Transforming growth factor beta 1 and renal injury following subtotal nephrectomy in the rat: role of the renin-angiotensin system

Translation Animal Models of Diabetic Kidney Disease: Biochemical and Histological Phenotypes, Advantages and Limitations

Animal models play a crucial role in studying the pathogenesis of diseases, developing new drugs, identifying disease risk markers, and improving means of prevention and treatment. However, modeling diabetic kidney disease (DKD) has posed a challenge for scientists. Although numerous models have been successfully developed, none of them can encompass all the key characteristics of human DKD. It is essential to choose the appropriate model according to the research needs, as different models develop different phenotypes and have their limitations. This paper provides a comprehensive overview of biochemical and histological phenotypes, modeling mechanisms, advantages and limitations of DKD animal models, in order to update relevant model information and provide insights and references for generating or selecting the appropriate animal models to fit different experimental needs.

Canagliflozin protects the cardiovascular system through effects on the gut environment in non-diabetic nephrectomized rats

BACKGROUND

The gut produces toxins that contribute to the cardiovascular complications of chronic kidney disease. Canagliflozin, a sodium glucose cotransporter (SGLT) 2 inhibitor that is used as an anti-diabetic drug, has a weak inhibitory effect against SGLT1 and may affect the gut glucose concentration and environment.

METHODS

Here, we determined the effect of canagliflozin on the gut microbiota and the serum gut-derived uremic toxin concentrations in 5/6th nephrectomized (Nx) rats.

RESULTS

Canagliflozin increased the colonic glucose concentration and restored the number of Lactobacillus bacteria, which was low in Nx rats. In addition, the expression of tight junction proteins in the ascending colon was low in Nx rats, and this was partially restored by canagliflozin. Furthermore, the serum concentrations of gut-derived uremic toxins were significantly increased by Nx and reduced by canagliflozin. Finally, the wall of the thoracic aorta was thicker and there was more cardiac interstitial fibrosis in Nx rats, and these defects were ameliorated by canagliflozin.

CONCLUSIONS

The increases in colonic glucose concentration, Lactobacillus numbers and tight junction protein expression, and the decreases in serum uremic toxin concentrations and cardiac interstitial fibrosis may have been caused by the inhibition of SGLT1 by canagliflozin because similar effects were not identified in tofogliflozin-treated rats.

MCP-1/IL-12 ratio expressions correlated with adventitial collagen depositions in renal vessels and IL-4/IFN-γ expression correlated with interstitial collagen depositions in the kidneys of dogs with canine leishmaniasis

Collagen deposition is a common event in chronic inflammation, and canine Leishmaniosis (CanL) is generally associated with a long and chronic evolution. Considering that the kidney shows fibrinogenic changes during CanL, and the balance of cytokines/chemokines regulates the profibrinogenic and antifibrinogenic immune responses differently, it can be hypothesized that the balance of cytokines/chemokines can be differentially expressed in the renal tissue in order to determine the expression of collagen depositions in the kidneys. This study aimed to measure collagen deposition and to evaluate cytokine/chemokine expressions in the kidney by means of qRT-PCR in sixteen Leishmania-infected dogs and six uninfected controls. Kidney fragments were stained with hematoxylin & eosin (H&E), Masson's Trichrome, Picrosirius Red, and Gomori's reticulin. Intertubular and adventitial collagen depositions were evaluated by the morphometric approach. Cytokine RNA expressions were measured by means of qRT-PCR to identify molecules involved in chronic collagen depositions in kidneys with CanL. Collagen depositions were related to the presence of clinical signs, and more intense intertubular collagen depositions occurred in infected dogs. Adventitial collagen deposition, as morphometrically measured by the average area of the collagen, was more intense in clinically affected dogs than in subclinically infected dogs. TNF-α/TGF-β, MCP1/IL-12, CCL5/IL-12, IL-4/IFN-γ, and IL-12/TGF-β expressions were associated with clinical manifestations in dogs with CanL. The IL-4/IFN-α ratio was more commonly expressed and upregulated in clinically affected dogs, and downregulated in subclinically infected dogs. Furthermore, MCP-1/IL-12 and CCL5/IL-12 were more commonly expressed in subclinically infected dogs. Strong positive correlations were detected between morphometric values of interstitial collagen depositions and MCP-1/IL-12, IL-12, and IL-4 mRNA expression levels in the renal tissues. Adventitial collagen deposition was correlated with TGF-β, IL-4/IFN-γ, and TNF-α/TGF-β. In conclusion, our results showed the association of MCP-1/IL-12 and CCL5/IL-12 ratios with an absence of clinical signs, as well as an IL-4/IFN-α ratio with adventitial and intertubular collagen depositions in dogs with visceral leishmaniosis.

The compound losartan cream inhibits scar formation via TGF-β/Smad pathway

The role of angiotensin receptor blocker in wound healing and cutaneous fibrosis has become a hotspot in recent years. We have developed a losartan cream that is comparable to triamcinolone ointment in inhibiting scarring. Considering the effects of chitosan and asiaticoside on wound healing and scarring, we added them to the losartan cream this time and improved the formula, expecting to get a better anti-scarring effect. The effects of creams were investigated on mouse scar model with triamcinolone ointment, onion extract gel, and commercial asiaticoside cream set as positive controls. A preliminary exploration of the mechanism involved in TGF-β/Smad pathway was performed in vivo and in vitro. With all results of anti-scarring, the compound losartan cream (containing chitosan, asiaticoside, and losartan) shows the best effect, followed by the chitosan asiaticoside cream. The treatment of the compound losartan cream inhibited expression of TGF-β1, collagen, and Smads, and decreased phosphorylation of Smad in vivo. These inhibitory effects were also confirmed in vitro. Our findings indicated that the compound losartan cream could inhibit scarring via TGF-β/Smad pathway. This cream might be an effective option for scar treatment.

The effect of γ-linolenic acid on Polycystic Ovary Syndrome associated Focal Segmental Glomerulosclerosis via TGF-β pathway

BACKGROUND

In recent years, female infertility from Polycystic Ovary Syndrome (PCOS) has gained scientific interest. PCOS alters the metabolic and endocrine functioning in females. The elevation in androgens can damage the androgen receptors present on the kidney giving rise to renal disorders like Focal Segmental Glomerulosclerosis (FSGS). Transforming Growth Factor Beta (TGF-β) in the ovary is activated by activin for Follicle Stimulating Hormone (FSH) secretion and in the kidney by thrombospondin 1 (TSP1) for cell growth and apoptosis. Studies show that gamma-linolenic acid (GLA) effectively treats breast cancer, eczema, inflammatory conditions and PCOS.

AIM

The study aimed to find out the possibility of FSGS development in PCOS and to understand the effect of GLA on FSGS via the TGF-β pathway.

METHOD

To carry out the study, the dehydroepiandrosterone (DHEA) induced PCOS model was used. Three groups namely vehicle control, DHEA, and DHEA+GLA, were used with six animals in each. TGF-β1, TGF-β2, and TSP1 genes were studied using real-time PCR.

RESULTS

The study showed an increase in the level of renal fibrosis biomarker, TSP1, in the DHEA group, which was further decreased by an anti-inflammatory agent, GLA. The TGF-β1 and TGF-β2 genes associated with the TGF-β pathway were seen to be increased in DHEA-induced PCOS rats which showed a possible relation between the two conditions.

CONCLUSION

The study shows a possible development of renal fibrosis in the DHEA-induced PCOS model. The GLA might act as a ligand to regulate TGF-β signaling in glomerulosclerosis in a DHEA-induced PCOS model.

Late intervention in the remnant kidney model attenuates proteinuria but not glomerular filtration rate decline

AIM

The use of animal models to predict the response to new therapies in humans is a vexing issue in nephrology. Unlike patients with chronic kidney disease (CKD), few rodent models develop a progressive decline in glomerular filtration rate (GFR) so that experimental studies frequently report a reduction in proteinuria as the primary efficacy outcome. Moreover, while humans present with established kidney disease that continues to progress, many experimental studies investigate therapies in the prevention rather than in a therapeutic setting.

METHODS

We used the remnant kidney (subtotal nephrectomy [SNX]) rat model that develops a decline in GFR in conjunction with heavy proteinuria and hypertension along with the histological hallmarks of CKD in humans, glomerulosclerosis and tubulointerstitial fibrosis. Using agents that had been shown to improve GFR as well as proteinuria in the prevention setting, angiotensin-converting enzyme (ACE) inhibition with enalapril and SIRT1 activation with SRT3025, treatment was initiated 6 weeks after SNX.

RESULTS

While enalapril reduced blood pressure, proteinuria and histological injury, it did not improve GFR, as measured by inulin clearance. SRT3025 improved neither GFR nor structural damage despite a reduction in proteinuria.

CONCLUSION

These findings demonstrate that neither a reduction in proteinuria nor a reversal of structural damage in the kidney will necessarily translate to a restoration of kidney function.

The phosphodiesterase 5 inhibitor tadalafil has renoprotective effects in a rat model of chronic kidney disease

Phosphodiesterase 5 inhibitors are widely used to treat erectile dysfunction and lower urinary tract symptoms with benign prostatic hyperplasia. Recent studies have indicated the renoprotective effects of this class of compounds. Whether renoprotection depends on blood pressure reduction remains controversial. In this study, we investigated the renoprotective effects of the phosphodiesterase 5 inhibitor, tadalafil, in a rat model of high-salt induced kidney injury with hypertension. Dahl salt-sensitive rats were fed a normal diet, high-salt (8% sodium chloride) diet, or high-salt diet with oral administration of either low- or high-dose tadalafil (1 and 10 mg kg-1  day-1 , respectively). Serum creatinine, urinary protein, and blood pressure were measured at baseline and after 8 weeks, at which point the rats were examined for glomerular injury and fibrosis. PAI1 mRNA levels were also evaluated. After 8 weeks, blood pressure, serum creatinine, and urinary protein levels were significantly higher in the high-salt group than those in the normal-salt group. Serum creatinine and urinary protein were significantly lower in both tadalafil groups than those in the high-salt group, while only high-dose tadalafil affected blood pressure. In addition, glomerulosclerosis and α-smooth muscle actin expression significantly decreased in both tadalafil treatment groups. PAI1 mRNA increased significantly in the high-salt group but decreased in both tadalafil-treated groups. Our results indicated that both low- and high-dose tadalafil prevented fibrosis and glomerular injury in a chronic kidney disease rat model. Mechanistically, these effects may be associated with PAI1 expression and glomerular structure protection.

TGF-β1 Induced by High Glucose is Controlled by Angiotensin-Converting Enzyme Inhibitor and Angiotensin II Receptor Blocker on Cultured Human Peritoneal Mesothelial Cells

Background

Loss of peritoneal function is a major complication associated with long-term peritoneal dialysis. Observed changes include loss and degeneration of the mesothelium, submesothelial thickening, alterations in the structure and number of blood vessels, and reduplication of the vascular basement membrane. Exposure to high glucose concentrations in peritoneal dialysis solutions is known to cause injury to cultured human peritoneal mesothelial cells (HPMC) as a result of overexpression of transforming growth factor beta 1 (TGF-β1). Previous studies have demonstrated that angiotensin II (AII) increases expression of TGF-β1 in a number of different cell types; although this has not been demonstrated in HPMC.

Objective

To clarify possible mechanisms involved in peritoneal fibrosis, we investigated whether HPMC expressed AII-forming pathway mRNA and whether increases in AII induced by high glucose contribute to the production of TGF-β1. We also examined the effects of the angiotensin-converting enzyme inhibitor (ACEI) perindoprilat and the AII receptor blocker (ARB) candesartan on expression of TGF-β1 and proliferation of HPMC.

Methods

Expression of mRNA for the AII-forming pathway and TGF-β1 in HPMC was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative RT-PCR. Levels of AII and TGF-β1 following 48 hours of incubation of the cells in a range of glucose concentrations were measured by enzyme immunoassay and enzyme linked immunosorbent assay respectively. The effect of glucose on cell proliferation was examined using the water-soluble tetrazolium salt WST-1 and [3H]-thymidine uptake. We also investigated the effect of ACEI and ARB on the expression of TGF-β1 and the proliferation of HPMC incubated at high glucose for 48 hours.

Results

AII-forming pathway mRNA was detected in HPMC, with expression of angiotensinogen, angiotensin-converting enzyme (ACE), AII type 1 receptor, and TGF-β1 mRNA increasing following exposure to glucose according to glucose concentration. High glucose was also shown to increase the production of AII and TGF-β1 and decrease the proliferation of HPMC. In contrast, we found that both the ACEI and the ARB attenuated the increase in TGF-β1 production and reduced cell proliferation caused by exposure to high glucose. These effects were greater with a combination of the two drugs.

Conclusion

The present study provides evidence that ( 1 ) HPMC express mRNA for the AII-forming pathway; ( 2 ) ACEI and ARB inhibit the TGF-β1 production induced by high glucose; ( 3 ) the AII-forming pathway is one mechanism by which high glucose causes production of TGF-β1. In addition to having antihypertensive and renal-protective effects, combination therapy with an ACEI and an ARB may also be effective in preventing loss of peritoneal function and decreasing peritoneal fibrosis.

Effect of glabridin on collagen deposition in liver and amelioration of hepatocyte destruction in diabetes rats

Abnormalities in insulin hormone levels leads to a hyperglycemic condition of diabetic mellitus. Hyperglycemia seriously induces organ and system destructions. The excessive accumulation of collagen fiber deposits occurs in inflammatory and reorganization processes of chronic liver diseases in type I insulin-dependent diabetes. Regarding the research objective, glabridin (GLB), an active compound of licorice, was used as a daily supplement (40 mg/kg) in order to decrease hepatocyte destruction and collagen deposition in liver tissue of diabetic animals induced by streptozotocin. A total of 40 were randomly allocated to five groups (each, n=10), control, control treated with GLB (GLB), diabetic rats (DM) injected with single dose of streptozotocin (60 mg/kg) to induce a diabetic condition, diabetic rats receiving GLB (DM+GLB; 40 mg/kg) and diabetic rats treated with glibenclamide (DM+GL; 4 mg/kg). Characteristic histopathological changes in liver cells and tissues of rats were determined by Masson's trichrome staining and transmission electron microscopy (TEM). Western blotting was used to detect the expression of the key markers, collagen type I and fibronectin proteins. The histological investigation of liver tissue of the DM group revealed that the collagen fiber deposition was increased in the periportal, pericentral and perisinusoidal spaces compared with controls. Hepatocytes appeared as small and fragmented cells in TEM examination. Collagenization of the perisinusoidal space was recently demonstrated to represent a new aspect of the microvascular abnormalities and liver fibrosis. Healthy hepatocytes with round nucleus were observed following supplementation of glabridin. In addition, collagen fiber deposition was reduced in the area adjacent to the perisinusoidal space. The expression of collagen type I and fibronectin decreased strongly following glabridin supplementation in DM+GLB rats compared with DM rats, indicating that the hepatic tissue reorganization regained its normal morphology. These findings suggest that it may be beneficial to examine the role of glabridin as a therapeutic agent in diabetes treatment in future research.

Impaired SIRT1 activity leads to diminution in glomerular endowment without accelerating age-associated GFR decline

Glomerular filtration rate (GFR) declines with age such that the prevalence of chronic kidney disease is much higher in the elderly. SIRT1 is the leading member of the sirtuin family of NAD+ -dependent lysine deacetylases that mediate the health span extending properties of caloric restriction. Since reduction in energy intake has also been shown to decrease age-related kidney disease in rodents, we hypothesized that a diminution in SIRT1 activity would accelerate the GFR decline and structural injury with age. To test this hypothesis, we compared changes in the kidney structure and function in control mice and mice that carry a point mutation at a conserved histidine (H355Y) of SIRT1 that renders the enzyme catalytically inactive. Taking advantage of this mouse model along with the disector/fractionator technique for glomerular counting and direct measurements of GFR by inulin clearance, we assessed the impact of SIRT1 inactivity on kidney aging. At 14 months of age, SIRT1 catalytically inactive (Sirt1Y/Y ) mice had lower GFRs and fewer glomeruli than their wild-type (Sirt1+/+ ) counterparts. This was not, however, due to either accelerated GFR decline or increased glomerulosclerosis and loss, but rather to reduced glomerular endowment in Sirt1Y/Y mice. Moreover, the compensatory glomerular hypertrophy and elevated single nephron GFR that customarily accompany reduction in nephron number were absent in Sirt1Y/Y mice. These findings suggest a role for SIRT1 not only in determining nephron endowment but also in orchestrating the response to it.

Reversing CXCL10 Deficiency Ameliorates Kidney Disease in Diabetic Mice

The excessive accumulation of extracellular matrix material in the kidney is a histopathologic hallmark of diabetic kidney disease that correlates closely with declining function. Although considerable research has focused on the role of profibrotic factors, comparatively little attention has been paid to the possibility that a diminution in endogenous antifibrotic factors may also contribute. Among the latter, the ELR^- CXC chemokines, CXCL9, CXCL10, and CXCL11, have been shown to provide a stop signal to prevent excessive fibrosis. Although the plasma concentrations of CXCL9 and CXCL11 were similar, those of CXCL10 were markedly lower in diabetic db/db mice compared with control db/m mice. In cell culture, CXCL10 inhibited kidney fibroblast collagen production in response to high glucose and the prosclerotic growth factor, transforming growth factor-β. In vivo, recombinant murine CXCL10 reduced mesangial and peritubular matrix expansion, albuminuria, and glomerular hypertrophy in db/db mice. In bone marrow, a major source of circulating chemokines, the concentration of CXCL10 was lower in cells derived from diabetic mice than from their nondiabetic counterparts. Silencing of CXCR3, the cognate receptor for CXCL10, abrogated the antifibrotic effects of bone marrow-derived secretions. In conclusion, experimental diabetes is a state of CXCL10 deficiency and that restoration of CXCL10 abundance prevented fibrosis and the development of diabetic kidney disease in mice.

Oral adsorbent AST-120 ameliorates gut environment and protects against the progression of renal impairment in CKD rats

Background

Oral charcoal adsorbent AST-120 (AST) is reported to ameliorate renal dysfunction by the absorption of toxic substance in the gut. Recent study revealed that, in CKD, gut environment is disturbed including the decrease in tight junctions and Lactobacillus (Lact). In this study, we examined whether AST improves the renal dysfunction through gut environment.

Method

Six-week-old spontaneously hypertensive rats (SHR) were rendered CKD by 5/6th nephrectomy (Nx). SHRs were divided into SHR (Sham), SHR with Nx (Nx), and Nx given AST (Nx + AST) (n = 10, each). After 12 weeks, rats were killed and biochemical parameters were explored. The gut flora was analyzed. Furthermore, gut molecular changes in tight junctions and toll-like receptors were examined. We also investigated the effects of the combination therapy with AST and Lact.

Results

The increase in serum urea nitrogen and urinary protein excretion in Nx was restored in Nx + AST. The increased renal glomerulosclerosis in Nx was ameliorated in Nx + AST. Increases in serum uremic toxins and IL-6 in Nx were ameliorated in Nx + AST. The gut flora analysis revealed that the decrease in Lact in Nx was restored in Nx + AST. The downregulation in the tight junction and TLR2 in Nx was mitigated by AST. However, combination therapy failed to exhibit additional effects.

Conclusion

AST ameliorated renal function with the restoration of Lact and tight junction through TLR pathway, which would mitigate systemic inflammation and contributed to their renoprotective effects. Our study provides a novel mechanism of the renoprotective effects by AST.

Combining streptozotocin and unilateral nephrectomy is an effective method for inducing experimental diabetic nephropathy in the 'resistant' C57Bl/6J mouse strain

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease. Animal models are essential tools for designing new strategies to prevent DN. C57Bl/6 (B6) mice are widely used for transgenic mouse models, but are relatively resistant to DN. This study aims to identify the most effective method to induce DN in a type 1 (T1D) and a type 2 diabetes (T2D) model in B6 mice. For T1D-induced DN, mice were fed a control diet, and randomised to streptozotocin (STZ) alone, STZ+unilateral nephrectomy (UNx), or vehicle/sham. For T2D-induced DN, mice were fed a western (high fat) diet, and randomised to either STZ alone, STZ+UNx, UNx alone, or vehicle/sham. Mice subjected to a control diet with STZ +UNx developed albuminuria, glomerular lesions, thickening of the glomerular basement membrane, and tubular injury. Mice on control diet and STZ developed only mild renal lesions. Furthermore, kidneys from mice on a western diet were hardly affected by diabetes, UNx or the combination. We conclude that STZ combined with UNx is the most effective model to induce T1D-induced DN in B6 mice. In our hands, combining western diet and STZ treatment with or without UNx did not result in a T2D-induced DN model in B6 mice.

GLP-1 receptor agonist ameliorates obesity-induced chronic kidney injury via restoring renal metabolism homeostasis

Increasing evidence indicates that obesity is highly associated with chronic kidney disease (CKD). GLP-1 receptor (GLP-1R) agonist has shown benefits on kidney diseases, but its direct role on kidney metabolism in obesity is still not clear. This study aims to investigate the protection and metabolic modulation role of liraglutide (Lira) on kidney of obesity. Rats were induced obese by high-fat diet (HFD), and renal function and metabolism changes were evaluated by metabolomic, biological and histological methods. HFD rats exhibited systemic metabolic disorders such as obesity, hyperlipidemia and impaired glucose tolerance, as well as renal histological and function damages, while Lira significantly ameliorated these adverse effects in HFD rats. Metabolomic data showed that Lira directly reduced renal lipids including fatty acid residues, cholesterol, phospholipids and triglycerides, and improved mitochondria metabolites such as succinate, citrate, taurine, fumarate and nicotinamide adenine dinucleotide (NAD+) in the kidney of HFD rats. Furthermore, we revealed that Lira inhibited renal lipid accumulation by coordinating lipogenic and lipolytic signals, and partly rescued renal mitochondria function via Sirt1/AMPK/PGC1α pathways in HFD rats. This study suggested that Lira alleviated HFD-induced kidney injury at least partly via directly restoring renal metabolism, thus GLP-1R agonist is a promising therapy for obesity-associated CKD.

Combined Inhibition of Soluble Epoxide Hydrolase and Renin-Angiotensin System Exhibits Superior Renoprotection to Renin-Angiotensin System Blockade in 5/6 Nephrectomized Ren-2 Transgenic Hypertensive Rats with Established Chronic Kidney Disease

BACKGROUND/AIMS

We found recently that increasing renal epoxyeicosatrienoic acids (EETs) levels by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, shows renoprotective actions and retards the progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX). This prompted us to examine if additional protection is provided when sEH inhibitor is added to the standard renin-angiotensin system (RAS) blockade, specifically in rats with established CKD.

METHODS

For RAS blockade, an angiotensin-converting enzyme inhibitor along with an angiotensin II type receptor blocker was used. RAS blockade was compared to sEH inhibition added to the RAS blockade. Treatments were initiated 6 weeks after 5/6 NX in TGR and the follow-up period was 60 weeks.

RESULTS

Combined RAS and sEH blockade exhibited additional positive impact on the rat survival rate, further reduced albuminuria, further reduced glomerular and tubulointerstitial injury, and attenuated the decline in creatinine clearance when compared to 5/6 NX TGR subjected to RAS blockade alone. These additional beneficial actions were associated with normalization of the intrarenal EETs deficient and a further reduction of urinary angiotensinogen excretion.

CONCLUSION

This study provides evidence that addition of pharmacological inhibition of sEH to RAS blockade in 5/6 NX TGR enhances renoprotection and retards progression of CKD, notably, when applied at an advanced stage.

Sirtuin 1 Activation Reduces Transforming Growth Factor-β1-Induced Fibrogenesis and Affords Organ Protection in a Model of Progressive, Experimental Kidney and Associated Cardiac Disease

Most forms of chronic, progressive kidney disease are characterized by fibrosis whereby the prototypical prosclerotic growth factor, transforming growth factor β (TGF-β), is thought to play a pivotal role. With the recent understanding that TGF-β's canonical signaling pathway may be modified by acetylation as well as phosphorylation, we explored the role of the NAD⁺-dependent lysine deacetylase, sirtuin 1 (SIRT1) in fibrogenesis in the cell culture, animal model, and human settings. In vitro, the increase in collagen production that results from TGF-β1 stimulation was ameliorated by the allosteric modifier of Sirt1 deacetylase, SRT3025, in association with a reduction in Smad3 reporter activity. In the remnant kidney model (subtotally or 5/6 nephrectomized rats) that develops progressive kidney disease in association with TGF-β overexpression, administration of SRT3025 attenuated glomerular filtration rate decline and proteinuria without affecting blood pressure. Glomerulosclerosis and tubulointerstitial fibrosis were similarly reduced with Sirt1 activation as were cardiac structure and function in this rodent model of primary kidney and secondary cardiac disease. Relating these findings to the human setting, we noted a reduction in SIRT1 mRNA in kidney biopsies obtained from individuals with focal glomerulosclerosis. Together these studies highlight the potential of SIRT1 activation as a therapeutic strategy in progressive, fibrotic kidney disease.

Suppression of NLRP3 Inflammasome Activation Ameliorates Chronic Kidney Disease-Induced Cardiac Fibrosis and Diastolic Dysfunction

Cardiac fibrosis is a common finding in patients with chronic kidney disease. Here, we investigate the cardio-renal effects of theracurmin, a novel formulation of the polyphenolic compound curcumin, in a rat model of chronic kidney disease. Briefly, Sprague-Dawley rats were randomized to undergo sham or subtotal nephrectomy (SNx) surgery. At 3 weeks post surgery, SNx animals were further randomized to received theracurmin via once daily oral gavage or vehicle for 5 consecutive weeks. At 8 weeks post surgery, cardiac function was assessed via echocardiography and pressure volume loop analysis, followed by LV and renal tissue collection for analysis. SNx animals developed key hallmarks of renal injury including hypertension, proteinuria, elevated blood urea nitrogen, and glomerulosclerosis. Renal injury in SNx animals was also associated with significant diastolic dysfunction, macrophage infiltration, and cardiac NLRP3 inflammasome activation. Treatment of SNx animals with theracurmin improved structural and functional manifestations of cardiac injury associated with renal failure and also attenuated cardiac NLRP3 inflammasome activation and mature IL-1β release. Taken together, our findings suggest a significant role for the NLRP3 inflammasome in renal injury-induced cardiac dysfunction and presents inflammasome attenuation as a unique strategy to prevent adverse cardiac remodeling in the setting of chronic kidney disease.

Progenitor cell secretory products exert additive renoprotective effects when combined with ace inhibitors in experimental CKD

Hypothesis/introduction:

Renal fibrovascular injury often persists in chronic kidney disease patients treated with renin-angiotensin system blockers. Intriguingly, early outgrowth cell-derived factor infusion also inhibits chronic renal injury. We sought to determine whether early outgrowth cell-derived factor administration provides further renoprotection when added to renin-angiotensin system blockade.

Materials and methods:

Conditioned medium was generated by incubating rat early outgrowth cells with serum-free endothelial basal medium-2 to collect their secreted factors. Subtotal nephrectomy rats received enalapril 0.5 mg/L in drinking water or placebo, beginning 8 weeks post-surgery. Four weeks later, enalapril-treated rats received intravenous injections of either conditioned medium or control endothelial basal medium-2 for 2 weeks. Glomerular filtration rate, urinary protein excretion and renal structure were assessed 4 weeks later at 16 weeks post-surgery.

Results:

Enalapril-treated subtotal nephrectomy rats receiving control endothelial basal medium-2 injections experienced only partial renoprotection when compared to vehicle-treated subtotal nephrectomy rats. In contrast, conditioned medium infusion, when administered in addition to enalapril, attenuated the progression of renal dysfunction in subtotal nephrectomy rats, improving glomerular filtration rate and reducing proteinuria without affecting blood pressure.

Conclusions:

Early outgrowth cell-derived factors exert additive renoprotective effects on top of angiotensin-converting enzyme inhibitor therapy in experimental chronic kidney disease, providing the rationale for clinical trials of early outgrowth cell-based therapies for chronic kidney disease.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Sodium-Glucose Linked Cotransporter-2 Inhibition Does Not Attenuate Disease Progression in the Rat Remnant Kidney Model of Chronic Kidney Disease

Pharmacological inhibition of the proximal tubular sodium-glucose linked cotransporter-2 (SGLT2) leads to glycosuria in both diabetic and non-diabetic settings. As a consequence of their ability to modulate tubuloglomerular feedback, SGLT2 inhibitors, like agents that block the renin-angiotensin system, reduce intraglomerular pressure and single nephron GFR, potentially affording renoprotection. To examine this further we administered the SGLT2 inhibitor, dapagliflozin, to 5/6 (subtotally) nephrectomised rats, a model of progressive chronic kidney disease (CKD) that like CKD in humans is characterised by single nephron hyperfiltration and intraglomerular hypertension and where angiotensin converting enzyme inhibitors and angiotensin receptor blockers are demonstrably beneficial. When compared with untreated rats, both sham surgery and 5/6 nephrectomised rats that had received dapagliflozin experienced substantial glycosuria. Nephrectomised rats developed hypertension, heavy proteinuria and declining GFR that was unaffected by the administration of dapagliflozin. Similarly, SGLT2 inhibition did not attenuate the extent of glomerulosclerosis, tubulointerstitial fibrosis or overexpression of the profibrotic cytokine, transforming growth factor-ß1 mRNA in the kidneys of 5/6 nephrectomised rats. While not precluding beneficial effects in the diabetic setting, these findings indicate that SGLT2 inhibition does not have renoprotective effects in this classical model of progressive non-diabetic CKD.

The Histone Methyltransferase Enzyme Enhancer of Zeste Homolog 2 Protects against Podocyte Oxidative Stress and Renal Injury in Diabetes

Epigenetic regulation of oxidative stress is emerging as a critical mediator of diabetic nephropathy. In diabetes, oxidative damage occurs when there is an imbalance between reactive oxygen species generation and enzymatic antioxidant repair. Here, we investigated the function of the histone methyltransferase enzyme enhancer of zeste homolog 2 (EZH2) in attenuating oxidative injury in podocytes, focusing on its regulation of the endogenous antioxidant inhibitor thioredoxin interacting protein (TxnIP). Pharmacologic or genetic depletion of EZH2 augmented TxnIP expression and oxidative stress in podocytes cultured under high-glucose conditions. Conversely, EZH2 upregulation through inhibition of its regulatory microRNA, microRNA-101, downregulated TxnIP and attenuated oxidative stress. In diabetic rats, depletion of EZH2 decreased histone 3 lysine 27 trimethylation (H3K27me3), increased glomerular TxnIP expression, induced podocyte injury, and augmented oxidative stress and proteinuria. Chromatin immunoprecipitation sequencing revealed H3K27me3 enrichment at the promoter of the transcription factor Pax6, which was upregulated on EZH2 depletion and bound to the TxnIP promoter, controlling expression of its gene product. In high glucose-exposed podocytes and the kidneys of diabetic rats, the lower EZH2 expression detected coincided with upregulation of Pax6 and TxnIP. Finally, in a gene expression array, TxnIP was among seven of 30,854 genes upregulated by high glucose, EZH2 depletion, and the combination thereof. Thus, EZH2 represses the transcription factor Pax6, which controls expression of the antioxidant inhibitor TxnIP, and in diabetes, downregulation of EZH2 promotes oxidative stress. These findings expand the extent to which epigenetic processes affect the diabetic kidney to include antioxidant repair.

MicroRNAs mediate the cardioprotective effect of angiotensin-converting enzyme inhibition in acute kidney injury

Cardiovascular disease, including cardiac hypertrophy, is common in patients with kidney disease and can be partially attenuated using blockers of the renin-angiotensin system (RAS). It is unknown whether cardiac microRNAs contribute to the pathogenesis of cardiac hypertrophy or to the protective effect of RAS blockade in kidney disease. Using a subtotal nephrectomy rat model of kidney injury, we investigated changes in cardiac microRNAs that are known to have direct target genes involved in the regulation of apoptosis, fibrosis, and hypertrophy. The effect of treatment with the angiotensin-converting enzyme (ACE) inhibitor ramipril on cardiac microRNAs was also investigated. Kidney injury led to a significant increase in cardiac microRNA-212 and microRNA-132 expression. Ramipril reduced cardiac hypertrophy, attenuated the increase in microRNA-212 and microRNA-132, and significantly increased microRNA-133 and microRNA-1 expression. There was altered expression of caspase-9, B cell lymphoma-2, transforming growth factor-β, fibronectin 1, collagen type 1A1, and forkhead box protein O3, which are all known to be involved in the regulation of apoptosis, fibrosis, and hypertrophy in cardiac cells while being targets for the above microRNAs. ACE inhibitor treatment increased expression of microRNA-133 and microRNA-1. The inhibitory action of ACE inhibitor treatment on increased cardiac NADPH oxidase isoform 1 expression after subtotal nephrectomy surgery suggests that inhibition of oxidative stress is also one of mechanism of ACE inhibitor-mediated cardioprotection. These finding suggests the involvement of microRNAs in the cardioprotective action of ACE inhibition in acute renal injury, which is mediated through an inhibitory action on profibrotic and proapoptotic target genes and stimulatory action on antihypertrophic and antiapoptotic target genes.

Molecular mechanisms of renal blood flow autoregulation

Diabetes and hypertension are the leading causes of chronic kidney disease and their incidence is increasing at an alarming rate. Both are associated with impairments in the autoregulation of renal blood flow (RBF) and greater transmission of fluctuations in arterial pressure to the glomerular capillaries. The ability of the kidney to maintain relatively constant blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure is mediated by the myogenic response of afferent arterioles working in concert with tubuloglomerular feedback that adjusts the tone of the afferent arteriole in response to changes in the delivery of sodium chloride to the macula densa. Despite intensive investigation, the factors initiating the myogenic response and the signaling pathways involved in the myogenic response and tubuloglomerular feedback remain uncertain. This review focuses on current thought regarding the molecular mechanisms underlying myogenic control of renal vascular tone, the interrelationships between the myogenic response and tubuloglomerular feedback, the evidence that alterations in autoregulation of RBF contributes to hypertension and diabetes-induced nephropathy and the identification of vascular therapeutic targets for improved renoprotection in hypertensive and diabetic patients.

Functional interaction between angiotensin II receptor type 1 and chemokine (C-C motif) receptor 2 with implications for chronic kidney disease

Understanding functional interactions between G protein-coupled receptors is of great physiological and pathophysiological importance. Heteromerization provides one important potential mechanism for such interaction between different signalling pathways via macromolecular complex formation. Previous studies suggested a functional interplay between angiotensin II receptor type 1 (AT1) and Chemokine (C-C motif) Receptor 2 (CCR2). However the molecular mechanisms are not understood. We investigated AT1-CCR2 functional interaction in vitro using bioluminescence resonance energy transfer in HEK293 cells and in vivo using subtotal-nephrectomized rats as a well-established model for chronic kidney disease. Our data revealed functional heteromers of these receptors resulting in CCR2-Gαi1 coupling being sensitive to AT1 activation, as well as apparent enhanced β-arrestin2 recruitment with agonist co-stimulation that is synergistically reversed by combined antagonist treatment. Moreover, we present in vivo findings where combined treatment with AT1- and CCR2-selective inhibitors was synergistically beneficial in terms of decreasing proteinuria, reducing podocyte loss and preventing renal injury independent of blood pressure in the subtotal-nephrectomized rat model. Our findings further support a role for G protein-coupled receptor functional heteromerization in pathophysiology and provide insights into previous observations indicating the importance of AT1-CCR2 functional interaction in inflammation, renal and hypertensive disorders.

Application of Modular Therapy for Renoprotection in Experimental Chronic Kidney Disease

Cell-based regenerative therapies offer a new alternative approach to the treatment of chronic disease. Specifically, studies by our laboratory and others have shown that a subpopulation of cells derived from the bone marrow, known as early outgrowth cells (EOCs), are able to attenuate the progression of chronic kidney disease (CKD). In this study we examined the efficacy of a tissue engineering system, in which EOCs were embedded into submillimeter-sized collagen cylinders. These small individual units are referred to as modules and together form a functional microtissue. Due to their resemblance to endothelial cells, late outgrowth cells (LOCs) were used to coat the module surface, hypothesizing that as such they would promote vascularization and enhance engraftment of the encapsulated EOCs. These coated modules were transplanted subcutaneously into the subtotally nephrectomized rat model of CKD. While coated module therapy significantly improved both renal structure and function, noncoated modules with embedded EOCs were unable to reproduce these salutary effects on the kidney. Nevertheless, in both treatments, the embedded EOCs quickly degraded the modular environment and were seen to migrate to the liver, spleen, and bone marrow as early as 6 days after transplantation. With the efflux of EOCs, and unexpectedly no evidence of vascularization, we hypothesized that the LOCs did not enhance EOC engraftment, but rather augmented the renoprotection provided by EOCs by secretion of their own soluble and potent antifibrotic factors. To the best of our knowledge, this is the first study to document an effective subcutaneous approach for renoprotection.

The endothelium in diabetic nephropathy

Diabetes is characterised by widespread endothelial cell dysfunction that underlies the development of both the micro- and macrovascular complications of the disease, including nephropathy, cardiomyopathy, and non-proliferative retinopathy. In the kidney, major changes are noted in glomerular endothelial cell structure in their fenestrations and glycocalyx. These changes, along with endothelial cell loss and capillary rarefaction in both the glomerulus and tubulointerstitium, lead to the progressive loss of glomerular filtration that render diabetes the most common cause of end-stage renal disease in much of the developed world. New treatments in diabetes that directly address the abnormal structure and function of the endothelial cell are desperately needed.

Clusterin/apolipoprotein J attenuates angiotensin II-induced renal fibrosis

The blockade of angiotensin II (Ang II) is a major therapeutic strategy for diabetic nephropathy. The main roles of Ang II in renal disease are mediated via the Ang type 1 receptor (AT1R). Upregulation of clusterin/apolipoprotein J has been reported in nephropathy models, suggesting it has a protective role in nephropathogenesis. Here, we studied how clusterin acts against Ang II-induced renal fibrosis. Levels of AT1R and fibrotic markers in clusterin-/- mice and Ang II infused rats transfected with an adenovirus encoding clusterin were evaluated by immunoblot analysis, real time RT-PCR, and immunohistochemical staining. The effect of clusterin on renal fibrosis was evaluated in NRK-52E cells, a cultured renal tubular epithelial cell line, using immunoblot analysis and real time RT-PCR. Nuclear localization of NF-κB was evaluated using immunofluorecence and co-immunoprecipitation. Renal fibrosis and expression of AT1R was higher in the kidneys of clusterin^-/- mice than in those of wild-type mice. Furthermore, loss of clusterin accelerated Ang II-stimulated renal fibrosis and AT1R expression. Overexpression of clusterin in proximal tubular epithelial cells decreased the levels of Ang II-stimulated fibrotic markers and AT1R. Moreover, intrarenal delivery of clusterin attenuated Ang II-mediated expression of fibrotic markers and AT1R in rats. Fluorescence microscopy and co-immunoprecipitation in conjunction with western blot revealed that clusterin inhibited Ang II-stimulated nuclear localization of p-NF-κB via a direct physical interaction and subsequently decreased the AT1R level in proximal tubular epithelial cells. These data suggest that clusterin attenuates Ang II-induced renal fibrosis by inhibition of NF-κB activation and subsequent downregulation of AT1R. This study raises the possibility that clusterin could be used as a therapeutic target for Ang II-induced renal diseases.

Cell therapy for diabetic nephropathy: is the future, now?

Cell-based therapy, designed to promote angiogenesis and improve organ function, has been under investigation for the treatment of ischemic heart disease for more than 10 years. Although believed to work primarily by repairing the microvasculature, this form of therapy has not been examined in the setting of chronic kidney disease caused by diabetes in which capillary rarefaction plays a pivotal pathogenetic role. Indeed, despite disease-associated dysfunction, the favorable safety profile of autologous, bone marrow-derived angiogenic cells and their efficacy in animal studies of chronic kidney disease would seem to provide a basis for clinical trials in advanced diabetic nephropathy.

Direct renin inhibition prevents cardiac dysfunction in a diabetic mouse model: comparison with an angiotensin receptor antagonist and angiotensin-converting enzyme inhibitor

Hyperglycaemia up-regulates intracellular AngII (angiotensin II) production in cardiac myocytes, effects of which are blocked more effectively by renin inhibition than ARBs (angiotensin receptor blockers) or ACEis (angiotensin-converting enzyme inhibitors). In the present study, we determined whether renin inhibition is more effective at preventing diabetic cardiomyopathy than an ARB or ACEi. Diabetes was induced in adult mice for 10 weeks by STZ (streptozotocin). Diabetic mice were treated with insulin, aliskiren (a renin inhibitor), benazeprilat (an ACEi) or valsartan (an ARB) via subcutaneous mini-pumps. Significant impairment in diastolic and systolic cardiac functions was observed in diabetic mice, which was completely prevented by all three RAS (renin-angiotensin system) inhibitors. Hyperglycaemia significantly increased cardiac oxidative stress and circulating inflammatory cytokines, which were blocked by aliskiren and benazeprilat, whereas valsartan was partially effective. Diabetes increased cardiac PRR (prorenin receptor) expression and nuclear translocation of PLZF (promyelocytic zinc finger protein), which was completely prevented by aliskiren and valsartan, and partially by benazeprilat. Renin inhibition provided similar protection of cardiac function to ARBs and ACEis. Activation of PLZF by PRR represented a novel mechanism in diabetic cardiomyopathy. Differential effects of the three agents on oxidative stress, cytokines and PRR expression suggested subtle differences in their mechanisms of action.

Regression of albuminuria and hypertension and arrest of severe renal injury by a losartan-hydrochlorothiazide association in a model of very advanced nephropathy

Treatments that effectively prevent chronic kidney disease (CKD) when initiated early often yield disappointing results when started at more advanced phases. We examined the long-term evolution of renal injury in the 5/6 nephrectomy model (Nx) and the effect of an association between an AT-1 receptor blocker, losartan (L), and hydrochlorothiazide (H), shown previously to be effective when started one month after Nx. Adult male Munich-Wistar rats underwent Nx, being divided into four groups: Nx+V, no treatment; Nx+L, receiving L monotherapy; Nx+LH, receiving the L+H association (LH), and Nx+AHHz, treated with the calcium channel blocker, amlodipine, the vascular relaxant, hydralazine, and H. This latter group served to assess the effect of lowering blood pressure (BP). Rats undergoing sham nephrectomy (S) were also studied. In a first protocol, treatments were initiated 60 days after Nx, when CKD is at a relatively early stage. In a second protocol, treatments were started 120 days after Nx, when glomerulosclerosis and interstitial fibrosis are already advanced. In both protocols, L treatment promoted only partial renoprotection, whereas LH brought BP, albuminuria, tubulointerstitial cell proliferation and plasma aldosterone below pretreatment levels, and completely detained progression of renal injury. Despite normalizing BP, the AHHz association failed to prevent renal damage, indicating that the renoprotective effect of LH was not due to a systemic hemodynamic action. These findings are inconsistent with the contention that thiazides are innocuous in advanced CKD. In Nx, LH promotes effective renoprotection even at advanced stages by mechanisms that may involve anti-inflammatory and intrarenal hemodynamic effects, but seem not to require BP normalization.

A purpose-synthesised anti-fibrotic agent attenuates experimental kidney diseases in the rat

Background and Purpose

Locally-active growth factors have been implicated in the pathogenesis of many diseases in which organ fibrosis is a characteristic feature. In the setting of chronic kidney disease (CKD), two such pro-fibrotic factors, transforming growth factor-ß (TGF-ß) and platelet-derived growth factor (PDGF) have emerged as lead potential targets for intervention. Given the incomplete organ protection afforded by blocking the actions of TGF-ß or PDGF individually, we sought to determine whether an agent that inhibited the actions of both may have broader effects in ameliorating the key structural and functional abnormalities of CKD.

Experimental Approach

Accordingly, we studied the effects of a recently described, small molecule anti-fibrotic drug, 3-methoxy-4-propargyloxycinnamoyl anthranilate (FT011, Fibrotech Therapeutics, Australia), which should have these effects.

Key Results

In the in vitro setting, FT011 inhibited both TGF-ß1 and PDGF-BB induced collagen production as well as PDGF-BB-mediated mesangial proliferation. Consistent with these in vitro actions, when studied in a robust model of non-diabetic kidney disease, the 5/6 nephrectomised rat, FT011 attenuated the decline in GFR, proteinuria and glomerulosclerosis (p<0.05 for all). Similarly, in the streptozotocin-diabetic Ren-2 rat, a model of advanced diabetic nephropathy, FT011 reduced albuminuria, glomerulosclerosis and tubulointerstitial fibrosis.

Conclusions and Implications

Together these studies suggest that broadly antagonising growth factor actions, including those of TGF-ß1 and PDGF-BB, has the potential to protect the kidney from progressive injury in both the diabetic and non-diabetic settings.

Bone marrow cell therapies for endothelial repair and their relevance to kidney disease

Endothelial injury is a characteristic finding in chronic kidney disease and is associated with both markedly increased cardiovascular risk and chronic kidney disease progression. The past decade has seen a remarkable surge of interest in the role of bone marrow-derived cells for the protection, repair, and regeneration of injured endothelium. In particular, despite controversies regarding their mechanisms of action, endothelial progenitor cells have garnered considerable attention, with multiple reports suggesting that these cells exhibit remarkable pro-angiogenic effects. Recent advances in our understanding of how the bone marrow responds to endothelial injury now suggest that multiple bone marrow cell populations, including both endothelial progenitor cells and a novel group of cells called early outgrowth cells, promote endothelial repair and regeneration through different, yet complementary, mechanisms. Moreover, certain subsets of bone marrow-derived cells also appear to have novel, potent, angiogenesis-independent tissue-protective properties. The bone marrow should thus now be viewed not only as a hematopoiesis organ, but also as a rich reservoir of cells capable of protecting and even regenerating nonhematopoietic tissues such as the kidney. To harness the prognostic and therapeutic potential of the bone marrow, the renal community must be aware of recent advances in our understanding of the nature and therapeutic potential of these cells.

Upregulation of nestin in proximal tubules may participate in cell migration during renal repair

The characteristics of renal tubular progenitor/precursor cells and the role of renal tubule regeneration in the repair of remnant kidneys (RKs) after nephrectomy are not well known. In the present study of a murine model of subtotal nephrectomy, we used immunofluorescence (IF), immunoblot analysis, and in situ hybridization methods to demonstrate that nestin expression was transiently upregulated in tubule cells near the incision edges of RKs. The nestin-positive tubules were immature proximal tubules that colabeled with lotus tetragonolobus agglutinin but not with markers of mature tubules (aquaporin-1, Tamm-Horsfall protein, and aquaporin-2). In addition, many of the nestin-expressing tubule cells were actively proliferative cells, as indicated by colabeling with bromodeoxyuridine. Double-label IF and immunoblot analysis also showed that the upregulation of tubular nestin was associated with enhanced transforming growth factor-β1 (TGF-β1) expression in the incision edge of RKs but not α-smooth muscle actin, which is a marker of fibrosis. In cultured human kidney proximal tubule cells (HKC), immunoblot analysis indicated that TGF-β1 induced nestin expression and loss of E-cadherin expression, suggesting an association of nestin expression and cellular dedifferentiation. Knockdown of nestin expression by a short hairpin RNA-containing plasmid led to decreased migration of HKC cells that were induced by TGF-β1. Taken together, our results suggest that the tubule repair that occurs during the recovery process following nephrectomy may involve TGF-β1-induced nestin expression in immature renal proximal tubule cells and the promotion of renal cell migration.

Early-outgrowth bone marrow cells attenuate renal injury and dysfunction via an antioxidant effect in a mouse model of type 2 diabetes

Cell therapy has been extensively investigated in heart disease but less so in the kidney. We considered whether cell therapy also might be useful in diabetic kidney disease. Cognizant of the likely need for autologous cell therapy in humans, we sought to assess the efficacy of donor cells derived from both healthy and diabetic animals. Eight-week-old db/db mice were randomized to receive a single intravenous injection of PBS or 0.5 × 10(6) early-outgrowth cells (EOCs) from db/m or db/db mice. Effects were assessed 4 weeks after cell infusion. Untreated db/db mice developed mesangial matrix expansion and tubular epithelial cell apoptosis in association with increased reactive oxygen species (ROS) and overexpression of thioredoxin interacting protein (TxnIP). Without affecting blood glucose or blood pressure, EOCs not only attenuated mesangial and peritubular matrix expansion, as well as tubular apoptosis, but also diminished ROS and TxnIP overexpression in the kidney of db/db mice. EOCs derived from both diabetic db/db and nondiabetic db/m mice were equally effective in ameliorating kidney injury and oxidative stress. The similarly beneficial effects of cells from healthy and diabetic donors highlight the potential of autologous cell therapy in the related clinical setting.

A nonerythropoietic derivative of erythropoietin inhibits tubulointerstitial fibrosis in remnant kidney

BACKGROUND

The tissue-protective effects of erythropoietin (EPO) have been extensively investigated, and EPO administration can raise the hemoglobin (Hb) concentration. Recently, we reported that carbamylated erythropoietin (CEPO) protected kidneys from ischemia-reperfusion injury as well as EPO.

METHODS

To investigate the clinical applications of CEPO, we next evaluated the long-term therapeutic effect of CEPO using a tubulointerstitial model rat. We randomized remnant kidney model rats to receive saline, EPO, or CEPO for 8 weeks.

RESULTS

CEPO- and EPO-treated rats had improved serum creatinine levels compared with saline-treated remnant kidney model rats, although the Hb level was significantly increased in EPO-treated rats. Two-photon microscopy revealed that EPO/CEPO significantly ameliorated tubular epithelial cell damage assessed by endocytosis. In addition, CEPO or EPO protected endothelial cells with a sustained blood flow rate. EPO or CEPO suppressed the number of TUNEL-positive apoptotic cells with weak αSMA staining. Furthermore, PCR analysis demonstrated that TGF-β and type I collagen expression was attenuated in EPO- or CEPO-treated rats, accompanied by a significant decrease in interstitial fibrosis.

CONCLUSION

We established a long-term therapeutic approach to protect tubulointerstitial injury with CEPO, and thus, the therapeutic value of this approach warrants further attention and preclinical studies.

Amiloride off-target effect inhibits podocyte urokinase receptor expression and reduces proteinuria

The urokinase receptor (uPAR) and its soluble form play a key role in the pathogenesis of focal segmental glomerulosclerosis (FSGS). The modification of uPAR pathological actions on podocytes will become an important task for the development of improved nephroprotective therapeutics. Here we show that podocyte uPAR expression can be reduced using amiloride. Amiloride has a significant role in the reduction of podocyte cell motility in vitro and proteinuria in mice. Amiloride inhibited the induction of uPAR protein and PLAUR messenger RNA (encoding uPAR) and with that it reduced uPAR-mediated β3 integrin activation in lipopolysaccharide (LPS)-treated podocytes. Transwell migration assay and wound healing assay showed that directed and random podocyte motility of LPS-treated podocytes were increased and substantially reduced by amiloride. The off-target effect of amiloride was independent of its function as epithelial sodium channel blocker and different from triamterene. Amiloride was also effective in the LPS mouse model of transient proteinuria (LPS mice) and in the 5/6 nephrectomy rat FSGS model (NTX) by significantly inhibiting podocyte uPAR induction, reducing proteinuria. In addition, amiloride attenuated glomerulosclerosis, as determined by glomerulosclerotic index. Thus, our observations show that amiloride inhibits podocyte uPAR induction and reduces proteinuria in NTX rats and LPS mice. Given the pathological relevance of the uPAR-β3 integrin signaling axis in FSGS, amiloride may be utilized in patients with FSGS.

1H NMR spectroscopy analysis of metabolites in the kidneys provides new insight into pathophysiological mechanisms: applications for treatment with Cordyceps sinensis

BACKGROUND

The number of patients with chronic kidney disease (CKD) is continuously growing worldwide. Treatment with traditional Chinese medicine might slow the progression of CKD.

METHODS

In this study, we evaluated the renal protective effects of the Chinese herb Cordyceps sinensis in rats with 5/6 nephrectomy. Male Sprague-Dawley mice (weighing 150-200 g) were subjected to 5/6 nephrectomy. The rats were divided into three groups: (i) untreated nephrectomized group (OP group, n = 16), (ii) oral administration of C. sinensis-treated (4 mg/kg/day) nephrectomized group (CS group, n = 16) and (iii) sham-operated group (SO group, n = 16). The rats were sacrificed at 4 and 8 weeks after 5/6 nephrectomy, and the kidneys, serum and urine were collected for (1)H nuclear magnetic resonance spectral analysis. Multivariate statistical techniques and statistical metabolic correlation comparison analysis were performed to identify metabolic changes in aqueous kidney extracts between these groups.

RESULTS

Significant differences between these groups were discovered in the metabolic profiles of the biofluids and kidney extracts. Pathways including the citrate cycle, branched-chain amino acid metabolism and the metabolites that regulate permeate pressure were disturbed in the OP group compared to the SO group; in addition, these pathways were reversed by C. sinensis treatment. Biochemistry and electron microscopic images verified that C. sinensis has curative effects on chronic renal failure. These results were confirmed by metabonomics results.

CONCLUSION

Our study demonstrates that C. sinensis has potential curative effects on CKD, and our metabonomics results provided new insight into the mechanism of treatment of this traditional Chinese medicine.

Keishibukuryogan reduces renal injury in the early stage of renal failure in the remnant kidney model

The effects of keishibukuryogan on the early stage of progressive renal failure were examined in rats subjected to 5/6 nephrectomy. Keishibukuryogan, one of the traditional herbal formulations, was given orally at a dose of 1% (w/w) and 3% (w/w) in chow. Administration of keishibukuryogan was started at 1 week after 5/6 nephrectomy and was continued for 4 weeks. At the end of the experiment, Azan staining did not reveal any severe histological changes in the kidneys of the nephrectomized rats. On the other hand, significant increases in mRNA expressions of transforming growth factor-β₁ and fibronectin related to tissue fibrosis, as examined by Reverse Transcriptase-Polymerase Chain Reaction, were observed in nephrectomized rats, and they were significantly suppressed by 3% keishibukuryogan treatment. Against gene expressions related to macrophage infiltration, 3% keishibukuryogan treatment significantly suppressed osteopontin mRNA levels, and monocyte chemoattractant protein-1 and vascular cell adhesion molecule-1 mRNA levels showed a tendency to decrease, but without statistical significance. It was also observed that 3% keishibukuryogan attenuated serum urea nitrogen and urinary protein excretion levels. From these results, it was suggested that keishibukuryogan exerts beneficial effects that result in slowing the progression of chronic renal failure.

ACE inhibitors in cardiac surgery: current studies and controversies

Major complications associated with cardiac surgery are still common and carry great prognostic significance. Current medical interventions to prevent these cardiovascular complications include antiplatelet therapy, statins, β-blockers and angiotensin-converting enzyme (ACE) inhibitors. Both experimental studies and clinical trials have shown that ACE inhibitors hold promise as cardiovascular protective agents for cardiac surgery patients. Several lines of evidence support this hypothesis. First, long-term use of ACE inhibitors has been well established to provide cardiovascular protection and reduce ischemic events and complications, independent of their effect on heart function and blood pressure. Second, early ACE inhibitor therapy has been demonstrated to produce remarkable survival and heart function benefits in patients with acute myocardial infarction. Third, ACE blockage can prevent or delay the development or progression of renal disease at all stages, from subclinical microalbuminuria to end-stage renal disease. Nevertheless, perioperative studies of the effects of ACE inhibitors remain few and inconclusive. Results from recent clinical trials and observational studies are conflicting and raise more questions than answers. Further studies, both retrospective and larger-scale prospective studies, are critically needed to examine whether ACE inhibitors reduce mortality and major complications in patients undergoing cardiac surgery.

Tubular cell-enriched subpopulation of primary renal cells improves survival and augments kidney function in rodent model of chronic kidney disease

Established chronic kidney disease (CKD) may be identified by severely impaired renal filtration that ultimately leads to the need for dialysis or kidney transplant. Dialysis addresses only some of the sequelae of CKD, and a significant gap persists between patients needing transplant and available organs, providing impetus for development of new CKD treatment modalities. Some postulate that CKD develops from a progressive imbalance between tissue damage and the kidney's intrinsic repair and regeneration processes. In this study we evaluated the effect of kidney cells, delivered orthotopically by intraparenchymal injection to rodents 4-7 wk after CKD was established by two-step 5/6 renal mass reduction (NX), on the regeneration of kidney function and architecture as assessed by physiological, tissue, and molecular markers. A proof of concept for the model, cell delivery, and systemic effect was demonstrated with a heterogeneous population of renal cells (UNFX) that contained cells from all major compartments of the kidney. Tubular cells are known contributors to kidney regeneration in situ following acute injury. Initially tested as a control, a tubular cell-enriched subpopulation of UNFX (B2) surprisingly outperformed UNFX. Two independent studies (3 and 6 mo in duration) with B2 confirmed that B2 significantly extended survival and improved renal filtration (serum creatinine and blood urea nitrogen). The specificity of B2 effects was verified by direct comparison to cell-free vehicle controls and an equivalent dose of non-B2 cells. Quantitative histological evaluation of kidneys at 6 mo after treatment confirmed that B2 treatment reduced severity of kidney tissue pathology. Treatment-associated reduction of transforming growth factor (TGF)-β1, plasminogen activator inhibitor (PAI)-1, and fibronectin (FN) provided evidence that B2 cells attenuated canonical pathways of profibrotic extracellular matrix production.

Effects of Bupleurum falcatum and its combination with an angiotensin II receptor blocker on cytokine and chemokine expression in human mesangial cells

This study aimed to investigate the inhibitory effect of Bupleurum falcatum and its combination with angiotensin II receptor blocker (ARB) on cytokine and chemokine production in cultured human mesangial cells. Human mesangial cells were isolated and cultured in Dulbecco's modified Eagle's medium culture medium. Bupleurum falcatum, ARB, and the combination of the two were added to human mesangial cells. Cytokine and chemokine levels were analysed using an enzyme-linked immunosorbent assay. There were no significant differences in the expression of IL-1ss, IL-2 or TNF-a between controls and the experimental groups. However, IL-11 and monocyte chemoattractant protein-1 (MCP-1) levels were significantly reduced in response to ARB, Bupleurum falcatum, or their combination when compared with controls. IL-8 expression was reduced significantly only in cells treated with ARB. Both Bupleurum falcatum and ARB treatments alone reduced the cytokine concentration, but there was not a stronger reduction when the two drugs were combined. It was shown that Bupleurum falcatum inhibited cytokine production in human mesangial cells. However, there were no additive effects on the suppression of cytokine production when Bupleurum falcatum was combined with ARB. Further studies are needed to elucidate the renoprotective effects of Bupleurum falcatum.

The renin-angiotensin-aldosterone system in peritoneal dialysis: is what is good for the kidney also good for the peritoneum?

Morphological changes of the peritoneal membrane that occur over time among patients on peritoneal dialysis include fibrosis and neoangiogenesis. While the pathophysiologic mechanisms underlying these changes are not fully understood, the activation of the renin-angiotensin-aldosterone system (RAAS) may have an important role. Components of the RAAS are constitutively expressed within peritoneal mesothelial cells, and are upregulated in the presence of acute inflammation and chronic exposure to peritoneal dialysate. The high glucose concentration, low pH, and the presence of glucose degradation products in peritoneal dialysis solutions have all been implicated in modulation of peritoneal RAAS. Furthermore, activation of the RAAS, as well as the downstream production of transforming growth factor-beta, contributes to epithelial-to-mesenchymal transformation of mesothelial cells, resulting in progressive fibrosis of the peritoneal membrane. This process also leads to increased vascular endothelial growth factor production, which promotes peritoneal neoangiogenesis. Functionally, these changes translate into reduced ultrafiltration capacity of the peritoneal membrane, which is an important cause of technique failure among patients on long-term peritoneal dialysis. This brief review will describe our current state of knowledge about the role of peritoneal RAAS in peritoneal membrane damage and potential strategies to protect the membrane.

Culture-modified bone marrow cells attenuate cardiac and renal injury in a chronic kidney disease rat model via a novel antifibrotic mechanism

BACKGROUND

Most forms of chronic kidney disease are characterized by progressive renal and cardiac fibrosis leading to dysfunction. Preliminary evidence suggests that various bone marrow-derived cell populations have antifibrotic effects. In exploring the therapeutic potential of bone marrow derived cells in chronic cardio-renal disease, we examined the anti-fibrotic effects of bone marrow-derived culture modified cells (CMCs) and stromal cells (SCs).

METHODOLOGY/PRINCIPAL FINDINGS

In vitro, CMC-conditioned medium, but not SC-conditioned medium, inhibited fibroblast collagen production and cell signalling in response to transforming growth factor-beta. The antifibrotic effects of CMCs and SCs were then evaluated in the 5/6 nephrectomy model of chronic cardio-renal disease. While intravascular infusion of 10(6) SCs had no effect, 10(6) CMCs reduced renal fibrosis compared to saline in the glomeruli (glomerulosclerosis index: 0.8+/-0.1 v 1.9+/-0.2 arbitrary units) and the tubulointersitium (% area type IV collagen: 1.2+/-0.3 v 8.4+/-2.0, p<0.05 for both). Similarly, 10(6) CMCs reduced cardiac fibrosis compared to saline (% area stained with picrosirius red: 3.2+/-0.3 v 5.1+/-0.4, p<0.05), whereas 10(6) SCs had no effect. Structural changes induced by CMC therapy were accompanied by improved function, as reflected by reductions in plasma creatinine (58+/-3 v 81+/-11 micromol/L), urinary protein excretion (9x/divided by 1 v 64x/divided by 1 mg/day), and diastolic cardiac stiffness (left ventricular end-diastolic pressure-volume relationship: 0.030+/-0.003 v 0.058+/-0.011 mm Hg/microL, p<0.05 for all). Despite substantial improvements in structure and function, only rare CMCs were present in the kidney and heart, whereas abundant CMCs were detected in the liver and spleen.

CONCLUSIONS/SIGNIFICANCE

Together, these findings provide the first evidence suggesting that CMCs, but not SCs, exert a protective action in cardio-renal disease and that these effects may be mediated by the secretion of diffusible anti-fibrotic factor(s).

Protein kinase C-beta inhibition attenuates the progression of nephropathy in non-diabetic kidney disease

BACKGROUND

Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy where therapy targeting the beta isoform of this enzyme is in advanced clinical development. However, PKC-beta is also increased in various forms of human glomerulonephritis with several potentially nephrotoxic factors, other than high glucose, resulting in PKC-beta activation. Accordingly, we sought to examine the effects of PKC-beta inhibition in a non-diabetic model of progressive kidney disease.

METHODS

Subtotally nephrectomized (STNx) rats were randomly assigned to receive either the selective PKC-beta inhibitor, ruboxistaurin or vehicle. In addition to functional and structural parameters, gene expression of the podocyte slit-pore diaphragm protein, nephrin, was also assessed.

RESULTS

STNx animals developed hypertension, proteinuria and reduced glomerular filtration rate (GFR) in association with marked glomerulosclerosis and tubulointerstitial fibrosis. Glomerular nephrin expression was also reduced. Without affecting blood pressure, ruboxistaurin treatment attenuated the impairment in GFR and reduced the extent of both glomerulosclerosis and tubulointerstitial fibrosis in STNx rats. In contrast, neither proteinuria nor the reduction in nephrin expression was improved by ruboxistaurin.

CONCLUSIONS

These findings indicate firstly that PKC-beta inhibition may provide a new therapeutic strategy in non-diabetic kidney disease and secondly that improvement in GFR is not inextricably linked to reduction in proteinuria.

Fibrosis in diabetes complications: pathogenic mechanisms and circulating and urinary markers

Diabetes mellitus is characterized by a lack of insulin causing elevated blood glucose, often with associated insulin resistance. Over time, especially in genetically susceptible individuals, such chronic hyperglycemia can cause tissue injury. One pathological response to tissue injury is the development of fibrosis, which involves predominant extracellular matrix (ECM) accumulation. The main factors that regulate ECM in diabetes are thought to be pro-sclerotic cytokines and protease/anti-protease systems. This review will examine the key markers and regulators of tissue fibrosis in diabetes and whether their levels in biological fluids may have clinical utility.

Prevention of aortic fibrosis by N-acetyl-seryl-aspartyl-lysyl-proline in angiotensin II-induced hypertension

Fibrosis is an important component of large conduit artery disease in hypertension. The endogenous tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) has anti-inflammatory and antifibrotic effects in the heart and kidney. However, it is not known whether Ac-SDKP has an anti-inflammatory and antifibrotic effect on conduit arteries such as the aorta. We hypothesize that in ANG II-induced hypertension Ac-SDKP prevents aortic fibrosis and that this effect is associated with decreased protein kinase C (PKC) activation, leading to reduced oxidative stress and inflammation and a decrease in the profibrotic cytokine transforming growth factor-beta1 (TGF-beta1) and phosphorylation of its second messenger Smad2. To test this hypothesis we used rats with ANG II-induced hypertension and treated them with either vehicle or Ac-SDKP. In this hypertensive model we found an increased collagen deposition and collagen type I and III mRNA expression in the aorta. These changes were associated with increased PKC activation, oxidative stress, intercellular adhesion molecule (ICAM)-1 mRNA expression, and macrophage infiltration. TGF-beta1 expression and Smad2 phosphorylation also increased. Ac-SDKP prevented these effects without decreasing blood pressure or aortic hypertrophy. Ac-SDKP also enhanced expression of inhibitory Smad7. These data indicate that in ANG II-induced hypertension Ac-SDKP has an aortic antifibrotic effect. This effect may be due in part to inhibition of PKC activation, which in turn could reduce oxidative stress, ICAM-1 expression, and macrophage infiltration. Part of the effect of Ac-SDKP could also be due to reduced expression of the profibrotic cytokine TGF-beta1 and inhibition of Smad2 phosphorylation.

Pathological regression by angiotensin II type 1 receptor blockade in patients with mesangial proliferative glomerulonephritis

Although angiotensin II type 1 receptor blocker (ARB) therapy reduces proteinuria and retards the progression of renal injury in patients with glomerulonephritis, whether these drugs actually ameliorate pathological damages in human glomerulonephritis has not been determined. Fifteen patients with biopsy-proven mild-to-moderate mesangial proliferative glomerulonephritis (10 with immunoglobulin A [IgA] nephropathy and 5 with non-IgA mesangial proliferative glomerulonephritis) received ARB monotherapy. In these patients, repeated renal biopsy was performed after a mean of 28.1 months, and pathological changes (including the mesangial matrix expansion ratio and interstitial fibrosis expansion ratio) were quantitatively examined using an image analyzer. Clinical markers were also evaluated, including the serum creatinine, serum IgA, creatinine clearance (Ccr), 24-h urinary protein excretion, urinary N-acetyl-beta-D-glucosaminidase (NAG), and blood pressure. ARB therapy significantly reduced urinary protein excretion (0.68+/-0.63 to 0.20+/-0.32 g/day, p=0.016) and the blood pressure (systolic: 133.3+/-18.2 to 123.4+/-10.5 mmHg, p=0.041; diastolic: 79.4+/-11.9 to 72.0+/-8.2 mmHg, p=0.038). Although the global glomerular sclerosis ratio was unchanged (6.3+/-8.5% to 10.7+/-16.1%, p=0.33), the mesangial matrix expansion ratio (33.1+/-10.8% to 22.7+/-7.8%, p=0.001) and the interstitial fibrosis ratio (19.9+/-5.8% to 13.8+/-4.4%, p=0.034) were significantly reduced by ARB treatment. The levels of pathological improvement were similar between patients with IgA nephropathy and those with non-IgA mesangial proliferative glomerulonephritis. The results of the present study strongly suggest that ARB monotherapy can significantly reverse pathological changes, including mesangial matrix expansion and interstitial fibrosis, in human glomerulonephritis.