Macrophages and progressive tubulointerstitial disease

Role of miRNAs in macrophage-mediated kidney injury

Macrophages, crucial components of the human immune system, can be polarized into M1/M2 phenotypes, each with distinct functions and roles. Macrophage polarization has been reported to be significantly involved in the inflammation and fibrosis observed in kidney injury. MicroRNA (miRNA), a type of short RNA lacking protein-coding function, can inhibit specific mRNA by partially binding to its target mRNA. The intricate association between miRNAs and macrophages has been attracting increasing interest in recent years. This review discusses the role of miRNAs in regulating macrophage-mediated kidney injury. It shows how miRNAs can influence macrophage polarization, thereby altering the biological function of macrophages in the kidney. Furthermore, this review highlights the significance of miRNAs derived from exosomes and extracellular vesicles as a crucial mediator in the crosstalk between macrophages and kidney cells. The potential of miRNAs as treatment applications and biomarkers for macrophage-mediated kidney injury is also discussed.

RGS1 mediates renal interstitial fibrosis through activation of the inflammatory response

Renal interstitial fibrosis (RIF) is considered as a common pathway for all patients with chronic kidney disease (CKD) to progress to end-stage kidney disease (ESRD). The basic pathological manifestation is the increase of matrix component in the tubular interstitium, while the injury of tubular epithelial cells in the renal interstitium and the excessive accumulation of matrix will eventually lead to tubular atrophy and obstruction, loss of effective renal units, and finally impaired renal filtration function. The relevant mechanism of RIF remains unclear. The present study will investigate the function and relevant mechanism of RGS1 in RIF. The RIF-related microarrays GSE22459 and GSE76882 were downloaded and analyzed. Renal parenchymal atrophic calyx tissues were collected from clinical RIF patients. Cellular inflammation, fibrosis and animal RIF models were constructed using Lipopolysaccharide (LPS), TGF-β1 and unilateral ureteral occlusion (UUO). HE and Masson staining were performed to detect morphological alterations of renal tissue samples. qRT-PCR, Western blot and ELISA were carried out to detect the expression of relevant genes/proteins. RGS1 is a gene co-differentially expressed by GSE22459 and GSE76882. RGS1 expression was elevated in renal tissues of RIF patients, cells and animal RIF models. Knockdown of RGS1 inhibited renal cell inflammatory response, fibrosis and renal fibrosis in RIF mice. Overexpression of RGS1 plays the opposite role. Knockdown of RGS1 inhibited the inflammatory response in the RIF cell and mouse model. Targeting RGS1 might be a potential therapeutic strategy for RIF treatment.

Unusual acetylated flavonol glucuronides, oxyphyllvonides A-H with renoprotective activities from the fruits of Alpinae oxyphylla

As a widely consumed spice and Traditional Chinese Medicine, Alpinae oxyphylla has been used to treat conditions such as diarrhea, ulcers, dementia, and enuresis. Fruits of A. oxyphylla were phytochemically studied and the bioactive constituents against renal fibrosis were identified. Eight previously undescribed acetylated flavonol glucuronides named oxyphyllvonides A-H (1-7 and 10), two known acetylated flavonol glucuronides (8 and 9), together with seven known flavone glycosides (11-17) were isolated from the fruits of A. oxyphylla. Among them, flavonol glucuronides were discovered in Zingiberaceae for the first time. The planar structures of 1-7 and 10 were determined using HRESIMS and extensive spectroscopic techniques (UV, IR, 1D-NMR, and 2D-NMR). The absolute configurations of the sugar moiety in these compounds were determined by using LC-MS analysis of acid-hydrolyzed derivatized monosaccharides. Biological evaluation showed that 7-10, 13, 14, 16 and 17 inhibit renal fibrosis in TGF-β1-induced kidney proximal tubular cells. In addition, 7, 8 and 14 were superior to nootkatone in inhibiting Fibronectin expression. The finding has significant relevance to our ongoing research on the anti-renal fibrosis activity of A. oxyphylla.

Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates

Chronic kidney disease (CKD) is caused by hypoxia in the renal tissue, leading to inflammation and increased migration of pathogenic cells. Studies showed that leukocytes directly sense hypoxia and respond by initiating gene transcription, encoding the 2-integrin adhesion molecules. Moreover, other mechanisms participate in hypoxia, including anemia. CKD-associated anemia is common, which induces and worsens hypoxia, contributing to CKD progression. Anemia correction can slow CKD progression, but it should be cautiously approached. In this comprehensive review, the underlying pathophysiology mechanisms and the impact of renal tissue hypoxia and anemia in CKD onset and progression will be reviewed and discussed in detail. Searching for the latest updates in PubMed Central, Medline, PubMed database, Google Scholar, and Google search engines were conducted for original studies, including cross-sectional studies, cohort studies, clinical trials, and review articles using different keywords, phrases, and texts such as "CKD progression, anemia in CKD, CKD, anemia effect on CKD progression, anemia effect on CKD progression, and hypoxia and CKD progression". Kidney tissue hypoxia and anemia have an impact on CKD onset and progression. Hypoxia causes nephron cell death, enhancing fibrosis by increasing interstitium protein deposition, inflammatory cell activation, and apoptosis. Severe anemia correction improves life quality and may delay CKD progression. Detection and avoidance of the risk factors of hypoxia prevent recurrent acute kidney injury (AKI) and reduce the CKD rate. A better understanding of kidney hypoxia would prevent AKI and CKD and lead to new therapeutic strategies.

Clinical Relevance of Computationally Derived Attributes of Peritubular Capillaries from Kidney Biopsies

Key Points

Computational image analysis allows for the extraction of new information from whole-slide images with potential clinical relevance. Peritubular capillary (PTC) density is decreased in areas of interstitial fibrosis and tubular atrophy when measured in interstitial fractional space. PTC shape (aspect ratio) is associated with clinical outcome in glomerular diseases.

Background

The association between peritubular capillary (PTC) density and disease progression has been studied in a variety of kidney diseases using immunohistochemistry. However, other PTC attributes, such as PTC shape, have not been explored yet. The recent development of computer vision techniques provides the opportunity for the quantification of PTC attributes using conventional stains and whole-slide images.

Methods

To explore the relationship between PTC characteristics and clinical outcome, n =280 periodic acid–Schiff-stained kidney biopsies (88 minimal change disease, 109 focal segmental glomerulosclerosis, 46 membranous nephropathy, and 37 IgA nephropathy) from the Nephrotic Syndrome Study Network digital pathology repository were computationally analyzed. A previously validated deep learning model was applied to segment cortical PTCs. Average PTC aspect ratio (PTC major to minor axis ratio), size (PTC pixels per PTC segmentation), and density (PTC pixels per unit cortical area) were computed for each biopsy. Cox proportional hazards models were used to assess associations between these PTC parameters and outcome (40% eGFR decline or kidney failure). Cortical PTC characteristics and interstitial fractional space PTC density were compared between areas of interstitial fibrosis and tubular atrophy (IFTA) and areas without IFTA.

Results

When normalized PTC aspect ratio was below 0.6, a 0.1, increase in normalized PTC aspect ratio was significantly associated with disease progression, with a hazard ratio (95% confidence interval) of 1.28 (1.04 to 1.59) (P = 0.019), while PTC density and size were not significantly associated with outcome. Interstitial fractional space PTC density was lower in areas of IFTA compared with non-IFTA areas.

Conclusions

Computational image analysis enables quantification of the status of the kidney microvasculature and the discovery of a previously unrecognized PTC biomarker (aspect ratio) of clinical outcome.

Roflumilast alleviates adenine-induced chronic kidney disease by regulating inflammatory biomarkers

The present investigation was carried out to explore the role of roflumilast, a PDE4 inhibitor, as a potential treatment option for chronic kidney disease. Forty-six male Wistar rats were divided into five groups: Control, Disease control (50 mg/kg Adenine p.o.), Adenine + Roflumilast (0.5, 1 and 1.5 mg/kg, p.o.). Various urinary and serum biomarkers, antioxidant status, histopathology, and protein expression of inflammatory markers were measured to investigate the effects of roflumilast on kidney functions. Adenine was found to elevate the levels of serum creatinine, urea, uric acid, sodium, potassium, chloride, magnesium, and phosphorus and reduce the level of serum calcium. Further, adenine significantly increased the serum TGF-β levels and reduced the anti-oxidant indices. Significant elevation was observed in protein expression of IL-1β, TNF-α, MCP-1, ICAM-1, and Fibronectin. Histopathologically, adenine caused thickening of the glomerular basement membrane, inflammatory cells infiltration, atrophy, and glomeruli deterioration. However, Roflumilast administration (1 mg/kg) remarkably decrease serum creatinine, urea, uric acid, sodium, potassium, chloride, magnesium, phosphorus by 61%, 40%, 44%, 41%, 49%, 58%, 59% and 42% respectively, and increase in calcium by 158%. Moreover, Roflumilast (1 mg/kg) significantly reduced serum TGF-β levels by 50% and elevated anti-oxidant indices by 257%, 112%, and 60%, respectively. The protein expression was significantly reduced by 5.5-fold, 7-fold, 5.7-fold, 6.2-fold, and 5.1-fold individually. Roflumilast noticeably improved the structure of glomeruli, tubules, and cellular functioning. The study confirmed that Roflumilast has the potential to ameliorate renal injury by reducing and regulating inflammatory responses.

Quercetin alleviates tubulointerstitial inflammation by inhibiting exosomes-mediated crosstalk between tubular epithelial cells and macrophages

BACKGROUND

Tubulointerstitial inflammation (TII) is a critical pathological feature of kidney disease leading to renal fibrosis, and its treatment remains a major clinical challenge. We sought to explore the role of quercetin, a potential exosomes inhibitor, in exosomes release and TII.

METHODS

The effects of quercetin on exosomes release and TII were examined by two TII mouse models: the unilateral ureteral obstruction (UUO) models and the LPS-induced mouse models. In vitro, exosomes-mediated crosstalk between tubular epithelial cells (TECs) and macrophages was performed to investigate the mechanisms by which quercetin inhibited exosomes and TII.

RESULTS

In this study, we found that exosomes-mediated crosstalk between TECs and macrophages contributed to the development of TII. In vitro, exosomes released from LPS-stimulated TECs induced increased expression of inflammatory cytokines and fibrotic markers in Raw264·7 cells and vice versa. Interestingly, heat shock protein 70 (Hsp70) or Hsp90 proteins could control exosomes release from TECs and macrophages both in vivo and in vitro. Importantly, quercetin, a previously recognized heat shock protein inhibitor, could significantly reduce exosomes release in TII models by down-regulating Hsp70 or Hsp90. Quercetin abrogated exosomes-mediated intercellular communication, which attenuated TII and renal fibrosis accordingly.

CONCLUSION

Quercetin could serve as a novel strategy for treatment of tubulointerstitial inflammation by inhibiting the exosomes-mediated crosstalk between tubules and macrophages.

Increased urinary albumin leakage is related to injuries of glomerular glycocalyx and podocytes, and associated with tubular dysfunction in preeclampsia

OBJECTIVE

The pathogenesis of preeclampsia (PE) is known to be endothelial cell damage; however, the existence of dysfunction in glomerular endothelial glycocalyx, podocytes and tubules remains unclear. The glomerular endothelial glycocalyx, basement membrane, podocytes, and tubules are permeability barriers against albumin excretion. This study aimed to assess the relationship between urinary albumin leakage and injuries of the glomerular endothelial glycocalyx, podocytes, and tubules in patients with PE.

METHODS

A total of 81 women with uncomplicated pregnancies (control, n = 22), PE (PE, n = 36), or gestational hypertension (GH) (GH, n = 23) were enrolled. We assessed urinary albumin and serum hyaluronan for glycocalyx injuries, podocalyxin for podocytes injuries, and urinary N-acetyl-β-d-glucosaminidase (NAG) and liver-type fatty acid-binding protein (l-FABP) for renal tubular dysfunctions.

RESULTS

The serum hyaluronan and the urinary podocalyxin levels were higher in the PE and GH groups. The urinary NAG and l-FABP levels were higher in the PE group. Urinary NAG and l-FABP levels positively correlated with urinary albumin excretion.

CONCLUSIONS

Our findings suggest that increased urinary albumin leakage is related to injuries of the glycocalyx and podocytes, and associated with tubular dysfunction in pregnant women with PE. The clinical trial described in this paper was registered at the UMIN Clinical Trials Registry under registration number UMIN000047875. URL of registration: https://centre6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000054437.

Notch Blockade Specifically in Bone Marrow-Derived FSP-1-Positive Cells Ameliorates Renal Fibrosis

BACKGROUND

The infiltration of inflammatory cells during a kidney injury stimulates myofibroblast activation leading to kidney fibrosis. Fibroblast-specific protein 1 (FSP-1) positive cells have been reported as either myofibroblasts or monocytes during tissue fibrosis. The functions of FSP-1⁺ cells that are associated with the development of renal fibrosis and the signaling pathways that regulate FSP-1⁺ cell activation have not been well defined.

METHODS

In mice with unilateral ureteral obstruction (UUO), we characterized FSP-1⁺ cells and determined the role of the Notch signaling pathway in the activation of bone marrow-derived FSP-1⁺ cells during kidney fibrosis.

RESULTS

In kidneys from mice with UUO, the FSP-1⁺ cells accumulated significantly in the tubulointerstitial area. By using immunostaining and FSP-1 reporter mice, we found that FSP-1 was co-stained with inflammatory cell markers, but not myofibroblast markers. Results from mice with bone marrow transplantations showed that FSP-1⁺ cells in obstructed kidneys represent a bone marrow-derived population of inflammatory cells. In cultured FSP-1⁺ cells, the inhibition of Notch signaling suppressed the activation and cytokine secretion of FSP-1⁺ cells that were induced by LPS but not by IL-4. The specific KO or blockade of Notch signaling in bone marrow-derived FSP-1⁺ cells suppressed UUO-induced ECM deposition, the infiltration of FSP-1⁺ inflammatory cells, and cytokine production. These responses ameliorated myofibroblast accumulation and renal fibrosis in obstructed kidneys.

CONCLUSION

Our study reveals that most FSP-1⁺ cells in obstructed kidneys are activated macrophages that are derived from bone marrow and that Notch signaling activates the production of M1 cytokines in FSP-1⁺ monocytes/macrophages, which is important for renal inflammation and fibrosis.

Esaxerenone inhibits the macrophage-to-myofibroblast transition through mineralocorticoid receptor/TGF-β1 pathway in mice induced with aldosterone

Renal fibrosis is the inevitable pathway of the progression of chronic kidney disease to end-stage renal disease, which manifests as progressive glomerulosclerosis and renal interstitial fibrosis. In a previous study, we observed severe interstitial fibrosis in the contralateral kidneys of 6-month unilateral ureteral obstruction (UUO) rats, which was accompanied by increased macrophage infiltration and phenotypic transformation; after eplerenone administration, these effects were reduced. Therefore, we hypothesized that this effect was closely related to mineralocorticoid receptor (MR) activation induced by the increased aldosterone (ALD) level. In this study, we used uninephrectomy plus continuous aldosterone infusion in mice to observe whether aldosterone induced macrophage-to-myofibroblast transition (MMT) and renal fibrosis and investigated the signaling pathways. Notably, aldosterone induced predominantly M1 macrophage-to-myofibroblast transition by activating MR and upregulating TGF-β1 expression, which promoted renal fibrosis. These effects were antagonized by the MR blocker esaxerenone. These findings suggest that targeting the MR/TGF-β1 pathway may be an effective therapeutic strategy for renal fibrosis.

Hydrogen-rich water reduced oxidative stress and renal fibrosis in rats with unilateral ureteral obstruction

BACKGROUND

Congenital obstructive nephropathy (CKD) is commonly implicated in the pathophysiology of chronic kidney disease occurring in the pediatric and adolescent age groups and the release of reactive oxygen species contribute to the worsening of renal fibrosis. Molecular hydrogen (H₂) protects against tissue injury by reducing oxidative stress. We evaluated the efficacy of oral H₂-rich water (HW) intake in preventing unilateral ureteral obstruction (UUO)-induced renal injury in rats.

METHODS

Male Sprague-Dawley UUO or control rats were administered with distilled water (DW) or HW for 2 weeks post-surgery. Histopathological and immunohistochemical analyses of kidney samples were performed.

RESULTS

Histological changes were not apparent in the sham-operated kidneys. However, UUO kidneys were found to have widened interstitial spaces and tubular dilatation. Compared with the UUO + DW group, HW administration attenuated tubulointerstitial injury and reduced interstitial fibrotic area, causing a substantial decline in the frequency of α-SMA-, ED-1-, and TGF-β1-positive cells in the UUO + HW group. The decrease in the klotho mRNA expression in the UUO + HW group was less pronounced than that in the UUO + DW group.

CONCLUSION

Oral HW intake reduced oxidative stress and prevented interstitial fibrosis in UUO kidneys, potentially involving klotho in the underlying mechanism.

IMPACT

Oral intake of hydrogen-rich water (HW) can reduce oxidative stress and suppress interstitial fibrosis in unilateral ureteral obstruction-induced renal injury in rats. This mechanism possibly involves klotho, which is known for its antiaging roles. The association between molecular hydrogen and klotho in renal fibrosis is well known; this is the first report on the association in a unilateral ureteral obstruction model. Drinking HW is a safe and convenient treatment for oxidative stress-induced pathologies, without side effects. As a prospect for future research, oral HW intake to treat oxidative stress may improve renal fibrosis in congenital obstructive nephropathy.

Monocytes transition to macrophages within the inflamed vasculature via monocyte CCR2 and endothelial TNFR2

Monocytes undergo phenotypic and functional changes in response to inflammatory cues, but the molecular signals that drive different monocyte states remain largely undefined. We show that monocytes acquire macrophage markers upon glomerulonephritis and may be derived from CCR2+CX3CR1+ double-positive monocytes, which are preferentially recruited, dwell within glomerular capillaries, and acquire proinflammatory characteristics in the nephritic kidney. Mechanistically, the transition to immature macrophages begins within the vasculature and relies on CCR2 in circulating cells and TNFR2 in parenchymal cells, findings that are recapitulated in vitro with monocytes cocultured with TNF-TNFR2–activated endothelial cells generating CCR2 ligands. Single-cell RNA sequencing of cocultures defines a CCR2-dependent monocyte differentiation path associated with the acquisition of immune effector functions and generation of CCR2 ligands. Immature macrophages are detected in the urine of lupus nephritis patients, and their frequency correlates with clinical disease. In conclusion, CCR2-dependent functional specialization of monocytes into macrophages begins within the TNF-TNFR2–activated vasculature and may establish a CCR2-based autocrine, feed-forward loop that amplifies renal inflammation.

Sacubitril/Valsartan Improves Progression of Early Diabetic Nephropathy in Rats Through Inhibition of NLRP3 Inflammasome Pathway

PURPOSE

Diabetic nephropathy (DN), a global disease, is the leading cause of end-stage renal disease. There is a lack of specific treatment for this disease, and early intervention in disease progression is essential. In this paper, we used a rat model of early diabetic nephropathy to explore the therapeutic mechanism of sacubitril/valsartan in rats with early diabetic nephropathy.

MATERIALS AND METHODS

Rats were grouped into 1 normal group; 2. Model group (DN group): STZ (45 mg/kg/d) induced early diabetic nephropathy rats; 3. Sac group: DN rats + Sac group (orally, 60 mg/kg/d) for 6 weeks. After 6 weeks, the levels of serum albumin (ALB), glucose (GLU), creatinine (Cr), urea nitrogen (BUN) and 24-h urinary protein excretion were measured. In renal tissue homogenates, NLRP3 inflammasome, proinflammatory factors IL1-β and TNF-α, oxidative stress MDA and pro-fibrotic cytokine TGF-β1 were performed. Histological analysis of kidneys by hematoxylin and eosin (HE), PAS and Masson trichrome staining.

RESULTS

1. Sacubitril/valsartan (Sac) significantly improved renal hypertrophy, proteinuria and serum albumin levels in rats with early diabetic nephropathy (P < 0.001), and decreased GLU, Scr (P<0.001), and BUN levels (P < 0.01).2. Light microscopy of renal tissues showed glomerular hypertrophy and interstitial inflammatory cell infiltration, and mean glomerular area (MGA) and mean glomerular volume (MGV) were crucially increased in early diabetic nephropathy (P < 0.001), and the Sac group showed reduced renal pathology and improved MGA and MGV (P < 0.001).3. Kidney tissue homogenate levels of NLRP3, Caspase-1, IL1-β, TNF-α, MDA and TGF-β1 were critically, increased in DN rats (P < 0.001), and SOD was significantly decreased. All these indicators above were improved after treatment (P < 0.0001).

CONCLUSION

Nlrp3-inflammasome promote progression of diabetic nephropathy through inflammation, fibrosis and oxidative stress; sacubitril/valsartan ameliorated early diabetes-induced renal damage by inhibiting NLRP3 pathway activation.

Protective Effects of Nootkatone on Renal Inflammation, Apoptosis, and Fibrosis in a Unilateral Ureteral Obstructive Mouse Model

Nootkatone is one of the major active ingredients of Alpiniae oxyphyllae, which has been used as both food and medicinal plants for the treatment of diarrhea, ulceration, and enuresis. In this study, we aimed to investigate whether nootkatone treatment ameliorated the progression of chronic kidney diseases (CKD) and clarified its underlying mechanisms in an obstructive nephropathy (unilateral ureteral obstructive; UUO) mouse model. Our results revealed that nootkatone treatment preventively decreased the pathological changes and significantly mitigated the collagen deposition as well as the protein expression of fibrotic markers. Nootkatone could also alleviate oxidative stress-induced injury, inflammatory cell infiltration, and renal cell apoptotic death in the kidneys of UUO mice. These results demonstrated for the first time that nootkatone protected against the progression of CKD in a UUO mouse model. It may serve as a potential therapeutic candidate for CKD intervention.

Intrarenal modulation of NF-κB activity attenuates cardiac injury in a swine model of CKD: a renal-cardio axis

Patients with chronic kidney disease (CKD) have a high cardiovascular mortality. CKD and heart failure (HF) coexist in up to 50% of patients, and both associate with inflammation. We aimed to define the cardiac phenotype of a novel swine model of CKD and test the hypothesis that inflammation of renal origin propels the development of precursors of HF in CKD. CKD was induced in 14 pigs, which were followed for 14 wk. Renal (multidetector computed tomography) and cardiac (echocardiography) hemodynamics were quantified before and 8 wk after single intrarenal administration of placebo or a biopolymer-fused peptide inhibitor of NF-κB that blocks NF-κB activity and decreases inflammatory activity (SynB1-ELP-p50i). Blood was collected to quantify cytokines (TNF-α, monocyte chemoattractant protein-1, and interleukins), markers of inflammation (C-reactive protein), and biomarkers of HF (atrial and brain natriuretic peptides). Pigs were then euthanized, and kidneys and hearts were studied ex vivo. Normal pigs were used as time-matched controls. Renal dysfunction in CKD was accompanied by cardiac hypertrophy and fibrosis, diastolic dysfunction, increased renal and cardiac expression of TNF-α, monocyte chemoattractant protein-1, and interleukins, canonical and noncanonical mediators of NF-κB signaling, circulating inflammatory factors, and biomarkers of HF. Notably, most of these changes were improved after intrarenal SynB1-SynB1-ELP-p50i, although cardiac inflammatory signaling remained unaltered. The translational traits of this model support its use as a platform to test novel technologies to protect the kidney and heart in CKD. A targeted inhibition of renal NF-κB signaling improves renal and cardiac function, suggesting an inflammatory renal-cardio axis underlying early HF pathophysiology in CKD.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a progressive disorder with high cardiovascular morbidity and mortality. This work supports the role of inflammatory cytokines of renal origin in renal-cardio pathophysiology in CKD and that the heart may be a target. Furthermore, it supports the feasibility of a new strategy in a translational fashion, using targeted inhibition of renal NF-κB signaling to offset the development of cardiac injury in CKD.

Genetic and pharmacological inhibition of fatty acid-binding protein 4 alleviated inflammation and early fibrosis after toxin induced kidney injury

Considerable data have suggested that acute kidney injury (AKI) is often incompletely repaired and could lead to chronic kidney disease (CKD). As we known, toxin-induced nephropathy triggers the rapid production of proinflammatory mediators and the prolonged inflammation allows the injured kidneys to develop interstitial fibrosis. In our previous study, fatty acid-binding protein 4 (Fabp4) has been reported to be involved in the process of AKI. However, whether Fabp4 plays crucial roles in toxin-induced kidney injury remained unclear. To explore the effect and mechanism of Fabp4 on toxin induced kidney injury, folic acid (FA) and aristolochic acid (AA) animal models were used. Both FA and AA injected mice developed severe renal dysfunction and dramatically inflammatory response (IL-6, MCP1 and TNF-a), which further lead to early fibrosis confirmed by the accumulation of extracellular matrix proteins (α-Sma, Fn, Col1 and Col4). Importantly, we found that FA and AA induced-kidney injury triggered the high expression of Fabp4 mRNA/protein in tubular epithelial cells. Furthermore, pharmacological and genetic inhibition of Fabp4 significantly attenuated FA and AA induced renal dysfunction, pathological damage, and early fibrosis via the regulation of inflammation, which is mediated by suppressing p-p65/p-stat3 expression via enhancing Pparγ activity. In summary, Fabp4 in tubular epithelial cells exerted the deleterious effects during the recovery of FA and AA induced kidney injury and the inhibition of Fabp4 might be an effective therapeutic strategy against the progressive AKI.

Macrophage interactions with collecting duct epithelial cells are capable of driving tubulointerstitial inflammation and fibrosis in immunoglobulin A nephropathy

BACKGROUND

Tubulointerstitial fibrosis is a powerful predictor of future progression inimmunoglobulin A (IgA) nephropathy (IgAN). Proximal tubular epithelial cells (PTECs), in concert with infiltrating macrophages, are regarded as the agents provocateurs for driving this fibrotic process. However, evidence is now emerging for a contributory role of the distal nephron. The aim of this study was to examine the potential influence of macrophages on collecting duct epithelial cells (CDECs) and their combined role in the progression of IgAN.

METHODS

CDECs were cultured with macrophage-conditioned media (MCM) generated from human monocyte cell lines U937 and THP-1 stimulated with or without 100 μg/mL galactose-deficient IgA1. CDECs were analysed for evidence of inflammation and fibrosis.

RESULTS

Staining of IgAN biopsies for CD68+ macrophages revealed the presence of macrophages juxtaposed to collecting ducts and within their lumina. CDEC exposed to MCM from IgA1-stimulated THP-1 cells (THP-1-IgA-MCM) exhibited markedly increased expression of neutrophil-associated gelatinase (NGAL) and proinflammatory cytokinesinterleukin (IL)-1β, tumour necrosis factor-α, IL-6 and IL-8 compared with MCM from non-IgA-stimulated THP-1 cells (THP-1-MCM). U937-IgA-MCM increased fibronectin levels and reduced E-cadherinmRNA expression. THP-1-IgA-MCM-derived exosomes induced similar increases in NGAL and cytokine expression while in cross-over experiments exosomes extracted from IL-1β-exposed CDEC induced IL-1β and IL-6 mRNA expression in both sets of macrophages. MiRnome analysis revealed that microRNA (miR)-146a, -155 and -200b exhibited a >2-fold increase in expression in CDEC treated with THP-1-IgA-MCM compared with THP-1-MCM. Enforced miR-146a suppression further enhanced NGAL expression, while ectopic miR-146a over-expression downregulated it. NGAL mRNA and miR-146a were upregulated in the biopsies of patients with progressive IgAN compared with non-progressive IgAN.

CONCLUSIONS

Taken together, these data suggest that CDEC-macrophage interactions potentially contribute to the tubulointerstitial fibrosis characteristic of progressive IgAN.

Specific populations of urinary extracellular vesicles and proteins differentiate type 1 primary hyperoxaluria patients without and with nephrocalcinosis or kidney stones

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is associated with nephrocalcinosis (NC) and calcium oxalate (CaOx) kidney stones (KS). Populations of urinary extracellular vesicles (EVs) can reflect kidney pathology. The aim of this study was to determine whether urinary EVs carrying specific biomarkers and proteins differ among PH1 patients with NC, KS or with neither disease process.

METHODS

Mayo Clinic Rare Kidney Stone Consortium bio-banked cell-free urine from male and female PH1 patients without (n = 10) and with NC (n = 6) or KS (n = 9) and an eGFR > 40 mL/min/1.73 m2 were studied. Urinary EVs were quantified by digital flow cytometer and results expressed as EVs/ mg creatinine. Expressions of urinary proteins were measured by customized antibody array and results expressed as relative intensity. Data were analyzed by ANCOVA adjusting for sex, and biomarkers differences were considered statistically significant among groups at a false discovery rate threshold of Q < 0.20.

RESULTS

Total EVs and EVs from different types of glomerular and renal tubular cells (11/13 markers) were significantly (Q < 0.20) altered among PH1 patients without NC and KS, patients with NC or patients with KS alone. Three cellular adhesion/inflammatory (ICAM-1, MCP-1, and tissue factor) markers carrying EVs were statistically (Q < 0.20) different between PH1 patients groups. Three renal injury (β2-microglobulin, laminin α5, and NGAL) marker-positive urinary EVs out of 5 marker assayed were statistically (Q < 0.20) different among PH1 patients without and with NC or KS. The number of immune/inflammatory cell-derived (8 different cell markers positive) EVs were statistically (Q < 0.20) different between PH1 patients groups. EV generation markers (ANO4 and HIP1) and renal calcium/phosphate regulation or calcifying matrixvesicles markers (klotho, PiT1/2) were also statistically (Q < 0.20) different between PH1 patients groups. Only 13 (CD14, CD40, CFVII, CRP, E-cadherin, EGFR, endoglin, fetuin A, MCP-1, neprilysin, OPN, OPGN, and PDGFRβ) out of 40 proteins were significantly (Q < 0.20) different between PH1 patients without and with NC or KS.

CONCLUSIONS

These results imply activation of distinct renal tubular and interstitial cell populations and processes associated with KS and NC, and suggest specific populations of urinary EVs and proteins are potential biomarkers to assess the pathogenic mechanisms between KS versus NC among PH1 patients.

Anti-Inflammatory, Antioxidant, and Antifibrotic Effects of Kefir Peptides on Salt-Induced Renal Vascular Damage and Dysfunction in Aged Stroke-Prone Spontaneously Hypertensive Rats

The increased prevalence of renal dysfunction and chronic kidney disease (CKD) and the high costs and poor outcomes of treatment are a significant health issue. The consequence of chronic high blood pressure is the increased prevalence of target organ end-stage renal disease, which has been proven to be a strong independent risk factor for adverse cardiovascular disease. A previous study showed that kefir products have anti-inflammatory and anti-hypertensive activities and immunological modulation functions. However, no data regarding the beneficial effects of kefir peptides (KPs) on salt-induced renal damage or related kidney diseases are available. In this study, KPs were orally administered to aged salt-induced stroke-prone spontaneously hypertensive (SHRSP) rats, and the effects of KPs against inflammation and oxidative stress and their ability to protect against renal dysfunction were evaluated. Fifty-five-week-old SHRSP rats under induction with 1% NaCl in drinking water for 4 weeks showed multiple renal injuries with increased renal inflammation, fibrosis, oxidative stress, tubular atrophy, and glomerulosclerosis. In contrast, oral gavage with KPs reduced the urine protein to creatinine (UPC) ratio, the fractional excretion of electrolytes (FeNa and FeCl), extracellular matrix deposition, and the interstitial fibrotic α-smooth muscle actin (α-SMA) levels in salt-induced SHRSP rats. The renal infiltration of inflammatory cells; the release of monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), endothelin-1 (ET-1), and the cytokine nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) and transforming growth factor-β (TGF-β); the reactive oxygen species (ROS) levels; and histopathological lesions were also decreased in salt-induced SHRSP rats. Furthermore, KP treatment significantly increased the renal superoxide dismutase (SOD) activity and the glomerular filtration rate (GFR), which exerted potent protection against salt-induced chronic kidney disease in SHRSP rats. The results of this study suggest that KPs ameliorate salt-induced renal damage, tubular atrophy, and glomerular dysfunction through anti-inflammatory, antioxidative stress, and antifibrotic activities, and might be a promising protective agent against high salt-induced renovascular-related diseases.

Electrophoretic analysis (sds-page) of canine urinary proteins according to the stage of chronic kidney disease

ABSTRACT Glomerular proteinuria is characterized by the loss of high-molecular-weight proteins (HMWPs), while tubulointerstitial proteinuria is characterized by the loss of low-molecular-weight proteins (LMWPs). The objective was to assess the molecular weight of urinary proteins (MWUP) in dogs with naturally acquired CKD and determine the proportion of HMWPs and LMWPs according to CKD stage. Twenty-eight dogs with CKD were recruited and divided into 4 groups based on serum creatinine (Cr) levels (group1: Cr<1,4, n=8; group2: 1,4<Cr<2,0, n=6; group3: 2,1<Cr<5, n=9; group4: Cr>5,0, n=5). The control group consisted of 5 healthy dogs. The MWUP was determined by SDS-PAGE. The urinary protein-to-creatinine ratio (UP/C) was used to quantitatively assess proteinuria. The electrophoresis pattern revealed a proportionally greater loss of HMWPthan of LMWP in all groups with CKD and an increased loss of LMWP in group 4 (P<0.05). These results suggest a predominance of glomerular injuries throughout all stages of CKD in these dogs and an increase in tubulointerstitial injury towards the end-stage of the disease. The results of the present study support the recommendation of SDS-PAGE as an effective technique for the qualitative assessment of proteinuria, as well as a method for assessing the severity and location of renal injury.

Inflammaging and Complement System: A Link Between Acute Kidney Injury and Chronic Graft Damage

The aberrant activation of complement system in several kidney diseases suggests that this pillar of innate immunity has a critical role in the pathophysiology of renal damage of different etiologies. A growing body of experimental evidence indicates that complement activation contributes to the pathogenesis of acute kidney injury (AKI) such as delayed graft function (DGF) in transplant patients. AKI is characterized by the rapid loss of the kidney's excretory function and is a complex syndrome currently lacking a specific medical treatment to arrest or attenuate progression in chronic kidney disease (CKD). Recent evidence suggests that independently from the initial trigger (i.e., sepsis or ischemia/reperfusions injury), an episode of AKI is strongly associated with an increased risk of subsequent CKD. The AKI-to-CKD transition may involve a wide range of mechanisms including scar-forming myofibroblasts generated from different sources, microvascular rarefaction, mitochondrial dysfunction, or cell cycle arrest by the involvement of epigenetic, gene, and protein alterations leading to common final signaling pathways [i.e., transforming growth factor beta (TGF-β), p16 ink4a , Wnt/β-catenin pathway] involved in renal aging. Research in recent years has revealed that several stressors or complications such as rejection after renal transplantation can lead to accelerated renal aging with detrimental effects with the establishment of chronic proinflammatory cellular phenotypes within the kidney. Despite a greater understanding of these mechanisms, the role of complement system in the context of the AKI-to-CKD transition and renal inflammaging is still poorly explored. The purpose of this review is to summarize recent findings describing the role of complement in AKI-to-CKD transition. We will also address how and when complement inhibitors might be used to prevent AKI and CKD progression, therefore improving graft function.

Pharmacological effects of icariin

Icariin (ICA) is a principal active component from traditional Chinese medicine Epimedium grandiflorum. To explain its traditional medical usages by modern science, a variety of pharmacological effects have been studied for ICA. In this review, we summarized the pharmacokinetics of ICA as well as its pharmacological mechanisms in neurodegenerative disease, cardiovascular disease, anti-osteoporosis, anti-inflammation, anti-oxidative stress, anti-depression and anti-tumors.

LncRNA HOXA11-AS regulates calcium oxalate crystal-induced renal inflammation via miR-124-3p/MCP-1

Long noncoding RNA (lncRNA) has been suggested to play an important role in a variety of diseases over the past decade. In a previous study, we identified a novel lncRNA, termed HOXA11‐AS, which was significantly up‐regulated in calcium oxalate (CaOx) nephrolithiasis. However, the biological function of HOXA11‐AS in CaOx nephrolithiasis remains poorly defined. Here, we demonstrated that HOXA11‐AS was significantly up‐regulated in CaOx nephrolithiasis both in vivo and in vitro. Gain‐/loss‐of‐function studies revealed that HOXA11‐AS inhibited proliferation, promoted apoptosis and aggravated cellular damage in HK‐2 cells exposed to calcium oxalate monohydrate (COM). Further investigations showed that HOXA11‐AS regulated monocyte chemotactic protein 1 (MCP‐1) expression in HK‐2 cell model of CaOx nephrolithiasis. In addition, online bioinformatics analysis and dual‐luciferase reporter assay results showed that miR‐124‐3p directly bound to HOXA11‐AS and the 3'UTR of MCP‐1. Furthermore, rescue experiment results revealed that HOXA11‐AS functioned as a competing endogenous RNA to regulate MCP‐1 expression through sponging miR‐124‐3p and that overexpression of miR‐124‐3p restored the inhibitory effect of proliferation, promotion effects of apoptosis and cell damage induced by HOXA11‐AS overexpression. Taken together, HOXA11‐AS mediated CaOx crystal–induced renal inflammation via the miR‐124‐3p/MCP‐1 axis, and this outcome may provide a good potential therapeutic target for nephrolithiasis.

Complement Activation in Progression of Chronic Kidney Disease

Chronic kidney disease (CKD) is a public health problem worldwide, with increasing incidence and prevalence. The mechanisms underlying the progression to end-stage renal disease (ESRD) is not fully understood. The complement system was traditionally regarded as an important part of innate immunity required for host protection against infection and for maintaining host hemostasis. However, compelling evidence from both clinical and experimental studies has strongly incriminated complement activation as a pivotal pathogenic mediator of the development of multiple renal diseases and progressive replacement of functioning nephrons by fibrosis. Both anaphylatoxins, i.e., C3a and C5a, and membrane attack complex (MAC) contribute to the damage that occurs during chronic renal progression through various mechanisms including direct proinflammatory and fibrogenic activity, chemotactic effect, activation of the renal renin-angiotensin system, and enhancement of T-cell immunity. Evolving understanding of the mechanisms of complement-mediated renal injury has led to the emergence of complement-targeting therapeutics. A variety of specific antibodies and inhibitors targeting complement components have shown efficacy in reducing disease in animal models. Moreover, building on these advances, targeting complement has gained encouraging success in treating patients with renal diseases such as atypical hemolytic uremic syndrome (aHUS). Nevertheless, it still requires a great deal of effort to develop inhibitors that can be applied to treat more patients effectively in routine clinical practice.

Interleukin‑33 promotes obstructive renal injury via macrophages

Chronic kidney disease is the outcome of most kidney diseases, and renal fibrosis is a pathological process involved in the progression of these disorders. The role of interleukin (IL)‑33 was previously investigated in fibrotic disorders affecting various organs, including liver, lungs and heart; however, its role in renal fibrosis remains unclear. Previous studies have demonstrated that macrophages are involved in obstructive renal injury. In the present study, the roles of IL‑33 and macrophages on renal fibrosis were investigated using a mouse model of unilateral ureteral obstruction (UUO). Compared with non‑obstructed kidneys, the expression levels of IL‑33 and its receptor, interleukin 1 receptor like 1, increased after UUO. Furthermore, the infiltration of macrophages and the degree of renal fibrosis increased after treatment with IL‑33. Additionally, the expression level of arginase‑1, a marker of M2 macrophages, increased in renal tissue. After depletion of macrophages, the administration of exogenous IL‑33 was not sufficient to reverse the reduction in fibrosis caused by elimination of these cells. Collectively, the present results suggested that IL‑33 promoted renal fibrosis in UUO‑induced renal injury by regulating macrophage polarization.

The antifibrotic and anti-inflammatory effects of icariin on the kidney in a unilateral ureteral obstruction mouse model

BACKGROUND

The pathology change of renal tubulointerstitial fibrosis is a critical feature of chronic kidney disease (CKD), regardless of the primary insults. The infiltration of inflammatory cells and the consecutive secretion of profibrotic factors are frequently and conspicuously observed during the development of renal fibrosis. Icariin, an active polyphenol of the Epimedium genus, has been found to alleviate the symptoms of chronic diseases like diabetes, neurodegeneration, and heart and renal diseases. The effect and mechanism of icariin on the prevention of CKD-associated renal fibrosis still needed clarification.

PURPOSE

The aims of this study were to investigate whether icariin treatment improves the development of CKD-associated renal fibrosis and its possible mechanism.

METHODS

An experimental unilateral ureteral obstruction (UUO)-induced chronic renal fibrosis mouse model was used. Mice were orally administered with icariin (20 mg/kg/day) for 3 consecutive days before and 14 consecutive days after UUO surgery.

RESULTS

The pathological changes, collagen deposition, and protein expressions of profibrotic factors (transforming growth factor-β and connective tissue growth factor) and fibrotic markers (α-smooth muscle actin and fibronectin), which were significantly elevated in the kidneys of UUO mice, could be significantly reversed by icariin treatment. Icariin treatment also significantly inhibited the increased Smad2/3 and decreased E-cadherin protein expressions in the kidneys of UUO mice. Icariin treatment prominently mitigated the protein expression of proinflammatory factors like nuclear factor-κB, cyclooxygenase-2, interleukin 1-β and prooxidative enzyme (NADPH oxidase-4), and it increased the protein expression of antioxidative enzymes (superoxide dismutase and catalase).

CONCLUSION

Icariin treatment protects against CKD-associated renal fibrosis via its antifibrotic and anti-inflammatory properties. Icariin may serve as a therapeutic agent in the prevention of CKD-associated renal fibrosis.

FABP4 contributes to renal interstitial fibrosis via mediating inflammation and lipid metabolism

Fatty acid binding protein 4 (FABP4), a subtype of fatty acid-binding protein family, shows critical roles in metabolism and inflammation. However, its roles on regulating renal interstitial fibrosis (RIF) remain unclear. In this work, LPS-stimulated in vitro models on NRK-52E and NRK-49F cells, and in vivo UUO models in rats and mice were established. The results showed that comparing with control groups or sham groups, the expression levels of α-SMA, COL1A, COL3A, IL-1β, IL-6, and TNF-α in LPS-stimulated cells or UUO animals were significantly increased. Meanwhile, the levels of TC, TG, and free fatty acid were also significantly increased as well as the obvious lipid droplets, and the serum levels of BUN, Cr were significantly increased with large amounts of collagen deposition in renal tissues. Further investigation showed that compared with control groups or sham groups, the expression levels of FABP4 in LPS-stimulated cells and UUO animals were significantly increased, resulting in down- regulating the expression levels of PPARγ, upregulating the levels of p65 and ICAM-1, and decreasing the expression levels of ACADM, ACADL, SCP-2, CPT1, EHHADH, and ACOX1. To deeply explore the mechanism of FABP4 in RIF, FABP4 siRNA and inhibitor interfered cell models, and UUO model on FABP4 knockout (KO) mice were used. The results showed that the expression levels of α-SMA, COL1A, and COL3A were significantly decreased, the deposition of lipid droplets decreased, and the contents of TC, TG, and free fatty acids were significantly decreased after gene silencing. Meanwhile, the expression levels of PPAR-γ, ACADM, ACADL, SCP-2, CPT1, EHHADH, and ACOX1 were upregulated, the levels of p65 and ICAM-1 were downregulated, and the mRNA levels of IL-1β, IL-6, and TNF-α were decreased. Our results supported that FABP4 contributed to RIF via promoting inflammation and lipid metabolism, which should be considered as one new drug target to treat RIF.

Understanding and managing atherosclerotic renovascular disease: still a work in progress

Atherosclerotic renovascular disease (ARVD) is an unresolved therapeutic dilemma despite extensive pre-clinical and clinical studies. The pathophysiology of the disease has been widely studied, and many factors that may be involved in progressive renal injury and cardiovascular risk associated with ARVD have been identified. However, therapies and clinical trials have focused largely on attempts to resolve renal artery stenosis without considering the potential need to treat the renal parenchyma beyond the obstruction. The results of these trials show a staggering consistence: although nearly 100% of the patients undergoing renal angioplasty show a resolution of the vascular obstruction, they do not achieve significant improvements in renal function or blood pressure control compared with those patients receiving medical treatment alone. It seems that we may need to take a step back and reconsider the pathophysiology of the disease in order to develop more effective therapeutic strategies. This mini-review discusses potential therapeutic alternatives that focus on the renal parenchyma distal to the vascular obstruction and may provide additional tools to enhance current treatment of ARVD.

The use of hydrogels for cell-based treatment of chronic kidney disease

Chronic kidney disease (CKD) is a major and growing public health concern with increasing incidence and prevalence worldwide. The therapeutic potential of stem cell therapy, including mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) holds great promise for treatment of CKD. However, there are significant bottlenecks in the clinical translation due to the reduced number of transplanted cells and the duration of their presence at the site of tissue damage. Bioengineered hydrogels may provide a route of cell delivery to enhance treatment efficacy and optimise the targeting effectiveness while minimising any loss of cell function. In this review, we highlight the advances in stem cell therapy targeting kidney disease and discuss the emerging role of hydrogel delivery systems to fully realise the potential of adult stem cells as a regenerative therapy for CKD in humans. MSCs and EPCs mediate kidney repair through distinct paracrine effects. As a delivery system, hydrogels can prolong these paracrine effects by improving retention at the site of injury and protecting the transplanted cells from the harsh inflammatory microenvironment. We also discuss the features of a hydrogel, which may be tuned to optimise the therapeutic potential of encapsulated stem cells, including cell-adhesive epitopes, material stiffness, nanotopography, modes of gelation and degradation and the inclusion of bioactive molecules. This review concludes with a discussion of the challenges to be met for the widespread clinical use of hydrogel delivery system of stem cell therapy for CKD.

High-glucose-induced changes in macrophage secretome: regulation of immune response

Secretory products from infiltrating macrophages have been thought to play crucial roles in development and progression of diabetic complications in various tissues/organs. Nevertheless, diabetes-induced changes in macrophage secretory products remained largely unknown. We thus analyzed high-glucose (HG)-induced changes in secretome of human macrophages derived from U937 human monocytic cell line after phorbol 12-myristate 13-acetate (PMA) activation. Serum-free culture supernatants were collected from macrophages exposed to 5.5 mM glucose (NG-M-sup) (normal control), 25 mM glucose (HG-M-sup), or 5.5 mM glucose + 19.5 mM mannitol (MN-M-sup) (osmotic control) for 16 h. After dialysis and lyophilization, secreted proteins were subjected to 2-DE analysis (n = 5 gels derived from 5 independent cultures per group). Quantitative analysis and statistics revealed 23 protein spots whose secretory levels significantly differed among the three conditions. These proteins were successfully identified by nanoLC-ESI-MS/MS analyses and changes in levels of heat shock protein 90 (HSP90), HSP70, HSP60, and β-actin were confirmed by Western blotting. Global protein network and functional enrichment analyses revealed that the altered proteins in HG-M-sup were involved mainly in regulation of immune response that might communicate with other bystander cells through the release of extracellular vesicles. These data may lead to a wider view of pathogenic mechanisms of diabetic complications.

Bone marrow‑derived mesenchymal stem cell‑conditioned medium attenuates tubulointerstitial fibrosis by inhibiting monocyte mobilization in an irreversible model of unilateral ureteral obstruction

Mesenchymal stem cell‑conditioned medium (MSC‑CM) contains various cytokines (osteopontin and macrophage colony stimulating factor 1) secreted by MSCs and may modulate the immune response in tubulointerstitial fibrosis. The aim of the present study was to investigate whether MSC‑CM treatment may affect B cell‑dependent immune responses, which have previously been reported to facilitate the renal fibrotic processes following unilateral ureteral obstruction (UUO). In the present study, histological analysis, flow cytometry, western blotting and reverse transcription‑quantitative polymerase chain reaction were performed. MSC‑CM treatment was observed to impede renal infiltration of B lymphocytes and the expression of CC chemokine ligand‑2. Additionally, UUO suppressed the subsequent recruitment of monocytes/macrophages to the kidney, limited local inflammation and attenuated renal fibrosis. The findings of the present study identified a potential mechanism of MSC‑CM in ameliorating the UUO‑kidney.

Role of hypoxia-inducible factor-1 in the development of renal fibrosis in mouse obstructed kidney: Special references to HIF-1 dependent gene expression of profibrogenic molecules

The aim of the study is to clarify the role of hypoxia-inducible factor-1 (HIF-1) in the development of renal fibrosis in mouse obstructive nephropathy. We used mice with floxed HIF-1α alleles and tamoxifen-inducible Cre/ERT2 recombinase under ubiquitin C promoter to induce global HIF-1α deletion. Following tamoxifen administration, mice were subjected to unilateral ureteral obstruction (UUO). At 3, 7 and 14 days after UUO, renal gene expression profiles and interstitial fibrosis were assessed. HIF-1 dependent up-regulation of prolyl hydroxylase 3 and glucose transporter-1 was observed in the obstructed kidney at 3 and 7 days but not at 14 days after UUO. Various factors promoting fibrosis were up-regulated during the development of fibrosis. HIF-1 dependent gene expression of profibrotic molecules, plasminogen activator inhibitor 1, connective tissue growth factor, lysyl oxidase like 2 and transglutaminase 2 was observed in the obstructed kidney but such HIF-1 dependency was limited to the early onset of renal fibrosis. Global HIF-1 deletion tended to attenuate interstitial collagen I deposition at 3 days but had no effects thereafter. It is suggested that HIF-1 dependent profibrogenic mechanisms are operating at the early onset of renal fibrosis but its contribution declines with the progression in mouse UUO model.

Reducing Inflammatory Cytokine Production from Renal Collecting Duct Cells by Inhibiting GATA2 Ameliorates Acute Kidney Injury

Acute kidney injury (AKI) is a leading cause of chronic kidney disease. Proximal tubules are considered to be the primary origin of pathogenic inflammatory cytokines in AKI. However, it remains unclear whether other cell types, including collecting duct (CD) cells, participate in inflammatory processes. The transcription factor GATA2 is specifically expressed in CD cells and maintains their cellular identity. To explore the pathophysiological function of GATA2 in AKI, we generated renal tubular cell-specific Gata2 deletion (G2CKO) mice and examined their susceptibility to ischemia reperfusion injury (IRI). Notably, G2CKO mice exhibited less severe kidney damage, with reduced granulomacrophagic infiltration upon IRI. Transcriptome analysis revealed that a series of inflammatory cytokine genes were downregulated in GATA2-deficient CD cells, suggesting that GATA2 induces inflammatory cytokine expression in diseased kidney CD cells. Through high-throughput chemical library screening, we identified a potent GATA inhibitor. The chemical reduces cytokine production in CD cells and protects the mouse kidney from IRI. These results revealed a novel pathological mechanism of renal IRI, namely, that CD cells produce inflammatory cytokines and promote IRI progression. In injured kidney CD cells, GATA2 exerts a proinflammatory function by upregulating inflammatory cytokine gene expression. GATA2 can therefore be considered a therapeutic target for AKI.

Influence and analysis of low-dosage steroid therapy in severe aristolochic acid nephropathy patients

AIM

To investigate the effect of low-dosage steroid therapy in patients with severe aristolochic acid nephropathy (AAN).

METHODS

Forty-three chronic AAN patients in the Peking Union Medical College Hospital and the First Affiliated Hospital of Xinxiang Medical College were included in this study from November 1998 to October 2013. According to the treatment method, the patients were divided into a steroid group (SG, n = 25) and a control group (CG, n = 18). The serum biochemical indicators at the basement in the two groups exhibited no obvious statistical differences. In comparison with the baseline data, the levels of serum creatinine at 3, 6, 9, and 12 months were analyzed. The blood pressure, haemoglobin, serum biochemical indicators, and the side-effects of steroid application were also observed. Urinary macrophage chemoattractant protein-1 (MCP-1) and transforming growth factor-1 (TGF-1) amounts were measured as well.

RESULTS

(i) The serum creatinine content in the CG group was significantly higher than the baseline level during the follow-up(6, 9, and 12 months later), whereas in the SG group it decreased during the 3-6 month period and remained stable within 1 year. (ii) The biochemical indicators, blood pressure, and haemoglobin persisted stable. (iii) The side-effects of low-dosage steroid therapy were not severe and were tolerated by the AAN patients. (4) Urinary MCP-1 and TGF-1 concentrations were positively correlated with serum creatinine and decreased in the SG group.

CONCLUSION

Low-dosage steroid therapy reversed or delayed the renal failure progression in severe chronic AAN patients, which may be associated with the suppression of MCP-1 and TGF-β1 activities.

Kidney Injury Molecule-1 is Elevated in Nephropathy and Mediates Macrophage Activation via the Mapk Signalling Pathway

BACKGROUND/AIMS

Kidney injury molecule-1 (KIM-1) is highly expressed in renal tubular cells after injury and is usually regarded as an early biomarker of acute kidney injury(AKI). The aim of this study was to determine the role of KIM-1 in the development of renal tubular injury Methods: Clinical samples, three different animal models and in vitro experiments were utilized to determine the possible mechanism underlying the involvement of KIM-1 in kidney injury.

RESULTS

Both plasma and urinary KIM-1 expression levels were significantly higher in AKI and chronic kidney disease (CKD) patients than in healthy volunteers, and urinary KIM-1 expression was significantly higher in CKD patients than in AKI patients. According to the results of our research involving three different mouse models, KIM-1 expression was significantly increased during the early stage of kidney injury and was persistently elevated in renal fibrosis. Our immunofluorescence staining results indicated that KIM-1-positive tubules were surrounded by macrophage infiltrates in regions of kidney injury. Moreover, our transwell, western blotting and real-time PCR data showed that macrophage migration and phenotype transitions were mediated by KIM-1 through the mitogen-activated protein kinase (MAPK) pathway. MAPK pathway inhibition could significantly reverse the effects of KIM-1 with respect to these macrophage phenotype changes and migration.

CONCLUSIONS

KIM-1 expression was markedly elevated in both acute and chronic kidney injury and may play a pivotal role in macrophage activation via the MAPK pathway in kidney disease.

CCR2 contributes to the recruitment of monocytes and leads to kidney inflammation and fibrosis development

Chemokines are a large family of proteins that, once associated to its receptor on leukocytes, stimulate their movement and migration from blood to tissues. Once in the tissue, immune cells trigger inflammation that, when uncontrolled, leads to fibrosis development. Among the immune cells, macrophages take a special role in fibrosis formation, since macrophage depletion reflects less collagen deposition. The majority of tissue macrophages is derived from monocytes, especially monocytes expressing the chemokine receptor CCR2. Here, we investigated the role of infiltrating CCR2⁺ cells in the development of fibrosis, and specifically, the dynamic of infiltration of these cells into kidneys under chronic obstructive lesion. Using liposome-encapsulated clodronate, we observed that macrophage depletion culminated in less collagen deposition and reduced chemokines milieu that were released in the damaged kidney after obstructive nephropathy. We also obstructed the kidneys of CCL3^-/-, CCR2^-/-, CCR4^-/-, CCR5^-/-, and C57BL/6 mice and we found that among all animals, CCR2^-/- mice demonstrated the more robust protection, reflected by less inflammatory and Th17-related cytokines and less collagen formation. Next we evaluated the dynamic of CCR2^+/rfp cell infiltration and we observed that they adhere onto the vessels at early stages of disease, culminating in increased recruitment of CCR2^+/rfp cells at later stages. On the other hand, CCR2^rfp/rfp animals exhibited less fibrosis formation and reduced numbers of recruited cells at later stages. We have experimentally demonstrated that inflammatory CCR2⁺ cells that reach the injured kidney at initial stages after tissue damage are responsible for the fibrotic pattern observed at later time points in the context of UUO.

Endoplasmic reticulum stress inhibition attenuates hypertensive chronic kidney disease through reduction in proteinuria

Endoplasmic reticulum (ER) stress is implicated in chronic kidney disease (CKD) development in patients and in animal models. Here we show that ER stress inhibition through 4-phenylbutyric acid (4-PBA) administration decreases blood pressure, albuminuria, and tubular casts in an angiotensin II/deoxycorticosterone acetate/salt murine model of CKD. Lower albuminuria in 4-PBA-treated mice was associated with higher levels of cubilin protein in renal tissue membrane fractions. 4-PBA decreased renal interstitial fibrosis, renal CD3⁺ T-cell and macrophage infiltration, mRNA expression of TGFβ1, Wnt signaling molecules, and ER stress-induced pro-inflammatory genes. CHOP deficient mice that underwent this model of CKD developed hypertension comparable to wild type mice, but had less albuminuria and tubular casts. CHOP deficiency resulted in higher nephrin levels and decreased glomerulosclerosis compared to wild type mice; this effect was accompanied by lower macrophage infiltration and fibrosis. Our findings portray ER stress inhibition as a means to alleviate hypertensive CKD by preserving glomerular barrier integrity and tubular function. These results demonstrate ER stress modulation as a novel target for preserving renal function in hypertensive CKD.

Presentation, pathology and prognosis of renal disease in type 2 diabetes

OBJECTIVE

Non-diabetic renal disease (NDRD) is common in patients with type 2 diabetes (T2D), but the relationship between its presentation and prognosis is unknown.

RESEARCH DESIGN AND METHODS

In a retrospective cohort study, we compared renal and patient survival among 263 patients with T2D who had native renal biopsies between 2002 and 2008 from three Auckland hospitals in New Zealand. The presence of diabetic nephropathy (DN), NDRD or mixed (DN and NDRD) was determined from biopsy. We examined clinical associations according to NDRD etiologies and mode of presentation-acute (defined by acute kidney injury (AKI)) or non-acute. Patients were followed until end-stage renal disease, death or December 2015. Survival was compared using Log-rank test.

RESULTS

94 (36%) patients had DN, 72 (27%) had NDRD, and 97 (37%) had mixed pathologies. Obesity-related focal segmental glomerulosclerosis was the most common NDRD (46%) in patients with non-acute presentations, whereas interstitial nephritis or immune-complex glomerulonephritides were the most prevalent in those with acute presentations (60%). DN was commonly associated with AKI (p<0.001). The prevalence of DN increased with diabetes duration (p<0.001), but NDRD was still found in 55% of subjects with ≥14 years T2D. NDRD was strongly associated with the absence of retinopathy (p<0.001). Renal survival was best in the NDRD group (p<0.001). Among those with DN, renal prognosis was worse in those with more advanced DN lesions and those with an acute presentation (p<0.001). The proportion of all-cause mortality was similar in all three groups, but overall survival was poorest in the DN group (p=0.025).

CONCLUSIONS

Renal disease in patients with T2D is heterogeneous. The renal prognosis differs markedly according to histopathological diagnosis and mode of presentation.

Transfusion of CD206+ M2 Macrophages Ameliorates Antibody-Mediated Glomerulonephritis in Mice

Macrophages are multifunctional immune cells that may either drive or modulate disease pathogenesis, depending on the activated phenotype. In this study, we investigated the protective effects of CD206⁺ M2 macrophages against nephrotoxic serum nephritis in mice. We found that these immunosuppressive macrophages, derived from bone marrow and stimulated with IL-4/IL-13 [CD206⁺ M2 bone marrow-derived macrophages (M2BMMs)], protected against renal injury, decreased proteinuria, and diminished the infiltration of CD68⁺ macrophages, neutrophils, and T cells into glomerular tissue. Comparable therapeutic results were obtained with CD206⁺ M2 cells derived from induced pluripotent stem cells. Notably, CD206⁺ M2BMMs, which retained an M2 signature, could elicit a switch of M1 to M2 phenotype in co-cultured macrophages. Moreover, these cells were found to induce the production of regulatory T cells in the spleen and renal draining lymph node. Accordingly, mRNA expression of the T helper 1 cytokines tumor necrosis factor-α, interferon-β, interferon-γ, and IL-12 was significantly reduced in kidneys from mice treated with CD206⁺ M2BMMs. Taken together, the data suggest that CD206⁺ M2 may have therapeutic potential against antibody-mediated glomerular injury and presents its therapeutic value for the treatment of crescentic nephritis in humans.

Inhibition of Macrophage Migration Inhibitory Factor Protects against Inflammation and Matrix Deposition in Kidney Tissues after Injury

Background. Macrophage migration inhibitory factor (MIF) is an important immunoregulatory cytokine involved in inflammation, which may be one important reason resulting in matrix deposition in renal tissues after injury. However, the underlying mechanisms have not yet been elucidated. Methods and Results. We uncovered a crucial role of MIF in inflammation and collagen deposition in vivo and in vitro. In rats, ureteral obstruction induced tubular injury, matrix accumulation, and inflammatory cell infiltration. Additionally, enhanced MIF levels in the obstructed kidneys were closely related to the increasing numbers of CD68-positive macrophages. These obstruction-induced injuries can be relieved by recanalization, consequently resulting in downregulated expression of MIF and its receptor CD74. Similarly, ischemia reperfusion induced renal injury, and it was accompanied by elevated MIF levels and macrophages infiltration. In cultured tubular epithelial cells (TECs), aristolochic acid (AA) promoted matrix production and increased MIF expression, as well as the release of macrophage-related factors. Inhibition of MIF with an antagonist ISO-1 resulted in the abolishment of these genotypes in AA-treated TECs. Conclusion. MIF plays an important role in macrophage-related inflammation and matrix deposition in kidney tissues following injury. MIF as a specific inhibitor may have therapeutic potential for patients with inflammatory and fibrotic kidney diseases.

The urine albumin-to-creatinine ratio is a reliable indicator for evaluating complications of chronic kidney disease and progression in IgA nephropathy in China

OBJECTIVE

This study investigated the correlation between the albumin-to-creatinine ratio in the urine and 24-hour urine proteinuria and whether the ratio can predict chronic kidney disease progression even more reliably than 24-hour proteinuria can, particularly in primary IgA nephropathy.

METHODS

A total of 182 patients with primary IgA nephropathy were evaluated. Their mean urine albumin-to-creatinine ratio and 24-hour proteinuria were determined during hospitalization. Blood samples were also analyzed. Follow-up data were recorded for 44 patients. A cross-sectional study was then conducted to test the correlation between these parameters and their associations with chronic kidney disease complications. Subsequently, a canonical correlation analysis was employed to assess the correlation between baseline proteinuria and parameters of the Oxford classification. Finally, a prospective observational study was performed to evaluate the association between proteinuria and clinical outcomes. Our study is registered in the Chinese Clinical Trial Registry, and the registration number is ChiCTR-OCH-14005137.

RESULTS

A strong correlation (r=0.81, p<0.001) was found between the ratio and 24-hour proteinuria except in chronic kidney disease stage 5. First-morning urine albumin-to-creatinine ratios of ≥125.15, 154.44 and 760.31 mg/g reliably predicted equivalent 24-hour proteinuria 'thresholds' of ≥0.15, 0.3 and 1.0 g/24 h, respectively. In continuous analyses, the albumin-to-creatinine ratio was significantly associated with anemia, acidosis, hypoalbuminemia, hyperphosphatemia, hyperkalemia, hypercholesterolemia and higher serum cystatin C. However, higher 24-hour proteinuria was only associated with hypoalbuminemia and hypercholesterolemia. Higher tubular atrophy and interstitial fibrosis scores were also associated with a greater albumin-to-creatinine ratio, as observed in the canonical correlation analysis. Finally, the albumin-to-creatinine ratio and 24-hour proteinuria were associated with renal outcomes in univariate analyses.

CONCLUSION

This study supports the recommendation of using the albumin-to-creatinine ratio, rather than 24-hour proteinuria, to monitor proteinuria and prognosis in primary IgA nephropathy.

Deletion of Rac1GTPase in the Myeloid Lineage Protects against Inflammation-Mediated Kidney Injury in Mice

Macrophage-mediated inflammation has been implicated in various kidney diseases. We previously reported that Rac1, a Rho family small GTP-binding protein, was overactivated in several chronic kidney disease models, and that Rac1 inhibitors ameliorated renal injury, in part via inhibition of inflammation, but the detailed mechanisms have not been clarified. In the present study, we examined whether Rac1 in macrophages effects cytokine production and the inflammatory mechanisms contributing to kidney derangement. Myeloid-selective Rac1 flox control (M-Rac1 FC) and knockout (M-Rac1 KO) mice were generated using the cre-loxP system. Renal function under basal conditions did not differ between M-Rac1 FC and KO mice. Accordingly, lipopolysaccharide (LPS)-evoked kidney injury model was created. LPS elevated blood urea nitrogen and serum creatinine, enhanced expressions of kidney injury biomarkers, Kim-1 and Ngal, and promoted tubular injury in M-Rac1 FC mice. By contrast, deletion of myeloid Rac1 almost completely prevented the LPS-mediated renal impairment. LPS triggered a marked induction of macrophage-derived inflammatory cytokines, IL-6 and TNFα, in M-Rac1 FC mice, which was accompanied by Rac1 activation, stimulation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and reactive oxygen species overproduction. These changes were inhibited in M-Rac1 KO mice. LPS evoked F4/80-positive macrophages accumulation in the kidney, which was not affected by myeloid Rac1 deficiency. We further tested the role of Rac1 signaling in cytokine production using macrophage cell line, RAW264.7. Exposure to LPS increased IL-6 and TNFα mRNA expression. The LPS-driven cytokine induction was dose-dependently blocked by the Rac1 inhibitor EHT1864, NADPH oxidase inhibitor diphenyleneiodonium, and NF-κB inhibitor BAY11-7082. In conclusion, genetic ablation of Rac1 in the myeloid lineage protected against LPS-induced renal inflammation and injury, by suppressing macrophage-derived cytokines, IL-6 and TNFα, without blocking recruitment. Our data suggest that Rac1 in macrophage is a novel target for the treatment of kidney disease through inhibition of cytokine production.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

The lymphotoxin β receptor is a potential therapeutic target in renal inflammation

Accumulation of inflammatory cells in different renal compartments is a hallmark of progressive kidney diseases including glomerulonephritis (GN). Lymphotoxin β receptor (LTβR) signaling is crucial for the formation of lymphoid tissue, and inhibition of LTβR signaling has ameliorated several non-renal inflammatory models. Therefore, we tested whether LTβR signaling could also have a role in renal injury. Renal biopsies from patients with GN were found to express both LTα and LTβ ligands, as well as LTβR. The LTβR protein and mRNA were localized to tubular epithelial cells, parietal epithelial cells, crescents, and cells of the glomerular tuft, whereas LTβ was found on lymphocytes and tubular epithelial cells. Human tubular epithelial cells, mesangial cells, and mouse parietal epithelial cells expressed both LTα and LTβ mRNA upon stimulation with TNF in vitro. Several chemokine mRNAs and proteins were expressed in response to LTβR signaling. Importantly, in a murine lupus model, LTβR blockade improved renal function without the reduction of serum autoantibody titers or glomerular immune complex deposition. Thus, a preclinical mouse model and human studies strongly suggest that LTβR signaling is involved in renal injury and may be a suitable therapeutic target in renal diseases.

Characterization of calcium oxalate crystal-induced changes in the secretome of U937 human monocytes

This is the first study to characterize changes in the secretome of human monocytes induced by calcium oxalate crystals.

Serum Renalase Levels Correlate with Disease Activity in Lupus Nephritis

Introduction

Lupus nephritis (LN) is among the most serious complications of systemic lupus erythematosus (SLE), which causes significant morbidity and mortality. Renalase is a novel, kidney-secreted cytokine-like protein that promotes cell survival. Here, we aimed to investigate the relationship of serum renalase levels with LN and its role in the disease progression of LN.

Methods

For this cross-sectional study, 67 LN patients and 35 healthy controls were enrolled. Seventeen active LN patients who received standard therapies were followed up for six months. Disease activity was determined by the SLE Disease Activity–2000 (SLEDAI-2K) scoring system and serum renalase amounts were determined by ELISA. Predictive value of renalase for disease activity was assessed. Furthermore, the expression of renalase in the kidneys of patients and macrophage infiltration was assessed by immunohistochemistry.

Results

Serum renalase amounts were significantly higher in LN patients than in healthy controls. Moreover, patients with proliferative LN had more elevated serum renalase levels than Class V LN patients. In proliferative LN patients, serum renalase levels were significantly higher in patients with active LN than those with inactive LN. Serum renalase levels were positively correlated with SLEDAI-2K, 24-h urine protein excretion, ds-DNA and ESR but inversely correlated with serum albumin and C3. Renalase amounts decreased significantly after six-months of standard therapy. The performance of renalase as a marker for diagnosis of active LN was 0.906 with a cutoff value of 66.67 μg/ml. We also observed that the amount of renalase was significantly higher in glomerular of proliferative LN along with the co-expression of macrophages.

Conclusion

Serum renalase levels were correlated with disease activity in LN. Serum renalase might serve as a potential indicator for disease activity in LN. The marked increase of glomerular renalase and its association with macrophages suggest that it might play an important role in disease progression of LN.

Mefunidone attenuates tubulointerstitial fibrosis in a rat model of unilateral ureteral obstruction

BACKGROUND

Inflammation has a crucial role in renal interstitial fibrosis, which is the common pathway of chronic kidney diseases. Mefunidone (MFD) is a new compound which could effectively inhibit the proliferation of renal fibroblasts in vitro. However, the overall effect of Mefunidone in renal fibrosis remains unknown.

METHODS

Sprague-Dawley rats were randomly divided intro 6 groups: sham operation, unilateral ureteral obstruction (UUO), UUO/Mefunidone (25, 50, 100mg/kg/day) and UUO/PFD (500mg/kg/day). The rats were sacrificed respectively on days 3, 7, and 14 after the operation. Tubulointerstitial injury index, interstitial collagen deposition, expression of fibronectin (FN), α-smooth muscle actin (α-SMA), type I and III collagen and the number of CD3+ and CD68+ cells were determined. The expressions of proinflammatory cytokines, p-ERK, p-IκB, and p-STAT3 were measured in human renal proximal tubular epithelial cells of HK-2 or macrophages.

RESULTS

Mefunidone treatment significantly attenuated tubulointerstitial injury, interstitial collagen deposition, expression of FN, α-SMA, type I and III collagen in the obstructive kidneys, which correlated with significantly reduced the number of T cells and macrophages in the obstructive kidneys. Mechanistically, Mefunidone significantly inhibited tumor necrosis factor-α (TNF-α-) or lipopolysaccharide (LPS)-induced production of proinflammatory cytokines. This effect is possibly due to the inhibition of phosphorylation of ERK, IκB, and STAT3.

CONCLUSION

Mefunidone treatment attenuated tubulointerstitial fibrosis in a rat model of UUO, at least in part, through inhibition of inflammation.