Leukocytes induce epithelial to mesenchymal transition after unilateral ureteral obstruction in neonatal mice

Up-regulation of the human-specific CHRFAM7A gene protects against renal fibrosis in mice with obstructive nephropathy

Renal fibrosis is a major factor in the progression of chronic kidney diseases. Obstructive nephropathy is a common cause of renal fibrosis, which is also accompanied by inflammation. To explore the effect of human-specific CHRFAM7A expression, an inflammation-related gene, on renal fibrosis during obstructive nephropathy, we studied CHRFAM7A transgenic mice and wild type mice that underwent unilateral ureteral obstruction (UUO) injury. Transgenic overexpression of CHRFAM7A gene inhibited UUO-induced renal fibrosis, which was demonstrated by decreased fibrotic gene expression and collagen deposition. Furthermore, kidneys from transgenic mice had reduced TGF-β1 and Smad2/3 expression following UUO compared with those from wild type mice with UUO. In addition, the overexpression of CHRFAM7A decreased release of inflammatory cytokines in the kidneys of UUO-injured mice. In vitro, the overexpression of CHRFAM7A inhibited TGF-β1-induced increase in expression of fibrosis-related genes in human renal tubular epithelial cells (HK-2 cells). Additionally, up-regulated expression of CHRFAM7A in HK-2 cells decreased TGF-β1-induced epithelial-mesenchymal transition (EMT) and inhibited activation f TGF-β1/Smad2/3 signalling pathways. Collectively, our findings demonstrate that overexpression of the human-specific CHRFAM7A gene can reduce UUO-induced renal fibrosis by inhibiting TGF-β1/Smad2/3 signalling pathway to reduce inflammatory reactions and EMT of renal tubular epithelial cells.

The significance of NAD + metabolites and nicotinamide N-methyltransferase in chronic kidney disease

Dysregulation of nicotinamide adenine dinucleotide (NAD +) metabolism contributes to the initiation and progression of age-associated diseases, including chronic kidney disease (CKD). Nicotinamide N-methyltransferase (NNMT), a nicotinamide (NAM) metabolizing enzyme, regulates both NAD + and methionine metabolism. Although NNMT is expressed abundantly in the kidney, its role in CKD and renal fibrosis remains unclear. We generated NNMT-deficient mice and a unilateral ureter obstruction (UUO) model and conducted two clinical studies on human CKD to investigate the role of NNMT in CKD and fibrosis. In UUO, renal NNMT expression and the degraded metabolites of NAM increased, while NAD + and NAD + precursors decreased. NNMT deficiency ameliorated renal fibrosis; mechanistically, it (1) increased the DNA methylation of connective tissue growth factor (CTGF), and (2) improved renal inflammation by increasing renal NAD + and Sirt1 and decreasing NF-κB acetylation. In humans, along with CKD progression, a trend toward a decrease in serum NAD + precursors was observed, while the final NAD + metabolites were accumulated, and the level of eGFR was an independent variable for serum NAM. In addition, NNMT was highly expressed in fibrotic areas of human kidney tissues. In conclusion, increased renal NNMT expression induces NAD + and methionine metabolism perturbation and contributes to renal fibrosis.

Dasatinib mitigates renal fibrosis in a rat model of UUO via inhibition of Src/STAT-3/NF-κB signaling

This research aimed to investigate the reno-protective impact of the tyrosine kinase inhibitor dasatinib (DAS) against renal fibrosis induced by unilateral ureteral obstruction (UUO) in rats. DAS administration improved renal function and mitigated renal oxidative stress with paralleled reduction in the ligated kidney mass index, significant retraction in renal histopathological alterations and suppression of renal interstitial fibrosis. Nevertheless, DAS administration attenuated renal expression of phosphorylated Src (p-Src), Abelson (c-Abl) tyrosine kinases, nuclear factor-kappaB (NF-κB) p65, and phosphorylated signal transducer and activator of transcription-3 (p-STAT-3)/STAT-3 with paralleled reduction in renal contents of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1). DAS diminished interstitial macrophage infiltration and decreased renal profibrotic transforming growth factor-β1 (TGF-β1) levels and suppressed interstitial expression of renal α-smooth muscle actin (α-SMA) and fibronectin. Collectively, DAS slowed the progression of renal interstitial fibrosis, possibly via attenuating renal oxidative stress, impairing Src/STAT-3/NF-κB signaling, and reducing renal inflammation.

Kappa-opioid receptor-mediated thermal analgesia evoked by the intrathecal administration of the chemokine CCL1 in mice

BACKGROUND

The chemokine CC motif ligand 1 (CCL1) participates in immune cell recruitment and, as other chemokines, is also involved in nociceptive processing. In contrast with previous reports indicating its participation in allodynia and cold hypernociception when spinally administered, its ability to evoke heat thermal analgesia, mediated by circulating leukocytes and endocannabinoids, after systemic administration has recently been reported.

OBJECTIVES

Aiming to explore the role played by CCL1 on spinal nociception, we study here the effect of its intrathecal administration on thermal nociception in mice.

METHODS

Behavioral nociceptive assays, immunohistochemical experiments, white cell blood depletion procedures and qRT-PCR experiments were performed.

RESULTS

The intrathecal administration of CCL1 (0.3-30 ng) produced analgesia as measured by the unilateral hot plate test. This effect peaked 1 h after injection, was prevented by the CCR8 antagonist R243 and was accompanied by a reduction of c-Fos expression in spinal neurons. Whereas blood leukocyte depletion did not modify it, analgesia was abolished by the microglial inhibitor minocycline, but not the astroglial inhibitor aminoadipate. Furthermore, antinociception remained unmodified by the coadministration of cannabinoid type 1 or 2 receptors antagonists. However, it was reversed by naloxone but not by selective blockade of mu- or delta-opioid receptors. The inhibitory effect induced by the selective kappa-opioid receptor antagonist, nor-binaltorphimine, and by an anti-dynorphin A 1-17 antibody indicates that analgesia evoked by spinal CCL1 is mediated by endogenous dynorphins acting on kappa-opioid receptors.

CONCLUSIONS

Endogenous dynorphin and microglia behave as key players in heat thermal analgesia evoked by spinal CCL1 in mice.

Centella asiatica Extract Attenuates Kidney Fibrosis Through Reducing Mesenchymal Transition and Inflammation in Ureteral Ligation Model in Mice

Background: Kidney fibrosis is the common final pathway of chronic kidney disease (CKD), and is characterized by inflammation, mesenchymal transition with myofibroblast formation and epithelial to mesenchymal transition (EMT). Centella asiatia (CeA) is an herb that has a reno-protective effect. However, its mechanism of action in kidney fibrosis has not been elucidated.

Aim: To elucidate the effect of CeA in amelioration of kidney fibrosis in a unilateral ureteral obstruction (UUO) model and focus on mesenchymal transition and inflammation.

Methods: Unilateral ureteral obstruction was performed in male Swiss-background mice (age: 2–3 months, weight: 30–40 g, UUO group n = 6) to induce kidney fibrosis. Two doses of CeA extract with oral administration, 210 and 840 mg/kg body weight were added in UUO (U+C210 and U+C840 groups, each n = 6). The sham operation procedure was performed for the control group (SO, n = 6). The mice were euthanized at day-14 after operation. Tubular injury and interstitial fibrosis area fractions in kidney tissues of the mice were quantified based on periodic acid-Schiff (PAS) and Sirius Red (SR) staining. Immunostaining was performed for examination of fibroblast (PDGFR-β), myofibroblast (α-SMA), Monocyte Chemoattractant Protein-1 (MCP-1) and macrophage (CD68), meanwhile double immunofluorescence was performed with PDGFR-β and α-SMA. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to examine mRNA expression of TGF-β, Collagen-1, Snail, E-cadherin, vimentin, fibroblast-specific protein 1 (FSP-1), CD68, toll-like receptor 4 (TLR4), and MCP-1.

Results: We observed a significantly higher interstitial fibrosis area fraction and tubular injury (p < 0.001) with fibroblast expansion and myofibroblast formation in the UUO group than in the SO group. These findings were associated with higher mRNA expression of TGF-β, Collagen-1, Snail, vimentin, FSP-1, CD68, TLR4, and MCP-1 and lower mRNA expression of E-cadherin. The U+C840 group had a significantly lower tubular injury score and interstitial fibrosis area fraction, which associated with downregulation of mRNA expression of TGF-β, Collagen-1, Snail, vimentin, FSP-1, CD68, TLR4, and MCP-1, with upregulation of mRNA expression of E-cadherin. Immunostaining observation revealed the U+C840 group demonstrated reduction of macrophage infiltration and myofibroblast expansion.

Conclusion: CeA treatment with dose-dependently ameliorates mesenchymal transition and inflammation in kidney fibrosis in mice.

Nifuroxazide suppresses UUO-induced renal fibrosis in rats via inhibiting STAT-3/NF-κB signaling, oxidative stress and inflammation

The current work explored the influences of nifuroxazide, an in vivo inhibitor of signal transducer and activator of transcription-3 (STAT-3) activation, on tubulointerstitial fibrosis in rats with obstructive nephropathy using unilateral ureteral obstruction (UUO) model. Thirty-two male Sprague Dawley rats were assigned into 4 groups (n = 8/group) at random. Sham and UUO groups were orally administered 0.5% carboxymethyl cellulose (CMC) (2.5 mL/kg/day), while Sham-NIF and UUO-NIF groups were treated with 20 mg/kg/day of NIF (suspended in 0.5% CMC, orally). NIF or vehicle treatments were started 2 weeks after surgery and continued for further 2 weeks. NIF treatment ameliorated kidney function in UUO rats, where it restored serum creatinine, blood urea, serum uric acid and urinary protein and albumin to near-normal levels. NIF also markedly reduced histopathological changes in tubules and glomeruli and attenuated interstitial fibrosis in UUO-ligated kidneys. Mechanistically, NIF markedly attenuated renal immunoexpression of E-cadherin and α-smooth muscle actin (α-SMA), diminished renal oxidative stress (↓ malondialdehyde (MDA) levels and ↑ superoxide dismutase (SOD) activity), lessened renal protein expression of phosphorylated-STAT3 (p-STAT-3), phosphorylated-Src (p-Src) kinase, the Abelson tyrosine kinase (c-Abl) and phosphorylated nuclear factor-kappaB p65 (pNF-κB p65), decreased renal cytokine levels of transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) and reduced number of cluster of differentiation 68 (CD68) immunolabeled macrophages in UUO renal tissues, compared to levels in untreated UUO kidneys. Taken together, NIF treatment suppressed interstitial fibrosis in UUO renal tissues, probably via inhibiting STAT-3/NF-κB signaling and attenuating renal oxidative stress and inflammation.

Quantitative Proteome of Infant Stenotic Ureters Reveals Extracellular Matrix Organization and Oxidative Stress Dysregulation Underlying Ureteropelvic Junction Obstruction

PURPOSE

Ureteropelvic junction obstruction (UPJO) is the most frequent cause of congenital hydronephrosis in child. To better investigate the molecular mechanisms of this pathological process, the stenotic ureter proteome of UPJO in infants is compared with their own normal pre-stenotic segments.

EXPERIMENTAL DESIGN

Data independent acquisition-based proteomics are performed to compare proteome between pre-stenotic and stenotic ureter from nine UPJO infants. Gene ontology analysis, hierarchical cluster analysis, and network interaction are performed to characterize biological functions of significantly altered proteins. Selected significantly altered proteins are validated by western blot on another three UPJO infants.

RESULTS

15 proteins are up-regulated and 33 proteins are down-regulated during stenotic pathology. Significantly altered proteins are involved in decreased extracellular matrix and cytoskeleton organization, increased regulation of oxidative activity, and altered inflammatory associated exocytosis. Significant expression of biglycan, fibulin-1, myosin-10, cytochrome b5 are validated providing possible mechanism in UPJO which could be associated impaired smooth muscle cell, epithelial integrity, and increased oxidative stress. CONCLUSIONS AND CLINICAL RELEVANCE: This study provides molecular evidence of dysregulated extracellular matrix organization, impaired smooth muscle cell, and oxidative stress during UPJO pathology, indicating that biglycan, fibulin-1, myosin-10, cytochrome b5 might reflect the pathology of UPJO.

Tyrphostin AG490 reduces inflammation and fibrosis in neonatal obstructive nephropathy

BACKGROUND

Congenital obstructive nephropathy is the main cause of end-stage renal disease in infants and children. Renal insufficiency is due to impaired growth and maturation in the developing kidney with obstruction. Congenital obstructive nephropathy leads to cytokine mediated inflammation and the development of interstitial fibrosis. The Janus kinase-2 (JAK-2) and Signal Transducer and Activator of Transcription'-3 (STAT3) are involved in cytokine production, inflammation, and interstitial fibrosis.

METHODS

We studied the role of JAK2/STAT3 in a model of congenital obstructive nephropathy using unilateral ureteral obstruction (UUO) in neonatal mice at the second day of life. Cytokine production, inflammation, and interstitial fibrosis were analyzed in obstructed and sham operated kidneys of neonatal mice treated with or without JAK2/STAT3 inhibitor Tyrphostin AG490. To mimic obstruction and distension, proximal tubular cells were stretched in vitro.

RESULTS

We show that STAT3 is highly activated in the developing kidney with obstruction and in proximal tubular cells following stretch. JAK2/STAT3 activation mediates cytokine release and leukocyte recruitment into neonatal kidneys after UUO. Pharmacological blockade of JAK2/STAT3 by Tyrphostin AG490 reduced inflammation, tubular apoptosis, and interstitial fibrosis. JAK2/STAT3 blockade decreased pro-inflammatory and profibrotic mediators in tubular cells.

CONCLUSION

Our findings provide evidence that JAK2/STAT3 mediates inflammation and fibrosis in the developing kidney with obstruction. Blocking JAK2/STAT3 may prove beneficial in congenital obstructive nephropathy in children.

Neonatal obstructive nephropathy induces necroptosis and necroinflammation

Urinary tract obstruction during kidney development causes tubular apoptosis, tubular necrosis, and interstitial inflammation. Necroptosis is a subtype of programmed necrosis mediated by the receptor-interacting serine/threonine-protein kinase-3 (RIPK3) and the pseudokinase mixed lineage kinase domain-like (MLKL). Necrosis induces inflammation and stimulates cell death in an autoamplification loop named necroinflammation. Here, we studied necroptosis and necroinflammation in obstructive nephropathy induced by unilateral ureteral obstruction (UUO) in neonatal C57Bl/6J mice. Ureteral obstruction induced tubular dilatation, tubular basement membrane thickening, cast formation, and increased expression of kidney injury molecule-1 (KIM-1). Morphological investigations showed either apoptotic or necrotic cells in the tubular compartment. Biochemical analysis revealed increased caspase-8 activity and upregulation of RIPK3 as well as phosphorylated-MLKL in UUO-kidneys. Pro-inflammatory cytokines (IL-1α, INF-γ, TNF-α) were upregulated following UUO. Taken together we show that necroptosis and necroinflammation are accompanied phenomena in neonatal kidneys with obstruction. These findings may help to develop novel strategies to treat congenital obstructive nephropathy.

Ursolic acid inhibits epithelial-mesenchymal transition in vitro and in vivo

CONTEXT

Ursolic acid (UA; 3β-hydroxy-urs-12-en-28-oic acid), one of the pentacyclic triterpenoids found in various plants and herbs, possesses some beneficial effects under pathological conditions, including combating hepatic fibrosis.

OBJECTIVE

This study investigates the effects of UA on renal tubulointerstitial fibrosis in vivo and in vitro.

MATERIALS AND METHODS

In vivo, 24 male C57BL6 mice were divided into four groups. Eighteen mice were subjected to unilateral ureteral obstruction (UUO) and the remaining six sham-operated mice served as control. UUO mice received either vehicle or UA (50 or 100 mg/kg) by gastric gavage for 6 days. In vitro, HK-2 cells were treated with 10 or 50 μM UA and 10 ng/mL recombinant human transforming growth factor-β1 (TGF-β1). The molecular mechanisms of fibrosis were investigated.

RESULTS

UUO induced marked interstitial collagen I and fibronectin deposition and epithelial-mesenchymal transition (EMT), as evidenced by increased α-smooth muscle actin (α-SMA) and decreased E-cadherin. However, UA treatment significantly reduced collagen I and fibronectin accumulation in the fibrotic kidney. UA treatment also decreased α-SMA and preserved E-cadherin in vivo. In vitro, TGF-β1-treated HK-2 cells demonstrated elevated α-SMA, snail1, slug, TGF-β1, and p-smad3, as well as diminished E-cadherin. UA pretreatment prevented E-cadherin loss and diminished α-SMA expression in HK-2 cells. UA downregulated mRNA expression of snail1 and slug. UA also lowered TGF-β1 protein expression and p-Smad3 in HK-2 cells.

CONCLUSIONS

UA attenuated renal tubulointerstitial fibrosis by inhibiting EMT, and such inhibition may be achieved by decreasing profibrotic factors. UA may be a novel therapeutic agent for renal fibrosis.

Kidney osteoclast factors and matrix metalloproteinase expression in a mice model of diet-induced obesity and diabetes

The role of RANKL/RANK/OPG system on bone remodeling is well known, and there is evidence that it is also important to cardiovascular and kidney pathology, although the underlying mechanisms are not elucidated so far. Thus, we investigated in a mice model of diet-induced obesity and diabetes if renal histopathological changes are associated with the expression of RANKL/RANK/OPG system and matrix metalloproteinases (MMPs). Three months old C57BL/6 mice were fed with control (C) AIN93 M diet or high-fat high sucrose (HFHS) diets for 21 weeks (CEUA/UFF #647/15). The two groups presented weight gain, but it was higher in the HFHS group compared to the C group (+35%, P = 0.0001). The HFHS group also had increased epididymal, inguinal and retroperitoneal fat pad weight (+121%, P = 0.0006; +287%, P = 0.0007 and; +286%, P < 0.0001, respectively), and hyperglycemia (+43%, P = 0.02). The kidney of some HFHS fed mice displayed mononuclear inflammatory cell infiltrate (40%), perivascular fibrosis (20%), and focal tubule mineralization (20%). Glomeruli hypertrophy was not detected. Unexpectedly, OPG, RANK, MMP-2, and MMP-9 expression was not altered in HFHS groups (Western blot analysis). In conclusion, the expression of RANKL/RANK/OPG system proteins and MMPs was not influenced by diet-induced obesity and diabetes in the kidney of male C57BL/6 mice, although some adverse histopathological remodeling is noticed in the renal tissue.

Inhibition of p300/CBP-Associated Factor Attenuates Renal Tubulointerstitial Fibrosis through Modulation of NF-kB and Nrf2

p300/CBP-associated factor (PCAF), a histone acetyltransferase, is involved in many cellular processes such as differentiation, proliferation, apoptosis, and reaction to cell damage by modulating the activities of several genes and proteins through the acetylation of either the histones or transcription factors. Here, we examined a pathogenic role of PCAF and its potential as a novel therapeutic target in the progression of renal tubulointerstitial fibrosis induced by non-diabetic unilateral ureteral obstruction (UUO) in male C57BL/6 mice. Administration of garcinol, a PCAF inhibitor, reversed a UUO-induced increase in the renal expression of total PCAF and histone 3 lysine 9 acetylation and reduced positive areas of trichrome and α-smooth muscle actin and collagen content. Treatment with garcinol also decreased mRNA levels of transforming growth factor-β, matrix metalloproteinase (MMP)-2, MMP-9, and fibronectin. Furthermore, garcinol suppressed nuclear factor-κB (NF-κB) and pro-inflammatory cytokines such as tumor necrosis factor-α and IL-6, whereas it preserved the nuclear expression of nuclear factor erythroid-derived 2-like factor 2 (Nrf2) and levels of Nrf2-dependent antioxidants including heme oxygense-1, catalase, superoxide dismutase 1, and NAD(P)H:quinone oxidoreductase 1. These results suggest that the inhibition of inordinately enhanced PCAF could mitigate renal fibrosis by redressing aberrant balance between inflammatory signaling and antioxidant response through the modulation of NF-κB and Nrf2.

Thioredoxin-interacting protein deficiency ameliorates kidney inflammation and fibrosis in mice with unilateral ureteral obstruction

Thioredoxin-interacting protein (TXNIP) is associated with inflammation, tubulointerstitial fibrosis, and oxidative stress in diabetic kidney disease, yet the potential role of TXNIP in nondiabetic renal injury is not well known. This study aimed to investigate the effect of TXNIP on renal injury by creating a unilateral ureteral obstruction (UUO) model in TXNIP knockout (TKO) mice. We performed sham or UUO surgery in 8-week-old TXNIP KO male mice and age and sex-matched wild-type (WT) mice. Animals were killed at 3, 5, 7, or 14 days after surgery, and renal tissues were obtained for RNA, protein, and other analysis. Our results show that the expression of TXNIP was increased in a time-dependent manner in the ligated kidneys. TXNIP deletion reduced renal fibrosis, apoptosis, α-SMA, TGF-β1 and CTGF expression, and activation of Smad3, p38 MAPK, and ERK1/2 in UUO kidneys. We also found UUO-induced renal F4/80+ macrophage infiltration, MCP-1 expression and activation of NF-κB and NLRP3 inflammasome were attenuated in TKO mice. Furthermore, our study revealed that TXNIP deficiency inhibited the expression of 8-OHdG, heme oxygenase-1 (HO-1) and NADPH oxidase 4 (Nox4) in UUO kidney. In summary, our study suggests that TXNIP plays a key role in the renal inflammation and fibrosis induced by UUO. Inhibition of TXNIP may be a strategy to slow the progression of chronic kidney diseases.

Snail and kidney fibrosis

Snail family zinc finger 1 (SNAI1) is a transcription factor expressed during renal embryogenesis, and re-expressed in various settings of acute kidney injury (AKI). Subjected to tight regulation, SNAI1 controls major biological processes responsible for renal fibrogenesis, including mesenchymal reprogramming of tubular epithelial cells, shutdown of fatty acid metabolism, cell cycle arrest and inflammation of the microenvironment surrounding tubular epithelial cells. The present review describes in detail the interactions of SNAI1 with AKI-associated signalling pathways. We also discuss how this central factor has been iteratively (and promisingly) targeted in a number of animal models in order to prevent or slow down renal fibrogenesis.

miR-128 Regulates Genes Associated with Inflammation and Fibrosis of Rat Kidney Cells In Vitro

microRNAs (miRNAs) regulate diverse cellular functions and signaling pathways via inhibiting the expression of their target genes. Given that miR-128 mediates mitogen-activated protein kinase signaling and production of reactive oxygen species and pro-inflammatory chemokines in various types of cells and tissues, and that miR-128 is differentially expressed in aged and diseased kidneys, we hypothesized that miR-128 may play key roles in kidney inflammation. Hence, in this study, we evaluated the biological effects of miR-128 in normal rat kidney (NRK) cells in vitro. Our results revealed that overexpression of miR-128 enhanced expression of genes associated with inflammation, pro-inflammatory cytokines and fibrosis in NRK cells. The recent reports showing that expression of miR-128 is increased in liver and lung fibrosis, together with the findings in this study, suggest that miR-128 may be a pro-fibrotic miRNA that regulates fibrosis in various tissues. Anat Rec, 301:913-921, 2018. © 2017 Wiley Periodicals, Inc.

Correlation Between Single-Nucleotide Polymorphisms Within miR-30a and Related Target Genes and Risk or Prognosis of Nephrotic Syndrome

This study was aimed to figure out the association of single-nucleotide polymorphisms (SNPs) within miR-30a and its downstream molecules (i.e., Notch1, Snail1, p53, CD73, and TET1) with susceptibility to and prognosis of nephrotic syndrome (NS). In the aggregate, 265 patients and 281 healthy controls were gathered, and related laboratory indicators were examined. The miR-30a, Notch1, Snail1, TET1, p53, and CD73 expressions were also evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry, or enzyme-linked immunosorbent assay. Besides, the SNPs were genotyped by RT-PCR with aid of ABI-PRISM^™ 377 DNA sequencing instrument. As a result, the NS patients were correlated with remarkably higher 24-h protein excretion, random urine protein/creatinine (UPCR), and serum creatinine, along with lower estimated glomerular filtration rate and serum albumin, when compared with normal subjects (p < 0.05). Furthermore, significant correlations were present between miR-30a expression and the expressions of Notch1 (r_s = -0.350), p53 (r_s = -0.339), CD73 (r_s = -0.300), TET1 (r_s = -0.249), and Snail1 (r_s = -0.829) (all p < 0.05). The SNPs of miR-30a [i.e., rs2222722 (C>T)], Notch1 [i.e., rs3124599 (G>A), rs3124591 (C>T), and rs139994842 (G>A)], Snail1 [i.e., rs6020178 (T>C)], p53 [i.e., rs1042522 (C>G)], and CD73 [i.e., rs9444348 (G>A) and rs4431401 (T>C)] were significantly correlated with both differed NS risk and altered hormone sensitivity to NS (all p < 0.05). Moreover, haplotype AC of CD73 and haplotype ATG of Notch1 were the helpful factors against NS (p < 0.05), yet haplotype GT of CD73 functioned oppositely (p < 0.05). The haplotype AT of CD73 was beneficial to the NS patients for that the carriers could be treated with hormones without severe complications (p < 0.05). Conclusively, the SNPs situated within miR-30a and its downstream molecules (i.e., Notch1, Snail1, p53, CD73, and TET1) could become the promising biomarkers for both NS diagnosis and prediction of NS prognosis.

Emerging role of Twist1 in fibrotic diseases

Epithelial–mesenchymal transition (EMT) is a pathological process that occurs in a variety of diseases, including organ fibrosis. Twist1, a basic helix–loop–helix transcription factor, is involved in EMT and plays significant roles in various fibrotic diseases. Suppression of the EMT process represents a promising approach for the treatment of fibrotic diseases. In this review, we discuss the roles and the underlying molecular mechanisms of Twist1 in fibrotic diseases, including those affecting kidney, lung, skin, oral submucosa and other tissues. We aim at providing new insight into the pathogenesis of various fibrotic diseases and facilitating the development of novel diagnostic and therapeutic methods for their treatment.

Epigallocatechin-3-gallate inhibits inflammation and epithelial‑mesenchymal transition through the PI3K/AKT pathway via upregulation of PTEN in asthma

Asthma is a chronic disease associated with hyper-responsiveness, obstruction and remodeling of the airways. Epithelial-mesenchymal transition (EMT) has an important role in these alterations and may account for the accumulation of subepithelial mesenchymal cells, thus contributing to airway hyperresponsiveness and remodeling. Epigallo-catechin-3-gallate (EGCG), which is a type of polyphenol, is the most potent ingredient in green tea, and exhibits antibacterial, antiviral, antioxidative, anticancer and chemopreventive activities. Recently, numerous studies have investigated the protective effects of EGCG against asthma and other lung diseases. In the present study, the role of EGCG in ovalbumin (OVA)-challenged asthmatic mice was determined. In addition, the inhibitory effects of EGCG against transforming growth factor (TGF)-β1-induced EMT and migration of 16HBE cells, and the underlying mechanisms of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway, were investigated by immunofluorescence, Transwell, wound healing assay and western blot analysis, respectively. The results indicated that EGCG may suppress inflammation and inflammatory cell infiltration into the lungs of OVA-challenged asthmatic mice, and may also inhibit EMT via the PI3K/AKT signaling pathway through upregulating the expression of phosphatase and tensin homolog (PTEN) in vivo and in vitro. The present study also revealed the anti-migratory effects of EGCG in TGF-β1-induced 16HBE cells, thus suggesting it may reduce airway remodeling. The present study provides a novel insight into understanding the protective effects of EGCG on airway remodeling in asthma, and indicates that EGCG may be useful as an adjuvant therapy for bronchial asthma.

Tissue-type plasminogen activator modulates macrophage M2 to M1 phenotypic change through annexin A2-mediated NF-κB pathway

Macrophage accumulation is one of the hallmarks of progressive kidney disease. In response to injury, macrophages undergo a phenotypic polarization to become two functionally distinct subsets: M1 and M2 macrophages. Macrophage polarization is a dynamic process, and recent work indicates that macrophages, in response to kidney injury, can shift their polarity. However, the underlying mechanisms remain largely unknown. Tissue-type plasminogen activator (tPA), a protease up-regulated in the chronically injured kidneys, has been shown to preferably promote M1 macrophage accumulation and renal inflammation. We hypothesized that tPA may be an endogenous factor that modulates macrophage M2 to M1 phenotypic change contributing to the accumulation of M1 macrophages in the injured kidneys. It was found that obstruction-induced renal M1 chemokine expression was alleviated in tPA knockout mice, and these knockout mice displayed increased M2 markers. In vitro, resting J774 macrophages were treated with IL-4 to induce M2 phenotype as indicated by de novo expression of arginase 1, Ym1, and IL-10, as well as suppression of iNOS, TNF-α, and IL-1β. Intriguingly, these IL-4-induced M2 macrophages, after tPA treatment, not only lost their M2 markers such as arginase 1, Ym1, and IL-10, but also displayed increased M1 chemokines including iNOS, TNF-α, and IL-1β. Possible endotoxin contamination was also excluded as heat-inactivated tPA lost its effect. Additionally, tPA-mediated macrophage M2 to M1 phenotypic change required its receptor annexin A2, and SN50, a specific NF-κB inhibitor, abolished tPA's effect. Thus, it's clear that tPA promotes macrophage M2 to M1 phenotypic change through annexin A2-mediated NF-κB pathway.

Epoxyeicosatrienoic Acid Analog Decreases Renal Fibrosis by Reducing Epithelial-to-Mesenchymal Transition

Renal fibrosis, which is a critical pathophysiological event in chronic kidney diseases, is associated with renal epithelial-to-mesenchymal transition (EMT). Epoxyeicosatrienoic acids (EETs) are Cyp epoxygenase arachidonic acid metabolites that demonstrate biological actions that result in kidney protection. Herein, we investigated the ability of 14,15-EET and its synthetic analog, EET-A, to reduce kidney fibrosis induced by unilateral ureter obstruction (UUO). C57/BL6 male mice underwent sham or UUO surgical procedures and were treated with 14,15-EET or EET-A in osmotic pump (i.p.) for 10 days following UUO surgery. UUO mice demonstrated renal fibrosis with an 80% higher kidney-collagen positive area and 70% higher α-smooth muscle actin (SMA) positive renal areas compared to the sham group. As a measure of collagen content, kidney hydroxyproline content was also higher in UUO (6.4 ± 0.5 μg/10 mg) compared to sham group (2.5 ± 0.1 μg/10 mg). Along with marked renal fibrosis, UUO mice had reduced renal expression of EET producing Cyp epoxygenase enzymes. Endogenous 14,15-EET or EET-A demonstrated anti-fibrotic action in UUO by reducing kidney-collagen positive area (50–60%), hydroxyproline content (50%), and renal α-SMA positive area (85%). In UUO mice, renal expression of EMT inducers, Snail1 and ZEB1 were higher compared to sham group. Accordingly, renal epithelial marker E-cadherin expression was reduced and mesenchymal marker expression was elevated in the UUO compared to sham mice. Interestingly, EET-A reduced EMT in UUO mice by deceasing renal Snail1 and ZEB1 expression. EET-A treatment also opposed the decrease in renal E-cadherin expression and markedly reduced several prominent renal mesenchymal/myofibroblast markers in UUO mice. Overall, our results demonstrate that EET-A is a novel anti-fibrotic agent that reduces renal fibrosis by decreasing renal EMT.

Nano-sized carriers in gene therapy for renal fibrosis in vivo

Renal fibrosis is the final common pathway leading to end-stage renal failure regardless of underlying initial nephropathies. No specific therapy has been established for renal fibrosis. Gene therapy is a promising strategy for the treatment of renal fibrosis. Nano-sized carriers including viral vectors and non-viral vectors have been shown to enhance the delivery and treatment effects of gene therapy for renal fibrosis in vivo. This review focuses on the mechanisms of renal fibrosis and the in vivo technologies and methodologies of nano-sized carriers in gene therapy for renal fibrosis. RESPONSIBLE EDITOR Alexander Seifalian Director of Nanotechnology & Regenerative Medicine Ltd., The London BioScience Innovation Centre, London, UNITED KINGDOM.

Snail1-induced partial epithelial-to-mesenchymal transition drives renal fibrosis in mice and can be targeted to reverse established disease

Progressive kidney fibrosis contributes greatly to end-stage renal failure, and no specific treatment is available to preserve organ function. During renal fibrosis, myofibroblasts accumulate in the interstitium of the kidney, leading to massive deposition of extracellular matrix and organ dysfunction. The origin of myofibroblasts is manifold, but the contribution of an epithelial-to-mesenchymal transition (EMT) undergone by renal epithelial cells during kidney fibrosis is still debated. We show that the reactivation of Snai1 (encoding snail family zinc finger 1, known as Snail1) in mouse renal epithelial cells is required for the development of fibrosis in the kidney. Damage-mediated Snail1 reactivation induces a partial EMT in tubular epithelial cells that, without directly contributing to the myofibroblast population, relays signals to the interstitium to promote myofibroblast differentiation and fibrogenesis and to sustain inflammation. We also show that Snail1-induced fibrosis can be reversed in vivo and that obstructive nephropathy can be therapeutically ameliorated in mice by targeting Snail1 expression. These results reconcile conflicting data on the role of the EMT in renal fibrosis and provide avenues for the design of novel anti-fibrotic therapies.

Fibroblast-epithelial cell interactions drive epithelial-mesenchymal transition differently in cells from normal and COPD patients

BACKGROUND

Epithelial-to-mesenchymal transition (EMT), which involves changes in cellular morphology of highly polarized epithelial cells and the gain of mesenchymal cell phenotype with migratory and invasive capacities, is implicated in smoking-related chronic obstructive pulmonary disease (COPD). However, the interactions of fibroblasts and epithelial cells and the participation of fibroblasts in the EMT processes in COPD are poorly understood. Here, we investigated the hypothesis that EMT is active in human bronchial epithelial (HBE) cells of COPD patients, and that mediators secreted by lung fibroblasts from COPD patients induce EMT.

METHODS

Primary HBE cells from normal subjects and COPD patients were purchased from LONZA. HLFs were derived from resected lung obtained from normal (N) and COPD (D) subjects and their conditioned medium (CM) was collected after 2-day culture in serum-free medium. The expression of epithelial and mesenchymal markers as well as EMT-related transcription factors in lung biopsies, and in HBE cells following stimulation with CM from both normal human lung fibroblasts (NHLF) and COPD human lung fibroblasts (DHLF) was evaluated by immunohistochemistry, qRT-PCR and western blot.

RESULTS

Basal mRNA expression of mesenchymal markers and EMT-related transcription factors were increased in DHBE cells compared to normal human bronchial epithelial cells (NHBE) cells as well as in COPD lungs. CM from NHLF significantly induced vimentin expression in both NHBE and COPD human bronchial epithelial cells (DHBE) cells, but only increased N-cadherin expression in DHBE cells. CM from NHLF significantly induced Twist1 and Twist2 expression in NHBE cells and increased Snai2 (Slug) expression in DHBE cells. While CM from NHLF had no effect on such EMT markers, CM from DHLF significantly increased the protein expression of E-cadherin and vimentin in NHBE cells compared to control. N-cadherin expression was upregulated to a greater degree in NHBE cells than DHBE cells. Only CM from DHLF significantly increased E-/N-cadherin ratio in DHBE cells.

CONCLUSIONS

Our results suggest that DHBE cells have partially undergone EMT under baseline conditions. DHLF-CM promoted EMT in NHBE, suggesting that interactions between fibroblast and epithelial cells may play an important role in the EMT process in COPD.

Hydrogen Sulfide as a Potential Therapeutic Target in Fibrosis

Hydrogen sulfide (H₂S), produced endogenously by the activation of two major H₂S-generating enzymes (cystathionine β-synthase and cystathionine γ-lyase), plays important regulatory roles in different physiologic and pathologic conditions. The abnormal metabolism of H₂S is associated with fibrosis pathogenesis, causing damage in structure and function of different organs. A number of in vivo and in vitro studies have shown that both endogenous H₂S level and the expressions of H₂S-generating enzymes in plasma and tissues are significantly downregulated during fibrosis. Supplement with exogenous H₂S mitigates the severity of fibrosis in various experimental animal models. The protective role of H₂S in the development of fibrosis is primarily attributed to its antioxidation, antiapoptosis, anti-inflammation, proangiogenesis, and inhibition of fibroblasts activities. Future studies might focus on the potential to intervene fibrosis by targeting the pathway of endogenous H₂S-producing enzymes and H₂S itself.

Delivery of microRNA-146a with polyethylenimine nanoparticles inhibits renal fibrosis in vivo

Renal fibrosis is the final common pathway leading to end-stage renal disease. Although microRNA (miR) was recently shown to be involved in the development of renal fibrosis, few studies have focused on the effects on renal fibrosis of exogenous miR delivered in an in vivo therapeutic setting. The study reported here investigated the effects of miR-146a delivery using polyethylenimine nanoparticles (PEI-NPs) on renal fibrosis in vivo. PEI-NPs bearing miR-146 or control-miR (nitrogen/phosphate ratio: 6) were injected into the tail vein of a mouse model of renal fibrosis induced by unilateral ureteral obstruction. PEI-NPs bearing miR-146 significantly enhanced miR-146a expression in the obstructed kidney compared with the control group, while inhibiting the renal fibrosis area, expression of alpha-smooth muscle actin, and infiltration of F4/80-positive macrophages into the obstructed kidney. In addition, PEI-NPs bearing miR-146a inhibited the transforming growth factor beta 1–Smad and tumor necrosis factor receptor-associated factor 6–nuclear factor kappa B signaling pathways. Control-miR-PEI-NPs did not show any of these effects. These results suggest that the delivery of miR-146a attenuated renal fibrosis by inhibiting pro-fibrotic and inflammatory signaling pathways and that the delivery of appropriate miRs may be a therapeutic option for preventing renal fibrosis in vivo.

Tissue-type plasminogen activator (tPA) promotes M1 macrophage survival through p90 ribosomal S6 kinase (RSK) and p38 mitogen-activated protein kinase (MAPK) pathway

Macrophage accumulation is one of the hallmarks of progressive kidney disease. Resting macrophages have a finite lifespan, but become resistant to apoptosis in response to pathogenic cues, whereas the underlying mechanism remains unknown. Tissue-type plasminogen activator (tPA), a protease up-regulated in the kidneys with chronic injury, has been shown to promote macrophage accumulation and renal inflammation. We hypothesized that tPA may be the endogenous factor that promotes macrophage survival and extends their lifespan that leads to their accumulation in the injured kidneys. We examined the role of tPA in macrophage survival, and found that tPA protected macrophages from both staurosporine and H2O2-induced apoptosis. tPA promoted the survival of both resting and lipopolysaccharide- or interferon-γ-induced M1 macrophages, but failed to do so in the interleukin 4 (IL4)-induced M2 macrophages. In the kidneys with unilateral ureteral obstruction, there were significantly more apoptotic M1 macrophages in tPA-deficient mice than their wild-type counterparts, and obstruction-induced M1 macrophages accumulation and M1 chemokine expression were markedly reduced in these knock-out mice. The cytoprotective effect of tPA required its receptor, LDL receptor-related protein-1 (LRP-1). tPA induced the phosphorylation of Erk1/2, p90 ribosomal S6 kinase (RSK), and p38 in a temporal order. The tPA-mediated macrophage survival was eliminated by PD98059, BI-D1870, or sc68376, the specific inhibitors for Erk1/2, p90RSK, or p38, respectively. Thus, it is clear that tPA promoted M1 macrophage survival through its receptor LRP-1-mediated novel signaling cascade involving Erk1/2, p90RSK, and p38, which leads to the accumulation of these cells in the injured kidneys.

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.

Ulinastatin attenuates renal interstitial inflammation and inhibits fibrosis progression in rats under unilateral ureteral obstruction

The aim of the present study was to examine the protective effects of the urinary trypsin inhibitor ulinastatin (UTI) on renal interstitial inflammation and fibrosis in rats subjected to unilateral ureteral obstruction (UUO). A total of 24 male Wistar rats were randomly divided into the three groups; the sham operation (SOR) group (n=8), the UUO group (n=8) and the UUO+UTI group (post‑UUO UTI treatment, n=8). UUO was performed with complete ligation of the left ureter. As a medical intervention, saline (4 ml kg‑1 d‑1) and UTI (40000 units kg‑1 d‑1) were injected, respectively, into the animals of the corresponding groups on day one following surgery. The rats in all three groups were euthanized on day seven post surgery. Blood samples were harvested for blood urea nitrogen (BUN) and serum creatinine (Scr) content measurements. The degree of interstitial pathological changes in the tissues from the obstructed kidneys were observed through hematoxylin and eosin (H&E) and Masson staining. The CD68+ macrophage amount, tumor necrosis factor‑α (TNF‑α), interleukin 1β (IL‑1β), nuclear factor‑κB (NF‑κB), transforming growth factor‑β1 (TGF‑β1) and type I collagen (Col‑I) levels were examined immunohistochemically. The protein expression levels of NF‑κB were examined using western blot analysis. Total superoxide dismutase (SOD) activity and malondialdehyde (MDA) content of homogenates were measured spectrophotometrically. The results revealed that ulinastatin had no statistically significant effect on the BUN and Scr levels (P>0.05). However, in comparison with the SOR group, the UUO group exhibited significantly more severe renal interstitial pathological injury in terms of tubular dilation, epithelial atrophy, renal interstitial inflammatory cell infiltration and proliferation of fibrous tissues, as well as significantly elevated levels of interstitial CD68+ macrophages, IL‑1β, TNF‑α, NF‑κB, TGF‑β1 and Col‑I (P<0.01). UTI treatment significantly reduced UUO‑induced renal interstitial damage with reduced levels of interstitial CD68+ macrophages, IL‑1β, TNF‑α, NF‑κB, TGF‑β1 and Col‑I and MDA (P<0.05), and increased SOD levels (P<0.05). In conclusion, the present study indicated that UTI is able to effectively inhibit UUO‑side renal interstitial inflammatory reaction and fibrosis in UUO‑inflicted rats.

Wnt pathway activation in long term remnant rat model

Progression of chronic kidney disease (CKD) is characterized by deposition of extracellular matrix. This is an irreversible process that leads to tubulointerstitial fibrosis and finally loss of kidney function. Wnt/ β-catenin pathway was reported to be aberrantly activated in the progressive damage associated with chronic organ failure. Extensive renal ablation is an experimental model widely used to gain insight into the mechanisms responsible for the development of CKD, but it was not evaluated for Wnt/ β-catenin pathway. This study aimed to elucidate if the rat 5/6 renal mass reduction model (RMR) is a good model for the Wnt/ β-catenin activation and possible next modulation. RMR model was evaluated at 12 and 18 weeks after the surgery, when CKD is close to end-stage kidney disease demonstrated by molecular and histological studies. Wnt pathway components were analyzed at mRNA and protein level. Our results demonstrate that Wnt pathway is active by increase of β-catenin at mRNA level and nuclear translocation in tubular epithelium as well as some target genes. These results validate the RMR model for future modulation of Wnt pathway, starting at shorter time after the surgery.

Monocyte implication in renal allograft dysfunction

Macrophages are involved in the development and progression of kidney fibrosis. The aim of this study was to analyse the phenotype of circulating monocytes and their ability to predict kidney allograft dysfunction in living kidney transplant recipients. Whole blood samples from 25 kidney recipients and 17 donors were collected at five time-points. Monocyte phenotype was analysed by flow cytometry, and interleukin (IL)-10 and soluble CD163 by enzyme-linked immunosorbent assay. One week after transplantation, surface CD163 and IL-10 levels increased significantly from baseline [2·99 ± 1·38 mean fluorescence intensity (MFI) to 5·18 ± 2·42 MFI for CD163; 4·5 ± 1·46 pg/ml to 6·7 ± 2·5 pg/ml for IL-10]. This CD163 increase correlated with 4-month creatinine levels (r = 0·4394, P = 0·04). However, soluble CD163 decreased significantly from baseline at 1 week (797·11 ± 340·45 ng/ml to 576·50 ± 293·60 ng/ml). CD14(+) CD16(-) monocytes increased at 4 months and correlated positively with creatinine levels at 12 and 24 months (r = 0·6348, P = 0·002 and r = 0·467, P = 0·028, respectively) and negatively with Modification of Diet in Renal Disease (MDRD) at 12 months (r = 0·6056, P = 0·003). At 4 months, IL-10 decreased significantly (P = 0·008) and correlated positively with creatinine at 2 years (r = 0·68, P = 0·010) and with CD14(+) CD16(-) monocytes at 4 months (r = 0·732, P = 0·004). At 24 h, levels of human leucocyte antigen D-related declined from 12·12 ± 5·99 to 5·21 ± 3·84 and CD86 expression decreased from 2·76 ± 1·08 to 1·87 ± 0·95. Both markers recovered progressively until 12 months, when they decreased again. These results indicate that monitoring monocytes could be a promising new prognostic tool of graft dysfunction in renal transplant patients.

Proteomic identification of early changes in the renal cytoskeleton in obstructive uropathy

Bilateral ureteral obstruction (BUO) is associated with renal damage and impaired ability to concentrate urine and is known to induce alterations in an array of kidney proteins. The aim of this study was to identify acute proteomic alterations induced by BUO. Rats were subjected to BUO for 2, 6, or 24 h. Mass spectrometry-based proteomics was performed on the renal inner medulla, and protein changes in the obstructed group were identified. Significant changes were successfully identified for 109 proteins belonging to different biological classes. Interestingly, proteins belonging to the cytoskeleton and proteins related to cytoskeletal regulation were found to be biologically enriched in BUO using online-accessible tools. Western blots confirmed the selected results, demonstrating acute downregulation of proteins belonging to all three cytoskeletal components. The microfilament protein β-actin and the intermediate filament proteins pankeratin and vimentin were all downregulated. β-Tubulin, an important microtubular protein, was found to be significantly downregulated after 24 h. Also, there was significant upregulation of cofilin, an actin-binding protein known to be upregulated in other nephropathy models. Furthermore, both upregulation and downregulation of cytoskeletal motor and regulatory proteins were observed. These findings were confirmed by immunohistochemistry, which clearly showed alterations in labeling in the inner medulla. Interestingly, we were able to confirm selected results in mpkCCD cells exposed to mechanical stretch. Our findings add to the knowledge of BUO-induced acute changes in the renal cytoskeleton and suggest that these molecular changes are partly mediated by increased stretch of the cells during obstruction.

Total glucosides of paeony attenuate renal tubulointerstitial injury in STZ-induced diabetic rats: role of Toll-like receptor 2

Accumulating evidence suggested that macrophages induce tubulointerstitial injury. Total glucosides of paeony (TGP), extracted from Paeonia lactiflora, has presented anti-inflammatory activities in diabetic kidney disease. This research will investigate the protective effect of TGP on renal tubulointerstitium and its mechanism in streptozotocin-induced diabetic rats. TGP was administered orally at a dose of 50, 100, and 200 mg·kg(-1)·d(-1) for 8 weeks. Tubulointerstitial injury was quantified, followed by immunohistochemistry analysis of renal α-smooth muscle actin (α-SMA), E-cadherin (E-cad) expression, nuclear factor kappa B (NF-κB)-p-p-65(+), Toll-like receptor (TLR)2(+), and ED-1(+) cell infiltration in renal tubulointerstitium. Renal TLR2(+) macrophages were detected by double immunohistochemical staining. Western blotting was used to detect the TLR2 expression. Histologically, there was marked accumulation of TLR2(+), NF-κB-p-p-65(+), ED-1(+) cells, and ED-1(+)TLR2(+) cells (macrophages) in the diabetic kidney and TGP treatment could alleviate it. Accompanying with that, the tubulointerstitial injury was ameliorated, α-SMA expression was lower, and E-cad expression was higher compared with the diabetic rats. Western blot analysis showed that the expression of TLR2 protein was significantly increased in the kidney of the diabetic rats, whereas TGP treatment reduced it. Our study showed that TGP could prevent renal tubulointerstitium injury in diabetic rats through a mechanism that may be at least partly correlated with suppression of increased macrophage infiltration and the expression of TLR2.

Unilateral ureteral obstruction: beyond obstruction

Unilateral ureteral obstruction is a popular experimental model of renal injury. However, the study of the kidney response to urinary tract obstruction is only one of several advantages of this model. Unilateral ureteral obstruction causes subacute renal injury characterized by tubular cell injury, interstitial inflammation and fibrosis. For this reason, it serves as a model both of irreversible acute kidney injury and of events taking place during human chronic kidney disease. Being a unilateral disease, it is not useful to study changes in global kidney function, but has the advantage of a low mortality and the availability of an internal control (the non-obstructed kidney). Experimental unilateral ureteral obstruction has illustrated the molecular mechanisms of apoptosis, inflammation and fibrosis, all three key processes in kidney injury of any cause, thus providing information beyond obstruction. Recently this model has supported key concepts on the role in kidney fibrosis of epithelial-mesenchymal transition, tubular epithelial cell G2/M arrest, the anti-aging hormone Klotho and renal innervation. We now review the experimental model and its contribution to identifying novel therapeutic targets in kidney injury and fibrosis, independently of the noxa.

Matrix metalloproteinases contribute to kidney fibrosis in chronic kidney diseases

Matrix metalloproteinases (MMPs) are members of the neutral proteinase family. They were previously thought to be anti-fibrotic because of their ability to degrade and remodel of extracellular matrix. However, recent studies have shown that MMPs are implicated in initiation and progression of kidney fibrosis through tubular cell epithelial–mesenchymal transition (EMT) as well as activation of resident fibroblasts, endothelial-mesenchymal transition (EndoMT) and pericyte-myofibroblast transdifferentiation. Interstitial macrophage infiltration has also been shown to correlate with the severity of kidney fibrosis in various chronic kidney diseases. MMPs secreted by macrophages, especially MMP-9, has been shown by us to be profibrotic by induction of tubular cells EMT. EMT is mainly induced by transforming growth factor-β (TGF-β). However, MMP-9 was found by us and others to be up-regulated by TGF-β1 in kidney tubular epithelial cells and secreted by activated macrophages, resulting in EMT and ultimately kidney fibrosis. Therefore, MMP-9 may serve as a potential therapeutic target to prevent kidney fibrosis in chronic kidney disease. This review, by a particular focus on EMT, seeks to provide a comprehensive understanding of MMPs, especially MMP-9, in kidney fibrosis.

Norcantharidin inhibits renal interstitial fibrosis by blocking the tubular epithelial-mesenchymal transition

Epithelial–mesenchymal transition (EMT) is thought to contribute to the progression of renal tubulointerstitial fibrosis. Norcantharidin (NCTD) is a promising agent for inhibiting renal interstitial fibrosis. However, the molecular mechanisms of NCTD are unclear. In this study, a unilateral ureteral obstruction (UUO) rat model was established and treated with intraperitoneal NCTD (0.1 mg/kg/day). The UUO rats treated with NCTD showed a reduction in obstruction-induced upregulation of α-SMA and downregulation of E-cadherin in the rat kidney (P<0.05). Human renal proximal tubule cell lines (HK-2) stimulated with TGF-β₁ were treated with different concentrations of NCTD. HK-2 cells stimulated by TGF-β₁ in vitro led to downregulation of E-cadherin and increased de novo expression of α-SMA; co-treatment with NCTD attenuated all of these changes (P<0.05). NCTD reduced TGF-β₁-induced expression and phosphorylation of Smad2/3 and downregulated the expression of Snail1 (P<0.05). These results suggest that NCTD antagonizes tubular EMT by inhibiting the Smad pathway. NCTD may play a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.

Eosinophils promote epithelial to mesenchymal transition of bronchial epithelial cells

Eosinophilic inflammation and remodeling of the airways including subepithelial fibrosis and myofibroblast hyperplasia are characteristic pathological findings of bronchial asthma. Epithelial to mesenchymal transition (EMT) plays a critical role in airway remodelling. In this study, we hypothesized that infiltrating eosinophils promote airway remodelling in bronchial asthma. To demonstrate this hypothesis we evaluated the effect of eosinophils on EMT by in vitro and in vivo studies. EMT was assessed in mice that received intra-tracheal instillation of mouse bone marrow derived eosinophils and in human bronchial epithelial cells co-cultured with eosinophils freshly purified from healthy individuals or with eosinophilic leukemia cell lines. Intra-tracheal instillation of eosinophils was associated with enhanced bronchial inflammation and fibrosis and increased lung concentration of growth factors. Mice instilled with eosinophils pre-treated with transforming growth factor(TGF)-β1 siRNA had decreased bronchial wall fibrosis compared to controls. EMT was induced in bronchial epithelial cells co-cultured with human eosinophils and it was associated with increased expression of TGF-β1 and Smad3 phosphorylation in the bronchial epithelial cells. Treatment with anti-TGF-β1 antibody blocked EMT in bronchial epithelial cells. Eosinophils induced EMT in bronchial epithelial cells, suggesting their contribution to the pathogenesis of airway remodelling.

RAGE-mediated interstitial fibrosis in neonatal obstructive nephropathy is independent of NF-κB activation

Urinary tract obstruction during nephron development causes tubular apoptosis, tubular atrophy, and interstitial fibrosis. Leukocyte recruitment is critical in the development of obstructive nephropathy leading to interstitial inflammation and renal fibrosis. RAGE, the receptor of advanced glycation end products, is implicated in chronic inflammation and has been recently identified as a novel receptor for the β2-integrin Mac-1, cooperating with ICAM-1 and thereby directly mediating leukocyte recruitment in vivo. Here, we studied the role of RAGE and ICAM-1 in a model of unilateral ureteral obstruction in neonatal mice. Interestingly, the number of infiltrating leukocytes was independent of RAGE and ICAM-1 in the ureteral obstructed neonatal kidney. By contrast, galectin-3, a marker for profibrogenic M2 macrophages, was strongly reduced in ureteral obstructed RAGE and RAGE-Icam1 knockout mice. Snail expression and loss of E-cadherin but not NF-κB activation were attenuated in both knockout models. Epithelial cell cycle arrest at G2/M, which mediates kidney fibrosis, and transforming growth factor-β expression were reduced in ureteral obstructed RAGE knockout mice. Thus, RAGE and ICAM-1 promote renal fibrosis in the developing kidney upon ureteral obstruction. Combined RAGE- and ICAM-1-blocking strategies may prove beneficial in neonatal obstructive nephropathy.

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.

Matrix metalloproteinase-9 of tubular and macrophage origin contributes to the pathogenesis of renal fibrosis via macrophage recruitment through osteopontin cleavage

A pro-fibrotic role of matrix metalloproteinase-9 (MMP-9) in tubular cell epithelial-mesenchymal transition (EMT) is well established in renal fibrosis; however studies from our group and others have demonstrated some previously unrecognized complexity of MMP-9 that has been overlooked in renal fibrosis. Therefore, the aim of this study was to determine the expression pattern, origin and the exact mechanism underlying the contribution of MMP-9 to unilateral ureteral obstruction (UUO), a well-established model of renal fibrosis via MMP-9 inhibition. Renal MMP-9 expression in BALB/c mice with UUO was examined on day 1, 3, 5, 7, 9, 11 and 14. To inhibit MMP-9 activity, MMP-2/9 inhibitor or MMP-9-neutralizing antibody was administered daily for 4 consecutive days from day 0-3, 6-9 or 10-13 and tissues harvested at day 14. In UUO, there was a bi-phasic early- and late-stage upregulation of MMP-9 activity. Interestingly, tubular epithelial cells (TECs) were the predominant source of MMP-9 during early stage, whereas TECs, macrophages and myofibroblasts produced MMP-9 during late-stage UUO. Early- and late-stage inhibition of MMP-9 in UUO mice significantly reduced tubular cell EMT and renal fibrosis. Moreover, MMP-9 inhibition caused a significant reduction in MMP-9-cleaved osteopontin and macrophage infiltration in UUO kidney. Our in vitro study showed MMP-9-cleaved osteopontin enhanced macrophage transwell migration and MMP-9 of both primary TEC and macrophage induced tubular cell EMT. In summary, our result suggests that MMP-9 of both TEC and macrophage origin may directly or indirectly contribute to the pathogenesis of renal fibrosis via osteopontin cleavage, which, in turn further recruit macrophage and induce tubular cell EMT. Our study also highlights the time dependency of its expression and the potential of stage-specific inhibition strategy against renal fibrosis.

Tissue plasminogen activator activates NF-κB through a pathway involving annexin A2/CD11b and integrin-linked kinase

NF-κB activation is central to the initiation and progression of inflammation, which contributes to the pathogenesis of CKD. Tissue plasminogen activator (tPA) modulates the NF-κB pathway, but the underlying mechanism remains unknown. We investigated the role of tPA signaling in macrophage NF-κB activation and found that tPA activated NF-κB in a time- and dose-dependent manner. tPA also induced the expression of the NF-κB-dependent chemokines IP-10 and MIP-1α. The protease-independent action of tPA required its membrane receptor, annexin A2. tPA induced the aggregation and interaction of annexin A2 with integrin CD11b, and ablation of CD11b or administration of anti-CD11b neutralizing antibody abolished the effect of tPA. Knockdown of the downstream effector of CD11b, integrin-linked kinase, or disruption of its engagement with CD11b also blocked tPA-induced NF-κB signaling. In vivo, tPA-knockout mice had reduced NF-κB signaling, fewer renal macrophages, and less collagen deposition than their counterparts. Taken together, these data suggest that tPA activates the NF-κB pathway in macrophages through a signaling pathway involving annexin A2/CD11b-mediated integrin-linked kinase.

Suramin alleviates glomerular injury and inflammation in the remnant kidney

BACKGROUND

Recently, we demonstrated that suramin, a compound that inhibits the interaction of multiple cytokines/growth factors with their receptors, inhibits activation and proliferation of renal interstitial fibroblasts, and attenuates the development of renal interstitial fibrosis in the murine model of unilateral ureteral obstruction (UUO). However, it remains unclear whether suramin can alleviate glomerular and vascular lesions, which are not typical pathological changes in the UUO model. So we tested the efficacy of suramin in the remnant kidney after 5/6 nephrectomy, a model characterized by the slow development of glomerulosclerosis, vascular sclerosis, tubulointerstitial fibrosis and renal inflammation, mimicking human disease.

METHODS/FINDINGS

5/6 of normal renal mass was surgically ablated in male rats. On the second week after surgery, rats were randomly divided into suramin treatment and non-treatment groups. Suramin was given at 10 mg/kg once per week for two weeks. In the remnant kidney of mice receiving suramin, glomerulosclerosis and vascular sclerosis as well as inflammation were ameliorated. Suramin also attenuated tubular expression of two chemokines, monocyte chemoattractant protein-1 and regulated upon expression normal T cell expressed and secreted (RANTES). After renal mass ablation, several intracellular molecules associated with renal fibrosis, including NF-kappaB p65, Smad-3, signal transducer and activator of transcription-3 and extracellular regulated kinase 1/2, are phosphorylated; suramin treatment inhibited their phosphorylation. Futhermore, suramin abolished renal ablation-induced phosphorylation of epidermal growth factor receptor and platelet derived growth factor receptor, two receptors that mediate renal fibrosis.

CONCLUSIONS AND SIGNIFICANCE

These findings suggest that suramin attenuates glomerular and vascular injury and reduces inflammatory responses by suppression of multiple growth factor receptor-mediated profibrotic signaling pathways. Therefore, suramin may be a useful drug in preventing the fibrosis and sclerosis that characterizes progression of chronic kidney disease.

The critical role of TAK1 in accentuated epithelial to mesenchymal transition in obliterative bronchiolitis after lung transplantation

Therapies to limit or reverse fibrosis have proven unsuccessful, highlighting the need for a greater understanding of basic mechanisms that drive fibrosis and, in particular, the link between fibrosis and inflammation. It has been shown that pro-fibrotic transforming growth factor β1 (TGF-β1)-driven epithelial-to-mesenchymal transition (EMT) can be accentuated by tumor necrosis factor α (TNF-α). TGF-β-activated kinase 1 (TAK1) is activated by both TGF-β1 and TNF-α, activating both nuclear factor kappa-light-chain-enhancer of activated B cells and mitogen-activated protein kinase signaling pathways. In this study, we evaluated the potential for TAK1 to modulate the synergistic effect between TGF-β1 and TNF-α in driving EMT. Co-stimulation with TGF-β1 and TNF-α induced an accentuated and extended phosphorylation of TAK1 compared to either alone. TAK1 signaled downstream via nuclear factor kappa-light-chain-enhancer of activated B cells, and Jun N-terminal kinase-2, but independent of Jun N-terminal kinase-1, extracellular signal-regulated kinase-1/2, or p38 mitogen-activated protein kinase signaling to drive EMT in bronchial epithelial cells. Blocking either TAK1 or Jun N-terminal kinase-2 inhibited EMT. TAK1 phosphorylation was increased in the airway epithelium of patients with fibrotic airway disease. These data identify factors leading to and affected by accentuated and extended TAK1 phosphorylations potential novel therapeutic targets in inflammation-driven fibrotic diseases.

Adipose tissue-derived stem cell treatment prevents renal disease progression

Adipose tissue-derived stem cells (ASCs) are an attractive source of stem cells with regenerative properties that are similar to those of bone marrow stem cells. Here, we analyze the role of ASCs in reducing the progression of kidney fibrosis. Progressive renal fibrosis was achieved by unilateral clamping of the renal pedicle in mice for 1 h; after that, the kidney was reperfused immediately. Four hours after the surgery, 2 × 10(5) ASCs were intraperitoneally administered, and mice were followed for 24 h posttreatment and then at some other time interval for the next 6 weeks. Also, animals were treated with 2 × 10(5) ASCs at 6 weeks after reperfusion and sacrificed 4 weeks later to study their effect when interstitial fibrosis is already present. At 24 h after reperfusion, ASC-treated animals showed reduced renal dysfunction and enhanced regenerative tubular processes. Renal mRNA expression of IL-6 and TNF was decreased in ASC-treated animals, whereas IL-4, IL-10, and HO-1 expression increased despite a lack of ASCs in the kidneys as determined by SRY analysis. As expected, untreated kidneys shrank at 6 weeks, whereas the kidneys of ASC-treated animals remained normal in size, showed less collagen deposition, and decreased staining for FSP-1, type I collagen, and Hypoxyprobe. The renal protection seen in ASC-treated animals was followed by reduced serum levels of TNF-α, KC, RANTES, and IL-1α. Surprisingly, treatment with ASCs at 6 weeks, when animals already showed installed fibrosis, demonstrated amelioration of functional parameters, with less tissue fibrosis observed and reduced mRNA expression of type I collagen and vimentin. ASC therapy can improve functional parameters and reduce progression of renal fibrosis at early and later times after injury, mostly due to early modulation of the inflammatory response and to less hypoxia, thereby reducing the epithelial-mesenchymal transition.