The role of TGF-β and epithelial-to mesenchymal transition in diabetic nephropathy

Livin is involved in TGF-β1-induced renal tubular epithelial-mesenchymal transition through lncRNA-ATB

Background

Renal interstitial fibrosis is accepted as a crucial component of chronic kidney diseases (CKD). Epithelial-mesenchymal transition (EMT) is an important factor contributing to renal interstitial fibrosis. Livin, due to its ability to induce EMT, is an important regulator of many types of tumors and might also be involved in human renal tubular EMT.

Methods

We confirmed that Livin and lncRNA-ATB could aggravate EMT in vivo and in vitro, lncRNA-ATB could be suppressed by the silencing of Livin whereas Livin expression was nearly stable when lncRNA-ATB was overexpressed or knocked out.

Results

Livin was upregulated in vivo and in vitro at the similar rate as the occurrence of EMT, which could be relieved when Livin was silenced. LncRNA-ATB, which is another important regulator of EMT, was also found highly expressed during this process. The silencing of lncRNA-ATB could lessen the severity of EMT, and the overexpression of lncRNA-ATB could aggravate EMT without affecting the expression of Livin.

Conclusions

Livin promotes EMT through the regulation of lncRNA-ATB. The silencing of Livin might be an effective targeted therapy for renal fibrosis.

microRNA Crosstalk Influences Epithelial-to-Mesenchymal, Endothelial-to-Mesenchymal, and Macrophage-to-Mesenchymal Transitions in the Kidney

microRNAs (miRNAs) are small, non-coding nucleotides that regulate diverse biological processes. Altered microRNA biosynthesis or regulation contributes to pathological processes including kidney fibrosis. Kidney fibrosis is characterized by deposition of excess extracellular matrix (ECM), which is caused by infiltration of immune cells, inflammatory cells, altered chemokines, and cytokines as well as activation and accumulation of fibroblasts in the kidney. These activated fibroblasts can arise from epithelial cells via epithelial-to-mesenchymal transition (EMT), from bone marrow-derived M2 phenotype macrophages via macrophage-to-mesenchymal transition (MMT), from endothelial cells via endothelial-to-mesenchymal transition (EndMT), from resident fibroblasts, and from bone marrow-derived monocytes and play a crucial role in fibrotic events. Disrupted microRNA biosynthesis and aberrant regulation contribute to the activation of mesenchymal programs in the kidney. miR-29 regulates the interaction between dipeptidyl peptidase-4 (DPP-4) and integrin β1 and the associated active transforming growth factor β (TGFβ) and pro-EndMT signaling; however, miR-let-7 targets transforming growth factor β receptors (TGFβRs) to inhibit TGFβ signaling. N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous anti-fibrotic peptide, which is associated with fibroblast growth factor receptor 1 (FGFR1) phosphorylation and subsequently responsible for the production of miR-let-7. miR-29 and miR-let-7 family clusters participate in crosstalk mechanisms, which are crucial for endothelial cell homeostasis. The physiological level of AcSDKP is vital for the activation of anti-fibrotic mechanisms including restoration of anti-fibrotic microRNA crosstalk and suppression of profibrotic signaling by mitigating DPP-4-associated mesenchymal activation in the epithelial cells, endothelial cells, and M2 phenotype macrophages. The present review highlights recent advancements in the understanding of both the role of microRNAs in the development of kidney disease and their potential as novel therapeutic targets for fibrotic disease states.

Hydrogen Sulfide: Recent Progression and Perspectives for the Treatment of Diabetic Nephropathy

Diabetic kidney disease develops in approximately 40% of diabetic patients and is a major cause of chronic kidney diseases (CKD) and end stage kidney disease (ESKD) worldwide. Hydrogen sulfide (H₂S), the third gasotransmitter after nitric oxide (NO) and carbon monoxide (CO), is synthesized in nearly all organs, including the kidney. Though studies on H₂S regulation of renal physiology and pathophysiology are still in its infancy, emerging evidence shows that H₂S production by renal cells is reduced under disease states and H₂S donors ameliorate kidney injury. Specifically, aberrant H₂S level is implicated in various renal pathological conditions including diabetic nephropathy. This review presents the roles of H₂S in diabetic renal disease and the underlying mechanisms for the protective effects of H₂S against diabetic renal damage. H₂S may serve as fundamental strategies to treat diabetic kidney disease. These H₂S treatment modalities include precursors for H₂S synthesis, H₂S donors, and natural plant-derived compounds. Despite accumulating evidence from experimental studies suggests the potential role of the H₂S signaling pathway in the treatment of diabetic nephropathy, these results need further clinical translation. Expanding understanding of H₂S in the kidney may be vital to translate H₂S to be a novel therapy for diabetic renal disease.

Markers of renal fibrosis: How do they correlate with podocyte damage in glomerular diseases?

BACKGROUND

Renal fibrosis is the result of the interaction of cellular and molecular pathways, which is induced by sustained glomerular injury and involves the podocytes and multiple profibrotic factors. In this study, we investigated the correlation of the mRNA expression of podocyte proteins and profibrotic factors with renal fibrosis measured in renal biopsies of patients with primary and secondary glomerulopathies.

METHODS

Eighty-four adult patients with primary or secondary glomerular diseases and 12 controls were included. Demographic and clinical data were collected. Seventy-two percent of the renal biopsies were done less than one year from clinical disease manifestation. The quantification of the podocyte-associated mRNAs of alpha-actinin-4, podocin, and podocalyxin, as well as of the profibrotic factors TGF-β1, CTGF, and VEGF-A were quantified by real-time polymerase chain reaction. The percent positive area of renal fibrosis was measured by immunohistochemistry staining, using anti-CTGF and anti-HHF35 antibodies and unpolarized Sirius Red. Correlations between the expression of tissue mRNAs and the positive area of fibrosis for the measured markers were made by Spearman's rank correlation coefficient.

RESULTS

In relation to control biopsies, podocyte-specific proteins were downregulated in podocytopathies, in proliferative nephritis, in diabetic kidney disease (DRD), and in IgA nephropathy (IgAN). Messenger RNA of TGF-β1, CTGF, and VEGF-A was upregulated in patients with podocytopathies and in DRD but not in proliferative nephritis and IgAN. Tissue mRNA expression of TGF-β1, CTGF, and VEGF-A were strongly correlated with renal fibrosis, as measured by HHF35; however, the correlation, albeit significant, was moderate for Sirius Red and weak for CTGF. The percent positive area of renal fibrosis measured by Sirius Red was similar between podocytopathies and DRD and significantly higher in podocytopathies compared to IgAN or proliferative nephritis.

CONCLUSIONS

In patients with glomerular diseases, the mRNA of TGF-β1, CTGF, and VEGF-A correlated positively with the extent of renal fibrosis, and the positive area of fibrosis was larger in the podocytopathies and in DRD as measured by Sirius Red. The pathways connecting podocyte damage and activation of profibrotic factors to kidney tissue fibrosis need to be better investigated.

High-Mobility Group Nucleosome-Binding Protein 1 Mediates Renal Fibrosis Correlating with Macrophages Accumulation and Epithelial-to-Mesenchymal Transition in Diabetic Nephropathy Mice Model

Background/Aim: Renal fibrosis is essential for the progression of diabetic nephropathy (DN). Macrophages accumulate in diabetic kidneys and are involved in epithelial-to-mesenchymal transition (EMT), a vital mechanism leading to renal fibrosis. Recently, high-mobility group nucleosome-binding protein 1(HMGN1) was documented in promoting the recruitment and activation of antigen-presenting cells. In this study, we first reported its roles in renal fibrosis and the underlying mechanism associated with macrophage filtration and EMT. Methods: Twenty C57BL/6J mice were administered streptozotocin (STZ) to induce diabetes for 6 weeks and then divided into 4 groups: normal control group; DN group; benazepril-treated group, and insulin-treated group. Blood glucose, creatinine, and albumin in urine, hematoxylin and eosin, and Sirius red staining of kidney tissues were used to assess the renal pathology. ELISA, immunochemistry, and in situ hybridization were performed to determine the expression of HMGN1, CD68, F4/80, α-smooth muscle actin, and E-cadherin. Results: The renal expression levels of HMGN1, macrophage markers, and EMT makers were increased in DN group, and insulin treatment could reduce the overexpression of these indicators with a better effect than benazepril treatment. Both treatments could not obviously ameliorate urine albumin-to-creatinine ratio, collagen expression, and renal histological changes in STZ-induced diabetic mice. Correlation analysis indicated that there was a relationship among HMGN1, macrophage markers, EMT markers, and collagen expression in DN mice. Conclusion: HMGN1 may promote macrophages accumulation and EMT, suggesting a potential therapeutic target for preventing renal fibrosis development in DN.

Growing a new human kidney

There are 3 reasons to generate a new human kidney. The first is to learn more about the biology of the developing and mature organ. The second is to generate tissues with which to model congenital and acquired kidney diseases. In particular, growing human kidneys in this manner ultimately should help us understand the mechanisms of common chronic kidney diseases such as diabetic nephropathy and others featuring fibrosis, as well as nephrotoxicity. The third reason is to provide functional kidney tissues that can be used directly in regenerative medicine therapies. The second and third reasons to grow new human kidneys are especially compelling given the millions of persons worldwide whose lives depend on a functioning kidney transplant or long-term dialysis, as well as those with end-stage renal disease who die prematurely because they are unable to access these treatments. As shown in this review, the aim to create healthy human kidney tissues has been partially realized. Moreover, the technology shows promise in terms of modeling genetic disease. In contrast, barely the first steps have been taken toward modeling nongenetic chronic kidney diseases or using newly grown human kidney tissue for regenerative medicine therapies.

Identification of potential therapeutic target genes in mouse mesangial cells associated with diabetic nephropathy using bioinformatics analysis

The aim of the present study was to identify genes under the effect of transforming growth factor-β (TGF-β1), high glucose (HG) and glucosamine (GlcN) in MES-13 mesangial cells and elucidate the molecular mechanisms of diabetic nephropathy (DN). The gene expression datasets GSE2557 and GSE2558 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were independently screened using the GEO2R online tool. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery. The protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes and Cytoscape software. The hub genes were identified by the NetworkAnalyzer plugin. Overlapping genes were subjected to molecular docking analysis using SystemsDock. A total of 202 upregulated and 158 downregulated DEGs from the HG-treated groups, 138 upregulated and 103 downregulated DEGs from the GlcN-treated groups, and 81 upregulated and 44 downregulated DEGs from the TGF-β1-treated groups were identified. The majority of the DEGs were independently enriched in 'nucleosome assembly', 'chromatin silencing' and 'xenobiotic glucuronidation'. In addition, KEGG pathways were significantly enriched in 'systemic lupus erythematosus', 'protein processing in endoplasmic reticulum' and 'aldarate metabolism pathway', and 'TNF signaling pathway' intersected in the TGF-β1-treated and HG-treated groups. In total, eight hub genes, Jun, prostaglandin-endoperoxide synthase 2 (Ptgs2), fibronectin 1 (Fn1), cyclin-dependent kinase (Cdk)2, Fos, heat shock protein family A (Hsp70) member 5 (Hspa5), Hsp90b1 and homo sapiens hypoxia upregulated 1 (Hyou1), and three overlapping genes, Ras homolog gene family, member B (RHOB), complement factor H (CFH) and Krüppel-like factor 15 (KLF15), were selected. Valsartan with RHOB, and fosinopril with CFH and KLF15 had preferential binding activity. In conclusion, Jun, Ptgs2, Fn1, Cdk2, Fos, Hspa5, Hsp90b1, Hyou1, RHOB, CFH and KLF15 may be potential therapeutic targets for mesangial cells associated with DN, which may provide insight into DN treatment strategies.

TGF-β1 Induces Epithelial-Mesenchymal Transition of Chronic Sinusitis with Nasal Polyps through MicroRNA-21

OBJECTIVES

To characterize the epithelial-mesenchymal transition (EMT) in chronic rhinosinusitis with nasal polyps (CRSwNP) and to investigate the mechanism by which microRNA-21 (miR-21) regulates EMT in CRSwNP.

METHOD

(1) Tissue experiments: Mucosa tissues were collected from 13 patients with CRSwNP and 12 patients with CRS without nasal polyps (CRSsNP), as well as 11 patients without CRS (controls). Protein localization and quantification were achieved by immunofluorescence staining and Western blotting, involving the epithelial marker protein E-cadherin and the mesenchymal marker proteins α-smooth muscle actin (α-SMA), fibronectin, and vimentin. Quantitative RT-PCR was used to detect the relative expression levels of miR-21 and TGF-β1 mRNAs. (2) Cellular experiments: Primary human nasal epithelial cells (PHNECs) treated with TGF-β1, or TGF-β1 with miR-21 inhibitor, or miR-21 mimics alone were observed for morphology changes under a phase-contrast microscope. The expression levels of epithelial/mesenchymal marker proteins were determined as aforementioned. PTEN and phosphorylated Akt were detected by Western blotting.

RESULTS

(1) Tissue experiments: Compared with the CRSsNP and control groups, the expression of E-cadherin was downregulated in the CRSwNP group, whereas the expression of TGF-β1, α-SMA, fibronectin, and vimentin was upregulated. The expression levels of miR-21 and TGF-β1 mRNAs in CRSwNP were significantly higher than those in CRSsNP and controls. (2) Cellular experiments: TGF-β1 induced EMT-like transformation in PHNECs, featured by changes in cell morphology and upregulation of mesenchymal proteins and miR-21. The miR-21 inhibitor, as well as the Akt-specific -inhibitor, suppressed TGF-β1-induced EMT. Mechanically, downregulation of miR-21 resulted in increased PTEN and decreased Akt phosphorylation. Furthermore, overexpression of miR-21 had the opposite effects.

CONCLUSIONS

Our findings suggest that the TGF-β1-miR-21-PTEN-Akt axis may contribute to the pathogenesis of CRSwNP. miR-21 might be a reliable target for treating nasal polyp genesis through EMT suppression. Moreover, miR-21 inhibitors could be a novel class of antipolyp drug that modulates PTEN expression and Akt activation. In addition, further investigation regarding the reason underlying miR-21 overexpression in CRSwNP could provide a molecular target for novel treatment strategies for nasal polyposis.

Enhanced TGF-β Signaling Contributes to the Insulin-Induced Angiogenic Responses of Endothelial Cells

Angiogenesis, the development of new blood vessels, is a key process in disease. We reported that insulin promotes translocation of transforming growth factor β (TGF-β) receptors to the plasma membrane of epithelial and fibroblast cells, thus enhancing TGF-β responsiveness. Since insulin promotes angiogenesis, we addressed whether increased autocrine TGF-β signaling participates in endothelial cell responses to insulin. We show that insulin enhances TGF-β responsiveness and autocrine TGF-β signaling in primary human endothelial cells, by inducing a rapid increase in cell surface TGF-β receptor levels. Autocrine TGF-β/Smad signaling contributed substantially to insulin-induced gene expression associated with angiogenesis, including TGF-β target genes encoding angiogenic mediators; was essential for endothelial cell migration; and participated in endothelial cell invasion and network formation. Blocking TGF-β signaling impaired insulin-induced microvessel outgrowth from neonatal aortic rings and modified insulin-stimulated blood vessel formation in zebrafish. We conclude that enhanced autocrine TGF-β signaling is integral to endothelial cell and angiogenic responses to insulin.

Kidney fibrosis induced by various irrigation pressures in mouse models of mild and severe hydronephrosis

OBJECTIVE

We want to study whether the degree of fibrosis in the mild and severe hydronephrosis is different, and whether the irrigation pressure will affect the fibrosis of the hydronephrosis.

METHODS

Animal models of mild and severe hydronephrosis in the left kidney were established: 72 healthy C57BL/6 mice were randomly divided into nine groups (eight in each group). The N group was used as a control group, and 0 mmHg pressure perfusion was given. The M and S groups were used as mild and severe hydronephrosis groups, respectively. The mild and severe hydronephrosis groups were subdivided into eight subgroups, M0-M3 and S0-S3. Among them, groups 0, 1, 2, and 3 were perfused with 0 mmHg, 20 mmHg, 60 mmHg, and 100 mmHg, respectively. We investigated the effects of irrigation pressures on renal fibrosis in mild (group M) and heavy (group S) hydronephrosis by quantitative real-time polymerase chain reaction, Western blot analysis, Masson staining and immunohistochemistry staining in mouse models.

RESULTS

Compared with group N, EMT and ECM deposits were significantly aggravated in both the mild and severe hydronephrosis groups, TGF-β signaling pathway-related molecules significantly changed too. In terms of ECM deposition, S2 and S3 are significantly increased compared to S0.The EMT of M2 and M3 changed significantly compared with M0; the EMT of S1, S2 and S3 changed significantly compared with S0.The molecules related to TGF-β signaling pathway also changed: M0 and S0 changed significantly compared with N; M1, M2 and M3 changed significantly compared with M0; compared with S0, S1, S2 and S3 changed significantly.

CONCLUSION

Compared with mild hydronephrosis, renal fibrosis in severe hydronephrosis is more severe and its tolerance to perfusion pressure is lower. These changes may be related to the TGF-β signalling pathway.

Astragaloside IV ameliorates high glucose‑induced renal tubular epithelial‑mesenchymal transition by blocking mTORC1/p70S6K signaling in HK‑2 cells

Astragaloside IV (AST) is the major active saponin in Astragalus membranaceus and, reportedly, has a variety of pharmacological activities. However, the potential of AST to ameliorate high glucose‑mediated renal tubular epithelial‑mesenchymal transition (EMT) remains undetermined. The aim of the present research was to explore the effect and mechanism of AST in EMT of renal tubular epithelial cells, as an underlying mechanism of renal fibrosis and a vital feature involved in diabetic nephropathy. The effect of AST on the EMT of renal tubular epithelial cells (HK‑2) stimulated by high glucose was investigated and it was attempted to elucidate the potential underlying mechanism. The expression of E‑cadherin and α‑smooth muscle actin were determined by western blotting and immunofluorescence assays. The expression of the mammalian target of rapamycin complex 1 (mTORC1)/ ribosomal protein S6 kinase β‑1 (p70S6K) signaling pathway and protein levels of four transcriptional factors (snail, slug, twist and zinc finger E‑box‑binding homeobox 1) were also determined by western blotting. Additionally, extracellular matrix components, including fibronectin (FN) and collagen type IV (Col IV) were detected by ELISA. The results suggested that the EMT of HK‑2 cells and the mTORC1/p70S6K pathway were activated by high glucose. The expression of snail and twist in HK‑2 cells was elevated by high glucose. Furthermore, extracellular matrix components, FN and Col IV, were increased in HK‑2 cells cultured with high glucose. In turn, treatment with AST reduced EMT features in HK‑2 cells, inhibited mTORC1/p70S6K pathway activation, downregulated expression of snail and twist, and reduced secretion of FN and Col IV. In summary, the findings suggested that AST ameliorates high glucose‑mediated renal tubular EMT by blocking the mTORC1/p70S6K signaling pathway in HK‑2 cells.

ROS induces epithelial-mesenchymal transition via the TGF-β1/PI3K/Akt/mTOR pathway in diabetic nephropathy

Oxidative stress has been reported to serve an important role in the development and progression of diabetic nephropathy (DN). Epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells promotes renal fibrosis in DN, while the mechanism of reactive oxygen species (ROS)-mediated EMT is not fully understood. The aim of the present study was to investigate the effect of high glucose-induced ROS on the activation of the transforming growth factor (TGF)-β1/phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway in a normal rat kidney tubular epithelial cell line (NRK-52E) and rats with type 1 diabetes. In vitro, high glucose-stimulated ROS production resulted in increased TGF-β1 expression as well as an increase in the Akt and mTOR phosphorylation ratio, resulting in EMT. When cells were pre-treated with ROS inhibitors, changes in TGF-β1, Akt and mTOR were significantly ameliorated. In vivo, diabetic rats experienced a significant decline in renal function and severe renal fibrosis compared with control rats at 8 weeks following streptozocin injection. Levels of malondialdehyde and TGF-β1/PI3K/Akt/mTOR pathway activation were increased in the renal cortex of rats with diabetes compared with the control rats. Furthermore, renal fibrosis was further aggravated in DN compared with the control rats. The results of the present study suggest that ROS serves an important role in mediating high glucose-induced EMT and inhibits activation of the TGF-β1/PI3K/Akt/mTOR pathway. ROS may therefore have potential as a treatment approach to prevent renal fibrosis in DN.

Early growth response protein-1 upregulates long noncoding RNA Arid2-IR to promote extracellular matrix production in diabetic kidney disease

Diabetic kidney disease (DKD) has surpassed chronic glomerulonephritis as the leading cause of end-stage renal disease. Previously, we showed that early growth response protein-1 (Egr1) plays a key role in DKD by enhancing mesangial cell proliferation and extracellular matrix (ECM) production. The long noncoding RNA (lncRNA) AT-rich interactive domain 2-IR (Arid2-IR) has been identified as a mothers against decapentaplegic homolog 3 (Smad3)-associated lncRNA in unilateral ureteral obstructive kidney disease. However, the effect of Egr1 on Arid2-IR in the development of DKD is still unknown. In this study, we found that Arid2-IR was increased in mice with high-fat diet and streptozotocin-induced type 2 diabetes and in mouse mesangial cells cultured with high glucose to mimic diabetes. Knockdown of Arid2-IR in mouse mesangial cells reduced the high expression levels of collagen-α₁(I) (Col1a1) and α-smooth muscle actin (α-SMA) induced by high glucose. Furthermore, Arid2-IR expression changed the increased expression of Col1a1 and α-SMA caused by overexpression of Egr1. Overall, these data suggest that increased Arid2-IR likely contributes to ECM production in DKD and that Egr1 promotes ECM production in DKD partly by upregulating Arid2-IR. Thus, Arid2-IR may be a new target in the treatment of DKD.

Triptolide Attenuates Renal Tubular Epithelial-mesenchymal Transition Via the MiR-188-5p-mediated PI3K/AKT Pathway in Diabetic Kidney Disease

Triptolide possesses the trait of renal protection. Epithelial-mesenchymal transition (EMT) is closely linked to the pathogenesis of diabetic kidney disease (DKD). MicroRNAs have recently emerged as critical regulators of DKD. However, it is poorly understood whether triptolide alleviates renal EMT by regulating microRNAs in DKD. In this study, we found that triptolide decreased albuminuria, improved the renal structure and reduced renal EMT in rats with DKD. Furthermore, activation of the PI3K/AKT signaling pathway was increased in diabetic rats, which was partly reversed by triptolide. Triptolide also alleviated glucose-induced EMT in HK-2 cells in vitro. PI3K/AKT signaling pathway activation was reduced after triptolide treatment. Moreover, triptolide decreased the increase in miR-188-5p expression stimulated by high glucose levels in HK-2 cells. miR-188-5p inhibited PTEN expression by directly interacting with the PTEN 3'-untranslated region. Additionally, downregulation of miR-188-5p, which imitates the effects of triptolide, attenuated the activation of the PI3K/AKT pathway and HG-induced EMT, whereas miR-188-5p overexpression reversed the effects of triptolide on the PI3K/AKT pathway and EMT. In conclusion, we demonstrated that triptolide ameliorates renal EMT via the PI3K/AKT signaling pathway through the interaction between miR-188-5p and PTEN, indicating that miR-188-5p may be a therapeutic target of triptolide in DKD.

Downregulation of microRNA-429 contributes to angiotensin II-induced profibrotic effect in rat kidney

MicroRNA (miR) 429 has been shown to inhibit epithelial-to-mesenchymal transition (EMT) in cancer cells. However, the role of miR429 in EMT in non-cancer cells has not been defined, especially in the kidneys. The present study determined whether miR429 participated in angiotensin (ANG) II-induced EMT and fibrogenesis in renal cells. In NRK-52E cells, a rat proximal tubular cell line, incubation of ANG II (10^-9 M) for 24 h significantly reduced the level of miR429 by 60% and increased the protein levels of mesenchymal markers α-smooth muscle actin and fibroblast-specific protein-1 by threefold and decreased epithelial marker E-cadherin by 60%, which was blocked by losartan, an AT1 receptor antagonist. Treatment of cells with miR429 inhibitor produced similar changes in the above EMT markers to that induced by ANG II. In cells overexpressed with miR429 transgene, ANG II-induced increases in collagen were abolished. Male Sprague-Dawley rats were infused with ANG II (200 ng·kg^-1·min^-1) for 12 days, and the levels of miR429 in the kidneys were reduced by 75%. Intrarenal transfection of lentivirus expressing miR429 also reversed the ANG II-induced changes in the EMT markers and collagen in the kidneys. The ANG II-induced increase in urinary albumin was significantly inhibited by miR429 transgene. There was no difference in the increases of blood pressure between ANG II- and ANG II+miR429 transgene-treated rats. These data suggest that ANG II-induced inhibition of miR429 contributes to ANG II-induced transdifferentiation and fibrogenesis in renal cells and that miR429 protects against ANG II-induced kidney damages.

Coumarins improved type 2 diabetes induced by high-fat diet and streptozotocin in mice via antioxidation

Coumarins extensively exist in plants and are utilized against diabetes in some folk medicines. Recent studies have demonstrated that oxidative stress plays a crucial role in the etiology and pathogenesis of diabetes mellitus. We investigated the antioxidant ability of 3 coumarins (osthole, esculin, and fraxetin) in type 2 diabetes. After being fed a high-fat diet, ICR mice were exposed to low doses of streptozotocin and then treated with experimental coumarins for 5 weeks. We found osthole, esculin, and metformin significantly lowered fasting blood glucose, HOMA-IR, and 3 blood lipids (total cholesterol, total triglyceride, free fatty acids), and increased insulin levels, while fraxetin only enhanced insulin levels and lessened free fatty acids. Both osthole and esculin had antioxidative effects in pancreas through elevating the activities of glutathione peroxidase, catalase, and superoxide dismutase; fraxetin, however, merely heightened catalase activity. By contrast, 3 coumarins significantly increased those antioxidase activities in liver. Hematoxylin and eosin staining revealed 3 coumarins, especially osthole, attenuated cellular derangement, blurry fringes of hepatic sinusoid and extensive vacuolization due to hepatocellular lipid accumulation, and lessened inflammatory infiltration in pancreas. The glomerular and islet structure of diabetic mice were improved, with reduced mesangial matrix and glomerular basement membrane thickening. Therefore, our study supports that coumarins could be promising candidates against type 2 diabetes through antioxidative mechanisms.

Tubulointerstitial Biomarkers for Diabetic Nephropathy

Patients with diabetic nephropathy have a higher risk of mortality, mostly from cardiovascular complications. Standard biomarkers including serum creatinine, estimated glomerular filtration rate, and albuminuria are imprecise, do not directly measure renal tissue injury, and are relatively insensitive to small changes in renal function. Thus, availability of novel biomarkers that are sensitive, specific, and precise as well as able to detect kidney injury and predict clinically significant outcomes would be widely useful in diabetic nephropathy. Novel biomarkers of the processes that induce tubulointerstitial changes may ultimately prove to better predict renal progression and prognosis in type 2 diabetes. Recently, certain biomarkers, which were initially identified in acute kidney injury, also have been reported to confer value in evaluating patients with chronic kidney disease. Biomarkers such as cystatin C, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), angiotensinogen, periostin, and monocyte chemoattractant protein-1 (MCP-1) reflect tubular injury. In this article, we focused on the potential applications of these biomarkers in diabetic nephropathy.

miR302a-3p May Modulate Renal Epithelial-Mesenchymal Transition in Diabetic Kidney Disease by Targeting ZEB1

BACKGROUND

Recent study found that microRNA (miRNA) are involved in diabetic kidney disease (DKD). The objective of this study is to determine the role of miR302a-3p in the process of renal epithelial-mesenchymal transition (EMT) in DKD.

METHODS

The miRNA expression profiling of the cell line stimulated by high glucose was performed by a microarray analysis. Then real-time polymerase chain reaction (PCR) were used to determine the expression of one of the miRNAs significantly upregulated in cell line stimulated by high glucose, miR302a-3p. miR302a-3p mimics and inhibitor were transfected to HK-2 cells following exposure to high glucose and normal glucose, respectively. The expressions of E-cadherin, vimentin, and Zinc finger E-box-binding protein 1 (ZEB-1) were determined by real-time PCR and Western blot. Finally, the levels of miR302a-3p in the plasma of DKD patients were detected by real-time PCR, and then the relationship of miR302a-3p and urinary albumin excretion (UAE) or estimated glomerular filtration rate (eGFR) was analyzed.

RESULTS

The expression of miR-302a-3p, 513a-5p, 1291 and the other 17 miRNA were increased significantly in HK-2 cell line after high glucose stimulation; on the other hand, miRNA490-3p, 638, 3203 and the other 19 miRNA were decreased significantly. In vitro, miR-302a-3p expression in HG group increased at 6 h and ascended to the highest level at 12 and 24 h and then gradually decreased from 48 to 72 h. More interesting, ZEB1 protein expression had an opposite change, which gradually decreased from 6 to 24 h and then gradually increased from 48 to 72 h. Moreover, overexpression of miR-302a-3p suppressed expression of ZEB1 in the post-transcriptional level and reversed high glucose-mediated downregulation of E-cadherin and upregulation of vimentin. Meanwhile, loss of miR-302a-3p expression can lead to EMT of HK-2 cells just as high glucose stimulation. Further study demonstrated that the expression of circulating miR-302a-3p was significantly increased in the diabetes mellitus (DM) with normoalbuminuria (DM group, n = 22) compared with control (healthy persons, n = 30) and then decreased in DM with microalbuminuria (DNE group, n = 20). Furthermore, its expression in DM with macroalbuminuria (DNC group, n = 18) was decreased significantly compared with DM group. Circulating miR-302a-3p had negative relevance with UAE in DNE group (r = -0.649, p = 0.002) and DNC group (r = -0.681, p = 0.006). Circulating miR-302a-3p had positive relevance with eGFR in DNC group (r = 0.486, p = 0.041).

CONCLUSIONS

These findings suggest that miR-302a-3p may play a protective role by targeting ZEB1 in renal EMT in DKD. In view of these findings, it is conceivable that miR-302a-3p may serve as a potential novel target in pre-EMT states for the amelioration renal fibrosis seen in DKD.

ALA/LA ameliorates glucose toxicity on HK-2 cells by attenuating oxidative stress and apoptosis through the ROS/p38/TGF-β1 pathway

BACKGROUND

Growing evidence indicates that oxidative stress (OS) plays a pivotal role in Diabetic nephropathy (DN). In a previous study we demonstrated that ALA/LA protected HK-2 cells against high glucose-induced cytotoxicity. So we aimed to establish the glucose injury model of HK-2 cells and investigate the beneficial effects of ALA/LA on high glucose-induced excessive production of TGF-β1 and the possible mechanisms mediating the effects.

METHODS

The expression of OS markers in high glucose-induced HK-2 cells treated with ALA/LA., including the antioxidant enzymes and reactive oxygen species (ROS) production, as well as the apoptosis rate were assayed by ELISA and flow cytometry. The p38/transforming growth factor β1 (TGF-β1) signal pathway were measured by real-time RT-PCR and western blot.

RESULTS

The modeling condition of glucose toxicity on HK-2 cells was at the glucose concentration of 40.9 mM. ALA/LA can significantly increase the activities of antioxidant enzymes and decrease ROS production stimulated by high glucose. The study also found that ALA/LA caused a decrease in the apoptosis rate and TGF-β1 level of HK-2 cells under high glucose stress through the ROS/p38 pathway.

CONCLUSIONS

ALA/LA exerts protective effects in vitro through inhibition of ROS generation, down regulation of the activation of the p38MAPK pathway and the expression of TGF-β1 in HK-2 cells.

Transforming growth factor β1 promotes migration and invasion in HepG2 cells: Epithelial‑to‑mesenchymal transition via JAK/STAT3 signaling

Transforming growth factor β1 (TGFβ1) is a cytokine with multiple functions. TGFβ1 significantly induces migration and invasion of liver cancer cells. However, the molecular mechanisms underlying this effect remain unclear. Epithelial‑to‑mesenchymal transition (EMT) is crucial for the development of invasion and metastasis in human cancers. The aim of the present study was to determine whether TGFβ1‑induced EMT promoted migration and invasion in HepG2 cells. The underlying mechanism and the effect of EMT on HepG2 cells were also investigated. The results demonstrated that TGFβ1 may induce EMT to promote migration and invasion of HepG2 cells, and this effect depends on activation of the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway. JAK/STAT3 signaling is involved in human malignancies, including lung cancer, and is implicated in cell transformation, tumorigenicity, EMT and metastasis. In the present study, TGFβ1 also activated JAK/STAT3 signaling in HepG2 cells and promoted Twist expression, but these events were abolished by treatment with the STAT3 inhibitor AG490. Additionally, Twist siRNA blocked TGFβ1‑induced EMT. Thus, TGFβ1 was shown to induce EMT, thereby promoting the migration and invasion of HepG2 cells via JAK/STAT3/Twist signaling.

miR-30e targets GLIPR-2 to modulate diabetic nephropathy: in vitro and in vivo experiments

The objectives of this study are to investigate the effect of miR-30e targeting GLIPR-2 on the pathological mechanism of DN. The renal tissues of db/db and db/m mice at different age of weeks were stained with PAS. qRT-PCR was applied to detect the expression of miR-30e and GLIPR-2, not only in the renal tissues of mice but also in the renal tubular epithelial cells (RTECs). By luciferase reporter gene assays, we found the 3'-UTR of the GLIPR-2 mRNA as a direct target of miR-30e. The RTECs cultured in high glucose were divided into blank control, NC, miR-30e mimics, miR-30e inhibitors, miR-30e inhibitor + si-GLIPR-2 and si-GLIPR-2 groups. MTT and flow cytometry were utilized to measure the proliferation and apoptosis of RTECs, while qRT-PCR and Western blot to detect the expression of GLIPR-2- and EMT-related factors. The following results were obtained: In the renal tissues of over 8-week-old db/db mice and the RTECs cultured for 6 h in high glucose, miR-30e was downexpressed while GLIPR-2 was upregulated in a time-dependent manner. Besides, overexpression of miR-30e and si-GLIPR-2 can not only greatly improve the proliferation of RTECs cultured in high glucose, but also downregulate the apoptosis rate of RTECs and the expressions of GLIPR-2, vimentin, α-SMA, Col-I and FN and upregulate E-cadherin. Moreover, si-GLIPR-2 can reverse the proliferation reduction, GLIPR-2 and EMT occurrence caused by the downexpression of miR-30e in RTECs. In conclusion, miR-30e is downregulated in DN, and the overexpression of miR-30e can inhibit GLIPR-2, promote the proliferation of RTECs and inhibit EMT, ultimately avoid leading to renal fibrosis in DN.

Down-regulation of miR-23a inhibits high glucose-induced EMT and renal fibrogenesis by up-regulation of SnoN

It has been reported that transforming growth factor-β1 (TGF-β1) signaling plays an important role in the development of diabetic nephropathy (DN). The nuclear transcription co-repressor Ski-related novel protein N (SnoN) is a critical negative regulator of TGF-β1/Smad signal pathway, involving in tubule epithelial-mesenchymal transition (EMT), extracellular matrix (ECM) accumulation, and tubulointerstitial fibrosis. In this study, we focused on miR-23a as a regulator of SnoN. Our purpose is to study the effects of miR-23a on high glucose (HG)-induced EMT process and ECM deposition in HK2 cells. We found that miR-23a was up-regulated in renal tissues of diabetic patients and HG-induced HK2 cells. Besides, the high level of miR-23a was closely associated with decreased SnoN expression. Knockdown of miR-23a increased SnoN expression and in turn suppressed HG-induced EMT and renal fibrogenesis. Introduction of miR-23a decreased SnoN expression and enhanced the profibrogenic effects of HG on HK2 cells. Next, bioinformatics analysis predicted that the SnoN was a potential target gene of miR-23a. Luciferase reporter assay demonstrated that miR-23a could directly target SnoN. We demonstrated that overexpression of SnoN was sufficient to inhibit HG-induced EMT and renal fibrogenesis in HK2 cells. Furthermore, down-regulation of SnoN partially reversed the protective effect of miR-23a knockdown on HG-induced EMT and renal fibrogenesis in HK2 cells. Collectively, miR-23a and SnoN significantly impact on the progression of HG-induced EMT and renal fibrogenesis in vitro, and they may represent novel targets for the prevention strategies of renal fibrosis in the context of DN.

Defective CFTR leads to aberrant β-catenin activation and kidney fibrosis

Cystic fibrosis transmembrane conductance regulator (CFTR), known as a cAMP-activated Cl⁻ channel, is widely expressed at the apical membrane of epithelial cells in a wide variety of tissues. Of note, despite the abundant expression of CFTR in mammalian kidney, the role of CFTR in kidney disease development is unclear. Here, we report that CFTR expression is downregulated in the UUO (unilateral ureteral obstruction)-induced kidney fibrosis mouse model and human fibrotic kidneys. Dysfunction or downregulation of CFTR in renal epithelial cells leads to alteration of genes involved in Epithelial-Mesenchymal Transition (EMT) and kidney fibrosis. In addition, dysregulation of CFTR activates canonical Wnt/β-catenin signaling pathways, whereas the β-catenin inhibitor reverses the effects of CFTR downregulation on EMT marker. More interestingly, CFTR interacts with Dishevelled 2 (Dvl2), a key component of Wnt signaling, thereby suppressing the activation of β-catenin. Compared to wild type, deltaF508 mice with UUO treatment exhibit significantly higher β-catenin activity with aggregated kidney fibrogenesis, which is reduced by forced overexpression of CFTR. Taken together, our study reveals a novel mechanism by which CFTR regulates Wnt/β-catenin signaling pertinent to progression of kidney fibrosis and indicates a potential treatment target.

Sodium-Glucose Cotransporter 2 Inhibitors with Renoprotective Effects

BACKGROUND

Diabetes is the leading cause of end-stage renal disease (ESRD) and accounts for 40-50% of patients requiring renal replacement therapy. The main pathophysiology of diabetic nephropathy comprises glucose-dependent pathways, hemodynamic pathways, and genetic factors.

SUMMARY

Glucose-dependent pathways, known as advanced glycation, polyols, and protein kinase C activation have been implicated in the pathogenesis of diabetic nephropathy. Current studies have indicated that intensified glycemic control retards the rate of development of albuminuria and impairs renal function in both patients with type 1 and 2 diabetes. However, therapeutic options have substantially increased over the last decade, but have not yet been translated to remarkably reduce the incidence of ESRD from diabetic nephropathy. Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a novel class of glucose-lowering agents with potential renoprotective effects.

KEY MESSAGE

SGLT2 inhibitors represent a promising therapeutic approach to prevent and improve nephropathy among patients with type 2 diabetes. The current data strongly support that SGLT2 inhibitors have renoprotective properties not only by improving glycemic control but also through hemodynamic and nonhemodynamic renal effects. This review focuses on the latest published data dealing with hypoglycemic agents and SGLT2 inhibitors regarding the progression of kidney disease.

SnoN upregulation ameliorates renal fibrosis in diabetic nephropathy

Progressive reduction of SnoN is associated with gradual elevation of TGF-β1 during diabetic nephropathy progression, suggesting SnoN to be a possible mediator of TGF-β1 signaling, with potential therapeutic benefits against TGF- β1 –induced renal fibrosis. To characterize SnoN for its role in renal fibrosis, we assessed SnoN expression patterns in response to high glucose stress, and evaluated the effects of upregulating SnoN on renal fibrosis. High glucose stress induced significantly elevated SnoN, TGF-β1, and Arkadia transcription; however, significantly reduced SnoN protein levels were observed under these conditions. Upregulating the SnoN protein was achieved by Arkadia knockdown, which resulted in inhibited high glucose-induced epithelial-mesenchymal transition (EMT) in renal tubular cells, the onset phase of renal fibrosis. Alternatively, EMT was suppressed by dominantly expressed exogenous SnoN without interfering with TGF-β1. Overall, renal SnoN upregulation ameliorates renal fibrosis by relieving high glucose-induced EMT; these findings support a translational approach targeting SnoN for the treatment of diabetic nephropathy.

Prolyl oligopeptidase attenuates hepatic stellate cell activation through induction of Smad7 and PPAR-γ

Prolyl oligopeptidase (POP) is a serine endopeptidase widely distributed in vivo with high activity in the liver. However, its biological functions in the liver have remained largely elusive. A previous study by our group has shown that POP produced N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) and thereby exerted an anti-fibrogenic effect on hepatic stellate cells (HSCs) in vitro. It was therefore hypothesized that POP may affect the activation state of HSCs and has an important role in liver fibrosis. The HSC-T6 immortalized rat liver stellate cell line was treated with the POP inhibitor S17092 or transfected with recombinant lentivirus to overexpress POP. Cell proliferation and apoptosis were determined using a Cell Counting Kit-8 and flow cytometry, respectively. The activation status of HSCs was determined by examination of the expression of α-smooth muscle actin (α-SMA), collagen I, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor (TGF)-β-Smad signaling and peroxisome proliferator activated receptor-γ (PPAR-γ). Inhibition by S17092 decreased, whereas lentiviral expression increased the activity of POP and cell proliferation, while neither of the treatments affected cell apoptosis. Of note, S17092 significantly increased, whereas POP overexpression decreased the expression of α-SMA and MCP-1 without affecting the expression of collagen I and TGF-β1. Furthermore, S17092 caused a reduction, whereas POP overexpression caused an upregulation of Smad7 protein and PPAR-γ, but not phosphorylated-Smad2/3 expression. In conclusion, POP attenuated the activation of HSCs through inhibition of TGF-β signaling and induction of PPAR-γ, which may have therapeutic potential in liver fibrosis.

The coordinated roles of miR-26a and miR-30c in regulating TGFβ1-induced epithelial-to-mesenchymal transition in diabetic nephropathy

MicroRNAs (miRNAs) play vital roles in the development of diabetic nephropathy. Here, we compared the protective efficacies of miR-26a and miR-30c in renal tubular epithelial cells (NRK-52E) and determined whether they demonstrated additive effects in the attenuation of renal fibrosis. TGFβ1 suppressed miR-26a and miR-30c expression but up-regulated pro-fibrotic markers in NRK-52E cells, and these changes were also found in the kidney cortex of 40-week-old diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Bioinformatic analyses and luciferase assays further demonstrated that both miR-26a and miR-30c targeted connective tissue growth factor (CTGF); additionally, Snail family zinc finger 1 (Snail1), a potent epithelial-to-mesenchymal transition (EMT) inducer, was targeted by miR-30c. Overexpression of miR-26a and miR-30c coordinately decreased CTGF protein levels and subsequently ameliorated TGFβ1-induced EMT in NRK-52E cells. Co-silencing of miR-26a and miR-30c exhibited the opposite effect. Moreover, miR-26a and miR-30c co-silenced CTGF to decrease ERK1/2 and p38 MAPK activation. Furthermore, miR-26a was up-regulated in urinary extracellular vesicles of diabetic nephropathy patients. Our study provides evidence for the cooperative roles of miR-26a and miR-30c in the pathogenesis of diabetic nephropathy, and the co-targeting of miR-26a and miR-30c could provide a new direction for diabetic nephropathy treatment.

Mesenchymal stem cell therapy ameliorates diabetic nephropathy via the paracrine effect of renal trophic factors including exosomes

Bone marrow-derived mesenchymal stem cells (MSCs) have contributed to the improvement of diabetic nephropathy (DN); however, the actual mediator of this effect and its role has not been characterized thoroughly. We investigated the effects of MSC therapy on DN, focusing on the paracrine effect of renal trophic factors, including exosomes secreted by MSCs. MSCs and MSC-conditioned medium (MSC-CM) as renal trophic factors were administered in parallel to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. Both therapies showed approximately equivalent curative effects, as each inhibited the exacerbation of albuminuria. They also suppressed the excessive infiltration of BMDCs into the kidney by regulating the expression of the adhesion molecule ICAM-1. Proinflammatory cytokine expression (e.g., TNF-α) and fibrosis in tubular interstitium were inhibited. TGF-β1 expression was down-regulated and tight junction protein expression (e.g., ZO-1) was maintained, which sequentially suppressed the epithelial-to-mesenchymal transition of tubular epithelial cells (TECs). Exosomes purified from MSC-CM exerted an anti-apoptotic effect and protected tight junction structure in TECs. The increase of glomerular mesangium substrate was inhibited in HFD-diabetic mice. MSC therapy is a promising tool to prevent DN via the paracrine effect of renal trophic factors including exosomes due to its multifactorial action.

Arg tyrosine kinase modulates TGF-β1 production in human renal tubular cells under high-glucose conditions

Renal tubular cells are involved in the tubular interstitial fibrosis observed in diabetic nephropathy. It is debated whether epithelial-mesenchymal transition (EMT) affects tubular cells, which under high-glucose conditions overproduce transforming growth factor-β (TGF-β), a fibrogenic cytokine involved in interstitial fibrosis development. Our study investigated the involvement of non-receptor tyrosine kinase Arg (also called Abl2) in TGF-β production. Human primary tubular cell cultures exposed to high-glucose conditions were used. These cells showed an elongated morphology, stress fibers and vimentin increment but maintained most of the epithelial marker expression and distribution. In these cells exposed to high glucose, which overexpressed and secreted active TGF-β1, Arg protein and activity was downregulated. A further TGF-β1 increase was induced by Arg silencing with siRNA, as with the Arg tyrosine kinase inhibitor Imatinib. In the cells exposed to high glucose, reactive oxygen species (ROS)-dependent Arg kinase downregulation induced both RhoA activation, through p190RhoGAPA (also known as ARHGAP35) modulation, and proteasome activity inhibition. These data evidence a new specific involvement of Arg kinase into the regulation of TGF-β1 expression in tubular cells under high-glucose conditions and provide cues for new translational approaches in diabetic nephropathy.

HRD1-Mediated IGF-1R Ubiquitination Contributes to Renal Protection of Resveratrol in db/db Mice

Many studies have provided evidence to demonstrate the beneficial renal effects of resveratrol (RESV) due to its antioxidant character and its capacity for activation of surtuin 1. However, the molecular mechanisms underlying the protective role of RESV against kidney injury are still incompletely understood. The present study used Lepr db/db (db/db) and Lepr db/m (db/m) mice as models to evaluate the effect of RESV on diabetic nephropathy (DN). RESV reduced proteinuria and attenuated the progress of renal fibrosis in db/db mice. Treatment with RESV markedly attenuated the diabetes-induced changes in renal superoxide dismutase copper/zinc, superoxide dismutase manganese, catalase, and malonydialdehyde as well as the renal expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), α-smooth muscle actin (α-SMA), and E-cadherin in db/db mice. The kidney expression of the IGF-1 receptor (IGF-1R) was increased in db/db mice, but the expression of 3-hydroxy-3-methylglutaryl reductase degradation (HRD1), a ubiquitin E3 ligase, was significantly decreased in the DN model. RESV treatment dramatically decreased IGF-1R and increased HRD1 expressions, consistent with data obtained with HKC-8 cells. HRD1 physically interacted with IGF-1R in HKC-8 cells and liquid chromatography and tandem mass spectrometry (LC-MS/MS) data supported the concept that IGF-1R is one of the HRD1 substrates. HRD1 promoted the IGF-1R ubiquitination for degradation in HKC-8 cells, and the down-regulation of HRD1 reversed the protective effects of RESV in HKC-8 cells. In summary, we have demonstrated that RESV reduces proteinuria and attenuates the progression of renal fibrosis in db/db mice. These protective effects of RESV on DN were associated with the up-regulation of HRD1, induced by RESV, and the promotion of IGF-1R ubiquitination and degradation.

Oxymatrine Inhibits Renal Tubular EMT Induced by High Glucose via Upregulation of SnoN and Inhibition of TGF-β1/Smad Signaling Pathway

Transforming growth factor-β1 (TGF-β1) signaling has been shown to play a critical role in the development of diabetic nephropathy (DN). The nuclear transcription co-repressor Ski-related novel protein N (SnoN) is an important negative regulator of TGF-β1/Smad signal transduction, and subsequent biological responses including tubule epithelial-mesenchymal transition (EMT), extracellular matrix accumulation and tubulointerstitial fibrosis. Oxymatrine (OM) is an alkaloid extracted from the Chinese herb Sophora japonica and has been demonstrated to prevent fibrosis. However, the anti-fibrosis effect of OM in DN is still unclear. In this study, we cultured normal rat renal tubular epithelial cells (NRK52Es) in high glucose and high glucose plus OM, and detected the expression of E-cadherin, α-SMA, FN, TGF-β1, SnoN, Arkadia, p-Smad2 and p-Smad3 and poly-ubiquitination of SnoN. The results showed that E-cadherin and SnoN expression in NRK52Es decreased significantly, but poly-ubiquitination of SnoN, TGF-β1, α-SMA, FN, Arkadia, p-Smad2 and p-Smad3 expression significantly increased due to high glucose stimulation, which could be almost completely reversed by OM, suggesting that OM may alleviate EMT induced by high glucose via upregulating SnoN expression and inhibiting TGF-β1/Smad signaling pathway activation. Hence, OM could be a novel therapeutic for DN.

Astragalus membranaceus ameliorates renal interstitial fibrosis by inhibiting tubular epithelial-mesenchymal transition in vivo and in vitro

Epithelial-mesenchymal transition (EMT) induces the progression of renal tubulointerstitial fibrosis. Astragalus membranaceus (AM) is a traditional Chinese herbal medicine that has been demonstrated to exert anti-inflammatory and anti-cancer effects, in addition to protecting and supporting the immune system. The present study investigated the effects of AM on renal fibrosis. A mouse model of unilateral ureteral obstruction (UUO) was established and treated with various concentrations of AM (100, 200 or 400 mg/kg/day). Interstitial fibrosis markedly increased in the UUO mice. AM significantly reduced the obstruction-induced upregulation of α-smooth muscle actin (α-SMA) and downregulation of E-cadherin in the kidneys of the UUO mice (P<0.05). Furthermore, AM treatment significantly inhibited the induction of EMT and the deposition of extracellular matrix. In addition, a transforming growth factor (TGF)-β1-stimulated murine renal proximal tubule cell line (NRK-52E) was treated with various concentrations of AM (10, 20, and 40 µg/ml). E-cadherin expression levels significantly decreased and those of α-SMA significantly increased in NRK-52E cells stimulated with TGF-β1 in vitro (P<0.05). Co-treatment with AM reversed these effects (P<0.05), and AM treatment reduced TGF-β1-induced expression and Smad2/3 phosphorylation (P<0.05). These results suggested that AM antagonizes tubular EMT by inhibiting the Smad signaling pathway.

Blockade of Orai1 Store-Operated Calcium Entry Protects against Renal Fibrosis

Evidence supports an important role of Ca²⁺ release-activated Ca²⁺ channel protein 1 (Orai1)-mediated Ca²⁺ entry in the development of renal fibrosis, a common pathologic feature of CKDs that lead to ESRD, but the molecular mechanisms remain unclear. We determined the role of Orai1 calcium channel in renal fibrosis induced by high-fat diet and by unilateral ureteral obstruction. Mouse kidneys with fibrosis had higher levels of Orai1 protein expression than did kidneys without fibrosis. In vivo knockdown of Orai1 with adenovirus harboring Orai1-short hairpin RNA or inhibition of Orai1 with SKF96365 dramatically prevented renal fibrosis and significantly decreased protein expression of fibronectin, α‑smooth muscle actin, and TGF‑β1 in the kidney cortex of ApoE^-/- mice on a high-fat diet and in the obstructed kidneys of mice with unilateral ureteral obstruction. Compared with kidney biopsy specimens of patients with glomerular minimal change disease, those of patients with fibrotic nephropathy had higher expression levels of Orai1. In cultured human proximal tubule epithelial cells (HK2), knockdown of Orai1 Ca²⁺ channel with adenovirus-Orai1-short hairpin RNA markedly inhibited TGF-β1-induced intracellular Ca²⁺ influx and phosphorylation of smad2/3. Knockdown or blockade of the Orai1 Ca²⁺ channel in HK2 cells also prevented epithelial-to-mesenchymal transition induced by TGF‑β1. In conclusion, blockade of the Orai1 Ca²⁺ channel prevented progression of renal fibrosis in mice, likely by suppressing smad2/3 phosphorylation and TGF-β1-induced epithelial-to-mesenchymal transition. These results render the Orai1 Ca²⁺ channel a potential therapeutic target against renal fibrosis.

Novel Tubular Biomarkers Predict Renal Progression in Type 2 Diabetes Mellitus: A Prospective Cohort Study

Background. Tubulointerstitial injury is both a key feature of diabetic nephropathy and an important predictor of renal dysfunction. Novel tubular biomarkers related to renal injury in diabetic nephropathy could improve risk stratification and prediction. Methods. A total of 303 type 2 diabetic patients were followed up. The baseline urine values of cystatin-C to creatinine ratio (UCCR), angiotensinogen to creatinine ratio (UANG), NGAL to creatinine ratio (UNGAL), and KIM-1 to creatinine ratio (UKIM-1) were measured. The primary outcome was a decline in estimated GFR of ≥25% yearly from baseline. Results. Urine tubular biomarkers of UCCR, UANG, UNGAL, and UKIM-1 were significantly higher according to the degree of albuminuria and all were significantly higher among patients with rapid decline in estimated GFR of ≥25% yearly from baseline. All biomarkers predicted primary outcomes with ROC for UCCR of 0.72; 95% CI 0.64-0.79, for UANG of 0.71; 95% CI 0.63-0.79, for UNGAL of 0.64; 95% CI 0.56-0.72, and for UKIM-1 of 0.71; 95% CI 0.63-0.79. Using multivariate Cox regression analysis, the number of patients with rapid renal progression was higher among those in the upper quartiles of all biomarkers than in those in the lower quartiles. Conclusions. Type 2 diabetic patients with high levels of urine tubular biomarkers had a more rapid decline in renal function.

Transforming growth factor-β1 and diabetic nephropathy

Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy.

Xiaokeping mixture inhibits diabetic nephropathy in streptozotocin-induced rats through blocking TGF-β1/Smad7 signaling

Background

Diabetic nephropathy (DN) is a major cause of chronic kidney failure and characterized by excessive deposition of extracellular matrix. Evidence have shown that transforming growth factor-β1 (TGF-β1) is a key mediator in the development of DN. However, treatment of DN by blocking the TGF-β1/Smad7 pathway remains limited. Xiaokeping mixture (XKP), a traditional Chinese herbal compound, has been used for treatment in patients with DN for many years.

Methods

In the present study, TGF-β1/Smad7 pathway analysis was used to evaluate the therapeutic effect of XKP on DN rats induced by streptozotocin and to address the underlying molecular mechanism. Male rats were divided into four groups: normal control, untreated control group (fed with high fat), irbesartan-treated DN, and XKP-treated DN, respectively. Levels of serum creatinine, blood urea nitrogen, urine protein of 24 hours, and triacylglycerol were detected. Pathological changes of renal tissues were observed by hematoxylin–eosin staining. Immunohistochemical and Western blot analysis were used to detect the expressions of TGF-β1 and Smad7.

Results

The results demonstrated that XKP can effectively reduce the levels of glucose, serum creatinine, blood urea nitrogen, urine protein of 24 hours, and triacylglycerol. Further studies indicated that inhibition of DN in XKP-treated DN rats was associated with inhibition of TGF-β1/Smad7 signaling as demonstrated by downregulation of TGF-β1 but upregulation of Smad7.

Conclusion

The data obtained from the present study indicate that XKP may be a therapeutic agent for DN.

Transition of mesothelial cell to fibroblast in peritoneal dialysis: EMT, stem cell or bystander?

Long-term peritoneal dialysis (PD) can lead to fibrotic changes in the peritoneum, characterized by loss of mesothelial cells (MCs) and thickening of the submesothelial area with an accumulation of collagen and myofibroblasts. The origin of myofibroblasts is a central question in peritoneal fibrosis that remains unanswered at present. Numerous clinical and experimental studies have suggested that MCs, through epithelial-mesenchymal transition (EMT), contribute to the pool of peritoneal myofibroblasts. However, recent work has placed significant doubts on the paradigm of EMT in organ fibrogenesis (in the kidney particularly), highlighting the need to reconsider the role of EMT in the generation of myofibroblasts in peritoneal fibrosis. In particular, selective cell isolation and lineage-tracing experiments have suggested the existence of progenitor cells in the peritoneum, which are able to switch to fibroblast-like cells when stimulated by the local environment. These findings highlight the plastic nature of MCs and its contribution to peritoneal fibrogenesis. In this review, we summarize the key findings and caveats of EMT in organ fibrogenesis, with a focus on PD-related peritoneal fibrosis, and discuss the potential of peritoneal MCs as a source of myofibroblasts.

MiR-30a Inhibits the Epithelial--Mesenchymal Transition of Podocytes through Downregulation of NFATc3

MicroRNAs (miRNAs) possess an important regulating effect among numerous renal diseases, while their functions in the process of epithelial-to-mesenchymal transition (EMT) after podocyte injury remain unclear. The purpose of our study is to identify the potential functions of miR-30a in EMT of podocytes and explore the underlying mechanisms of miR-30a in the impaired podocytes. The results revealed that downregulation of miR-30a in podocyte injury animal models and patients, highly induced the mesenchymal markers of EMT including Collagen I, Fibronectin and Snail. Furthermore, overexpression of miR-30a enhances epithelial markers (E-cadherin) but diminished mesenchymal markers (Collagen I, Fibronectin and Snail) in podocytes. In addition, we established miR-30a target NFATc3, an important transcription factor of Non-canonical Wnt signaling pathway. More importantly, our findings demonstrated that the augmentation of miR-30a level in podocytes inhibits the nuclear translocation of NFATc3 to protect cytoskeleton disorder or rearrangement. In summary, we uncovered the protective function of miR30a targeting NFATc3 in the regulation of podocyte injury response to EMT.

Epithelial-to-Mesenchymal Transition in Diabetic Nephropathy: Fact or Fiction?

The pathophysiology of diabetic nephropathy (DN), one of the most serious complications in diabetic patients and the leading cause of end-stage renal disease worldwide, is complex and not fully elucidated. A typical hallmark of DN is the excessive deposition of extracellular matrix (ECM) proteins in the glomerulus and in the renal tubulointerstitium, eventually leading to glomerulosclerosis and interstitial fibrosis. Although it is obvious that myofibroblasts play a major role in the synthesis and secretion of ECM, the origin of myofibroblasts in DN remains the subject of controversial debates. A number of studies have focused on epithelial-to-mesenchymal transition (EMT) as one source of matrix-generating fibroblasts in the diseased kidney. EMT is characterized by the acquisition of mesenchymal properties by epithelial cells, preferentially proximal tubular cells and podocytes. In this review we comprehensively review the literature and discuss arguments both for and against a function of EMT in renal fibrosis in DN. While the precise extent of the contribution to nephrotic fibrosis is certainly arduous to quantify, the picture that emerges from this extensive body of literature suggests EMT as a major source of myofibroblasts in DN.

The insulin response integrates increased TGF-β signaling through Akt-induced enhancement of cell surface delivery of TGF-β receptors

Increased activity of transforming growth factor-β (TGF-β), which binds to and stimulates cell surface receptors, contributes to cancer progression and fibrosis by driving epithelial cells toward a migratory mesenchymal phenotype and increasing the abundance of extracellular matrix proteins. The abundance of TGF-β receptors at the cell surface determines cellular responsiveness to TGF-β, which is often produced by the same cells that have the receptors, and thus serves as an autocrine signal. We found that Akt-mediated phosphorylation of AS160, a RabGAP [guanosine triphosphatase (GTPase)-activating protein], promoted the translocation of TGF-β receptors from intracellular stores to the plasma membrane of mouse embryonic fibroblasts and NMuMG epithelial cells. Consequently, insulin, which is commonly used to treat hyperglycemia and activates Akt signaling, increased the amount of TGF-β receptors at the cell surface, thereby enhancing TGF-β responsiveness. This insulin-induced increase in autocrine TGF-β signaling contributed to insulin-induced gene expression responses, attenuated the epithelial phenotype, and promoted the migration of NMuMG cells. Furthermore, the enhanced delivery of TGF-β receptors at the cell surface enabled insulin to increase TGF-β-induced gene responses. The enhancement of TGF-β responsiveness in response to Akt activation may help to explain the biological effects of insulin, the progression of cancers in which Akt is activated, and the increased incidence of fibroses in diabetes.

MicroRNA-590 is an EMT-suppressive microRNA involved in the TGFβ signaling pathway

Over the last few decades, the epithelial-to-mesenchymal transition (EMT) has been identified as being involved in a number of aspects of physiological processes and various pathological events, including embryonic development and renal fibrosis. Transforming growth factor-β receptor 2 (TGFβR2) is a widely studied gene, which fulfils a vital role in the TGFβ signaling pathway and exerts a crucial function in the progression of EMT. Previous studies demonstrated that the dysregulation of microRNAs (miRNAs) is considered to be associated with the EMT process. However, the precise functional involvement of miRNAs in EMT remains to be fully elucidated. In the present study, the level of miR-590 was decreased in an EMT model in vitro and in vivo. Furthermore, the overexpression of miR-590 inhibited EMT by upregulating the epithelial marker, E-cadherin, and downregulating the mesenchymal markers, laminin, α-smooth muscle actin (α-SMA) and collagen, in the human kidney 2 (HK2) cell line. Furthermore, TGFβR2 was negatively regulated by miR-590. In addition, performing a knockdown of TGFβR2 with small-interfering RNA had an effect similar to miR-590 on EMT in the HK2 cell line, whereas the transfection of pCMV-tag2B-TGFβR2 reversed the effect of miR-590 on EMT in HK2 cells. Taken together, the present study demonstrated that miR-590 is a novel EMT-suppressive microRNA, which targets TGFβR2.

Mycophenolate mofetil ameliorates diabetic nephropathy through epithelial mesenchymal transition in rats

Recent studies in animal models have revealed that mycophenolate mofetil (MMF) has certain protective effects against experimental diabetic nephropathy. The present study therefore aimed to investigate the hypothesis that diabetic nephropathy may be ameliorated by mycophenolate mofetil and benazepril treatment alone or in combination, and identify the potential underlying mechanisms in a rat model. Diabetes was induced in rats by a single intraperitoneal injection of streptozotocin. Rats were subsequently treated with benazepril, MMF or a combination of the two drugs, and blood glucose, normalized kidney weight, urine protein and serum creatinine were determined. The pathological changes in renal tissue were also observed. In addition, indices of epithelial mesenchymal transition, including α‑smooth muscle actin (α‑SMA) and transforming growth factor (TGF)‑β1 expression, were examined. Normalized kidney weight, urine protein and serum creatinine levels were significantly improved in the diabetic rats treated with benazepril or mycophenolate mofetil, compared with those of rats in the untreated diabetic group. Pathological changes in the kidney were detected concurrently with increasing kidney weight and urinary albumin excretion, with a similar trend in variation among groups. In addition, the expression of epithelial mesenchymal transition indices, including α‑SMA and TGF‑β1, in the renal tubule interstitium were significantly decreased in the benazepril‑ and MMF‑treated groups compared with those of the diabetic group. As expected, the aforementioned indices were markedly lower in the benazepril and MMF combined treatment group than those in the single medication groups. These data suggested that MMF may have a protective role in diabetic nephropathy, and that the underlying mechanism may be partially dependent upon the suppression of the epithelial mesenchymal transition. Furthermore, the combination of benazepril and MMF conferred enhanced efficacy over monotherapies in the treatment of diabetic nephropathy.

Substrate-specific gene expression profiles in different kidney cell types are associated with Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the gene encoding the α-galactosidase A (α-Gal A) lysosomal enzyme, which results in globotriaosylceramide (Gb3) storage in vascular endothelial cells and different cell types throughout the body. Involvement of the kidney and heart is life threatening, and fibrosis of these organs is considered to be involved in the pathogenesis of Fabry disease. An increased concentration of deacylated Gb3 (lyso‑Gb3) in the plasma of symptomatic patients has also been suggested as a causative molecular event. To elucidate the molecular mechanisms involved in renal fibrosis in Fabry disease, the present analyzed the changes in global gene expression prior to and following Gb3 or lyso‑Gb3 treatment in two types of kidney cell lines, human proximal renal tubular epithelial (HK‑2) and mouse renal glomerular mesangial (SV40 MES 13) cells. Gb3 and lyso‑Gb3 treatment regulated the expression of 199 and 328 genes in each cell type, demonstrating a >2.0‑fold change. The majority of the biological functions of the regulated genes were associated with fibrogenesis or epithelial‑mesenchymal transition (EMT). The gene expression patterns of sphingolipid‑treated HK‑2 cells were distinguishable from the patterns in the SV40 MES 13 cells. Several genes associated with the EMT were selected and evaluated further in kidney cells and in Fabry mouse kidney tissues. In the SV40 MES 13 cells, the DLL1, F8, and HOXA11 genes were downregulated, and FOXP2 was upregulated by treatment with Gb3 or lyso‑Gb3. In the HK‑2 cells, the ADAMTS6, BEST1, IL4, and MYH11 genes were upregulated. Upregulation of the FOXP2, COL15A1, IL4, and MYH11 genes was also observed in the Fabry mouse kidney tissues. The gene expression profiles in kidney cells following the addition of Gb3 or lyso‑Gb3 revealed substrate‑specific and cell‑specific patterns. These findings suggested that Gb3 and lyso‑Gb3 lead to renal fibrosis in Fabry disease through different biochemical modulations.

Hyperglycemia in the absence of cilia accelerates cystogenesis and induces renal damage

In polycystic kidney disease (PKD), the rate of cyst formation and disease progression is highly variable. The lack of predictability in disease progression may be due to additional environmental factors or pathophysiological processes called "third hits." Diabetes is a growing epidemic, and recent studies suggest that PKD patients may be at an increased risk for this disease. We sought to determine if hyperglycemia enhances the initiation and rate of cystogenesis. Tamoxifen was administered to adult Ift88 conditional floxed allele mice to induce cilia loss in the presence of Cre. Subsequent administration of streptozotocin resulted in equivalent hyperglycemia in cilia(+) and cilia(-) mice. Hyperglycemia with loss of cilia increased the rate of cyst formation and cell proliferation. Structural and functional alterations in the kidney, including focal glomerular foot process effacement, interstitial inflammation, formation of primitive renal tubules, polyuria, and increased proteinuria, were also observed in hyperglycemic cilia(-) mice. Gene array analysis indicated enhanced Wnt and epithelial-to-mesenchymal transition signaling in the kidney of hyperglycemic cilia(-) mice. These data show that hyperglycemia, in the absence of cilia, results in renal structural and functional damage and accelerates cystogenesis, suggesting that diabetes is a risk factor in the progression of PKD.

Mind the gap: connexins and cell-cell communication in the diabetic kidney

Connexins, assembled as a hexameric connexon, form a transmembrane hemichannel that provides a conduit for paracrine signalling of small molecules and ions to regulate the activity and function of adjacent cells. When hemichannels align and associate with similar channels on opposing cells, they form a continuous aqueous pore or gap junction, allowing the direct transmission of metabolic and electrical signals between coupled cells. Regulation of gap junction synthesis and channel activity is critical for cell function, and a number of diseases can be attributed to changes in the expression/function of these important proteins. Diabetic nephropathy is associated with several complex metabolic and inflammatory responses characterised by defects at the molecular, cellular and tissue level. In both type 1 and type 2 diabetes, glycaemic injury of the kidney is the leading cause of end-stage renal failure, a consequence of multiple aetiologies, including increased deposition of extracellular matrix, glomerular hyperfiltration, albuminuria and tubulointerstitial fibrosis. In diabetic nephropathy, loss of connexin mediated cell-cell communication within the nephron may represent an early sign of disease; however, our current knowledge of the role of connexins in the diabetic kidney is sparse. This review highlights recent evidence demonstrating that maintenance of connexin-mediated cell-cell communication could benefit region-specific renal function in diabetic nephropathy and suggests that these proteins should be viewed as a tantalising novel target for therapeutic intervention.

The effects of the water-extraction of Astragali Radix and Lycopi herba on the Pathway of TGF-smads-UPP in a rat model of Diabetic Nephropathy

Background:

Astragali Radix and Lycopi Herba were widely used in clinical practice for treating the diabetic nephropathy (DN), but their therapeutic mechanisms were not clear.

Objective:

To observe the effects of the water-extraction of Astragali Radix and Lycopi Herba on the signaling pathway of TGF-Smads-UPP in streptozotocin (STZ)-induced DN.

Materials and Methods:

Sprague-Dawley (SD) rats were randomly divided into the normal control (NC) group and the model group. The NC group was fed with a standard diet and the other five diabetic groups received a high-fat diet. After 4 weeks, five diabetic groups were treated with STZ (30mg/kg i.p.). The NC group rats were treated with citrate buffer. Tail random blood glucose (RBG) was measured 72h later using a strip-operated blood glucose sensor and monitored every 2 weeks until drug intervention. Rats with RBG levels less than 16.7mmol/L were excluded from the diabetic groups. At the end of 4 weeks after STZ injection, 24h microalbuminuria was collected and detected. The microalbuminuria was measured by radioimmunoassay (RIA). The blood glucose was tested using a blood glucose meter. The kidney was dissected from each SD rat. Proteins and mRNA of TGF-β1, Smads and Smurf were tested by western-blot and real-time PCR analysis, and 26S proteasome activity was measured by an ELISA kit.

Results:

The water-extraction of Astragali Radix and Lycopi Herba significantly lowered fasting glucose and urine albumin in diabetic rats through inhibition of TGF-β1 mRNA and protein expression in the STZ-induced diabetic rats, and regulation of the Smad3, Smad7, Smurf1, Smurf2 mRNA and protein expression, as well as elevated 26S proteasome activity to play control effect in DN.

Conclusion:

0.9 g/ml water-extraction of Astragali Radix and Lycopi Herba group has significant therapeutic effects on the STZ-induced diabetic rats, and this regulation depends on TGF-Smads-UPP signaling pathway.

γ-Secretase inhibition promotes fibrotic effects of albumin in proximal tubular epithelial cells

BACKGROUND AND PURPOSE

Albuminuria is an important biomarker of renal dysfunction and is a major mediator of renal damage and fibrosis during kidney disease. The mechanisms underlying albumin-induced renal fibrosis remain unclear. There has been significant interest in γ-secretase activity in tubular epithelial cells in recent times; however, its potential role in albumin-induced fibrosis has not been investigated.

EXPERIMENTAL APPROACH

The primary aim of this study was to examine the role of γ-secretase in albumin-induced fibrotic effects in proximal tubular cells. The effects of increasing albumin concentrations on fibrosis indicators and mediators in the human HK-2 cell line were examined in the presence and absence of a γ-secretase inhibitor, compound E.

KEY RESULTS

Treatment with albumin resulted in a number of pro-fibrotic effects, including up-regulation of fibronectin, TGF-β1 and the EGF-R. Interestingly, similar effects were observed in response to treatment with the γ-secretase inhibitor, compound E. Co-treatment of cells with albumin and an EGF-R inhibitor, AG-1478, resulted in significant inhibition of the observed pro-fibrotic effects, suggesting a major role for the EGF-R in albumin-induced fibrotic events. Albumin-induced effects on the EGF-R appeared to be mediated through inhibition of γ-secretase activity and were dependent on ERK-MAPK signalling.

CONCLUSIONS AND IMPLICATIONS

These results provide novel insights into the mechanisms of albumin-induced fibrotic effects in tubular epithelial cells, suggesting important roles for the γ-secretase and the EGF-R. These results suggest that the proposed use of γ-secretase inhibitors as anti-fibrotic agents requires further investigation.

Maternal diabetes modulates kidney formation in murine progeny: the role of hedgehog interacting protein (HHIP)

AIMS/HYPOTHESIS

We hypothesised that maternal diabetes impairs kidney formation in offspring via augmented expression of hedgehog interacting protein (HHIP). Our gene-array results were performed in neonatal kidneys from our murine model of maternal diabetes and indicated that Hhip expression was significantly modulated by maternal diabetes.

METHODS

We systematically examined the functional role of HHIP in kidney formation in our murine maternal diabetes model and elucidated the potential mechanisms related to dysnephrogenesis in vitro.

RESULTS

The kidneys of the offspring of diabetic dams, compared with those of the offspring of control non-diabetic dams, showed retardation of development--small kidneys and less ureteric bud (UB) branching morphogenesis. Augmented HHIP expression was observed in the offspring of diabetic dams, initially localised to differentiated metanephric mesenchyme and UB epithelium and subsequently in maturing glomerular endothelial and tubulointerstitial cells. The heightened HHIP targeting TGF-β1 signalling was associated with dysmorphogenesis. In vitro, HHIP overexpression decreased sonic hedgehog and paired box gene 2 proteins (SHH and PAX2, respectively) and increased transcriptional nuclear factor-kappa B (NFκB, p50/p65), phosphorylation of p53, and TGF-β1 expression. In contrast, overexpression of PAX2 inhibited HHIP and NFκB and activated SHH, N-myc and p27(Kip1) expression. Moreover, high glucose stimulated HHIP expression, and then targeted TGF-β1 signalling. Thus, PAX2, via a negative autocrine feedback mechanism, attenuated the stimulatory effect of high glucose on HHIP expression.

CONCLUSIONS/INTERPRETATION

Maternal diabetes modulates kidney formation in young progeny mediated, at least in part, via augmented HHIP expression.

The biological significance of angiotensin-converting enzyme inhibition to combat kidney fibrosis

Both angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker have been recognized as renin-angiotensin system (RAS) inhibitors. These two RAS inhibitors are rarely recognized as drugs with distinct pharmacological effects in the clinic or most clinical trials. Some preclinical basic research and clinical trials indicate that ACE-I might display superior organ-protective effects, especially anti-fibrotic effects. Such anti-fibrotic effects of ACE-I could be associated with an endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). In this review, we focused on the anti-fibrotic effects of RAS inhibition and the endogenous anti-fibrotic peptide AcSDKP.