Matrix metalloproteinase-7 as a surrogate marker predicts renal Wnt/β-catenin activity in CKD

Mutual antagonism of Wilms' tumor 1 and β-catenin dictates podocyte health and disease

Activation of β-catenin, the intracellular mediator of canonical Wnt signaling, has a critical role in mediating podocyte injury and proteinuria. However, the underlying mechanisms remain poorly understood. Here, we show that β-catenin triggers ubiquitin-mediated protein degradation of Wilms' tumor 1 (WT1) and functionally antagonizes its action. In mice injected with adriamycin, WT1 protein was progressively lost in glomerular podocytes at 1, 3, and 5 weeks after injection. Notably, loss of WT1 apparently did not result from podocyte depletion but was closely associated with upregulation of β-catenin. This change in WT1/β-catenin ratio was accompanied by loss of podocyte-specific nephrin, podocalyxin, and synaptopodin and acquisition of mesenchymal markers Snail1, α-smooth muscle actin, and fibroblast-specific protein 1. In vitro, overexpression of β-catenin induced WT1 protein degradation through the ubiquitin proteasomal pathway, which was blocked by MG-132. WT1 and β-catenin also competed for binding to common transcriptional coactivator CREB-binding protein and mutually repressed the expression of their respective target genes. In glomerular miniorgan culture, activation of β-catenin by Wnt3a repressed WT1 and its target gene expression. In vivo, blockade of Wnt/β-catenin signaling by endogenous antagonist Klotho induced WT1 and restored podocyte integrity in adriamycin nephropathy. These results show that β-catenin specifically targets WT1 for ubiquitin-mediated degradation, leading to podocyte dedifferentiation and mesenchymal transition. Our data also suggest that WT1 and β-catenin have opposing roles in podocyte biology, and that the ratio of their expression levels dictates the state of podocyte health and disease in vivo.

Multiple genes of the renin-angiotensin system are novel targets of Wnt/β-catenin signaling

Activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. However, current anti-RAS therapy only has limited efficacy, partly because of compensatory upregulation of renin expression. Therefore, a treatment strategy to simultaneously target multiple RAS genes is necessary to achieve greater efficacy. By bioinformatics analyses, we discovered that the promoter regions of all RAS genes contained putative T-cell factor (TCF)/lymphoid enhancer factor (LEF)-binding sites, and β-catenin induced the binding of LEF-1 to these sites in kidney tubular cells. Overexpression of either β-catenin or different Wnt ligands induced the expression of all RAS genes. Conversely, a small-molecule β-catenin inhibitor ICG-001 abolished RAS induction. In a mouse model of nephropathy induced by adriamycin, either transient therapy or late administration of ICG-001 abolished established proteinuria and kidney lesions. ICG-001 inhibited renal expression of multiple RAS genes in vivo and abolished the expression of other Wnt/β-catenin target genes. Moreover, ICG-001 therapy restored expression of nephrin, podocin, and Wilms' tumor 1, attenuated interstitial myofibroblast activation, repressed matrix expression, and inhibited renal inflammation and fibrosis. Collectively, these studies identify all RAS genes as novel downstream targets of Wnt/β-catenin. Our results indicate that blockade of Wnt/β-catenin signaling can simultaneously repress multiple RAS genes, thereby leading to the reversal of established proteinuria and kidney injury.

Cleavage of transmembrane junction proteins and their role in regulating epithelial homeostasis

Epithelial tissues form a selective barrier that separates the external environment from the internal tissue milieu. Single epithelial cells are densely packed and associate via distinct intercellular junctions. Intercellular junction proteins not only control barrier properties of the epithelium but also play an important role in regulating epithelial homeostasis that encompasses cell proliferation, migration, differentiation and regulated shedding. Recent studies have revealed that several proteases target epithelial junction proteins during physiological maturation as well as in pathologic states such as inflammation and cancer. This review discusses mechanisms and biological consequences of transmembrane junction protein cleavage. The influence of junction protein cleavage products on pathogenesis of inflammation and cancer is discussed.

Kidney tubular β-catenin signaling controls interstitial fibroblast fate via epithelial-mesenchymal communication

Activation of β-catenin, the principal mediator of canonical Wnt signaling, is a common pathologic finding in a wide variety of chronic kidney diseases (CKD). While β-catenin is induced predominantly in renal tubular epithelium in CKD, surprisingly, depletion of tubular β-catenin had little effect on the severity of renal fibrosis. Interestingly, less apoptosis was detected in interstitial fibroblasts in knockout mice, which was accompanied by a decreased expression of Bax and Fas ligand (FasL). Tubule-specific knockout of β-catenin diminished renal induction of matrix metalloproteinase (MMP-7), which induced FasL expression in interstitial fibroblasts and potentiated fibroblast apoptosis in vitro. These results demonstrate that loss of tubular β-catenin resulted in enhanced interstitial fibroblast survival due to decreased MMP-7 expression. Our studies uncover a novel role of the tubular β-catenin/MMP-7 axis in controlling the fate of interstitial fibroblasts via epithelial-mesenchymal communication.

Urinary excretion of RAS, BMP, and WNT pathway components in diabetic kidney disease

The renin–angiotensin system (RAS), bone morphogenetic protein (BMP), and WNT pathways are involved in pathogenesis of diabetic kidney disease (DKD). This study characterized assays for urinary angiotensinogen (AGT), gremlin‐1, and matrix metalloproteinase 7 (MMP‐7), components of the RAS, BMP, and WNT pathways and examined their excretion in DKD. We measured urine AGT, gremlin‐1, and MMP‐7 in individuals with type 1 diabetes and prevalent DKD (n = 20) or longstanding (n = 61) or new‐onset (n = 10) type 1 diabetes without DKD. These urine proteins were also quantified in type 2 DKD (n = 11) before and after treatment with candesartan. The utilized immunoassays had comparable inter‐ and intra‐assay and intraindividual variation to assays used for urine albumin. Median (IQR) urine AGT concentrations were 226.0 (82.1, 550.3) and 13.0 (7.8, 20.0) μg/g creatinine in type 1 diabetes with and without DKD, respectively (P < 0.001). Median (IQR) urine gremlin‐1 concentrations were 48.6 (14.2, 254.1) and 3.6 (1.7, 5.5) μg/g, respectively (P < 0.001). Median (IQR) urine MMP‐7 concentrations were 6.0 (3.8, 10.5) and 1.0 (0.4, 2.9) μg/g creatinine, respectively (P < 0.001). Treatment with candesartan was associated with a reduction in median (IQR) urine AGT/creatinine from 23.5 (1.6, 105.1) to 2.0 (1.4, 13.7) μg/g, which did not reach statistical significance. Urine gremlin‐1 and MMP‐7 excretion did not decrease with candesartan. In conclusion, DKD is characterized by markedly elevated urine AGT, MMP‐7, and gremlin‐1. AGT decreased in response to RAS inhibition, suggesting that this marker reflects therapeutic response. Urinary components of the RAS, BMP, and WNT pathways may identify risk of DKD and aid development of novel therapeutics.

Urine angiotensinogen, matrix metalloproteinase‐7, and gremlin‐1 concentrations are markedly elevated in people with type 1 diabetes and kidney disease, compared with those with recently diagnosed type 1 diabetes or longstanding type 1 diabetes without kidney disease. Treatment with an inhibitor of the renin–angiotensin system tended to reduce urine angiotensinogen concentration, but not urine matrix metalloproteinase‐7 or gremlin‐1.

Inhibition of cancer cell migration and invasion through suppressing the Wnt1-mediating signal pathway by G-quadruplex structure stabilizers

WNT1 encodes a multifunctional signaling glycoprotein that is highly expressed in several malignant tumors. Patients with Wnt1-positive cancer are usually related to advanced metastasis. Here, we found that a stretch of G-rich sequences located at the WNT1 promoter region is capable of forming G-quadruplex structures. The addition of G-quadruplex structure stabilizers, BMVC and BMVC4, raises the melting temperature of the oligonucleotide formed by the WNT1 promoter G-rich sequences. Significantly, the expression of WNT1 was repressed by BMVC or BMVC4 in a G-quadruplex-dependent manner, suggesting that they can be used to modulate WNT1 expression. The role of G-quadruplex stabilizers on Wnt1-mediated cancer migration and invasion was further analyzed. The protein levels of β-catenin, a mediator of the Wnt-mediated signaling pathway, and the downstream targets MMP7 and survivin were down-regulated upon BMVC or BMVC4 treatments. Moreover, the migration and invasion activities of cancer cells were inhibited by BMVC and BMVC4, and the inhibitory effects can be reversed by WNT1-overexpression. Thus the Wnt1 expression and its downstream signaling pathways can be regulated through the G-quadruplex sequences located at its promoter region. These findings provide a novel approach for future drug development to inhibit migration and invasion of cancer cells.

The urine microRNA profile may help monitor post-transplant renal graft function

Noninvasive, cost-effective biomarkers that allow accurate monitoring of graft function are needed in kidney transplantation. Since microRNAs (miRNAs) have emerged as promising disease biomarkers, we sought to establish an miRNA signature in urinary cell pellets comparing kidney transplant patients diagnosed with chronic allograft dysfunction (CAD) with interstitial fibrosis and tubular atrophy and those recipients with normal graft function. Overall, we evaluated 191 samples from 125 deceased donor primary kidney transplant recipients in the discovery, initial validation, and the longitudinal validation studies for noninvasive monitoring of graft function. Of 1733 mature miRNAs studied using microarrays, 22 were found to be differentially expressed between groups. Ontology and pathway analyses showed inflammation as the principal biological function associated with these miRNAs. Twelve selected miRNAs were longitudinally evaluated in urine samples of an independent set of 66 patients, at two time points after kidney transplant. A subset of these miRNAs was found to be differentially expressed between groups early after kidney transplant before histological allograft injury was evident. Thus, a panel of urine miRNAs was identified as potential biomarkers for monitoring graft function and anticipating progression to CAD in kidney transplant patients.

Epithelial-mesenchymal transition in colorectal cancer tissue of patients with Lynch syndrome

AIM: To explore the epithelial-mesenchymal transition (EMT) in tissue from patients with Lynch syndrome, and to interpret biological behaviour of Lynch syndrome.

METHODS: Sixty-eight formalin-fixed and paraffin embedded tissue blocks were analyzed in this study, including tissues from Lynch syndrome (n = 30), sporadic colorectal carcinoma (CRC) (n = 30), and tumor-adjacent tissues (n = 8). Tissue sections were stained for human mutS homolog 2 (hMSH2), human mutL homolog 1 (hMLH1), transforming growth factor-β type II receptor (TGFβRII), E-cadherin, β-catenin, matrix metalloproteinase-7 (MMP-7) and tissue inhibitor of metalloproteinase-2 (TIMP-2) by immunohistochemical staining. Furthermore, clinical data such as age, gender and tumor-node-metastasis stage were also collected retrospectively.

RESULTS: The positive expression rates of hMSH2, hMLH1, TGFβRII, E-cadherin, β-catenin, MMP-7 and TIMP-2 were significantly related to the depth of invasion and lymph node metastasis, but not to sex or tumour size or location. The differences in the positive expression rates of hMSH2, hMLH1, TGFβRII, E-cadherin, cytomembrane β-catenin, cytoplasmic β-catenin, MMP-7 and TIMP-2 were significant between sporadic CRC and Lynch syndrome. The expression of hMSH2 had a positive correlation with that of hMLH1 in Lynch syndrome and sporadic CRC. The expression of TGFβRII had a positive correlation with that of hMSH2, hMLH1 and MMP-7, and a negative correlation with that of TIMP-2. The expression of MMP-7 had a negative correlation with that of TIMP-2 in Lynch syndrome and sporadic CRC. The expression of E-cadherin was positively correlated with that of cytomembrane β-catenin. However, the expression of cytomembrane β-catenin was negatively correlated with that of cytoplasmic β-catenin, and the expression of cytoplasmic β-catenin was positively correlated with that of MMP-7.

CONCLUSION: EMT may play an important role in the development and progression of Lynch syndrome. Lynch syndrome was caused by the mutations of mismatch repair genes, mainly hMSH2 and hMLH1, which also beget the mutational inactivation of TGFβRII. Therefore, the colorectal cancer of Lynch syndrome can escape the inhibitory effect of TGFβ1. However, TGFβ1 can up-regulate the expression of MMP-7 and down-regulate the expression of TIMP-2 in tumors by disassembling the E-cadherin/β-catenin complex in the cytomembrane.

DKK1 promotes hepatocellular carcinoma cell migration and invasion through β-catenin/MMP7 signaling pathway

Background

Recently several reports have indicated that elevated expression of DKK1 is tightly associated with the progression of hepatocellular carcinoma (HCC). However, the biological function of DKK1 in HCC has not yet been well documented.

Methods

In this study, the role of DKK1 in tumor cell proliferation, migration and invasion was investigated using MTT, colony formation, wound scratch, transwell assays, and also human HCC samples.

Results

Both gain- and loss-of-function studies showed that DKK1 did not influence the tumor cell proliferation and colony formation, while dramatically promoted HCC cell migration and invasion. Subsequent investigations revealed that β-catenin was an important target of DKK1. The blocking of β-catenin by pharmacological inhibitor antagonized the function of DKK1, whereas introduction of β-catenin by transfection with plasmids or treatment with GSK3β inhibitor phenocopied the pro-migration and pro-invasion effects of DKK1. We further disclosed that DKK1 exerted its pro-invasion function, at least in part, by promoting β-catenin expression, in turn, upregulating the expression of matrix metalloproteinase 7 (MMP7), which was independent of the canonical Wnt signaling pathway. Moreover, introduction of MMP7 significantly enhanced the ability of HCC cells to invade extracellular matrix gel in vitro. Consistently, in human HCC tissues, DKK1 level was positively correlated with β-catenin expression, as well as tumor metastasis.

Conclusion

Taken together, these results demonstrated that DKK1 is overexpressed in HCC; moreover, ectopic expression DKK1 promotes HCC cell migration and invasion at least partly through β-catenin/MMP7 signaling axis, suggesting that DKK1 may be a promising target for HCC therapy.

Protective effect of exogenous matrix metalloproteinase-9 on chronic renal failure

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have pivotal functions in extracellular matrix turnover and are involved in chronic kidney diseases. However, the exact functions of MMPs in chronic renal failure (CRF) have yet to be demonstrated. The aim of the present study was to examine the effects of MMP-9 on CRF. An adenine-induced model of CRF was generated in rabbits. Following the injection of MMP-9 into the renal arteries of the rabbits, significant improvements in renal morphology and serum levels of creatinine and urea nitrogen were observed. Furthermore, MMP-9 administration was shown to decrease the serum TIMP-1 concentration and upregulate renal MMP-9 expression. These results demonstrate a directly protective role for MMP-9 in CRF.

Loss of Klotho contributes to kidney injury by derepression of Wnt/β-catenin signaling

Aging is an independent risk factor for CKD, but the molecular mechanisms that link aging and CKD are not well understood. The antiaging protein Klotho may be an endogenous antagonist of Wnt/β-catenin signaling, which promotes fibrogenesis, suggesting that loss of Klotho may contribute to CKD through increased Wnt/β-catenin activity. Here, normal adult kidneys highly expressed Klotho in the tubular epithelium, but various models of nephropathy exhibited markedly less expression of Klotho. Loss of Klotho was closely associated with increased β-catenin in the diseased kidneys, suggesting an inverse correlation between Klotho and canonical Wnt signaling. In vitro, both full-length and secreted Klotho bound to multiple Wnts, including Wnt1, Wnt4, and Wnt7a. Klotho repressed gene transcription induced by Wnt but not by active β-catenin. Furthermore, Klotho blocked Wnt-triggered activation and nuclear translocation of β-catenin, as well as the expression of its target genes in tubular epithelial cells. Investigating potential mediators of Klotho loss in CKD, we found that TGF-β1 suppressed Klotho expression and concomitantly activated β-catenin; conversely, overexpression of Klotho abolished fibrogenic effects of TGF-β1. In two mouse models of CKD induced by unilateral ureteral obstruction or adriamycin, in vivo expression of secreted Klotho inhibited the activation of renal β-catenin and expression of its target genes. Secreted Klotho also suppressed myofibroblast activation, reduced matrix expression, and ameliorated renal fibrosis. Taken together, these results suggest that Klotho is an antagonist of endogenous Wnt/β-catenin activity; therefore, loss of Klotho may contribute to kidney injury by releasing the repression of pathogenic Wnt/β-catenin signaling.

Acetyl-11-keto-β-boswellic acid (AKBA) inhibits human gastric carcinoma growth through modulation of the Wnt/β-catenin signaling pathway

BACKGROUND

Acetyl-11-keto-beta-boswellic acid (AKBA) is a derivative of boswellic acid, an active component of Boswellia serrata gum resin. We examined the effect of AKBA on human gastric carcinoma growth and explored the underlying molecular mechanisms.

METHODS

Inhibition of cancer cell growth was estimated by colorimetric and clonogenic assays. Cell cycle distribution was analyzed by flow cytometry and apoptosis determined using Annexin V-FITC/PI staining and DNA ladder quantification. After three weeks of oral AKBA administration in nude mice bearing cancer xenografts, animals were sacrificed and xenografts removed for TUNEL staining and western blot analysis.

RESULTS

AKBA exhibited anti-cancer activity in vitro and in vivo. With oral application in mice, AKBA significantly inhibited SGC-7901 and MKN-45 xenografts without toxicity. This effect might be associated with its roles in cell cycle arrest and apoptosis induction. The results also showed activation of p21(Waf1/Cip1) and p53 in mitochondria and increased cleaved caspase-9, caspase-3, and PARP and Bax/Bcl-2 ratio after AKBA treatment. Further analysis suggested that these effects might arise from AKBA's modulation of the aberrant Wnt/β-catenin signaling pathway. Upon AKBA treatment, β-catenin expression in nuclei was inhibited, and membrane β-catenin was activated. In the same sample, active GSK3β was increased and its non-active form decreased. Levels of cyclin D1, PCNA, survivin, c-Myc, MMP-2, and MMP-7, downstream targets of Wnt/β-catenin, were inhibited.

CONCLUSIONS

AKBA effects on human gastric carcinoma growth were associated with its activity in modulating the Wnt/β-catenin signaling pathway.

GENERAL SIGNIFICANCE

AKBA could be useful in the treatment of gastric cancers.

Biomarkers in idiopathic pulmonary fibrosis

PURPOSE OF REVIEW

This review examines the recent literature on molecular biomarkers of idiopathic pulmonary fibrosis (IPF). Specific attention is dedicated to the recent studies that identified the genes associated with IPF and the peripheral blood biomarkers that predict outcome in IPF.

RECENT FINDINGS

Multiple studies attempted to identify diagnostic and predictive biomarkers in IPF. Until recently, these studies were limited in size and lacked replication, but still when taken together provided convincing evidence that changes in blood proteins (KL-6, SP-A, MMP-7, CCL-18, among others) or cells (fibrocytes and T-cell subpopulations) are indicative of the disease presence and outcome. More recently, larger studies have identified gene polymorphisms associated with IPF, as well as protein markers and integrated clinical and molecular prediction rules that accurately predict outcome in patients with IPF.

SUMMARY

The peripheral blood contains disease presence and outcome relevant information, and suggests distinct biologically defined outcome trajectories in patients with IPF. Although recently identified biomarkers should still be validated in multiple clinical contexts, there is sufficient evidence to suggest that collection of peripheral blood biomarkers needs to be incorporated in the design of drug studies and that some of these markers be clinically evaluated in lung transplant prioritization.

Wnt/β-Catenin Signaling: a Promising New Target for Fibrosis Diseases

Wnt/β-catenin signaling is involved in virtually every aspect of embryonic development and also controls homeostatic self-renewal in a number of adult tissues. Recently, emerging evidence from researches of organ fibrosis suggest that sustained Wnt/β-catenin pathway reactivation is linked to the pathogenesis of fibrotic disorders. Here we focus on Wnt/β-catenin-related pathogenic effects in different organs, such as lung fibrosis, liver fibrosis, skin fibrosis and renal fibrosis. Additionally, Wnt/β-catenin signaling works in a combinatorial manner with TGF-β signaling in the process of fibrosis, and TGF-β signaling can induce expression of Wnt/β-catenin superfamily members and vice versa. Moreover, network analysis, based on pathway databases, revealed that key factors in the Wnt pathway were targeted by some differentially expressed microRNAs detected in fibrosis diseases. These findings demonstrated the crosstalks between Wnt/β-catenin pathway and TGF-β signalings, and microRNAs, highlighting the role of Wnts in organ fibrogenesis. Most importantly, nowadays there is a variety of Wnt pathway inhibitors which give us the potential therapeutic feasibility, modulation of the Wnt pathway may, therefore, present as a suitable and promising therapeutic strategy in the future.

Matrix metalloproteinases in kidney homeostasis and diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that have been increasingly linked to both normal physiology and abnormal pathology in the kidney. Collectively able to degrade all components of the extracellular matrix, MMPs were originally thought to antagonize the development of fibrotic diseases solely through digestion of excessive matrix. However, increasing evidence has shown that MMPs play a wide variety of roles in regulating inflammation, epithelial-mesenchymal transition, cell proliferation, angiogenesis, and apoptosis. We now have robust evidence for MMP dysregulation in a multitude of renal diseases including acute kidney injury, diabetic nephropathy, glomerulonephritis, inherited kidney disease, and chronic allograft nephropathy. The goal of this review is to summarize current findings regarding the role of MMPs in kidney diseases as well as the mechanisms of action of this family of proteases.