Disruption of the Smad7 gene promotes renal fibrosis and inflammation in unilateral ureteral obstruction (UUO) in mice

Inhibition of class I HDACs attenuates renal interstitial fibrosis in a murine model

Renal interstitial fibrosis is the most common of all the forms of chronic kidney disease (CKD). Research has shown that histone deacetylases (HDACs) participate in the process leading to renal fibrosis. However, the effects of class I HDAC inhibitors on the mechanisms of onset and progression of renal interstitial fibrosis are still unclear. Here, we present the effects and mechanisms of action of FK228 (a selective inhibitor of class I HDACs) in the murine model of unilateral ureteral obstruction (UUO) and in vitro models. We investigated the antifibrotic role of FK228 in a murine model of UUO. We used two key effector cell populations, rat renal interstitial fibroblasts and renal tubular epithelial cells exposed to recombinant transforming growth factor-beta 1 (TGF-β1), to explore the mechanistic pathways among in vitro models. The results indicated that FK228 significantly suppressed the production of extracellular matrix (ECM) in both in vivo and in vitro models. FK228 inhibited renal fibroblast activation and proliferation and increased the acetylation of histone H3. We found that FK228 also inhibited the small mothers against decapentaplegic (Smad) and non-Smad signaling pathways. So FK228 could significantly suppress renal interstitial fibrosis via Smad and non-Smad pathways. FK228 may be the basis for a new and effective medicine for alleviating renal fibrosis in the future.

Loss of Smad7 Promotes Inflammation in Rheumatoid Arthritis

Objective: Smad7 is an inhibitory Smad and plays a protective role in many inflammatory diseases. However, the roles of Smad7 in rheumatoid arthritis (RA) remain unexplored, which were investigated in this study.

Methods: The activation of TGF-β/Smad signaling was examined in synovial tissues of patients with RA. The functional roles and mechanisms of Smad7 in RA were determined in a mouse model of collagen-induced arthritis (CIA) in Smad7 wild-type (WT) and knockout (KO) CD-1 mice, a strain resistant to autoimmune arthritis induction.

Results: TGF-β/Smad3 signaling was markedly activated in synovial tissues of patients with RA, which was associated with the loss of Smad7, and enhanced Th17 and Th1 immune response. The potential roles of Smad7 in RA were further investigated in a mouse model of CIA in Smad7 WT/KO CD-1 mice. As expected, Smad7-WT CD-1 mice did not develop CIA. Surprisingly, CD-1 mice with Smad7 deficiency developed severe arthritis including severe joint swelling, synovial hyperplasia, cartilage damage, massive infiltration of CD3⁺ T cells and F4/80⁺ macrophages, and upregulation of proinflammatory cytokines IL-1β, TNFα, and MCP-1. Further studies revealed that enhanced arthritis in Smad7 KO CD-1 mice was associated with increased Th1, Th2 and, importantly, Th17 over the Treg immune response with overactive TGF-β/Smad3 and proinflammatory IL-6 signaling in the joint tissues.

Conclusions: Smad7 deficiency increases the susceptibility to autoimmune arthritis in CD-1 mice. Enhanced TGF-β/Smad3-IL-6 signaling and Th17 immune response may be a mechanism through which disrupted Smad7 causes autoimmune arthritis in CD-1 mice.

Dicer deficiency in proximal tubules exacerbates renal injury and tubulointerstitial fibrosis and upregulates Smad2/3

Renal fibrosis is a common pathological feature in chronic kidney disease (CKD), including diabetic kidney disease (DKD) and obstructive nephropathy. Multiple microRNAs have been implicated in the pathogenesis of both DKD and obstructive nephropathy, although the overall role of microRNAs in tubular injury and renal fibrosis in CKD is unclear. Dicer (a key RNase III enzyme for microRNA biogenesis) was specifically ablated from kidney proximal tubules in mice via the Cre-lox system to deplete micoRNAs. Proximal tubular Dicer knockout (PT- Dicer KO) mice and wild-type (WT) littermates were subjected to streptozotocin (STZ) treatment to induce DKD or unilateral ureteral obstruction (UUO) to induce obstructive nephropathy. Renal hypertrophy, renal tubular apoptosis, kidney inflammation, and tubulointerstitial fibrosis were examined. Compared with WT mice, PT- Dicer KO mice showed more severe tubular injury and renal inflammation following STZ treatment. These mice also developed higher levels of tubolointerstitial fibrosis. Meanwhile, PT- Dicer KO mice had a significantly higher Smad2/3 expression in kidneys than WT mice (at 6 mo of age) in both control and STZ-treated mice. Similarly, UUO induced more severe renal injury, inflammation, and interstitial fibrosis in PT- Dicer KO mice than WT. Although we did not detect obvious Smad2/3 expression in sham-operated mice (2-3 mo old), significantly more Smad2/3 was induced in obstructed PT- Dicer KO kidneys. These results supported a protective role of Dicer-dependent microRNA synthesis in renal injury and fibrosis development in CKD, specifically in DKD and obstructive nephropathy. Depletion of Dicer and microRNAs may upregulate Smad2/3-related signaling pathway to enhance the progression of CKD.

MicroRNA-21-5p promotes proliferation of gastric cancer cells through targeting SMAD7

Background

MicroRNAs could target multiple genes by regulating the translation or degradation of mRNAs, and are involved in functions such as signal transduction pathways affecting the physiological functions of normal or tumor cells.

Methods

In this study, the expressions of miRNA-21-5p in gastric cancer tissues and SGC-7901 cells were analyzed, and the effects of miRNA-21-5p on cell proliferation, migration, invasion, and apoptosis and the expressions of target proteins SMADs in SGC-7901 cells were evaluated. Inflammatory factors interleukin 1β and tumor necrosis factor α in siRNA-transfected SGC-7901 cells were determined by enzyme-linked immunosorbent assay.

Results

MiRNA-21-5p was consistently upregulated in gastric cancer tissues and SGC-7901 cells compared to normal tissues or cells. The knockdown of miRNA-21-5p with antisense oligonucleotides suppressed cell proliferation, migration, and invasion as well as inflammatory response, and promoted cell apoptosis and SMAD7 expression.

Conclusion

These results indicate SMAD7 may mediate the oncogenic properties of miRNA-21-5p in gastric cancer, and miRNA-21-5p would be a promising strategy for the treatment of gastric cancer.

Acetyl-11-keto-β-boswellic acid ameliorates renal interstitial fibrosis via Klotho/TGF-β/Smad signalling pathway

Acetyl‐11‐keto‐β‐boswellic acid (AKBA), an active triterpenoid compound from the extract of Boswellia serrate, has been reported previously in our group to alleviate fibrosis in vascular remodelling. This study aimed to elucidate the in vivo and in vitro efficacy and mechanism of AKBA in renal interstitial fibrosis. The experimental renal fibrosis was produced in C57BL/6 mice via unilateral ureteral obstruction (UUO). Hypoxia‐induced HK‐2 cells were used to imitate the pathological process of renal fibrosis in vitro. Results showed that the treatment of AKBA significantly alleviated UUO‐induced impairment of renal function and improved the renal fibrosis by decreasing the expression of TGF‐β1, α‐SMA, collagen I and collagen IV in UUO kidneys. In hypoxia‐induced HK‐2 cells, AKBA displayed remarkable cell protective effects and anti‐fibrotic properties by increasing the cell viability, decreasing the lactate dehydrogenase (LDH) release and inhibiting fibrotic factor expression. Moreover, in obstructed kidneys and HK‐2 cells, AKBA markedly down‐regulated the expression of TGFβ‐RI, TGFβ‐RII, phosphorylated‐Smad2/3 (p‐Smad2/3) and Smad4 in a dose‐dependent fashion while up‐regulated the expression of Klotho and Smad7 in the same manner. In addition, the effects of AKBA on the Klotho/TGF‐β/Smad signalling were reversed by transfecting with siRNA‐Klotho in HK‐2 cells. In conclusion, our findings provide evidence that AKBA can effectively protect kidney against interstitial fibrosis, and this renoprotective effect involves the Klotho/TGF‐β/Smad signalling pathway. Therefore, AKBA could be considered as a promising candidate drug for renal interstitial fibrosis.

The preventive and therapeutic implication for renal fibrosis by targetting TGF-β/Smad3 signaling

It is well established that Smad3 is a key downstream effector of transforming growth factor-β (TGF-β) signaling in tissue fibrogenesis. We reported here that targetting Smad3 specifically with a Smad3 inhibitor SIS3 is able to prevent or halt the progression of renal fibrosis in a mouse model of unilateral ureteral obstructive nephropathy (UUO). We found that preventive treatment with SIS3 at the time of disease induction largely suppressed progressive renal fibrosis by inhibiting α-smooth muscle actin (α-SMA) + myofibroblast accumulation and extracellular matrix (collagen I (Col.I) and fibronectin (FN)) production. Importantly, we also found that treatment with SIS3 on established mouse model of UUO from day 4 after UUO nephropathy halted the progression of renal fibrosis. Mechanistically, the preventive and therapeutic effects of SIS3 on renal fibrosis were associated with the inactivation of Smad3 signaling and inhibition of TGF-β1 expression in the UUO kidney. In conclusion, results from the present study suggest that targetting Smad3 may be a specific and effective therapy for renal fibrosis.

Non-invasive detection of the early phase of kidney injury by photoacoustic/computed tomography imaging

The early diagnosis of kidney diseases, which can remarkably impair the quality of life and are costly, has encountered great difficulties. Therefore, the development of methods for early diagnosis has great clinical significance. In this study, we used an emerging technique of photoacoustic (PA) imaging, which has relatively high spatial resolution and good imaging depth. Two kinds of PA gold nanoparticle (GNP)-based bioprobes were developed based on their superior photo detectability, size controllability and biocompatibility. The kidney injury mouse model was developed by unilateral ureteral obstruction for 96 h and the release of obstruction model). Giving 3.5 and 5.5 nm bioprobes by tail vein injection, we found that the 5.5 nm probe could be detected in the bladder in the model group, but not in the control group. These results were confirmed by computed tomography imaging. Furthermore, the model group did not show changes in the blood biochemical indices (BUN and Scr) and histologic examination. The 5.5 nm GNPs were found to be the critical point for early diagnosis of kidney injury. This new method was faster and more sensitive and accurate for the detection of renal injury, compared with conventional methods, and can be used for the development of a PA GNP-based bioprobe for diagnosing renal injury.

Central role of dysregulation of TGF-β/Smad in CKD progression and potential targets of its treatment

Chronic kidney disease (CKD) has emerged as a major cause of morbidity and mortality worldwide. Interstitial fibrosis, glomerulosclerosis and inflammation play the central role in the pathogenesis and progression of CKD to end stage renal disease (ESRD). Transforming growth factor-β1 (TGF-β1) is the central mediator of renal fibrosis and numerous studies have focused on inhibition of TGF-β1 and its downstream targets for treatment of kidney disease. However, blockade of TGF-β1 has not been effective in the treatment of CKD patients. This may be, in part due to anti-inflammatory effect of TGF-β1. The Smad signaling system plays a central role in regulation of TGF-β1 and TGF-β/Smad pathway plays a key role in progressive renal injury and inflammation. This review provides an overview of the role of TGF-β/Smad signaling pathway in the pathogenesis of renal fibrosis and inflammation and an effective target of anti-fibrotic therapies. Under pathological conditions, Smad2 and Smad3 expression are upregulated, while Smad7 is downregulated. In addition to TGF-β1, other pathogenic mediators such as angiotensin II and lipopolysaccharide activate Smad signaling through both TGF-β-dependent and independent pathways. Smads also interact with other pathways including nuclear factor kappa B (NF-κB) to regulate renal inflammation and fibrosis. In the context of renal fibrosis and inflammation, Smad3 exerts profibrotic effect, whereas Smad2 and Smad7 play renal protective roles. Smad4 performs its dual functions by transcriptionally promoting Smad3-dependent renal fibrosis but simultaneously suppressing NF-κB-mediated renal inflammation via Smad7-dependent mechanism. Furthermore, TGF-β1 induces Smad3 expression to regulate microRNAs and Smad ubiquitination regulatory factor (Smurf) to exert its pro-fibrotic effect. In conclusion, TGF-β/Smad signaling is an important pathway that mediates renal fibrosis and inflammation. Thus, an effective anti-fibrotic therapy via inhibition of Smad3 and upregulation of Smad7 signaling constitutes an attractive approach for treatment of CKD.

Cyclophilin D promotes tubular cell damage and the development of interstitial fibrosis in the obstructed kidney

Cyclophilin D (CypD) is an important component in mitochondrial-dependent tubular cell death in acute kidney injury. However, it is not known whether CypD contributes to tubular cell damage in chronic interstitial fibrosis. We investigated this question in the unilateral ureter obstruction (UUO) model of renal interstitial fibrosis. Groups of CypD-/- and wild type (WT) mice were killed 7 or 12 days after UUO surgery. The significant tubular cell apoptosis seen in WT UUO was significantly reduced in CypD-/- UUO based on TUNEL and cleaved caspase 3 staining. Other markers of tubular cell damage; loss of E-cadherin and AQP1 expression, were also reduced in the CypD-/- UUO kidney. This reduced tubular damage was associated with less inflammation and a partial protection against loss of peritubular capillaries. The prominent accumulation of α-SMA+ myofibroblasts and interstitial collagen deposition seen in WT UUO was significantly reduced in CypD-/- UUO on day 12, but not day 7. Activation of several pro-fibrotic signalling pathways (p38 MAPK, JNK and Smad3) was unaltered in CypD-/- UUO, arguing that CypD acts independently to promote renal fibrosis. CypD deletion in cultured tubular cells attenuated oxidative stress-induced pro-inflammatory, pro-fibrotic and apoptotic responses; however, responses to angiotensin II and LPS were unaffected. In contrast, CypD deletion in cultured renal fibroblasts did not affect PDGF-induced proliferation or TGF-β1-induced collagen I expression, suggesting no direct role of CypD in the fibroblast response. In conclusion, we have identified a role for CypD in chronic tubular cell damage and in the development of renal interstitial fibrosis.

Therapeutic effect of intra-articular injection of ribbon-type decoy oligonucleotides for hypoxia inducible factor-1 on joint contracture in an immobilized knee animal model

BACKGROUND

Limited range of motion (ROM) as a result of joint contracture in treatment associated with joint immobilization or motor paralysis is a critical issue. However, its molecular mechanism has not been fully clarified and a therapeutic approach is not yet established.

METHODS

In the present study, we investigated its molecular mechanism, focusing on the role of a transcription factor, hypoxia inducible factor-1 (HIF-1), which regulates the expression of connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF), and evaluated the possibility of molecular therapy to inhibit HIF-1 activation by ribbon-type decoy oligonucleotides (ODNs) for HIF-1 using immobilized knee animal models.

RESULTS

In a mouse model, ROM of the immobilized knee significantly decreased in a time-dependent manner, accompanied by synovial hypertrophy. Immunohistochemical studies suggested that CTGF and VEGF are implicated in synovial hypertrophy with fibrosis. CTGF and VEGF were up-regulated at both the mRNA and protein levels at 1 and 2 weeks after immobilization, subsequent to up-regulation of HIF-1 mRNA and transcriptional activation of HIF-1. Of importance, intra-articular transfection of decoy ODNs for HIF-1 in a rat model successfully inhibited transcriptional activation of HIF-1, followed by suppression of expression of CTGF and VEGF, resulting in attenuation of restricted ROM, whereas transfection of scrambled decoy ODNs did not.

CONCLUSIONS

The present study demonstrates the important role of HIF-1 in the initial progression of immobilization-induced joint contracture, and indicates the possibility of molecular treatment to prevent the progression of joint contracture prior to intervention with physical therapy. Copyright © 2016 John Wiley & Sons, Ltd.

C/EBP homologous protein (CHOP) deficiency ameliorates renal fibrosis in unilateral ureteral obstructive kidney disease

Renal tubulointerstitial fibrosis is an important pathogenic feature in chronic kidney disease and end-stage renal disease, regardless of the initiating insults. A recent study has shown that CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) is involved in acute ischemia/reperfusion-related acute kidney injury through oxidative stress induction. However, the influence of CHOP on chronic kidney disease-correlated renal fibrosis remains unclear. Here, we investigated the role of CHOP in unilateral ureteral obstruction (UUO)-induced experimental chronic tubulointerstital fibrosis. The CHOP knockout and wild type mice with or without UUO were used. The results showed that the increased expressions of renal fibrosis markers collagen I, fibronectin, α-smooth muscle actin, and plasminogen activator inhibitor-1 in the kidneys of UUO-treated wild type mice were dramatically attenuated in the kidneys of UUO-treated CHOP knockout mice. CHOP deficiency could also ameliorate lipid peroxidation and endogenous antioxidant enzymes depletion, tubular apoptosis, and inflammatory cells infiltration in the UUO kidneys. These results suggest that CHOP deficiency not only attenuates apoptotic death and oxidative stress in experimental renal fibrosis, but also reduces local inflammation, leading to diminish UUO-induced renal fibrosis. Our findings support that CHOP may be an important signaling molecule in the progression of chronic kidney disease.

Targeting c-fms kinase attenuates chronic aristolochic acid nephropathy in mice

Aristolochic acid nephropathy (AAN) is a progressive kidney disease caused by some Chinese herbal medicines, but treatment remains ineffective. Macrophage accumulation is an early feature in human and experimental AAN; however, the role of macrophages in chronic AAN is unknown. We report here that targeting macrophages with fms-I, a selective inhibitor of the tyrosine kinase activity of the macrophage colony-stimulating factor receptor, suppressed disease progression in a mouse model of chronic AAN. Treatment with fms-I (10mg/kg/BID) from day 0 to 28 (prevention study) or from day 14 to 28 (intervention study) substantially inhibited macrophage accumulation and significantly improved renal dysfunction including a reduction in proteinuria and tubular damage. Progressive interstitial fibrosis (myofibroblast accumulation and collagen deposition) and renal inflammation (increased expression of MCP-1, MIF, and TNF-α) were also attenuated by fms-I treatment. These protective effects involved inhibition of TGF-β/Smad3 and NF-kB signaling. In conclusion, the present study establishes that macrophages are key inflammatory cells that exacerbates progressive tubulointerstitial damage in chronic AAN via mechanisms associated with TGF-β/Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation. Targeting macrophages via a c-fms kinase inhibitor may represent a novel therapy for chronic AAN.

TGF-β Mediates Renal Fibrosis via the Smad3-Erbb4-IR Long Noncoding RNA Axis

Transforming growth factor β (TGF-β)/Smad3 signaling plays a role in tissue fibrosis. We report here that Erbb4-IR is a novel long non-coding RNA (lncRNA) responsible for TGF-β/Smad3-mediated renal fibrosis and is a specific therapeutic target for chronic kidney disease. Erbb4-IR was induced by TGF-β1 via a Smad3-dependent mechanism and was highly upregulated in the fibrotic kidney of mouse unilateral ureteral obstructive nephropathy (UUO). Silencing Erbb4-IR blocked TGF-β1-induced collagen I and alpha-smooth muscle actin (α-SMA) expressions in vitro and effectively attenuated renal fibrosis in the UUO kidney by blocking TGF-β/Smad3 signaling. Mechanistic studies revealed that Smad7, a downstream negative regulator of TGF-β/Smad signaling, is a target gene of Erbb4-IR because a binding site of Erbb4-IR was found on the 3' UTR of Smad7 gene. Mutation of this binding site prevented the suppressive effect of Erbb4-IR on the Smad7 reporter activity; in contrast, overexpression of Erbb4-IR largely inhibited Smad7 but increased collagen I and α-SMA transcriptions. Thus, kidney-specific silencing of Erbb4-IR upregulated renal Smad7 and thus blocked TGF-β/Smad3-mediated renal fibrosis in vivo and in vitro. In conclusion, the present study identified that Erbb4-IR is a novel lncRNA responsible for TGF-β/Smad3-mediated renal fibrosis by downregulating Smad7. Targeting Erbb4-IR may represent a precise therapeutic strategy for progressive renal fibrosis.

Smad7 protects against acute kidney injury by rescuing tubular epithelial cells from the G1 cell cycle arrest

Smad7 plays a protective role in chronic kidney disease; however, its role in acute kidney injury (AKI) remains unexplored. Here, we report that Smad7 protects against AKI by rescuing the G1 cell cycle arrest of tubular epithelial cells (TECs) in ischemia/reperfusion-induced AKI in mice in which Smad7 gene is disrupted or restored locally into the kidney. In Smad7 gene knockout (KO) mice, more severe renal impairment including higher levels of serum creatinine and massive tubular necrosis was developed at 48 h after AKI. In contrast, restored renal Smad7 gene locally into the kidney of Smad7 KO mice protected against AKI by promoting TEC proliferation identified by PCNA+ and BrdU+ cells. Mechanistic studies revealed that worsen AKI in Smad7 KO mice was associated with a marked activation of TGF-β/Smad3-p21/p27 signaling and a loss of CDK2/cyclin E activities, thereby impairing TEC regeneration at the G1 cell cycle arrest. In contrast, restored Smad7 locally into the kidneys of Smad7 KO mice protected TECs from the G1 cell cycle arrest and promoted TEC G1/S transition via a CDK2/cyclin E-dependent mechanism. In conclusion, Smad7 plays a protective role in AKI. Blockade of TGF-β/Smad3-p21/p27-induced G1 cell cycle arrest may be a key mechanism by which Smad7 treatment inhibits AKI. Thus, Smad7 may be a novel therapeutic agent for AKI.

Regulation of TGF-β Family Signaling by Inhibitory Smads

Inhibitory Smads (I-Smads) have conserved carboxy-terminal MH2 domains but highly divergent amino-terminal regions when compared with receptor-regulated Smads (R-Smads) and common-partner Smads (co-Smads). Smad6 preferentially inhibits Smad signaling initiated by the bone morphogenetic protein (BMP) type I receptors ALK-3 and ALK-6, whereas Smad7 inhibits both transforming growth factor β (TGF-β)- and BMP-induced Smad signaling. I-Smads also regulate some non-Smad signaling pathways. Here, we discuss the vertebrate I-Smads, their roles as inhibitors of Smad activation and regulators of receptor stability, as scaffolds for non-Smad signaling, and their possible roles in the nucleus. We also discuss the posttranslational modification of I-Smads, including phosphorylation, ubiquitylation, acetylation, and methylation.

Preventing peritoneal membrane fibrosis in peritoneal dialysis patients

Long-term peritoneal dialysis causes morphologic and functional changes in the peritoneal membrane. Although mesothelial-mesenchymal transition of peritoneal mesothelial cells is a key process leading to peritoneal fibrosis, and bioincompatible peritoneal dialysis solutions (glucose, glucose degradation products, and advanced glycation end products or a combination) are responsible for altering mesothelial cell function and proliferation, mechanisms underlying these processes remain largely unclear. Peritoneal fibrosis has 2 cooperative parts, the fibrosis process itself and the inflammation. The link between these 2 processes is frequently bidirectional, with each one inducing the other. This review outlines our current understanding about the definition and pathophysiology of peritoneal fibrosis, recent studies on key fibrogenic molecular machinery in peritoneal fibrosis, such as the role of transforming growth factor-β/Smads, transforming growth factor-β β/Smad independent pathways, and noncoding RNAs. The diagnosis of peritoneal fibrosis, including effluent biomarkers and the histopathology of a peritoneal biopsy, which is the gold standard for demonstrating peritoneal fibrosis, is introduced in detail. Several interventions for peritoneal fibrosis based on biomarkers, cytology, histology, functional studies, and antagonists are presented in this review. Recent experimental trials in animal models, including pharmacology and gene therapy, which could offer novel insights into the treatment of peritoneal fibrosis in the near future, are also discussed in depth.

C-Reactive Protein Promotes Diabetic Kidney Disease in db/db Mice via the CD32b-Smad3-mTOR signaling Pathway

C-reactive protein (CRP) is associated with progressive diabetic nephropathy in patients with type-2 diabetes (T2DN). However, role of CRP in T2DN remains unclear. We report here that CRP is pathogenic in T2DN in db/db mice that express human CRP (CRPtg-db/db). Compared to the littermate db/db mice, CRPtg-db/db developed more severe T2DN, showing higher levels of fasting blood glucose and microalbuminuria and more progressive renal inflammation and fibrosis. Enhanced T2DN in CRPtg-db/db mice were associated with over-activation of CRP-CD32b, NF-κB, TGF-β/Smad3, and mTOR signaling. Further studies in vitro defined that CRP activated Smad3 directly at 15 mins via the CD32b- ERK/p38 MAP kinase crosstalk pathway and indirectly at 24 hours through a TGF-β1-dependent mechanism. Importantly, CRP also activated mTOR signaling at 30 mins via a Smad3-dependent mechanism as Smad3 bound mTOR physically and CRP-induced mTOR signaling was abolished by a neutralizing CD32b antibody and a specific Smad3 inhibitor. Finally, we also found that CRP induced renal fibrosis through a CD32b-Smad3-mTOR pathway because blocking mTOR signaling with rapamycin inhibited CRP-induced CTGF and collagen I expression. Thus, CRP is pathogenic in T2DN. CRP may promote CD32b- NF-κB signaling to mediate renal inflammation; whereas, CRP may enhance renal fibrosis in T2DN via CD32b-Smad3-mTOR signaling.

TGF-β: the master regulator of fibrosis

Transforming growth factor-β (TGF-β) is the primary factor that drives fibrosis in most, if not all, forms of chronic kidney disease (CKD). Inhibition of the TGF-β isoform, TGF-β1, or its downstream signalling pathways substantially limits renal fibrosis in a wide range of disease models whereas overexpression of TGF-β1 induces renal fibrosis. TGF-β1 can induce renal fibrosis via activation of both canonical (Smad-based) and non-canonical (non-Smad-based) signalling pathways, which result in activation of myofibroblasts, excessive production of extracellular matrix (ECM) and inhibition of ECM degradation. The role of Smad proteins in the regulation of fibrosis is complex, with competing profibrotic and antifibrotic actions (including in the regulation of mesenchymal transitioning), and with complex interplay between TGF-β/Smads and other signalling pathways. Studies over the past 5 years have identified additional mechanisms that regulate the action of TGF-β1/Smad signalling in fibrosis, including short and long noncoding RNA molecules and epigenetic modifications of DNA and histone proteins. Although direct targeting of TGF-β1 is unlikely to yield a viable antifibrotic therapy due to the involvement of TGF-β1 in other processes, greater understanding of the various pathways by which TGF-β1 controls fibrosis has identified alternative targets for the development of novel therapeutics to halt this most damaging process in CKD.

Smad7 protects against chronic aristolochic acid nephropathy in mice

Chronic Aristolochic Acid Nephropathy (AAN) is a progressive chronic kidney disease related to herb medicine. However, treatment for chronic AAN remains ineffective. We report here that Smad7 is protective and has therapeutic potential for chronic AAN. In a mouse model of chronic AAN, progressive renal injury was associated with a loss of renal Smad7 and disruption of Smad7 largely aggravated the severity of chronic AAN as demonstrated by a significant increase in levels of 24-hour urinary protein excretion, serum creatinine, and progressive renal fibrosis and inflammation. In contrast, restored Smad7 locally in the kidneys of Smad7 knockout mice prevented the progression of chronic AAN. Further studies revealed that worsen chronic AAN in Smad7 knockout mice was associated with enhanced activation of TGF-β/Smad3 and NF-κB signaling pathways, which was reversed when renal Smad7 was restored. Importantly, we also found that overexpression of Smad7 locally in the kidneys with established chronic AAN was capable of attenuating progressive chronic AAN by inactivating TGF-β/Smad3-medated renal fibrosis and NF-κB-driven renal inflammation. In conclusion, Smad7 plays a protective role in the pathogenesis of chronic AAN and overexpression of Smad7 may represent a novel therapeutic potential for chronic AAN.

Nanosized titanium dioxide resulted in the activation of TGF-β/Smads/p38MAPK pathway in renal inflammation and fibration of mice

Titanium dioxide nanoparticles (TiO2 NPs) have been demonstrated to damage the kidneys. However, whether chronic nephritis leads to renal fibration or the fibrosis is associated with the activation of TGF-β/Smads/p38MAPK pathway caused by TiO2 NPs exposure is not well understood. Forty male mice were separately exposed to 0, 2.5, 5, or 10 mg/kg body weight TiO2 NPs for 6 months. Renal biochemical functions and levels of TGF-β/Smads/p38MAPK pathway-related markers and extracellular matrix (ECM) expression in the kidneys were investigated. The findings showed that subchronic TiO2 NPs exposure increased levels of urinary creatisix (Cr), N-acetyl-glucosaminidase, and vanin-1, resulted in severe renal inflammation and fibration. Furthermore, TiO2 NP exposure upregulated expression of transforming growth factor-β1 (TGF-β1, 0.07- to 2.72-fold), Smad2 (0.42- to 1.63-fold), Smad3 (0.02- to 1.94-fold), ECM (0.15- to 2.75-fold), α-smooth muscle actin (0.14- to 3.06-fold), p38 mitogen-activated protein kinase (p38MAPK, 0.11- to 3.78-fold), and nuclear factor-κB (0.4- to 2.27-fold), and downregulated Smad7 (0.05- to 0.61-fold) expression in mouse kidney. Subchronic TiO2 NPs exposure induced changes of renal characteristics towards inflammation and fibration may be mediated via TGF-β/Smads/p38MAPK pathway, and the uses of TiO2 NPs should be carried out cautiously, especially in humans. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1452-1461, 2016.

Therapeutic Effects of Tangshen Formula on Diabetic Nephropathy in Rats

Objective

Inflammation and fibrosis are essential promoters in the pathogenesis of diabetic nephropathy (DN) in type 2 diabetes. The present study examined the anti-inflammation and anti-fibrosis effect of Tangshen Formula (TSF), a traditional Chinese medicine, on DN.

Research Design and Methods

Protective role of TSF in DN was examined in a rat model of type 2 DN that was established by high-fat diet-fed and low-dose-streptozotocin injection. TSF was suspended in 0.5% CMC-Na solution and delivered by oral gavage at a dosage of 1.67g/Kg body weight/day. The therapeutic effects and mechanisms of TSF on diabetic kidney injury were examined.

Results

We found that TSF treatment for 20 weeks attenuated DN by significantly inhibiting urinary excretion of albumin and renal histological injuries. These beneficial effects were associated with an inactivation of NF-κB signaling, thereby blocking the upregulation of pro-inflammatory cytokines (IL-1β, TNFα), chemokine (MCP-1), and macrophage infiltration in the TSF-treated rats with type 2 DN. In addition, TSF treatment also inactivated TGF-β/Smad3 signaling and therefore suppressed renal fibrosis including expressions of fibronectin, collagen I, and collagen IV. Further studies revealed that the inhibitory effect of TSF on TGF-β/Smad3 and NF-κB signaling in DN was associated with inhibition of Smurf2-dependent ubiquitin degradation of Smad7.

Conclusions

The present study reveals that TSF has therapeutic potential for type 2 DN in rats. Blockade of NF-κB-driven renal inflammation and TGF-β/Smad3-mediated renal fibrosis by preventing the Smurf2-mediated Smad7 degradation pathway may be mechanisms through which TSF inhibits type 2 DN.

TGF-β signaling in the kidney: profibrotic and protective effects

Transforming growth factor-β (TGF-β) is generally considered as a central mediator of fibrotic diseases. Indeed, much focus has been placed on inhibiting TGF-β and its downstream targets as ideal therapeutic strategies. However, pharmacological blockade of TGF-β has not yet translated into successful therapy for humans, which may be due to pleiotropic effects of TGF-β signaling. Equally, TGF-β signaling as a protective response in kidney injury has been relatively underexplored. An emerging body of evidence from experimental kidney disease models indicates multifunctionality of TGF-β capable of inducing profibrotic and protective effects. This review discusses recent advances highlighting the diverse roles of TGF-β in promoting not only renal fibrosis but also protective responses of TGF-β signaling. We review, in particular, growing evidence that supports protective effects of TGF-β by mechanisms which include inhibiting inflammation and induction of autophagy. Additional detailed studies are required to fully understand the diverse mechanisms of TGF-β actions in renal fibrosis and inflammation that will likely direct toward effective antifibrotic therapies.

T helper (Th)-cytokines in the urine of patients with primary glomerulonephritis treated with immunosuppressive drugs: Can they predict outcome?

BACKGROUND

Glomerulonephritides (GNs) represent common causes of chronic kidney disease associated with a wide spectrum of clinical and histological features. Various factors that activate the inflammatory cascade are involved in the development of kidney injury. The aim of this study was to estimate the urinary excretion of pro-inflammatory (IL-2, INF-γ, TNF-α, IL-6, IL-17) and anti-inflammatory (IL-4, IL-10, TGF-β1) cytokines, as well as the chemokine MCP-1 in patients with various types of GN treated by immunosuppressive drugs and to identify any prognostic value of excreted cytokines for future renal function.

PATIENTS AND METHODS

Ninety-seven patients (62 M/35 F, age 53.1 ± 15.6 years) with primary glomerulonephritis and 32 healthy controls were studied. The original diagnoses were membranous nephropathy (MN, n=36), IgA nephropathy (IgAN, n=31) and minimal changes disease or focal segmental glomerulosclerosis (MCD/FSGS, n=30). All patients had been treated with immunosuppressive drugs and, at the time of measurement of urinary cytokine excretion, were either in clinical remission or still had active disease with persistent proteinuria.

RESULTS

GN patients had significantly higher levels of all cytokines and MCP-1 compared to healthy controls. A strong positive correlation between TGF-β1 and MCP-1 concentrations was observed in all GN patients. Increased urinary excretion of all tested cytokines apart from TNF-α and TGF-β1 was observed even in patients with clinical remission. The main difference between patients with proteinuria and those in clinical remission was the level of MCP-1 urinary excretion. The urinary excretion of MCP-1 and TGF-β1 was significantly higher in patients with MN who showed deterioration of renal function over a follow-up period of five years.

CONCLUSIONS

Increased levels of cytokines are observed in the urine of patients with different types of glomerulonephritis, even after the achievement of clinical remission with the administration of immunosuppressive drugs. Urinary excretion of MCP-1 and TGF-β1 indicates the ongoing inflammatory and fibrotic processes in the kidney and is probably related to unfavourable outcomes.

Treatment of renal fibrosis by rebalancing TGF-β/Smad signaling with the combination of asiatic acid and naringenin

We recently showed that imbalance of TGF-β/Smad signaling with over-activation of Smad3 but lower levels of Smad7 is a central mechanism of tissue fibrosis. In the present study, we report here that inhibition of Smad3 with naringenin (NG) and upregulation of Smad7 with asiatic acid (AA) produced an additive effect on inhibition of renal fibrosis in a mouse model of obstructive nephropathy. We found that AA, a triterpene from Centella Asiatica, functioned as a Smad7 agonist and suppressed TGF-β/Smad3-mediated renal fibrosis by inducing Smad7. Whereas, NG, a flavonoid from grapefruits and citrus fruits, was a Smad3 inhibitor that inhibited renal fibrosis by blocking Smad3 phosphorylation and transcription. The combination of AA and NG produced an additive effect on inhibition of renal fibrosis by blocking Smad3 while upregulating Smad7. Thus, rebalancing the disorder of TGF-β/Smad signaling by treatment with AA and NG may represent as a novel and effective therapy for chronic kidney disease associated with fibrosis.

N-Acetyl-seryl-aspartyl-lysyl-proline Alleviates Renal Fibrosis Induced by Unilateral Ureteric Obstruction in BALB/C Mice

To expand the armamentarium of treatment for chronic kidney disease (CKD), we explored the utility of boosting endogenously synthesized N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), which is augmented by inhibition of the angiotensin converting enzyme. Male BALB/c mice underwent unilateral ureteral ligation (UUO) or sham operation and received exogenously administered Ac-SDKP delivered via a subcutaneous osmotic minipump or Captopril treatment by oral gavage. Seven days after UUO, there were significant reductions in the expression of both collagen 1 and collagen 3 in kidneys treated with Ac-SDKP or Captopril, and there was a trend towards reductions in collagen IV, α-SMA, and MCP-1 versus control. However, no significant attenuation of interstitial injury or macrophage infiltration was observed. These findings are in contrary to observations in other models and underscore the fact that a longer treatment time frame may be required to yield anti-inflammatory effects in BALB/c mice treated with Ac-SDKP compared to untreated mice. Finding an effective treatment regimen for CKD requires fine-tuning of pharmacologic protocols.

Ubiquitination and regulation of Smad7 in the TGF-β1/Smad signaling of aristolochic acid nephropathy

Aristolochic acid I (AAI) affects TGF-β1/Smad signaling, which causes AA nephropathy (AAN), but the mechanisms are not fully understood. We aimed to clarify whether Arkadia and UCH37 participate in TGF-β1/Smad signaling via Smad7, and the regulatory mechanisms of Smad7. One side, mice and cultured mouse renal tubular epithelial cells (RTECs) were treated with various AAI doses and concentrations, respectively; on the other side, RTECs were transfected with small interfering RNA (siRNA) expression vectors against Arkadia and UCH37 and then treated with 10 µg/ml AAI. And then detect the mRNA and protein levels of Smad7, UCH37, Arkadia and any other relative factors by RT-PCR and Western blotting. In kidney tissues and RTECs, the mRNA and protein levels of Smad7 decreased with increasing AAI doses concentrations by real-time PCR and Western blotting, whereas those of Arkadia, UCH37, Smad2, Smad3 and TβRI increased. Cells transfected with the Arkadia siRNA expression vector showed reduced mRNA and protein levels of vimentin, α-SMA, Smad2, Smad3 and TβRI after AAI treatment, while those of CK18 and Smad7 increased compared with those of untransfected RTECs. Conversely, cells transfected with the UCH37 siRNA expression vector showed the opposite effect on analyzed signaling molecules after AAI treatment. Arkadia and UCH37 participate in TGF-β1/Smad signaling-mediated renal fibrosis, and Smad7 blocks TGF-β1 signaling by inhibiting Smad2/Smad3 phosphorylation and enhancing the degradation of TβRI.

TGF-β/Smad signaling in renal fibrosis

TGF-β (transforming growth factor-β) is well identified as a central mediator in renal fibrosis. TGF-β initiates canonical and non-canonical pathways to exert multiple biological effects. Among them, Smad signaling is recognized as a major pathway of TGF-β signaling in progressive renal fibrosis. During fibrogenesis, Smad3 is highly activated, which is associated with the down-regulation of an inhibitory Smad7 via an ubiquitin E3-ligases-dependent degradation mechanism. The equilibrium shift between Smad3 and Smad7 leads to accumulation and activation of myofibroblasts, overproduction of ECM (extracellular matrix), and reduction in ECM degradation in the diseased kidney. Therefore, overexpression of Smad7 has been shown to be a therapeutic agent for renal fibrosis in various models of kidney diseases. In contrast, another downstream effecter of TGF-β/Smad signaling pathway, Smad2, exerts its renal protective role by counter-regulating the Smad3. Furthermore, recent studies demonstrated that Smad3 mediates renal fibrosis by down-regulating miR-29 and miR-200 but up-regulating miR-21 and miR-192. Thus, overexpression of miR-29 and miR-200 or down-regulation of miR-21 and miR-192 is capable of attenuating Smad3-mediated renal fibrosis in various mouse models of chronic kidney diseases (CKD). Taken together, TGF-β/Smad signaling plays an important role in renal fibrosis. Targeting TGF-β/Smad3 signaling may represent a specific and effective therapy for CKD associated with renal fibrosis.

Long Noncoding RNA Arid2-IR Is a Novel Therapeutic Target for Renal Inflammation

Increasing evidence shows that microRNAs play an important role in kidney disease. However, functions of long noncoding RNAs (lncRNAs) in kidney diseases remain undefined. We have previously shown that TGF-β1 plays a diverse role in renal inflammation and fibrosis and Smad3 is a key mediator in this process. In this study, we used RNA-sequencing to identify lncRNAs related to renal inflammation and fibrosis in obstructive nephropathy induced in Smad3 wild-type and knockout mice. We found that Arid2-IR was a Smad3-associated lncRNA as a Smad3 binding site was found in the promoter region of Arid2-IR and deletion of Smad3 abolished upregulation of Arid2-IR in the diseased kidney. In vitro knockdown of Arid2-IR from tubular epithelial cells produced no effect on TGF-β-induced Smad3 signaling and fibrosis but inhibited interleukin-1β-stimulated NF-κB-dependent inflammatory response. In contrast, overexpression of Arid2-IR promoted interleukin-1β-induced NF-κB signaling and inflammatory cytokine expression without alteration of TGF-β1-induced fibrotic response. Furthermore, treatment of obstructed kidney with Arid2-IR shRNA blunted NF-κB-driven renal inflammation without effect on TGF-β/Smad3-mediated renal fibrosis. Thus, Arid2-IR is a novel lncRNA that functions to promote NF-κB-dependent renal inflammation. Blockade of Arid2-IR may represent a novel and specific therapy for renal inflammatory disease.

Oryeongsan suppressed high glucose-induced mesangial fibrosis

Background

The pathological change of kidney in diabetic nephropathy is represented hypertrophy, inflammation, and renal fibrosis. Oryeongsan, traditional oriental herbal formula, is widely used for the treatment of nephrosis, dropsy, and uremia. This study was examined whether Oryeongsan attenuate high-glucose (HG)-promoted rat mesangial cell fibrosis and matrix accumulation, major features of diabetic glomerulosclerosis.

Methods

Oryeongsan was mixed traditional herbal medicine, Alisma orientale Juz, Polyporus umbellatus Fries, Atractylodes macrocephala Koidez, Poria cocos Wolf and Cinnamomum Cassia Presl (5:3:3:1). Renoprotective role in diabetic nephropathy of Oryeongsan was evaluated by [³H]-thymidine incorporation, Western blot, RT-qPCR and immunofluorescence microscopy assay.

Results

Rat mesangial cell proliferation induced by HG was significantly accelerated, which was inhibited by Oryeongsan in a dose dependent manner. HG enhanced expression of fibrosis biomarkers such as collagen IV and connective tissue growth factor (CTGF), which was markedly attenuated by Oryeongsan. Oryeongsan increased HG-inhibited membrane type-1 matrix metalloproteinase expression (MT1-MMP) and MMP-2 promotor activity, whereas suppressed HG-induced tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) expression. Moreover, Oryeongsan promoted extracellular matrix degradation through disturbing transforming growth factor β (TGF-β)–Smad signaling. This study further revealed that Oryeongsan ameliorated HG-induced mesangial inflammation accompanying induction of intracellular cell adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1). Moreover, pretreatment of Oryeongsan inhibited NF-κB translocation in HG-exposed mesangial cell.

Conclusion

These results demonstrate that Oryeongsan has protective effect against renal proliferation, fibrosis, and inflammation. Therefore Oryeongsan may be specific therapies targeting renal dysfunction leading to diabetic nephropathy.

MicroRNAs in renal fibrosis

MicroRNAs (miRNAs) are endogenous short non-coding RNAs that regulate most of important cellular processes by inhibiting gene expression through the post-transcriptional repression of their target mRNAs. In kidneys, miRNAs have been associated in renal development, homeostasis, and physiological functions. Results from clinical and experimental animal studies demonstrate that miRNAs play essential roles in the pathogenesis of various renal diseases. Chronic kidney diseases (CKD) is characterized by renal fibrosis. Transforming growth factor beta (TGF-β) is recognized as a major mediator of renal fibrosis because it is able to stimulate the accumulation of extracellular matrix (ECM) proteins to impair normal kidney function. Recently, emerging evidence demonstrate the relationship between TGF-β signaling and miRNAs expression during renal diseases. TGF-β regulates expression of several microRNAs, such as miR-21, miR-192, miR-200, miR-433, and miR-29. MiR-21, miR-192, and miR-433 which are positively induced by TGF-β signaling play a pathological role in kidney diseases. In contrast, members in both miR-29 and miR-200 families which are inhibited by TGF-β signaling protect kidneys from renal fibrosis by suppressing the deposition of ECM and preventing epithelial-to-mesenchymal transition, respectively. Clinically, the presence of miRNAs in blood and urine has been examined to be early biomarkers for detecting renal diseases. From experimental animal studies of CKD, targeting microRNAs also provides evidence about therapeutic potential of miRNAs during renal diseases. Now, it comes to the stage to examine the exact mechanisms of miRNAs during the initiation and progression of renal diseases. Therefore, determining the function of miRNAs in renal fibrosis may facilitate the development of both early diagnosis and treatment of renal diseases.

Latent transforming growth factor-β1 protects against bleomycin-induced lung injury in mice

Transforming growth factor (TGF)-β1 is a potent mediator known to induce lung fibrosis. However, the role of latent TGF-β1 in lung inflammation and fibrosis is unclear. To investigate the role of circulating latent TGF-β1 in bleomycin-induced lung injury, lung disease was induced in keratin-5 promoter-driven TGF-β1(wt) transgenic (Tg) mice by bleomycin. The role of latent TGF-β1 in pulmonary inflammation and fibrosis was examined at Days 7 and 28 after administration of bleomycin. Compared with littermate wild-type (WT) mice, TGF-β1(wt) Tg mice had over twofold-higher levels of latent TGF-β1 in both plasma and lung tissue, and were protected from bleomycin-induced pulmonary inflammation, such as up-regulation of IL-1β, TNF-α, and macrophage chemotactic protein-1, and infiltration of CD3(+) T cells and F4/80(+) macrophages. In addition, the severity of lung fibrosis with massive collagen matrix accumulation was markedly reduced in TGF-β1(wt) Tg mice. These protective effects were associated with higher levels of Smad7 and inactivation of both NF-κB and TGF-β/Smad3 signaling pathways, in addition to an increase in forkhead box P3 (Foxp3)-dependent regulatory T cells, but inhibition of T helper 17-mediated lung injury. In summary, mice overexpressing latent TGF-β1 are protected from bleomycin-induced lung injury. Triggering the Smad7 negative feedback mechanism to inhibit both NF-κB and TGF-β/Smad signaling pathways, and enhancing the regulatory T cell response to counter-regulate T helper 17-mediated lung injury, are potential mechanisms by which latent TGF-β1 protects against bleomycin-induced lung injury.

KS370G, a caffeamide derivative, attenuates unilateral ureteral obstruction-induced renal fibrosis by the reduction of inflammation and oxidative stress in mice

Unilateral ureteral obstruction (UUO) is an established animal model used to study renal nephropathy. Caffeic acid phenethyl ester, a natural phenolic compound, possesses antifibrotic, anti-inflammation and anti-oxidative stress effects; however, rapid decomposition by esterases substantially decreases its bioavailability. The goal of this study was to investigate the beneficial effects of KS370G, a synthetic caffeamide derivative, on UUO-induced renal injury. Following the UUO, KS370G (10mg/kg) was administered by oral gavage once a day. Renal injury was analyzed at 14 days post-operation. Our results show that KS370G significantly attenuated collagen deposition in the obstructed kidney and inhibited UUO-induced renal fibrosis markers expression, including fibronectin, type I collagen, vimentin, and α-smooth muscle actin (α-SMA). KS370G significantly lowered the expression of renal inflammatory chemokines/adhesion molecules and monocyte cells marker (MCP-1, VCAM-1, ICAM-1 and CD11b). KS370G also reduced renal malondialdehyde levels and reversed the expression of renal antioxidant enzymes (SOD and catalase) after UUO. Furthermore, KS370G significantly inhibited UUO-induced elevated plasma AngII and TGF-β1 levels, TGF-β1 protein expression and Smad3 phosphorylation. These findings demonstrate that KS370G reduces renal obstructive nephropathy by possibly inhibiting AngII, TGF-β and Smad3 signaling pathways.

The role of Smad7 in oral mucositis

Oral mucositis, a severe oral ulceration, is a common toxic effect of radio- or chemoradio-therapy and a limiting factor to using the maximum dose of radiation for effective cancer treatment. Among cancer patients, at least 40% and up to 70%, of individuals treated with standard chemotherapy regimens or upper-body radiation, develop oral mucositis. To date, there is no FDA approved drug to treat oral mucositis in cancer patients. The key challenges for oral mucositis treatment are to repair and protect ulcerated oral mucosa without promoting cancer cell growth. Oral mucositis is the result of complex, multifaceted pathobiology, involving a series of signaling pathways and a chain of interactions between the epithelium and submucosa. Among those pathways and interactions, the activation of nuclear factor-kappa B (NF-κB) is critical to the inflammation process of oral mucositis. We recently found that activation of TGFβ (transforming growth factor β) signaling is associated with the development of oral mucositis. Smad7, the negative regulator of TGFβ signaling, inhibits both NF-κB and TGFβ activation and thus plays a pivotal role in the prevention and treatment of oral mucositis by attenuating growth inhibition, apoptosis, and inflammation while promoting epithelial migration. The major objective of this review is to evaluate the known functions of Smad7, with a particular focus on its molecular mechanisms and its function in blocking multiple pathological processes in oral mucositis.

Inhibitory SMADs: potential regulators of ovarian function

Transforming growth factor beta (TGFB) superfamily signaling regulates essential reproductive functions. Dysregulation of TGFB signaling results in cellular and molecular deficiencies in the ovary, leading to reproductive diseases and cancer development. SMAD proteins are canonical TGFB signaling components consisting of receptor-regulated SMADs (SMAD1/2/3/5/9), a common SMAD (SMAD4), and inhibitory SMADs (SMAD6/7). Inhibitory SMADs are negative regulators of TGFB and bone morphogenetic protein signaling, and their reproductive functions are poorly defined. Emerging evidence supports that inhibitory SMADs are potential regulators of ovarian function. Further efforts and new genetic models are needed to unveil the role of inhibitory SMADs in the ovary.

L-Endoglin overexpression increases renal fibrosis after unilateral ureteral obstruction

Transforming growth factor-β (TGF-β) plays a pivotal role in renal fibrosis. Endoglin, a 180 KDa membrane glycoprotein, is a TGF-β co-receptor overexpressed in several models of chronic kidney disease, but its function in renal fibrosis remains uncertain. Two membrane isoforms generated by alternative splicing have been described, L-Endoglin (long) and S-Endoglin (short) that differ from each other in their cytoplasmic tails, being L-Endoglin the most abundant isoform. The aim of this study was to assess the effect of L-Endoglin overexpression in renal tubulo-interstitial fibrosis. For this purpose, a transgenic mouse which ubiquitously overexpresses human L-Endoglin (L-ENG+) was generated and unilateral ureteral obstruction (UUO) was performed in L-ENG+ mice and their wild type (WT) littermates. Obstructed kidneys from L-ENG+ mice showed higher amounts of type I collagen and fibronectin but similar levels of α-smooth muscle actin (α-SMA) than obstructed kidneys from WT mice. Smad1 and Smad3 phosphorylation were significantly higher in obstructed kidneys from L-ENG+ than in WT mice. Our results suggest that the higher increase of renal fibrosis observed in L-ENG+ mice is not due to a major abundance of myofibroblasts, as similar levels of α-SMA were observed in both L-ENG+ and WT mice, but to the higher collagen and fibronectin synthesis by these fibroblasts. Furthermore, in vivo L-Endoglin overexpression potentiates Smad1 and Smad3 pathways and this effect is associated with higher renal fibrosis development.

Bone Morphogenetic Protein (BMP) signaling in development and human diseases

Bone Morphogenetic Proteins (BMPs) are a group of signaling molecules that belongs to the Transforming Growth Factor-β (TGF-β) superfamily of proteins. Initially discovered for their ability to induce bone formation, BMPs are now known to play crucial roles in all organ systems. BMPs are important in embryogenesis and development, and also in maintenance of adult tissue homeostasis. Mouse knockout models of various components of the BMP signaling pathway result in embryonic lethality or marked defects, highlighting the essential functions of BMPs. In this review, we first outline the basic aspects of BMP signaling and then focus on genetically manipulated mouse knockout models that have helped elucidate the role of BMPs in development. A significant portion of this review is devoted to the prominent human pathologies associated with dysregulated BMP signaling.

MicroRNA-21 in glomerular injury

TGF-β(1) is a pleotropic growth factor that mediates glomerulosclerosis and podocyte apoptosis, hallmarks of glomerular diseases. The expression of microRNA-21 (miR-21) is regulated by TGF-β(1), and miR-21 inhibits apoptosis in cancer cells. TGF-β(1)-transgenic mice exhibit accelerated podocyte loss and glomerulosclerosis. We determined that miR-21 expression increases rapidly in cultured murine podocytes after exposure to TGF-β(1) and is higher in kidneys of TGF-β(1)-transgenic mice than wild-type mice. miR-21-deficient TGF-β(1)-transgenic mice showed increased proteinuria and glomerular extracellular matrix deposition and fewer podocytes per glomerular tuft compared with miR-21 wild-type TGF-β(1)-transgenic littermates. Similarly, miR-21 expression was increased in streptozotocin-induced diabetic mice, and loss of miR-21 in these mice was associated with increased albuminuria, podocyte depletion, and mesangial expansion. In cultured podocytes, inhibition of miR-21 was accompanied by increases in the rate of cell death, TGF-β/Smad3-signaling activity, and expression of known proapoptotic miR-21 target genes p53, Pdcd4, Smad7, Tgfbr2, and Timp3. In American-Indian patients with diabetic nephropathy (n=48), albumin-to-creatinine ratio was positively associated with miR-21 expression in glomerular fractions (r=0.6; P<0.001) but not tubulointerstitial fractions (P=0.80). These findings suggest that miR-21 ameliorates TGF-β(1) and hyperglycemia-induced glomerular injury through repression of proapoptotic signals, thereby inhibiting podocyte loss. This finding is in contrast to observations in murine models of tubulointerstitial kidney injury but consistent with findings in cancer models. The aggravation of glomerular disease in miR-21-deficient mice and the positive association with albumin-to-creatinine ratio in patients with diabetic nephropathy support miR-21 as a feedback inhibitor of TGF-β signaling and functions.

Vasohibin-1 deficiency enhances renal fibrosis and inflammation after unilateral ureteral obstruction

Tubulointerstitial injuries are known to predict the deterioration of renal function in chronic kidney disease (CKD). We recently reported the protective role of Vasohibin‐1(VASH‐1), a negative feedback regulator of angiogenesis, in diabetic nephropathy, but its impact on tubulointerstitial injuries remains to be elucidated. In the present study, we evaluated the role of endogenous VASH‐1 in regulating the tubulointerstitial alterations induced by unilateral ureteral obstruction (UUO), and assessed its role on fibrogenesis and the activation of Smad3 signaling in renal fibroblasts. UUO was induced in female Vasohibin‐1 heterozygous knockout mice (VASH‐1^+/−) or wild‐type (WT) (VASH‐1^+/+) littermates. Mice were sacrificed on Day 7 after left ureter ligation, and the kidney tissue was obtained. Interstitial fibrosis, the accumulation of type I and type III collagen and monocytes/macrophages infiltration in the obstructed kidneys (OBK) were significantly exacerbated in VASH‐1^+/− mice compared with WT mice (Day 7). The increases in the renal levels of TGF‐β1, pSmad3, NF‐κB pp65, CCL2 mRNA, and the number of interstitial fibroblast‐specific protein‐1 (FSP‐1)⁺ fibroblasts in the OBK were significantly aggravated in VASH‐1^+/− mice. In addition, treatment with VASH‐1 siRNA enhanced the TGF‐β1‐induced phosphorylation of Smad3, the transcriptional activation of the Smad3 pathway and the production of type I/type III collagen in fibroblasts, in vitro. Taken together, our findings demonstrate a protective role for endogenous VASH‐1 on tubulointerstitial alterations via its regulation of inflammation and fibrosis and also show the direct anti‐fibrotic effects of VASH‐1 on renal fibroblasts through its modulation of TGF‐β1 signaling.

In the present study, we evaluated the role of endogenous Vasohibn‐1 VASH‐1 in regulating tubulointerstitial alterations induced by unilateral ureteral obstruction (UUO), and assessed its regulatory role on fibrogenesis and the activation of TGF‐beta/Smad3 signaling in renal fibroblasts. This is the first study to demonstrate the potential protective role for endogenous VASH‐1 on tubulointerstitial alterations via regulating inflammation and fibrosis, partly mediated via its direct anti‐fibrotic effects on renal fibroblasts through modulating TGF‐β1 signaling.

Smad7 inhibits AngII-mediated hypertensive nephropathy in a mouse model of hypertension

The TGFβ (transforming growth factor β)/SMAD and NF-κB (nuclear factor κB) signalling pathways play a key role in hypertensive nephropathy. The present study examined whether targeting these pathways by SMAD7, a downstream inhibitor of both pathways, blocks AngII (angiotensin II)-induced hypertensive kidney disease in mice. A doxycycline-inducible SMAD7-expressing plasmid was delivered into the kidney by a non-invasive ultrasound-microbubble technique before and after AngII infusion. Results showed that pre-treatment with SMAD7 prevented AngII-induced progressive renal injury by inhibiting an increase in proteinuria and serum creatinine while improving the glomerular filtration rate. Similarly, treatment with SMAD7 in the established hypertensive nephropathy at day 14 after AngII infusion halted the progressive renal injury. These preventive and therapeutic effects of SMAD7 on hypertensive kidney injury were associated with inhibition of AngII-induced up-regulation of SMURF2 (SMAD-specific E3 ubiquitin protein ligase 2) and Sp1 (specificity protein 1), blockade of TGFβ/Smad3-mediated renal fibrosis and suppression of NF-κB-driven renal inflammation. Moreover, overexpression of SMAD7 also prevented AngII-induced loss of renal miR-29b, an miRNA with an inhibitory role in both TGFβ/Smad3 and NF-κB pathways. In conclusion, SMAD7 may be a therapeutic agent for AngII-mediated hypertensive nephropathy. Inhibition of the Sp1/SMAD3/NF-κB/miR-29b regulatory network may be a mechanism by which SMAD7 inhibits hypertensive nephropathy.

Astragaloside IV inhibits renal tubulointerstitial fibrosis by blocking TGF-β/Smad signaling pathway in vivo and in vitro

Astragaloside IV (AS-IV) is a major active ingredient from Radix astragali, which has been considered as a renoprotective agent; however, its molecular mechanisms are unclear. Thus, we designed to investigate the renoprotective effects and mechanisms of AS-IV in rat model of renal fibrosis induced by unilateral ureteral obstruction (UUO) in vivo and TGF-β1-stimulated rat renal fibroblasts (NRK-49F) in vitro. Sprague-Dawley rats were randomly divided into six groups: sham operation, UUO, UUO/AS-IV (3.3, 10, 33 mg·kg(-1)·d(-1)), and UUO/enalapril (4 mg·kg(-1)·d(-1)). Renal function, tubulointerstitial damage index score, extracellular matrix (ECM) deposition, and the expressions of TGF-β1, connective tissue growth factor (CTGF), α-SMA, fibronectin, collagen I, III, Smad2/3, phosphorylated-Smad2/3, and Smad7 were measured. In addition, the expressions of CTGF, α-SMA, fibronectin, collagen I, III, Smad2/3, phosphorylated-Smad2/3, and Smad7 were measured in TGF-β1-stiumlated NRK-49F cell line. AS-IV significantly decreased UUO-induced renal fibrosis and functional impairment, which are associated with inhibition of TGF-β1, CTGF, α-SMA, and collagen matrix expression, and a decrease in serum creatinine and urea nitrogen. The renoprotective effects of AS-IV on fibrosis were associated with up-regulation of Smad7, thereby blocking up-regulations of TGF-β1, CTGF, and α-SMA, and activation of phosphorylated-Smad2/3. These effects were further conformed in NRK-49F cell line stimulated by TGF-β1. Moreover, knockdown of Smad7 gene in NRK-49F cells was able to prevent AS-IV-induced inhibition to Smad2/3 signaling activation, expression of CTGF, α-SMA, and ECM proteins in response to TGF-β1. Renal tubulointerstitial fibrosis was attenuated by treatment with AS-IV, which was closely related to induction of Smad7, thereby inhibiting TGF-β/Smad signaling.

Effects of astragalus injection on the TGFβ/Smad pathway in the kidney in type 2 diabetic mice

Background

In traditional Chinese medicine, astragalus injection is used to treat diabetic nephropathy (DN). The current study was conducted to determine the effects of astragalus injection on DN by assessing potential modulation of the transforming growth factor beta TGFβ/Smad signaling pathway.

Methods

Diabetic, male KKAy mice, aged 14 weeks were randomly divided into a model group and an astragalus treatment group, while age-matched male C57BL/6J mice were selected as controls. The treatment group received daily intraperitoneal injections of astragalus (0.03 ml/10 g.d), while the model group received injections of an equivalent volume of saline. Mice were euthanized after 24 weeks. Serum samples were obtained from animals in each group, and blood glucose, creatinine, and urea nitrogen levels were measured. Tissue samples from the kidney were used for morphometric studies. The expression of TGFβ1, TGFβR-Ι, Smad3, and Smad7 were evaluated using reverse transcription-polymerase chain reaction (RT-PCR), and western blot analysis.

Results

Mice in the model group became obese, and suffered complications, including hyperglycemia, polyuria, and proteinuria. Astragalus treatment significantly reduced albuminuria, improved renal function, and ameliorated changes in renal histopathology. Moreover, administration of astragalus injection increased Smad7 expression, and inhibited the expression of TGFβR-Ι, Smad3 and its phosphorylation, and decreased the mRNA level of TGFβ1.

Conclusions

The TGFβ/Smad signaling pathway plays an important role in the development of DN. Administration of astragalus injection could prevent or mitigate DN by rebalancing TGFβ/Smad signaling, and could play a protective role in DN-induced renal damage in KKAy mice.

Activation of platelet-activating factor receptor exacerbates renal inflammation and promotes fibrosis

Platelet-activating factor (PAF) is a lipid mediator with important pro-inflammatory effects, being synthesized by several cell types including kidney cells. Although there is evidence of its involvement in acute renal dysfunction, its role in progressive kidney injury is not completely known. In the present study, we investigated the role of PAF receptor (PAFR) in an experimental model of chronic renal disease. Wild-type (WT) and PAFR knockout (KO) mice underwent unilateral ureter obstruction (UUO), and at kill time, urine and kidney tissue was collected. PAFR KO animals compared with WT mice present: (a) less renal dysfunction, evaluated by urine protein/creatinine ratio; (b) less fibrosis evaluated by collagen deposition, type I collagen, Lysyl Oxidase-1 (LOX-1) and transforming growth factor β (TGF-β) gene expression, and higher expression of bone morphogenetic protein 7 (BMP-7) (3.3-fold lower TGF-β/BMP-7 ratio); (c) downregulation of extracellular matrix (ECM) and adhesion molecule-related machinery genes; and (d) lower levels of pro-inflammatory cytokines. These indicate that PAFR engagement by PAF or PAF-like molecules generated during UUO potentiates renal dysfunction and fibrosis and might promote epithelial-to-mesenchymal transition (EMT). Also, early blockade of PAFR after UUO leads to a protective effect, with less fibrosis deposition. In conclusion, PAFR signaling contributes to a pro-inflammatory environment in the model of obstructive nephropathy, favoring the fibrotic process, which lately will generate renal dysfunction and progressive organ failure.