Obstructive nephropathy and renal fibrosis: The role of bone morphogenic protein-7 and hepatocyte growth factor

The roles of TRPC6 in renal tubular disorders: a narrative review

The transient receptor potential canonical 6 (TRPC6) channel, a nonselective cation channel that allows the passage of Ca2+, plays an important role in renal diseases. TRPC6 is activated by Ca2+ influx, oxidative stress, and mechanical stress. Studies have shown that in addition to glomerular diseases, TRPC6 can contribute to renal tubular disorders, such as acute kidney injury, renal interstitial fibrosis, and renal cell carcinoma (RCC). However, the tubule-specific physiological functions of TRPC6 have not yet been elucidated. Its pathophysiological role in ischemia/reperfusion (I/R) injury is debatable. Thus, TRPC6 may have dual roles in I/R injury. TRPC6 induces renal fibrosis and immune cell infiltration in a unilateral ureteral obstruction (UUO) mouse model. Additionally, TRPC6 overexpression may modify G2 phase transition, thus altering the DNA damage checkpoint, which can cause genomic instability and RCC tumorigenesis and can control the proliferation of RCC cells. This review highlights the importance of TRPC6 in various conditions of the renal tubular system. To better understand certain renal disorders and ultimately identify new therapeutic targets to improve patient care, the pathophysiology of TRPC6 must be clarified.

A single administration of FGF2 after renal ischemia-reperfusion injury alleviates post-injury interstitial fibrosis

BACKGROUND

Despite lack of clinical therapy in acute kidney injury (AKI) or its progression to chronic kidney disease (CKD), administration of growth factors shows great potential in the treatment of renal repair and further fibrosis. At an early phase of AKI, administration of exogenous fibroblast growth factor 2 (FGF2) protects against renal injury by inhibition of mitochondrial damage and inflammatory response. Here, we investigated whether this treatment attenuates the long-term renal interstitial fibrosis induced by ischemia-reperfusion (I/R) injury.

METHODS

Unilateral renal I/R with contralateral nephrectomy was utilized as an in vivo model for AKI and subsequent CKD. Rats were randomly divided into four groups: Sham-operation group, I/R group, I/R-FGF2 group and FGF2-3D group. These groups were monitored for up to 2 months. Serum creatinine, inflammatory response and renal histopathology changes were detected to evaluate the role of FGF2 in AKI and followed renal interstitial fibrosis. Moreover, the expression of vimentin, α-SMA, CD31 and CD34 were examined.

RESULTS

Two months after I/R injury, the severity of renal interstitial fibrosis was significantly attenuated in both of I/R-FGF2 group and FGF2-3D group, compared with the I/R group. The protective effects of FGF2 administration were associated with the reduction of high-mobility group box 1 (HMGB1)-mediated inflammatory response, the inhibition of transforming growth factor beta (TGF-β1)/Smads signaling-induced epithelial-mesenchymal transition and the maintenance of peritubular capillary structure.

CONCLUSIONS

A single dose of exogenous FGF2 administration 1 h or 3 days after reperfusion inhibited renal fibrogenesis and thus blocked the transition of AKI to CKD. Our findings provided novel insight into the role of FGF signaling in AKI-to-CKD progression and underscored the potential of FGF-based therapy for this devastating disease.

Recurrent nephrolithiasis and loss of kidney function: a cohort study

PURPOSE

To evaluate whether symptomatic recurrent nephrolithiasis leads to loss of kidney function.

METHODS

Adults who presented to the Emergency Department at least twice with symptomatic and radiologically confirmed nephrolithiasis were retrospectively recruited. Primary endpoint was the change in glomerular filtration rate (GFR) between baseline and at the time of data collection. Secondary endpoints include GFR slope defined as the mean rate of change in GFR from baseline to the end of the study period.

RESULTS

240 patients had recurrent symptomatic nephrolithiasis. Median follow-up was 5.4 years. The median age of first acute presentation was 51.6 years and the median baseline serum creatinine (bsCr) was 85.5 umol/l. 17.5% (n = 42) had worsening GFR, with the average change in GFR of - 8.64 ml/min/1.73 m² per year. Four patients progressed to ESKD requiring haemodialysis. 14.5% (n = 35) had calcium oxalate stones. Univariate analysis showed older patients (p < 0.001), more symptomatic stone episodes (p < 0.001) and non-calcium-containing stones (p < 0.001) were strongly associated with deteriorating kidney function. Age (p = 0.002) and number of acute stone episodes (p = 0.011) were significant predictive factors when unadjusted to co-morbidities. Age (p = 0.018) was the only predictive factor of worsening GFR when adjusted for co-morbidities. Average mean GFR slope was - 2.83/min/1.73 m² per year.

CONCLUSIONS

Recurrent symptomatic nephrolithiasis is associated with loss of kidney function, in older patients, increased episodes of symptomatic nephrolithiasis and non-calcium-containing stones. Age is the only predictive factor for progression to chronic kidney disease in this subgroup.

Overexpression of miR-19a and miR-20a in iPS-MSCs preserves renal function of chronic kidney disease with acute ischaemia-reperfusion injury in rat

This study tested the hypothesis that therapy with double overexpression of miR‐19a‐3p and miR‐20a‐5p (miR^DOE) to human inducible pluripotent stem cell–derived mesenchymal stem cells (iPS‐MSCs) was superior to iPS‐MSCs alone for preserving renal function in rat with pre‐existing chronic kidney disease (CKD), followed by ischaemia‐reperfusion (IR) injury. In vitro study demonstrated that the protein expressions of oxidative stress (NOX‐1/NOX‐2/NOX4/oxidized protein/p22phox), inflammatory downstream signalling (TLR2&4/MyD88/TRAF6/IKK‐ß/p‐NFκB/IL‐1ß/IL‐6/MMP‐9) and cell apoptosis/death signalling (cleaved caspase‐3/mitochondrial Bax/p‐ERKs/p‐JNK/p‐p38) at time‐points of 24‐hour/48‐hour cell cultures were significantly increased in p‐Cresol‐treated NRK‐52E cells than in the control that was significantly reversed by miR‐19a‐3p‐transfected iPS‐MSC (all P < .001). Animals were categorized into group 1 (sham‐operated control), group 2 (CKD‐IR), group 3 (CKD‐IR + oligo‐miR^DOE of iPS‐MSCs/6.0 ×10⁵/intra‐renal artery transfusion/3 hours after IR procedure), group 4 (CKD‐IR + iPS‐MSCs) and group 5 (CKD‐IR + miR^DOE of iPS‐MSCs/6.0 ×10^5/intra‐renal artery transfusion/3 hour after IR procedure). By day 35, the creatinine/BUN levels were lowest in group 1, highest in group 2 and significantly lower in group 5 than in groups 3 and 4 (all P < .0001) but they showed no difference between the latter two groups. The protein expressions of oxidative stress, inflammatory downstream signalling and cell apoptosis/death signalling exhibited an identical pattern of creatinine level among the five groups (all P < .00001). Also, the microscopic findings demonstrated that the kidney injury score/fibrotic area/number of inflammatory cells (CD14+/CD68+) exhibited an identical pattern of creatine level (all P < .0001). The miR^DOE of iPS‐MSCs was superior to iPS‐MSCs for preserving the residual kidney function and architecture in CKD‐IR rat.

Transient Receptor Potential Channel 6 Knockout Ameliorates Kidney Fibrosis by Inhibition of Epithelial-Mesenchymal Transition

Kidney fibrosis is generally confirmed to have a significant role in chronic kidney disease, resulting in end-stage kidney failure. Epithelial–mesenchymal transition (EMT) is an important molecular mechanism contributing to fibrosis. Tubular epithelial cells (TEC), the major component of kidney parenchyma, are vulnerable to different types of injuries and are a significant source of myofibroblast by EMT. Furthermore, TRPC6 knockout plays an anti-fibrotic role in ameliorating kidney damage. However, the relationship between TRPC6 and EMT is unknown. In this study, TRPC6^−/− and wild-type (WT) mice were subjected to a unilateral ureteric obstruction (UUO) operation. Primary TEC were treated with TGF-β1. Western blot and immunofluorescence data showed that fibrotic injuries alleviated with the inhibition of EMT in TRPC6^−/− mice compared to WT mice. The activation of AKT-mTOR and ERK1/2 pathways was down-regulated in the TRPC6^−/− mice, while the loss of Na⁺/K⁺-ATPase and APQ1 was partially recovered. We conclude that TRPC6 knockout may ameliorate kidney fibrosis by inhibition of EMT through down-regulating the AKT-mTOR and ERK1/2 pathways. This could contribute to the development of effective therapeutic strategies on chronic kidney diseases.

IRF-1 promotes renal fibrosis by downregulation of Klotho

Although the key role of renal fibrosis in the progression of chronic kidney disease (CKD) is well known, the causes of renal fibrosis are not fully clarified. In this study, interferon regulatory factor 1 (IRF-1), a mammalian transcription factor, was highly expressed in fibrotic kidney of CKD patients. Concordantly, the expression level of IRF-1 was significantly elevated in the kidney of unilateral ureteral obstruction (UUO) and Adriamycin nephropathy (ADR) mice. In tubular epithelial cells, overexpression of IRF-1 could induce profibrotic markers expression, which accompanied by dramatic downregulation of Klotho, an important inhibitor of renal fibrosis. Luciferase reporter analysis and ChIP assay revealed that IRF-1 repressed Klotho expression by downregulation of C/EBP-β, which regulates Klotho gene transcription via directly binding to its promoter. Further investigation showed that tumor necrosis factor-alpha may be an important inducement for the increase of IRF-1 in tubular epithelial cells after UUO and genetic deletion of IRF-1 attenuated renal fibrosis in UUO mice. Hence, these findings demonstrate that IRF-1 contributes to the pathogenesis of renal fibrosis by downregulation of Klotho, and suppresses IRF-1 may be a potential therapeutic target for CKD.

MiR-802 causes nephropathy by suppressing NF-κB-repressing factor in obese mice and human

Obesity is associated with significant microvascular complications including renal injuries and may induce end-stage renal disease. Emerging studies have demonstrated microRNAs (miRNAs) are potential mediators in the pathophysiological process of nephropathy. The present study aimed to investigate the role of miR-802 in obesity-related nephropathy and potential molecular mechanisms. Through utilizing obese mouse model and human subjects, we explored the therapeutic benefits and clinical application of miR-802 in protecting against nephropathy. Renal miR-802 level was positively correlated with functional parameters, including blood urea nitrogen and creatinine in obese mice. Specific silencing of renal miR-802 improved high fat diet (HFD)-induced renal dysfunction, structural disorders and fibrosis. The up-regulated inflammatory response and infiltrated macrophages were also significantly decreased in miR-802 inhibitor-treated obese mice. Mechanistically, miR-802 directly bond to 3'-UTR of NF-κB-repressing factor (NRF) and suppressed its expression. In clinical study, the circulating miR-802 level was significantly increased in obese subjects, and positively correlated with plasma creatinine level but negatively correlated with creatinine clearance. Taken together, our findings provided evidence that miR-802/NRF signalling was an important pathway in mediating obesity-related nephropathy. It is a possible useful clinical approach of treating miR-802 inhibitor to combat nephropathy.

Febuxostat inhibits TGF‑β1‑induced epithelial‑mesenchymal transition via downregulation of USAG‑1 expression in Madin‑Darby canine kidney cells in vitro

Our previous study demonstrated that febuxostat, a xanthine oxidase inhibitor, can alleviate kidney dysfunction and ameliorate renal tubulointerstitial fibrosis in a rat unilateral ureteral obstruction (UUO) model; however, the underlying mechanisms remain unknown. Increasing evidence has revealed that epithelial-mesenchymal transition (EMT) is one of the key mechanisms mediating the progression of renal tubulointerstitial fibrosis in chronic kidney disease (CKD). Uterine sensitization-associated gene-1 (USAG-1), a kidney-specific bone morphogenetic protein antagonist, is involved in the development of numerous types of CKDs. The present study aimed to investigate the role of febuxostat in the process of EMT in Madin-Darby canine kidney (MDCK) cells in vitro. Western blotting, reverse transcription-semiquantitative polymerase chain reaction analysis and immunofluorescence staining were used to evaluate the expression levels of bone morphogenetic protein 7, USAG-1, α-smooth muscle actin (α-SMA) and E-cadherin, respectively. The results demonstrated that the expression of USAG-1 and α-SMA increased, and that of E-cadherin decreased significantly in MDCK cells following treatment with transforming growth factor-β1 (TGF-β1). The application of small interfering RNA-USAG-1 potently inhibited TGF-β1-induced EMT. Subsequently, the effects of febuxostat on TGF-β1-induced EMT was investigated. The results demonstrated that febuxostat downregulated the expression of USAG-1, and reversed TGF-β1-induced EMT in MDCK cells. Furthermore, pretreatment with febuxostat significantly restored the decreased expression levels of phosphorylated Smad1/5/8 induced by TGF-β1 in MDCK cells. The results of the present study suggested that USAG-1 may be involved in the EMT process of MDCK cells induced by TGF-β1, and febuxostat inhibited EMT by activating the Smad1/5/8 signaling pathway via downregulating the expression of USAG-1 in MDCK cells.

HL156A, a novel pharmacological agent with potent adenosine-monophosphate-activated protein kinase (AMPK) activator activity ameliorates renal fibrosis in a rat unilateral ureteral obstruction model

Background

Renal fibrosis is characterized by excessive production and deposition of extracellular matrix (ECM), which leads to progressive renal failure. Adenosine-monophosphate-activated protein kinase (AMPK) is a highly conserved kinase that plays a key role in Smad-3 signaling. Here, we examined the effect of a novel AMPK activator, HL156A, on the inhibition of renal fibrosis in in vivo and in vitro models.

Methods

Unilateral ureteral obstruction (UUO) was induced in male Wistar rats. Rats with UUO were administered HL156A (20mg/kg/day), and then the kidneys were harvested 10 days after ligation for further analysis.

Results

In the rat UUO model, HL156A attenuated ECM protein deposition. After HL156A treatment, expressions of TGF-β1, p-Smad3, α-SMA, fibronectin, and type IV collagen were suppressed, and E-cadherin expression was up-regulated. In the in vitro experiment, NRK52E cells were treated with HL156A before TGF-β1 stimulation. The inhibitory effects of HL156A upon the signaling pathways and markers of the epithelial-to-mesenchymal transition (EMT) were analyzed. In TGF-β1-treated NRK-52E cells, HL156A co-treatment inhibited the TGF-β1-induced Smad3 signaling pathway and EMT markers.

Conclusion

Taken together, the above findings suggest that HL156A, a novel AMPK activator, ameliorates renal fibrosis in vivo and in vitro.

Novel Combination BMP7 and HGF Gene Therapy Instigates Selective Myofibroblast Apoptosis and Reduces Corneal Haze In Vivo

Purpose

We tested the potential of bone morphogenic protein 7 (BMP7) and hepatocyte growth factor (HGF) combination gene therapy to treat preformed corneal fibrosis using established rabbit in vivo and human in vitro models.

Methods

Eighteen New Zealand White rabbits were used. Corneal fibrosis was produced by alkali injury. Twenty-four hours after scar formation, cornea received topically either balanced salt solution (BSS; n = 6), polyethylenimine-conjugated gold nanoparticle (PEI2-GNP)-naked plasmid (n = 6) or PEI2-GNP plasmids expressing BMP7 and HGF genes (n = 6). Donor human corneas were used to obtain primary human corneal fibroblasts and myofibroblasts for mechanistic studies. Gene therapy effects on corneal fibrosis and ocular safety were evaluated by slit-lamp microscope, stereo microscopes, quantitative real-time PCR, immunofluorescence, TUNEL, modified MacDonald-Shadduck scoring system, and Draize tests.

Results

PEI2-GNP–mediated BMP7+HGF gene therapy significantly decreased corneal fibrosis in live rabbits in vivo (Fantes scale was 0.6 in BMP7+HGF-treated eyes compared to 3.3 in −therapy group; P < 0.001). Corneas that received BMP7+HGF demonstrated significantly reduced mRNA levels of profibrotic genes: α-SMA (3.2-fold; P < 0.01), fibronectin (2.3-fold, P < 0.01), collagen I (2.1-fold, P < 0.01), collagen III (1.6-fold, P < 0.01), and collagen IV (1.9-fold, P < 0.01) compared to the −therapy corneas. Furthermore, BMP7+HGF-treated corneas showed significantly fewer myofibroblasts compared to the −therapy controls (83%; P < 0.001). The PEI2-GNP introduced >10⁴ gene copies per microgram DNA of BMP7 and HGF genes. The recombinant HGF rendered apoptosis in corneal myofibroblasts but not in fibroblasts. Localized topical BMP7+HGF therapy showed no ocular toxicity.

Conclusions

Localized topical BMP7+HGF gene therapy treats corneal fibrosis and restores transparency in vivo mitigating excessive healing and rendering selective apoptosis in myofibroblasts.

Bone Morphogenetic Protein-Based Therapeutic Approaches

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the transforming growth factor (TGF)-β family of ligands and exert most of their effects through the canonical effectors Smad1, 5, and 8. Appropriate regulation of BMP signaling is critical for the development and homeostasis of numerous human organ systems. Aberrations in BMP pathways or their regulation are increasingly associated with diverse human pathologies, and there is an urgent and growing need to develop effective approaches to modulate BMP signaling in the clinic. In this review, we provide a wide perspective on diseases and/or conditions associated with dysregulated BMP signal transduction, outline the current strategies available to modulate BMP pathways, highlight emerging second-generation technologies, and postulate prospective avenues for future investigation.

Uric acid stones increase the risk of chronic kidney disease

The aim of this study was to compare the clinical characteristics of uric acid stones and their potential risk for chronic kidney disease (CKD). A total of 401 patients (196 with uric acid stone and 205 without) were enrolled from our database of patients with urolithiasis. We analyzed the clinical demographic features, stone location, urine chemistries, and renal function. There was a significant difference (p < 0.001) between the two groups in terms of age, with the higher mean age in the uric acid group. Patients with uric acid stones had much lower pH of urine (p < 0.001) and higher serum uric acid level (p = 0.002). Notably, those with uric acid stones had worse eGFR than those with non-uric acid stones. Multivariate analysis confirmed that age over 60 years (ORs = 9.19; 95% CI 3.5-24.3), female sex (ORs = 4.01; 95% CI 1.8-9.0), hyperuricemia (ORs = 8.47; 95% CI 1.6-43.5), and uric acid stone (OR = 2.86; 95% CI 1.2-6.7) were the independent predictors of poor prognoses in CKD. Therefore, an association exists between uric acid stones and higher prevalence of CKD. Patients with uric acid stones may need close monitoring of renal function during follow-up.

Investigated the safety of intra-renal arterial transfusion of autologous CD34+ cells and time courses of creatinine levels, endothelial dysfunction biomarkers and micro-RNAs in chronic kidney disease patients-phase I clinical trial

This was a phase I clinical trial to investigate the safety of autologous peripheral-blood-derived CD34+ cell therapy for patients with chronic kidney disease (CKD-treatment) (i.e., at Stages III and IV). Between November 2014 and October 2015, a total of 10 study patients were prospectively enrolled into this phase I trial. Patients who failed to enroll into the trial in the initial state of eligibility assessment were served as CKD-control group (n = 9). The health-control group was composed of 10 volunteers for the purposes of comparing (1) circulation level of endothelial progenitor cells (EPCs), (2) angiogenesis ability, and (3) anti-apoptotic miRNAs between healthy subjects and CKD patients. CD34+ cells (5.0 x 107) were transfused into right-renal artery after subcutaneous G-CSF injection (5μg/kg/twice a day for 4 days). Circulating EPC number, angiogenesis capacity (i.e., Matrigel assay) and anti-apoptotic miRNAs (miR-374a-5p/miR-19a-3p/ miR-106b-5p/miR-26b-5p/ miR-20a-5p) were significantly lower in CKD patients than in healthy subjects (all p < 0.001). Flow-cytometric analysis of renal-vein blood samplings (i.e., at 0/5/10/30 mins after cell transfusion) showed the EPC level was significantly progressively increased (p < 0.001). Procedural safety was 100% with all patients uneventfully discharged and one-year survival rate was 100%. The paired-t test showed serum creatinine maintained the same level between the baseline and at the end of one-year follow-up (all p > 0.4), whereas the net increase between initial and final creatinine level was higher in CKD-control than in CKD-treatment. In conclusion, CD34+ cell therapy was safe and maintained the renal function in stationary state at the end of study period.

Protective Role of Melatonin and Coenzyme Q10 in Ochratoxin A Toxicity in Rat Liver and Kidney

Melatonin (MEL) and coenzyme Q10 (CoQ10) both display antioxidant and free radical scavenger properties. In the present study, the effect of MEL and CoQ10 on the oxidative stress and fibrosis induced by ochratoxin A (OTA) administration in rats was investigated. Rats were divided into five equal groups, each consisting of seven rats: (1) controls; (2) OTA-treated rats (289 μg/kg/day); (3) OTA+MEL–treated rats (289 μg/kg/day OTA + 10 mg/kg/day MEL); and (4) OTA+CoQ10–treated rats (289 μg/kg/day OTA +1 mg/100 g/day body weight (bw) CoQ10). After 4 weeks of treatment, the level of malondialdehyde (MDA), glutathione peroxidase (GPx), and hydroxyproline (Hyp) were measured in the homogenates of liver and kidney. In the OTA-treated group, the levels of MDA and Hyp in both liver and kidney were significantly increased when compared with the levels of control, whereas GPx activities decreased. In OTA+MEL–treated rats, the levels of MDA and Hyp in both liver and kidney were significantly decreased when compared with the levels of OTA-treated rats; however; GPX activities increased. In the OTA+CoQ10–treated group, the levels of MDA and Hyp were decreased when compared with the levels of OTA-treated rats, whereas GPx activities increased. In the OTA+CoQ 10–treated group, the levels of MDA, Hyp, and GPx were not significantly changed in kidney when compared with OTA-treated group. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and fibrosis both liver and kidney. Although CoQ10 has protective effect against OTA toxicity in liver tissue, it has no effect in kidney tissue.

Alpha-lipoic acid ameliorates the epithelial mesenchymal transition induced by unilateral ureteral obstruction in mice

The epithelial-to-mesenchymal transition (EMT) is one of mechanisms that induce renal interstitial fibrosis. Understanding EMT in renal fibrosis has important therapeutic implications for patients with kidney disease. Alpha-lipoic acid (ALA) is a natural compound with antioxidant properties. Studies for ALA are performed in acute kidney injury with renal tubular apoptosis, renal inflammation, and oxidative stress. We investigated the effects of ALA on EMT-mediated renal interstitial fibrosis in mice with unilateral ureteral obstruction (UUO). UUO mice developed severe tubular atrophy and tubulointerstitial fibrosis, with a robust EMT response and ECM deposition after 7 postoperative days. In contrast, ALA-treated UUO mice showed only moderate injury and minimal fibrosis and also larger reductions in the expression of ECM proteins, inflammatory factors, and EMT markers. ALA was shown to be involved in the suppression of infiltrating macrophages associated with EMT and the progression of interstitial fibrosis. It also lessened the destruction of the tubular basement membrane, by reducing the expression of matrix metalloproteinases. This is the first study to show that ALA modulates EMT in a UUO mouse model. Our results suggest that ALA merits further exploration as a therapeutic agent in the prevention and treatment of chronic kidney disease.

TIMAP repression by TGFβ and HDAC3-associated Smad signaling regulates macrophage M2 phenotypic phagocytosis

TIMAP (TGFβ-inhibited membrane-associated protein) is an endothelium-enriched TGFβ downstream protein and structurally belongs to the targeting subunit of myosin phosphatase; however, the mechanism of TGFβ repressing TIMAP and its functional relevance to TGFβ bioactivity remain largely unknown. Here, we report that TIMAP is reduced in TGFβ-elevated mouse fibrotic kidney and highly expressed in macrophages. TGFβ repression of TIMAP is associated with HDAC3 upregulation and its recruitment by Smad2/3 at the Smad binding element on TIMAP promoter, whereas specific HDAC3 inhibition reversed the TIMAP repression, suggesting that TGFβ transcriptionally downregulates TIMAP through HDAC3-associated Smad signaling. Further investigation showed that TIMAP over-expression interrupted TGFβ-associated Smad signaling and TIMAP repression by TGFβ correlated with TGFβ-induced macrophage M2 polarization markers, migration, and phagocytosis-the processes promoted by phosphorylation of the putative TIMAP substrate myosin light chain (MLC). Consistently, TIMAP dephosphorylated MLC in macrophages and TGFβ induced macrophage migration and phagocytosis in TIMAP- and MLC phosphorylation-dependent manners, suggesting that TIMAP dephosphorylation of MLC constitutes an essential regulatory loop mitigating TGFβ-associated macrophage M2 phenotypic activities. Given that hyperactive TGFβ often causes excessive macrophage phagocytic activities potentially leading to various chronic disorders, the strategies targeting HDAC3/TIMAP axis might improve TGFβ-associated pathological processes.

KEY MESSAGE

TIMAP is enriched in the endothelium and highly expressed in macrophages. TIMAP is suppressed by TGFβ via HDAC3-associated Smad signaling. TIMAP inhibits TGFβ signaling and TGFβ-associated macrophage M2 polarization. TIMAP dephosphorylation of MLC counteracts TGFβ-induced macrophage phagocytosis.

Expression of intronic miRNAs and their host gene Igf2 in a murine unilateral ureteral obstruction model

The objective of this study was to determine the expression of miR-483 and miR-483* and the relationship among them, their host gene (Igf2), and other cytokines in a murine model of renal fibrosis. The extent of renal fibrosis was visualized using Masson staining, and fibrosis was scored 3 days and 1 and 2 weeks after unilateral ureteral obstruction (UUO). Expression of miR-483, miR-483* and various cytokine mRNAs was detected by real-time polymerase chain reaction (PCR). Expression of miR-483 and miR-483* was significantly upregulated in the UUO model, particularly miR-483 expression was the greatest 2 weeks after surgery. Additionally, miR-483 and miR-483* expression negatively correlated with Bmp7 expression and positively correlated with Igf2, Tgfβ, Hgf, and Ctgf expression, as determined by Pearson's correlation analysis. Hgf expression significantly increased at 1 and 2 weeks after the surgery compared to the control group. This study showed that miR-483 and miR-483* expression was upregulated in a murine UUO model. These data suggest that miR-483 and miR-483* play a role in renal fibrosis and that miR-483* may interact with miR-483 in renal fibrosis. Thus, these miRNAs may play a role in the pathogenesis of renal fibrosis and coexpression of their host gene Igf2.

What is the best way to measure renal fibrosis?: A pathologist's perspective

Interstitial fibrosis is a hallmark structural correlate of progressive and chronic kidney disease. There remain many uncertainties about how to best measure interstitial fibrosis both in research settings and in evaluations of renal biopsies performed for management of individual patients. Areas of uncertainty include determination of the composition of the matrix in a fibrotic parenchyma, the definition of how the interstitium is involved by fibrosing injuries, the choice of histologic stains for evaluation of renal fibrosis, and the reproducibility and robustness of measures currently employed by pathologists, both with and without the assistance of computerized imaging and assessments. In this review, we address some of these issues while citing the key studies that illustrate these difficulties. We point to future approaches that may allow a more accurate and meaningful assessment of renal interstitial fibrosis.

Rotenone remarkably attenuates oxidative stress, inflammation, and fibrosis in chronic obstructive uropathy

Mitochondrial abnormality has been shown in many kidney disease models. However, its role in the pathogenesis of chronic kidney diseases (CKDs) is still uncertain. In present study, a mitochondrial complex I inhibitor rotenone was applied to the mice subjected to unilateral ureteral obstruction (UUO). Following 7-days rotenone treatment, a remarkable attenuation of tubular injury was detected by PAS staining. In line with the improvement of kidney morphology, rotenone remarkably blunted fibrotic response as shown by downregulation of fibronectin (FN), plasminogen activator inhibitor-1 (PAI-1), collagen I, collagen III, and α-SMA, paralleled with a substantial decrease of TGF-β₁. Meanwhile, the oxidative stress markers thiobarbituric acid-reactive substances (TBARS) and heme oxygenase 1 (HO-1) and inflammatory markers TNF-α, IL-1β, and ICAM-1 were markedly decreased. More importantly, the reduction of mitochondrial DNA copy number and mitochondrial NADH dehydrogenase subunit 1 (mtND1) expression in obstructed kidneys was moderately but significantly restored by rotenone, suggesting an amelioration of mitochondrial injury. Collectively, mitochondrial complex I inhibitor rotenone protected kidneys against obstructive injury possibly via inhibition of mitochondrial oxidative stress, inflammation, and fibrosis, suggesting an important role of mitochondrial dysfunction in the pathogenesis of obstructive kidney disease.

BMP-7 represses albumin-induced chemokine synthesis in kidney tubular epithelial cells through destabilization of NF-κB-inducing kinase

Protein overload activates proximal tubule epithelial cells (PTECs) to release chemokines. Bone morphogenetic protein-7 (BMP-7) reduces infiltrating cells and tissue damage in acute and chronic renal injuries. The present study examines the inhibitory effect and related molecular mechanism of BMP-7 on chemokine and adhesion molecule synthesis by PTECs activated with human serum albumin (HSA). The expression profiles of chemokines and adhesion molecules in cultured human PTECs were screened by PCR array. Expression of CXCL1, CXCL2 and vascular cell adhesion protein 1 (VCAM-1) by PTECs was significantly upregulated by HSA and reduced by BMP-7. HSA activated both the canonical and noncanonical nuclear factor (NF)-κB pathways in PTECs, as indicated by the increased nuclear translocation of NF-κB p50 and p52 subunits. The nuclear translocation of NF-κB p52 was completely abrogated by BMP-7, whereas NF-κB p50 activation was only partially repressed. BMP-7 increased the expression of cellular inhibitor of apoptosis 1 (cIAP1), tumor necrosis factor receptor-associated factor (TRAF)2 and TRAF3, but not of NF-κB-inducing kinase (NIK) that was significantly upregulated by HSA. Silencing NIK recapitulated the partial inhibitory effect on HSA-induced chemokine synthesis by BMP-7. Complete abolishment of the chemokine synthesis was only achieved by including additional blockade of the NF-κB p65 translocation on top of NIK silencing. Our data suggest that BMP-7 represses the NIK-dependent chemokine synthesis in PTECs activated with HSA through blocking the noncanonical NF-κB pathway and partially interfering with the canonical NF-κB pathway.

Nephrolithiasis and loss of kidney function

PURPOSE OF REVIEW

The prevalence of nephrolithiasis has been on the rise over recent decades. There have also been extensive efforts to identify risk factors for chronic kidney disease (CKD). The purpose of this review is to highlight recent evidence on the association of nephrolithiasis with the development of CKD and end-stage renal disease (ESRD).

RECENT FINDINGS

Several epidemiologic studies over the past decade assessed the relationship between history of nephrolithiasis and CKD. Across several studies, patients with nephrolithiasis had about a two-fold higher risk for decreased renal function or need for renal replacement therapy. This risk appears to be independent of risk factors for CKD that are common in stone formers such as hypertension and diabetes mellitus. Specific risk factors for CKD in stone formers include recurrent urinary tract infections, struvite and possibly uric acid stone composition, symptomatic stones, solitary kidney, ileal conduit, neurogenic bladder, and hydronephrosis.

SUMMARY

Recent evidence has shown a consistent relationship between nephrolithiasis history and an increased risk of CKD and ESRD. Understanding the characteristics that predispose to CKD may better inform how to optimally manage patients with nephrolithiasis and prevent this complication.

Induced autologous stem cell transplantation for treatment of rabbit renal interstitial fibrosis

Introduction

Renal interstitial fibrosis (RIF) is a significant cause of end-stage renal failure. The goal of this study was to characterize the distribution of transplanted induced autologous stem cells in a rabbit model of renal interstitial fibrosis and evaluate its therapeutic efficacy for treatment of renal interstitial fibrosis.

Methods

A rabbit model of renal interstitial fibrosis was established. Autologous fibroblasts were cultured, induced and labeled with green fluorescent protein (GFP). These labeled stem cells were transplanted into the renal artery of model animals at 8 weeks.

Results

Eight weeks following transplantation of induced autologous stem cells, significant reductions (P < 0.05) were observed in serum creatinine (SCr) (14.8 ± 1.9 mmol/L to 10.1 ± 2.1 mmol/L) and blood urea nitrogen (BUN) (119 ± 22 µmol/L to 97 ± 13 µmol/L), indicating improvement in renal function.

Conclusions

We successfully established a rabbit model of renal interstitial fibrosis and demonstrated that transplantation of induced autologous stem cells can repair kidney damage within 8 weeks. The repair occurred by both inhibition of further development of renal interstitial fibrosis and partial reversal of pre-existing renal interstitial fibrosis. These beneficial effects lead to the development of normal tissue structure and improved renal function.

ALK1-Smad1/5 signaling pathway in fibrosis development: friend or foe?

Fibrosis is a common phenomenon associated with several pathologies, characterized by an excessive extracellular matrix deposition that leads to a progressive organ dysfunction. Thus fibrosis has a relevant role in chronic diseases affecting the kidney, the liver, lung, skin (scleroderma) and joints (arthritis), among others. The pathogenesis of fibrosis in different organs share numerous similarities, being one of them the presence of activated fibroblasts, denominated myofibroblast, which act as the main source of extracellular matrix proteins. Transforming growth factor beta-1 (TGF-β1) is a profibrotic cytokine that plays a pivotal role in fibrosis. The TGF-β1/ALK5/Smad3 signaling pathway has been studied in fibrosis extensively. However, an increasing number of studies involving the ALK1/Smad1 pathway in the fibrotic process exist. In this review we offer a perspective of the function of ALK1/Smad1 pathway in renal fibrosis, liver fibrosis, scleroderma and osteoarthritis, suggesting this pathway as a powerful therapeutical target. We also propose several strategies to modulate the activity of this pathway and its consequences in the fibrotic process.

Excessive urinary tract dilatation and proteinuria in pregnancy: a common and overlooked association?

BACKGROUND

Proteinuria and dilatation of the urinary tract are both relatively common in pregnancy, the latter with a spectrum of symptoms, from none to severe pain and infection. Proteinuria is a rare occurrence in acute obstructive nephropathy; it has been reported in pregnancy, where it may pose a challenging differential diagnosis with pre-eclampsia.The aim of the present study is to report on the incidence of proteinuria (≥ 0.3; ≥ 0.5 g/day) in association with symptomatic-severe urinary tract dilatation in pregnancy.

METHODS

Case series.

SETTING

Nephrological-Obstetric Unit dedicated to pregnancy and kidney diseases (January 2000-April 2011).

SOURCE

database prospectively updated since the start of the Unit. Retrospective review of clinical charts identified as relevant on the database, by a nephrologist and an obstetrician.

RESULTS

From January 2000 to April 2011, 262 pregnancies were referred. Urinary tract dilatation with or without infection was the main cause of referral in 26 cases (predominantly monolateral in 19 cases): 23 singletons, 1 lost to follow-up, 1 twin and 1 triplet. Patients were referred for urinary tract infection (15 cases) and/or renal pain (10 cases); 6 patients were treated by urologic interventions ("JJ" stenting). Among them, 11 singletons and 1 triple pregnancy developed proteinuria ≥ 0.3 g/day (46.1%). Proteinuria was ≥ 0.5 g/day in 6 singletons (23.1%). Proteinuria resolved after delivery in all cases. No patient developed hypertension; in none was an alternative cause of proteinuria evident. No significant demographic difference was observed in patients with renal dilatation who developed proteinuria versus those who did not. An association with the presence of "JJ" stenting was present (5/6 cases with proteinuria ≥ 0.5 g/day), which may reflect both severer obstruction and a role for vescico-ureteral reflux, induced by the stent.

CONCLUSIONS

Symptomatic urinary tract dilatation may be associated with proteinuria in pregnancy. This association should be kept in mind in the differential diagnosis with other causes of proteinuria in pregnancy, including pre-eclampsia.

Role of the TGF-β/BMP-7/Smad pathways in renal diseases

TGF-β (transforming growth factor-β) and BMP-7 (bone morphogenetic protein-7), two key members in the TGF-β superfamily, play important but diverse roles in CKDs (chronic kidney diseases). Both TGF-β and BMP-7 share similar downstream Smad signalling pathways, but counter-regulate each other to maintain the balance of their biological activities. During renal injury in CKDs, this balance is significantly altered because TGF-β signalling is up-regulated by inducing TGF-β1 and activating Smad3, whereas BMP-7 and its downstream Smad1/5/8 are down-regulated. In the context of renal fibrosis, Smad3 is pathogenic, whereas Smad2 and Smad7 are renoprotective. However, this counter-balancing mechanism is also altered because TGF-β1 induces Smurf2, a ubiquitin E3-ligase, to target Smad7 as well as Smad2 for degradation. Thus overexpression of renal Smad7 restores the balance of TGF-β/Smad signalling and has therapeutic effect on CKDs. Recent studies also found that Smad3 mediated renal fibrosis by up-regulating miR-21 (where miR represents microRNA) and miR-192, but down-regulating miR-29 and miR-200 families. Therefore restoring miR-29/miR-200 or suppressing miR-21/miR-192 is able to treat progressive renal fibrosis. Furthermore, activation of TGF-β/Smad signalling inhibits renal BMP-7 expression and BMP/Smad signalling. On the other hand, overexpression of renal BMP-7 is capable of inhibiting TGF-β/Smad3 signalling and protects the kidney from TGF-β-mediated renal injury. This counter-regulation not only expands our understanding of the causes of renal injury, but also suggests the therapeutic potential by targeting TGF-β/Smad signalling or restoring BMP-7 in CKDs. Taken together, the current understanding of the distinct roles and mechanisms of TGF-β and BMP-7 in CKDs implies that targeting the TGF-β/Smad pathway or restoring BMP-7 signalling may represent novel and effective therapies for CKDs.

α2-Adrenoceptor agonist dexmedetomidine protects septic acute kidney injury through increasing BMP-7 and inhibiting HDAC2 and HDAC5

Bone morphogenetic protein (BMP)-7 protects sepsis-induced acute kidney injury (AKI). Dexmedetomidine (DEX), an α2-adrenoceptor (α2-AR) agonist, has anti-inflammatory effects. We investigated the protective effects of DEX on sepsis-induced AKI and the expression of BMP-7 and histone deacetylases (HDACs). In vitro , the effects of DEX or trichostatin A (TSA, an HDAC inhibitor) on TNF-α, monocyte chemotactic protein (MCP-1), BMP-7, and HDAC mRNA expression in LPS-stimulated rat renal tubular epithelial NRK52E cells, was determined using real-time PCR. In vivo, mice were intraperitoneally injected with DEX (25 μg/kg) or saline immediately and 12 h after cecal ligation and puncture (CLP) surgery. Twenty-four hours after CLP, we examined kidney injury and renal TNF-α, MCP-1, BMP-7, and HDAC expression. Survival was monitored for 120 h. LPS increased HDAC2, HDAC5, TNF-α, and MCP-1 expression, but decreased BMP-7 expression in NRK52E cells. DEX treatment decreased the HDAC2, HDAC5, TNF-α, and MCP-1 expression, but increased BMP-7 and acetyl histone H3 expression, whose effects were blocked by yohimbine, an α2-AR antagonist. With DEX treatment, the LPS-induced TNF-α expression and cell death were attenuated in scRNAi-NRK52E but not BMP-7 RNAi-NRK52E cells. In CLP mice, DEX treatment increased survival and attenuated AKI. The expression of HDAC2, HDAC5, TNF-α, and MCP-1 mRNA in the kidneys of CLP mice was increased, but BMP-7 was decreased. However, DEX treatment reduced those changes. DEX reduces sepsis-induced AKI by decreasing TNF-α and MCP-1 and increasing BMP-7, which is associated with decreasing HDAC2 and HDAC5, as well as increasing acetyl histone H3.

Renal protective effect of xiao-chai-hu-tang on diabetic nephropathy of type 1-diabetic mice

Xiao-Chai-Hu-Tang (XCHT), a traditional Chinese medicine formula consisting of seven medicinal plants, is used in the treatment of various diseases. We show here that XCHT could protect type-1 diabetic mice against diabetic nephropathy, using streptozotocin (STZ)-induced diabetic mice and high-glucose (HG)-exposed rat mesangial cell (RMC) as models. Following 4 weeks of oral administration with XCHT, renal functions and renal hypertrophy significantly improved in the STZ-diabetic mice, while serum glucose was only moderately reduced compared to vehicle treatment. Treatment with XCHT in the STZ-diabetic mice and HG-exposed RMC resulted in a decrease in expression levels of TGF-β1, fibronectin, and collagen IV, with concomitant increase in BMP-7 expression. Data from DPPH assay, DHE stain, and CM-H₂DCFDA analysis indicated that XCHT could scavenge free radicals and inhibit high-glucose-induced ROS in RMCs. Taken together, these results suggest that treatment with XCHT can improve renal functions in STZ-diabetic mice, an effect that is potentially mediated through decreasing oxidative stress and production of TGF-β1, fibronectin, and collagen IV in the kidney during development of diabetic nephropathy. XCHT, therefore merits further investigation for application to improve renal functions in diabetic disorders.

Transforming growth factor-β induces vascular endothelial growth factor-C expression leading to lymphangiogenesis in rat unilateral ureteral obstruction

Inflammation is recognized as an important contributor to lymphangiogenesis; however, in tubulointerstitial lesions in human chronic kidney diseases, this process is better correlated with the presence of myofibroblasts rather than macrophages. As little is known about the interaction between lymphangiogenesis and renal fibrosis, we utilized the rat unilateral ureteral obstruction model to analyze inflammation, fibrosis, lymphangiogenesis, and growth factor expression. Additionally, we determined the relationship between vascular endothelial growth factor-C (VEGF-C), an inducer of lymphangiogenesis, and the profibrotic factor, transforming growth factor-β1 (TGF-β1). The expression of both TGF-β1 and VEGF-C was detected in tubular epithelial and mononuclear cells, and gradually increased, peaking 14 days after ureteral obstruction. The kinetics and localization of VEGF-C were similar to those of TGF-β1, and the expression of these growth factors and lymphangiogenesis were linked with the progression of fibrosis. VEGF-C expression was upregulated by TGF-β1 in cultured proximal tubular epithelial cells, collecting duct cells, and macrophages. Both in vitro and in vivo, the induction of VEGF-C along with the overall appearance of lymphatics in vivo was specifically suppressed by the TGF-β type I receptor inhibitor LY364947. Thus, TGF-β1 induces VEGF-C expression, which leads to lymphangiogenesis.

Primary IgA nephropathy: new insights into pathogenesis

Since its first description more than 40 years ago, IgA nephropathy has become the most common pattern of primary glomerulonephritis identified in all areas of the world where renal biopsy is routinely performed. This review discusses advances in our understanding of the pathogenesis of IgA nephropathy, principally focusing on work published in the past 5 years. It has been recognized for some time that one of the most consistent features of IgA nephropathy is an alteration in the complement of serum IgA1 O-glycoforms, with an overrepresentation of poorly galactosylated IgA1 O-glycoforms both in the serum and mesangial deposits of patients with IgA nephropathy. New data suggest that poorly galactosylated IgA1 O-glycoforms might act either as autoantigens driving the formation of glycan-specific antibodies, or antigens for cross-reactive antimicrobial antibodies. Formation of these circulating and mesangial IgA-containing immune complexes appears pivotal to the pathogenesis of IgA nephropathy and there is strong in vitro data to support their role in activation of mesangial cells, induction of podocyte injury, and activation of proximal tubular epithelial cells. Genetic factors are likely to influence many facets of pathogenesis both in primary and familial IgA nephropathy, however, to date work in this area has failed to identify consistent candidate genes.

Why kidneys fail in autosomal dominant polycystic kidney disease

The weight of evidence gathered from studies in humans with hereditary polycystic kidney disease (PKD)1 and PKD2 disorders, as well as from experimental animal models, indicates that cysts are primarily responsible for the decline in glomerular filtration rate that occurs fairly late in the course of the disease. The processes underlying this decline include anatomic disruption of glomerular filtration and urinary concentration mechanisms on a massive scale, coupled with compression and obstruction by cysts of adjacent nephrons in the cortex, medulla and papilla. Cysts prevent the drainage of urine from upstream tributaries, which leads to tubule atrophy and loss of functioning kidney parenchyma by mechanisms similar to those found in ureteral obstruction. Cyst-derived chemokines, cytokines and growth factors result in a progression to fibrosis that is comparable with the development of other progressive end-stage renal diseases. Treatment of renal cystic disorders early enough to prevent or reduce cyst formation or slow cyst growth, before the secondary changes become widespread, is a reasonable strategy to prolong the useful function of kidneys in patients with autosomal dominant polycystic kidney disease.

Role of Bone Morphogenetic Proteins-7 (BMP-7) in the Renal Improvement Effect of DangGui (Angelica sinensis) in Type-1 Diabetic Rats

Hyperglycemia induced reactive oxygen species (ROS) generation is believed as major factors leading to diabetic nephropathy (DN). DangGui (Angelica sinensis) is mentioned to show renal protective effect in combination with other herbs. Bone morphogenetic proteins-7 (BMP-7) is produced merit in protection of DN. The role of BMP-7 in DangGui-induced renal improvement is not clear. The present study investigated the effects of DangGui on renal functions, BMP-7 expression and the levels of ROS in streptozotocin (STZ)-induced diabetic rats and high glucose-exposed rat mesangial cells (RMCs). After 1- or 4-week treatment, DangGui improved renal functions and increased renal BMP-7 expression in diabetic rats. The BMP-7 expression in RMCs was reduced by high glucose treatment and this could be reversed by DangGui. Moreover, RMCs exposed to high glucose were expired by BMP-7 RNAi transfection but those cells remained alive by scramble transfection. Thus, we employed regular RMCs to knock down BMP-7 with RNAi and we found that DangGui increased BMP-7 expression in these RMCs. Direct activation of BMP-7 expression by DangGui could be considered. The results of DPPH assay, DHE stain and lucigenin assay indicated that DangGui could inhibit high glucose-induced ROS in RMCs. These results suggest that DangGui has an ability to improve renal functions in STZ-diabetic rats through increasing endogenous BMP-7 expression and decreasing oxidative stress in kidney. The present study suggest that DangGui could be applied to improve renal functions in diabetic disorders.

Role of Bone Morphogenetic Proteins-7 (BMP-7) in the Renal Improvement Effect of DangGui (Angelica sinensis) in Type-1 Diabetic Rats

Hyperglycemia induced reactive oxygen species (ROS) generation is believed as major factors leading to diabetic nephropathy (DN). DangGui (Angelica sinensis) is mentioned to show renal protective effect in combination with other herbs. Bone morphogenetic proteins-7 (BMP-7) is produced merit in protection of DN. The role of BMP-7 in DangGui-induced renal improvement is not clear. The present study investigated the effects of DangGui on renal functions, BMP-7 expression and the levels of ROS in streptozotocin (STZ)-induced diabetic rats and high glucose-exposed rat mesangial cells (RMCs). After 1- or 4-week treatment, DangGui improved renal functions and increased renal BMP-7 expression in diabetic rats. The BMP-7 expression in RMCs was reduced by high glucose treatment and this could be reversed by DangGui. Moreover, RMCs exposed to high glucose were expired by BMP-7 RNAi transfection but those cells remained alive by scramble transfection. Thus, we employed regular RMCs to knock down BMP-7 with RNAi and we found that DangGui increased BMP-7 expression in these RMCs. Direct activation of BMP-7 expression by DangGui could be considered. The results of DPPH assay, DHE stain and lucigenin assay indicated that DangGui could inhibit high glucose-induced ROS in RMCs. These results suggest that DangGui has an ability to improve renal functions in STZ-diabetic rats through increasing endogenous BMP-7 expression and decreasing oxidative stress in kidney. The present study suggest that DangGui could be applied to improve renal functions in diabetic disorders.

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.

The role of cell plasticity in progression and reversal of renal fibrosis

The need for novel insights into the mechanisms of progression of renal disease has become urgent during the last several years because of the increasing incidence of chronic renal disease worldwide. Independent of the underlying disease, the subsequent progression of renal fibrosis is characterized mainly by both an exaggerated synthesis and abnormal accumulation of extracellular matrix proteins produced by mesenchymal cells within the kidney. These cells are mainly myofibroblasts deriving from a variety of renal cells such as vascular smooth muscle, mesangial, resident stem, tubular epithelial, vascular endothelial cells or pericytes. The appearance of myofibroblasts is a reversible process, as suggested by studies in experimental models showing regression of renal fibrosis during therapy with antagonists and/or blockers of the renin-angiotensin system. An additional factor that can also affect the mechanisms of progression/regression of fibrosis is the plasticity of podocytes controlling glomerular filtration.

Amelioration of cisplatin-induced rat renal lesions by a cyclooxygenase (COX)-2 selective inhibitor

Cyclooxygenase (COX)-2, an inducible form of COX, plays important roles in inflammatory lesions. We investigated effects of a COX-2 selective inhibitor, NS-398, on cisplatin (CDDP)-induced rat renal lesions. As compared with rats injected with a single dose of CDDP (6 mg/kg; CDDP group), rats who were treated everyday with NS-398 (3mg/kg) after the CDDP injection (inhibitor group), showed the declines of blood urea nitrogen and creatinine values, and the delay of the peak of regenerating renal epithelial cell number (demonstrable with 5'-bromo-2'-deoxyuridine immunohistochemistry); these findings suggested cytoprotective effects of the inhibitor. Furthermore, the numbers of ED1-immunopositive macrophages and α-smooth muscle actin (α-SMA)-immunopositive myofibroblasts were lower in the inhibitor group than in the CDDP group; mRNA expression of transforming growth factor-β1 (TGF-β1) was also decreased in the inhibitor group. Because the fibrotic area seen after CDDP injection were tended to decrease in the inhibitor group compared with the CDDP group, it was considered that the decreased number of infiltrating macrophages by the inhibitor might lead to the decreased production of TGF-β1, thereby resulting in the reduced number of α-SMA-positive myofibroblasts responsible for fibrosis. Collectively, although these differences between the CDDP and inhibitor groups were not always marked, the COX-2 inhibitor used in this study could ameliorate the CDDP-induced rat renal lesions.

Oxidative stress in obstructive nephropathy

Unilateral ureteric obstruction (UUO) is one of the most commonly applied rodent models to study the pathophysiology of renal fibrosis. This model reflects important aspects of inflammation and fibrosis that are prominent in human kidney diseases. In this review, we present an overview of the factors contributing to the pathophysiology of UUO, highlighting the role of oxidative stress.

TLR4 promotes fibrosis but attenuates tubular damage in progressive renal injury

Toll-like receptors (TLRs) can orchestrate an inflammatory response upon activation by pathogen-associated motifs and release of endogenous stress ligands during tissue injury. The kidney constitutively expresses most TLRs, including TLR4. The function of TLR4 during the inflammation, tubular atrophy, and fibrosis that accompany progressive renal injury is unknown. Here, we subjected wild-type (WT) and TLR4-deficient mice to unilateral ureteral obstruction and observed elevated levels of TLR4 mRNA in the kidney after obstruction. One day after unilateral ureteral obstruction, TLR4-deficient mice had fewer proliferating tubular epithelial cells and more tubular damage than WT mice; however, TLR4-deficient mice developed considerably less renal fibrosis despite decreased matrix metalloproteinase activity and without significant differences in myofibroblast accumulation. In vitro, TLR4-deficient primary tubular epithelial cells and myofibroblasts produced significantly less type I collagen mRNA after TGF-beta stimulation than WT cells. The reduced fibrosis in TLR4-deficient mice associated with an upregulation of Bambi, a negative regulator of TGF-beta signaling. In conclusion, TLR4 attenuates tubular damage but promotes renal fibrosis by modulating the susceptibility of renal cells to TGF-beta. These data suggest that TLR4 signaling may be a therapeutic target for the prevention of renal fibrosis.

Bone morphogenetic protein (BMP)-4 and BMP-7 regulate differentially transforming growth factor (TGF)-beta1 in normal human lung fibroblasts (NHLF)

Background

Airway remodelling is thought to be under the control of a complex group of molecules belonging to the Transforming Growth Factor (TGF)-superfamily. The Bone Morphogenetic Proteins (BMPs) belong to this family and have been shown to regulate fibrosis in kidney and liver diseases. However, the role of BMPs in lung remodelling remains unclear. BMPs may regulate tissue remodelling in asthma by controlling TGF-β-induced profibrotic functions in lung fibroblasts.

Methods

Cell cultures were exposed to TGF-β1 alone or in the presence of BMP-4 or BMP-7; control cultures were exposed to medium only. Cell proliferation was assessed by quantification of the incorporation of [3H]-thymidine. The expression of the mRNA encoding collagen type I and IV, tenascin C and fibronectin in normal human lung fibroblasts (NHLF) was determined by real-time quantitative PCR and the main results were confirmed by ELISA. Cell differentiation was determined by the analysis of the expression of α-smooth muscle actin (α-SMA) by western blot and immunohistochemistry. The effect on matrix metalloproteinase (MMP) activity was assessed by zymography.

Results

We have demonstrated TGF-β1 induced upregulation of mRNAs encoding the extracellular matrix proteins, tenascin C, fibronectin and collagen type I and IV when compared to unstimulated NHLF, and confirmed these results at the protein level. BMP-4, but not BMP-7, reduced TGF-β1-induced extracellular matrix protein production. TGF-β1 induced an increase in the activity of the pro-form of MMP-2 which was inhibited by BMP-7 but not BMP-4. Both BMP-4 and BMP-7 downregulated TGF-β1-induced MMP-13 release compared to untreated and TGF-β1-treated cells. TGF-β1 also induced a myofibroblast-like transformation which was partially inhibited by BMP-7 but not BMP-4.

Conclusions

Our study suggests that some regulatory properties of BMP-7 may be tissue or cell type specific and unveil a potential regulatory role for BMP-4 in the regulation of lung fibroblast function.

[Aristolochic acid induces renal tubular injury and inhibits expression of bone morphogenetic protein-7 mRNA in renal tissue of rats]

OBJECTIVE

To investigate the pathogenic mechanism of aristolochic acid nephropathy (AAN) by observing the renal tubular injury and the change of the expression of bone morphogenetic protein-7 (BMP-7) mRNA in renal tissue of rats induced by aristolochic acid (AA), an active constituent in Caulis Aristolochiae Manshuriensis (CAM).

METHODS

Forty-six male Wistar rats were randomly divided into normal control group (n=20) and AA-treated group (n=26). Rats in AA-treated group were intragastrically administered with AA 20 mg/(kg.d), and rats in control group were treated with equal volume of potable water. At the end of the 4th, 8th and 12th week of administration, the 24 h-urine was collected by metabolic cage for detecting the activity of N-acetyl-beta-D-glucosaminidase (NAG) and the blood samples were obtained from abdominal aorta for detecting serum creatinine (SCr). Pathological change and the degree of injury of the kidneys were observed by microscopy. The expression of proliferative cell nuclear antigen (PCNA) was detected by immunohistochemical method, and mRNA expression of bone morphogenetic protein-7 (BMP-7) in the renal tissue was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Compared with the normal control group, the activity of NAG and the ratio of SCr vs body weight were markedly increased in rats of the AA-treated group after treatment (P<0.05 and P<0.01). Pathological section of renal tissue showed that most renal tubules had cloudy swelling, and vacuolar degenerating in tubular epithelial cells, with brush border dropping off, and parts of tubular basement membrane were exposed. The degrees of injuries were aggravated depending on treating time. The tubulointerstitial injury (TI) parameter in rats of AA-treated group was higher than that of the normal control group. The positive expression of PCNA was observed in the damaged tubular cells. The proliferation index of PCNA was significantly increased after 4- and 8-week treatment (P<0.01), but was decreased after 12-week treatment (P<0.05). The mRNA expression of BMP-7 was markedly decreased in the AA-treated group compared with the normal control group after 4-week treatment (P<0.05), and decreased with the extension of treatment time.

CONCLUSION

AA can induce injury of the renal tubules, impair the cell regeneration, and inhibit the expression of BMP-7 mRNA in renal tissue. This may be one of the pathogenic mechanisms of AAN.

Heme oxygenase-1 deficiency promotes epithelial-mesenchymal transition and renal fibrosis

Induction of heme oxygenase-1 (HO-1) is associated with potential antifibrogenic effects. The effects of HO-1 expression on epithelial-mesenchymal transition (EMT), which plays a critical role in the development of renal fibrosis, are unknown. In this study, HO-1(-/-) mice demonstrated significantly more fibrosis after 7 d of unilateral ureteral obstruction compared with wild-type mice, despite similar degrees of hydronephrosis. The obstructed kidneys of HO-1(-/-) mice also had greater macrophage infiltration and renal tubular TGF-beta1 expression than wild-type mice. In addition, the degree of EMT was more extensive in obstructed HO-1(-/-) kidneys, as assessed by alpha-smooth muscle actin and expression of S100A4 in proximal tubular epithelial cells. In vitro studies using proximal tubular cells isolated from HO-1(-/-) and wild-type kidneys confirmed these observations. In conclusion, HO-1 deficiency is associated with increased fibrosis, tubular TGF-beta1 expression, inflammation, and enhanced EMT in obstructive kidney disease. Modulation of the HO-1 pathway may provide a new therapeutic approach to progressive renal diseases.

BMP-7 protects mesangial cells from injury by polymeric IgA

Bone morphogenetic protein-7 (BMP-7) is a potential therapeutic agent for acute and chronic renal diseases. Here we found that addition of polymeric IgA, isolated from patients with IgA nephropathy, increased the synthesis of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), transforming growth factor-beta (TGF-beta) and fibronectin in cultured human mesangial cells, effects blunted by BMP-7. When mesangial cells were cultured with both polymeric IgA and BMP-7 there was an increase in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). The activation of NF kappaB and TNF-alpha synthesis induced by polymeric IgA or TNF-alpha were downregulated by BMP-7 or rosiglitazone. BMP-7 inhibited TNF-alpha release from polymeric IgA-stimulated mesangial cells by activation of PPAR-gamma but suppressed TGF-beta release by mechanisms independent of PPAR-gamma. The expression of inhibitory Smad6 and 7 was increased whereas the expression of active Smad2 and 3 was reduced in these mesangial cells by BMP-7. Our study shows that BMP-7 ameliorates IgA nephropathy-derived polymeric IgA-induced TNF-alpha and TGF-beta synthesis in human mesangial cells through multiple mechanisms involving inhibitory Smads and PPAR-gamma.

Accumulation of free adduct glycation, oxidation, and nitration products follows acute loss of renal function

Glycation, oxidation, and nitration of endogenous proteins occur spontaneously and these modifications are also present in foods. Increased levels of these chemical changes are associated with chronic renal failure; however, little is known about acute kidney failure. We measured these modifications of plasma protein and related free adducts in plasma following bilateral nephrectomy and bilateral ureteral obstruction. Advanced glycation end-product (AGE) residues of plasma protein were increased 3 h post-surgery, and thereafter slowly decreased in all groups, reflecting changes in plasma protein synthesis and transcapillary flow post-surgery. Ureteral ligation increased oxidation and nitration adduct residues. There were, however, marked increases in AGE, dityrosine, or 3-nitrotyrosine free adducts in both nephrectomized and ureter-ligated rats compared to rats that had undergone sham operations. There were lower modified adduct concentrations in the ureter-ligated compared to the nephrectomized rats, reflecting residual glomerular filtration and tubular removal. There was no increase in glycated, oxidized, and nitrated proteins. Glyoxal and methylglyoxal were also increased in both renal failure models. Our study shows that the acute loss of renal function and urinary excretion leads to the accumulation of AGE, oxidation, and nitration free adducts in the plasma.

The management of CKD: a look into the future

The increasing global prevalence of chronic kidney disease (CKD) and end-stage renal disease with the associated spiraling cost has profound public health and economic implications. This has made slowing the progression of CKD, a major health-care priority. CKD is invariably characterized by progressive kidney fibrosis and at present, treatment aiming to slow the progression of CKD is limited to aggressive blood pressure control, with few therapies targeting the fibrotic process itself. In this review, we explore the potential of experimental therapeutic strategies, based on preventing or reversing the pathophysiologic steps of kidney remodeling that lead to fibrosis.

Phenotypic transitions and fibrosis in diabetic nephropathy

The cause of renal fibrosis in diabetic nephropathy is widely believed to be phenotypic switching of fibroblasts to an activated state. However, emerging evidence suggests that diabetes also alters the phenotype of normal, non-fibroblast kidney cells, such as mesangial cells, tubular epithelial cells, and bone marrow-derived progenitors. Experiments have shown that cytokines, high glucose, and advanced glycation end products induce profibrotic changes in kidney cell phenotype by the processes of myofibroblast transdifferentiation and epithelial-mesenchymal transition. As a result, differentiated kidney cells become reprogrammed to secrete and accumulate extracellular matrix. This revised view implies that inhibiting phenotypic transitions in nonfibroblasts might limit fibrosis in diabetic nephropathy.