Tubulointerstitial injury and the progression of chronic kidney disease

Modified Zhenwu Tang delays chronic renal failure progression by modulating oxidative stress and hypoxic responses in renal proximal tubular epithelial cells

Background

Tubulointerstitial fibrosis (TIF) is a critical pathological feature of chronic renal failure (CRF), with oxidative stress (OS) and hypoxic responses in renal proximal tubular epithelial cells playing pivotal roles in disease progression. This study explores the effects of Modified Zhenwu Tang (MZWT) on these processes, aiming to uncover its potential mechanisms in slowing CRF progression.

Methods

We used adenine (Ade) to induce CRF in rats, which were then treated with benazepril hydrochloride (Lotensin) and MZWT for 8 weeks. Assessments included liver and renal function, electrolytes, blood lipids, renal tissue pathology, OS levels, the hypoxia-inducible factor (HIF) pathway, inflammatory markers, and other relevant indicators. In vitro, human renal cortical proximal tubular epithelial cells were subjected to hypoxia and lipopolysaccharide for 72 h, with concurrent treatment using MZWT, FM19G11, and N-acetyl-l-cysteine. Measurements taken included reactive oxygen species (ROS), HIF pathway activity, inflammatory markers, and other relevant indicators.

Results

Ade treatment induced significant disruptions in renal function, blood lipids, electrolytes, and tubulointerstitial architecture, alongside heightened OS, HIF pathway activation, and inflammatory responses in rats. In vivo, MZWT effectively ameliorated proteinuria, renal dysfunction, lipid and electrolyte imbalances, and renal tissue damage; it also suppressed OS, HIF pathway activation, epithelial-mesenchymal transition (EMT) in proximal tubular epithelial cells, and reduced the production of inflammatory cytokines and collagen fibers. In vitro findings demonstrated that MZWT decreased apoptosis, reduced ROS production, curbed OS, HIF pathway activation, and EMT in proximal tubular epithelial cells, and diminished the output of inflammatory cytokines and collagen.

Conclusion

OS and hypoxic responses significantly contribute to TIF development. MZWT mitigates these responses in renal proximal tubular epithelial cells, thereby delaying the progression of CRF.

TMAO enhances TNF-α mediated fibrosis and release of inflammatory mediators from renal fibroblasts

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite and TNF-α is proinflammatory cytokine, both known to be associated with renal inflammation, fibrosis and chronic kidney disease. However, today there are no data showing the combined effect of TMAO and TNF-α on renal fibrosis-and inflammation. The aim of this study was to investigate whether TMAO can enhance the inflammatory and fibrotic effects of TNF-α on renal fibroblasts. We found that the combination of TNF-α and TMAO synergistically increased fibronectin release and total collagen production from renal fibroblasts. The combination of TMAO and TNF-α also promoted increased cell proliferation. Both renal proliferation and collagen production were mediated through Akt/mTOR/ERK signaling. We also found that TMAO enhanced TNF-α mediated renal inflammation by inducing the release of several cytokines (IL-6, LAP TGF-beta-1), chemokines (CXCL-6, MCP-3), inflammatory-and growth mediators (VEGFA, CD40, HGF) from renal fibroblasts. In conclusion, we showed that TMAO can enhance TNF-α mediated renal fibrosis and release of inflammatory mediators from renal fibroblasts in vitro. Our results can promote further research evaluating the combined effect of TMAO and inflammatory mediators on the development of kidney disease.

Single-cell transcriptomics reveals the ameliorative effect of rosmarinic acid on diabetic nephropathy-induced kidney injury by modulating oxidative stress and inflammation

Diabetic nephropathy (DN) is a severe complication of diabetes, characterized by changes in kidney structure and function. The natural product rosmarinic acid (RA) has demonstrated therapeutic effects, including anti-inflammation and anti-oxidative-stress, in renal damage or dysfunction. In this study, we characterized the heterogeneity of the cellular response in kidneys to DN-induced injury and RA treatment at single cell levels. Our results demonstrated that RA significantly alleviated renal tubular epithelial injury, particularly in the proximal tubular S1 segment and on glomerular epithelial cells known as podocytes, while attenuating the inflammatory response of macrophages, oxidative stress, and cytotoxicity of natural killer cells. These findings provide a comprehensive understanding of the mechanisms by which RA alleviates kidney damage, oxidative stress, and inflammation, offering valuable guidance for the clinical application of RA in the treatment of DN.

Role of ferroptosis in chronic kidney disease

Chronic kidney disease (CKD) has historically been a significant global health concern, profoundly impacting both life and well-being. In the process of CKD, with the gradual loss of renal function, the incidence of various life-threatening complications, such as cardiovascular diseases, cerebrovascular accident, infection and stroke, is also increasing rapidly. Unfortunately, existing treatments exhibit limited ability to halt the progression of kidney injury in CKD, emphasizing the urgent need to delve into the precise molecular mechanisms governing the occurrence and development of CKD while identifying novel therapeutic targets. Renal fibrosis, a typical pathological feature of CKD, plays a pivotal role in disrupting normal renal structures and the loss of renal function. Ferroptosis is a recently discovered iron-dependent form of cell death characterized by lipid peroxide accumulation. Ferroptosis has emerged as a potential key player in various diseases and the initiation of organ fibrosis. Substantial evidence suggests that ferroptosis may significantly contribute to the intricate interplay between CKD and its progression. This review comprehensively outlines the intricate relationship between CKD and ferroptosis in terms of iron metabolism and lipid peroxidation, and discusses the current landscape of pharmacological research on ferroptosis, shedding light on promising avenues for intervention. It further illustrates recent breakthroughs in ferroptosis-related regulatory mechanisms implicated in the progression of CKD, thereby providing new insights for CKD treatment. Video Abstract.

The Molecular Mechanism of Renal Tubulointerstitial Inflammation Promoting Diabetic Nephropathy

Diabetic nephropathy (DN) is a common complication affecting many diabetic patients, leading to end-stage renal disease. However, its pathogenesis still needs to be fully understood to enhance the effectiveness of treatment methods. Traditional theories are predominantly centered on glomerular injuries and need more explicit explanations of recent clinical observations suggesting that renal tubules equally contribute to renal function and that tubular lesions are early features of DN, even occurring before glomerular lesions. Although the conventional view is that DN is not an inflammatory disease, recent studies indicate that systemic and local inflammation, including tubulointerstitial inflammation, contributes to the development of DN. In patients with DN, intrinsic tubulointerstitial cells produce many proinflammatory factors, leading to medullary inflammatory cell infiltration and activation of inflammatory cells in the interstitial region. Therefore, understanding the molecular mechanism of renal tubulointerstitial inflammation contributing to DN injury is of great significance and will help further identify key factors regulating renal tubulointerstitial inflammation in the high glucose environment. This will aid in developing new targets for DN diagnosis and treatment and expanding new DN treatment methods.

Is serum hemoglobin level an independent prognostic factor for IgA nephropathy?: a systematic review and meta-analysis of observational cohort studies

BACKGROUND

Decreased serum hemoglobin (Hb) level is associated with Immunoglobulin A nephropathy (IgAN) progression. However, whether serum Hb level is an independent prognostic factor of IgAN remains controversial. Herein, we aimed to investigate the prognostic value of serum Hb level in IgAN.

METHODS

The Cochrane Library, Embase, PubMed and Open Grey databases were systematically searched and reviewed. Kidney disease progression of IgAN was defined as a doubling of serum creatinine (SCr), a 30% reduction in estimated glomerular filtration rate (eGFR), end-stage renal disease (ESRD), or death. We evaluated the hazard ratio (HR) between serum Hb level and the incidence of kidney disease progression in IgAN before and after adjusting for relevant covariates.

RESULTS

We included nine studies with 10006 patients in the meta-analysis. As a continuous variable, we found that serum Hb was an independent prognostic factor of IgAN [unadjusted HR = 0.89, 95% confidence interval (CI) = 0.84-0.95, I² = 98%; adjusted HR = 0.85, 95% CI = 0.79-0.91, I² = 0%]. The sensitivity analysis confirmed the stability of these results. Consistently, as a dichotomous variable defined as the below/above cutoff for anemia, we observed a positive correlation between serum Hb and kidney disease progression in IgAN (unadjusted HR = 2.12, 95% CI = 1.44-3.12, I² = 79%; adjusted HR = 1.65, 95% CI = 1.20-2.27, I² = 0%).

CONCLUSION

Serum Hb level was independently correlated with the incidence of kidney disease progression in IgAN.

Interleukin-6 and epidermal growth factor as noninvasive biomarkers of progression in chronic glomerulonephritis

Several cytokines and chemokines are involved in the pathogenesis and progressive injury of renal tissues in patients with primary chronic glomerulonephritis (CGN). The objective of this study was to determine whether the urinary excretion of interleukin-6 (IL-6), transforming growth factor β1 (TGFβ1), monocytes chemoattractant protein (MCP-1), soluble tumor necrosis factor receptor 1 (sTNFR1), and epidermal growth factor (EGF) in patients with newly recognized CGN can serve as prognostic biomarkers in patients with newly recognized CGN and whether they can be effective in predicting a progressive reduction of renal function in prospective observation. The study included 150 Caucasian patients. UIL-6, UTGFβ1, UMCP-1, UsTNFR1, and UEGF were measured using enzyme-linked immunosorbent assay (ELISA) methods (Quantikine R&D System). UIL-6, UTGFβ1, UMCP-1, and UsTNFR1 were significantly higher, yet UEGF excretion was significantly lower in nephrotic patients, in patients with estimated glomerular filtration rate (eGFR) < 60/min/1.73 m2 at presentation, as well as in the progressor (PG) subgroup. In a multivariate regression analysis basal eGFR correlated with UsTNFR1, UIL-6, and UEGF excretion, although in the follow-up, ΔeGFR (delta estimated glomerular filtration rate) significantly correlated only with UEGF excretion. A logistic regression analysis showed that the most significant independent risk factors for the deterioration of renal function with time are initial high (>11.8 pg/mgCr) UIL-6 excretion, initial low (<15.5 ng/mgCr) urinary UEGF excretion, and male gender. In patients with newly diagnosed CGN, UIL-6, and UEGF can serve as prognostic biomarkers for the progression of the disease.NEW & NOTEWORTHY Baseline high urinary interleukin-6 (IL-6) excretion and low urinary epidermal growth factor (EGF) excretion and particularly high IL-6/EGF ratio were stronger predictive factors of the progression of the deterioration of the kidney function than initial estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 or proteinuria. In patients with newly diagnosed chronic glomerulonephritis, UIL-6 and UEGF can serve as prognostic biomarkers for the progression of the disease.

Renoprotective Effect of TP0472993, a Novel and Selective 20-Hydroxyeicosatetraenoic Acid Synthesis Inhibitor, in Mouse Models of Renal Fibrosis

Kidney fibrosis is considered the essential pathophysiological process for the progression of chronic kidney disease (CKD) toward renal failure. 20-Hydroxyeicosatetraenoic acid (20-HETE) has crucial roles in modulating the vascular response in the kidney and the progression of albuminuria. However, the roles of 20-HETE in kidney fibrosis are largely unexplored. In the current research, we hypothesized that if 20-HETE has important roles in the progression of kidney fibrosis, 20-HETE synthesis inhibitors might be effective against kidney fibrosis. To verify our hypothesis, this study investigated the effect of a novel and selective 20-HETE synthesis inhibitor, TP0472993, on the development of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice. Chronic treatment with TP0472993 at doses of 0.3 and 3 mg/kg twice a day attenuated the degree of kidney fibrosis in the folic acid nephropathy and the unilateral ureteral obstruction (UUO) mice, as demonstrated by reductions in Masson's trichrome staining and the renal collagen content. In addition, TP0472993 reduced renal inflammation, as demonstrated by markedly reducing interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) levels in the renal tissue. Chronic treatment with TP0472993 also reduced the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) in the kidney of UUO mice. Our observations indicate that inhibition of 20-HETE production with TP0472993 suppresses the kidney fibrosis progression via a reduction in the ERK1/2 and STAT3 signaling pathway, suggesting that 20-HETE synthesis inhibitors might be a novel treatment option against CKD. SIGNIFICANCE STATEMENT: In this study, we demonstrate that the pharmacological blockade of 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis using TP0472993 suppresses the progression of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice, indicating that 20-HETE might have key roles in the pathogenesis of kidney fibrosis. TP0472993 has the potential to be a novel therapeutic approach against chronic kidney disease.

Crotamine/siRNA Nanocomplexes for Functional Downregulation of Syndecan-1 in Renal Proximal Tubular Epithelial Cells

Proteinuria drives progressive tubulointerstitial fibrosis in native and transplanted kidneys, mainly through the activation of proximal tubular epithelial cells (PTECs). During proteinuria, PTEC syndecan-1 functions as a docking platform for properdin-mediated alternative complement activation. Non-viral gene delivery vectors to target PTEC syndecan-1 could be useful to slow down alternative complement activation. In this work, we characterize a PTEC-specific non-viral delivery vector composed of the cell-penetrating peptide crotamine complexed with a syndecan-1 targeting siRNA. Cell biological characterization was performed in the human PTEC HK2 cell line, using confocal microscopy, qRT-PCR, and flow cytometry. PTEC targeting in vivo was carried out in healthy mice. Crotamine/siRNA nanocomplexes are positively charged, about 100 nm in size, resistant to nuclease degradation, and showed in vitro and in vivo specificity and internalization into PTECs. The efficient suppression of syndecan-1 expression in PTECs mediated by these nanocomplexes significantly reduced properdin binding (p < 0.001), as well as the subsequent complement activation by the alternative complement pathway (p < 0.001), as observed in either normal or activated tubular conditions. To conclude, crotamine/siRNA-mediated downregulation of PTEC syndecan-1 reduced the activation of the alternative complement pathway. Therefore, we suggest that the present strategy opens new venues for targeted proximal tubular gene therapy in renal diseases.

Continuous positive airway pressure treatment reduces renal tubular damage in patients with obstructive sleep apnea: A retrospective single-center cohort study

BACKGROUND

Chronic intermittent hypoxia (IH) plays a significant role in the pathogenesis of obstructive sleep apnea (OSA) comorbidities. The prevalence of chronic kidney disease is higher in patients with OSA than the general population, and renal function decline is well correlated with renal tubular injury. However, little is known about the impact of OSA-induced chronic IH on the renal tubules.

METHODS

We conducted a retrospective survey of clinical records performing multiple regression analysis and cluster analysis with particular attention to the 3% oxygen desaturation index (ODI) and urinary N-acetyl-β-d-glucosaminidase (NAG).

RESULTS

In patients with suspicion of OSA, urinary NAG creatinine ratio (UNCR) was elevated as their 3% ODI increased (n = 197, p < 0.001), and the elevated UNCR decreased following CPAP treatment in patients with OSA (n = 46, p = 0.014). Multiple regression analysis showed that 3% ODI was associated with UNCR. Cluster analysis identified three clusters of patients with OSA, including two younger age clusters, one of which was characterized by high BMI, high 3% ODI, and high prevalence of major comorbidities. In a comparative analysis of younger age cases (age ≤ 55, n = 82), the UNCR level was higher in patients with severe 3% ODI (3% ODI > 40 events/h, n = 24) (p = 0.014).

CONCLUSIONS

Our results indicate that even at younger ages, OSA patients with severe chronic IH and major comorbidities are susceptible to renal tubular damage. Early treatment with CPAP may attenuate renal tubular injury and progression toward end-stage renal disease.

Long non-coding RNA FABP5P3/miR-22 axis improves TGFβ1-induced fatty acid oxidation deregulation and fibrotic changes in proximal tubular epithelial cells of renal fibrosis

Severe hydronephrosis increases the risk of urinary tract infection and irretrievable renal fibrosis. While TGFβ1-mediated fibrotic changes in proximal tubular epithelial cells and fatty acid oxidation (FAO) deregulation contribute to renal fibrosis and hydronephrosis. Firstly, a few elements were analyzed in this paper, including differentially-expressed long non-coding RNAs (lncRNAs), and miRNAs correlated to CPT1A, RXRA, and NCOA1. This paper investigated TGFβ1 effects on lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression and fibrotic changes in HK-2 cells and FABP5P3 overexpression effects on TGFβ1-induced changes. Moreover, this paper predicted and proved that miR-22 binding to lncRNA FABP5P3, 3'UTR of CPT1A, RXRA, and NCOA1 was validated. The dynamic effects of the FABP5P3/miR-22 axis on TGFβ1-induced changes were investigated. A Renal fibrosis model was established in unilateral ureteral obstruction (UUO) mice, and FABP5P3 effects were investigated. Eventually, this paper concluded that TGFβ1 inhibited lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression, induced fibrotic changes in HK-2 cells, and induced metabolic reprogramming within HK-2 cells, especially lower FAO. FABP5P3 overexpression partially reversed TGFβ1-induced changes. miR-22 targeted lncRNA FABP5P3, CPT1A, RXRA, and NCOA1. LncRNA FABP5P3 counteracted miR-22 inhibition of CPT1A, NCOA1, and RXRA through competitive binding. TGFβ1 stimulation induced the activation of TGFβ/SMAD and JAG/Notch signaling pathways; Nocth2 knockdown reversed TGFβ1 suppression on lncRNA FABP5P3. FABP5P3 overexpression attenuated renal fibrosis in unilateral ureteral obstruction mice. The LncRNA FABP5P3/miR-22 axis might be a potent target for improving the FAO deregulation and fibrotic changes in proximal TECs under TGFβ1 stimulation.

Effects of dietary phosphorus concentration and phosphate salt form on renal tubule function in unilateral nephrectomized rats

Background: Excessive consumption of phosphorus (P) impairs renal tubule function; however, the effects of different dietary phosphate salts on chronic kidney disease (CKD) are unclear. Aim: To examine the effects of potassium dihydrogen phosphate (KH2PO4) and potassium tripolyphosphate (K5P3O10) and P concentration on renal function in a rat model of early CKD. Methods: Male sham-operated Sprague-Dawley rats were fed a diet containing KH2PO4 with a normal P level. Kidney injury was induced by unilateral nephrectomy (UNx), and the rats were divided into four groups fed dietary KH2PO4 or K5P3O10 with a normal (UNx-NKH, UNx-NKP) or high (UNx-HKH, UNx-HKP) P concentration, respectively, for 21 days. Results: UNx-NKH rats showed significantly lower creatinine clearance (CCr) and higher albumin (ALB) compared with those of sham rats, confirming UNx-induced kidney injury. The urinary levels of liver-type fatty acid-binding protein (L-FABP) and ALB were significantly higher in UNx-HKP rats than in UNx-HKH rats. However, other markers of renal tubule function, such as CCr, serum creatinine (CRE), calcium (Ca), and hormones, only differed among groups according to the P concentration and not the dietary phosphate salt form. Histological examination showed higher incidence and severity of tubulointerstitial lesions, tubule regeneration, tubule dilation, and calcification in the high-phosphorus than in the normal-phosphorus UNx groups. These changes were more severe in the UNx-HKP group compared with the UNx-HKH group. Conclusion: This study highlights the importance of controlling dietary P intake in terms of both concentration and source to prevent the progression of CKD.

TMAO Suppresses Megalin Expression and Albumin Uptake in Human Proximal Tubular Cells Via PI3K and ERK Signaling

Trimethylamine-N-oxide (TMAO) is a uremic toxin, which has been associated with chronic kidney disease (CKD). Renal tubular epithelial cells play a central role in the pathophysiology of CKD. Megalin is an albumin-binding surface receptor on tubular epithelial cells, which is indispensable for urine protein reabsorption. To date, no studies have investigated the effect of TMAO on megalin expression and the functional properties of human tubular epithelial cells. The aim of this study was first to identify the functional effect of TMAO on human renal proximal tubular cells and second, to unravel the effects of TMAO on megalin-cubilin receptor expression. We found through global gene expression analysis that TMAO was associated with kidney disease. The microarray analysis also showed that megalin expression was suppressed by TMAO, which was also validated at the gene and protein level. High glucose and TMAO was shown to downregulate megalin expression and albumin uptake similarly. We also found that TMAO suppressed megalin expression via PI3K and ERK signaling. Furthermore, we showed that candesartan, dapagliflozin and enalaprilat counteracted the suppressive effect of TMAO on megalin expression. Our results may further help us unravel the role of TMAO in CKD development and to identify new therapeutic targets to counteract TMAOs effects.

PGC1 plays a pivotal role in renal fibrosis via regulation of fatty acid metabolism in renal tissue

Renal fibrosis is a common and irreversible pathological feature of end-stage renal disease caused by multiple etiologies. The role of inflammation in renal fibrosis tissue has been generally accepted. The latest view is that fatty acid metabolism disorder contributes to renal fibrosis. peroxisome proliferator activated receptor-gamma coactivator 1α (PGC1α) plays a key role in fatty acid metabolism, regulating fatty acid uptake and oxidized protein synthesis, preventing the accumulation of lipid in the cytoplasm, and maintaining a dynamic balanced state of intracellular lipid. In multiple animal models of renal fibrosis caused by acute or chronic kidney disease, or even age-related kidney disease, almost all of the kidney specimens show the down-regulation of PGC1α. Upregulation of PGC1α can reduce the degree of renal fibrosis in animal models, and PGC1α knockout animals exhibit severe renal fibrosis. Studies have demonstrated that AMP-activated protein kinase (AMPK), MAPK, Notch, tumor necrosis factor-like weak inducer of apoptosis (TWEAK), epidermal growth factor receptor (EGFR), non-coding RNA (ncRNAs), liver kinase B1 (LKB1), hairy and enhancer of split 1 (Hes1), and other pathways regulate the expression of PGC1α and affect fatty acid metabolism. But some of these pathways interact with each other, and the effect of the integrated pathway on renal fibrosis is not clear.

Combination of Perindopril Erbumine and Huangqi-Danshen Decoction Protects Against Chronic Kidney Disease via Sirtuin3/Mitochondrial Dynamics Pathway

Background

Chronic kidney disease (CKD) is a major public health problem worldwide. Treatment with renin-angiotensin system inhibitors can achieve only partial efficacy on renal function decline and renal fibrosis in CKD patients. Huangqi-Danshen decoction (HDD) is a basic Chinese herbal pair which is commonly used to treat CKD with good efficacy.

Objectives

The current study aimed to investigate the effect of perindopril erbumine (PE), an angiotensin-converting enzyme inhibitor, combined with HDD on adenine-induced CKD rat model and explore the possible mechanism from Sirtuin3/mitochondrial dynamics pathway.

Method

CKD rat model was established by feeding of 0.75% w/w adenine containing diet for 3 weeks. At the same time, the treatment groups were given PE (0.42 mg/kg/d) or HDD (4.7 g/kg/d) or PE combined with HDD by gavage for 4 weeks. Renal function was evaluated by the levels of serum creatinine (Scr) and blood urea nitrogen (BUN). The renal pathological injury was observed by periodic acid-Schiff (PAS) and Masson's trichrome staining. Proteins expression was determined by Western blot analysis. Mitochondrial morphology was observed by transmission electron microscopy.

Results

PE in combination with HDD significantly improved renal function, reduced tubular injury and interstitial fibrosis in adenine-induced CKD rats. Moreover, PE + HDD treatment mainly activated the Sirtuin3 expression level. In addition, PE + HDD exhibited bidirectional regulation on mitochondrial dynamics by suppressing mitochondrial fission protein dynaminrelated protein 1 expression and elevating mitochondrial fusion protein optic atrophy 1 expression, resulted in restraint of mitochondrial fragmentation.

Conclusion

The combination of PE and HDD attenuated adenine-induced CKD in rats, which was possibly associated with Sirtuin3/mitochondrial dynamics pathway.

Urinary Epidermal Growth Factor: A Promising "Next Generation" Biomarker in Kidney Disease

BACKGROUND

The epidermal growth factor (EGF) is a globular protein that is generated in the kidney, especially in the loop of Henle and the distal convoluted tubule. While EGF is nonexistent or hardly detectable in plasma, it is present in normal people's urine. Until now, risk stratification and chronic kidney disease (CKD) diagnosis have relied on estimated glomerular filtration rate (eGFR) and urine albumin/creatinine ratio (uACR), both of which reflect glomerular function or impairment. Tubular dysfunction, on the other hand, may also be associated with renal failure.

SUMMARY

Because decreased urine EGF (uEGF) indicates tubular atrophy and interstitial fibrosis, this biomarker, together with eGFR and uACR, may be employed in the general population for risk assessment and diagnosis of CKD. uEGF levels have been shown to correlate with intrarenal EGF mRNA expression and have been found to decrease in a variety of glomerular and non-glomerular kidney disorders.

KEY MESSAGE

uEGF, uEGF/creatinine, or uEGF/monocyte chemotactic peptide-1 are possible "new generation" biomarkers linked to a variety of kidney diseases that deserve further investigation as a single biomarker or as part of a multi-biomarker panel.

Rhein Improves Renal Fibrosis by Restoring Cpt1a-Mediated Fatty Acid Oxidation through SirT1/STAT3/twist1 Pathway

The latest progress in the field of renal fibrosis mainly focuses on the new concept of “partial epithelial-mesenchymal transition (pEMT)” to explain the contribution of renal tubular epithelial (RTE) cells to renal fibrosis and the crucial role of fatty acid oxidation (FAO) dysfunction in RTE cells for the development of renal fibrosis. FAO depression is considered to be secondary or occur simultaneously with pEMT. We explored the relationship between pEMT and FAO and the effect of rhein on them. Intragastric administration of rhein significantly improved the levels of BUN, Scr, α-SMA, collagen 1A and histopathological changes in UUO-rats. Transcriptomic and metabolomic analyses revealed that abnormal signaling pathways were involved in EMT and FAO disorders. RTE cell experiments showed that TGF-β could inhibit the activity of Cpt1a, resulting in ATP depletion and lipid deposition. Cpt1a inhibitor induced EMT, while Cpt1 substrate or rhein inhibited EMT, indicating that Cpt1a-mediated FAO dysfunction is essential for RTE cells EMT. Further studies showed that Cpt1a activity were regulated by SirT1/STAT3/Twist1 pathway. Rhein inhibits RTE cell EMT by promoting Cpt1a-mediated FAO through the SirT1/STAT3/Twist1 pathway. Surprisingly and importantly, our experiments showed that FAO depression occurs before EMT, and EMT is one of the results of FAO depression.

The Signaling Pathway of TNF Receptors: Linking Animal Models of Renal Disease to Human CKD

Chronic kidney disease (CKD) has been recognized as a global public health problem. Despite the current advances in medicine, CKD-associated morbidity and mortality remain unacceptably high. Several studies have highlighted the contribution of inflammation and inflammatory mediators to the development and/or progression of CKD, such as tumor necrosis factor (TNF)-related biomarkers. The inflammation pathway driven by TNF-α, through TNF receptors 1 (TNFR1) and 2 (TNFR2), involves important mediators in the pathogenesis of CKD. Circulating levels of TNFRs were associated with changes in other biomarkers of kidney function and injury, and were described as predictors of disease progression, cardiovascular morbidity, and mortality in several cohorts of patients. Experimental studies describe the possible downstream signaling pathways induced upon TNFR activation and the resulting biological responses. This review will focus on the available data on TNFR1 and TNFR2, and illustrates their contributions to the pathophysiology of kidney diseases, their cellular and molecular roles, as well as their potential as CKD biomarkers. The emerging evidence shows that TNF receptors could act as biomarkers of renal damage and as mediators of the disease. Furthermore, it has been suggested that these biomarkers could significantly improve the discrimination of clinical CKD prognostic models.

Urinary Galectin-3 as a Novel Biomarker for the Prediction of Renal Fibrosis and Kidney Disease Progression

Plasma galectin-3 (Gal-3) is associated with organ fibrosis, but whether urinary Gal-3 is a potential biomarker of kidney disease progression has never been explored. Between 2018 and 2021, we prospectively enrolled 280 patients who underwent renal biopsy and were divided into three groups based on their urinary Gal-3 levels (<354.6, 354.6−510.7, and ≥510.8 pg/mL) to assess kidney disease progression (defined as ≥40% decline in the estimated glomerular filtration rate or end-stage renal disease) and renal histology findings. Patients in the highest urinary Gal-3 tertile had the lowest eGFRs and highest proteinuria levels. In multivariate Cox regression models, patients in the highest tertile had the highest risk of kidney disease progression (adjusted hazard ratio, 4.60; 95% confidence interval, 2.85−7.71) compared to those in the lowest tertile. Higher urinary Gal-3 levels were associated with more severe renal fibrosis. Intrarenal mRNA expression of LGALS3 (Gal-3-encoded gene) was most correlated with the renal stress biomarkers (IGFBP7 and TIMB2), renal function biomarkers (PTGDS) and fibrosis-associated genes (TGFB1). The urinary Gal-3 level may be useful for the identification of patients at high risk of kidney disease progression and renal fibrosis, and for the early initiation of treatments for these patients.

Adverse Effects of fine particulate matter on human kidney functioning: a systematic review

BACKGROUND

Ambient fine particulate matter (PM < 2.5 μm, PM2.5) is gaining increasing attention as an environmental risk factor for health. The kidneys are considered a particularly vulnerable target to the toxic effects that PM2.5 exerts. Alteration of kidney function may lead to a disrupted homeostasis, affecting disparate tissues in the body. This review intends to summarize all relevant knowledge published between January 2000 and December 2021 on the effects of ambient PM2.5 and the adverse effects on kidney function in adults (≥ 18 years).

RESULTS AND DISCUSSION

Studies published in peer-reviewed journals, written in English, regarding the effects of PM2.5 on kidney function and the development and/or exacerbation of kidney disease(s) were included. Of the 587 nonduplicate studies evaluated, 40 were included, comprising of studies on healthy or diagnosed with pre-existing disease (sub)populations. Most of the studies were cohort studies (n = 27), followed by 10 cross-sectional, 1 ecological and 2 time-series studies. One longitudinal study was considered intermediate risk of bias, the other included studies were considered low risk of bias. A large portion of the studies (n = 36) showed that PM2.5 exposure worsened kidney outcome(s) investigated; however, some studies show contradictory results. Measurement of the estimated glomerular filtration rate, for instance, was found to be positively associated (n = 8) as well as negatively associated (n = 4) with PM2.5.

LIMITATIONS AND CONCLUSION

The main limitations of the included studies include residual confounding (e.g., smoking) and lack of individual exposure levels. The majority of included studies focused on specific subpopulations, which may limit generalizability. Evidence of the detrimental effects that ambient PM2.5 may exert on kidney function is emerging. However, further investigations are required to determine how and to what extent air pollution, specifically PM2.5, exerts adverse effects on the kidney and alters its function.

REGISTRATION

The systematic review protocol was submitted and published by the International Prospective Register of Systematic Reviews (PROSPERO; CRD42020175615 ).

The Human Microbiome in Chronic Kidney Disease: A Double-Edged Sword

Chronic kidney disease (CKD) is an increasing global health burden. Current treatments for CKD include therapeutics to target factors that contribute to CKD progression, including renin–angiotensin–aldosterone system inhibitors, and drugs to control blood pressure and proteinuria control. Recently, associations between chronic disease processes and the human microbiota and its metabolites have been demonstrated. Dysbiosis—a change in the microbial diversity—has been observed in patients with CKD. The relationship between CKD and dysbiosis is bidirectional; gut-derived metabolites and toxins affect the progression of CKD, and the uremic milieu affects the microbiota. The accumulation of microbial metabolites and toxins is linked to the loss of kidney functions and increased mortality risk, yet renoprotective metabolites such as short-chain fatty acids and bile acids help restore kidney functions and increase the survival rate in CKD patients. Specific dietary interventions to alter the gut microbiome could improve clinical outcomes in patients with CKD. Low-protein and high-fiber diets increase the abundance of bacteria that produce short-chain fatty acids and anti-inflammatory bacteria. Fluctuations in the urinary microbiome are linked to increased susceptibility to infection and antibiotic resistance. In this review, we describe the potential role of the gut, urinary and blood microbiome in CKD pathophysiology and assess the feasibility of modulating the gut microbiota as a therapeutic tool for treating CKD.

The serum free triiodothyronine to free thyroxine ratio as a potential prognostic biomarker of chronic kidney disease in patients with glomerular crescents: A retrospective study

BACKGROUND

Crescent formation indicates severe glomerular pathology, and hypothyroidism usually predicts poor prognosis for severe diseases. However, the relationship between thyroid function and the progression of chronic kidney disease (CKD) is unclear. This study analysed the prognostic predictive value of the serum free triiodothyronine (FT3) to free thyroxine (FT4) ratio and its correlation with renal function in patients with CKD with crescent formation.

METHODS

This single-centre study included 162 CKD patients with glomerular crescents confirmed by renal pathology between March 2012 and December 2014. According to the first tertile (0.284) of FT3/FT4 ratio, the patients were divided into high and low FT3/FT4 ratio groups. Kaplan-Meier and Cox regression analyses were performed to evaluate the prognostic value of the FT3/FT4 ratio.

RESULTS

The age, haemoglobin, eGFR, urinary albumin-to-creatinine ratio, cardiac troponin T, N-terminal brain natriuretic peptide precursor, FT3, FT4, percentage of total crescents in non-globally sclerotic glomeruli, prevalences of hypertension, moderate to severe renal tubulopathy and crescentic nephritis, and proportion of patients receiving glucocorticoids and immunosuppressants were significantly different between high and low FT3/FT4 ratio groups (P < 0.05). Multivariate Cox regression analysis showed that when compared with patients with a high FT3/FT4 ratio (>0.284), those with intermediate and low FT3/FT4 ratios (≤0.284) had an increased risk of the long-term composite endpoint (P < 0.05 for various adjustment models).

CONCLUSIONS

A low FT3/FT4 ratio is associated with increased mortality and worse outcome risk in CKD patients with crescent pathology.

Development of a unilateral ureteral obstruction model in cynomolgus monkeys

Background

Chronic kidney disease (CKD) has a high global prevalence and large unmet need. Central to developing new CKD therapies are in vivo models in CKD. However, next-generation antibody, protein, and gene therapies are highly specific, meaning some do not cross-react with rodent targets. This complicates preclinical development, as established in vivo rodent models cannot be utilized unless tool therapeutics are also developed. Tool compounds can be difficult to develop and, if available, typically have different epitopes, sequences, and/or altered affinity, making it unclear how efficacious the lead therapeutic may be, or what dosing regimen to investigate. To address this, we aimed to develop a nonhuman primate model of CKD.

Methods

In vivo rodent unilateral ureteral obstruction (UUO) models kidney fibrosis and is commonly used due to its rapidity, consistency, and ease. We describe translation of this model to the cynomolgus monkey, specifically optimizing the model duration to allow adequate time for assessment of novel therapeutics prior to the fibrotic plateau.

Results

We demonstrated that disease developed more slowly in cynomolgus monkeys than in rodents post-UUO, with advanced fibrosis developing by 6 weeks. The tubulointerstitial fibrosis in cynomolgus monkeys was more consistent with human obstructive disease than in rodents, having a more aggressive tubular basement expansion and a higher fibroblast infiltration. The fibrosis was also associated with increased transglutaminase activity, consistent with that seen in patients with CKD.

Conclusion

This cynomolgus monkey UUO model can be used to test potential human-specific therapeutics in kidney fibrosis.

Time-Varying Proteinuria and the Risk of Cardiovascular Disease and Graft Failure in Kidney Transplant Recipients

Introduction: Proteinuria is recognized as an independent risk factor for cardiovascular disease in kidney transplant recipients, but previous studies have not considered the impact of changes in urine protein over time. Research Question and Design: We used time-dependent, multivariable Cox proportional hazards models in this observational cohort study of adult kidney transplant recipients to evaluate whether proteinuria measured by dipstick on random spot urine samples starting from 1-month post-transplant was associated with the risk of major adverse cardiac events and graft loss. Results: A total of 144 major adverse cardiac events, defined as acute myocardial infarction, cerebrovascular accident, revascularization, or all-cause mortality, were observed in 1106 patients over 5728.7 person-years. Any level of proteinuria greater or equal to trace resulted in a two-fold increase in the risk of major adverse cardiac events (hazard ratio 2.00 [95% confidence interval 1.41, 2.84]). This relationship was not found to be dose-dependent (hazard ratios of 2.98, 1.76, 1.63, and 1.54 for trace, 1+, 2+, and 3+ urine protein, respectively). There was an increased risk of graft failure with greater urine protein concentration (hazard ratios 2.22, 2.85, 6.41, and 19.71 for trace, 1+, 2+, and 3+, respectively). Conclusion: Urine protein is associated with major adverse cardiac events and graft loss in kidney transplant recipients. The role of interventions to reduce proteinuria on decreasing the risk of adverse cardiovascular and graft outcomes in kidney transplant recipients requires further study.

RTEC-intrinsic IL-17-driven inflammatory circuit amplifies antibody-induced glomerulonephritis and is constrained by Regnase-1

Antibody-mediated glomerulonephritis (AGN) is a clinical manifestation of many autoimmune kidney diseases for which few effective treatments exist. Chronic inflammatory circuits in renal glomerular and tubular cells lead to tissue damage in AGN. These cells are targeted by the cytokine IL-17, which has recently been shown to be a central driver of the pathogenesis of AGN. However, surprisingly little is known about the regulation of pathogenic IL-17 signaling in the kidney. Here, using a well-characterized mouse model of AGN, we show that IL-17 signaling in renal tubular epithelial cells (RTECs) is necessary for AGN development. We also show that Regnase-1, an RNA binding protein with endoribonuclease activity, is a negative regulator of IL-17 signaling in RTECs. Accordingly, mice with a selective Regnase-1 deficiency in RTECs exhibited exacerbated kidney dysfunction in AGN. Mechanistically, Regnase-1 inhibits IL-17-driven expression of the transcription factor IκBξ and, consequently, its downstream gene targets, including Il6 and Lcn2. Moreover, deletion of Regnase-1 in human RTECs reduced inflammatory gene expression in a IκBξ-dependent manner. Overall, these data identify an IL-17-driven inflammatory circuit in RTECs during AGN that is constrained by Regnase-1.

Acetic acid treatment causes renal inflammation and chronic kidney disease in mice

We established a novel mouse model of chronic kidney disease (CKD) using acetic acid and compared it with the 5/6-nephrectomized mouse model. In our novel model, significant increases were observed in blood biochemical values and urinary parameters. Moreover, a decrease in creatinine clearance (Ccr) was observed. This model also demonstrated a higher survival rate than the 5/6-nephrectomized model. Observed histological changes in our model included cell infiltration in the renal interstitium, tubular dilation, regenerated tubules, and glomerulosclerosis. Inflammation of the renal interstitium was particularly remarkable. TNF-α, IL-1β, and ICAM-1 mRNA expression were up-regulated prior to elevation of mean blood pressure and prior to changes in blood biochemical values and urinary parameters. Up-regulation of TGF-β mRNA and down-regulation of nephrin mRNA were also observed at 12 weeks after acetic acid treatment. However, no correlation between the progression of CKD and the decrease in renal blood flow was observed. Finally, repeated losartan administration attenuated the effects of acetic acid-induced renal injury. Our findings suggest that chronic kidney conditions associated with this model may be triggered by interstitial inflammation. Moreover, we suggest that this model is useful for understanding the pathophysiological mechanisms of CKD, and for evaluating the effects of therapeutic agents.

Shen Shuai II Recipe Attenuates Renal Interstitial Fibrosis by Improving Hypoxia via the IL-1β/c-Myc Pathway

Background

Renal interstitial fibrosis is a pathological manifestation of progression of chronic kidney disease induced by various factors. Shen Shuai II Recipe (SSR) has been used in clinical practice for more than 20 years, and clinical studies have confirmed that SSR significantly improves the renal function of patients with chronic kidney disease. However, the specific mechanisms underlying its efficacy require further research. This study aims to explore the influencing factors of renal interstitial fibrosis in the context of hypoxia via the IL-1β/c-Myc pathway and the potential molecular mechanisms of SSR intervention in vivo and in vitro.

Methods

A rat model of chronic renal failure was developed by performing 5/6 (ablation/infarction, A/I) surgery on randomly selected, male Sprague Dawley rats. Thirty-six successfully modeled rats were randomly divided into three groups: 5/6 (A/I), 5/6 (A/I) + SSR, and 5/6 (A/I) + losartan. Another 12 rats were used as the sham group. After 8 weeks of the corresponding intervention, renal function, liver function, and protein expression of renal-fibrosis-related factors, HIF-1α, IL-1β, and c-Myc, were detected. In vitro analysis was performed using hypoxia-induced rat renal tubular epithelial cells (NRK-52E) and IL-1β-stimulated rat renal interstitial fibroblasts (NRK-49F). IL-1β concentration in the culture medium and IL-1β protein expression in hypoxic NRK-52E treated with different concentrations of SSR were investigated. Furthermore, we also studied the changes in protein expression of c-Myc and fibrosis-related factors after c-Myc gene silencing in IL-1β-stimulated NRK-49F treated with SSR.

Results

Shen Shuai II Recipe significantly reduced RIF and downregulated the expression of HIF-1α, c-Myc, and IL-1β proteins in 5/6 (A/I) rats with chronic renal failure. It also inhibited IL-1β secretion from NRK-52E induced by hypoxia, which in turn inhibited fibroblast activation mediated by the IL-1β/c-Myc pathway, and finally reduced the overproduction of the extracellular matrix.

Conclusion

The renoprotective effects of SSR in rats with chronic renal failure may be related to its inhibition of hypoxia via the IL-1β/c-Myc pathway. Thus, SSR is a potentially effective drug for delaying the progression of renal interstitial fibrosis.

A Systematic Review of Renal Pathology in Chronic Kidney Disease of Uncertain Etiology

INTRODUCTION

Despite much research on chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka and the Mesoamerican nephropathy, the etiology and pathogenesis of this disease remains elusive. The pathology has broadly been described as chronic tubulointerstitial nephritis and no specific signature lesions have been identified.

METHODS

A scoping review was conducted through MEDLINE and Google Scholar databases for peer-reviewed publications on biopsy studies related to CKDu - Sri Lanka and Mesoamerican nephropathy to develop a comparative and critical analysis of the renal pathology found in these patients.

RESULTS

Thirteen studies met the selection criteria. Interstitial fibrosis was the predominant lesion in all the studies. Tubulointerstitial and glomerular abnormalities showed a more variable distribution. No characteristic histopathological feature was reported other than a proximal tubular lysosomal inclusion body which was claimed to indicate a toxic etiology. Three main pathogenetic mechanisms were postulated: repeated acute insults leading to scarring, low-grade chronic insults leading to non-inflammatory fibrosis, and tubulointerstitial damage in combination with glomerular injury. The main limitations in the interpretation and comparative analysis of these studies were the heterogeneity in case selection and biopsy reporting.

CONCLUSIONS

Although no characteristic histopathological feature could be found in CKDu-Sri Lanka or Mesoamerican nephropathy, there are noticeable differences between these two groups in the frequency and severity of the glomerular and tubulointerstitial changes which warrant more explorative studies preferably on kidneys in early stages of the disease. Future strategies should ensure that more uniform selection criteria and reporting methods are used.

Aetiology, course and treatment of acute tubulointerstitial nephritis in paediatric patients: a cross-sectional web-based survey

BACKGROUND

Acute tubulointerstitial nephritis (TIN) is a significant cause of acute renal failure in paediatric and adult patients. There are no large paediatric series focusing on the aetiology, treatment and courses of acute TIN.

PATIENTS, DESIGN AND SETTING

We collected retrospective clinical data from paediatric patients with acute biopsy-proven TIN by means of an online survey. Members of four professional societies were invited to participate.

RESULTS

Thirty-nine physicians from 18 countries responded. 171 patients with acute TIN were included (54% female, median age 12 years). The most frequent causes were tubulointerstitial nephritis and uveitis syndrome in 31% and drug-induced TIN in 30% (the majority of these caused by non-steroidal anti-inflammatory drugs). In 28% of patients, no initiating noxae were identified (idiopathic TIN). Median estimated glomerular filtration rate (eGFR) rose significantly from 31 at time of renal biopsy to 86 mL/min/1.73 m² 3-6 months later (p<0.001). After 3-6 months, eGFR normalised in 41% of patients (eGFR ≥90 mL/min/1.73 m²), with only 3% having severe or end-stage impairment of renal function (<30 mL/min/1.73 m²). 80% of patients received corticosteroid therapy. Median eGFR after 3-6 months did not differ between steroid-treated and steroid-untreated patients. Other immunosuppressants were used in 18% (n=31) of patients, 21 of whom received mycophenolate mofetil.

CONCLUSIONS

Despite different aetiologies, acute paediatric TIN had a favourable outcome overall with 88% of patients showing no or mild impairment of eGFR after 3-6 months. Prospective randomised controlled trials are needed to evaluate the efficacy of glucocorticoid treatment in paediatric patients with acute TIN.

Renal and non-renal response of ABC and SLC transporters in chronic kidney disease

INTRODUCTION

The solute carrier (SLC) and the ATP-binding cassette (ABC) transporter superfamilies play essential roles in the disposition of small molecules (endogenous metabolites, uremic toxins, drugs) in the blood, kidney, liver, intestine, and other organs. In chronic kidney disease (CKD), the loss of renal function is associated with altered function of remote organs. As renal function declines, many molecules accumulate in the plasma. Many studies now support the view that ABC and SLC transporters as well as drug metabolizing enzymes (DMEs) in renal and non-renal tissues are directly or indirectly affected by the presence of various types of uremic toxins, including those derived from the gut microbiome; this can lead to aberrant inter-organ communication.

AREAS COVERED

Here, the expression, localization and/or function of various SLC and ABC transporters as well as DMEs in the kidney and other organs are discussed in the context of CKD and systemic pathophysiology.

EXPERT OPINION

According to the Remote Sensing and Signaling Theory (RSST), a transporter and DME-centric network that optimizes local and systemic metabolism maintains homeostasis in the steady state and resets homeostasis following perturbations due to renal dysfunction. The implications of this view for pharmacotherapy of CKD are also discussed.

Chronic treatment with the (iso-)glutaminyl cyclase inhibitor PQ529 is a novel and effective approach for glomerulonephritis in chronic kidney disease

Glomeruli and renal tubule injury in chronic kidney disease (CKD) is reported to involve induction of macrophage activation through the CCL2/CCR2 axis. The effects of inhibitors of the CCL2/CCR2 axis, such as anti-CCL2 antibody and CCR2 antagonist, on kidney function in animal models or humans with kidney dysfunction have been demonstrated. The N-terminal glutamine on immature CCL2 is replaced with pyroglutamate (pE) by glutaminyl cyclase (QC) and isoQC. pE-CCL2 is stable and resistant to peptidases. We hypothesized that inhibiting QC/isoQC activity would lead to the degradation of CCL2, thereby ameliorating CKD and reducing kidney inflammation. To test this hypothesis, we investigated the renoprotective properties of the QC/isoQC inhibitor PQ529 in anti-glomerular basement membrane (GBM) antibody-induced glomerulonephritis Wistar Kyoto (WKY) rats. Three-week repeated administration of PQ529 (30 and 100 mg/kg, twice daily) significantly reduced the serum and urine CCL2 and urinary protein excretion in a dose-dependent manner. Correlations between the urinary protein level and serum or urinary CCL2 levels were confirmed in tested animals. Repeated administration of PQ529 significantly reduced the expression of CD68, a macrophage marker, in the kidney cortex and mononuclear infiltration into the tubulointerstitium. In addition, decreased levels of urinary KIM-1, β2 microglobulin, and clusterin were detected, suggesting the inhibition of inflammation in both the proximal and distal tubules. These results suggest that PQ529 suppresses the progression of inflammation-induced renal dysfunction by inhibiting the CCL2/CCR2 axis. Inhibition of QC/isoQC may thus be a viable alternative therapeutic approach for treating glomerulonephritis and CKD patients.

Relation between Vitamin D Level and Cyclin-Dependent Kinase-1 Gene Expression in Egyptian Patients with Lupus Nephritis and their Impact on Disease Activity

Introduction:

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus. Vitamin D and cycline-dependent kinase-1 (CDK1) have been implicated in its pathogenesis. The aim of this study was to determine the relation between vitamin D level and CDK-1 in lupus nephritis patients and their impact on disease activity.

Patients and Methods:

The current study was conducted on 50 LN patients and 20 control subjects from Egyptian population using ELISA to assess vitamin D level in serum and TaqMan assay for CDK1 gene expression.

Results:

Serum vitamin D level was significantly lower in LN patients and CDK-1 gene was down expressed in the majority of LN patients. A significant inverse correlation was found between vitamin D level and 24 h protein in urine, ANA, anti-dsDNA, CRP, with a significant positive correlation with renal biopsy indices, eGFR. There was a non-significant inverse correlation between vitamin D and CDK-1 (before RO-3306 addition) and a positive correlation after RO-3306. A significant positive correlation was found between CDK-1 gene expressions with urinary albumin/creatinine ratio. However, a significant positive correlation was found between CDK-1 (after RO-3306 addition) and proteinuria. While a significant positive correlation was found between CDK-1 expression (after RO-3306 addition) and ANA, a significant positive correlation was found between CDK-1 expression (before RO-3306 addition) and anti-dsDNA but CDK-1 is not associated with renal biopsy indices nor with activity indices of SLE. There was a positive correlation between CDK-1 gene expression and CRP before and after RO-3306 addition.

Conclusions:

Vitamin D deficiency acts as a risk factor for developing LN. CDK-1 may have an association with the diagnosis of LN but its association with the progression of staging of LN is still confusing

Netrin-1 and clusterin: Innovative potential diagnostic biomarkers for early renal damage in β-thalassemia major children

BACKGROUND

Children with β-thalassemia major (β-TM) suffer from tubular dysfunction even before the onset of any renal impairment symptoms and/or clinical signs. Therefore, identifying innovative biomarkers allowing early renal damage detection has focused attention.

AIM

This study aims to preliminary assess Netrin-1(NTN-1) and clusterin (CLU) in β-TM children and explore their possible roles as surrogate noninvasive biomarkers of renal tubular dysfunction.

SUBJECTS AND METHODS

In this study, 40 β-TM children and 30 healthy children were enrolled. Routine serum and urinary biochemical variables were determined. Urinary NTN-1 and CLU levels were measured using ELISA and their mRNA expression in PBMCs were assayed using real-time PCR. Serum TNF-α, MDA levels and GST activity were measured.

RESULTS

Urinary NTN-1 and CLU concentrations and mRNA relative expression levels in PBMCs were significantly increased in β-TM children relative to controls. Oxidative stress and inflammatory markers revealed significant elevation in β-TM children compared to controls. The change in these parameters correlated significantly with other renal parameters. ROC curves analysis showed that urinary NTN-1 and CLU levels are of promising diagnostic performance.

CONCLUSION

Our results suggest that NTN-1 and CLU are qualified as new noninvasive biomarker panels for early detection of renal injury in β-TM children. Moreover, urinary NTN-1 is recommended as a precise one during the clinical practices.

MR Elastography of the Abdomen: Basic Concepts

Magnetic resonance elastography (MRE) is an emerging imaging modality that maps the elastic properties of tissue such as the shear modulus. It allows for noninvasive assessment of stiffness, which is a surrogate for fibrosis. MRE has been shown to accurately distinguish absent or low stage fibrosis from high stage fibrosis, primarily in the liver. Like other elasticity imaging modalities, it follows the general steps of elastography: (1) apply a known cyclic mechanical vibration to the tissue; (2) measure the internal tissue displacements caused by the mechanical wave using magnetic resonance phase encoding method; and (3) infer the mechanical properties from the measured mechanical response (displacement), by generating a simplified displacement map. The generated map is called an elastogram.While the key interest of MRE has traditionally been in its application to liver, where in humans it is FDA approved and commercially available for clinical use to noninvasively assess degree of fibrosis, this is an area of active research and there are novel upcoming applications in brain, kidney, pancreas, spleen, heart, lungs, and so on. A detailed review of all the efforts is beyond the scope of this chapter, but a few specific examples are provided. Recent application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney diseases. Development and applications of MRE in preclinical models is necessary primarily to validate the measurement against "gold-standard" invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRE acquisitions in preclinical settings involves challenges in terms of available hardware, logistics, and data acquisition. This chapter will introduce the concepts of MRE and provide some illustrative applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by another separate chapter describing the experimental protocol and data analysis.

Protective Role of Nrf2 in Renal Disease

Chronic kidney disease (CKD) is one of the fastest-growing causes of death and is predicted to become by 2040 the fifth global cause of death. CKD is characterized by increased oxidative stress and chronic inflammation. However, therapies to slow or prevent CKD progression remain an unmet need. Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that plays a key role in protection against oxidative stress and regulation of the inflammatory response. Consequently, the use of compounds targeting Nrf2 has generated growing interest for nephrologists. Pre-clinical and clinical studies have demonstrated that Nrf2-inducing strategies prevent CKD progression and protect from acute kidney injury (AKI). In this article, we review current knowledge on the protective mechanisms mediated by Nrf2 against kidney injury, novel therapeutic strategies to induce Nrf2 activation, and the status of ongoing clinical trials targeting Nrf2 in renal diseases.

Increased Levels of Renal Lysophosphatidic Acid in Rodent Models with Renal Disease

Lysophosphatidic acid (LPA) is a bioactive lipid mediator that has been implicated in the pathophysiology of kidney disease. However, few studies have attempted to measure changes in the levels of various LPA species in the kidney after the development of renal disease. The present study measured the renal LPA levels during the development of kidney disease in rat models of hypertension, diabetes, and obstructive nephropathy using liquid chromatography/mass spectrometry/mass spectrometry. LPA levels (sum of 16:0, 18:0, 18:1, 18:2, and 20:4 LPA) were higher in the renal cortex of hypertensive Dahl salt-sensitive (Dahl S) rats fed a high-salt diet than those in normotensive rats fed a low-salt diet (296.6 ± 22.9 vs. 196.3 ± 8.5 nmol/g protein). LPA levels were elevated in the outer medulla of the kidney of streptozotocin-induced type 1 diabetic Dahl S rats compared with control rats (624.6 ± 129.5 vs. 318.8 ± 17.1 nmol/g protein). LPA levels were also higher in the renal cortex of 18-month-old, type 2 diabetic nephropathy (T2DN) rats with more severe renal injury than in 6-month-old T2DN rats (184.9 ± 20.9 vs. 116.9 ± 6.0 nmol/g protein). LPA levels also paralleled the progression of renal fibrosis in the renal cortex of Sprague-Dawley rats after unilateral ureteral obstruction (UUO). Administration of an LPA receptor antagonist, Ki16425, reduced the degree of renal fibrosis in UUO rats. These results suggest that the production of renal LPA increases during the development of renal injury and contributes to renal fibrosis. SIGNIFICANCE STATEMENT: The present study reveals that the lysophosphatidic acid (LPA) levels increase in the kidney in rat models of hypertension, diabetes, and obstructive nephropathy, and administration of an LPA receptor antagonist attenuates renal fibrosis. Therapeutic approaches that target the formation or actions of renal LPA might be renoprotective and have therapeutic potential.

Stabilization of hypoxia-inducible factor ameliorates glomerular injury sensitization after tubulointerstitial injury

Previously, we found that mild tubulointerstitial injury sensitizes glomeruli to subsequent injury. Here, we evaluated whether stabilization of hypoxia-inducible factor-α (HIF-α), a key regulator of tissue response to hypoxia, ameliorates tubulointerstitial injury and impact on subsequent glomerular injury. Nep25 mice, which express the human CD25 receptor on podocytes under control of the nephrin promotor and develop glomerulosclerosis when a specific toxin is administered were used. Tubulointerstitial injury, evident by week two, was induced by folic acid, and mice were treated with an HIF stabilizer, dimethyloxalylglycine or vehicle from week three to six. Uninephrectomy at week six assessed tubulointerstitial fibrosis. Glomerular injury was induced by podocyte toxin at week seven, and mice were sacrificed ten days later. At week six tubular injury markers normalized but with patchy collagen I and interstitial fibrosis. Pimonidazole staining, a hypoxia marker, was increased by folic acid treatment compared to vehicle while dimethyloxalylglycine stimulated HIF-2α expression and attenuated tubulointerstitial hypoxia. The hematocrit was increased by dimethyloxalylglycine along with downstream effectors of HIF. Tubular epithelial cell injury, inflammation and interstitial fibrosis were improved after dimethyloxalylglycine, with further reduced mortality, interstitial fibrosis, and glomerulosclerosis induced by specific podocyte injury. Thus, our findings indicate that hypoxia contributes to tubular injury and consequent sensitization of glomeruli to injury. Hence, restoring HIFs may blunt this adverse crosstalk of tubules to glomeruli.

Urine hepcidin, netrin-1, neutrophil gelatinase-associated lipocalin and C-C motif chemokine ligand 2 levels in multicystic dysplastic kidney

Introduction:

Glomerular hyperfiltration may lead to proteinuria and chronic kidney disease in unilateral multicystic dysplastic kidney (MCDK). We aimed to investigate the urine neutrophil-gelatinase-associated lipocalin (NGAL), netrin-1, hepcidin, and C-C motif chemokine ligand-2 (MCP-1/CCL-2) levels in patients with MCDK.

Methods:

Thirty-two patients and 25 controls were included. The urine hepcidin, netrin-1, NGAL, and MCP-1/CCL-2 levels were determined by ELISA.

Results:

The patients had higher serum creatinine (Cr) levels, urine albumin, and netrin-1/ Cr ratio with lower GFR. There were positive correlations between urine protein/Cr, MCP-1/CCL-2/Cr, and netrin-1 with NGAL (r = 0.397, p = 0.031; r = 0.437, p = 0.041, r = 0.323, p = 0.042, respectively). Urine netrin-1/Cr was positively correlated with MCP-1/ CCL-2/Cr (r = 0.356, p = 0.045). There were positive associations between the presence of proteinuria and netrin-1/ Cr, MCP-1/CCL-2/Cr, and NGAL/Cr [Odds ratio (OR): 1.423, p = 0.037, OR: 1.553, p = 0.033, OR: 2.112, p = 0.027, respectively)]. ROC curve analysis showed that netrin-1/Cr, MCP-1/CCL-2/Cr, and NGAL/Cr had high predictive values for determining proteinuria p = 0.027, p = 0.041, p = 0.035, respectively). Urine hepcidin/ Cr was negatively correlated with tubular phosphorus reabsorption and was positively correlated with urine NGAL/Cr (r = -0.418, p = 0.019; r = 0.682, p = 0.000; respectively).

Conclusions:

MCP-1/CCL-2 may play a role in the development of proteinuria in MCDK. Netrin-1 may be a protective factor against proteinuria-induced renal injury. Urine hepcidin/Cr may reflect proximal tubule damage in MCDK. Urine NGAL/Cr may be a predictor of tubule damage by proteinuria.

Praliciguat inhibits progression of diabetic nephropathy in ZSF1 rats and suppresses inflammation and apoptosis in human renal proximal tubular cells

Praliciguat, a clinical-stage soluble guanylate cyclase (sGC) stimulator, increases cGMP via the nitric oxide-sGC pathway. Praliciguat has been shown to be renoprotective in rodent models of hypertensive nephropathy and renal fibrosis. In the present study, praliciguat alone and in combination with enalapril attenuated proteinuria in the obese ZSF1 rat model of diabetic nephropathy. Praliciguat monotherapy did not affect hemodynamics. In contrast, enalapril monotherapy lowered blood pressure but did not attenuate proteinuria. Renal expression of genes in pathways involved in inflammation, fibrosis, oxidative stress, and kidney injury was lower in praliciguat-treated obese ZSF1 rats than in obese control rats; fasting glucose and cholesterol were also lower with praliciguat treatment. To gain insight into how tubular mechanisms might contribute to its pharmacological effects on the kidneys, we studied the effects of praliciguat on pathological processes and signaling pathways in cultured human primary renal proximal tubular epithelial cells (RPTCs). Praliciguat inhibited the expression of proinflammatory cytokines and secretion of monocyte chemoattractant protein-1 in tumor necrosis factor-α-challenged RPTCs. Praliciguat treatment also attenuated transforming growth factor-β-mediated apoptosis, changes to a mesenchyme-like cellular phenotype, and phosphorylation of SMAD3 in RPTCs. In conclusion, praliciguat improved proteinuria in the ZSF1 rat model of diabetic nephropathy, and its actions in human RPTCs suggest that tubular effects may contribute to its renal benefits, building upon strong evidence for the role of cGMP signaling in renal health.

Impaired renal hemodynamics and glomerular hyperfiltration contribute to hypertension-induced renal injury

Recently, we reported a mutation in γ-adducin (ADD3) was associated with an impaired myogenic response of the afferent arteriole and hypertension-induced chronic kidney disease (CKD) in fawn hooded hypertensive (FHH) rats. However, the mechanisms by which altered renal blood flow (RBF) autoregulation promotes hypertension-induced renal injury remain to be determined. The present study compared the time course of changes in renal hemodynamics and the progression of CKD during the development of DOCA-salt hypertension in FHH 1^BN congenic rats [wild-type (WT)] with an intact myogenic response versus FHH 1^BN Add3KO (Add3KO) rats, which have impaired myogenic response. RBF was well autoregulated in WT rats but not in Add3KO rats. Glomerular capillary pressure rose by 6 versus 14 mmHg in WT versus Add3KO rats when blood pressure increased from 100 to 150 mmHg. After 1 wk of hypertension, glomerular filtration rate increased by 38% and glomerular nephrin expression decreased by 20% in Add3KO rats. Neither were altered in WT rats. Proteinuria doubled in WT rats versus a sixfold increase in Add3KO rats. The degree of renal injury was greater in Add3KO than WT rats after 3 wk of hypertension. RBF, glomerular filtration rate, and glomerular capillary pressure were lower by 20%, 28%, and 19% in Add3KO rats than in WT rats, which was associated with glomerular matrix expansion and loss of capillary filtration area. The results indicated that impaired RBF autoregulation and eutrophic remodeling of preglomerular arterioles increase the transmission of pressure to glomeruli, which induces podocyte loss and accelerates the progression of CKD in hypertensive Add3KO rats.

Impact of intentional accessory renal artery coverage on renal outcomes after fenestrated-branched endovascular aortic repair

OBJECTIVE

The objective of this study was to evaluate the impact of intentional coverage of accessory renal arteries (ARAs) on renal outcomes after fenestrated-branched endovascular aortic repair (FB-EVAR) for pararenal aortic aneurysms or thoracoabdominal aortic aneurysms.

METHODS

We analyzed the clinical data of 296 patients enrolled in a prospective nonrandomized study to evaluate outcomes of FB-EVAR between 2013 and 2018. Patients with solitary kidneys, intraoperative loss of main renal arteries, or pre-existing stage V chronic kidney disease were excluded. Two groups were analyzed: patients with intentional ARA coverage; and controls, who had complete preservation. End points included 30-day mortality; major adverse events; acute kidney injury (AKI), defined by RIFLE criteria (Risk, Injury, Failure, Loss of kidney function, and End-stage renal disease); renal function deterioration (RFD), defined by >30% decline in baseline estimated glomerular filtration rate; and presence of renal infarcts.

RESULTS

There were 254 patients (184 male; mean age, 75 ± 8 years) included in the study, 56 (22%) with intentional ARA coverage and 198 controls, of whom 16 had ARA preservation. ARA diameter was smaller in patients who had intentional coverage vs preservation (2.7 ± 0.9 mm vs 3.4 ± 0.2 mm; P < .001). There was no difference in demographics, cardiovascular risk factors, and aneurysm extent. All ARAs intended to be incorporated were successfully stented. Patients with ARA coverage had a higher frequency of kidney infarction (75% vs 25%; P < .001). There were two (1%) deaths within 30 days, both among controls. Patients with ARA coverage had more major adverse events (32% vs 19%; P = .04) because of higher incidence of AKI (21% vs 9%; P = .02). None of the 16 patients who had ARA preservation developed AKI. At 3 years, freedom from RFD was lower for patients who had ARA coverage compared with controls (55% ± 9% vs 76% ± 5%; log-rank, P = .02). By multivariate analysis, predictors of AKI were ARA coverage (odds ratio, 2.8; 95% confidence interval [CI], 1.2-6.2; P = .01) and estimated blood loss >1 L (odds ratio, 3.8; 95% CI, 1.2-12.3; P = .03). Postoperative AKI (hazard ratio [HR], 4.4; 95% CI, 2.4-8.1; P < .001), renal reintervention for stenosis (HR, 3.2; 95% CI, 1.6-6.7; P = .002), aneurysm diameter (HR, 1.04; 95% CI, 1.02-1.06; P < .001), and ARA coverage (HR, 2.0; 95% CI, 2.4-8.1; P = .02) were predictors of RFD.

CONCLUSIONS

Intentional ARA coverage during FB-EVAR was associated with a threefold increase in AKI and with lower freedom from RFD. Factors associated with RFD included postoperative AKI, renal reinterventions for stenosis, and ARA coverage. Incorporation of ARAs during FB-EVAR, when it is technically feasible, helps decrease risk of AKI and RFD.

Profibrotic gene transcription in renal tissues from cats with ischemia-induced chronic kidney disease

OBJECTIVE

To characterize transcription of profibrotic mediators in renal tissues of cats with ischemia-induced chronic kidney disease (CKD).

SAMPLE

Banked renal tissues from 6 cats with experimentally induced CKD (RI group) and 8 healthy control cats.

PROCEDURES

For cats of the RI group, both kidneys were harvested 6 months after ischemia was induced for 90 minutes in 1 kidney. For control cats, the right kidney was evaluated. All kidney specimens were histologically examined for fibrosis, inflammation, and tubular atrophy. Renal tissue homogenates underwent reverse transcription quantitative PCR assay evaluation to characterize gene transcription of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase (MMP)-2, MMP-7, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), transforming growth factor-β1, and vascular endothelial growth factor A. Gene transcription and histologic lesions were compared among ischemic and contralateral kidneys of the RI group and control kidneys.

RESULTS

Ischemic kidneys had greater transcript levels of MMP-7, MMP-9, and transforming growth factor-β1 relative to control kidneys and of MMP-2 relative to contralateral kidneys. Transcription of TIMP-1 was upregulated and that of vascular endothelial growth factor A was downregulated in ischemic and contralateral kidneys relative to control kidneys. Transcription of HIF-1α did not differ among kidney groups. For ischemic kidneys, there were strong positive correlations between transcription of HIF-1α, MMP-2, MMP-7, and TIMP-1 and severity of fibrosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Transcription of genes involved in profibrotic pathways remained altered in both kidneys 6 months after transient renal ischemia. This suggested that a single unilateral renal insult can have lasting effects on both kidneys.

Four-dimensional (4D) phase velocity optical coherence elastography in heterogeneous materials and biological tissue

The variations of mechanical properties in soft tissues are biomarkers used for clinical diagnosis and disease monitoring. Optical coherence elastography (OCE) has been extensively developed to investigate mechanical properties of various biological tissues. These methods are generally based on time-domain data and measure the time-of-flight of the localized shear wave propagations to estimate the group velocity. However, there is considerable information that can be obtained from examining the mechanical properties such as wave propagation velocities at different frequencies. Here we propose a method to evaluate phase velocity, wave velocity at various frequencies, in four-dimensional space (x, y, z, f), called 4D-OCE phase velocity. The method enables local estimates of the phase velocity of propagating mechanical waves in a medium. We acquired and analyzed data with this method from a homogeneous reference phantom, a heterogeneous phantom material with four different excitation cases, and ex vivo porcine kidney tissue. The 3D-OCE group velocity was also estimated to compare with 4D-OCE phase velocity. Moreover, we performed numerical simulation of wave propagations to illustrate the boundary behavior of the propagating waves. The proposed 4D-OCE phase velocity is capable of providing further information in OCE to better understand the spatial variation of mechanical properties of various biological tissues with respect to frequency.

Reno-protective effects of oral alkalizing agents in chronic kidney disease with aciduria: protocol for a randomized cohort study

Background

Aciduria caused by urinary excretion of acidic metabolic wastes produced in daily life is known to be augmented in patients with chronic kidney disease (CKD). To evaluate the reno-protective effect of oral alkalizing agents for the improvement of metabolic acidosis and neutralization of intratubular pH in the patients with mild stages of CKD. Also, to identify reno-protective surrogate markers in the serum and urine that can closely associate the effect of urine alkalization.

Methods

In this single-centered, open-labeled, randomized cohort study, patients with CKD stages G2, G3a and G3b, who visited and were treated at Tohoku University Hospital during the enrollment period were registered. We administered sodium bicarbonate or sodium-potassium citrate as the oral alkalinizing agents. A total of 150 patients with CKD will be randomly allocated into the following three groups: sodium bicarbonate, sodium-potassium citrate and standard therapy group without any alkalinizing agents. The data of performance status, venous blood test, spot urine test, venous blood-gas test, electrocardiogram, renal arterial ultrasonography and chest X-ray will be collected at 0, 6, 12 and 24 weeks (short-term study) from starting the interventions. These data will be also collected at 1 and 2 years (long-term study). The samples of plasma and serum and early-morning urine at every visit will be acquired for the analysis of renal function and surrogate uremic biomarkers.

The recruitment for this cohort study terminated in March, 2018, and the follow-up period for all the enrolled subjects will be terminated in December, 2020. The primary endpoint will be the development of originally-defined significant renal dysfunction or the occurrence of any cerebrovascular disease in the short-term study. The secondary endpoint will be the same endpoints as in the long-term study, or the patients with significant changes in the suggested the surrogate biomarkers.

Discussion

The findings of this study will address the importance of taking oral alkalizing agents in the patients with early stages of CKD, furthermore they could address any new surrogate biomarkers that can be useful from early stage CKD.

Trial registration

Registered Report Identifier: UMIN000010059 and jRCT021180043.

The trial registration number; 150.

Date of registration; 2013/02/26.

Magnetic resonance elastography-derived stiffness of the kidneys and its correlation with water perfusion

Stiffness plays an important role in diagnosing renal fibrosis. However, kidney stiffness is altered by perfusion changes in many kidney diseases. Therefore, the aim of the current study is to determine the correlation of kidney stiffness with water intake. We hypothesize that kidney stiffness will increase with 1 L of water intake due to increased water perfusion to the kidneys. Additionally, stiffness of the kidneys will correlate with apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values before and after water intake. A 3 T MRI scanner was used to perform magnetic resonance elastography and diffusion tensor imaging of the kidneys on 24 healthy subjects (age range: 22-66 years) before and after water intake of 1 L. A 3D T1-weighted bladder scan was also performed to measure bladder volume before and after water intake. A paired t-test was performed to evaluate the effect of water intake on the stiffness of kidneys, in addition to bladder volume. A Spearman correlation test was performed to determine the association between stiffness, bladder volume, ADC and FA values of both kidneys before and after water intake. The results show a significant increase in stiffness in different regions of the kidney (ie, percentage increase ranged from 3.6% to 7.5%) and bladder volume after water intake (all P < 0.05). A moderate significant negative correlation was observed between change in kidney stiffness and bladder volume (concordance correlation coefficient = -0.468, P < 0.05). No significant correlation was observed between stiffness and ADC or FA values before and after water intake in both kidneys (P > 0.05). Water intake caused a significant increase in the stiffness of the kidneys. The negative correlation between the change in kidney stiffness and bladder volume, before and after water intake, indicates higher perfusion pressure in the kidneys, leading to increased stiffness.

The association of renal tubular inflammatory and injury markers with uric acid excretion in chronic kidney disease patients

AIM

To investigate the correlation of renal tubular inflammatory and injury markers with renal uric acid excretion in chronic kidney disease (CKD) patients.

METHODS

Seventy-three patients with CKD were enrolled. Fasting blood and morning urine sample were collected for routine laboratory measurements. At the same time, 24 h of urine was collected for urine biochemistry analyses, and 10 ml was extracted from the 24-h urine sample to further detect renal tubular inflammatory and injury markers, including interleukin-18 (IL-18), interleukin 1β (IL-1β), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). The patients were divided into three tertile groups according to their 24-h urinary uric acid (24-h UUA) levels (UUA1: 24-h UUA ≤ 393.12 mg; UUA2: 393.12 < 24-h UUA ≤ 515.76 mg; UUA3: 24-h UUA > 515.76 mg). The general clinical and biochemical indexes were compared. Multivariable linear regression models were used to test the association of IL-18/Urinary creatinine concentration (IL-18/CR), IL-1β/CR, NGAL/CR and KIM-1/CR with renal uric acid excretion indicators.

RESULTS

All of tested renal tubular inflammation- and injury-related urinary markers were negatively associated with 24-h UUA and UEUA, and the negative correlation still persisted after adjusting for multiple influencing factors including urinary protein and eGFR. Further group analyses showed that these makers were significantly higher in the UUA1 than in the UUA3 group.

CONCLUSIONS

Our findings suggest that markers of urinary interstitial inflammation and injury in CKD patients are significantly correlated with 24-h UUA and Urinary excretion of uric acid (UEUA), and those with high 24-h UUA have lower levels of these markers. Renal uric acid excretion may also reflect the inflammation and injury of renal tubules under certain conditions.

Calcitriol Ameliorates Kidney Injury Through Reducing Podocytopathy, Tubular Injury, Inflammation and Fibrosis in 5/6 Subtotal Nephrectomy Model in Rats

Chronic kidney diseases (CKDs) lead to end-stage renal diseases (ESRD) which are characterized by glomerulosclerosis, tubular injury, anemia, inflammation, and interstitial fibrosis. Vitamin D is known to have renal protective effects. However, its effects relate to low and high doses of Vitamin D in CKD model is still unknown. CKD was performed using 5/6 subtotal nephrectomy procedure in male Sprague Dawley rats (3 months old, 200-300 grams, SN group; n=6), then rats were sacrificed on day 14 after operation. Sham operation was used for control (SO group; n=6). Calcitriol was administered in two doses : 0.01 µg/mL/100 gramsBW/day (SND1 group; n=6) and 0.05 µg/mL/100 gramsBW/day (SND2 group; n=6) intraperitoneally for 14 days. Glomerulosclerosis and tubular injury score were examined using PAS staining, meanwhile, interstitial fibrosis area fraction was assessed with Sirius Red staining. RT-PCR was performed for assessing nephrin, podocin, IL-6, CD68, Collagen-1, and TGF-β1 mRNA expressions. Immunostaining (IHC) was carried out to observe macrophage (CD68) and myofibroblast (α-SMA). SN demonstrated CKD condition with higher tubular injury, glomerulosclerosis, interstitial fibrosis, and inflammation compared to SO. Calcitriol-treated group (especially SND2) demonstrated significant lower tubular injury, glomerulosclerosis, and interstitial fibrosis compared to SN. SND2 group showed not only significantly lower CD68, IL-6, Collagen-1, and TGF-β1 mRNA expressions, but also higher mRNA expressions of nephrin and podocin. SND2 group also demonstrated reduction of macrophages infiltration and myofibroblasts expansion based on its histopathological appearance. Vitamin D may have a renoprotective effect on 5/6 subtotal nephrectomy model by attenuating podocytopathy, tubular injury, inflammation and interstitial fibrosis.

Targeting the progression of chronic kidney disease

Chronic kidney disease (CKD) is a devastating condition that is reaching epidemic levels owing to the increasing prevalence of diabetes mellitus, hypertension and obesity, as well as ageing of the population. Regardless of the underlying aetiology, CKD is slowly progressive and leads to irreversible nephron loss, end-stage renal disease and/or premature death. Factors that contribute to CKD progression include parenchymal cell loss, chronic inflammation, fibrosis and reduced regenerative capacity of the kidney. Current therapies have limited effectiveness and only delay disease progression, underscoring the need to develop novel therapeutic approaches to either stop or reverse progression. Preclinical studies have identified several approaches that reduce fibrosis in experimental models, including targeting cytokines, transcription factors, developmental and signalling pathways and epigenetic modulators, particularly microRNAs. Some of these nephroprotective strategies are now being tested in clinical trials. Lessons learned from the failure of clinical studies of transforming growth factor β1 (TGFβ1) blockade underscore the need for alternative approaches to CKD therapy, as strategies that target a single pathogenic process may result in unexpected negative effects on simultaneously occurring processes. Additional promising avenues include preventing tubular cell injury and anti-fibrotic therapies that target activated myofibroblasts, the main collagen-producing cells.

Effect and Regulation of the NLRP3 Inflammasome During Renal Fibrosis

Renal fibrosis is a common pathological process where certain primary or secondary kidney diseases can continue to progress to the end-stage of the kidney disease; however, the molecular mechanisms underlying renal fibrosis remain unclear. Recently, research focusing on examining the function of inflammasomes has attracted a great deal of attention, and data derived from these research projects have increased our understanding of the effects and regulation of inflammasomes during renal fibrosis. Based on this, the present review summarizes recent findings in regard to NLRP3 inflammasome functions during various kidney diseases, and these findings indicate that the NLRP3 inflammasome not only mediates the inflammatory response but is also associated with pyroptosis, mitochondrial regulation, and myofibroblast differentiation during renal fibrosis. These novel findings provide us with a more in-depth understanding of the pathogenesis of renal fibrosis and will aid in the identification of new targets that can be used for the prevention and treatment of this disease.