confirmed by chromatin immunoprecipitation studies, while MT1-MMP expression was suppressed by treatment with the calcineurin inhibitor, cyclosporin A. These studies are the first demonstration that a specific NFAT isoform enhances transcription of an MMP (MT1-MMP) that plays a major role in the proteolytic events that are a dominant feature of acute glomerular inflammation. Suppression of MT1-MMP by commonly used calcineurin inhibitors may play a role in the development of renal fibrosis following renal transplantation.

Molecular dissection of mouse soluble guanylyl cyclase alpha1 promoter

Soluble guanylyl cyclase (sGC) is the only known receptor for nitric oxide (NO) and is downregulated in aging and hypertension. Little is known about sGC gene transcriptional regulation. In order to characterize the sGC transcriptional system, we cloned and sequenced the 5(') flanking region of mouse sGC alpha(1) gene (AY116663). Structurally, it is a non-canonical TATA-less promoter that we mapped to chromosome 3 with many putative regulation sites for Sp-1, NF-kappaB, and AP-1 transcription factors amongst others, and two (TG:CA)(n) dinucleotide microsatellites near the transcriptional start point. The cloned upstream sequence produced a 5-fold increase in luciferase activity in Cos7, HeLa, NIH3T3, and 293 cells as well as in mouse VSMC-like kidney mesangial cells. In the latter cell type, we showed that sGC alpha(1) promoter activity was dependent on the presence of its 5(') unstranslated region (5(')UTR).

Non-helical type IV collagen polypeptides in human placenta

Our previous reports showed that cultured human cells secrete non-disulfide-bonded non-helical alpha1(IV) and alpha2(IV) chains under physiological conditions. In the present report we show that the alpha(IV) chains in non-helical form were reactive to lectin ABA (Agaricus bisporus agglutinin), whereas the alpha(IV) chains secreted in triple-helical form were not. These results indicate that ABA could be used to distinguish the two conformational isomers of type IV collagen polypeptides. An alpha1(IV) chain isolated from human placenta with an antibody-coupled column showed a positive reaction to ABA, indicating that gelatin form of the type IV collagen alpha1(IV) chain is produced and retained in the tissue in vivo. A possible significance of the gelatin form is discussed from the finding that the non-helical alpha1(IV) chain purified with EDTA-free buffer contained degraded polypeptides including NC1-size domain and showed an apparent inhibition against activated pro-MMP-9. This is the first report to show that a gelatin form of protein exists in vivo.

Regulation of Plasma Hemopexin Activity by Stimulated Endothelial or Mesangial Cells

The pathogenesis of glomerular alterations and proteinuria in corticosteroid-responsive nephrotic syndrome (CRNS) is unknown. As an isoform of plasma hemopexin (Hx) with protease activity may be implicated in this disease, we have studied the inhibition of Hx by ADP and reactivation to its active form by endothelial or mesangial cells in vitro. We hypothesized that these cells might potentially be able to convert the inactivated form of Hx (Hxi) to active Hx (Hxa) in vitro, mediated by cellular ecto-ADPase. Since ecto-ADPase (CD39) is upregulated after stimulation of these cells with lipopolysaccharide (LPS) or certain cytokines, we postulated that this conversion might occur specifically after inflammatory stimulation of these cells. Human endothelial or mesangial cell cultures were incubated overnight with or without LPS (10.0 ng/ml) or TNFalpha (10.0 ng/ml), washed and subsequently incubated with Hxi (1.5 mg/ml) in serum-free conditions (Hxi was prepared by treatment of Hxa with ADP or ADP-beta-S). After 60 min, supernatants were tested for their capacity to alter glomerular extracellular matrix molecules (i.e. ecto-apyrase) in vitro using standard methods, and compared with Hxi that had not been incubated with cells. Supernatants containing Hxa (1.5 mg/ml) served as positive control. The results show significant activity in supernatants with Hxi (prepared using native ADP). However, Hxi inactivated by ADP-beta-S (which is non-hydrolyzable) could not be reactivated after contact with LPS-stimulated or unstimulated cells in vitro. As ecto-ADPase of these cells is upregulated by LPS, we believe that reactivation of Hxi to Hxa is mediated by cellular ecto-ADPase. Although the relevance of this inflammation-mediated activation mechanism of Hx in patients with CRNS requires further experimentation, our preliminary observations suggesting that this mechanism is corticosteroid dependent may support a potential role of Hxa in CRNS.

Roles of connective tissue growth factor and prostanoids in early streptozotocin-induced diabetic rat kidney: the effect of aspirin treatment

BACKGROUND

Connective tissue growth factor (CTGF) is a cysteine-rich growth factor induced by transforming growth factor-beta (TGF-beta) and is thought to play a critical role in TGF-beta-stimulated extracellular matrix accumulation. To explore its involvement in early diabetic nephropathy, we investigated the time course of CTGF gene expression and its regulation in streptozotocin (STZ)-induced diabetic rat kidney.

METHODS

Northern blot analysis for CTGF, TGF-beta, and fibronectin expression was performed in the glomeruli of STZ-induced diabetic rats from 3 days to 12 weeks after the induction of diabetes, together with histological examination. To investigate the role of prostanoids in this process, aspirin was administered in one group of diabetic rats. Furthermore, CTGF expression was analyzed in rat mesangial cells cultured under high-glucose conditions.

RESULTS

Glomerular expression of CTGF and TGF-beta1 mRNA was coordinately upregulated as early as day 3, followed by fibronectin induction and mesangial matrix accumulation. Chronic aspirin treatment in diabetic rats significantly attenuated mesangial expansion, and effectively suppressed CTGF induction, as well as inhibiting the upregulation of TGF-beta1 and fibronectin expression. In cultured mesangial cells, aspirin treatment abolished high glucose-stimulated CTGF upregulation.

CONCLUSIONS

These results indicate that CTGF expressed in the glomeruli is upregulated in the early stage of STZ-induced diabetic nephropathy in rats, and could be a critical mediator of the development of diabetic glomerulosclerosis. In addition, the modulatory effects of aspirin during this process suggest a role of the cyclooxygenase pathway in the progression of diabetic nephropathy.

Methylglyoxal modifies heat shock protein 27 in glomerular mesangial cells

Methylglyoxal (MGO) can modify tissue proteins through the Maillard reaction, resulting in advanced glycation end products (AGEs), which can alter protein structure and functions. Several MGO-derived AGEs have been described, including argpyrimidine, a fluorescent product of the MGO reaction with arginine residues. We detected significant amount of argpyrimidine in rat kidney mesangial cells cultured in media containing high concentrations of glucose. Heat shock protein 27 (Hsp27) was identified by liquid chromatography tandem mass spectrometry as a major anti-argpyrimidine immunoreactive protein. We confirmed this finding by reciprocal co-immunoprecipitation and by Western analysis. Diabetic rats contained more argpyrimidine-modified glomerular Hsp27 than non-diabetic animals. Additional studies showed that MGO-induced modification of Hsp27 decreased its binding to cytochrome c. Our results suggest that Hsp27 is a major target for MGO modification in mesangial cells.

Insights into mechanisms responsible for mesangial alterations associated with fibrogenic glomerulopathic light chains

Our previous studies have shown that human mesangial cells (HMCs) incubated with fibrogenic glomerulopathic monoclonal light chains (G-LCs) obtained from the urine of patients with light chain deposition disease produce increased extracellular matrix (ECM) when compared with HMCs not exposed to fibrogenic LCs. This overproduction of ECM proteins is regulated by transforming growth factor-beta (TGF-beta); blocking TGF-beta normalizes the production of ECM proteins. All ECM proteins, after synthesis, have to go through the secretory pathway in the endoplasmic reticulum (ER) and Golgi complex for final maturation and secretion. Blocking the secretory pathway may reduce the accumulation of ECM proteins. We tested the effect of tunicamycin, a specific inhibitor of N-linked glycosylation in the ER which inhibited glycosylation and brefeldin A, an inhibitor of vesicle transport between the endoplasmic reticulum and the Golgi complex, on ECM protein production, both resulting in subsequent upregulation of glucose-regulated protein 78. Overproduction of fibronectin and tenascin by HMCs was normalized by tunicamycin and brefeldin A. Similarly, when HMCs were exposed to exogenous TGF-beta, the increase in fibronectin was reversed by tunicamycin and brefeldin A. Exogenous platelet-derived growth factor-beta (PDGF-beta) did not induce fibronectin overproduction but significantly stimulated proliferation of HMCs. In summary, this study further supports the notion that fibrogenic G-LCs promote the accumulation of ECM proteins, through the actions of TGF-beta. Importantly, the data indicate that altering protein trafficking in the ER results in impairment of secretion of proteins into the ECM. Furthermore, the data also reveal that PDGF-beta and TGF-beta act independently and that PDGF-beta activation by itself cannot increase ECM proteins directly, but only by increasing the number of HMCs.

[Isolation, identification and in vitro culture of human glomerular mesangial cells]

OBJECTIVE

To define the optimal condition to culture human glomerular mesangial cells in vitro.

METHODS

With a three-layer micropore filter device, we separated the glomerular mesangial cells from normal human, with were subjected to identification with immunohistochemical method. Fluorescein isothiocyanate (FITC) staining was performed for labeling of the monoclonal antibodies so as to identify the cells' superficial markers including factor VIII, keratin, cytokeratin, desmine, et al. Glomerular endothelial cells isolated from the same human tissues were also cultured in vitro under the same condition, serving as negative control.

RESULTS AND CONCLUSION

The antibodies related to anti-factor VIII, and those of antikeratin and anticytokeratin were negative in the isolated glomerular mesangial cells, while the antibodies for desmine, anti-collagen IV, anti-fibronectin, and anti-laminin were positive, offering evidence for confirming the identification of the isolated and cultured mesangial cells.

Anti-mouse mesangial cell serum induces acute glomerulonephropathy in mice

In order to develop a model in mouse similar to anti- Thy-1 nephritis in the rat, we prepared sheep antiserum against SV40-transformed mouse mesangial (MES 13) cells. In vivo, the anti-mouse mesangial cell serum-treated mice showed severe azotemia that peaked at day 6 and proteinuria that peaked at day 8, in a dose-dependent fashion. Light microscopy and electron microscopy showed duplication of glomerular basement membranes, mesangiolysis, subendothelial and mesangial electron-dense deposits, and foot process effacement. Intraglomerular tuft cell number was significantly reduced at day 4 and there were increased numbers of apoptotic cells at days 2 and 4. SCID mice and mice lacking C3 manifested similar responses to anti-mouse mesangial cell serum, suggesting that T cells, B cells and complement are not required for glomerular injury in this model. In vitro, anti-mouse mesangial cell serum treated mesangial cells showed greater release of lactate dehydrogenase, decreased cell survival, and increased apoptotic cell death. Anti-mouse mesangial cell serum induces glomerulopathy characterized by mesangiolysis and mesangial cell apoptosis, and followed by cellular proliferation.

Expression and cellular localisation of renal endothelin-1 and endothelin receptor subtypes in autosomal-dominant polycystic kidney disease

The major factors influencing the rate of progression of chronic renal disease in autosomal-dominant polycystic kidney disease (ADPKD) are unknown and there are currently no effective treatments for slowing the progression of chronic renal failure in ADPKD patients. As a first step in investigating the potential role of endothelin-1 (ET1) and its receptors (ETA and ETB) in the pathophysiology of progression in ADPKD, we have studied their expression and cellular localisation in ADPKD kidney. Immunoreactive ET1 was detected in cyst epithelia, mesangial cells and vascular smooth muscle cells suggesting continuing ET1 synthesis in the cystic kidney. Compared to healthy controls, ETA mRNA was 5-10-fold higher in ADPKD cystic kidney. In cystic kidney, neo-expression of ETA receptors was found overlying glomeruli and cysts and markedly increased in medium-sized renal arteries by microautoradiography. This is the first study to demonstrate a specific upregulation of ETA receptors in human renal disease. Future studies should address whether ETA selective antagonists may be effective in slowing renal disease progression in ADPKD.

In vitro effects of Habu snake venom on cultured mesangial cells

BACKGROUND

Habu snake venom (HSV)-induced glomerulonephritis is a unique model showing a progressive course of mesangial proliferation. To elucidate the in vitro effects of HSV, we examined whether HSV itself could have direct effects on the cultured mesangial cells, such as cell proliferation and activation of chemokine gene expression.

METHODS

The incorporation of 5-[(125)I]iodo-2'-deoxyuridine was measured with a gamma-counter, and gene expressions of growth factors, chemokines and cytokines were evaluated by a real time quantitative PCR.

RESULTS

We demonstrated that excessive or continuous HSV stimulation decreased a mesangial cell viability. However, adequate and temporary HSV stimulation induced proliferation of mesangial cells in vitro along with a significant elevation of monocyte chemoattractant protein-1 (MCP-1) mRNA levels. In addition to these in vitro results, we showed that MCP-1 mRNA levels increased in renal cortices of glomerulonephritis induced by HSV. Immunohistochemistry also showed a positive staining for MCP-1 in the marginal area of glomerulus with mesangiolysis.

CONCLUSIONS

These data suggest that HSV itself may elicit direct biological effects on mesangial cells which may participate in pathophysiology of glomerulonephritis induced by HSV.

The lack of cyclin kinase inhibitor p27(Kip1) ameliorates progression of diabetic nephropathy

Cyclin kinase inhibitor p27(Kip(1)) (p27) has been shown to be upregulated in glomeruli of diabetic animals and mesangial cells cultured under high glucose. This study was an investigation of the role of p27 in the progression of diabetic nephropathy. Mice deficient in p27 (p27 -/-) and wild-type mice (p27 +/+) were studied 12 wk after diabetes induction by streptozotocin. Blood glucose and BP were comparable between diabetic p27 +/+ and p27 -/- mice. The kidney weight to body weight ratio and glomerular volume increased in diabetic p27 +/+ mice. In contrast, these parameters did not change in diabetic p27 -/- mice. Similarly, albuminuria developed in diabetic p27 +/+ mice but not in diabetic p27 -/- mice. The mesangial expansion was significantly milder in diabetic p27 -/- mice than that in diabetic p27 +/+ mice. These changes were associated with a similar increase in glomerular TGF-beta expression in diabetic p27 +/+ and p27 -/- mice. However, glomerular protein expression of fibronectin, a target of TGF-beta, increased only in diabetic p27 +/+ mice. In mesangial cells cultured from p27 +/+ mice, exposure to high glucose caused significant increases in total protein content and [(3)H]-leucine incorporation. On the other hand, high glucose caused a significant reduction in these parameters in cells from p27 -/- mice. Phosphorylation of 4E-BP1, the translation inhibitor, increased after exposure to high glucose in p27 +/+ cells. In p27 -/- cells, the level of phosphorylated 4E-BP1 was higher than that in control p27 +/+ cells and decreased under high glucose conditions. In conclusion, renal hypertrophy, glomerular hypertrophy, and albuminuria did not develop, and mesangial expansion was milder in diabetic p27 -/- mice despite glomerular TGF-beta upregulation. These results suggest that controlling p27 function may ameliorate diabetic nephropathy.

An inhibitor of advanced glycation end product formation reduces N epsilon-(carboxymethyl)lysine accumulation in glomeruli of diabetic rats

BACKGROUND

An inhibitor of advanced glycation, OPB-9195, retards the progression of nephropathy in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of non-insulin-dependent diabetes mellitus. The aim of this study is to evaluate histologically the role of N(epsilon)-(carboxymethyl)lysine (CML) in the development of diabetic nephropathy and investigate whether inhibition of CML accumulation by OPB-9195 is associated directly with the prevention of glomerular lesions in OLETF rats.

METHODS

Kidneys of OLETF and Long-Evans Tokushima Otsuka rats were obtained at ages 7, 20, 50, and 68 weeks after collecting their blood and urine samples. OPB-9195 had been administered to the rats from age 24 weeks to the end of the experiments. CML in kidneys was detected by using a monoclonal antibody against CML according to an indirect immunofluorescence technique. CML-positive glomerular area was measured using NIH Image software (Research Services Branch of NIMH, Bethesda, MD). Hyalinized and/or sclerotic areas in glomeruli and mesangial and glomerular volume were measured using a point-counting technique.

RESULTS

CML-positive area in glomeruli correlated closely not only with urinary albumin excretion (r = 0.912; P = 0.001), but also with volumes of mesangium and hyalinized and/or sclerotic lesions (r = 0.859; P = 0.0019 and r = 0.833; P = 0.0027, respectively). Treatment with OPB-9195 reduced CML-positive area and prevented the increase in mesangial volume, with no significant change in glomerular volume at age 68 weeks. The volume of hyalinized and/or sclerotic lesions also decreased by treatment with OPB-9195 in three of four rats at age 68 weeks.

CONCLUSION

CML is a major advanced glycation end product contributing to the development of diabetic nephropathy, and inhibition of its accumulation by OPB-9195 results in amelioration of glomerular lesions in OLETF rats.

Macrophage-induced rat mesangial cell expression of the 24p3-like protein alpha-2-microglobulin-related protein

During screening of a murine macrophage cDNA repertoire for factors potentially able to modulate glomerular cell responses to injury, we identified a gene coding for the murine protein 24p3 lipocalin. Immunostaining of normal rat kidney sections showed positive 24p3-like staining in distal tubules/collecting ducts and small muscular arteries. Although most glomeruli were negative, some did exhibit small numbers of positively stained cells. Cultured rat glomeruli and glomerular mesangial cells secreted the 24p3-like protein in response to macrophage-conditioned medium (MPCM) and the cytokine IL-1beta. MPCM derived from TGFbeta-pretreated macrophages enhanced mesangial cell 24p3 secretion. In contrast, addition of anti-IL-1beta neutralising antibody to MPCM or IL-1beta resulted in suppression of 24p3 secretion. Co-culture of mesangial cells with varying numbers of non-LPS-treated macrophages resulted in dose-dependent secretion of 24p3 into culture supernatants. Archival sections from polyvinyl alcohol-treated and cholesterol-fed rats showed positive glomerular staining for 24p3 in and around glomerular foam cells. Nucleotide sequencing of rat mesangial cell-derived 24p3 cDNA revealed it to be identical to rat alpha-2-microglobulin-related protein (alpha2microGRP), the rat homologue of murine 24p3. These data provide the first description of rat alpha2microGRP in the context of mesangial cell pathophysiology.

Transcriptional profiling of gene expression patterns during sphingosine 1-phosphate-induced mesangial cell proliferation

Sphingosine 1-phosphate (S1P) is known to regulate cell proliferation, apoptosis, and motility. Recently, we have reported that S1P and its analogue dihydro-S1P (DHS1P) promote proliferation of rat cultured mesangial cells. To investigate the signaling mechanisms underlying S1P- and DHS1P-induced mesangial cell proliferation, we performed cDNA microarray analysis of gene expression during mesangial cell proliferation. In terms of the overall pattern, gene expression waves induced by S1P and DHS1P were similar to those induced by a potent mesangial mitogen platelet-derived growth factor (PDGF), whereas we found several genes, such as two growth factors, connective tissue growth factor (CTGF) and heparin-binding EGF-like growth factor (HB-EGF), which were induced by the sphingolipids, but not by PDGF. Cluster analysis also identified calcium-dependent molecules highly expressed in DHS1P-stimulated cells compared to S1P-stimulated cells. Calcium mobilization analysis showed that DHS1P had higher magnitudes of intracellular calcium mobilization than S1P, suggesting that S1P and DHS1P differentially regulate intracellular calcium mobilization, possibly leading to different gene expression in mesangial cells. The large-scale monitoring of gene expression performed here allows us to identify S1P-induced transcriptional properties during mesangial cell proliferation.

Decay-accelerating factor expression in the rat kidney is restricted to the apical surface of podocytes

BACKGROUND

Decay-accelerating factor (DAF) has inhibitory activity toward complement C3 and C5 convertases. DAF is present in human glomeruli and on cultured human glomerular visceral epithelial cells (GEC). We studied the distribution and function of rat DAF.

METHODS

Function-neutralizing antibodies (Abs) were raised against DAF. The distribution of DAF in vivo was determined by immunoelectron microscopy. Functional studies were performed in cultured GEC and following IV injection of anti-DAF Abs into rats.

RESULTS

DAF was present exclusively on the apical surfaces of GEC, and was not present on the basal surfaces of GEC, nor other glomerular or kidney cells. DAF was functionally active on cultured GEC, and served to limit complement activation in concert with CD59, an inhibitor of C5b-9 formation. Upon injection into normal rats, anti-DAF F(ab')2 Abs bound to GEC in vivo, yet there was no evidence for complement activation and animals did not develop abnormal albuminuria. Anti-megalin complement-activating IgG Abs were "planted" on GEC, which activated complement as evidenced by the presence of C3d on GEC. Attempts to inhibit DAF function with anti-DAF Abs did not affect the quantity of complement activation by these anti-megalin Abs, nor did it lead to development of abnormal albuminuria. In contrast, in the puromycin aminonucleoside model of GEC injury and proteinuria, anti-DAF Abs slowed the recovery from renal failure that occurs in this model.

CONCLUSION

In cultured rat GEC, DAF is an effective complement regulator. In vivo, DAF is present on GEC apical surfaces. Yet, it appears that DAF is not essential to prevent complement activation from occurring under normal circumstances and in those cases in which complement-activating Abs are present on the basal surfaces of GEC in vivo. However, in proteinuric conditions, DAF appears to be protective to GEC.

Glucocorticoid regulation of proteoglycan synthesis in mesangial cells

BACKGROUND

Proteoglycans are integral components of the mesangial matrix and glomerular permeability barrier. Recent studies have shown that changes in glomerular proteoglycan expression may play a major role in the pathogenesis of renal disease. Steroid hormones are used as first-choice therapy for the treatment of glomerular diseases, however, the effects of glucocorticoids on expression of glomerular proteoglycans are unknown.

METHODS

This study examined the effects of in vitro and in vivo administration of dexamethasone on proteoglycan synthesis and gene expression of proteoglycan core proteins using rat (RMC) and human (HMC) mesangial cells.

RESULTS

Treatment of cultured RMC with dexamethasone resulted in a dose- and time-dependent decrease (P < 0.05) in both cell-associated and secreted proteoglycan synthesis to approximately 50% of control levels. This effect was inhibited by the glucocorticoid antagonist mifepristone, and mimicked by prednisolone or corticosterone treatment. Separation of proteoglycans by ion-exchange and gel permeation chromatography suggested that chondroitin sulfate/dermatan sulfate proteoglycans were down-regulated after steroid treatment. Northern blot analysis, RT-PCR, Western blot, and promoter activity assays revealed that dexamethasone caused a significant decrease in decorin mRNA (to 61 +/- 8% of controls), whereas biglycan expression and promoter activity were increased after steroid treatment. A similar trend was found in glomeruli isolated from rats treated in vivo with dexamethasone.

CONCLUSIONS

These results demonstrate that treatment of mesangial cells with steroids results in a decrease in total proteoglycan synthesis, as well as subtype-specific changes in proteoglycan core protein gene expression by transcriptional control, furthering our understanding of the effects of steroid treatment on the renal glomeruli.

Putative subunits of the rat mesangial KATP: a type 2B sulfonylurea receptor and an inwardly rectifying K+ channel

BACKGROUND

Sulfonylurea agents exert their physiological effects in many cell types via binding to specific sulfonylurea receptors (SUR). SUR couple to inwardly-rectifying K+ channel (Kir6.x) to form tetradimeric ATP-sensitive K+ channels (KATP). The SUR subunits confer ATP-sensitivity on KATP and also provide the binding sites for sulfonylureas and other pharmacological agents. Our previous work demonstrated that the exposure of mesangial cells (MC) to sulfonylureas generated profound effects on MC glucose uptake and matrix metabolism and induced heightened cell contractility in association with Ca2+ transients. Because these responses likely resulted from the binding of sulfonylurea to a mesangial SUR2, we subsequently documented [3H]-glibenclamide binding to MC and the gene expression of several mesangial SUR2 transcripts. From these data, we inferred that MC expressed the components of a mesangial KATP and sought to establish their presence in primary MC.

METHODS

To obtain mesangial SUR2 cDNA sequences, rapid amplification of cDNA ends (RACE) was utilized. DNA sequences were established by the fluorescent dye termination method. Gene expression of mesangial SUR2 and Kir6.1/2 was examined by reverse transcription polymerase chain reaction (RT-PCR) and Northern analysis. SUR2 proteins were identified by immunoblotting of mesangial proteins from membrane-enriched fractions with polyclonal antiserum directed against SUR2.

RESULTS

RACE cloning yielded two mesangial SUR2 cDNAs of 4.8 and 6.7 kbp whose open reading frames translated proteins of 964 and 1535 aa, respectively. Using probes specific to each cDNA, the presence of a unique, 5.5 kbp serum-regulated mesangial SUR2 splice variant was established. The sequence of this mesangial SUR2 (mcSUR2B) shares identity with the recently cloned rat SUR2B (rSUR2B), but, in comparison to rSUR2B, is truncated by 12 exons at the N-terminus where it contains a unique insert of 16 aa. Immunoblotting studies with anti-SUR2 antiserum demonstrated SUR2 proteins of 108 and 170 kD in membrane-enriched fractions of MC protein extracts. Complementary studies showed abundant gene expression of Kir6.1, thereby establishing gene expression of both components of KATP.

CONCLUSIONS

Based upon analogy to vascular smooth muscle cells (VSMC), there are at least two putative mesangial KATP that most likely represent hetero-octamers, comprised of either rSUR2B or mcSUR2 in complex with Kir6.1. Our results define the mesangial SUR2B as the possible first link in a chain of cellular events that culminates in MC contraction and altered extracellular matrix metabolism following exposure to sulfonylureas. In addition, our results serve as the basis for the future elucidation of the electrophysiologic characteristics of the mesangial KATP and the study of endogenous regulators of mesangial cell contractility.

Distribution, cellular localization, and postnatal development of VASP and Mena expression in mouse tissues

Vasodilator-stimulated phosphoprotein (VASP) and mammalian Enabled (Mena) are members of the proline-rich Ena/VASP protein family that links the cell membrane proteins, signal transduction pathways, and the actin cytoskeleton. VASP and Mena, substrates of cyclic nucleotide-dependent protein kinases, are associated in different cell types with microfilaments, focal adhesions, cell-cell contacts, and highly dynamic membrane regions. Here, the analysis of mRNA and protein expression, cellular localization, and postnatal development of VASP in different mouse tissues is reported and compared with that of Mena. The expression levels of VASP and Mena differ markedly among various tissues and cell types. The highest levels of VASP are observed in platelets, but stomach, intestine, spleen, lung, and blood vessels are also rich sources of VASP. Mena is abundantly expressed in brain, whereas it is not detectable in platelets and spleen. In intestine and stomach, prominent VASP and Mena immunoreactivity is detected in intestinal smooth muscle cells and blood vessels and cellular membranes of epithelial cells. In kidney, VASP and Mena are abundantly expressed in glomerular mesangial cells and in papilla. VASP and Mena immunoreactivity in heart is associated with blood vessels and with the intercalated discs of cardiac myocytes, where they colocalize with connexin-43. During postnatal development of heart, the level of VASP and Mena expression gradually decreases from neonatal to adult animals. The data demonstrate a clear colocalization of VASP and Mena in cells of stomach, intestine, kidney, and heart. These data and other recent developments suggest that proteins of the Ena/VASP family exert similar functions and may compensate for each other in these tissues.

Bacitracin inhibits fibronectin matrix assembly by mesangial cells in high glucose

BACKGROUND

Accumulation of mesangial extracellular matrix is a major characteristic of diabetic nephropathy (DN). Expression of several extracellular matrix proteins is up-regulated in human mesangial cells (HMC) cultured in high glucose. One protein, fibronectin (FN), associates to form an insoluble disulfide-linked matrix and possesses inherent protein-disulfide isomerase (PDI) activity. Bacitracin is a known PDI inhibitor. We tested the hypothesis that inhibiting FN-PDI activity with bacitracin would disrupt excessive FN-matrix assembly by cultured HMCs grown under high glucose conditions.

METHODS

The effect of bacitracin on FN-PDI activity was tested using an RNase-refolding assay. High glucose cultures of HMC were labeled with (3)H-leucine, with and without bacitracin, and (3)H-FN immunoprecipitated from the medium and sequential extracts of cell layers to distinguish insoluble FN. FN transcription was assessed by reverse transcription-polymerase chain reaction (RT-PCR). Pericellular FN-matrix was examined by immunohistology.

RESULTS

Bacitracin inhibited the PDI activity of FN, with maximal inhibition at 1.0 mmol/L. Treatment of HMC cultures grown in high glucose with bacitracin brought about changes in the distribution of newly synthesized FN. With increasing concentrations of bacitracin there was a significant reduction in the level of FN present as an insoluble matrix of HMC cultures maintained in high glucose, and a corresponding increase in FN in medium. Decreases in FN matrix laid down by HMCs treated with different concentrations of bacitracin were seen by immunohistology. FN mRNA levels were unchanged.

CONCLUSION

PDI inhibition of FN reduces its association into an insoluble matrix and potentially provides a new approach to reduce excessive matrix deposition in DN.

Activation of PKC-beta(I) in glomerular mesangial cells is associated with specific NF-kappaB subunit translocation

Changes in expression and activity of protein kinase C (PKC) isoforms and early transcription factors may account for alterations in cell behavior seen in diabetes. We studied the expression of PKC-beta(I) in rat glomerular mesangial cells (MCs) cultured in normal or high glucose and compared it with the temporal and spatial expression of dimeric transcription factor (NF-kappaB) p50 and p65. The results show that in unstimulated cells PKC-beta(I) and NF-kappaB p50 are distributed in the cytosol and, on stimulation, their distribution is perinuclear and they are localized to the membrane. Serum-starved MCs cultured in high-glucose medium exhibit a predominantly cytosolic localization of PKC-beta(I) and both p50 and p65 NF-kappaB. However, phorbol 12-myristate 13-acetate (PMA) stimulation of cells grown in the presence of high glucose resulted in membrane translocation of PKC-beta(I) that was associated with nuclear translocation of NF-kappaB p65, but not NF-kappaB p50. Moreover, the translocation to the nucleus for NF-kappaB p65 was significantly higher in MCs exposed to high glucose compared with those exposed to normal glucose. These observations indicate that the NF-kappaB p65, but not NF-kappaB p50, expression and translocation pattern mirrors that of PKC-beta(I), which may be one important pathway by which signaling is enhanced in the high-glucose state.

LRP: a new adhesion molecule for endothelial and smooth muscle cells

We recently generated a monoclonal antibody that disrupted the association of endothelial cells with their target location during kidney development. Here, we purified the antigen of this monoclonal antibody to homogeneity using rat mesangial cell cytosol. Sequence revealed that it is a previously identified protein, termed the "laminin receptor precursor" (LRP). We found that this protein is expressed in most tissues, but immunocytochemistry revealed that it is present largely or entirely in blood vessels where it is located underneath endothelial cells and in between smooth muscle cells of the vascular wall. Vascular smooth muscle cells such as mesangial cells produce and secrete LRP into their extracellular matrix where it is present in several molecular weight forms. Endothelial cells produce very little if any of the protein, but they bind avidly to LRP-coated dishes. Anti-LRP antibodies prevent the binding of smooth muscle cells to uncoated plates, implying that cells that secrete it use it for attachment. In an assay for heterologous cell-to-cell interaction, antibodies to LRP inhibited the binding of smooth muscle cells to endothelial cells. Maturation and differentiation of blood vessels require interaction between endothelial and smooth muscle cells. LRP is a new component of the mesangial matrix, and we propose that it is an adhesion molecule that mediates an interaction between smooth muscle cells and endothelia.

Mesangial IgA1 in IgA nephropathy exhibits aberrant O-glycosylation: observations in three patients

BACKGROUND

In IgA nephropathy (IgAN), circulating IgA1 molecules display an abnormal pattern of O-glycosylation. This abnormality may potentially contribute to mesangial IgA1 deposition, but this is unproven because the O-glycosylation of mesangial IgA1 has not been analyzed.

METHODS

IgA1 was eluted from glomeruli isolated from the kidneys of three IgAN patients obtained after nephrectomy or at postmortem. Serum from these patients, other patients with IgAN, and controls was subjected to the same treatment as the glomerular eluates. The O-glycosylation of eluted and serum IgA1 was measured by lectin binding using an enzyme-linked immunosorbent assay-based system.

RESULTS

In all three cases, the lectin binding of IgA1 eluted from the glomeruli of IgAN patients was markedly higher than that of the serum IgA1 of the same individual, and also all but one of a series of serum IgA1 samples from other patients and controls.

CONCLUSIONS

The higher lectin binding of glomerular compared with serum IgA1 suggests that O-glycosylated IgA1 molecules abnormally and selectively deposit in the kidney. These results provide the first evidence that mesangial IgA1 is abnormally O-glycosylated, and support a direct role for abnormal IgA1 O-glycosylation in the mechanism of mesangial IgA deposition in IgAN.

Cloning of rodent megsin revealed its up-regulation in mesangioproliferative nephritis

BACKGROUND

We recently cloned a new human mesangium-predominant gene, megsin. Megsin is a novel member of the serine protease inhibitor (serpin) superfamily. To elucidate functional roles of this gene, we cloned megsin in rodents and investigated its role in a rat nephritis model.

METHODS

Megsin homologues were cloned from cultured rat and mouse mesangial cDNAs utilizing polymerase chain reaction (PCR) with degenerative primers. Expression of megsin in three different types of resident glomerular cells was investigated by PCR. Levels of megsin mRNA expression at various time points in the anti-Thy1 rat nephritis model were studied by semiquantitative PCR and Northern blotting analysis. In order to investigate megsin protein expression in anti-Thy1 nephritis rats, we raised antibody against rat megsin-specific synthetic peptide, with which immunohistochemical studies were performed.

RESULTS

Rat and mouse megsins were composed of 380 amino acids, which revealed 75.3 and 73.9% identity, respectively, with human megsin at the amino acid level. Characteristic features as an inhibitory serpin were conserved in both rat and megsin megsins. PCR analysis revealed expression of megsin in cultured mesangial cells but not in glomerular epithelial or endothelial cells. In anti-Thy1 nephritis rats, semiquantitative PCR and Northern blotting showed that expression of megsin mRNA was up-regulated in glomeruli at day 8. Immunohistochemical studies demonstrated the prominent accumulation of megsin in glomeruli at the same time point. Megsin was mainly localized in mesangial area. The megsin expression level returned to the basal level at day 28.

CONCLUSION

Sequences of megsin were well conserved among different species. Rat megsin was also predominantly expressed in mesangial cells. Expression of megsin was up-regulated at the peak of hypercellularity and matrix accumulation in the mesangioproliferative glomerulonephritis model, suggesting that megsin may participate in the process of glomerulosclerosis by modulating extracellular matrix deposition or cell survival.

Quantitation of TGF-beta1 mRNA in porcine mesangial cells by comparative kinetic RT/PCR: comparison with ribonuclease protection assay and in situ hybridization

Gene expression can be examined with different techniques including ribonuclease protection assay (RPA), in situ hybridisation (ISH), and quantitative reverse transcription-polymerase chain reaction (RT/PCR). These methods differ considerably in their sensitivity and precision in detecting and quantifying low abundance mRNA. Although there is evidence that RT/PCR can be performed in a quantitative manner, the quantitative capacity of this method is generally underestimated. To demonstrate that the comparative kinetic RT/PCR strategy-which uses a housekeeping gene as internal standard-is a quantitative method to detect significant differences in mRNA levels between different samples, the inhibitory effect of heparin on phorbol 12-myristate 13-acetate (PMA)-induced-TGF-beta1 mRNA expression was evaluated by RT/PCR and RPA, the standard method of mRNA quantification, and the results were compared. The reproducibility of RT/PCR amplification was calculated by comparing the quantity of G3PDH and TGF-beta1 PCR products, generated during the exponential phases, estimated from two different RT/PCR (G3PDH, r = 0.968, P = 0.0000; TGF-beta1, r = 0.966, P = 0.0000). The quantitative capacity of comparative kinetic RT/PCR was demonstrated by comparing the results obtained from RPA and RT/PCR using linear regression analysis. Starting from the same RNA extraction, but using only 1% of the RNA for the RT/PCR compared to RPA, significant correlation was observed (r = 0.984, P = 0.0004). Moreover the morphometric analysis of ISH signal was applied for the semi-quantitative evaluation of the expression and localisation of TGF-beta1 mRNA in the entire cell population. Our results demonstrate the close similarity of the RT/PCR and RPA methods in giving quantitative information on mRNA expression and indicate the possibility to adopt the comparative kinetic RT/PCR as reliable quantitative method of mRNA analysis.

Composition of nephritic factor-generated glomerular deposits in membranoproliferative glomerulonephritis type 2

Two observations suggest that nephritic factors (NFs) may be nephritogenic. First, glomerulonephritis is present in unusual frequency in three conditions in which the function of factor H is blocked, a dysfunction also produced by NFS: Second, in membranoproliferative glomerulonephritis (MPGN) type 2, subepithelial deposits on the paramesangial portion of the glomerular basement membrane are found only in renal biopsy specimens obtained during hypocomplementemia when NF is presumably present. In the present study, the composition of these deposits with respect to C3 derivatives was assessed by immunohistological evaluation using anti-C3c and anti-C3d. The assessment used routinely obtained photomicrographs, as well as immunohistologic examination of freshly cut tissue using the double-antibody method. Deposits in patients with typical hypocomplementemic MPGN type 2 reacted only with anti-C3c, whereas those in two patients with rapidly progressive MPGN type 2, six patients with poststreptococcal acute glomerulonephritis, and five patients with juvenile acute nonproliferative glomerulitis reacted with anti-C3d, as well as anti-C3c. Because all products derived from the breakdown of C3 except C3c react with anti-C3d, the deposits in typical MPGN type 2 must be composed only of C3c. With complete breakdown of bound C3b, C3c is released into the fluid phase. Therefore, the C3c in the deposits cannot be a product of a glomerular complement reaction, but instead must be formed in the circulation by the reaction of NF with native C3. Supporting C3c as the only constituent of these deposits is the observation that they are devoid of properdin and C5 is present in only small amounts.

Distribution of alphavbeta3, alphavbeta5 integrins and the integrin associated protein--IAP (CD47) in human glomerular diseases

The alphav integrins present on the membrane of numerous cells, mediate attachment to matrix proteins, cell proliferation, migration and survival. We studied the expression of alphav integrinis and CD47 (a beta3 chain integrin associated protein) in various forms of glomerulonephritis (GN) characterized by mesangial proliferation and/or increased mesangial matrix. In normal glomeruli, epithelial cells expressed alphavbeta3, alphavbeta5 and CD47; endothelial cells expressed alpha5beta1 and CD47; mesangial cells expressed alphavbeta5, CD47, and to a less extent alphavbeta3. In acute post infectious GN (APIGN), membrano-proliferative GN (MPGN) and diabetic nephropathy(DN), we observed that the beta3 chain, normally expressed by mesangial cells, was not detectable in the mesangium while its expression by epithelial cells was not modified. Parallel to the disappearance of alphavbeta3, the CD47 expression was decreased on the mesangial cells in MPGN, APIGN and DN. The expression of alphavbeta5 was clearly increased on podocytes and on proliferating mesangial cells in APIGN. By contrast, the mesangial expression of alphavbeta was normal or decreased in DN. The alpha5 chain of integrin, absent on normal mesangial cell, was expressed on proliferating mesangial cells in MPGN and APIGN. Thus, we observed modifications of alphavbeta3 and alphavbeta5 expression during human GN. The modulations of alphavbeta3 and alphavbeta5 expression differed according to the different glomerular cell types and were not parallel in glomerular cells: alphavbeta3 was decreased (and alphavbeta5 unchanged) on proliferating mesangial cells and alphavbeta5 was increased (and alphavbeta3 unchanged) in podocytes. This may reflect the existence of two distinct regulatory pathways.

Heterogeneous expression of nonmuscle myosin heavy chain-B in mesangial cells of patients with Gitelman's syndrome

AIMS

It has been suggested that angiotensin II (Ang II) promotes hypertrophy and hyperplasia of mesangial cells. Nonmuscle myosin heavy chain-B (NMHC-B) and alpha-smooth muscle (SM) actin are considered to be molecular markers for phenotypic change ofproliferative mesangial cells. One of the clinical characteristics in Gitelman's syndrome (GS) is the elevation of plasma Ang II. However, little is known about the relation between Ang II and phenotypic change of mesangial cells in patients with GS. In this report, we examined the expression of NMHC-B and alpha-SM actin in mesangial cells of two GS patients.

MATERIALS AND METHODS

Plasma renin activity, and the concentrations of Ang II, 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), urinary kallikrein, and 6-keto-PGF1alpha were measured. Immunohistochemical staining of NMHC-B and alpha-SM actin in mesangial cells of GS patients was also performed.

RESULTS

Both cases of GS showed normal glomerular function, few histological abnormalities, and higher than normal plasma concentrations of renin and Ang II. Furthermore, one case showed a high urinary concentration of kallikrein and the expression of both NMHC-B and alpha-SM actin in mesangial cells. The other case showed a high urinary concentration of 6-keto-PGF1alpha but not kallikrein and without the expression of NMHC-B and alpha-SM actin.

CONCLUSION

Not only plasma kinin-kallikrein and prostaglandins, but the renal expression of NMHC-B and alpha-SM actin may be variable in different patients with GS.

Expression of basic helix-loop-helix proteins in the glomeruli

BACKGROUND

Basic helix loop helix (bHLH) proteins play a critical role in the differentiation of not only striated muscle cells but also adipocytes, neuron cells and smooth muscle cells. Previous studies have established in vitro mouse mesangial cells (MCs) to maintain the differentiated smooth muscle phenotype.

MATERIALS AND METHODS

The purpose of the present study was to clone bHLH proteins from these MCs using the primers designed from a homologous sequence specific to bHLH, and to analyze the presence of bHLH proteins in normal kidney in vivo. From the cloning of MCs in vitro, we identified myf5 and herculin mRNA but not myoD. The expression of bHLH proteins in vivo was examined by immunohistochemistry with each specific antibody.

RESULTS

The MCs in newborn mice possessed Id but did not express either protein herculin or myoD. On the other hand, mature MCs expressed both myf5 and herculin. The Id protein disappeared in mature glomeruli.

CONCLUSION

These results suggest that bHLH proteins are an important factor for mature MCs in vivo.

Anti-dsDNA antibody up-regulates interleukin 6, but not cyclo-oxygenase, gene expression in glomerular mesangial cells: a marker of immune-mediated renal damage?

OBJECTIVE AND DESIGN

To determine whether anti-double stranded DNA antibody (anti-dsDNA) can affect the synthesis of eicosanoids and cytokines in rat glomerular mesangial cells (RMC).

MATERIALS OR SUBJECTS

Glomerular mesangial cells were isolated and subcultured from Sprague-Dawley rats. Monoclonal anti-dsDNA (12B3 clone) was derived from autoimmune MRL-lpr/lpr mouse by hybridoma technology.

METHODS

The mRNA expression of cyclo-oxygenase type 1 (COX-1), type 2 (COX-2), Th1 (IL-2 and IFN-gamma)/Th2 (IL-4 and IL-10) and proinflammatory (IL-6 and TNF-alpha) and anti-inflammatory (TGF-beta) cytokines of RMC +/- anti-dsDNA was detected by RT-PCR. The PGE2 production by RMC +/- anti-dsDNA was measured by ELISA. The statistical significance was assessed by non-parametric Wilcoxon signed rank test.

RESULTS

We found RMC spontaneously expressed COX-1, but not COX-2. The incubation of RMC with anti-dsDNA (50 ng/ml) did not affect COX expression and PGE2 production by RMC. RMC also spontaneously expressed IL-6, TNF-alpha and TGF-beta mRNA. However, only IL-6 was up-regulated by anti-dsDNA.

CONCLUSIONS

Increased IL-6 expression in RMC may become a marker of anti-dsDNA-mediated immune damage of mesangial cells.

IgA nephropathy with complement deficiency

We treated a female patient suffering from immunoglobulin A (IgA) nephropathy and congenital deficiency of the ninth component of the complement system (C9). She was admitted with hematuria and proteinuria, and the C9 deficiency was diagnosed based on the low hemolytic activity of 50 % of the hemolytic unit of the complements (CH50) and the normal C3 level in the plasma. Renal biopsy revealed mild mesangial proliferation, and immunofluorescence examination revealed mild mesangial deposits of IgA and C3 with the same distribution. We discuss the pathogenesis of IgA nephropathy and the role of the complements in its progression.

F-actin fiber distribution in glomerular cells: structural and functional implications

BACKGROUND

Glomerular distention is associated with cellular mechanical strain. In addition, glomerular distention/contraction is assumed to influence the filtration rate through changes in filtration surface area. A contractile cytoskeleton in podocytes and mesangial cells, formed by F-actin-containing stress fibers, maintains structural integrity and modulates glomerular expansion. In this study, the glomerular cell distribution of F-actin and vimentin filaments was studied in normal control and nine-month streptozotocin-diabetic rats. Results in situ were compared with observations in tissue culture.

METHODS

Microdissected rat glomeruli were perfused to obtain a physiological 25% glomerular expansion over the basal value. Fixation was done without change in glomerular volume. Dual fluorescent labeling of F-actin and vimentin was carried out, and samples were examined by confocal laser scanning microscopy.

RESULTS

The podocyte cell bodies and their cytoplasmic projections, including the foot processes, contained bundles of vimentin-containing fibers. Except for a thin layer at the base of foot processes, they did not demonstrate F-actin. While mesangial cells in culture had F-actin as long stress fibers resembling tense cables, mesangial cells stretched in situ contained a maze of short tortuous F-actin fibers organized in bundles that often encircled vascular spaces. This fibrillar organization was disrupted in diabetic glomeruli.

CONCLUSION

Mesangial cells, but not podocytes, contain a cytoskeleton capable of contraction that is disorganized in long-term diabetes. Together with previous observations, the distribution of this cytoskeleton suggests that mesangial cell contraction may be involved in the redistribution of glomerular capillary blood flow, but not substantially in the modulation of glomerular distention. Disorganization of stress fibers may be a cause of hyperfiltration in diabetes.

Troglitazone halts diabetic glomerulosclerosis by blockade of mesangial expansion

BACKGROUND

Renal complications of long-term, poorly controlled type 2 diabetes mellitus include glomerulosclerosis and interstitial fibrosis. The onset and progression of these complications are influenced by underlying pathophysiologies such as hyperglycemia, hypertriglyceridemia, and hypercholesterolemia. Troglitazone, a thiazolidinedione, has been shown to ameliorate these metabolic defects. However, it was not known whether therapeutic intervention with troglitazone would prevent the onset and progression of glomerulosclerosis.

METHODS

Sixty male ZDF/Gmitrade mark rats and 30 age-matched Zucker lean rats were in the study. The ZDF/Gmitrade mark rats were divided into two groups, one in which blood glucose levels were uncontrolled (30 animals) and another (30) in which blood glucose was controlled via dietary administration of troglitazone. Ten animals from each group were sacrificed at one, three, and six months into the study. The kidneys were harvested and processed for immunostaining with BM-CSPG, a marker for mesangial matrix. Images of 200 glomeruli per animal were captured using digital imaging microscopy, and the index of mesangial expansion (total area mesangium/total area of tuft) per glomerular section was measured.

RESULTS

The administration of troglitazone ameliorated the metabolic defects associated with type 2 diabetes mellitus. Moreover, the glomeruli from tissue sections of animals given troglitazone showed no mesangial expansion when compared with normoglycemic control animals, whereas the uncontrolled diabetic animals showed significant mesangial expansion at all time intervals.

CONCLUSIONS

Therapeutic intervention with the thiazolidinedione troglitazone halts the early onset and progression of mesangial expansion in the ZDF/Gmitrade mark rat, preventing the development of glomerulosclerosis in this animal model of type 2 diabetes mellitus.

Effect of dilazep hydrochlorideon the Im munohistopathology of IgA nephropathy in ddY mice

We determined the clinical and immunopathological effects of dilazep hydrochloride (dilazep) on IgA nephropathy of ddY mice. Group I (early-treatment group, n = 10) was orally treated with 300 mg/kg body weight of this drug from 12 weeks of age until 60 weeks of age, and group II (late-treatment group, n = 10) was also treated with the same dosage of this drug from 20 weeks of age until 60 weeks of age. Group III (control group, n = 10) received drinking water. On immunofluorescence, distribution and intensity of IgA and C3 depositions in glomeruli of group I and group II animals were significantly decreased as compared with those in group III. The expression of fibronectin, laminin, or type IV collagen in glomeruli was basically similar in the three groups treated with or without dilazep. On light microscopy, the expansion of glomerular mesangial areas and the average number of intraglomerular cells were markedly decreased as compared with those in group III. The levels of urinary protein excretion in groups I and II were significantly lower than those in group III (p < 0.01 and p < 0.05). These findings suggest that treatment with dilazep might improve the clinical and immunopathological findings in IgA nephropathy of ddY mice.