Effect of combination therapy with enalapril and the TGF-β antagonist 1D11 in unilateral ureteral obstruction

Repurposing of Angiotensin-converting-enzyme Inhibitor on Prevention of Post-surgical Tendon Adhesion

BACKGROUND

Formation of adhesion bands is a frequent clinical complication after tendon injury or surgery with limited treatment options. This study investigates the repurposing of Angiotensin-Converting-Enzyme Inhibitor (ACEI) in attenuating post-operative tendon-sheath adhesion bands in an Achilles tendon rat model.

METHODS

Structural, mechanical, histological, and biochemical characteristics of the Achilles tendons were compared in the presence and absence of oral ACEI (enalapril) using the Achilles tendon adhesion (TA) model in rats. Inflammation and total fibrosis of tendon tissues were compared between groups using molecular investigations along with macroscopic and histological scoring methods.

RESULTS

ACEI significantly alleviated the severity, length, and density of Achilles TAs. Moreover, histopathological changes, recruitment of inflammatory cells, and inflammation were significantly decreased in post-operative tissue samples as quantified with the Moran scoring model. We showed that ACEI treatment elicits a potent anti-fibrotic effect on tendon tissue samples, as illustrated by decreasing the severity and extent of the formed fibrotic tissue and collagen accumulation at the site of surgery when scored either by Tang or Ishiyama grading systems. The H&E staining showed no histopathological changes or damage to the principal organs.

CONCLUSION

Our results showed that ACEI is a safe and effective therapeutic candidate with potent immunomodulatory and anti-fibrotic features to alleviate surgery-induced development of fibrotic adhesive tissue. However, its efficacy needs to be further validated in clinical studies.

Using Advanced Bioinformatics Tools to Identify Novel Therapeutic Candidates for Proliferative Vitreoretinopathy

Purpose

Proliferative vitreoretinopathy (PVR) is the dreaded cause of failure following retinal detachment repair; however, no cures or preventative therapies exist to date. The purpose of this study was to use bioinformatics tools to identify drugs or compounds that interact with biomarkers and pathways involved in PVR pathogenesis that could be eligible for further testing for the prevention and treatment of PVR.

Methods

We queried PubMed to compile a comprehensive list of genes described in PVR to date from human studies, animal models, and genomic studies found in the National Center for Biotechnology Information database. Gene enrichment analysis was performed using ToppGene on PVR-related genes against drug-gene interaction databases to construct a pharmacome and estimate the statistical significance of overrepresented compounds. Compounds with no clinical indications were filtered out from the resulting drug lists.

Results

Our query identified 34 unique genes associated with PVR. Out of 77,146 candidate drugs or compounds in the drug databases, our analysis revealed multiple drugs and compounds that have significant interactions with genes involved in PVR, including antiproliferatives, corticosteroids, cardiovascular agents, antioxidants, statins, and micronutrients. Top compounds, including curcumin, statins, and cardiovascular agents such as carvedilol and enalapril, have well-established safety profiles and potentially could be readily repurposed for PVR. Other significant compounds such as prednisone and methotrexate have shown promising results in ongoing clinical trials for PVR.

Conclusions

This bioinformatics approach of studying drug-gene interactions can identify drugs that may affect genes and pathways implicated in PVR. Predicted bioinformatics studies require further validation by preclinical or clinical studies; however, this unbiased approach could identify potential candidates among existing drugs and compounds that could be repurposed for PVR and guide future investigations.

Translational Relevance

Novel repurposable drug therapies for PVR can be found using advanced bioinformatics models.

TGF-beta pathway inhibition as the therapeutic acceleration of diabetic bone regeneration

Bone regeneration and fracture healing are impaired in diabetic patients due to defective functions of associated cells. Thus, the search for molecular causes and new treatment strategies are of particular clinical relevance. We investigated the gene expression profile of bones from type 2 diabetic (db^- /db^- ) mice and wild-type (wt) mice by comparative microarray analyses before and after placing tibial defects and examined the expression of several osteogenesis- and osteoclastogenesis-related markers by quantitative real-time polymerase chain reaction. In regenerating wt bones, pathways related to, for example, inhibition of matrix metalloproteases were activated, whereas in db^- /db^- bones activation of pathways related to, for example, osteoarthritis, transforming growth factor-beta (Tgfb), or hypoxia-inducible factor 1a were detected during regeneration. We defined the Tgfb pathway as a potential therapeutic target and locally applied a single dose (0.5 µg) of the Tgfb 1, 2, and 3 neutralizing antibody 1D11 on tibial defects in db^- /db^- mice (n = 7). Seven days postoperation, histological and immunohistochemical stainings were performed. Decreased bone regeneration, osteogenic differentiation, osteoclast invasion, and angiogenesis in db^- /db^- mice were significantly restored by local 1D11 application in comparison to the phosphate-buffered saline controls. Thus, local treatment of db^- /db^- bony defects with Tgfb neutralizing antibody 1D11 might be considered a good candidate for the successful acceleration of bone regeneration.

Nicotinamide N-methyltransferase ameliorates renal fibrosis by its metabolite 1-methylnicotinamide inhibiting the TGF-β1/Smad3 pathway

Chronic kidney disease (CKD), a disease involving damage to the kidney structure and function, is a global public health problem. Tubulointerstitial fibrosis (TIF) is both an inevitable pathological change in individuals with CKD and a driving force in the progression of renal fibrosis. Nicotinamide N-methyltransferase (NNMT) and its metabolite 1-methylnicotinamide (MNAM) have been shown to protect against lipotoxicity-induced kidney tubular injury. However, the biological roles of NNMT and MNAM in regulating TIF remain elusive. This study aimed to investigate the protective effect of NNMT and MNAM on TIF and the mechanisms involved. We explored the functions and mechanisms of NNMT and MNAM in TIF, as well as the interaction between NNMT and MNAM, using unilateral ureteral obstruction (UUO) mice and cultured mouse tubular epithelial cells (mTECs) stimulated with transforming growth factor-β1 (TGF-β1). Several important findings were obtained as follows: (1) NNMT expression was upregulated in the kidneys of UUO mice and TGF-β1-induced mTECs, and this upregulation was proposed to be a protective compensatory response to TIF. (2) MNAM was a potentially effective antifibrotic and anti-inflammatory medication in UUO mice. (3) The antifibrotic effect of NNMT overexpression was exerted by increasing the concentration of MNAM. (4) The renoprotective role of MNAM depended on the selective blockade of the interaction of Smad3 with TGFβ receptor I. Overall, our study shows that NNMT is involved in the development and progression of CKD and that its metabolite MNAM may be a novel inhibitor of the TGF-β1/Smad3 pathway with great therapeutic potential for CKD.

Functional and molecular evaluation of using aliskiren during acute and chronic partial ureteral obstruction in rat solitary kidney

AIMS

To study the effect of direct renin inhibitor (aliskiren) on the renal function during acute and chronic partial ureteral obstruction (PUO) in rat solitary kidney.

MAIN METHODS

Sixty male Sprague-Dawley rats were randomly allocated into three groups (20 rats each); sham, PUO and aliskiren groups. Right nephrectomy was performed in all groups. Rats in PUO and aliskiren groups were subjected to left PUO and received no treatment and aliskiren (10 mg/kg, orally, once per day till sacrification), respectively. Blood samples were then collected for biochemical measurements. Ten rats from each group were sacrificed after two weeks, while the remaining rats were sacrificed after four weeks. Left kidneys were harvested for histopathological examination, BCL-2, interleukin (IL)-6, transforming growth factor (TGF)-β1, collagen I and fibronectin relative gene expression and assessment of glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA) and nitric oxide (NO) activity.

KEY FINDINGS

After two and four weeks of PUO, aliskiren significantly recompensed the rise of serum creatinine (Scr) and blood urea nitrogen (BUN). Aliskiren also revealed significantly better histopathological results regarding cortical and medullary necrosis, regeneration and inflammatory cell infiltration. Aliskiren group showed statistically significant up-regulation of BCL-2 and down-regulation of IL-6, TGF-β1, collagen I and fibronectin relative gene expression. Aliskiren significantly increased GSH and SOD activity and reduced MDA and NO activity. Moreover, aliskiren administration for four weeks after PUO significantly yielded more renoprotective effect compared to its administration for two weeks.

SIGNIFICANCE

Aliskiren ameliorates the deterioration of the renal function during acute and chronic PUO in a solitary kidney.

Ultrasound Assisted a Peroxisome Proliferator-Activated Receptor (PPAR)γ Agonist-Loaded Nanoparticle-Microbubble Complex to Attenuate Renal Interstitial Fibrosis

Objective

To investigate the antifibrotic effect of the combination of a PPARγ agonist-loaded nanoparticle-microbubble complex with ultrasound (US) exposure on renal interstitial fibrosis (RIF).

Materials and Methods

Polylactide-co-glycolide (PLGA) nanoparticles were used to load PPARγ agonist (rosiglitazone, RSG) and prepare PLGA-RSG nanoparticles (PLNPs-RSG); then, a novel complex between PLNPs-RSG and SonoVue microbubbles (MBs) (PLNPs-RSG-MBs) was prepared. The size distribution, zeta potentials, RSG-loading capacity and entrapment efficiency were measured, and the release of RSG was assessed using a UV-vis spectrophotometer. The in vitro cytotoxicity and in vivo systemic toxicity assays were performed. The cellular uptake assessment was performed using a confocal laser scanning microscope (CLSM). The in vivo biodistribution assessment was performed using fluorescence imaging with a near-infrared (NIR) imaging system. Furthermore, this complex was administered to a unilateral ureteral obstruction (UUO) rat model with the assistance of US exposure to investigate the antifibrotic effect.

Results

This PLNPs-RSG-MBs complex had a size of 2199.5± 988.1 nm and a drug-loading efficiency of 28.5%. In vitro cytotoxicity and in vivo systemic toxicity assays indicated that the PLNPs-RSG-MBs complex displayed excellent biocompatibility. In addition, the complex showed high cellular uptake efficiency in vitro and kidney-targeting ability in vivo. In a UUO rat model, the combination of the PLNPs-RSG-MBs complex with US exposure significantly reduced collagen deposition and successfully attenuated renal fibrosis.

Conclusion

The combination of the PLNPs-RSG-MBs complex with US exposure may be a promising approach for the treatment of RIF.

Prevention of renal apoB retention is protective against diabetic nephropathy: role of TGF-β inhibition

Animal studies demonstrate that hyperlipidemia and renal lipid accumulation contribute to the pathogenesis of diabetic nephropathy (DN). We previously demonstrated that renal lipoproteins colocalize with biglycan, a renal proteoglycan. The purpose of this study was to determine whether prevention of renal lipid (apoB) accumulation attenuates DN. Biglycan-deficient and biglycan wild-type Ldlr^-/- mice were made diabetic via streptozotocin and fed a high cholesterol diet. As biglycan deficiency is associated with elevated transforming growth factor-β (TGF-β), in some experiments mice were injected with either the TGF-β-neutralizing antibody, 1D11, or with 13C4, an irrelevant control antibody. Biglycan deficiency had no significant effect on renal apoB accumulation, but led to modest attenuation of DN with ∼30% reduction in albuminuria; however, biglycan deficiency caused a striking elevation in TGF-β. Use of 1D11 led to sustained suppression of TGF-β for approximately 8 weeks at a time. The 1D11 treatment caused decreased renal apoB accumulation, decreased albuminuria, decreased renal hypertrophy, and improved survival, compared with the 13C4 treatment. Thus, prevention of renal apoB accumulation is protective against development of DN. Furthermore, this study demonstrates that prevention of renal apoB accumulation is a mechanism by which TGF-β inhibition is nephroprotective.

The influence of systemic renin-angiotensin-inhibition on ocular cytokines related to proliferative vitreoretinopathy

PURPOSE

The renin-angiotensin system is involved in the pathogenesis of fibrosis in several organs via induction of transforming growth factor (TGF) beta. In the pathogenesis of proliferative vitreoretinopathy (PVR) TGF-beta plays a pivotal role, promoting transition of retinal pigment epithelial (RPE) cells into myofibroblasts. We studied the influence of angiotensin converting enzyme-inhibition (ACEI) on cytokines and growth factors, related to PVR in aqueous humor.

METHODS

We performed a post hoc analysis of a prospectively conducted interventional case series. From patients with rhegmatogenous retinal detachment (RRD) aqueous humor was obtained during primary surgery and analyzed using multiplex bead analysis for interferon gamma, tumor necrosis factor alpha, CC-chemokine ligand (CCL) 2 / monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1 beta, IL-2, IL-4, IL-6, IL-8, vascular endothelial growth factor (VEGF)-A, platelet derived growth factor (PDGF)-aa, TGF-beta 1, TGF-beta 2, TGF-beta 3, fibroblast growth factor (FGF)-aa, and FGF-bb. We recorded information about systemic ACEI from the medical history.

RESULTS

In the primary study elevated levels of TGF-beta 1 and 2, IL 6 and 8 and CCL2/MCP-1 were a risk factor for later PVR development. Here, systemic ACEI neither influenced levels of these cytokines and growth factors, nor of any other tested in this study (p ≥ 0.438, respectively). Also the incidence of PVR development was unaffected (p = 0.201).

CONCLUSION

The systemic intake of ACEI for arterial hypertension does not influence levels of profibrotic cytokines/growth factors in aqueous humor. Further studies need to clarify if relevant levels of ACEI accumulate in the eye, and if direct administration of ACEI in experimental PVR could be beneficial.

Renal Fibrosis mRNA Classifier: Validation in Experimental Lithium-Induced Interstitial Fibrosis in the Rat Kidney

Accurate diagnosis of fibrosis is of paramount clinical importance. A human fibrosis classifier based on metzincins and related genes (MARGS) was described previously. In this investigation, expression changes of MARGS genes were explored and evaluated to examine whether the MARGS-based algorithm has any diagnostic value in a rat model of lithium nephropathy. Male Wistar rats (n = 12) were divided into 2 groups (n = 6). One group was given a diet containing lithium (40 mmol/kg food for 7 days, followed by 60mmol/kg food for the rest of the experimental period), while a control group (n = 6) was fed a normal diet. After six months, animals were sacrificed and the renal cortex and medulla of both kidneys removed for analysis. Gene expression changes were analysed using 24 GeneChip^® Affymetrix Rat Exon 1.0 ST arrays. Statistically relevant genes (p-value<0.05, fold change>1.5, t-test) were further examined. Matrix metalloproteinase-2 (MMP2), CD44, and nephroblastoma overexpressed gene (NOV) were overexpressed in the medulla and cortex of lithium-fed rats compared to the control group. TGFβ2 was overrepresented in the cortex of lithium-fed animals 1.5-fold, and 1.3-fold in the medulla of the same animals. In Gene Set Enrichment Analysis (GSEA), both the medulla and cortex of lithium-fed animals showed an enrichment of the MARGS, TGFβ network, and extracellular matrix (ECM) gene sets, while the cortex expression signature was enriched in additional fibrosis-related-genes and the medulla was also enriched in immune response pathways. Importantly, the MARGS-based fibrosis classifier was able to classify all samples correctly. Immunohistochemistry and qPCR confirmed the up-regulation of NOV, CD44, and TGFβ2. The MARGS classifier represents a cross-organ and cross-species classifier of fibrotic conditions and may help to design a test to diagnose and to monitor fibrosis. The results also provide evidence for a common pathway in the pathogenesis of fibrosis.

Pentoxifylline Ameliorates Cardiac Fibrosis, Pathological Hypertrophy, and Cardiac Dysfunction in Angiotensin II-induced Hypertensive Rats

Inflammation induces cardiac fibrosis and hypertrophy in multiple cardiovascular diseases, contributing to cardiac dysfunction. We tested the hypothesis that pentoxifylline (PTX), a phosphodiesterase inhibitor with anti-inflammatory property, would attenuate cardiac fibrosis and hypertrophy, and prevent cardiac dysfunction in angiotensin (ANG) II-induced hypertensive rats. Sprague-Dawley rats were divided into control and ANG II-infused groups treated with or without PTX for 2 weeks. PTX had no effect on ANG II-induced hypertension, but significantly attenuated cardiac fibrosis and hypertrophy, and ameliorated cardiac dysfunction in ANG II-induced hypertensive rats. In addition, ANG II-induced increase in circulating and cardiac proinflammatory cytokines were attenuated by PTX, which reduced cardiac nuclear factor-kappa B activity. Furthermore, PTX decreased cardiac expression of genetic markers important for fibrosis, hypertrophy, and endothelial dysfunction, and reduced migration and infiltration of macrophages. In contrast, PTX had no effects on the above parameters in control rats. The findings suggest that PTX ameliorates cardiac fibrosis, pathological hypertrophy, and cardiac dysfunction by suppressing inflammatory responses in angiotensin II-induced hypertension, and that these benefits were independent of the blood pressure lowering effect. The PTX by its anti-inflammatory property may be a potential therapeutic option for the prevention of cardiac remodeling and dysfunction in ANG II-induced hypertension.

RNA Sequencing Identifies Novel Translational Biomarkers of Kidney Fibrosis

CKD is the gradual, asymptomatic loss of kidney function, but current tests only identify CKD when significant loss has already happened. Several potential biomarkers of CKD have been reported, but none have been approved for preclinical or clinical use. Using RNA sequencing in a mouse model of folic acid-induced nephropathy, we identified ten genes that track kidney fibrosis development, the common pathologic finding in patients with CKD. The gene expression of all ten candidates was confirmed to be significantly higher (approximately ten- to 150-fold) in three well established, mechanistically distinct mouse models of kidney fibrosis than in models of nonfibrotic AKI. Protein expression of these genes was also high in the folic acid model and in patients with biopsy-proven kidney fibrosis. mRNA expression of the ten genes increased with increasing severity of kidney fibrosis, decreased in response to therapeutic intervention, and increased only modestly (approximately two- to five-fold) with liver fibrosis in mice and humans, demonstrating specificity for kidney fibrosis. Using targeted selected reaction monitoring mass spectrometry, we detected three of the ten candidates in human urine: cadherin 11 (CDH11), macrophage mannose receptor C1 (MRC1), and phospholipid transfer protein (PLTP). Furthermore, urinary levels of each of these three proteins distinguished patients with CKD (n=53) from healthy individuals (n=53; P<0.05). In summary, we report the identification of urinary CDH11, MRC1, and PLTP as novel noninvasive biomarkers of CKD.

Poly(ADP-ribose) polymerase 1 activation links ischemic acute kidney injury to interstitial fibrosis

Inactivation of poly(ADP-ribose) polymerase 1 (PARP1) has been found to be protective in several disease models; however, the role of PARP1 in acute kidney injury-induced interstitial fibrosis has not been studied. Herein, we tested whether PARP1 inactivation by treatment with PJ34 (a PARP1 inactivator; 10 mg/kg body weight/day, intraperitoneal implantation of a miniosmotic pump at 2 days after the onset) contributed to the decrease in interstitial fibrosis induced by ischemia-reperfusion injury (IRI) in mouse kidneys. IRI increased PARP1 activation represented by poly(ADP-ribose) expression from 4 to 16 days postinjury, whereas treatment with PJ34 at 2 days after the onset efficaciously abolished the increase in PARP1 activation at 4, 8 and 16 days after IRI. Pharmacological inactivation of PARP1 significantly reduced interstitial fibrosis as represented by the collagen deposition and transforming growth factor-β1 level at 8 and 16 days after IRI. Consistent with collagen deposition, myofibroblast activation represented by α-smooth muscle actin expression was also reduced by PARP1 inactivation at 8 and 16 days after IRI. Furthermore, IRI enhanced macrophage influx, but PARP1 inactivaton remarkably reduced macrophage influx for 4 through 16 days after the injury. Among the chemoattractants for monocytes/macrophages and neutrophils, monocyte chemotactic protein-1 (MCP-1) production in IRI kidneys was significantly reduced by PARP1 inactivation from 4 to 16 days postinjury. These data demonstrate that PARP1 activation contributes to IRI-induced MCP-1 production and in turn to macrophage influx, resulting in the promotion of interstitial fibrosis.

Inhibition of STAT3 acetylation is associated with angiotesin renal fibrosis in the obstructed kidney

AIM

To explore the relationship between the signal transducer and activator of transcription 3 (STAT3) signaling and renal fibrosis.

METHODS

Rat renal tubular epithelial NRK-52E cells were treated with angiotesin II (Ang II), nicotinamide (an inhibitor of NAD+-dependent class III protein deacetylases, SIRT1-7), or resveratrol (an activator of SIRT1). Mice underwent unilateral ureteral obstruction (UUO) were used for in vivo studies. Renal interstitial fibrosis was observed with HE and Masson's trichrome staining. STAT3 acetylation and phosphorylation, fibronectin, collagen I, collagen IV, and α-smooth muscle actin (α-SMA) levels were examined using Western blotting.

RESULTS

Nicotinamide (0.625-10 mmol/L) dose-dependently increased STAT3 acetylation on Lys685 and phosphorylation on Tyr705 in NRK-52E cells, accompanied by accumulation of fibronectin and collagen IV. Ang II increased STAT3 phosphorylation on Tyr705 and the expression of fibronectin, collagen IV and α-SMA in the cells. Pretreatment with resveratrol (12.5 μmol/L) blocked Ang II-induced effects in the cells. UUO induced marked STAT3 phosphorylation, fibronectin, collagen IV and α-SMA accumulation, and renal interstitial fibrosis in the obstructed kidneys, which were significantly attenuated by daily administration of resveratrol (100 mg/kg).

CONCLUSION

STAT3 acetylation plays an important role in activation of STAT3 signaling pathway and consequent renal fibrosis.

Effect of angiotensin II and small GTPase Ras signaling pathway inhibition on early renal changes in a murine model of obstructive nephropathy

Tubulointerstitial fibrosis is a major feature of chronic kidney disease. Unilateral ureteral obstruction (UUO) in rodents leads to the development of renal tubulointerstitial fibrosis consistent with histopathological changes observed in advanced chronic kidney disease in humans. The purpose of this study was to assess the effect of inhibiting angiotensin II receptors or Ras activation on early renal fibrotic changes induced by UUO. Animals either received angiotensin II or underwent UUO. UUO animals received either losartan, atorvastatin, and farnesyl transferase inhibitor (FTI) L-744,832, or chaetomellic acid A (ChA). Levels of activated Ras, phospho-ERK1/2, phospho-Akt, fibronectin, and α-smooth muscle actin were subsequently quantified in renal tissue by ELISA, Western blot, and/or immunohistochemistry. Our results demonstrate that administration of angiotensin II induces activation of the small GTPase Ras/Erk/Akt signaling system, suggesting an involvement of angiotensin II in the early obstruction-induced activation of renal Ras. Furthermore, upstream inhibition of Ras signalling by blocking either angiotensin AT1 type receptor or by inhibiting Ras prenylation (atorvastatin, FTI o ChA) reduced the activation of the Ras/Erk/Akt signaling system and decreased the early fibrotic response in the obstructed kidney. This study points out that pharmacological inhibition of Ras activation may hold promise as a future strategy in the prevention of renal fibrosis.

Renoprotective activity of aliskiren, a renin inhibitor in cyclosporine A induced hypertensive nephropathy in dTG mice

BACKGROUND

Hypertensive nephropathy is moving up the charts to number 2 after diabetic nephropathy in terms of diagnostic frequency cited as causing end stage renal disease (ESRD).

METHOD

Hypertensive nephropathy was produced in mildly hypertensive C57BL/6-(hREN)/(hAGT) double transgenic (dTG) mice with 20 mg/kg of cyclosporine A (CsA) administered subcutaneously (sc) daily for 28 days. CsA dose 20 mg/kg was selected for the study as this dose offered significant alteration in blood pressure, biochemical parameters and moderate nephropathy in kidney. Effect of aliskiren oral treatment twice daily consequently for 28 days at 10 mg/kg body weight was evaluated against CsA induced hypertensive nephropathy. Systolic blood pressure (SBP) was measured by non invasive tail cuff method. Kidney function test (blood urea nitrogen, serum creatinine, urea and uric acid) and kidney injury biomarker (tumor necrosis factor-alpha (TNF-α) and interlekin-6) level was assessed in serum, TNF-α, IL-6, transforming growth factor-beta1 (TGF-β1) and kidney injury molecule-1 (KIM-1) was assayed in kidney homogenate. Urinary KIM-1 levels were assessed as an early biomarker of nephropathy.

RESULT

Significant hypertensive nephropathy and increase in serum levels of biomarkers was observed in CsA treated animals when compared with Control group. Aliskiren treatment elicited significant renoprotection by preventing the increase in blood pressure and levels of serum biomarkers and also reduced the nephropathic alterations in the kidney histoarchitecture.

CONCLUSION

A correlation between pharmacological, biochemical and histological findings has been established in mouse model. The present findings have indicated the renoprotective activity of aliskiren in CsA induced hypertensive nephropathy, which may be due to its antihypertensive, anti-inflammatory as well as anti-apoptopic action.

Unilateral ureteral obstruction: beyond obstruction

Unilateral ureteral obstruction is a popular experimental model of renal injury. However, the study of the kidney response to urinary tract obstruction is only one of several advantages of this model. Unilateral ureteral obstruction causes subacute renal injury characterized by tubular cell injury, interstitial inflammation and fibrosis. For this reason, it serves as a model both of irreversible acute kidney injury and of events taking place during human chronic kidney disease. Being a unilateral disease, it is not useful to study changes in global kidney function, but has the advantage of a low mortality and the availability of an internal control (the non-obstructed kidney). Experimental unilateral ureteral obstruction has illustrated the molecular mechanisms of apoptosis, inflammation and fibrosis, all three key processes in kidney injury of any cause, thus providing information beyond obstruction. Recently this model has supported key concepts on the role in kidney fibrosis of epithelial-mesenchymal transition, tubular epithelial cell G2/M arrest, the anti-aging hormone Klotho and renal innervation. We now review the experimental model and its contribution to identifying novel therapeutic targets in kidney injury and fibrosis, independently of the noxa.

Reduction of chronic rejection of renal allografts by anti-transforming growth factor-β antibody therapy in a rat model

There is no effective treatment for chronic rejection (CR) that largely limits long-term survival of kidney transplants. Transforming growth factor (TGF)-β is a fibrogenic factor for tissue fibrosis. This study was to test the efficacy of an anti-TGF-β antibody in preventing the CR of renal allografts in a preclinical model. Male Lewis rats (RT1¹) were orthotopically transplanted with donor kidneys from male Fischer 344 (RT11v1) rats and were treated with either anti-TGF-β or a control antibody. The CR of renal allografts was assessed by semiquantitative histological analyses, and intragraft cytokines and fibrosis-related genes ware examined by PCR arrays. Compared with the control antibody, anti-TGF-β antibody treatment significantly reduced recipients' proteinuria (P = 0.0002), and CR in renal transplants, which was indicated by the fewer injured renal tubules, glomeruli, and interlobular arterioles or arteries, and by less mononuclear cell infiltration and interstitial fibrosis in the anti-TGF-β antibody-treated group (P < 0.05), but not significantly attenuate the ratios of different infiltrating leukocytes. These pathological changes were associated with downregulation of TGF-β1, TGF-β2, and proinflammatory cytokines, or with upregulation of anti-fibrotic HGF, BMP5, and BMP7. The therapeutic effect of the anti-TGF-β antibody was further confirmed by its prevention of graft dysfunction, indicated by lower levels of serum creatinine and blood urea nitrogen or higher creatinine clearance in anti-TGF-β antibody-treated recipients compared with those in control recipients (P < 0.05). In conclusion, the anti-TGF-β antibody (1D11) treatment significantly reduces CR of renal allografts in rats, suggesting the therapeutic potential of this antibody therapy for treating CR of kidney transplants in patients.

Cysteine-rich protein 61 plays a proinflammatory role in obstructive kidney fibrosis

Cysteine-rich protein 61 (Cyr61) is a secreted matrix-associated protein that regulates a broad spectrum of biological and cellular activities. This study aimed to investigate the role of Cyr61 in progressive kidney fibrosis induced by unilateral ureteral obstruction (UUO) surgery in mice. The expression of Cyr61 transcripts and proteins in the obstructed kidneys were increased from day 1 and remained high until day 10 after surgery. Immunohistochemistry indicated that Cyr61 was expressed mainly in renal tubular epithelial cells. The upregulated Cyr61 in UUO kidneys was reduced in mice treated with pan-transforming growth factor-β (TGF-β) antibody. The role of TGF-β in tubular Cyr61 upregulation after obstructive kidney injury was further supported by experiments showing that TGF-β1 stimulated Cyr61 expression in cultured tubular epithelial cells. Notably, the upregulation of Cyr61 in UUO kidneys was followed by a marked increase in monocyte chemoattractant protein 1 (MCP-1) transcripts and macrophage infiltration, which were attenuated in mice treated with anti-Cyr61 antibodies. This proinflammatory property of Cyr61 in inducing MCP-1 expression was further confirmed in tubular epithelial cells cultured with Cyr61 protein. The anti-Cyr61 antibody in UUO mice also reduced the levels of collagen type 1-α1 transcripts, collagen fibril accumulation evaluated by picrosirius red staining, and the levels of α-smooth muscle actin (α-SMA) transcripts and proteins on day 4 after surgery; however, the antifibrotic effect was not sustained. In conclusion, the TGF-β-mediated increase in tubular Cyr61 expression involved renal inflammatory cell infiltration through MCP-1 induction during obstructive kidney injury. The Cyr61 blockade attenuated kidney fibrosis in the early phase, but the antifibrotic effect could not be sustained.

Transforming growth factor-β inhibition and endothelin receptor blockade in rats with monocrotaline-induced pulmonary hypertension

Transforming growth factor-β (TGF-β) inhibition is an investigational therapy for pulmonary arterial hypertension with promising results in experimental studies. The present work compared this approach with endothelin-receptor blockade and evaluated the effects of combined administration. Pulmonary arterial hypertension was induced by single monocrotaline injection (60 mg/kg) in 75 Wistar rats and 15 rats served as controls. Intervention groups consisted of treatment with an antibody against TGF-β-ligand, bosentan, both or none, initiated four weeks after monocrotaline injection. Right ventricular systolic pressure, pulmonary vascular remodeling, and exercise tolerance were evaluated eight weeks after monocrotaline injection. Either treatment, alone or in combination, lowered mortality. Comparable efficacy was found in the three treatment groups in terms of right ventricular systolic pressure (~45% decrease) and hypertrophy (~30% decrease), as well as exercise capacity. The three treatment groups equally ameliorated pulmonary vascular remodeling, evidenced by decreased vessel-wall thickness (in vessels 50-200 μm) and a smaller number of pre-capillary arterioles (< 50 μm) with a muscularized media. Treatment either with an antibody against TGF-β or with endothelin receptor blockade are equally effective in experimental pulmonary hypertension. Their combination provides no added benefit, indicating common mechanisms of action.

Resident mesenchymal cells and fibrosis

Fibrosis is a major clinical problem associated with as many as 45% of all natural deaths in developed nations. It can affect all organs and accumulating evidence indicates that fibrogenesis is not merely a bystander product of injury, but is a central pathological problem directly contributing to loss of organ function. In the majority of clinical cases, fibrogenesis is strongly associated with the recruitment of leukocytes, even in the absence of infection. Although chronic infections are a significant cause of fibrogenesis, in most cases fibrotic disease occurs in the context of sterile injury, such as microvascular disease, toxic epithelial injury or diabetes mellitus. Fibrogenesis is a direct consequence of the activation of extensive, and previously poorly appreciated, populations of mesenchymal cells in our organs which are either wrapped around capillaries and known as 'pericytes', or embedded in interstitial spaces between cell structures and known as resident 'fibroblasts'. Recent fate-mapping and complementary studies in several organs indicate that these cells are the precursors of the scar-forming myofibroblasts that appear in our organs in response to injury. Here we will review the literature supporting a central role for these cells in fibrogenesis, and highlight some of the critical cell to cell interactions that are necessary for the initiation and continuation of the fibrogenic process. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Transforming growth factor β-1 stimulates profibrotic epithelial signaling to activate pericyte-myofibroblast transition in obstructive kidney fibrosis

Pericytes have been identified as the major source of precursors of scar-producing myofibroblasts during kidney fibrosis. The underlying mechanisms triggering pericyte-myofibroblast transition are poorly understood. Transforming growth factor β-1 (TGF-β1) is well recognized as a pluripotent cytokine that drives organ fibrosis. We investigated the role of TGF-β1 in inducing profibrotic signaling from epithelial cells to activate pericyte-myofibroblast transition. Increased expression of TGF-β1 was detected predominantly in injured epithelium after unilateral ureteral obstruction, whereas downstream signaling from the TGF-β1 receptor increased in both injured epithelium and pericytes. In mice with ureteral obstruction that were treated with the pan anti-TGF-β antibody (1D11) or TGF-β receptor type I inhibitor (SB431542), kidney pericyte-myofibroblast transition was blunted. The consequence was marked attenuation of fibrosis. In addition, epithelial cell cycle G2/M arrest and production of profibrotic cytokines were both attenuated. Although TGF-β1 alone did not trigger pericyte proliferation in vitro, it robustly induced α smooth muscle actin (α-SMA). In cultured kidney epithelial cells, TGF-β1 stimulated G2/M arrest and production of profibrotic cytokines that had the capacity to stimulate proliferation and transition of pericytes to myofibroblasts. In conclusion, this study identified a novel link between injured epithelium and pericyte-myofibroblast transition through TGF-β1 during kidney fibrosis.

Novel insights into pericyte-myofibroblast transition and therapeutic targets in renal fibrosis

Renal fibrosis is a disease affecting millions worldwide and is a harbinger of progressive renal failure. Understanding the mechanisms of renal fibrosis is important for discovering new therapies that are required to prevent loss of renal function. Recently, we identified pericytes that line the kidney microvasculature as the precursor cells of the scar-producing myofibroblasts during kidney injury. Kidney pericytes are extensively branched cells embedded within the capillary basement membrane and stabilize the capillary network through tissue inhibitor of metalloproteinase 3 and angiogenic growth factors. Pericytes detach from endothelial cells and migrate into the interstitial space where they undergo a transition into myofibroblasts after injury. Activation of endothelium, pericyte-myofibroblast transition, and recruitment of inflammatory macrophages lead to capillary rarefaction and fibrosis. Targeting endothelium-pericyte crosstalk by inhibiting vascular endothelial cell growth factor receptors and platelet-derived growth factor receptors in response to injury have been identified as new therapeutic interventions. Furthermore, targeting macrophage activation has also been proven as a novel and safe therapeutic approach for pericyte-myofibroblast transition. However, we are still far from understanding the interaction between pericytes and other cellular elements in normal physiology and during kidney fibrosis. Further studies will be required to translate into more specific therapeutic approaches.

Loss of poly(ADP-ribose) polymerase 1 attenuates renal fibrosis and inflammation during unilateral ureteral obstruction

Poly(ADP-ribose) polymerase 1 (PARP1) contributes to necrotic cell death and inflammation in several disease models; however, the role of PARP1 in fibrogenesis remains to be defined. Here, we tested whether PARP1 was involved in the pathogenesis of renal fibrosis using the unilateral ureteral obstruction (UUO) mouse model. UUO was performed by ligation of the left ureter near the renal pelvis in Parp1-knockout (KO) and wild-type (WT) male mice. After 10 days of UUO, renal PARP1 expression and activation were strongly increased by 6- and 13-fold, respectively. Interstitial fibrosis induced by UUO was significantly attenuated in Parp1-KO kidneys compared with that in WT kidneys at 10 days, but not at 3 days, based on collagen deposition, α-smooth muscle actin (α-SMA), and fibronectin expression. Intriguingly, the UUO kidneys in Parp1-KO mice showed a dramatic decrease in infiltration of neutrophil and reduction in expression of proinflammatory proteins including intercellular adhesion molecule-1, tumor necrosis factor-α, inducible nitric oxide synthase, and toll-like receptor 4 as well as phosphorylation of nuclear factor-κB p65, but not transforming growth factor-β1 (TGF-β1) at both 3 and 10 days. Pharmacological inhibition of PARP1 in rat renal interstitial fibroblast (NRK-49F) cell line or genetic ablation in primary mouse embryonic fibroblast cells did not affect TGF-β1-induced de novo α-SMA expression. Parp1 deficiency significantly attenuated UUO-induced histological damage in the kidney tubular cells, but not apoptosis. These data suggest that PARP1 induces necrotic cell death and contributes to inflammatory signaling pathways that trigger fibrogenesis in obstructive nephropathy.

Fluorofenidone inhibits Ang II-induced apoptosis of renal tubular cells through blockage of the Fas/FasL pathway

OBJECTIVES

The present study was designed to investigate the inhibitory effects of fluorofenidone on Ang II-induced apoptosis in renal tubular cells and the related signaling pathway.

METHODS

Rat proximal tubular epithelial cells (NRK-52E) were used to examine the anti-apoptosis effects of fluorofenidone. Cell proliferation was assessed by methyl thiazolyl tetrazolium assay. Apoptosis was examined by AO/EB staining and TUNEL assay. The expression of Fas/FasL pathway members, including Fas, FasL, Bax, Bcl-2, Caspase-8, and Caspase-3 was detected by real-time RT-PCR and/or Western blot, respectively. The activity of Caspase-8 and Caspase-3 was detected by spectrophotometry.

RESULTS

Fluorofenidone didn't affect the proliferation of NRK-52E cells, but significantly inhibited the apoptosis of NRK-52E cells induced by Ang II. Fluorofenidone significantly reduced Ang II-induced increases in Fas, FasL, Bax, Caspase-8 and Caspase-3 at the mRNA level. Consistent with these observations, fluorofenidone also prevented Ang II-mediated up-regulation of FasL and Bax at the protein level. Additionally, Ang II-induced activation of Caspase-8 and Caspase-3 as well as Ang II-initiated downregulation of Bcl-2 at both mRNA and protein levels was all prevented by fluorofenidone.

CONCLUSIONS

Fluorofenidone can inhibit Ang II-induced apoptosis of renal tubular cells through blockage of the Fas/FasL pathway.

Recoverability of renal function after relief of chronic partial unilateral ureteric obstruction: The effect of an angiotensin-converting enzyme inhibitor (enalapril)

Objectives

We evaluated the effect of an angiotensin-converting enzyme inhibitor (enalapril) on renal function during and after the relief of partial unilateral ureteric obstruction (UUO).

Materials and methods

Thirty-two male mongrel dogs were classified into three groups: sham (eight), control (12; left partial UUO + no medication) and study (12; left partial UUO + enalapril). Dogs in the study and control groups were subjected to 4 weeks of partial UUO. After that, the dogs were re-opened and subjected to Lich-Gregoir vesico-ureteric re-implantation, and were killed humanely by the end of the eighth week after relief of obstruction. The study and control groups were evaluated at baseline, after 4 weeks of obstruction and at 4 and 8 weeks after relief of obstruction, by measuring selective creatinine clearance (CCr), selective renographic clearance (RCr) and renal resistive index (RI). The sham group had sham surgery at 4 and 8 weeks and was evaluated as the other two groups.

Results

Sham surgery showed no significant effect on any of the evaluated variables. Compared with the control, enalapril offset the reductions of CCr and RCr by an extra 11% and 12% of the basal values by the end of the fourth week of obstruction, respectively. Moreover, compared with the control, enalapril enhanced the recovery of CCr by an extra 10% and of RCr by an extra 23% of the basal values at 8 weeks after relief of the 4-week obstruction. In addition, the increase in RI was significantly less in the enalapril group.

Conclusion

Enalapril decreases the deterioration of renal function in partial UUO and enhances the recoverability of renal function after relief of obstruction.

Klotho inhibits transforming growth factor-beta1 (TGF-beta1) signaling and suppresses renal fibrosis and cancer metastasis in mice

Fibrosis is a pathological process characterized by infiltration and proliferation of mesenchymal cells in interstitial space. A substantial portion of these cells is derived from residing non-epithelial and/or epithelial cells that have acquired the ability to migrate and proliferate. The mesenchymal transition is also observed in cancer cells to confer the ability to metastasize. Here, we show that renal fibrosis induced by unilateral ureteral obstruction and metastasis of human cancer xenografts are suppressed by administration of secreted Klotho protein to mice. Klotho is a single-pass transmembrane protein expressed in renal tubular epithelial cells. The extracellular domain of Klotho is secreted by ectodomain shedding. Secreted Klotho protein directly binds to the type-II TGF-β receptor and inhibits TGF-β1 binding to cell surface receptors, thereby inhibiting TGF-β1 signaling. Klotho suppresses TGF-β1-induced epithelial-to-mesenchymal transition (EMT) responses in cultured cells, including decreased epithelial marker expression, increased mesenchymal marker expression, and/or increased cell migration. In addition to TGF-β1 signaling, secreted Klotho has been shown to inhibit Wnt and IGF-1 signaling that can promote EMT. These results have raised the possibility that secreted Klotho may function as an endogenous anti-EMT factor by inhibiting multiple growth factor signaling pathways simultaneously.

Effect of Astragalus membranaceus and Angelica sinensis combined with Enalapril in rats with obstructive uropathy

ACE inhibitors (ACEi) reduce renal tubulointerstitial fibrosis but are not completely effective. Combined extract of Astragalus membranaceus and Angelica sinensis (A&A) is a traditional antifibrotic agent in China. The present investigation aimed to determine whether an ACEi (Enalapril) and A&A together have a better antifibrotic effect in unilateral ureteral obstruction (UUO) than monotherapy with either agent. Male Sprague-Dawley rats (N = 4 per group) had either sham operation or UUO alone, with A&A (combined aqueous and ethanol extract equivalent to 2.1 g dried herbs), with Enalapril (in drinking water at 200 mg/mL) or with both treatments. Kidney and liver were collected for protein extraction or fixed for histologic stains, immunohistochemistry (IHC), microscopy. Enalapril or A&A individually were antifibrotic. Transforming growth factor-beta1, fibroblast activation, collagen deposition, macrophage accumulation and tubular cell apoptosis were all decreased. The combination of the two drugs was significantly more effective than Enalapril alone in reducing tumor necrosis factor-alpha, collagen accumulation, activation of fibroblasts, and tubular cell apoptosis. In conclusion, Enalapril with A&A significantly decreased tubulointerstitial fibrosis to a greater extent than treatment with Enalapril alone. Further studies focusing on the isolation of the active constituents of A&A and the clinical application of the combination of ACEi plus A&A are warranted to determine the value of this treatment in humans.

Toll-like receptor 4: a novel signaling pathway during renal fibrogenesis

BACKGROUND

The toll-like receptor (TLR) family serves an important regulatory role in the innate immune system, and recent evidence has implicated TLR signaling in the pro-inflammatory response of a variety of endogenous and exogenous stimuli within the kidney. The role of TLR signaling in fibrotic renal injury, however, remains unknown.

MATERIALS AND METHODS

C3H/HeJ TLR4 hyporesponsive mice (TLR4(Lps-d)) or WT controls (C3H/HeOu/J) underwent either sham operation or 1 wk of unilateral ureteral obstruction (UUO). The kidneys were harvested and tissues were analyzed for TLR4 expression (Western blot; RTPCR), E-cadherin and alpha smooth muscle actin (α-SMA) expression (Western blot), fibroblast accumulation (fibroblast specific protein (FSP-1+) staining), renal fibrosis (collagen I RTPCR, total collagen assay, Masson's trichrome staining), cytokine gene expression (tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta1 (TGF-β1) RTPCR), and pSMAD2 and integrin α1 expression (Western blot).

RESULTS

Mice with intact TLR4 signaling demonstrate a significant increase in TLR4 expression, α-SMA expression, fibroblast accumulation, collagen deposition, and interstitial fibrosis, and a significant decrease in E-cadherin expression in response to UUO. TLR4 deficient mice, however, exhibit a significant reduction in obstruction-induced α-SMA expression, fibroblast accumulation, and renal fibrosis, with preservation of E-cadherin expression. TLR4's influence on fibroblast accumulation and renal fibrosis occurred independent of any alterations in TNF-α, TGF-β1, or pSMAD2 expression, but did involve alterations integrin α1 expression.

CONCLUSION

TLR4 appears to be a significant mediator of fibrotic renal injury. While TLR4 signaling is recognized as a critical component of the innate immune response, this is the first study to demonstrate a novel role for TLR4 in renal fibroblast accumulation and tubulointerstitial fibrosis.

Contribution of chymase-dependent angiotensin II formation to the progression of tubulointerstitial fibrosis in obstructed kidneys in hamsters

Recent studies indicate a role of chymase in the regulation of angiotensin II (AngII) formation in cardiovascular and renal tissues. We investigated a possible contribution of chymase to AngII formation and to renal fibrosis in unilateral ureteral obstruction (UUO). Eight-week-old Syrian hamsters were subjected to UUO and treated with vehicle, the specific chymase inhibitor (CI) 4-[1-(4-methyl-benzo[b]thiophen-3-ylmethyl)-1H-benzimidazol-2-ylsulfanyl]-butyric acid (50 mg/kg, twice a day, p.o.), or the selective AT(1)-receptor blocker olmesartan (10 mg/kg per day, p.o.) for 14 days. UUO-induced renal interstitial fibrosis was associated with increases in renal mRNA levels of alpha-smooth muscle actin (SMA), type I collagen, and transforming growth factor (TGF)-beta. The UUO hamsters showed markedly higher AngII contents and increased AT(1)-receptor mRNA level in the obstructed kidney than sham-operated ones. In contrast, angiotensin-converting enzyme (ACE) protein expression was significantly lower in UUO hamsters. In UUO hamsters, treatment with CI or olmesartan significantly decreased AngII levels in renal tissue and mRNA levels of alpha-SMA, type I collagen, and TGF-beta and ameliorated tubulointerstitial injury. On the other hand, neither CI nor olmesartan changed systolic blood pressure, renal ACE, and AT(1)-receptor protein levels. These data suggest that chymase-dependent intrarenal AngII formation contributes to the pathogenesis of interstitial fibrosis in obstructed kidneys of hamsters.

Simultaneous transforming growth factor beta-tumor necrosis factor activation and cross-talk cause aberrant remodeling response and myocardial fibrosis in Timp3-deficient heart

The pleiotropic cytokines, transforming growth factor beta1 (TGFbeta1), and tumor necrosis factor (TNF) play critical roles in tissue homeostasis in response to injury and are implicated in multiple human diseases and cancer. We reported that the loss of Timp3 (tissue inhibitor of metalloproteinase 3) leads to abnormal TNF signaling and cardiovascular function. Here we show that parallel deregulation of TGFbeta1 and TNF signaling in Timp3(-/-) mice amplifies their cross-talk at the onset of cardiac response to mechanical stress (pressure overload), resulting in fibrosis and early heart failure. Microarray analysis showed a distinct gene expression profile in Timp3(-/-) hearts, highlighting activation of TGFbeta1 signaling as a potential mechanism underlying fibrosis. Neonatal cardiomyocyte-cardiofibroblast co-cultures were established to measure fibrogenic response to agonists known to be induced following mechanical stress in vivo. A stronger response occurred in neonatal Timp3(-/-) co-cultures, as determined by increased Smad signaling and collagen expression, due to increased TNF processing and precocious proteolytic maturation of TGFbeta1 to its active form. The relationship between TGFbeta1 and TNF was dissected using genetic and pharmacological manipulations. Timp3(-/-)/Tnf(-/-) mice had lower TGFbeta1 than Timp3(-/-), and anti-TGFbeta1 antibody (1D11) negated the abnormal TNF response, indicating their reciprocal stimulatory effects, with each manipulation abolishing fibrosis and improving heart function. Thus, TIMP3 is a common innate regulator of TGFbeta1 and TNF in tissue response to injury. The matrix-bound TIMP3 balances the anti-inflammatory and proinflammatory processes toward constructive tissue remodeling.

Rosiglitazone treatment attenuates renal tissue inflammation generated by urinary tract obstruction

AIM

Peroxisome proliferator-activated receptor (PPAR)-gamma activation by rosiglitazone decreases manifestation of intrarenal inflammatory hallmarks. Inflammation significantly aggravates renal injury following urinary tract obstruction. The effect of rosiglitazone on renal inflammation following unilateral ureteral obstruction was investigated.

METHODS

Ninety-six Sprague-Dawley rats were subjected to unilateral ureteral ligation, or to sham operation. Half of each group received rosiglitazone, 5 mg/kg bodyweight per day. The animals were killed and their kidneys allocated following 1 h, 24 h or 2 weeks, for pathological examination or for intrarenal transforming growth factor (TGF)-beta, interleukin (IL)-4, IL-6, IL-10 and nitric oxide (NO) assessment by specific enzyme-linked immunosorbent assays. Apoptosis rates, extracellular matrix deposition, PPAR-gamma, alpha-smooth muscle actin (alpha-SMA) expression and macrophage infiltration were assessed by specific immunohistological stainings.

RESULTS

PPAR-gamma receptor expression was downregulated, and infiltration of macrophages decreased, in all rosiglitazone-treated kidneys. Rosiglitazone significantly decreased apoptosis, TGF-beta, IL-6, alpha-SMA expression and NO availability in obstructed kidneys. Synthesis of IL-10 was unaltered, while IL-4 augmented by Rosiglitazone. Rosiglitazone also affected NO and IL-4 production in sham-operated controls.

CONCLUSION

(i) Rosiglitazone attenuates profibrotic and pro-inflammatory responses in a rat model of ureteral obstruction-induced renal inflammation; (ii) rosiglitazone stimulates counteractive anti-inflammatory responses in the damaged kidneys; (iii) in part, rosiglitazone exerts comparable anti-inflammatory effects on obstructed kidneys and unobstructed healthy controls. Taken together, this ascertains the importance of the anti-inflammatory role of rosiglitazone treatment in amelioration of ureteral obstruction-induced renal damage.

Effects of transforming growth factor-beta1 on human vocal fold fibroblasts

OBJECTIVES

We studied the effect of transforming growth factor (TGF)-beta on immortalized human vocal fold fibroblasts.

METHODS

Normal human vocal fold fibroblasts were subjected to sequential lentiviral transduction with genes for human telomerase (hTERT) and SV40 large T antigen in order to produce an "immortalized" cell line of normal phenotype. After confirmation of vocal fold fibroblast transfection, these cells, referred to as HVOX, were treated with various concentrations of exogenous TGF-beta1 and assayed for collagen secretion, migration, and proliferation. In addition, components of the TGF-beta signaling pathway were examined in this cell line.

RESULTS

TGF-beta stimulated collagen secretion and migration without altering proliferation of HVOX. HVOX constitutively expressed type I and II TGF-beta receptors, as well as messenger RNA for the Smad signaling proteins and for all TGF-beta isoforms. Exogenous TGF-beta1 induced temporally dependent alterations in Smad2 and Smad3 gene expression. TGF-beta increased Smad7 expression at both 4 and 24 hours. Prolonged exposure to TGF-beta decreased TGF-beta1 gene expression.

CONCLUSIONS

Insight into the underlying pathophysiology of vocal fold fibrosis is likely to yield improved therapeutic strategies to mitigate vocal fold scarring. Our data suggest that TGF-beta signaling may be both paracrine and autocrine in this vocal fold fibroblast cell line, and we therefore propose that TGF-beta may be a reasonable target for therapies to prevent and/or treat vocal fold fibrosis, given its putative role in both acute and chronic vocal fold injury, as well as its effects on vocal fold fibroblasts.

Amitriptyline attenuates interstitial inflammation and ameliorates the progression of renal fibrosis

Amitriptyline is a pleiotropic tricyclic antidepressant, which has anti-oxidant and anti-inflammatory properties. We tested whether amitriptyline might be useful in the treatment of chronic renal disease using the mouse model of unilateral ureteral obstruction. Amitriptyline caused a significant reduction of interstitial fibrosis, determined by Masson's staining, with minimal myofibroblast formation and macrophage infiltration following ureteral obstruction. Using quantitative PCR we found that this treatment significantly reduced the expression of key molecular markers of progressive tubulointerstitial injury such as osteopontin, MCP-1, ICAM-1, and TGF-beta1 compared to their level in a saline-treated control group. Sublethal X-irradiation or mycophenolate mofetil, treatments that reduce inflammation, were comparable to amitriptyline in the reduction of interstitial fibrosis and macrophage infiltration. These studies in animals suggest that amitriptyline is worth testing as a therapeutic agent that might preserve renal function by blocking inflammation and renal fibrosis.

A novel cell-permeable antioxidant peptide decreases renal tubular apoptosis and damage in unilateral ureteral obstruction

Unilateral ureteral obstruction (UUO) is characterized by decreases in renal function, increased interstitial fibrosis, tubular apoptosis, and cellular infiltration. It has been suggested that inhibition of tubular apoptosis may protect against renal damage in obstruction. We have recently developed a series of peptides which are concentrated in the inner mitochondrial membrane and prevent cell death. These peptides are also active in vivo, in myocardial infraction, ischemic brain injury, and amyotrophic lateral sclerosis models. We therefore used SS-31, a prototype of these peptides, and assessed its effects on renal damage and oxidative stress in a 14-day obstruction model. SS-31 (1 or 3 mg/kg) or saline was given 1 day before and throughout the 14 days of obstruction. Kidneys were harvested and assessed for apoptosis (terminal transferase-dUTP-nick-end labeling, caspase 3 expression), fibrosis (trichrome staining), macrophage infiltration, fibroblast expression (immunoperoxidase), and oxidative damage (8-OH deoxyguanosine and heme oxygenase-1 expression), cytokines, and signaling pathways (transforming growth factor-beta, CCR-1, p38-MAPK, NF-kappaB). SS-31 significantly attenuated the effects of obstruction on all aspects of renal damage which were examined, with both the 1 and 3 mg/kg doses showing efficacy. We noted increased oxidative stress in obstruction, which was also attenuated by SS-31 treatment. Signaling via NF-kappaB and p38 MAPK pathways were both affected by SS-31 treatment. This study provides a proof of concept that peptides which protect mitochondria in vitro can provide protection from renal damage in a UUO model. The mechanism by which protection is afforded requires further studies both in vitro and in vivo.