A Klotho-Based Machine Learning Model for Prediction of both Kidney and Cardiovascular Outcomes in Chronic Kidney Disease.

Introduction: This study aimed to develop and validate machine learning (ML) models based on serum Klotho for predicting end-stage kidney disease (ESKD) and cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Methods: Five different ML models were trained to predict the risk of ESKD and CVD at three different time points (3, 5, and 8 years) using a cohort of 400 non-dialysis CKD patients. The dataset was divided into a training set (70%) and an internal validation set (30%). These models were informed by data comprising 47 clinical features, including serum Klotho. The best-performing model was selected and used to identify risk factors for each outcome. Model performance was assessed using various metrics. Results: The findings showed that the least absolute shrinkage and selection operator regression model had the highest accuracy (C-index = 0.71) in predicting ESKD. The features mainly included in this model were estimated glomerular filtration rate, 24-h urinary microalbumin, serum albumin, phosphate, parathyroid hormone, and serum Klotho, which achieved the highest area under the curve (AUC) of 0.930 (95% CI: 0.897-0.962). In addition, for the CVD risk prediction, the random survival forest model with the highest accuracy (C-index = 0.66) was selected and achieved the highest AUC of 0.782 (95% CI: 0.633-0.930). The features mainly included in this model were age, history of primary hypertension, calcium, tumor necrosis factor-alpha, and serum Klotho. Conclusion: We successfully developed and validated Klotho-based ML risk prediction models for CVD and ESKD in CKD patients with good performance, indicating their high clinical utility.

Genetic diagnosis of Alport syndrome in 16 Chinese families.

BACKGROUND: Alport syndrome (AS) is a genetically heterogeneous disorder resulting from mutations in the collagen IV genes COL4A3, COL4A4, and COL4A5. The genetic diagnosis of AS is very important to make precise diagnosis and achieve optimal outcomes. METHODS: In this study, 16 Chinese families with suspected AS were recruited after pedigree analysis, and the clinical presentations were analyzed by a nephrologist. The genetic diagnosis was performed by whole-exome sequencing (WES) and the disease-causing variants were confirmed by Sanger sequencing. RESULTS: The cohort of probands included seven men and nine women, with a mean age of 19.9 years. Pathological analysis showed slight-to-moderate mesangial proliferation, and thin basement membrane was the main findings. Pathogenic variants were revealed by WES in each family, and the co-segregation with renal presentation was confirmed by PCR. In addition, RT-PCR analysis showed that the intronic variant led to aberrant splicing. CONCLUSION: Our findings expand the spectrum of AS gene variation, which will inform genetic diagnosis and add to the theoretical basis for the prevention of AS.

A Novel Mutation of UMOD in a Chinese Family with IgA Nephropathy: A Case Report.

IgA nephropathy (IgAN) is the most prevalent primary glomerulonephritis worldwide, with varying clinical presentations. The hereditary susceptibility to IgAN is rather complex. In this report, a Chinese case of IgAN was recruited. Renal biopsy showed the tubular atrophy and dilatation, but the glomerular lesions were rather weak except slight mesangial hyperplasia. Immunological staining of kidney tissue revealed the positive immunological staining of IgA and C3. By using whole-exome sequencing, a heterozygous variant in UMOD gene was found and was confirmed by Sanger sequencing. The variant in UMOD gene might contribute to the disease and this case helps understand the correlation of genotype and phenotypes of UMOD mutations.

Townes-Brocks syndrome with adult renal impairment in a Chinese family: A case report.

BACKGROUND: Townes-Brocks syndrome (TBS) is a rare autosomal dominant syndrome that is characterized by a triad of imperforate anus, dysplastic ears, and thumb malformations. Heterozygous variants of SALL1 are responsible for this syndrome. Renal structural abnormalities and functional impairments are often reported in TBS patients. CASE SUMMARY: We report a case of TBS in a Chinese family. The index patients showed obvious renal atrophy and renal failure. TBS was suggested after a physical examination and pedigree analysis. Whole exome sequencing revealed a heterozygous variant of SALL1. The variant (NM_001127892 c.1289_c.1290 insC) led to a read-frame shift of the encoded protein, which was confirmed by Sanger sequencing. The variant cosegregated with the phenotype among affected members. CONCLUSION: A novel variant in SALL1 gene may be the molecular pathogenic basis of this disorder.

IL-37 Ameliorates Renal Fibrosis by Restoring CPT1A-Mediated Fatty Acid Oxidation in Diabetic Kidney Disease.

Introduction: Diabetic kidney disease (DKD) is a major source of chronic kidney disease and end-stage renal disease. The injury of glomerulus in DKD is the primary focus; however, proximal tubulopathy also is an indispensable factor in the progression of DKD. Interleukin-37 (IL-37), an anti-inflammatory cytokine of IL-1 family member, has been demonstrated to be associated with diabetes and its relative complications in recent years, but the effect of IL-37 on renal fibrosis in DKD is unclear. Methods: We established streptozotocin plus high fat diet-induced DKD mice model with wild type or IL-37 transgenic mice. Masson and HE staining, immunostaining, and Western blot were used to observe renal fibrosis. In addition, RNA-sequencing was applied to explore the potential mechanisms of IL-37. In vitro, treatment of human proximal tubular (HK-2) cells with 30 mmol/L high glucose or 300 ng/mL recombinant IL-37 further elucidated the possible mechanism of IL-37 inhibition of DKD renal fibrosis. Results: In this work, we first verified the decreased expression of IL-37 in kidney of DKD patient and its correlation with clinical features of renal impairment. Moreover, IL-37 expression markedly attenuated proteinuria and renal fibrosis in DKD mice. Using RNA-sequencing, we found and confirmed a novel role of IL-37 in ameliorating fatty acid oxidation (FAO) reduction of renal tubular epithelial cells both in vivo and in intro. In addition, further mechanistic studies showed that IL-37 alleviated the FAO reduction in HK-2 cells and renal fibrosis in DKD mice through upregulating carnitine palmitoyl-transferase 1A (CPT1A), an important catalyzer for FAO pathway. Conclusion: These data suggest that IL-37 attenuates renal fibrosis via regulating FAO in renal epithelial cells. Upregulation of IL-37 levels might be an effective therapeutic avenue for DKD.

A Pathogenic Variant of PBX1 Identified by Whole Exome Sequencing in a Chinese CAKUTHED Case.

Congenital anomalies of kidney and urinary tract syndrome with or without hearing loss, abnormal ears, or developmental delay (CAKUTHED) is a rare autosomal dominant disorder and variants in PBX1 are involved in the etiology of this syndrome. Precise diagnosis is difficult without genetic test. We described a Chinese CAKUTHED patient, whose characteristics were collected from medical records. The potential responsible variants were explored by whole exome sequencing. A heterozygous variant in the PBX1 gene (NM_002585 c.862C>T, p.R288*) was found in the proband, which was confirmed by Sanger sequencing. This heterozygous variant in the PBX1 gene was the molecular pathogenic basis of this disorder. It is necessary to perform a genetic test for diagnosing chronic nephritis with unknown reason.

Activation of EP4 alleviates AKI-to-CKD transition through inducing CPT2-mediated lipophagy in renal macrophages.

Acute kidney injury (AKI) is a common clinical syndrome with complex pathogenesis, characterized by a rapid decline in kidney function in the short term. Worse still, the incomplete recovery from AKI increases the risk of progression to chronic kidney disease (CKD). However, the pathogenesis and underlying mechanism remain largely unknown. Macrophages play an important role during kidney injury and tissue repair, but its role in AKI-to-CKD transition remains elusive. Herein, single nucleus RNA sequencing (snRNA-Seq) and flow cytometry validations showed that E-type prostaglandin receptor 4 (EP4) was selectively activated in renal macrophages, rather than proximal tubules, in ischemia-reperfusion injury (IRI)-induced AKI-to-CKD transition mouse model. EP4 inhibition aggravated AKI-to-CKD transition, while EP4 activation impeded the progression of AKI to CKD though regulating macrophage polarization. Mechanistically, network pharmacological analysis and subsequent experimental verifications revealed that the activated EP4 inhibited macrophage polarization through inducing Carnitine palmitoyltransferase 2 (CPT2)-mediated lipophagy in macrophages. Further, CPT2 inhibition abrogated the protective effect of EP4 on AKI-to-CKD transition. Taken together, our findings demonstrate that EP4-CPT2 signaling-mediated lipophagy in macrophages plays a pivotal role in the transition of AKI to CKD and targeting EP4-CPT2 axis could serve as a promising therapeutic approach for retarding AKI and its progression to CKD.

Arteriolar hyalinosis and renal outcomes in patients with immunoglobulin A nephropathy.

BACKGROUND: The relationship between arteriolar hyalinosis and renal progression in immunoglobulin A nephropathy (IgAN) is not fully understood. We aimed to investigate the clinicopathological features and outcomes of IgAN with or without arteriolar hyalinosis. METHODS: A total of 762 diagnosed with IgAN patients were retrospectively analyzed. We classified IgAN patients into two groups with or without arteriolar hyalinosis. Then, the clinicopathological characteristics of the two groups were compared. We used Kaplan-Meier survival analysis to compare the composite kidney outcome of the two groups and applied multivariate Cox regression analyses to test the association between arteriolar hyalinosis and composite kidney outcome. RESULTS: Overall, 412 (54.1%) patients had arteriolar hyalinosis, including 173 patients diagnosed with hypertension. IgAN patients with arteriolar hyalinosis were older and had higher proteinuria, urea, uric acid, and blood pressure, while lower eGFR than those without arteriolar hyalinosis. Subgroup analysis showed similar results in IgAN patients with hypertension. Kaplan-Meier survival analysis showed that IgAN patients with arteriolar hyalinosis had worse composite kidney outcome than those without arteriolar hyalinosis. In addition, subgroup analysis revealed that patients with hypertension have worse composite kidney outcome than those without hypertension. Multivariate Cox regression analyses confirm that arteriolar hyalinosis (HR 2.57; 95% CI 1.41-4.69; p = 0.002) is an independent risk factor for renal prognosis in IgAN patients. CONCLUSIONS: Our study demonstrated that arteriolar hyalinosis is a common vascular lesion in IgAN patients. Arteriolar hyalinosis connects closely with hypertension, and arteriolar hyalinosis is an independent risk factor for renal prognosis in patients with IgAN.

Kidney Histopathology Features of Suspected Intra-Kidney Venous Thromboembolism in Patients with Primary Glomerulonephritis.

Introduction: Renal vein thromboembolism is a severe complication of nephrotic syndrome. Small thrombus in the intra-kidney venous system cannot be recognized by ultrasonography. The current study was to investigate the kidney pathological features of intra-kidney venous thrombus and their values in clinical practice. Methods: Kidney pathological features of glomerular capillary dilatation and congestion, peritubular capillary dilatation and congestion, and intraglomerular neutrophil infiltration were screened and scored during kidney biopsy information interpretation. Eighty-four consecutive patients with these features and primary glomerulonephritis were analyzed, comparing to another 84 control patients without these features who were matched according to the pathological types of glomerulonephritis. Results: In the patients with pathological features of suspected intra-kidney venous thrombus, the levels of proteinuria (5.2 vs. 3.2 g/24 h, p = 0.005), serum creatinine (80.9 vs. 71.2 µmol/L, p < 0.001), platelet count (274.0 vs. 254.5 ×109/L, p = 0.020), D-dimer (0.2 vs. 0.2 mg/L, p = 0.002), and fibrin degradation products (1.9 vs. 1.0 mg/L, p = 0.003) were significantly higher than those in control patients. The levels of serum albumin (24.2 vs. 28.6 g/L, p = 0.003) and eGFR (92.1 vs. 103.9 mL/min/1.73 m2, p < 0.001) were significantly lower. The scores of these pathological features were positively correlated with the levels of D-dimer (r = 0.21, p = 0.05). During follow-up, 9 (10.7%) patients with pathological features of suspected intra-kidney venous thrombus developed venous thromboembolism, which was significantly more than that of control patients (0%, p = 0.006). Conclusions: Kidney pathological features could indicate intra-kidney venous thromboembolism, and their scores represent the possibility of thrombus. The notice of these features may provide clinical alerts for venous thromboembolism possibility.

Hepatocyte nuclear factor 1B mutation in a Chinese family with renal cysts and diabetes syndrome: A case report.

BACKGROUND: Renal cysts and diabetes (RCAD) syndrome is an autosomal dominant diabetic renal disease. Precise molecular diagnosis of RCAD syndrome has proven valuable for understanding its mechanism and personalized therapy. CASE SUMMARY: A RCAD patient and her family were studied to investigate potential responsible genes by the whole exome sequencing (WES). Candidate pathogenic variants were validated by Sanger sequencing. The clinical characteristics of RCAD patient were collected from medical records. Unlike those typical RCAD patients, we observed renal manifestation and prediabetes phenotype, but not reproductive organ phenotype and hypomagnesaemia. A novel 7-bp deletion mutation in exon 4 of the hepatocyte nuclear factor 1B, NM_000458: c.882_888del (p.V294fs), was identified by WES and confirmed by Sanger sequencing. CONCLUSION: This novel mutation identified in a Chinese family with RCAD syndrome might be the molecular pathogenic basis of this disorder.

Clinicopathological features, risk factors, and outcomes of immunoglobulin A nephropathy associated with hepatitis B virus infection.

BACKGROUND: Hepatitis B virus (HBV) infections are associated with an increased risk of kidney diseases. However, the effects of HBV infection on the prognosis of immunoglobulin A nephropathy (IgAN) are unclear. METHODS: A total of 838 patients with biopsy-confirmed IgAN were enrolled in this retrospective cohort study. The patients were categorized into either affected by IgAN and HBV infection (HBsAg-IgAN) or by primary IgAN with no sign of HBV infection (P-IgAN). A 1:1 propensity-score matching was performed between the two groups, followed by a Kaplan-Meier survival analysis, to compare the prognoses, and a Cox regression analysis, to identify factors influencing the HBsAg-IgAN outcomes. RESULTS: A total of 176 pairs of patients were successfully matched. A significant difference in the systolic blood pressure and urea, serum creatinine, uric acid, and 24-h urine protein levels was observed between the groups. A renal pathological analysis also revealed a significant difference in the mesangial hypercellularity between the groups. During a median follow-up period of 2.4 years, Kaplan-Meier analysis also revealed a significant difference in the renal survival between the groups. Furthermore, multivariate Cox analysis confirmed that HBV infection is an independent risk factor for IgAN progression (hazard ratio [HR] 2.096; 95% confidence interval [CI] 1.091-4.026). Finally, the HBsAg-IgAN patients who received treatment with renin-angiotensin-aldosterone system inhibitors had a better overall prognosis than those who received immunosuppressive therapy and antiviral treatment. CONCLUSION: Our results indicate that the clinicopathological features and outcomes of patients with IgAN differ significantly between those with and without HBV infection, and that HBV is an independent risk factor for IgAN progression.

Potential Role of the Renal Arterial Resistance Index in the Differential Diagnosis of Diabetic Kidney Disease.

Aims: To investigate the potential role of renal arterial resistance index (RI) in the differential diagnosis between diabetic kidney disease (DKD) and non-diabetic kidney disease (NDKD) and establish a better-quantified differential diagnostic model. Materials and Methods: We consecutively reviewed 469 type 2 diabetes patients who underwent renal biopsy in our center. According to the renal biopsy results, eligible patients were classified into the DKD group and the NDKD group. The diagnostic significance of RI was evaluated by receiver operating characteristic (ROC) curve analysis. Logistic regression analysis was used to search for independent risk factors associated with DKD. Then a novel diagnostic model was established using multivariate logistic regression analysis. Results: A total of 332 DKD and 137 NDKD patients were enrolled for analysis. RI was significantly higher in the DKD group compared with those in the NDKD group (0.70 vs. 0.63, p< 0.001). The optimum cutoff value of RI for predicting DKD was 0.66 with sensitivity (69.2%) and specificity (80.9%). Diabetic retinopathy, diabetes duration ≥ 60 months, HbA1c ≥ 7.0(%), RI ≥ 0.66, and body mass index showed statistical significance in the multivariate logistic regression analysis. Then, we constructed a new diagnostic model based on these results. And the validation tests indicated that the new model had good sensitivity (81.5%) and specificity (78.6%). Conclusions: RI has a potential role in discriminating DKD from NDKD. The RI-based predicting model can be helpful for differential diagnosis of DKD and NDKD.

Indoxyl sulfate induces intestinal barrier injury through IRF1-DRP1 axis-mediated mitophagy impairment.

Rationale: The dysfunctional gut-kidney axis forms a vicious circle, which eventually becomes a catalyst for the progression of chronic kidney disease (CKD) and occurrence of related complications. However, the pathogenic factors of CKD-associated intestinal dysfunction and its mechanism remain elusive. Methods: We first identified the protein-bound uremic toxin indoxyl sulfate (IS) as a possible contributor to intestinal barrier injury. Transepithelial electrical resistance, permeability assay and transmission electron microscopy were carried out to evaluate the damaging effect of IS on intestinal barrier in intestinal epithelial cells, IS-injected mice and CKD mice. In vitro and in vivo experiments were performed to investigate the role of IS in intestinal barrier injury and the underlying mechanism. Finally, CKD mice treated with AST-120 (an oral adsorbent for IS) and gene knockout mice were used to verify the mechanism and to explore possible interventions for IS-induced intestinal barrier injury. Results: Transepithelial electrical resistance and the expressions of tight junction-related genes were significantly suppressed by IS in intestinal epithelial cells. In vitro experiments demonstrated that IS inhibited the expression of dynamin-related protein 1 (DRP1) and mitophagic flux, whereas DRP1 overexpression attenuated IS-induced mitophagic inhibition and intestinal epithelial cell damage. Furthermore, IS suppressed DRP1 by upregulating the expression of interferon regulatory factor 1 (IRF1), and IRF1 could directly bind to the promoter region of DRP1. Additionally, the decreased expression of DRP1 and autophagosome-encapsulated mitochondria were observed in the intestinal tissues of CKD patients. Administration of AST-120 or genetic knockout of IRF1 attenuated IS-induced DRP1 reduction, mitophagic impairment and intestinal barrier injury in mice. Conclusions: These findings suggest that reducing IS accumulation or targeting the IRF1-DRP1 axis may be a promising therapeutic strategy for alleviating CKD-associated intestinal dysfunction.

Klotho is regulated by transcription factor Sp1 in renal tubular epithelial cells.

BACKGROUND: Klotho is a multifunctional protein, which exists both in a membrane bound and a soluble form. In renal tubules, Klotho is involved in cell senescence, anti-oxidant response, and renal fibrosis, thus regulation of its expression is critical to understand its roles in renal diseases. Indeed, reduced expression was observed in various renal disease. However, the mechanisms underlying transcriptional regulation of the human klotho gene (KL) largely remain unknown. RESULTS: Here we demonstrated that the Klotho expression in human renal tubular epithelial cells (RTECs) was enhanced by overexpression of the transcription factor Sp1. On the contrary, Klotho expression was decreased by Sp1 knockdown. Besides, increased expression of Sp1 alleviated TGF-ß1-induced fibrosis in HK-2 cells by inducing Klotho expression. Luciferase reporter assays and chromatin immunoprecipitation assays further identified the binding site of Sp1 was located in - 394 to - 289 nt of the KL promoter, which was further confirmed by mutation analysis. CONCLUSIONS: These data demonstrate that KL is a transcriptional target of Sp1 and TGF-ß1-induced fibrosis was alleviated by Sp1 in human RTECs by directly modulating Klotho expression, which help to further understand the transcriptional regulation of Klotho in renal disease models.

Serum Klotho, Cardiovascular Events, and Mortality in Nondiabetic Chronic Kidney Disease.

BACKGROUND: Experimental studies indicate that Klotho deficiency is a pathogenic factor for CKD-related complications, including cardiovascular disease (CVD). However, the association between serum Klotho and clinical outcomes in nondiabetic CKD patients needs to be further clarified. We aimed to determine whether serum Klotho levels are associated with CVD events and mortality in predialysis CKD patients without diabetes. METHODS: A total of 336 CKD stage 2-5 predialysis patients without diabetes were recruited and followed from the end of 2014 to January 2019 for CVD events and overall mortality. Serum Klotho was detected by ELISA and divided into quartiles (lowest, middle, second highest, and highest quartiles) according to their serum Klotho category. RESULTS: After a median follow-up of 3.52 years (IQR 3.34-3.76), Kaplan-Meier analysis showed that, compared to participants with a Klotho level in the highest quartile (the reference category), those in the lowest Klotho quartile were associated with a higher all-cause mortality risk (HR = 7.05; 95% CI 1.59-31.25) and a higher CVD event risk (HR = 3.02; 95% CI 1.45-6.30). In addition, the middle Klotho quartile was also associated with CVD event risk (HR = 2.56; 95% CI 1.21-5.41). Moreover, in the multivariate-adjusted model, the lowest Klotho quartile remained significantly associated with all-cause mortality (HR = 5.17; 95% CI 1.07-24.96), and the middle Klotho quartile maintained a significant association with CVD event risk (HR = 2.32; 95% CI 1.03-5.21). CONCLUSION: These results suggest that lower serum Klotho levels are independently associated with overall mortality and CVD events in nondiabetic predialysis CKD patients.

IRF-1 promotes renal fibrosis by downregulation of Klotho.

Although the key role of renal fibrosis in the progression of chronic kidney disease (CKD) is well known, the causes of renal fibrosis are not fully clarified. In this study, interferon regulatory factor 1 (IRF-1), a mammalian transcription factor, was highly expressed in fibrotic kidney of CKD patients. Concordantly, the expression level of IRF-1 was significantly elevated in the kidney of unilateral ureteral obstruction (UUO) and Adriamycin nephropathy (ADR) mice. In tubular epithelial cells, overexpression of IRF-1 could induce profibrotic markers expression, which accompanied by dramatic downregulation of Klotho, an important inhibitor of renal fibrosis. Luciferase reporter analysis and ChIP assay revealed that IRF-1 repressed Klotho expression by downregulation of C/EBP-ß, which regulates Klotho gene transcription via directly binding to its promoter. Further investigation showed that tumor necrosis factor-alpha may be an important inducement for the increase of IRF-1 in tubular epithelial cells after UUO and genetic deletion of IRF-1 attenuated renal fibrosis in UUO mice. Hence, these findings demonstrate that IRF-1 contributes to the pathogenesis of renal fibrosis by downregulation of Klotho, and suppresses IRF-1 may be a potential therapeutic target for CKD.

Klotho inhibits PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy.

Diabetic nephropathy (DN) is a progressive disease, the main pathogeny of which is podocyte injury. As a calcium-dependent serine/threonine protein kinase involved in podocyte injury, protein kinase C isoform α (PKCα) was reported to regulate the phosphorylation of p66SHC. However, the role of PKCα/p66SHC in DN remains unknown. Klotho, an anti-aging protein with critical roles in protecting kidney, is expressed predominantly in the kidney and secreted in the blood. Nonetheless, the mechanism underlying amelioration of podocyte injury by Klotho in DN remains unclear. Our data showed that Klotho was decreased in STZ-treated mice and was further declined in diabetic KL ± mice. As expected, Klotho deficiency aggravated diabetes-induced proteinuria and podocyte injury, accompanied by the activation of PKCα and p66SHC. In contrast, overexpression of Klotho partially ameliorated PKCα/p66SHC-mediated podocyte injury and proteinuria. In addition, in vitro experiments showed that activation of PKCα and subsequently increased intracellular reactive oxygen species (ROS) was involved in podocytic apoptosis induced by high glucose (HG), which could be partially reversed by Klotho. Hence, we conclude that Klotho might inhibit PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy.

Klotho restrain RIG-1/NF-κB signaling activation and monocyte inflammatory factor release under uremic condition.

AIMS: Systemic inflammation is a main hallmark of chronic kidney disease (CKD), but the underlying mechanisms of pathogenesis of CKD-associated systemic inflammation is unclear. Current study was designed to investigate the relationship between indoxyl sulphate (IS) and CKD-associated systemic inflammation along with the protective effects of Klotho in CKD. METHODS: IS serum levels from patients were detected by high-performance liquid chromatography (HPLC), and Serum Klotho, IL-6 and TNF-α were measured separately by ELISA and Real-Time PCR analysis. Monocytes were incubated with or without Klotho, while the expressions of retinoic acid-inducible gene I (RIG-I) and NF-κB were analyzed through Western blot assay. Heterozygous kl/kl (kl/+) mice or WT mice were treated with 5/6 renal damage. Thereafter, the CKD mice were intraperitoneally injected with recombinant Klotho protein or PBS. KEY FINDINGS: It shows that in 286 CKD patients, the serum levels of inflammatory factors were positively related with IS, but negatively related with Klotho. Klotho significantly inhibited IS-induced RIG-I/NF-κB activation and productions of both IL-6 and TNF-α in cultured monocytes. In vivo, along with the increase of IS and decrease of Klotho in the serum, the activation of RIG-I/NF-κB signaling was observed in peripheral blood monocytes in both CKD mice and patients. Notably, higher levels of IL-6 and TNF-α were detected in kl+/- mice given CKD. Klotho administration has evidently attenuated RIG-I/NF-κB activation in monocytes and systemic inflammation in CKD mice. SIGNIFICANCE: The findings suggest that Klotho can suppress CKD-associated systemic inflammation through inhibiting IS-induced RIG-1/NF-κB activation and monocyte inflammatory factor release.

MicroRNA-34a Promotes Renal Fibrosis by Downregulation of Klotho in Tubular Epithelial Cells.

Renal fibrosis is the main pathological characteristic of chronic kidney disease (CKD), whereas the underlying mechanisms of renal fibrosis are not clear yet. Herein, we found an increased expression of microRNA-34a (miR-34a) in renal tubular epithelial cells of patients with renal fibrosis and mice undergoing unilateral ureteral obstruction (UUO). In miR-34a-/- mice, miR-34a deficiency attenuated the progression of renal fibrosis following UUO surgery. The miR-34a overexpression promoted epithelial-to-mesenchymal transition (EMT) in cultured human renal tubular epithelial HK-2 cells, which was accompanied by sharp downregulation of Klotho, an endogenous inhibitor of renal fibrosis. Luciferase reporter assay revealed that miR-34a downregulated Klotho expression though direct binding with the 3' UTR of Klotho. Conversely, overexpression of Klotho prevented miR-34a-induced EMT in HK-2 cells. Furthermore, results showed that miR-34a was induced by transforming growth factor ß1 (TGF-ß1) through p53 activation, whereas dihydromyricetin could inhibit TGF-ß1-induced miR-34a overexpression. Accordingly, dihydromyricetin administration dramatically restored the aberrant upregulation of miR-34a and Klotho reduction in obstructed kidney, and markedly ameliorated renal fibrosis in the Adriamycin nephropathy and UUO model mice. These findings suggested that miR-34a plays an important role in the progression of renal fibrosis, which provides new insights into the pathogenesis and treatment of CKD.

High Phosphate-Induced Calcification of Vascular Smooth Muscle Cells is Associated with the TLR4/NF-κb Signaling Pathway.

BACKGROUND/AIMS: Hyperphosphatemia is one of the most notable features of chronic kidney disease (CKD). Numerous epidemiological and clinical studies have found that high serum phosphate concentrations are associated with calcification in the coronary arteries. However, the mechanisms underlying the vascular calcification induced by high phosphate have not been understood fully. METHODS: Vascular smooth muscle cells (VSMCs) were cultured in high-phosphate media to induce vascular calcification, which was detected by Alizarin red S staining. Gene expression and protein levels of differentiation markers were determined by real-time RT-PCR and western blotting, respectively. Protein levels of phosphorylated NF-κB and TLR4 were detected by western blotting, and the role of NF-κB/TLR4 was further confirmed by using an NF-κB inhibitor or TLR4 siRNA. RESULTS: Our results showed that high-phosphate media induced obvious calcification of VSMCs. Simultaneously, VSMC differentiation was confirmed by the increased expression of bone morphogenetic protein-2 and Runt-related transcription factor 2 and decreased expression of the VSMC-specific marker SM22α, which was accompanied by the increased expression of inflammatory cytokines. Moreover, a significant upregulation of TLR4 and phosphorylated NF-κB was also detected in VSMCs with high-phosphate media. In contrast, VSMC calcification and the increased expression of inflammatory cytokines were markedly attenuated by pretreatment with TLR4 siRNA and pyrrolidine dithiocarbamic acid, an NF-κB inhibitor. CONCLUSION: These data suggest that high-phosphate conditions directly induce vascular calcification via the activation of TLR4/NF-κB signaling in VSMCs. Moreover, inhibition of the TLR4/NF-κB signaling pathway might be a key intervention to prevent vascular calcification in patients with CKD.