Inhibition of TGF-beta 1 expression by antisense oligonucleotides suppressed extracellular matrix accumulation in experimental glomerulonephritis

The effects of platelet-derived growth factor antagonism in experimental glomerulonephritis are independent of the transforming growth factor-beta system

Platelet-derived growth factor B-chain (PDGF-B)- and transforming growth factor beta (TGF-beta)-mediated accumulation of extracellular matrix proteins contributes to many progressive renal diseases. In vivo, specific antagonism of either PDGF-B or TGF-beta in experimental mesangioproliferative glomerulonephritis resulted in an almost complete inhibition of matrix protein accumulation, which suggests an interaction between signaling pathways of these two growth factors. Because nothing is known on the nature of this possible interaction, PDGF-B was antagonized in the rat anti-Thy 1.1 model of glomerulonephritis by use of specific aptamers and its effects on the TGF-beta system were investigated. Antagonism of PDGF-B led to a significant reduction of glomerular matrix accumulation compared with scrambled aptamer-treated nephritic controls. PDGF-B antagonism had no effect on the overexpression of glomerular TGF-beta mRNA, TGF-beta protein, or the expression of TGF-beta receptor type I and II mRNA. By immunohistology, it was possible to detect overexpression of the cytoplasmic TGF-beta signaling molecules Smad2 (agonistic) and Smad7 (antagonistic) in glomeruli of nephritic control rats which peaked on day 7 after disease induction, i.e., the peak of mesangial cell proliferation in this model. However, immunohistology and Western blot analysis again revealed no difference in the glomerular expression of both Smad proteins between PDGF-B antagonized and nonantagonized nephritic animals. In addition, no difference in the glomerular expression of phosphorylated Smad2 (P-Smad2) was detected between the differently treated nephritic groups. These observations suggest that the effects of PDGF-B antagonism are independent of TGF-beta in mesangioproliferative glomerulonephritides.

Pirfenidone treatment decreases transforming growth factor-beta1 and matrix proteins and ameliorates fibrosis in chronic cyclosporine nephrotoxicity

Chronic cyclosporine (CsA) nephrotoxicity is characterized by tubulointerstitial fibrosis. Pirfenidone (PFD) is a novel antifibrotic compound that was shown to prevent and even reverse fibrosis. The mechanism of action of PFD is unclear but involves inhibition of transforming growth factor-beta (TGF-beta). Salt-depleted rats were administered CsA, CsA + PFD, vehicle (VH) or VH + PFD and sacrificed at 28days. Physiologic and histologic changes were studied in addition to TGF-beta1, plasminogen activator inhibitor-1 (PAI-1) and biglycan mRNA expressions by Northern blot. TGF-beta1 immunohistochemistry was also performed. Treatment with PFD ameliorated CsA-induced fibrosis by about 50% (p < 0.05). CsA-induced decrease in creatinine clearance improved with PFD but the difference was not significant. TGF-beta1, PAI-1 and biglycan mRNA expressions increased with CsA (p < 0.05 vs. VH) but strikingly improved with PFD treatment (p < 0.05 vs. CsA), which brought the levels down to VH levels. PFD treatment also decreased TGF-beta1 protein expression by 80%. These results demonstrate that PFD can attenuate renal fibrosis in this model. PFD was associated with a decrease in TGF-beta1 expression, which, in turn, was associated with a decrease in matrix deposition. These experiments suggest that PFD can be clinically useful for preventing chronic CsA nephrotoxicity and may prove to be helpful in other progressive renal diseases.

Lefty contributes to the remodeling of extracellular matrix by inhibition of connective tissue growth factor and collagen mRNA expression and increased proteolytic activity in a fibrosarcoma model

Homeostasis of the extracellular matrix (ECM) of tissues is regulated by controlling deposition and degradation of ECM proteins. The breakdown of ECM is essential in blastocyst implantation and embryonic development, tissue morphogenesis, menstrual shedding, bone formation, tissue resorption after delivery, and tumor growth and invasion. TGF-beta family members are one of the classes of proteins that actively participate in the homeostasis of ECM. Here, we report on the effect of lefty, a novel member of the TGF-beta family, on the homeostasis of extracellular matrix in a fibrosarcoma model. Fibroblastic cells forced to express lefty by retroviral transduction lost their ability to deposit collagen in vivo. This event was associated with down-regulation of the steady-state level of connective tissue growth factor that induces collagen type I mRNA. In addition, lefty transduction significantly decreased collagen type I mRNA expression and simultaneously increased collagenolytic, gelatinolytic, elastolytic, and caseinolytic activities in vivo by the transduced fibroblasts. These findings provide a new insight on the actions of lefty and suggest that this cytokine plays an active role in remodeling of the extracellular matrix in vivo.

Glomerular beta-galactosidase expression following transduction with microsphere-adenoviral complexes

The aortic injection of adenoviral-microsphere complexes is a useful technique for in vivo gene transfer (transduction) to the glomerulus. In this approach, the appearance of the foreign transprotein in the glomerulus may result from glomerular cell gene transfer and local synthesis or hepatic cell transduction followed by synthesis, secretion, and deposition in the glomerulus. We postulated that glomerular expression of the foreign transgene was the result of glomerular cell transduction. To test this question, male SD rats underwent aortic injections with adenovirus containing the LacZ expression cassette [expressing beta-galactosidase (betagal)] coupled to 16 microm diameter microspheres. After 48 hours, histologic staining confirmed glomerular expression of the betagal transprotein and reverse transcription in situ polymerase chain reaction demonstrated the presence of the betagal transgene in the glomerulus. In addition, hepatic expression of the betagal transprotein was minimal and substantially less than that observed in the glomeruli. These data support the contention that adenoviral-microsphere complexes result in glomerular cell transduction with the desired transgene, followed by local transprotein synthesis. This approach may prove useful for facilitating glomerular gene transfer in the development of gene therapy for glomerulonephritis.

Targeting growth factors to the kidney: myth or reality?

Growth factors and cytokines play a crucial role in the progression of renal diseases. A growing body of evidence has been obtained from experimental studies, suggesting that manipulation of the activity of growth factors and cytokines is a potential form of therapy for renal diseases. To preserve the renal function structure in progressive renal diseases, this approach is achieved by inhibition of apoptosis of renal intrinsic cells and by decrease in the fibrotic signal. Inhibition of transforming growth factor beta, platelet-derived growth factor, interleukin-1 and tumor necrosis factor alpha, and supplementation of hepatocyte growth factor, vascular endothelial growth factor and bone morphogenic protein-7 may be beneficial. Recent progress in therapeutic implements including humanized antibodies, chimeric soluble receptors, aptamers, antisense oligonucleotides, and gene therapy allow us to target the causal molecules. Administration of a combination of growth factors and cytokines is a potential therapeutic approach. Targeting signal transduction molecules and their co-factors and regulators is another possibility because the signals from various growth factors use a common pathway. Thus, targeting growth factors and cytokines in renal diseases could be a promising therapeutic approach.

Peritoneal Dialysis in the 21st Century: The Potential of Gene Therapy

ABSTRACT. One of the greatest biotechnologic advances of the last 25 yr is genetic engineering—the ability to identify and isolate individual genes and transfer genetic elements between cells. Genetic engineering forms the basis of a unique biotechnology platform called gene therapy: an approach to treating disease through genetic manipulation. It is becoming clear that during peritoneal dialysis, the peritoneal membrane undergoes various structural and functional changes that compromise the dialyzing efficiency of the membrane and eventually lead to membrane failure. A gene therapy strategy based on genetic modification of the peritoneal membrane could improve the practice of peritoneal dialysis through the production of proteins that would be of therapeutic value in preventing membrane damage and preserving its dialyzing capacity. The peritoneal membrane can be genetically modified by either ex vivo or in vivo gene transfer strategies with a variety of potentially therapeutic genes, including those for anti-inflammatory cytokines, fibrinolytic factors, and antifibrotic molecules. These genes could be administered either on an acute basis, such as in response to peritonitis, or on an intermittent basis to maintain physiologic homeostasis and perhaps to prevent the adverse changes in the membrane that occur over time. The anticipated effect of a gene therapy strategy could be measured in maintenance of desired transport characteristics and in patients being able to remain on the therapy for longer periods of time without the negative outcomes. In summary, the use of a gene therapy strategy to enhance peritoneal dialysis is an innovative and exciting concept with the potential to provide new treatment platforms for patients with end-stage renal disease.

Response of mesangial cells to low-density lipoprotein and angiotensin II in diabetic (OLETF) rats

BACKGROUND

Progression of diabetic nephropathy is closely associated with morphological changes in glomeruli, such as thickening of the glomerular basement membrane, mesangial expansion, and glomerulosclerosis. To elucidate early glomerular events, we compared the mitogenic activity and extracellular matrix production in mesangial cells (MC) isolated from diabetic rats prior to the manifestation of nephropathy and those showing overt nephropathy. This study may help to clarify the mechanisms underlying diabetic nephropathy and provide clues about early therapeutic interventions for preventing or slowing this process.

METHODS

Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a chronic model for human type 2 diabetes mellitus, and age-matched control (LETO) rats were used. Glomerular cell numbers, expression of immediate early genes (c-Fos and c-Myc) and proliferating cell nuclear antigen (PCNA), and low-density lipoprotein (LDL) deposition were determined in renal tissue sections from rats aged 15 to 75 weeks. Mesangial cells (MCs) from OLETF rats at two different stages of the disease, that is, young (12- to 14-week-old) OLETF rats (y-OLETF) prior to the manifestation of nephropathy and old (48- to 50-week-old) OLETF rats (o-OLETF) showing nephropathy, were isolated and cultured. After stimulation with native (n-) or oxidized (ox-) LDL or angiotensin II (Ang II), DNA synthesis and extracellular matrix (ECM) production were examined. Cellular expression of LDL/scavenger receptors was analyzed using fluorescence-labeled LDL and binding to 125I-labeled-LDL.

RESULTS

The number of cells per glomerular cross section was significantly higher in OLETF rats than in LETO rats between 25 and 65 weeks of age. In OLETF glomeruli, c-Fos, c-Myc, and PCNA were transiently expressed in the early phase. Glomerular LDL deposition increased with the age of OLETF rats. Addition of a low dose of n-LDL (10 microg/mL) to the culture medium significantly stimulated DNA synthesis of y-OLETF MCs, as compared with o-OLETF MCs and LETO MCs (P < 0.05). A high dose of n-LDL (100 microg/mL) caused cytotoxic effects in all cells. Exposure to ox-LDL minimally affected DNA synthesis of OLETF or LETO MCs. LDL receptors and scavenger receptors were predominant in y-OLETF and o-OLETF, respectively. After stimulation with n-LDL and ox-LDL, expression of type I and type III collagen, along with transforming growth factor-beta (TGF-beta), was higher in o-OLETF MCs that in y-OLETF MCs or LETO MCs. Exposure to Ang II markedly induced DNA synthesis and ECM mRNA expression in y-OLETF MCs and o-OLETF MCs, respectively.

CONCLUSIONS

These findings indicate that the cell proliferation process precedes the evolution of diabetic glomerulopathy. The responses of OLETF MCs to n-LDL/ox-LDL and Ang II differed depending on the stage of diabetes. In the early phase, MCs were prone to proliferate, whereas in the late stage, MCs, which expressed higher levels of TGF-beta, tended to synthesize ECM. A functional switch in MCs may contribute to the development of glomerulosclerosis in diabetic nephropathy.

Effects of retinoids on the TGF-beta system and extracellular matrix in experimental glomerulonephritis

Transforming growth factor-beta1 (TGF-beta 1) overexpression plays a key role in the glomerular accumulation of extracellular matrix proteins in renal disease. Retinoids have previously been shown to significantly limit glomerular damage in rat experimental glomerulonephritis. Therefore, the effects of all-trans retinoic acid and isotretinoin on the components of the TGF-beta system and extracellular matrix proteins in anti-Thy1.1-nephritis (Thy-GN) were investigated. Vehicle-injected control rats were compared with rats treated with daily subcutaneous injections of 10 mg/kg body wt all-trans retinoic acid or 40 mg/kg body wt isotretinoin (n = 9 per group) either with a pretreatment (day -2 through 8) or posttreatment protocol (day +3 through 8), i.e., starting before or after induction of Thy-GN, respectively. Urinary TGF-beta 1 excretion was 60% lower in all-trans retinoic acid-treated animals with Thy-GN (P < 0.025). The increase of cortical TGF-beta 1 gene expression in Thy-GN rats was significantly attenuated with all-trans retinoic acid and even more with isotretinoin treatment as compared with untreated animals (P < 0.025). Cortical expression of TGF receptor II, but not receptor I gene expression, was significantly lower in animals treated with all-trans retinoic acid or isotretinoin (P < 0.05). In all-trans retinoic acid-treated animals with Thy-GN, the increase of glomerular TGF-beta 1 protein (P < 0.008) and TGF-beta 1 (P < 0.025) and TGF receptor II mRNA (P < 0.015) was significantly less. Immunohistochemistry revealed less glomerular staining for TGF-beta 1 and TGF receptor II in the presence of all-trans retinoic acid. TGF-beta 1 immunostaining was not restricted to monocytes and macrophages, as indicated by double-staining. Glomerular staining for collagen IV and collagen III was less in animals treated with isotretinoin (P < 0.02 for both) in contrast to all-trans retinoic acid, whereas fibronectin remained unchanged. It was concluded that the beneficial effects of retinoids on glomerular damage are presumably due to a marked reduction in renal TGF-beta 1 and TGF receptor II expression.

Effects of anti-TGF-beta type II receptor antibody on experimental glomerulonephritis

BACKGROUND

Renal fibrosis, characterized by the accumulation of extracellular matrix (ECM), is a common histopathological feature of progressive renal disease of diverse etiology. Interaction between transforming growth factor-beta (TGF-beta) and TGF-beta type II receptor (TGF-betaIIR) may play an important role in the ongoing fibrotic process. TGF-betaIIR and TGF-beta have been reported to be up-regulated in human glomerulopathies. In order to block the TGF-beta system, many studies have inhibited TGF-beta itself, but not its receptors. Our study explored the effects of fully human monoclonal antibody against TGF-betaIIR (hTGF-betaIIRAb) on experimental proliferative glomerulonephritis.

METHODS

hTGF-betaIIRAb was generated from Xenomice. The expression of TGF-betaIIR was studied by immunohistochemistry in normal and anti-Thy-1 nephritis rats. hTGF-betaIIRAb or control Ab was injected intraperitoneally at day 0 and day 4 of anti-Thy-1 nephritis, and rats were sacrificed at day 7. Effects of hTGF-betaIIRAb were assessed by histological and immunopathological measurements.

RESULTS

The specificity of hTGF-betaIIRAb was confirmed by ELISA and Western blot analysis. By immunostaining, TGF-betaIIR expression was up-regulated in the proliferative lesions of anti-Thy-1 nephritis at day 7. In the hTGF-betaIIRAb-treated group, the extent of mesangial expansion was less than that in the control group. By immunohistology, alpha-smooth muscle actin, fibronectin-EDA, and type I collagen were significantly reduced in the hTGF-betaIIRAb-treated group.

CONCLUSIONS

Anti-TGF-betaIIR antibody ameliorated ECM accumulation in anti-Thy-1 nephritis. Our data suggest that TGF-betaIIR may be one of the therapeutic targets, and that fully human monoclonal antibody against TGF-betaIIR may have a new therapeutic potential for renal fibrosis.

Selective inhibition of the renal angiotensin type 2 receptor increases blood pressure in conscious rats

The angiotensin II type 2 (AT(2)) receptor is present in rat kidney; however, its function is not well understood. The purpose of this study was to evaluate the role of the AT(2) receptor in blood pressure (BP) regulation. The effects of selective inhibition of the renal AT(2) receptor with phosphorothioated antisense oligodeoxynucleotide (AS-ODN) were examined in conscious uninephrectomized rats. Oligodeoxynucleotides (AS-ODN or scrambled [S-ODN]) were infused directly into the renal interstitial space by using an osmotic pump at 1 microL/h for 7 days. Texas red-labeled AS-ODN was distributed in renal tubules in the infused but not the contralateral kidney of normal rats. Continuous renal interstitial infusion of the AS-ODN, but not S-ODN, caused a significant (P<0.01) increase in BP 1 to 5 days after the initiation of the infusion. AS-ODN-treated rats experienced an increase in systolic BP from 109+/-4 to 130+/-4 mm Hg (n=8, P<0.01), whereas S-ODN-treated (n=8) and vehicle-treated (n=8) rats did not show any significant change in BP. On day 5 of the oligodeoxynucleotide infusion, AS-ODN-treated rats exhibited a greater pressor response to systemic angiotensin II infusion (30 ng/kg per hour) than did S-ODN-treated rats (P<0.01). Renal interstitial fluid cGMP decreased from 11.9+/-0.8 to 3.6+/-0.5 pmol/mL (P<0.001), and bradykinin decreased from 0.05+/-0.05 to 0.18+/-0.03 ng/mL (P<0.001) in response to AS-ODN, but they were not significantly changed in response to S-ODN. To evaluate the effects of AS-ODN and S-ODN on AT(2) receptor expression, Western Blot analysis was performed on treated kidneys. Kidneys treated with AS-ODN had approximately 40% less expression of AT(2) receptor than did kidneys treated with S-ODN or vehicle (P<0.05). These results suggest that AS-ODN directed selectively against the renal AT(2) receptor decreased receptor expression and caused an increase in BP. We conclude that the renal AT(2) receptor plays an important role in the regulation of BP via a bradykinin/cGMP vasodilator signaling cascade.

Electroporation-mediated PDGF receptor-IgG chimera gene transfer ameliorates experimental glomerulonephritis

BACKGROUND

Mesangial cell proliferation and phenotypic alteration occur in an early phase of glomerular injury and precede increased extracellular matrix accumulation. A critical growth factor responsible for mesangial proliferation is platelet-derived growth factor (PDGF), which has proved to be a potent mitogen.

METHODS

We generated a chimeric cDNA encoding an extracellular domain of the beta-PDGF receptor fused with IgG-Fc, termed PDGFR/Fc, and examined the feasibility of gene therapy targeting PDGF using PDGFR/Fc.

RESULTS

Chimeric PDGFR/Fc molecule completely inhibited the tyrosine phosphorylation of beta-PDGF receptors and cellular proliferation induced by PDGF in vitro. We then introduced the PDGFR/Fc expression vector into the muscle of anti-Thy-1 model of glomerulonephritic rats by electroporation. The plasma concentration of chimeric PDGFR/Fc levels was 244.4 +/- 89.8 ng/mL four days after transfection. On day 5, PDGFR/Fc gene transfer significantly reduced the number of PCNA-positive cells and glomerular cell numbers by 59.6 and 23.2%, respectively. Northern blot analysis demonstrated that glomerular mRNA levels of alpha-smooth muscle action, transforming growth factor-beta 1, and type I collagen were also suppressed on days 5 and 7 by the PDGFR/Fc transfection. There was a significant reduction in the matrix score of the transfected nephritic rats (2.91 +/- 0.75 and 2.06 +/- 0.95; disease control group vs. treated group, P < 0.001).

CONCLUSION

These results suggest that gene therapy by the manipulation of PDGF action using electroporation-mediated PDGFR/Fc gene transfer to the skeletal muscle might be a useful treatment for mesangioproliferative glomerulonephritis.

Electroporation-mediated gene transfer that targets glomeruli

Electroporation has been applied to introducing DNA into several organs; however, gene expression was localized around the injected area. Examined was the efficiency of intrarenal injection of DNA followed by in vivo electroporation, using FITC-labeled oligodeoxynucleotides (FITC-ODN) and plasmid DNA expressing beta-galactosidase or luciferase. FITC-ODN or expression vectors were injected into the left renal artery; thereafter, the left kidney was electroporated between a pair of tweezer-type electrodes. FITC-ODN were transferred into all glomeruli, and transfected cells were identified as mesangial cells. Four d after transfection of the pCAGGS-LacZ gene, beta-galactosidase expression was observed in 75% of glomeruli. To compare the transfection efficacy by electroporation with that by the hemagglutinating virus of Japan (HVJ) liposome method, a luciferase reporter gene, pActLuc, was transferred into glomeruli by either electroporation or the HVJ liposome method. On day 4, electroporation resulted in higher glomerular luciferase activity than did the HVJ liposome method. We also observed that co-transfection of pcEBNA, an expression vector for Epstein-Barr virus nuclear antigen, and poriP-cLuc, oriP-harboring vector, resulted in an eightfold higher luciferase gene expression than simple poriP-cLUC: No histologic damages were seen in glomeruli or tubular epithelial cells. In conclusion, gene transfer into renal artery followed by electroporation was an effective and simple strategy for gene transfer that targets glomerular mesangial cells.

Prolonged transgene expression in glomeruli using an EBV replicon vector system combined with HVJ liposomes

BACKGROUND

Various gene transfer vectors as well as delivery systems have been developed; however, many problems remain to be solved. We already achieved a technique to introduce genes into glomerular mesangial cells by hemagglutinating virus of Japan (HVJ) liposome-mediated gene transfer via renal artery. The main limitation of this method is the transient transgene expression.

METHOD

For long-term gene expression in glomeruli, Epstein-Barr virus (EBV) replicon-based plasmid was employed, containing the latent viral DNA replication origin (oriP) and EBV nuclear antigen-1 (EBNA-1), which are the minimum EBV component of transgene-nuclear retention. To examine the effect of EBV replicon apparatus on the duration of transgene expression in glomeruli in vivo, the EBV replicon vector pEBActLuc, and the control plasmid vector pActLuc were adopted. These plasmid vectors were transferred into the kidney via renal artery by using artificial viral envelope (AVE)-type HVJ liposome method, and glomerular luciferase activities were analyzed at various time points after transfection.

RESULTS

On day 4, pEBActLuc and pActLuc transfer resulted in equal glomerular luciferase activity, and the luciferase gene expression was sustained for at least 56 days in glomeruli transfected with pEBActLuc, whereas it was reduced on seven days in glomeruli transfected with pActLuc.

CONCLUSION

The combination of EBV replicon apparatus and HVJ liposomes appears to be a powerful tool for long-term gene expression in vivo, and furthermore, it may be a promising new therapeutic method for the progression of renal disease.

Endoglin expression in human and rat mesangial cells and its upregulation by TGF-beta1

Endoglin is a component of the TGF-beta receptor complex present in the kidney at the human glomerular mesangium. Since the cellular origin of the glomerular endoglin is unknown, in the present study we investigated the expression of endoglin in mesangial cells in culture, as well as their response to TGF-beta1. Western and Northern blot analysis identified the expression of endoglin protein and mRNA transcript in both human and rat mesangial cells. Flow cytometry and immunocytochemistry analyses revealed that endoglin is present on the cell membrane. Exogenous TGF-beta1 stimulated not only the expression of collagen alpha1 (I) I and TGF-beta1, but also that of endoglin. These data provide the first evidence for the expression of endoglin in mesangial cells, as well as its upregulation by TGF-beta1, thus suggesting that endoglin may have a role in modulating the effects of TGF-beta1 on the glomerular mesangium.

A novel model to study renal myofibroblast formation in vitro

BACKGROUND

In chronic renal disease, the decrease of excretory renal function closely correlates with the extent of interstitial fibrosis. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. We studied the transformation of renal fibroblasts into myofibroblasts in vitro as a model to elucidate the mechanisms underlying this process.

METHODS

Primary cultures of freshly isolated rat inner medullary fibroblasts were established as reported previously. mRNA expression of myofibroblast markers and interstitial collagens was examined by Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Phenotypic expression was investigated by immunolabeling. Endogenous transforming growth factor-beta (TGF-beta) production was inhibited by addition of a neutralizing antibody or by TGF-beta 1 antisense oligodeoxynucleotides (ODNs).

RESULTS

Initially and during the first 36 hours, primary culture cells expressed neither alpha-smooth muscle actin nor desmin mRNA. From day 2 of primary culture, we observed a strong increase in these mRNAs, as evaluated by RT-PCR, followed by the phenotypic expression of these myofibroblast markers. Collagen type I mRNA was first detectable from day 4 of primary culture and showed a strong increase in its expression level during the following days, with phenotypic expression predominantly in myofibroblasts. The transformation rate of fibroblasts to myofibroblasts largely decreased in cocultures with collecting duct cells. This effect could be reversed by reducing the seeding density. We examined in this system the effect of TGF-beta 1 to define further its putative fibrogenic activity. However, neither the addition of exogenous TGF-beta 1 nor the inhibition of endogenous TGF-beta production showed any significant effect on fibroblast transformation, suggesting that this cytokine exerts its effects at other levels or requires a cofactor.

CONCLUSIONS

We present a novel model to examine the de novo expression of myofibroblast markers and collagen type I in freshly isolated fibroblasts under defined conditions in primary culture. This model could provide a strategy for the molecular characterization of myofibroblast formation and the phenomena associated with this process.

Cytokines and hormones with anti-inflammatory effects: new tools for therapeutic intervention

The inflammation that is involved in the development of glomerulonephritis is tightly regulated by the expression of anti-inflammatory factors. These include circulating hormones, such as glucocorticoids, and mediators that are produced by intrinsic cells and infiltrating leucocytes. The present review focuses on these anti-inflammatory factors, summarizing in particular their activities in existing models of glomerulonephritis. In addition, experimental evidence is presented that anti-inflammatory mediators are able to increase glucocorticoid binding or signalling in target cells. These data help to explain the in-vivo efficacy of anti-inflammatory mediators, and offer a promising new avenue for therapeutic intervention.

Glycosaminoglycan therapy prevents TGF-beta1 overexpression and pathologic changes in renal tissue of long-term diabetic rats

Chronic induction of the prosclerotic cytokine transforming growth factor beta (TGF-beta) has been implicated in the pathogenesis of diabetic nephropathy. In a rat model of diabetes mellitus-induced glomerulosclerosis, daily administration of a modified heparin (mH) glycosaminoglycan (GAG) preparation with low anticoagulant activity prevented glomerular and tubular matrix accumulation, as well as overexpression of TGF-beta1 mRNA and albuminuria, without obvious side effects. To elucidate the molecular mechanisms of GAG/mH inhibitory actions on TGF-beta1, studies using cultured mesangial cells were also performed. In these cells, high glucose-induced, dose-dependent increases in TGF-beta1 mRNA and bioactive TGF-beta protein expression were inhibited by GAG/mH treatment, whereas basal TGF-beta1 expression was not affected. Both the heparin-derived GAG and dermatan sulfate were effective, indicating that the heparin chemical structure is not necessary for inhibitory activity. Coincubation of GAG with active TGF-beta1 demonstrated no inhibitory effect on TGF-beta1 bioactivity, excluding a neutralizing effect of GAG on TGF-beta1 a the protein level. Furthermore, it was demonstrated that GAG inhibited phorbol myristate acetate-induced translocation of protein kinase C-alpha (PKC-alpha) and -beta1 and activation of PKC-alpha, as well as high glucose-induced activation of PKC-alpha. These results suggest that GAG inhibit TGF-beta1 overexpression at the transcriptional level, possibly via inhibition of high glucose-activated PKC. The findings indicate the potential of GAG therapy for the prevention of diabetic glomerulosclerosis by the inhibition of chronic disease-induced TGF-beta1 mRNA overexpression.

Critical Aspects of Viral Vectors for Gene Transfer into the Kidney

Abstract.Viral vectors have been usedin vitroandin vivofor more than a decade, with some significant results in specific situations,e.g., when recombinant adeno-associated virus is used for the long-term transduction of skeletal muscle in coagulation factor IX-deficient patients. However, the kidney has been quite difficult to transduce with any viral vector currently available. When viral transduction occurs, it is often heterogeneous, transient, and eventually associated with immune and toxic side effects. However, recombinant adeno-associated virus and lentiviral vectors remain to be fully evaluated in the kidney; the former is small enough to be filtered through the glomerular basement membrane. This may be critical, because glomerular filtration is required for DNA complex-mediated transduction of tubular cells. An alternative toin siturenal gene transfer is secretion of a therapeutic protein from a distant site, such as skeletal muscle. Several examples provide evidence that this could be a clinically relevant approach. It also may allow accurate determination of the pathophysiologic mechanisms involved in the establishment and maintenance of experimental glomerulonephritis.

Transforming growth factor-beta 1 antisense oligodeoxynucleotides block interstitial fibrosis in unilateral ureteral obstruction

BACKGROUND

Interstitial expression of transforming growth factor-beta1 (TGF-beta1) is important in tubulointerstitial fibrosis, a common process in most progressive renal diseases. However, no effective therapy for progressive interstitial fibrosis is known. Recently, we developed an artificial viral envelope (AVE)-type hemagglutinating virus of Japan (HVJ) liposome-mediated retrograde ureteral gene transfer method, which allowed us to introduce the genetic material selectively into renal interstitial fibroblasts.

METHOD

We introduced antisense or scrambled oligodeoxynucleotides (ODNs) for TGF-beta 1 into interstitial fibroblasts in rats with unilateral ureteral obstruction, a model of interstitial fibrosis, to block interstitial fibrosis by retrograde ureteral injection of AVE-type HVJ liposomes.

RESULTS

TGF-beta 1 and type I collagen mRNA increased markedly in the interstitium of untreated obstructed kidneys, and those were not affected by scrambled ODN transfection. Northern analysis and in situ hybridization revealed that the levels of TGF-beta 1 and type I collagen mRNA were dramatically decreased in antisense ODN-transfected obstructed kidneys. Consequently, the interstitial fibrotic area of the obstructed kidneys treated with antisense ODN was significantly less than that of the obstructed kidneys untreated or treated with scrambled ODN.

CONCLUSION

The introduction of TGF-beta 1 antisense ODN into interstitial fibroblasts may be a potential therapeutic maneuver for interstitial fibrosis.

Integrin alpha1beta1 and transforming growth factor-beta1 play distinct roles in alport glomerular pathogenesis and serve as dual targets for metabolic therapy

Alport syndrome is a genetic disorder resulting from mutations in type IV collagen genes. The defect results in pathological changes in kidney glomerular and inner-ear basement membranes. In the kidney, progressive glomerulonephritis culminates in tubulointerstitial fibrosis and death. Using gene knockout-mouse models, we demonstrate that two different pathways, one mediated by transforming growth factor (TGF)-beta1 and the other by integrin alpha1beta1, affect Alport glomerular pathogenesis in distinct ways. In Alport mice that are also null for integrin alpha1 expression, expansion of the mesangial matrix and podocyte foot process effacement are attenuated. The novel observation of nonnative laminin isoforms (laminin-2 and/or laminin-4) accumulating in the glomerular basement membrane of Alport mice is markedly reduced in the double knockouts. The second pathway, mediated by TGF-beta1, was blocked using a soluble fusion protein comprising the extracellular domain of the TGF-beta1 type II receptor. This inhibitor prevents focal thickening of the glomerular basement membrane, but does not prevent effacement of the podocyte foot processes. If both integrin alpha1beta1 and TGF-beta1 pathways are functionally inhibited, glomerular foot process and glomerular basement membrane morphology are primarily restored and renal function is markedly improved. These data suggest that integrin alpha1beta1 and TGF-beta1 may provide useful targets for a dual therapy aimed at slowing disease progression in Alport glomerulonephritis.

Plasminogen activator inhibitor type 1 is a potential target in renal fibrogenesis

Plasminogen activator inhibitor type 1 is a potential target in renal fibrogenesis. The progression of renal lesions to fibrosis involves several mechanisms, among which the inhibition of extracellular matrix (ECM) degradation appears to play an important role. Two interrelated proteolytic systems are involved in matrix degradation: the plasminogen activation system and the matrix metalloproteinase system. The plasminogen activator inhibitor type 1 (PAI-1), as the main inhibitor of plasminogen activation, regulates fibrinolysis and the plasmin-mediated matrix metalloproteinase activation. PAI-1 is also a component of the ECM, where it binds to vitronectin. PAI-1 is not expressed in the normal human kidney but is strongly induced in various forms of kidney diseases, leading to renal fibrosis and terminal renal failure. Thrombin, angiotensin II, and transforming growth factor-beta are potent in vitro and in vivo agonists in increasing PAI-1 synthesis. Several experimental and clinical studies support a role for PAI-1 in the renal fibrogenic process occurring in chronic glomerulonephritis, diabetic nephropathy, focal segmental glomerulosclerosis, and other fibrotic renal diseases. Experimental models of renal diseases in PAI-1-deficient animals are in progress, and preliminary results indicate a role for PAI-1 in renal fibrogenesis. Inhibition of PAI-1 activity or of PAI-1 synthesis by specific antibodies, peptidic antagonists, antisense oligonucleotides, or decoy oligonucleotides has been obtained in vitro, but needs to be evaluated in vivo for the prevention or the treatment of renal fibrosis.

Microsphere-adenoviral complexes target and transduce the glomerulus in vivo

BACKGROUND

Developing new treatments for glomerulonephritis makes the glomerulus a logical target for gene therapy. Microspheres may lodge in the glomerulus, and replication-deficient recombinant adenoviruses are potent mediators of gene transfer. We postulated that adenoviral-microsphere complexes could result in DNA transfer (transduction) into glomerular cells in vivo.

METHODS

Two adenoviruses, each one containing a luciferase or beta-galactosidase (beta-gal) transgene expression cassette, were complexed to polystyrene microspheres. To assess in vivo glomerular transduction with this tool, male Sprague-Dawley rats underwent aortic injections with adenovirus linked to 11 or 16 microm diameter microspheres.

RESULTS

After 48 hours, adenoviral-microsphere complexes resulted in transduction of up to 19% of glomeruli per kidney section. Endothelial and mesangial cells were transduced with this approach, and transprotein expression persisted for 21 days. Transduction efficiency was greater in the 16 microm group. For all rats, there was a strong correlation between kidney luciferase levels and the number of beta-gal-positive glomeruli (r = 0.87), indicating that transgene expression was primarily glomerular in location. This was supported by reverse transcriptase in situ polymerase chain reaction, which demonstrated glomerular localization of the beta-gal transgene.

CONCLUSIONS

The aortic injection of adenoviral-microsphere complexes transduces the glomerulus in vivo and may be a useful tool in developing approaches to gene therapy of glomerular disease.

Gene therapy for kidney disease

Gene therapy has distinct potential to treat disease at the most fundamental level. However, the ability to pursue gene therapy for renal disease has been limited by the availability of an adequate system for gene delivery to the kidney and for regulation of transgene expression. Presently, there are several limitations to overcome before clinical use of viral vector systems for targeting kidney can be considered. Non-viral vectors such as haemagglutinating virus of Japan (HVJ)-liposome mediated gene transfer and cationic liposome are promising but need to be improved. Given that the systemic delivery of the functional protein can serve as therapy for the renal diseases, skeletal muscle targeting gene therapy might be an alternative strategy for the treatment of renal disease. Gene therapy to the transplant kidney may potentially improve the graft outcome by reducing acute and chronic rejection. We review emerging strategies of gene transfer with reference to the kidney and discuss the potential application of gene therapy to renal diseases.

Gene transfer targeting interstitial fibroblasts by the artificial viral envelope-type hemagglutinating virus of Japan liposome method

BACKGROUND

Tubulointerstitial inflammation and fibrosis are commonly associated with most human glomerular diseases. The degree of tubulointerstitial damage, rather than the glomerular injury, could correlate with the degree of renal functional impairment and accurately predict long-term prognosis. In an effort to understand the pathogenesis of the progressive interstitial fibrosis, we developed a new strategy of gene transfer to the interstitial fibroblasts.

METHODS

Either fluorescein isothiocyanate (FITC)-labeled oligodeoxynucleotides (ODNs) or pEBAct-NlacF expression vector was introduced into the kidney of normal rats retrogradely via ureter by using the artificial viral envelope (AVE)-type hemagglutinating virus of Japan (HVJ) liposome method.

RESULTS

FITC-labeled ODNs were accumulated diffusely in the nuclei of the interstitial cells in the transfected kidney 10 minutes after transfection, and the interstitial cells were identified as interstitial fibroblasts by immunostaining with ER-TR7. To examine the gene expression in the interstitium, pEBAct-NlacF gene-conjugated HVJ liposome was injected retrogradely through the ureter, and in consequence, nuclear beta-galactosidase activity was continuously observed in interstitial cells at least two weeks after transfection.

CONCLUSION

This new strategy of gene transfer to the interstitial fibroblasts is useful for the investigation of the pathophysiology of tubulointerstitial lesion, and furthermore, it may be a promising new therapeutic method for the progression of interstitial fibrosis.

Hypertension-induced organ damage in African Americans: transforming growth factor-beta(1) excess as a mechanism for increased prevalence

Hypertension is prevalent world-wide, and it affects over 50 million individuals in the United States alone. African Americans (blacks) have a high prevalence of hypertension, develop it at an earlier age, and suffer excessively from severe or malignant hypertension. They also have a high prevalence of target organ damage attributable to hypertension, including left ventricular hypertrophy, stroke, end-stage renal disease (ESRD) and coronary artery disease. Hypertensive nephrosclerosis is particularly more prevalent in blacks compared to whites, and there is evidence that factors in addition to elevated blood pressure contribute to its pathogenesis. Transforming growth factor-beta 1 (TGF-beta1) is a fibrogenic cytokine that has been implicated in the development and progression of experimental and human renal diseases. We have demonstrated that blacks with ESRD have higher circulating levels of TGF-beta1 protein compared to whites with ESRD. We have also found that hyperexpression of TGF-beta1 is more frequent in blacks with hypertension than in whites. We propose that TGF-beta1 hyperexpression may be an important mediator of hypertension and hypertensive nephrosclerosis. We hypothesize also that the increased frequency of TGF-beta1 hyperexpression may contribute to the excess burden of ESRD in blacks. Based on our hypotheses, and the observations that angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists reduce angiotensin II-mediated stimulation of TGF-beta1 production, we propose that treatment with these agents might be efficacious in preventing or slowing the progression of target organ damage in hypertensive blacks.

Therapy with antisense TGF-beta1 oligodeoxynucleotides reduces kidney weight and matrix mRNAs in diabetic mice

Inhibition of gene expression by antisense oligodeoxynucleotides (ODNs) relies on their ability to bind complementary mRNA sequences and prevent translation. The proximal tubule is a suitable target for ODN therapy in vivo because circulating ODNs accumulate in the proximal tubule in high concentrations. Because increased proximal tubular transforming growth factor- beta1 (TGF-beta1) expression may mediate diabetic renal hypertrophy, we investigated the effects of antisense TGF-beta1 ODN on the high-glucose-induced proximal tubular epithelial cell hypertrophy in tissue culture and on diabetic renal hypertrophy in vivo. Mouse proximal tubular cells grown in 25 mM D-glucose and exposed to sense ODN as control (1 microM) exhibited increased (3)[H]leucine incorporation by 120% and total TGF-beta1 protein by 50% vs. culture in 5.5 mM D-glucose. Antisense ODN significantly decreased the high-glucose-stimulated TGF-beta1 secretion and leucine incorporation. Continuous infusion for 10 days of ODN (100 microg/day) was achieved via osmotic minipumps in diabetic and nondiabetic mice. Sense ODN-treated streptozotocin-diabetic mice had 15.3% increase in kidney weight, 70% increase in alpha1(IV) collagen and 46% increase in fibronectin mRNA levels compared with nondiabetic mice. Treatment of diabetic mice with antisense ODN partially but significantly decreased kidney TGF-beta1 protein levels and attenuated the increase in kidney weight and the alpha1(IV) collagen and fibronectin mRNAs. In conclusion, therapy with antisense TGF-beta1 ODN decreases TGF-beta1 production and attenuates high-glucose-induced proximal tubular cell hypertrophy in vitro and partially prevents the increase in kidney weight and extracellular matrix expression in diabetic mice.

Transforming growth factor-beta 1 hyperexpression in African-American hypertensives: A novel mediator of hypertension and/or target organ damage

Hypertension, a remediable risk factor for stroke, cardiovascular disease, and renal failure, affects 50 million individuals in the United States alone. African Americans (blacks) have a higher incidence and prevalence of hypertension and hypertension-associated target organ damage compared with Caucasian Americans (whites). Herein, we explored the hypotheses that transforming growth factor-beta(1) (TGF-beta(1)) is hyperexpressed in hypertensives compared with normotensives and that TGF-beta(1) overexpression is more frequent in blacks compared with whites. These hypotheses were stimulated by our recent demonstration that TGF-beta(1) is hyperexpressed in blacks with end-stage renal disease compared with white end-stage renal disease patients and by the biological attributes of TGF-beta(1), which include induction of endothelin-1 expression, stimulation of renin release, and promotion of vascular and renal disease when TGF-beta(1) is produced in excess. TGF-beta(1) profiles were determined in black and white hypertensive subjects and normotensive controls and included circulating protein concentrations, mRNA steady-state levels, and codon 10 genotype. Our investigation demonstrated that TGF-beta(1) protein levels are highest in black hypertensives, and TGF-beta(1) protein as well as TGF-beta(1) mRNA levels are higher in hypertensives compared with normotensives. The proline allele at codon 10 (Pro(10)) was more frequent in blacks compared with whites, and its presence was associated with higher levels of TGF-beta(1) mRNA and protein. Our findings support the idea that TGF-beta(1) hyperexpression is a risk factor for hypertension and hypertensive complications and provides a mechanism for the excess burden of hypertension in blacks.

Transforming growth factor- 1 hyperexpression in African-American hypertensives: A novel mediator of hypertension and/or target organ damage

Hypertension, a remediable risk factor for stroke, cardiovascular disease, and renal failure, affects 50 million individuals in the United States alone. African Americans (blacks) have a higher incidence and prevalence of hypertension and hypertension-associated target organ damage compared with Caucasian Americans (whites). Herein, we explored the hypotheses that transforming growth factor-beta(1) (TGF-beta(1)) is hyperexpressed in hypertensives compared with normotensives and that TGF-beta(1) overexpression is more frequent in blacks compared with whites. These hypotheses were stimulated by our recent demonstration that TGF-beta(1) is hyperexpressed in blacks with end-stage renal disease compared with white end-stage renal disease patients and by the biological attributes of TGF-beta(1), which include induction of endothelin-1 expression, stimulation of renin release, and promotion of vascular and renal disease when TGF-beta(1) is produced in excess. TGF-beta(1) profiles were determined in black and white hypertensive subjects and normotensive controls and included circulating protein concentrations, mRNA steady-state levels, and codon 10 genotype. Our investigation demonstrated that TGF-beta(1) protein levels are highest in black hypertensives, and TGF-beta(1) protein as well as TGF-beta(1) mRNA levels are higher in hypertensives compared with normotensives. The proline allele at codon 10 (Pro(10)) was more frequent in blacks compared with whites, and its presence was associated with higher levels of TGF-beta(1) mRNA and protein. Our findings support the idea that TGF-beta(1) hyperexpression is a risk factor for hypertension and hypertensive complications and provides a mechanism for the excess burden of hypertension in blacks.

Quantitation of mRNA expression in glomeruli using laser-manipulated microdissection and laser pressure catapulting

BACKGROUND

Laser-manipulated microdissection (LMM) is a method to cut out a single cell or limited tiny region from a specimen under microscopic observation by a laser beam. Laser pressure catapulting (LPC) is a method to push up and collect samples that were microdissected using a strong laser.

METHODS

To induce experimental glomerulonephritis, anti-Thy1.1 monoclonal antibody (OX-7) was injected intravenously into rats. Control and disease model kidneys were obtained. Six-micrometer thick cryostat sections were mounted onto a 1.35 microm thin polyethylene membrane. Ten glomeruli were collected from 6 microm frozen sections of rat kidney by LMM and LPC. Isolated glomeruli were used to quantitate the expression of mRNA by real-time polymerase chain reaction (PCR).

RESULTS

Transforming growth factor-beta1 (TGF-beta1) mRNA was not detected in glomeruli isolated by the LMM and the LPC methods on day 0, although G3PDH mRNA was measurable in the same samples. On day 7 after the treatment with OX-7, the ratio of TGF-beta1/G3PDH mRNA was 1.89 +/- 0.96 (N = 6).

CONCLUSIONS

We established methods to isolate glomeruli from standard histochemical specimens by LMM and LPC, and to quantify mRNA expression in the targeted glomeruli using real-time PCR. We confirmed the up-regulation of TGF-beta1 mRNA expression in isolated glomeruli from frozen sections of the anti-Thy1.1 glomerulonephritis model.

Effects of ICAM-1 antisense oligonucleotide on the tubulointerstitium in mice with unilateral ureteral obstruction

Effects of ICAM-1 antisense oligonucleotide on the renal tubulointerstitium in mice with unilateral ureteral obstruction.

BACKGROUND

To extend our previous study of the therapy of the renal lesions of unilateral ureteral obstruction (UUO) in mice by an inhibitor of intercellular adhesion molecule-1 (ICAM-1), we investigated the blocking effects of ICAM-1 antisense oligonucleotides (ASONs) on the ICAM-1 expression in mouse kidney.

METHODS

First, ICAM-1 ASON was transducted into mouse renal tubular epithelial cells to investigate the effects of ICAM-1 ASON in vitro. Second, fluorescein isothiocyanate (FITC)-labeled ICAM-1 ASON was injected intravenously to determine the distribution of the ASON in vivo. Third, the expression of ICAM-1 in kidney and the changes of renal morphology were observed to investigate the therapeutic effects of ICAM-1 ASON on the UUO mice in vivo.

RESULTS

The expressions of ICAM-1 in the epithelial cells induced by interleukin-1beta were inhibited by ICAM-1 ASON at the dosages of 100 and 200 nmol/L. Twenty-four hours after an introvenous injection with FITC-labeled ICAM-1 ASON, the highest level of fluorescein was detected within the proximal tubules in mouse kidney. Results of immunohistology and Northern blot showed that the ICAM-1 expression was markedly reduced in the obstructed kidney after treatment with ICAM-1 ASON. The ASON also alleviated the infiltration of inflammatory cells and accumulation of the extracellular matrix in the tubulointerstitium of UUO mice without apparent side effects.

CONCLUSION

Our data demonstrate that ICAM-1 ASON is taken up primarily by the proximal tubular cells of mouse kidney. ICAM-1 ASON can selectively inhibit the ICAM-1 expression of the renal tubular cells both in vitro and in vivo.

TGF-beta and fibrosis

Transforming growth factor-beta (TGF-beta) isoforms are multifunctional cytokines that play a central role in wound healing and in tissue repair. TGF-beta is found in all tissues, but is particularly abundant in bone, lung, kidney and placental tissue. TGF-beta is produced by many but not all parenchymal cell types, and is also produced or released by infiltrating cells such as lymphocytes, monocytes/macrophages, and platelets. Following wounding or inflammation, all these cells are potential sources of TGF-beta. In general, the release and activation of TGF-beta stimulates the production of various extracellular matrix proteins and inhibits the degradation of these matrix proteins, although exceptions to these principles abound. These actions of TGF-beta contribute to tissue repair, which under ideal circumstances leads to the restoration of normal tissue architecture and may involve a component of tissue fibrosis. In many diseases, excessive TGF-beta contributes to a pathologic excess of tissue fibrosis that compromises normal organ function, a topic that has been the subject of numerous reviews [1-3]. In the following chapter, we will discuss the role of TGF-beta in tissue fibrosis, with particular emphasis on renal fibrosis.

Transfection of rat kidney with human 15-lipoxygenase suppresses inflammation and preserves function in experimental glomerulonephritis

The human 15-lipoxygenase (15-LO) gene was transfected into rat kidneys in vivo via intra-renal arterial injection. Three days later, acute (passive) or accelerated forms of antiglomerular basement membrane antibody-mediated glomerulonephritis were induced in transfected and nontransfected or sham-transfected controls. Studies of glomerular functions (filtration and protein excretion) and ex vivo glomerular leukotriene B(4) biosynthesis at 3 hr, and up to 4 days, after induction of nephritis revealed preservation or normalization of these parameters in transfected kidneys that expressed human 15-LO mRNA and mature protein, but not in contralateral control kidneys or sham-transfected animals. The results provide in vivo-derived data supporting a direct anti-inflammatory role for 15-LO during immune-mediated tissue injury.

TGF-beta1 activates MAP kinase in human mesangial cells: a possible role in collagen expression

BACKGROUND

Although the pathogenic relevance of transforming growth factor-beta (TGF-beta) to glomerular sclerosis has been established, the intracellular mechanisms by which TGF-beta induces extracellular matrix accumulation are not fully understood. We examined whether the mitogen-activated protein (MAP) kinase pathway is involved in TGF-beta1-induced collagen expression by cultured human mesangial cells.

METHODS

The activation of MAP kinase pathways by TGF-beta1 was assessed by immunoblot with anti-phospho-ERK or -JNK antibodies and by transfection of plasmids expressing pathway-specific transcription activators fused to the DNA-binding domain of GAL4, as well as a GAL4 response element-luciferase reporter gene. The role of MAP kinase was assessed using biochemical inhibitors and transiently expressed dominant negative mutant constructs. The effects on TGF-beta1-induced alpha1(I) collagen expression were evaluated by Northern blot and by activation of a transiently transfected alpha1(I) promoter-luciferase reporter construct.

RESULTS

ERK and JNK phosphorylation occurred 30 minutes and one hour, respectively, after TGF-beta1 treatment. A biochemical blockade of the ERK pathway inhibited TGF-beta1-induced alpha1(I) collagen expression. A dominant negative mutant of ERK1 but not of JNK decreased alpha1(I) gene promoter activation. Activation of the TGF-beta-responsive p3TP-Lux construct was partially inhibited by cotransfection of an ERK1 dominant negative mutant.

CONCLUSION

These data indicate that MAP kinase pathways can be activated by TGF-beta1 in mesangial cells and that the ERK MAP kinase plays a role in TGF-beta-stimulated collagen I expression. Because we have shown previously that SMADs mediate TGF-beta1-stimulated collagen I expression, our findings raise the possibility of interactions between the MAP kinase and the SMAD pathways.

Role for transforming growth factor-beta1 in alport renal disease progression

BACKGROUND

Alport syndrome results from mutations in either the alpha3(IV), alpha4(IV), or alpha5(IV) collagen genes. The disease is characterized by a progressive glomerulonephritis usually associated with a high-frequency sensorineural hearing loss. A mouse model for an autosomal form of Alport syndrome [collagen alpha3(IV) knockout] was produced and characterized. In this study, the model was exploited to demonstrate a potential role for transforming growth factor-beta1 (TGF-beta1) in Alport renal disease pathogenesis.

METHODS

Kidneys from normal and Alport mice, taken at different stages during the course of renal disease progression, were analyzed by Northern blot, in situ hybridization, and immunohistology for expression of TGF-beta1 and components of the extracellular matrix. Normal and Alport human kidney was examined for TGF-beta1 expression using RNase protection.

RESULTS

The mRNAs encoding TGF-beta1 (in both mouse and human), entactin, fibronectin, and the collagen alpha1(IV) and alpha2(IV) chains were significantly induced in total kidney as a function of Alport renal disease progression. The induction of these specific mRNAs was observed in the glomerular podocytes of animals with advanced disease. Type IV collagen, laminin-1, and fibronectin were markedly elevated in the tubulointerstitium at 10 weeks, but not at 6 weeks, suggesting that elevated expression of specific mRNAs on Northern blots reflects events associated with tubulointerstitial fibrosis.

CONCLUSIONS

The concomitant accumulation of mRNAs encoding TGF-beta1 and extracellular matrix components in the podocytes of diseased kidneys may reflect key events in Alport renal disease progression. These data suggest a role for TGF-beta1 in both glomerular and tubulointerstitial damage associated with Alport syndrome.

LDL stimulates collagen mRNA synthesis in mesangial cells through induction of PKC and TGF-beta expression

Abnormal lipid accumulation in glomeruli could be implicated in the pathogenesis of glomerulosclerosis. Low-density lipoprotein (LDL) stimulates collagen mRNA expression in cultured human mesangial cells (HMC). To explore the possible molecular mechanisms by which LDL promotes collagen gene expression, we examined the effects of LDL on protein kinase C (PKC) activity and transforming growth factor-beta (TGF-beta) expression in relation to collagen gene regulation in HMC. LDL (200 microg/ml) induced an acute increase in PKC activity, particularly PKC-alpha and -delta, within 15 min, which decreased to control value at 2 h. LDL stimulated TGF-beta1, and alpha1(I) and alpha1(IV) collagen mRNA expression within 30 min of incubation with HMC, and levels remained elevated until hour 4. LDL induced the secretion of TGF-beta by HMC. This TGF-beta was shown by CCL-64 mink lung cell assay to be, in part, bioactive. The stimulatory effects of LDL on collagen gene regulation in HMC were blocked by the inhibition of PKC using GF-109203X (GFX) or the downregulation of PKC using phorbol myristate acetate. Neutralizing antibody to TGF-beta inhibited the increased collagen mRNA expression by HMC exposed to LDL. The downregulation or inhibition of PKC did not affect the stimulatory effect of LDL on TGF-beta mRNA or protein expression. These results suggest that in HMC, LDL stimulates collagen mRNA expression through the rapid activation of PKC-alpha and -delta and transcriptional upregulation of TGF-beta. Thus PKC and TGF-beta may function as independent key signaling intermediaries in the pathway by which LDL upregulates collagen gene expression in HMC.

Glucose-mediated regulation of transforming growth factor-beta (TGF-beta) and TGF-beta receptors in human retinal endothelial cells

PURPOSE

Diabetic retinopathy is a micro-angiopathy affecting predominantly small vessels of the retina. Clinical trials have demonstrated a strong association between tight glucose control and a reduction in the incidence and the severity of diabetic retinopathy. Transforming growth factor beta (TGF-beta) is involved in the control of endothelial cell proliferation, adhesion, and deposition of extracellular matrix, thus TGF-beta may play a role in the control of endothelial cell proliferation seen in the disease. We wished to investigate the regulation of transforming growth factor beta and its receptors (type I and II) in human retinal endothelial cells exposed to a range of glucose concentrations.

METHODS

Human retinal endothelial cells were isolated from donor eyes, cultured in vitro and exposed to a range of glucose concentrations (0-25 mmol/l). TGF-beta protein and mRNA levels were determined by ELISA and Northern analysis, respectively. The binding affinities and TGF-beta receptor numbers were defined using a binding assay.

RESULTS

Northern hybridisation and ELISA showed that after 8 hours, the level of TGF-beta mRNA and protein was significantly higher at 15mmol/l compared to 5, 20 or 25mmol/ l. Binding assays showed that for high glucose (25 mmol/l), human retinal endothelial cells express a population of TGF-beta receptors with higher affinity for its ligand than at 5 or 15 mmol/l.

CONCLUSIONS

These results demonstrate that glucose regulates TGF-beta mRNA and protein production and also TGF-beta receptor expression in human retinal endothelial cells. Thus, the glucose-mediated changes that occur in diabetic patients may expose human retinal endothelial cells to potential angiogenic factors which may influence disease progression.

Role of intron 1 in smooth muscle alpha-actin transcriptional regulation in activated mesangial cells in vivo

BACKGROUND

The activation of glomerular mesangial cells is one of the early, important features of progressive glomerular disease. Smooth muscle alpha-actin (SMalphaA) is an excellent marker of activated mesangial cells. However, the mechanisms of SMalphaA regulation are only available from in vitro investigation.

METHODS

We examined in vivo promoter analysis of the SMalphaA gene-utilizing transgenic mice harboring different promoter regions of the SMalphaA gene fused to chloramphenicol acetyl transferase (CAT). CAT activities were tested in primary cultured mesangial cells and in glomerular legions of Habu venom glomerulonephritis.

RESULTS

The DNA sequence -891 to +3828, which contains exon 1, intron 1, and the first 14 bp of exon 2 in addition to the 5'-flanking sequence of the SMalphaA gene, induced high levels of transcription in activated mesangial cells in in vivo habu venom glomerulonephritis and in cultured mesangial cells derived from transgenic mice. The DNA region -891 to -124 was a positive element in mesangial cells derived from transgenic mice. Deletions (3316 or 137 bp) in intron 1 reduced transcription to undetectable levels. The 137 bp sequence is highly conserved among several species, containing one CArG box element, which is one of the key motifs for transcriptional activation of contractile-related proteins. In vitro transfection analysis failed to demonstrate these positive effects of intron 1 and region -891 to -124. Conclusions. In vivo promoter analysis of the SMalphaA gene provided new information about the transcriptional regulation of SMalphaA in activated mesangial cells. The DNA region -891 to -124 has a positive effect on SMalphaA transcription in cultured mesangial cells. The intron 1 region (+1088 to +1224) plays a pivotal role in SMalphaA transcription in activated mesangial cells in vivo. Further analysis of this conserved region in intron 1, including the CArG motif, will be of great value in understanding the molecular mechanisms of mesangial activation.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Transforming growth factor-beta is a potent inhibitor of extracellular matrix degradation by cultured human mesangial cells

Accumulation of the glomerular extracellular matrix (ECM) is a pivotal event in the progression from acute glomerular injury to end-stage renal disease. Although enhanced ECM synthesis has been demonstrated to contribute to ECM accumulation, the role of decreased ECM degradation is largely unknown. It was previously shown that glomerular ECM degradation is mediated by a plasminogen activator (PA)/plasmin/matrix metalloproteinase 2 (MMP-2) cascade. However, little information is available regarding the factors that regulate the activity of this degradative cascade in normal or pathologic states. Transforming growth factor-beta1 (TGF-beta1) is shown here to be a potent inhibitor of ECM degradation by cultured human mesangial cells. Using human mesangial cells grown on thin films of 125I-labeled Matrigel, dose-dependent inhibition of ECM degradation in the presence of TGF-beta1 was observed, reaching >90% inhibition with 0.4 ng/ml TGF-beta1. Addition of anti-TGF-beta antibodies (4 microg/ml) in the absence of exogenous TGF-beta increased ECM degradation (1.8+/-0.2-fold versus controls, P<0.05). In contrast, platelet-derived growth factor, at concentrations up to 10 ng/ml, had no effect on ECM degradation. TGF-beta completely blocked the conversion of plasminogen to plasmin and markedly reduced the conversion of latent MMP-2 to active MMP-2. TGF-beta did not significantly alter the levels of tissue PA, total MMP-2, or tissue inhibitor of metalloproteinase-1, but did increase the levels of PA inhibitor- (1.8-fold, P<0.05), the major physiologic inhibitor of PA. These data document that TGF-beta is a potent inhibitor of ECM degradation by cultured human mesangial cells, and they suggest that decreased mesangial matrix degradation, caused by TGF-beta-mediated decreases in the activity of the PA/plasmin/MMP-2 cascade, may contribute to the glomerular matrix accumulation that occurs in progressive renal disease.

Up-regulation of glomerular extracellular matrix and transforming growth factor-beta expression in RF/J mice

BACKGROUND

RF/J mice were first reported as a murine model of spontaneous glomerulosclerosis by Gude and Lupton in 1960, but the precise histologic characteristics and immunopathological background of this mouse have not been investigated further.

METHODS

Measurements of serum levels of immunoglobulins, anti-single strand DNA (anti-ss-DNA) antibody, complement (C3), and circulating immune complex (IC) were performed. Analyses of glomerular histological and immunopathological lesions in association with the detection of mRNA expression of collagen IV, TGF-beta, matrix protein turnover related enzymes, matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase-2 (TIMP-2) and platelet-derived growth factor (PDGF) were also performed in young (10-week-old) and elderly (60-week-old) RF/J mice with age-matched BALB/C mice as the controls.

RESULTS

High levels of serum IgA and IgG from as early as 20 weeks of age were noted in the RF/J mice. Serum anti-ss-DNA antibody of aged RF/J mice increased up to 23% of that of aged MRL-lpr/lpr mice, and serum C3 concentration significantly decreased with age, reaching lower levels than that of BALB/c mice. IgA-IC levels were significantly high compared to BALB/C mice both in the early and late stages of life, whereas IgG-IC levels were high only in mice younger than 20 weeks. Semiquantitative and quantitative analyzes of renal histopathological findings revealed significantly marked and age-related mesangial matrix expansion in RF/J mice, with increasing frequency of global glomerular sclerosis and tubulointerstitial damage. On the other hand, although precise measurements of glomerular cell numbers also showed an apparent augmentation in both young and old RF/J mice compared to BALB/C mice, glomerular cellularity decreased with age in RF/J mice. Immunohistochemical study revealed massive immunoglobulin deposition from a young age in association with significantly higher accumulation of matrix proteins, such as types I and IV collagen and laminin from the early stage of life. In addition, in these glomeruli, transforming growth factor-beta1 (TGF-beta1) was highly expressed both in young and old mice. The mRNA expression of MMP-2 was up-regulated only in the early stage of life. Although PDGF mRNA of RF/J mice was significantly up-regulated in the early stage of life, the differences between the mice disappeared in the late stage of life.

CONCLUSIONS

These findings suggest that in RF/J mice, an immunopathological background inducing high serum immunoglobulin and IC levels from the early stage of life is closely related to mesangioproliferative glomerular lesions mediated by PDGF, and that development of massive extracellular matrix accumulation in glomeruli was induced by up-regulated expression of TGF-beta with inappropriate regulation of protein turnover-related enzyme production.

Gene therapy by transforming growth factor-beta receptor-IgG Fc chimera suppressed extracellular matrix accumulation in experimental glomerulonephritis

BACKGROUND

The evidence that transforming growth factor-beta (TGF-beta) is a key mediator in the pathogenesis of fibrotic diseases is now supported by several lines of investigation. This evidence provides a certain base for targeting TGF-beta as an antifibrotic agent.

METHODS

We generated a chimeric cDNA, termed TGF beta RII/Fc, encoding an extracellular domain of the TGF-beta type II receptor fused to the IgG-Fc domain, and tested whether TGF beta RII/Fc could be a novel strategy for treating glomerular diseases.

RESULTS

In cultured BNul-7 cells, recombinant TGF beta RII/Fc reversed the antiproliferative response induced by TGF-beta 1. In addition, TGF beta RII/Fc diminished the TGF-beta 1-induced production of EIIIA-positive fibronectin in cultured normal rat kidney cells. We then introduced the chimeric cDNA into the muscle of the nephritic rats by the hemagglutinating virus of Japan liposome-mediated gene transfer method in order to block the TGF-beta activity in nephritic glomeruli through systemic delivery of chimeric molecules. Treatment with TGF beta RII/Fc gene transfection could suppress the glomerular TGF-beta mRNA in nephritic rats with a comparable effect in the reduction of extracellular matrix accumulation.

CONCLUSION

TGF beta RII/Fc successfully inhibited the action of TGF-beta in vitro and in vivo, and gene therapy by chimeric TGF beta RII/Fc might be feasible for the therapy of glomerulosclerosis.

Gene Therapy for Diabetic Nephropathy

Gene therapy has been considered for a broad array of diseases. Recent investigation has suggested that gene therapy may be applied to the treatment of diabetes mellitus and associated pathologies involving several organs. In the kidney, glomerulopathy is the most typical pathologic feature. This article addresses potential strategies towards gene therapy for diabetic glomerular disease.

Adenovirus-mediated gene expression in the septal cells of cirrhotic rat livers

BACKGROUND/AIMS

Liver cirrhosis is characterized by the formation of fibrous septa following hepatic necrosis and fibrosis, and finally progression to severe hepatic failure and/or hepatocellular carcinoma. To establish effective therapy for cirrhosis using a designed gene, we examined whether recombinant adenovirus vectors could transfer foreign genes into the septal cells of cirrhotic livers.

METHODS

Rats with cirrhosis induced by 4-8 weeks treatment with carbon tetrachloride were intravenously infected with a recombinant adenovirus Adex1CALacZ bearing a bacterial lacZ gene. Expression of the transferred gene was determined by X-gal staining. The infectivity of the vectors in vitro was examined using slice cultures from the cirrhotic rat livers.

RESULTS

In normal rat livers, almost all hepatocytes expressed beta-galactosidase from the recombinant adenovirus vectors. In rat liver fibrosis, the adenovirus-mediated gene transfer to hepatocytes is markedly reduced compared with normal rat liver. In cirrhosis, there is an even stronger reduction in the number of transduced hepatocytes. On the other hand, in vitro infection to the slice culture demonstrated that the cirrhotic hepatocytes still maintained adenovirus infectivity. Moreover, in the kidney, which is the second target organ of adenovirus, there was no difference in infectivity between normal and cirrhotic rats.

CONCLUSION

The recombinant adenovirus intravenously transmitted the foreign gene to septal cells in extranodular fibrous septa, rather than to hepatocytes within small nodules. Therefore, septal cells in the cirrhotic liver should be targeted with the adenovirus vector for a successful in vivo therapeutic strategy.

Selective inhibition of the renal dopamine subtype D1A receptor induces antinatriuresis in conscious rats

Both dopamine D1-like (D1A and D1B) and D2-like (D2, D3, and D4) receptor subfamilies are present in the kidney. Blockade of the intrarenal D1-like receptor family is associated with natriuresis and diuresis. Because the D1A and D1B receptor subtypes are not distinguishable by currently available dopaminergic agents, their functional role remains undefined. In the present study, the effect of selective inhibition of the renal D1A receptor with phosphorothioated antisense oligodeoxynucleotide (AS-ODN) was investigated in conscious uninephrectomized rats. After renal interstitial administration of Texas red-labeled D1A receptor AS-ODN, intense fluorescent signal was localized in the renal tubular epithelium and vasculature. In rats on normal salt intake, AS-ODN injected interstitially into the kidney reduced daily urinary sodium excretion (1.4+/-0.04 versus 0.8+/-0.2 mEq/d, n=5, P<0.05) and urine output (16.9+/-3.8 versus 12.5+/-3.6 mL/d, n=5, P<0.05). In rats on high sodium intake, continuous renal interstitial administration of D1A receptor AS-ODN transiently decreased daily urinary sodium excretion (5.4+/-0.5 versus 4.2+/-0.3 mEq/d, n=7, P<0.01) and urine output (27.6+/-4.5 versus 18.1+/-1.8 mL/d, n=7, P<0.01). Neither vehicle nor sense oligodeoxynucleotide had significant effects. Systolic blood pressure remained unchanged. The renal D1A receptor protein was significantly decreased by 35% and 46% at the end of the study in AS-ODN-treated rats on normal and high salt intake, respectively, whereas the D1B receptor and beta-actin were not affected. These results provide the first direct evidence that the renal D1A receptor subtype plays an important role in the control of sodium excretion.

Establishment of the enzyme-linked immunosorbent assay for connective tissue growth factor (CTGF) and its detection in the sera of biliary atresia

Connective tissue growth factor (CTGF) is a mitogenic, chemotactic, and cell matrix-inducing factor for fibroblasts. We generated murine monoclonal antibodies against CTGF and established a sandwich enzyme-linked immunosorbent assay (ELISA) for detection of CTGF. By using the ELISA, we confirmed that CTGF was specifically induced in human fibroblasts by TGF-beta but not by PDGF, FGF, IGF-I, or EGF. We also found that the serum levels of CTGF were significantly correlated with the progression of hepatic fibrosis in biliary atresia. These results indicated that CTGF is potentially a useful parameter for monitoring certain types of fibrotic disorders.

Protein kinases C: potential targets for intervention in diabetic nephropathy

Protein kinases C are a family of serine threonine protein kinases that play key roles in extracellular signal transduction. Inappropriate activation of protein kinase C has been implicated in the pathophysiology of many diseases, including diabetes mellitus. Indeed, protein kinase C activation may contribute not only to the pathogenesis of diabetic complications such as nephropathy and retinopathy, but also to insulin resistance. Growing awareness that protein kinase C isoforms subserve specific subcellular functions has led to the development of isoform-specific inhibitors, which may be useful investigational tools and therapeutic agents for attenuating the effects of inappropriate protein kinase C activity. Here we review the role played by protein kinases C in diabetic nephropathy and the recent progress that has been made to modulate its activity using specific inhibitors.

Regulation of human mesangial cell collagen expression by transforming growth factor-beta1

Transforming growth factor (TGF)-beta1 has been implicated in glomerular extracellular matrix accumulation. Since the spectrum and mechanism of changes in collagen turnover have not been fully characterized, we evaluated effects of TGF-beta1 on collagen expression by human mesangial cells. TGF-beta1 induced increased alpha1(I), alpha1(III), and alpha1(IV) collagen mRNA expression. Greater mRNA expression of matrix metalloproteinase (MMP)-2 was compensated by increased tissue inhibitor of metalloproteinases (TIMP)-2 mRNA. There was no change in TIMP-1 or membrane-type MMP mRNA expression, whereas MMP-1 mRNA decreased. Types I and IV collagen protein accumulated in both the cell layer and medium. Changes in collagen mRNA and protein occurred within 4 and 8 h, respectively. MMP-2 and TIMP-1 and -2 activities showed little change. Cycloheximide markedly decreased collagen detection within 4 h and reversed late, but not early, changes in alpha1(I) collagen mRNA. In this system, increased synthesis may be more significant than degradation for collagen accumulation, but collagen is short-lived in culture. Diverse TGF-beta1 actions on collagen turnover may be either immediate or mediated through synthesis of regulatory molecules.