Kick it up a notch: Notch signaling and kidney fibrosis

Oleuropein attenuates the nephrotoxic effect of sunitinib in rats: Unraveling the potential role of SIRT6/Notch-1/NLRP-3/IL-1β axis

Sunitinib (SUN) is a chemotherapeutic agent clinically approved for treatment of metastatic renal carcinoma. Despite its remarkable benefits, various renal toxicities have been reported that limit its clinical uses. Oleuropein (OLE) is the main polyphenolic constituent of olive tree and mediates the majority of its valuable pharmacological activities. The current study examined the probable renoprotective effects of OLE against SUN-induced nephrotoxicity. Adult male albino rats were co-treated by SUN (25 mg/kg, 3 times/week, PO) with either a drug vehicle or OLE (60 mg/kg/day, daily, PO) for four weeks. A control group comprising of age-matched rats was used. Four weeks later, blood specimens were collected to assess kidney functions. Kidneys were harvested for biochemical and histopathological analyses. Administration of SUN induced kidney dysfunction, along with marked rises in endothelin-1 (ET-1) and monocyte chemotactic protein-1 (MCP-1) levels in renal tissues. Histological abnormalities were also detected in kidneys of SUN-treated rats including glomerular and tubular interstitial congestion along with interstitial fibrosis. On molecular levels, there was a decline in renal SIRT6 expression along with significant up-regulation of Notch-1, NLRP-3, interleukin -1β (IL-1β) and cleaved caspsase-3. All these changes were almost alleviated by OLE co-treatment. These findings suggest the implication of SIRT6/Notch-1/NLRP3/IL-1β axis in the pathogenesis of SUN-induced nephrotoxicity and highlight OLE as a prospective renoprotective agent during SUN chemotherapy to halt its renal toxicity likely through promotion of SIRT6 and suppression of Notch-1/NLRP3/IL-1β signaling pathway.

Molecular pathogenesis of subretinal fibrosis in neovascular AMD focusing on epithelial-mesenchymal transformation of retinal pigment epithelium

Age-related macular degeneration (AMD) is a leading cause of vision loss among elderly people in developed countries. Neovascular AMD (nAMD) accounts for more than 90% of AMD-related vision loss. At present, intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) is widely used as the first-line therapy to decrease the choroidal and retinal neovascularizations, and thus to improve or maintain the visual acuity of the patients with nAMD. However, about 1/3 patients still progress to irreversible visual impairment due to subretinal fibrosis even with adequate anti-VEGF treatment. Extensive literatures support the critical role of epithelial-mesenchymal transformation (EMT) of retinal pigment epithelium (RPE) in the pathogenesis of subretinal fibrosis in nAMD, but the underlying mechanisms still remain largely unknown. This review summarized the molecular pathogenesis of subretinal fibrosis in nAMD, especially focusing on the transforming growth factor-β (TGF-β)-induced EMT pathways. It was also discussed how these pathways crosstalk and respond to signals from the microenvironment to mediate EMT and contribute to the progression of nAMD-related subretinal fibrosis. Targeting EMT signaling pathways might provide a promising and effective therapeutic strategy to treat subretinal fibrosis secondary to nAMD.

Leptospirosis kidney disease: Evolution from acute to chronic kidney disease

Leptospirosis is a neglected bacterial disease caused by leptospiral infection that carries a substantial mortality risk in severe cases. Research has shown that acute, chronic, and asymptomatic leptospiral infections are closely linked to acute and chronic kidney disease (CKD) and renal fibrosis. Leptospires affect renal function by infiltrating kidney cells via the renal tubules and interstitium and surviving in the kidney by circumventing the immune system. The most well-known pathogenic molecular mechanism of renal tubular damage caused by leptospiral infection is the direct binding of the bacterial outer membrane protein LipL32 to toll-like receptor-2 expressed in renal tubular epithelial cells (TECs) to induce intracellular inflammatory signaling pathways. These pathways include the production of tumor necrosis factor (TNF)-α and nuclear factor kappa activation, resulting in acute and chronic leptospirosis-related kidney injury. Few studies have investigated the relationship between acute and chronic renal diseases and leptospirosis and further evidence is necessary. In this review, we intend to discuss the roles of acute kidney injury (AKI) to/on CKD in leptospirosis. This study reviews the molecular pathways underlying the pathogenesis of leptospirosis kidney disease, which will assist in concentrating on potential future research directions.

Serelaxin Alleviates Fibrosis in Thyroid-Associated Ophthalmopathy via the Notch Pathway

Fibrosis is the late stage of thyroid-associated ophthalmopathy (TAO), resulting in serious complications. Effective therapeutic drugs are still lacking. We aimed to explore the mechanism of TAO fibrosis and to find a targeted drug. High-throughput RNA sequencing was performed on orbital connective tissues from twelve patients with TAO and six healthy controls. Protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING) database and we identified the hub gene by Cytoscape software. Additionally, the RNA sequencing results were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Bioinformatic prediction identified the functions of differentially expressed genes (DEGs). Further orbital connective tissue and serum samples of the TAO and control groups were collected for subsequent experiments. Histologic staining, Western blotting (WB), qRT-PCR, enzyme-linked immunosorbent assays (ELISAs), gene overexpression through lentiviral infection or silencing gene by short interfering RNA (siRNA) were performed. We found that the relaxin signaling pathway is an important regulatory pathway in TAO fibrosis pathogenesis. Serelaxin exerts antifibrotic and anti-inflammatory effects in TAO. Furthermore, the downstream Notch pathway was activated by serelaxin and was essential to the antifibrotic effect of serelaxin in TAO. The antifibrotic effect of serelaxin is dependent on RXFP1.

Integrated analysis of transcriptome-wide m6A methylation in a Cd-induced kidney injury rat model

BACKGROUND

Accumulating evidence has demonstrated that N6-methyladenosine (m⁶A) plays important roles in a variety of diseases. However, the specific functions of m⁶A in CdCl₂-induced kidney injury remain unclear.

OBJECTIVE

Here, we investigate a transcriptome-wide map of m⁶A modifications and explore the effects of m⁶A on Cd-induced kidney injury.

MATERIALS AND METHODS

The rat kidney injury model was constructed by subcutaneous injection of CdCl₂ (0.5, 1.0, and 2.0 mg/kg). The m⁶A levels were measured by colorimetry. The level of expression of m⁶A-related enzymes were detected by reverse transcription quantitative real-time PCR analysis. Transcriptome-wide m⁶A methylome in CdCl₂ (2.0 mg/kg) and the control group were profiled by methylated RNA immunoprecipitation sequencing (MeRIP-seq). Subsequently, the sequencing data were analyzed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), while gene set enrichment analysis (GSEA) confirmed the functional enrichment pathways of sequencing genes. In addition, a protein-protein interaction (PPI) network was applied to select hub genes.

RESULTS

The levels of m⁶A and m⁶A regulators (METTL3, METTL14, WTAP, YTHDF2) were significantly increased in CdCl₂ groups. We identified a total of 2615 differentially expressed m⁶A peaks, 868 differentially expressed genes and 200 genes with significant changes in both m⁶A modification and gene expression levels. GO, KEGG, and GSEA analyses indicated that these genes were mainly enriched in inflammation and metabolism-related pathways such as in IL-17 signaling and fatty acid metabolism. According the result of the conjoint analysis, we identified the top ten hub genes (Fos, Hsp90aa1, Gata3, Fcer1g, Cftr, Cspg4, Atf3, Cdkn1a, Ptgs2, and Npy) which may be regulated by m⁶A and involve in CdCl₂-induced kidney damage.

CONCLUSION

This study established a m⁶A transcriptional map in a CdCl₂-induced kidney injury model and suggested that m⁶A may affect CdCl₂ induced kidney injury via regulated the inflammation and metabolism related gene.

ADAM10 and ADAM17, Major Regulators of Chronic Kidney Disease Induced Atherosclerosis?

Chronic kidney disease (CKD) is a major health problem, affecting millions of people worldwide, in particular hypertensive and diabetic patients. CKD patients suffer from significantly increased cardiovascular disease (CVD) morbidity and mortality, mainly due to accelerated atherosclerosis development. Indeed, CKD not only affects the kidneys, in which injury and maladaptive repair processes lead to local inflammation and fibrosis, but also causes systemic inflammation and altered mineral bone metabolism leading to vascular dysfunction, calcification, and thus, accelerated atherosclerosis. Although CKD and CVD individually have been extensively studied, relatively little research has studied the link between both diseases. This narrative review focuses on the role of a disintegrin and metalloproteases (ADAM) 10 and ADAM17 in CKD and CVD and will for the first time shed light on their role in CKD-induced CVD. By cleaving cell surface molecules, these enzymes regulate not only cellular sensitivity to their micro-environment (in case of receptor cleavage), but also release soluble ectodomains that can exert agonistic or antagonistic functions, both locally and systemically. Although the cell-specific roles of ADAM10 and ADAM17 in CVD, and to a lesser extent in CKD, have been explored, their impact on CKD-induced CVD is likely, yet remains to be elucidated.

COVID-19 and fibrosis: Mechanisms, clinical relevance, and future perspectives

Coronavirus 2019 (COVID-19), caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has had significant impacts worldwide since its emergence in December, 2019. Despite a high recovery rate, there is a growing concern over its residual, long-term effects. However, because of a lack of long-term data, we are still far from establishing a consensus on post-COVID-19 complications. The deposition of excessive extracellular matrix (ECM), known as fibrosis, has been observed in numerous survivors of COVID-19. Given the exceptionally high number of individuals affected, there is an urgent need to address the emergence of fibrosis post-COVID-19. In this review, we discuss the clinical relevance of COVID-19-associated fibrosis, the current status of antifibrotic agents, novel antifibrotic targets, and challenges to its management.

Effects of HIF-1α on renal fibrosis in cisplatin-induced chronic kidney disease

Cisplatin (Cis) can cause chronic kidney disease (CKD) and promote renal fibrosis, but the underlying mechanism is not fully understood. Hypoxia inducible factor-1α (HIF-1α) can promote renal fibrosis in some kidney diseases, but its role in Cis-induced CKD is still unknown. Notch-1 is a recognized molecule that promotes renal fibrosis under pathological circumstances, and evidence shows that HIF-1α and Notch-1 are closely related to each other. In the present study, mice with HIF-1α gene knockout in proximal tubular cells (PTCs) (PT-HIF-1α-KO) were generated and treated with Cis to induce CKD. A human proximal tubular cell line (HK-2) and primary mouse PTCs were used for in vitro studies. The results showed that HIF-1α was increased in the kidneys of Cis-treated wild-type mice, accompanied by elevated Notch-1, Notch-1 intracellular domain (N1ICD), Hes-1 and renal fibrosis. However, these alterations were partially reversed in PT-HIF-1α-KO mice. Similar results were observed in HK-2 cells and primary mouse PTCs. In addition, treating the cells with Cis induced a marked interaction of HIF-1α and N1ICD. Further inhibiting Notch-1 significantly reduced cellular fibrogenesis but did not affect HIF-1α expression. The data suggested that HIF-1α could promote renal fibrosis in Cis-induced CKD by activating Notch-1 both transcriptionally and post-transcriptionally and that HIF-1α may serve as a potential therapeutic target for Cis-induced CKD.

A Homozygous Dab1-/- Is a Potential Novel Cause of Autosomal Recessive Congenital Anomalies of the Mice Kidney and Urinary Tract

This study aimed to explore morphology changes in the kidneys of Dab1^−/− (yotari) mice, as well as expression patterns of reelin, NOTCH2, LC3B, and cleaved caspase3 (CASP3) proteins, as potential determinants of normal kidney formation and function. We assumed that Dab1 functional inactivation may cause disorder in a wide spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). Animals were sacrificed at postnatal days P4, P11, and P14. Paraffin-embedded kidney tissues were sectioned and analyzed by immunohistochemistry using specific antibodies. Kidney specimens were examined by bright-field, fluorescence, and electron microscopy. Data were analyzed by two-way ANOVA and t-tests. We noticed that yotari kidneys were smaller in size with a reduced diameter of nephron segments and thinner cortex. TEM microphotographs revealed foot process effacement in the glomeruli (G) of yotari mice, whereas aberrations in the structure of proximal convoluted tubules (PCT) and distal convoluted tubules (DCT) were not observed. A significant increase in reelin expression, NOTCH2, LC3B and cleaved CASP3 proteins was observed in the glomeruli of yotari mice. Renal hypoplasia in conjunction with foot process effacement and elevation in the expression of examined proteins in the glomeruli revealed CAKUT phenotype and loss of functional kidney tissue of yotari.

Proteomics and metabolomics studies exploring the pathophysiology of renal dysfunction in autosomal dominant polycystic kidney disease and other ciliopathies

The primary cilium (PC) was considered as a vestigial organelle with no significant physiological importance, until the discovery that PC perturbation disturbs several signalling pathways and results in the dysfunction of a variety of organs. Genetic studies have demonstrated that mutations affecting PC proteins or its anchoring structure, the basal body, underlie a class of human disorders (known as ciliopathies) characterized by a constellation of clinical signs. Further investigations have demonstrated that the PC is involved in a broad range of biological processes, in both developing and mature tissues. Kidney disease is a common clinical feature of cilia disorders, supporting the hypothesis of a crucial role of the PC in kidney homoeostasis. Clinical proteomics and metabolomics are an expanding research area. Interestingly, the application of these methodologies to the analysis of urine, a biological sample that can be collected in a non-invasive fashion and possibly in large amounts, makes these studies feasible also in patients. The present article describes the most recent proteomic and metabolomic studies exploring kidney dysfunction in the setting of ciliopathies, showing the potential of these methodologies in the elucidation of disease pathophysiology and in the discovery of biomarkers.

The Role of Notch3 Signaling in Kidney Disease

Notch receptors are transmembrane proteins that are members of the epidermal growth factor-like family. These receptors are widely expressed on the cell surface and are highly conserved. Binding to ligands on adjacent cells results in cleavage of these receptors, and their intracellular domains translocate into the nucleus, where target gene transcription is initiated. In the mammalian kidney, Notch receptors are activated during nephrogenesis and become silenced in the normal kidney after birth. Reactivation of Notch signaling in the adult kidney could be due to the genetic activation of Notch signaling or kidney injury. Notch3 is a mammalian heterodimeric transmembrane receptor in the Notch gene family. Notch3 activation is significantly increased in various glomerular diseases, renal tubulointerstitial diseases, glomerular sclerosis, and renal fibrosis and mediates disease occurrence and development. Here, we discuss numerous recently published papers describing the role of Notch3 signaling in kidney disease.

The efficacy of taking traditional Chinese medicine orally in renal interstitial fibrosis: A protocol for a systematic review and meta-analysis

BACKGROUND

By now, the incidence of chronic kidney disease (CKD) is increasing. The development of various CKD is attributed to the continuous aggravation of renal interstitial fibrosis (RIF) in the process of end-stage renal disease (ESRD). Oral treatment of traditional Chinese medicine (TCM) is one of the therapies for RIF. Randomized controlled trials (RCTs) of TCM treatment RIF have been reported, but its effectiveness and safety have yet been systematically investigated. Therefore, through the systematic analysis and meta-analysis, our study will summarize the effectiveness and safety of oral treatment RIF of TCM, in order to provides scientific reference for clinical practice.

METHODS

This protocol follows Preferred Reporting Items for Systematic Evaluation and Meta-Analysis. RCTs will be only selected. Such databases as the PubMed, China National Knowledge Infrastructure (CNKI), China Science and Technology Journal Database (VIP), Excerpt Medical Database (Embase), WanFan Data, Chinese Biomedical Literature Database (CBM), WHO International Clinical Trials Registry Platform will be searched from the inception to June, 2020 to collect the RCTs about taking TCM orally in treating RIF. The literature according to the inclusion and exclusion criteria, data-extracted and the methodological quality evaluated will be performed independently by 2 reviewers. The clinical outcomes including renal function indices (Scr, BUN, 24-hour urinary protein quantity) and Indicators of RIF (TGF-β1, Notch1, Jagged-1). The risk of bias included in the RCTs will be evaluated by the bias risk assessment tool provided in the Cochrane System Evaluation Manual 5.1.0. Review Manager 5.3 provided by the Cochrane collaboration network will be used to process the data.

RESULTS AND CONCLUSION

Some more targeted and practical results about the efficacy of taking TCM orally in RIF have been provided by our study. The available evidence suggests that the therapeutic effects of combining TCM with Western medicine therapies is much better for RIF than Western medicine therapies only.

Fibrosis and Immune Cell Infiltration Are Separate Events Regulated by Cell-Specific Receptor Notch3 Expression

BACKGROUND

Kidney injuries that result in chronic inflammation initiate crosstalk between stressed resident cells and infiltrating immune cells. In animal models, whole-body receptor Notch3 deficiency protects from leukocyte infiltration and organ fibrosis. However, the relative contribution of Notch3 expression in tissue versus infiltrating immune cells is unknown.

METHODS

Chimeric mice deficient for Notch3 in hematopoietic cells and/or resident tissue cells were generated, and kidney fibrosis and inflammation after unilateral ureteral obstruction (UUO) were analyzed. Adoptive transfer of labeled bone marrow-derived cells validated the results in a murine Leishmania ear infection model. In vitro adhesion assays, integrin activation, and extracellular matrix production were analyzed.

RESULTS

Fibrosis follows UUO, but inflammatory cell infiltration mostly depends upon Notch3 expression in hematopoietic cells, which coincides with an enhanced proinflammatory milieu (e.g., CCL2 and CCL5 upregulation). Notch3 expression on CD45⁺ leukocytes plays a prominent role in efficient cell transmigration. Functionally, leukocyte adhesion and integrin activation are abrogated in the absence of receptor Notch3. Chimeric animal models also reveal that tubulointerstitial fibrosis develops, even in the absence of prominent leukocyte infiltrates after ureteral obstruction. Deleting Notch3 receptors on resident cells blunts kidney fibrosis, ablates NF-κB signaling, and lessens matrix deposition.

CONCLUSIONS

Cell-specific receptor Notch3 signaling independently orchestrates leukocyte infiltration and organ fibrosis. Interference with Notch3 signaling may present a novel therapeutic approach in inflammatory as well as fibrotic diseases.

Molecular pathways involved in injury-repair and ADPKD progression

The major hallmark of Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the formation of many fluid-filled cysts in the kidneys, which ultimately impairs the normal renal structure and function, leading to end-stage renal disease (ESRD). A large body of evidence suggests that injury-repair mechanisms are part of ADPKD progression. Once cysts have been formed, proliferation and fluid secretion contribute to the cyst size increase, which eventually causes stress on the surrounding tissue resulting in local injury and fibrosis. In addition, renal injury can cause or accelerate cyst formation. In this review, we will describe the various mechanisms activated during renal injury and tissue repair and show how they largely overlap with the molecular mechanisms activated during PKD progression. In particular, we will discuss molecular mechanisms such as proliferation, inflammation, cell differentiation, cytokines and growth factors secretion, which are activated following the renal injury to allow the remodelling of the tissue and a proper organ repair. We will also underline how, in a context of PKD-related gene mutations, aberrant or chronic activation of these developmental pathways and repair/remodelling mechanisms results in exacerbation of the disease.

DLX5 gene regulates the Notch signaling pathway to promote glomerulosclerosis and interstitial fibrosis in uremic rats

Uremia largely results from the accumulation of organic waste products normally cleared by the kidneys, which commonly accompanies kidney failure and chronic kidney disease. However, genetic investigations in a uremia remain largely unclear. This study aimed to determine the expression patterns of distal-less homeobox 5 (DLX5) in uremia rat model and further to study its effects on glomerulosclerosis and interstitial fibrosis. Uremic expression chip was applied to screen differentially expressed genes in uremia. Next, we used small interfering RNA-mediated RNA interference to specifically silence DLX5 in experimental uremic rats to understand the regulatory mechanism of DLX5. To understand effect of Notch1 signaling pathway in uremia, we also treated experimental uremic rats with γ-secretase inhibitor (GSI), an inhibitor of Notch1 signaling pathway. The expression of fibronectin (FN), laminin (LN), transforming growth factor-β1 (TGF-β1), Hes1, Hes5, and Jagged2 was determined. The semiquantitative assessment was applied to verify the effects of DLX5 on glomerulosclerosis. In the uremic expression chip, we found that DLX5 was upregulated in uremia samples, and considered to regulate the Notch signaling pathway. We found that small interfering RNA-mediated DLX5 inhibition or Notch1 signaling pathway inhibitory treatment relieved and delayed the kidney injury and glomerulosclerosis in uremia. Meanwhile, inhibition of DLX5 or Nothch1 signaling pathway reduced expression of FN, LN, Nothch1, TGF-β1, Hes1, Hes5, and Jagged2. Intriguingly, we discovered that Notch1 signaling pathway was inhibited after silencing DLX5. In conclusion, these findings highlight that DLX5 regulates Notch signaling, which may, in turn, promote complications of uremia such as kidney fibrosis, providing a novel therapeutic target for treating uremia.

Blockade of ERK1/2 by U0126 alleviates uric acid-induced EMT and tubular cell injury in rats with hyperuricemic nephropathy

Extracellular signal-regulated kinases 1 and 2 (ERK1/2) are serine/threonine kinases and function as regulators of cellular proliferation and differentiation. Recently, we demonstrated that inhibition of ERK1/2 alleviates the development and progression of hyperuricemia nephropathy (HN). However, its potential roles in uric acid-induced tubular epithelial-mesenchymal transition (EMT) and tubular epithelial cell injury are unknown. In this study, we showed that hyperuricemic injury induced EMT as characterized by downregulation of E-cadherin and upregulation of vimentin and Snail1 in a rat model of HN. This was coincident with epithelial cells arrested at the G₂/M phase of cell cycle, activation of Notch1/Jagged-1 and Wnt/β-catenin signaling pathways, and upregulation of matrix metalloproteinase-2 (MMP-2) and MMP-9. Administration of U0126, a selective inhibitor of ERK1/2, blocked all these responses. U0126 was also effective in inhibiting renal tubular cell injury, as shown by decreased expression of lipocalin-2 and kidney injury molecule-1 and active forms of caspase-3. U0126 or ERK1/2 siRNA can inhibit tubular cell EMT and cell apoptosis as characterized with decreased expression of cleaved caspase-3. Moreover, ERK1/2 inhibition suppressed hyperuricemic injury-induced oxidative stress as indicated by decreased malondialdehyde and increased superoxide dismutase. Collectively, ERK1/2 inhibition-elicited renal protection is associated with inhibition of EMT through inactivation of multiple signaling pathways and matrix metalloproteinases, as well as attenuation of renal tubule injury by enhancing cellular resistance to oxidative stress.

Nrf2-Heme Oxygenase-1 Attenuates High-Glucose-Induced Epithelial-to-Mesenchymal Transition of Renal Tubule Cells by Inhibiting ROS-Mediated PI3K/Akt/GSK-3β Signaling

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is thought to play a significant role in the advancement to chronic kidney disease and contributes to the deposition of extracellular matrix proteins and renal fibrosis relating to diabetic nephropathy.

METHOD

We studied the effect of Nrf2-HO-1 signaling on high-glucose- (HG-) induced EMT in normal human tubular epithelial cells, that is, HK2 cells. In short, we treated HK2 cells with HG and sulforaphane (SFN) as an Nrf2 activator. EMT was evaluated by the expression activity of the epithelial marker E-cadherin and mesenchymal markers such as vimentin and fibronectin.

RESULTS

Exposure of HK2 cells to HG (60 mM) activated the expression of vimentin and fibronectin but decreased E-cadherin. Treatment of HK2 cells with SFN caused HG-induced attenuation in EMT markers with activated Nrf2-HO-1. We found that SFN decreased HG-induced production of reactive oxygen species (ROS), phosphorylation of PI3K/Akt at serine 473, and inhibitory phosphorylation of serine/threonine kinase glycogen synthase kinase-3β (GSK-3β) at serine 9. Subsequently, these signaling led to the downregulation of the Snail-1 transcriptional factor and the recovery of E-cadherin.

CONCLUSION

The present study suggests that Nrf2-HO-1 signaling has an inhibitory role in the regulation of EMT through the modulation of ROS-mediated PI3K/Akt/GSK-3β activity, highlighting Nrf2-HO-1 and GSK-3β as potential therapeutic targets in diabetic nephropathy.

Renal ADAM10 and 17: Their Physiological and Medical Meanings

A disintegrin and metalloproteinases (ADAMs) are a Zn²⁺-dependent transmembrane and secreted metalloprotease superfamily, so-called “molecular scissors,” and they consist of an N-terminal signal sequence, a prodomain, zinc-binding metalloprotease domain, disintegrin domain, cysteine-rich domain, transmembrane domain and cytoplasmic tail. ADAMs perform proteolytic processing of the ectodomains of diverse transmembrane molecules into bioactive mediators. This review summarizes on their most well-known members, ADAM10 and 17, focusing on the kidneys. ADAM10 is expressed in renal tubular cells and affects the expression of specific brush border genes, and its activation is involved in some renal diseases. ADAM17 is weakly expressed in normal kidneys, but its expression is markedly induced in the tubules, capillaries, glomeruli, and mesangium, and it is involved in interstitial fibrosis and tubular atrophy. So far, the various substrates have been identified in the kidneys. Shedding fragments become released ligands, such as Notch and EGFR ligands, and act as the chemoattractant factors including CXCL16. Their ectodomain shedding is closely correlated with pathological factors, which include inflammation, interstitial fibrosis, and renal injury. Also, the substrates of both ADAMs contain the molecules that play important roles at the plasma membrane, such as meaprin, E-cadherin, Klotho, and CADM1. By being released into urine, the shedding products could be useful for biomarkers of renal diseases, but ADAM10 and 17 per se are also notable as biomarkers. Furthermore, ADAM10 and/or 17 inhibitions based on various strategies such as small molecules, antibodies, and their recombinant prodomains are valuable, because they potentially protect renal tissues and promote renal regeneration. Although temporal and spatial regulations of inhibitors are problems to be solved, their inhibitors could be useful for renal diseases.

Jagged1/Notch2 controls kidney fibrosis via Tfam-mediated metabolic reprogramming

While Notch signaling has been proposed to play a key role in fibrosis, the direct molecular pathways targeted by Notch signaling and the precise ligand and receptor pair that are responsible for kidney disease remain poorly defined. In this study, we found that JAG1 and NOTCH2 showed the strongest correlation with the degree of interstitial fibrosis in a genome-wide expression analysis of a large cohort of human kidney samples. Transcript analysis of mouse kidney disease models, including folic-acid (FA)-induced nephropathy, unilateral ureteral obstruction (UUO), or apolipoprotein L1 (APOL1)-associated kidney disease, indicated that Jag1 and Notch2 levels were higher in all analyzed kidney fibrosis models. Mice with tubule-specific deletion of Jag1 or Notch2 (Kspcre/Jag1flox/flox and Kspcre/Notch2flox/flox) had no kidney-specific alterations at baseline but showed protection from FA-induced kidney fibrosis. Tubule-specific genetic deletion of Notch1 and global knockout of Notch3 had no effect on fibrosis. In vitro chromatin immunoprecipitation experiments and genome-wide expression studies identified the mitochondrial transcription factor A (Tfam) as a direct Notch target. Re-expression of Tfam in tubule cells prevented Notch-induced metabolic and profibrotic reprogramming. Tubule-specific deletion of Tfam resulted in fibrosis. In summary, Jag1 and Notch2 play a key role in kidney fibrosis development by regulating Tfam expression and metabolic reprogramming.

Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells

Reactivation of Notch signaling in kidneys of animal models and patients with chronic kidney disease (CKD) has been shown to contribute to epithelial injury and fibrosis development. Here, we investigated the mechanisms of Notch-induced injury in renal epithelial cells. We performed genome-wide transcriptome analysis to identify Notch target genes using an in vitro system of cultured tubular epithelial cells expressing the intracellular domain of Notch1. One of the top downregulated genes was Disabled-2 ( Dab2). With the use of Drosophila nephrocytes as a model system, we found that Dab (the Drosophila homolog of Dab2) knockdown resulted in a significant filtration defect, indicating that loss of Dab2 plays a functional role in kidney disease development. We showed that Dab2 expression in cultured tubular epithelial cells is involved in endocytic regulation and that it also protects cells from TGF-β-induced epithelial-to-mesenchymal transition. In vivo correlation studies indicated its additional role in renal ischemia-induced injury. Together, these data suggest that Dab2 plays a versatile role in the kidney and may impact on acute and CKDs.-Schütte-Nütgen, K., Edeling, M., Mendl, G., Krahn, M. P., Edemir, B., Weide, T., Kremerskothen, J., Michgehl, U., Pavenstädt, H. Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.

The antihelmenthic phosphate niclosamide impedes renal fibrosis by inhibiting homeodomain-interacting protein kinase 2 expression

Renal fibrosis is the final common pathway of all varieties of progressive chronic kidney disease. However, there are no effective therapies to prevent or slow the progression of renal fibrosis. Niclosamide is a US Food and Drug Administration-approved oral antihelminthic drug used for treating most tapeworm infections. Here, we demonstrated that phosphate niclosamide, the water-soluble form of niclosamide, significantly reduced proteinuria, glomerulosclrotic lesions, and interstitial fibrosis in a murine model of adriamycin nephropathy. In addition, phosphate niclosamide significantly ameliorated established renal interstitial fibrosis a murine model of unilateral ureteral obstruction. Mechanistically, phosphate niclosamide directly inhibited TGF-β-induced expression of homeodomain-interacting protein kinase 2 (HIPK2) by interfering with the binding of Smad3 to the promoter of the HIPK2 gene, and subsequently mitigated the activation of its downstream signaling pathways including Smad, Notch, NF-κB and Wnt/β-catenin pathway both in vitro and in vivo. Thus, phosphate niclosamide mitigates renal fibrosis at least partially by inhibiting HIPK2 expression. Hence, phosphate niclosamide might be a potential therapeutic agent for renal fibrosis.

Systems biology combining human- and animal-data miRNA and mRNA data identifies new targets in ureteropelvic junction obstruction

Background

Although renal fibrosis and inflammation have shown to be involved in the pathophysiology of obstructive nephropathies, molecular mechanisms underlying evolution of these processes remain undetermined. In an attempt towards improved understanding of obstructive nephropathy and improved translatability of the results to clinical practice we have developed a systems biology approach combining omics data of both human and mouse obstructive nephropathy.

Results

We have studied in parallel the urinary miRNome of infants with ureteropelvic junction obstruction and the kidney tissue miRNome and transcriptome of the corresponding neonatal partial unilateral ureteral obstruction (UUO) mouse model. Several hundreds of miRNAs and mRNAs displayed changed abundance during disease. Combination of miRNAs in both species and associated mRNAs let to the prioritization of five miRNAs and 35 mRNAs associated to disease. In vitro and in vivo validation identified consistent dysregulation of let-7a-5p and miR-29-3p and new potential targets, E3 ubiquitin-protein ligase (DTX4) and neuron navigator 1 (NAV1), potentially involved in fibrotic processes, in obstructive nephropathy in both human and mice that would not be identified otherwise.

Conclusions

Our study is the first to correlate a mouse model of neonatal partial UUO with human UPJ obstruction in a comprehensive systems biology analysis. Our data revealed let-7a and miR-29b as molecules potentially involved in the development of fibrosis in UPJ obstruction via the control of DTX4 in both man and mice that would not be identified otherwise.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0411-7) contains supplementary material, which is available to authorized users.

Signalling pathways involved in hypoxia-induced renal fibrosis

Renal fibrosis is the common pathological hallmark of progressive chronic kidney disease (CKD) with diverse aetiologies. Recent researches have highlighted the critical role of hypoxia during the development of renal fibrosis as a final common pathway in end‐stage kidney disease (ESKD), which joints the scientist's attention recently to exploit the molecular mechanism underlying hypoxia‐induced renal fibrogenesis. The scaring formation is a multilayered cellular response and involves the regulation of multiple hypoxia‐inducible signalling pathways and complex interactive networks. Therefore, this review will focus on the signalling pathways involved in hypoxia‐induced pathogenesis of interstitial fibrosis, including pathways mediated by HIF, TGF‐β, Notch, PKC/ERK, PI3K/Akt, NF‐κB, Ang II/ROS and microRNAs. Roles of molecules such as IL‐6, IL‐18, KIM‐1 and ADO are also reviewed. A comprehensive understanding of the roles that these hypoxia‐responsive signalling pathways and molecules play in the context of renal fibrosis will provide a foundation towards revealing the underlying mechanisms of progression of CKD and identifying novel therapeutic targets. In the future, promising new effective therapy against hypoxic effects may be successfully translated into the clinic to alleviate renal fibrosis and inhibit the progression of CKD.

Sonic hedgehog signaling in kidney fibrosis: a master communicator

The hedgehog signaling cascade is an evolutionarily conserved pathway that regulates multiple aspects of embryonic development and plays a decisive role in tissue homeostasis. As the best studied member of three hedgehog ligands, sonic hedgehog (Shh) is known to be associated with kidney development and tissue repair after various insults. Recent studies uncover an intrinsic link between dysregulated Shh signaling and renal fibrogenesis. In various types of chronic kidney disease (CKD), Shh is upregulated specifically in renal tubular epithelium but targets interstitial fibroblasts, thereby mediating a dynamic epithelial- mesenchymal communication (EMC). Tubule-derived Shh acts as a growth factor for interstitial fibroblasts and controls a hierarchy of fibrosis-related genes, which lead to the excessive deposition of extracellular matrix in renal interstitium. In this review, we recapitulate the principle of Shh signaling, its activation and regulation in a variety of kidney diseases. We also discuss the potential mechanisms by which Shh promotes renal fibrosis and assess the efficacy of blocking this signaling in preclinical settings. Continuing these lines of investigations will provide novel opportunities for designing effective therapies to improve CKD prognosis in patients.

Notch in fibrosis and as a target of anti-fibrotic therapy

The Notch pathway represents a highly conserved signaling network with essential roles in regulation of key cellular processes and functions, many of which are critical for development. Accumulating evidence indicates that it is also essential for fibrosis and thus the pathogenesis of chronic fibroproliferative diseases in diverse organs and tissues. Different effects of Notch activation are observed depending on cellular and tissue context as well as in both physiologic and pathologic states. Close interactions of Notch signaling pathway with other signaling pathways have been identified. In this review, current knowledge on the role of the Notch signaling with special focus on fibrosis and its potential as a therapeutic target is summarized.

[Therapeutic effect of baicalin in treatment of renal interstitial fibrosis in rats with unliateral ureteral obstruction and related mechanisms]

OBJECTIVE

To investigate the therapeutic effect of baicalin at different doses administered for different periods of time in the treatment of renal interstitial fibrosis in rats with unliateral ureteral obstruction (UUO) and related mechanisms.

METHODS

Sixty-four Sprague-Dawley rats were randomly divided into sham-operation, model, low-dose baicalin, and high-dose baicalin groups, and each group was further randomly divided into 7-day and 14-day groups (n=8 each). Left ureteral ligation was used to establish the rat model of UUO. Hematoxylin and eosin staining was used to observe the pathological changes in the kidney. ELISA was used to measure the serum levels of transforming growth factor-β1 (TGF-β1), Notch1, and Jagged1. Immunohistochemistry was used to measure the expression of TGF-β1 and Notch1. The Pearson correlation analysis was used for correlation analysis.

RESULTS

Hematoxylin and eosin staining showed inflammatory cell infiltration and edema in renal interstitium, tubular dilation and structure disorder, degeneration and necrosis of renal tubular epithelial cells, and a basically normal structure of the glomeruli on days 7 and 14 in the model group, and these lesions were alleviated in the low- and high-dose baicalin groups. Compared with the sham-operation group, the model group had a significantly higher serum level of TGF-β1 and a significantly higher number of TGF-β1-positive cells in renal tissues on days 7 and 14 (P<0.05). Compared with the model group at the same time points, the high- and low-dose baicalin groups had a significantly lower serum level of TGF-β1 and a significantly lower number of TGF-β1-positive cells in renal tissues on days 7 and 14 (P<0.05). The serum level of Jagged1 showed no significant differences between any two groups on days 7 and 14 (P>0.05). The serum level of TGF-β1 was positively correlated with that of Notch1 (r=0.650, P<0.01), and the serum level of Notch1 was positively correlated with that of Jagged1 (r=0.727, P<0.01). TGF-β1 level in renal tissues was also positively correlated with the number of Notch1-positive cells (r=0.743, P<0.01).

CONCLUSIONS

Baicalin can alleviate renal interstitial fibrosis in UUO rats, probably by inhibiting Notch1 signaling pathway and the expression of TGF-β1.

miTALOS v2: Analyzing Tissue Specific microRNA Function

MicroRNAs are involved in almost all biological processes and have emerged as regulators of signaling pathways. We show that miRNA target genes and pathway genes are not uniformly expressed across human tissues. To capture tissue specific effects, we developed a novel methodology for tissue specific pathway analysis of miRNAs. We incorporated the most recent and highest quality miRNA targeting data (TargetScan and StarBase), RNA-seq based gene expression data (EBI Expression Atlas) and multiple new pathway data sources to increase the biological relevance of the predicted miRNA-pathway associations. We identified new potential roles of miR-199a-3p, miR-199b-3p and the miR-200 family in hepatocellular carcinoma, involving the regulation of metastasis through MAPK and Wnt signaling. Also, an association of miR-571 and Notch signaling in liver fibrosis was proposed. To facilitate data update and future extensions of our tool, we developed a flexible database backend using the graph database neo4j. The new backend as well as the novel methodology were included in the updated miTALOS v2, a tool that provides insights into tissue specific miRNA regulation of biological pathways. miTALOS v2 is available at http://mips.helmholtz-muenchen.de/mitalos.